Proline transport in Leishmania donovani amastigotes: dependence on pH gradients and membrane potential.

PubMed

Glaser, T A; Mukkada, A J

1992-03-01

Amastigotes of Leishmania donovani develop and multiply within the acidic phagolysosomes of mammalian macrophages. Isolated amastigotes are acidophilic; they catabolize substrates and synthesize macromolecules optimally at pH 5.5. Substrate transport in amastigotes has not been characterized. Here we show that amastigotes exhibit an uphill transport of proline (active transport) with an acid pH optimum (pH 5.5). It is dependent upon metabolic energy and is driven by proton motive force. Agents which selectively disturb the component forces of proton motive force, such as carbonyl cyanide chlorophenylhydrazone, nigericin and valinomycin, inhibit proline transport. Transport is sensitive to dicyclohexylcarbodiimide and insensitive to ouabain, demonstrating the involvement of a proton ATPase in the maintenance of proton motive force. It is suggested that the plasma membrane pH gradient probably makes the greatest contribution to proton motive force that drives substrate transport in the amastigote stage.

Proton Gradient-Driven Nickel Uptake by Vacuolar Membrane Vesicles of Saccharomyces cerevisiae

PubMed Central

Nishimura, Ken; Igarashi, Kazuei; Kakinuma, Yoshimi

1998-01-01

A vacuolar H+-ATPase-negative mutant of Saccharomyces cerevisiae was highly sensitive to nickel ion. Accumulation of nickel ion in the cells of this mutant of less than 60% of the value for the parent strain arrested growth, suggesting a role for this ATPase in sequestering nickel ion into vacuoles. An artificially imposed pH gradient (interior acid) induced transient nickel ion uptake by vacuolar membrane vesicles, which was inhibited by collapse of the pH difference but not of the membrane potential. Nickel ion transport into vacuoles in a pH gradient-dependent manner is thus important for its detoxification in yeast. PMID:9537401

Analysis of low molecular weight acids by monolithic immobilized pH gradient-based capillary isoelectric focusing coupled with mass spectrometry.

PubMed

Wang, Tingting; Fekete, Agnes; Gaspar, Andras; Ma, Junfeng; Liang, Zhen; Yuan, Huiming; Zhang, Lihua; Schmitt-Kopplin, Philippe; Zhang, Yukui

2011-02-01

A novel method for the separation and detection of low molecular weight (LMW) acids was developed using monolithic immobilized pH gradient-based capillary isoelectric focusing coupled with mass spectrometry. Two main parameters, focusing conditions and delivery buffer conditions, which might affect separation efficiency, were optimized with the focusing time of 7 min at 350 V/cm and the delivery buffer of 50% (v/v) acetonitrile in 10 mmol/L ammonium formate (pH 3.0). Under these conditions, the linear correlation between the volume of delivery solvent and the pK(a) of the model components was observed. In addition, the separation mechanism of LMW acids was proposed as well. We suppose that this method may provide a useful tool for the characterization of LMW components (e.g. natural organic matter of different origins). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Archaeal Abundance across a pH Gradient in an Arable Soil and Its Relationship to Bacterial and Fungal Growth Rates

PubMed Central

Sterngren, Anna E.; Rousk, Johannes

2012-01-01

Soil pH is one of the most influential factors for the composition of bacterial and fungal communities, but the influence of soil pH on the distribution and composition of soil archaeal communities has yet to be systematically addressed. The primary aim of this study was to determine how total archaeal abundance (quantitative PCR [qPCR]-based estimates of 16S rRNA gene copy numbers) is related to soil pH across a pH gradient (pH 4.0 to 8.3). Secondarily, we wanted to assess how archaeal abundance related to bacterial and fungal growth rates across the same pH gradient. We identified two distinct and opposite effects of pH on the archaeal abundance. In the lowest pH range (pH 4.0 to 4.7), the abundance of archaea did not seem to correspond to pH. Above this pH range, there was a sharp, almost 4-fold decrease in archaeal abundance, reaching a minimum at pH 5.1 to 5.2. The low abundance of archaeal 16S rRNA gene copy numbers at this pH range then sharply increased almost 150-fold with pH, resulting in an increase in the ratio between archaeal and bacterial copy numbers from a minimum of 0.002 to more than 0.07 at pH 8. The nonuniform archaeal response to pH could reflect variation in the archaeal community composition along the gradient, with some archaea adapted to acidic conditions and others to neutral to slightly alkaline conditions. This suggestion is reinforced by observations of contrasting outcomes of the (competitive) interactions between archaea, bacteria, and fungi toward the lower and higher ends of the examined pH gradient. PMID:22706045

Archaeal abundance across a pH gradient in an arable soil and its relationship to bacterial and fungal growth rates.

PubMed

Bengtson, Per; Sterngren, Anna E; Rousk, Johannes

2012-08-01

Soil pH is one of the most influential factors for the composition of bacterial and fungal communities, but the influence of soil pH on the distribution and composition of soil archaeal communities has yet to be systematically addressed. The primary aim of this study was to determine how total archaeal abundance (quantitative PCR [qPCR]-based estimates of 16S rRNA gene copy numbers) is related to soil pH across a pH gradient (pH 4.0 to 8.3). Secondarily, we wanted to assess how archaeal abundance related to bacterial and fungal growth rates across the same pH gradient. We identified two distinct and opposite effects of pH on the archaeal abundance. In the lowest pH range (pH 4.0 to 4.7), the abundance of archaea did not seem to correspond to pH. Above this pH range, there was a sharp, almost 4-fold decrease in archaeal abundance, reaching a minimum at pH 5.1 to 5.2. The low abundance of archaeal 16S rRNA gene copy numbers at this pH range then sharply increased almost 150-fold with pH, resulting in an increase in the ratio between archaeal and bacterial copy numbers from a minimum of 0.002 to more than 0.07 at pH 8. The nonuniform archaeal response to pH could reflect variation in the archaeal community composition along the gradient, with some archaea adapted to acidic conditions and others to neutral to slightly alkaline conditions. This suggestion is reinforced by observations of contrasting outcomes of the (competitive) interactions between archaea, bacteria, and fungi toward the lower and higher ends of the examined pH gradient.

Two-dimensional pH distributions and dynamics in bioturbated marine sediments

NASA Astrophysics Data System (ADS)

Zhu, Qingzhi; Aller, Robert C.; Fan, Yanzhen

2006-10-01

The seafloor is the site of intense biogeochemical and mineral dissolution-precipitation reactions which generate strong gradients in pH near the sediment-overlying water interface. These gradients are usually measured in one-dimension vertically with depth. Two-dimensional pH distributions in marine sediments were examined at high resolution (65 × 65 μm pixel) and analytical precision over areas of ˜150 to 225 cm 2 using a newly developed pH planar fluorosensor. Dramatic three-dimensional gradients, complex heterogeneity, and dynamic changes of pH occur in the surficial zone of deposits inhabited by macrofauna. pH can vary by ±2 units horizontally as well as vertically over millimeter scales. pH minima zones often form in association with redoxclines within a few millimeters of inner burrow walls, and become more pronounced with time if burrows remain stable and irrigated for extended periods. Microenvironmental pH minima also form locally around decaying biomass and relict burrow tracks, and dissipate with time (˜5 d). H + concentrations and fluxes in sandy mud show complex acid-base reaction distributions with net H + fluxes around burrows up to ˜12 nmol cm -2 d -1 and maximum net reaction rates varying between -90 (consumption) to 120 (production) μM d -1 (˜90 nmol cm -1 d -1 burrow length). Acid producing zones that surround irrigated burrows are largely balanced by acid titration zones along inner burrow walls and outer radial boundaries. The geometry and scaling of pH microenvironments are functions of diagenetic reaction rates and three-dimensional transport patterns determined by sediment properties, such as diffusive tortuosity, and by benthic community characteristics such as the abundance, mobility, and size of infauna. Previously, undocumented biogeochemical phenomena such as low pH regions associated with in-filled relict biogenic structures and burrowing tracks are readily demonstrated by two-dimensional and time-dependent images of pH and sedimentary structure.

A comparative review of cutaneous pH.

PubMed

Matousek, Jennifer L; Campbell, Karen L

2002-12-01

This review describes the role of pH in cutaneous structure and function. We first describe the molecules that contribute to the acidity or alkalinity of the skin. Next, differences in cutaneous pH among species, among individuals of the same species and within individuals are described. The potential functions of cutaneous pH in normal and diseased skin are analysed. For example, cutaneous pH has a role in the selection and maintenance of the normal cutaneous microbiota. In addition, cutaneous acidity may protect the skin against infection by microbes. Finally, there is evidence that a cutaneous pH gradient activates pH-dependent enzymes involved in the process of keratinization.

Prediction of the chromatographic retention of acid-base compounds in pH buffered methanol-water mobile phases in gradient mode by a simplified model.

PubMed

Andrés, Axel; Rosés, Martí; Bosch, Elisabeth

2015-03-13

Retention of ionizable analytes under gradient elution depends on the pH of the mobile phase, the pKa of the analyte and their evolution along the programmed gradient. In previous work, a model depending on two fitting parameters was recommended because of its very favorable relationship between accuracy and required experimental work. It was developed using acetonitrile as the organic modifier and involves pKa modeling by means of equations that take into account the acidic functional group of the compound (carboxylic acid, protonated amine, etc.). In this work, the two-parameter predicting model is tested and validated using methanol as the organic modifier of the mobile phase and several compounds of higher pharmaceutical relevance and structural complexity as testing analytes. The results have been quite good overall, showing that the predicting model is applicable to a wide variety of acid-base compounds using mobile phases prepared with acetonitrile or methanol. Copyright © 2015 Elsevier B.V. All rights reserved.

Acid-inducible proton influx currents in the plasma membrane of murine osteoclast-like cells.

PubMed

Kuno, Miyuki; Li, Guangshuai; Moriura, Yoshie; Hino, Yoshiko; Kawawaki, Junko; Sakai, Hiromu

2016-05-01

Acidification of the resorption pits, which is essential for dissolving bone, is produced by secretion of protons through vacuolar H(+)-ATPases in the plasma membrane of bone-resorbing cells, osteoclasts. Consequently, osteoclasts face highly acidic extracellular environments, where the pH gradient across the plasma membrane could generate a force driving protons into the cells. Proton influx mechanisms during the acid exposure are largely unknown, however. In this study, we investigated extracellular-acid-inducible proton influx currents in osteoclast-like cells derived from a macrophage cell line (RAW264). Decreasing extracellular pH to <5.5 induced non-ohmic inward currents. The reversal potentials depended on the pH gradients across the membrane and were independent of concentrations of Na(+), Cl(-), and HCO3 (-), suggesting that they were carried largely by protons. The acid-inducible proton influx currents were not inhibited by amiloride, a widely used blocker for cation channels/transporters, or by 4,4'-diisothiocyanato-2,2'-stilbenesulfonate(DIDS) which blocks anion channels/transporters. Additionally, the currents were not significantly affected by V-ATPase inhibitors, bafilomycin A1 and N,N'-dicyclohexylcarbodiimide. Extracellular Ca(2+) (10 mM) did not affect the currents, but 1 mM ZnCl2 decreased the currents partially. The intracellular pH in the vicinity of the plasma membrane was dropped by the acid-inducible H(+) influx currents, which caused overshoot of the voltage-gated H(+) channels after removal of acids. The H(+) influx currents were smaller in undifferentiated, mononuclear RAW cells and were negligible in COS7 cells. These data suggest that the acid-inducible H(+) influx (H(+) leak) pathway may be an additional mechanism modifying the pH environments of osteoclasts upon exposure to strong acids.

Short-column anion-exchange chromatography for soil and peat humic substances profiling by step-wise gradient of high pH aqueous sodium ethylenediaminetetraacetate.

PubMed

Hutta, Milan; Ráczová, Janka; Góra, Róbert; Pessl, Juraj

2015-08-21

Novel anion-exchange liquid chromatographic method with step gradient of aqueous EDTA(4-) based mobile phase elution has been developed to profile available Slovak soil humic substances and alkaline extracts of various soils. The method utilize short glass column (30mm×3mm) filled in with hydrolytically stable particles (60μm diameter) Separon HEMA-BIO 1000 having (diethylamino)ethyl functional groups. Step gradient was programmed by mixing mobile phase composed of aqueous solution of sodium EDTA (pH 12.0; 5mmolL(-1)) and mobile phase constituted of aqueous solution of sodium EDTA (pH 12.0, 500mmolL(-1)). The FLD of HSs was set to excitation wavelength 480nm and emission wavelength 530nm (λem). Separation mechanism was studied by use of selected aromatic acids related to humic acids with the aid of UV spectrophotometric detection at 280nm. The proposed method benefits from high ionic strength (I=5molL(-1)) of the end mobile phase buffer and provides high recovery of humic acids (98%). Accurate and reproducible profiling of studied humic substances, alkaline extracts of various types of soils enables straightforward characterization and differentiation of HSs in arable and forest soils. Selected model aromatic acids were used for separation mechanism elucidation. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of extracellular pH on growth, viability, cell size, acidification activity, and intracellular pH of Lactococcus lactis in batch fermentations.

PubMed

Hansen, Gunda; Johansen, Claus Lindvald; Marten, Gunvor; Wilmes, Jacqueline; Jespersen, Lene; Arneborg, Nils

2016-07-01

In this study, we investigated the influence of three extracellular pH (pHex) values (i.e., 5.5, 6.5, and 7.5) on the growth, viability, cell size, acidification activity in milk, and intracellular pH (pHi) of Lactococcus lactis subsp. lactis DGCC1212 during pH-controlled batch fermentations. A universal parameter (e.g., linked to pHi) for the description or prediction of viability, specific acidification activity, or growth behavior at a given pHex was not identified. We found viability as determined by flow cytometry to remain high during all growth phases and irrespectively of the pH set point. Furthermore, regardless of the pHex, the acidification activity per cell decreased over time which seemed to be linked to cell shrinkage. Flow cytometric pHi determination demonstrated an increase of the averaged pHi level for higher pH set points, while the pH gradient (pHi-pHex) and the extent of pHi heterogeneity decreased. Cells maintained positive pH gradients at a low pHex of 5.5 and even during substrate limitation at the more widely used pHex 6.5. Moreover, the strain proved able to grow despite small negative or even absent pH gradients at a high pHex of 7.5. The larger pHi heterogeneity at pHex 5.5 and 6.5 was associated with more stressful conditions resulting, e.g., from higher concentrations of non-dissociated lactic acid, while the low pHi heterogeneity at pHex 7.5 most probably corresponded to lower concentrations of non-dissociated lactic acid which facilitated the cells to reach the highest maximum active cell counts of the three pH set points.

Application of linear pH gradients for the modeling of ion exchange chromatography: Separation of monoclonal antibody monomer from aggregates.

PubMed

Kluters, Simon; Wittkopp, Felix; Jöhnck, Matthias; Frech, Christian

2016-02-01

The mobile phase pH is a key parameter of every ion exchange chromatography process. However, mechanistic insights into the pH influence on the ion exchange chromatography equilibrium are rare. This work describes a mechanistic model capturing salt and pH influence in ion exchange chromatography. The pH dependence of the characteristic protein charge and the equilibrium constant is introduced to the steric mass action model based on a protein net charge model considering the number of amino acids interacting with the stationary phase. This allows the description of the adsorption equilibrium of the chromatographed proteins as a function of pH. The model parameters were determined for a monoclonal antibody monomer, dimer, and a higher aggregated species based on a manageable set of pH gradient experiments. Without further modification of the model parameters the transfer to salt gradient elution at fixed pH is demonstrated. A lumped rate model was used to predict the separation of the monoclonal antibody monomer/aggregate mixture in pH gradient elution and for a pH step elution procedure-also at increased protein loadings up to 48 g/L packed resin. The presented model combines both salt and pH influence and may be useful for the development and deeper understanding of an ion exchange chromatography separation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mathematical model for steady state, simple ampholyte isoelectric focusing: Development, computer simulation and implementation

NASA Technical Reports Server (NTRS)

Palusinski, O. A.; Allgyer, T. T.

1979-01-01

The elimination of Ampholine from the system by establishing the pH gradient with simple ampholytes is proposed. A mathematical model was exercised at the level of the two-component system by using values for mobilities, diffusion coefficients, and dissociation constants representative of glutamic acid and histidine. The constants assumed in the calculations are reported. The predictions of the model and computer simulation of isoelectric focusing experiments are in direct importance to obtain Ampholine-free, stable pH gradients.

Isoelectric focusing of dansylated amino acids in immobilized pH gradients

NASA Technical Reports Server (NTRS)

Bianchi-Bosisio, Adriana; Righetti, Pier Giorgio; Egen, Ned B.; Bier, Milan

1986-01-01

The 21 free amino acids commonly encountered in proteins have been transformed into 'carrier ampholyte' species by reacting their primary amino groups with dansyl chloride. These derivatives can thus be focused in an immobilized pH gradient covering the pH interval 3.1 to 4.1, except for arginine, which still retains a pI of 8.8. Due to their inherent fluorescence, the dansyl derivatives are revealed in UV light, with a sensitivity of the order of 2-4 ng/sq mm. All nearest neighbors are separated except for the following couples: Asn-Gln, Gly-Thr, Val-Ile and Cys-Cys2, with a resolving power, in a Delta(pI) scale, of the order of 0.0018 pH units. Except for a few cases (notably the aromatic amino acids), the order of pI values is well correlated with the pK values of carboxyl groups, suggesting that the latter are not altered by dansylation. From the set of pK(COOH)-pI values of the different amino acids, the pK of the tertiary amino group in the dansyl label has been calculated to be 5.11 + or - 0.06. Knowing the pK of the amino-dansyl and the pI of the excess, free dansyl label (pI = 3.34), a pK of 1.57 is derived for its sulfonic acid group.

Ancient Living Organisms Escaping from, or Imprisoned in, the Vents?

PubMed Central

Jackson, J. Baz

2017-01-01

We have recently criticised the natural pH gradient hypothesis which purports to explain how the difference in pH between fluid issuing from ancient alkali vents and the more acidic Hadean ocean could have driven molecular machines that catalyse reactions that are useful in prebiotic and autotrophic chemistry. In this article, we temporarily suspend our earlier criticism while we consider difficulties for primitive organisms to have managed their energy supply and to have left the vents and become free-living. We point out that it may have been impossible for organisms to have acquired membrane-located proton (or sodium ion) pumps to replace the natural pH gradient, and independently to have driven essential molecular machines such as the ATP synthase. The volumes of the ocean and of the vent fluids were too large for a membrane-located pump to have generated a significant ion concentration gradient. Our arguments apply to three of the four concurrent models employed by the proponents of the natural pH gradient hypothesis. A fourth model is exempt from these arguments but has other intrinsic difficulties that we briefly consider. We conclude that ancient organisms utilising a natural pH gradient would have been imprisoned in the vents, unable to escape and become free-living. PMID:28914790

Concentration and fractionation of hydrophobic organic acid constituents from natural waters by liquid chromatography

USGS Publications Warehouse

Thurman, E.M.; Malcolm, R.L.

1979-01-01

A scheme is presented which used adsorption chromatography with pH gradient elution and size-exclusion chromatography to concentrate and separate hydrophobic organic acids from water. A review of chromatographic processes involved in the flow scheme is also presented. Organic analytes which appear in each aqueous fraction are quantified by dissolved organic carbon analysis. Hydrophobic organic acids in a water sample are concentrated on a porous acrylic resin. These acids usually constitute approximately 30-50 percent of the dissolved organic carbon in an unpolluted water sample and are eluted with an aqueous eluent (dilute base). The concentrate is then passed through a column of polyacryloylmorpholine gel, which separates the acids into high- and low-molecular-weight fractions. The high- and low-molecular-weight eluates are reconcentrated by adsorption chromatography, then are eluted with a pH gradient into strong acids (predominately carboxylic acids) and weak acids (predominately phenolic compounds). For standard compounds and samples of unpolluted waters, the scheme fractionates humic substances into strong and weak acid fractions that are separated from the low molecular weight acids. A new method utilizing conductivity is also presented to estimate the acidic components in the methanol fraction.

Hollow Fiber Supported Liquid Membrane Extraction Combined with HPLC-UV for Simultaneous Preconcentration and Determination of Urinary Hippuric Acid and Mandelic Acid

PubMed Central

Bahrami, Abdulrahman; Ghamari, Farhad; Yamini, Yadollah; Ghorbani Shahna, Farshid; Moghimbeigi, Abbas

2017-01-01

This work describes a new extraction method with hollow-fiber liquid-phase microextraction based on facilitated pH gradient transport for analyzing hippuric acid and mandelic acid in aqueous samples. The factors affecting the metabolites extraction were optimized as follows: the volume of sample solution was 10 mL with pH 2 containing 0.5 mol·L−1 sodium chloride, liquid membrane containing 1-octanol with 20% (w/v) tributyl phosphate as the carrier, the time of extraction was 150 min, and stirring rate was 500 rpm. The organic phase immobilized in the pores of a hollow fiber was back-extracted into 24 µL of a solution containing sodium carbonate with pH 11, which was placed inside the lumen of the fiber. Under optimized conditions, the high enrichment factors of 172 and 195 folds, detection limit of 0.007 and 0.009 µg·mL−1 were obtained. The relative standard deviation (RSD) (%) values for intra- and inter-day precisions were calculated at 2.5%–8.2% and 4.1%–10.7%, respectively. The proposed method was successfully applied to the analysis of these metabolites in real urine samples. The results indicated that hollow-fiber liquid-phase microextraction (HF-LPME) based on facilitated pH gradient transport can be used as a sensitive and effective method for the determination of mandelic acid and hippuric acid in urine specimens. PMID:28208685

Calixarene-Mediated Liquid-Membrane Transport of Choline Conjugates.

PubMed

Adhikari, Birendra Babu; Fujii, Ayu; Schramm, Michael P

2014-05-01

A series of supramolecular calixarenes efficiently transport distinct molecular species through a liquid membrane when attached to a receptor-complementary choline handle. Calix-[6]arene hexacarboxylic acid was highly effective at transporting different target molecules against a pH gradient. Both carboxylic- and phosphonic-acid-functionalized calix[4]arenes effect transport without requiring a pH or ion gradient. NMR binding studies, two-phase solvent extraction, and three-phase transport experiments reveal the necessary and subtle parameters to effect the transport of molecules attached to a choline "handle". On the other hand, rescorin[4]arene cavitands, which have similar guest recognition profiles, did not transport guest molecules. These developments reveal new approaches towards attempting synthetic-receptor-mediated selective small-molecule transport in vesicular and cellular systems.

Unravelling the effects of mobile phase additives in supercritical fluid chromatography. Part I: Polarity and acidity of the mobile phase.

PubMed

West, Caroline; Melin, Jodie; Ansouri, Hassna; Mengue Metogo, Maïly

2017-04-07

The mobile phases employed in current supercritical fluid chromatography (SFC) are usually composed of a mixture of pressurized carbon dioxide and a co-solvent. The co-solvent is most often an alcohol and may contain a third component in small proportions, called an additive (acid, base or salt). The polarity of such mobile phase compositions is here re-evaluated with a solvatochromic dye (Nile Red), particularly to assess the contribution of additives. It appears that additives, when employed in usual concentration range (0.1% or 20mM) do not modify the polarity in the immediate environment of the probe. In addition, the combination of carbon dioxide and an alcohol is known to form alkoxylcarbonic acid, supposedly conferring some acidic character to SFC mobile phases. Direct measurements of the apparent pH are impossible, but colour indicators of pH can be used to define the range of apparent pH provided by carbon dioxide-alcohol mixtures, with or without additives. Five colour indicators (Thymol Blue, Bromocresol Green, Methyl Red, Bromocresol Purple, and Bromothymol Blue) were selected to provide a wide range of aqueous pK a values (from 1.7 to 8.9). UV-vis absorption spectra measured in liquid phases of controlled pH were compared to those measured with a diode-array detector employed in SFC, with the help of chemometric methods. Based on these observations, it is concluded that the apparent pH range in carbon dioxide-methanol mobile phases is close to 5. Increasing the proportion of methanol (in the course of a gradient elution for instance) causes decreasing apparent pH. Strong acids can further decrease the apparent pH below 1.7; strong bases have little influence on the apparent pH, probably because, in this range of concentrations, they are titrated by alkoxylcarbonic acid or form ion pairs with alkoxycarbonate. However, bases and salts could stabilize the acidity in the course of gradient runs. Copyright © 2017 Elsevier B.V. All rights reserved.

Life at acidic pH imposes an increased energetic cost for a eukaryotic acidophile.

PubMed

Messerli, Mark A; Amaral-Zettler, Linda A; Zettler, Erik; Jung, Sung-Kwon; Smith, Peter J S; Sogin, Mitchell L

2005-07-01

Organisms growing in acidic environments, pH<3, would be expected to possess fundamentally different molecular structures and physiological controls in comparison with similar species restricted to neutral pH. We begin to investigate this premise by determining the magnitude of the transmembrane electrochemical H+ gradient in an acidophilic Chlamydomonas sp. (ATCC PRA-125) isolated from the Rio Tinto, a heavy metal laden, acidic river (pH 1.7-2.5). This acidophile grows most rapidly at pH 2 but is capable of growth over a wide pH range (1.5-7.0), while Chlamydomonas reinhardtii is restricted to growth at pH>or=3 with optimal growth between pH 5.5 and 8.5. With the fluorescent H+ indicator, 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF), we show that the acidophilic Chlamydomonas maintains an average cytosolic pH of 6.6 in culture medium at both pH 2 and pH 7 while Chlamydomonas reinhardtii maintains an average cytosolic pH of 7.1 in pH 7 culture medium. The transmembrane electric potential difference of Chlamydomonas sp., measured using intracellular electrodes at both pH 2 and 7, is close to 0 mV, a rare value for plants, animals and protists. The 40,000-fold difference in [H+] could be the result of either active or passive mechanisms. Evidence for active maintenance was detected by monitoring the rate of ATP consumption. At the peak, cells consume about 7% more ATP per second in medium at pH 2 than at pH 7. This increased rate of consumption is sufficient to account for removal of H+ entering the cytosol across a membrane with relatively high permeability to H+ (7x10(-8) cm s-1). Our results indicate that the small increase in the rate of ATP consumption can account for maintenance of the transmembrane H+ gradient without the imposition of cell surface H+ barriers.

Differences in functional traits between invasive and native Amaranthus species under simulated acid deposition with a gradient of pH levels

NASA Astrophysics Data System (ADS)

Wang, Congyan; Wu, Bingde; Jiang, Kun; Zhou, Jiawei

2018-05-01

Co-occurring invasive plant species (invaders hereafter) and natives receive similar or even the same environmental selection pressures. Thus, the differences in functional traits between natives and invaders have become widely recognized as a major driving force of the success of plant invasion. Meanwhile, increasing amounts of acid are deposited into ecosystems. Thus, it is important to elucidate the potential effects of acid deposition on the functional traits of invaders in order to better understand the potential mechanisms for the successful invasion. This study aims to address the differences in functional traits between native red amaranth (Amaranthus tricolor L.; amaranth hereafter) and invasive redroot pigweed (A. retroflexus L.; pigweed hereafter) under simulated acid deposition with a gradient of pH levels. Pigweed was significantly taller than amaranth under most treatments. The greater height of pigweed can lead to greater competitive ability for resource acquisition, particularly for sunlight. Leaf shape index of pigweed was also significantly greater than that of amaranth under all treatments. The greater leaf shape index of pigweed can enhance the efficiency of resource capture (especially sunlight capture) via adjustments to leaf shape and size. Thus, the greater height and leaf shape index of pigweed can significantly enhance its competitive ability, especially under acid deposition. Acid deposition of pH 5.6 significantly increased amaranth leaf width in the co-cultivation due to added nutrients. The pH 4.5 acid deposition treatment significantly increased the specific leaf area of amaranth in the monoculture compared with the pH 5.6 acid deposition treatment and the control. The main mechanism explaining this pattern may be due to acid deposition mediating a hormesis effect on plants, promoting plant growth. The values of the relative competition intensity between amaranth and pigweed for most functional traits were lower than zero under most treatments. Thus, competitive performance arose in most treatments when the two species were grown together. This may be due to the enhanced competitive intensity under interspecific coexistence. However, the values of the relative competition intensity of the leaf functional traits between amaranth and pigweed were all higher than zero under the pH 5.6 simulated acid deposition treatment. Thus, interspecific facilitation occurs when the two species are co-cultivated under the pH 5.6 simulated acid deposition treatment. This may be due the positive nutritional effects induced in the pH 5.6 simulated acid deposition treatment.

Characteristics of H+ current transients induced by adverse H+ gradient pulses in toad bladder.

PubMed

Nero, A C; Schwartz, J H; Furtado, M R

1987-10-01

Acidification in the toad bladder occurs as a result of electrogenic H+ secretion (JH). When a pH gradient is applied in a stepwise fashion in the absence of exogenous CO2, JH decreases linearly with the mucosal (M) solution pH and is null when pHm is approximately 4.5. When pHm is returned to initial values (7.4) in a stepwise fashion, JH increases linearly with pHm. However, on this return, higher values of JH are initially obtained. To investigate this hysteresis, hemibladders mounted in chambers were used to measure the change in the H+ current before and after acid pulses were applied to the mucosal solution. In the absence of exogenous CO2, the application of graded acid pulses to mucosa for 1, 2, 4, and 8 min resulted in a graded decrease in JH. The restoration of pHm to 7.4 was followed by an immediate transient overshoot of reversed short-circuit current (Irsc), which was related to the time of exposure and the magnitude of the acid pulse. The longer the acid pulse or the larger the pulse, the greater the Irsc overshoot. The addition of protonophores, dinitrophenol, or salicylate, into the mucosal solution enhanced this overshoot. Similar Irsc overshoots could be obtained with the application of pulses of adverse electrical gradients. Introduction of exogenous CO2 into the system (3%) completely inhibited the overshoot in JH after an acid pulse. In conclusion, when pHm is decreased JH is reduced and the cell pH presumably decreases because of continued exit of alkali at the serosal side of the cell and entry of H+ from the mucosal solution. The decrease in cell pH then triggers the pump to produce a sharp overshoot in JH when pHm returns to 7.4.

Calixarene-Mediated Liquid-Membrane Transport of Choline Conjugates

PubMed Central

Adhikari, Birendra Babu; Fujii, Ayu

2015-01-01

A series of supramolecular calixarenes efficiently transport distinct molecular species through a liquid membrane when attached to a receptor-complementary choline handle. Calix-[6]arene hexacarboxylic acid was highly effective at transporting different target molecules against a pH gradient. Both carboxylic- and phosphonic-acid-functionalized calix[4]arenes effect transport without requiring a pH or ion gradient. NMR binding studies, two-phase solvent extraction, and three-phase transport experiments reveal the necessary and subtle parameters to effect the transport of molecules attached to a choline “handle”. On the other hand, rescorin[4]arene cavitands, which have similar guest recognition profiles, did not transport guest molecules. These developments reveal new approaches towards attempting synthetic-receptor-mediated selective small-molecule transport in vesicular and cellular systems. PMID:26161034

Electroneutral, HCO3(-)-independent, pH gradient-dependent uphill transport of Cl- by ileal brush-border membrane vesicles. Possible role in the pathogenesis of chloridorrhea.

PubMed Central

Vasseur, M; Caüzac, M; Alvarado, F

1989-01-01

By applying a rapid filtration technique to isolated brush border membrane vesicles from guinea pig ileum, 36Cl uptake was quantified in the presence and absence of electrical, pH and alkali-metal ion gradients. A mixture of 20 mM-Hepes and 40 mM-citric acid, adjusted to the desired pH with Tris base, was found to be the most suitable buffer. Malate and Mes could be used to replace the citrate, but succinate, acetate and maleate proved to be unsuitable. In the absence of a pH gradient (pHout:pHin = 7.5:7.5), Cl- uptake increased slightly when an inside-positive membrane potential was applied, but uphill transport was never observed. A pH gradient (pHout:pHin = 5.0:7.5) induced both a 400% increase in the initial Cl- influx rate and a long-lasting (20 to 300 s) overshoot, indicating that a proton gradient can furnish the driving force for uphill Cl- transport. Under pH gradient conditions, initial Cl- entry rates had the following characteristics. (1) They were unaffected by cis-Na+ and/or -K+, indicating the absence of Cl-/K+, Cl-/Na+ or Cl-/K+/Na+ symport activity. (2) Inhibition by 20-100 mM-trans-Na+ and/or -K+ occurred, independent of the existence of an ion gradient. (3) Cl- entry was practically unaffected by short-circuiting the membrane potential with equilibrated potassium and valinomycin. (4) Carbonyl cyanide m-chlorophenylhydrazone was strongly inhibitory and so, to a lesser extent, was 4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic acid [(SITS)], independent of the sign and size of the membrane potential. (5) Cl- entry was negligibly increased (less than 30%) by either trans-Cl- or -HCO3-, indicating the absence of an obligatory Cl-/anion antiport activity. In contrast, the height of the overshoot at 60 s was increased by trans-Cl-, indicating time-dependent inhibition of 36Cl efflux. That competitive inhibition of 36Cl fluxes by anions is involved here is supported by initial influx rate experiments demonstrating: (1) the saturability of Cl- influx, which was found to exhibit Michaelis-Menten kinetics; and (2) competitive inhibition of influx by cis-Cl- and -Br-. Quantitatively, the conclusion is warranted that over 85% of the total initial Cl- uptake energized by a pH gradient involves an electroneutral Cl-/H+ symporter or its physicochemical equivalent, a Cl-/OH- antiporter, exhibiting little Cl- uniport and either Cl-/Cl- or Cl-/HCO3- antiport activities.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2597129

Improved Acid Stress Survival of Lactococcus lactis Expressing the Histidine Decarboxylation Pathway of Streptococcus thermophilus CHCC1524*

PubMed Central

Trip, Hein; Mulder, Niels L.; Lolkema, Juke S.

2012-01-01

Degradative amino acid decarboxylation pathways in bacteria generate secondary metabolic energy and provide resistance against acid stress. The histidine decarboxylation pathway of Streptococcus thermophilus CHCC1524 was functionally expressed in the heterologous host Lactococcus lactis NZ9000, and the benefits of the newly acquired pathway for the host were analyzed. During growth in M17 medium in the pH range of 5–6.5, a small positive effect was observed on the biomass yield in batch culture, whereas no growth rate enhancement was evident. In contrast, a strong benefit for the engineered L. lactis strain was observed in acid stress survival. In the presence of histidine, the pathway enabled cells to survive at pH values as low as 3 for at least 2 h, conditions under which the host cells were rapidly dying. The flux through the histidine decarboxylation pathway in cells grown at physiological pH was under strict control of the electrochemical proton gradient (pmf) across the membrane. Ionophores that dissipated the membrane potential (ΔΨ) and/or the pH gradient (ΔpH) strongly increased the flux, whereas the presence of glucose almost completely inhibited the flux. Control of the pmf over the flux was exerted by both ΔΨ and ΔpH and was distributed over the transporter HdcP and the decarboxylase HdcA. The control allowed for a synergistic effect between the histidine decarboxylation and glycolytic pathways in acid stress survival. In a narrow pH range around 2.5 the synergism resulted in a 10-fold higher survival rate. PMID:22351775

Transport in Halobacterium Halobium: Light-Induced Cation-Gradients, Amino Acid Transport Kinetics, and Properties of Transport Carriers

NASA Technical Reports Server (NTRS)

Lanyi, Janos K.

1977-01-01

Cell envelope vesicles prepared from H. halobium contain bacteriorhodopsin and upon illumination protons are ejected. Coupled to the proton motive force is the efflux of Na(+). Measurements of Na-22 flux, exterior pH change, and membrane potential, Delta(psi) (with the dye 3,3'-dipentyloxadicarbocyanine) indicate that the means of Na(+) transport is sodium/proton exchange. The kinetics of the pH changes and other evidence suggests that the antiport is electrogenic (H(+)/Na(++ greater than 1). The resulting large chemical gradient for Na(+) (outside much greater than inside), as well as the membrane potential, will drive the transport of 18 amino acids. The I9th, glutamate, is unique in that its accumulation is indifferent to Delta(psi): this amino acid is transported only when a chemical gradient for Na(+) is present. Thus, when more and more NaCl is included in the vesicles glutamate transport proceeds with longer and longer lags. After illumination the gradient of H+() collapses within 1 min, while the large Na(+) gradient and glutamate transporting activity persists for 10- 15 min, indicating that proton motive force is not necessary for transport. A chemical gradient of Na(+), arranged by suspending vesicles loaded with KCl in NaCl, drives glutamate transport in the dark without other sources of energy, with V(sub max) and K(sub m) comparable to light-induced transport. These and other lines of evidence suggest that the transport of glutamate is facilitated by symport with Na(+), in an electrically neutral fashion, so that only the chemical component of the Na(+) gradient is a driving force.

Transport of K+ and other cations across phospholipid membranes by nonesterified fatty acids.

PubMed

Sharpe, M A; Cooper, C E; Wrigglesworth, J M

1994-07-01

The rate of change of internal pH and transmembrane potential has been monitored in liposomes following the external addition of various cation salts. Oleic acid increases the transmembrane movement of H+ following the imposition of a K+ gradient. An initial fast change in internal pH is seen followed by a slower rate of alkalinization. High concentrations of the fatty acid enhance the rate comparable to that seen in the presence of nigericin in contrast to the effect of FCCP (carbonyl cyanide p-(tri-fluoromethoxy)phenyl hydrazone) which saturates at an intermediate value. The ability of nonesterified fatty acids to catalyze the movement of cations across the liposome membrane increases with the degree of unsaturation and decreases with increasing chain length. Li and Na salts cause a similar initial fast pH change but have less effect on the subsequent slower rate. Similarly, the main effect of divalent cation salts is on the initial fast change. The membrane potential can enhance or inhibit cation transport depending on its polarity with respect to the cation gradient. It is concluded that nonesterified fatty acids have the capability to complex with, and transport, a variety of cations across phospholipid bilayers. However, they do not act simply as proton/cation exchangers analogous to nigericin nor as protonophores analogous to FCCP. The full cycle of ionophoric action involves a combination of both functions.

The weak acid preservative sorbic acid inhibits conidial germination and mycelial growth of Aspergillus niger through intracellular acidification.

PubMed

Plumridge, Andrew; Hesse, Stephan J A; Watson, Adrian J; Lowe, Kenneth C; Stratford, Malcolm; Archer, David B

2004-06-01

The growth of the filamentous fungus Aspergillus niger, a common food spoilage organism, is inhibited by the weak acid preservative sorbic acid (trans-trans-2,4-hexadienoic acid). Conidia inoculated at 10(5)/ml of medium showed a sorbic acid MIC of 4.5 mM at pH 4.0, whereas the MIC for the amount of mycelia at 24 h developed from the same spore inoculum was threefold lower. The MIC for conidia and, to a lesser extent, mycelia was shown to be dependent on the inoculum size. A. niger is capable of degrading sorbic acid, and this ability has consequences for food preservation strategies. The mechanism of action of sorbic acid was investigated using (31)P nuclear magnetic resonance (NMR) spectroscopy. We show that a rapid decline in cytosolic pH (pH(cyt)) by more than 1 pH unit and a depression of vacuolar pH (pH(vac)) in A. niger occurs in the presence of sorbic acid. The pH gradient over the vacuole completely collapsed as a result of the decline in pH(cyt). NMR spectra also revealed that sorbic acid (3.0 mM at pH 4.0) caused intracellular ATP pools and levels of sugar-phosphomonoesters and -phosphodiesters of A. niger mycelia to decrease dramatically, and they did not recover. The disruption of pH homeostasis by sorbic acid at concentrations below the MIC could account for the delay in spore germination and retardation of the onset of subsequent mycelial growth.

Nitrogen dynamics in oak forest soils along a historical deposition gradient

Treesearch

Ralph E. J. Boerner; Elaine Kennedy Sutherland

1995-01-01

This study quantified soil nutrient status and N mineralization/nitrification potentials in soils of oakdominated, unmanaged forest stands in seven experimental forests ranging along a historical and current acidic deposition gradient from southern Illinois to central West Virginia, U.S.A. Among these seven sites (that spanned 8.5º of longitude) soil pH and Ca...

Detachable strong cation exchange monolith, integrated with capillary zone electrophoresis and coupled with pH gradient elution, produces improved sensitivity and numbers of peptide identifications during bottom-up analysis of complex proteomes.

PubMed

Zhang, Zhenbin; Yan, Xiaojing; Sun, Liangliang; Zhu, Guijie; Dovichi, Norman J

2015-04-21

A detachable sulfonate-silica hybrid strong cation-exchange monolith was synthesized in a fused silica capillary, and used for solid phase extraction with online pH gradient elution during capillary zone electrophoresis-tandem mass spectrometry (CZE-MS/MS) proteomic analysis. Tryptic digests were prepared in 50 mM formic acid and loaded onto the strong cation-exchange monolith. Fractions were eluted using a series of buffers with lower concentration but higher pH values than the 50 mM formic acid background electrolyte. This combination of elution and background electrolytes results in both sample stacking and formation of a dynamic pH junction and allows use of relatively large elution buffer volumes while maintaining reasonable peak efficiency and resolution. A series of five pH bumps were applied to elute E. coli tryptic peptides from the monolith, followed by analysis using CZE coupled to an LTQ-Orbitrap Velos mass spectrometer; 799 protein groups and 3381 peptides were identified from 50 ng of the digest in a 2.5 h analysis, which approaches the identification rate for this organism that was obtained with an Orbitrap Fusion. We attribute the improved numbers of peptide and protein identifications to the efficient fractionation by the online pH gradient elution, which decreased the complexity of the sample in each elution step and improved the signal intensity of low abundance peptides. We also performed a comparative analysis using a nanoACQUITY UltraPerformance LCH system. Similar numbers of protein and peptide identifications were produced by the two methods. Protein identifications showed significant overlap between the two methods, whereas peptide identifications were complementary.

Acid-base relations in epithelium of turtle bladder: site of active step in acidification and role of metabolic CO2.

PubMed

Steinmetz, P R

1969-07-01

The acid-base relations across the two surfaces of the epithelium of the turtle bladder were examined. By means of the 5,5-dimethyl-2,4-oxazolidinedione (DMO) technique the intracellular OH(-) concentration was measured in the presence and absence of a transepithelial pH gradient. When both sides of the bladder were bathed with solutions free of exogenous CO(2) and bicarbonate at pH 7.41 ([OH(-)] = 239 nmoles/liter), the epithelial cells were alkaline, the mean intracellular [OH(-)] being 347nmoles/liter. This alkalinity of the cells was preserved in bladders that secreted H(+) against a gradient of over 2 pH units. In bathing solutions stirred with 4.85% CO(2) and buffered with 25 mM HCO(3) (-) at pH 7.41 the intracellular [OH(-)] was lower than in CO(2)-free solutions and close to the extracellular [OH(-)]. In the CO(2)-free system anaerobiosis caused increased alkalinity of the cells and inhibition of H(+) secretion presumably by decreased metabolic CO(2) production. Carbonic acid inhibitors reduced H(+) secretion, but had no significant effect on the alkalinity of the cells. An inactive analogue of acetazolamide had no effect on H(+) secretion. The results indicate that the active step in acidification is located near the mucosal surface of the epithelium and that the alkali formed within the epithelial cells moves passively into the serosal solution along an electro-chemical gradient. The inhibitory effect of certain sulfonamides on H(+) secretion by the bladder is directly correlated with their known carbonic anhydrase inhibitory activity, but not associated with a measurable change in the mean intracellular [OH(-)].

Ratiometric Imaging of Extracellular pH in Dental Biofilms.

PubMed

Schlafer, Sebastian; Dige, Irene

2016-03-09

The pH in bacterial biofilms on teeth is of central importance for dental caries, a disease with a high worldwide prevalence. Nutrients and metabolites are not distributed evenly in dental biofilms. A complex interplay of sorption to and reaction with organic matter in the biofilm reduces the diffusion paths of solutes and creates steep gradients of reactive molecules, including organic acids, across the biofilm. Quantitative fluorescent microscopic methods, such as fluorescence life time imaging or pH ratiometry, can be employed to visualize pH in different microenvironments of dental biofilms. pH ratiometry exploits a pH-dependent shift in the fluorescent emission of pH-sensitive dyes. Calculation of the emission ratio at two different wavelengths allows determining local pH in microscopic images, irrespective of the concentration of the dye. Contrary to microelectrodes the technique allows monitoring both vertical and horizontal pH gradients in real-time without mechanically disturbing the biofilm. However, care must be taken to differentiate accurately between extra- and intracellular compartments of the biofilm. Here, the ratiometric dye, seminaphthorhodafluor-4F 5-(and-6) carboxylic acid (C-SNARF-4) is employed to monitor extracellular pH in in vivo grown dental biofilms of unknown species composition. Upon exposure to glucose the dye is up-concentrated inside all bacterial cells in the biofilms; it is thus used both as a universal bacterial stain and as a marker of extracellular pH. After confocal microscopic image acquisition, the bacterial biomass is removed from all pictures using digital image analysis software, which permits to exclusively calculate extracellular pH. pH ratiometry with the ratiometric dye is well-suited to study extracellular pH in thin biofilms of up to 75 µm thickness, but is limited to the pH range between 4.5 and 7.0.

Cholic acid accumulation and its diminution by short-chain fatty acids in bifidobacteria.

PubMed

Kurdi, Peter; Tanaka, Hiroshi; Van Veen, Hendrik W; Asano, Kozo; Tomita, Fusao; Yokota, Atsushi

2003-08-01

Cholic acid (CA) transport was investigated in nine intestinal Bifidobacterium strains. Upon energization with glucose, all of the bifidobacteria accumulated CA. The driving force behind CA accumulation was found to be the transmembrane proton gradient (Delta pH, alkaline interior). The levels of accumulated CA generally coincided with the theoretical values, which were calculated by the Henderson-Hasselbalch equation using the measured internal pH values of the bifidobacteria, and a pK(a) value of 6.4 for CA. These results suggest that the mechanism of CA accumulation is based on the diffusion of a hydrophobic weak acid across the bacterial cell membrane, and its dissociation according to the Delta pH value. A mixture of short-chain fatty acids (acetate, propionate and butyrate) at the appropriate colonic concentration (117 mM in total) reduced CA accumulation in Bifidobacterium breve JCM 1192(T). These short-chain fatty acids, which are weak acids, reduced the Delta pH, thereby decreasing CA accumulation in a dose-dependent manner. The bifidobacteria did not alter or modify the CA molecule. The probiotic potential of CA accumulation in vivo is discussed in relation to human bile acid metabolism.

Light-dependent cation gradients and electrical potential in Halobacterium halobium cell envelope vesicles

NASA Technical Reports Server (NTRS)

Lanyi, J. K.; Macdonald, R. E.

1977-01-01

Vesicles can be prepared from Halobacterium halobium cell envelopes, which contain properly oriented bacteriorhodopsin and which extrude H(+) during illumination. The pH difference that is generated across the membranes is accompanied by an electrical potential of 90 to 100 mV (interior negative) and the movements of other cations. Among these is the efflux of Na(+), which proceeds against its electrochemical potential. The relationship between the size and direction of the light-induced pH gradient and the rate of depletion of Na(+) from the vesicles, as well as other evidence, suggest that the active Na(+) extrusion is facilitated by a membrane component that exchanges H(+) for Na(+) with a stoichiometry greater than 1. The gradients of H(+) and Na(+) are thus coupled to one another. The Na(+) gradient (efflux much larger than influx), which arises during illumination, plays a major role in energizing the active transport of amino acids.

Apigenin and quercetin promote. Delta. pH-dependent accumulation of IAA in membrane vesicles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woolard, D.D.; Clark, K.A.

1990-05-01

Flavonoids may act as regulators of polar auxin transport. In the presence of a pH gradient (pH 8{sub in}/6{sub out}) the flavonoids quercetin and apigenin, as well as the synthetic herbicide napthylphthalamic acid (NPA), promote the accumulation of IAA in membrane vesicles from dark-grown zucchini hypocotyls. Simultaneous accumulation of {sup 3}H-IAA (10 nM) and {sup 14}C-butyric acid (5 {mu}M; included as a pH probe) was determined by a filtration assay after incubating the vesicles with 3 nM to 100 {mu}M quercetin, apigenin, NPA or unlabeled IAA. Maximal stimulation (% of Control) was observed with 3 {mu}M NPA (130%), 1 {mu}Mmore » quercetin (120%), or 3 {mu}M apigenin (115%); {Delta}pH was not affected by these concentrations. As reported by others, IAA uptake was saturable: 1 {mu}M unlabeled IAA eliminated {Delta}pH-dependent uptake of {sup 3}H-IAA without altering {Delta}pH. However, at 30 to 100 {mu}M, every compound tested collapsed the imposed pH gradient and therefore abolished specific {sup 3}H-IAA uptake.« less

Using amino acids for the chromatofocusing of metal ions on silica with bonded tetraethylenepentamine groups

NASA Astrophysics Data System (ADS)

Ivanov, A. V.

2014-09-01

Amino acid-based eluents are used for the chromatofocusing of metal ions on Tetren-SiO2 chelating sorbent (silica with bonded tetraethylenepentamine groups) for the first time. The smoothest quasilinear pH gradients form for eluents based on glutamic and aspartic acids. The separation of Mn2+, Cr3+, Co2+, Ni2+, and Cu2+ is achieved.

Characterization of Cultures Enriched from Acidic Polycyclic Aromatic Hydrocarbon-Contaminated Soil for Growth on Pyrene at Low pH▿

PubMed Central

Uyttebroek, Maarten; Vermeir, Steven; Wattiau, Pierre; Ryngaert, Annemie; Springael, Dirk

2007-01-01

Two polycyclic aromatic hydrocarbon (PAH)-contaminated soils of pH 2 were successfully used as inoculum to enrich cultures growing on phenanthrene and pyrene at different pHs, including pH 3. Selected pyrene-utilizing cultures obtained at pH 3, pH 5, and pH 7 were further characterized. All showed rapid [14C]pyrene mineralization at pH 3 and pH 5 and grew on pyrene at pH values ranging from 2 to 6. Eubacterial and mycobacterial 16S rRNA gene denaturing gradient gel electrophoresis fingerprinting and sequencing indicated that the cultures were dominated by a single bacterium closely related to Mycobacterium montefiorense, belonging to the slow-growing Mycobacterium sp. In contrast, a culture enriched on pyrene at pH 7 from a slightly alkaline soil sampled at the same site was dominated by Pseudomonas putida and a fast-growing Mycobacterium sp. The M. montefiorense-related species dominating the pyrene-utilizing cultures enriched from the acidic soils was also the dominant Mycobacterium species in the acidic soils. Our data indicate that a slow-growing Mycobacterium species is involved in PAH degradation in that culture and show that bacteria able to degrade high-molecular-weight PAHs at low pH are present in acidic PAH-contaminated soil. PMID:17369339

Bacterial Profile of Dentine Caries and the Impact of pH on Bacterial Population Diversity

PubMed Central

Kianoush, Nima; Adler, Christina J.; Nguyen, Ky-Anh T.; Browne, Gina V.; Simonian, Mary; Hunter, Neil

2014-01-01

Dental caries is caused by the release of organic acids from fermentative bacteria, which results in the dissolution of hydroxyapatite matrices of enamel and dentine. While low environmental pH is proposed to cause a shift in the consortium of oral bacteria, favouring the development of caries, the impact of this variable has been overlooked in microbial population studies. This study aimed to detail the zonal composition of the microbiota associated with carious dentine lesions with reference to pH. We used 454 sequencing of the 16S rRNA gene (V3–V4 region) to compare microbial communities in layers ranging in pH from 4.5–7.8 from 25 teeth with advanced dentine caries. Pyrosequencing of the amplicons yielded 449,762 sequences. Nine phyla, 97 genera and 409 species were identified from the quality-filtered, de-noised and chimera-free sequences. Among the microbiota associated with dentinal caries, the most abundant taxa included Lactobacillus sp., Prevotella sp., Atopobium sp., Olsenella sp. and Actinomyces sp. We found a disparity between microbial communities localised at acidic versus neutral pH strata. Acidic conditions were associated with low diversity microbial populations, with Lactobacillus species including L. fermentum, L. rhamnosus and L. crispatus, being prominent. In comparison, the distinctive species of a more diverse flora associated with neutral pH regions of carious lesions included Alloprevotella tanerrae, Leptothrix sp., Sphingomonas sp. and Streptococcus anginosus. While certain bacteria were affected by the pH gradient, we also found that ∼60% of the taxa associated with caries were present across the investigated pH range, representing a substantial core. We demonstrated that some bacterial species implicated in caries progression show selective clustering with respect to pH gradient, providing a basis for specific therapeutic strategies. PMID:24675997

Migration of 18 trace elements from ceramic food contact material: influence of pigment, pH, nature of acid and temperature.

PubMed

Demont, M; Boutakhrit, K; Fekete, V; Bolle, F; Van Loco, J

2012-03-01

The effect of pH, nature of acid and temperature on trace element migration from ceramic ware treated with 18 commercially available glazes was studied. Besides of the well-studied lead and cadmium, migration of other toxic and non toxic elements such as aluminum, boron, barium, cobalt, chrome, copper, iron, lithium, magnesium, manganese, nickel, antimony, tin, strontium, titanium, vanadium, zinc and zirconium was investigated in order to evaluate their potential health hazards. Trace element concentrations were determined with Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). This study suggests that there is indeed a health risk concerning the possible migration of other elements than lead and cadmium. At low pH (2

Experimental generation and computational modeling of intracellular pH gradients in cardiac myocytes.

PubMed

Swietach, Pawel; Leem, Chae-Hun; Spitzer, Kenneth W; Vaughan-Jones, Richard D

2005-04-01

It is often assumed that pH(i) is spatially uniform within cells. A double-barreled microperfusion system was used to apply solutions of weak acid (acetic acid, CO(2)) or base (ammonia) to localized regions of an isolated ventricular myocyte (guinea pig). A stable, longitudinal pH(i) gradient (up to 1 pH(i) unit) was observed (using confocal imaging of SNARF-1 fluorescence). Changing the fractional exposure of the cell to weak acid/base altered the gradient, as did changing the concentration and type of weak acid/base applied. A diffusion-reaction computational model accurately simulated this behavior of pH(i). The model assumes that H(i)(+) movement occurs via diffusive shuttling on mobile buffers, with little free H(+) diffusion. The average diffusion constant for mobile buffer was estimated as 33 x 10(-7) cm(2)/s, consistent with an apparent H(i)(+) diffusion coefficient, D(H)(app), of 14.4 x 10(-7) cm(2)/s (at pH(i) 7.07), a value two orders of magnitude lower than for H(+) ions in water but similar to that estimated recently from local acid injection via a cell-attached glass micropipette. We conclude that, because H(i)(+) mobility is so low, an extracellular concentration gradient of permeant weak acid readily induces pH(i) nonuniformity. Similar concentration gradients for weak acid (e.g., CO(2)) occur across border zones during regional myocardial ischemia, raising the possibility of steep pH(i) gradients within the heart under some pathophysiological conditions.

Assessing the utility of bipolar membranes for use in photoelectrochemical water-splitting cells.

PubMed

Vargas-Barbosa, Nella M; Geise, Geoffrey M; Hickner, Michael A; Mallouk, Thomas E

2014-11-01

Membranes are important in water-splitting solar cells because they prevent crossover of hydrogen and oxygen. Here, bipolar membranes (BPMs) were tested as separators in water electrolysis cells. Steady-state membrane and solution resistances, electrode overpotentials, and pH gradients were measured at current densities relevant to solar photoelectrolysis. Under forward bias conditions, electrodialysis of phosphate buffer ions creates a pH gradient across a BPM. Under reverse bias, the BPM can maintain a constant buffer pH on both sides of the cell, but a large membrane potential develops. Thus, the BPM does not present a viable solution for electrolysis in buffered electrolytes. However, the membrane potential is minimized when the anode and cathode compartments of the cell contain strongly basic and acidic electrolytes, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Watershed factors affecting stream acidification in the White Mountains of New Hampshire, USA

Treesearch

Scott W. Bailey; James W. Hornbeck; C. Wayne Martin; Donald C. Buso

1987-01-01

The streams tributary to acidic Cone Pond, pH 4.5-4.8, and circumneutral Black Pond, pH 5.3-6.4, in the White Mountains of New Hampshire, USA, were monitored for a year. The watersheds of these two ponds were characterized in terms of geology and stream hydrology. Chemical gradients and patterns in rock weathering and groundwater discharge explain many of the...

Biological amine transport in chromaffin ghosts. Coupling to the transmembrane proton and potential gradients.

PubMed

Johnson, R G; Pfister, D; Carty, S E; Scarpa, A

1979-11-10

The effect of the transmembrane proton gradient (delta pH) and potential gradient (delta psi) upon the rate and extent of amine accumulation was investigated in chromaffin ghosts. The chromaffin ghosts were formed by hypo-osmotic lysis of isolated bovine chromaffin granules and extensive dialysis in order to remove intragranular binding components and dissipate the endogenous electrochemical gradients. Upon ATP addition to suspensions of chromaffin ghosts, a transmembrane proton gradient alone, a transmembrane gradient alone, or both, could be established, depending upon the compositions of the media in which the ghosts were formed and resuspended. When chloride was present in the medium, addition of ATP resulted in the generation of a transmembrane proton gradient, acidic inside of 1 pH unit (measured by [14C]methylamine distribution), and no transmembrane potential (measured by [14C]-thiocyanate distribution). When ATP was added to chromaffin ghosts suspended in a medium in which chloride was substituted by isethionate, a transmembrane potential, inside positive, of 45 mV and no transmembrane proton gradient, was measured. In each medium, the addition of agents known to affect proton or potential gradients, respectively, exerted a predictable mechanism of action. Accumulation of [14C]epinephrine or [14C]5-hydroxytryptamine was over 1 order of magnitude greater in the presence of the transmembrane proton gradient or the transmembrane potential than in the absence of any gradient and, moreover, was related to the magnitude of the proton or potential gradient in a dose-dependent manner. When ghosts were added to a medium containing chloride and isethionate, both a delta pH and delta psi could be generated upon addition of ATP. In this preparation, the maximal rate of amine accumulation was observed. The results indicate that amine accumulation into chromaffin ghosts can occur in the presence of either a transmembrane proton gradient, or a transmembrane potential gradient, and that the maximal rate of accumulation may exist when both components of the protonmotive force are present.

A microfluidic chip with a staircase pH gradient generator, a packed column and a fraction collector for chromatofocusing of proteins.

PubMed

Rho, Hoon Suk; Hanke, Alexander Thomas; Ottens, Marcel; Gardeniers, Han J G E

2018-04-01

A microfluidic device for pH gradient chromatofocusing is presented, which performs creation of a micro-column, pH gradient generation, and fraction collection in a single device. Using a sieve micro-valve, anion exchange particles were packed into a microchannel in order to realize a solid-phase absorption column. To fractionate proteins according to their isoelectric points, elution buffer solutions with a stepwise pH gradient were prepared in 16 parallel mixing reactors and flowed through the micro-column, wherein a protein mixture was previously loaded. The volume of the column is only 20 nL, hence it allows extremely low sample consumption and fast analysis compared with a conventional system. We demonstrated separation of two proteins, albumin-fluorescein isothiocyanate conjugate (FITC-BSA) and R-Phycoerythrin (R-PE), by using a microcolumn of commercial charged polymeric particles (Source 15Q). The microfluidic device can be used as a rapid diagnostic tool to analyse crude mixtures of proteins or nucleic acids and determine adsorption/desorption characteristics of various biochemical products, which can be helpful for scientific fundamental understanding as well as instrumental in various industrial applications, especially in early stage screening and process development. © 2018 The Authors Electrophoresis Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bacterial community dynamics and product distribution during pH-adjusted fermentation of vegetable wastes.

PubMed

Ye, N-F; Lü, F; Shao, L-M; Godon, J-J; He, P-J

2007-10-01

To estimate the effect of pH on the structures of bacterial community during fermentation of vegetable wastes and to investigate the relationship between bacterial community dynamics and product distribution. The bacterial communities in five batch tests controlled at different pH values [uncontrolled (about pH 4), 5, 6, 7 and 8] were monitored by denaturing gradient gel electrophoresis (DGGE) and single-strand conformation polymorphism (SSCP). The two fingerprinting methods provided consistent results and principal component analysis indicated a close similarity of bacterial community at pH 7 and 8 in addition to those at pH 4-6. This clustering also corresponded to dominant metabolic pathway. Thus, pH 7-8 shifted from alcohol-forming to acid-forming, especially butyric acid, whereas both alcohol-forming and acid-forming dominated at pH 5-6, and at pH 4, fermentation was inhibited. Shannon-weaver index was calculated to analyse the DGGE profiles, which revealed that the bacterial diversities at pH 7 and 8 were the highest while those at pH 5 and 4 (uncontrolled) were the lowest. According to sequencing results of the bands excised from DGGE gels, lactic acid bacteria and Clostridium sp. were predominant at all pH values, but varieties in species were observed as pH changed and time prolonged. The bacterial community during fermentation was materially influenced by pH and the diverse product distribution was related to the shift of different bacterial population. The study reveals that the impact of pH on fermentation product distribution is implemented primarily by changes of bacterial community. It also provides information about the comparison of two fingerprinting methods, DGGE and SSCP.

Quantification of urinary zwitterionic organic acids using weak-anion exchange chromatography with tandem MS detection.

PubMed

Bishop, Michael Jason; Crow, Brian S; Kovalcik, Kasey D; George, Joe; Bralley, James A

2007-04-01

A rapid and accurate quantitative method was developed and validated for the analysis of four urinary organic acids with nitrogen containing functional groups, formiminoglutamic acid (FIGLU), pyroglutamic acid (PYRGLU), 5-hydroxyindoleacetic acid (5-HIAA), and 2-methylhippuric acid (2-METHIP) by liquid chromatography tandem mass spectrometry (LC/MS/MS). The chromatography was developed using a weak anion-exchange amino column that provided mixed-mode retention of the analytes. The elution gradient relied on changes in mobile phase pH over a concave gradient, without the use of counter-ions or concentrated salt buffers. A simple sample preparation was used, only requiring the dilution of urine prior to instrumental analysis. The method was validated based on linearity (r2>or=0.995), accuracy (85-115%), precision (C.V.<12%), sample preparation stability (

Hydrophilic interaction liquid chromatography-mass spectrometry of (lyso)phosphatidic acids, (lyso)phosphatidylserines and other lipid classes.

PubMed

Cífková, Eva; Hájek, Roman; Lísa, Miroslav; HolĿapek, Michal

2016-03-25

The goal of this work is a systematic optimization of hydrophilic interaction liquid chromatography (HILIC) separation of acidic lipid classes (namely phosphatidic acids-PA, lysophosphatidic acids-LPA, phosphatidylserines-PS and lysophosphatidylserines-LPS) and other lipid classes under mass spectrometry (MS) compatible conditions. The main parameters included in this optimization are the type of stationary phases used in HILIC, pH of the mobile phase, the type and concentration of mobile phase additives. Nine HILIC columns with different chemistries (unmodified silica, modified silica using diol, 2-picolylamine, diethylamine and 1-aminoanthracene and hydride silica) are compared with the emphasis on peak shapes of acidic lipid classes. The optimization of pH is correlated with the theoretical calculation of acidobasic equilibria of studied lipid classes. The final method using the hydride column, pH 4 adjusted by formic acid and the gradient of acetonitrile and 40 mmol/L of aqueous ammonium formate provides good peak shapes for all analyzed lipid classes including acidic lipids. This method is applied for the identification of lipids in real samples of porcine brain and kidney extracts. Copyright © 2016 Elsevier B.V. All rights reserved.

Determination of hydrolyzable tannins in the fruit of Terminalia chebula Retz. by high-performance liquid chromatography and capillary electrophoresis.

PubMed

Juang, Lih-Jeng; Sheu, Shuenn-Jyi; Lin, Ta-Chen

2004-06-01

A RP-HPLC method for determining fourteen components (gallic acid, chebulic acid, 1,6-di-O-galloyl-D-glucose, punicalagin, 3,4,6-tri-O-galloyl-D-glucose, casuarinin, chebulanin, corilagin, neochebulinic acid, terchebulin, ellagic acid, chebulagic acid, chebulinic acid, and 1,2,3,4,6-penta-O-galloyl-D-glucose) in the fruit of Terminalia chebula Retz. is described. The separation was achieved within 80 min using a binary gradient with mobile phases consisting of a pH 2.7 phosphoric acid solution and an 80% CH3CN solution. Capillary electrophoretic analyses were also attempted, and it was found that CZE (25 mM Na2B4O7, 5 mM NaH2PO4, pH 7.0) was an efficient method for the separation of gallotannins, while an MEKC method (25 mM Na2B4O7, 5 mM NaH2PO4, 20 mM SDS, pH 7.0, and 10% acetonitrile) provided a better separation for most of the tannins examined. The HPLC and CE methods developed were both successfully applied to the assay of tannins in commercial samples of Chebulae Fructus.

A physics-based model for maintenance of the pH gradient in the gastric mucus layer.

PubMed

Lewis, Owen L; Keener, James P; Fogelson, Aaron L

2017-12-01

It is generally accepted that the gastric mucus layer provides a protective barrier between the lumen and the mucosa, shielding the mucosa from acid and digestive enzymes and preventing autodigestion of the stomach epithelium. However, the precise mechanisms that contribute to this protective function are still up for debate. In particular, it is not clear what physical processes are responsible for transporting hydrogen protons, secreted within the gastric pits, across the mucus layer to the lumen without acidifying the environment adjacent to the epithelium. One hypothesis is that hydrogen may be bound to the mucin polymers themselves as they are convected away from the mucosal surface and eventually degraded in the stomach lumen. It is also not clear what mechanisms prevent hydrogen from diffusing back toward the mucosal surface, thereby lowering the local pH. In this work we investigate a physics-based model of ion transport within the mucosal layer based on a Nernst-Planck-like equation. Analysis of this model shows that the mechanism of transporting protons bound to the mucus gel is capable of reproducing the trans-mucus pH gradients reported in the literature. Furthermore, when coupled with ion exchange at the epithelial surface, our analysis shows that bicarbonate secretion alone is capable of neutralizing the epithelial pH, even in the face of enormous diffusive gradients of hydrogen. Maintenance of the pH gradient is found to be robust to a wide array of perturbations in both physiological and phenomenological model parameters, suggesting a robust physiological control mechanism. NEW & NOTEWORTHY This work combines modeling techniques based on physical principles, as well as novel numerical simulations to test the plausibility of one hypothesized mechanism for proton transport across the gastric mucus layer. Results show that this mechanism is able to maintain the extreme pH gradient seen in in vivo experiments and suggests a highly robust regulation mechanism to maintain this gradient in the face of dynamic lumen composition. Copyright © 2017 the American Physiological Society.

Primordial soup or vinaigrette: did the RNA world evolve at acidic pH?

PubMed Central

2012-01-01

Background The RNA world concept has wide, though certainly not unanimous, support within the origin-of-life scientific community. One view is that life may have emerged as early as the Hadean Eon 4.3-3.8 billion years ago with an atmosphere of high CO2 producing an acidic ocean of the order of pH 3.5-6. Compatible with this scenario is the intriguing proposal that life arose within alkaline (pH 9-11) deep-sea hydrothermal vents like those of the 'Lost City', with the interface with the acidic ocean creating a proton gradient sufficient to drive the first metabolism. However, RNA is most stable at pH 4-5 and is unstable at alkaline pH, raising the possibility that RNA may have first arisen in the acidic ocean itself (possibly near an acidic hydrothermal vent), acidic volcanic lake or comet pond. As the Hadean Eon progressed, the ocean pH is inferred to have gradually risen to near neutral as atmospheric CO2 levels decreased. Presentation of the hypothesis We propose that RNA is well suited for a world evolving at acidic pH. This is supported by the enhanced stability at acidic pH of not only the RNA phosphodiester bond but also of the aminoacyl-(t)RNA and peptide bonds. Examples of in vitro-selected ribozymes with activities at acid pH have recently been documented. The subsequent transition to a DNA genome could have been partly driven by the gradual rise in ocean pH, since DNA has greater stability than RNA at alkaline pH, but not at acidic pH. Testing the hypothesis We have proposed mechanisms for two key RNA world activities that are compatible with an acidic milieu: (i) non-enzymatic RNA replication of a hemi-protonated cytosine-rich oligonucleotide, and (ii) specific aminoacylation of tRNA/hairpins through triple helix interactions between the helical aminoacyl stem and a single-stranded aminoacylating ribozyme. Implications of the hypothesis Our hypothesis casts doubt on the hypothesis that RNA evolved in the vicinity of alkaline hydrothermal vents. The ability of RNA to form protonated base pairs and triples at acidic pH suggests that standard base pairing may not have been a dominant requirement of the early RNA world. Reviewers This article was reviewed by Eugene Koonin, Anthony Poole and Charles Carter (nominated by David Ardell). PMID:22264281

Comparison of fractionation strategies for offline two-dimensional liquid chromatography tandem mass spectrometry analysis of proteins from mouse adipose tissue.

PubMed

Sajic, Tatjana; Varesio, Emmanuel; Szanto, Ildiko; Hopfgartner, Gérard

2015-09-01

In the frame of protein identification from mouse adipose tissue, two strategies were compared for the offline elution of peptides from a strong cation exchange (SCX) column in two-dimensional liquid chromatography tandem mass spectrometry (2D-LC-MS/MS) analyses. First, the salt gradient (using K(+) as displacing agent) was evaluated from 25 to 500mM KCl. Then, a less investigated elution mode using a pH gradient (using citric acid and ammonium hydroxide) was carried out from pH 2.5 to 9.0. Equal amounts of peptide digest derived from mouse adipose tissue were loaded onto the SCX column and fractionated according to the two approaches. A total of 15 fractions were collected in two independent experiments for each SCX elution strategy. Then, each fraction was analyzed on a nanoLC-MS/MS platform equipped with a column-switching unit for desalting and enrichment. No substantial differences in peptide quality characteristics (molecular weight, isoelectric point, or GRAVY [grand average of hydropathicity] index distributions) were observed between the two datasets. The pH gradient approach was found to be superior, with 27.5% more unique peptide identifications and 10% more distinct protein identifications compared with the salt-based elution method. In conclusion, our data imply that the pH gradient SCX fractionation is more desirable for proteomics analysis of entire adipose tissue. Copyright © 2015 Elsevier Inc. All rights reserved.

Novel Technique to improve the pH of Acidic Barren Soil using Electrokinetic-bioremediation with the application of Vetiver Grass

NASA Astrophysics Data System (ADS)

Azhar, A. T. S.; Nabila, A. T. A.; Nurshuhaila, M. S.; Zaidi, E.; Azim, M. A. M.; Zahin, A. M. F.

2016-11-01

Residual acidic slopes which are not covered by vegetation greatly increases the risk of soil erosion. In addition, low soil pH can bring numerous problems such as Al and Fe toxicity, land degradation issues and some problems related to vegetation. In this research, a series of electrokinetic bioremediation (EK-Bio) treatments using Bacillus sphaericus, Bacillus subtilis and Pseudomonas putida with a combination of Vetiver grass were performed in the laboratory. Investigations were conducted for 14 days and included the observation of changes in the soil pH and the mobilization of microorganism cells through an electrical gradient of 50 V/m under low pH. Based on the results obtained, this study has successfully proven that the pH of soil increases after going through electrokinetic bioremediation (EK-Bio). The treatment using Bacillus sphaericus increases the pH from 2.95 up to 4.80, followed by Bacillus subtilis with a value of 4.66. Based on the overall performance, Bacillus sphaericus show the highest number of bacterial cells in acidic soil with a value of 6.6 × 102 cfu/g, followed by Bacillus subtilis with a value of 5.7 × 102 cfu/g. In conclusion, Bacillus sphaericus and Bacillus subtilis show high survivability and is suitable to be used in the remediation of acidic soil.

Mutation of the oxaloacetate decarboxylase gene of Lactococcus lactis subsp. lactis impairs the growth during citrate metabolism.

PubMed

Augagneur, Y; Garmyn, D; Guzzo, J

2008-01-01

Citrate metabolism generates metabolic energy through the generation of a membrane potential and a pH gradient. The purpose of this work was to study the influence of oxaloacetate decarboxylase in citrate metabolism and intracellular pH maintenance in relation to acidic conditions. A Lactococcus lactis oxaloacetate decarboxylase mutant [ILCitM (pFL3)] was constructed by double homologous recombination. During culture with citrate, and whatever the initial pH, the growth rate of the mutant was lower. In addition, the production of diacetyl and acetoin was altered in the mutant strain. However, our results indicated no relationship with a change in the maintenance of intracellular pH. Experiments performed on resting cells clearly showed that oxaloacetate accumulated temporarily in the supernatant of the mutant. This accumulation could be involved in the perturbations observed during citrate metabolism, as the addition of oxaloacetate in M17 medium inhibited the growth of L. lactis. The mutation of oxaloacetate decarboxylase perturbed citrate metabolism and reduced the benefits of its utilization during growth under acidic conditions. This study allows a better understanding of citrate metabolism and the role of oxaloacetate decarboxylase in the tolerance of lactic acid bacteria to acidic conditions.

THE SEPARATION OF DIFFERENT CELL CLASSES FROM LYMPHOID ORGANS

PubMed Central

Shortman, Ken; Seligman, Kathrin

1969-01-01

1. Mammalian erythrocytes swell as the pH of the isotonic suspending medium is lowered, as a direct consequence of the specialized permeability properties of the erythrocyte membrane. Lymphocytes and granulocytes from a variety of sources did not exhibit this property. 2. The behaviour of mouse bone marrow erythroid cells at various stages of differentiation was studied by using a change in buoyant density with pH as an index of swelling. The ability to swell with a pH drop was acquired while the cell was still nucleated. All non-nucleated cells showed swelling. Most small erythroblasts shared this property, whereas most large erythroblasts did not. 3. The density shift with pH was used to provide a purification scheme specific for erythroid cells. The bone marrow cells were first centrifuged to equilibrium in an isotonic albumin density gradient at neutral pH. Regions of the gradient containing the erythroid cells were collected, and the cells were recovered and redistributed in an albumin gradient at acid pH. The erythroid cells showed a specific density shift which removed them from contaminants. Preparations containing 90–97% erythroblasts were obtained by this technique. 4. Differentiation within the erythroid series was accompanied by a general increase in cell buoyant density at neutral pH. This density increase may have been a discontinuous process, since erythroid cells appeared to form a number of density peaks. 5. The pH shift technique, in association with established density distribution and sedimentation velocity procedures, provides a range of cell separation techniques for biological or biochemical studies of erythroid cell differentiation in the complex cell mixtures in bone marrow or spleen. PMID:5801428

Carbonate species as OH- carriers for decreasing the pH gradient between cathode and anode in biological fuel cells.

PubMed

Torres, César I; Lee, Hyung-Sool; Rittmann, Bruce E

2008-12-01

Anodes of biological fuel cells (BFCs) normally must operate at a near-neutral pH in the presence of various ionic species required for the function of the biological catalyst (e.g., substrate, nutrients, and buffers). These ionic species are in higher concentration than protons (H+) and hydroxides (OH-); slow transport of H+ and OH- equivalents between anode and cathode compartments can lead to a large pH gradient that can inhibit the function of biological components, decrease voltage efficiency in BFCs, or both. We evaluate the use of carbonate species as OH- carriers from the cathode to the anode compartment. This is achieved by adding CO2 to the influent air in the cathode. CO2 is an acid that combines with OH- in the cathode to produce bicarbonate and carbonate. These species can migrate to the anode compartment as OH- carriers at a rate much greater than can OH- itself when the pH is not extremely high in the cathode compartment We demonstrate this concept by feeding different air/CO2 mixtures to the cathode of a dual-chamber microbial fuel cell (MFC) fed with acetate as substrate. Our results show a 45% increase in power density (from 1.9 to 2.8 W/m2) by feeding air augmented with 2-10% CO2. The cell voltage increased by as much as 120 mV, indicating that the pH gradient decreased by as much as 2 pH units. Analysis of the anode effluent showed an average increase of 4.9 mM in total carbonate, indicating that mostly carbonate was transferred from the cathode compartment This process provides a simple way to minimize potential losses in BFCs due to pH gradients between anode and cathode compartments.

Electrophoretic separation of proteins in space

NASA Technical Reports Server (NTRS)

Brown, R. K.

1976-01-01

Commercially available and synthetic wide range and short range ampholytes used in the isoelectric focusing of proteins was analyzed by ion exchange chromatography. A pH gradient over the pH range 3.8 to 11.0 was used to elute the ampholytes from a column of a sulfonated polystyrene resin. The wide range ampholytes were resolved into some 60 to 70 ninhydrin positive components. The recovery obtained with the method was quantitative. Acid short range ampholytes have approximately 35 components which elute readily from the ion exchange resin. Basic short range ampholytes gave about 50 components, most of which eluted at alkaline pH.

An Acidic Microenvironment Increases NK Cell Killing of Cryptococcus neoformans and Cryptococcus gattii by Enhancing Perforin Degranulation

PubMed Central

Islam, Anowara; Li, Shu Shun; Oykhman, Paul; Timm-McCann, Martina; Huston, Shaunna M.; Stack, Danuta; Xiang, Richard F.; Kelly, Margaret M.; Mody, Christopher H.

2013-01-01

Cryptococcus gattii and Cryptococcus neoformans are encapsulated yeasts that can produce a solid tumor-like mass or cryptococcoma. Analogous to malignant tumors, the microenvironment deep within a cryptococcoma is acidic, which presents unique challenges to host defense. Analogous to malignant cells, NK cells kill Cryptococcus. Thus, as in tumor defense, NK cells must kill yeast cells across a gradient from physiologic pH to less than 6 in the center of the cryptococcoma. As acidic pH inhibits anti-tumor activities of NK cells, we sought to determine if there was a similar reduction in the anticryptococcal activity of NK cells. Surprisingly, we found that both primary human NK cells and the human NK cell line, YT, have preserved or even enhanced killing of Cryptococcus in acidic, compared to physiological, pH. Studies to explore the mechanism of enhanced killing revealed that acidic pH does not increase the effector to target ratio, binding of cytolytic cells to Cryptococcus, or the active perforin content in effector cells. By contrast, perforin degranulation was greater at acidic pH, and increased degranulation was preceded by enhanced ERK1/2 phosphorylation, which is essential for killing. Moreover, using a replication defective ras1 knockout strain of Cryptococcus increased degranulation occurred during more rapid replication of the organisms. Finally, NK cells were found intimately associated with C. gattii within the cryptococcoma of a fatal infection. These results suggest that NK cells have amplified signaling, degranulation, and greater killing at low pH and when the organisms are replicating quickly, which would help maintain microbicidal host defense despite an acidic microenvironment. PMID:23853583

Systematic generation of buffer systems for pH gradient ion exchange chromatography and their application.

PubMed

Kröner, Frieder; Hubbuch, Jürgen

2013-04-12

pH gradient protein separations are widely used techniques in the field of protein analytics, of which isoelectric focusing is the most well known application. The chromatographic variant, based on the formation of pH gradients in ion exchange columns is only rarely applied due to the difficulties to form controllable, linear pH gradients over a broad pH range. This work describes a method for the systematic generation of buffer compositions with linear titration curves, resulting in well controllable pH gradients. To generate buffer compositions with linear titration curves an in silico method was successfully developed. With this tool, buffer compositions for pH gradient ion exchange chromatography with pH ranges spanning up to 7.5 pH units were established and successfully validated. Subsequently, the buffer systems were used to characterize the elution behavior of 22 different model proteins in cation and anion exchange pH gradient chromatography. The results of both chromatographic modes as well as isoelectric focusing were compared to describe differences in between the methods. Copyright © 2013 Elsevier B.V. All rights reserved.

The acidic pH-induced structural changes in Pin1 as revealed by spectral methodologies

NASA Astrophysics Data System (ADS)

Wang, Jing-Zhang; Xi, Lei; Zhu, Guo-Fei; Han, Yong-Guang; Luo, Yue; Wang, Mei; Du, Lin-Fang

2012-12-01

Pin1 is closely associated with the pathogenesis of cancers and Alzheimer's disease (AD). Previously, we have shown the characteristics of the thermal denaturation of Pin1. Herein, the acid-induced denaturation of Pin1 was determined by means of fluorescence emission, synchronous fluorescence, far-UV CD, ANS fluorescence and RLS spectroscopies. The fluorescence emission spectra and the synchronous fluorescence spectra suggested the partially reversible unfolding (approximately from pH 7.0 to 4.0) and refolding (approximately from pH 4.0 to 1.0) of the structures around the chromophores in Pin1, apparently with an intermediate state at about pH 4.0-4.5. The far-UV CD spectra indicated that acidic pH (below pH 4.0) induced the structural transition from α-helix and random coils to β-sheet in Pin1. The ANS fluorescence and the RLS spectra further suggested the exposure of the hydrophobic side-chains of Pin1 and the aggregation of it especially below pH 2.3, and the aggregation possibly resulted in the formation of extra intermolecular β-sheet. The present work primarily shows that acidic pH can induce kinds of irreversible structural changes in Pin1, such as the exposure of the hydrophobic side-chains, the transition from α-helix to β-sheet and the aggregation of Pin1, and also explains why Pin1 loses most of its activity below pH 5.0. The results emphasize the important role of decreased pH in the pathogenesis of some Pin1-related diseases, and support the therapeutic approach for them by targeting acidosis and modifying the intracellular pH gradients.

A dynamic system for the simulation of fasting luminal pH-gradients using hydrogen carbonate buffers for dissolution testing of ionisable compounds.

PubMed

Garbacz, Grzegorz; Kołodziej, Bartosz; Koziolek, Mirko; Weitschies, Werner; Klein, Sandra

2014-01-23

The hydrogen carbonate buffer is considered as the most biorelevant buffer system for the simulation of intestinal conditions and covers the physiological pH range of the luminal fluids from pH 5.5 to about pH 8.4. The pH value of a hydrogen carbonate buffer is the result of a complex and dynamic interplay of the concentration of hydrogen carbonate ions, carbonic acid, the concentration of dissolved and solvated carbon dioxide and its partial pressure above the solution. The complex equilibrium between the different ions results in a thermodynamic instability of hydrogen carbonate solutions. In order to use hydrogen carbonate buffers with pH gradients in the physiological range and with the dynamics observed in vivo without changing the ionic strength of the solution, we developed a device (pHysio-grad®) that provides both acidification of the dissolution medium by microcomputer controlled carbon dioxide influx and alkalisation by degassing. This enables a continuous pH control and adjustment during dissolution of ionisable compounds. The results of the pH adjustment indicate that the system can compensate even rapid pH changes after addition of a basic or acidic moiety in amounts corresponding up to 90% of the overall buffer capacity. The results of the dissolution tests performed for a model formulation containing ionizable compounds (Nexium 20mg mups) indicate that both the simulated fasting intraluminal pH-profiles and the buffer species can significantly affect the dissolution process by changing the lag time prior to initial drug release and the release rate of the model compound. A prediction of the in vivo release behaviour of this formulation is thus most likely strongly related to the test conditions such as pH and buffer species. Copyright © 2013 Elsevier B.V. All rights reserved.

Urbanization in China drives soil acidification of Pinus massoniana forests.

PubMed

Huang, Juan; Zhang, Wei; Mo, Jiangming; Wang, Shizhong; Liu, Juxiu; Chen, Hao

2015-09-24

Soil acidification instead of alkalization has become a new environmental issue caused by urbanization. However, it remains unclear the characters and main contributors of this acidification. We investigated the effects of an urbanization gradient on soil acidity of Pinus massoniana forests in Pearl River Delta, South China. The soil pH of pine forests at 20-cm depth had significantly positive linear correlations with the distance from the urban core of Guangzhou. Soil pH reduced by 0.44 unit at the 0-10 cm layer in urbanized areas compared to that in non-urbanized areas. Nitrogen deposition, mean annual temperature and mean annual precipitation were key factors influencing soil acidification based on a principal component analysis. Nitrogen deposition showed significant linear relationships with soil pH at the 0-10 cm (for ammonium N(NH4+(-N)), P < 0.05; for nitrate N(NO3-(-N)), P < 0.01) and 10-20 cm (for NO3-(-N), P < 0.05) layers. However, there was no significant loss of exchangeable non-acidic cations along the urbanization gradient, instead their levels were higher in urban than in urban/suburban area at the 0-10 cm layer. Our results suggested N deposition particularly under the climate of high temperature and rainfall, greatly contributed to a significant soil acidification occurred in the urbanized environment.

pH regulation of mitochondrial branch chain alpha-keto acid transport and oxidation in rat heart mitochondria.

PubMed

Hutson, S M

1987-07-15

The kinetics of branched chain alpha-keto acid uptake and efflux were studied as a function of varied external and matrix pH. Matrix pH was determined by the distribution of 5,5'-dimethyloxazolidine-2,4-dione. When rat heart mitochondria were incubated under transport conditions at pH 7.0 with succinate as respiratory substrate, the matrix pH was significantly greater than 8.0. Matrix pH remained greater than or equal to 8.0 when the medium pH was varied from 6.3 to 8.3, and it was lowered below 8.0 by addition of 5 mM phosphate or uncoupler. No pH gradient was detectable when mitochondria were incubated in the presence of valinomycin and uncoupler. Efflux of alpha-ketoisocaproate or alpha-ketoisovalerate from rat heart mitochondria obeyed first order kinetics. Varying the external pH from 6.6 to 8.3 had no significant effect on efflux, and at an external pH of 7.0, the first order rate constant for efflux was not affected by decreasing the matrix pH. On the other hand, exchange was sensitive to changes in medium but not matrix pH. The K0.5 for external branched chain alpha-keto acid was lowered by changing the medium pH from 7.6 to 6.3. At medium pH values greater than or equal to 8.0 both K0.5 and Vmax were affected. Uptake was determined either by measuring initial rates or was calculated after measuring the first order approach to a final equilibrium value. Unlike efflux, uptake was sensitive to changes in both external and matrix pH. The rate of branched chain alpha-keto acid uptake was stimulated by decreasing the medium pH from 8.3 to 6.3 and by alkalinization of the mitochondrial matrix. The estimated external pK for proton binding was 6.9. The data indicate that the branched chain alpha-keto acid transporter is asymmetric, that is, binding sites for substrate on the inside and outside of the mitochondrial membrane are not identical. alpha-Ketoisocaproate oxidation was measured at 37 degrees C in isolated mitochondria over the pH range of 6.6 to 8.1. Changes in the rate of branched chain alpha-keto acid oxidation, particularly when ATP was added (increase delta pH), were found to parallel the pH effects observed on branched chain alpha-keto acid uptake. Therefore, transport, and by implication oxidation, can be regulated by pH changes within the physiological range. Furthermore, intracellular pH may affect the degree of compartmentation between the cytosolic and mitochondrial branched chain alpha-keto acid pools.

pH-dependent antitumor activity of proton pump inhibitors against human melanoma is mediated by inhibition of tumor acidity.

PubMed

De Milito, Angelo; Canese, Rossella; Marino, Maria Lucia; Borghi, Martina; Iero, Manuela; Villa, Antonello; Venturi, Giulietta; Lozupone, Francesco; Iessi, Elisabetta; Logozzi, Mariantonia; Della Mina, Pamela; Santinami, Mario; Rodolfo, Monica; Podo, Franca; Rivoltini, Licia; Fais, Stefano

2010-07-01

Metastatic melanoma is associated with poor prognosis and still limited therapeutic options. An innovative treatment approach for this disease is represented by targeting acidosis, a feature characterizing tumor microenvironment and playing an important role in cancer malignancy. Proton pump inhibitors (PPI), such as esomeprazole (ESOM) are prodrugs functionally activated by acidic environment, fostering pH neutralization by inhibiting proton extrusion. We used human melanoma cell lines and xeno-transplated SCID mice to provide preclinical evidence of ESOM antineoplastic activity. Human melanoma cell lines, characterized by different mutation and signaling profiles, were treated with ESOM in different pH conditions and evaluated for proliferation, viability and cell death. SCID mice engrafted with human melanoma were used to study ESOM administration effects on tumor growth and tumor pH by magnetic resonance spectroscopy (MRS). ESOM inhibited proliferation of melanoma cells in vitro and induced a cytotoxicity strongly boosted by low pH culture conditions. ESOM-induced tumor cell death occurred via rapid intracellular acidification and activation of several caspases. Inhibition of caspases activity by pan-caspase inhibitor z-vad-fmk completely abrogated the ESOM-induced cell death. ESOM administration (2.5 mg kg(-1)) to SCID mice engrafted with human melanoma reduced tumor growth, consistent with decrease of proliferating cells and clear reduction of pH gradients in tumor tissue. Moreover, systemic ESOM administration dramatically increased survival of human melanoma-bearing animals, in absence of any relevant toxicity. These data show preclinical evidence supporting the use of PPI as novel therapeutic strategy for melanoma, providing the proof of concept that PPI target human melanoma modifying tumor pH gradients.

Biocompatible click chemistry enabled compartment-specific pH measurement inside E. coli.

PubMed

Yang, Maiyun; Jalloh, Abubakar S; Wei, Wei; Zhao, Jing; Wu, Peng; Chen, Peng R

2014-09-19

Bioorthogonal reactions, especially the Cu(I)-catalysed azide-alkyne cycloaddition, have revolutionized our ability to label and manipulate biomolecules under living conditions. The cytotoxicity of Cu(I) ions, however, has hindered the application of this reaction in the internal space of living cells. By systematically surveying a panel of Cu(I)-stabilizing ligands in promoting protein labelling within the cytoplasm of Escherichia coli, we identify a highly efficient and biocompatible catalyst for intracellular modification of proteins by azide-alkyne cycloaddition. This reaction permits us to conjugate an environment-sensitive fluorophore site specifically onto HdeA, an acid-stress chaperone that adopts pH-dependent conformational changes, in both the periplasm and cytoplasm of E. coli. The resulting protein-fluorophore hybrid pH indicators enable compartment-specific pH measurement to determine the pH gradient across the E. coli cytoplasmic membrane. This construct also allows the measurement of E. coli transmembrane potential, and the determination of the proton motive force across its inner membrane under normal and acid-stress conditions.

Watershed scale fungal community characterization along a pH gradient in a subsurface environment co-contaminated with uranium and nitrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jasrotia, Puja; Green, Stefan; Canion, Andy

2014-01-01

The objective of this study was to characterize fungal communities in a subsurface environment co-contaminated with uranium and nitrate at the watershed scale, and to determine the potential contribution of fungi to contaminant transformation (nitrate attenuation). The abundance, distribution and diversity of fungi in subsurface groundwater samples were determined using quantitative and semi-quantitative molecular techniques, including quantitative PCR of eukaryotic SSU rRNA genes and pyrosequencing of fungal internal transcribed spacer (ITS) regions. Potential bacterial and fungal denitrification was assessed in sediment-groundwater slurries amended with antimicrobial compounds and in fungal pure cultures isolated from subsurface. Our results demonstrate that subsurface fungalmore » communities are dominated by members of the phylum Ascomycota, and a pronounced shift in fungal community composition occurs across the groundwater pH gradient at the field site, with lower diversity observed under acidic (pH < 4.5) conditions. Fungal isolates recovered from subsurface sediments were shown to reduce nitrate to nitrous oxide, including cultures of the genus Coniochaeta that were detected in abundance in pyrosequence libraries of site groundwater samples. Denitrifying fungal isolates recovered from the site were classified, and found to be distributed broadly within the phylum Ascomycota, and within a single genus within the Basidiomycota. Potential denitrification rate assays with sediment-groundwater slurries showed the potential for subsurface fungi to reduce nitrate to nitrous oxide under in situ acidic pH conditions.« less

Watershed-Scale Fungal Community Characterization along a pH Gradient in a Subsurface Environment Cocontaminated with Uranium and Nitrate

PubMed Central

Jasrotia, Puja; Green, Stefan J.; Canion, Andy; Overholt, Will A.; Prakash, Om; Wafula, Denis; Hubbard, Daniela; Watson, David B.; Schadt, Christopher W.; Brooks, Scott C.

2014-01-01

The objective of this study was to characterize fungal communities in a subsurface environment cocontaminated with uranium and nitrate at the watershed scale and to determine the potential contribution of fungi to contaminant transformation (nitrate attenuation). The abundance, distribution, and diversity of fungi in subsurface groundwater samples were determined using quantitative and semiquantitative molecular techniques, including quantitative PCR of eukaryotic small-subunit rRNA genes and pyrosequencing of fungal internal transcribed spacer (ITS) regions. Potential bacterial and fungal denitrification was assessed in sediment-groundwater slurries amended with antimicrobial compounds and in fungal pure cultures isolated from the subsurface. Our results demonstrate that subsurface fungal communities are dominated by members of the phylum Ascomycota, and a pronounced shift in fungal community composition occurs across the groundwater pH gradient at the field site, with lower diversity observed under acidic (pH <4.5) conditions. Fungal isolates recovered from subsurface sediments, including cultures of the genus Coniochaeta, which were detected in abundance in pyrosequence libraries of site groundwater samples, were shown to reduce nitrate to nitrous oxide. Denitrifying fungal isolates recovered from the site were classified and found to be distributed broadly within the phylum Ascomycota and within a single genus of the Basidiomycota. Potential denitrification rate assays with sediment-groundwater slurries showed the potential for subsurface fungi to reduce nitrate to nitrous oxide under in situ acidic pH conditions. PMID:24389927

Can the eastern red-backed salamander (Plethodon cinereus) persist in an acidified landscape?

USGS Publications Warehouse

Bondi, Cheryl A; Beier, Colin M.; Ducey, Peter K; Lawrence, Gregory B.; Bailey, Scott W.

2016-01-01

Hardwood forests of eastern North America have experienced decades of acidic deposition, leading to soil acidification where base cation supply was insufficient to neutralize acid inputs. Negative impacts of soil acidity on amphibians include disrupted embryonic development, lower growth rates, and habitat loss. However, some amphibians exhibit intraspecific variation in acid tolerance, suggesting the potential for local adaptation in areas where soils are naturally acidic. The eastern red-backed salamander (Plethodon cinereus) is a highly abundant top predator of the northern hardwood forest floor. Early research found that P. cinereus was sensitive to acidic soils, avoiding substrates with pH < 3.8 and experiencing decreased growth rates in acidic habitats. However, recent studies have documented P. cinereus populations in lower pH conditions than previously observed, suggesting some populations may persist in acidic conditions. Here, we evaluated relationships between organic horizon soil pH and P. cinereus abundance, adult health (body size and condition), and microhabitat selection, based on surveys of 34 hardwood forests in northeastern United States that encompass a regional soil pH gradient. We found no associations between soil pH and P. cinereus abundance or health, and observed that this salamander used substrates with pH similar to that available, suggesting that pH does not mediate their fine-scale distributions. The strongest negative predictor of P. cinereus abundance was the presence of dusky salamanders (Desmognathus spp.), which were most abundant in the western Adirondacks. Our results indicate that P. cinereus occupies a wider range of soil pH than has been previously thought, which has implications for their functional role in forest food webs and nutrient cycles in acid-impaired ecosystems. Tolerance of P. cinereus for more acidic habitats, including anthropogenically acidified forests, may be due to local adaptation in reproductively isolated populations and/or generalist life history traits that allow them to exploit a wider resource niche.

Acid/Salt/pH Gradient Improved Resolution and Sensitivity in Proteomics Study Using 2D SCX-RP LC-MS.

PubMed

Zhu, Ming-Zhi; Li, Na; Wang, Yi-Tong; Liu, Ning; Guo, Ming-Quan; Sun, Bao-Qing; Zhou, Hua; Liu, Liang; Wu, Jian-Lin

2017-09-01

The usage of strong cation exchange (SCX) chromatography in proteomics is limited by its poor resolution and nonspecific hydrophobic interactions with peptides, which lead to peptide overlap across fractions and change of peptide retention, respectively. The application of high concentration of salt (up to 1000 mM) in SCX also restricted its use in online 2D SCX-RP LC. In the present research, we first exploited the chromatographic ability of online 2D SCX-RP LC by combination of acid, salt, and pH gradient, three relatively independent modes of eluting peptides from SCX column. 50% ACN was added to elution buffer for eliminating hydrophobic interactions between SCX matrix and peptides, and the concentration of volatile salt was reduced to 50 mM. Acid/salt/pH gradient showed superior resolution and sensitivity as well as uniform distribution across fractions, consequently leading to significant improvements in peptide and protein identification. 112 191 unique peptides and 7373 proteins were identified by acid/salt/pH fractionation, while 69 870 unique peptides and 4536 proteins were identified by salt elution, that is, 62.5 and 60.6% more proteins and unique peptides, respectively, identified by the former. Fraction overlap was also significantly minimized by acid/salt/pH approach. Furthermore, acid/salt/pH elution showed more identification for acidic peptides and hydrophilic peptides.

Penetrating cation/fatty acid anion pair as a mitochondria-targeted protonophore

PubMed Central

Severin, Fedor F.; Severina, Inna I.; Antonenko, Yury N.; Rokitskaya, Tatiana I.; Cherepanov, Dmitry A.; Mokhova, Elena N.; Vyssokikh, Mikhail Yu.; Pustovidko, Antonina V.; Markova, Olga V.; Yaguzhinsky, Lev S.; Korshunova, Galina A.; Sumbatyan, Nataliya V.; Skulachev, Maxim V.; Skulachev, Vladimir P.

2010-01-01

A unique phenomenon of mitochondria-targeted protonophores is described. It consists in a transmembrane H+-conducting fatty acid cycling mediated by penetrating cations such as 10-(6’-plastoquinonyl)decyltriphenylphosphonium (SkQ1) or dodecyltriphenylphosphonium (C12TPP). The phenomenon has been modeled by molecular dynamics and directly proved by experiments on bilayer planar phospholipid membrane, liposomes, isolated mitochondria, and yeast cells. In bilayer planar phospholipid membrane, the concerted action of penetrating cations and fatty acids is found to result in conversion of a pH gradient (ΔpH) to a membrane potential (Δψ) of the Nernstian value (about 60 mV Δψ at ΔpH = 1). A hydrophobic cation with localized charge (cetyltrimethylammonium) failed to substitute for hydrophobic cations with delocalized charge. In isolated mitochondria, SkQ1 and C12TPP, but not cetyltrimethylammonium, potentiated fatty acid-induced (i) uncoupling of respiration and phosphorylation, and (ii) inhibition of H2O2 formation. In intact yeast cells, C12TPP stimulated respiration regardless of the extracellular pH value, whereas a nontargeted protonophorous uncoupler (trifluoromethoxycarbonylcyanide phenylhydrazone) stimulated respiration at pH 5 but not at pH 3. Hydrophobic penetrating cations might be promising to treat obesity, senescence, and some kinds of cancer that require mitochondrial hyperpolarization. PMID:20080732

A fluorescent pH probe for acidic organelles in living cells.

PubMed

Chen, Jyun-Wei; Chen, Chih-Ming; Chang, Cheng-Chung

2017-09-26

A water-soluble pH sensor, 2-(6-(4-aminostyryl)-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)-N, N-dimethylethanamine (ADA), was synthesized based on the molecular design of photoinduced electron transfer (PET) and intramolecular charge transfer (ICT). The fluorescence emission response against a pH value is in the range 3-6, which is suitable for labelling intracellular pH-dependent microenvironments. After biological evolution, ADA is more than a pH biosensor because it is also an endocytosis pathway tracking biosensor that labels endosomes, late endosomes, and lysosome pH gradients. From this, the emissive aggregates of ADA and protonated-ADA in these organs were evaluated to explore how this probe stresses emission colour change to cause these unique cellular images.

Chiral separation with gradient elution isotachophoresis for future in situ extraterrestrial analysis.

PubMed

Danger, Grégoire; Ross, David

2008-10-01

The first results of chiral separations with the gradient elution isotachophoresis method are presented. As previously described, citrate is used in the run buffer as the leading ion and borate in the sample buffer as the terminating ion. Modulation of parameters such as electrolyte pH, pressure scan rate, chiral selector concentration, combinations of CD or the percentage of ampholytes provides an easy optimization of the separations. To perform fluorescent detection 5-carboxyfluorescein succinimidyl ester and two fluorogenic-labeling agents, fluorescamine (Fluram) and 3-(4-carboxybenzoyl)quinoline-2-carboxaldehyde, are used to label amino acids. With the 5-carboxyfluorescein amino acids, chiral separations are easily obtained using a neutral CD ((2-hydroxypropyl)-beta-CD) at a low concentration (2 mmol/L). With Fluram amino acids, the situation is more complicated due to the formation of diastereoisomers and due to weak interactions with the different CDs used. The use of the 3-(4-carboxybenzoyl)quinoline-2-carboxaldehyde-labeling agent solves the problems observed with the Fluram agent while retaining the fluorogenic properties. These first results demonstrate the simplicity and the feasibility of gradient elution isotachophoresis for chiral separations.

pH is the primary determinant of the bacterial community structure in agricultural soils impacted by polycyclic aromatic hydrocarbon pollution

PubMed Central

Wu, Yucheng; Zeng, Jun; Zhu, Qinghe; Zhang, Zhenfa; Lin, Xiangui

2017-01-01

Acidification and pollution are two major threats to agricultural ecosystems; however, microbial community responses to co-existed soil acidification and pollution remain less explored. In this study, arable soils of broad pH (4.26–8.43) and polycyclic aromatic hydrocarbon (PAH) gradients (0.18–20.68 mg kg−1) were collected from vegetable farmlands. Bacterial community characteristics including abundance, diversity and composition were revealed by quantitative PCR and high-throughput sequencing. The bacterial 16S rRNA gene copies significantly correlated with soil carbon and nitrogen contents, suggesting the control of nutrients accessibility on bacterial abundance. The bacterial diversity was strongly related to soil pH, with higher diversity in neutral samples and lower in acidic samples. Soil pH was also identified by an ordination analysis as important factor shaping bacterial community composition. The relative abundances of some dominant phyla varied along the pH gradient, and the enrichment of a few phylotypes suggested their adaptation to low pH condition. In contrast, at the current pollution level, PAH showed marginal effects on soil bacterial community. Overall, these findings suggest pH was the primary determinant of bacterial community in these arable soils, indicative of a more substantial influence of acidification than PAH pollution on bacteria driven ecological processes. PMID:28051171

pH is the primary determinant of the bacterial community structure in agricultural soils impacted by polycyclic aromatic hydrocarbon pollution

NASA Astrophysics Data System (ADS)

Wu, Yucheng; Zeng, Jun; Zhu, Qinghe; Zhang, Zhenfa; Lin, Xiangui

2017-01-01

Acidification and pollution are two major threats to agricultural ecosystems; however, microbial community responses to co-existed soil acidification and pollution remain less explored. In this study, arable soils of broad pH (4.26-8.43) and polycyclic aromatic hydrocarbon (PAH) gradients (0.18-20.68 mg kg-1) were collected from vegetable farmlands. Bacterial community characteristics including abundance, diversity and composition were revealed by quantitative PCR and high-throughput sequencing. The bacterial 16S rRNA gene copies significantly correlated with soil carbon and nitrogen contents, suggesting the control of nutrients accessibility on bacterial abundance. The bacterial diversity was strongly related to soil pH, with higher diversity in neutral samples and lower in acidic samples. Soil pH was also identified by an ordination analysis as important factor shaping bacterial community composition. The relative abundances of some dominant phyla varied along the pH gradient, and the enrichment of a few phylotypes suggested their adaptation to low pH condition. In contrast, at the current pollution level, PAH showed marginal effects on soil bacterial community. Overall, these findings suggest pH was the primary determinant of bacterial community in these arable soils, indicative of a more substantial influence of acidification than PAH pollution on bacteria driven ecological processes.

Preparation and evaluation of Vinpocetine self-emulsifying pH gradient release pellets.

PubMed

Liu, Mengqi; Zhang, Shiming; Cui, Shuxia; Chen, Fen; Jia, Lianqun; Wang, Shu; Gai, Xiumei; Li, Pingfei; Yang, Feifei; Pan, Weisan; Yang, Xinggang

2017-11-01

The main objective of this study was to develop a pH gradient release pellet with self-emulsifying drug delivery system (SEDDS), which could not only improve the oral bioavailability of Vinpocetine (VIN), a poor soluble drug, but reduce the fluctuation of plasma concentration. First, the liquid VIN SEDDS formulation was prepared. Then the self-emulsifying pH gradient release pellets were prepared by extrusion spheronization technique, and formulation consisted by the liquid SEDDS, absorbent (colloidal silicon dioxide), penetration enhancer (sodium chloride), microcrystalline cellulose, ethyl alcohol, and three coating materials (HPMC, Eudragit L30D55, Eudragit FS30D) were eventually selected. Three kinds of coated pellets were mixed in capsules with the mass ratio of 1:1:1. The release curves of capsules were investigated in vitro under the simulated gastrointestinal conditions. In addition, the oral bioavailability and pharmacokinetics of VIN self-emulsifying pH gradient release pellets, commercial tablets and liquid VIN SEDDS were evaluated in Beagle dogs. The oral bioavailability of self-emulsifying pH gradient release pellets was about 149.8% of commercial VIN tablets, and it was about 86% of liquid VIN SEDDS, but there were no significant difference between liquid SEDDS and self-emulsifying pH gradient release pellets. In conclusion, the self-emulsifying pH gradient release pellets could significantly enhance the absorption of VIN and effectively achieve a pH gradient release. And the self-emulsifying pH gradient release pellet was a promising method to improve bioavailability of insoluble drugs.

Permeation of membranes by the neutral form of amino acids and peptides: relevance to the origin of peptide translocation

NASA Technical Reports Server (NTRS)

Chakrabarti, A. C.; Deamer, D. W.; Miller, S. L. (Principal Investigator)

1994-01-01

The flux of amino acids and other nutrient solutes such as phosphate across lipid bilayers (liposomes) is 10(5) slower than facilitated inward transport across biological membranes. This suggest that primitive cells lacking highly evolved transport systems would have difficulty transporting sufficient nutrients for cell growth to occur. There are two possible ways by which early life may have overcome this difficulty: (1) The membranes of the earliest cellular life-forms may have been intrinsically more permeable to solutes; or (2) some transport mechanism may have been available to facilitate transbilayer movement of solutes essential for cell survival and growth prior to the evolution of membrane transport proteins. Translocation of neutral species represents one such mechanism. The neutral forms of amino acids modified by methylation (creating protonated weak bases) permeate membranes up to 10(10) times faster than charged forms. This increased permeability when coupled to a transmembrane pH gradient can result in significantly increased rates of net unidirectional transport. Such pH gradients can be generated in vesicles used to model protocells that preceded and were presumably ancestral to early forms of life. This transport mechanism may still play a role in some protein translocation processes (e.g. for certain signal sequences, toxins and thylakoid proteins) in vivo.

Water balance creates a threshold in soil pH at the global scale.

PubMed

Slessarev, E W; Lin, Y; Bingham, N L; Johnson, J E; Dai, Y; Schimel, J P; Chadwick, O A

2016-11-21

Soil pH regulates the capacity of soils to store and supply nutrients, and thus contributes substantially to controlling productivity in terrestrial ecosystems. However, soil pH is not an independent regulator of soil fertility-rather, it is ultimately controlled by environmental forcing. In particular, small changes in water balance cause a steep transition from alkaline to acid soils across natural climate gradients. Although the processes governing this threshold in soil pH are well understood, the threshold has not been quantified at the global scale, where the influence of climate may be confounded by the effects of topography and mineralogy. Here we evaluate the global relationship between water balance and soil pH by extracting a spatially random sample (n = 20,000) from an extensive compilation of 60,291 soil pH measurements. We show that there is an abrupt transition from alkaline to acid soil pH that occurs at the point where mean annual precipitation begins to exceed mean annual potential evapotranspiration. We evaluate deviations from this global pattern, showing that they may result from seasonality, climate history, erosion and mineralogy. These results demonstrate that climate creates a nonlinear pattern in soil solution chemistry at the global scale; they also reveal conditions under which soils maintain pH out of equilibrium with modern climate.

Water balance creates a threshold in soil pH at the global scale

NASA Astrophysics Data System (ADS)

Slessarev, E. W.; Lin, Y.; Bingham, N. L.; Johnson, J. E.; Dai, Y.; Schimel, J. P.; Chadwick, O. A.

2016-12-01

Soil pH regulates the capacity of soils to store and supply nutrients, and thus contributes substantially to controlling productivity in terrestrial ecosystems. However, soil pH is not an independent regulator of soil fertility—rather, it is ultimately controlled by environmental forcing. In particular, small changes in water balance cause a steep transition from alkaline to acid soils across natural climate gradients. Although the processes governing this threshold in soil pH are well understood, the threshold has not been quantified at the global scale, where the influence of climate may be confounded by the effects of topography and mineralogy. Here we evaluate the global relationship between water balance and soil pH by extracting a spatially random sample (n = 20,000) from an extensive compilation of 60,291 soil pH measurements. We show that there is an abrupt transition from alkaline to acid soil pH that occurs at the point where mean annual precipitation begins to exceed mean annual potential evapotranspiration. We evaluate deviations from this global pattern, showing that they may result from seasonality, climate history, erosion and mineralogy. These results demonstrate that climate creates a nonlinear pattern in soil solution chemistry at the global scale; they also reveal conditions under which soils maintain pH out of equilibrium with modern climate.

Extractive Fermentation of Lactic Acid in Lactic Acid Bacteria Cultivation: A Review.

PubMed

Othman, Majdiah; Ariff, Arbakariya B; Rios-Solis, Leonardo; Halim, Murni

2017-01-01

Lactic acid bacteria are industrially important microorganisms recognized for their fermentative ability mostly in their probiotic benefits as well as lactic acid production for various applications. Nevertheless, lactic acid fermentation often suffers end-product inhibition which decreases the cell growth rate. The inhibition of lactic acid is due to the solubility of the undissociated lactic acid within the cytoplasmic membrane and insolubility of dissociated lactate, which causes acidification of cytoplasm and failure of proton motive forces. This phenomenon influences the transmembrane pH gradient and decreases the amount of energy available for cell growth. In general, the restriction imposed by lactic acid on its fermentation can be avoided by extractive fermentation techniques, which can also be exploited for product recovery.

Extractive Fermentation of Lactic Acid in Lactic Acid Bacteria Cultivation: A Review

PubMed Central

Othman, Majdiah; Ariff, Arbakariya B.; Rios-Solis, Leonardo; Halim, Murni

2017-01-01

Lactic acid bacteria are industrially important microorganisms recognized for their fermentative ability mostly in their probiotic benefits as well as lactic acid production for various applications. Nevertheless, lactic acid fermentation often suffers end-product inhibition which decreases the cell growth rate. The inhibition of lactic acid is due to the solubility of the undissociated lactic acid within the cytoplasmic membrane and insolubility of dissociated lactate, which causes acidification of cytoplasm and failure of proton motive forces. This phenomenon influences the transmembrane pH gradient and decreases the amount of energy available for cell growth. In general, the restriction imposed by lactic acid on its fermentation can be avoided by extractive fermentation techniques, which can also be exploited for product recovery. PMID:29209295

Theory and applications of a novel ion exchange chromatographic technology using controlled pH gradients for separating proteins on anionic and cationic stationary phases.

PubMed

Tsonev, Latchezar I; Hirsh, Allen G

2008-07-25

pISep is a major new advance in low ionic strength ion exchange chromatography. It enables the formation of externally controlled pH gradients over the very broad pH range from 2 to 12. The gradients can be generated on either cationic or anionic exchangers over arbitrary pH ranges wherein the stationary phases remain totally charged. Associated pISep software makes possible the calculation of either linear, nonlinear or combined, multi-step, multi-slope pH gradients. These highly reproducible pH gradients, while separating proteins and glycoproteins in the order of their electrophoretic pIs, provide superior chromatographic resolution compared to salt. This paper also presents a statistical mechanical model for protein binding to ion exchange stationary phases enhancing the electrostatic interaction theory for the general dependence of retention factor k, on both salt and pH simultaneously. It is shown that the retention factors computed from short time isocratic salt elution data of a model protein can be used to accurately predict its salt elution concentration in varying slope salt elution gradients formed at varying isocratic pH as well as the pH at which it will be eluted from an anionic exchange column by a pISep pH gradient in the absence of salt.

Product development studies of amino acid conjugate of Aceclofenac.

PubMed

Singh, Ajay Pal; Ramadan, Wafa Mossa; Dahiya, Rajiv; Sarpal, A S; Pathak, Kamla

2009-04-01

The prodrugs designed by classical approach increase lipophilicity of the drug, which decreases the water solubility thus decreasing the concentration gradient, which controls drug absorption. To overcome the limitations of traditional prodrug approach, water soluble prodrugs can be designed by adding selected amino acid to the drug moiety that are the substrates for the enzyme located at the intestinal brush border thus overcoming pharmaceutical problem without compromising bioavailability. ACaa (Amino acid conjugate of Aceclofenac) was synthesized by conjugation with l-phenylalanine by conventional coupling method using N, N-dicyclohexylcarbodiimide and ACaa was characterized by melting point, TLC, photomicrograph, UV, FT-IR, FT-NMR, MS-FAB, XRD and DSC. As a part of product development study ACaa was subjected to studies like In-vivo in albino rats and in-vitro like ACaa reversion to AC (Aceclofenac) in aqueous buffers of pH 1.21, 2.38. 3.10, 6.22 and 7.41, at a constant concentration (0.05M), ionic strength (micro = 0.5) and at a temperature of 37 degrees C +/- 0.5 degrees C, ACaa showed negligible reversion (2.15 %) up to 24 hrs study at acidic pH thus suggesting stability in acidic environment of stomach, the rate of reversion increased as pH of medium increased. pH- partition profile, pH- solubility profile and micromeritic studies were also carried out in comparison to pure drug. The solubility and lipophilicity of ACaa exhibited higher values at all pH range when compared to AC. The micromeritic properties also evaluated in terms of particle shape and size, IQCS and kurtosis. Resulting IQCS value approached zero thus suggesting reducing in the degree of skewness.

Proton pump inhibitors induce apoptosis of human B-cell tumors through a caspase-independent mechanism involving reactive oxygen species.

PubMed

De Milito, Angelo; Iessi, Elisabetta; Logozzi, Mariantonia; Lozupone, Francesco; Spada, Massimo; Marino, Maria Lucia; Federici, Cristina; Perdicchio, Maurizio; Matarrese, Paola; Lugini, Luana; Nilsson, Anna; Fais, Stefano

2007-06-01

Proton pumps like the vacuolar-type H+ ATPase (V-ATPase) are involved in the control of cellular pH in normal and tumor cells. Treatment with proton pump inhibitors (PPI) induces sensitization of cancer cells to chemotherapeutics via modifications of cellular pH gradients. It is also known that low pH is the most suitable condition for a full PPI activation. Here, we tested whether PPI treatment in unbuffered culture conditions could affect survival and proliferation of human B-cell tumors. First, we showed that PPI treatment increased the sensitivity to vinblastine of a pre-B acute lymphoblastic leukemia (ALL) cell line. PPI, per se, induced a dose-dependent inhibition of proliferation of tumor B cells, which was associated with a dose- and time-dependent apoptotic-like cytotoxicity in B-cell lines and leukemic cells from patients with pre-B ALL. The effect of PPI was mediated by a very early production of reactive oxygen species (ROS), that preceded alkalinization of lysosomal pH, lysosomal membrane permeabilization, and cytosol acidification, suggesting an early destabilization of the acidic vesicular compartment. Lysosomal alterations were followed by mitochondrial membrane depolarization, release of cytochrome c, chromatin condensation, and caspase activation. However, inhibition of caspase activity did not affect PPI-induced cell death, whereas specific inhibition of ROS by an antioxidant (N-acetylcysteine) significantly delayed cell death and protected both lysosomal and mitochondrial membranes. The proapoptotic activity of PPI was consistent with a clear inhibition of tumor growth following PPI treatment of B-cell lymphoma in severe combined immunodeficient mice. This study further supports the importance of acidity and pH gradients in tumor cell homeostasis and suggests new therapeutic approaches for human B-cell tumors based on PPI.

Effects of acidic recharge on groundwater at the St. Kevin Gulch site, Leadville, Colorado

USGS Publications Warehouse

Paschke, S.S.; Harrison, W.J.; Walton-Day, K.

2001-01-01

The acid rock drainage-affected stream of St. Kevin Gulch recharges the Quaternary sand and gravel aquifer of Tennessee Park, near Leadville, Colorado, lowering pH and contributing iron, cadmium, copper, zinc and sulphate to the ground-water system. Dissolved metal mobility is controlled by the seasonal spring runoff as well as oxidation/reduction (redox) reactions in the aquifer. Oxidizing conditions occur in the unconfined portions of the aquifer whilst sulphate-reducing conditions are found down gradient where semi-confined groundwater flow occurs beneath a natural wetland. Iron-reducing conditions occur in the transition from unconfined to semi-confined groundwater flow. Dissolved iron concentrations are low to not detectable in the alluvial fan recharge zone and increase in a down gradient direction. The effects of low-pH, metal-rich recharge are pronounced during low-flow in the fall when there is a defined area of low pH groundwater with elevated concentrations of dissolved zinc, cadmium, copper and sulphate adjacent to St. Kevin Gulch. Dissolved metal and sulphate concentrations in the recharge zone are diluted during spring runoff, although the maximum concentrations of dissolved zinc, cadmium, copper and sulphate occur at selected down gradient locations during high flow. Dissolved zinc, cadmium and copper concentrations are low to not detectable, whereas dissolved iron concentrations are greatest, in groundwater samples from the sulphate-reducing zone. Attenuation of zinc, cadmium and copper beneath the wetland suggests sulphide mineral precipitation is occurring in the semi-confined aquifer, in agreement with previous site investigations and saturation index calculations. Adsorption of dissolved zinc, cadmium and copper onto iron hydroxides is a minor attenuation process due to the low pH of the groundwater system.

pH regulates genes for flagellar motility, catabolism, and oxidative stress in Escherichia coli K-12.

PubMed

Maurer, Lisa M; Yohannes, Elizabeth; Bondurant, Sandra S; Radmacher, Michael; Slonczewski, Joan L

2005-01-01

Gene expression profiles of Escherichia coli K-12 W3110 were compared as a function of steady-state external pH. Cultures were grown to an optical density at 600 nm of 0.3 in potassium-modified Luria-Bertani medium buffered at pH 5.0, 7.0, and 8.7. For each of the three pH conditions, cDNA from RNA of five independent cultures was hybridized to Affymetrix E. coli arrays. Analysis of variance with an alpha level of 0.001 resulted in 98% power to detect genes showing a twofold difference in expression. Normalized expression indices were calculated for each gene and intergenic region (IG). Differential expression among the three pH classes was observed for 763 genes and 353 IGs. Hierarchical clustering yielded six well-defined clusters of pH profiles, designated Acid High (highest expression at pH 5.0), Acid Low (lowest expression at pH 5.0), Base High (highest at pH 8.7), Base Low (lowest at pH 8.7), Neutral High (highest at pH 7.0, lower in acid or base), and Neutral Low (lowest at pH 7.0, higher at both pH extremes). Flagellar and chemotaxis genes were repressed at pH 8.7 (Base Low cluster), where the cell's transmembrane proton potential is diminished by the maintenance of an inverted pH gradient. High pH also repressed the proton pumps cytochrome o (cyo) and NADH dehydrogenases I and II. By contrast, the proton-importing ATP synthase F1Fo and the microaerophilic cytochrome d (cyd), which minimizes proton export, were induced at pH 8.7. These observations are consistent with a model in which high pH represses synthesis of flagella, which expend proton motive force, while stepping up electron transport and ATPase components that keep protons inside the cell. Acid-induced genes, on the other hand, were coinduced by conditions associated with increased metabolic rate, such as oxidative stress. All six pH-dependent clusters included envelope and periplasmic proteins, which directly experience external pH. Overall, this study showed that (i) low pH accelerates acid consumption and proton export, while coinducing oxidative stress and heat shock regulons; (ii) high pH accelerates proton import, while repressing the energy-expensive flagellar and chemotaxis regulons; and (iii) pH differentially regulates a large number of periplasmic and envelope proteins.

Acidic, neutral and alkaline forest ponds as a landscape element affecting the biodiversity of freshwater snails

NASA Astrophysics Data System (ADS)

Spyra, Aneta

2017-10-01

In recent years, the number of areas remaining under the influence of acidity has increased. At all levels of ecosystems, biodiversity decreases with acidification, due to the elimination of species that are most sensitive to low pH. Forest ponds belong to a specific group that varied in location, a huge amount of leaf litter, and isolation from other aquatic environments. They are crucial in the industrial landscape with well-developed industry and human activity. The aim was to investigate the relative importance of water chemistry in explaining snail assemblage compositions and species richness in forest ponds of contrasting pH. Patterns in gastropod communities were determined from an analysis in 26 forest ponds with multivariate gradient analysis. Ponds ranged in a base mean pH from 3.0 to 9.0. pH has been found to be an important factor influencing gastropod fauna. Neutral ponds support diverse communities, typical of small water bodies. In two acidic pond types, snail fauna was different. Among the species characteristic for acidic ponds (pH < 6) were Anisus spirorbis and Aplexa hypnorum. The greatest distinct characterised alkaline ponds with the numerous appearance of alien Physa acuta. The most diverse gastropod fauna was found in neutral ponds, whereas the lowest degree of diversity was found in ponds with the lowest pH. Current knowledge of pH-associated changes in aquatic ecosystems is still incomplete because anthropogenic acidification is a recent phenomenon. It is extremely important in forest habitats, since they react more intensively to climatic factors and are often used in landscape management and planning.

Urbanization in China drives soil acidification of Pinus massoniana forests

NASA Astrophysics Data System (ADS)

Huang, Juan; Zhang, Wei; Mo, Jiangming; Wang, Shizhong; Liu, Juxiu; Chen, Hao

2015-09-01

Soil acidification instead of alkalization has become a new environmental issue caused by urbanization. However, it remains unclear the characters and main contributors of this acidification. We investigated the effects of an urbanization gradient on soil acidity of Pinus massoniana forests in Pearl River Delta, South China. The soil pH of pine forests at 20-cm depth had significantly positive linear correlations with the distance from the urban core of Guangzhou. Soil pH reduced by 0.44 unit at the 0-10 cm layer in urbanized areas compared to that in non-urbanized areas. Nitrogen deposition, mean annual temperature and mean annual precipitation were key factors influencing soil acidification based on a principal component analysis. Nitrogen deposition showed significant linear relationships with soil pH at the 0-10 cm (for ammonium N (-N), P < 0.05 for nitrate N (-N), P < 0.01) and 10-20 cm (for -N, P < 0.05) layers. However, there was no significant loss of exchangeable non-acidic cations along the urbanization gradient, instead their levels were higher in urban than in urban/suburban area at the 0-10 cm layer. Our results suggested N deposition particularly under the climate of high temperature and rainfall, greatly contributed to a significant soil acidification occurred in the urbanized environment.

Urbanization in China drives soil acidification of Pinus massoniana forests

PubMed Central

Huang, Juan; Zhang, Wei; Mo, Jiangming; Wang, Shizhong; Liu, Juxiu; Chen, Hao

2015-01-01

Soil acidification instead of alkalization has become a new environmental issue caused by urbanization. However, it remains unclear the characters and main contributors of this acidification. We investigated the effects of an urbanization gradient on soil acidity of Pinus massoniana forests in Pearl River Delta, South China. The soil pH of pine forests at 20-cm depth had significantly positive linear correlations with the distance from the urban core of Guangzhou. Soil pH reduced by 0.44 unit at the 0–10 cm layer in urbanized areas compared to that in non-urbanized areas. Nitrogen deposition, mean annual temperature and mean annual precipitation were key factors influencing soil acidification based on a principal component analysis. Nitrogen deposition showed significant linear relationships with soil pH at the 0–10 cm (for ammonium N (-N), P < 0.05; for nitrate N (-N), P < 0.01) and 10–20 cm (for -N, P < 0.05) layers. However, there was no significant loss of exchangeable non-acidic cations along the urbanization gradient, instead their levels were higher in urban than in urban/suburban area at the 0–10 cm layer. Our results suggested N deposition particularly under the climate of high temperature and rainfall, greatly contributed to a significant soil acidification occurred in the urbanized environment. PMID:26400019

Fluoroquinolone resistance of Serratia marcescens: sucrose, salicylate, temperature, and pH induction of phenotypic resistance.

PubMed

Begic, Sanela; Worobec, Elizabeth A

2007-11-01

Serratia marcescens is a nosocomial agent with a natural resistance to a broad spectrum of antibiotics, making the treatment of its infections very challenging. This study examines the influence of salicylate, sucrose, temperature, and pH variability on membrane permeability and susceptibility of S. marcescens to norfloxacin (hydrophilic fluoroquinolone) and nalidixic acid (hydrophobic quinolone). Resistance of wild-type S. marcescens UOC-67 (ATCC 13880) to norfloxacin and nalidixic acid was assessed by minimal inhibitory concentration (MIC) assays after growth in the presence of various concentrations of sucrose and salicylate and different temperatures and pH values. Norfloxacin and nalidixic acid accumulation was determined in the absence and presence of (i) carbonyl cyanide m-chlorophenylhydrazone (CCCP), a proton-motive-force collapser, and (ii) Phe-Arg beta-naphthylamide (PAbetaN), an efflux pump inhibitor. Accumulation of norfloxacin decreased when S. marcescens was grown in high concentrations of salicylate (8 mmol/L) and sucrose (10% m/v), at high temperature (42 degrees C), and at pH 6, and it was restored in the presence of CCCP because of the collapse of proton-gradient-dependent efflux in S. marcescens. Although nalidixic acid accumulation was observed, it was not affected by salicylate, sucrose, pH, or temperature changes. In the absence of PAbetaN, and either in the presence or absence of CCCP, a plateau was reached in the nalidixic acid accumulation for all environmental conditions. With the addition of 20 mg/L PAbetaN nalidixic acid accumulation is restored for all environmental conditions, suggesting that this quinolone is recognized by a yet to be identified S. marcescens pump that does not use proton motive force as its energy source.

pH Regulation of Electrogenic Sugar/H+ Symport in MFS Sugar Permeases

PubMed Central

Bazzone, Andre; Madej, M. Gregor; Kaback, H. Ronald

2016-01-01

Bacterial sugar symporters in the Major Facilitator Superfamily (MFS) use the H+ (and in a few cases Na+) electrochemical gradients to achieve active transport of sugar into the cell. Because a number of structures of MFS sugar symporters have been solved recently, molecular insight into the transport mechanism is possible from detailed functional analysis. We present here a comparative electrophysiological study of the lactose permease (LacY), the fucose permease (FucP) and the xylose permease (XylE), which reveals common mechanistic principles and differences. In all three symporters energetically downhill electrogenic sugar/H+ symport is observed. Comparison of the pH dependence of symport at symmetrical pH exhibits broad bell-shaped pH profiles extending over 3 to 6 pH units and a decrease at extremely alkaline pH ≥ 9.4 and at acidic to neutral pH = 4.6–7.5. The pH dependence can be described by an acidic to neutral apparent pK (pKapp) and an alkaline pKapp. Experimental evidence suggests that the alkaline pKapp is due to H+ depletion at the protonation site, while the acidic pKapp is due to inhibition of deprotonation. Since previous studies suggest that a single carboxyl group in LacY (Glu325) may be the only side chain directly involved in H+ translocation and a carboxyl side chain with similar properties has been identified in FucP (Asp46) and XylE (Asp27), the present results imply that the pK of this residue is switched during H+/sugar symport in all three symporters. PMID:27227677

Cation-dependent nutrient transport in shrimp digestive tract.

PubMed

Simmons, Tamla; Mozo, Julie; Wilson, Jennifer; Ahearn, Gregory A

2012-02-01

Purified epithelial brush border membrane vesicles (BBMV) were produced from the hepatopancreas of the Atlantic White shrimp, Litopeneaus setiferus, using standard methods originally developed for mammalian tissues and previously applied to other crustacean and echinoderm epithelia. These vesicles were used to study the cation dependency of sugar and amino acid transport across luminal membranes of hepatopancreatic epithelial cells. (3)H-D: -glucose uptake by BBMV against transient sugar concentration gradients occurred when either transmembrane sodium or potassium gradients were the only driving forces for sugar accumulation, suggesting the presence of a possible coupled transport system capable of using either cation. (3)H-L: -histidine transport was only stimulated by a transmembrane potassium gradient, while (3)H-L: -leucine uptake was enhanced by either a sodium or potassium gradient. These responses suggest the possible presence of a potassium-dependent transporter that accommodates either amino acid and a sodium-dependent system restricted only to L: -leucine. Uptake of (3)H-L: -leucine was significantly stimulated (P < 0.05) by several metallic cations (e.g., Zn(2+), Cu(2+), Mn(2+), Cd(2+), or Co(2+)) at external pH values of 7.0 or 5.0 (internal pH 7.0), suggesting a potential synergistic role of the cations in the transmembrane transfer of amino acids. (3)H-L: -histidine influxes (15 suptakes) were hyperbolic functions of external [zinc] or [manganese], following Michaelis-Menten kinetics. The apparent affinity constant (e.g., K (m)) for manganese was an order of magnitude smaller (K (m) = 0.22 μM Mn) than that for zinc (K (m) = 1.80 μM Zn), while no significant difference (P > 0.05) occurred between their maximal transport velocities (e.g., J (max)). These results suggest that a number of cation-dependent nutrient transport systems occur on the shrimp brush border membrane and aid in the absorption of these important dietary elements.

Multiple Acid Sensors Control Helicobacter pylori Colonization of the Stomach.

PubMed

Huang, Julie Y; Goers Sweeney, Emily; Guillemin, Karen; Amieva, Manuel R

2017-01-01

Helicobacter pylori's ability to respond to environmental cues in the stomach is integral to its survival. By directly visualizing H. pylori swimming behavior when encountering a microscopic gradient consisting of the repellent acid and attractant urea, we found that H. pylori is able to simultaneously detect both signals, and its response depends on the magnitudes of the individual signals. By testing for the bacteria's response to a pure acid gradient, we discovered that the chemoreceptors TlpA and TlpD are each independent acid sensors. They enable H. pylori to respond to and escape from increases in hydrogen ion concentration near 100 nanomolar. TlpD also mediates attraction to basic pH, a response dampened by another chemoreceptor TlpB. H. pylori mutants lacking both TlpA and TlpD (ΔtlpAD) are unable to sense acid and are defective in establishing colonization in the murine stomach. However, blocking acid production in the stomach with omeprazole rescues ΔtlpAD's colonization defect. We used 3D confocal microscopy to determine how acid blockade affects the distribution of H. pylori in the stomach. We found that stomach acid controls not only the overall bacterial density, but also the microscopic distribution of bacteria that colonize the epithelium deep in the gastric glands. In omeprazole treated animals, bacterial abundance is increased in the antral glands, and gland colonization range is extended to the corpus. Our findings indicate that H. pylori has evolved at least two independent receptors capable of detecting acid gradients, allowing not only survival in the stomach, but also controlling the interaction of the bacteria with the epithelium.

The voltage-gated proton channel: a riddle, wrapped in a mystery, inside an enigma

PubMed Central

DeCoursey, Thomas E.

2016-01-01

The main properties of voltage gated proton channels are described, along with what is known about how the channel protein structure accomplishes these functions. Just as protons are unique among ions, proton channels are unique among ion channels. Their four transmembrane helices sense voltage, the pH gradient, and conduct protons exclusively. Selectivity is achieved by the unique ability of H3O+ to protonate an Asp-Arg salt bridge. Pathognomonic sensitivity of gating to the pH gradient ensures channel opening only when acid extrusion will result, which is crucial to most biological functions. An exception occurs in dinoflagellates in which H+ influx through HV1 triggers the bioluminescent flash. Pharmacological interventions that promise to ameliorate cancer, asthma, brain damage in ischemic stroke, Alzheimer’s disease, autoimmune diseases, and numerous other conditions, await future progress. PMID:25964989

Biocompatible click chemistry enabled compartment-specific pH measurement inside E. coli

PubMed Central

Yang, Maiyun; Jalloh, Abubakar S.; Wei, Wei

2014-01-01

Bioorthogonal reactions, especially the Cu(I)-catalyzed azide-alkyne cycloaddition, have revolutionized our ability to label and manipulate biomolecules under living conditions. The cytotoxicity of Cu(I) ions, however, has hindered the application of this reaction in the internal space of living cells. By systematically surveying a panel of Cu(I)-stabilizing ligands in promoting protein labeling within the cytoplasm of E. coli, here we identify a highly efficient and biocompatible catalyst for intracellular modification of proteins by azide-alkyne cycloaddition. This reaction permits us to conjugate an environment-sensitive fluorophore site-specifically onto HdeA, an acid-stress chaperone that adopts pH-dependent conformational changes, in both the periplasm and cytoplasm of E. coli. The resulting protein-fluorophore hybrid pH indicators enable compartment-specific pH measurement to determine the pH gradient across the E. coli cytoplasmic membrane. This construct also allows the measurement of E. coli transmembrane potential, and the determination of the proton motive force across its inner membrane under normal and acid-stress conditions. PMID:25236616

Near shore groundwater acidification during and after a hydrological drought in the Lower Lakes, South Australia.

PubMed

Leyden, Emily; Cook, Freeman; Hamilton, Benjamin; Zammit, Benjamin; Barnett, Liz; Lush, Ann Marie; Stone, Dylan; Mosley, Luke

2016-06-01

An extreme hydrological drought in the Lower Lakes of the Murray-Darling Basin (Ramsar listed site) resulted in exposure of large areas of lake bed (25% of pre-drought lake area), containing the reduced iron (Fe) sulfide mineral pyrite. The pyrite oxidised and the resulting acidification (pH<4) posed risks of acid and metals entering shallow groundwater and potentially discharging to the remaining lake water body. Piezometer transects were installed at four locations and monitoring of the groundwater levels and quality was undertaken for six years from 2009 (drought) to 2014 (4years post-reinundation). Acidic (pH3-5) groundwater was recorded at three of the four piezometer locations and included sites close to the lake water. The acidic groundwater (0.5-2m below lake bed) at these sites is likely to have originated from the transport of acid from the upper oxidised sediment layer formed during the drought. High soluble metal (Fe, Al, Mn) levels were also recorded at acidic locations. Acidic shallow groundwater has persisted at many sites for over 4years following reinundation post-drought, and is likely due to slow diffusion and limited sulfate reduction. Increases in dissolved Fe and Mn with decreases in redox potential suggest that reductive dissolution of Fe and Mn hydrous oxides and Fe oxy-hydroxysulfate minerals (e.g. jarosite) occurred post-drought. Groundwater hydraulic head gradients were low, indicating there was limited potential for groundwater to discharge to the lake. The hydraulic gradients at all locations were dynamic with complex relationships along the near-shore environment. The results highlight the long lasting and severe effects on groundwater that can occur following hydrological drought in aquatic environments with sulfidic sediments. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

Near shore groundwater acidification during and after a hydrological drought in the Lower Lakes, South Australia

NASA Astrophysics Data System (ADS)

Leyden, Emily; Cook, Freeman; Hamilton, Benjamin; Zammit, Benjamin; Barnett, Liz; Lush, Ann Marie; Stone, Dylan; Mosley, Luke

2016-06-01

An extreme hydrological drought in the Lower Lakes of the Murray-Darling Basin (Ramsar listed site) resulted in exposure of large areas of lake bed (25% of pre-drought lake area), containing the reduced iron (Fe) sulfide mineral pyrite. The pyrite oxidised and the resulting acidification (pH < 4) posed risks of acid and metals entering shallow groundwater and potentially discharging to the remaining lake water body. Piezometer transects were installed at four locations and monitoring of the groundwater levels and quality was undertaken for six years from 2009 (drought) to 2014 (4 years post-reinundation). Acidic (pH 3-5) groundwater was recorded at three of the four piezometer locations and included sites close to the lake water. The acidic groundwater (0.5-2 m below lake bed) at these sites is likely to have originated from the transport of acid from the upper oxidised sediment layer formed during the drought. High soluble metal (Fe, Al, Mn) levels were also recorded at acidic locations. Acidic shallow groundwater has persisted at many sites for over 4 years following reinundation post-drought, and is likely due to slow diffusion and limited sulfate reduction. Increases in dissolved Fe and Mn with decreases in redox potential suggest that reductive dissolution of Fe and Mn hydrous oxides and Fe oxy-hydroxysulfate minerals (e.g. jarosite) occurred post-drought. Groundwater hydraulic head gradients were low, indicating there was limited potential for groundwater to discharge to the lake. The hydraulic gradients at all locations were dynamic with complex relationships along the near-shore environment. The results highlight the long lasting and severe effects on groundwater that can occur following hydrological drought in aquatic environments with sulfidic sediments.

Evaluation of differences between dual salt-pH gradient elution and mono gradient elution using a thermodynamic model: Simultaneous separation of six monoclonal antibody charge and size variants on preparative-scale ion exchange chromatographic resin.

PubMed

Lee, Yi Feng; Jöhnck, Matthias; Frech, Christian

2018-02-21

The efficiencies of mono gradient elution and dual salt-pH gradient elution for separation of six mAb charge and size variants on a preparative-scale ion exchange chromatographic resin are compared in this study. Results showed that opposite dual salt-pH gradient elution with increasing pH gradient and simultaneously decreasing salt gradient is best suited for the separation of these mAb charge and size variants on Eshmuno ® CPX. Besides giving high binding capacity, this type of opposite dual salt-pH gradient also provides better resolved mAb variant peaks and lower conductivity in the elution pools compared to single pH or salt gradients. To have a mechanistic understanding of the differences in mAb variants retention behaviors of mono pH gradient, parallel dual salt-pH gradient, and opposite dual salt-pH gradient, a linear gradient elution model was used. After determining the model parameters using the linear gradient elution model, 2D plots were used to show the pH and salt dependencies of the reciprocals of distribution coefficient, equilibrium constant, and effective ionic capacity of the mAb variants in these gradient elution systems. Comparison of the 2D plots indicated that the advantage of opposite dual salt-pH gradient system with increasing pH gradient and simultaneously decreasing salt gradient is the noncontinuous increased acceleration of protein migration. Furthermore, the fitted model parameters can be used for the prediction and optimization of mAb variants separation in dual salt-pH gradient and step elution. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018. © 2018 American Institute of Chemical Engineers.

Refuges from ocean acidification: determining tolerances of coralline algae to naturally low-pH water

NASA Astrophysics Data System (ADS)

Cooper, H.; Paytan, A.; Potts, D. C.

2014-12-01

Anthropogenic carbon dioxide dissolving into the world's oceans is causing a profound and rapid shift in ocean chemistry referred to as ocean acidification (OA) that causes carbonate structures to dissolve more readily in seawater with negative effects for organisms relying on calcified skeletons or shells (e.g. corals, mollusks, coralline algae). Crustose coralline algae (CCA) are ubiquitous and essential on coral reefs, providing both ecological and structural benefits to the reefs. However, CCA are adversely affected by low pH water, with severe reductions in recruitment, survival, growth and productivity. The ability of different species of CCA to adapt to low pH waters was tested using a system of natural submarine springs (called "ojos") near Puerto Morelos on the Yucatan Peninsula, Mexico. These ojos continuously discharge groundwater that is close to seawater salinity but more acidic (pH 6.70-7.30) and under saturated (0.3 Ω to 0.97 Ω) than the ambient seawater (pH 8.03, 3.60 Ω ). Both corals and coralline algae grow in the water from these springs, suggesting that some calcifying species differ in their tolerance to low pH waters. Corallines were sampled along a pH gradient at five springs in December 2013 using underwater transects. Differences in percent cover, species abundance and diversity of CCA by pH levels will be discussed. This work utilizes a unique natural laboratory for studying properties of calcifying biota along pH gradients and provides insight into the ability of CCA to tolerate or adapt to future conditions.

Proton gradients in intact cyanobacteria

NASA Technical Reports Server (NTRS)

Belkin, S.; Mehlhorn, R. J.; Packer, L.

1987-01-01

The internal pH values of two unicellular cyanobacterial strains were determined with electron spin resonance probes, over an external pH range of 6 to 9, in the light and in the dark. The slow growing, thylakoid-lacking Gloeobacter violaceus was found to have a low capacity for maintaining a constant internal pH. The distribution pattern of weak acid and amine nitroxide spin probes across the cell membranes of this organism, in the light and in the dark, was consistent with the assumption that it contains a single intracellular compartment. At an external pH of 7.0, intracellular pH was 6.8 in the dark and 7.2 in the light. The cells of Agmenellum quadruplicatum, a marine species, were found to contain two separate compartments; in the dark, the pH of the cytoplasmic and the intrathylakoid spaces were calculated to be 7.2 and 5.5, respectively. Upon illumination, the former increased and the latter decreased by about 0.5 pH units.

Separation of certain carboxylic acids utilizing cation exchange membranes

DOEpatents

Chum, H.L.; Sopher, D.W.

1983-05-09

A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100/sup 0/C and brought in contact with one side of a perfluorinated cation exchange membrane having sulfonate or carboxylate groups or mixtures thereof with the mixture containing the protonated acids. A pressure gradient can be established across the membrane with the mixture being under higher pressure, so that protonated monofunctional lower carboxylic acids pass through the membrane at a substantially faster rate than the remainder of the mixture thereby substantially separating the acids from the mixture.

Separation of certain carboxylic acids utilizing cation exchange membranes

DOEpatents

Chum, Helena L.; Sopher, David W.

1984-01-01

A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100.degree. C. and brought in contact with one side of a perfluorinated cation exchange membrane having sulfonate or carboxylate groups or mixtures thereof with the mixture containing the protonated acids. A pressure gradient can be established across the membrane with the mixture being under higher pressure, so that protonated monofunctional lower carboxylic acids pass through the membrane at a substantially faster rate than the remainder of the mixture thereby substantially separating the acids from the mixture.

The role of groundwater chemistry in the transport of bacteria to water-supply wells

USGS Publications Warehouse

Harvey, R.W.; Metge, D.W.

1999-01-01

Static mini-columns and in situ injection and recovery tests were used to assess the effects of modest changes in groundwater chemistry upon the pH-dependence of bacterial attachment, a primary determinant of bacterial mobility in drinking water aquifers. In uncontaminated groundwater (<1 mg l-1 dissolved organic carbon, DOC), bacterial attachment to aquifer grain surfaces declined steadily from 93 to 20% in response to an increase in pH from 5.8 to 7.8. However, bacterial attachment in modestly-contaminated groundwater (4 mg l-1 DOC) was relatively insensitive to pH change from pH 3.5 to pH 8, as was bacterial attachment in uncontaminated groundwater amended with only ~3 mg l-1 of purified humic acid. Destruction by UV-oxidation of the DOC in contaminated groundwater partially restored the pH-dependence of bacterial attachment. Results from static column tests and from a small-scale (3.6 m) natural-gradient injection and recovery study suggest that low concentrations of surfactants can also substantively alter the attraction of groundwater bacteria for grain surfaces and, therefore can alter the transport of bacteria to water-supply wells. This phenomenon was pH-sensitive and dependent upon the nature of the surfactant. At pH 7.6, 200 mg l-1 of the non-ionic surfactant, Imbentin, caused a doubling of fractional bacterial attachment in aquifer-sediment columns, but had little effect under slightly acidic conditions (e.g. at pH 5.8). In contrast, 1 mg l-1 of linear alkylbenzene sulphonate (LAS) surfactant, a common sewage-derived contaminant, decreased the fractional bacterial attachment by more than 30% at pH 5.8, but had little effect at pH 7.3.Static mini-columns and in situ injection and recovery tests were used to assess the effects of modest changes in groundwater chemistry upon the pH-dependence of bacterial attachment, a primary determinant of bacterial mobility in drinking water aquifers. In uncontaminated groundwater (<1 mg l-1 dissolved organic carbon, DOC), bacterial attachment to aquifer grain surfaces declined steadily from 93 to 20% in response to an increase in pH from 5.8 to 7.8. However, bacterial attachment in modestly-contaminated groundwater (4 mg l-1 DOC) was relatively insensitive to pH change from pH 3.5 to pH 8, as was bacterial attachment in uncontaminated groundwater amended with only approx. 3 mg l-1 of purified humic acid. Destruction of UV-oxidation of the DOC in contaminated groundwater partially restored the pH-dependence of bacterial attachment. Results from the static column tests and from a small-scale (3.6 m) natural-gradient injection and recovery study suggest that low concentrations of surfactants can also substantively alter the attraction of groundwater bacteria for grain surfaces and, therefore can alter the transport of bacteria to water-supply wells. This phenomenon was pH-sensitive and dependent upon the nature of the surfactant. At pH 7.6, 200 mg l-1 of the non-ionic surfactant, Imbentin, caused a doubling of fractional bacterial attachment in aquifer-sediment columns, but had little effect under slightly acidic conditions (e.g. at pH 5.8). In contrast, 1 mg l-1 of linear alkylbenzene sulphonate (LAS) surfactant, a common sewage-derived contaminant, decreased the fractional bacterial attachment by more than 30% at pH 5.8, but had little effect at pH 7.3.

Acidic, neutral and alkaline forest ponds as a landscape element affecting the biodiversity of freshwater snails.

PubMed

Spyra, Aneta

2017-08-22

In recent years, the number of areas remaining under the influence of acidity has increased. At all levels of ecosystems, biodiversity decreases with acidification, due to the elimination of species that are most sensitive to low pH. Forest ponds belong to a specific group that varied in location, a huge amount of leaf litter, and isolation from other aquatic environments. They are crucial in the industrial landscape with well-developed industry and human activity. The aim was to investigate the relative importance of water chemistry in explaining snail assemblage compositions and species richness in forest ponds of contrasting pH. Patterns in gastropod communities were determined from an analysis in 26 forest ponds with multivariate gradient analysis. Ponds ranged in a base mean pH from 3.0 to 9.0. pH has been found to be an important factor influencing gastropod fauna. Neutral ponds support diverse communities, typical of small water bodies. In two acidic pond types, snail fauna was different. Among the species characteristic for acidic ponds (pH < 6) were Anisus spirorbis and Aplexa hypnorum. The greatest distinct characterised alkaline ponds with the numerous appearance of alien Physa acuta. The most diverse gastropod fauna was found in neutral ponds, whereas the lowest degree of diversity was found in ponds with the lowest pH. Current knowledge of pH-associated changes in aquatic ecosystems is still incomplete because anthropogenic acidification is a recent phenomenon. It is extremely important in forest habitats, since they react more intensively to climatic factors and are often used in landscape management and planning.

Tidally driven water column hydro-geochemistry in a remediating acidic wetland

NASA Astrophysics Data System (ADS)

Johnston, Scott G.; Keene, Annabelle F.; Bush, Richard T.; Sullivan, Leigh A.; Wong, Vanessa N. L.

2011-10-01

SummaryManaged tidal inundation is a newly evolved technique for remediating coastal acid sulphate soil (CASS) wetlands. However, there remains considerable uncertainty regarding the hydro-geochemical pathways and spatiotemporal dynamics of residual H + and metal(loid) mobilisation into the tidal fringe surface waters of these uniquely iron-rich landscapes. Here, we examine the hydrology and water column chemistry across the intertidal slope of a remediating CASS wetland during several tide cycles. There was extreme spatial and temporal dynamism in water column chemistry, with pH fluctuating by ˜3 units (˜3.5-6.5) during a single tide cycle. Acute acidity was spatially confined to the upper intertidal slope, reflecting surface sediment properties, and tidal overtopping is an important pathway for mobilisation of residual H + and Al 3+ to the water column. Marine derived HCO3- was depleted from surface waters migrating across the intertidal slope and a strong gradient in HCO3- was observed from the tidal fringe to the adjacent tributary channel and nearby estuary. Tidal forcing generated oscillating hydraulic gradients in the shallow fringing aquifer, favouring ebb-tide seepage and driving rapid, heterogeneous advection of groundwater on the lower intertidal slope via surface connected macropores. A combination of diffusive and advective flux across the sediment-water interface led to persistent, elevated surface water Fe 2+ (˜10-1000 μM). The geochemical processes associated with Fe 2+ mobilisation displayed distinct spatial zonation, with low pH, proton-promoted desorption occurring on the upper intertidal slope, whilst circum-neutral pH, Fe(III)-reducing processes dominated the lower intertidal slope. Arsenic was also mobilised into surface waters on the lower intertidal slope under moderate pH (˜6.0) conditions and was strongly positively correlated with Fe 2+. Saturation index values for aragonite were substantially depressed (-1 to -5) and significantly negatively correlated with elevation, thereby presenting a barrier to re-colonisation of the upper intertidal slope by calcifying benthic organisms. These findings highlight the spatially complex hydrological and geochemical controls on surface water quality that can occur in tidally inundated acid sulphate soil environments.

Synergetic effect of pH and biochemical components on bacterial diversity during mesophilic anaerobic fermentation of biomass-origin waste.

PubMed

Lü, F; Shao, L M; Bru, V; Godon, J J; He, P J

2009-02-01

To investigate the synergetic effect of pH and biochemical components on bacterial community structure during mesophilic anaerobic degradation of solid wastes with different origins, and under acidic or neutral conditions. The bacterial community in 16 samples of solid wastes with different biochemical compositions and origins was evaluated during mesophilic anaerobic degradation at acidic and neutral pH. Denaturing gradient gel electrophoresis (DGGE) and single-strand conformation polymorphism (SSCP) were used to compare the communities. Multivariate analysis of the DGGE and SSCP results revealed that most of the dominant microbes were dependent on the content of easily degradable carbohydrates in the samples. Furthermore, the dominant microbes were divided into two types, those that preferred an acid environment and those that preferred a neutral environment. A shift in pH was found to change their preference for medium substrates. Although most of the substrates with similar origin and biochemical composition had similar microbial diversity during fermentation, some microbes were found only in substrates with specific origins. For example, two microbes were only found in substrate that contained lignocellulose and animal protein without starch. These microbes were related to micro-organisms that are found in swine manure, as well as in other intestinal or oral niches. In addition, the distribution of fermentation products was less sensitive to the changes in pH and biochemical components than the microbial community. Bacterial diversity during anaerobic degradation of organic wastes was affected by both pH and biochemical components; however, pH exerted a greater effect. The results of this study reveal that control of pH may be an effective method to produce a stable bacterial community and relatively similar product distribution during anaerobic digestion of waste, regardless of variation in the waste feedstocks.

Energetics of Amino Acid Synthesis in Alkaline Hydrothermal Environments

NASA Astrophysics Data System (ADS)

Kitadai, Norio

2015-12-01

Alkaline hydrothermal systems have received considerable attention as candidates for the origin and evolution of life on the primitive Earth. Nevertheless, sufficient information has not yet been obtained for the thermodynamic properties of amino acids, which are necessary components for life, at high temperatures and alkaline pH. These properties were estimated using experimental high-temperature volume and heat capacity data reported in the literature for several amino acids, together with correlation algorithms and the revised Helgeson-Kirkham-Flowers (HKF) equations of state. This approach enabled determination of a complete set of the standard molal thermodynamic data and the revised HKF parameters for the 20 protein amino acids in their zwitterionic and ionization states. The obtained dataset was then used to evaluate the energetics of amino acid syntheses from simple inorganic precursors (CO2, H2, NH3 and H2S) in a simulated alkaline hydrothermal system on the Hadean Earth. Results show that mixing between CO2-rich seawater and the H2-rich hydrothermal fluid can produce energetically favorable conditions for amino acid syntheses, particularly in the lower-temperature region of such systems. Together with data related to the pH and temperature dependences of the energetics of amino acid polymerizations presented in earlier reports, these results suggest the following. Hadean alkaline hydrothermal settings, where steep pH and temperature gradients may have existed between cool, slightly acidic Hadean ocean water and hot, alkaline hydrothermal fluids at the vent-ocean interface, may be energetically the most suitable environment for the synthesis and polymerization of amino acids.

Energetics of Amino Acid Synthesis in Alkaline Hydrothermal Environments.

PubMed

Kitadai, Norio

2015-12-01

Alkaline hydrothermal systems have received considerable attention as candidates for the origin and evolution of life on the primitive Earth. Nevertheless, sufficient information has not yet been obtained for the thermodynamic properties of amino acids, which are necessary components for life, at high temperatures and alkaline pH. These properties were estimated using experimental high-temperature volume and heat capacity data reported in the literature for several amino acids, together with correlation algorithms and the revised Helgeson-Kirkham-Flowers (HKF) equations of state. This approach enabled determination of a complete set of the standard molal thermodynamic data and the revised HKF parameters for the 20 protein amino acids in their zwitterionic and ionization states. The obtained dataset was then used to evaluate the energetics of amino acid syntheses from simple inorganic precursors (CO2, H2, NH3 and H2S) in a simulated alkaline hydrothermal system on the Hadean Earth. Results show that mixing between CO2-rich seawater and the H2-rich hydrothermal fluid can produce energetically favorable conditions for amino acid syntheses, particularly in the lower-temperature region of such systems. Together with data related to the pH and temperature dependences of the energetics of amino acid polymerizations presented in earlier reports, these results suggest the following. Hadean alkaline hydrothermal settings, where steep pH and temperature gradients may have existed between cool, slightly acidic Hadean ocean water and hot, alkaline hydrothermal fluids at the vent-ocean interface, may be energetically the most suitable environment for the synthesis and polymerization of amino acids.

Serpentinite and the dawn of life

PubMed Central

Sleep, Norman H.; Bird, Dennis K.; Pope, Emily C.

2011-01-01

Submarine hydrothermal vents above serpentinite produce chemical potential gradients of aqueous and ionic hydrogen, thus providing a very attractive venue for the origin of life. This environment was most favourable before Earth's massive CO2 atmosphere was subducted into the mantle, which occurred tens to approximately 100 Myr after the moon-forming impact; thermophile to clement conditions persisted for several million years while atmospheric pCO2 dropped from approximately 25 bar to below 1 bar. The ocean was weakly acid (pH ∼ 6), and a large pH gradient existed for nascent life with pH 9–11 fluids venting from serpentinite on the seafloor. Total CO2 in water was significant so the vent environment was not carbon limited. Biologically important phosphate and Fe(II) were somewhat soluble during this period, which occurred well before the earliest record of preserved surface rocks approximately 3.8 billion years ago (Ga) when photosynthetic life teemed on the Earth and the oceanic pH was the modern value of approximately 8. Serpentinite existed by 3.9 Ga, but older rocks that might retain evidence of its presence have not been found. Earth's sequesters extensive evidence of Archaean and younger subducted biological material, but has yet to be exploited for the Hadean record. PMID:21930576

Multiple Acid Sensors Control Helicobacter pylori Colonization of the Stomach

PubMed Central

Huang, Julie Y.; Goers Sweeney, Emily; Guillemin, Karen

2017-01-01

Helicobacter pylori’s ability to respond to environmental cues in the stomach is integral to its survival. By directly visualizing H. pylori swimming behavior when encountering a microscopic gradient consisting of the repellent acid and attractant urea, we found that H. pylori is able to simultaneously detect both signals, and its response depends on the magnitudes of the individual signals. By testing for the bacteria’s response to a pure acid gradient, we discovered that the chemoreceptors TlpA and TlpD are each independent acid sensors. They enable H. pylori to respond to and escape from increases in hydrogen ion concentration near 100 nanomolar. TlpD also mediates attraction to basic pH, a response dampened by another chemoreceptor TlpB. H. pylori mutants lacking both TlpA and TlpD (ΔtlpAD) are unable to sense acid and are defective in establishing colonization in the murine stomach. However, blocking acid production in the stomach with omeprazole rescues ΔtlpAD’s colonization defect. We used 3D confocal microscopy to determine how acid blockade affects the distribution of H. pylori in the stomach. We found that stomach acid controls not only the overall bacterial density, but also the microscopic distribution of bacteria that colonize the epithelium deep in the gastric glands. In omeprazole treated animals, bacterial abundance is increased in the antral glands, and gland colonization range is extended to the corpus. Our findings indicate that H. pylori has evolved at least two independent receptors capable of detecting acid gradients, allowing not only survival in the stomach, but also controlling the interaction of the bacteria with the epithelium. PMID:28103315

A Reliable and Non-destructive Method for Monitoring the Stromal pH in Isolated Chloroplasts Using a Fluorescent pH Probe.

PubMed

Su, Pai-Hsiang; Lai, Yen-Hsun

2017-01-01

The proton gradient established by the pH difference across a biological membrane is essential for many physiological processes, including ATP synthesis and ion and metabolite transport. Currently, ionophores are used to study proton gradients, and determine their importance to biological functions of interest. Because of the lack of an easy method for monitoring the proton gradient across the inner envelope membrane of chloroplasts (ΔpH env ), whether the concentration of ionophores used can effectively abolish the ΔpH env is not proven for most experiments. To overcome this hindrance, we tried to setup an easy method for real-time monitoring of the stromal pH in buffered, isolated chloroplasts by using fluorescent pH probes; using this method the ΔpH env can be calculated by subtracting the buffer pH from the measured stromal pH. When three fluorescent dyes, BCECF-AM [2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester], CFDA-SE [5(6)-Carboxyfluorescein diacetate succinimidyl ester] and SNARF-1 carboxylic acid acetate succinimidyl ester were incubated with isolated chloroplasts, BCECF-AM and CFDA-SE, but not the ester-formed SNARF-1 were taken up by chloroplasts and digested with esterase to release high levels of fluorescence. According to its relatively higher pKa value (6.98, near the physiological pH of the stroma), BCECF was chosen for further development. Due to shielding of the excitation and emission lights by chloroplast pigments, the ratiometric fluorescence of BCECF was highly dependent on the concentration of chloroplasts. By using a fixed concentration of chloroplasts, a highly correlated standard curve of pH to the BCECF ratiometric fluorescence with an r -square value of 0.98 was obtained, indicating the reliability of this method. Consistent with previous reports, the light-dependent formation of ΔpH env can be detected ranging from 0.15 to 0.33 pH units upon illumination. The concentration of the ionophore nigericin required to collapse the ΔpH env was then studied. The establishment of a non-destructive method of monitoring the stromal pH will be valuable for studying the roles of the ΔpH env in chloroplast physiology.

Simultaneous determination of 16 purine derivatives in urinary calculi by gradient reversed-phase high-performance liquid chromatography with UV detection.

PubMed

Safranow, Krzysztof; Machoy, Zygmunt

2005-05-25

A reversed-phase high-performance liquid chromatography (HPLC) method with ultraviolet detection has been developed for the analysis of purines in urinary calculi. The method using gradient of methanol concentration and pH was able to separate 16 compounds: uric acid, 2,8-dihydroxyadenine, xanthine, hypoxanthine, allopurinol and oxypurinol as well as 10 methyl derivatives of uric acid or xanthine (1-, 3-, 7- and 9-methyluric acid, 1,3-, 1,7- and 3,7-dimethyluric acid, 1-, 3- and 7-methylxanthine). Limits of detection for individual compounds ranged from 0.006 to 0.035 mg purine/g of the stone weight and precision (CV%) was 0.5-2.4%. The method enabled us to detect in human uric acid stones admixtures of nine other purine derivatives: natural metabolites (hypoxanthine, xanthine, 2,8-dihydroxyadenine) and methylated purines (1-, 3- and 7-methyluric acid, 1,3-dimethyluric acid, 3- and 7-methylxanthine) originating from the metabolism of methylxanthines (caffeine, theophylline and theobromine). The method allows simultaneous quantitation of all known purine constituents of urinary stones, including methylated purines, and may be used as a reference one for diagnosing disorders of purine metabolism and research on the pathogenesis of urolithiasis.

Microbial Diversity of Acidic Hot Spring (Kawah Hujan B) in Geothermal Field of Kamojang Area, West Java-Indonesia

PubMed Central

Aditiawati, Pingkan; Yohandini, Heni; Madayanti, Fida; Akhmaloka

2009-01-01

Microbial communities in an acidic hot spring, namely Kawah Hujan B, at Kamojang geothermal field, West Java-Indonesia was examined using culture dependent and culture independent strategies. Chemical analysis of the hot spring water showed a characteristic of acidic-sulfate geothermal activity that contained high sulfate concentrations and low pH values (pH 1.8 to 1.9). Microbial community present in the spring was characterized by 16S rRNA gene combined with denaturing gradient gel electrophoresis (DGGE) analysis. The majority of the sequences recovered from culture-independent method were closely related to Crenarchaeota and Proteobacteria phyla. However, detail comparison among the member of Crenarchaeota showing some sequences variation compared to that the published data especially on the hypervariable and variable regions. In addition, the sequences did not belong to certain genus. Meanwhile, the 16S Rdna sequences from culture-dependent samples revealed mostly close to Firmicute and gamma Proteobacteria. PMID:19440252

Microbial diversity of acidic hot spring (kawah hujan B) in geothermal field of kamojang area, west java-indonesia.

PubMed

Aditiawati, Pingkan; Yohandini, Heni; Madayanti, Fida; Akhmaloka

2009-01-01

Microbial communities in an acidic hot spring, namely Kawah Hujan B, at Kamojang geothermal field, West Java-Indonesia was examined using culture dependent and culture independent strategies. Chemical analysis of the hot spring water showed a characteristic of acidic-sulfate geothermal activity that contained high sulfate concentrations and low pH values (pH 1.8 to 1.9). Microbial community present in the spring was characterized by 16S rRNA gene combined with denaturing gradient gel electrophoresis (DGGE) analysis. The majority of the sequences recovered from culture-independent method were closely related to Crenarchaeota and Proteobacteria phyla. However, detail comparison among the member of Crenarchaeota showing some sequences variation compared to that the published data especially on the hypervariable and variable regions. In addition, the sequences did not belong to certain genus. Meanwhile, the 16S Rdna sequences from culture-dependent samples revealed mostly close to Firmicute and gamma Proteobacteria.

Acid-tolerant microaerophilic Fe(II)-oxidizing bacteria promote Fe(III)-accumulation in a fen.

PubMed

Lüdecke, Claudia; Reiche, Marco; Eusterhues, Karin; Nietzsche, Sandor; Küsel, Kirsten

2010-10-01

The ecological importance of Fe(II)-oxidizing bacteria (FeOB) at circumneutral pH is often masked in the presence of O(2) where rapid chemical oxidation of Fe(II) predominates. This study addresses the abundance, diversity and activity of microaerophilic FeOB in an acidic fen (pH ∼ 5) located in northern Bavaria, Germany. Mean O(2) penetration depth reached 16 cm where the highest dissolved Fe(II) concentrations (up to 140 µM) were present in soil water. Acid-tolerant FeOB cultivated in gradient tubes were most abundant (10(6) cells g(-1) peat) at the 10-20 cm depth interval. A stable enrichment culture was active at up to 29% O(2) saturation and Fe(III) accumulated 1.6 times faster than in abiotic controls. An acid-tolerant, microaerophilic isolate (strain CL21) was obtained which was closely related to the neutrophilic, lithoautotrophic FeOB Sideroxydans lithotrophicus strain LD-1. CL21 oxidized Fe(II) between pH 4 and 6.0, and produced nanoscale-goethites with a clearly lower mean coherence length (7 nm) perpendicular to the (110) plane than those formed abiotically (10 nm). Our results suggest that an acid-tolerant population of FeOB is thriving at redox interfaces formed by diffusion-limited O(2) transport in acidic peatlands. Furthermore, this well-adapted population is successfully competing with chemical oxidation and thereby playing an important role in the microbial iron cycle. © 2010 Society for Applied Microbiology and Blackwell Publishing Ltd.

Permeability of membranes to amino acids and modified amino acids: mechanisms involved in translocation

NASA Technical Reports Server (NTRS)

Chakrabarti, A. C.; Deamer, D. W. (Principal Investigator); Miller, S. L. (Principal Investigator)

1994-01-01

The amino acid permeability of membranes is of interest because they are one of the key solutes involved in cell function. Membrane permeability coefficients (P) for amino acid classes, including neutral, polar, hydrophobic, and charged species, have been measured and compared using a variety of techniques. Decreasing lipid chain length increased permeability slightly (5-fold), while variations in pH had only minor effects on the permeability coefficients of the amino acids tested in liposomes. Increasing the membrane surface charge increased the permeability of amino acids of the opposite charge, while increasing the cholesterol content decreased membrane permeability. The permeability coefficients for most amino acids tested were surprisingly similar to those previously measured for monovalent cations such as sodium and potassium (approximately 10(-12)-10(-13) cm s-1). This observation suggests that the permeation rates for the neutral, polar and charged amino acids are controlled by bilayer fluctuations and transient defects, rather than partition coefficients and Born energy barriers. Hydrophobic amino acids were 10(2) more permeable than the hydrophilic forms, reflecting their increased partition coefficient values. External pH had dramatic effects on the permeation rates for the modified amino acid lysine methyl ester in response to transmembrane pH gradients. It was established that lysine methyl ester and other modified short peptides permeate rapidly (P = 10(-2) cm s-1) as neutral (deprotonated) molecules. It was also shown that charge distributions dramatically alter permeation rates for modified di-peptides. These results may relate to the movement of peptides through membranes during protein translocation and to the origin of cellular membrane transport on the early Earth.

Confocal Raman Microscopy for pH-Gradient Preconcentration and Quantitative Analyte Detection in Optically Trapped Phospholipid Vesicles.

PubMed

Hardcastle, Chris D; Harris, Joel M

2015-08-04

The ability of a vesicle membrane to preserve a pH gradient, while allowing for diffusion of neutral molecules across the phospholipid bilayer, can provide the isolation and preconcentration of ionizable compounds within the vesicle interior. In this work, confocal Raman microscopy is used to observe (in situ) the pH-gradient preconcentration of compounds into individual optically trapped vesicles that provide sub-femtoliter collectors for small-volume samples. The concentration of analyte accumulated in the vesicle interior is determined relative to a perchlorate-ion internal standard, preloaded into the vesicle along with a high-concentration buffer. As a guide to the experiments, a model for the transfer of analyte into the vesicle based on acid-base equilibria is developed to predict the concentration enrichment as a function of source-phase pH and analyte concentration. To test the concept, the accumulation of benzyldimethylamine (BDMA) was measured within individual 1 μm phospholipid vesicles having a stable initial pH that is 7 units lower than the source phase. For low analyte concentrations in the source phase (100 nM), a concentration enrichment into the vesicle interior of (5.2 ± 0.4) × 10(5) was observed, in agreement with the model predictions. Detection of BDMA from a 25 nM source-phase sample was demonstrated, a noteworthy result for an unenhanced Raman scattering measurement. The developed model accurately predicts the falloff of enrichment (and measurement sensitivity) at higher analyte concentrations, where the transfer of greater amounts of BDMA into the vesicle titrates the internal buffer and decreases the pH gradient. The predictable calibration response over 4 orders of magnitude in source-phase concentration makes it suitable for quantitative analysis of ionizable compounds from small-volume samples. The kinetics of analyte accumulation are relatively fast (∼15 min) and are consistent with the rate of transfer of a polar aromatic molecule across a gel-phase phospholipid membrane.

Lipase activities in castor bean endosperm during germinaion. [Ricinus communis; glyoxysomes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muto, S.; Beevers, H.

1974-01-01

Two lipases were found in extracts from castor bean (Ricinus communis L.) endosperm. One, with optimal activity at pH 5.0 (acid lipase), was present in dry seeds and displayed high activity during the first 2 days of germination. The second, with an alkaline pH optimum (alkaline lipase), was particularly active during days 3 to 5. When total homogenates of endosperm were fractionated into fat layer, supernatant, and particulate fractions, the acid lipase was recovered in the fat layer, and the alkaline lipase was located primarily in the particulate fraction. Sucrose density gradient centrifugation showed that the alkaline lipase was locatedmore » mainly in glyoxysomes, with some 30 percent of the activity in the endoplasmic reticulum. When glyoxysomes were broken by osmotic shock and exposed to KCl, which solubilizes most of the enzymes, the alkaline lipase remained particulate and was recovered with the glyoxysomal ''ghosts'' at equilibrium density 1.21 g/cm/sup 3/ on the sucrose gradient. Association of the lipase with the glyoxysomal membrane was supported by the responses to detergents and to butanol. The alkaline lipase hydrolyzed only monosubstituted glycerols. The roles of the two lipases in lipid utilization during germination of castor bean are discussed.« less

Variation in bacterial ATP concentration during rapid changes in extracellular pH and implications for the activity of attached bacteria.

PubMed

Albert, Lynal S; Brown, Derick G

2015-08-01

In this study we investigated the relationship between a rapid change in extracellular pH and the alteration of bacterial ATP concentration. This relationship is a key component of a hypothesis indicating that bacterial bioenergetics - the creation of ATP from ADP via a proton gradient across the cytoplasmic membrane - can be altered by the physiochemical charge-regulation effect, which results in a pH shift at the bacteria's surface upon adhesion to another surface. The bacterial ATP concentration was measured during a rapid change in extracellular pH from a baseline pH of 7.2 to pH values between 3.5 and 10.5. Experiments were conducted with four neutrophilic bacterial strains, including the Gram-negative Escherichia coli and Pseudomonas putida and the Gram-positive Bacillus subtilis and Staphylococcus epidermidis. A change in bulk pH produced an immediate response in bacterial ATP, demonstrating a direct link between changes in extracellular pH and cellular bioenergetics. In general, the shifts in ATP were similar across the four bacterial strains, with results following an exponential relationship between the extracellular pH and cellular ATP concentration. One exception occurred with S. epidermidis, where there was no variation in cellular ATP at acidic pH values, and this finding is consistent with this species' ability to thrive under acidic conditions. These results provide insight into obtaining a desired bioenergetic response in bacteria through (i) the application of chemical treatments to vary the local pH and (ii) the selection and design of surfaces resulting in local pH modification of attached bacteria via the charge-regulation effect. Copyright © 2015 Elsevier B.V. All rights reserved.

A motor-driven syringe-type gradient maker for forming immobilized pH gradient gels.

PubMed

Fawcett, J S; Sullivan, J V; Chidakel, B E; Chrambach, A

1988-05-01

A motor driven gradient maker based on the commercial model (Jule Inc., Trumbull, CT) was designed for immobilized pH gradient gels to provide small volumes, rapid stirring and delivery, strict volume and temperature control and air exclusion. The device was constructed and by a convenient procedure yields highly reproducible gradients either in solution or on polyacrylamide gels.

Solar energy powered microbial fuel cell with a reversible bioelectrode.

PubMed

Strik, David P B T B; Hamelers, Hubertus V M; Buisman, Cees J N

2010-01-01

The solar energy powered microbial fuel cell is an emerging technology for electricity generation via electrochemically active microorganisms fueled by solar energy via in situ photosynthesized metabolites from algae, cyanobacteria, or living higher plants. A general problem with microbial fuel cells is the pH membrane gradient which reduces cell voltage and power output. This problem is caused by acid production at the anode, alkaline production at the cathode, and the nonspecific proton exchange through the membrane. Here we report a solution for a new kind of solar energy powered microbial fuel cell via development of a reversible bioelectrode responsible for both biocatalyzed anodic and cathodic electron transfer. Anodic produced protons were used for the cathodic reduction reaction which held the formation of a pH membrane gradient. The microbial fuel cell continuously generated electricity and repeatedly reversed polarity dependent on aeration or solar energy exposure. Identified organisms within biocatalyzing biofilm of the reversible bioelectrode were algae, (cyano)bacteria and protozoa. These results encourage application of solar energy powered microbial fuel cells.

Growth condition and bacterial community for maximum hydrolysis of suspended organic materials in anaerobic digestion of food waste-recycling wastewater.

PubMed

Kim, Man Deok; Song, Minkyung; Jo, Minho; Shin, Seung Gu; Khim, Jee Hyeong; Hwang, Seokhwan

2010-02-01

This paper reports the effects of changing pH (5-7) and temperature (T, 40-60 degrees C) on the efficiencies of bacterial hydrolysis of suspended organic matter (SOM) in wastewater from food waste recycling (FWR) and the changes in the bacterial community responsible for this hydrolysis. Maximum hydrolysis efficiency (i.e., 50.5% reduction of volatile suspended solids) was predicted to occur at pH 5.7 and T = 44.5 degrees C. Changes in short-chain volatile organic acid profiles and in acidogenic bacterial communities were investigated under these conditions. Propionic and butyric acids concentrations increased rapidly during the first 2 days of incubation. Several band sequences consistent with Clostridium spp. were detected using denaturing gel gradient electrophoresis. Clostridium thermopalmarium and Clostridium novyi seemed to contribute to butyric acid production during the first 1.5 days of acidification of FWR wastewater, and C. thermopalmarium was a major butyric acid producer afterward. C. novyi was an important propionic acid producer. These two species appear to be important contributors to hydrolysis of SOM in the wastewater. Other acidogenic anaerobes, Aeromonas sharmana, Bacillus coagulans, and Pseudomonas plecoglossicida, were also indentified.

Alkaliphilic Bacteria with Impact on Industrial Applications, Concepts of Early Life Forms, and Bioenergetics of ATP Synthesis

PubMed Central

Preiss, Laura; Hicks, David B.; Suzuki, Shino; Meier, Thomas; Krulwich, Terry Ann

2015-01-01

Alkaliphilic bacteria typically grow well at pH 9, with the most extremophilic strains growing up to pH values as high as pH 12–13. Interest in extreme alkaliphiles arises because they are sources of useful, stable enzymes, and the cells themselves can be used for biotechnological and other applications at high pH. In addition, alkaline hydrothermal vents represent an early evolutionary niche for alkaliphiles and novel extreme alkaliphiles have also recently been found in alkaline serpentinizing sites. A third focus of interest in alkaliphiles is the challenge raised by the use of proton-coupled ATP synthases for oxidative phosphorylation by non-fermentative alkaliphiles. This creates a problem with respect to tenets of the chemiosmotic model that remains the core model for the bioenergetics of oxidative phosphorylation. Each of these facets of alkaliphilic bacteria will be discussed with a focus on extremely alkaliphilic Bacillus strains. These alkaliphilic bacteria have provided a cogent experimental system to probe adaptations that enable their growth and oxidative phosphorylation at high pH. Adaptations are clearly needed to enable secreted or partially exposed enzymes or protein complexes to function at the high external pH. Also, alkaliphiles must maintain a cytoplasmic pH that is significantly lower than the pH of the outside medium. This protects cytoplasmic components from an external pH that is alkaline enough to impair their stability or function. However, the pH gradient across the cytoplasmic membrane, with its orientation of more acidic inside than outside, is in the reverse of the productive orientation for bioenergetic work. The reversed gradient reduces the trans-membrane proton-motive force available to energize ATP synthesis. Multiple strategies are hypothesized to be involved in enabling alkaliphiles to circumvent the challenge of a low bulk proton-motive force energizing proton-coupled ATP synthesis at high pH. PMID:26090360

Alkaliphilic Bacteria with Impact on Industrial Applications, Concepts of Early Life Forms, and Bioenergetics of ATP Synthesis.

PubMed

Preiss, Laura; Hicks, David B; Suzuki, Shino; Meier, Thomas; Krulwich, Terry Ann

2015-01-01

Alkaliphilic bacteria typically grow well at pH 9, with the most extremophilic strains growing up to pH values as high as pH 12-13. Interest in extreme alkaliphiles arises because they are sources of useful, stable enzymes, and the cells themselves can be used for biotechnological and other applications at high pH. In addition, alkaline hydrothermal vents represent an early evolutionary niche for alkaliphiles and novel extreme alkaliphiles have also recently been found in alkaline serpentinizing sites. A third focus of interest in alkaliphiles is the challenge raised by the use of proton-coupled ATP synthases for oxidative phosphorylation by non-fermentative alkaliphiles. This creates a problem with respect to tenets of the chemiosmotic model that remains the core model for the bioenergetics of oxidative phosphorylation. Each of these facets of alkaliphilic bacteria will be discussed with a focus on extremely alkaliphilic Bacillus strains. These alkaliphilic bacteria have provided a cogent experimental system to probe adaptations that enable their growth and oxidative phosphorylation at high pH. Adaptations are clearly needed to enable secreted or partially exposed enzymes or protein complexes to function at the high external pH. Also, alkaliphiles must maintain a cytoplasmic pH that is significantly lower than the pH of the outside medium. This protects cytoplasmic components from an external pH that is alkaline enough to impair their stability or function. However, the pH gradient across the cytoplasmic membrane, with its orientation of more acidic inside than outside, is in the reverse of the productive orientation for bioenergetic work. The reversed gradient reduces the trans-membrane proton-motive force available to energize ATP synthesis. Multiple strategies are hypothesized to be involved in enabling alkaliphiles to circumvent the challenge of a low bulk proton-motive force energizing proton-coupled ATP synthesis at high pH.

Systematic interpolation method predicts protein chromatographic elution with salt gradients, pH gradients and combined salt/pH gradients.

PubMed

Creasy, Arch; Barker, Gregory; Carta, Giorgio

2017-03-01

A methodology is presented to predict protein elution behavior from an ion exchange column using both individual or combined pH and salt gradients based on high-throughput batch isotherm data. The buffer compositions are first optimized to generate linear pH gradients from pH 5.5 to 7 with defined concentrations of sodium chloride. Next, high-throughput batch isotherm data are collected for a monoclonal antibody on the cation exchange resin POROS XS over a range of protein concentrations, salt concentrations, and solution pH. Finally, a previously developed empirical interpolation (EI) method is extended to describe protein binding as a function of the protein and salt concentration and solution pH without using an explicit isotherm model. The interpolated isotherm data are then used with a lumped kinetic model to predict the protein elution behavior. Experimental results obtained for laboratory scale columns show excellent agreement with the predicted elution curves for both individual or combined pH and salt gradients at protein loads up to 45 mg/mL of column. Numerical studies show that the model predictions are robust as long as the isotherm data cover the range of mobile phase compositions where the protein actually elutes from the column. Copyright © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The formation of stable pH gradients with weak monovalent buffers for isoelectric focusing in free solution

NASA Technical Reports Server (NTRS)

Mosher, Richard A.; Thormann, Wolfgang; Graham, Aly; Bier, Milan

1985-01-01

Two methods which utilize simple buffers for the generation of stable pH gradients (useful for preparative isoelectric focusing) are compared and contrasted. The first employs preformed gradients comprised of two simple buffers in density-stabilized free solution. The second method utilizes neutral membranes to isolate electrolyte reservoirs of constant composition from the separation column. It is shown by computer simulation that steady-state gradients can be formed at any pH range with any number of components in such a system.

High-performance cation-exchange chromatofocusing of proteins.

PubMed

Kang, Xuezhen; Frey, Douglas D

2003-03-28

Chromatofocusing using high-performance cation-exchange column packings, as opposed to the more commonly used anion-exchange column packings, is investigated with regard to the performance achieved and the range of applications possible. Linear or convex gradients in the range from pH 2.6 to 9 were formed using a variety of commercially available column packings that provide a buffering capacity in different pH ranges, and either polyampholytes or simple mixtures having a small number (three or fewer) of buffering species as the elution buffer. The resolutions achieved using cation-exchange or anion-exchange chromatofocusing were in general comparable, although for certain pairs of proteins better resolution could be achieved using one type of packing as compared to the other, evidently due to the way electrostatic charges are distributed on the protein surface. Several chromatofocusing methods were investigated that take advantage of the acid-base properties of commercially available cation-exchange column packings. These include the use of gradients with a composite shape, the use of very low pH ranges, and the use of elution buffers containing a single buffering species. The advantages of chromatofocusing over ion-exchange chromatography using a salt gradient at constant pH were illustrated by employing the former method and a cation-exchange column packing to separate beta-lactoglobulins A and B, which is a separation reported to be impossible using the latter method and a cation-exchange column packing. Trends in the apparent isoelectric points determined using cation- and anion-exchange chromatofocusing were interpreted using applicable theories. Results of this study indicate that cation-exchange chromatofocusing is a useful technique which is complementary to anion-exchange chromatofocusing and isoelectric focusing for separating proteins at both the analytical and preparative scales.

Soil microbial community responses to acid exposure and neutralization treatment.

PubMed

Shin, Doyun; Lee, Yunho; Park, Jeonghyun; Moon, Hee Sun; Hyun, Sung Pil

2017-12-15

Changes in microbial community induced by acid shock were studied in the context of potential release of acids to the environment due to chemical accidents. The responses of microbial communities in three different soils to the exposure to sulfuric or hydrofluoric acid and to the subsequent neutralization treatment were investigated as functions of acid concentration and exposure time by using 16S-rRNA gene based pyrosequencing and DGGE (Denaturing Gradient Gel Electrophoresis). Measurements of soil pH and dissolved ion concentrations revealed that the added acids were neutralized to different degrees, depending on the mineral composition and soil texture. Hydrofluoric acid was more effectively neutralized by the soils, compared with sulfuric acid at the same normality. Gram-negative ß-Proteobacteria were shown to be the most acid-sensitive bacterial strains, while spore-forming Gram-positive Bacilli were the most acid-tolerant. The results of this study suggest that the Gram-positive to Gram-negative bacterial ratio may serve as an effective bio-indicator in assessing the impact of the acid shock on the microbial community. Neutralization treatments helped recover the ratio closer to their original values. The findings of this study show that microbial community changes as well as geochemical changes such as pH and dissolved ion concentrations need to be considered in estimating the impact of an acid spill, in selecting an optimal remediation strategy, and in deciding when to end remedial actions at the acid spill impacted site. Copyright © 2017 Elsevier Ltd. All rights reserved.

Gradient HPLC of antibiotics in urine, ground water, chicken muscle, hospital wastewater, and pharmaceutical samples using C-18 and RP-amide columns.

PubMed

Kumar, Ashwini; Kumar Malik, Ashok; Kumar Tewary, Dhananjay; Singh, Baldev

2008-02-01

A simple and highly sensitive high pressure liquid chromatographic (HPLC-UV) method has been developed for the determination of ofloxacin, lomefloxacin, cinoxacin, and nalidixic acid, in mobile phase citrate buffer (0.001 M) of pH 4.5 prepared in water (X), methanol (Y), and ACN (Z) using gradient at a flow rate of 1.0 mL/min by direct UV absorbance detection at lambda = 280 nm. Separation of analytes was studied on the C-18 and RP-amide columns and best results were observed on the RP-amide column with LODs (3.3 x S/m) 0.89, 0.55, 0.67, and 1.41 ng/mL for ofloxacin, lomefloxacin, cinoxacin, and nalidixic acid, respectively, and better RSD than the C-18 column. The recovery of Fluoroquinolones (FQs) in urine, ground water, hospital wastewater, and chicken muscle using this method is more than 90%. The method was successfully applied to the analysis of ofloxacin, lomefloxacin, cinoxacin, and nalidixic acid in urine, ground water, pharmaceutical dosage forms, hospital wastewater, and chicken muscle.

Regulation of intracellular pH in LLC-PK1 cells by Na+/H+ exchange.

PubMed

Montrose, M H; Murer, H

1986-01-01

Suspensions of LLC-PK1 cells (a continuous epitheliod cell line with renal characteristics) are examined for mechanisms of intracellular pH regulation using the fluorescent probe BCECF. Initial experiments determine suitable calibration procedures for use of the BCECF fluorescent signal. They also determine that the cell suspension contains cells which (after 4 hr in suspension) have Na+ and K+ gradients comparable to those of cells in monolayer culture. The steady-state intracellular pH (7.05 +/- 0.01, n = 5) of cells which have recovered in (pH 7.4) Na+-containing medium is not affected over several minutes by addition of 100 microM amiloride or removal of extracellular Na+ (Na+o less than 1 mM). In contrast, when the cells recover from an acid load (caused by NH4 preincubation and removal), the recovery is largely Na+ dependent and is sensitive to 100 microM amiloride. These results suggest that with resting pH near neutrality, both Na+o/H+i and Na+i/H+o exchange reactions are functionally inactive (compared to cellular buffering capacity). In contrast, Na+o/H+i exchange is activated by an increased cellular acid load. This activation may be observed directly either as a stimulation of net H+ efflux or net Na+ influx with decreasing intracellular pH. The extrapolation of this latter data suggests a "set point" of Na+/H+ exchange of approximately pH 7.0, consistent with the observed resting intracellular pH of approximately 7.05.

Counterbalancing hydrodynamic sample distortion effects increases resolution of free-flow zone electrophoresis.

PubMed

Weber, G; Bauer, J

1998-06-01

On fractionation of highly heterogeneous protein mixtures, optimal resolution was achieved by forcing proteins to migrate through a preestablished pH gradient, until they entered a medium with a pH similar but not equal to their pIs. For this purpose, up to seven different media were pumped through the electrophoresis chamber so that they were flowing adjacently to each other, forming a pH gradient declining stepwise from the cathode to the anode. This gradient had a sufficiently strong band-focusing effect to counterbalance sample distortion effects of the flowing medium as proteins approached their isoelectric medium closer than 0.5 pH units. Continuous free-flow zone electrophoresis (FFZE) with high throughput capability was applicable if proteins did not precipitate or aggregate in these media. If components of heterogeneous protein mixtures had already started to precipitate or aggregate, in a medium with a pH exceeding their pI by more than 0.5 pH units, the application of interval modus and media forming flat pH gradients appeared advantageous.

Surprising abundance of Gallionella-related iron oxidizers in creek sediments at pH 4.4 or at high heavy metal concentrations

USGS Publications Warehouse

Fabisch, Maria; Beulig, Felix; Akob, Denise M.; Küsel, Kirsten

2013-01-01

We identified and quantified abundant iron-oxidizing bacteria (FeOB) at three iron-rich, metal-contaminated creek sites with increasing sediment pH from extremely acidic (R1, pH 2.7), to moderately acidic (R2, pH 4.4), to slightly acidic (R3, pH 6.3) in a former uranium-mining district. The geochemical parameters showed little variations over the 1.5 year study period. The highest metal concentrations found in creek sediments always coincided with the lowest metal concentrations in creek water at the slightly acidic site R3. Sequential extractions of R3 sediment revealed large portions of heavy metals (Ni, Cu, Zn, Pb, U) bound to the iron oxide fraction. Light microscopy of glass slides exposed in creeks detected twisted stalks characteristic of microaerobic FeOB of the family Gallionellaceae at R3 but also at the acidic site R2. Sequences related to FeOB such as Gallionella ferruginea, Sideroxydans sp. CL21, Ferritrophicum radicicola, and Acidovorax sp. BrG1 were identified in the sediments. The highest fraction of clone sequences similar to the acidophilic “Ferrovum myxofaciens” was detected in R1. Quantitative PCR using primer sets specific for Gallionella spp., Sideroxydans spp., and “Ferrovum myxofaciens” revealed that ~72% (R2 sediment) and 37% (R3 sediment) of total bacterial 16S rRNA gene copies could be assigned to groups of FeOB with dominance of microaerobic Gallionella spp. at both sites. Gallionella spp. had similar and very high absolute and relative gene copy numbers in both sediment communities. Thus, Gallionella-like organisms appear to exhibit a greater acid and metal tolerance than shown before. Microaerobic FeOB from R3 creek sediment enriched in newly developed metal gradient tubes tolerated metal concentrations of 35 mM Co, 24 mM Ni, and 1.3 mM Cd, higher than those in sediments. Our results will extend the limited knowledge of FeOB at contaminated, moderately to slightly acidic environments.

Simultaneous pH-sensitive and oxygen-sensitive MRI of human gliomas at 3 T using multi-echo amine proton chemical exchange saturation transfer spin-and-gradient echo echo-planar imaging (CEST-SAGE-EPI).

PubMed

Harris, Robert J; Yao, Jingwen; Chakhoyan, Ararat; Raymond, Catalina; Leu, Kevin; Liau, Linda M; Nghiemphu, Phioanh L; Lai, Albert; Salamon, Noriko; Pope, Whitney B; Cloughesy, Timothy F; Ellingson, Benjamin M

2018-04-06

To introduce a new pH-sensitive and oxygen-sensitive MRI technique using amine proton CEST echo spin-and-gradient echo (SAGE) EPI (CEST-SAGE-EPI). pH-weighting was obtained using CEST estimations of magnetization transfer ratio asymmetry (MTR asym ) at 3 ppm, and oxygen-weighting was obtained using R2' measurements. Glutamine concentration, pH, and relaxation rates were varied in phantoms to validate simulations and estimate relaxation rates. The values of MTR asym and R2' in normal-appearing white matter, T 2 hyperintensity, contrast enhancement, and macroscopic necrosis were measured in 47 gliomas. Simulation and phantom results confirmed an increase in MTR asym with decreasing pH. The CEST-SAGE-EPI estimates of R 2 , R2*, and R2' varied linearly with gadolinium diethylenetriamine penta-acetic acid concentration (R 2  = 6.2 mM -1 ·sec -1 and R2* = 6.9 mM -1 ·sec -1 ). The CEST-SAGE-EPI and Carr-Purcell-Meiboom-Gill estimates of R 2 (R 2  = 0.9943) and multi-echo gradient-echo estimates of R2* (R 2  = 0.9727) were highly correlated. T 2 lesions had lower R2' and higher MTR asym compared with normal-appearing white matter, suggesting lower hypoxia and high acidity, whereas contrast-enhancement tumor regions had elevated R2' and MTR asym , indicating high hypoxia and acidity. The CEST-SAGE-EPI technique provides simultaneous pH-sensitive and oxygen-sensitive image contrasts for evaluation of the brain tumor microenvironment. Advantages include fast whole-brain acquisition, in-line B 0 correction, and simultaneous estimation of CEST effects, R 2 , R2*, and R2' at 3 T. © 2018 International Society for Magnetic Resonance in Medicine.

In vivo intracellular pH measurements in tobacco and Arabidopsis reveal an unexpected pH gradient in the endomembrane system.

PubMed

Martinière, Alexandre; Bassil, Elias; Jublanc, Elodie; Alcon, Carine; Reguera, Maria; Sentenac, Hervé; Blumwald, Eduardo; Paris, Nadine

2013-10-01

The pH homeostasis of endomembranes is essential for cellular functions. In order to provide direct pH measurements in the endomembrane system lumen, we targeted genetically encoded ratiometric pH sensors to the cytosol, the endoplasmic reticulum, and the trans-Golgi, or the compartments labeled by the vacuolar sorting receptor (VSR), which includes the trans-Golgi network and prevacuoles. Using noninvasive live-cell imaging to measure pH, we show that a gradual acidification from the endoplasmic reticulum to the lytic vacuole exists, in both tobacco (Nicotiana tabacum) epidermal (ΔpH -1.5) and Arabidopsis thaliana root cells (ΔpH -2.1). The average pH in VSR compartments was intermediate between that of the trans-Golgi and the vacuole. Combining pH measurements with in vivo colocalization experiments, we found that the trans-Golgi network had an acidic pH of 6.1, while the prevacuole and late prevacuole were both more alkaline, with pH of 6.6 and 7.1, respectively. We also showed that endosomal pH, and subsequently vacuolar trafficking of soluble proteins, requires both vacuolar-type H(+) ATPase-dependent acidification as well as proton efflux mediated at least by the activity of endosomal sodium/proton NHX-type antiporters.

Effect of a pH Gradient on the Protonation States of Cytochrome c Oxidase: A Continuum Electrostatics Study.

PubMed

Magalhães, Pedro R; Oliveira, A Sofia F; Campos, Sara R R; Soares, Cláudio M; Baptista, António M

2017-02-27

Cytochrome c oxidase (CcO) couples the reduction of dioxygen to water with transmembrane proton pumping, which leads to the generation of an electrochemical gradient. In this study we analyze how one of the components of the electrochemical gradient, the difference in pH across the membrane, or ΔpH, influences the protonation states of residues in CcO. We modified our continuum electrostatics/Monte Carlo (CE/MC) method in order to include the ΔpH and applied it to the study of CcO, in what is, to our best knowledge, the first CE/MC study of CcO in the presence of a pH gradient. The inclusion of a transmembrane pH gradient allows for the identification of residues whose titration behavior depends on the pH on both sides of the membrane. Among the several residues with unusual titration profiles, three are well-known key residues in the proton transfer process of CcO: E286 I , Y288 I , and K362 I . All three residues have been previously identified as being critical for the catalytic or proton pumping functions of CcO. Our results suggest that when the pH gradient increases, these residues may be part of a regulatory mechanism to stem the proton flow.

Control of electron transfer in the cytochrome system of mitochondria by pH, transmembrane pH gradient and electrical potential. The cytochromes b-c segment.

PubMed

Papa, S; Lorusso, M; Izzo, G; Capuano, F

1981-02-15

1. A study is presented of the effects of pH, transmembrane pH gradient and electrical potential on oxidoreductions of b and c cytochromes in ox heart mitochondria and 'inside-out' submitochondrial particles. 2. Kinetic analysis shows that, in mitochondria at neutral pH, there is a restraint on the aerobic oxidation of cytochrome b566 with respect to cytochrome b562. Valinomycin plus K+ accelerates cytochrome b566 oxidation and retards net oxidation of cytochrome b562. At alkaline pH the rate of cytochrome b566 oxidation approaches that of cytochrome b562 and the effects of valinomycin on b cytochromes are impaired. 3. At slightly acidic pH, oxygenation of antimycin-supplemented mitochondria causes rapid reduction of cytochrome b566 and small delayed reduction of cytochrome b562. Valinomycin or a pH increase in the medium promote reduction of cytochrome b562 and decrease net reduction of cytochrome b566. 4. Addition of valinomycin to mitochondria and submitochondrial particles in the respiring steady state causes, at pH values around neutrality, preferential oxidation of cytochrome b566 with respect to cytochrome b562. The differential effect of valinomycin on oxidation of cytochromes b566 and b562 is enhanced by substitution of 1H2O of the medium with 2H2O and tends to disappear as the pH of the medium is raised to alkaline values. 5. Nigericin addition in the aerobic steady state causes, both in mitochondria and submitochondrial particles, preferential oxidation of cytochrome b562 with respect to cytochrome b566. This is accompanied by c cytochrome oxidation in mitochondria but c cytochrome reduction in submitochondrial particles. 6. In mitochondria as well as in submitochondrial particles, the aerobic transmembrane potential (delta psi) does not change by raising the pH of the external medium from neutrality to alkalinity. The transmembrane pH gradient (delta pH) on the other hand, decrease slightly. 7. The results presented provide evidence that the delta psi component of the aerobic delta microH+ (the sum of the proton chemical and electrical activities) exerts a pH-dependent constraint on forward electron flow from cytochrome b566 to cytochrome b562. This effect is explained as a consequence of anisotropic location of cytochromes b566 and b562 in the membrane and the pH-dependence of the redox function of these cytochromes. Transmembrane delta pH, on the other hand, exerts control on electron flow from cytochrome b562 to c cytochromes.

Evidence for the Stepwise Stress Model: Gambusia holbrooki and Daphnia magna under acid mine drainage and acidified reference water stress.

PubMed

Gerhardt, Almut; Janssens de Bisthoven, Luc; Soares, Amadeu M V

2005-06-01

The Stepwise Stress Model (SSM) states that a cascade of regulative behavioral responses with different intrinsic sensitivities and threshold values offers increased behavioral plasticity and thus a wider range of tolerance for environmental changes or pollutant exposures. We tested the SSM with a widely introduced fish Gambusia holbrooki (Girard) (Pisces, Poeciliidae) and the standard laboratory test species Daphnia magna Straus (Crustacea, Daphniidae). The stress was simulated by short-term exposure to acid mine drainage (AMD) and to acidified reference water (ACID). Recording of behavioral responses with the multispecies freshwater biomonitor (MFB) generated continuous time-dependent dose-response data that were modeled in three-dimensional (3D) surface plots. Both the pH-dependent mortalities and the strong linear correlations between pH and aqueous metals confirmed the toxicity of the AMD and ACID gradients, respectively, for fish and Daphnia, the latter being more sensitive. AMD stress at pH < or = 5.5 amplified circadian rhythmicity in both species, while ACID stress did so only in G. holbrooki. A behavioral stepwise stress response was found in both species: D. magna decreased locomotion and ventilation (first step) (AMD, ACID), followed by increased ventilation (second step) (AMD). G. holbrooki decreased locomotion (first step) (AMD, ACID) and increased ventilation at intermediate pH levels (second step) (AMD). Both species, although from different taxonomic groups and feeding habits, followed the SSM, which might be expanded to a general concept for describing the behavioral responses of aquatic organims to pollution. Stepwise stress responses might be applied in online biomonitors to provide more sensitive and graduated alarm settings, hence optimizing the "early warning" detection of pollution waves.

Metal resistance in acidophilic microorganisms and its significance for biotechnologies.

PubMed

Dopson, Mark; Holmes, David S

2014-10-01

Extremely acidophilic microorganisms have an optimal pH of <3 and are found in all three domains of life. As metals are more soluble at acid pH, acidophiles are often challenged by very high metal concentrations. Acidophiles are metal-tolerant by both intrinsic, passive mechanisms as well as active systems. Passive mechanisms include an internal positive membrane potential that creates a chemiosmotic gradient against which metal cations must move, as well as the formation of metal sulfate complexes reducing the concentration of the free metal ion. Active systems include efflux proteins that pump metals out of the cytoplasm and conversion of the metal to a less toxic form. Acidophiles are exploited in a number of biotechnologies including biomining for sulfide mineral dissolution, biosulfidogenesis to produce sulfide that can selectively precipitate metals from process streams, treatment of acid mine drainage, and bioremediation of acidic metal-contaminated milieux. This review describes how acidophilic microorganisms tolerate extremely high metal concentrations in biotechnological processes and identifies areas of future work that hold promise for improving the efficiency of these applications.

Remote-loading labeling of liposomes with (99m)Tc-BMEDA and its stability evaluation: effects of lipid formulation and pH/chemical gradient.

PubMed

Li, Shihong; Goins, Beth; Phillips, William T; Bao, Ande

2011-03-01

Efficient, convenient, and stable radiolabeling plays a critical role for the monitoring of liposome behavior via either blood sampling, organ distribution, or noninvasive nuclear imaging. The direct labeling of liposome-carrying drugs without any prior modification undoubtedly is convenient and optimal for liposomal drug testing. In this article, we investigated the effect of various lipid formulations and pH/chemical gradients on the radiolabeling efficiency and entrapment stability of technetium-99m ((99m)Tc) remotely loaded into liposomes, using (99m)Tc-N,N-bis(2-mercaptoethyl)-N',N'-diethyl-ethylenediamine ((99m)Tc-BMEDA) complex. The tested liposomes either contained unsaturated lipid or possessed various surface charges. (99m)Tc could be efficiently loaded into various premanufactured liposomes containing either an ammonium sulfate pH, citrate pH, or glutathione (GSH) chemical gradient. (99m)Tc-entrapment stabilities of these liposomes in phosphate-buffered saline (PBS; pH 7.4) buffer at 25°C were mainly dependent on the pH/chemical gradient, but not lipid formulation. Stability sequence was ammonium sulfate pH-gradient>citrate pH-gradient>GSH-gradient. Stabilities of (99m)Tc-liposomes in 50% fetal bovine serum (FBS)/PBS (pH 7.4) buffer at 37°C are dependent on both lipid formulation and pH/chemical gradient. Specifically, (99m)Tc labeling of the ammonium sulfate pH-gradient liposomes were less stable in 50% FBS/PBS than in PBS, whereas noncationic liposomes with citrate pH- or GSH-gradient displayed higher stability, except that anionic citrate pH-gradient liposomes showed no stability difference in these two media. Cationic liposomes aggregated in 50% FBS/PBS, forming a new discrete fraction with larger particle sizes. These in vitro characterization results have indicated the optimism of using (99m)Tc-BMEDA for labeling pH/GSH gradient liposomes without the requirement of modifying lipid formulation for liposomal therapeutic-agent development.

Opposing Seasonal Trends in Seawater pH and Aragonite Saturation State on the Bermuda Coral Reef Platform Reveal Complex Controls on Seawater Chemistry by Biological and Physical Processes

NASA Astrophysics Data System (ADS)

Andersson, A. J.; Bates, N. R.; dePutron, S.; Collins, A.; Neely, K.; Best, M.; Noyes, T.

2011-12-01

To accurately predict future consequences of ocean acidification on coastal environments and ecosystems, it is critical to understand present conditions and variability. As part of the Bermuda ocean acidification and coral reef investigation (BEACON), significant efforts have been dedicated to characterize the complete surface seawater carbonic-acid system at different temporal and spatial scales on the Bermuda coral reef platform to understand current levels and variability in seawater CO2 parameters, reef metabolism, and future potential changes arising from ocean acidification. A four years monthly time-series of seawater carbonic-acid parameters at eight different locations on the Bermuda coral reef platform reveals strong seasonal patterns in dissolved inorganic carbon (DIC), total alkalinity (TA), pH, pCO2, and [HCO3-], and somewhat weaker trends in [CO32-] and saturation state with respect to CaCO3 minerals. Strong spatial gradients are also observed in DIC and TA during summertime owing to reef metabolism, but no or weak spatial gradients of these parameters are observed in the wintertime. Interestingly, maximum pH-sws (~8.15) is observed during wintertime when minimum aragonite saturation state (<3.0) is observed. In contrast, minimum pH-sws (~7.95) is observed in the summertime when maximum aragonite saturation state (>3.70) is observed. The observed trends and gradients point to complex relationships and interactions between seawater chemistry, biology and physics that need to be considered in the context of ocean acidification and in making future predictions on the effects of this perturbation on coral reefs and coastal ecosystems.

Iron Hydroxide Minerals Drive Organic and Phosphorus Chemistry in Subsurface Redox / pH Gradients

NASA Astrophysics Data System (ADS)

Flores, E.; Barge, L. M.; VanderVelde, D.; Baum, M.

2017-12-01

Iron minerals, particularly iron oxides and oxyhydroxides, are prevalent on Mars and may exist in mixed valence or even reduced states beneath the oxidized surface. Iron (II,III) hydroxides, including green rust, are reactive and potentially catalytic minerals that can absorb and concentrate charged species, while also driving chemical reactions. These minerals are highly redox-sensitive and the presence of organics and/or phosphorus species could affect their mineralogy and/or stability. Conversely, the minerals might be able to drive chemical processes such as amino acid formation, phosphorus oxyanion reactions, or could simply selectively preserve organic species via surface adsorption. In an open aqueous sediment column, soluble products of mineral-driven reactions could also diffuse to sites of different chemical conditions to react even further. We synthesized Fe-hydroxide minerals under various conditions relevant to early Earth and ancient Mars (>3.0 Gyr), anoxically and in the presence of salts likely to have been present in surface or ground waters. Using these minerals we conducted experiments to test whether iron hydroxides could promote amino acid formation, and how the reaction is affected by subsurface gradients of redox, pH, and temperature. We also tested the adsorption of organic and phosphorus species onto Fe-hydroxide minerals at different conditions within the gradients. The suite of organic or phosphorus signatures that may be found in a particular mineral system is a combination of what is synthesized there, what is preferentially concentrated / retained there, and what is preserved against degradation. Further work is needed to determine how these processes could have proceeded on Mars and what mineral-organic signatures, abiotic or otherwise, would be produced from such processes.

Development of novel separation techniques for biological samples in capillary electrophoresis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Huan -Tsung

1994-07-27

This dissertation includes three different topics: general introduction of capillary electrophoresis (CE); gradient in CE and CE in biological separations; and capillary gel electrophoresis (CGE) for DNA separation. Factors such as temperature, viscosity, pH, and the surface of capillary walls affecting the separation performance are demonstrated. A pH gradient between 3.0 and 5.2 is useful to improve the resolution among eight different organic acids. A flow gradient due to the change in the concentration of surfactant, which is able to coat to the capillary wall to change the flow rate and its direction, is also shown as a good waymore » to improve the resolution for organic compounds. A temperature gradient caused by joule heat is shown by voltage programming to enhance the resolution and shorten the separation time for several phenolic compounds. The author also shows that self-regulating dynamic control of electroosmotic flow in CE by simply running separation in different concentrations of surfactant has less matrix effect on the separation performance. One of the most important demonstrations in this dissertation is that the author proposes on-column reaction which gives several advantages including the use of a small amount of sample, low risk of contamination, and time saving and kinetic features. The author uses this idea with laser induced fluorescence (LIF) as a detection mode to detect an on-column digestion of sub-ng of protein. This technique also is applied to single cell analysis in the group.« less

A macrocyclic polyamine as an anion receptor in the capillary electrochromatographic separation of carbohydrates.

PubMed

Liu, Chuen-Ying; Chen, Tse-Hsien; Misra, Tarun Kumar

2007-06-22

An analytical approach of the 32-membered macrocyclic polyamine, 1,5,9,13,17,21,25,29-octaazacyclodotriacontane ([32]ane-N8) was described for the capillary electrochromatographic (CEC) separation of derivatized mono- and disaccharides. The column displayed reversal electroosmotic flow (EOF) at pH below 7.0, while a cathodic EOF was shown at pH above 7.0. The reductive amination of saccharides was carried out with p-aminobenzoic acid. Some parameters that affect the CEC separations were investigated. Several competitive ligands, such as Tris, EDTA and phosphate were also examined for the effect on the performance. We achieved a complete separation of all compounds as well as the excess derivatizing agent by using borate buffer (pH 9.0) in a mode of concentration gradient (60 mM inlet side and 70 mM outlet side). The relative standard deviation of the retention time measured for each sample was less than 4% in six continuous runs, suggesting that the bonded phase along with the gradient formed inside the column was quite stable. With the mixing modes of anion coordination, anion exchange, and shape discrimination, the interaction adequately accomplishes the separation of carbohydrates which are epimers or have different glycosidic linkage, although the electrophoretic migration is also involved in the separation mechanism.

Multifarious selection through environmental change: acidity and predator-mediated adaptive divergence in the moor frog (Rana arvalis)

PubMed Central

Egea-Serrano, Andrés; Hangartner, Sandra; Laurila, Anssi; Räsänen, Katja

2014-01-01

Environmental change can simultaneously cause abiotic stress and alter biological communities, yet adaptation of natural populations to co-changing environmental factors is poorly understood. We studied adaptation to acid and predator stress in six moor frog (Rana arvalis) populations along an acidification gradient, where abundance of invertebrate predators increases with increasing acidity of R. arvalis breeding ponds. First, we quantified divergence among the populations in anti-predator traits (behaviour and morphology) at different rearing conditions in the laboratory (factorial combinations of acid or neutral pH and the presence or the absence of a caged predator). Second, we evaluated relative fitness (survival) of the populations by exposing tadpoles from the different rearing conditions to predation by free-ranging dragonfly larvae. We found that morphological defences (relative tail depth) as well as survival of tadpoles under predation increased with increasing pond acidity (under most experimental conditions). Tail depth and larval size mediated survival differences among populations, but the contribution of trait divergence to survival was strongly dependent on prior rearing conditions. Our results indicate that R. arvalis populations are adapted to the elevated predator pressure in acidified ponds and emphasize the importance of multifarious selection via both direct (here: pH) and indirect (here: predators) environmental changes. PMID:24552840

Multifarious selection through environmental change: acidity and predator-mediated adaptive divergence in the moor frog (Rana arvalis).

PubMed

Egea-Serrano, Andrés; Hangartner, Sandra; Laurila, Anssi; Räsänen, Katja

2014-04-07

Environmental change can simultaneously cause abiotic stress and alter biological communities, yet adaptation of natural populations to co-changing environmental factors is poorly understood. We studied adaptation to acid and predator stress in six moor frog (Rana arvalis) populations along an acidification gradient, where abundance of invertebrate predators increases with increasing acidity of R. arvalis breeding ponds. First, we quantified divergence among the populations in anti-predator traits (behaviour and morphology) at different rearing conditions in the laboratory (factorial combinations of acid or neutral pH and the presence or the absence of a caged predator). Second, we evaluated relative fitness (survival) of the populations by exposing tadpoles from the different rearing conditions to predation by free-ranging dragonfly larvae. We found that morphological defences (relative tail depth) as well as survival of tadpoles under predation increased with increasing pond acidity (under most experimental conditions). Tail depth and larval size mediated survival differences among populations, but the contribution of trait divergence to survival was strongly dependent on prior rearing conditions. Our results indicate that R. arvalis populations are adapted to the elevated predator pressure in acidified ponds and emphasize the importance of multifarious selection via both direct (here: pH) and indirect (here: predators) environmental changes.

Chromatofocusing and isoelectric focusing in immobilized pH gradients compared for characterization of human hemoglobin variants.

PubMed

Paleari, R; Arcelloni, C; Paroni, R; Fermo, I; Mosca, A

1989-03-01

We compared the performance of two highly resolving methods, chromatofocusing (CRF) and isoelectric focusing in immobilized pH gradients (IPGF), for the separation of human hemoglobin variants. Lysates containing 13 different hemoglobins, including variants of clinical and geographical importance, and four electrophoretically "silent" variants (Hb Brockton, Hb Cheverly, Hb Köln, and Hb Waco) were analyzed. Both techniques showed a good intrarun precision (CV = 0.87% for CRF, 0.27% for IPGF) and high and similar resolving power (0.010 pH units, with the pH gradients used in this work). The use of an ultranarrow IPGF range (pH 7.15-7.35; pH gradient = 0.019 pH/cm) allowed the resolution between Hb Brockton, Hb Köln, and Hb A. In some cases (Hb D-Los Angeles, Hb F, Hb Waco), the variants were separated from Hb A in different orders, depending on which technique was used, probably because of the different analytical principles of the two methods. As a second-level test, both procedures are informative for characterization of human hemoglobin variants.

Viscous fingering of HCI through gastric mucin

NASA Astrophysics Data System (ADS)

Bhaskar, K. Ramakrishnan; Garik, Peter; Turner, Bradley S.; Bradley, James Douglas; Bansil, Rama; Stanley, H. Eugene; Lamont, J. Thomas

1992-12-01

THE HCI in the mammalian stomach is concentrated enough to digest the stomach itself, yet the gastric epithelium remains undamaged. One protective factor is gastric mucus, which forms a protective layer over the surface epithelium1-4 and acts as a diffusion barrier5,6 Bicarbonate ions secreted by the gastric epithelium7 are trapped in the mucus gel, establishing a gradient from pH 1-2 at the lumen to pH 6-7 at the cell surface8-10. How does HCI, secreted at the base of gastric glands by parietal cells, traverse the mucus layer without acidifying it? Here we demonstrate that injection of HCI through solutions of pig gastric mucin produces viscous fingering patterns11-18 dependent on pH, mucin concentration and acid flow rate. Above pH 4, discrete fingers are observed, whereas below pH 4, HCI neither penetrates the mucin solution nor forms fingers. Our in vitro results suggest that HCI secreted by the gastric gland can penetrate the mucus gel layer (pH 5-7) through narrow fingers, whereas HC1 in the lumen (pH 2) is prevented from diffusing back to the epithelium by the high viscosity of gastric mucus gel on the luminal side.

Proton motive force, energy recycling by end product excretion, and metabolic uncoupling during anaerobic growth of Pseudomonas mendocina.

PubMed Central

Verdoni, N; Aon, M A; Lebeault, J M; Thomas, D

1990-01-01

Batch cultures of Pseudomonas mendocina, grown in rich medium with glucose excess, showed metabolic differences dependent upon whether the growth conditions were aerobic or anaerobic, with or without added electron acceptor. Under anaerobic conditions in the absence of nitrate, P. mendocina reached the stationary phase of growth after 2 or 3 days, followed by a stationary phase of 4 to 5 days. Under these conditions, a mixed-type fermentative metabolism (formic, lactic, and acetic acids) appeared. A fivefold-higher specific rate of glucose consumption and eightfold-higher production of organic acids, compared with aerobic cultures, were shown by this microorganism growing anaerobically in the absence of exogenous electron acceptors. The gradients of organic acid produced by P. mendocina under these conditions reached a maximum (lactate, 180 mV; formate, 150 mV; acetate, 215 mV) between days 2 and 3 of culture. The proton motive force (delta p) decreased during growth from -254 to -71 mV. The intracellular pH remained alkaline during the culture, reaching a steady-state value of 7.9. The gradients of organic acids apparently contributed to the generation of a delta p, which, according to the Energy Recycling Model (P. A. M. Michels, J. P. J. Michels, J. Boonstra, and W. N. Konings, FEMS Microbiol. Lett. 5:357-364, 1979), would produce an average energy gain of 1 or 1.5 mol of ATP equivalents per mol of glucose consumed with H+/ATP stoichiometry of 3 or 2, respectively. Low YATP and Yglucose values were observed, suggesting that an uncoupled metabolism exists; i.e., ATP produced by catabolic processes is not directly used for biomass synthesis. This metabolic uncoupling could be induced at least in part by organic acids and the ATP wastage could be induced by a membrane-bound ATPase involved in intracellular pH regulation. PMID:2254245

Stream pH as an abiotic gradient influencing distributions of trout in Pennsylvania streams

USGS Publications Warehouse

Kocovsky, P.M.; Carline, R.F.

2005-01-01

Elevation and stream slope are abiotic gradients that limit upstream distributions of brook trout Salvelinus fontinalis and brown trout Salmo trutta in streams. We sought to determine whether another abiotic gradient, base-flow pH, may also affect distributions of these two species in eastern North America streams. We used historical data from the Pennsylvania Fish and Boat Commission's fisheries management database to explore the effects of reach elevation, slope, and base-flow pH on distributional limits to brook trout and brown trout in Pennsylvania streams in the Appalachian Plateaus and Ridge and Valley physiographic provinces. Discriminant function analysis (DFA) was used to calculate a canonical axis that separated allopatric brook trout populations from allopatric brown trout populations and allowed us to assess which of the three independent variables were important gradients along which communities graded from allopatric brook trout to allopatric brown trout. Canonical structure coefficients from DFA indicated that in both physiographic provinces, stream base-flow pH and slope were important factors in distributional limits; elevation was also an important factor in the Ridge and Valley Province but not the Appalachian Plateaus Province. Graphs of each variable against the proportion of brook trout in a community also identified apparent zones of allopatry for both species on the basis of pH and stream slope. We hypothesize that pH-mediated interspecific competition that favors brook trout in competition with brown trout at lower pH is the most plausible mechanism for segregation of these two species along pH gradients. Our discovery that trout distributions in Pennsylvania are related to stream base-flow pH has important implications for brook trout conservation in acidified regions. Carefully designed laboratory and field studies will be required to test our hypothesis and elucidate the mechanisms responsible for the partitioning of brook trout and brown trout along pH gradients. ?? Copyright by the American Fisheries Society 2005.

Non-invasive technique to measure biogeochemical parameters (pH and O2) in a microenvironment: Design and applications

NASA Astrophysics Data System (ADS)

Li, Biting; Seliman, Ayman; Pales, Ashley; Liang, Weizhen; Sams, Allison; Darnault, Christophe; Devol, Timothy

2017-04-01

The primary objectives of this research are to do the pH and O2 sensor foils calibration and then to test them in applications. Potentially, this project can be utilized to monitor the fate and transport of radionuclides in porous media. The information for physical and chemical parameters (e.g. pH and O2) is crucial to know when determining contaminants' behavior and transport in the environment. As a non-invasive method, optical imaging technique using a DSLR camera could capture data on the foil when it fluoresces, and gives a high temporal and spatial resolution during the experimental period. The calibration procedures were done in cuvettes in a row. The preliminary experiments could measure pH value in the range from 4.5 to 7.5, and O2 concentration from 0 mg/L to 20.74 mg/L. Applications of sensor foils have involved nano zero valent and acid rain experiments in order to obtain a gradient of parameter changes.

Currents through Hv1 channels deplete protons in their vicinity.

PubMed

De-la-Rosa, Víctor; Suárez-Delgado, Esteban; Rangel-Yescas, Gisela E; Islas, León D

2016-02-01

Proton channels have evolved to provide a pH regulatory mechanism, affording the extrusion of protons from the cytoplasm at all membrane potentials. Previous evidence has suggested that channel-mediated acid extrusion could significantly change the local concentration of protons in the vicinity of the channel. In this work, we directly measure the proton depletion caused by activation of Hv1 proton channels using patch-clamp fluorometry recordings from channels labeled with the Venus fluorescent protein at intracellular domains. The fluorescence of the Venus protein is very sensitive to pH, thus behaving as a genetically encoded sensor of local pH. Eliciting outward proton currents increases the fluorescence intensity of Venus. This dequenching is related to the magnitude of the current and not to channel gating and is dependent on the pH gradient. Our results provide direct evidence of local proton depletion caused by flux through the proton-selective channel. © 2016 De-la-Rosa et al.

Genome-Wide Analysis Reveals the Vacuolar pH-Stat of Saccharomyces cerevisiae

PubMed Central

Brett, Christopher L.; Kallay, Laura; Hua, Zhaolin; Green, Richard; Chyou, Anthony; Zhang, Yongqiang; Graham, Todd R.; Donowitz, Mark; Rao, Rajini

2011-01-01

Protons, the smallest and most ubiquitous of ions, are central to physiological processes. Transmembrane proton gradients drive ATP synthesis, metabolite transport, receptor recycling and vesicle trafficking, while compartmental pH controls enzyme function. Despite this fundamental importance, the mechanisms underlying pH homeostasis are not entirely accounted for in any organelle or organism. We undertook a genome-wide survey of vacuole pH (pHv) in 4,606 single-gene deletion mutants of Saccharomyces cerevisiae under control, acid and alkali stress conditions to reveal the vacuolar pH-stat. Median pHv (5.27±0.13) was resistant to acid stress (5.28±0.14) but shifted significantly in response to alkali stress (5.83±0.13). Of 107 mutants that displayed aberrant pHv under more than one external pH condition, functional categories of transporters, membrane biogenesis and trafficking machinery were significantly enriched. Phospholipid flippases, encoded by the family of P4-type ATPases, emerged as pH regulators, as did the yeast ortholog of Niemann Pick Type C protein, implicated in sterol trafficking. An independent genetic screen revealed that correction of pHv dysregulation in a neo1ts mutant restored viability whereas cholesterol accumulation in human NPC1−/− fibroblasts diminished upon treatment with a proton ionophore. Furthermore, while it is established that lumenal pH affects trafficking, this study revealed a reciprocal link with many mutants defective in anterograde pathways being hyperacidic and retrograde pathway mutants with alkaline vacuoles. In these and other examples, pH perturbations emerge as a hitherto unrecognized phenotype that may contribute to the cellular basis of disease and offer potential therapeutic intervention through pH modulation. PMID:21423800

Correlating Microbial Diversity Patterns with Geochemistry in an Extreme and Heterogeneous Environment of Mine Tailings

PubMed Central

Liu, Jun; Hua, Zheng-Shuang; Chen, Lin-Xing; Kuang, Jia-Liang; Li, Sheng-Jin; Shu, Wen-Sheng

2014-01-01

Recent molecular surveys have advanced our understanding of the forces shaping the large-scale ecological distribution of microbes in Earth's extreme habitats, such as hot springs and acid mine drainage. However, few investigations have attempted dense spatial analyses of specific sites to resolve the local diversity of these extraordinary organisms and how communities are shaped by the harsh environmental conditions found there. We have applied a 16S rRNA gene-targeted 454 pyrosequencing approach to explore the phylogenetic differentiation among 90 microbial communities from a massive copper tailing impoundment generating acidic drainage and coupled these variations in community composition with geochemical parameters to reveal ecological interactions in this extreme environment. Our data showed that the overall microbial diversity estimates and relative abundances of most of the dominant lineages were significantly correlated with pH, with the simplest assemblages occurring under extremely acidic conditions and more diverse assemblages associated with neutral pHs. The consistent shifts in community composition along the pH gradient indicated that different taxa were involved in the different acidification stages of the mine tailings. Moreover, the effect of pH in shaping phylogenetic structure within specific lineages was also clearly evident, although the phylogenetic differentiations within the Alphaproteobacteria, Deltaproteobacteria, and Firmicutes were attributed to variations in ferric and ferrous iron concentrations. Application of the microbial assemblage prediction model further supported pH as the major factor driving community structure and demonstrated that several of the major lineages are readily predictable. Together, these results suggest that pH is primarily responsible for structuring whole communities in the extreme and heterogeneous mine tailings, although the diverse microbial taxa may respond differently to various environmental conditions. PMID:24727268

Diffusion of lactate and ammonium in relation to growth of Geotrichum candidum at the surface of solid media.

PubMed

Aldarf, M; Fourcade, F; Amrane, A; Prigent, Y

2004-07-05

Geotrichum candidum was cultivated at the surface of solid model media containing peptone to simulate the composition of Camembert cheese. The surface growth of G. candidum induced the diffusion of substrates from the core to the rind and the diffusion of produced metabolites from the rind to the core. In the range of pH measured during G. candidum growth, constant diffusion coefficients were found for lactate and ammonium, 0.4 and 0.8 cm(2) day(-1), respectively, determined in sterile culture medium. Growth kinetics are described using the Verlhust model and both lactate consumption and ammonium production are considered as partially linked to growth. The experimental diffusion gradients of lactate and ammonium recorded during G. candidum growth have been fitted. The diffusion/reaction model was found to match with experimental data until the end of growth, except with regard to ammonium concentration gradients in the presence of lactate in the medium. Indeed, G. candidum preferentially assimilated peptone over lactate as a carbon source, resulting in an almost cessation of ammonium release before the end of growth. On peptone, it was found that the proton transfer did not account for the ammonium concentration gradients. Indeed, amino acids, being positively charged, are involved in the proton transfer at the beginning of growth. This effect can be neglected in the presence of lactate within the medium, and the sum of both lactate consumption and ammonium release gradients corresponded well to the proton transfer gradients, confirming that both components are responsible for the pH increase observed during the ripening of soft Camembert cheese. Copyright 2004 Wiley Periodicals, Inc.

Protonation free energy levels in complex molecular systems.

PubMed

Antosiewicz, Jan M

2008-04-01

All proteins, nucleic acids, and other biomolecules contain residues capable of exchanging protons with their environment. These proton transfer phenomena lead to pH sensitivity of many molecular processes underlying biological phenomena. In the course of biological evolution, Nature has invented some mechanisms to use pH gradients to regulate biomolecular processes inside cells or in interstitial fluids. Therefore, an ability to model protonation equilibria in molecular systems accurately would be of enormous value for our understanding of biological processes and for possible rational influence on them, like in developing pH dependent drugs to treat particular diseases. This work presents a derivation, by thermodynamic and statistical mechanical methods, of an expression for the free energy of a complex molecular system at arbitrary ionization state of its titratable residues. This constitutes one of the elements of modeling protonation equilibria. Starting from a consideration of a simple acid-base equilibrium of a model compound with a single tritratable group, we arrive at an expression which is of general validity for complex systems. The only approximation used in this derivation is the postulating that the interaction energy between any pair of titratable sites does not depend on the protonation states of all the remaining ionizable groups.

Use of the pH sensitive fluorescence probe pyranine to monitor internal pH changes in Escherichia coli membrane vesicles.

PubMed

Damiano, E; Bassilana, M; Rigaud, J L; Leblanc, G

1984-01-23

Measurements of the fluorescent properties of 8-hydroxy-1,3,6-pyrenetrisulfonate (pyranine) enclosed within the internal space of Escherichia coli membrane vesicles enable recordings and quantitative analysis of: (i) changes in intravesicular pH taking place during oxidation of electron donors by the membrane respiratory chain; (ii) transient alkalization of the internal aqueous space resulting from the creation of outwardly directed acetate diffusion gradients across the vesicular membrane. Quantitation of the fluorescence variations recorded during the creation of transmembrane acetate gradients shows a close correspondence between the measured shifts in internal pH value and those expected from the amplitude of the imposed acetate gradients.

Single-laboratory validation of a high-performance liquid chromatographic-diode array detector-fluorescence detector/mass spectrometric method for simultaneous determination of water-soluble vitamins in multivitamin dietary tablets.

PubMed

Chen, Pei; Atkinson, Renata; Wolf, Wayne R

2009-01-01

The purpose of this study was to develop a single-laboratory validated (SLV) method using high-performance liquid chromatography with different detectors [diode array detector (DAD); fluorescence detector (FLD); and mass spectrometry (MS)] for determination of 7 B-complex vitamins (B1-thiamin, B2-riboflavin, B3-nicotinamide, B6-pyridoxine, B9-folic acid, pantothenic acid, and biotin) and vitamin C in multivitamin/multimineral dietary supplements. The method involves the use of a reversed-phase octadecylsilyl column (4 microm, 250 x 2.0 mm id) and a gradient mobile phase profile. Gradient elution was performed at a flow rate of 0.25 mL/min. After a 5 min isocratic elution at 100% A (0.1% formic acid in water), a linear gradient to 50% A and 50% B (0.1% formic acid in acetonitrile) at 15 min was employed. Detection was performed with a DAD as well as either an FLD or a triple-quadrupole MS detector in the multiple reaction monitoring mode. SLV was performed using Standard Reference Material (SRM) 3280 Multivitamin/Multimineral Tablets, being developed by the National Institute of Standards and Technology, with support by the Office of Dietary Supplements of the National Institutes of Health. Phosphate buffer (10 mM, pH 2.0) extracts of the NIST SRM 3280 were analyzed by the liquid chromatographic (LC)-DAD-FLDIMS method. Following extraction, the method does not require any sample cleanup/preconcentration steps except centrifugation and filtration.

Single-Laboratory Validation of a High-Performance Liquid Chromatographic-Diode Array Detector-Fluorescence Detector/Mass Spectrometric Method for Simultaneous Determination of Water-Soluble Vitamins in Multivitamin Dietary Tablets

PubMed Central

Chen, Pei; Atkinson, Renata; Wolf, Wayne R.

2014-01-01

The purpose of this study was to develop a single-laboratory validated (SLV) method using high-performance liquid chromatography with different detectors [diode array detector (DAD); fluorescence detector (FLD); and mass spectrometry (MS)] for determination of 7 B-complex vitamins (B1-thiamin, B2-riboflavin, B3-nicotinamide, B6-pyridoxine, B9-folic acid, pantothenic acid, and biotin) and vitamin C in multivitamin/multimineral dietary supplements. The method involves the use of a reversed-phase octadecylsilyl column (4 µm, 250 × 2.0 mm id) and a gradient mobile phase profile. Gradient elution was performed at a flow rate of 0.25 mL/min. After a 5 min isocratic elution at 100% A (0.1% formic acid in water), a linear gradient to 50% A and 50% B (0.1% formic acid in acetonitrile) at 15 min was employed. Detection was performed with a DAD as well as either an FLD or a triple-quadrupole MS detector in the multiple reaction monitoring mode. SLV was performed using Standard Reference Material (SRM) 3280 Multivitamin/Multimineral Tablets, being developed by the National Institute of Standards and Technology, with support by the Office of Dietary Supplements of the National Institutes of Health. Phosphate buffer (10 mM, pH 2.0) extracts of the NIST SRM 3280 were analyzed by the liquid chromatographic (LC)-DAD-FLD/MS method. Following extraction, the method does not require any sample cleanup/preconcentration steps except centrifugation and filtration. PMID:19485230

In Vivo Intracellular pH Measurements in Tobacco and Arabidopsis Reveal an Unexpected pH Gradient in the Endomembrane System[W

PubMed Central

Martinière, Alexandre; Bassil, Elias; Jublanc, Elodie; Alcon, Carine; Reguera, Maria; Sentenac, Hervé; Blumwald, Eduardo; Paris, Nadine

2013-01-01

The pH homeostasis of endomembranes is essential for cellular functions. In order to provide direct pH measurements in the endomembrane system lumen, we targeted genetically encoded ratiometric pH sensors to the cytosol, the endoplasmic reticulum, and the trans-Golgi, or the compartments labeled by the vacuolar sorting receptor (VSR), which includes the trans-Golgi network and prevacuoles. Using noninvasive live-cell imaging to measure pH, we show that a gradual acidification from the endoplasmic reticulum to the lytic vacuole exists, in both tobacco (Nicotiana tabacum) epidermal (ΔpH −1.5) and Arabidopsis thaliana root cells (ΔpH −2.1). The average pH in VSR compartments was intermediate between that of the trans-Golgi and the vacuole. Combining pH measurements with in vivo colocalization experiments, we found that the trans-Golgi network had an acidic pH of 6.1, while the prevacuole and late prevacuole were both more alkaline, with pH of 6.6 and 7.1, respectively. We also showed that endosomal pH, and subsequently vacuolar trafficking of soluble proteins, requires both vacuolar-type H+ ATPase–dependent acidification as well as proton efflux mediated at least by the activity of endosomal sodium/proton NHX-type antiporters. PMID:24104564

Direct injection analysis of fatty and resin acids in papermaking process waters by HPLC/MS.

PubMed

Valto, Piia; Knuutinen, Juha; Alén, Raimo

2011-04-01

A novel HPLC-atmospheric pressure chemical ionization/MS (HPLC-APCI/MS) method was developed for the rapid analysis of selected fatty and resin acids typically present in papermaking process waters. A mixture of palmitic, stearic, oleic, linolenic, and dehydroabietic acids was separated by a commercial HPLC column (a modified stationary C(18) phase) using gradient elution with methanol/0.15% formic acid (pH 2.5) as a mobile phase. The internal standard (myristic acid) method was used to calculate the correlation coefficients and in the quantitation of the results. In the thorough quality parameters measurement, a mixture of these model acids in aqueous media as well as in six different paper machine process waters was quantitatively determined. The measured quality parameters, such as selectivity, linearity, precision, and accuracy, clearly indicated that, compared with traditional gas chromatographic techniques, the simple method developed provided a faster chromatographic analysis with almost real-time monitoring of these acids. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Imaging of Intracellular pH in Tumor Spheroids Using Genetically Encoded Sensor SypHer2.

PubMed

Zagaynova, Elena V; Druzhkova, Irina N; Mishina, Natalia M; Ignatova, Nadezhda I; Dudenkova, Varvara V; Shirmanova, Marina V

2017-01-01

Intracellular pH (pHi) is one of the most important parameters that regulate the physiological state of cells and tissues. pHi homeostasis is crucial for normal cell functioning. Cancer cells are characterized by having a higher (neutral to slightly alkaline) pHi and lower (acidic) extracellular pH (pHe) compared to normal cells. This is referred to as a "reversed" pH gradient, and is essential in supporting their accelerated growth rate, invasion and migration, and in suppressing anti-tumor immunity, the promotion of metabolic coupling with fibroblasts and in preventing apoptosis. Moreover, abnormal pH, both pHi and pHe, contribute to drug resistance in cancers. Therefore, the development of methods for measuring pH in living tumor cells is likely to lead to better understanding of tumor biology and to open new ways for cancer treatment. Genetically encoded, fluorescent, pH-sensitive probes represent promising instruments enabling the subcellular measurement of pHi with unrivaled specificity and high accuracy. Here, we describe a protocol for pHi imaging at a microscopic level in HeLa tumor spheroids, using the genetically encoded ratiometric (dual-excitation) pHi indicator, SypHer2.

Authigenic apatite and octacalcium phosphate formation due to adsorption-precipitation switching across estuarine salinity gradients

NASA Astrophysics Data System (ADS)

Oxmann, J. F.; Schwendenmann, L.

2015-02-01

Mechanisms governing phosphorus (P) speciation in coastal sediments remain largely unknown due to the diversity of coastal environments and poor analytical specificity for P phases. We investigated P speciation across salinity gradients comprising diverse ecosystems in a P-enriched estuary. To determine P load effects on P speciation we compared the high P site with a low P site. Octacalcium phosphate (OCP), authigenic apatite (carbonate fluorapatite, CFAP) and detrital apatite (fluorapatite) were quantitated in addition to Al/Fe-bound P (Al/Fe-P) and Ca-bound P (Ca-P). Gradients in sediment pH strongly affected P fractions across ecosystems and independent of the site-specific total P status. We found a pronounced switch from adsorbed Al/Fe-P to mineral Ca-P with decreasing acidity from land to sea. This switch occurred at near-neutral sediment pH and has possibly been enhanced by redox-driven phosphate desorption from iron oxyhydroxides. The seaward decline in Al/Fe-P was counterbalanced by the precipitation of Ca-P. Correspondingly, two location-dependent accumulation mechanisms occurred at the high P site due to the switch, leading to elevated Al/Fe-P at pH < 6.6 (landward; adsorption) and elevated Ca-P at pH > 6.6 (seaward; precipitation). Enhanced Ca-P precipitation by increased P loads was also evident from disproportional accumulation of metastable Ca-P (Ca-Pmeta) at the high P site. Here, sediments contained on average 6-fold higher Ca-Pmeta levels compared with the low P site, although these sediments contained only 2-fold more total Ca-P than the low P sediments. Phosphorus species distributions indicated that these elevated Ca-Pmeta levels resulted from transformation of fertilizer-derived Al/Fe-P to OCP and CFAP in nearshore areas. Formation of CFAP as well as its precursor, OCP, results in P retention in coastal zones and can thus lead to substantial inorganic P accumulation in response to anthropogenic P input.

Application of lime (CaCO3) to promote forest recovery from severe acidification increases potential for earthworm invasion

USGS Publications Warehouse

Homan, Caitlin; Beirer, Colin M; McCay, Timothy S; Lawrence, Gregory B.

2016-01-01

The application of lime (calcium carbonate) may be a cost-effective strategy to promote forest ecosystem recovery from acid impairment, under contemporary low levels of acidic deposition. However, liming acidified soils may create more suitable habitat for invasive earthworms that cause significant damage to forest floor communities and may disrupt ecosystem processes. We investigated the potential effects of liming in acidified soils where earthworms are rare in conjunction with a whole-ecosystem liming experiment in the chronically acidified forests of the western Adirondacks (USA). Using a microcosm experiment that replicated the whole-ecosystem treatment, we evaluated effects of soil liming on Lumbricus terrestris survivorship and biomass growth. We found that a moderate lime application (raising pH from 3.1 to 3.7) dramatically increased survival and biomass of L. terrestris, likely via increases in soil pH and associated reductions in inorganic aluminum, a known toxin. Very few L. terrestris individuals survived in unlimed soils, whereas earthworms in limed soils survived, grew, and rapidly consumed leaf litter. We supplemented this experiment with field surveys of extant earthworm communities along a gradient of soil pH in Adirondack hardwood forests, ranging from severely acidified (pH < 3) to well-buffered (pH > 5). In the field, no earthworms were observed where soil pH < 3.6. Abundance and species richness of earthworms was greatest in areas where soil pH > 4.4 and human dispersal vectors, including proximity to roads and public fishing access, were most prevalent. Overall our results suggest that moderate lime additions can be sufficient to increase earthworm invasion risk where dispersal vectors are present.

Sodium provides unique insights into transgenerational effects of ocean acidification on bivalve shell formation.

PubMed

Zhao, Liqiang; Schöne, Bernd R; Mertz-Kraus, Regina; Yang, Feng

2017-01-15

Ocean acidification is likely to have profound impacts on marine bivalves, especially on their early life stages. Therefore, it is imperative to know whether and to what extent bivalves will be able to acclimate or adapt to an acidifying ocean over multiple generations. Here, we show that reduced seawater pH projected for the end of this century (i.e., pH7.7) led to a significant decrease of shell production of newly settled juvenile Manila clams, Ruditapes philippinarum. However, juveniles from parents exposed to low pH grew significantly faster than those from parents grown at ambient pH, exhibiting a rapid transgenerational acclimation to an acidic environment. The sodium composition of the shells may shed new light on the mechanisms responsible for beneficial transgenerational acclimation. Irrespective of parental exposure, the amount of Na incorporated into shells increased with decreasing pH, implying active removal of excessive protons through the Na + /H + exchanger which is known to depend on the Na + gradient actively built up by the Na + /K + -ATPase as a driving force. However, the shells with a prior history of transgenerational exposure to low pH recorded significantly lower amounts of Na than those with no history of acidic exposure. It therefore seems very likely that the clams may implement less costly and more ATP-efficient ion regulatory mechanisms to maintain pH homeostasis in the calcifying fluid following transgenerational acclimation. Our results suggest that marine bivalves may have a greater capacity to acclimate or adapt to ocean acidification by the end of this century than currently understood. Copyright © 2016 Elsevier B.V. All rights reserved.

Changing roles of ammonia-oxidizing bacteria and archaea in a continuously acidifying soil caused by over-fertilization with nitrogen.

PubMed

Song, He; Che, Zhao; Cao, Wenchao; Huang, Ting; Wang, Jingguo; Dong, Zhaorong

2016-06-01

Nitrification coupled with nitrate leaching contributes to soil acidification. However, little is known about the effect of soil acidification on nitrification, especially on ammonia oxidation that is the rate-limiting step of nitrification and performed by ammonia-oxidizing bacteria (AOB) and archaea (AOA). Serious soil acidification occurs in Chinese greenhouses due to the overuse of N-fertilizer. In the present study, greenhouse soils with 1, 3, 5, 7, and 9 years of vegetable cultivation showed a consistent pH decline (i.e., 7.0, 6.3, 5.6, 4.9, and 4.3). Across the pH gradient, we analyzed the community structure and abundance of AOB and AOA by pyrosequencing and real-time PCR techniques, respectively. The recovered nitrification potential (RNP) method was used to determine relative contributions of AOA and AOB to nitrification potential. The results revealed that soil acidification shaped the community structures of AOA and AOB. In acidifying soil, soil pH, NH3 concentration, and DOC content were critical factors shaping ammonia oxidizer community structure. AOB abundance, but not AOA, was strongly influenced by soil acidification. When soil pH was below 5.0, AOA rather than AOB were responsible for almost all of the RNP. However, when soil pH ranged from 5.6 to 7.0, AOB were the major contributors to RNP. The group I.1a-associatied AOA had more relative abundance in low pH (pH<6.3), whereas group I.1b tended to prefer neutral pH. Clusters 2, 10, and 12 in AOB were more abundant in acidic soil (pH <5.6), while Nitrosomonas-like lineage and unclassified lineage 3 were prevailing in neutral soil and slightly acidic soil (pH, 6.0-6.5), respectively. These results suggested that soil acidification had a profound impact on ammonia oxidation and more specific lineages in AOB occupying different pH-associated niches required further investigation.

HILIC separation and quantitation of water-soluble vitamins using diol column.

PubMed

Karatapanis, Andreas E; Fiamegos, Yiannis C; Stalikas, Constantine D

2009-04-01

Hydrophilic interaction liquid-chromatography (HILIC) in conjunction with diode array detection has been applied for the separation of selected-water-soluble vitamins using an end-capped HILIC-diol column. Vitamins with significant biological importance, such as thiamine (B(1)), riboflavin (B(2)), nicotinic acid (B(3)), nicotinamide (B(3)), pyridoxine (B(6)), folic acid (B(9)), cyanocobalamin (B(12)) and ascorbic acid (vitamin C) were simultaneously separated. Chromatographic conditions including type and percentage of organic modifier in the mobile phase, pH, type and concentration of buffer salt and flow rate were investigated. ACN was shown to offer superior separation for the compounds tested as compared to methanol, isopropanol and THF. Isocratic separation and analysis were achieved for six vitamins (B(1), B(2), nicotinic acid/nicotinamide, B(6) and C) at ACN-H(2)O 90:10, containing ammonium acetate 10 mM, triethylamine 20 mM, pH 5.0, using a flow rate of 0.8 mL/min, while a gradient was necessary to resolve a mixture of all eight water-soluble vitamins. The HILIC method was validated and successfully applied to the analysis of a pharmaceutical formulation and an energy drink negating the need for time consuming clean-up steps.

Nitrification of archaeal ammonia oxidizers in acid soils is supported by hydrolysis of urea

PubMed Central

Lu, Lu; Han, Wenyan; Zhang, Jinbo; Wu, Yucheng; Wang, Baozhan; Lin, Xiangui; Zhu, Jianguo; Cai, Zucong; Jia, Zhongjun

2012-01-01

The hydrolysis of urea as a source of ammonia has been proposed as a mechanism for the nitrification of ammonia-oxidizing bacteria (AOB) in acidic soil. The growth of Nitrososphaera viennensis on urea suggests that the ureolysis of ammonia-oxidizing archaea (AOA) might occur in natural environments. In this study, 15N isotope tracing indicates that ammonia oxidation occurred upon the addition of urea at a concentration similar to the in situ ammonium content of tea orchard soil (pH 3.75) and forest soil (pH 5.4) and was inhibited by acetylene. Nitrification activity was significantly stimulated by urea fertilization and coupled well with abundance changes in archaeal amoA genes in acidic soils. Pyrosequencing of 16S rRNA genes at whole microbial community level demonstrates the active growth of AOA in urea-amended soils. Molecular fingerprinting further shows that changes in denaturing gradient gel electrophoresis fingerprint patterns of archaeal amoA genes are paralleled by nitrification activity changes. However, bacterial amoA and 16S rRNA genes of AOB were not detected. The results strongly suggest that archaeal ammonia oxidation is supported by hydrolysis of urea and that AOA, from the marine Group 1.1a-associated lineage, dominate nitrification in two acidic soils tested. PMID:22592820

Nitrification of archaeal ammonia oxidizers in acid soils is supported by hydrolysis of urea.

PubMed

Lu, Lu; Han, Wenyan; Zhang, Jinbo; Wu, Yucheng; Wang, Baozhan; Lin, Xiangui; Zhu, Jianguo; Cai, Zucong; Jia, Zhongjun

2012-10-01

The hydrolysis of urea as a source of ammonia has been proposed as a mechanism for the nitrification of ammonia-oxidizing bacteria (AOB) in acidic soil. The growth of Nitrososphaera viennensis on urea suggests that the ureolysis of ammonia-oxidizing archaea (AOA) might occur in natural environments. In this study, (15)N isotope tracing indicates that ammonia oxidation occurred upon the addition of urea at a concentration similar to the in situ ammonium content of tea orchard soil (pH 3.75) and forest soil (pH 5.4) and was inhibited by acetylene. Nitrification activity was significantly stimulated by urea fertilization and coupled well with abundance changes in archaeal amoA genes in acidic soils. Pyrosequencing of 16S rRNA genes at whole microbial community level demonstrates the active growth of AOA in urea-amended soils. Molecular fingerprinting further shows that changes in denaturing gradient gel electrophoresis fingerprint patterns of archaeal amoA genes are paralleled by nitrification activity changes. However, bacterial amoA and 16S rRNA genes of AOB were not detected. The results strongly suggest that archaeal ammonia oxidation is supported by hydrolysis of urea and that AOA, from the marine Group 1.1a-associated lineage, dominate nitrification in two acidic soils tested.

Analyzing chromatographic data using multilevel modeling.

PubMed

Wiczling, Paweł

2018-06-01

It is relatively easy to collect chromatographic measurements for a large number of analytes, especially with gradient chromatographic methods coupled with mass spectrometry detection. Such data often have a hierarchical or clustered structure. For example, analytes with similar hydrophobicity and dissociation constant tend to be more alike in their retention than a randomly chosen set of analytes. Multilevel models recognize the existence of such data structures by assigning a model for each parameter, with its parameters also estimated from data. In this work, a multilevel model is proposed to describe retention time data obtained from a series of wide linear organic modifier gradients of different gradient duration and different mobile phase pH for a large set of acids and bases. The multilevel model consists of (1) the same deterministic equation describing the relationship between retention time and analyte-specific and instrument-specific parameters, (2) covariance relationships relating various physicochemical properties of the analyte to chromatographically specific parameters through quantitative structure-retention relationship based equations, and (3) stochastic components of intra-analyte and interanalyte variability. The model was implemented in Stan, which provides full Bayesian inference for continuous-variable models through Markov chain Monte Carlo methods. Graphical abstract Relationships between log k and MeOH content for acidic, basic, and neutral compounds with different log P. CI credible interval, PSA polar surface area.

Stimulation of pyruvate transport in metabolizing mitochondria through changes in the transmembrane pH gradient induced by glucagon treatment of rats.

PubMed

Halestrap, A P

1978-06-15

Glucagon treatment of rats allowed the isolation of liver mitochondria with enhanced rates of pyruvate metabolism measured in either sucrose or KCl media. No change in the activity of the pyruvate carrier itself was apparent, but under metabolizing conditions, use of the inhibitor of pyruvate transport, alpha-cyano-4-hydroxycinnamate, demonstrated that pyruvate transport limited the rate of pyruvate metabolism. The maximum rate of transport under metabolizing conditions was enhanced by glucagon treatment. Problems involved in measuring the transmembrane pH gradient under metabolizing conditions are discussed and a variety of techniques are used to estimate the matrix pH. From the distribution of methylamine, ammonia and D-lactate and the Ki for inhibition by alpha-cyano-4-hydroxycinnamate it is concluded that the matrix is more acid than the medium and that the pH of the matrix rises after glucagon treatment. The increase in matrix pH stimulates pyruvate transport. The membrane potential, ATP concentration and O2 uptake were also increased under metabolizing conditions in glucagon-treated mitochondria. These changes were correlated with a stimulation of the respiratory chain which can be observed in uncoupled mitochondria [Yamazaki (1975) J. Biol. Chem. 250, 7924--7930]. The mitochondrial Mg2+ content (mean +/- S.E.M.) was increased from 38.8 +/- 1.2 (n = 26) to 47.5 +/- 2.0 (n = 26) ng-atoms/mg by glucagon and the K+ content from 126.7 +/- 10.3 (n = 19) ng-atoms/mg. This may represent a change in membrane potential induced by glucagon in vivo. The physiological significance of these results in the control of gluconeogenesis is discussed.

Localized effects of coal mine drainage on fish assemblages in a Cumberland Plateau stream in Tennessee

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schorr, M.S.; Backer, J.C.

2006-03-15

The upper watershed of North Chickamauga Creek (NCC), a fourth-order tributary to the Tennessee River, Tennessee, has been impacted by decades of acid mine drainage (AMD) from abandoned coal mines. We assessed fish assemblages, pH, conductivity, and sediment coverage at 12 study reaches (six AMD sites and six reference sites) in the Cumberland Plateau region of the NCC system, May-September 1998. Stream pH increased (3.6 to 6.0) and conductivity decreased (296 to 49 {mu}S/cm) downstream of the AMD-impacted area; however, no discernable gradient was observed in sediment cover. Elevated conductivity at AMD-impacted sites reflected increased concentrations of dissolved metals andmore » other inorganic ions. Reference sites exhibited higher pH (6.0-6.4) and lower conductivity (13-28 {mu}S/cm). Acidified reaches were characterized by low fish species richness and abundance; no fish were observed at sites where the mean pH was {lt} 5. Centrarchids (mostly bluegill (Lepomis macrochirus) and green sunfish (L. cyanellus)) comprised {gt} 90 % of the catch at AMD sites, whereas cypriniids (creek chub (Semotilus atromaculatus) and blacknose dace (Rhinichthys atratulus)) accounted for {gt} 90 % of the catch at reference sites. Findings from this study document the negative effects of acid drainage from coal mines on fish assemblages in a Cumberland Plateau stream.« less

Berry composition and climate: responses and empirical models.

PubMed

Barnuud, Nyamdorj N; Zerihun, Ayalsew; Gibberd, Mark; Bates, Bryson

2014-08-01

Climate is a strong modulator of berry composition. Accordingly, the projected change in climate is expected to impact on the composition of berries and of the resultant wines. However, the direction and extent of climate change impact on fruit composition of winegrape cultivars are not fully known. This study utilised a climate gradient along a 700 km transect, covering all wine regions of Western Australia, to explore and empirically describe influences of climate on anthocyanins, pH and titratable acidity (TA) levels in two or three cultivars of Vitis vinifera (Cabernet Sauvignon, Chardonnay and Shiraz). The results showed that, at a common maturity of 22° Brix total soluble solids, berries from the warmer regions had low levels of anthocyanins and TA as well as high pH compared to berries from the cooler regions. Most of these regional variations in berry composition reflected the prevailing climatic conditions of the regions. Thus, depending on cultivar, 82-87 % of TA, 83 % of anthocyanins and about half of the pH variations across the gradient were explained by climate-variable-based empirical models. Some of the variables that were relevant in describing the variations in berry attributes included: diurnal ranges and ripening period temperature (TA), vapour pressure deficit in October and growing degree days (pH), and ripening period temperatures (anthocyanins). Further, the rates of change in these berry attributes in response to climate variables were cultivar dependent. Based on the observed patterns along the climate gradient, it is concluded that: (1) in a warming climate, all other things being equal, berry anthocyanins and TA levels will decline whereas pH levels will rise; and (2) despite variations in non-climatic factors (e.g. soil type and management) along the sampling transect, variations in TA and anthocyanins were satisfactorily described using climate-variable-based empirical models, indicating the overriding impact of climate on berry composition. The models presented here are useful tools for assessing likely changes in berry TA and anthocyanins in response to changing climate for the wine regions and cultivars covered in this study.

Berry composition and climate: responses and empirical models

NASA Astrophysics Data System (ADS)

Barnuud, Nyamdorj N.; Zerihun, Ayalsew; Gibberd, Mark; Bates, Bryson

2014-08-01

Climate is a strong modulator of berry composition. Accordingly, the projected change in climate is expected to impact on the composition of berries and of the resultant wines. However, the direction and extent of climate change impact on fruit composition of winegrape cultivars are not fully known. This study utilised a climate gradient along a 700 km transect, covering all wine regions of Western Australia, to explore and empirically describe influences of climate on anthocyanins, pH and titratable acidity (TA) levels in two or three cultivars of Vitis vinifera (Cabernet Sauvignon, Chardonnay and Shiraz). The results showed that, at a common maturity of 22° Brix total soluble solids, berries from the warmer regions had low levels of anthocyanins and TA as well as high pH compared to berries from the cooler regions. Most of these regional variations in berry composition reflected the prevailing climatic conditions of the regions. Thus, depending on cultivar, 82-87 % of TA, 83 % of anthocyanins and about half of the pH variations across the gradient were explained by climate-variable-based empirical models. Some of the variables that were relevant in describing the variations in berry attributes included: diurnal ranges and ripening period temperature (TA), vapour pressure deficit in October and growing degree days (pH), and ripening period temperatures (anthocyanins). Further, the rates of change in these berry attributes in response to climate variables were cultivar dependent. Based on the observed patterns along the climate gradient, it is concluded that: (1) in a warming climate, all other things being equal, berry anthocyanins and TA levels will decline whereas pH levels will rise; and (2) despite variations in non-climatic factors (e.g. soil type and management) along the sampling transect, variations in TA and anthocyanins were satisfactorily described using climate-variable-based empirical models, indicating the overriding impact of climate on berry composition. The models presented here are useful tools for assessing likely changes in berry TA and anthocyanins in response to changing climate for the wine regions and cultivars covered in this study.

Density functional theory based probe of the affinity interaction of saccharide ligands with extra-cellular sialic acid residues.

PubMed

Patel, Anjali; Tiwari, Sanjay; Jha, Prafulla K

2018-05-10

Changes in glycosylation pattern leads to malignant transformations among the cells. In combination with upregulated actions of sialyltransferases, it ultimately leads to differential expression of sialic acid (SA) at cell surface. Given its negative charge and localization to extracellular domain, SA has been exploited for the development of targeted theranostics using approaches, such as, cationization and appending recognition saccharides on carrier surface. In this study, we have performed quantum mechanical calculations based on density functional theory (DFT) to study the interaction of saccharides with extracellular SA. Gradient-corrected DFT with the three parameter function (B3) was utilized for the calculation of Lee-Yang-Parr (LYP) correlation function. Atomic charge, vibrational frequencies and energy of the optimized structures were calculated through B3LYP. Our calculations demonstrate a stronger galactose-sialic acid interaction at tumour-relevant low pH and hyperthermic condition. These results support the application of pH responsive delivery vehicles and targeted hyperthermic chemotherapy for eradicating solid tumour deposits. These studies, conducted a priori, can guide the formulation scientists over appropriate choice of ligands and their applications in the design of 'smart' theranostic tools.

Fast loading ester fluorescent Ca2+ and pH indicators into pollen of Pyrus pyrifolia.

PubMed

Qu, Haiyong; Jiang, Xueting; Shi, Zebin; Liu, Lianmei; Zhang, Shaoling

2012-01-01

Loading of Ca(2+)-sensitive fluorescent probes into plant cells is an essential step to measure activities of free Ca(2+) ions in cytoplasm with a fluorescent imaging technique. Fluo-3 is one of the most suitable Ca(2+) indicators for CLSM. We loaded pollen with fluo-3/AM at three different temperatures. Fluo-3/AM was successfully loaded into pollen at both low (4°C) and high (37°C) temperatures. However, high loading temperature was best suited for pollen, because germination rate of pollen and growth of pollen tubes were relatively little impaired and loading time was shortened. Moreover, Ca(2+) distribution increased in the three apertures of pollen after hydration and showed a Ca(2+) gradient, similar to the tip of growing pollen tubes. The same protocol can be used with the AM-forms of other fluorescent dyes for effective labeling. When loading BCECF-AM into pollen at high temperature, the pollen did not show a pH gradient after hydration. Ca(2+) activities and fluxes had the same periodicity as pollen germination, but pH did not show the same phase and mostly lagged behind. However, the clear zone was alkaline when pollen tube growth was slowed or stopped and turned acidic when growth recovered. It is likely that apical pH(i) regulated pollen tube growth.

[Composition diversity of lactic acid bacteria (LAB) community Al2 used for alfalfa silage].

PubMed

Wang, Xiao-Fen; Gao, Li-Juan; Yang, Hong-Yan; Wang, Wei-Dong; Cui, Zong-Jun

2006-10-01

Alfalfa is the most important forage grass that is difficult to ensile for good quality. Using silage inoculants are the important way for preservation of alfalfa silage. Through continuous restricted subcultivation, a lactic acid bacteria (LAB) community Al2 was selected from well-fermented alfalfa silage. Plate isolation and Denaturing Gradient Gel Electrophoresis (DGGE), construction of 16S rDNA clone library were used to identify the composition diversity of Al2 community, with 7 strains detected, and they were all belonged to Lactobacillus. The composition ratios of the 7 strains were 55.21%, 19.79%, 14.58%, 3.13%, 3.13%, 3.13%, 1.03% according to 16S rDNA clone library. Al2-1i, Al2-2i, Al2-3i, corresponding to L. plantarum (99.9%), L. kimchii (99.4%), L. farciminis (100%) were detected by plate isolation. Among 3 isolates, Al2-1i had the highest ability of dropping pH and producing lactic acid, and the amount of lactic acid was reach to 18g/L at 24h cultivated in MRS media. The ability of dropping pH and producing lactic acid of Al2-3i was the lowest. From DGGE profiles, the dominant strains in Al2 community were L. plantarum and L. kimchii. L. plantarum was detected during the whole process, and L. kimchii was detected in the later phase.

Chemical and biological status of lakes and streams in the upper midwest: assessment of acidic deposition effects

USGS Publications Warehouse

Wiener, J.G.; Eilers, J.M.

1987-01-01

Many lakes in three areas in the Upper Midwest - northeastern Minnesota, northern Wisconsin, and the Upper Peninsula of Michigan - have low acid neutralizing capacity (ANC) and may be susceptible to change by acidic deposition. Northcentral Wisconsin and the Upper Peninsula of Michigan together contain about 150-300 acidic lakes (ANC ≤ 0), whereas none have been found in Minnesota. These acidic lakes are precipitation-dominated, Clearwater seepage lakes having small surface area, shallow depth, and low concentrations of dissolved organic carbon. The spatial distribution of these acidic lakes parallels a west to east gradient of increasing sulfate and hydrogen ion deposition. Several of these acidic lakes exhibit chemical characteristics and biological changes consistent with those observed elsewhere in waters reported to be acidified by acidic deposition. However, an hypothesis of recent lake acidification is not supported by analyses of either historical chemical data or diatom remains in lake sediments, and natural sources of acidity and alternative ecological processes have not been conclusively eliminated as causative factors. Streams in this three-state region have high ANC and appear to be insensitive to acidic deposition. The species richness and composition of lacustrine fish communities in the region are partly related to pH and associated chemical factors. Sport fishes considered acid-sensitive and of primary concern with regard to acidification include walleye, smallmouth bass, and black crappie. The fishery in at least one lake, Morgan Lake in Wisconsin (pH 4.6), may have declined because of acidification. Given the general lack of quantitative fishery data for acidic Wisconsin and Michigan lakes, however, more general conclusions concerning impacts or the absence of impacts of acidification on the region's fishery resources are not possible.

Adaptation of H+-pumping and plasma membrane H+ ATPase activity in proteoid roots of white lupin under phosphate deficiency.

PubMed

Yan, Feng; Zhu, Yiyong; Müller, Caroline; Zörb, Christian; Schubert, Sven

2002-05-01

White lupin (Lupinus albus) is able to adapt to phosphorus deficiency by producing proteoid roots that release a huge amount of organic acids, resulting in mobilization of sparingly soluble soil phosphate in rhizosphere. The mechanisms responsible for the release of organic acids by proteoid root cells, especially the trans-membrane transport processes, have not been elucidated. Because of high cytosolic pH, the release of undissociated organic acids is not probable. In the present study, we focused on H+ export by plasma membrane H+ ATPase in active proteoid roots. In vivo, rhizosphere acidification of active proteoid roots was vanadate sensitive. Plasma membranes were isolated from proteoid roots and lateral roots from P-deficient and -sufficient plants. In vitro, in comparison with two types of lateral roots and proteoid roots of P-sufficient plants, the following increase of the various parameters was induced in active proteoid roots of P-deficient plants: (a) hydrolytic ATPase activity, (b) Vmax and Km, (c) H+ ATPase enzyme concentration of plasma membrane, (d) H+-pumping activity, (e) pH gradient across the membrane of plasmalemma vesicles, and (f) passive H+ permeability of plasma membrane. In addition, lower vanadate sensitivity and more acidic pH optimum were determined for plasma membrane ATPase of active proteoid roots. Our data support the hypothesis that in active proteoid root cells, H+ and organic anions are exported separately, and that modification of plasma membrane H+ ATPase is essential for enhanced rhizosphere acidification by active proteoid roots.

Effects of pH and Redox Gradients on Prebiotic Organic Synthesis and the Generation of Free Energy in Simulated Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Barge, L. M.; Flores, E.; Abedian, Y.; Maltais, T.; Cameron, R.; Hermis, N.; Chin, K.; Russell, M. J.; Baum, M. M.

2017-07-01

Hydrothermal minerals in alkaline vents can promote phosphorus and organic concentration, redox reactions driven by catalytic metal sulfides, and the ambient pH and redox gradients can affect the synthesis of organics.

Techniques for Loading Technetium-99m and Rhenium-186/188 Radionuclides into Preformed Liposomes for Diagnostic Imaging and Radionuclide Therapy.

PubMed

Goins, Beth; Bao, Ande; Phillips, William T

2017-01-01

Liposomes can serve as carriers of radionuclides for diagnostic imaging and therapeutic applications. Herein, procedures are outlined for radiolabeling liposomes with the gamma-emitting radionuclide, technetium-99m ( 99m Tc), for noninvasive detection of disease and for monitoring the pharmacokinetics and biodistribution of liposomal drugs, and/or with therapeutic beta-emitting radionuclides, rhenium-186/188 ( 186/188 Re), for radionuclide therapy. These efficient and practical liposome radiolabeling methods use a post-labeling mechanism to load 99m Tc or 186/188 Re into preformed liposomes prepared in advance of the labeling procedure. For all liposome radiolabeling methods described, a lipophilic chelator is used to transport 99m Tc or 186/188 Re across the lipid bilayer of the preformed liposomes. Once within the liposome interior, the pre-encapsulated glutathione or ammonium sulfate (pH) gradient provides for stable entrapment of the 99m Tc and 186/188 Re within the liposomes. In the first method, 99m Tc is transported across the lipid bilayer by the lipophilic chelator, hexamethylpropyleneamine oxime (HMPAO) and 99m Tc-HMPAO becomes trapped by interaction with the pre-encapsulated glutathione within the liposomes. In the second method, 99m Tc or 186/188 Re is transported across the lipid bilayer by the lipophilic chelator, N,N-bis(2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA), and 99m Tc-BMEDA or 186/188 Re-BMEDA becomes trapped by interaction with pre-encapsulated glutathione within the liposomes. In the third method, an ammonium sulfate (pH) gradient loading technique is employed using liposomes with an extraliposomal pH of 7.4 and an interior pH of 5.1. BMEDA, which is lipophilic at pH 7.4, serves as a lipophilic chelator for 99m Tc or 186/188 Re to transport the radionuclides across the lipid bilayer. Once within the more acidic liposome interior, 99m Tc/ 186/188 Re-BMEDA complex becomes protonated and more hydrophilic, which results in stable entrapment of the 99m Tc/ 186/188 Re-BMEDA complex within the liposomes. Since many commercially available liposomal drugs use an ammonium sulfate (pH) gradient for drug loading, these liposomal drugs can be directly radiolabeled with 99m Tc-BMEDA for noninvasive monitoring of tissue distribution during treatment or with 186/188 Re-BMEDA for combination chemo-radionuclide therapy.

Mechanistic basis of adaptive maternal effects: egg jelly water balance mediates embryonic adaptation to acidity in Rana arvalis.

PubMed

Shu, Longfei; Suter, Marc J-F; Laurila, Anssi; Räsänen, Katja

2015-11-01

Environmental stress, such as acidification, can challenge persistence of natural populations and act as a powerful evolutionary force at ecological time scales. The ecological and evolutionary responses of natural populations to environmental stress at early life-stages are often mediated via maternal effects. During early life-stages, maternal effects commonly arise from egg coats (the extracellular structures surrounding the embryo), but the role of egg coats has rarely been studied in the context of adaptation to environmental stress. Previous studies on the moor frog Rana arvalis found that the egg coat mediated adaptive divergence along an acidification gradient in embryonic acid stress tolerance. However, the exact mechanisms underlying these adaptive maternal effects remain unknown. Here, we investigated the role of water balance and charge state (zeta potential) of egg jelly coats in embryonic adaptation to acid stress in three populations of R. arvalis. We found that acidic pH causes severe water loss in the egg jelly coat, but that jelly coats from an acid-adapted population retained more water than jelly coats from populations not adapted to acidity. Moreover, embryonic acid tolerance (survival at pH 4.0) correlated with both water loss and charge state of the jelly, indicating that negatively charged glycans influence jelly water balance and contribute to embryonic adaptation to acidity. These results indicate that egg coats can harbor extensive intra-specific variation, probably facilitated in part via strong selection on water balance and glycosylation status of egg jelly coats. These findings shed light on the molecular mechanisms of environmental stress tolerance and adaptive maternal effects.

pH dependent transfer of nano-pores into membrane of cancer cells to induce apoptosis

NASA Astrophysics Data System (ADS)

Wijesinghe, Dayanjali; Arachchige, Mohan C. M.; Lu, Andrew; Reshetnyak, Yana K.; Andreev, Oleg A.

2013-12-01

Proper balance of ions in intracellular and extracellular space is the key for normal cell functioning. Changes in the conductance of membranes for ions will lead to cell death. One of the main differences between normal and cancerous cells is the low extracellular pHe and the reverse pH gradient: intracellular pHi is higher than extracellular pHe. We report here pH-selective transfer of nano-pores to cancer cells for the dis-regulation of balance of monovalent cations to induce cell death at mildly acidic pHe as it is in most solid tumors. Our approach is based on the pH-sensitive fusion of cellular membrane with the liposomes containing gramicidin A forming cation-conductive β-helix in the membrane. Fusion is promoted only at low extracellular pH by the pH (Low) Insertion Peptide (pHLIP®) attached to the liposomes. Gramicidin channels inserted into the cancer cells open flux of protons into the cytoplasm and disrupt balance of other monovalent cations, which induces cell apoptosis.

The V-ATPase membrane domain is a sensor of granular pH that controls the exocytotic machinery.

PubMed

Poëa-Guyon, Sandrine; Ammar, Mohamed Raafet; Erard, Marie; Amar, Muriel; Moreau, Alexandre W; Fossier, Philippe; Gleize, Vincent; Vitale, Nicolas; Morel, Nicolas

2013-10-28

Several studies have suggested that the V0 domain of the vacuolar-type H(+)-adenosine triphosphatase (V-ATPase) is directly implicated in secretory vesicle exocytosis through a role in membrane fusion. We report in this paper that there was a rapid decrease in neurotransmitter release after acute photoinactivation of the V0 a1-I subunit in neuronal pairs. Likewise, inactivation of the V0 a1-I subunit in chromaffin cells resulted in a decreased frequency and prolonged kinetics of amperometric spikes induced by depolarization, with shortening of the fusion pore open time. Dissipation of the granular pH gradient was associated with an inhibition of exocytosis and correlated with the V1-V0 association status in secretory granules. We thus conclude that V0 serves as a sensor of intragranular pH that controls exocytosis and synaptic transmission via the reversible dissociation of V1 at acidic pH. Hence, the V-ATPase membrane domain would allow the exocytotic machinery to discriminate fully loaded and acidified vesicles from vesicles undergoing neurotransmitter reloading.

The V-ATPase membrane domain is a sensor of granular pH that controls the exocytotic machinery

PubMed Central

Poëa-Guyon, Sandrine; Ammar, Mohamed Raafet; Erard, Marie; Amar, Muriel; Moreau, Alexandre W.; Fossier, Philippe; Gleize, Vincent

2013-01-01

Several studies have suggested that the V0 domain of the vacuolar-type H+-adenosine triphosphatase (V-ATPase) is directly implicated in secretory vesicle exocytosis through a role in membrane fusion. We report in this paper that there was a rapid decrease in neurotransmitter release after acute photoinactivation of the V0 a1-I subunit in neuronal pairs. Likewise, inactivation of the V0 a1-I subunit in chromaffin cells resulted in a decreased frequency and prolonged kinetics of amperometric spikes induced by depolarization, with shortening of the fusion pore open time. Dissipation of the granular pH gradient was associated with an inhibition of exocytosis and correlated with the V1–V0 association status in secretory granules. We thus conclude that V0 serves as a sensor of intragranular pH that controls exocytosis and synaptic transmission via the reversible dissociation of V1 at acidic pH. Hence, the V-ATPase membrane domain would allow the exocytotic machinery to discriminate fully loaded and acidified vesicles from vesicles undergoing neurotransmitter reloading. PMID:24165939

Development and validation of stability indicating the RP-HPLC method for the estimation of related compounds of guaifenesin in pharmaceutical dosage forms.

PubMed

Reddy, Sunil Pingili; Babu, K Sudhakar; Kumar, Navneet; Sekhar, Y V V Sasi

2011-10-01

A stability-indicating gradient reverse phase liquid chromatographic (RP-LC) method was developed for the quantitative determination of related substances of guaifenesin in pharmaceutical formulations. The baseline separation for guaifenesin and all impurities was achieved by utilizing a Water Symmetry C18 (150 mm × 4.6 mm) 5 μm column particle size and a gradient elution method. The mobile phase A contains a mixture of 0.02 M KH2PO4 (pH 3.2) and methanol in the ratio of 90:10 v/v, while the mobile phase B contains 0.02 M KH2PO4 (pH 3.2) and methanol in the ratio of 10:90 v/v, respectively. The flow rate of the mobile phase was 0.8 ml/min with a column temperature of 25°C and detection wavelength at 273 nm. Guaifenesin was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal, and photolytic degradation. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection and quantification, accuracy, precision, and robustness.

Development and validation of stability indicating the RP-HPLC method for the estimation of related compounds of guaifenesin in pharmaceutical dosage forms

PubMed Central

Reddy, Sunil Pingili; Babu, K. Sudhakar; Kumar, Navneet; Sekhar, Y. V. V. Sasi

2011-01-01

Aim and background: A stability-indicating gradient reverse phase liquid chromatographic (RP-LC) method was developed for the quantitative determination of related substances of guaifenesin in pharmaceutical formulations. Materials and methods: The baseline separation for guaifenesin and all impurities was achieved by utilizing a Water Symmetry C18 (150 mm × 4.6 mm) 5 μm column particle size and a gradient elution method. The mobile phase A contains a mixture of 0.02 M KH2PO4 (pH 3.2) and methanol in the ratio of 90:10 v/v, while the mobile phase B contains 0.02 M KH2PO4 (pH 3.2) and methanol in the ratio of 10:90 v/v, respectively. The flow rate of the mobile phase was 0.8 ml/min with a column temperature of 25°C and detection wavelength at 273 nm. Results: Guaifenesin was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal, and photolytic degradation. Conclusion: The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection and quantification, accuracy, precision, and robustness. PMID:23781462

Plasma membrane H+-ATPase regulation is required for auxin gradient formation preceding phototropic growth

PubMed Central

Hohm, Tim; Demarsy, Emilie; Quan, Clément; Allenbach Petrolati, Laure; Preuten, Tobias; Vernoux, Teva; Bergmann, Sven; Fankhauser, Christian

2014-01-01

Phototropism is a growth response allowing plants to align their photosynthetic organs toward incoming light and thereby to optimize photosynthetic activity. Formation of a lateral gradient of the phytohormone auxin is a key step to trigger asymmetric growth of the shoot leading to phototropic reorientation. To identify important regulators of auxin gradient formation, we developed an auxin flux model that enabled us to test in silico the impact of different morphological and biophysical parameters on gradient formation, including the contribution of the extracellular space (cell wall) or apoplast. Our model indicates that cell size, cell distributions, and apoplast thickness are all important factors affecting gradient formation. Among all tested variables, regulation of apoplastic pH was the most important to enable the formation of a lateral auxin gradient. To test this prediction, we interfered with the activity of plasma membrane H+-ATPases that are required to control apoplastic pH. Our results show that H+-ATPases are indeed important for the establishment of a lateral auxin gradient and phototropism. Moreover, we show that during phototropism, H+-ATPase activity is regulated by the phototropin photoreceptors, providing a mechanism by which light influences apoplastic pH. PMID:25261457

Energy coupling to nitrate uptake into the denitrifying cells of Paracoccus denitrificans.

PubMed

Kucera, Igor

2005-09-05

This study deals with the effects of the agents that dissipate the individual components of the proton motive force (short-chain fatty acids, nigericin, and valinomycin) upon the methyl viologen-coupled nitrate reductase activity in intact cells. Substitution of butyrate or acetate for chloride in Tris-buffered assay media resulted in a marked inhibition at pH 7. In a Tris--chloride buffer of neutral pH, the reaction was almost fully inhibitable by nigericin. Alkalinisation increased the IC(50) value for nigericin and decreased the maximal inhibition attained. Both types of inhibitions could be reversed by the permeabilisation of cells or by the addition of nitrite, and that caused by nigericin disappeared at high extracellular concentrations of potassium. These data indicate that nitrate transport step relies heavily on the pH gradient at neutral pH. Since the affinity of cells for nitrate was strongly diminished by imposing an inside-positive potassium (or lithium) diffusion potential at alkaline external pH, a potential dependent step may be of significance in the transporter cycle under these conditions. Experiments with sodium-depleted media provided no hints for Na(+) as a possible H(+) substitute.

An acid-loading chloride transport pathway in the intraerythrocytic malaria parasite, Plasmodium falciparum.

PubMed

Henry, Roselani I; Cobbold, Simon A; Allen, Richard J W; Khan, Asif; Hayward, Rhys; Lehane, Adele M; Bray, Patrick G; Howitt, Susan M; Biagini, Giancarlo A; Saliba, Kevin J; Kirk, Kiaran

2010-06-11

The intraerythrocytic malaria parasite exerts tight control over its ionic composition. In this study, a combination of fluorescent ion indicators and (36)Cl(-) flux measurements was used to investigate the transport of Cl(-) and the Cl(-)-dependent transport of "H(+)-equivalents" in mature (trophozoite stage) parasites, isolated from their host erythrocytes. Removal of extracellular Cl(-), resulting in an outward [Cl(-)] gradient, gave rise to a cytosolic alkalinization (i.e. a net efflux of H(+)-equivalents). This was reversed on restoration of extracellular Cl(-). The flux of H(+)-equivalents was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and, when measured in ATP-depleted parasites, showed a pronounced dependence on the pH of the parasite cytosol; the flux was low at cytosolic pH values < 7.2 but increased steeply with cytosolic pH at values > 7.2. (36)Cl(-) influx measurements revealed the presence of a Cl(-) uptake mechanism with characteristics similar to those of the Cl(-)-dependent H(+)-equivalent flux. The intracellular concentration of Cl(-) in the parasite was estimated to be approximately 48 mm in situ. The data are consistent with the intraerythrocytic parasite having in its plasma membrane a 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid-sensitive transporter that, under physiological conditions, imports Cl(-) together with H(+)-equivalents, resulting in an intracellular Cl(-) concentration well above that which would occur if Cl(-) ions were distributed passively in accordance with the parasite's large, inwardly negative membrane potential.

Isoelectric focusing of red blood cells in a density gradient stabilized column

NASA Technical Reports Server (NTRS)

Smolka, A. J. K.; Miller, T. Y.

1980-01-01

The effects of Ficoll and cell application pH on red blood cell electrophoretic mobility and focusing pH were investigated by focusing cells in a density gradient stabilized column. Sample loading, cell dispersion, column conductivity, resolution of separation, and the effect of Ampholines were examined.

Microbial sulfate reduction and metal attenuation in pH 4 acid mine water

USGS Publications Warehouse

Church, C.D.; Wilkin, R.T.; Alpers, Charles N.; Rye, R.O.; Blaine, R.B.

2007-01-01

Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured for anaerobic bacteria over a range of pH (4.0 to 7.5). The molecular biology of sediments and cultures was studied to determine whether sulfate-reducing bacteria (SRB) were active in moderately acidic conditions present in the underground mine workings. Here we document multiple, independent analyses and show evidence that sulfate reduction and associated metal attenuation are occurring in the pH-4 mine environment. Water-chemistry analyses of the mine water reveal: (1) preferential complexation and precipitation by H2S of Cu and Cd, relative to Zn; (2) stable isotope ratios of 34S/32S and 18O/16O in dissolved SO4 that are 2-3 ??? heavier in the mine water, relative to those in surface waters; (3) reduction/oxidation conditions and dissolved gas concentrations consistent with conditions to support anaerobic processes such as sulfate reduction. Scanning electron microscope (SEM) analyses of sediment show 1.5-micrometer, spherical ZnS precipitates. Phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria. Cultures of sediment from the mine produced dissolved sulfide at pH values near 7 and near 4, forming precipitates of either iron sulfide or elemental sulfur. DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures. ?? 2007 Church et al; licensee BioMed Central Ltd.

Microbial sulfate reduction and metal attenuation in pH 4 acid mine water

PubMed Central

Church, Clinton D; Wilkin, Richard T; Alpers, Charles N; Rye, Robert O; McCleskey, R Blaine

2007-01-01

Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured for anaerobic bacteria over a range of pH (4.0 to 7.5). The molecular biology of sediments and cultures was studied to determine whether sulfate-reducing bacteria (SRB) were active in moderately acidic conditions present in the underground mine workings. Here we document multiple, independent analyses and show evidence that sulfate reduction and associated metal attenuation are occurring in the pH-4 mine environment. Water-chemistry analyses of the mine water reveal: (1) preferential complexation and precipitation by H2S of Cu and Cd, relative to Zn; (2) stable isotope ratios of 34S/32S and 18O/16O in dissolved SO4 that are 2–3 ‰ heavier in the mine water, relative to those in surface waters; (3) reduction/oxidation conditions and dissolved gas concentrations consistent with conditions to support anaerobic processes such as sulfate reduction. Scanning electron microscope (SEM) analyses of sediment show 1.5-micrometer, spherical ZnS precipitates. Phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria. Cultures of sediment from the mine produced dissolved sulfide at pH values near 7 and near 4, forming precipitates of either iron sulfide or elemental sulfur. DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures. PMID:17956615

Physio-chemical and morphological characteristics of avian encephalomyelitis virus

USGS Publications Warehouse

Gosting, L.H.; Grinnell, B.W.; Matsumoto, M.

1980-01-01

Avian encephalomyelitis virus (AEV) was purified from infected chick embryos by a gradient centrifugation in cesium chloride. The virus had a buoyant density of 1.31 to 1.32 g/ml and a sedimentation coefficient of 148 S. The purified AEV was resistant to treatments with chloroform, acid pH or trypsin. The presence of Mg++ stabilized the virus against heat inactivation (56°C, 1 h). Electron microscopic study showed the virus to be 24 to 32 nm in diameter. The surface structure of the purified virus was not easily discernable. Nevertheless, with uranyl acetate-stained particles, Markham's rotation technique revealed that AEV has five-fold symmetry with 32 or 42 capsomers. Exact classification of AEV awaits characterization of the viral nucleic acid.

Pedogenic formation of montmorillonite from a 2:1-2:2 intergrade clay mineral

USGS Publications Warehouse

Malcolm, R.L.; Nettleton, W.D.; McCracken, R.J.

1968-01-01

Montmorillonite was found to be the dominant clay mineral in surface horizons of certain soils of the North Carolina Coastal Plain whereas a 2:1-2:2 intergrade clay mineral was dominant in subjacent horizons. In all soils where this clay mineral sequence was found, the surface horizon was low in pH (below 4⋅5) and high in organic matter content. In contrast, data from studies of other soils of this region (Weed and Nelson, 1962) show that: (1) montmorillonite occurs infrequently; (2) maximum accumulation of the 2:1-2:2 intergrade normally occurs in the surface horizon and decreases with depth in the profile; (3) organic matter contents are low; and (4) pH values are only moderately acid (pH 5-6).It is theorized that the montmorillonite in the surface horizon of the soils studied originated by pedogenic weathering of the 2:1-2:2 intergrade clay mineral. The combined effects of low pH (below 4⋅5) and high organic matter content in surface horizons are believed to be the agents responsible for this mineral transformation. The protonation and solubilization (reverse of hydrolysis) of Al-polymers in the interlayer of expansible clay minerals will occur at or below pH 4⋅5 depending on the charge and steric effects of the interlayer. A low pH alone may cause this solubilization and thus mineral transformation, but in the soils studied the organic matter is believed to facilitate and accelerage the transformation. The intermediates of organic matter decomposition provide an acid environment, a source of protons, and a source of watersoluble mobile organic substances (principally fulvic acids) which have the ability to complex the solubilized aluminum and move it down the profile. This continuous removal of solubilized aluminum would provide for a favorable gradient for aluminum solubilization.The drainage class or position in a catena is believed to be less important than the chemical factors in formation of montmorillonite from 2:1-2:2 intergrade, because montmorillonite is present in all drainage classes if the surface horizon is low in pH and high in organic matter.

Single-vesicle imaging reveals different transport mechanisms between glutamatergic and GABAergic vesicles.

PubMed

Farsi, Zohreh; Preobraschenski, Julia; van den Bogaart, Geert; Riedel, Dietmar; Jahn, Reinhard; Woehler, Andrew

2016-02-26

Synaptic transmission is mediated by the release of neurotransmitters, which involves exo-endocytotic cycling of synaptic vesicles. To maintain synaptic function, synaptic vesicles are refilled with thousands of neurotransmitter molecules within seconds after endocytosis, using the energy provided by an electrochemical proton gradient. However, it is unclear how transmitter molecules carrying different net charges can be efficiently sequestered while maintaining charge neutrality and osmotic balance. We used single-vesicle imaging to monitor pH and electrical gradients and directly showed different uptake mechanisms for glutamate and γ-aminobutyric acid (GABA) operating in parallel. In contrast to glutamate, GABA was exchanged for protons, with no other ions participating in the transport cycle. Thus, only a few components are needed to guarantee reliable vesicle filling with different neurotransmitters. Copyright © 2016, American Association for the Advancement of Science.

Dissipation of the Proton Electrochemical Potential in Intact Chloroplasts (II. The pH Gradient Monitored by Cytochrome f Reduction Kinetics).

PubMed Central

Nishio, J. N.; Whitmarsh, J.

1993-01-01

The potency of various uncouplers for collapsing the light-induced pH gradient across thylakoid membranes in intact chloroplasts was investigated by time-resolved optical spectroscopy. The thylakoid transmembrane pH gradient ([delta]pH) was monitored indirectly by measuring the rate of cytochrome (Cyt) f reduction following a light flash of sufficient duration to create a sizable [delta]pH. The results show that the rate of Cyt f reduction is controlled in part by the internal pH of the thylakoid inner aqueous space. At pH values from 6.5 to 8.0, the Cyt f reduction rate was maximal, whereas at lower pH values from 6.5 to 5.5 the reduction rate decreased to 25% of the maximal rate. The ability of three uncouplers, nigericin, carbonylcyanide m-chlorophenylhydrazone, and gramicidin, to accelerate the rate of Cyt f reduction was determined for intact chloroplasts isolated from spinach (Spinacia oleracea). The efficacy of the uncouplers for collapsing the [delta]pH was determined using the empirical relationship between the [delta]pH and the Cyt f reduction rate. For intact chloroplasts, nigericin was the most effective uncoupler, followed by carbonylcyanide m-chlorophenylhydrazone, which interacted strongly with bovine serum albumin. Gramicidin D, even at high gramicidin:chlorophyll ratios, did not completely collapse the pH gradient, probably because it partitions in the envelope membranes and does not enter the intact chloroplast. PMID:12231669

Voltage and pH sensing by the voltage-gated proton channel, HV1.

PubMed

DeCoursey, Thomas E

2018-04-01

Voltage-gated proton channels are unique ion channels, membrane proteins that allow protons but no other ions to cross cell membranes. They are found in diverse species, from unicellular marine life to humans. In all cells, their function requires that they open and conduct current only under certain conditions, typically when the electrochemical gradient for protons is outwards. Consequently, these proteins behave like rectifiers, conducting protons out of cells. Their activity has electrical consequences and also changes the pH on both sides of the membrane. Here we summarize what is known about the way these proteins sense the membrane potential and the pH inside and outside the cell. Currently, it is hypothesized that membrane potential is sensed by permanently charged arginines (with very high p K a ) within the protein, which results in parts of the protein moving to produce a conduction pathway. The mechanism of pH sensing appears to involve titratable side chains of particular amino acids. For this purpose their p K a needs to be within the operational pH range. We propose a 'counter-charge' model for pH sensing in which electrostatic interactions within the protein are selectively disrupted by protonation of internally or externally accessible groups. © 2018 The Author.

Voltage and pH sensing by the voltage-gated proton channel, HV1

PubMed Central

2018-01-01

Voltage-gated proton channels are unique ion channels, membrane proteins that allow protons but no other ions to cross cell membranes. They are found in diverse species, from unicellular marine life to humans. In all cells, their function requires that they open and conduct current only under certain conditions, typically when the electrochemical gradient for protons is outwards. Consequently, these proteins behave like rectifiers, conducting protons out of cells. Their activity has electrical consequences and also changes the pH on both sides of the membrane. Here we summarize what is known about the way these proteins sense the membrane potential and the pH inside and outside the cell. Currently, it is hypothesized that membrane potential is sensed by permanently charged arginines (with very high pKa) within the protein, which results in parts of the protein moving to produce a conduction pathway. The mechanism of pH sensing appears to involve titratable side chains of particular amino acids. For this purpose their pKa needs to be within the operational pH range. We propose a ‘counter-charge’ model for pH sensing in which electrostatic interactions within the protein are selectively disrupted by protonation of internally or externally accessible groups. PMID:29643227

Microbial plant litter decomposition in aquatic and terrestrial boreal systems along a natural fertility gradient

NASA Astrophysics Data System (ADS)

Soares, A. Margarida P. M.; Kritzberg, Emma S.; Rousk, Johannes

2017-04-01

Plant litter decomposition is a global ecosystem process, with a crucial role in carbon and nutrient cycling. The majority of litter processing occurs in terrestrial systems, but an important fraction also takes place in inland waters. Among environmental factors, pH impacts the litter decomposition through its selective influence on microbial decomposers. Fungal communities are less affected by pH than bacteria, possibly owing to a wider pH tolerance by this group. On the other hand, bacterial pH optima are constrained to a narrower range of pH values. The microbial decomposition of litter is universally nutrient limited; but few comparisons exist between terrestrial and aquatic systems. We investigated the microbial colonisation and decomposition of plant litter along a fertility gradient, which varied in both pH and N availability in both soil and adjacent water. To do this we installed litterbags with birch (Betula pendula) in streams and corresponding soils in adjacent riparian areas in a boreal system, in Krycklan, Sweden. During the four months covering the ice-free growth season we monitored the successional dynamics of fungal (acetate incorporation into ergosterol) and bacterial growth (thymidine incorporation), microbial respiration in leaf litter, and quantitative and qualitative changes in litter over time. We observed that bacterial growth rates were initially higher in litter decomposing in streams than those in soils, but differences between terrestrial and aquatic bacterial production converged towards the end of the experiment. In litter bags installed in soils, bacterial growth was lower at sites with more acidic pH and lower N availability, while aquatic bacteria were relatively unaffected by the fertility level. Fungal growth rates were two-fold higher for litter decomposing in streams than in soils. In aquatic systems, fungal growth was initially lower in low fertility sites, but differences gradually disappeared over the time course. Fungal growth rates measured on litter-bags in soils were relatively stable over time, with unclear links to fertility. Microbial respiration rates were highest in litterbags buried in soils, and only initially negatively affected by pH. There was a large decrease in litter mass loss initially in aquatic systems. Subsequently the rates of loss stabilized to similar values to those in terrestrial systems, to finally be exceeded by the rates of loss in terrestrial systems. In conclusion, initial decomposition of litter appeared to be N-limited in aquatic systems, which was associated with a fungal dominance. In contrast, litter decomposition in terrestrial systems appeared to be lower in acidic sites, which coincided with lower growth rates of bacteria. Litter degradation was initially faster in aquatic systems, but overall mass-loss over the full time course was higher in terrestrial systems.

Effect of simulated acid rain on the litter decomposition of Quercus acutissima and Pinus massoniana in forest soil microcosms and the relationship with soil enzyme activities.

PubMed

Wang, Congyan; Guo, Peng; Han, Guomin; Feng, Xiaoguang; Zhang, Peng; Tian, Xingjun

2010-06-01

With the continuing increase in human activities, ecologists are increasingly interested in understanding the effects of acid rain on litter decomposition. Two dominant litters were chosen from Zijin Mountain in China: Quercus acutissima from a broad-leaved forest and Pinus massoniana from a coniferous forest. The litters were incubated in microcosms and treated with simulated acid rain (gradient pH levels). During a six-month incubation, changes in chemical composition (i.e., lignin, total carbohydrate, and nitrogen), litter mass losses, soil pH values, and activities of degradative enzymes were determined. Results showed that litter mass losses were depressed after exposure to acid rain and the effects of acid rain on the litter decomposition rates of needles were higher than on those of leaves. Results also revealed that simulated acid rain restrained the activities of cellulase, invertase, nitrate reductase, acid phosphatase, alkaline phosphatase, polyphenol oxidase, and urease, while it enhanced the activities of catalase in most cases during the six-month decomposition process. Catalase and polyphenol oxidase were primarily responsible for litter decomposition in the broad-leaved forest, while invertase, nitrate reductase, and urease were primarily responsible for litter decomposition in the coniferous forest. The results suggest acid rain-restrained litter decomposition may be due to the depressed enzymatic activities. According to the results of this study, soil carbon in subtropical forests would accumulate as a long-term consequence of continued acid rain. This may presumably alter the balance of ecosystem carbon flux, nutrient cycling, and humus formation, which may, in turn, have multiple effects on forest ecosystems. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Uptake of 2, 4-Dichlorophenoxyacetic acid by Pseudomonas fluorescens

USGS Publications Warehouse

Wedemeyer, G.A.

1966-01-01

Factors influencing the uptake of the sodium salt of 2,4-dichlorophenoxyacetic acid (2,4-D), under conditions in which no net metabolism occurred, were investigated in an effort to determine both the significance of “nonmetabolic” uptake as a potential agent in reducing pesticide levels and the mechanisms involved. Uptake of 2,4-D was affected by pH, temperature, and the presence of other organic and inorganic compounds. Uptake was more pronounced at pH values less than 6, which implies that there may be some interaction between charged groups on the cell and the ionized carboxyl group of 2,4-D. Active transport, carriermediated diffusion, passive diffusion, and adsorption were considered as possible mechanisms. Though uptake was inhibited by glucose, sodium azide, and fluorodinitrobenzene (but not by uranylion), 2,4-D was not accumulated against a concentration gradient, a necessary consequence of an active transport system, nor was isotope counterflow found to occur. Thus, carrier-mediated diffusion was finally precluded, implying that uptake probably occurs by a two-step process: sorption onto the cell wall followed by passive diffusion into the cytoplasm.

Uptake of 2,4-dichlorophenoxyacetic acid by Pseudomonas fluorescens

USGS Publications Warehouse

Wedemeyer, Gary

1966-01-01

Factors influencing the uptake of the sodium salt of 2,4-dichlorophenoxyacetic acid (2,4-D), under conditions in which no net metabolism occurred, were investigated in an effort to determine both the significance of “non-metabolic” uptake as a potential agent in reducing pesticide levels and the mechanisms involved. Uptake of 2,4-D was affected by pH, temperature, and the presence of other organic and inorganic compounds. Uptake was more pronounced at pH values less than 6, which implies that there may be some interaction between charged groups on the cell and the ionized carboxyl group of 2,4-D. Active transport, carrier-mediated diffusion, passive diffusion, and adsorption were considered as possible mechanisms. Though uptake was inhibited by glucose, sodium azide, and fluorodinitrobenzene (but not by uranyl ion), 2,4-D was not accumulated against a concentration gradient, a necessary consequence of an active transport system, nor was isotope counterflow found to occur. Thus, carrier-mediated diffusion was finally precluded, implying that uptake probably occurs by a two-step process: sorption onto the cell wall followed by passive diffusion into the cytoplasm.

Photophosphorylation capacity of stable spheroplast preparations of anabaena.

PubMed

Spiller, H

1980-09-01

Spheroplasts from Anabaena 7119 (formerly designated Nostoc muscorum) were prepared in the presence of serum albumin in 0.5 molar sucrose. Electron transport and photophosphorylation were preserved (> 70% of the maximum rate for 1 week). The pH profile of electron transport and photophosphorylation in the reactions H(2)O --> NADP, H(2)O --> methyl viologen, and H(2)O --> ferricyanide shows that uncoupling by ammonia is small throughout and increases slightly with higher pH. ADP + Pi increased NADP reduction from H(2)O by 2.5-fold. The ratios of ATP formed per electron pair transported ranged from 0.9 to 1.5. Effects of catalase and superoxide dismutase on the overall O(2) balance implicate pseudocyclic electron transport and phosphorylation. The quenching of 9-aminoacridine fluorescence indicates the formation of a Delta pH from 2 to 2.6 during illumination. This pH gradient is abolished by uncouplers; however, complete uncoupling is achieved only by 3-chlorocarbonyl cyanide phenylhydrazone or valinomycin + NH(4) (+). In the presence of NH(4) (+) alone, the membrane potential may act as the driving force for photophosphorylation.Increasing amounts of bovine serum albumin protected phosphorylation from uncoupling by silicomolybdic acid. 3-(3,4-Dichlorophenyl)-1, 1-dimethylurea-insensitive water oxidation by silicomolybdic acid provides evidence that the site for 3-(3,4-dichlorophenyl)-1, 1-dimethylurea action is on the acceptor and not donor side of photosystem II in the procaryote Anabaena. It is concluded that stable spheroplasts retain coupled electron transport approaching in vivo rates.

Dispersed phase volume fraction, weak acids and Tween 80 in a model emulsion: Effect on the germination and growth of Bacillus weihenstephanensis KBAB4 spores.

PubMed

Léonard-Akkari, Lucie; Guégan, Stéphanie; Courand, Fabienne; Couvert, Olivier; Lepage, Jean-François; Rondeau-Mouro, Corinne; Desriac, Noémie; Mathot, Anne-Gabrielle; Leguérinel, Ivan; Coroller, Louis; Decourcelle, Nicolas

2018-07-01

In foodstuffs, physico-chemical interactions and/or physical constraints between spores, inhibitors and food components may exist. Thus, the objective of this study was to investigate such interactions using a model emulsion as a microbial medium in order to improve bacterial spore control with better knowledge of the interactions in the formulation. Emulsions were prepared with hexadecane mixed with nutrient broth using sonication and were stabilized by Tween 80 and Span 80. The hexadecane ratio was either 35% (v/v) or 50% (v/v) and each emulsion was studied in the presence of organic acid (acetic, lactic or hexanoic) at two pH levels (5.5 and 6). Self-diffusion coefficients of emulsion components and the organic acids were measured by Pulsed Field Gradient-Nuclear Magnetic Resonance (PFG-NMR). The inhibition effect on the spore germination and cell growth of Bacillus weihenstephanensis KBAB4 was characterized by the measure of the probability of growth using the most probable number methodology, and the measure of the time taken for the cells to germinate and grow using a single cell Bioscreen® method and using flow cytometry. The inhibition of spore germination and growth in the model emulsion depended on the dispersed phase volume fraction and the pH value. The effect of the dispersed phase volume fraction was due to a combination of (i) the lipophilicity of the biocide, hexanoic acid, that may have had an impact on the distribution of organic acid between hexadecane and the aqueous phases and (ii) the antimicrobial activity of the emulsifier Tween 80 detected at the acidic pH value. The interface phenomena seemed to have a major influence. Future work will focus on the exploration of these phenomena at the interface. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of a copper-tolerant grass (Agrostis capillaris) on the ecosystem of a copper-contaminated arable soil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boon, G.T.; Bouwman, L.A.; Bloem, J.

1998-10-01

To test how a dysfunctioning ecosystem of a severely metal-polluted soil responds to renewed plant growth, a pot experiment was conducted with soil from an experimental arable field with pH and copper gradients imposed 13 years ago. In this experiment, four pH/copper combinations from this field were either planted with a pH- and copper-resistant grass cultivar or remained fallow. During a 10-week period, the dynamics of the microbial activity and of the abundances of bacteria, protozoa. and nematodes were measured, as were the dynamics of several chemical soil parameters. After 13 years of copper, which had resulted in severely reducedmore » crop growth, no effects were observed on bacterial numbers, respiration, or protozoan numbers, but bacterial growth was strongly reduced in the low pH plots, and even more so in low pH plots enriched with copper. Of the organisms, only nematodes were negatively affected under conditions of high copper load at low pH. In these plots, numbers belonging to all feeding categories were strongly reduced. Planting of a copper-tolerant grass variety, Agrostis capillaris L. var. Parys Mountain, resulted within 10 weeks in faster bacterial growth and more protozoa and bacterivorous nematodes in comparison with fallow controls; these effects were markedly strongest in the acidic, copper-enriched soils. During incubation, fungivorous nematodes increased in all treatments, in fallow and in planted pots and in the pots with high-copper, low-pH soil. The results of this experiment suggest that introduction of plant growth is one of the major causes of increased biological activity in acidic contaminated soils. Planting such soils with metal-tolerant plant species can reestablish the necessary food base to support soil organism growth, and this can lead to numerous positive effects, reversing the loss of soil functions due to the high copper levels under acidic conditions.« less

Precision Sensing by Two Opposing Gradient Sensors: How Does Escherichia coli Find its Preferred pH Level?

PubMed Central

Hu, Bo; Tu, Yuhai

2013-01-01

It is essential for bacteria to find optimal conditions for their growth and survival. The optimal levels of certain environmental factors (such as pH and temperature) often correspond to some intermediate points of the respective gradients. This requires the ability of bacteria to navigate from both directions toward the optimum location and is distinct from the conventional unidirectional chemotactic strategy. Remarkably, Escherichia coli cells can perform such a precision sensing task in pH taxis by using the same chemotaxis machinery, but with opposite pH responses from two different chemoreceptors (Tar and Tsr). To understand bacterial pH sensing, we developed an Ising-type model for a mixed cluster of opposing receptors based on the push-pull mechanism. Our model can quantitatively explain experimental observations in pH taxis for various mutants and wild-type cells. We show how the preferred pH level depends on the relative abundance of the competing sensors and how the sensory activity regulates the behavioral response. Our model allows us to make quantitative predictions on signal integration of pH and chemoattractant stimuli. Our study reveals two general conditions and a robust push-pull scheme for precision sensing, which should be applicable in other adaptive sensory systems with opposing gradient sensors. PMID:23823247

[Simultaneous analysis of four diuretic drugs by HPLC and its application to health food supplements advertising weight reduction].

PubMed

Goto, Tomomi; Mikami, Eiichi; Ohno, Tsutomu; Matsumoto, Hiroshi

2002-04-01

A high-performance liquid chromatographic (HPLC) method for the simultaneous analysis of triamterene, trichlormethiazide, furosemide and spironolactone is presented for application in the examination of health food supplements advertising weight reduction and in the analysis of pharmaceuticals. The HPLC assay was performed under gradient conditions using a Wakosil ODS 5C18 column (5 microns, 150 x 4.6 mm i.d.). The mobile phase consisted of a gradient program with a mixture of water and acetonitrile containing 0.1% triethylamine adjusted with phosphoric acid to pH 3.0: from 0 to 6 min, 15% acetonitrile; from 6 to 20 min, linear gradient from 15 to 50% acetonitrile; and from 20 to 40 min, 50% acetonitrile. The column effluent was monitored from 0 to 20 min at 260 nm and from 20 to 40 min at 235 nm. The calibration curves of the four drugs showed good linearity and the correlation coefficients were better than 0.999 in all cases. The lower limits of detection were approximately 40 ng for each drug. Commercially available health food supplements and pharmaceuticals were analyzed after extraction with a mixture of methanol and acetic acid (99:1). The procedure described here is suitable for the screening of four diuretic drugs in adulterated supplements and for the quality control of pharmaceuticals with minimal sample preparation.

Molecular mechanisms for generating transmembrane proton gradients

PubMed Central

Gunner, M.R.; Amin, Muhamed; Zhu, Xuyu; Lu, Jianxun

2013-01-01

Membrane proteins use the energy of light or high energy substrates to build a transmembrane proton gradient through a series of reactions leading to proton release into the lower pH compartment (P-side) and proton uptake from the higher pH compartment (N-side). This review considers how the proton affinity of the substrates, cofactors and amino acids are modified in four proteins to drive proton transfers. Bacterial reaction centers (RCs) and photosystem II (PSII) carry out redox chemistry with the species to be oxidized on the P-side while reduction occurs on the N-side of the membrane. Terminal redox cofactors are used which have pKas that are strongly dependent on their redox state, so that protons are lost on oxidation and gained on reduction. Bacteriorhodopsin is a true proton pump. Light activation triggers trans to cis isomerization of a bound retinal. Strong electrostatic interactions within clusters of amino acids are modified by the conformational changes initiated by retinal motion leading to changes in proton affinity, driving transmembrane proton transfer. Cytochrome c oxidase (CcO) catalyzes the reduction of O2 to water. The protons needed for chemistry are bound from the N-side. The reduction chemistry also drives proton pumping from N- to P-side. Overall, in CcO the uptake of 4 electrons to reduce O2 transports 8 charges across the membrane, with each reduction fully coupled to removal of two protons from the N-side, the delivery of one for chemistry and transport of the other to the P-side. PMID:23507617

Contrasting trends in distribution of four major planktonic betaproteobacterial groups along a pH gradient of epilimnia of 72 freshwater habitats.

PubMed

Jezbera, Jan; Jezberová, Jitka; Koll, Ulrike; Horňák, Karel; Šimek, Karel; Hahn, Martin W

2012-08-01

The distribution and abundance of Betaproteobacteria and three of its genera - Limnohabitans (R-BT065 lineage), Polynucleobacter (including subclusters Polynucleobacter necessarius and Polynucleobacter acidiphobus/Polynucleobacter difficilis), and Methylophilus - across the epilimnia of 72 limnologically diverse freshwater habitats were investigated using fluorescence in situ hybridization. Moreover, seasonal development of Betaproteobacteria subgroups along the longitudinal axis of a reservoir was followed. Betaproteobacteria comprised on average 29.1%, Polynucleobacter 11.6%, P. necessarius 10.1%, P. acidiphobus/difficilis 0.5%, Limnohabitans 8.9%, and Methylophilus 0.9% of total bacterioplankton cells in the investigated habitats. Polynucleobacter necessarius and Limnohabitans coexisted in the majority of habitats but showed contrasting abundance patterns along the pH gradient of habitats (pH, 3.8-8.5). The observed distribution patterns could theoretically be explained by different preferences for substrate sources, that is, substances of humic origin in acidic waters and algal-derived substances in alkaline waters. However, substrate utilization patterns observed in laboratory experiments indicate no coherent group-specific differences in substrate preferences. Interestingly, similar distribution patterns were revealed for Limnohabitans and P. acidiphobus/difficilis, suggesting similar ecological adaptations of these distantly related taxa. Our findings further emphasize that at least two taxa of freshwater Betaproteobacteria represent ecologically diversified groups. Investigations at higher phylogenetic resolution are required for obtaining further insights into their ecology. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Contributions of nuclear magnetic resonance to renal biochemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, B.; Freeman, D.; Chan, L.

/sup 31/P NMR as a descriptive technique is of interest to nephrologists. Particular contributions of /sup 31/P NMR to our understanding of renal function may be enumerated.: Free metabolite levels are different from those classically accepted; in particular, ADP and Pi are low with implications for the control of renal metabolism and Pi transport, and, via the phosphorylation potential, for Na+ transport. Renal pH is heterogeneous; between cortex, outer medulla, and papilla, and between cell and lumen, a large pH gradient exists. Also, quantitation between cytosol and mitochondrion of the pH gradient is now feasible. In acute renal failure ofmore » either ischemic or nonischemic origin, both ATP depletion and acidification of the renal cell result in damage, with increasing evidence for the importance of the latter. Measurements of renal metabolic rate in vivo suggest the existence of a prodromal phase of acute renal failure, which could lead to its detection at an earlier and possibly reversible stage. Human renal cancers show a unique /sup 31/P NMR spectrum and a very acidic environment. Cancer chemotherapy may alter this and detection of such changes with NMR offers a method of therapeutic monitoring with significance beyond nephrology. Renal cortex and medulla have a different T1 relaxation time, possibly due to differences in lipid composition. It seems that NMR spectroscopy has much to offer to the future understanding of the relationship between renal biochemistry and function. 56 references.« less

An analytical method to screen for six thyreostatic drug residues in the thyroid gland and muscle tissues of food producing animals by liquid chromatography with ultraviolet absorption detection and liquid chromatography/mass spectrometry.

PubMed

Asea, Philip E; MacNeil, James D; Boison, Joe O

2006-01-01

A method was developed and validated to screen for residues of the thyreostatic drugs, tapazole (TAP), mercaptobenzimidazole (MBI), thiouracil (TU), methylthiouracil (MTU), propylthiouracil (PrTU), and phenylthiouracil (PhTU) in bovine, equine, ovine, and porcine thyroid and muscle tissues at concentrations > or = 5 ng/g using 2-methoxy-mercaptobenzimidazole (MeMBI) and dimethylthiouracil (DMTU) as internal standards. In this method, the drugs were solvent extracted from thyroid and muscle tissue and cleaned up on an amino-propyl solid-phase extraction (SPE) cartridge. The unretained fraction containing TAP and MBI and the internal standard, MeMBI, was collected as Fraction 1. The retained fraction containing TU, MTU, PrTU, PhTU, and the internal standard, DMTU, was eluted with 3% acetic acid-isopropanol as Fraction 2. Fraction 1 was further cleaned up on an alumina B SPE cartridge and analyzed by gradient elution on a C18 high-performance liquid chromatography (HPLC) column with ultraviolet detection at wavelengths of 255 and 300 nm. Fraction 2 was taken to dryness, derivatized with 4-chloro-7-nitrobenzo-2-furazan at pH 8, and analyzed by gradient elution on a C18 LC column with mass spectrometry (MS) detection. Any "presumptive positive" test results were submitted for further analysis by LC/MS/MS. The validated method was applied to the analysis of over 300 thyroid tissue samples.

Plasma membrane H⁺ -ATPase regulation is required for auxin gradient formation preceding phototropic growth.

PubMed

Hohm, Tim; Demarsy, Emilie; Quan, Clément; Allenbach Petrolati, Laure; Preuten, Tobias; Vernoux, Teva; Bergmann, Sven; Fankhauser, Christian

2014-09-26

Phototropism is a growth response allowing plants to align their photosynthetic organs toward incoming light and thereby to optimize photosynthetic activity. Formation of a lateral gradient of the phytohormone auxin is a key step to trigger asymmetric growth of the shoot leading to phototropic reorientation. To identify important regulators of auxin gradient formation, we developed an auxin flux model that enabled us to test in silico the impact of different morphological and biophysical parameters on gradient formation, including the contribution of the extracellular space (cell wall) or apoplast. Our model indicates that cell size, cell distributions, and apoplast thickness are all important factors affecting gradient formation. Among all tested variables, regulation of apoplastic pH was the most important to enable the formation of a lateral auxin gradient. To test this prediction, we interfered with the activity of plasma membrane H⁺ -ATPases that are required to control apoplastic pH. Our results show that H⁺ -ATPases are indeed important for the establishment of a lateral auxin gradient and phototropism. Moreover, we show that during phototropism, H⁺ -ATPase activity is regulated by the phototropin photoreceptors, providing a mechanism by which light influences apoplastic pH. © 2014 The Authors. Published under the terms of the CC BY 4.0 license.

Influence of elevated temperature and acid mine drainage on mortality of the crayfish Cambarus bartonii

USGS Publications Warehouse

Hartman, K.J.; Hom, C.D.; Mazik, P.M.

2010-01-01

Effects of elevated temperature and acid mine drainage (AMD) on crayfish mortality were investigated in the Stony River, Grant County, West Virginia. During summers 2003 and 2004, four-week in situ bioassays were performed along a thermal and AMD gradient with the native crayfish Cambarus bartonii. Crayfish mortality was analyzed in conjunction with temperature and AMD related variables (pH, specific conductivity). Mortality was significantly higher (48-88%) at sites with high temperatures during 2003 (max = 33.0??C), but no significant differences were observed in 2004 (max = 32.0??C). Temperatures were higher in 2003 than 2004 due to increased discharge from a cooling reservoir flowing into the river. Additionally, duration of high temperature was approximately four days in 2003 as compared with only one day in 2004. No significant relationship between acid mine drainage variables and crayfish mortality was apparent.

Adenine nucleotide transport in sonic submitochondrial particles. Kinetic properties and binding of specific inhibitors.

PubMed

Lauquin, G J; Villiers, C; Michejda, J W; Hryniewiecka, L V; Vignais, P V

1977-05-11

1. A procedure for preparation of sonic submitochondrial particles competent for adenine nucleotide transport is described. ADP or ATP transport was assayed, in the presence of oligomycin, in a saline medium made of 0.125 M KCl, 1 mM EDTA, 10 mM 4-morpholinopropane sulfonic acid buffer, pH 6.5. 2. Sonic particles transport ADP and ATP by an exchange diffusion process. Externally added ADP (or ATP) is exchanged with internal ADP and ATP with a stoichiometry of one to one. The V value for ADP transport 5 degrees C was between 2 and 3 nmol/min per mg protein. 3. The transport system in sonic particles is specific for ADP and ATP. It is strongly dependent on temperature. The activation energy between 0 and 9 degrees C is approx. 35 kcal/mol. The optimum pH is 6.5, 4, Like in intact mitochondria, externally added ADP is transported into sonic particles faster at a given concentration than externally added ATP. The V value for ADP transport is 1.5-2 times higher than the V value for ATP transport. 5. The transition from the energized to the deenergized state in sonic particles results in a decrease of the pH gradient across the membrane (internal pH less than external pH) and in a 2-4 fold increase in the Km value for ATP. This latter effect is opposite that found for transport of added ATP in intact mitochondria (Souverijn, J.H.M., Huisman, L.A., Rosing J. and Kemp, Jr., A. (1973) Biochim. Biophys. Acta 305, 185-198). Energization has no effect on the V value of ATP transport in sonic particles. 6. In contrast to intact mitochondria, inhibition of ADP transport in sonic particles by bongkrekic acid does not have any lag-time and does not depend on pH. The inhibition caused by bongkrekic acid is a mixed type inhibition with a Ki value of 1.2 micronM. Atractyloside and carboxyatractyloside do not inhibit ADP transport in sonic particles, unless the particles have been preloaded with these inhibitors during the sonication. 7. Palmityl-CoA added to sonic particles inhibits efficiently ADP transport. The mixed type inhibition found with palmityl-CoA has a Ki value of 1.6 micronM. 8. [3H]Bongkrekic acid binds to sonic particles readily and with high affinity. Bongkrekic acic binding to sonic particles does not depend on pH and it has a saturation plateau, corresponding approximately to 1.3 mol of site per mol of cytochrome a. The number of [3H]atracytloside binding sites is much lower (one-fifth of the bongkrekic acid). External carboxyatractyloside does not compete with [3H]bongkrekic acid for binding to sonic particles. However, when carboxyatractyloside is present inside the particles, it inhibits the binding of [3H]bongkrekic acid.

Trophic Status Controls Mercury Methylation Pathways in Northern Peats

NASA Astrophysics Data System (ADS)

Hines, M. E.; Zhang, L.; Barkay, T.; Krabbenhoft, D. P.; Schaefer, J.; Hu, H.; Sidelinger, W.; Liu, X.; Wang, Y.

2015-12-01

Methyl mercury (MeHg) can be produced by a variety of microbes including syntrophs, methanogens, acetogens, and fermenters, besides sulfate (SO42-, SRB) and iron- reducing bacteria. Many freshwater wetlands are deficient in electron acceptors that support the traditional respiratory pathways of methylation, yet they accumulate high levels of MeHg. To investigate methylation in these wetlands and to connect these pathways with vegetation and microbial communities, incubation experiments were conducted using peats from 26 sites in Alaska. The sites were clustered using multiple factor analysis based on pH, temp, CH4 and volatile fatty acids production rates, and surface vegetation composition. Three clusters were generated and corresponded to three trophic levels that were manifested by three pH levels (3.5, 4.5, and 5). Hg methylation activity in laboratory incubations was determined using the short-lived radioisotope 197Hg. In the low pH, Sphagnum-dominated cluster, methylation rates were less than 1% day-1 and likely conducted by primary fermenters. Conversely, the high pH trophic cluster dominated by Carex aquatilis and active syntrophy exhibited Hg methylation rates as high as 12% day-1. In intermediate sites, rich in Sphagnum magellanicum with less Carex, a gradient in syntrophy and Hg methylation paths was observed. Amendments with process-stimulators and inhibitors revealed no evidence of SO42- reduction, but suggested that SRB, metabolizing either syntrophically with methanogens and/or by fermentation, likely methylated Hg. While on going metatranscriptomics studies are required to verify the role of syntrophs, fermenters, and methanogens as methylators, these results revealed that Hg methylation pathways change greatly along trophic gradients with a dominance of respiratory pathways in mineral-rich sites, syntrophy dominance in intermediate sites, and fermentation dominance in nutrient-poor sites.

HPLC confirmatory method development for the determination of seven quinolones in salmon tissue (Salmo salar L.) validated according to the European Union Decision 2002/657/EC.

PubMed

Evaggelopoulou, Evaggelia N; Samanidou, Victoria F

2013-01-15

A confirmatory high pressure liquid chromatographic method for the determination of seven quinolone antibiotics in tissue of Atlantic salmon (Salmo salar L.) was developed. Ciprofloxacin (CIP), danofloxacin (DAN), enrofloxacin (ENR), sarafloxacin (SAR), oxolinic acid (OXO), nalidixic acid (NAL) and flumequine (FLU) were separated on a Perfectsil ODS-2 120 (250 mm × 4 mm, 5 μm) column by gradient elution with a mobile phase consisting of 0.1% trifluoroacetic acid (pH=1), acetonitrile and methanol at 25°C within 22 min. Analytes were monitored at 255 nm (for the determination of OXO, NAL and FLU) and 275 nm (for CIP, DAN, ENR and SAR) by means of photodiode array detector. Examined quinolones were isolated from salmon tissue by extraction with citrate buffer solution (pH=4.7) and purified by solid phase extraction using Oasis HLB (200mg/6 mL) cartridges. The developed method was fully validated in terms of selectivity, linearity, accuracy, precision, stability and sensitivity according to the European Union Decision 2002/657/EC. The accuracy of the method was additionally proved by its application to certified reference material of salmon tissue (BCR® 725). Copyright © 2012 Elsevier Ltd. All rights reserved.

Isoelectric focusing analysis of antibody clonotype changes occurring during immune responses using immobilized pH gradients

NASA Technical Reports Server (NTRS)

Knisley, Keith A.; Rodkey, L. Scott

1988-01-01

Serum was collected from rabbits at 2-day intervals following a single injection with tetanus toxoid or at weekly intervals following multiple injections with Micrococcus lysodeikticus cell walls. These sera were analyzed for the presence of individual clonotypes of specific antitetanus or antimicrococcal antibodies by isoelectric focusing in immobilized pH gradients with added carrier ampholytes followed by affinity immunoblotting. The affinity immunoblots obtained clearly defined both the rapid disappearance and late appearance of distinct subsets of antibody clonotypes during the response. These data demonstrate the application of affinity immunoblotting combined with immobilized pH gradients for detecting the subtle changes in specific antibody clonotype patterns which occur during an immune response.

pH-sensitive interaction of HMG-CoA reductase inhibitors (statins) with organic anion transporting polypeptide 2B1.

PubMed

Varma, Manthena V; Rotter, Charles J; Chupka, Jonathan; Whalen, Kevin M; Duignan, David B; Feng, Bo; Litchfield, John; Goosen, Theunis C; El-Kattan, Ayman F

2011-08-01

The human organic anion transporting polypeptide 2B1 (OATP2B1, SLCO2B1) is ubiquitously expressed and may play an important role in the disposition of xenobiotics. The present study aimed to examine the role of OATP2B1 in the intestinal absorption and tissue uptake of 3-hydroxy-3-methylglutaryl-Coenzyme A (HMG-CoA) reductase inhibitors (statins). We first investigated the functional affinity of statins to the transporter as a function of extracellular pH, using OATP2B1-transfeced HEK293 cells. The results indicate that OATP2B1-mediated transport is significant for rosuvastatin, fluvastatin and atorvastatin, at neutral pH. However, OATP2B1 showed broader substrate specificity as well as enhanced transporter activity at acidic pH. Furthermore, uptake at acidic pH was diminished in the presence of proton ionophore, suggesting proton gradient as the driving force for OATP2B1 activity. Notably, passive transport rates are predominant or comparable to active transport rates for statins, except for rosuvastatin and fluvastatin. Second, we studied the effect of OATP modulators on statin uptake. At pH 6.0, OATP2B1-mediated transport of atorvastatin and cerivastatin was not inhibitable, while rosuvastatin transport was inhibited by E-3-S, rifamycin SV and cyclosporine with IC(50) values of 19.7 ± 3.3 μM, 0.53 ± 0.2 μM and 2.2 ± 0.4 μM, respectively. Rifamycin SV inhibited OATP2B1-mediated transport of E-3-S and rosuvastatin with similar IC(50) values at pH 6.0 and 7.4, suggesting that the inhibitor affinity is not pH-dependent. Finally, we noted that OATP2B1-mediated transport of E-3-S, but not rosuvastatin, is pH sensitive in intestinal epithelial (Caco-2) cells. However, uptake of E-3-S and rosuvastatin by Caco-2 cells was diminished in the presence of proton ionophore. The present results indicate that OATP2B1 may be involved in the tissue uptake of rosuvastatin and fluvastatin, while OATP2B1 may play a significant role in the intestinal absorption of several statins due to their transporter affinity at acidic pH.

Fermentation pH influences the physiological-state dynamics of Lactobacillus bulgaricus CFL1 during pH-controlled culture.

PubMed

Rault, Aline; Bouix, Marielle; Béal, Catherine

2009-07-01

This study aims at better understanding the effects of fermentation pH and harvesting time on Lactobacillus bulgaricus CFL1 cellular state in order to improve knowledge of the dynamics of the physiological state and to better manage starter production. The Cinac system and multiparametric flow cytometry were used to characterize and compare the progress of the physiological events that occurred during pH 6 and pH 5 controlled cultures. Acidification activity, membrane damage, enzymatic activity, cellular depolarization, intracellular pH, and pH gradient were determined and compared during growing conditions. Strong differences in the time course of viability, membrane integrity, and acidification activity were displayed between pH 6 and pH 5 cultures. As a main result, the pH 5 control during fermentation allowed the cells to maintain a more robust physiological state, with high viability and stable acidification activity throughout growth, in opposition to a viability decrease and fluctuation of activity at pH 6. This result was mainly explained by differences in lactate concentration in the culture medium and in pH gradient value. The elevated content of the ionic lactate form at high pH values damaged membrane integrity that led to a viability decrease. In contrast, the high pH gradient observed throughout pH 5 cultures was associated with an increased energetic level that helped the cells maintain their physiological state. Such results may benefit industrial starter producers and fermented-product manufacturers by allowing them to better control the quality of their starters, before freezing or before using them for food fermentation.

Synthesis and Fabrication of Nanocomposite Fibers of Collagen-Cellulose Nanocrystals by Coelectrocompaction.

PubMed

Cudjoe, Elvis; Younesi, Mousa; Cudjoe, Edward; Akkus, Ozan; Rowan, Stuart J

2017-04-10

An electrochemical process has been used to compact cellulose nanocrystals (CNC) and access aligned micron-sized CNC fibers. Placing a current across aqueous solutions of carboxylic acid functionalized CNCs (t-CNC-COOH) or carboxylic acid/primary amine functionalized CNCs (t-CNC-COOH-NH 2 ) creates a pH gradient between the electrodes, which results in the migration and concentration of the CNC fibers at their isoelectric point. By matching the carboxylic acid/amine ratio of CNCs and collagen (ca. 30:70 carboxylic acid:amine ratio), it is possible to coelectrocompact both nanofibers and access aligned nanocomposite fibers. t-CNC-COOH-NH 2 /collagen fibers showed a maximum increase in mechanical properties at 5 wt % of t-CNC-COOH-NH 2 . Compared to collagen/CNC films which have no alignment in the plane of the films, the tensile properties of the aligned fibers show a significant enhancement in the wet mechanical properties (40 MPa vs 230 MPa) for the 5 wt % of t-CNC-COOH-NH 2 /collagen films and fiber, respectively.

Iron and aluminum solid phase dynamics and carbon storage across a water balance gradient in volcanic soils

NASA Astrophysics Data System (ADS)

Bateman, J. B.; Fendorf, S. E.; Vitousek, P.

2017-12-01

Iron (Fe) and Aluminum (Al) are major components of volcanic soils, and strongly influence the stability of soil carbon (C). The stability of Fe and Al phases is dictated by the redox conditions and pH of soils, respectively. The water balance of a soil, defined as annual precipitation minus evapotranspiration, ultimately controls pH and redox conditions. Consequently, we hypothesize that water balance influences Fe/Al solid phase dynamics in volcanic soils when the climatic regime has persisted on timescales of 20 ky. To test this hypothesis, we collected soils from a naturally occurring water balance gradient on the windward side of Mauna Kea Volcano in Hawaii, across which water balance ranges from -1270 mm/y to +2000 mm/y. Sampling included complete soil profiles, and 30 cm surface soil samples. We determined the solid phases of Fe/Al with selective extractions and total C via combustion. Extracted Fe/Al were then partitioned into operational pools: organically bound, amorphous, crystalline, primary mineral, primary glass, and residual. All soils in the study were acidic, with pH between 3.4 and 6.4. Soil C varied considerably across the gradient, from <1% C to >15% C by weight. Across sites, soil pH, Fe in primary minerals and glasses, and residual Al are negatively correlated with water balance, while soil C, organic Fe and Al, and crystalline Fe correlated positively with water balance. Organically bound Al increases linearly with water balance, while organically bound Fe is uncorrelated with water balance in soils where water balance is negative and is positively correlated with water balance in wetter sites. These results show that soils developing from the same parent material, though under different water balance regimes, range from lightly weathered ash deposits with little C accumulation in the driest regions, to heavily weathered soils composed of crystalline Fe, organic matter, and organically bound Fe/Al in the wettest regions. Al appears to be the primary stabilizer for organic matter in many of these soils, though Fe plays a role when both water availability and soil C are high. The pattern of organic Fe/Al indicate that pH is a stronger controller on C storage in these soils when water balance is low or negative, and that redox reactions become increasingly important as water balance becomes more positive.

Na+, HCO3--cotransporter NBCn1 increases pHi gradients, filopodia, and migration of smooth muscle cells and promotes arterial remodelling.

PubMed

Boedtkjer, Ebbe; Bentzon, Jacob F; Dam, Vibeke S; Aalkjaer, Christian

2016-08-01

Arterial remodelling can cause luminal narrowing and obstruct blood flow. We tested the hypothesis that cellular acid-base transport facilitates proliferation and migration of vascular smooth muscle cells (VSMCs) and enhances remodelling of conduit arteries. [Formula: see text]-cotransport via NBCn1 (Slc4a7) mediates net acid extrusion and controls steady-state intracellular pH (pHi) in VSMCs of mouse carotid arteries and primary aortic explants. Carotid arteries undergo hypertrophic inward remodelling in response to partial or complete ligation in vivo, but the increase in media area and thickness and reduction in lumen diameter are attenuated in arteries from NBCn1 knock-out compared with wild-type mice. With [Formula: see text] present, gradients for pHi (∼0.2 units magnitude) exist along the axis of VSMC migration in primary explants from wild-type but not NBCn1 knock-out mice. Knock-out or pharmacological inhibition of NBCn1 also reduces filopodia and lowers initial rates of VSMC migration after scratch-wound infliction. Interventions to reduce H(+)-buffer mobility (omission of [Formula: see text] or inhibition of carbonic anhydrases) re-establish axial pHi gradients, filopodia, and migration rates in explants from NBCn1 knock-out mice. The omission of [Formula: see text] also lowers global pHi and inhibits proliferation in primary explants. Under physiological conditions (i.e. with [Formula: see text] present), NBCn1-mediated [Formula: see text] uptake raises VSMC pHi and promotes filopodia, VSMC migration, and hypertrophic inward remodelling. We propose that axial pHi gradients enhance VSMC migration whereas global acidification inhibits VSMC proliferation and media hypertrophy after carotid artery ligation. These findings support a key role of acid-base transport, particularly via NBCn1, for development of occlusive artery disease. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

Niche specialization of terrestrial archaeal ammonia oxidizers.

PubMed

Gubry-Rangin, Cécile; Hai, Brigitte; Quince, Christopher; Engel, Marion; Thomson, Bruce C; James, Phillip; Schloter, Michael; Griffiths, Robert I; Prosser, James I; Nicol, Graeme W

2011-12-27

Soil pH is a major determinant of microbial ecosystem processes and potentially a major driver of evolution, adaptation, and diversity of ammonia oxidizers, which control soil nitrification. Archaea are major components of soil microbial communities and contribute significantly to ammonia oxidation in some soils. To determine whether pH drives evolutionary adaptation and community structure of soil archaeal ammonia oxidizers, sequences of amoA, a key functional gene of ammonia oxidation, were examined in soils at global, regional, and local scales. Globally distributed database sequences clustered into 18 well-supported phylogenetic lineages that dominated specific soil pH ranges classified as acidic (pH <5), acido-neutral (5 ≤ pH <7), or alkalinophilic (pH ≥ 7). To determine whether patterns were reproduced at regional and local scales, amoA gene fragments were amplified from DNA extracted from 47 soils in the United Kingdom (pH 3.5-8.7), including a pH-gradient formed by seven soils at a single site (pH 4.5-7.5). High-throughput sequencing and analysis of amoA gene fragments identified an additional, previously undiscovered phylogenetic lineage and revealed similar pH-associated distribution patterns at global, regional, and local scales, which were most evident for the five most abundant clusters. Archaeal amoA abundance and diversity increased with soil pH, which was the only physicochemical characteristic measured that significantly influenced community structure. These results suggest evolution based on specific adaptations to soil pH and niche specialization, resulting in a global distribution of archaeal lineages that have important consequences for soil ecosystem function and nitrogen cycling.

pH-sensitive nanocarrier based on gold/silver core-shell nanoparticles decorated multi-walled carbon manotubes for tracing drug release in living cells.

PubMed

Chen, Peng; Wang, Zhuyuan; Zong, Shenfei; Zhu, Dan; Chen, Hui; Zhang, Yizhi; Wu, Lei; Cui, Yiping

2016-01-15

We fabricate a multifunctional nanocarrier based on multi-walled carbon nanotubes (MWCNTs) decorated with gold/silver core-shell nanoparticles (Au@Ag NPs) and fluorescein isothiocyanate (FITC) for tracking the intracellular drug release process. In the demonstrated nanocarrier, the Au@Ag NPs adsorbed on the surface of MWCNTs were labeled with the pH-dependent SERS reporter 4-Mercaptobenzoic acid (4MBA) for SERS based pH sensing. FITC was conjugated on MWCNTs to provide fluorescence signal for tracing the MWCNTs. Fluorescent doxorubicin (DOX) was used as the model drug which can be loaded onto MWCNTs via π-π stacking and released from the MWCNTs under acidic condition. By detecting the SERS spectrum of 4MBA, the pH value around the nanocarrier could be monitored. Besides, by tracing the fluorescence of FITC and DOX, we can also investigate the drug release process in cells. Experimental results show that the proposed nanocarrier retained a well pH-sensitive performance in living cells, and the DOX detached from MWCNTs inside the lysosomes and entered into the cytoplasm with the MWCNTs being left in lysosomes. To further investigate the drug release dynamics, 2-D color-gradient pH mapping were plotted, which were calculated from the SERS spectra of 4MBA. The detailed release process and carrier distribution have been recorded as environmental pH changes during cell endocytosis. Furthermore, we also confirmed that the proposed nanocarrier has a good biocompatibility. It indicates that the designed nanocarrier have a great potential in intraceable drug delivery, cancer cells imaging and pH monitoring. Copyright © 2015 Elsevier B.V. All rights reserved.

Microbial Community Structure and Dynamics of Dark Fire-Cured Tobacco Fermentation▿ †

PubMed Central

Di Giacomo, Michele; Paolino, Marianna; Silvestro, Daniele; Vigliotta, Giovanni; Imperi, Francesco; Visca, Paolo; Alifano, Pietro; Parente, Dino

2007-01-01

The Italian Toscano cigar production includes a fermentation step that starts when dark fire-cured tobacco leaves are moistened and mixed with ca. 20% prefermented tobacco to form a 500-kg bulk. The dynamics of the process, lasting ca. 18 days, has never been investigated in detail, and limited information is available on microbiota involved. Here we show that Toscano fermentation is invariably associated with the following: (i) an increase in temperature, pH, and total microbial population; (ii) a decrease in reducing sugars, citric and malic acids, and nitrate content; and (iii) an increase in oxalic acid, nitrite, and tobacco-specific nitrosamine content. The microbial community structure and dynamics were investigated by culture-based and culture-independent approaches, including denaturing gradient gel electrophoresis and single-strand conformational polymorphism. Results demonstrate that fermentation is assisted by a complex microbial community, changing in structure and composition during the process. During the early phase, the moderately acidic and mesophilic environment supports the rapid growth of a yeast population predominated by Debaryomyces hansenii. At this stage, Staphylococcaceae (Jeotgalicoccus and Staphylococcus) and Lactobacillales (Aerococcus, Lactobacillus, and Weissella) are the most commonly detected bacteria. When temperature and pH increase, endospore-forming low-G+C content gram-positive bacilli (Bacillus spp.) become evident. This leads to a further pH increase and promotes growth of moderately halotolerant and alkaliphilic Actinomycetales (Corynebacterium and Yania) during the late phase. To postulate a functional role for individual microbial species assisting the fermentation process, a preliminary physiological and biochemical characterization of representative isolates was performed. PMID:17142368

Precision sensing by two opposing gradient sensors: how does Escherichia coli find its preferred pH level?

PubMed

Hu, Bo; Tu, Yuhai

2013-07-02

It is essential for bacteria to find optimal conditions for their growth and survival. The optimal levels of certain environmental factors (such as pH and temperature) often correspond to some intermediate points of the respective gradients. This requires the ability of bacteria to navigate from both directions toward the optimum location and is distinct from the conventional unidirectional chemotactic strategy. Remarkably, Escherichia coli cells can perform such a precision sensing task in pH taxis by using the same chemotaxis machinery, but with opposite pH responses from two different chemoreceptors (Tar and Tsr). To understand bacterial pH sensing, we developed an Ising-type model for a mixed cluster of opposing receptors based on the push-pull mechanism. Our model can quantitatively explain experimental observations in pH taxis for various mutants and wild-type cells. We show how the preferred pH level depends on the relative abundance of the competing sensors and how the sensory activity regulates the behavioral response. Our model allows us to make quantitative predictions on signal integration of pH and chemoattractant stimuli. Our study reveals two general conditions and a robust push-pull scheme for precision sensing, which should be applicable in other adaptive sensory systems with opposing gradient sensors. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Techniques for loading technetium-99m and rhenium-186/188 radionuclides into pre-formed liposomes for diagnostic imaging and radionuclide therapy.

PubMed

Goins, Beth; Bao, Ande; Phillips, William T

2010-01-01

Liposomes can serve as carriers of radionuclides for diagnostic imaging and therapeutic applications. Herein, procedures are outlined for radiolabeling liposomes with the gamma-emitting radionuclide, technetium-99m ((99m)Tc), for non-invasive detection of disease and for monitoring the pharmacokinetics and biodistribution of liposomal drugs, and/or with therapeutic beta-emitting radionuclides, rhenium-186/188 ((186/188)Re), for radionuclide therapy. These efficient and practical liposome radiolabeling methods use a post-labeling mechanism to load (99m)Tc or (186/188)Re into pre-formed liposomes prepared in advance of the labeling procedure. For all liposome radiolabeling methods described, a lipophilic chelator is used to transport (99m)Tc or (186/188)Re across the lipid bilayer of the pre-formed liposomes. Once within the liposome interior, the pre-encapsulated glutathione or ammonium sulfate (pH) gradient provides for stable entrapment of the (99m)Tc and (186/188)Re within the liposomes. In the first method, (99m)Tc is transported across the lipid bilayer by the lipophilic chelator, hexamethylpropyleneamine oxime (HMPAO) and (99m)Tc-HMPAO becomes trapped by interaction with the pre-encapsulated glutathione within the liposomes. In the second method, (99m)Tc or (186/188)Re is transported across the lipid bilayer by the lipophilic chelator, N,N-bis(2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA), and (99m)Tc-BMEDA or (186/188)Re-BMEDA becomes trapped by interaction with pre-encapsulated glutathione within the liposomes. In the third method, an ammonium sulfate (pH) gradient loading technique is employed using liposomes with an extraliposomal pH of 7.4 and an interior pH of 5.1. BMEDA, which is lipophilic at pH 7.4, serves as a lipophilic chelator for (99m)Tc or (186/188)Re to transport the radionuclides across the lipid bilayer. Once within the more acidic liposome interior, (99m)Tc/(186/188)Re-BMEDA complex becomes protonated and more hydrophilic, which results in stable entrapment of the (99m)Tc/(186/188)Re-BMEDA complex within the liposomes. Since many commercially available liposomal drugs use an ammonium sulfate (pH) gradient for drug loading, these liposomal drugs can be directly radiolabeled with (99m)Tc-BMEDA for non-invasive monitoring of tissue distribution during treatment or with (186/188)Re-BMEDA for combination chemo-radionuclide therapy.

Calcium phosphate formation due to pH-induced adsorption/precipitation switching along salinity gradients

NASA Astrophysics Data System (ADS)

Oxmann, J. F.; Schwendenmann, L.

2014-07-01

Mechanisms governing phosphorus (P) speciation in coastal sediments remain unknown due to the diversity of coastal environments and poor analytical specificity for P phases. We investigated P speciation along salinity gradients comprising diverse ecosystems in a P-enriched estuary. To determine P load effects on P speciation we compared the high P site with a P-unenriched site. To improve analytical specificity, octacalcium phosphate (OCP), authigenic apatite (carbonate fluorapatite; CFAP) and detrital apatite (fluorapatite) were quantitated in addition to Al/Fe-bound P (Al/Fe-P) and Ca-bound P (Ca-P). Sediment pH primarily affected P fractions across ecosystems and independent of the P status. Increasing pH caused a pronounced downstream transition from adsorbed Al/Fe-P to mineral Ca-P. Downstream decline in Al/Fe-P was counterbalanced by the precipitation of Ca-P. This marked upstream-to-downstream switch occurred at near-neutral sediment pH and was enhanced by increased P loads. Accordingly, the site comparison indicated two location-dependent accumulation mechanisms at the P-enriched site, which mainly resulted in elevated Al/Fe-P at pH < 6.6 (upstream; adsorption) and elevated Ca-P at pH > 6.6 (downstream; precipitation). Enhanced Ca-P precipitation by increased loads was also evident from disproportional accumulation of metastable Ca-P (Ca-PMmeta). The average Ca-Pmeta concentration was six-fold, whereas total Ca-P was only twofold higher at the P-enriched site compared to the P-unenriched site. Species concentrations showed that these largely elevated Ca-Pmeta levels resulted from transformation of fertilizer-derived Al/Fe-P to OCP and CFAP due to decreasing acidity from land to the sea. Formation of OCP and CFAP results in P retention in coastal zones, which may lead to substantial inorganic P accumulation by anthropogenic P input in near-shore sediments.

Gradient-free determination of isoelectric points of proteins on chip.

PubMed

Łapińska, Urszula; Saar, Kadi L; Yates, Emma V; Herling, Therese W; Müller, Thomas; Challa, Pavan K; Dobson, Christopher M; Knowles, Tuomas P J

2017-08-30

The isoelectric point (pI) of a protein is a key characteristic that influences its overall electrostatic behaviour. The majority of conventional methods for the determination of the isoelectric point of a molecule rely on the use of spatial gradients in pH, although significant practical challenges are associated with such techniques, notably the difficulty in generating a stable and well controlled pH gradient. Here, we introduce a gradient-free approach, exploiting a microfluidic platform which allows us to perform rapid pH change on chip and probe the electrophoretic mobility of species in a controlled field. In particular, in this approach, the pH of the electrolyte solution is modulated in time rather than in space, as in the case for conventional determinations of the isoelectric point. To demonstrate the general approachability of this platform, we have measured the isoelectric points of representative set of seven proteins, bovine serum albumin, β-lactoglobulin, ribonuclease A, ovalbumin, human transferrin, ubiquitin and myoglobin in microlitre sample volumes. The ability to conduct measurements in free solution thus provides the basis for the rapid determination of isoelectric points of proteins under a wide variety of solution conditions and in small volumes.

Molecular mechanisms of the cytotoxicity of human α-lactalbumin made lethal to tumor cells (HAMLET) and other protein-oleic acid complexes.

PubMed

Nakamura, Takashi; Aizawa, Tomoyasu; Kariya, Ryusho; Okada, Seiji; Demura, Makoto; Kawano, Keiichi; Makabe, Koki; Kuwajima, Kunihiro

2013-05-17

Although HAMLET (human α-lactalbumin made lethal to tumor cells), a complex formed by human α-lactalbumin and oleic acid, has a unique apoptotic activity for the selective killing of tumor cells, the molecular mechanisms of expression of the HAMLET activity are not well understood. Therefore, we studied the molecular properties of HAMLET and its goat counterpart, GAMLET (goat α-lactalbumin made lethal to tumor cells), by pulse field gradient NMR and 920-MHz two-dimensional NMR techniques. We also examined the expression of HAMLET-like activities of complexes between oleic acid and other proteins that form a stable molten globule state. We observed that both HAMLET and GAMLET at pH 7.5 were heterogeneous, composed of the native protein, the monomeric molten globule-like state, and the oligomeric species. At pH 2.0 and 50 °C, HAMLET and GAMLET appeared in the monomeric state, and we identified the oleic acid-binding site in the complexes by two-dimensional NMR. Rather surprisingly, the binding site thus identified was markedly different between HAMLET and GAMLET. Furthermore, canine milk lysozyme, apo-myoglobin, and β2-microglobulin all formed the HAMLET-like complex with the anti-tumor activity, when the protein was treated with oleic acid under conditions in which their molten globule states were stable. From these results, we conclude that the protein portion of HAMLET, GAMLET, and the other HAMLET-like protein-oleic acid complexes is not the origin of their cytotoxicity to tumor cells and that the protein portion of these complexes plays a role in the delivery of cytotoxic oleic acid molecules into tumor cells across the cell membrane.

Molecular Mechanisms of the Cytotoxicity of Human α-Lactalbumin Made Lethal to Tumor Cells (HAMLET) and Other Protein-Oleic Acid Complexes*

PubMed Central

Nakamura, Takashi; Aizawa, Tomoyasu; Kariya, Ryusho; Okada, Seiji; Demura, Makoto; Kawano, Keiichi; Makabe, Koki; Kuwajima, Kunihiro

2013-01-01

Although HAMLET (human α-lactalbumin made lethal to tumor cells), a complex formed by human α-lactalbumin and oleic acid, has a unique apoptotic activity for the selective killing of tumor cells, the molecular mechanisms of expression of the HAMLET activity are not well understood. Therefore, we studied the molecular properties of HAMLET and its goat counterpart, GAMLET (goat α-lactalbumin made lethal to tumor cells), by pulse field gradient NMR and 920-MHz two-dimensional NMR techniques. We also examined the expression of HAMLET-like activities of complexes between oleic acid and other proteins that form a stable molten globule state. We observed that both HAMLET and GAMLET at pH 7.5 were heterogeneous, composed of the native protein, the monomeric molten globule-like state, and the oligomeric species. At pH 2.0 and 50 °C, HAMLET and GAMLET appeared in the monomeric state, and we identified the oleic acid-binding site in the complexes by two-dimensional NMR. Rather surprisingly, the binding site thus identified was markedly different between HAMLET and GAMLET. Furthermore, canine milk lysozyme, apo-myoglobin, and β2-microglobulin all formed the HAMLET-like complex with the anti-tumor activity, when the protein was treated with oleic acid under conditions in which their molten globule states were stable. From these results, we conclude that the protein portion of HAMLET, GAMLET, and the other HAMLET-like protein-oleic acid complexes is not the origin of their cytotoxicity to tumor cells and that the protein portion of these complexes plays a role in the delivery of cytotoxic oleic acid molecules into tumor cells across the cell membrane. PMID:23580643

Capillary electrochromatographic separation of peptides using a macrocyclic polyamine for molecular recognition.

PubMed

Chen, Tse-Hsien; Misra, Tarun Kumar; Liu, Chuen-Ying

2008-04-01

A macrocyclic polyamine, 1,5,9,13,17,21,25,29-octaazacyclodotriacontane ([32]ane-N(8)), in the bonded phase was employed as a molecular receptor for CEC separation of oligopeptides. Parameters affecting the performance of the separations were considered. Baseline separation for the mixture of angiotensin I, angiotensin II, [Sar(1), Thr(8)]-angiotensin II, beta-casomorphin bovine, beta-casomorphin human, oxytocin acetate, tocinoic acid, vasopressin, and FMRF amide could be achieved using phosphate buffer (30 mM, pH 7) as the mobile phase. Column efficiency with average theoretical plate numbers of 69 000 plates/m and RSDs of <1% (n = 6) was achieved. [Met(5)]-enkephalin and [Leu(5)]-enkephalin, which have identical pI values and similar masses could be completely separated using acetate buffer (30 mM) with pH gradient (pH 3 inlet side and pH 4 outlet side). The results suggest that the mechanism for the peptide separation was mediated by a combination of electrophoretic migration and chromatographic retention involving anion coordination and anion exchange. After long-term use, the deviation of the EOF of the column after more than 600 injections was still within 6.0% of that for a freshly prepared column.

Tumor-specific pH-responsive peptide-modified pH-sensitive liposomes containing doxorubicin for enhancing glioma targeting and anti-tumor activity.

PubMed

Zhao, Yang; Ren, Wei; Zhong, Ting; Zhang, Shuang; Huang, Dan; Guo, Yang; Yao, Xin; Wang, Chao; Zhang, Wei-Qiang; Zhang, Xuan; Zhang, Qiang

2016-01-28

The pH environment in gliomas is acidic. Therefore, in the present research, we selected our previously reported tumor-specific pH-responsive peptide H7K(R2)2 as a targeting ligand, which could respond to the acidic pH environment in gliomas, possessing CPP characteristics. The pH-sensitive liposomes were selected as carriers which could also respond to the acidic pH environment in gliomas triggering encapsulated drug release from these pH-sensitive liposomes. The H7K(R2)2-modified pH-sensitive liposomes containing doxorubicin (DOX-PSL-H7K(R2)2) were designed and prepared in order to evaluate their potential targeting of glioma tumor cells and their anti-tumor activity in mice with glioma tumor cells. DOX-PSL-H7K(R2)2 was prepared by the thin-film hydration method followed by remote loading using an ammonium sulfate gradient method. The in vitro release of DOX from pH-sensitive liposomes was tested and the in vitro targeting characteristics of H7K(R2)2-modified liposomes regarding C6 (rat C6 glioma cells) and U87-MG (human glioblastoma cells) were evaluated. The in vivo anti-tumor activity of DOX-PSL-H7K(R2)2 was also investigated in C6 tumor-bearing mice and in U87-MG orthotopic tumor-bearing nude mice. A specific targeting effect triggered by an acidic pH was observed in our in vitro experiments in C6 and U87-MG glioma cells. The pH-triggered DOX release from the pH-sensitive liposomes under acidic conditions was also confirmed in our in vitro experiment. Anti-tumor activity of DOX-PSL-H7K(R2)2 was found in C6 tumor-bearing mice and U87-MG orthotopic tumor-bearing nude mice in in vivo experiments. The antiangiogenic activity of DOX-PSL-H7K(R2)2 was confirmed in C6 tumor-bearing mice in the in vivo experiment. These H7K(R2)2-modified pH-sensitive liposomes containing anti-tumor drugs developed in this study are a promising delivery system involving the response stimuli at the acidic pH in the glioma tumor microenvironment and are suitable for anti-tumor therapy. Copyright © 2015 Elsevier B.V. All rights reserved.

Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lipson, David A.; Raab, Theodore K.; Parker, Melanie

2015-08-01

Summary This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth andmore » were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes,« less

Electrokinetic remediation of contaminated soil with waste-lubricant oils and zinc.

PubMed

Park, Sung-Woo; Lee, Jae-Young; Yang, Jung-Seok; Kim, Kyoung-Jo; Baek, Kitae

2009-09-30

The feasibility of electrokinetic technology on the remediation of mixed-waste-contaminated railroad soil, contaminated by lubricant oil and zinc, was investigated. To enhance the removal efficiency, catholyte purging with 0.1M HNO(3) and a supply of non-ionic surfactant, secondary alcohol ethoxylate, was applied to the anode to remove Zn and to solubilize the lubricant oil. The catholyte purging maintained the soil pH as acidic and enhanced desorption of zinc from the soil, where the zeta potential of the acidic soil became positive. Thereafter, the direction of electro-osmotic flow was changed from the cathode to anode and the flow rate was reduced. The lesser in magnitude reverse electro-osmotic flow inhibited the migration of zinc and the lubricant oil was removed by the electro-osmotic flow. The removal of zinc and lubricant oil was enhanced with an increase in voltage gradient; however, a higher voltage gradient resulted in higher energy expenditure. After electrokinetic operation over 17 days, the removal efficiency of zinc was 22.1-24.3%, and that of lubricant oil was 45.1-55.0%. Although the removal of lubricant oil was quite high, the residual concentration did not meet Korean regulation levels.

A selective and sensitive optical sensor for dissolved ammonia detection via agglomeration of fluorescent Ag nanoclusters and temperature gradient headspace single drop microextraction.

PubMed

Dong, Jiang Xue; Gao, Zhong Feng; Zhang, Ying; Li, Bang Lin; Li, Nian Bing; Luo, Hong Qun

2017-05-15

In this paper, a simple sensor platform is presented for highly selective and sensitive detection of dissolved ammonia in aqueous solutions without pretreatment based on temperature gradient headspace single drop microextraction (HS-SDME) technique, and fluorescence and UV-vis spectrophotometry are utilized with the Ag nanoclusters (Ag NCs) functioned by citrate and glutathione as the probe. The sensing mechanism is based on the volatility of ammonia gas and the active response of Ag NCs to pH change caused by the introduction of ammonia. High pH can make the Ag NCs agglomerate and lead to the obvious decrease of fluorescence intensity and absorbance of Ag NCs solution. Moreover, the presented method exhibits a remarkably high selectivity toward dissolved ammonia over most of inorganic ions and amino acid, and shows a good linear range of 10-350μM (0.14-4.9mgNL -1 ) with a low detection limit of 336nM (4.70μgNL -1 ) at a signal-to-noise ratio of 3. In addition, the practical applications of the sensor have been successfully demonstrated by detecting dissolved ammonia in real samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Separation of charge-regulated polyelectrolytes by pH-assisted diffusiophoresis.

PubMed

Hsu, Jyh-Ping; Hsu, Yen-Rei; Shang-Hung, Hsieh; Tseng, Shiojenn

2017-03-29

The potential of separating colloidal particles through simultaneous application of a salt gradient and a pH gradient, or pH-assisted diffusiophoresis, is evaluated by considering the case of spherical polyelectrolytes (PEs) having different equilibrium dissociation constants in an aqueous solution with KCl as the background salt. The simulation results gathered reveal that the dependence of the particle velocity on pH is more sensitive than that in pH-assisted electrophoresis, where an electric field and a pH gradient are applied simultaneously. This implies that the separation efficiency of pH-assisted diffusiophoresis can be better than that of pH-assisted electrophoresis. In particular, two types of PE having different equilibrium dissociation constants can be separated effectively by applying the former by enhancing/reducing their diffusiophoretic velocities.

Acid Gradient across Plasma Membrane Can Drive Phosphate Bond Synthesis in Cancer Cells: Acidic Tumor Milieu as a Potential Energy Source

PubMed Central

Dhar, Gautam; Sen, Suvajit; Chaudhuri, Gautam

2015-01-01

Aggressive cancers exhibit an efficient conversion of high amounts of glucose to lactate accompanied by acid secretion, a phenomenon popularly known as the Warburg effect. The acidic microenvironment and the alkaline cytosol create a proton-gradient (acid gradient) across the plasma membrane that represents proton-motive energy. Increasing experimental data from physiological relevant models suggest that acid gradient stimulates tumor proliferation, and can also support its energy needs. However, direct biochemical evidence linking extracellular acid gradient to generation of intracellular ATP are missing. In this work, we demonstrate that cancer cells can synthesize significant amounts of phosphate-bonds from phosphate in response to acid gradient across plasma membrane. The noted phenomenon exists in absence of glycolysis and mitochondrial ATP synthesis, and is unique to cancer. Biochemical assays using viable cancer cells, and purified plasma membrane vesicles utilizing radioactive phosphate, confirmed phosphate-bond synthesis from free phosphate (Pi), and also localization of this activity to the plasma membrane. In addition to ATP, predominant formation of pyrophosphate (PPi) from Pi was also observed when plasma membrane vesicles from cancer cells were subjected to trans-membrane acid gradient. Cancer cytosols were found capable of converting PPi to ATP, and also stimulate ATP synthesis from Pi from the vesicles. Acid gradient created through glucose metabolism by cancer cells, as observed in tumors, also proved critical for phosphate-bond synthesis. In brief, these observations reveal a role of acidic tumor milieu as a potential energy source and may offer a novel therapeutic target. PMID:25874623

Effective Removal of Tetracycline from Aqueous Solution by Organic Acid-Coated Magnetic Nanoparticles.

PubMed

Guo, Liang; Liang, Yuyan; Chen, Xuelan; Xu, Wei; Wu, Kesheng; Wei, Hua; Xiong, Yonghua

2016-03-01

Self-assembled iron oxide nanocomposites are good magnetic nano-adsorbents that can be prepared using simple methods. Four types of organic acid-functionalised (oleic acid, undecenoic acid, caprylic acid or hexanoic acid) magnetic nanoparticles (MNPs) were synthesised through a one-pot chemisorption method for the removal of tetracycline (TC) from aqueous solution. The undecenoic acid-coated MNPs (UA-MNPs) exhibited the highest adsorption efficiency and can be easily retrieved with a low-gradient magnetic separator (0.4 Tesla) at pH 5.0 aqueous solution. The TC adsorption process on the UA-MNPs followed the Langmuir isotherm and the maximum adsorption capacities increased from 86.96 mg g(-1) to 222.2 mg g(-1) with the increase in temperature from 288 K to 318 K. The kinetics of adsorption fits pseudo-second-order model perfectly with a rate constant, 5.946 g mg(-1) min(-1) at 298 K. The positive values of the enthalpy (AH) and the negative value of the free energy (AG) indicated an endothermic and spontaneous adsorption process of TC on the UA-MNPs. Moreover, the UA-MNPs possessed excellent ability to adsorb the other three major types of TC antibiotics, including chlortetracycline, oxytetracycline and doxycycline.

Potassium extrusion by the moderately halophilic and alkaliphilic methanogen methanolobus taylorii GS-16 and homeostasis of cytosolic pH.

PubMed Central

Ni, S; Boone, J E; Boone, D R

1994-01-01

Methanolobus taylorii GS-16, a moderately halophilic and alkaliphilic methanogen, grows over a wide pH range, from 6.8 to 9.0. Cells suspended in medium with a pH above 8.2 reversed their transmembrane pH gradient (delta pH), making their cytosol more acidic than the medium. The decreased energy in the proton motive force due to the reversed delta pH was partly compensated by an increased electric membrane potential (delta psi). The cytosolic acidification by M. taylorii at alkaline pH values was accompanied by K+ extrusion. The cytosolic K+ concentration was 110 mM in cells suspended at pH 8.7, but it was 320 mM in cells suspended at neutral pH values. High external K+ concentrations (210 mM or higher) inhibited the growth of M. taylorii at alkaline pH values, perhaps by preventing K+ extrusion. Cells suspended at pH 8.5 and 300 mM external K+ failed to acidify their cytosol. The key observation indicative of the involvement of K+ transport in cytosolic acidification was that valinomycin (0.8 microM), a K+ uniporter, inhibited the growth of M. taylorii only at alkaline pH values. Experiments with resting cells indicated that at alkaline pH values valinomycin uncoupled catabolic reactions from ATP synthesis. Thus, K+/H+ antiport activity was proposed to account for the K+ extrusion and the uncoupling effect of valinomycin at alkaline pH values. Such antiport activity was demonstrated by the sharp drop in pH of the bulk medium of the cell suspension upon the addition of 0.1 M KCl. The antiporter appeared to be active only at alkaline pH values, which was in accordance with a possible role in pH homeostasis by M. taylorii growing at alkaline pH values. PMID:7961499

Live imaging of intra- and extracellular pH in plants using pHusion, a novel genetically encoded biosensor

PubMed Central

Gjetting, Kisten Sisse Krag; Ytting, Cecilie Karkov; Schulz, Alexander; Fuglsang, Anja Thoe

2012-01-01

Changes in pH are now widely accepted as a signalling mechanism in cells. In plants, proton pumps in the plasma membrane and tonoplast play a key role in regulation of intracellular pH homeostasis and maintenance of transmembrane proton gradients. Proton transport in response to external stimuli can be expected to be finely regulated spatially and temporally. With the ambition to follow such changes live, a new genetically encoded sensor, pHusion, has been developed. pHusion is especially designed for apoplastic pH measurements. It was constitutively expressed in Arabidopsis and targeted for expression in either the cytosol or the apoplast including intracellular compartments. pHusion consists of the tandem concatenation of enhanced green fluorescent protein (EGFP) and monomeric red fluorescent protein (mRFP1), and works as a ratiometric pH sensor. Live microscopy at high spatial and temporal resolution is highly dependent on appropriate immobilization of the specimen for microscopy. Medical adhesive often used in such experiments destroys cell viability in roots. Here a novel system for immobilizing Arabidopsis seedling roots for perfusion experiments is presented which does not impair cell viability. With appropriate immobilization, it was possible to follow changes of the apoplastic and cytosolic pH in mesophyll and root tissue. Rapid pH homeostasis upon external pH changes was reflected by negligible cytosolic pH fluctuations, while the apoplastic pH changed drastically. The great potential for analysing pH regulation in a whole-tissue, physiological context is demonstrated by the immediate alkalinization of the subepidermal apoplast upon external indole-3-acetic acid administration. This change is highly significant in the elongation zone compared with the root hair zone and control roots. PMID:22407646

Live imaging of intra- and extracellular pH in plants using pHusion, a novel genetically encoded biosensor.

PubMed

Gjetting, Kisten Sisse Krag; Ytting, Cecilie Karkov; Schulz, Alexander; Fuglsang, Anja Thoe

2012-05-01

Changes in pH are now widely accepted as a signalling mechanism in cells. In plants, proton pumps in the plasma membrane and tonoplast play a key role in regulation of intracellular pH homeostasis and maintenance of transmembrane proton gradients. Proton transport in response to external stimuli can be expected to be finely regulated spatially and temporally. With the ambition to follow such changes live, a new genetically encoded sensor, pHusion, has been developed. pHusion is especially designed for apoplastic pH measurements. It was constitutively expressed in Arabidopsis and targeted for expression in either the cytosol or the apoplast including intracellular compartments. pHusion consists of the tandem concatenation of enhanced green fluorescent protein (EGFP) and monomeric red fluorescent protein (mRFP1), and works as a ratiometric pH sensor. Live microscopy at high spatial and temporal resolution is highly dependent on appropriate immobilization of the specimen for microscopy. Medical adhesive often used in such experiments destroys cell viability in roots. Here a novel system for immobilizing Arabidopsis seedling roots for perfusion experiments is presented which does not impair cell viability. With appropriate immobilization, it was possible to follow changes of the apoplastic and cytosolic pH in mesophyll and root tissue. Rapid pH homeostasis upon external pH changes was reflected by negligible cytosolic pH fluctuations, while the apoplastic pH changed drastically. The great potential for analysing pH regulation in a whole-tissue, physiological context is demonstrated by the immediate alkalinization of the subepidermal apoplast upon external indole-3-acetic acid administration. This change is highly significant in the elongation zone compared with the root hair zone and control roots.

Variation in pH optima of hydrolytic enzyme activities in tropical rain forest soils.

PubMed

Turner, Benjamin L

2010-10-01

Extracellular enzymes synthesized by soil microbes play a central role in the biogeochemical cycling of nutrients in the environment. The pH optima of eight hydrolytic enzymes involved in the cycles of carbon, nitrogen, phosphorus, and sulfur, were assessed in a series of tropical forest soils of contrasting pH values from the Republic of Panama. Assays were conducted using 4-methylumbelliferone-linked fluorogenic substrates in modified universal buffer. Optimum pH values differed markedly among enzymes and soils. Enzymes were grouped into three classes based on their pH optima: (i) enzymes with acidic pH optima that were consistent among soils (cellobiohydrolase, β-xylanase, and arylsulfatase), (ii) enzymes with acidic pH optima that varied systematically with soil pH, with the most acidic pH optima in the most acidic soils (α-glucosidase, β-glucosidase, and N-acetyl-β-glucosaminidase), and (iii) enzymes with an optimum pH in either the acid range or the alkaline range depending on soil pH (phosphomonoesterase and phosphodiesterase). The optimum pH values of phosphomonoesterase were consistent among soils, being 4 to 5 for acid phosphomonoesterase and 10 to 11 for alkaline phosphomonoesterase. In contrast, the optimum pH for phosphodiesterase activity varied systematically with soil pH, with the most acidic pH optima (3.0) in the most acidic soils and the most alkaline pH optima (pH 10) in near-neutral soils. Arylsulfatase activity had a very acidic optimum pH in all soils (pH ≤3.0) irrespective of soil pH. The differences in pH optima may be linked to the origins of the enzymes and/or the degree of stabilization on solid surfaces. The results have important implications for the interpretation of hydrolytic enzyme assays using fluorogenic substrates.

Culture-independent bacterial community analysis of the salty-fermented fish paste products of Thailand and Laos.

PubMed

Marui, Junichiro; Boulom, Sayvisene; Panthavee, Wanchai; Momma, Mari; Kusumoto, Ken-Ichi; Nakahara, Kazuhiko; Saito, Masayoshi

2015-01-01

A bacterial community analysis, using a culture-independent method (polymerase chain reaction-denaturing gradient gel electrophoresis), detected 17 species of bacteria including species of the genera Tetragenococcus, Lactobacillus, Pediococcus, Weissella Halanaerobium, Clostridium, and Sphingomonas in a traditional salty-fermented fish paste known as pla-ra or pa-daek in Thailand and Laos, which is used as a storage-stable multi-purpose seasoning. The representative genus of lactic acid bacteria seemed to vary in the 10 products collected from Thailand and Laos. Tetragenococci were common in products from central Thailand and Vientiane in Laos which had salinities of not less than 11% and pH values ranging from 5.6 to 6.1. However, lactobacilli were common in products from northern Thailand which had the lowest salinities (8.3-8.6%) and pH values (4.5-4.8) of all the samples examined. Two Lactobacillus and one Tetragenococcus species were detected in one product from northeastern Thailand containing 10% salt. These results suggest that salinity in pla-ra/pa-daek is an important determinant of the representative genus of lactic acid bacteria such as, Tetragenococcus or Lactobacillus. Additionally, differences in the acidity between these two groups seemed to be related to the production of d-/l-lactic acid in the lactic acid bacteria in each product. This is the first study to report a correlation between bacterial community structure and taste components in pla-ra/pa-daek products from various regions. This scientific work on a traditional fermented food will be useful in helping local producers meet differing consumer preferences in various regions.

Bioindicator responses and performance of plant species along a vehicular pollution gradient in western Himalaya.

PubMed

Kashyap, Rachit; Sharma, Rohit; Uniyal, Sanjay Kr

2018-04-21

Loss of green cover, and increasing pollution is a prime global concern. The problem calls for screening of pollution-tolerant tree species that can be integrated into plantation drives. Recognizing this, the study analyzed bio-indicator responses and performance of commonly occurring plant species along a pollution gradient in western Himalaya. Based on distance from the road, three sites viz., highly polluted (HP), moderately polluted (MP), and least polluted (LP), were identified. From these sites, leaves of commonly occurring 26 tree species were collected and analyzed for dust accumulation, total chlorophyll, relative water content (RWC), ascorbic acid, and pH using standard protocols. Later, assessment of Air Pollution Tolerance Index (APTI) and Anticipated Performance Indices (API) was carried out. The results revealed variations in biochemical characteristics. The pH, RWC, and total chlorophyll increased with decreasing pollution while ascorbic acid increased with increasing pollution. Dust capturing potential of Ficus carica (1.191 mg/m 2 ) and Toona ciliata (0.820 mg/m 2 ) was relatively higher. Based on the results of APTI, Grevillea robusta was classified as tolerant. It scored significantly higher values (21.06, 21.19, and 19.61 in LP, MP, and HP sites, respectively). Quercus floribunda, G. robusta (68.75% each), Juglans regia (68.7%), and T. ciliata (62.50%) were good performers in HP sites. Acer caesium, Betula utilis, and Morus alba that had low API scores (43.75%) were predicted as poor performers. Thus, G. robusta, Q. floribunda, J. regia, T. ciliata, and F. carica were evaluated as best performers. They could be integrated into plantations drives for environmental management.

Acid Rain, pH & Acidity: A Common Misinterpretation.

ERIC Educational Resources Information Center

Clark, David B.; Thompson, Ronald E.

1989-01-01

Illustrates the basis for misleading statements about the relationship between pH and acid content in acid rain. Explains why pH cannot be used as a measure of acidity for rain or any other solution. Suggests that teachers present acidity and pH as two separate and distinct concepts. (RT)

Multiple, simultaneous, independent gradients for a versatile multidimensional liquid chromatography. Part II: Application 1 - Large increases in isoform resolution of human transferrin by use of dual simultaneous independent gradients of pH & acetonitrile on a mixed bed (anion exchange plus reversed phase) stationary phase.

PubMed

Tsonev, Latchezar I; Hirsh, Allen G

2016-10-14

We have previously described a liquid chromatographic (LC) method for uncoupling controlled, wide range pH gradients and simultaneous controlled gradients of a non-buffering solute on ion exchange resins (Hirsh and Tsonev, 2012) [1]. Here we report the application of this two dimensional LC technique to the problem of resolving Human Transferrin (HT) isoforms. This important iron transporting protein should theoretically occur in several thousand glycoforms, but only about a dozen have been reported. Using dual simultaneous independent gradients (DSIGs) of acetonitrile (ACN) and pH on a mixed bed stationary phase (SP) consisting of a mixture of an anion exchange resin and a reversed phase (RP) resin we partially resolve about 60 isoforms. These are likely to be partially refolded glycoforms generated by interaction of HT with the highly hydrophobic RP SP, as well as distinct folded glycoforms. Thus this study should have interesting implications for both glycoform separation and the study of protein folding. Copyright © 2016 Elsevier B.V. All rights reserved.

Models of Metabolic Community Structure in Martian Habitable Environments: Constraints from a Terrestrial Analog Acid-Sulfate Fumarole Environment, Cerro Negro Volcano, Nicaragua

NASA Astrophysics Data System (ADS)

Rogers, K. L.; McCollom, T. M.; Hynek, B. M.

2014-12-01

Microbial habitability in extreme environments on Earth is described by microscale geochemical conditions that constrain metabolic niches in concert with long-term habitat stability that is governed by dynamic geologic processes. Using terrestrial analogs to identify habitable martian environments requires correlating microscale geochemical constraints with reconstructions of past martian environments that are based on global-scale observations. While past martian environments can be characterized by primary parameters (e.g. pH, redox, mineralogy, thermal history), microbial habitability on Earth is a complex function of both primary and derived parameters (e.g. metabolic reaction energetics, chemical & thermal gradients, flow dynamics). In recent years we have been investigating acid-sulfate fumaroles at the Mars analog site, Cerro Negro Volcano, Nicaragua, where habitability is constrained by steep thermal gradients, spatially- and temporally-variable vent dynamics, and limited water and nutrient availability. The most common niche identified thus far is found in fumaroles that host mixed photosynthetic and chemosynthetic endolithic microbial communities. One such endolith is dominated by acidic red algae (Cyanidiales), aerobic bacterial heterotrophs (Ktedonobacteria), and archaeal thermoacidophiles (Hyperthermus, Caldisphaera, and Thermofilum). An analysis of the metabolic structure suggests that primary production by the red algae supports the growth of heterotrophic thermoacidophiles. Diversification among the chemoheterotrophs with respect to temperature and oxygen tolerance suggests community adaptation to environmental gradients or variable venting dynamics. Furthermore, individual cells within the endolith are silica-encrusted, providing the possibility for biosignature formation and preservation. Putative hydrothermal environments on early Mars with similar conditions could have supported endolithic communities with comparable metabolic strategies. Even on a generally cold and dry Mars, volcanic craters likely provided long-lived warm and wet conditions that could have supported diverse assemblages of thermoacidophilic organisms with various metabolic strategies adapted to environmental conditions of acid-sulfate fumaroles.

Hydrogen Peroxide Formation and pH Changes at Rock-Water Interface during Stressing

NASA Astrophysics Data System (ADS)

Xie, S.; Kulahci, I.; Cyr, G.; Tregloan-Reed, J.; Balk, M.; Rothschild, L. J.; Freund, F. T.

2008-12-01

Common igneous and high-grade metamorphic rocks contain dormant defects, which become activated when stressed. They release electronic charge carriers, in particular defect electrons associated with O- states in a matrix of O2-. Known as 'positive holes' or pholes for short, the O- states can spread out of the stressed rock volume, travel along stress gradients over distances on the order of meters in the lab and probably over kilometers in the field. They carry a current, which can flow through meters of rock in the laboratory, probably tens of kilometers in the field. At rock-water interfaces the O- states turn into O radicals, which subtract H from H2O, forming OH- in the rock surface and PH radicals in the water. Two OH combine to H2O2. In the process the pH becomes more acidic. The discovery of H2O2 formation at rock-water interfaces as part of stress- activated currents on the tectonically active Earth may help us better understand the oxidation of the early Earth and the evolution of early Life.

Metal release from contaminated coastal sediments under changing pH conditions: Implications for metal mobilization in acidified oceans.

PubMed

Wang, Zaosheng; Wang, Yushao; Zhao, Peihong; Chen, Liuqin; Yan, Changzhou; Yan, Yijun; Chi, Qiaoqiao

2015-12-30

To investigate the impacts and processes of CO2-induced acidification on metal mobilization, laboratory-scale experiments were performed, simulating the scenarios where carbon dioxide was injected into sediment-seawater layers inside non-pressurized chambers. Coastal sediments were sampled from two sites with different contamination levels and subjected to pre-determined pH conditions. Sediment samples and overlying water were collected for metal analysis after 10-days. The results indicated that CO2-induced ocean acidification would provoke increased metal mobilization causing adverse side-effects on water quality. The mobility of metals from sediment to the overlying seawater was correlated with the reduction in pH. Results of sequential extractions of sediments illustrated that exchangeable metal forms were the dominant source of mobile metals. Collectively, our data revealed that high metal concentrations in overlying seawater released from contaminated sediments under acidic conditions may strengthen the existing contamination gradients in Maluan Bay and represent a potential risk to ecosystem health in coastal environments. Copyright © 2015 Elsevier Ltd. All rights reserved.

Influence of Glucose Deprivation on Membrane Potentials of Plasma Membranes, Mitochondria and Synaptic Vesicles in Rat Brain Synaptosomes.

PubMed

Hrynevich, Sviatlana V; Pekun, Tatyana G; Waseem, Tatyana V; Fedorovich, Sergei V

2015-06-01

Hypoglycemia can cause neuronal cell death similar to that of glutamate-induced cell death. In the present paper, we investigated the effect of glucose removal from incubation medium on changes of mitochondrial and plasma membrane potentials in rat brain synaptosomes using the fluorescent dyes DiSC3(5) and JC-1. We also monitored pH gradients in synaptic vesicles and their recycling by the fluorescent dye acridine orange. Glucose deprivation was found to cause an inhibition of K(+)-induced Ca(2+)-dependent exocytosis and a shift of mitochondrial and plasma membrane potentials to more positive values. The sensitivity of these parameters to the energy deficit caused by the removal of glucose showed the following order: mitochondrial membrane potential > plasma membrane potential > pH gradient in synaptic vesicles. The latter was almost unaffected by deprivation compared with the control. The pH-dependent dye acridine orange was used to investigate synaptic vesicle recycling. However, the compound's fluorescence was shown to be enhanced also by the mixture of mitochondrial toxins rotenone (10 µM) and oligomycin (5 µg/mL). This means that acridine orange can presumably be partially distributed in the intermembrane space of mitochondria. Glucose removal from the incubation medium resulted in a 3.7-fold raise of acridine orange response to rotenone + oligomycin suggesting a dramatic increase in the mitochondrial pH gradient. Our results suggest that the biophysical characteristics of neuronal presynaptic endings do not favor excessive non-controlled neurotransmitter release in case of hypoglycemia. The inhibition of exocytosis and the increase of the mitochondrial pH gradient, while preserving the vesicular pH gradient, are proposed as compensatory mechanisms.

Hydrogen ion secretion by the collecting duct as a determinant of the urine to blood PCO2 gradient in alkaline urine

DOE Office of Scientific and Technical Information (OSTI.GOV)

DuBose, T.D. Jr.

1982-01-01

Several theories have been advanced to explain the elevation in urinary PCO/sub 2/ during bicarbonate loading and include: (a) H+ secretion, (b) countercurrent system for CO/sub 2/, (c) the ampholyte properties of bicarbonate, and (d) mixing of urine of disparate bicarbonate and butter concentrations. In this study microelectrodes were used to measure in situ and equilibrium pH (pHis and pHeq) and PCO/sub 2/ in control and bicarbonate loaded rats before and after infusion of carbonic anhydrase. The disequilibrium pH method (pHdq . pHis - pHeq) was used to demonstrate H+ secretion. Control rats excreting an acid urine (pH . 6.04more » +/- 0.06) failed to display a significant disequilibrium pH at the base (BCD), or tip (TCD) of the papillary collecting duct. Urine pH (7.54 +/- 0.12), and urine to blood (U-B) PCO/sub 2/ increased significantly during NaHCO/sub 3/ loading while PCO/sub 2/ at the BCD and TCD also increased (95 +/- 4 and 122 +/- 4). Furthermore, an acid disequilibrium pH was present at both the BCD and TCD (-0.42 +/- 0.04 and -0.36 +/- 0.03) and was obliterated by carbonic anhydrase. Comparison of the PCO/sub 2/ in the BCD or TCD with the adjacent vasa recta revealed similar values (r . 0.97). It is concluded that H+ secretion by the collecting duct into bicarbonate containing fluid with delayed dehydration of H/sub 2/CO/sub 3/, is the most likely determinant of the U-B PCO/sub 2/ in alkaline urine. Similar values for PCO/sub 2/ in the collecting duct and the adjacent vasa recta suggests trapping of CO/sub 2/ in the medullary countercurrent system. The rise in PCO/sub 2/ occurs both along the collecting duct and after exit from the papilla.« less

Assembly processes under severe abiotic filtering: adaptation mechanisms of weed vegetation to the gradient of soil constraints.

PubMed

Nikolic, Nina; Böcker, Reinhard; Kostic-Kravljanac, Ljiljana; Nikolic, Miroslav

2014-01-01

Effects of soil on vegetation patterns are commonly obscured by other environmental factors; clear and general relationships are difficult to find. How would community assembly processes be affected by a substantial change in soil characteristics when all other relevant factors are held constant? In particular, can we identify some functional adaptations which would underpin such soil-induced vegetation response? Eastern Serbia: fields partially damaged by long-term and large-scale fluvial deposition of sulphidic waste from a Cu mine; subcontinental/submediterranean climate. We analysed the multivariate response of cereal weed assemblages (including biomass and foliar analyses) to a strong man-made soil gradient (from highly calcareous to highly acidic, nutrient-poor soils) over short distances (field scale). The soil gradient favoured a substitution of calcicoles by calcifuges, and an increase in abundance of pseudometallophytes, with preferences for Atlantic climate, broad geographical distribution, hemicryptophytic life form, adapted to low-nutrient and acidic soils, with lower concentrations of Ca, and very narrow range of Cu concentrations in leaves. The trends of abundance of the different ecological groups of indicator species along the soil gradient were systematically reflected in the maintenance of leaf P concentrations, and strong homeostasis in biomass N:P ratio. Using annual weed vegetation at the field scale as a fairly simple model, we demonstrated links between gradients in soil properties (pH, nutrient availability) and floristic composition that are normally encountered over large geographic distances. We showed that leaf nutrient status, in particular the maintenance of leaf P concentrations and strong homeostasis of biomass N:P ratio, underpinned a clear functional response of vegetation to mineral stress. These findings can help to understand assembly processes leading to unusual, novel combinations of species which are typically observed as a consequence of strong environmental filtering, as for instance on sites affected by industrial activities.

Assembly Processes under Severe Abiotic Filtering: Adaptation Mechanisms of Weed Vegetation to the Gradient of Soil Constraints

PubMed Central

Nikolic, Nina; Böcker, Reinhard; Kostic-Kravljanac, Ljiljana; Nikolic, Miroslav

2014-01-01

Questions Effects of soil on vegetation patterns are commonly obscured by other environmental factors; clear and general relationships are difficult to find. How would community assembly processes be affected by a substantial change in soil characteristics when all other relevant factors are held constant? In particular, can we identify some functional adaptations which would underpin such soil-induced vegetation response? Location Eastern Serbia: fields partially damaged by long-term and large-scale fluvial deposition of sulphidic waste from a Cu mine; subcontinental/submediterranean climate. Methods We analysed the multivariate response of cereal weed assemblages (including biomass and foliar analyses) to a strong man-made soil gradient (from highly calcareous to highly acidic, nutrient-poor soils) over short distances (field scale). Results The soil gradient favoured a substitution of calcicoles by calcifuges, and an increase in abundance of pseudometallophytes, with preferences for Atlantic climate, broad geographical distribution, hemicryptophytic life form, adapted to low-nutrient and acidic soils, with lower concentrations of Ca, and very narrow range of Cu concentrations in leaves. The trends of abundance of the different ecological groups of indicator species along the soil gradient were systematically reflected in the maintenance of leaf P concentrations, and strong homeostasis in biomass N:P ratio. Conclusion Using annual weed vegetation at the field scale as a fairly simple model, we demonstrated links between gradients in soil properties (pH, nutrient availability) and floristic composition that are normally encountered over large geographic distances. We showed that leaf nutrient status, in particular the maintenance of leaf P concentrations and strong homeostasis of biomass N:P ratio, underpinned a clear functional response of vegetation to mineral stress. These findings can help to understand assembly processes leading to unusual, novel combinations of species which are typically observed as a consequence of strong environmental filtering, as for instance on sites affected by industrial activities. PMID:25474688

Acidity and Alkalinity in mine drainage: Practical considerations

USGS Publications Warehouse

Cravotta, III, Charles A.; Kirby, Carl S.

2004-01-01

In this paper, we emphasize that the Standard Method hot peroxide treatment procedure for acidity determination (hot acidity) directly measures net acidity or net alkalinity, but that more than one water-quality measure can be useful as a measure of the severity of acid mine drainage. We demonstrate that the hot acidity is related to the pH, alkalinity, and dissolved concentrations of Fe, Mn, and Al in fresh mine drainage. We show that the hot acidity accurately indicates the potential for pH to decrease to acidic values after complete oxidation of Fe and Mn, and it indicates the excess alkalinity or that required for neutralization of the sample. We show that the hot acidity method gives consistent, interpretable results on fresh or aged samples. Regional data for mine-drainage quality in Pennsylvania indicated the pH of fresh samples was predominantly acidic (pH 2.5 to 4) or near neutral (pH 6 to 7); approximately 25 percent of the samples had intermediate pH values. This bimodal frequency distribution of pH was distinctive for fully oxidized samples; oxidized samples had acidic or near-neutral pH, only. Samples that had nearneutral pH after oxidation had negative hot acidity; samples that had acidic pH after oxidation had positive hot acidity. Samples with comparable pH values had variable hot acidities owing to variations in their alkalinities and dissolved Fe, Mn, and Al concentrations. The hot acidity was comparable to net acidity computed on the basis of initial pH and concentrations of Fe, Mn, and Al minus the initial alkalinity. Acidity computed from the pH and dissolved metals concentrations, assuming equivalents of 2 per mole of Fe and Mn and 3 per mole of Al, was comparable to that computed on the basis of aqueous species and FeII/FeIII. Despite changes in the pH, alkalinity, and metals concentrations, the hot acidities were comparable for fresh and aged samples. Thus, meaningful “net” acidity can be determined from a measured hot acidity or by calculation from the pH, alkalinity, and dissolved metals concentrations. Together, these water-quality data can be useful for evaluating the potential for toxicity, corrosion, or encrustation and can be helpful for determining the appropriate remediation. By demonstrating the measurements on fresh and aged samples, we hope to encourage (1) consistent use of the hot peroxide treatment procedure for acidity determination and (2) consistent reporting of negative acidity values.

The relationship between the electrochemical proton gradient and active transport in Escherichia coli membrane vesicles.

PubMed

Ramos, S; Kaback, H R

1977-03-08

In the previous paper [ramos, S., and Kaback, H.R. (1977), Biochemistry 16 (preceding paper in this issue)], it was demonstrated that Escherichia coli membrane vesicles generate a large electrochemical proton gradient (delta-muH+) under appropriate conditions, and some of the properties of delta-muH+ and its component forces [i.e., the membrane potential (delta psi) and the chemical gradient of protons (deltapH)] were described. In this paper, the relationship between delta-muH+, delta psi, and deltapH and the active transport of specific solutes is examined. Addition of lactose or glucose 6-phosphate to membrane vesicles containing the appropriate transport systems results in partial collapse of deltapH, providing direct evidence for the suggestion that respiratory energy can drive active transport via the pH gradient across the membrane. Titration studies with valinomycin and nigericin lead to the conclusion that, at pH 5.5, there are two general classes of transport systems: those that are driven primarily by delta-muH+ (lactose, proline, serine, glycine, tyrosine, glutamate, leucine, lysine, cysteine, and succinate) and those that are driven primarily by deltapH (glucose 6-phosphate, D-lactate, glucuronate, and gluconate). Importantly, however, it is also demonstrated that at pH 7.5, all of these transport systems are driven by delta psi which comprises the only component of delta-muH+ at this external pH. In addition, the effect of external pH on the steady-state levels of accumulation of different solutes is examined, and it is shown that none of the pH profiles correspond to those observed for delta-muH+, delta psi, or deltapH. Moreover, at external pH values above 6.0-6.5, delta-muH+ is insufficient to account for the concentration gradients established for each substrate unless the stoichiometry between protons and accumulated solutes is greater than unity. The results confirm many facets of the chemiosmotic hypothesis, but they also extend the concept in certain important respects and allow explanations for some earlier observations which seemed to preclude the involvement of chemiosmotic phenomena in active transport.

Niche specialization of terrestrial archaeal ammonia oxidizers

PubMed Central

Gubry-Rangin, Cécile; Hai, Brigitte; Quince, Christopher; Engel, Marion; Thomson, Bruce C.; James, Phillip; Schloter, Michael; Griffiths, Robert I.; Prosser, James I.; Nicol, Graeme W.

2011-01-01

Soil pH is a major determinant of microbial ecosystem processes and potentially a major driver of evolution, adaptation, and diversity of ammonia oxidizers, which control soil nitrification. Archaea are major components of soil microbial communities and contribute significantly to ammonia oxidation in some soils. To determine whether pH drives evolutionary adaptation and community structure of soil archaeal ammonia oxidizers, sequences of amoA, a key functional gene of ammonia oxidation, were examined in soils at global, regional, and local scales. Globally distributed database sequences clustered into 18 well-supported phylogenetic lineages that dominated specific soil pH ranges classified as acidic (pH <5), acido-neutral (5≤ pH <7), or alkalinophilic (pH ≥7). To determine whether patterns were reproduced at regional and local scales, amoA gene fragments were amplified from DNA extracted from 47 soils in the United Kingdom (pH 3.5–8.7), including a pH-gradient formed by seven soils at a single site (pH 4.5–7.5). High-throughput sequencing and analysis of amoA gene fragments identified an additional, previously undiscovered phylogenetic lineage and revealed similar pH-associated distribution patterns at global, regional, and local scales, which were most evident for the five most abundant clusters. Archaeal amoA abundance and diversity increased with soil pH, which was the only physicochemical characteristic measured that significantly influenced community structure. These results suggest evolution based on specific adaptations to soil pH and niche specialization, resulting in a global distribution of archaeal lineages that have important consequences for soil ecosystem function and nitrogen cycling. PMID:22158986

Transepithelial SCFA fluxes link intracellular and extracellular pH regulation of mouse colonocytes.

PubMed

Chu, S; Montrose, M H

1997-10-01

We have studied pH regulation in both intracellular and extracellular compartments of mouse colonic crypts, using distal colonic mucosa with intact epithelial architecture. In this work, we question how transepithelial SCFA gradients affect intracellular pH (pHi) and examine interactions between extracellular pH (pHo) and pHi regulation in crypts of distal colonic epithelium from mouse. We studied pH regulation in three adjacent compartments of distal colonic epithelium (crypt lumen, crypt epithelial cell cytosol, and lamina propria) with SNARF-1 (a pH sensitive fluorescent dye), digital imaging microscopy (for pHi), and confocal microscopy (for pHo). Combining results from the three compartments allows us to find how pHi and pHo are regulated and related under the influence of physiological transepithelial SCFA gradients, and develop a better understanding of pH regulation mechanisms in colonic crypts. Results suggest a complex interdependency between SCFA fluxes and pHo values, which can directly affect how strongly SCFAs acidify colonocytes.

Microbiological and chemical characteristics of Brazilian kefir during fermentation and storage processes.

PubMed

Leite, A M O; Leite, D C A; Del Aguila, E M; Alvares, T S; Peixoto, R S; Miguel, M A L; Silva, J T; Paschoalin, V M F

2013-07-01

The microbial community composition and chemical characteristics of a Brazilian milk kefir sample produced during its manufacturing and refrigerated storage were investigated by culture-dependent and -independent methods and HPLC. Lactococcus lactis ssp. cremoris and ssp. lactis, Leuconostoc mesenteroides, Acetobacter lovaniensis, and Saccharomyces cerevisiae were isolated, whereas the detected bands on denaturing gel gradient electrophoresis corresponded to Lactobacillus kefiranofaciens, Lactobacillus kefiri, Lactobacillus parakefiri, and S. cerevisiae. After fermentation, lactic acid bacteria were present at levels of 10 log units, whereas acetic acid bacteria and yeast were present at levels of 7.8 and 6 log units, respectively. The lactic acid bacteria and yeast counts remained constant, whereas acetic acid bacteria counts decreased to 7.2 log units during storage. From fermentation to final storage, the pH, lactose content and citric acid of the kefir beverage decreased, followed by an increase in the concentrations of glucose, galactose, ethanol, and lactic, acetic, butyric, and propionic acids. These microbiological and chemical characteristics contribute to the unique taste and aroma of kefir. This research may serve as a basis for the future industrial production of this beverage in Brazil. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Possible Association of Ferrous Phosphates and Ferric Sulfates in S-rich Soil on Mars

NASA Astrophysics Data System (ADS)

Mao, J.; Schroeder, C.; Haderlein, S.

2012-12-01

NASA Mars Exploration Rover (MER) Spirit explored Gusev Crater to look for signs of ancient aqueous activity, assess past environmental conditions and suitability for life. Spirit excavated light-toned, S-rich soils at several locations. These are likely of hydrothermal, possibly fumarolic origin. At a location dubbed Paso Robles the light-toned soil was also rich in P - a signature from surrounding rock. While S is mainly bound in ferric hydrated sulfates [1], the mineralogy of P is ill-constrained [2]. P is a key element for life and its mineralogy constrains its availability. Ferrous phases observed in Paso Robles Mössbauer spectra may represent olivine and pyroxene from surrounding basaltic soil [1] or ferrous phosphate minerals [3]. Phosphate is well-known to complex and stabilize Fe 2+ against oxidation to Fe 3+ . Schröder et al. [3] proposed a formation pathway of ferrous phosphate/ferric sulfate associations: sulfuric acid reacts with basalt containing apatite, forming CaSO4 and phosphoric acid. The phosphoric and/or excess sulfuric acid reacts with olivine, forming Fe2+-phosphate and sulfate. The phosphate is less soluble and precipitates. Ferrous sulfate remains in solution and is oxidized as pH increases. To verify this pathway, we dissolved Fe2+-chloride and Na-phosphate salts in sulfuric acid inside an anoxic glovebox. The solution was titrated to pH 6 by adding NaOH when a first precipitate formed, which was ferrous phosphate according to Mössbauer spectroscopy (MB). At that point the solution was removed from the glovebox and allowed to evaporate in the presence of atmospheric oxygen, leading to the oxidation of Fe2+. The evaporation rate was controlled by keeping the suspensions at different temperatures; pH was monitored during the evaporation process. The final precipitates were analyzed by MB and X-Ray Fluorescence (XRF), comparable to MER MB and Alpha Particle X-ray Spectrometer instrument datasets, and complementary techniques such as X-ray diffraction. Fourier Transform Infrared spectroscopy measurements to compare to MER miniature thermal emission spectrometer data are planned. We observed differences depending on the heat source during evaporation. The closest match to Martian data on the basis of Mössbauer spectra was achieved with a suspension evaporated at 80°C on a hot plate, i.e. heated from below with a temperature gradient in the bottle. The Fe2+/FeT ratio matched, and ferrous phases were all phosphate. When heated in a water bath, i.e. without a temperature gradient in the bottle, Fe2+/FeT ratios increased and ferrous sulfates precipitated also. These results indicate that the Martian light-toned S-rich deposits formed by evaporation on the surface where temperature gradients would be expected rather than underground. They confirm that ferrous phosphate/ferric sulfate associations are possible on Mars and could be preserved in the oxygen-free Martian atmosphere. References: [1] Morris et al., J.Geophys. Res. 111 (2006) E02S13; [2] Ming et al., J. Geophys. Res. 111 (2006) E02S12; [3] Schröder et al., GSA Annual Meeting 2008, Paper No. 171-3.

Intrinsic H+ ion mobility in the rabbit ventricular myocyte

PubMed Central

Vaughan-Jones, R D; Peercy, B E; Keener, J P; Spitzer, K W

2002-01-01

The intrinsic mobility of intracellular H+ ions was investigated by confocally imaging the longitudinal movement of acid inside rabbit ventricular myocytes loaded with the acetoxymethyl ester (AM) form of carboxy-seminaphthorhodafluor-1 (carboxy-SNARF-1). Acid was diffused into one end of the cell through a patch pipette filled with an isotonic KCl solution of pH 3.0. Intracellular H+ mobility was low, acid taking 20-30 s to move 40 μm down the cell. Inhibiting sarcolemmal Na+-H+ exchange with 1 mm amiloride had no effect on this time delay. Net Hi+ movement was associated with a longitudinal intracellular pH (pHi) gradient of up to 0.4 pH units. Hi+ movement could be modelled using the equations for diffusion, assuming an apparent diffusion coefficient for H+ ions (DappH) of 3.78 × 10−7 cm2 s−1, a value more than 300-fold lower than the H+ diffusion coefficient in a dilute, unbuffered solution. Measurement of the intracellular concentration of SNARF (≈400 μM) and its intracellular diffusion coefficient (0.9 × 10−7 cm2 s−1) indicated that the fluorophore itself exerted an insignificant effect (between 0.6 and 3.3 %) on the longitudinal movement of H+ equivalents inside the cell. The longitudinal movement of intracellular H+ is discussed in terms of a diffusive shuttling of H+ equivalents on high capacity mobile buffers which comprise about half (≈11 mm) of the total intrinsic buffering capacity within the myocyte (the other half being fixed buffer sites on low mobility, intracellular proteins). Intrinsic Hi+ mobility is consistent with an average diffusion coefficient for the intracellular mobile buffers (Dmob) of ≈9 × 10−7 cm2 s−1. PMID:12015426

Analysis of β-Subgroup Proteobacterial Ammonia Oxidizer Populations in Soil by Denaturing Gradient Gel Electrophoresis Analysis and Hierarchical Phylogenetic Probing

PubMed Central

Stephen, John R.; Kowalchuk, George A.; Bruns, Mary-Ann V.; McCaig, Allison E.; Phillips, Carol J.; Embley, T. Martin; Prosser, James I.

1998-01-01

A combination of denaturing gradient gel electrophoresis (DGGE) and oligonucleotide probing was used to investigate the influence of soil pH on the compositions of natural populations of autotrophic β-subgroup proteobacterial ammonia oxidizers. PCR primers specific to this group were used to amplify 16S ribosomal DNA (rDNA) from soils maintained for 36 years at a range of pH values, and PCR products were analyzed by DGGE. Genus- and cluster-specific probes were designed to bind to sequences within the region amplified by these primers. A sequence specific to all β-subgroup ammonia oxidizers could not be identified, but probes specific for Nitrosospira clusters 1 to 4 and Nitrosomonas clusters 6 and 7 (J. R. Stephen, A. E. McCaig, Z. Smith, J. I. Prosser, and T. M. Embley, Appl. Environ. Microbiol. 62:4147–4154, 1996) were designed. Elution profiles of probes against target sequences and closely related nontarget sequences indicated a requirement for high-stringency hybridization conditions to distinguish between different clusters. DGGE banding patterns suggested the presence of Nitrosomonas cluster 6a and Nitrosospira clusters 2, 3, and 4 in all soil plots, but results were ambiguous because of overlapping banding patterns. Unambiguous band identification of the same clusters was achieved by combined DGGE and probing of blots with the cluster-specific radiolabelled probes. The relative intensities of hybridization signals provided information on the apparent selection of different Nitrosospira genotypes in samples of soil of different pHs. The signal from the Nitrosospira cluster 3 probe decreased significantly, relative to an internal control probe, with decreasing soil pH in the range of 6.6 to 3.9, while Nitrosospira cluster 2 hybridization signals increased with increasing soil acidity. Signals from Nitrosospira cluster 4 were greatest at pH 5.5, decreasing at lower and higher values, while Nitrosomonas cluster 6a signals did not vary significantly with pH. These findings are in agreement with a previous molecular study (J. R. Stephen, A. E. McCaig, Z. Smith, J. I. Prosser, and T. M. Embley, Appl. Environ. Microbiol 62:4147–4154, 1996) of the same sites, which demonstrated the presence of the same four clusters of ammonia oxidizers and indicated that selection might be occurring for clusters 2 and 3 at acid and neutral pHs, respectively. The two studies used different sets of PCR primers for amplification of 16S rDNA sequences from soil, and the similar findings suggest that PCR bias was unlikely to be a significant factor. The present study demonstrates the value of DGGE and probing for rapid analysis of natural soil communities of β-subgroup proteobacterial ammonia oxidizers, indicates significant pH-associated differences in Nitrosospira populations, and suggests that Nitrosospira cluster 2 may be of significance for ammonia-oxidizing activity in acid soils. PMID:9687457

Mechanisms of zinc transport into pig small intestine brush-border membrane vesicles.

PubMed Central

Tacnet, F; Lauthier, F; Ripoche, P

1993-01-01

1. The purpose of the present work was to examine certain membrane transport mechanisms likely to carry zinc across the brush-border membrane of pig small intestine, isolated in a vesicular form. 2. In initial velocity conditions, saturation kinetics revealed a great effect of pH on zinc transport: optimal conditions were observed with an intravesicular pH of around 6.6 with or without a H+ gradient; however, this did not allow us to conclude the existence of a neutral exchange between Zn2+ and H+ ions. 3. By measuring 36Cl uptakes, the presence of the Cl(-)-HCO3- or Cl(-)-OH-antiporter with typical 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) sensitivity was detected in vesicles; zinc did not alter this anionic exchange activity. A 65Zn time course, performed in conditions identical with those for 36Cl uptake, was DIDS insensitive and was greatly inhibited by an outward OH- gradient. This could argue against a transport of zinc as a complex with Cl- and HCO3- through the anion antiporter. 4. When external Cl- and HCO3- were replaced by SCN-, able to form a Zn(SCN)4(2-) complex, we observed a stimulating effect of outward HCO3- gradients on 65Zn uptake but neither DIDS nor diphenylamine-2-carboxylate (DPC) inhibited the transport in these conditions. This suggested that the intestinal anion antiporter was not a major route for zinc reabsorption. 5. The tripeptide Gly-Gly-His at low concentrations stimulated 65Zn uptake, then inhibited it in a dose-dependent manner either in the presence of an inward H+ gradient or in the presence of a membrane potential 'negative inside' or in both situations. These conditions are necessary for the active transport of the peptide and this strongly suggests that zinc can be transported as a [Gly-Gly-His-Zn] complex, utilizing the peptide carrier system. PMID:8229851

Acidic and basic solutions dissolve protein plugs made of lithostathine complicating choledochal cyst/pancreaticobiliary maljunction.

PubMed

Kaneko, Kenitiro; Ono, Yasuyuki; Tainaka, Takahisa; Sumida, Wataru; Ando, Hisami

2009-07-01

Symptoms of choledochal cysts are caused by protein plugs made of lithostathine, which block the long common channel and increase pancreaticobiliary ductal pressure. Agents that dissolve protein plugs can provide relief from or prevent symptoms. In the present study, drugs reportedly effective for pancreatic and biliary stones were used in dissolution tests. Protein plugs were obtained from choledochal cysts during surgery in two children (5- and 6-year-old girls). Plugs approximately 2 mm in diameter were immersed in citric acid, tartaric acid, dimethadione, bromhexine, dehydrocholic acid, sodium citrate, hydrochloric acid, and sodium hydroxide solutions under observation with a digital microscope. The pH of each solution was measured using a pH meter. Plugs dissolved in citric acid (5.2 mM; pH 2.64), tartaric acid (6.7 mM; pH 2.51), dimethadione (75 mM; pH 3.70), hydrochloric acid (0.5 mM; pH 3.13), and sodium hydroxide (75 mM; pH 12.75) solutions. Plugs did not dissolve in dimethadione (7.5 mM; pH 4.31), bromhexine (0.1%; pH 4.68), dehydrocholic acid (5%; pH 7.45), and sodium citrate (75 mM; pH 7.23) solutions. Protein plugs in choledochal cysts are dissolved in acidic and basic solutions, which may eliminate longitudinal electrostatic interactions of the lithostathine protofibrils.

Determination of vigabatrin in human plasma and urine by high-performance liquid chromatography with UV-Vis detection.

PubMed

Cetin, Sevil Müge; Atmaca, Sedef

2004-03-26

A simple and reliable high-performance liquid chromatographic (HPLC) method with UV-Vis detection has been developed and validated for the determination of vigabatrin (VG) in human plasma and urine. The samples were pre-column derivatizated with 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS). A good chromatographic separation was achieved on a C18 column with a mobile phase consisting of acetonitrile and 10 mM orthophosphoric acid (pH 2.5) gradient elution. Tranexamic acid was used as an internal standard (I.S.). The method was linear over the concentration range of 0.8-30.0 microg/ml for both samples. The method is precise (relative standard deviation (R.S.D.) <9.13%) and accurate (relative mean error (RME) <-8.75%); analytical recoveries were 81.07% for plasma and 83.05% for urine. The assay was applied to pharmacokinetic study in a healthy volunteer after a single oral administration of 1 g of vigabatrin.

Large scale micro-photometry for high resolution pH-characterization during electro-osmotic pumping and modular micro-swimming

NASA Astrophysics Data System (ADS)

Niu, Ran; Khodorov, Stanislav; Weber, Julian; Reinmüller, Alexander; Palberg, Thomas

2017-11-01

Micro-fluidic pumps as well as artificial micro-swimmers are conveniently realized exploiting phoretic solvent flows based on local gradients of temperature, electrolyte concentration or pH. We here present a facile micro-photometric method for monitoring pH gradients and demonstrate its performance and scope on different experimental situations including an electro-osmotic pump and modular micro-swimmers assembled from ion exchange resin beads and polystyrene colloids. In combination with the present microscope and DSLR camera our method offers a 2 μm spatial resolution at video frame rate over a field of view of 3920 × 2602 μm2. Under optimal conditions we achieve a pH-resolution of 0.05 with about equal contributions from statistical and systematical uncertainties. Our quantitative micro-photometric characterization of pH gradients which develop in time and reach out several mm is anticipated to provide valuable input for reliable modeling and simulations of a large variety of complex flow situations involving pH-gradients including artificial micro-swimmers, microfluidic pumping or even electro-convection.

Chemotaxis of Amoeba proteus in the developing pH gradient within a pocket-like chamber studied with the computer assisted method.

PubMed

Korohoda, W; Golda, J; Sroka, J; Wojnarowicz, A; Jochym, P; Madeja, Z

1997-01-01

A new "U" shaped, pocket-like chamber was used to observe the chemotactic responses of individual cells. This method permits monitoring of both the development of the concentration gradient of a tested substance and cell locomotion. We investigated the chemotactic responses of Amoeba proteus and observed that the amoebae moved in positively and negatively developing [H+] gradients towards the solution of lower pH in a pH range 5.75-7.75. The chemotactic response of amoebae to [H+] gradients required the presence of extracellular calcium ions. It was blocked and random locomotion was restored by the replacement of calcium with magnesium in the cell medium. Time-lapse video recording and data processing were accomplished with computer-assisted methods. This made it possible to compare selected methods of data presentation and analysis for cells locomoting in isotropic and anisotropic conditions. The cell trajectories were determined and displayed in circular diagrams, lengths of cell tracks and final cell displacements were estimated and a few parameters characterizing cell locomotion were computed.

Rapid determination of amino acids in biological samples using a monolithic silica column.

PubMed

Song, Yanting; Funatsu, Takashi; Tsunoda, Makoto

2012-05-01

A high-performance liquid chromatography method in which fluorescence detection is used for the simultaneous determination of 21 amino acids is proposed. Amino acids were derivatized with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) and then separated on a monolithic silica column (MonoClad C18-HS, 150 mm×3 mm i.d.). A mixture of 25 mM citrate buffer containing 25 mM sodium perchlorate (pH 5.5) and acetonitrile was used as the mobile phase. We found that the most significant factor in the separation was temperature, and a linear temperature gradient from 30 to 49°C was used to control the column temperature. The limits of detection and quantification for all amino acids ranged from 3.2 to 57.2 fmol and 10.8 to 191 fmol, respectively. The calibration curves for the NBD-amino acid had good linearity within the range of 40 fmol to 40 pmol when 6-aminocaproic acid was used as an internal standard. Using only conventional instruments, the 21 amino acids could be analyzed within 10 min. This method was found to be suitable for the quantification of the contents of amino acids in mouse plasma and adrenal gland samples.

Alteration of chemical behavior of L-ascorbic acid in combination with nickel sulfate at different pH solutions in vitro

PubMed Central

Maniyar, Shaheen A; Jargar, Jameel G; Das, Swastika N; Dhundasi, Salim A; Das, Kusal K

2012-01-01

Objective To evaluate the alteration of chemical behavior of L-ascorbic acid (vitamin C) with metal ion (nickel) at different pH solutions in vitro. Methods Spectra of pure aqueous solution of L-ascorbic acid (E mark) compound and NiSO4 (H2O) (sigma USA) were evaluated by UV visible spectrophotometer. Spectral analysis of L-ascorbic acid and nickel at various pH (2.0, 7.0, 7.4 and 8.6) at room temperature of 29 °C was recorded. In this special analysis, combined solution of L-ascorbic acid and nickel sulfate at different pH was also recorded. Results The result revealed that λmax (peak wavelength of spectra) of L-ascorbic acid at pH 2.0 was 289.0 nm whereas at neutral pH 7.0, λmax was 295.4 nm. In alkaline pH 8.6, λmax was 295.4 nm and at pH 7.4 the λmax of L-ascorbic acid remained the same as 295.4 nm. Nickel solution at acidic pH 2.0 was 394.5 nm, whereas at neutral pH 7.0 and pH 7.4 were the same as 394.5 nm. But at alkaline pH 8.6, λmax value of nickel sulfate became 392.0 nm. The combined solution of L-ascorbic acid and nickel sulfate (6 mg/mL each) at pH 2.0 showed 292.5 nm and 392.5 nm, respectively whereas at pH 7.0, L-ascorbic acid showed 296.5 nm and nickel sulfate showed 391.5 nm. At pH 7.4, L-ascorbic acid showed 297.0 nm and nickel sulfate showed 394.0 nm in the combined solution whereas at pH 8.6 (alkaline) L-ascorbic acid and nickel sulfate were showing 297.0 and 393.5 nm, respectively. Conclusions Results clearly indicate an altered chemical behavior of L-ascorbic acid either alone or in combination with nickel sulfate in vitro at different pH. Perhaps oxidation of L-ascorbic acid to L-dehydro ascorbic acid via the free radical (HSc*) generation from the reaction of H2ASc + Ni (II) is the cause of such alteration of λmax value of L-ascorbic acid in the presence of metal nickel. PMID:23569901

Acidic pH modulation of Na+ channels in trigeminal mesencephalic nucleus neurons.

PubMed

Kang, In-Sik; Cho, Jin-Hwa; Choi, In-Sun; Kim, Do-Yeon; Jang, Il-Sung

2016-12-07

Cell bodies of trigeminal mesencephalic nucleus (Vmes) neurons are located within the central nervous system, and therefore, peripheral as well as central acidosis can modulate the excitability of Vmes neurons. Here, we report the effect of acidic pH on voltage-gated Na channels in acutely isolated rat Vmes neurons using a conventional whole-cell patch clamp technique. Acidic pH (pH 6.0) slightly but significantly shifted both the activation and steady-state fast inactivation relationships toward depolarized potentials. However, acidic pH (pH 6.0) had a minor effect on the inactivation kinetics of voltage-gated Na channels. Less sensitivity of voltage-gated Na channels to acidic pH may allow Vmes neurons to transduce the precise proprioceptive information even under acidic pH conditions.

Gastric mucosal protective mechanisms: roles of epithelial bicarbonate and mucus secretions.

PubMed

Garner, A; Flemström, G; Allen, A; Heylings, J R; McQueen, S

1984-01-01

Secretion of HCO3 (amounting to 2-10% of maximum H+ secretion) in conjunction with the adherent mucus gel layer (functioning as a mixing barrier) protects gastric mucosa from luminal acid by a process of surface neutralization. Gastric HCO3 secretion is augmented by cholinergic agonists, prostaglandins and low luminal pH. Ulcerogens attenuate HCO3 secretion although passive diffusion of alkali consequent upon an increase in mucosal permeability may mask these inhibitory actions. Studies in vitro indicate that HCO3 transport in the stomach is dependent on oxidative metabolism, carbonic anhydrase activity and involves a CL exchange mechanism. Mucus, synthesized and released from epithelial cells, adheres to the mucosal surface as a thin (less than 80 microns in rat) but continuous gel layer. Prostaglandins and carbachol induced release of preformed mucus and thereby increase thickness, whereas acute exposure to ulcerogens has little effect on overall dimensions of the surface mucus layer. Measurements of pH gradients adjacent to gastric mucosa indicate that the disposal of luminal H+ occurs by extracellular neutralization. However, the fall in pH at the apical cell membrane when luminal pH is low (pH 1.5) suggests that while a mucus-bicarbonate barrier comprises the first line of mucosal defence, other factors are involved in the overall process of mucosal protection in the stomach.

Demonstration of in situ product recovery of butyric acid via CO2 -facilitated pH swings and medium development in two-phase partitioning bioreactors.

PubMed

Peterson, Eric C; Daugulis, Andrew J

2014-03-01

Production of organic acids in solid-liquid two-phase partitioning bioreactors (TPPBs) is challenging, and highly pH-dependent, as cell growth occurs near neutral pH, while acid sorption occurs only at low pH conditions. CO2 sparging was used to achieve acidic pH swings, facilitating undissociated organic acid uptake without generating osmotic stress inherent in traditional acid/base pH control. A modified cultivation medium was formulated to permit greater pH reduction by CO2 sparging (pH 4.8) compared to typical media (pH 5.3), while still possessing adequate nutrients for extensive cell growth. In situ product recovery (ISPR) of butyric acid (pKa = 4.8) produced by Clostridium tyrobutyricum was achieved through intermittent CO2 sparging while recycling reactor contents through a column packed with absorptive polymer Hytrel® 3078. This polymer was selected on the basis of its composition as a polyether copolymer, and the use of solubility parameters for predicting solute polymer affinity, and was found to have a partition coefficient for butyric acid of 3. Total polymeric extraction of 3.2 g butyric acid with no CO2 mediated pH swings was increased to 4.5 g via CO2 -facilitated pH shifting, despite the buffering capacity of butyric acid, which resists pH shifting. This work shows that CO2 -mediated pH swings have an observable positive effect on organic acid extraction, with improvements well over 150% under optimal conditions in early stage fermentation compared to CO2 -free controls, and this technique can be applied other organic acid fermentations to achieve or improve ISPR. © 2013 Wiley Periodicals, Inc.

A chemometric-assisted method for the simultaneous determination of malachite green and crystal violet in water based on absorbance-pH data generated by a homemade pH gradient apparatus.

PubMed

Yu, Shuling; Yuan, Xuejie; Yang, Jing; Yuan, Jintao; Shi, Jiahua; Wang, Yali; Chen, Yuewen; Gao, Shufang

2015-01-01

An attractive method of generating second-order data was developed by a dropping technique to generate pH gradient simultaneously coupled with diode-array spectrophotometer scanning. A homemade apparatus designed for the pH gradient. The method and the homemade apparatus were used to simultaneously determine malachite green (MG) and crystal violet (CV) in water samples. The absorbance-pH second-order data of MG or CV were obtained from the spectra of MG or CV in a series of pH values of HCl-KCl solution. The second-order data of mixtures containing MG and CV that coexisted with interferents were analyzed using multidimensional partial least-squares with residual bilinearization. The method and homemade apparatus were used to simultaneously determine MG and CV in fish farming water samples and in river ones with satisfactory results. The presented method and the homemade apparatus could serve as an alternative tool to handle some analysis problems. Copyright © 2015 Elsevier B.V. All rights reserved.

Soil pH determines fungal diversity along an elevation gradient in Southwestern China.

PubMed

Liu, Dan; Liu, Guohua; Chen, Li; Wang, Juntao; Zhang, Limei

2018-01-03

Fungi play important roles in ecosystem processes, and the elevational pattern of fungal diversity is still unclear. Here, we examined the diversity of fungi along a 1,000 m elevation gradient on Mount Nadu, Southwestern China. We used MiSeq sequencing to obtain fungal sequences that were clustered into operational taxonomic units (OTUs) and to measure the fungal composition and diversity. Though the species richness and phylogenetic diversity of the fungal community did not exhibit significant trends with increasing altitude, they were significantly lower at mid-altitudinal sites than at the base. The Bray-Curtis distance clustering also showed that the fungal communities varied significantly with altitude. A distance-based linear model multivariate analysis (DistLM) identified that soil pH dominated the explanatory power of the species richness (23.72%), phylogenetic diversity (24.25%) and beta diversity (28.10%) of the fungal community. Moreover, the species richness and phylogenetic diversity of the fungal community increased linearly with increasing soil pH (P<0.05). Our study provides evidence that pH is an important predictor of soil fungal diversity along elevation gradients in Southwestern China.

A multimodal histamine ligand for chromatographic purification of plasmid DNA.

PubMed

Černigoj, Urh; Vidic, Urška; Barut, Miloš; Podgornik, Aleš; Peterka, Matjaž; Štrancar, Aleš

2013-03-15

To exploit different chromatographic modes for efficient plasmid DNA (pDNA) purification a novel monolithic chromatographic support bearing multimodal histamine (HISA) groups was developed and characterized. Electrostatic charge of HISA groups depends on the pH of the mobile phase, being neutral above pH 7 and becoming positively charged below. As a consequence, HISA groups exhibit predominantly ion-exchange character at low pH values, which decreases with titration of the HISA groups resulting in increased hydrophobicity. This feature enabled separation of supercoiled (sc) pDNA from other plasmid isoforms (and other process related impurities) by adjusting salt or pH gradient. The dynamic binding capacity (DBC) for a 5.1kbp large plasmid at pH 5 was 4.0 mg/ml under low salt binding conditions, remaining relatively high (3.0 mg/ml) even in the presence of 1.0 M NaCl due to the multimodal nature of HISA ligand. Only slightly lower DBC (2.7 mg/ml) was determined under preferentially hydrophobic conditions in 3.0 M (NH(4))(2)SO(4), pH 7.4. Open circular and sc pDNA isoforms were baseline separated in descending (NH(4))(2)SO(4) gradient. Furthermore, an efficient plasmid DNA separation was possible both on analytical as well as on preparative scale by applying the descending pH gradient at a constant concentration (above 3.0 M) of (NH(4))(2)SO(4). Copyright © 2013 Elsevier B.V. All rights reserved.

Development of a Dual Solid-State pH-AT Sensor

NASA Astrophysics Data System (ADS)

Briggs, E.; Martz, T. R.; Kummel, A.; Sandoval, S.; Erten, A.

2016-02-01

Here we report on our progress toward development of a solid state, reagentless sensor capable of rapid and simultaneous measurement of pH and Total Alkalinity (AT) using ion sensitive field effect transistor (ISFET) technology. The goal of this work is to provide a means of continuous, direct measurement of the seawater carbon dioxide system through measurement of two "master variables" (pH and AT). ISFET-based pH sensors that achieve 0.001 precision are presently in widespread use on autonomous oceanographic platforms. Modifications to an ISFET allow a nL-scale acid-base titration of total alkalinity to be carried out in 10 s. Titrant, H+, is generated through the electrolysis of water on the surface of the chip eliminating the requirement of external reagents. Initial characterization has been performed titrating individual components (i.e. OH-, HCO3-, CO32-, PO43-) of seawater AT. Based on previous work by others in simple acid-base systems and our preliminary results in seawater we feel that it is within reach to set a benchmark goal of 10 μmol kg-1 precision in AT. The estimated resolution of this dual pH-AT sensor translates to approximately 0.5 and 0.7% error in Total Dissolved Inorganic Carbon (CT) and pCO2 respectively and would have a number of immediate applications for investigating biogeochemical processes where strong gradients exist over short distances and in rapidly changing environments.

Anomalous pH-Dependent Nanofluidic Salinity Gradient Power.

PubMed

Yeh, Li-Hsien; Chen, Fu; Chiou, Yu-Ting; Su, Yen-Shao

2017-12-01

Previous studies on nanofluidic salinity gradient power (NSGP), where energy associated with the salinity gradient can be harvested with ion-selective nanopores, all suggest that nanofluidic devices having higher surface charge density should have higher performance, including osmotic power and conversion efficiency. In this manuscript, this viewpoint is challenged and anomalous counterintuitive pH-dependent NSGP behaviors are reported. For example, with equal pH deviation from its isoelectric point (IEP), the nanopore at pH < IEP is shown to have smaller surface charge density but remarkably higher NSGP performance than that at pH > IEP. Moreover, for sufficiently low pH, the NSGP performance decreases with lowering pH (increasing nanopore charge density). As a result, a maximum osmotic power density as high as 5.85 kW m -2 can be generated along with a conversion efficiency of 26.3% achieved for a single alumina nanopore at pH 3.5 under a 1000-fold concentration ratio. Using the rigorous model with considering the surface equilibrium reactions on the pore wall, it is proved that these counterintuitive surface-charge-dependent NSGP behaviors result from the pH-dependent ion concentration polarization effect, which yields the degradation in effective concentration ratio across the nanopore. These findings provide significant insight for the design of next-generation, high-performance NSGP devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

pH-Induced precipitation behavior of weakly basic compounds: determination of extent and duration of supersaturation using potentiometric titration and correlation to solid state properties.

PubMed

Hsieh, Yi-Ling; Ilevbare, Grace A; Van Eerdenbrugh, Bernard; Box, Karl J; Sanchez-Felix, Manuel Vincente; Taylor, Lynne S

2012-10-01

To examine the precipitation and supersaturation behavior of ten weak bases in terms of the relationship between pH-concentration-time profiles and the solid state properties of the precipitated material. Initially the compound was dissolved at low pH, followed by titration with base to induce precipitation. Upon precipitation, small aliquots of acid or base were added to induce slight subsaturation and supersaturation respectively and the resultant pH gradient was determined. The concentration of the unionized species was calculated as a function of time and pH using mass and charge balance equations. Two patterns of behavior were observed in terms of the extent and duration of supersaturation arising following an increase in pH and this behavior could be rationalized based on the crystallization tendency of the compound. For compounds that did not readily crystallize, an amorphous precipitate was formed and a prolonged duration of supersaturation was observed. For compounds that precipitated to crystalline forms, the observed supersaturation was short-lived. This study showed that supersaturation behavior has significant correlation with the solid-state properties of the precipitate and that pH-metric titration methods can be utilized to evaluate the supersaturation behavior.

Intestinal bicarbonate secretion in Amphiuma measured by pH stat in vitro: relationship with metabolism and transport of sodium and chloride ions.

PubMed Central

Imon, M A; White, J F

1981-01-01

1. Isolated Amphiuma small intestine exposed on both surfaces to buffered or unbuffered media generated gradients of pH under short-circuited conditions consistent with secretion of HCO3(-). 2. When unbuffered mucosal medium was maintained at pH 7.4 by addition of acid, alkalinization of the mucosal medium occurred at a rate of 1-2 microequiv/hr cm2 under short-circuit conditions (Isc) and was reduced by anoxia, acetazolamide or removal of CO2. 3. The rate of HCO3(-) secretion (JHCO3(-)) was reduced at a mucosal pH above or below 7.4 and was proportional to serosal HCO3(-). 4. JHCO3(-) was reduced in Na+-free (choline) and Cl-free (SO4(2-) media and after exposure to the stilbene SITS. 5. The difference JHCO3(-)--Isc was consistent with net Cl- absorption. 6. The tissue resistance (Rt) was elevated upon exposure to serosal HCO3(-) and lowered by mucosal HCO3(-). 7. The intestinal mucosa exhibited carbonic anhydrase activity that was sensitive to ethoxazolamide. 8. It is concluded that HCO3(-) secretion is active, influenced by intracellular carbonic anhydrase activity and coupled to Cl- and possibly Na+ absorption. PMID:7310697

Intestinal bicarbonate secretion in Amphiuma measured by pH stat in vitro: relationship with metabolism and transport of sodium and chloride ions.

PubMed

Imon, M A; White, J F

1981-05-01

1. Isolated Amphiuma small intestine exposed on both surfaces to buffered or unbuffered media generated gradients of pH under short-circuited conditions consistent with secretion of HCO3(-). 2. When unbuffered mucosal medium was maintained at pH 7.4 by addition of acid, alkalinization of the mucosal medium occurred at a rate of 1-2 microequiv/hr cm2 under short-circuit conditions (Isc) and was reduced by anoxia, acetazolamide or removal of CO2. 3. The rate of HCO3(-) secretion (JHCO3(-)) was reduced at a mucosal pH above or below 7.4 and was proportional to serosal HCO3(-). 4. JHCO3(-) was reduced in Na+-free (choline) and Cl-free (SO4(2-) media and after exposure to the stilbene SITS. 5. The difference JHCO3(-)--Isc was consistent with net Cl- absorption. 6. The tissue resistance (Rt) was elevated upon exposure to serosal HCO3(-) and lowered by mucosal HCO3(-). 7. The intestinal mucosa exhibited carbonic anhydrase activity that was sensitive to ethoxazolamide. 8. It is concluded that HCO3(-) secretion is active, influenced by intracellular carbonic anhydrase activity and coupled to Cl- and possibly Na+ absorption.

Acidic pH promotes intervertebral disc degeneration: Acid-sensing ion channel -3 as a potential therapeutic target.

PubMed

Gilbert, Hamish T J; Hodson, Nathan; Baird, Pauline; Richardson, Stephen M; Hoyland, Judith A

2016-11-17

The aetiology of intervertebral disc (IVD) degeneration remains poorly understood. Painful IVD degeneration is associated with an acidic intradiscal pH but the response of NP cells to this aberrant microenvironmental factor remains to be fully characterised. The aim here was to address the hypothesis that acidic pH, similar to that found in degenerate IVDs, leads to the altered cell/functional phenotype observed during IVD degeneration, and to investigate the involvement of acid-sensing ion channel (ASIC) -3 in the response. Human NP cells were treated with a range of pH, from that of a non-degenerate (pH 7.4 and 7.1) through to mildly degenerate (pH 6.8) and severely degenerate IVD (pH 6.5 and 6.2). Increasing acidity of pH caused a decrease in cell proliferation and viability, a shift towards matrix catabolism and increased expression of proinflammatory cytokines and pain-related factors. Acidic pH resulted in an increase in ASIC-3 expression. Importantly, inhibition of ASIC-3 prevented the acidic pH induced proinflammatory and pain-related phenotype in NP cells. Acidic pH causes a catabolic and degenerate phenotype in NP cells which is inhibited by blocking ASIC-3 activity, suggesting that this may be a useful therapeutic target for treatment of IVD degeneration.

Mixed-bed ion exchange chromatography employing a salt-free pH gradient for improved sensitivity and compatibility in MudPIT.

PubMed

Mommen, Geert P M; Meiring, Hugo D; Heck, Albert J R; de Jong, Ad P J M

2013-07-16

In proteomics, comprehensive analysis of peptides mixtures necessitates multiple dimensions of separation prior to mass spectrometry analysis to reduce sample complexity and increase the dynamic range of analysis. The main goal of this work was to improve the performance of (online) multidimensional protein identification technology (MudPIT) in terms of sensitivity, compatibility and recovery. The method employs weak anion and strong cation mixed-bed ion exchange chromatography (ACE) in the first separation dimension and reversed phase chromatography (RP) in the second separation dimension (Motoyama et.al. Anal. Chem 2007, 79, 3623-34.). We demonstrated that the chromatographic behavior of peptides in ACE chromatography depends on both the WAX/SCX mixing ratio as the ionic strength of the mobile phase system. This property allowed us to replace the conventional salt gradient by a (discontinuous) salt-free, pH gradient. First dimensional separation of peptides was accomplished with mixtures of aqueous formic acid and dimethylsulfoxide with increasing concentrations. The overall performance of this mobile phase system was found comparable to ammonium acetate buffers in application to ACE chromatography, but clearly outperformed strong cation exchange for use in first dimensional peptide separation. The dramatically improved compatibility between (salt-free) ion exchange chromatography and reversed phase chromatography-mass spectrometry allowed us to downscale the dimensions of the RP analytical column down to 25 μm i.d. for an additional 2- to 3-fold improvement in performance compared to current technology. The achieved levels of sensitivity, orthogonality, and compatibility demonstrates the potential of salt-free ACE MudPIT for the ultrasensitive, multidimensional analysis of very modest amounts of sample material.

[Effects of simulated acid rain on Quercus glauca seedlings photosynthesis and chlorophyll fluorescence].

PubMed

Li, Jia; Jiang, Hong; Yu, Shu-quan; Jiang, Fu-wei; Yin, Xiu-min; Lu, Mei-juan

2009-09-01

Taking the seedlings of Quercus glauca, a dominant evergreen broadleaf tree species in subtropical area, as test materials, this paper studied their photosynthesis, chlorophyll fluorescence, and chlorophyll content under effects of simulated acid rain with pH 2.5, 4.0, and 5.6 (CK). After 2-year acid rain stress, the net photosynthetic rate of Q. glauca increased significantly with decreasing pH of acid rain. The acid rain with pH 2.5 and 4.0 increased the stomatal conductance and transpiration rate, and the effect was more significant under pH 2.5. The intercellular CO2 concentration decreased in the order of pH 2.5 > pH 5.6 > pH 4.0. The maximum photosynthetic rate, light compensation point, light saturation point, and dark respiration rate were significantly higher under pH 2.5 and 4.0 than under pH 5.6, while the apparent quantum yield was not sensitive to acid rain stress. The maximal photochemical efficiency of PS II and the potential activity of PS II under pH 2.5 and 4.0 were significantly higher than those under pH 5.6. The relative chlorophyll content was in the order of pH 2.5 > pH 5.6 > pH 4.0, and there was a significant difference between pH 2.5 and 4.0. All the results suggested that the photosynthesis and chlorophyll fluorescence of Q. glauca increased under the effects of acid rain with pH 2.5 and 4.0, and the acid rain with pH 2.5 had more obvious effects.

Purification of influenza deoxyribonucleic acid-based vaccine using agmatine monolith.

PubMed

Bicho, D; Caramelo-Nunes, C; Sousa, A; Sousa, F; Queiroz, J A; Tomaz, C T

2016-02-15

Lately, researchers have made several efforts to improve vaccine production to fight highly contagious respiratory diseases like influenza. One of the most promising options for reducing the impact of this virus is DNA vaccination. However, a large quantity of highly pure plasmid DNA (pDNA) is necessary to attain this goal. The present work describes the production and purification of the plasmid NTC7482-41H-VA2HA expressing influenza virus hemagglutinin using an agmatine monolith. This ligand was chosen to purify supercoiled (sc) pDNA from complex lysates because of its versatile multimodal character. Its natural intervention in several biological systems together with its similarity with the highly studied arginine ligand allowed the development of a simpler and more specific purification process. Agmatine works under two strategies: descending ammonium sulfate gradient and ascending sodium chloride gradient. Furthermore, pH manipulation revealed an important role in pDNA isoforms selectivity. Dynamic binding capacity (DBC) experiments were performed varying different parameters and showed an increase with pDNA concentration, while high flow rate and high pH had the opposite effect. Sc pDNA was purified with high yield and was efficient with respect to cell transfection and cell viability. This monolith showed to be appropriate to purify the plasmid NTC7482-41H-VA2HA, providing a valuable tool for pDNA influenza vaccines preparation. Copyright © 2016. Published by Elsevier B.V.

L-leucine, L-methionine, and L-phenylalanine share a Na(+)/K (+)-dependent amino acid transporter in shrimp hepatopancreas.

PubMed

Duka, Ada; Ahearn, Gregory A

2013-08-01

Hepatopancreatic brush border membrane vesicles (BBMV), made from Atlantic White shrimp (Litopenaeus setiferus), were used to characterize the transport properties of (3)H-L-leucine influx by these membrane systems and how other essential amino acids and the cations, sodium and potassium, interact with this transport system. (3)H-L-leucine uptake by BBMV was pH-sensitive and occurred against transient transmembrane concentration gradients in both Na(+)- and K(+)-containing incubation media, suggesting that either cation was capable of providing a driving force for amino acid accumulation. (3)H-L-leucine uptake in NaCl or KCl media were each three times greater in acidic pH (pH 5.5) than in alkaline pH (pH 8.5). The essential amino acid, L-methionine, at 20 mM significantly (p < 0.0001) inhibited the 2-min uptakes of 1 mM (3)H-L-leucine in both Na(+)- and K(+)-containing incubation media. The residual (3)H-L-leucine uptake in the two media were significantly greater than zero (p < 0.001), but not significantly different from each other (p > 0.05) and may represent an L-methionine- and cation-independent transport system. (3)H-L-leucine influxes in both NaCl and KCl incubation media were hyperbolic functions of [L-leucine], following the carrier-mediated Michaelis-Menten equation. In NaCl, (3)H-L-leucine influx displayed a low apparent K M (high affinity) and low apparent J max, while in KCl the transport exhibited a high apparent K M (low affinity) and high apparent J max. L-methionine or L-phenylalanine (7 and 20 mM) were competitive inhibitors of (3)H-L-leucine influxes in both NaCl and KCl media, producing a significant (p < 0.01) increase in (3)H-L-leucine influx K M, but no significant response in (3)H-L-leucine influx J max. Potassium was a competitive inhibitor of sodium co-transport with (3)H-L-leucine, significantly (p < 0.01) increasing (3)H-L-leucine influx K M in the presence of sodium, but having negligible effect on (3)H-L-leucine influx J max in the same medium. These results suggest that shrimp BBMV transport (3)H-L-leucine by a single L-methionine- and L-phenylalanine-shared carrier system that is enhanced by acidic pH and can be stimulated by either Na(+) or K(+) acting as co-transport drivers binding to shared activator sites.

Acid and Base Stress and Transcriptomic Responses in Bacillus subtilis▿†

PubMed Central

Wilks, Jessica C.; Kitko, Ryan D.; Cleeton, Sarah H.; Lee, Grace E.; Ugwu, Chinagozi S.; Jones, Brian D.; BonDurant, Sandra S.; Slonczewski, Joan L.

2009-01-01

Acid and base environmental stress responses were investigated in Bacillus subtilis. B. subtilis AG174 cultures in buffered potassium-modified Luria broth were switched from pH 8.5 to pH 6.0 and recovered growth rapidly, whereas cultures switched from pH 6.0 to pH 8.5 showed a long lag time. Log-phase cultures at pH 6.0 survived 60 to 100% at pH 4.5, whereas cells grown at pH 7.0 survived <15%. Cells grown at pH 9.0 survived 40 to 100% at pH 10, whereas cells grown at pH 7.0 survived <5%. Thus, growth in a moderate acid or base induced adaptation to a more extreme acid or base, respectively. Expression indices from Affymetrix chip hybridization were obtained for 4,095 protein-encoding open reading frames of B. subtilis grown at external pH 6, pH 7, and pH 9. Growth at pH 6 upregulated acetoin production (alsDS), dehydrogenases (adhA, ald, fdhD, and gabD), and decarboxylases (psd and speA). Acid upregulated malate metabolism (maeN), metal export (czcDO and cadA), oxidative stress (catalase katA; OYE family namA), and the SigX extracytoplasmic stress regulon. Growth at pH 9 upregulated arginine catabolism (roc), which generates organic acids, glutamate synthase (gltAB), polyamine acetylation and transport (blt), the K+/H+ antiporter (yhaTU), and cytochrome oxidoreductases (cyd, ctaACE, and qcrC). The SigH, SigL, and SigW regulons were upregulated at high pH. Overall, greater genetic adaptation was seen at pH 9 than at pH 6, which may explain the lag time required for growth shift to high pH. Low external pH favored dehydrogenases and decarboxylases that may consume acids and generate basic amines, whereas high external pH favored catabolism-generating acids. PMID:19114526

Acid and base stress and transcriptomic responses in Bacillus subtilis.

PubMed

Wilks, Jessica C; Kitko, Ryan D; Cleeton, Sarah H; Lee, Grace E; Ugwu, Chinagozi S; Jones, Brian D; BonDurant, Sandra S; Slonczewski, Joan L

2009-02-01

Acid and base environmental stress responses were investigated in Bacillus subtilis. B. subtilis AG174 cultures in buffered potassium-modified Luria broth were switched from pH 8.5 to pH 6.0 and recovered growth rapidly, whereas cultures switched from pH 6.0 to pH 8.5 showed a long lag time. Log-phase cultures at pH 6.0 survived 60 to 100% at pH 4.5, whereas cells grown at pH 7.0 survived <15%. Cells grown at pH 9.0 survived 40 to 100% at pH 10, whereas cells grown at pH 7.0 survived <5%. Thus, growth in a moderate acid or base induced adaptation to a more extreme acid or base, respectively. Expression indices from Affymetrix chip hybridization were obtained for 4,095 protein-encoding open reading frames of B. subtilis grown at external pH 6, pH 7, and pH 9. Growth at pH 6 upregulated acetoin production (alsDS), dehydrogenases (adhA, ald, fdhD, and gabD), and decarboxylases (psd and speA). Acid upregulated malate metabolism (maeN), metal export (czcDO and cadA), oxidative stress (catalase katA; OYE family namA), and the SigX extracytoplasmic stress regulon. Growth at pH 9 upregulated arginine catabolism (roc), which generates organic acids, glutamate synthase (gltAB), polyamine acetylation and transport (blt), the K(+)/H(+) antiporter (yhaTU), and cytochrome oxidoreductases (cyd, ctaACE, and qcrC). The SigH, SigL, and SigW regulons were upregulated at high pH. Overall, greater genetic adaptation was seen at pH 9 than at pH 6, which may explain the lag time required for growth shift to high pH. Low external pH favored dehydrogenases and decarboxylases that may consume acids and generate basic amines, whereas high external pH favored catabolism-generating acids.

A validated LC method for determination of 2,3-dichlorobenzoic acid and its associated regio isomers.

PubMed

Krishnaiah, Ch; Sri, Khagga Bhavya

2012-05-01

A simple, selective and sensitive gradient reversed-phase liquid chromatography method has been developed for the separation and determination of 2,3-dichlorobenzoic acid, which is an intermediate of the lamotrizine drug substance, and its regio isomers. The separation was achieved on a reversed-phase United States Pharmacopeia L1 (C-18) column using 0.01 M ammonium acetate buffer at pH 2.5 and methanol (50:50 v/v) mixture as mobile phase A and a methanol and water mixture (80:20 v/v) as mobile phase B in a gradient elution at flow rate 1.2 mL/min with ultraviolet detection at 210 nm. The method is found to be selective, precise, linear, accurate and robust. It was used for quality assurance and monitoring the synthetic reactions involved in the process development of lamotrizine. The method is found to be simple, rapid, specific and reliable for the determination of unreacted levels of raw materials and isomers in reaction mixtures and finished product lamotrizine. The method was fully validated as per International Conference of Harmonization guidelines and results from validation confirm that the method is highly suitable for its intended purpose. © The Author [2012]. Published by Oxford University Press. All rights reserved.

Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lipson, David A.; Raab, Theodore K.; Parker, Melanie

2015-07-21

This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska, and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and weremore » most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography, but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes, dominated by fermenters ( Bacteroidetes and Firmicutes).« less

Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils.

PubMed

Lipson, David A; Raab, Theodore K; Parker, Melanie; Kelley, Scott T; Brislawn, Colin J; Jansson, Janet

2015-08-01

This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes, dominated by fermenters (Bacteroidetes and Firmicutes). © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Diversity of the Sediment Microbial Community in the Aha Watershed (Southwest China) in Response to Acid Mine Drainage Pollution Gradients

PubMed Central

Sun, Weimin; Sun, Min; Dong, Yiran; Ning, Zengping; Xiao, Enzong; Tang, Song; Li, Jiwei

2015-01-01

Located in southwest China, the Aha watershed is continually contaminated by acid mine drainage (AMD) produced from upstream abandoned coal mines. The watershed is fed by creeks with elevated concentrations of aqueous Fe (total Fe > 1 g/liter) and SO42− (>6 g/liter). AMD contamination gradually decreases throughout downstream rivers and reservoirs, creating an AMD pollution gradient which has led to a suite of biogeochemical processes along the watershed. In this study, sediment samples were collected along the AMD pollution sites for geochemical and microbial community analyses. High-throughput sequencing found various bacteria associated with microbial Fe and S cycling within the watershed and AMD-impacted creek. A large proportion of Fe- and S-metabolizing bacteria were detected in this watershed. The dominant Fe- and S-metabolizing bacteria were identified as microorganisms belonging to the genera Metallibacterium, Aciditerrimonas, Halomonas, Shewanella, Ferrovum, Alicyclobacillus, and Syntrophobacter. Among them, Halomonas, Aciditerrimonas, Metallibacterium, and Shewanella have previously only rarely been detected in AMD-contaminated environments. In addition, the microbial community structures changed along the watershed with different magnitudes of AMD pollution. Moreover, the canonical correspondence analysis suggested that temperature, pH, total Fe, sulfate, and redox potentials (Eh) were significant factors that structured the microbial community compositions along the Aha watershed. PMID:25979900

Net alkalinity and net acidity 2: Practical considerations

USGS Publications Warehouse

Kirby, C.S.; Cravotta, C.A.

2005-01-01

The pH, alkalinity, and acidity of mine drainage and associated waters can be misinterpreted because of the chemical instability of samples and possible misunderstandings of standard analytical method results. Synthetic and field samples of mine drainage having various initial pH values and concentrations of dissolved metals and alkalinity were titrated by several methods, and the results were compared to alkalinity and acidity calculated based on dissolved solutes. The pH, alkalinity, and acidity were compared between fresh, unoxidized and aged, oxidized samples. Data for Pennsylvania coal mine drainage indicates that the pH of fresh samples was predominantly acidic (pH 2.5-4) or near neutral (pH 6-7); ??? 25% of the samples had pH values between 5 and 6. Following oxidation, no samples had pH values between 5 and 6. The Standard Method Alkalinity titration is constrained to yield values >0. Most calculated and measured alkalinities for samples with positive alkalinities were in close agreement. However, for low-pH samples, the calculated alkalinity can be negative due to negative contributions by dissolved metals that may oxidize and hydrolyze. The Standard Method hot peroxide treatment titration for acidity determination (Hot Acidity) accurately indicates the potential for pH to decrease to acidic values after complete degassing of CO2 and oxidation of Fe and Mn, and it indicates either the excess alkalinity or that required for neutralization of the sample. The Hot Acidity directly measures net acidity (= -net alkalinity). Samples that had near-neutral pH after oxidation had negative Hot Acidity; samples that had pH < 6.3 after oxidation had positive Hot Acidity. Samples with similar pH values before oxidation had dissimilar Hot Acidities due to variations in their alkalinities and dissolved Fe, Mn, and Al concentrations. Hot Acidity was approximately equal to net acidity calculated based on initial pH and dissolved concentrations of Fe, Mn, and Al minus the initial alkalinity. Acidity calculated from the pH and dissolved metals concentrations, assuming equivalents of 2 per mole of Fe and Mn and 3 per mole of Al, was equivalent to that calculated based on complete aqueous speciation of FeII/FeIII. Despite changes in the pH, alkalinity, and metals concentrations, the Hot Acidities were comparable for fresh and most aged samples. A meaningful "net" acidity can be determined from a measured Hot Acidity or by calculation from the pH, alkalinity, and dissolved metals concentrations. The use of net alkalinity = (Alkalinitymeasured - Hot Aciditymeasured) to design mine drainage treatment can lead to systems with insufficient Alkalinity to neutralize metal and H+ acidity and is not recommended. The use of net alkalinity = -Hot Acidity titration is recommended for the planning of mine drainage treatment. The use of net alkalinity = (Alkalinitymeasured - Aciditycalculated) is recommended with some cautions. ?? 2005 Elsevier Ltd. All rights reserved.

A high-performance liquid chromatography micromethod for the simultaneous determination of vigabatrin and gabapentin in serum.

PubMed

Ratnaraj, N; Patsalos, P N

1998-08-01

A gradient high-performance liquid chromatography micromethod is described for the simultaneous quantitation of vigabatrin and gabapentin in human serum. Chromatography was performed using a 125- x 3-mm ID Hypersil BDS C-18 column with a 3-microm mini-bore, eluted with a gradient system comprised of phosphate buffer (pH 6.5)-acetonitrile-methanol-water at a flow rate of 0.45 ml/minute. The column eluent was monitored on a fluorescence detector using excitation and emission wavelengths of 340 and 440 nm, respectively. The lower limit of quantitation for vigabatrin and for gabapentin was 5 micromol/l, and the within-batch and between-batch coefficients of variation were <5%. No interference from commonly prescribed antiepileptic drugs (carbamazepine and its metabolite carbamazepine epoxide, oxcarbazepine and its metabolite 10-hydroxycarbazepine, ethosuximide, lamotrigine, phenobarbitone, phenytoin, primidone, and valproic acid) was observed; thus, the method can be used to monitor vigabatrin and gabapentin in patients on polytherapy antiepileptic drug regimens.

Collection of Ni-bearing material from electroless plating waste by magnetic separation with HTS bulk magnet

NASA Astrophysics Data System (ADS)

Oka, T.; Fukazawa, H.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M.; Tsujimura, M.; Yokoyama, K.

2014-01-01

The magnetic separation experiment to collect the Ni compounds from the waste liquid of electroless plating processes was conducted in the open-gradient magnetic separation process with the high temperature superconducting bulk magnet system. The magnetic pole containing Gd-based bulk superconductors was activated to 3.45 T at 35 K in the static magnetic field of 5 T with use of a superconducting solenoid magnet. The coarse Ni-sulfate crystals were formed by adding the concentrated sulfuric acid to the Ni-phosphite precipitates which yielded from the plating waste liquid by controlling the temperature and the pH value. The open-gradient magnetic separation technique was employed to separate the Ni-sulfate crystals from the mixture of the Ni-sulfate and Ni-phosphite compounds by the difference between their magnetic properties. And we succeeded in collecting Ni-sulfate crystals preferentially to the Ni-phosphite by attracting them to the magnetic pole soon after the Ni-sulfate crystals began to grow.

Simultaneous determination of phenylephrine hydrochloride, guaifenesin, and chlorpheniramine maleate in cough syrup by gradient liquid chromatography.

PubMed

Amer, Sawsan M; Abbas, Samah S; Shehata, Mostafa A; Ali, Nahed M

2008-01-01

A simple and reliable high-performance liquid chromatographic method was developed for the simultaneous determination of mixture of phenylephrine hydrochloride (PHENYL), guaifenesin (GUAIF), and chlorpheniramine maleate (CHLO) either in pure form or in the presence of methylparaben and propylparaben in a commercial cough syrup dosage form. Separation was achieved on a C8 column using 0.005 M heptane sulfonic acid sodium salt (pH 3.4 +/- 0.1) and acetonitrile as a mobile phase by gradient elution at different flow rates, and detection was done spectrophotometrically at 210 nm. A linear relationship in the range of 30-180, 120-1800, and 10-60 microg/mL was obtained for PHENYL, GUAIF, and CHLO, respectively. The results were statistically analyzed and compared with those obtained by applying the British Pharmacopoeia (2002) method and showed that the proposed method is precise, accurate, and can be easily applied for the determination of the drugs under investigation in pure form and in cough syrup formulations.

Culture-independent bacterial community analysis of the salty-fermented fish paste products of Thailand and Laos

PubMed Central

MARUI, Junichiro; BOULOM, Sayvisene; PANTHAVEE, Wanchai; MOMMA, Mari; KUSUMOTO, Ken-Ichi; NAKAHARA, Kazuhiko; SAITO, Masayoshi

2015-01-01

A bacterial community analysis, using a culture-independent method (polymerase chain reaction-denaturing gradient gel electrophoresis), detected 17 species of bacteria including species of the genera Tetragenococcus, Lactobacillus, Pediococcus, Weissella Halanaerobium, Clostridium, and Sphingomonas in a traditional salty-fermented fish paste known as pla-ra or pa-daek in Thailand and Laos, which is used as a storage-stable multi-purpose seasoning. The representative genus of lactic acid bacteria seemed to vary in the 10 products collected from Thailand and Laos. Tetragenococci were common in products from central Thailand and Vientiane in Laos which had salinities of not less than 11% and pH values ranging from 5.6 to 6.1. However, lactobacilli were common in products from northern Thailand which had the lowest salinities (8.3–8.6%) and pH values (4.5–4.8) of all the samples examined. Two Lactobacillus and one Tetragenococcus species were detected in one product from northeastern Thailand containing 10% salt. These results suggest that salinity in pla-ra/pa-daek is an important determinant of the representative genus of lactic acid bacteria such as, Tetragenococcus or Lactobacillus. Additionally, differences in the acidity between these two groups seemed to be related to the production of d-/l-lactic acid in the lactic acid bacteria in each product. This is the first study to report a correlation between bacterial community structure and taste components in pla-ra/pa-daek products from various regions. This scientific work on a traditional fermented food will be useful in helping local producers meet differing consumer preferences in various regions. PMID:25918672

Influence of long-term exposure to simulated acid rain on development, reproduction and acaricide susceptibility of the carmine spider mite, Tetranychus cinnabarinus

PubMed Central

Wang, Jin-Jun; Zhang, Jian-Ping; He, Lin; Zhao, Zhi-Mo

2006-01-01

Development, reproduction and acaricide susceptibility of Tetranychus cinnabarinus (Boisduvals) (Acari: Tetranychidae) were investigated after long-term (about 40 generations) exposure to various levels of acid rain; pH 2.5, 3.0, 4.0, and 5.6. Deionized water (pH 6.8) served as a control. The mites were reared on eggplant leaves at 28°C, 80%RH and a photoperiod of 14:10 (L:D) in the laboratory. The results showed that the duration of the immature stage was significantly affected by acid rain exposure. The shortest duration (8.90 days) was recorded for populations exposed to pH 5.6 acid rain, while the longest duration (9.37 days) occurred after exposure to pH 2.5 acid rain. Compared with the control population, adult longevity was shortened with an increase in acidity. Similarly, the oviposition duration was also shortened by an increase in acidity. Statistically, female fecundity did not differ significantly between pH 5.6, pH 4.0 and control populations, but did differ significantly between the control population and those exposed to pH 2.5 and pH 3.0 acid rain. This suggested that the mite suffered reproductive defects after long-term exposure to acid rain with higher acidity (pH 2.5 and 3.0). The intrinsic rate of increase among different populations was not significantly affected, but the net reproductive rate of populations exposed to pH 2.5 and 3.0 acid rain was significantly less than pH4.0, 5.6, and control populations. Bioassay results showed that after long-term exposure to acid rain, susceptibility of the mites to two acaricides, dichlorvos and fenpropathrin, did not change significantly. PMID:19537978

Pulmonary hypertension in rheumatic mitral stenosis revisited.

PubMed

Pourafkari, L; Ghaffari, S; Ahmadi, M; Tajlil, A; Aslanabadi, N; Nader, N D

2017-12-01

In patients with mitral stenosis (MS), pulmonary hypertension (PH) is a significant contributor to the associated morbidity. We aimed to study factors associated with the presence of significant PH (sPH) and whether incorporating body surface area (BSA) in the mitral valve area (MVA) would improve the predictive value of the latter. The medical records of 558 patients with severe MS undergoing percutaneous balloon mitral commissurotomy were evaluated over a period of 8 years. Factors associated with the presence of significant PH (sPH) defined as mPAP ≥ 40 mm Hg were examined. A total of 558 patients (423 women) were enrolled. Overall, 153 (27%) patients had sPH. Patients with sPH were similar to the rest of the subjects in terms of demographics, body habitus, blood group, and incidence of atrial fibrillation. Among echocardiographic findings, absolute MVA, indexed MVA, and mean transmitral valve gradient were associated with the presence of sPH. Transmitral valve gradient during right heart catheterization had the highest area under the curve for an association with sPH. Age, gender, heart rhythm, and blood group were not associated with the presence of sPH in severe MS. The predictive value of the indexed MVA for the presence of sPH was not higher than that of absolute MVA.

In vitro probiotic characteristics of Lactobacillus plantarum ZDY 2013 and its modulatory effect on gut microbiota of mice.

PubMed

Huang, Renhui; Tao, Xueying; Wan, Cuixiang; Li, Shengjie; Xu, Hengyi; Xu, Feng; Shah, Nagendra P; Wei, Hua

2015-09-01

Lactobacillus plantarum ZDY 2013, a novel strain isolated from Chinese traditional fermented acid beans, was systematically evaluated for its survival capacity under stress conditions (pH, bile salt, simulated gastrointestinal tract, and antibiotics), production of exopolysaccharide and antagonism against 8 pathogens. Its effect on mice gut microbiota was also investigated by quantitative PCR and PCR-denaturing gradient gel electrophoresis. The results showed that ZDY 2013 can grow at pH 3.5 and survive at pH 2.0 for 6 h and at 0.45% bile salt for 3 h. The exopolysaccharide yield was up to 204±7.68 mg/L. The survival rate of ZDY 2013 in a simulated gastrointestinal tract was as high as 65.84%. Antagonism test with a supernatant of ZDY 2013 showed maximum halo of 28 mm against Listeria monocytogenes. The inhibition order was as follows: Listeria monocytogenes, Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa, Shigella sonnei, Enterobacter sakazakii, and Staphylococcus aureus. Lactobacillus plantarum ZDY 2013 was sensitive to some antibiotics (e.g., macrolide, sulfonamides, aminoglycoside, tetracyclines and β-lactams), whereas it was resistant to glycopeptides, quinolones, and cephalosporins antibiotics. Denaturing gradient gel electrophoresis profile demonstrated that ZDY 2013 administration altered the composition of the microbiota at various intestinal loci of the mice. Moreover, the quantitative PCR test showed that the administration of ZDY 2013 enhanced the populations of Bifidobacterium and Lactobacillus in either the colon or cecum, and reduced the potential enteropathogenic bacteria (e.g., Enterococcus, Enterobacterium, and Clostridium perfringens). Lactobacillus plantarum ZDY 2013 exhibited high resistance against low pH, bile salt, and gastrointestinal fluid, and possessed antibacterial and gut microbiota modulation properties with a potential application in the development of dairy food and nutraceuticals. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Effects of Vegetation Composition and Trophic Structure on Pathways of Mercury Methylation in Alaskan Peatlands

NASA Astrophysics Data System (ADS)

Hines, M. E.; Zhang, L.; Barkay, T.; Krabbenhoft, D. P.; Liu, X.

2016-12-01

Methyl mercury (MeHg) can be produced by diverse microbes including syntrophs, methanogens, and fermenters, besides sulfate (SO42-, SRB) and iron- reducing bacteria. Many freshwater wetlands are deficient in electron acceptors that support the traditional respiratory pathways of methylation, yet high levels of MeHg can accumulate. To investigate methylation pathways in these wetlands and to connect these pathways with surface vegetation and microbial communities, experiments were conducted using peats from 28 sites in Alaska collected during the summer of 2015. The sites were clustered using multiple factor analysis based on pH, temp, CH4 and volatile fatty acids production rates, and surface vegetation composition. Three clusters were generated and corresponded to three trophic levels that were manifested by three pH levels (4.2, 5.3, and 5.8). Hg methylation activity in laboratory incubations was determined using the short-lived radioisotope 197Hg. In the low pH, Sphagnum fuscum dominated cluster, methylation rates were less than 0.1% day-1. Conversely, the high pH trophic cluster dominated by Carex aquatilis, Carex tenuiflora, and active syntrophy, exhibited Hg methylation rates as high as 10% day-1. In intermediate sites, rich in Sphagnum magellanicum with less Carex, a gradient in syntrophy and Hg methylation paths was observed. Amendments with SO42- showed very active sulfate reduction but no stimulation of methylation; another set of amendments with methanogenic inhibitors greatly reduced methylation rates at intermediate and high trophic clusters. These results suggested that SRB, metabolizing either syntrophically with methanogens and/or by fermentation, likely methylated Hg. While metatranscriptomics studies are being conducted to verify the role of syntrophs, fermenters, and methanogens as methylators, these incubation results revealed that Hg methylation pathways change greatly along trophic gradients with a dominance of respiratory pathways in rich fens, syntrophy dominance in intermediate sites, and fermentation dominance in poor bogs.

Simultaneous analysis of different classes of phytohormones in coconut (Cocos nucifera L.) water using high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry after solid-phase extraction.

PubMed

Ma, Zhen; Ge, Liya; Lee, Anna S Y; Yong, Jean Wan Hong; Tan, Swee Ngin; Ong, Eng Shi

2008-03-10

Coconut (Cocos nucifera L.) water, which contains many uncharacterized phytohormones is extensively used as a growth promoting supplement in plant tissue culture. In this paper, a high-performance liquid chromatography (HPLC) method was developed for the simultaneous determination of various classes phytohormones, including indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), abscisic acid (ABA), gibberellic acid (GA), zeatin (Z), N(6)-benzyladenine (BA), alpha-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) in young coconut water (CW). The analysis was carried out using a reverse-phase HPLC gradient elution, with an aqueous mobile phase (containing 0.1% formic acid, pH adjusted to 3.2 with triethylamine (TEA)) modified by methanol, and solute detection made at 265 nm wavelength. The method was validated for specificity, quantification, accuracy and precision. After preconcentration of putative endogenous phytohormones in CW using C(18) solid-phase extraction (SPE) cartridges, the HPLC method was able to screen for putative endogenous phytohormones present in CW. Finally, the identities of the putative phytohormones present in CW were further confirmed using independent liquid chromatography-tandem mass spectrometry (LC-MS/MS) equipped with an electrospray ionization (ESI) interface.

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park: IV Acid-sulfate waters

USGS Publications Warehouse

Nordstrom, D. Kirk; McCleskey, R. Blaine; Ball, J.W.

2009-01-01

Many waters sampled in Yellowstone National Park, both high-temperature (30-94 ??C) and low-temperature (0-30 ??C), are acid-sulfate type with pH values of 1-5. Sulfuric acid is the dominant component, especially as pH values decrease below 3, and it forms from the oxidation of elemental S whose origin is H2S in hot gases derived from boiling of hydrothermal waters at depth. Four determinations of pH were obtained: (1) field pH at field temperature, (2) laboratory pH at laboratory temperature, (3) pH based on acidity titration, and (4) pH based on charge imbalance (at both laboratory and field temperatures). Laboratory pH, charge imbalance pH (at laboratory temperature), and acidity pH were in close agreement for pH ??10%, a selection process was used to compare acidity, laboratory, and charge balance pH to arrive at the best estimate. Differences between laboratory and field pH can be explained based on Fe oxidation, H2S or S2O3 oxidation, CO2 degassing, and the temperature-dependence of pK2 for H2SO4. Charge imbalances are shown to be dependent on a speciation model for pH values 350 mg/L Cl) decrease as the Cl- concentration increases from boiling which appears inconsistent with the hypothesis of H2S oxidation as a source of hydrothermal SO4. This trend is consistent with the alternate hypothesis of anhydrite solubility equilibrium. Acid-sulfate water analyses are occasionally high in As, Hg, and NH3 concentrations but in contrast to acid mine waters they are low to below detection in Cu, Zn, Cd, and Pb concentrations. Even concentrations of SO4, Fe, and Al are much lower in thermal waters than acid mine waters of the same pH. This difference in water chemistry may explain why certain species of fly larvae live comfortably in Yellowstone's acid waters but have not been observed in acid rock drainage of the same pH.

Fermentation and microbial population dynamics during the ensiling of native grass and subsequent exposure to air.

PubMed

Zhang, Qing; Wu, Baiyila; Nishino, Naoki; Wang, Xianguo; Yu, Zhu

2016-03-01

To study the microbial population and fermentation dynamics of large needlegrass (LN) and Chinese leymus (CL) during ensiling and subsequent exposure to air, silages were sampled and analyzed using culture-based techniques and denaturing gradient gel electrophoresis (DGGE). A total of 112 lactic acid bacteria (LAB) strains were isolated and identified using the 16S rRNA sequencing method. Lactic acid was not detected in the first 20 days in LN silage and the pH decreased to 6.13 after 45 days of ensiling. The temperature of the LN silage increased after approximately 30 h of air exposure and the CL silage showed a slight temperature variation. Enterococcus spp. were mainly present in LN silage. The proportion of Lactobacillus brevis in CL silage increased after exposure to air. LN silage with a higher proportion of Enterococcus spp. and propionic acid concentration did not show higher fermentation quality or aerobic stability than CL silage, which had a higher concentration of acetic acid, butyric acid and increased proportion of L. brevis after exposure to air. © 2015 Japanese Society of Animal Science.

Strain improvement of Sporolactobacillus inulinus ATCC 15538 for acid tolerance and production of D-lactic acid by genome shuffling.

PubMed

Zheng, Huijie; Gong, Jixian; Chen, Tao; Chen, Xun; Zhao, Xueming

2010-02-01

Improvement of acid tolerance and production of D-lactic acid by Sporolactobacillus inulinus ATCC 15538 was performed by using recursive protoplast fusion in a genome shuffling format. The starting population was generated by ultraviolet irradiation, diethyl sulfate mutagenesis, and pH-gradient filter and then, subjected for the recursive protoplast fusion. The concentration of lysozyme, time, and temperature for enzyme treatment were optimized by response surface methodology based on the central composite design. Based on contour plots and variance analysis, the model predicted a maximum Y (multiply protoplasts formation ratio by protoplasts regeneration ratio), 60.4%, and the corresponding above used values were 7.75 mg/ml lysozyme, 1.59 h, and 38 degrees C. A pH-5-resistant recombinant, F3-4, was obtained after three rounds of genome shuffling and its production of D-lactic acid reached 93.4 g/l in a 5 L bioreactor, which was increased by 39.8% and 119% in comparison with that of UV generated strain and the original strain S. inulinus ATCC 15538, respectively. The subculture experiments indicated that F3-4 was genetically stable.

Rhizosphere size

NASA Astrophysics Data System (ADS)

Kuzyakov, Yakov; Razavi, Bahar

2017-04-01

Estimation of the soil volume affected by roots - the rhizosphere - is crucial to assess the effects of plants on properties and processes in soils and dynamics of nutrients, water, microorganisms and soil organic matter. The challenges to assess the rhizosphere size are: 1) the continuum of properties between the root surface and root-free soil, 2) differences in the distributions of various properties (carbon, microorganisms and their activities, various nutrients, enzymes, etc.) along and across the roots, 3) temporal changes of properties and processes. Thus, to describe the rhizosphere size and root effects, a holistic approach is necessary. We collected literature and own data on the rhizosphere gradients of a broad range of physico-chemical and biological properties: pH, CO2, oxygen, redox potential, water uptake, various nutrients (C, N, P, K, Ca, Mg, Mn and Fe), organic compounds (glucose, carboxylic acids, amino acids), activities of enzymes of C, N, P and S cycles. The collected data were obtained based on the destructive approaches (thin layer slicing), rhizotron studies and in situ visualization techniques: optodes, zymography, sensitive gels, 14C and neutron imaging. The root effects were pronounced from less than 0.5 mm (nutrients with slow diffusion) up to more than 50 mm (for gases). However, the most common effects were between 1 - 10 mm. Sharp gradients (e.g. for P, carboxylic acids, enzyme activities) allowed to calculate clear rhizosphere boundaries and so, the soil volume affected by roots. The first analyses were done to assess the effects of soil texture and moisture as well as root system and age on these gradients. The most properties can be described by two curve types: exponential saturation and S curve, each with increasing and decreasing concentration profiles from the root surface. The gradient based distribution functions were calculated and used to extrapolate on the whole soil depending on the root density and rooting intensity. We conclude that despite the specific effects of plants and soil on the rhizosphere size, the most common distribution functions can be calculated for individual roots and extrapolated for the whole soil profile.

Studies on the oligosaccharide heterogeneity of the isoelectric forms of the lower molecular weight acid phosphatase of frog liver.

PubMed

Kubicz, A; Szalewicz, A; Chrambach, A

1991-01-01

1. The lower molecular weight, heterogeneous acid phosphatase (AcPase) from the frog liver (Rana esculenta) containing AcPase I, II, III and IV was separated into enzymatically active components by isoelectric focusing in an immobilized pH gradient. 2. The blotted enzyme bands were characterized by their different binding patterns obtained with the lectins concanavalin A, wheat germ agglutinin (WGA), Lens culinaris hemagglutinin (LcH) and peanut agglutinin (PNA). 3. In situ neuraminidase treatment reduced the staining intensity of some WGA-bands and increased that of PNA-bands. 4. The finding that AcPases I, II, III and IV differ in their carbohydrate chain composition, together with previous results showing different bioactivities of AcPases III and IV, indicates a correlation between the glycosylation state of enzyme forms and their physiological action.

Searching for Clues to the Processes and Conditions of Past Martian Environments: The Roles of Episodic Solutions, Analog Sites and Fe-O(-H) Phases

NASA Astrophysics Data System (ADS)

King, P. L.; De Deckker, P.

2012-12-01

On Mars, limited solutions (water/brine) were likely present episodically. Gradients in solution abundance may have caused salt precipitation and re-solution, brine reflux, pH gradients, and cycling of anions and cations; we provide an example of such processes in a playa lake. We propose that on Mars, the limited, episodic solutions, pH and abundant Fe-O(-H) phases are significant factors in salt precipitation and in promoting adsorption/desorption of anions and cations. FACTORS LEADING TO EPISODIC SOLUTIONS: Episodic movement of solutions may be driven by punctuated processes that 1) remove surface materials (e.g., impact and sedimentary mass wasting and deflation); 2) add surface materials (e.g., impact, volcanic and sedimentary processes); and 3) increase temperature and/or decrease atmospheric pressure (e.g., seasons, diurnal cycles, variation in obliquity). Removal and addition of surface materials results in topographic gradients that change pressure gradients of any potential groundwater, films, or buried ground ice. For example, episodic fluid flow and salt precipitation/re-solution may occur at topographic discontinuities like craters/basins, channel walls, mounds and dunes. Such areas provide the opportunity to sample multiple fluid sources (with different pH, Eh and total dissolved solids, TDS) and they may be the foci of subsurface solution flow and surface transport. EARTH ANALOG: Interplay of the three processes above is seen in Lake Tyrrell (playa), western Victoria, Australia (McCumber, P, 1991 http://vro.dpi.vic.gov.au). During wetter periods, springs from the regional groundwater (low pH, oxidized, mod-high TDS) mix with lake waters and saline 'reflux' brines (mod. pH, reduced, high TDS) at the lake edge at the base of higher ground. The Br/Cl of the reflux brines indicates mineral re-solution. Gypsum and Fe-O(-H) phases precipitate near the lake edge. During hot, dry climate episodes the lake precipitates gypsum and carbonate, efflorescent salts are common, and these salts may form eolian dunes with fine particles. We may expect similar processes and mineral and chemical gradients in craters/basins on Mars like Gale Crater, the site of the Mars Science Laboratory mission. ROLE OF Fe-O(-H) PHASES: Nanophase Fe-O(-H)-phases are abundant on Mars and their precipitation results in an Fe-poor solution and salts (like Lake Tyrrell). Fe-O(-H) phases precipitate most readily at near-neutral pH; however, the high Fe of Mars' surface allows for pH>1. Nanophase Fe-O(-H)-phases have surface species that promote adsorption; which may be important in dry conditions like Mars. If we take goethite (FeO(OH)), the surface species and aqueous ions in solution are Fe3+ (pH<~2); Fe(OH)2+ (pH~2-3.5); Fe(OH)2+ (pH~3.5-~8); and FeOH4- (pH>~8). Other Fe-O(-H) phases have slightly different pH limits. Thus, at pH<~8, Fe-O(-H) surfaces sequester anions in surface complexes or in Fe-bearing salts (e.g. Fe3+-phosphate and sulfates, especially at pH<4). PO43- species have high adsorption affinity, followed by SO42-, Cl-(O) and Br-(O) species. At pH>~8, adsorption and exchange of cations are likely. These chemical variations may provide us with clues of the past pH on Mars.

Microextraction of mebendazole across supported liquid membrane forced by pH gradient and electrical field.

PubMed

Eskandari, Mahboube; Yamini, Yadollah; Fotouhi, Lida; Seidi, Shahram

2011-04-05

In the present study, extraction of mebendazole across a supported-liquid membrane (SLM) was performed based on two different driving forces: (1) pH gradient over the SLM, and (2) electrical field sustained over the SLM. The extracted drug concentration was studied using reversed-phase HPLC-UV. At passive extraction conditions, mebendazole was extracted from alkaline samples (0.01 mmol L(-1) NaOH) into 1-undecanol immobilized in the pores of a porous hollow fiber of polypropylene (SLM), and then transported into 25 μL of 100mM HCl as the acceptor solution. Under electrokinetic migration conditions, mebendazole transported under applied voltage from acidic solutions (100 mmol L(-1) HCl) through 2-nitrophenyl octyl ether (NPOE) immobilized in the pores of hollow fiber, into 25 μL of 100 mmol L(-1) HCl as the acceptor solution. The effects of several factors including the nature of organic solvent, pH of donor and acceptor solutions, extraction time and stirring speed on the extraction efficiency of the drug were investigated and optimized. Under optimal conditions, preconcentration factors (PF) of 211 and 190 were obtained for the drug based on passive transport and electromembrane extraction (EME), respectively. Also, linear range of 0.5-1000 μg L(-1) with estimation of coefficient higher than 0.994 was obtained for both of the proposed methods. The results showed that EME has higher speed in comparison with simple passive transport. The methods were successfully applied to extract mebendazole from plasma and urine samples and satisfactory results were obtained. Copyright © 2010 Elsevier B.V. All rights reserved.

Influence of polysorbate 80 and cyclopropane fatty acid synthase activity on lactic acid production by Lactobacillus casei ATCC 334 at low pH.

PubMed

Broadbent, J R; Oberg, T S; Hughes, J E; Ward, R E; Brighton, C; Welker, D L; Steele, J L

2014-03-01

Lactic acid is an important industrial chemical commonly produced through microbial fermentation. The efficiency of acid extraction is increased at or below the acid's pKa (pH 3.86), so there is interest in factors that allow for a reduced fermentation pH. We explored the role of cyclopropane synthase (Cfa) and polysorbate (Tween) 80 on acid production and membrane lipid composition in Lactobacillus casei ATCC 334 at low pH. Cells from wild-type and an ATCC 334 cfa knockout mutant were incubated in APT broth medium containing 3 % glucose plus 0.02 or 0.2 % Tween 80. The cultures were allowed to acidify the medium until it reached a target pH (4.5, 4.0, or 3.8), and then the pH was maintained by automatic addition of NH₄OH. Cells were collected at the midpoint of the fermentation for membrane lipid analysis, and media samples were analyzed for lactic and acetic acids when acid production had ceased. There were no significant differences in the quantity of lactic acid produced at different pH values by wild-type or mutant cells grown in APT, but the rate of acid production was reduced as pH declined. APT supplementation with 0.2 % Tween 80 significantly increased the amount of lactic acid produced by wild-type cells at pH 3.8, and the rate of acid production was modestly improved. This effect was not observed with the cfa mutant, which indicated Cfa activity and Tween 80 supplementation were each involved in the significant increase in lactic acid yield observed with wild-type L. casei at pH 3.8.

[Effects of simulated acid rain on decomposition of soil organic carbon and crop straw].

PubMed

Zhu, Xue-Zhu; Huang, Yao; Yang, Xin-Zhong

2009-02-01

To evaluate the effects of acid rain on the organic carbon decomposition in different acidity soils, a 40-day incubation test was conducted with the paddy soils of pH 5.48, 6.70 and 8.18. The soils were amended with 0 and 15 g x kg(-1) of rice straw, adjusted to the moisture content of 400 g x kg(-1) air-dried soil by using simulated rain of pH 6.0, 4.5, and 3.0, and incubated at 20 degrees C. The results showed that straw, acid rain, and soil co-affected the CO2 emission from soil system. The amendment of straw increased the soil CO2 emission rate significantly. Acid rain had no significant effects on soil organic carbon decomposition, but significantly affected the straw decomposition in soil. When treated with pH 3.0 acid rain, the amount of decomposed straw over 40-day incubation in acid (pH 5.48) and alkaline (pH 8.18) soils was 8% higher, while that in neutral soil (pH 6.70) was 15% lower, compared to the treatment of pH 6.0 rain. In the treatment of pH 3.0 acid rain, the decomposition rate of soil organic C in acid (pH 5.48) soil was 43% and 50% (P < 0.05) higher than that in neutral (pH 6.70) and alkaline (pH 8.18) soils, while the decomposition rate of straw in neutral soil was 17% and 16% (P < 0.05) lower than that in acid and alkaline soils, respectively.

Importance of inoculum properties on the structure and growth of bacterial communities during Recolonisation of humus soil with different pH.

PubMed

Pettersson, Marie; Bååth, Erland

2013-08-01

The relationship between community structure and growth and pH tolerance of a soil bacterial community was studied after liming in a reciprocal inoculum study. An unlimed (UL) humus soil with a pH of 4.0 was fumigated with chloroform for 4 h, after which < 1 % of the initial bacterial activity remained. Half of the fumigated soil was experimentally limed (EL) to a pH of 7.6. Both the UL and the EL soil were then reciprocally inoculated with UL soil or field limed (FL) soil with a pH of 6.2. The FL soil was from a 15-year-old experiment. The structural changes were measured on both bacteria in soil and on bacteria able to grow on agar plates using phospholipids fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analysis. The developing community pH tolerance and bacterial growth were also monitored over time using thymidine incorporation. The inoculum source had a significant impact on both growth and pH tolerance of the bacterial community in the EL soil. These differences between the EL soil inoculated with UL soil and FL soil were correlated to structural changes, as evidenced by both PLFA and DGGE analyses on the soil. Similar correlations were seen to the fraction of the community growing on agar plates. There were, however, no differences between the soil bacterial communities in the unlimed soils with different inocula. This study showed the connection between the development of function (growth), community properties (pH tolerance) and the structure of the bacterial community. It also highlighted the importance of both the initial properties of the community and the selection pressure after environmental changes in shaping the resulting microbial community.

Diblock Terpolymers Are Tunable and pH Responsive Vehicles To Increase Hydrophobic Drug Solubility for Oral Administration.

PubMed

Tale, Swapnil; Purchel, Anatolii A; Dalsin, Molly C; Reineke, Theresa M

2017-11-06

Synthetic polymers offer tunable platforms to create new oral drug delivery vehicles (excipients) to increase solubility, supersaturation maintenance, and bioavailability of poorly aqueous soluble pharmaceutical candidates. Five well-defined diblock terpolymers were synthesized via reversible addition-fragmentation chain transfer polymerization (RAFT) and consist of a first block of either poly(ethylene-alt-propylene) (PEP), poly(N-isopropylacrylamide) (PNIPAm), or poly(N,N-diethylaminoethyl methacrylate) (PDEAEMA) and a second hydrophilic block consisting of a gradient copolymer of N,N-dimethylacrylamide (DMA) and 2-methacrylamidotrehalose (MAT). This family of diblock terpolymers offers hydrophobic, hydrophilic, or H-bonding functionalities to serve as noncovalent sites of drug binding. Drug-polymer spray dried dispersions (SDDs) were created with a model drug, probucol, and characterized by differential scanning calorimetry (DSC). These studies revealed that probucol crystallinity decreased with increasing H-bonding sites available in the polymer. The PNIPAm-b-P(DMA-grad-MAT) systems revealed the best performance at pH 6.5, where immediate probucol release and effective maintenance of 100% supersaturation was found, which is important for facilitating drug solubility in more neutral conditions (intestinal environment). However, the PDEAEMA-b-P(DMA-grad-MAT) system revealed poor probucol dissolution at pH 6.5 and 5.1. Alternatively, at an acidic pH of 3.1, a rapid and high dissolution profile and effective supersaturation maintenance of up to 90% of the drug was found, which could be useful for triggering drug release in acidic environments (stomach). The PEP-b-P(DMA-grad-MAT) system showed poor performance (only ∼20% of drug solubility at pH 6.5), which was attributed to the low solubility of the polymers in the dissolution media. This work demonstrates the utility of diblock terpolymers as a potential new excipient platform to optimize design parameters for triggered release and solubilizing hydrophobic drug candidates for oral delivery.

Effects of remediation on the bacterial community of an acid mine drainage impacted stream.

PubMed

Ghosh, Suchismita; Moitra, Moumita; Woolverton, Christopher J; Leff, Laura G

2012-11-01

Acid mine drainage (AMD) represents a global threat to water resources, and as such, remediation of AMD-impacted streams is a common practice. During this study, we examined bacterial community structure and environmental conditions in a low-order AMD-impacted stream before, during, and after remediation. Bacterial community structure was examined via polymerase chain reaction amplification of 16S rRNA genes followed by denaturing gradient gel electrophoresis. Also, bacterial abundance and physicochemical data (including metal concentrations) were collected and relationships to bacterial community structure were determined using BIO-ENV analysis. Remediation of the study stream altered environmental conditions, including pH and concentrations of some metals, and consequently, the bacterial community changed. However, remediation did not necessarily restore the stream to conditions found in the unimpacted reference stream; for example, bacterial abundances and concentrations of some elements, such as sulfur, magnesium, and manganese, were different in the remediated stream than in the reference stream. BIO-ENV analysis revealed that changes in pH and iron concentration, associated with remediation, primarily explained temporal alterations in bacterial community structure. Although the sites sampled in the remediated stream were in relatively close proximity to each other, spatial variation in community composition suggests that differences in local environmental conditions may have large impacts on the microbial assemblage.

Preparation of metal-resistant immobilized sulfate reducing bacteria beads for acid mine drainage treatment.

PubMed

Zhang, Mingliang; Wang, Haixia; Han, Xuemei

2016-07-01

Novel immobilized sulfate-reducing bacteria (SRB) beads were prepared for the treatment of synthetic acid mine drainage (AMD) containing high concentrations of Fe, Cu, Cd and Zn using up-flow anaerobic packed-bed bioreactor. The tolerance of immobilized SRB beads to heavy metals was significantly enhanced compared with that of suspended SRB. High removal efficiencies of sulfate (61-88%) and heavy metals (>99.9%) as well as slightly alkaline effluent pH (7.3-7.8) were achieved when the bioreactor was fed with acidic influent (pH 2.7) containing high concentrations of multiple metals (Fe 469 mg/L, Cu 88 mg/L, Cd 92 mg/L and Zn 128 mg/L), which showed that the bioreactor filled with immobilized SRB beads had tolerance to AMD containing high concentrations of heavy metals. Partially decomposed maize straw was a carbon source and stabilizing agent in the initial phase of bioreactor operation but later had to be supplemented by a soluble carbon source such as sodium lactate. The microbial community in the bioreactor was characterized by denaturing gradient gel electrophoresis (DGGE) and sequencing of partial 16S rDNA genes. Synergistic interaction between SRB (Desulfovibrio desulfuricans) and co-existing fermentative bacteria could be the key factor for the utilization of complex organic substrate (maize straw) as carbon and nutrients source for sulfate reduction. Copyright © 2016 Elsevier Ltd. All rights reserved.

Is Your Drinking Water Acidic? A Comparison of the Varied pH of Popular Bottled Waters.

PubMed

Wright, Kellie F

2015-06-01

Dental professionals continually educate patients on the dangers of consuming acidic foods and beverages due to their potential to contribute to dental erosion and tooth decay. Excess acid in the diet can also lead to acidosis, which causes negative systemic side effects. However, water is not typically categorized as acidic. The purpose of this in-vitro study was to investigate the pH levels of several popular brands of bottled water and compare them to various other acidic beverages. Two different brands of marketed alkaline water (with a pH of 8.8 or higher) were also studied, tested for acidity and described. A pilot in-vitro study was conducted to determine the pH levels of a convenience sample of popular brands of bottled water, tap water and other known acidic beverages in comparison with the pH values reported on the respective manufacturers' website. Each beverage was tested in a laboratory using a calibrated Corning pH meter model 240, and waters were compared to the corresponding company's testified pH value. Waters were also compared and contrasted based on their process of purification. The data was then compiled and analyzed descriptively. The pH values for the tested beverages and bottled waters were found to be predominantly acidic. Ten out of the 14 beverages tested were acidic (pH<7), 2 municipal (or "tap") waters were neutral (pH=7) and 2 bottled waters were alkaline (pH>7). The majority of waters tested had a more acidic pH when tested in the lab than the value listed in their water quality reports. It is beneficial for the health care provider to be aware of the potential acidity of popular bottled drinking waters and educate patients accordingly. Copyright © 2015 The American Dental Hygienists’ Association.

Aspect has a greater impact on alpine soil bacterial community structure than elevation.

PubMed

Wu, Jieyun; Anderson, Barbara J; Buckley, Hannah L; Lewis, Gillian; Lear, Gavin

2017-03-01

Gradients in environmental conditions, including climate factors and resource availability, occur along mountain inclines, providing a 'natural laboratory' to explore their combined impacts on microbial distributions. Conflicting spatial patterns observed across elevation gradients in soil bacterial community structure suggest that they are driven by various interacting factors at different spatial scales. Here, we investigated the relative impacts of non-resource (e.g. soil temperature, pH) and resource conditions (e.g. soil carbon and nitrogen) on the biogeography of soil bacterial communities across broad (i.e. along a 1500 m mountain elevation gradient) and fine sampling scales (i.e. along sunny and shady aspects of a mountain ridge). Our analysis of 16S rRNA gene data confirmed that when sampling across distances of < 1000 m, bacterial community composition was more closely related to the aspect of a site than its elevation. However, despite large differences in climate and resource-availability factors across elevation- and aspect-related gradients, bacterial community composition and richness were most strongly correlated with soil pH. These findings highlight the need to incorporate knowledge of multiple factors, including site aspect and soil pH for the appropriate use of elevation gradients as a proxy to explore the impacts of climate change on microbial community composition. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

K(+)- and HCO3(-)-dependent acid-base transport in squid giant axons. I. Base efflux

PubMed Central

1995-01-01

We used microelectrodes to monitor the recovery (i.e., decrease) of intracellular pH (pHi) after using internal dialysis to load squid giant axons with alkali to pHi values of 7.7, 8.0, or 8.3. The dialysis fluid (DF) contained 400 mM K+ but was free of Na+ and Cl-. The artificial seawater (ASW) lacked Na+, K+, and Cl-, thereby eliminating effects of known acid-base transporters on pHi. Under these conditions, halting dialysis unmasked a slow pHi decrease caused at least in part by acid-base transport we refer to as "base efflux." Replacing K+ in the DF with either NMDG+ or TEA+ significantly reduced base efflux and made membrane voltage (Vm) more positive. Base efflux in K(+)-dialyzed axons was stimulated by decreasing the pH of the ASW (pHo) from 8 to 7, implicating transport of acid or base. Although postdialysis acidifications also occurred in axons in which we replaced the K+ in the DF with Li+, Na+, Rb+, or Cs+, only with Rb+ was base efflux stimulated by low pHo. Thus, the base effluxes supported by K+ and Rb+ appear to be unrelated mechanistically to those observed with Li+, Na+, or Cs+. The combination of 437 mM K+ and 12 mM HCO3- in the ASW, which eliminates the gradient favoring a hypothetical K+/HCO3- efflux, blocked pHi recovery in K(+)-dialyzed axons. However, the pHi recovery was not blocked by the combination of 437 mM Na+, veratridine, and CO2/HCO3- in the ASW, a treatment that inverts electrochemical gradients for H+ and HCO3- and would favor passive H+ and HCO3- fluxes that would have alkalinized the axon. Similarly, the recovery was not blocked by K+ alone or HCO3- alone in the ASW, nor was it inhibited by the K-H pump blocker Sch28080 nor by the Na-H exchange inhibitors amiloride and hexamethyleneamiloride. Our data suggest that a major component of base efflux in alkali-loaded axons cannot be explained by metabolism, a H+ or HCO3- conductance, or by a K-H exchanger. However, this component could be mediated by a novel K/HCO3- cotransporter. PMID:8648294

Complexity in estimation of esomeprazole and its related impurities' stability in various stress conditions in low-dose aspirin and esomeprazole magnesium capsules.

PubMed

Reddy, Palavai Sripal; Hotha, Kishore Kumar; Sait, Shakil

2013-01-01

A complex, sensitive, and precise high-performance liquid chromatographic method for the profiling of impurities of esomeprazole in low-dose aspirin and esomeprazole capsules has been developed, validated, and used for the determination of impurities in pharmaceutical products. Esomeprazole and its related impurities' development in the presence of aspirin was traditionally difficult due to aspirin's sensitivity to basic conditions and esomeprazole's sensitivity to acidic conditions. When aspirin is under basic, humid, and extreme temperature conditions, it produces salicylic acid and acetic acid moieties. These two byproducts create an acidic environment for the esomeprazole. Due to the volatility and migration phenomenon of the produced acetic acid and salicylic acid from aspirin in the capsule dosage form, esomeprazole's purity, stability, and quantification are affected. The objective of the present research work was to develop a gradient reversed-phase liquid chromatographic method to separate all the degradation products and process-related impurities from the main peak. The impurities were well-separated on a RP8 column (150 mm × 4.6mm, X-terra, RP8, 3.5μm) by the gradient program using a glycine buffer (0.08 M, pH adjusted to 9.0 with 50% NaOH), acetonitrile, and methanol at a flow rate of 1.0 mL min(-1) with detection wavelength at 305 nm and column temperature at 30°C. The developed method was found to be specific, precise, linear, accurate, rugged, and robust. LOQ values for all of the known impurities were below reporting thresholds. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis, and thermal degradation in the presence of aspirin. The developed RP-HPLC method was validated according to the present ICH guidelines for specificity, linearity, accuracy, precision, limit of detection, limit of quantification, ruggedness, and robustness.

Acid-adapted strains of Escherichia coli K-12 obtained by experimental evolution.

PubMed

Harden, Mark M; He, Amanda; Creamer, Kaitlin; Clark, Michelle W; Hamdallah, Issam; Martinez, Keith A; Kresslein, Robert L; Bush, Sean P; Slonczewski, Joan L

2015-03-01

Enteric bacteria encounter a wide range of pHs throughout the human intestinal tract. We conducted experimental evolution of Escherichia coli K-12 to isolate clones with increased fitness during growth under acidic conditions (pH 4.5 to 4.8). Twenty-four independent populations of E. coli K-12 W3110 were evolved in LBK medium (10 g/liter tryptone, 5 g/liter yeast extract, 7.45 g/liter KCl) buffered with homopiperazine-N,N'-bis-2-(ethanosulfonic acid) and malate at pH 4.8. At generation 730, the pH was decreased to 4.6 with HCl. By 2,000 generations, all populations had achieved higher endpoint growth than the ancestor at pH 4.6 but not at pH 7.0. All evolving populations showed a progressive loss of activity of lysine decarboxylase (CadA), a major acid stress enzyme. This finding suggests a surprising association between acid adaptation and moderation of an acid stress response. At generation 2,000, eight clones were isolated from four populations, and their genomes were sequenced. Each clone showed between three and eight missense mutations, including one in a subunit of the RNA polymerase holoenzyme (rpoB, rpoC, or rpoD). Missense mutations were found in adiY, the activator of the acid-inducible arginine decarboxylase (adiA), and in gcvP (glycine decarboxylase), a possible acid stress component. For tests of fitness relative to that of the ancestor, lacZ::kan was transduced into each strain. All acid-evolved clones showed a high fitness advantage at pH 4.6. With the cytoplasmic pH depressed by benzoate (at external pH 6.5), acid-evolved clones showed decreased fitness; thus, there was no adaptation to cytoplasmic pH depression. At pH 9.0, acid-evolved clones showed no fitness advantage. Thus, our acid-evolved clones showed a fitness increase specific to low external pH. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Acid-Adapted Strains of Escherichia coli K-12 Obtained by Experimental Evolution

PubMed Central

Harden, Mark M.; He, Amanda; Creamer, Kaitlin; Clark, Michelle W.; Hamdallah, Issam; Martinez, Keith A.; Kresslein, Robert L.; Bush, Sean P.

2015-01-01

Enteric bacteria encounter a wide range of pHs throughout the human intestinal tract. We conducted experimental evolution of Escherichia coli K-12 to isolate clones with increased fitness during growth under acidic conditions (pH 4.5 to 4.8). Twenty-four independent populations of E. coli K-12 W3110 were evolved in LBK medium (10 g/liter tryptone, 5 g/liter yeast extract, 7.45 g/liter KCl) buffered with homopiperazine-N,N′-bis-2-(ethanosulfonic acid) and malate at pH 4.8. At generation 730, the pH was decreased to 4.6 with HCl. By 2,000 generations, all populations had achieved higher endpoint growth than the ancestor at pH 4.6 but not at pH 7.0. All evolving populations showed a progressive loss of activity of lysine decarboxylase (CadA), a major acid stress enzyme. This finding suggests a surprising association between acid adaptation and moderation of an acid stress response. At generation 2,000, eight clones were isolated from four populations, and their genomes were sequenced. Each clone showed between three and eight missense mutations, including one in a subunit of the RNA polymerase holoenzyme (rpoB, rpoC, or rpoD). Missense mutations were found in adiY, the activator of the acid-inducible arginine decarboxylase (adiA), and in gcvP (glycine decarboxylase), a possible acid stress component. For tests of fitness relative to that of the ancestor, lacZ::kan was transduced into each strain. All acid-evolved clones showed a high fitness advantage at pH 4.6. With the cytoplasmic pH depressed by benzoate (at external pH 6.5), acid-evolved clones showed decreased fitness; thus, there was no adaptation to cytoplasmic pH depression. At pH 9.0, acid-evolved clones showed no fitness advantage. Thus, our acid-evolved clones showed a fitness increase specific to low external pH. PMID:25556191

Interactions of calcium and fulvic acid at the goethite-water interface

NASA Astrophysics Data System (ADS)

Weng, Li Ping; Koopal, Luuk K.; Hiemstra, Tjisse; Meeussen, Johannes C. L.; Van Riemsdijk, Willem H.

2005-01-01

Interactions of calcium and fulvic acid (Strichen ) with the surface of goethite were studied with batch and titration experiments. The mutual influence of the interactions on the adsorption of fulvic acid, calcium ions and protons were examined. Adsorption of the fulvic acid to goethite decreased with increase in pH (pH range 3-11). Addition of Ca (1.0 mM) at intermediate and high pH significantly enhanced the adsorption of fulvic acid. Compared to the adsorption to pure goethite, the presence of fulvic acid enhanced the adsorption of Ca significantly. In comparison to the simple linear sum of Ca bound to fulvic acid and goethite, the interactions between goethite and fulvic acid led to a reduced adsorption of Ca at low pH and an enhanced adsorption at high pH. With the adsorption of fulvic acid, protons were released at low pH and coadsorbed at high pH. When Ca was added, fewer protons were released at low pH and fewer coadsorbed at high pH. The experimental results can be adequately described using a surface complexation model, the Ligand and Charge Distribution (LCD) model, in which the CD-MUSIC model for ion adsorption to mineral oxides and the NICA model for ion binding to humics are integrated. In the model calculations, adequate descriptions of the ternary system data (Ca-fulvic acid-goethite) were obtained with parameters derived from three binary systems (fulvic acid-goethite, Ca-goethite and Ca-fulvic acid) without further adjustment. The model calculations suggest that the interactions between Ca and fulvic acid at the surface of goethite are mainly due to the electrostatic effects.

Modeling and simulation of protein elution in linear pH and salt gradients on weak, strong and mixed cation exchange resins applying an extended Donnan ion exchange model.

PubMed

Wittkopp, Felix; Peeck, Lars; Hafner, Mathias; Frech, Christian

2018-04-13

Process development and characterization based on mathematic modeling provides several advantages and has been applied more frequently over the last few years. In this work, a Donnan equilibrium ion exchange (DIX) model is applied for modelling and simulation of ion exchange chromatography of a monoclonal antibody in linear chromatography. Four different cation exchange resin prototypes consisting of weak, strong and mixed ligands are characterized using pH and salt gradient elution experiments applying the extended DIX model. The modelling results are compared with the results using a classic stoichiometric displacement model. The Donnan equilibrium model is able to describe all four prototype resins while the stoichiometric displacement model fails for the weak and mixed weak/strong ligands. Finally, in silico chromatogram simulations of pH and pH/salt dual gradients are performed to verify the results and to show the consistency of the developed model. Copyright © 2018 Elsevier B.V. All rights reserved.

A novel acidic pH fluorescent probe based on a benzothiazole derivative

NASA Astrophysics Data System (ADS)

Ma, Qiujuan; Li, Xian; Feng, Suxiang; Liang, Beibei; Zhou, Tiqiang; Xu, Min; Ma, Zhuoyi

2017-04-01

A novel acidic pH fluorescent probe 1 based on a benzothiazole derivative has been designed, synthesized and developed. The linear response range covers the acidic pH range from 3.44 to 6.46, which is valuable for pH researches in acidic environment. The evaluated pKa value of the probe 1 is 4.23. The fluorescence enhancement of the studied probe 1 with an increase in hydrogen ions concentration is based on the hindering of enhanced photo-induced electron transfer (PET) process. Moreover, the pH sensor possesses a highly selective response to H+ in the presence of metal ions, anions and other bioactive small molecules which would be interfere with its fluorescent pH response. Furthermore, the probe 1 responds to acidic pH with short response time that was less than 1 min. The probe 1 has been successfully applied to confocal fluorescence imaging in live HeLa cells and can selectively stain lysosomes. All of such good properties prove it can be used to monitoring pH fluctuations in acidic environment with high sensitivity, pH dependence and short response time.

Evaluation of the efficacy of four weak acids as antifungal preservatives in low-acid intermediate moisture model food systems.

PubMed

Huang, Yang; Wilson, Mark; Chapman, Belinda; Hocking, Ailsa D

2010-02-01

The potential efficacy of four weak acids as preservatives in low-acid intermediate moisture foods was assessed using a glycerol based agar medium. The minimum inhibitory concentrations (MIC, % wt./wt.) of each acid was determined at two pH values (pH 5.0, pH 6.0) and two a(w) values (0.85, 0.90) for five food spoilage fungi, Eurotium herbariorum, Eurotium rubrum, Aspergillus niger, Aspergillus flavus and Penicillium roqueforti. Sorbic acid, a preservative commonly used to control fungal growth in low-acid intermediate moisture foods, was included as a reference. The MIC values of the four acids were lower at pH 5.0 than pH 6.0 at equivalent a(w) values, and lower at 0.85 a(w) than 0.90 a(w) at equivalent pH values. By comparison with the MIC values of sorbic acid, those of caprylic acid and dehydroacetic acid were generally lower, whereas those for caproic acid were generally higher. No general observation could be made in the case of capric acid. The antifungal activities of all five weak acids appeared related not only to the undissociated form, but also the dissociated form, of each acid.

Modelling of Pesticide Transport During An Injection Experiment In A Physical and Geochemical Heterogeneous Aquifer

NASA Astrophysics Data System (ADS)

Hojberg, A. L.; Engesgaard, P.; Bjerg, P. L.

The fate of selected pesticides under natural groundwater conditions was studied by natural gradient short and long term injection experiments in a shallow uncon- fined aerobic aquifer. Bentazone, DNOC, MCPP, dichlorprop, isoproturon, and BAM (dichlobenil metabolite) were injected in aqueous solution with bromide as a nonre- active tracer. The Bromide and pesticide plumes were sampled during the initial 25 m of migration in a dense monitoring net of multilevel samplers. The aquifer was physical and geochemical heterogeneous, which affected transport of several of the pesticides. A 3D reactive transport code was developed including one- and two-site linear/nonlinear equilibrium/nonequilibrium sorption and first-order as well as single Monod degradation kinetic coupled to microbial growth. Model simulations demon- strated that microbial growth was likely supported by the phenoxy acids MCPP and dichlorprop, while degradation of DNOC was adequately described by first-order degradation with no initial lag time. An observed vertical increase in pH was observed at the site and implemented in the transport code. The numerical analysis indicated that degradation of the three degradable pesticides may have been affected by vertical pH variations. Spatial variability in observed DNOC sorption was similarly suspected to be an effect of varying pH. pH dependency on DNOC sorption was confirmed by the model recognized by a match to observed breakthrough at the individual sampling points, when pH variation was included in the simulations.

Multimodal chemo-magnetic control of self-propelling microbots

NASA Astrophysics Data System (ADS)

Singh, Amit Kumar; Dey, Krishna Kanti; Chattopadhyay, Arun; Mandal, Tapas Kumar; Bandyopadhyay, Dipankar

2014-01-01

We report a controlled migration of an iron nanoparticle (FeNP) coated polymer micromotor. The otherwise diffusive motion of the motor was meticulously directed through an in situ pH-gradient and an external magnetic field. The self-propulsion owing to the asymmetric catalytic decomposition of peroxide fuel was directed through a pH gradient imposed across the motor-surface, while the magnetic field induced an external control on the movement and the speed of the motor. Interestingly, the sole influence of the pH gradient could move the motor as high as ~25 body lengths per second, which was further magnified by the external assistance from the magnetic field. Applying a magnetic field against the pH directed motion helped in the quantitative experimental estimation of the force-field required to arrest the chemotactic migration. The influence of the coupled internal and external fields could halt, steer or reverse the direction the motor inside a microchannel, rotate the motor around a target, and deliver the motor to a cluster of cells. This study showcases a multimodal chemical-magnetic field regulated migration of micro-machines for sensing, transport, and delivery inside a fluidic environment.We report a controlled migration of an iron nanoparticle (FeNP) coated polymer micromotor. The otherwise diffusive motion of the motor was meticulously directed through an in situ pH-gradient and an external magnetic field. The self-propulsion owing to the asymmetric catalytic decomposition of peroxide fuel was directed through a pH gradient imposed across the motor-surface, while the magnetic field induced an external control on the movement and the speed of the motor. Interestingly, the sole influence of the pH gradient could move the motor as high as ~25 body lengths per second, which was further magnified by the external assistance from the magnetic field. Applying a magnetic field against the pH directed motion helped in the quantitative experimental estimation of the force-field required to arrest the chemotactic migration. The influence of the coupled internal and external fields could halt, steer or reverse the direction the motor inside a microchannel, rotate the motor around a target, and deliver the motor to a cluster of cells. This study showcases a multimodal chemical-magnetic field regulated migration of micro-machines for sensing, transport, and delivery inside a fluidic environment. Electronic supplementary information (ESI) available: Scanning electron microscopy, transmission electron microscopy, X-ray diffraction pattern, vibrating sample magnetometry (VSM) hysteresis loop of freshly prepared FeNP coated micromotor and movies of micromotor motion. See DOI: 10.1039/c3nr05294j

Mechanisms of intragastric pH sensing.

PubMed

Goo, Tyralee; Akiba, Yasutada; Kaunitz, Jonathan D

2010-12-01

Luminal amino acids and lack of luminal acidity as a result of acid neutralization by intragastric foodstuffs are powerful signals for acid secretion. Although the hormonal and neural pathways underlying this regulatory mechanism are well understood, the nature of the gastric luminal pH sensor has been enigmatic. In clinical studies, high pH, tryptic peptides, and luminal divalent metals (Ca(2+) and Mg(2+)) increase gastrin release and acid production. The calcium-sensing receptor (CaSR), first described in the parathyroid gland but expressed on gastric G cells, is a logical candidate for the gastric acid sensor. Because CaSR ligands include amino acids and divalent metals, and because extracellular pH affects ligand binding in the pH range of the gastric content, its pH, metal, and nutrient-sensing functions are consistent with physiologic observations. The CaSR is thus an attractive candidate for the gastric luminal sensor that is part of the neuroendocrine negative regulatory loop for acid secretion.

Batch and fed-batch production of butyric acid by Clostridium butyricum ZJUCB

PubMed Central

He, Guo-qing; Kong, Qing; Chen, Qi-he; Ruan, Hui

2005-01-01

The production of butyric acid by Clostridium butyricum ZJUCB at various pH values was investigated. In order to study the effect of pH on cell growth, butyric acid biosynthesis and reducing sugar consumption, different cultivation pH values ranging from 6.0 to 7.5 were evaluated in 5-L bioreactor. In controlled pH batch fermentation, the optimum pH for cell growth and butyric acid production was 6.5 with a cell yield of 3.65 g/L and butyric acid yield of 12.25 g/L. Based on these results, this study then compared batch and fed-batch fermentation of butyric acid production at pH 6.5. Maximum value (16.74 g/L) of butyric acid concentration was obtained in fed-batch fermentation compared to 12.25 g/L in batch fermentation. It was concluded that cultivation under fed-batch fermentation mode could enhance butyric acid production significantly (P<0.01) by C. butyricum ZJUCB. PMID:16252341

Effect of ocean acidification on the structure and fatty acid composition of a natural plankton community in the Baltic Sea

NASA Astrophysics Data System (ADS)

Bermúdez, Rafael; Winder, Monika; Stuhr, Annegret; Almén, Anna-Karin; Engström-Öst, Jonna; Riebesell, Ulf

2016-12-01

Increasing atmospheric carbon dioxide (CO2) is changing seawater chemistry towards reduced pH, which affects various properties of marine organisms. Coastal and brackish water communities are expected to be less affected by ocean acidification (OA) as these communities are typically adapted to high fluctuations in CO2 and pH. Here we investigate the response of a coastal brackish water plankton community to increasing CO2 levels as projected for the coming decades and the end of this century in terms of community and biochemical fatty acid (FA) composition. A Baltic Sea plankton community was enclosed in a set of offshore mesocosms and subjected to a CO2 gradient ranging from natural concentrations ( ˜ 347 µatm fCO2) up to values projected for the year 2100 ( ˜ 1333 µatm fCO2). We show that the phytoplankton community composition was resilient to CO2 and did not diverge between the treatments. Seston FA composition was influenced by community composition, which in turn was driven by silicate and phosphate limitation in the mesocosms and showed no difference between the CO2 treatments. These results suggest that CO2 effects are dampened in coastal communities that already experience high natural fluctuations in pCO2. Although this coastal plankton community was tolerant of high pCO2 levels, hypoxia and CO2 uptake by the sea can aggravate acidification and may lead to pH changes outside the currently experienced range for coastal organisms.

Intestinal Targeting of Ganciclovir Release Employing a Novel HEC-PAA Blended Lyomatrix.

PubMed

Mabrouk, Mostafa; Mulla, Jameel A S; Kumar, Pradeep; Chejara, Dharmesh R; Badhe, Ravindra V; Choonara, Yahya E; du Toit, Lisa C; Pillay, Viness

2016-10-01

A hydroxyethylcellulose-poly(acrylic acid) (HEC-PAA) lyomatrix was developed for ganciclovir (GCV) intestine targeting to overcome its undesirable degradation in the stomach. GCV was encapsulated within the HEC-PAA lyomatrix prepared by lyophilization. Conventional tablets were also prepared with identical GCV concentrations in order to compare the GCV release behavior from the lyomatrix and tablets. GCV incorporation (75.12%) was confirmed using FTIR, DSC, and TGA. The effect of GCV loading on the microstructure properties of the lyomatrix was evaluated by SEM, AFM, and BET surface area measurements. The in vitro drug release study showed steady and rapid release profiles from the GCV-loaded lyomatrix compared with the tablet formulation at identical pH values. Minimum GCV release was observed at acidic pH (≤40%) and maximum release occurred at intestinal pH values (≥90%) proving the intestinal targeting ability of the lyomatrix. Kinetic modeling revealed that the GCV-loaded lyomatrix exhibited zero-order release kinetics (n = 1), while the tablets were best described via the Peppas model. Textural analysis highlighted enhanced matrix resilience and rigidity gradient (12.5%, 20 Pa) for the GCV-loaded lyomatrix compared to the pure (7%, 9.5 Pa) HEC-PAA lyomatrix. Bench-top MRI imaging was used to confirm the mechanism of GCV release behavior by monitoring the swelling and erosion rates. The swelling and erosion rate of the tablets was not sufficient to achieve rapid zero-order GCV release as with the lyomatrix. These combined results suggest that the HEC-PAA lyomatrix may be suitable for GCV intestinal targeting after oral administration.

Simultaneous separation and determination of six arsenic species in rice by anion-exchange chromatography with inductively coupled plasma mass spectrometry.

PubMed

Ma, Li; Yang, Zhaoguang; Tang, Jie; Wang, Lin

2016-06-01

The simultaneous separation and determination of arsenite As(III), arsenate As(V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), and arsenocholine (AsC) in rice samples have been carried out in one single anion-exchange column run by high-performance liquid chromatography with inductively coupled plasma mass spectrometry. To estimate the effect of variables on arsenic (As) speciation, the chromatographic conditions including type of competing anion, ionic strength, pH of elution buffer, and flow rate of mobile phase have been investigated by a univariate approach. Under the optimum chromatographic conditions, baseline separation of six As species has been achieved within 10 min by gradient elution program using 4 mM NH4 HCO3 at pH 8.6 as mobile phase A and 4 mM NH4 HCO3 , 40 mM NH4 NO3 at pH 8.6 as mobile phase B. The method detection limits for As(III), As(V), MMA, DMA, AsB, and AsC were 0.4, 0.9, 0.2, 0.4, 0.5, and 0.3 μg/kg, respectively. The proposed method has been applied to separation and quantification of As species in real rice samples collected from Hunan Province, China. The main As species detected in all samples were As(III), As(V) and DMA, with inorganic As accounting for over 80% of total As in these samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Strategies for regulation of hemolymph pH in acidic and alkaline water by the larval mosquito Aedes aegypti (L.) (Diptera; Culicidae).

PubMed

Clark, Thomas M; Vieira, Marcus A L; Huegel, Kara L; Flury, Dawn; Carper, Melissa

2007-12-01

The responses of larval Aedes aegypti to media of pH 4, 7 and 11 provide evidence for pH regulatory strategies. Drinking rates in pH 4 media were elevated 3- to 5-fold above those observed in pH 7 or 11. Total body water was elevated during acute exposure to acidic media. During chronic exposure, total body water was decreased and Malpighian tubule mitochondrial luminosity, quantified using Mitotracker Green FM, increased. Malpighian tubule secretion rates and energy demands thus appear to increase dramatically during acid exposure. In alkaline media, drinking rates were quite low. Larvae in pH 11 media excreted net acid (0.12 nequiv H(+) g(-1) h(-1)) and the pH indicators azolitmin and bromothymol blue revealed that the rectal lumen is acidic in vivo at all ambient pH values. The anal papillae (AP) were found to be highly permeant to acid-base equivalents. Ambient pH influenced the length, and the mass-specific length, of the AP in the presence of NaCl (59.9 mmol l(-1)). In contrast, the length and mass-specific length of AP were not influenced by ambient pH in low NaCl conditions. Mitochondrial luminosity was reduced in AP of larvae reared in acidic media, and was not elevated in alkaline media, relative to that of larvae reared in neutral media. These data suggest that the AP may compromise acid-base balance in acidic media, and may also be an important site of trade-offs between H(+) homeostasis and NaCl uptake in dilute, acidic media.

Acidic Extracellular pH Promotes Activation of Integrin αvβ3

PubMed Central

Paradise, Ranjani K.; Lauffenburger, Douglas A.; Van Vliet, Krystyn J.

2011-01-01

Acidic extracellular pH is characteristic of the cell microenvironment in several important physiological and pathological contexts. Although it is well established that acidic extracellular pH can have profound effects on processes such as cell adhesion and migration, the underlying molecular mechanisms are largely unknown. Integrin receptors physically connect cells to the extracellular matrix, and are thus likely to modulate cell responses to extracellular conditions. Here, we examine the role of acidic extracellular pH in regulating activation of integrin αvβ3. Through computational molecular dynamics simulations, we find that acidic extracellular pH promotes opening of the αvβ3 headpiece, indicating that acidic pH can thereby facilitate integrin activation. This prediction is consistent with our flow cytometry and atomic force microscope-mediated force spectroscopy assays of integrin αvβ3 on live cells, which both demonstrate that acidic pH promotes activation at the intact cell surface. Finally, quantification of cell morphology and migration measurements shows that acidic extracellular pH affects cell behavior in a manner that is consistent with increased integrin activation. Taken together, these computational and experimental results suggest a new and complementary mechanism of integrin activation regulation, with associated implications for cell adhesion and migration in regions of altered pH that are relevant to wound healing and cancer. PMID:21283814

Modeling the effects of sodium chloride, acetic acid, and intracellular pH on survival of Escherichia coli O157:H7.

PubMed

Hosein, Althea M; Breidt, Frederick; Smith, Charles E

2011-02-01

Microbiological safety has been a critical issue for acid and acidified foods since it became clear that acid-tolerant pathogens such as Escherichia coli O157:H7 can survive (even though they are unable to grow) in a pH range of 3 to 4, which is typical for these classes of food products. The primary antimicrobial compounds in these products are acetic acid and NaCl, which can alter the intracellular physiology of E. coli O157:H7, leading to cell death. For combinations of acetic acid and NaCl at pH 3.2 (a pH value typical for non-heat-processed acidified vegetables), survival curves were described by using a Weibull model. The data revealed a protective effect of NaCl concentration on cell survival for selected acetic acid concentrations. The intracellular pH of an E. coli O157:H7 strain exposed to acetic acid concentrations of up to 40 mM and NaCl concentrations between 2 and 4% was determined. A reduction in the intracellular pH was observed for increasing acetic acid concentrations with an external pH of 3.2. Comparing intracellular pH with Weibull model predictions showed that decreases in intracellular pH were significantly correlated with the corresponding times required to achieve a 5-log reduction in the number of bacteria.

Mineralogy and Geochemical Processes of Carbonate Mineral-rich Sulfide Mine Tailings, Zimapan, Mexico

NASA Astrophysics Data System (ADS)

McClure, R. J.; Deng, Y.; Loeppert, R.; Herbert, B. E.; Carrillo, R.; Gonzalez, C.

2009-12-01

Mining for silver, lead, zinc, and copper in Zimapan, Hidalgo State, Mexico has been ongoing since 1576. High concentrations of heavy metals have been found in several mine tailing heaps in the Zimapan area, with concentrations of arsenic observed as high as 28,690 mg/kg and levels of Pb as high as 2772 mg/kg. Unsecured tailings heaps and associated acid mine drainage has presented tremendous problems to revegetation, water quality, and dust emission control in the Zimapan area. Although acid mine drainage problems related to weathering of sulfide minerals have been extensively studied and are well known, the weathering products of sulfides in areas with a significant presence of carbonate minerals and their effect on the mobility of heavy metals warrant further study. Carbonate minerals are expected to neutralize sulfuric acid produced from weathering of sulfide minerals, however, in the Zimapan area localized areas of pH as low as 1.8 were observed within carbonate mineral-rich tailing heaps. The objectives of this study are to characterize (1) the heavy metal-containing sulfide minerals in the initial tailing materials, (2) the intermediate oxidation products of sulfide minerals within the carbonate-rich tailings, (3) chemical species of heavy metals within pH gradients between 1.8 and 8.2, the approximate natural pH of limestone, and (4) the mobility of soluble and colloidal heavy metals and arsenic within the carbonate-rich tailings. Representative mine tailings and their intermediate oxidation products have been sampled from the Zimapan area. Mineralogical characterization will be conducted with X-ray diffraction, infrared spectroscopy, electron microscopes and microprobes, and chemical methods. Chemical species will be extracted by selective dissolution methods. Preliminary results have identified calcite as the dominant mineral in the tailing heaps with a pH of 7, suggesting non-equilibrium with the acidic weathering products. Other minerals identified in the tailings include gypsum, quartz, pyrite, mica, talc, amphiboles, and feldspars. Oxidation products identified include copiapite as well as various iron oxides. Future results are expected to reveal most of the heavy metals to be adsorbed by or coprecipitate with iron oxides, with most of the oxidized arsenic staying in the soluble form. The mobility of the colloidal form of the oxides and associated heavy metals within the carbonate mineral-rich tailings need additional study.

Bacterial chitinolytic communities respond to chitin and pH alteration in soil.

PubMed

Kielak, Anna M; Cretoiu, Mariana Silvia; Semenov, Alexander V; Sørensen, Søren J; van Elsas, Jan Dirk

2013-01-01

Chitin amendment is a promising soil management strategy that may enhance the suppressiveness of soil toward plant pathogens. However, we understand very little of the effects of added chitin, including the putative successions that take place in the degradative process. We performed an experiment in moderately acid soil in which the level of chitin, next to the pH, was altered. Examination of chitinase activities revealed fast responses to the added crude chitin, with peaks of enzymatic activity occurring on day 7. PCR-denaturing gradient gel electrophoresis (DGGE)-based analyses of 16S rRNA and chiA genes showed structural changes of the phylogenetically and functionally based bacterial communities following chitin addition and pH alteration. Pyrosequencing analysis indicated (i) that the diversity of chiA gene types in soil is enormous and (i) that different chiA gene types are selected by the addition of chitin at different prevailing soil pH values. Interestingly, a major role of Gram-negative bacteria versus a minor one of Actinobacteria in the immediate response to the added chitin (based on 16S rRNA gene abundance and chiA gene types) was indicated. The results of this study enhance our understanding of the response of the soil bacterial communities to chitin and are of use for both the understanding of soil suppressiveness and the possible mining of soil for novel enzymes.

Separation of transition metals on a poly-iminodiacetic acid grafted polymeric resin column with post-column reaction detection utilising a paired emitter-detector diode system.

PubMed

Barron, Leon; O'Toole, Martina; Diamond, Dermot; Nesterenko, Pavel N; Paull, Brett

2008-12-05

The selectivity, retention and separation of transition metals on a short (2 mm x 50 mm) column packed with a poly-iminodiacetic acid functionalised polymer 10 microm resin (Dionex ProPac IMAC-10) are presented. This stationary phase, typically used for the separation of proteins, is composed of long chain poly-iminodiacetic acid groups grafted to a hydrophilic layer surrounding a 10 microm polymeric bead. Through the use of a combination of a multi-step pH and picolinic acid gradient, the separation of magnesium, iron, cobalt, cadmium, zinc, lead and copper was possible, followed by post-column reaction with 4-(2-pyridylazo) resorcinol (PAR) and absorbance detection at 510 nm using a novel and inexpensive optical detector, comprised of two light emitting diodes with one acting as a light source and the other as a detector. Column efficiency for selective transition metals was in excess of N=10,000, with the baseline separation of seven metal cations in <3 min possible under optimised conditions. Detection limits of between 5 and 81 microg/L were possible based upon a 50 microL injection volume.

Acid loading test (pH)

MedlinePlus

... medlineplus.gov/ency/article/003615.htm Acid loading test (pH) To use the sharing features on this page, please enable JavaScript. The acid loading test (pH) measures the ability of the kidneys to send ...

Acidogenic fermentation of food waste for volatile fatty acid production with co-generation of biohydrogen.

PubMed

Dahiya, Shikha; Sarkar, Omprakash; Swamy, Y V; Venkata Mohan, S

2015-04-01

Fermentation experiments were designed to elucidate the functional role of the redox microenvironment on volatile fatty acid (VFA, short chain carboxylic acid) production and co-generation of biohydrogen (H2). Higher VFA productivity was observed at pH 10 operation (6.3g/l) followed by pH 9, pH 6, pH 5, pH 7, pH 8 and pH 11 (3.5 g/l). High degree of acidification, good system buffering capacity along with co-generation of higher H2 production from food waste was also noticed at alkaline condition. Experiments illustrated the role of initial pH on carboxylic acids synthesis. Alkaline redox conditions assist solubilization of carbohydrates, protein and fats and also suppress the growth of methanogens. Among the carboxylic acids, acetate fraction was higher at alkaline condition than corresponding neutral or acidic operations. Integrated process of VFA production from waste with co-generation of H2 can be considered as a green and sustainable platform for value-addition. Copyright © 2015 Elsevier Ltd. All rights reserved.

Controlling Disulfide Bond Formation and Crystal Growth from 2-Mercaptobenzoic Acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rowland, Clare E.; Cantos, P. M.; Toby, B. H.

2011-03-02

We report disulfide bond formation from 2-mercaptobenzoic acid (2-MBA) under hydrothermal conditions as a function of pH. Under acidic conditions, 2-MBA remains unchanged. Upon increasing pH, however, we observe 50% oxidation to 2,2'-disulfanediyldibenzoic acid (2,2'-DSBA), which is isolated as a cocrystal of both the thiol and disulfide molecules. At neutral pH, we observe complete oxidation and concurrent crystal growth. The pH sensitivity of this system allows targeting crystals of specific composition from simple building units through a straightforward pH manipulation.

Effects of acid rain on grapevines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forsline, P.L.; Musselman, R.C.; Dee, R.J.

1983-01-01

Mature vineyard-growing Concord grapevines were sprayed with simulated acid rain solutions ranging from pH 2.5 to 5.5 both as acute treatments at anthesis and chronically throughout the season in 1980 and 1981. In 1981, 8 additional varieties were also treated with simulated acid rain solutions at pH 2.75 and 3.25. With Concord in 1981, few foliar lesions on leaves were visible at pH 2.75. In contrast, many leaf lesions with decreased fruit soluble solids were observed at pH 2.5 in 1980. The relationship between acid-rain and oxidant stipple, chlorosis, and soluble solids in the absence of acid rain leaf lesionsmore » at pH>2.5 remains unclear. Acute sprays (pH2.75) at anthesis reduced pollen germination in four grape cultivars. However, fruit set was reduced in only one of these. Grape yields were not influenced by acid rain treatments. There was no evidence that acid-rain at ambient pH levels had negative effects on grape production or fruit quality.« less

Linking Microbial Dynamics and Physicochemical Processes in High-temperature Acidic Fe(III)- Mineralizing Systems

NASA Astrophysics Data System (ADS)

Inskeep, W.

2014-12-01

Microbial activity is responsible for the mineralization of Fe(III)-oxides in high-temperature chemotrophic communities that flourish within oxygenated zones of low pH (2.5 - 4) geothermal outflow channels (Yellowstone National Park, WY). High-temperature Fe(II)-oxidizing communities contain several lineages of Archaea, and are excellent model systems for studying microbial interactions and spatiotemporal dynamics across geochemical gradients. We hypothesize that acidic Fe(III)-oxide mats form as a result of constant interaction among primary colonizers including Hydrogenobaculum spp. (Aquificales) and Metallosphaera spp. (Sulfolobales), and subsequent colonization by archaeal heterotrophs, which vary in abundance as a function of oxygen, pH and temperature. We are integrating a complementary suite of geochemical, stable isotope, genomic, proteomic and modeling analyses to study the role of microorganisms in Fe(III)-oxide mat development, and to elucidate the primary microbial interactions that are coupled with key abiotic events. Curated de novo assemblies of major phylotypes are being used to analyze additional -omics datasets from these microbial mats. Hydrogenobaculum spp. (Aquificales) are the dominant bacterial population(s) present, and predominate during early mat development (< 30 d). Other Sulfolobales populations known to oxidize Fe(II) and fix carbon dioxide (e.g., Metallosphaera spp.) represent a secondary stage of mat development (e.g., 14 - 30 d). Hydrogenobaculum filaments appear to promote the nucleation and subsequent mineralization of Fe(III)-oxides, which likely affect the growth and turnover rates of these organisms. Other heterotrophs colonize Fe(III)-oxide mats during succession (> 30 d), including novel lineages of Archaea and representatives within the Crenarchaeota, Euryarchaeota, Thaumarchaeota and Nanoarchaeota. In situ oxygen consumption rates show that steep gradients occur within the top 1 mm of mat surface, and which correlate with changes in the abundance of different organisms that occupy these microenvironments. The relative consumption of oxygen by different members of Fe(II)-oxidizing mat communities has implications for autotroph-heterotroph associations and the dynamic micromorphology of active Fe(III)-oxide terraces.

Uniformity of environmental conditions and plant growth in a hydroponic culture system for use in a growth room with aerial CO2 control

NASA Technical Reports Server (NTRS)

Vessey, J. K.; York, E. K.; Henry, L. T.; Raper, C. D. Jr; Raper CD, J. r. (Principal Investigator)

1988-01-01

A portable system of hydroponic culture was developed that maintained temperature, pH, and nutrient concentrations of circulating nutrient solutions. The hydroponic system is used within a controlled-environment room (CER) for control of aerial environment. The CER was equipped with an auto-calibrating system for atmospheric CO2 control. The control systems for the hydroponic chambers were able to maintain acidity within +/- 0.2 pH units and the temperature with +/- 0.5 degree C. Mixing time for the 200-liter volume of solution within a hydroponic chamber was less than 12 min. The CO2 control system was able to maintain aerial concentrations within +/- 10 ppm CO2 during the light period. The only gradient found to occur within the hydroponic chambers or CER was a slight gradient in aerial temperature along the length of hydroponic chambers. Growth of soybeans [Glycine max (L.) Merr.] was characterized during a 3-week period of vegetative development by leaf number and area, plant dry weight, total N content of plants, and N depletion from the nutrient solution. The growth characteristics among populations for three hydroponic chambers within the CER were not significantly different, and the percent standard errors of means of the measurements within populations from each chamber were nearly all less than 10%. Thus, the uniformity of plant growth reflected the uniformity of environmental conditions.

In vivo optical detection of pH in microscopic tissue samples of Arabidopsis thaliana.

PubMed

Kašík, Ivan; Podrazký, Ondřej; Mrázek, Jan; Martan, Tomáš; Matějec, Vlastimil; Hoyerová, Klára; Kamínek, Miroslav

2013-12-01

Minimally invasive in vivo measurement of pH in microscopic biological samples of μm or μl size, e.g. plant cells, tissues and saps, may help to explain complex biological processes. Consequently, techniques to achieve such measurements are a focus of interest for botanists. This paper describes a technique for the in vivo measurement of pH in the range pH5.0 to pH7.8 in microscopic plant tissue samples of Arabidopsis thaliana based on a ratiometric fluorescence method using low-loss robust tapered fiber probes. For this purpose tapered fiber probes were prepared and coated with a detection layer containing ion-paired fluorescent pH-transducer 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (c-HPTS). A fluorescence ratiometric approach was employed based on excitation at 415 nm and 450 nm and on the comparison of the fluorescence response at 515 nm. The suitability of tapered fiber probes for local detection of pH between 5.0 and 7.8 was demonstrated. A pH sensitivity of 0.15 pH units was achieved within the pH ranges 5.0-5.9 and 7.1-7.8, and this was improved to 0.04 pH units within the pH range 5.9-7.1. Spatial resolution of the probes was better than 20 μm and a time response within 15-20s was achieved. Despite the minute dimensions of the tapered fiber probes the setup developed was relatively robust and compact in construction and performed reliably. It has been successfully employed for the in vivo local determination of pH of mechanically resistant plant tissues of A. thaliana of microscopic scale. The detection of momentary pH gradients across the intact plant seems to be a good tool for the determination of changes in pH in response to experimental treatments affecting for example enzyme activities, availability of mineral nutrients, hormonal control of plant development and plant responses to environmental cues. © 2013.

[Relationship between simulated acid rain stress and leaf reflectance].

PubMed

Song, Xiao-dong; Jiang, Hong; Yu, Shu-quan; Zhou, Guo-mo; Jiang, Zi-shan

2010-01-01

Acid rain is a worldwide environmental problem. Serious acid rain pollution in subtropical China has constituted a potential threat to the health of the local forest. In the present paper, the changing properties of the chlorophyll concentration and spectral reflectance at the visible wavelengths for the six subtropical broad-leaved tree species leaves under simulated acid rain (SAR) treatment with different pH levels were studied. With the increasing strength of the SAR, the chlorophyll concentrations of the experimental species under pH 2.5 and pH 4.0 treatment were higher than that under pH 5.6; the spectral reflectance at the visible wavelengths for pH 2.5 and pH 4.0 were lower than that for pH 5.6 in general; while there weren't significant differences between pH 2.5 and pH 4.0. After the treatment with different levels of SAR, the differences in spectral reflectance at the visible wavelengths mainly focused around the green peak and red edge on the reflectance curve. The subtropical broad-leaved tree species studied were relatively not sensitive to acid rain stresses; some stronger acid rain may accelerate the growth of the tree species used here to some extent.

[Serum uric acid is associated with disease severity and an important predictor for clinical outcome in patients with pulmonary hypertension].

PubMed

Luo, D L; Zhang, C J; Huang, Y G; Huang, T; Li, H Z

2017-06-24

Objective: The growing body of literature showed a link between uric acid and pulmonary hypertension (PH), but the impact of hyperuremia on outcome of patients with PH has not been well defined. Therefore, the present study was performed to analyze the impact of uric acid on outcome of PH patients. Methods: One hundred seventy-three PH patients (112 females, mean age 38 years old), who were hospitalized in our department between January 2010 and December 2015, were included in our study, the PH diagnosis was made based on right heart catheterization examination result (mean pulmonary artery pressure≥25 mmHg(1 mmHg=0.133 kPa)). PH patients were divided into mild to moderate PH group (Rp/Rs≤0.6, n =97) and severe PH group (Rp/Rs>0.6, n =76). Fifty-one patients (33 females, mean age 45 years old) without PH based on right heart catheterization were included as control subjects. All participants were followed up for a median of 24 months(6-71 months). Clinical endpoints were defined as cardiogenic death or heart-and-lung transplantation. Results: Uric acid was positively correlated with pulmonary vascular resistance( r =0.398, P <0.01), systemic vascular resistance( r =0.244, P <0.01) and mean right atrial pressure ( r =0.26, P <0.01), and was negatively correlated with cardiac index( r =-0.278, P <0.01)and mixed venous oxygen saturation ( r =-0.322, P <0.01)in PH patients. Serum uric acid level was significantly higher in patients with severe PH than in patients with mild-to-moderate PH and the control subjects (both P <0.05). According to the receiver operating characteristic curve (ROC), 425.5 μmol/L was found to be the best cut-off value of serum uric acid level to predict the outcome of PH patients (sensitivity 50%, specificity 72%). During follow-up, patients with higher level of uric acid (>425.5 μmol/L) were linked with poorer clinical outcome compared to patients with uric acid <425.5 μmol/L( P =0.027). Conclusion: Our findings suggests that uric acid is associated with the severity of PH and higher uric acid level serves as an important predictor for poor clinical outcome of PH patients.

Convergence and contrast in the community structure of Bacteria, Fungi and Archaea along a tropical elevation-climate gradient.

PubMed

Peay, Kabir G; von Sperber, Christian; Cardarelli, Emily; Toju, Hirokazu; Francis, Christopher A; Chadwick, Oliver A; Vitousek, Peter M

2017-05-01

Changes in species richness along climatological gradients have been instrumental in developing theories about the general drivers of biodiversity. Previous studies on microbial communities along climate gradients on mountainsides have revealed positive, negative and neutral richness trends. We examined changes in richness and composition of Fungi, Bacteria and Archaea in soil along a 50-1000 m elevation, 280-3280 mm/yr precipitation gradient in Hawai'i. Soil properties and their drivers are exceptionally well understood along this gradient. All three microbial groups responded strongly to the gradient, with community ordinations being similar along axes of environmental conditions (pH, rainfall) and resource availability (nitrogen, phosphorus). However, the form of the richness-climate relationship varied between Fungi (positive linear), Bacteria (unimodal) and Archaea (negative linear). These differences were related to resource-ecology and limiting conditions for each group, with fungal richness increasing most strongly with soil carbon, ammonia-oxidizing Archaea increasing with nitrogen mineralization rate, and Bacteria increasing with both carbon and pH. Reponses to the gradient became increasingly variable at finer taxonomic scales and within any taxonomic group most individual OTUs occurred in narrow climate-elevation ranges. These results show that microbial responses to climate gradients are heterogeneous due to complexity of underlying environmental changes and the diverse ecologies of microbial taxa. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Evaluation of citric acid and GDL in the recovery at different pH levels of Clostridium sporogenes PA 3679 spores subjected to HTST treatment conditions.

PubMed

Silla Santos, M H; Torres Zarzo, J

1996-04-01

Spores of Clostridium sporogenes PA 3679 were treated at different temperatures (121, 126, 130 and 135 degrees C) in white asparagus purée (pH 5.8) and acidified with glucono-delta-lactone (GDL) and citric acid to pH levels of 5.5, 5.0 and 4.5. Afterwards, the spores were recovered in MPA3679 medium in various conditions: unacidified (pH 7.5), acidified with GDL (500 ppm) and acidified with citric acid (500 and 250 ppm) to pH levels of 6.5, 6.0 and 5.0. The results indicated that the pH levels, concentration and type of acid used act synergistically rather than independently. Citric acid has a stronger inhibiting effect than GDL on the recovery of C. sporogenes PA 3679 spores. At the higher heat treatments (130 and 135 degrees C) the major injury on the spores sensitize more than against the acids and low pH values.

Uptake of dyes by a promising locally available agricultural solid waste: coir pith.

PubMed

Namasivayam, C; Radhika, R; Suba, S

2001-01-01

The adsorption of rhodamine-B and acid violet by coir pith carbon was carried out by varying the parameters such as agitation time, dye concentration, adsorbent dose and pH. The adsorption followed both Langmuir and Freundlich isotherms. The adsorption capacity was found to be 2.56 mg and 8.06 mg dye per g of the adsorbent for rhodamine-B and acid violet, respectively. Adsorption of dyes followed first order rate kinetics. Acidic pH was favorable for the adsorption of acid violet and alkaline pH was favorable to rhodamine-B. Desorption studies showed that alkaline pH was favorable for the desorption of acid violet and acidic pH was favorable for the desorption of rhodamine-B.

Simultaneous quantification of flavonoids and triterpenoids in licorice using HPLC.

PubMed

Wang, Yuan-Chuen; Yang, Yi-Shan

2007-05-01

Numerous bioactive compounds are present in licorice (Glycyrrhizae Radix), including flavonoids and triterpenoids. In this study, a reversed-phase high-performance liquid chromatography (HPLC) method for simultaneous quantification of three flavonoids (liquiritin, liquiritigenin and isoliquiritigenin) and four triterpenoids (glycyrrhizin, 18alpha-glycyrrhetinic acid, 18beta-glycyrrhetinic acid and 18beta-glycyrrhetinic acid methyl ester) from licorice was developed, and further, to quantify these 7 compounds from 20 different licorice samples. Specifically, the reverse-phase HPLC was performed with a gradient mobile phase composed of 25 mM phosphate buffer (pH 2.5)-acetonitrile featuring gradient elution steps as follows: 0 min, 100:0; 10 min, 80:20; 50 min, 70:30; 73 min, 50:50; 110 min, 50:50; 125 min, 20:80; 140 min, 20:80, and peaks were detected at 254 nm. By using our technique, a rather good specificity was obtained regarding to the separation of these seven compounds. The regression coefficient for the linear equations for the seven compounds lay between 0.9978 and 0.9992. The limits of detection and quantification lay in the range of 0.044-0.084 and 0.13-0.25 microg/ml, respectively. The relative recovery rates for the seven compounds lay between 96.63+/-2.43 and 103.55+/-2.77%. Coefficient variation for intra-day and inter-day precisions lay in the range of 0.20-1.84 and 0.28-1.86%, respectively. Based upon our validation results, this analytical technique is a convenient method to simultaneous quantify numerous bioactive compounds derived from licorice, featuring good quantification parameters, accuracy and precision.

pH imaging of mouse kidneys in vivo using a frequency-dependent paraCEST agent

PubMed Central

Wu, Yunkou; Zhang, Shanrong; Soesbe, Todd C.; Yu, Jing; Vinogradov, Elena; Lenkinski, Robert E.; Sherry, A. Dean

2015-01-01

Purpose This study explored the feasibility of using a pH responsive paraCEST agent to image the pH gradient in kidneys of healthy mice. Methods CEST signals were acquired on an Agilent 9.4 T small animal MRI system using a steady-state gradient echo pulse sequence after a bolus injection of agent. The magnetic field inhomogeneity across each kidney was corrected using the WASSR method and pH maps were calculated by measuring the frequency of water exchange signal arising from the agent. Results Dynamic CEST studies demonstrated that the agent was readily detectable in kidneys only between 4 to 12 min post-injection. The CEST images showed a higher signal intensity in the pelvis and calyx regions and lower signal intensity in the medulla and cortex regions. The pH maps reflected tissue pH values spanning from 6.0 to 7.5 in kidneys of healthy mice. Conclusion This study demonstrated that pH maps of the kidney can be imaged in vivo by measuring the pH-dependent chemical shift of a single water exchange CEST peak without prior knowledge of the agent concentration in vivo. The results demonstrate the potential of using a simple frequency-dependent paraCEST agent for mapping tissue pH in vivo. PMID:26173637

Enhanced diffusion weighting generated by selective adiabatic pulse trains

NASA Astrophysics Data System (ADS)

Sun, Ziqi; Bartha, Robert

2007-09-01

A theoretical description and experimental validation of the enhanced diffusion weighting generated by selective adiabatic full passage (AFP) pulse trains is provided. Six phantoms (Ph-1-Ph-6) were studied on a 4 T Varian/Siemens whole body MRI system. Phantoms consisted of 2.8 cm diameter plastic tubes containing a mixture of 10 μm ORGASOL polymer beads and 2 mM Gd-DTPA dissolved in 5% agar (Ph-1) or nickel(II) ammonium sulphate hexahydrate doped (56.3-0.8 mM) water solutions (Ph-2-Ph-6). A customized localization by adiabatic selective refocusing (LASER) sequence containing slice selective AFP pulse trains and pulsed diffusion gradients applied in the phase encoding direction was used to measure 1H 2O diffusion. The b-value associated with the LASER sequence was derived using the Bloch-Torrey equation. The apparent diffusion coefficients measured by LASER were comparable to those measured by a conventional pulsed gradient spin-echo (PGSE) sequence for all phantoms. Image signal intensity increased in Ph-1 and decreased in Ph-2-Ph-6 as AFP pulse train length increased while maintaining a constant echo-time. These experimental results suggest that such AFP pulse trains can enhance contrast between regions containing microscopic magnetic susceptibility variations and homogeneous regions in which dynamic dephasing relaxation mechanisms are dominant.

Transfer of Oleic Acid between Albumin and Phospholipid Vesicles

NASA Astrophysics Data System (ADS)

Hamilton, James A.; Cistola, David P.

1986-01-01

The net transfer of oleic acid between egg phosphatidylcholine unilamellar vesicles and bovine serum albumin has been monitored by 13C NMR spectroscopy and 90% isotopically substituted [1-13C]oleic acid. The carboxyl chemical shifts of oleic acid bound to albumin were different from those for oleic acid in phospholipid vesicles. Therefore, in mixtures of donor particles (vesicles or albumin with oleic acid) and acceptor particles (fatty acid-free albumin or vesicles), the equilibrium distribution of oleic acid was determined from chemical shift and peak intensity data without separation of donor and acceptor particles. In a system containing equal masses of albumin and phospholipid and a stoichiometry of 4-5 mol of oleic acid per mol of albumin, the oleic acid distribution was pH dependent, with >= 80% of the oleic acid associated with albumin at pH 7.4; association was >= 90% at pH 8.0. Decreasing the pH below 7.4 markedly decreased the proportion of fatty acid bound to albumin; at pH 5.4, <= 10% of the oleic acid was bound to albumin and >90% was associated with vesicles. The distribution was reversible with pH and was independent of whether vesicles or albumin acted as a donor. These data suggest that pH may strongly influence the partitioning of fatty acid between cellular membranes and albumin. The 13C NMR method is also advantageous because it provides information about the structural environments of oleic acid bound to albumin or phospholipid, the ionization state of oleic acid in each environment, and the structural integrity of the vesicles. In addition, minimum and maximum limits for the exchange rates of oleic acid among different environments were obtained from the NMR data.

The Cytosolic pH of Individual Saccharomyces cerevisiae Cells Is a Key Factor in Acetic Acid Tolerance.

PubMed

Fernández-Niño, Miguel; Marquina, Maribel; Swinnen, Steve; Rodríguez-Porrata, Boris; Nevoigt, Elke; Ariño, Joaquín

2015-11-01

It was shown recently that individual cells of an isogenic Saccharomyces cerevisiae population show variability in acetic acid tolerance, and this variability affects the quantitative manifestation of the trait at the population level. In the current study, we investigated whether cell-to-cell variability in acetic acid tolerance could be explained by the observed differences in the cytosolic pHs of individual cells immediately before exposure to the acid. Results obtained with cells of the strain CEN.PK113-7D in synthetic medium containing 96 mM acetic acid (pH 4.5) showed a direct correlation between the initial cytosolic pH and the cytosolic pH drop after exposure to the acid. Moreover, only cells with a low initial cytosolic pH, which experienced a less severe drop in cytosolic pH, were able to proliferate. A similar correlation between initial cytosolic pH and cytosolic pH drop was also observed in the more acid-tolerant strain MUCL 11987-9. Interestingly, a fraction of cells in the MUCL 11987-9 population showed initial cytosolic pH values below the minimal cytosolic pH detected in cells of the strain CEN.PK113-7D; consequently, these cells experienced less severe drops in cytosolic pH. Although this might explain in part the difference between the two strains with regard to the number of cells that resumed proliferation, it was observed that all cells from strain MUCL 11987-9 were able to proliferate, independently of their initial cytosolic pH. Therefore, other factors must also be involved in the greater ability of MUCL 11987-9 cells to endure strong drops in cytosolic pH. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Effects of acidic pH on voltage-gated ion channels in rat trigeminal mesencephalic nucleus neurons.

PubMed

Han, Jin-Eon; Cho, Jin-Hwa; Choi, In-Sun; Kim, Do-Yeon; Jang, Il-Sung

2017-03-01

The effects of acidic pH on several voltage-dependent ion channels, such as voltage-dependent K + and Ca 2+ channels, and hyperpolarization-gated and cyclic nucleotide-activated cation (HCN) channels, were examined using a whole-cell patch clamp technique on mechanically isolated rat mesencephalic trigeminal nucleus neurons. The application of a pH 6.5 solution had no effect on the peak amplitude of voltage-dependent K + currents. A pH 6.0 solution slightly, but significantly inhibited the peak amplitude of voltage-dependent K + currents. The pH 6.0 also shifted both the current-voltage and conductance-voltage relationships to the depolarization range. The application of a pH 6.5 solution scarcely affected the peak amplitude of membrane currents mediated by HCN channels, which were profoundly inhibited by the general HCN channel blocker Cs + (1 mM). However, the pH 6.0 solution slightly, but significantly inhibited the peak amplitude of HCN-mediated currents. Although the pH 6.0 solution showed complex modulation of the current-voltage and conductance-voltage relationships, the midpoint voltages for the activation of HCN channels were not changed by acidic pH. On the other hand, voltage-dependent Ca 2+ channels were significantly inhibited by an acidic pH. The application of an acidic pH solution significantly shifted the current-voltage and conductance-voltage relationships to the depolarization range. The modulation of several voltage-dependent ion channels by an acidic pH might affect the excitability of mesencephalic trigeminal nucleus neurons, and thus physiological functions mediated by the mesencephalic trigeminal nucleus could be affected in acidic pH conditions.

The Cytosolic pH of Individual Saccharomyces cerevisiae Cells Is a Key Factor in Acetic Acid Tolerance

PubMed Central

Fernández-Niño, Miguel; Marquina, Maribel; Swinnen, Steve; Rodríguez-Porrata, Boris

2015-01-01

It was shown recently that individual cells of an isogenic Saccharomyces cerevisiae population show variability in acetic acid tolerance, and this variability affects the quantitative manifestation of the trait at the population level. In the current study, we investigated whether cell-to-cell variability in acetic acid tolerance could be explained by the observed differences in the cytosolic pHs of individual cells immediately before exposure to the acid. Results obtained with cells of the strain CEN.PK113-7D in synthetic medium containing 96 mM acetic acid (pH 4.5) showed a direct correlation between the initial cytosolic pH and the cytosolic pH drop after exposure to the acid. Moreover, only cells with a low initial cytosolic pH, which experienced a less severe drop in cytosolic pH, were able to proliferate. A similar correlation between initial cytosolic pH and cytosolic pH drop was also observed in the more acid-tolerant strain MUCL 11987-9. Interestingly, a fraction of cells in the MUCL 11987-9 population showed initial cytosolic pH values below the minimal cytosolic pH detected in cells of the strain CEN.PK113-7D; consequently, these cells experienced less severe drops in cytosolic pH. Although this might explain in part the difference between the two strains with regard to the number of cells that resumed proliferation, it was observed that all cells from strain MUCL 11987-9 were able to proliferate, independently of their initial cytosolic pH. Therefore, other factors must also be involved in the greater ability of MUCL 11987-9 cells to endure strong drops in cytosolic pH. PMID:26341199

Perturbation Analysis of Calcium, Alkalinity and Secretion during Growth of Lily Pollen Tubes

PubMed Central

Winship, Lawrence J.; Rounds, Caleb; Hepler, Peter K.

2016-01-01

Pollen tubes grow by spatially and temporally regulated expansion of new material secreted into the cell wall at the tip of the tube. A complex web of interactions among cellular components, ions and small molecule provides dynamic control of localized expansion and secretion. Cross-correlation studies on oscillating lily (Lilium formosanum Wallace) pollen tubes showed that an increase in intracellular calcium follows an increase in growth, whereas the increase in the alkaline band and in secretion both anticipate the increase in growth rate. Calcium, as a follower, is unlikely to be a stimulator of growth, whereas the alkaline band, as a leader, may be an activator. To gain further insight herein we reversibly inhibited growth with potassium cyanide (KCN) and followed the re-establishment of calcium, pH and secretion patterns as growth resumed. While KCN markedly slows growth and causes the associated gradients of calcium and pH to sharply decline, its removal allows growth and vital processes to fully recover. The calcium gradient reappears before growth restarts; however, it is preceded by both the alkaline band and secretion, in which the alkaline band is slightly advanced over secretion. Thus the pH gradient, rather than the tip-focused calcium gradient, may regulate pollen tube growth. PMID:28042810

Perturbation Analysis of Calcium, Alkalinity and Secretion during Growth of Lily Pollen Tubes.

PubMed

Winship, Lawrence J; Rounds, Caleb; Hepler, Peter K

2016-12-30

Pollen tubes grow by spatially and temporally regulated expansion of new material secreted into the cell wall at the tip of the tube. A complex web of interactions among cellular components, ions and small molecule provides dynamic control of localized expansion and secretion. Cross-correlation studies on oscillating lily ( Lilium formosanum Wallace) pollen tubes showed that an increase in intracellular calcium follows an increase in growth, whereas the increase in the alkaline band and in secretion both anticipate the increase in growth rate. Calcium, as a follower, is unlikely to be a stimulator of growth, whereas the alkaline band, as a leader, may be an activator. To gain further insight herein we reversibly inhibited growth with potassium cyanide (KCN) and followed the re-establishment of calcium, pH and secretion patterns as growth resumed. While KCN markedly slows growth and causes the associated gradients of calcium and pH to sharply decline, its removal allows growth and vital processes to fully recover. The calcium gradient reappears before growth restarts; however, it is preceded by both the alkaline band and secretion, in which the alkaline band is slightly advanced over secretion. Thus the pH gradient, rather than the tip-focused calcium gradient, may regulate pollen tube growth.

Tranexamic Acid for Trauma Patients: A Critical Review of the Literature

DTIC Science & Technology

2011-07-01

REVIEW ARTICLE Tranexamic Acid for Trauma Patients: A Critical Review of the Literature Andrew P. Cap, MD, PhD, David G. Baer, PhD, Jean A. Orman...MPH, ScD, James Aden, PhD, Kathy Ryan, PhD, and Lorne H. Blackbourne, MD Background: Tranexamic acid (TXA) is an antifibrinolytic that inhibits both...prospective clinical evidence to support this application. Key Words: Tranexamic acid , Antifibrinolytic agents, Hemorrhage/drug therapy, Wounds and injuries

Seasonal variations in the physiological stress response to discrete bouts of aerial exposure in the little skate, Leucoraja erinacea.

PubMed

Cicia, Angela M; Schlenker, Lela S; Sulikowski, James A; Mandelman, John W

2012-06-01

Aerial exposure and acute thermal stress have been shown to elicit profound physiological disruptions in obligate water-breathing teleosts. However, no study has investigated these responses in an elasmobranch. To address this, venous blood samples were collected and evaluated from little skates (Leucoraja erinacea) subjected to discrete aerial exposure durations (0, 15, and 50 min) coupled with differing abrupt thermal changes (gradient between seawater and air; winter: ΔT=-3 °C; summer: ΔT=+9 °C) in two distinct laboratory studies. In general, blood acid-base properties (e.g. decline in pH; elevation in PCO(2)) and select metabolites (elevated whole-blood lactate) and electrolytes (elevated plasma K(+)) were significantly disrupted by aerial exposure, and were most disturbed after skates were exposed to air for 50 min. However, the magnitude of the blood acid-base perturbations, metabolic contribution to the resulting blood acidosis, elevations to ionic and metabolic parameters, and delayed mortality were more extreme during the summer study, suggesting that acute thermal stress exacerbates the physiological impairments associated with aerial exposure in little skates. Conversely, a reduced thermal gradient (from seawater to air) may attenuate the magnitude of metabolic and ionic perturbations, resulting in a high physiological threshold for coping with extended aerial exposure. Copyright © 2011 Elsevier Inc. All rights reserved.

Diversity of the Sediment Microbial Community in the Aha Watershed (Southwest China) in Response to Acid Mine Drainage Pollution Gradients.

PubMed

Sun, Weimin; Xiao, Tangfu; Sun, Min; Dong, Yiran; Ning, Zengping; Xiao, Enzong; Tang, Song; Li, Jiwei

2015-08-01

Located in southwest China, the Aha watershed is continually contaminated by acid mine drainage (AMD) produced from upstream abandoned coal mines. The watershed is fed by creeks with elevated concentrations of aqueous Fe (total Fe > 1 g/liter) and SO4 (2-) (>6 g/liter). AMD contamination gradually decreases throughout downstream rivers and reservoirs, creating an AMD pollution gradient which has led to a suite of biogeochemical processes along the watershed. In this study, sediment samples were collected along the AMD pollution sites for geochemical and microbial community analyses. High-throughput sequencing found various bacteria associated with microbial Fe and S cycling within the watershed and AMD-impacted creek. A large proportion of Fe- and S-metabolizing bacteria were detected in this watershed. The dominant Fe- and S-metabolizing bacteria were identified as microorganisms belonging to the genera Metallibacterium, Aciditerrimonas, Halomonas, Shewanella, Ferrovum, Alicyclobacillus, and Syntrophobacter. Among them, Halomonas, Aciditerrimonas, Metallibacterium, and Shewanella have previously only rarely been detected in AMD-contaminated environments. In addition, the microbial community structures changed along the watershed with different magnitudes of AMD pollution. Moreover, the canonical correspondence analysis suggested that temperature, pH, total Fe, sulfate, and redox potentials (Eh) were significant factors that structured the microbial community compositions along the Aha watershed. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Succinate and artificial maintenance of normal body temperature synergistically correct lethal disorders in thiopental coma rat.

PubMed

Ivnitsky, Jury Ju; Rejniuk, Vladimir L; Schäfer, Timur V; Malakhovsky, Vladimir N

2006-01-20

Under modeling of thiopental coma influence of sodium succinate and (or) external warming for the support of normal body temperature (isothermal regimen) on the gas exchange, blood gas content, acid-base status and survival rate was studied in rats. In the absence of therapy hypothermia was developed (-9.4 degrees C), O(2) consumption decreased by a factor 5, oxygenation of arterial blood (pO(2)) did not change while that of venous blood increased, where with arteriovenous oxygen tension gradient decreased by half. Blood tension of carbon dioxide (pCO(2)) increased twice, respiratory and metabolic acidosis was developed. Survival rate under absence of a therapy was 42%, with isolated use of isothermal regimen or succinate therapy alike-50%; with their use in combination drastically increased up to 92%. Succinate increased arteriovenous gradient of pO(2), decreased deficit of buffer bases, increased bicarbonate concentration. At isothermal regimen accumulation of CO(2) in the blood was diminished, its excretion was increased, pH of blood approached normal values. Combined use of both therapy agents increased O(2) consumption and potentiated their positive influence on acid-base status. The implication is that hypothermia restrains effect of succinate in barbiturate coma; prevention of hypothermia in combination with succinate administration is highly effective method of experimental therapy of barbiturate intoxication.

Adaptive responses of Bacillus cereus ATCC14579 cells upon exposure to acid conditions involve ATPase activity to maintain their internal pH

PubMed Central

Senouci-Rezkallah, Khadidja; Jobin, Michel P; Schmitt, Philippe

2015-01-01

This study examined the involvement of ATPase activity in the acid tolerance response (ATR) of Bacillus cereus ATCC14579 strain. In the current work, B. cereus cells were grown in anaerobic chemostat culture at external pH (pHe) 7.0 or 5.5 and at a growth rate of 0.2 h−1. Population reduction and internal pH (pHi) after acid shock at pH 4.0 was examined either with or without ATPase inhibitor N,N’-dicyclohexylcarbodiimide (DCCD) and ionophores valinomycin and nigericin. Population reduction after acid shock at pH 4.0 was strongly limited in cells grown at pH 5.5 (acid-adapted cells) compared with cells grown at pH 7.0 (unadapted cells), indicating that B. cereus cells grown at low pHe were able to induce a significant ATR and Exercise-induced increase in ATPase activity. However, DCCD and ionophores had a negative effect on the ability of B. cereus cells to survive and maintain their pHi during acid shock. When acid shock was achieved after DCCD treatment, pHi was markedly dropped in unadapted and acid-adapted cells. The ATPase activity was also significantly inhibited by DCCD and ionophores in acid-adapted cells. Furthermore, transcriptional analysis revealed that atpB (ATP beta chain) transcripts was increased in acid-adapted cells compared to unadapted cells before and after acid shock. Our data demonstrate that B. cereus is able to induce an ATR during growth at low pH. These adaptations depend on the ATPase activity induction and pHi homeostasis. Our data demonstrate that the ATPase enzyme can be implicated in the cytoplasmic pH regulation and in acid tolerance of B. cereus acid-adapted cells. PMID:25740257

Microenvironmental pH measurement during sodium naproxenate dissolution in acidic medium by UV/vis imaging.

PubMed

Østergaard, Jesper; Jensen, Henrik; Larsen, Susan W; Larsen, Claus; Lenke, Jim

2014-11-01

Variable dissolution from sodium salts of drugs containing a carboxylic acid group after passing the acidic environment of the stomach may affect oral bioavailability. The aim of the present proof of concept study was to investigate pH effects in relation to the dissolution of sodium naproxenate in 0.01M hydrochloric acid. For this purpose a UV/vis imaging-based approach capable of measuring microenvironmental pH in the vicinity of the solid drug compact as well as monitoring drug dissolution was developed. Using a pH indicating dye real-time spatially resolved measurement of pH was achieved. Sodium naproxenate, can significantly alter the local pH of the dissolution medium, is eventually neutralized and precipitates as the acidic species naproxen. The developed approach is considered useful for detailed studies of pH dependent dissolution phenomena in dissolution testing. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhanced sensitivity of DNA- and rRNA-based stable isotope probing by fractionation and quantitative analysis of isopycnic centrifugation gradients.

PubMed

Lueders, Tillmann; Manefield, Mike; Friedrich, Michael W

2004-01-01

Stable isotope probing (SIP) of nucleic acids allows the detection and identification of active members of natural microbial populations that are involved in the assimilation of an isotopically labelled compound into nucleic acids. SIP is based on the separation of isotopically labelled DNA or rRNA by isopycnic density gradient centrifugation. We have developed a highly sensitive protocol for the detection of 'light' and 'heavy' nucleic acids in fractions of centrifugation gradients. It involves the fluorometric quantification of total DNA or rRNA, and the quantification of either 16S rRNA genes or 16S rRNA in gradient fractions by real-time PCR with domain-specific primers. Using this approach, we found that fully 13C-labelled DNA or rRNA of Methylobacterium extorquens was quantitatively resolved from unlabelled DNA or rRNA of Methanosarcina barkeri by cesium chloride or cesium trifluoroacetate density gradient centrifugation respectively. However, a constant low background of unspecific nucleic acids was detected in all DNA or rRNA gradient fractions, which is important for the interpretation of environmental SIP results. Consequently, quantitative analysis of gradient fractions provides a higher precision and finer resolution for retrieval of isotopically enriched nucleic acids than possible using ethidium bromide or gradient fractionation combined with fingerprinting analyses. This is a prerequisite for the fine-scale tracing of microbial populations metabolizing 13C-labelled compounds in natural ecosystems.

Influence of simulated acidic rain on root-infecting fungi

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shafer, S.R.

1983-01-01

Influences of the acidity of simulated rain on root-infecting fungi were investigated. Effects of rain acidity on Phytophthora cinnamomi were studied. Propagule densities in soil depended upon the acidity (pH 5.6, 4.0, 3.2, or 2.4) of simulated rain and soil depth (1, 2, 4, or 8 cm). Lowest densities occurred in 1 to 2 cm soil layers exposed to rains at pH 3.2 or 2.4. Sporangium production on radicles of Lupinus angustifolius in Lakeland sand moistened with rain solution at pH 2.4 was 47% less than production with solution at pH 5.6. A linear response to solution acidity was exhibited.more » Infection of L. angustifolius roots by zoospores demonstrated a linear response to acidity of rain. Approximately 44% fewer lesions occurred on roots of seedlings exposed to rain at pH 2.4 than on roots of seedlings exposed to rain at pH 5.6. The acidity (pH 5.6, 4.0, 3.2, or 2.4) of repeated rains had no consistent effect on disease progress among L. augustifolius seedlings planted in infested soil. The formation of ectomycorrhizae on Pinus taeda seedlings exhibited a quadratic response to acidity of repeated rains. The percentage of short roots that were ectomycorrhizal was greatest among seedlings exposed to rains at pH 2.4 and least among seedlings exposed to rains at pH 4.0. The density of Macrophomina phaseolina propagules in Lakeland sand exposed to repeated rains at pH 2.4 was an average of 20% less than densities associated with rains at pH 5.6, 4.0, or 3.2.« less

Anaerobic digestion of food waste for volatile fatty acids (VFAs) production with different types of inoculum: effect of pH.

PubMed

Wang, Kun; Yin, Jun; Shen, Dongsheng; Li, Na

2014-06-01

Food waste anaerobic fermentation was carried out under acidic conditions using inocula based on aerobic activated sludge (Inoculum AE) or anaerobic activated sludge (Inoculum AN) for volatile fatty acids (VFAs) production. The results showed that food waste hydrolysis increased obviously when Inoculum AN was used relative to Inoculum AE at any pH investigated. Hydrolysis at pH 4.0 and uncontrolled pH was higher than that at other pHs when either inoculum was used. Additionally, VFAs production at pH 6.0 was the highest, regardless of the inoculum used. The optimum VFA yields were 0.482g/gVSSremoval with Inoculum AE and 0.918g/gVSSremoval with Inoculum AN, which were observed after 4d and 20d of fermentation, respectively. VFAs composition analysis showed that butyrate acid was the prevalent acid at pH 6.0, followed by acetate acid and propionic acid. Copyright © 2014 Elsevier Ltd. All rights reserved.

Differential gene expression in tomato fruit and Colletotrichum gloeosporioides during colonization of the RNAi-SlPH tomato line with reduced fruit acidity and higher pH.

PubMed

Barad, Shiri; Sela, Noa; Dubey, Amit K; Kumar, Dilip; Luria, Neta; Ment, Dana; Cohen, Shahar; Schaffer, Arthur A; Prusky, Dov

2017-08-04

The destructive phytopathogen Colletotrichum gloeosporioides causes anthracnose disease in fruit. During host colonization, it secretes ammonia, which modulates environmental pH and regulates gene expression, contributing to pathogenicity. However, the effect of host pH environment on pathogen colonization has never been evaluated. Development of an isogenic tomato line with reduced expression of the gene for acidity, SlPH (Solyc10g074790.1.1), enabled this analysis. Total RNA from C. gloeosporioides colonizing wild-type (WT) and RNAi-SlPH tomato lines was sequenced and gene-expression patterns were compared. C. gloeosporioides inoculation of the RNAi-SlPH line with pH 5.96 compared to the WT line with pH 4.2 showed 30% higher colonization and reduced ammonia accumulation. Large-scale comparative transcriptome analysis of the colonized RNAi-SlPH and WT lines revealed their different mechanisms of colonization-pattern activation: whereas the WT tomato upregulated 13-LOX (lipoxygenase), jasmonic acid and glutamate biosynthesis pathways, it downregulated processes related to chlorogenic acid biosynthesis II, phenylpropanoid biosynthesis and hydroxycinnamic acid tyramine amide biosynthesis; the RNAi-SlPH line upregulated UDP-D-galacturonate biosynthesis I and free phenylpropanoid acid biosynthesis, but mainly downregulated pathways related to sugar metabolism, such as the glyoxylate cycle and L-arabinose degradation II. Comparison of C. gloeosporioides gene expression during colonization of the WT and RNAi-SlPH lines showed that the fungus upregulates ammonia and nitrogen transport and the gamma-aminobutyric acid metabolic process during colonization of the WT, while on the RNAi-SlPH tomato, it mainly upregulates the nitrate metabolic process. Modulation of tomato acidity and pH had significant phenotypic effects on C. gloeosporioides development. The fungus showed increased colonization on the neutral RNAi-SlPH fruit, and limited colonization on the WT acidic fruit. The change in environmental pH resulted in different defense responses for the two tomato lines. Interestingly, the WT line showed upregulation of jasmonate pathways and glutamate accumulation, supporting the reduced symptom development and increased ammonia accumulation, as the fungus might utilize glutamate to accumulate ammonia and increase environmental pH for better expression of pathogenicity factors. This was not found in the RNAi-SlPH line which downregulated sugar metabolism and upregulated the phenylpropanoid pathway, leading to host susceptibility.

Lower pH values of weakly acidic refluxes as determinants of heartburn perception in gastroesophageal reflux disease patients with normal esophageal acid exposure.

PubMed

de Bortoli, N; Martinucci, I; Savarino, E; Franchi, R; Bertani, L; Russo, S; Ceccarelli, L; Costa, F; Bellini, M; Blandizzi, C; Savarino, V; Marchi, S

2016-01-01

Multichannel impedance pH monitoring has shown that weakly acidic refluxes are able to generate heartburn. However, data on the role of different pH values, ranging between 4 and 7, in the generation of them are lacking. The aim of this study was to evaluate whether different pH values of weakly acidic refluxes play a differential role in provoking reflux symptoms in endoscopy-negative patients with physiological esophageal acid exposure time and positive symptom index and symptom association probability for weakly acidic refluxes. One hundred and forty-three consecutive patients with gastroesophageal reflux disease, nonresponders to proton pump inhibitors (PPIs), were allowed a washout from PPIs before undergoing: upper endoscopy, esophageal manometry, and multichannel impedance pH monitoring. In patients with both symptom index and symptom association probability positive for weakly acidic reflux, each weakly acidic reflux was evaluated considering exact pH value, extension, physical characteristics, and correlation with heartburn. Forty-five patients with normal acid exposure time and positive symptom association probability for weakly acidic reflux were identified. The number of refluxes not heartburn related was higher than those heartburn related. In all distal and proximal liquid refluxes, as well as in distal mixed refluxes, the mean pH value of reflux events associated with heartburn was significantly lower than that not associated. This condition was not confirmed for proximal mixed refluxes. Overall, a low pH of weakly acidic reflux represents a determinant factor in provoking heartburn. This observation contributes to better understand the pathophysiology of symptoms generated by weakly acidic refluxes, paving the way toward the search for different therapeutic approaches to this peculiar condition of esophageal hypersensitivity. © 2014 International Society for Diseases of the Esophagus.

PP-16 WEAK ACID REFLUX A TRIGGER FOR RECURRENT RESPIRATORY DISEASES IN CHILDREN.

PubMed

Kostovski, Aco; Zdraveska, Nikolina

2015-10-01

The main advantage of multichannel intraluminar impedance (MII) compared with pH monitoring is its ability to detect both acid and non-acid gastroesophageal reflux (GER) and to determine the characteristics of reflux (liquid or gas). To compare the value of pH monitoring and MII for diagnosis of GER in children who present with refractory respiratory symptoms. A prospective study that included 37 patients, aged 4.25 ± 3.15 years, using combined MII-pH monitoring was performed. Patients were referred for investigation because of suspected GER as the etiology of recurrent respiratory diseases, including recurrent obstructive bronchitis, recurrent pneumonia, laryngitis, and chronic cough. We analyzed the percentage of time during which the pH was less than 4, the numeric and percentile values of acid, weak acid, and non-acid reflux episodes, and the values of liquid and mixed reflux. Diagnostic values were determined separately for pH monitoring and MII using Fisher's exact test. Reflux was detected in 31 patients. pH monitoring was positive in 20 patients (% time during which pH <4 was 17.72 ± 12.06) and negative in 17 patients (2.93% ± 1.67). Both pH and MII were positive in 19 patients: in 11 patients, MII was positive and pH was negative, and in 6 patients, both were negative. Fisher's exact test showed significant statistical difference and superiority of MII in diagnosing GER (p = 0.033). Out of 30 patients with MII-positive results, 15 had both acid and weak acid reflux episodes, 3 had only acid reflux, 8 had weak acid reflux, and 3 had non-acid reflux. Sixteen patients had mixed (liquid and gas) reflux, and 14 had both liquid and mixed reflux. This study suggests that significant numbers of GER include weak acid reflux that cannot be detected by pH probes alone. The weak acid reflux could be a trigger for recurrent respiratory symptoms. Combining pH with MII monitoring is a valuable diagnostic method for diagnosing GER in children.

Computer simulation of two electrophoretic columns coupled for isoelectric focusing in simple buffers

NASA Technical Reports Server (NTRS)

Tsai, Amos; Mosher, Richard A.; Bier, Milan

1986-01-01

Computer simulation is used to analyze a system of two electrophoretic columns coupled by mixing the anolyte of one with the catholyte of the other. A mathematical model is presented which is used to predict the pH gradients formed by monovalent buffers in this system, when the currents in the columns are unequal. In the column with the higher current a pH gradient is created which increases from anode to cathode and is potentially useful for isoelectric focusing. The breadth of this gradient is dependent upon the ratio of the currents. The function of the second column is the compensation of buffer migration which occurs in the first column, thereby maintaining constant electrolyte composition. The effects of buffer pKs and mobilities are evaluated.

Effects of acid rain on grapevines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forsline, P.L.; Musselman, R.C.; Dee, R.J.

1983-01-01

Mature vineyard-growing Concord grapevines (Vitis labrusca, Bailey) were sprayed with simulated acid rain solutions ranging from pH 2.5 to pH 5.5 both as acute treatments at anthesis and chronically throughout the season in 1980 and 1981. In 1981, eight additional varieties were also treated with simulated acid rain solutions at pH 2.75 and pH 3.25. With Concord in 1981, few foliar lesions on leaves were visible at pH 2.75. In contrast, many leaf lesions with decreased fruit soluble solids in the absence of acid rain leaf lesions at pH>2.5 remains unclear. Acute sprays (pH 2.75) at anthesis reduced pollen germinationmore » in four grape cultivars. However, fruit set was reduced in only one of these. Only the cultivars de Chaunac and Ives had reduced berry soluble solids with chronic weekly sprays at pH 2.75. Reduction in soluble solids was not associated with increased oxidant stipple (ozone injury) in Concord and de Chaunac cultivars, but this association was observed in Ives. There was no evidence that acid rain in combination with ozone increased oxidant stipple as occurs when ozone and SO/sub 2/ are combined. Grape yields were not influenced by acid rain treatments. There was no evidence that acid rain at ambient pH levels had negative effects on grape production or fruit quality.« less

Ethylene glycol-linked amino acid diester prodrugs of oleanolic acid for PepT1-mediated transport: synthesis, intestinal permeability and pharmacokinetics.

PubMed

Cao, Feng; Jia, Jinghao; Yin, Zhi; Gao, Yahan; Sha, Lei; Lai, Yisheng; Ping, Qineng; Zhang, Yihua

2012-08-06

The purposes of this study were to expand the structure of parent drugs selected for peptide transporter 1 (PepT1)-targeted ester prodrug design and to improve oral bioavailability of oleanolic acid (OA), a Biopharmaceutics Classification System (BCS) class IV drug. Through an ethoxy linker the carboxylic acid group of OA was conjugated with the carboxylic acid group of different amino acid promoieties to form six diester prodrugs. The effective permeability (P(eff)) of prodrugs was screened by in situ rat single-pass intestinal perfusion (SPIP) model in two buffers with different pH (6.0 and 7.4) as PepT1 employs a proton-gradient as the driving force. Compared to OA, 2.5-fold, 2.3-fold, 2.2-fold, 2.1-fold, and 1.9-fold enhancement of P(eff) in buffer with pH 6.0 was observed for L-Phe ester (5c), L-Val ester (5a), L-Lys ester (5e), D-Phe ester (5d), and D-Val ester (5b), respectively. Furthermore, P(eff) of 5a, 5c, 5d and 5e in pH 6.0 was significantly higher than that in pH 7.4 (p < 0.01), respectively. These results showed that the H(+) concentration of perfusion solution had great effect on the transport of the prodrugs across intestinal membrane. For the further evaluation of affinity to PepT1, inhibition studies were performed by coperfusing 0.1 mM prodrug with 50 mM glycyl-sarcosine (Gly-Sar, a typical substrate of PepT1). It turned out that the P(eff) of 5a, 5b, 5c and L-Tyr ester (6f) significantly reduced in the presence of Gly-Sar (1.7-fold, 2.2-fold, 1.9-fold, and 1.4-fold, respectively). We supposed that it may be attributed to PepT1 mediated transport of these prodrugs. 5a and 6f were selected as the optimal target prodrugs for oral absorption in vivo. Following intragastric administration of 300 mg/kg (calculated as OA) 5a, 6f and OA in three groups of rats, compared with group OA, Cmax for the group of 5a and 6f was enhanced by 1.56-fold and 1.54-fold, respectively. Fapp of group 5a and 6f was 2.21- and 2.04-fold increased, respectively, indicating that 5a and 6f had better oral absorption than OA. The combined results also suggest that diester prodrugs which conjugated two carboxylic acid groups of proper amino acid promoieties and parent drug through a linker can be used for PepT1-targeted prodrug design. With this strategy, oral bioavailability of OA in rats could be improved significantly.

Characterization of a recombinant flocculent Saccharomyces cerevisiae strain that co-ferments glucose and xylose: II. influence of pH and acetic acid on ethanol production.

PubMed

Matsushika, Akinori; Sawayama, Shigeki

2012-12-01

The inhibitory effects of pH and acetic acid on the co-fermentation of glucose and xylose in complex medium by recombinant flocculent Saccharomyces cerevisiae MA-R4 were evaluated. In the absence of acetic acid, the fermentation performance of strain MA-R4 was similar between pH 4.0-6.0, but was negatively affected at pH 2.5. The addition of acetic acid to batch cultures resulted in negligible inhibition of several fermentation parameters at pH 6.0, whereas the interactive inhibition of pH and acetic acid on the maximum cell and ethanol concentrations, and rates of sugar consumption and ethanol production were observed at pH levels below 5.4. The inhibitory effect of acetic acid was particularly marked for the consumption rate of xylose, as compared with that of glucose. With increasing initial acetic acid concentration, the ethanol yield slightly increased at pH 5.4 and 6.0, but decreased at pH values lower than 4.7. Notably, ethanol production was nearly completely inhibited under low pH (4.0) and high acetic acid (150-200 mM) conditions. Together, these results indicate that the inhibitory effects of acetic acid and pH on ethanol fermentation by MA-R4 are highly synergistic, although the inhibition can be reduced by increasing the medium pH.

NMR structure of navel orangeworm moth pheromone-binding protein (AtraPBP1): implications for pH-sensitive pheromone detection.

PubMed

Xu, Xianzhong; Xu, Wei; Rayo, Josep; Ishida, Yuko; Leal, Walter S; Ames, James B

2010-02-23

The navel orangeworm, Amyelois transitella (Walker), is an agricultural insect pest that can be controlled by disrupting male-female communication with sex pheromones, a technique known as mating disruption. Insect pheromone-binding proteins (PBPs) provide fast transport of hydrophobic pheromones through the aqueous sensillar lymph and promote sensitive delivery of pheromones to receptors. Here we present the three-dimensional structure of a PBP from A. transitella (AtraPBP1) in solution at pH 4.5 determined by nuclear magnetic resonance (NMR) spectroscopy. Pulsed-field gradient NMR diffusion experiments, multiangle light scattering, and (15)N NMR relaxation analysis indicate that AtraPBP1 forms a stable monomer in solution at pH 4.5 in contrast to forming mostly dimers at pH 7. The NMR structure of AtraPBP1 at pH 4.5 contains seven alpha-helices (alpha1, L8-L23; alpha2, D27-F36; alpha3, R46-V62; alpha4, A73-M78; alpha5, D84-S100; alpha6, R107-L125; alpha7, M131-E141) that adopt an overall main-chain fold similar to that of PBPs found in Antheraea polyphemus and Bombyx mori. The AtraPBP1 structure is stabilized by three disulfide bonds formed by C19/C54, C50/C108, and C97/C117 and salt bridges formed by H69/E60, H70/E57, H80/E132, H95/E141, and H123/D40. All five His residues are cationic at pH 4.5, whereas H80 and H95 become neutral at pH 7.0. The C-terminal helix (alpha7) contains hydrophobic residues (M131, V133, V134, V135, V138, L139, and A140) that contact conserved residues (W37, L59, A73, F76, A77, I94, V111, and V115) suggested to interact with bound pheromone. Our NMR studies reveal that acid-induced formation of the C-terminal helix at pH 4.5 is triggered by a histidine protonation switch that promotes rapid release of bound pheromone under acidic conditions.

Protective Role of Acidic pH-Activated Chloride Channel in Severe Acidosis-Induced Contraction from the Aorta of Spontaneously Hypertensive Rats

PubMed Central

Ma, Zhiyong; Qi, Jia; Fu, Zhijie; Ling, Mingying; Li, Li; Zhang, Yun

2013-01-01

Severe acidic pH-activated chloride channel (ICl,acid) has been found in various mammalian cells. In the present study, we investigate whether this channel participates in reactions of the thoracic aorta to severe acidosis and whether it plays a role in hypertension. We measured isometric contraction in thoracic aorta rings from spontaneously hypertensive rats (SHRs) and normotensive Wistar rats. Severe acidosis induced contractions of both endothelium-intact and -denuded thoracic aorta rings. In Wistar rats, contractions did not differ at pH 6.4, 5.4 and 4.4. However, in SHRs, contractions were higher at pH 5.4 or 4.4 than pH 6.4, with no difference between contractions at pH 5.4 and 4.4. Nifedipine, ICl,acid blockers 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and 4,4′-diisothiocyanatostilbene-2, 2′-disulfonic acid (DIDS) inhibited severe acidosis-induced contraction of aortas at different pH levels. When blocking ICl,acid, the remnant contraction was greater at pH 4.4 than pH 5.4 and 6.4 for both SHRs and Wistar rats. With nifedipine, the remnant contraction was greatly reduced at pH 4.4 as compared with at pH 6.4 and 5.4. With NPPB or DIDS, the ratio of remnant contractions at pH 4.4 and 5.4 (R4.4/5.4) was lower for SHRs than Wistar rats (all <1). However, with nifedipine, the R4.4/5.4 was higher for SHRs than Wistar rats (both >1). Furthermore, patch clamp recordings of ICl,acid and intracellular Ca2+ measurements in smooth muscle cells confirmed these findings. ICl,acid may protect arteries against excess vasoconstriction under extremely acidic extracellular conditions. This protective effect may be decreased in hypertension. PMID:23580361

Acidic pH sensing in the bacterial cytoplasm is required for Salmonella virulence.

PubMed

Choi, Jeongjoon; Groisman, Eduardo A

2016-09-01

pH regulates gene expression, biochemical activities and cellular behaviors. A mildly acidic pH activates the master virulence regulatory system PhoP/PhoQ in the facultative intracellular pathogen Salmonella enterica serovar Typhimurium. The sensor PhoQ harbors an extracytoplasmic domain implicated in signal sensing, and a cytoplasmic domain controlling activation of the regulator PhoP. We now report that, surprisingly, a decrease in Salmonella's own cytoplasmic pH induces transcription of PhoP-activated genes even when the extracytoplasmic pH remains neutral. Amino acid substitutions in PhoQ's cytoplasmic domain hindered activation by acidic pH and attenuated virulence in mice, but did not abolish activation by low Mg(2+) or the antimicrobial peptide C18G. Conversely, removal of PhoQ's extracytoplasmic domains prevented the response to the latter PhoQ-activating signals but not to acidic pH. PhoP-dependent genes were minimally induced by acidic pH in the non-pathogenic species Salmonella bongori but were activated by low Mg(2+) and C18G as in pathogenic S. enterica. Our findings indicate that the sensor PhoQ enables S. enterica to respond to both host- and bacterial-derived signals that alter its cytoplasmic pH. © 2016 John Wiley & Sons Ltd.

Fast high-throughput method for the determination of acidity constants by capillary electrophoresis: I. Monoprotic weak acids and bases.

PubMed

Fuguet, Elisabet; Ràfols, Clara; Bosch, Elisabeth; Rosés, Martí

2009-04-24

A new and fast method to determine acidity constants of monoprotic weak acids and bases by capillary zone electrophoresis based on the use of an internal standard (compound of similar nature and acidity constant as the analyte) has been developed. This method requires only two electrophoretic runs for the determination of an acidity constant: a first one at a pH where both analyte and internal standard are totally ionized, and a second one at another pH where both are partially ionized. Furthermore, the method is not pH dependent, so an accurate measure of the pH of the buffer solutions is not needed. The acidity constants of several phenols and amines have been measured using internal standards of known pK(a), obtaining a mean deviation of 0.05 pH units compared to the literature values.

Effects of pH adjustment and sodium ions on sour taste intensity of organic acids

USDA-ARS?s Scientific Manuscript database

Protonated organic acid species have been shown to be the primary stimuli responsible for sour taste of organic acids. However, we have observed that sour taste may be modulated when the pH of acid solutions is raised using sodium hydroxide. Objectives were to evaluate the effect of pH adjustment on...

Stability of Tranexamic Acid after 12-Week Storage at Temperatures from -20 deg C to 50 deg C

DTIC Science & Technology

2013-07-01

PRELIMINARY REPORTS STABILITY OF TRANEXAMIC ACID AFTER 12-WEEK STORAGE AT TEMPERATURES FROM –20◦C TO 50◦C Rodolfo de Guzman, Jr., MT, I. Amy...Polykratis, BS, Jill L. Sondeen, PhD, Daniel N. Darlington, PhD, Andrew P. Cap, MD, PhD, Michael A. Dubick, PhD ABSTRACT Background. Tranexamic acid (TXA) is... tranexamic acid ; temperature stability; HPLC; thromboelastography; storage PREHOSPITAL EMERGENCY CARE 2013;17:394–400 BACKGROUND Hemorrhage is the leading

Morphology and structure of polymer layers protecting dental enamel against erosion.

PubMed

Beyer, Markus; Reichert, Jörg; Sigusch, Bernd W; Watts, David C; Jandt, Klaus D

2012-10-01

Human dental erosion caused by acids is a major factor for tooth decay. Adding polymers to acidic soft drinks is one important approach to reduce human dental erosion caused by acids. The aim of this study was to investigate the thickness and the structure of polymer layers adsorbed in vitro on human dental enamel from polymer modified citric acid solutions. The polymers propylene glycol alginate (PGA), highly esterified pectin (HP) and gum arabic (GA) were used to prepare polymer modified citric acids solutions (PMCAS, pH 3.3). With these PMCAS, enamel samples were treated for 30, 60 and 120s respectively to deposit polymer layers on the enamel surface. Profilometer scratches on the enamel surface were used to estimate the thickness of the polymer layers via atomic force microscopy (AFM). The composition of the deposited polymer layers was investigated with X-ray photoelectron spectroscopy (XPS). In addition the polymer-enamel interaction was investigated with zeta-potential measurements and scanning electron microscopy (SEM). It has been shown that the profilometer scratch depth on the enamel with deposited polymers was in the range of 10nm (30s treatment time) up to 25nm (120s treatment time). Compared to this, the unmodified CAS-treated surface showed a greater scratch depth: from nearly 30nm (30s treatment time) up to 60nm (120s treatment time). Based on XPS measurements, scanning electron microscopy (SEM) and zeta-potential measurements, a model was hypothesized which describes the layer deposited on the enamel surface as consisting of two opposing gradients of polymer molecules and hydroxyapatite (HA) particles. In this study, the structure and composition of polymer layers deposited on in vitro dental enamel during treatment with polymer modified citric acid solutions were investigated. Observations are consistent with a layer consisting of two opposing gradients of hydroxyapatite particles and polymer molecules. This leads to reduced erosive effects of citric acid solutions on dental enamel surfaces. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Rapid determination of the various native forms of vitamin B6 and B2 in cow's milk using ultra-high performance liquid chromatography.

PubMed

Schmidt, A; Schreiner, M G; Mayer, H K

2017-06-02

As the formation of pyridoxal phosphate, the active cofactor of vitamin B 6 , is dependent on riboflavin 5-phosphate, we propose a fast and simple ultra-high performance liquid chromatography method for the simultaneous determination of the native B 6 vitamers pyridoxal, pyridoxine, pyridoxamine, their mono phosphorus esters and 4-pyridoxic acid as well as vitamin B 2 as riboflavin and its phosphorus ester riboflavin 5-phosphate in milk. Separation was achieved under 6.0min by reversed-phase and pH gradient elution. Sample preparation was optimized regarding various acids and pH levels. Changes in those parameters led to significant deviations of sample matrix breakdown efficiency. The optimized method was then validated regarding specificity, accuracy, precision, linearity, range, detection and quantification limits. As the method performed satisfactory, is was used to study commercial liquid cow's milk (n=31), regarding effects of the employed preservation technique (pasteurization, extended shelf-life, ultra-high temperature) on the composition and content of B 6 and B 2 vitamers. In cow's milk, vitamin B 6 mostly consists of pyridoxal and its phosphate ester, with pyridoxal phosphate being the bulk component. The catabolite of the vitamin B 6 metabolism, 4-pyridoxic acid was present in significant amounts in all studied samples, with up to 2.69μmolL -1 . Vitamin B 2 was present as riboflavin and its phosphate ester up to 12.86μmolL -1 . Copyright © 2017 Elsevier B.V. All rights reserved.

Internal pH regulation facilitates in situ long-term acclimation of massive corals to end-of-century carbon dioxide conditions.

PubMed

Wall, M; Fietzke, J; Schmidt, G M; Fink, A; Hofmann, L C; de Beer, D; Fabricius, K E

2016-08-01

The resilience of tropical corals to ocean acidification depends on their ability to regulate the pH within their calcifying fluid (pHcf). Recent work suggests pHcf homeostasis under short-term exposure to pCO2 conditions predicted for 2100, but it is still unclear if pHcf homeostasis can be maintained throughout a corals lifetime. At CO2 seeps in Papua New Guinea, massive Porites corals have grown along a natural seawater pH gradient for decades. This natural gradient, ranging from pH 8.1-7.4, provides an ideal platform to determine corals' pHcf (using boron isotopes). Porites maintained a similar pHcf (~8.24) at both a control (pH 8.1) and seep-influenced site (pH 7.9). Internal pHcf was slightly reduced (8.12) at seawater pH 7.6, and decreased to 7.94 at a site with a seawater pH of 7.4. A growth response model based on pHcf mirrors the observed distribution patterns of this species in the field. We suggest Porites has the capacity to acclimate after long-time exposure to end-of-century reduced seawater pH conditions and that strong control over pHcf represents a key mechanism to persist in future oceans. Only beyond end-of-century pCO2 conditions do they face their current physiological limit of pH homeostasis and pHcf begins to decrease.

Comparing the acidities of aqueous, frozen, and freeze-dried phosphate buffers: Is there a "pH memory" effect?

PubMed

Vetráková, Ľubica; Vykoukal, Vít; Heger, Dominik

2017-09-15

The concept of "pH memory" has been established in the literature for the correlation between the pH of a pre-lyophilization solution and the ionization state of freeze-dried powder (lyophile). In this paper, the concept of "pH memory" is explored for the system of an aqueous solution, a frozen solution, and a lyophile. Sodium and potassium phosphate buffers in the pH range of 5-9 were frozen and lyophilized with sulfonephthalein indicators as acidity probes, and their Hammett acidity functions were compared to the initial pH of the aqueous solution. The results show that the acidities of the lyophiles are somewhat changed compared to the initial pHs, but the acidities in the frozen state differ more substantially. The Hammett acidity functions of the frozen buffers were found to be markedly dissimilar from the initial pH, especially in the sodium phosphate frozen at 233K, where an increase in the initial pH led to a decrease in the Hammett acidity function of the frozen state at a certain pH range. The large acidification observed after freezing the sodium phosphate buffer was not detected in the lyophiles after the sample had been dried; the phenomenon is explained considering the formed crystals analyzed by X-ray powder diffraction. The results suggest that monitoring the final acidity of a lyophile is not sufficient to predict all the acidity changes throughout the whole lyophilization process. The importance of well-controlled freezing and lyophilization conditions follows from the results of the research. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of feeding on luminal pH and morphology of the gastroesophageal junction of snakes.

PubMed

Bessler, Scott M; Secor, Stephen M

2012-10-01

At the gastroesophageal junction, most vertebrates possess a functional lower esophageal sphincter (LES) which may serve to regulate the passage of liquids and food into the stomach and prevent the reflux of gastric contents into the esophagus. Snakes seemingly lack an LES and consume meals large enough to extend anteriorly from the stomach into the esophagus thereby providing the opportunity for the reflux of gastric juices. To explore whether snakes experience or can prevent gastric reflux, we examined post-feeding changes of luminal pH of the distal esophagus and stomach, the fine scale luminal pH profile at the gastroesophageal junction, and the morphology of the gastroesophageal junction for the Burmese python (Python molurus), the African brown house snake (Lamprophis fuliginosus), and the diamondback water snake (Nerodia rhombifer). For each species fasted, there was no distension of the gastroesophageal junction and only modest changes in luminal pH from the distal esophagus into the stomach. Feeding resulted in marked distension and changes in tissue morphology of the gastroesophageal junction. Simultaneously, there was a significant decrease in luminal pH of the distal esophagus for pythons and house snakes, and for all three species a steep gradient in luminal pH decreasing across a 3-cm span from the distal edge of the esophagus into the proximal edge of the stomach. The moderate acidification of the distal most portion of the esophagus for pythons and house snakes suggests that there is some anterior movement of gastric juices across the gastroesophageal junction. Given that this modest reflux of gastric fluid is localized to the most distal region of the esophagus, snakes are apparently able to prevent and protect against acid reflux in the absence of a functional LES. Copyright © 2012 Elsevier GmbH. All rights reserved.

Ocean warming and acidification synergistically increase coral mortality

PubMed Central

Prada, F.; Caroselli, E.; Mengoli, S.; Brizi, L.; Fantazzini, P.; Capaccioni, B.; Pasquini, L.; Fabricius, K. E.; Dubinsky, Z.; Falini, G.; Goffredo, S.

2017-01-01

Organisms that accumulate calcium carbonate structures are particularly vulnerable to ocean warming (OW) and ocean acidification (OA), potentially reducing the socioeconomic benefits of ecosystems reliant on these taxa. Since rising atmospheric CO2 is responsible for global warming and increasing ocean acidity, to correctly predict how OW and OA will affect marine organisms, their possible interactive effects must be assessed. Here we investigate, in the field, the combined temperature (range: 16–26 °C) and acidification (range: pHTS 8.1–7.4) effects on mortality and growth of Mediterranean coral species transplanted, in different seasonal periods, along a natural pH gradient generated by a CO2 vent. We show a synergistic adverse effect on mortality rates (up to 60%), for solitary and colonial, symbiotic and asymbiotic corals, suggesting that high seawater temperatures may have increased their metabolic rates which, in conjunction with decreasing pH, could have led to rapid deterioration of cellular processes and performance. The net calcification rate of the symbiotic species was not affected by decreasing pH, regardless of temperature, while in the two asymbiotic species it was negatively affected by increasing acidification and temperature, suggesting that symbiotic corals may be more tolerant to increasing warming and acidifying conditions compared to asymbiotic ones. PMID:28102293

Cytoplasmic pH Response to Acid Stress in Individual Cells of Escherichia coli and Bacillus subtilis Observed by Fluorescence Ratio Imaging Microscopy

PubMed Central

Martinez, Keith A.; Kitko, Ryan D.; Mershon, J. Patrick; Adcox, Haley E.; Malek, Kotiba A.; Berkmen, Melanie B.

2012-01-01

The ability of Escherichia coli and Bacillus subtilis to regulate their cytoplasmic pH is well studied in cell suspensions but is poorly understood in individual adherent cells and biofilms. We observed the cytoplasmic pH of individual cells using ratiometric pHluorin. A standard curve equating the fluorescence ratio with pH was obtained by perfusion at a range of external pH 5.0 to 9.0, with uncouplers that collapse the transmembrane pH difference. Adherent cells were acid stressed by switching the perfusion medium from pH 7.5 to pH 5.5. The E. coli cytoplasmic pH fell to a value that varied among individual cells (range of pH 6.2 to 6.8), but a majority of cells recovered (to pH 7.0 to 7.5) within 2 min. In an E. coli biofilm, cells shifted from pH 7.5 to pH 5.5 failed to recover cytoplasmic pH. Following a smaller shift (from pH 7.5 to pH 6.0), most biofilm cells recovered fully, although the pH decreased further than that of isolated adherent cells, and recovery took longer (7 min or longer). Some biofilm cells began to recover pH and then failed, a response not seen in isolated cells. B. subtilis cells were acid shifted from pH 7.5 to pH 6.0. In B. subtilis, unlike the case with E. coli, cytoplasmic pH showed no “overshoot” but fell to a level that was maintained. This level of cytoplasmic pH post-acid shift varied among individual B. subtilis cells (range of pH, 7.0 to 7.7). Overall, the cytoplasmic pHs of individual bacteria show important variation in the acid stress response, including novel responses in biofilms. PMID:22427503

Cytoplasmic pH response to acid stress in individual cells of Escherichia coli and Bacillus subtilis observed by fluorescence ratio imaging microscopy.

PubMed

Martinez, Keith A; Kitko, Ryan D; Mershon, J Patrick; Adcox, Haley E; Malek, Kotiba A; Berkmen, Melanie B; Slonczewski, Joan L

2012-05-01

The ability of Escherichia coli and Bacillus subtilis to regulate their cytoplasmic pH is well studied in cell suspensions but is poorly understood in individual adherent cells and biofilms. We observed the cytoplasmic pH of individual cells using ratiometric pHluorin. A standard curve equating the fluorescence ratio with pH was obtained by perfusion at a range of external pH 5.0 to 9.0, with uncouplers that collapse the transmembrane pH difference. Adherent cells were acid stressed by switching the perfusion medium from pH 7.5 to pH 5.5. The E. coli cytoplasmic pH fell to a value that varied among individual cells (range of pH 6.2 to 6.8), but a majority of cells recovered (to pH 7.0 to 7.5) within 2 min. In an E. coli biofilm, cells shifted from pH 7.5 to pH 5.5 failed to recover cytoplasmic pH. Following a smaller shift (from pH 7.5 to pH 6.0), most biofilm cells recovered fully, although the pH decreased further than that of isolated adherent cells, and recovery took longer (7 min or longer). Some biofilm cells began to recover pH and then failed, a response not seen in isolated cells. B. subtilis cells were acid shifted from pH 7.5 to pH 6.0. In B. subtilis, unlike the case with E. coli, cytoplasmic pH showed no "overshoot" but fell to a level that was maintained. This level of cytoplasmic pH post-acid shift varied among individual B. subtilis cells (range of pH, 7.0 to 7.7). Overall, the cytoplasmic pHs of individual bacteria show important variation in the acid stress response, including novel responses in biofilms.

Development and validation of a sensitive LC-MS-MS method for the simultaneous determination of multicomponent contents in artificial Calculus Bovis.

PubMed

Peng, Can; Tian, Jixin; Lv, Mengying; Huang, Yin; Tian, Yuan; Zhang, Zunjian

2014-02-01

Artificial Calculus Bovis is a major substitute in clinical treatment for Niuhuang, a widely used, efficacious but rare traditional Chinese medicine. However, its chemical structures and the physicochemical properties of its components are complicated, which causes difficulty in establishing a set of effective and comprehensive methods for its identification and quality control. In this study, a simple, sensitive and reliable liquid chromatography-tandem mass spectrometry method was successfully developed and validated for the simultaneous determination of bilirubin, taurine and major bile acids (including six unconjugated bile acids, two glycine-conjugated bile acids and three taurine-conjugated bile acids) in artificial Calculus Bovis using a Zorbax SB-C18 column with a gradient elution of methanol and 10 mmol/L ammonium acetate in aqueous solution (adjusted to pH 3.0 with formic acid). The mass spectra were obtained in the negative ion mode using dehydrocholic acid as the internal standard. The content of each analyte in artificial Calculus Bovis was determined by monitoring specific ion pairs in the selected reaction monitoring mode. All analytes demonstrated perfect linearity (r(2) > 0.994) in a wide dynamic range, and 10 batches of samples from different sources were further analyzed. This study provided a comprehensive method for the quality control of artificial Calculus Bovis.

Algal Species and Light Microenvironment in a Low-pH, Geothermal Microbial Mat Community

PubMed Central

Ferris, M. J.; Sheehan, K. B.; Kühl, M.; Cooksey, K.; Wigglesworth-Cooksey, B.; Harvey, R.; Henson, J. M.

2005-01-01

Unicellular algae are the predominant microbial mat-forming phototrophs in the extreme environments of acidic geothermal springs. The ecology of these algae is not well known because concepts of species composition are inferred from cultivated isolates and microscopic observations, methods known to provide incomplete and inaccurate assessments of species in situ. We used sequence analysis of 18S rRNA genes PCR amplified from mat samples from different seasons and different temperatures along a thermal gradient to identify algae in an often-studied acidic (pH 2.7) geothermal creek in Yellowstone National Park. Fiber-optic microprobes were used to show that light for algal photosynthesis is attenuated to <1% over the 1-mm surface interval of the mat. Three algal sequences were detected, and each was present year-round. A Cyanidioschyzon merolae sequence was predominant at temperatures of ≥49°C. A Chlorella protothecoides var. acidicola sequence and a Paradoxia multisita-like sequence were predominant at temperatures of ≤39°C. PMID:16269755

Method for loading lipid like vesicles with drugs of other chemicals

DOEpatents

Mehlhorn, R.J.

1998-06-09

A method for accumulating drugs or other chemicals within synthetic, lipid-like vesicles by means of a pH gradient imposed on the vesicles just prior to use is described. The method is suited for accumulating molecules with basic or acid moieties which are permeable to the vesicles membranes in their uncharged form and for molecules that contain charge moieties that are hydrophobic ions and can therefore cross the vesicle membranes in their charged form. The method is advantageous over prior art methods for encapsulating biologically active materials within vesicles in that is achieves very high degrees of loading with simple procedures that are economical and require little technical expertise, furthermore kits which can be stored for prolonged periods prior to use without impairment of the capacity to achieve drug accumulation are described. A related application of the method consists of using this technology to detoxify animals that have been exposed to poisons with basic, weak acid or hydrophobic charge groups within their molecular structures. 2 figs.

Method for loading lipid like vesicles with drugs of other chemicals

DOEpatents

Mehlhorn, Rolf Joachim

1998-01-01

A method for accumulating drugs or other chemicals within synthetic, lipid-like vesicles by means of a pH gradient imposed on the vesicles just prior to use is described. The method is suited for accumulating molecules with basic or acid moieties which are permeable to the vesicles membranes in their uncharged form and for molecules that contain charge moieties that are hydrophobic ions and can therefore cross the vesicle membranes in their charged form. The method is advantageous over prior art methods for encapsulating biologically active materials within vesicles in that is achieves very high degrees of loading with simple procedures that are economical and require little technical expertise, furthermore kits which can be stored for prolonged periods prior to use without impairment of the capacity to achieve drug accumulation are described. A related application of the method consists of using this technology to detoxify animals that have been exposed to poisons with basic, weak acid or hydrophobic charge groups within their molecular structures.

Protonation of key acidic residues is critical for the K+-selectivity of the Na/K pump

PubMed Central

Yu, Haibo; Ratheal, Ian; Artigas, Pablo; Roux, Benoît

2011-01-01

The sodium-potassium (Na/K) pump is a P-type ATPase that generates Na+ and K+ concentration gradients across the cell membrane. For each ATP molecule, the pump extrudes three Na+ and imports two K+ by alternating between outward- and inward-facing conformations that preferentially bind K+ or Na+, respectively. Remarkably, the selective K+ and Na+ binding sites share several residues, and how the pump is able to achieve the selectivity required for the functional cycle is unclear. Here, free energy perturbation molecular dynamics (FEP/MD) simulations based on the crystal structures of the Na/K pump in a K+-loaded state (E2·Pi) reveal that protonation of the high-field acidic side-chains involved in the binding sites is critical to achieve the proper K+ selectivity. This prediction is tested with electrophysiological experiments showing that the selectivity of the E2P state for K+ over Na+ is affected by extracellular pH. PMID:21909093

Algal species and light microenvironment in a low-pH, geothermal microbial mat community.

PubMed

Ferris, M J; Sheehan, K B; Kühl, M; Cooksey, K; Wigglesworth-Cooksey, B; Harvey, R; Henson, J M

2005-11-01

Unicellular algae are the predominant microbial mat-forming phototrophs in the extreme environments of acidic geothermal springs. The ecology of these algae is not well known because concepts of species composition are inferred from cultivated isolates and microscopic observations, methods known to provide incomplete and inaccurate assessments of species in situ. We used sequence analysis of 18S rRNA genes PCR amplified from mat samples from different seasons and different temperatures along a thermal gradient to identify algae in an often-studied acidic (pH 2.7) geothermal creek in Yellowstone National Park. Fiber-optic microprobes were used to show that light for algal photosynthesis is attenuated to < 1% over the 1-mm surface interval of the mat. Three algal sequences were detected, and each was present year-round. A Cyanidioschyzon merolae sequence was predominant at temperatures of > or = 49 degrees C. A Chlorella protothecoides var. acidicola sequence and a Paradoxia multisita-like sequence were predominant at temperatures of < or = 39 degrees C.

Method of detoxifying animal suffering from overdose

DOEpatents

Mehlhorn, Rolf J.

1997-01-01

A method for accumulating drugs or other chemicals within synthetic, lipid-like vesicles by means of a pH gradient imposed on the vesicles just prior to use is described. The method is suited for accumulating molecules with basic or acid moieties which are permeable to the vesicles membranes in their uncharged form and for molecules that contain charge moieties that are hydrophobic ions and can therefore cross the vesicle membranes in their charged form. The method is advantageous over prior art methods for encapsulating biologically active materials within vesicles in that it achieves very high degrees of loading with simple procedures that are economical and require little technical expertise, furthermore kits which can be stored for prolonged periods prior to use without impairment of the capacity to achieve drug accumulation are described. A related application of the method consists of using this technology to detoxify animals that have been exposed to poisons with basic, weak acid or hydrophobic charge groups within their molecular structure.

Net acidity indicates the whole effluent toxicity of pH and dissolved metals in metalliferous saline waters.

PubMed

Degens, Bradley P; Krassoi, Rick; Galvin, Lynette; Reynolds, Brad; Micevska, Tina

2018-05-01

Measurements of potential acidity in water are used to manage aquatic toxicity risks of discharge from acid sulfate soils or acid mine drainage. Net acidity calculated from pH, dissolved metals and alkalinity is a common measurement of potential acidity but the relevance of current risk thresholds to aquatic organisms are unclear. Aquatic toxicity testing was carried out using four halophytic organisms with water from four saline sources in southern Western Australia (3 acidic drains and one alkaline river; 39-40 g TDS/L) where acidity was varied by adjusting pH to 4.5-6.5. The test species were brine shrimps (Artemia salina), locally sourced ostracods (Platycypris baueri), microalgae (Dunaliella salina) and amphipods (Allorchestes compressa). Testing found the EC 10 and IC 10 of net acidity ranged from -7.8 to 10.5 mg CaCO 3 /L with no survival or growth of any species at >47 mg CaCO 3 /L. Reduced net acidity indicated reduced whole effluent toxicity more reliably than increased pH alone with organisms tolerating pH up to 1.1 units lower in the absence of dissolved metals. Variation in toxicity indicated by net acidity was mostly attributed to reduced concentrations of dissolved Al and Fe combined with higher pH and alkalinity and some changes in speciation of Al and Fe with pH. These results indicate that rapid in-field assessments of net acidity in acidic, Al dominated waters may be an indicator of potential acute and sub-chronic impacts on aquatic organisms. Crown Copyright © 2018. Published by Elsevier Ltd. All rights reserved.

Navigational choice between reversal and curve during acidic pH avoidance behavior in Caenorhabditis elegans.

PubMed

Wakabayashi, Tokumitsu; Sakata, Kazumi; Togashi, Takuya; Itoi, Hiroaki; Shinohe, Sayaka; Watanabe, Miwa; Shingai, Ryuzo

2015-11-19

Under experimental conditions, virtually all behaviors of Caenorhabditis elegans are achieved by combinations of simple locomotion, including forward, reversal movement, turning by deep body bending, and gradual shallow turning. To study how worms regulate these locomotion in response to sensory information, acidic pH avoidance behavior was analyzed by using worm tracking system. In the acidic pH avoidance, we characterized two types of behavioral maneuvers that have similar behavioral sequences in chemotaxis and thermotaxis. A stereotypic reversal-turn-forward sequence of reversal avoidance caused an abrupt random reorientation, and a shallow gradual turn in curve avoidance caused non-random reorientation in a less acidic direction to avoid the acidic pH. Our results suggest that these two maneuvers were each triggered by a distinct threshold pH. A simulation study using the two-distinct-threshold model reproduced the avoidance behavior of the real worm, supporting the presence of the threshold. Threshold pH for both reversal and curve avoidance was altered in mutants with reduced or enhanced glutamatergic signaling from acid-sensing neurons. C. elegans employ two behavioral maneuvers, reversal (klinokinesis) and curve (klinotaxis) to avoid acidic pH. Unlike the chemotaxis in C. elegans, reversal and curve avoidances were triggered by absolute pH rather than temporal derivative of stimulus concentration in this behavior. The pH threshold is different between reversal and curve avoidance. Mutant studies suggested that the difference results from a differential amount of glutamate released from ASH and ASK chemosensory neurons.

Methylated purines in urinary stones.

PubMed

Safranow, Krzysztof; Machoy, Zygmunt

2005-08-01

The aim of the study was to measure the content of methylated purines that appear as admixtures in uric acid stones. We analyzed urinary calculi from 48 residents of Western Pomerania who underwent surgery at the urology ward in Szczecin. Stone samples were dissolved in 0.1 mol/L NaOH. Extracts were diluted in 50 mmol/L KH(2)PO(4) and analyzed by reversed-phase HPLC with ultraviolet detection and use of a gradient of methanol concentration and pH. Uric acid was the main component of 9 stones. All 9 showed admixtures of 9 other purine derivatives: endogenous purine breakdown products (xanthine, hypoxanthine, and 2,8-dihydroxyadenine) and exogenous methyl derivatives of uric acid and xanthine (1-, 3-, and 7-methyluric acid; 1,3-dimethyluric acid; and 3- and 7-methylxanthine). Amounts of these purine derivatives ranged from the limit of detection to 12 mg/g of stone weight and showed a strong positive correlation (Spearman rank correlation coefficients, 0.63-0.94) with the uric acid content of the samples. The main methylated purine in the stones was 1-methyluric acid. Urinary purines at concentrations below their saturation limits may coprecipitate in samples supersaturated with uric acid and appear as admixtures in urinary stones. The amount of each purine depends on its average urinary excretion, similarity to the chemical structure of uric acid, and concentration of the latter in the stone. These findings suggest that purines in stones represent a substitutional solid solution with uric acid as solvent. Methylxanthines, which are ubiquitous components of the diet, drugs, and uric acid calculi, may be involved in the pathogenesis of urolithiasis.

Simulating ocean acidification and CO2 leakages from carbon capture and storage to assess the effects of pH reduction on cladoceran Moina mongolica Daday and its progeny.

PubMed

Wang, Zaosheng; Wang, Youshao; Yan, Changzhou

2016-07-01

In order to evaluate the effects of pH reduction in seawater as a result of increasing levels of atmospheric CO2, laboratory-scale experiments simulating the scenarios of ocean acidification (OA) and CO2 leakages of carbon capture and storage (CCS) were performed using the model organism Moina mongolica Daday. The LpH50s calculated in cladoceran toxicity tests showed that M. mongolica exhibited intermediate sensitivity to OA, which varied among species and with ontogeny, when compared with different phyla or classes of marine biota. Survival, reproduction and fecundity of parthenogenetic females were evaluated after 21-day exposures. Results showed that increased acidity significantly reduced the rate of reproduction of M. mongolica resulting in a decreased intrinsic rate of natural increase (rm) across the gradients of pH reduction. The analysis of macromolecule contents in neonates suggested that nutritional status in progeny from all broods were significantly reduced as seawater pH decreased, with increasing magnitude in latter broods, except the contents of protein from two former broods and lipids from the first brood. Our findings clearly showed that for this ecologically and economically important fish species, the negative effects of pH reduction on both "quantity" and "quality" of progeny may have far-reaching implications, providing direct evidence that OA could influence the energetic transfer of marine food web and ecosystem functions in acidified oceans in the future. Copyright © 2016 Elsevier Ltd. All rights reserved.

Reduced Salinity Improves Marine Food Availability With Positive Feedbacks on pH in a Tidally-Dominated Estuary

NASA Astrophysics Data System (ADS)

Lowe, A. T.; Roberts, E. A.; Galloway, A. W. E.

2016-02-01

Coastal regions around the world are changing rapidly, generating many physiological stressors for marine organisms. Food availability, a major factor determining physiological condition of marine organisms, in these systems reflects the influence of biological and environmental factors, and will likely respond dramatically to long-term changes. Using observations of phytoplankton, detritus, and their corresponding fatty acids and stable isotopes of carbon, nitrogen and sulfur, we identified environmental drivers of pelagic food availability and quality along a salinity gradient in a large tidally influenced estuary (San Juan Archipelago, Salish Sea, USA). Variation in chlorophyll a (Chl a), biomarkers and environmental conditions exhibited a similar range at both tidal and seasonal scales, highlighting a tide-related mechanism controlling productivity that is important to consider for long-term monitoring. Multiple parameters of food availability were inversely and non-linearly correlated to salinity, such that availability of high-quality (based on abundance, essential fatty acid concentration and C:N) seston increased below a salinity threshold of 30. The increased marine productivity was associated with increased pH and dissolved oxygen (DO) at lower salinity. Based on this observation we predicted that a decrease of salinity to below the threshold would result in higher Chl a, temperature, DO and pH across a range of temporal and spatial scales, and tested the prediction with a meta-analysis of available data. At all scales, these variables showed significant and consistent increases related to the salinity threshold. This finding provides important context to the increased frequency of below-threshold salinity over the last 71 years in this region, suggesting greater food availability with positive feedbacks on DO and pH. Together, these findings indicate that many of the environmental factors predicted to increase physiological stress to benthic suspension feeders (e.g. decreased salinity) may simultaneously and paradoxically improve conditions for benthic organisms.

Diel behavior of iron and other heavy metals in a mountain stream with acidic to neutral pH: Fisher Creek, Montana, USA

USGS Publications Warehouse

Gammons, C.H.; Nimick, D.A.; Parker, S.R.; Cleasby, T.E.; McCleskey, R. Blaine

2005-01-01

Three simultaneous 24-h samplings at three sites over a downstream pH gradient were conducted to examine diel fluctuations in heavy metal concentrations in Fisher Creek, a small mountain stream draining abandoned mine lands in Montana. Average pH values at the upstream (F1), middle (F2), and downstream (F3) monitoring stations were 3.31, 5.46, and 6.80, respectively. The downstream increase in pH resulted in precipitation of hydrous ferric oxide (HFO) and hydrous aluminum oxide (HAO) on the streambed. At F1 and F2, Fe showed strong diel cycles in dissolved concentration and Fe(II)/Fe(III) ratio; these cycles were attributed to daytime photoreduction of Fe(III) to Fe(II), reoxidation of Fe(II) to Fe(III), and temperature-dependent hydrolysis and precipitation of HFO. At the near-neutral downstream station, no evidence of Fe(III) photoreduction was observed, and suspended particles of HFO dominated the total Fe load. HFO precipitation rates between F2 and F3 were highest in the afternoon, due in part to reoxidation of a midday pulse of Fe2+ formed by photoreduction in the upper, acidic portions of the stream. Dissolved concentrations of Fe(II) and Cu decreased tenfold and 2.4-fold, respectively, during the day at F3. These changes were attributed to sorption onto fresh HFO surfaces. Results of surface complexation modeling showed good agreement between observed and predicted Cu concentrations at F3, but only when adsorption enthalpies were added to the thermodynamic database to take into account diel temperature variations. The field and modeling results illustrate that the degree to which trace metals adsorb onto actively forming HFO is strongly temperature dependent. This study is an example of how diel Fe cycles caused by redox and hydrolysis reactions can induce a diel cycle in a trace metal of toxicological importance in downstream waters. Copyright ?? 2005 Elsevier Ltd.

Acidic extracellular pH neutralizes the autophagy-inhibiting activity of chloroquine: implications for cancer therapies.

PubMed

Pellegrini, Paola; Strambi, Angela; Zipoli, Chiara; Hägg-Olofsson, Maria; Buoncervello, Maria; Linder, Stig; De Milito, Angelo

2014-04-01

Acidic pH is an important feature of tumor microenvironment and a major determinant of tumor progression. We reported that cancer cells upregulate autophagy as a survival mechanism to acidic stress. Inhibition of autophagy by administration of chloroquine (CQ) in combination anticancer therapies is currently evaluated in clinical trials. We observed in 3 different human cancer cell lines cultured at acidic pH that autophagic flux is not blocked by CQ. This was consistent with a complete resistance to CQ toxicity in cells cultured in acidic conditions. Conversely, the autophagy-inhibiting activity of Lys-01, a novel CQ derivative, was still detectable at low pH. The lack of CQ activity was likely dependent on a dramatically reduced cellular uptake at acidic pH. Using cell lines stably adapted to chronic acidosis we could confirm that CQ lack of activity was merely caused by acidic pH. Moreover, unlike CQ, Lys-01 was able to kill low pH-adapted cell lines, although higher concentrations were required as compared with cells cultured at normal pH conditions. Notably, buffering medium pH in low pH-adapted cell lines reverted CQ resistance. In vivo analysis of tumors treated with CQ showed that accumulation of strong LC3 signals was observed only in normoxic areas but not in hypoxic/acidic regions. Our observations suggest that targeting autophagy in the tumor environment by CQ may be limited to well-perfused regions but not achieved in acidic regions, predicting possible limitations in efficacy of CQ in antitumor therapies.

Activity of earthworm in Latosol under simulated acid rain stress.

PubMed

Zhang, Jia-En; Yu, Jiayu; Ouyang, Ying

2015-01-01

Acid rain is still an issue of environmental concerns. This study investigated the impacts of simulated acid rain (SAR) upon earthworm activity from the Latosol (acidic red soil). Laboratory experiment was performed by leaching the soil columns grown with earthworms (Eisenia fetida) at the SAR pH levels ranged from 2.0 to 6.5 over a 34-day period. Results showed that earthworms tended to escape from the soil and eventually died for the SAR at pH = 2.0 as a result of acid toxicity. The catalase activity in the earthworms decreased with the SAR pH levels, whereas the superoxide dismutases activity in the earthworms showed a fluctuate pattern: decreasing from pH 6.5 to 5.0 and increasing from pH 5.0 to 4.0. Results implied that the growth of earthworms was retarded at the SAR pH ≤ 3.0.

The history and character of acid precipitation in eastern North America

Treesearch

Charles V. Cogbill

1976-01-01

The history and present distribution of precipitation acidity in eastern North America is reviewed. Precipitation chemistry from the 1920's indicates heavy ionic deposition, but low acidity (calculated) in Tennessee (pH 7.4) and New York (pH 6.15). However, high acidity was apparently widespread over northeast North America by 1955-56 and measured pH's below...

Determination of Acidity Constants by Gradient Flow-Injection Titration

ERIC Educational Resources Information Center

Conceicao, Antonio C. L.; Minas da Piedade, Manuel E.

2006-01-01

A three-hour laboratory experiment, designed for an advanced undergraduate course in instrumental analysis that illustrates the application of the gradient chamber flow-injection titration (GCFIT) method with spectrophotometric detection to determine acidity constants is presented. The procedure involves the use of an acid-base indicator to obtain…

A comparison of three pH control methods for revealing effects of undissociated butyric acid on specific butanol production rate in batch fermentation of Clostridium acetobutylicum

PubMed Central

2013-01-01

pH control has been essential for butanol production with Clostridium acetobutylicum. However, it is not very clear at what pH level the acid crash will occur, at what pH level butanol production will be dominant, and at what pH level butyric acid production will be prevailing. Furthermore, contradictory results have been reported about required acidic conditions for initiation of solventogenesis. In this study, with the aim of further understanding the role of undissociated butyric acid in butanol production, we investigated the correlation between undissociated butyric acid concentration and specific butanol production rate in batch fermentation of Clostridium acetobutylicum by comparing three pH control approaches: NaOH neutralization (at 12, 24 or 36 h), CaCO3 supplementation (2, 5, or 8 g/l) and NaOAc buffering (pH 4.6, 5.0 or 5.6). By neutralizing the fermentation pH to ~5.0 at different time, we observed that neutralization should take place at the beginning of exponential phase (12 h), and otherwise resulting in lower concentrations of undissociated butyric acid, cell biomass and final butanol. CaCO3 supplementation extended cell growth to 36 h and resulted in higher butyrate yield under 8 g/L of CaCO3. In the NaOAc buffering, the highest specific butanol rate (0.58 h−1) was associated with the highest undissociated butyric acid (1.92 g/L). The linear correlation of the undissociated butyric acid with the specific butanol production rates suggested the undissociated butyric acid could be the major driving force for butanol production. PMID:23294525

A comparison of three pH control methods for revealing effects of undissociated butyric acid on specific butanol production rate in batch fermentation of Clostridium acetobutylicum.

PubMed

Yang, Xuepeng; Tu, Maobing; Xie, Rui; Adhikari, Sushil; Tong, Zhaohui

2013-01-07

pH control has been essential for butanol production with Clostridium acetobutylicum. However, it is not very clear at what pH level the acid crash will occur, at what pH level butanol production will be dominant, and at what pH level butyric acid production will be prevailing. Furthermore, contradictory results have been reported about required acidic conditions for initiation of solventogenesis. In this study, with the aim of further understanding the role of undissociated butyric acid in butanol production, we investigated the correlation between undissociated butyric acid concentration and specific butanol production rate in batch fermentation of Clostridium acetobutylicum by comparing three pH control approaches: NaOH neutralization (at 12, 24 or 36 h), CaCO3 supplementation (2, 5, or 8 g/l) and NaOAc buffering (pH 4.6, 5.0 or 5.6). By neutralizing the fermentation pH to ~5.0 at different time, we observed that neutralization should take place at the beginning of exponential phase (12 h), and otherwise resulting in lower concentrations of undissociated butyric acid, cell biomass and final butanol. CaCO3 supplementation extended cell growth to 36 h and resulted in higher butyrate yield under 8 g/L of CaCO3. In the NaOAc buffering, the highest specific butanol rate (0.58 h-1) was associated with the highest undissociated butyric acid (1.92 g/L). The linear correlation of the undissociated butyric acid with the specific butanol production rates suggested the undissociated butyric acid could be the major driving force for butanol production.

pH imaging of mouse kidneys in vivo using a frequency-dependent paraCEST agent.

PubMed

Wu, Yunkou; Zhang, Shanrong; Soesbe, Todd C; Yu, Jing; Vinogradov, Elena; Lenkinski, Robert E; Sherry, A Dean

2016-06-01

This study explored the feasibility of using a pH responsive paramagnetic chemical exchange saturation transfer (paraCEST) agent to image the pH gradient in kidneys of healthy mice. CEST signals were acquired on an Agilent 9.4 Tesla small animal MRI system using a steady-state gradient echo pulse sequence after a bolus injection of agent. The magnetic field inhomogeneity across each kidney was corrected using the WASSR method and pH maps were calculated by measuring the frequency of water exchange signal arising from the agent. Dynamic CEST studies demonstrated that the agent was readily detectable in kidneys only between 4 to 12 min postinjection. The CEST images showed a higher signal intensity in the pelvis and calyx regions and lower signal intensity in the medulla and cortex regions. The pH maps reflected tissue pH values spanning from 6.0 to 7.5 in kidneys of healthy mice. This study demonstrated that pH maps of the kidney can be imaged in vivo by measuring the pH-dependent chemical shift of a single water exchange CEST peak without prior knowledge of the agent concentration in vivo. The results demonstrate the potential of using a simple frequency-dependent paraCEST agent for mapping tissue pH in vivo. Magn Reson Med 75:2432-2441, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Growth and survival kinetics of Yersinia enterocolitica IP 383 0:9 as affected by equimolar concentrations of undissociated short-chain organic acids.

PubMed

el-Ziney, M G; De Meyer, H; Debevere, J M

1997-03-03

The influence of different organic acids (lactic, acetic, formic and propionic acids) at equimolar concentrations of undissociated acid with pH range of 3.9, 5.8, on the aerobic and anaerobic growth and survival kinetics of the virulent strain of Y. enterocolitica IP 383 0:9, was determined in tryptone soy broth at 4 degrees C. Growth and survival data were analyzed and fitted by a modification of the Whiting and Cygnarowicz-Provost model, using the Minpack software library. Initial generation times, initial specific growth rates, lag time and dead rate were subsequently calculated from the model parameters. The results demonstrate that the inhibitory effects of the acids were divided into two categories dependent upon pH. At high pH (5.8) the order of inhibition was formic acid > acetic acid > propionic acid > lactic acid, whereas at lower pH it became formic acid > lactic acid > acetic acid > propionic acid. The inhibitory effect of lactic acid is enhanced under anaerobic condition. Nevertheless, when the organism was cultured anaerobically, it was shown to be more tolerant to formic and acetic acids. Moreover, these variables (type of organic acid, pH and atmosphere) did not lead to the loss of the virulence plasmid in growing and surviving cells. The mechanism of inhibitory effect for each of the acids are also discussed.

Implications of Deoxygenation and Acidification for Deep Sea Urchins in Southern California

NASA Astrophysics Data System (ADS)

Sato, Kirk Nicholas Suda

Implications of multiple climate drivers for sea urchins were investigated across a spectrum of biological organization ranging from the urchin guild scale, to individual life history traits, to the geochemistry, material properties and porosity of sea urchin calcium carbonate skeletal tests. Using pink fragile sea urchins (Strongylocentrotus fragilis) on the southern California upwelling margin as a model species, links between biological traits and environmental parameters in nature across multiple spatial and temporal scales revealed correlations with dissolved oxygen (DO), pH, and temperature. Temporal trends in sea urchin populations assessed from trawl surveys conducted in southern California over the last 20 years (1994-2013) revealed changes in deep-sea urchin densities and depth distributions that coincide with trends in DO and pH on multidecadal and interdecadal (El Nino Southern Oscillation) time scales. The shallower urchin species ( Lytechinus pictus) decreased in density in the upper 200 m by 80%, and the deeper S. fragilis increased in density by ˜300%, providing the first evidence of habitat compression and expansion in sea urchin populations associated with secular and interdecadal variability in DO and pH. In this context, marketable food quality properties of the roe were compared between S. fragilis and the currently fished California red urchin, Mesocentrotus franciscanus, to assess the feasibility of developing a climate change-tolerant future S. fragilis trap fishery. Although roe color, texture, and resilience were similar between the two species, smaller and softer S. fragilis roe suggest it may only supplement, but not replace M. franciscanus in future fisheries. In comparisons across natural margin depth and climate gradients from 100-1100 m, S. fragilis exhibited reduced gonad production, smaller, weaker and more porous calcified tests in the Oxygen Minimum Zone (DO < 22 mumol kg-1) and pH Minimum Zone (in situ pHTotal <7.57) than those collected from less acidic and more oxygenated shelf and oxygen limiting zones above and the lower OMZ below. Thus S. fragilis may be more vulnerable to crushing predators if low oxygen, low pH OMZs continue to shoal and intensify in the future. This research highlights the utility of quantifying natural variability in species' traits along natural gradients on upwelling margins to improve understanding about potential impacts of changing climate drivers.

Lactic acid fermentation of dahlia tuber starch and waste using Lactobacillus bulgaricus: A comparative study

NASA Astrophysics Data System (ADS)

Praputri, E.; Sundari, E.; Martynis, M.; Agenta, P.

2018-03-01

Lactic acid fermentation of dahlia tuber starch and waste was performed by means of Lactobacillus bulgaricus through enzymatic hydrolysis followed by fermentation process. The effect of pH condition on lactic acid production was investigated during the process. The selected bacteria produced lactic acid after 24 hours of fermentation and the productivity was increase after 24 hours of fermentation. After 120 hours of fermentation, it was found that dahlia tuber starch can produce up to 16.18% of lactic acid, whereas lactic acid produced from dahlia tuber waste was only 0.40% at pH of 4. The lactic acid production increase significantly for pH 3.5 and 4 until 96 hours of fermentation, then slowed down. On the other hand, for pH 4.5 the lactic acid production increase until 48 hours of fermentation and then slowed down. The identification of fermentation product indicated that the lactic acid produced in this study was 16.20%, acidic, yellow and cloudy with pH 3.4 – 4.2. The density of lactic acid produced ranged between 1.21 to 1.25 gr/ml.

Enhanced extraction of butyric acid under high-pressure CO2 conditions to integrate chemical catalysis for value-added chemicals and biofuels.

PubMed

Chun, Jaesung; Choi, Okkyoung; Sang, Byoung-In

2018-01-01

Extractive fermentation with the removal of carboxylic acid requires low pH conditions because acids are better partitioned into the solvent phase at low pH values. However, this requirement conflicts with the optimal near-neutral pH conditions for microbial growth. CO 2 pressurization was used, instead of the addition of chemicals, to decrease pH for the extraction of butyric acid, a fermentation product of Clostridium tyrobutyricum , and butyl butyrate was selected as an extractant. CO 2 pressurization (50 bar) improved the extraction efficiency of butyric acid from a solution at pH 6, yielding a distribution coefficient ( D ) 0.42. In situ removal of butyric acid during fermentation increased the production of butyric acid by up to 4.10 g/L h, an almost twofold increase over control without the use of an extraction process. In situ extraction of butyric acid using temporal CO 2 pressurization may be applied to an integrated downstream catalytic process for upgrading butyric acid to value-added chemicals in an organic solvent.

Mode of de-esterification of alkaline and acidic pectin methyl esterases at different pH conditions.

PubMed

Duvetter, Thomas; Fraeye, Ilse; Sila, Daniel N; Verlent, Isabel; Smout, Chantal; Hendrickx, Marc; Van Loey, Ann

2006-10-04

Highly esterified citrus pectin was de-esterified at pH 4.5 and 8.0 by a fungal pectin methyl esterase (PME) that was shown to have an acidic isoelectric pH (pI) and an acidic pH optimum and by a plant PME that was characterized by an alkaline pI and an alkaline pH optimum. Interchain and intrachain de-esterification patterns were studied by digestion of the pectin products with endo-polygalacturonase and subsequent analysis using size exclusion and anion-exchange chromatography. No effect of pH was observed on the de-esterification mode of either of the two enzymes. Acidic, fungal PME converted pectin according to a multiple-chain mechanism, with a limited degree of multiple attack at the intrachain level, both at pH 4.5 and at pH 8.0. A multiple-attack mechanism, with a high degree of multiple attack, was more appropriate to describe the action mode of alkaline, plant PME, both at pH 4.5 and at pH 8.0.

Wood ash amendment to biogas reactors as an alternative to landfilling? A preliminary study on changes in process chemistry and biology.

PubMed

Podmirseg, Sabine M; Seewald, Martin S A; Knapp, Brigitte A; Bouzid, Ourdia; Biderre-Petit, Corinne; Peyret, Pierre; Insam, Heribert

2013-08-01

Wood ash addition to biogas plants represents an alternative to commonly used landfilling by improving the reactor performance, raising the pH and alleviating potential limits of trace elements. This study is the first on the effects of wood ash on reactor conditions and microbial communities in cattle slurry-based biogas reactors. General process parameters [temperature, pH, electrical conductivity, ammonia, volatile fatty acids, carbon/nitrogen (C/N), total solids (TS), volatile solids, and gas quantity and quality] were monitored along with molecular analyses of methanogens by polymerase chain reaction- denaturing gradient gel electrophoresis and modern microarrays (archaea and bacteria). A prompt pH rise was observed, as was an increase in C/N ratio and volatile fatty acids. Biogas production was inhibited, but recovered to even higher production rates and methane concentration after single amendment. High sulphur levels in the wood ash generated hydrogen sulphide and potentially hampered methanogenesis. Methanosarcina was the most dominant methanogen in all reactors; however, diversity was higher in ash-amended reactors. Bacterial groups like Firmicutes, Proteobacteria and Acidobacteria were favoured, which could improve the hydrolytic efficiency of the reactors. We recommend constant monitoring of the chemical composition of the used wood ash and suggest that ash amendment is adequate if added to the substrate at a rate low enough to allow adaptation of the microbiota (e.g. 0.25 g g(-1) TS). It could further help to enrich digestate with important nutrients, for example phosphorus, calcium and magnesium, but further experiments are required for the evaluation of wood ash concentrations that are tolerable for anaerobic digestion.

Acidophilic sulfur disproportionation

NASA Astrophysics Data System (ADS)

Hardisty, Dalton S.; Olyphant, Greg A.; Bell, Jonathan B.; Johnson, Adam P.; Pratt, Lisa M.

2013-07-01

Bacterial disproportionation of elemental sulfur (S0) is a well-studied metabolism and is not previously reported to occur at pH values less than 4.5. In this study, a sediment core from an abandoned-coal-mine-waste deposit in Southwest Indiana revealed sulfur isotope fractionations between S0 and pyrite (Δ34Ses-py) of up to -35‰, inferred to indicate intense recycling of S0 via bacterial disproportionation and sulfide oxidation. Additionally, the chemistry of seasonally collected pore-water profiles were found to vary, with pore-water pH ranging from 2.2 to 3.8 and observed seasonal redox shifts expressed as abrupt transitions from Fe(III) to Fe(II) dominated conditions, often controlled by fluctuating water table depths. S0 is a common product during the oxidation of pyrite, a process known to generate acidic waters during weathering and production of acid mine drainage. The H2S product of S0 disproportionation, fractionated by up to -8.6‰, is rapidly oxidized to S0 near redox gradients via reaction with Fe(III) allowing for the accumulation of isotopically light S0 that can then become subject to further sulfur disproportionation. A mass-balance model for S0 incorporating pyrite oxidation, S0 disproportionation, and S0 oxidation readily explains the range of observed Δ34Ses-py and emphasizes the necessity of seasonally varying pyrite weathering and metabolic rates, as indicated by the pore water chemistry. The findings of this research suggest that S0 disproportionation is potentially a common microbial process at a pH < 4.5 and can create large sulfur isotope fractionations, even in the absence of sulfate reduction.

Sulfate-chloride exchange by lobster hepatopancreas is regulated by pH-sensitive modifier sites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cattey, M.A.; Ahearn, G.A.; Gerencser, G.A.

1991-03-15

{sup 35}SO{sub 4}{sup 2{minus}} uptake by Atlantic lobster (Homarus americanus) hepatopancreatic epithelial brush border membrane vesicles (BBMV) was stimulated by internal Cl{sup {minus}}, but not internal HCO{sub 3}{sup {minus}}, or external Na{sup +}. Sulfate-chloride exchange was stimulated by inside positive, and inhibited by inside negative, trans-membrane K diffusion potentials. {sup 35}SO{sub 4}{sup 2{minus}}-Cl{sup {minus}} exchange was strongly inhibited by 4,4{prime} diisothiocyanostilbene-2,2{prime}-disulfonic acid (DIDS), 4-acetamido-4{prime}-isotheocynaostilbene-2,2{prime}-disulfonic acid, (SITS), and thiosulfate. Chloride, bicarbonate, furosamide, and bumetanide slightly, yet significantly, cis-inhibited {sup 35}SO{sub 4}{sup 2{minus}}-Cl{sup {minus}} exchange. Altering bilateral pH from 8.0 to 5.4 stimulated {sup 35}SO{sub 4}{sup 2{minus}}-Cl{sup {minus}} exchange when vesicles weremore » loaded with Cl{sup {minus}}, but reduced bilateral pH alone or the presence of pH gradients did not affect {sup 35}SO{sub 4}{sup 2{minus}} transport in the absence of internal Cl{sup {minus}}. {sup 36}Cl uptake into SO{sub 4}{sup 2{minus}}-loaded BBMV was stimulated by an internal negative membrane potential and inhibited when the interior was electrically positive. A model is proposed which suggests that SO{sub 4}{sup 2{minus}}-Cl{sup {minus}} exchange is regulated by internal and external pH-sensitive modifier sites on the anion antiporter and by coupling to the electrogenic 2 Na{sup +}/1 H{sup +} antiporter and by coupling to the electrogenic 2 Na{sup +}/1 H{sup +} antiporter on the same membrane.« less

Human Neuronal Calcium Sensor-1 Protein Avoids Histidine Residues To Decrease pH Sensitivity.

PubMed

Gong, Yehong; Zhu, Yuzhen; Zou, Yu; Ma, Buyong; Nussinov, Ruth; Zhang, Qingwen

2017-01-26

pH is highly regulated in mammalian central nervous systems. Neuronal calcium sensor-1 (NCS-1) can interact with numerous target proteins. Compared to that in the NCS-1 protein of Caenorhabditis elegans, evolution has avoided the placement of histidine residues at positions 102 and 83 in the NCS-1 protein of humans and Xenopus laevis, possibly to decrease the conformational sensitivity to pH gradients in synaptic processes. We used all-atom molecular dynamics simulations to investigate the effects of amino acid substitutions between species on human NCS-1 by substituting Arg102 and Ser83 for histidine at neutral (R102H and S83H) and acidic pHs (R102H p and S83H p ). Our cumulative 5 μs simulations revealed that the R102H mutation slightly increases the structural flexibility of loop L2 and the R102H p mutation decreases protein stability. Community network analysis illustrates that the R102H and S83H mutations weaken the interdomain and strengthen the intradomain communications. Secondary structure contents in the S83H and S83H p mutants are similar to those in the wild type, whereas the global structural stabilities and salt-bridge probabilities decrease. This study highlights the conformational dynamics effects of the R102H and S83H mutations on the local structural flexibility and global stability of NCS-1, whereas protonated histidine decreases the stability of NCS-1. Thus, histidines at positions 102 and 83 may not be compatible with the function of NCS-1 whether in the neutral or protonated state.

In vitro metabolism of radiolabeled carbohydrates by protective cecal anaerobic bacteria.

PubMed

Hume, M E; Beier, R C; Hinton, A; Scanlan, C M; Corrier, D E; Peterson, D V; DeLoach, J R

1993-12-01

Cecal anaerobic bacteria from adult broilers were cultured in media containing .25% glucose or .25% lactose. Media also contained either [14C]-labeled lactose, glucose, galactose, or lactic acid as metabolic tracers. Cultures were analyzed at 4, 8, and 12 h for pH, radiolabeled and unlabeled volatile fatty acids, and lactic acid. The pH values of cultures containing .25% lactose were significantly (P < .05) higher than the pH values of cultures containing .25% glucose. Lactose cultures reached their lowest pH more slowly than glucose cultures. Concentrations of unlabeled volatile fatty acids increased and lactic acid decreased during incubation of the cultures. Radiolabeled sugars and lactic acid were more readily metabolized to volatile fatty acids in media containing lactose than in media containing glucose. The preferred metabolism of [14C]substrates, independent of media carbohydrate, was in the following order: lactic acid > galactose, lactose > glucose. The volatile fatty acids in which radiolabel was most concentrated were acetic acid, propionic acid, or butyric acid.

A pH-Sensing Optode for Mapping Spatiotemporal Gradients in 3D Paper-Based Cell Cultures.

PubMed

Kenney, Rachael M; Boyce, Matthew W; Whitman, Nathan A; Kromhout, Brenden P; Lockett, Matthew R

2018-02-06

Paper-based cultures are an emerging platform for preparing 3D tissue-like structures. Chemical gradients can be imposed upon these cultures, generating microenvironments similar to those found in poorly vascularized tumors. There is increasing evidence that the tumor microenvironment is responsible for promoting drug resistance and increased invasiveness. Acidosis, or the acidification of the extracellular space, is particularly important in promoting these aggressive cancer phenotypes. To better understand how cells respond to acidosis there is a need for 3D culture platforms that not only model relevant disease states but also contain sensors capable of quantifying small molecules in the extracellular environment. In this work, we describe pH-sensing optodes that are capable of generating high spatial and temporal resolution maps of pH gradients in paper-based cultures. This sensor was fabricated by suspending microparticles containing pH-sensitive (fluorescein) and pH-insensitive (diphenylanthracene) dyes in a polyurethane hydrogel, which was then coated onto a transparent film. The pH-sensing films have a fast response time, are reversible, stable in long-term culture environments, have minimal photobleaching, and are not cytotoxic. These films have a pK a of 7.61 ± 0.04 and are sensitive in the pH range corresponding to normal and tumorigenic tissues. With these optodes, we measured the spatiotemporal evolution of pH gradients in paper-based tumor models.

Acidic pH shock induced overproduction of ε-poly-L-lysine in fed-batch fermentation by Streptomyces sp. M-Z18 from agro-industrial by-products.

PubMed

Ren, Xi-Dong; Chen, Xu-Sheng; Zeng, Xin; Wang, Liang; Tang, Lei; Mao, Zhong-Gui

2015-06-01

ε-Poly-L-lysine (ε-PL) is produced by Streptomyces as a secondary metabolite with wide industrial applications, but its production still needs to be further enhanced. Environmental stress is an important approach for the promotion of secondary metabolites production by Streptomyces. In this study, the effect of acidic pH shock on enhancing ε-PL production by Streptomyces sp. M-Z18 was investigated in a 5-L fermenter. Based on the evaluation of acidic pH shock on mycelia metabolic activity and shock parameters optimization, an integrated pH-shock strategy was developed as follows: pre-acid-shock adaption at pH 5.0 to alleviate the damage caused by the followed pH shock, and then acidic pH shock at 3.0 for 12 h (including pH decline from 4.0 to 3.0) to positively regulate mycelia metabolic activity, finally restoring pH to 4.0 to provide optimal condition for ε-PL production. After 192 h of fed-batch fermentation, the maximum ε-PL production and productivity reached 54.70 g/L and 6.84 g/L/day, respectively, which were 52.50 % higher than those of control without pH shock. These results demonstrated that acidic pH shock is an efficient approach for improving ε-PL production. The information obtained should be useful for ε-PL production by other Streptomyces.

Biophysical feedbacks mediate carbonate chemistry in coastal ecosystems across spatiotemporal gradients.

PubMed

Silbiger, Nyssa J; Sorte, Cascade J B

2018-01-15

Ocean acidification (OA) projections are primarily based on open ocean environments, despite the ecological importance of coastal systems in which carbonate dynamics are fundamentally different. Using temperate tide pools as a natural laboratory, we quantified the relative contribution of community composition, ecosystem metabolism, and physical attributes to spatiotemporal variability in carbonate chemistry. We found that biological processes were the primary drivers of local pH conditions. Specifically, non-encrusting producer-dominated systems had the highest and most variable pH environments and the highest production rates, patterns that were consistent across sites spanning 11° of latitude and encompassing multiple gradients of natural variability. Furthermore, we demonstrated a biophysical feedback loop in which net community production increased pH, leading to higher net ecosystem calcification. Extreme spatiotemporal variability in pH is, thus, both impacting and driven by biological processes, indicating that shifts in community composition and ecosystem metabolism are poised to locally buffer or intensify the effects of OA.

Functional characteristics of pyruvate transport in Phycomyces blakesleeanus.

PubMed

Marcos, J A; de Arriaga, D; Busto, F; Soler, J

1998-12-01

A saturable and accumulative transport system for pyruvate has been detected in Phycomyces blakesleeanus NRRL 1555(-) mycelium. It was strongly inhibited by alpha-cyano-4-hydroxycinnamate. l-Lactate and acetate were competitive inhibitors of pyruvate transport. The initial pyruvate uptake velocity and accumulation ratio was dependent on the external pH. The Vmax of transport greatly decreased with increasing pH, whereas the affinity of the carrier for pyruvate was not affected. The pyruvate transport system mediated its homologous exchange, which was essentially pH independent, and efflux, which increased with increasing external pH. The uptake of pyruvate was energy dependent and was strongly inhibited by inhibitors of oxidative phosphorylation and of the formation of proton gradients. Glucose counteracted the inhibitory effect of the pyruvate transport produced by inhibitors of mitochondrial ATP synthesis. Our results are consistent with a pyruvate/proton cotransport in P. blakesleeanus probably driven by an electrochemical gradient of H+ generated by a plasma membrane H+-ATPase. Copyright 1998 Academic Press.

Sensing and adaptation to low pH mediated by inducible amino acid decarboxylases in Salmonella.

PubMed

Viala, Julie P M; Méresse, Stéphane; Pocachard, Bérengère; Guilhon, Aude-Agnès; Aussel, Laurent; Barras, Frédéric

2011-01-01

During the course of infection, Salmonella enterica serovar Typhimurium must successively survive the harsh acid stress of the stomach and multiply into a mild acidic compartment within macrophages. Inducible amino acid decarboxylases are known to promote adaptation to acidic environments. Three low pH inducible amino acid decarboxylases were annotated in the genome of S. Typhimurium, AdiA, CadA and SpeF, which are specific for arginine, lysine and ornithine, respectively. In this study, we characterized and compared the contributions of those enzymes in response to acidic challenges. Individual mutants as well as a strain deleted for the three genes were tested for their ability (i) to survive an extreme acid shock, (ii) to grow at mild acidic pH and (iii) to infect the mouse animal model. We showed that the lysine decarboxylase CadA had the broadest range of activity since it both had the capacity to promote survival at pH 2.3 and growth at pH 4.5. The arginine decarboxylase AdiA was the most performant in protecting S. Typhimurium from a shock at pH 2.3 and the ornithine decarboxylase SpeF conferred the best growth advantage under anaerobiosis conditions at pH 4.5. We developed a GFP-based gene reporter to monitor the pH of the environment as perceived by S. Typhimurium. Results showed that activities of the lysine and ornithine decarboxylases at mild acidic pH did modify the local surrounding of S. Typhimurium both in culture medium and in macrophages. Finally, we tested the contribution of decarboxylases to virulence and found that these enzymes were dispensable for S. Typhimurium virulence during systemic infection. In the light of this result, we examined the genomes of Salmonella spp. normally responsible of systemic infection and observed that the genes encoding these enzymes were not well conserved, supporting the idea that these enzymes may be not required during systemic infection.

Waste activated sludge hydrolysis and short-chain fatty acids accumulation under mesophilic and thermophilic conditions: effect of pH.

PubMed

Zhang, Peng; Chen, Yinguang; Zhou, Qi

2009-08-01

The effect of pH (4.0-11.0) on waste activated sludge (WAS) hydrolysis and short-chain fatty acids (SCFAs) accumulation under mesophilic and thermophilic conditions were investigated. The WAS hydrolysis increased markedly in thermophilic fermentation compared to mesophilic fermentation at any pH investigated. The hydrolysis at alkaline pHs (8.0-11.0) was greater than that at acidic pHs, but both of the acidic and alkaline hydrolysis was higher than that pH uncontrolled under either mesophilic or thermophilic conditions. No matter in mesophilic or thermophilic fermentation, the accumulation of SCFAs at alkaline pHs was greater than at acidic or uncontrolled pHs. The optimum SCFAs accumulation was 0.298g COD/g volatile suspended solids (VSS) with mesophilic fermentation, and 0.368 with thermophilic fermentation, which was observed respectively at pH 9.0 and fermentation time 5 d and pH 8.0 and time 9 d. The maximum SCFAs productions reported in this study were much greater than that in the literature. The analysis of the SCFAs composition showed that acetic acid was the prevalent acid in the accumulated SCFAs at any pH investigated under both temperatures, followed by propionic acid and n-valeric acid. Nevertheless, during the entire mesophilic and thermophilic fermentation the activity of methanogens was inhibited severely at acid or alkaline pHs, and the highest methane concentration was obtained at pH 7.0 in most cases. The studies of carbon mass balance showed that during WAS fermentation the reduction of VSS decreased with the increase of pH, and the thermophilic VSS reduction was greater than the mesophilic one. Further investigation indicated that most of the reduced VSS was converted to soluble protein and carbohydrate and SCFAs in two fermentations systems, while little formed methane and carbon dioxide.

Rise in the pH of an unfrozen solution in ice due to the presence of NaCl and promotion of decomposition of gallic acids owing to a change in the pH.

PubMed

Takenaka, Norimichi; Tanaka, Masayuki; Okitsu, Kenji; Bandow, Hiroshi

2006-09-14

Oxidative decomposition of gallic acid occurs in alkaline solutions but hardly arises in acidic solutions. We have found that the addition of sodium chloride promotes the decomposition of gallic acid caused by freezing even under neutral and acidic conditions. Even at pH 4.5, gallic acid was decomposed by freezing in the presence of NaCl; however, in the absence of NaCl, it was hardly decomposed by freezing at pH lower than 7. Chloride ions are more easily incorporated in ice than sodium ions when the NaCl solution is frozen. The unfrozen solution in ice becomes positively charged, and as a result, protons transfer from the unfrozen solution to the ice. We measured the pH in the unfrozen solution which coexists with single-crystal ice formed from a 5 mmol dm(-3) NaCl solution and determined the pH to be 8.6 at equilibrium with CO(2) of 380 ppm or 11.3 in the absence of CO(2) compared to pH 5.6 in the original solution. From the model calculation performed for gallic acid solution in the presence of 5 mmol dm(-3) NaCl, it can be estimated that the amount of OH(-) transferred from the ice to the solution corresponds to 1.26 x 10(-5) mol dm(-3). The amount of OH(-) transferred is concentrated into the unfrozen solution and affects the pH of the unfrozen solution. Therefore, the pH in an unfrozen gallic acid solution in ice becomes alkaline, and the decomposition of gallic acid proceeds. It is expected that other base-catalyzed reactions in weakly acidic solutions also proceed by freezing in the presence of NaCl without the need for any alkaline reagents.

Pro-hormone Secretogranin II Regulates Dense Core Secretory Granule Biogenesis in Catecholaminergic Cells*

PubMed Central

Courel, Maïté; Soler-Jover, Alex; Rodriguez-Flores, Juan L.; Mahata, Sushil K.; Elias, Salah; Montero-Hadjadje, Maïté; Anouar, Youssef; Giuly, Richard J.; O'Connor, Daniel T.; Taupenot, Laurent

2010-01-01

Processes underlying the formation of dense core secretory granules (DCGs) of neuroendocrine cells are poorly understood. Here, we present evidence that DCG biogenesis is dependent on the secretory protein secretogranin (Sg) II, a member of the granin family of pro-hormone cargo of DCGs in neuroendocrine cells. Depletion of SgII expression in PC12 cells leads to a decrease in both the number and size of DCGs and impairs DCG trafficking of other regulated hormones. Expression of SgII fusion proteins in a secretory-deficient PC12 variant rescues a regulated secretory pathway. SgII-containing dense core vesicles share morphological and physical properties with bona fide DCGs, are competent for regulated exocytosis, and maintain an acidic luminal pH through the V-type H+-translocating ATPase. The granulogenic activity of SgII requires a pH gradient along this secretory pathway. We conclude that SgII is a critical factor for the regulation of DCG biogenesis in neuroendocrine cells, mediating the formation of functional DCGs via its pH-dependent aggregation at the trans-Golgi network. PMID:20061385

Generation of a proton motive force by histidine decarboxylation and electrogenic histidine/histamine antiport in Lactobacillus buchneri.

PubMed

Molenaar, D; Bosscher, J S; ten Brink, B; Driessen, A J; Konings, W N

1993-05-01

Lactobacillus buchneri ST2A vigorously decarboxylates histidine to the biogenic amine histamine, which is excreted into the medium. Cells grown in the presence of histidine generate both a transmembrane pH gradient, inside alkaline, and an electrical potential (delta psi), inside negative, upon addition of histidine. Studies of the mechanism of histidine uptake and histamine excretion in membrane vesicles and proteoliposomes devoid of cytosolic histidine decarboxylase activity demonstrate that histidine uptake, histamine efflux, and histidine/histamine exchange are electrogenic processes. Histidine/histamine exchange is much faster than the unidirectional fluxes of these substrates, is inhibited by an inside-negative delta psi and is stimulated by an inside positive delta psi. These data suggest that the generation of metabolic energy from histidine decarboxylation results from an electrogenic histidine/histamine exchange and indirect proton extrusion due to the combined action of the decarboxylase and carrier-mediated exchange. The abundance of amino acid decarboxylation reactions among bacteria suggests that this mechanism of metabolic energy generation and/or pH regulation is widespread.

Pro-hormone secretogranin II regulates dense core secretory granule biogenesis in catecholaminergic cells.

PubMed

Courel, Maïté; Soler-Jover, Alex; Rodriguez-Flores, Juan L; Mahata, Sushil K; Elias, Salah; Montero-Hadjadje, Maïté; Anouar, Youssef; Giuly, Richard J; O'Connor, Daniel T; Taupenot, Laurent

2010-03-26

Processes underlying the formation of dense core secretory granules (DCGs) of neuroendocrine cells are poorly understood. Here, we present evidence that DCG biogenesis is dependent on the secretory protein secretogranin (Sg) II, a member of the granin family of pro-hormone cargo of DCGs in neuroendocrine cells. Depletion of SgII expression in PC12 cells leads to a decrease in both the number and size of DCGs and impairs DCG trafficking of other regulated hormones. Expression of SgII fusion proteins in a secretory-deficient PC12 variant rescues a regulated secretory pathway. SgII-containing dense core vesicles share morphological and physical properties with bona fide DCGs, are competent for regulated exocytosis, and maintain an acidic luminal pH through the V-type H(+)-translocating ATPase. The granulogenic activity of SgII requires a pH gradient along this secretory pathway. We conclude that SgII is a critical factor for the regulation of DCG biogenesis in neuroendocrine cells, mediating the formation of functional DCGs via its pH-dependent aggregation at the trans-Golgi network.

Response of citrus and other selected plant species to simulated HCL - acid rain

NASA Technical Reports Server (NTRS)

Knott, W. M.; Heagle, A. S.

1980-01-01

Mature valencia orange trees were sprayed with hydrochloric acid solutions (pH 7.8, 2.0, 1.0, and 0.5) in the field at the full bloom stage and at one month after fruit set. Potted valencia orange and dwarf citrus trees, four species of plants native to Merritt Island, and four agronomic species were exposed to various pH levels of simulated acid rain under controlled conditions. The acid rain was generated from dilutions of hydrochloric acid solutions or by passing water through an exhaust generated by burning solid rocket fuel. The plants were injured severely at pH levels below 1.0, but showed only slight injury at pH levels of 2.0 and above. Threshold injury levels were between 2.0 and 3.0 pH. The sensitivity of the different plant species to acid solutions was similar. Foliar injury symptoms were representative of acid rain including necrosis of young tissue, isolated necrotic spots or patches, and leaf abscission. Mature valencia orange trees sprayed with concentrations of 1.0 pH and 0.5 pH in the field had reduced fruit yields for two harvests after the treatment. All experimental trees were back to full productivity by the third harvest after treatment.

Effect of medium pH on chemical selectivity of oxalic acid biosynthesis by Aspergillus niger W78C in submerged batch cultures with sucrose as a carbon source.

PubMed

Walaszczyk, Ewa; Podgórski, Waldemar; Janczar-Smuga, Małgorzata; Dymarska, Ewelina

2018-01-01

The pH of the medium is the key environmental parameter of chemical selectivity of oxalic acid biosynthesis by Aspergillus niger . The activity of the enzyme oxaloacetate hydrolase, which is responsible for decomposition of oxaloacetate to oxalate and acetate inside the cell of the fungus, is highest at pH 6. In the present study, the influence of pH in the range of 3-7 on oxalic acid secretion by A. niger W78C from sucrose was investigated. The highest oxalic acid concentration, 64.3 g dm -3 , was reached in the medium with pH 6. The chemical selectivity of the process was 58.6% because of the presence of citric and gluconic acids in the cultivation broth in the amount of 15.3 and 30.2 g dm -3 , respectively. Both an increase and a decrease of medium pH caused a decrease of oxalic acid concentration. The obtained results confirm that pH 6 of the carbohydrate medium is appropriate for oxalic acid synthesis by A. niger , but the chemical selectivity of the process described in this paper was high in comparison to values reported previously in the literature.

Recovery of carboxylic acids produced during dark fermentation of food waste by adsorption on Amberlite IRA-67 and activated carbon.

PubMed

Yousuf, Ahasa; Bonk, Fabian; Bastidas-Oyanedel, Juan-Rodrigo; Schmidt, Jens Ejbye

2016-10-01

Amberlite IRA-67 and activated carbon were tested as promising candidates for carboxylic acid recovery by adsorption. Dark fermentation was performed without pH control and without addition of external inoculum at 37°C in batch mode. Lactic, acetic and butyric acids, were obtained, after 7days of fermentation. The maximum acid removal, 74%, from the Amberlite IRA-67 and 63% from activated carbon was obtained from clarified fermentation broth using 200gadsorbent/Lbroth at pH 3.3. The pH has significant effect and pH below the carboxylic acids pKa showed to be beneficial for both the adsorbents. The un-controlled pH fermentation creates acidic environment, aiding in adsorption by eliminating use of chemicals for efficient removal. This study proposes simple and easy valorization of waste to valuable chemicals. Copyright © 2016 Elsevier Ltd. All rights reserved.

Detecting Sulfuric and Nitric Acid Rain Stresses on Quercus glauca through Hyperspectral Responses

PubMed Central

Wang, Shanqian; Zhang, Xiuying; Ma, Yuandan; Li, Xinhui; Zhang, Xiaomin; Liu, Lei

2018-01-01

Acid rain, which has become one of the most severe global environmental issues, is detrimental to plant growth. However, effective methods for monitoring plant responses to acid rain stress are currently lacking. The hyperspectral technique provides a cost-effective and nondestructive way to diagnose acid rain stresses. Taking a widely distributed species (Quercus glauca) in Southern China as an example, this study aims to monitor the hyperspectral responses of Q. glauca to simulated sulfuric acid rain (SAR) and nitric acid rain (NAR). A total of 15 periods of leaf hyperspectral data under four pH levels of SAR and NAR were obtained during the experiment. The results showed that hyperspectral information could be used to distinguish plant responses under acid rain stress. An index (green peak area index, GPAI) was proposed to indicate acid rain stresses, based on the significantly variations in the region of 500–660 nm. Light acid rain (pH 4.5 SAR and NAR) promoted Q. glauca growth relative to the control groups (pH 5.6 SAR and NAR); moderate acid rain (pH 3.0 SAR) firstly promoted and then inhibited plant growth, while pH 3.0 NAR showed mild inhibitory effects during the experiment; and heavy acid rain (pH 2.0) significantly inhibited plant growth. Compared with NAR, SAR induced more serious damages to Q. glauca. These results could help monitor acid rain stress on plants on a regional scale using remote sensing techniques. PMID:29522488

Detecting Sulfuric and Nitric Acid Rain Stresses on Quercus glauca through Hyperspectral Responses.

PubMed

Wang, Shanqian; Zhang, Xiuying; Ma, Yuandan; Li, Xinhui; Cheng, Min; Zhang, Xiaomin; Liu, Lei

2018-03-09

Acid rain, which has become one of the most severe global environmental issues, is detrimental to plant growth. However, effective methods for monitoring plant responses to acid rain stress are currently lacking. The hyperspectral technique provides a cost-effective and nondestructive way to diagnose acid rain stresses. Taking a widely distributed species ( Quercus glauca ) in Southern China as an example, this study aims to monitor the hyperspectral responses of Q. glauca to simulated sulfuric acid rain (SAR) and nitric acid rain (NAR). A total of 15 periods of leaf hyperspectral data under four pH levels of SAR and NAR were obtained during the experiment. The results showed that hyperspectral information could be used to distinguish plant responses under acid rain stress. An index (green peak area index, GPAI) was proposed to indicate acid rain stresses, based on the significantly variations in the region of 500-660 nm. Light acid rain (pH 4.5 SAR and NAR) promoted Q. glauca growth relative to the control groups (pH 5.6 SAR and NAR); moderate acid rain (pH 3.0 SAR) firstly promoted and then inhibited plant growth, while pH 3.0 NAR showed mild inhibitory effects during the experiment; and heavy acid rain (pH 2.0) significantly inhibited plant growth. Compared with NAR, SAR induced more serious damages to Q. glauca . These results could help monitor acid rain stress on plants on a regional scale using remote sensing techniques.

[Effects of simulated acid rain on water physiological characteristics of Myrica rubra seedlings].

PubMed

Yaho, Zhao-bin; Jiang, Hong; Yu, Shu-quan; Lu, Mei-juan

2011-08-01

Taking the seedlings of typical subtropical economic tree species Myrica rubra in Zhejiang Province as test materials, a pot experiment was conducted to study their water physiological characteristics under effects of simulated acid rain (pH 2.5 and pH 4.0), with water (pH 5.6) as the control. Season, year, and acid rain all had significant effects on the photosynthetic rate (Pn). Among the treatments, the Pn had a greater difference in summer than in spring and autumn, and was higher in treatment acid rain (pH 4.0). Season, year, acid rain, and the interactions of season and year and of the three factors had significant effects on the stomata conductance (Gs), and also, the Gs had a greater difference among the treatments in summer than in spring and autumn. Acid rain had inhibitory effect on Gs. Season, year, acid rain, and the interactions of season and year and of season and acid rain affected the transpiration rate (Tr) significantly. Same as Pn and Gs, the Tr had a greater difference among the treatments in summer than in spring and autumn. Acid rain (pH 2.5) had the strongest inhibitory effect on Tr. Acid rain and the interactions of season and year and of season and acid rain had significant effects on the water use efficiency (WUE), and acid rain (pH 2.5) had definitely positive effect on the WUE.

Thermal resistance parameters of acid-adapted and unadapted Escherichia coli O157:H7 in apple-carrot juice blends: effect of organic acids and pH.

PubMed

Usaga, Jessie; Worobo, Randy W; Padilla-Zakour, Olga I

2014-04-01

Numerous outbreaks involving fresh juices contaminated with Escherichia coli O157:H7 have occurred in the United States and around the world, raising concern for the safety of these products. Until now, only a few studies regarding the thermal tolerance of this pathogen in acidic juices over a wide range of pH values have been published. Therefore, the effect of varying the pH with different organic acids on the thermal inactivation of non-acid-adapted and acid-adapted E. coli O157:H7 (strain C7927) was determined. The decimal reduction times (D-values) and the change in temperature required for the thermal destruction curve to traverse 1 log cycle (z-values) were calculated for non-acid-adapted E. coli in an apple-carrot juice blend (80:20) adjusted to three pH values (3.3, 3.5, and 3.7) by the addition of lactic, malic, or acetic acid and at a pH of 4.5 adjusted with NaOH. Thermal parameters were also determined for acid-adapted cells in juices acidified with malic acid. The effect of the soluble solids content on the thermal tolerance was studied in samples with a pH of 3.7 at 9.4 to 11.5 °Brix. The D-values were determined at 54, 56, and 58 °C, and trials were conducted in triplicate. Non-acid-adapted E. coli exhibited the highest thermal tolerance at pH 4.5 (D-value at 54 °C [D54 °C] of 20 ± 4 min and z-value of 6.2 °C), although on average, the D-values increased significantly (P < 0.01) due to acid adaptation. In acidified juices, the highest tolerance was observed in acid-adapted E. coli in samples adjusted to pH 3.7 with malic acid (D54 °C of 9 ± 2 min and z-value of 5.4 °C) and the lowest in unadapted E. coli at pH 3.3 acidified with acetic acid (D58 °C of 0.03 ± 0.01 min and z-value of 10.4 °C). For juices acidified to the same endpoint pH with different acids, E. coli was found to be more tolerant in samples acidified with malic acid, followed by lactic and acetic acids. Increasing the soluble solids content from 9.4 to 11.5 °Brix showed no significant effect on the thermal tolerance of E. coli (P > 0.01). The data from this study will be useful for establishing critical limits for safe thermal processing of pH-controlled juices and similar products.

[Effects of simulated acid rain on respiration rate of cropland system with different soil pH].

PubMed

Zhu, Xue-zhu; Zhang, Gao-chuan; Li, Hui

2009-10-15

To evaluate the effects of acid rain on the respiration rate of cropland system, an outdoor pot experiment was conducted with paddy soils of pH 5.48 (S1), pH 6.70 (S1) and pH 8.18 (S3) during the 2005-2007 wheat-growing seasons. The cropland system was exposed to acid rain by spraying the wheat foliage and irrigating the soil with simulated rainwater of T1 (pH 6.0), T2 (pH 6.0, ionic concentration was twice as rainwater T1), and T3 (pH 4.4, ionic concentration was twice as rainwater T1), respectively. The static opaque chamber-gas chromatograph method was used to measure CO2 fluxes from cropland system. The results showed that acid rain affected the respiration rate of cropland system through crop plant, and the cropland system could adapt to acid rain. Acid rainwater significantly increased the average respiration rate in alkaline soil (S3) cropland system, while it had no significant effects on the average respiration rate in neutral soil (S2) and acidic soil (S1) cropland systems. During 2005-2006, after the alkaline soil cropland system was treated with rainwater T3, the average respiration rate was 23.6% and 27.6% higher than that of alkaline soil cropland system treated with rainwater T1 and T2, respectively. During March to April, the respiration rate was enhanced with the increase of rainwater ionic concentration, while it was dropped with the decrease of rainwater pH value in acidic soil cropland system. It was demonstrated that soil pH and crop plant played important roles on the respiration rate of cropland system.

Improving clarity and stability of skim milk powder dispersions by dissociation of casein micelles at pH 11.0 and acidification with citric acid.

PubMed

Pan, Kang; Zhong, Qixin

2013-09-25

Casein micelles in milk cause turbidity and have poor stability at acidic conditions. In this study, skim milk powder dispersions were alkalized to pH 10.0 or 11.0, corresponding to reduced particle mass. In the following acidification with hydrochloric or citric acid, the re-formation of casein particles was observed. The combination of treatment at pH 11.0 and acidification with citric acid resulted in dispersions with the lowest turbidity and smallest particles, which enabled translucent dispersions at pH 5.5-7.0, corresponding to discrete nanoparticles. The concentration of ionic calcium was lower when acidified with citric acid than hydrochloric acid, corresponding to smaller particles with less negative zeta potential. The pH 11.0 treatment followed by acidification with citric acid also resulted in smaller particles than the simple chelating effects (directly implementing sodium citrate). The produced casein nanoparticles with reduced dimensions can be used for beverage and other novel applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forsline, P.L.; Musselman, R.C.; Kender, W.J.

Mature 'McIntosh', 'Empire', and 'Golden Delicious' apple trees (Malus domestica Borkh.) were sprayed with simulated acid rain solutions in the pH range of 2.5 to 5.5 at full bloom in 1980 and in 1981. In 1981, weekly sprays were applied at pH 2.75 and pH 3.25. Necrotic lesions developed on apple petals at pH 2.5 with slight injury appearing at pH 3.0 and pH 3.5. Apple foliage had no acid rain lesions at any of the pH levels tested. Pollen germination was reduced at ph 2.5 in 'Empire'. Slight fruit set reduction at pH 2.5 was observed in 'McIntosh'. Themore » incidence of russetting on 'Golden Delicious' fruits was ameliorated by the presence of rain-exclusion chambers but was not affected by acid rain. With season-long sprays at pH 2.75, there was a slight delay in maturity and lower weight of 'McIntosh' apples. Even at the lowest pH levels no detrimental effects of simulated acid rain were found on apple tree productivity and fruit quality when measured as fruit set, seed number per fruit, and fruit size and appearance.« less

Acidic pH retards the fibrillization of human Islet Amyloid Polypeptide due to electrostatic repulsion of histidines.

PubMed

Li, Yang; Xu, Weixin; Mu, Yuguang; Zhang, John Z H

2013-08-07

The human Islet Amyloid Polypeptide (hIAPP) is the major constituent of amyloid deposits in pancreatic islets of type-II diabetes. IAPP is secreted together with insulin from the acidic secretory granules at a low pH of approximately 5.5 to the extracellular environment at a neutral pH. The increased accumulation of extracellular hIAPP in diabetes indicates that changes in pH may promote amyloid formation. To gain insights and underlying mechanisms of the pH effect on hIAPP fibrillogenesis, all-atom molecular dynamics simulations in explicit solvent model were performed to study the structural properties of five hIAPP protofibrillar oligomers, under acidic and neutral pH, respectively. In consistent with experimental findings, simulation results show that acidic pH is not conducive to the structural stability of these oligomers. This provides a direct evidence for a recent experiment [L. Khemtemourian, E. Domenech, J. P. F. Doux, M. C. Koorengevel, and J. A. Killian, J. Am. Chem. Soc. 133, 15598 (2011)], which suggests that acidic pH inhibits the fibril formation of hIAPP. In addition, a complementary coarse-grained simulation shows the repulsive electrostatic interactions among charged His18 residues slow down the dimerization process of hIAPP by twofold. Besides, our all-atom simulations reveal acidic pH mainly affects the local structure around residue His18 by destroying the surrounding hydrogen-bonding network, due to the repulsive interactions between protonated interchain His18 residues at acidic pH. It is also disclosed that the local interactions nearby His18 operating between adjacent β-strands trigger the structural transition, which gives hints to the experimental findings that the rate of hIAPP fibril formation and the morphologies of the fibrillar structures are strongly pH-dependent.

Uric acid nephrolithiasis: An update.

PubMed

Cicerello, Elisa

2018-04-01

Uric acid nephrolithiasis appears to increase in prevalence. While a relationship between uric acid stones and low urinary pH has been for long known, additional association with various metabolic conditions and pathophysiological basis has recently been elucidated. Some conditions such as diabetes and metabolic syndrome disease, excessive dietary intake, and increased endogenous uric acid production and/or defect in ammoniagenesis are associated with low urinary pH. In addition, the phenomenon of global warming could result in an increase in areas with greater climate risk for uric acid stone formation. There are three therapeutic steps to be taken for management of uric acid stones: identification of urinary pH profiles, assessment of urinary volume status, and identification of disorders leading to excessive uric acid production. However, the most important factor for uric acid stone formation is acid urinary pH, which is a prerequisite for uric acid precipitation. This article reviews recent insights into the pathophysiology of uric acid stones and their management.

Continuous-flow electrophoresis: Membrane-associated deviations of buffer pH and conductivity

NASA Technical Reports Server (NTRS)

Smolka, A. J. K.; Mcguire, J. K.

1978-01-01

The deviations in buffer pH and conductivity which occur near the electrode membranes in continuous-flow electrophoresis were studied in the Beckman charged particle electrophoresis system and the Hanning FF-5 preparative electrophoresis instrument. The nature of the membranes separating the electrode compartments from the electrophoresis chamber, the electric field strength, and the flow rate of electrophoresis buffer were all found to influence the formation of the pH and conductivity gradients. Variations in electrode buffer flow rate and the time of electrophoresis were less important. The results obtained supported the hypothesis that a combination of Donnan membrane effects and the differing ionic mobilities in the electrophoresis buffer was responsible for the formation of the gradients. The significance of the results for the design and stable operation of continuous-flow electrophoresis apparatus was discussed.

Evaluation and application of a mixed-mode chromatographic stationary phase in two-dimensional liquid chromatography for the separation of traditional Chinese medicine.

PubMed

Wei, Zhishen; Fu, Qing; Cai, Jianfeng; Huan, Liyun; Zhao, Jianchao; Shi, Hui; Jin, Yu; Liang, Xinmiao

2016-06-01

In this study, two mixed-mode chromatography stationary phases (C8SAX and C8SCX) were evaluated and used to establish a two-dimensional liquid chromatography system for the separation of traditional Chinese medicine. The chromatographic properties of the mixed-mode columns were systematically evaluated by comparing with other three columns of C8, strong anion exchanger, and strong cation exchanger. The result showed that C8SAX and C8SCX had a mixed-mode retention mechanism including electrostatic interaction and hydrophobic interaction. Especially, they were suitable for separating acidic and/or basic compounds and their separation selectivities could be easily adjusted by changing pH value. Then, several off-line 2D-LC systems based on the C8SAX in the first dimension and C8SAX, C8SCX, or C8 columns in the second dimension were developed to analyze a traditional Chinese medicine-Uncaria rhynchophylla. The two-dimensional liquid chromatography system of C8SAX (pH 3.0) × C8SAX (pH 6.0) exhibited the most effective peak distribution. Finally, fractions of U. rhynchophylla prepared from the first dimension were successfully separated on the C8SAX column with a gradient pH. Thus, the mixed-mode stationary phase could provide a platform to separate the traditional Chinese medicine in practical applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Patterns of Limnohabitans Microdiversity across a Large Set of Freshwater Habitats as Revealed by Reverse Line Blot Hybridization

PubMed Central

Jezbera, Jan; Jezberová, Jitka; Kasalický, Vojtěch; Šimek, Karel; Hahn, Martin W.

2013-01-01

Among abundant freshwater Betaproteobacteria, only few groups are considered to be of central ecological importance. One of them is the well-studied genus Limnohabitans and mainly its R-BT subcluster, investigated previously mainly by fluorescence in situ hybridization methods. We designed, based on sequences from a large Limnohabitans culture collection, 18 RLBH (Reverse Line Blot Hybridization) probes specific for different groups within the genus Limnohabitans by targeting diagnostic sequences on their 16 S–23 S rRNA ITS regions. The developed probes covered in sum 92% of the available isolates. This set of probes was applied to environmental DNA originating from 161 different European standing freshwater habitats to reveal the microdiversity (intra-genus) patterns of the Limnohabitans genus along a pH gradient. Investigated habitats differed in various physicochemical parameters, and represented a very broad range of standing freshwater habitats. The Limnohabitans microdiversity, assessed as number of RLBH-defined groups detected, increased significantly along the gradient of rising pH of habitats. 14 out of 18 probes returned detection signals that allowed predictions on the distribution of distinct Limnohabitans groups. Most probe-defined Limnohabitans groups showed preferences for alkaline habitats, one for acidic, and some seemed to lack preferences. Complete niche-separation was indicated for some of the probe-targeted groups. Moreover, bimodal distributions observed for some groups of Limnohabitans, suggested further niche separation between genotypes within the same probe-defined group. Statistical analyses suggested that different environmental parameters such as pH, conductivity, oxygen and altitude influenced the distribution of distinct groups. The results of our study do not support the hypothesis that the wide ecological distribution of Limnohabitans bacteria in standing freshwater habitats results from generalist adaptations of these bacteria. Instead, our observations suggest that the genus Limnohabitans, as well as its R-BT subgroup, represent ecologically heterogeneous taxa, which underwent pronounced ecological diversification. PMID:23554898

Clostridium thermocellum LL1210 pH homeostasis mechanisms informed by transcriptomics and metabolomics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whitham, Jason M.; Moon, Ji Won; Rodriguez Jr, Miguel

Background: Clostridium (Ruminiclostridium) thermocellum is a model fermentative anaerobic thermophile being studied and engineered for consolidated bioprocessing of lignocellulosic feedstocks into fuels and chemicals. Engineering efforts have resulted in significant improvements in ethanol yields and titers although further advances are required to make the bacterium industry-ready. For instance, fermentations at lower pH could enable co-culturing with microbes that have lower pH optima, augment productivity, and reduce buffering cost. C. thermocellum is typically grown at neutral pH, and little is known about its pH limits or pH homeostasis mechanisms. To better understand C. thermocellum pH homeostasis we grew strain LL1210 (C.more » thermocellum DSM1313 Δhpt ΔhydG Δldh Δpfl Δpta-ack), currently the highest ethanol producing strain of C. thermocellum, at different pH values in chemostat culture and applied systems biology tools.Results: Clostridium thermocellum LL1210 was found to be growth-limited below pH 6.24 at a dilution rate of 0.1 h -1. F1F0-ATPase gene expression was upregulated while many ATP-utilizing enzymes and pathways were downregulated at pH 6.24. These included most flagella biosynthesis genes, genes for chemotaxis, and other motility-related genes (> 50) as well as sulfate transport and reduction, nitrate transport and nitrogen fixation, and fatty acid biosynthesis genes. Clustering and enrichment of differentially expressed genes at pH values 6.48, pH 6.24 and pH 6.12 (washout conditions) compared to pH 6.98 showed inverse differential expression patterns between the F1F0-ATPase and genes for other ATP-utilizing enzymes. At and below pH 6.24, amino acids including glutamate and valine; long-chain fatty acids, their iso-counterparts and glycerol conjugates; glycolysis intermediates 3-phosphoglycerate, glucose 6-phosphate, and glucose accumulated intracellularly. Glutamate was 267 times more abundant in cells at pH 6.24 compared to pH 6.98, and intercellular concentration reached 1.8 μmol/g pellet at pH 5.80 (stopped flow).Conclusions: Clostridium thermocellum LL1210 can grow under slightly acidic conditions, similar to limits reported for other strains. This foundational study provides a detailed characterization of a relatively acid-intolerant bacterium and provides genetic targets for strain improvement. Future studies should examine adding gene functions used by more acid-tolerant bacteria for improved pH homeostasis at acidic pH values.« less

Clostridium thermocellum LL1210 pH homeostasis mechanisms informed by transcriptomics and metabolomics

DOE PAGES

Whitham, Jason M.; Moon, Ji Won; Rodriguez Jr, Miguel; ...

2018-04-05

Background: Clostridium (Ruminiclostridium) thermocellum is a model fermentative anaerobic thermophile being studied and engineered for consolidated bioprocessing of lignocellulosic feedstocks into fuels and chemicals. Engineering efforts have resulted in significant improvements in ethanol yields and titers although further advances are required to make the bacterium industry-ready. For instance, fermentations at lower pH could enable co-culturing with microbes that have lower pH optima, augment productivity, and reduce buffering cost. C. thermocellum is typically grown at neutral pH, and little is known about its pH limits or pH homeostasis mechanisms. To better understand C. thermocellum pH homeostasis we grew strain LL1210 (C.more » thermocellum DSM1313 Δhpt ΔhydG Δldh Δpfl Δpta-ack), currently the highest ethanol producing strain of C. thermocellum, at different pH values in chemostat culture and applied systems biology tools.Results: Clostridium thermocellum LL1210 was found to be growth-limited below pH 6.24 at a dilution rate of 0.1 h -1. F1F0-ATPase gene expression was upregulated while many ATP-utilizing enzymes and pathways were downregulated at pH 6.24. These included most flagella biosynthesis genes, genes for chemotaxis, and other motility-related genes (> 50) as well as sulfate transport and reduction, nitrate transport and nitrogen fixation, and fatty acid biosynthesis genes. Clustering and enrichment of differentially expressed genes at pH values 6.48, pH 6.24 and pH 6.12 (washout conditions) compared to pH 6.98 showed inverse differential expression patterns between the F1F0-ATPase and genes for other ATP-utilizing enzymes. At and below pH 6.24, amino acids including glutamate and valine; long-chain fatty acids, their iso-counterparts and glycerol conjugates; glycolysis intermediates 3-phosphoglycerate, glucose 6-phosphate, and glucose accumulated intracellularly. Glutamate was 267 times more abundant in cells at pH 6.24 compared to pH 6.98, and intercellular concentration reached 1.8 μmol/g pellet at pH 5.80 (stopped flow).Conclusions: Clostridium thermocellum LL1210 can grow under slightly acidic conditions, similar to limits reported for other strains. This foundational study provides a detailed characterization of a relatively acid-intolerant bacterium and provides genetic targets for strain improvement. Future studies should examine adding gene functions used by more acid-tolerant bacteria for improved pH homeostasis at acidic pH values.« less

TRPM5 mediates acidic extracellular pH signaling and TRPM5 inhibition reduces spontaneous metastasis in mouse B16-BL6 melanoma cells.

PubMed

Maeda, Toyonobu; Suzuki, Atsuko; Koga, Kaori; Miyamoto, Chihiro; Maehata, Yojiro; Ozawa, Shigeyuki; Hata, Ryu-Ichiro; Nagashima, Yoji; Nabeshima, Kazuki; Miyazaki, Kaoru; Kato, Yasumasa

2017-10-03

Extracellular acidity is a hallmark of solid tumors and is associated with metastasis in the tumor microenvironment. Acidic extracellular pH (pH e ) has been found to increase intracellular Ca 2+ and matrix metalloproteinase-9 (MMP-9) expression by activating NF-κB in the mouse B16 melanoma model. The present study assessed whether TRPM5, an intracellular Ca 2+ -dependent monovalent cation channel, is associated with acidic pH e signaling and induction of MMP-9 expression in this mouse melanoma model. Treatment of B16 cells with Trpm5 siRNA reduced acidic pH e -induced MMP-9 expression. Enforced expression of Trpm5 increased the rate of acidic pH e -induced MMP-9 expression, as well as increasing experimental lung metastasis. This genetic manipulation did not alter the pH e critical for MMP-9 induction but simply amplified the percentage of inducible MMP-9 at each pH e . Treatment of tumor bearing mice with triphenylphosphine oxide (TPPO), an inhibitor of TRPM5, significantly reduced spontaneous lung metastasis. In silico analysis of clinical samples showed that high TRPM5 mRNA expression correlated with poor overall survival rate in patients with melanoma and gastric cancer but not in patients with cancers of the ovary, lung, breast, and rectum. These results showed that TRPM5 amplifies acidic pH e signaling and may be a promising target for preventing metastasis of some types of tumor.

[Effects of simulated acid rain on seed germination and seedling growth of different type corn Zea mays].

PubMed

Zhang, Hai-Yan

2013-06-01

Taking normal corn, waxy corn, pop corn, and sweet corn as test materials, this paper studied their seed germination and seedling growth under effects of simulated acid rain (pH 6.0, 5.0, 4.0, 3.0, 2.0, and 1.0). Simulated acid rain at pH 2.0-5.0 had no significant effects on the seed germination and seedling growth, but at pH 1.0, the germination rate of normal corn, waxy corn, pop corn, and sweet corn was 91.3%, 68.7%, 27.5%, and 11.7%, respectively. As compared with those at pH 6.0 (CK), the germination rate, germination index, vigor index, germination velocity, shoot height, root length, shoot and root dry mass, and the transformation rate of stored substances at pH 1.0 had significant decrease, and the average germination time extended apparently. At pH 1.0, the effects of acid rain were greater at seedling growth stage than at germination stage, and greater on underground part than on aboveground part. Due to the differences in gene type, normal corn and waxy corn had the strongest capability against acid rain, followed by pop corn, and sweet corn. It was suggested that corn could be categorized as an acid rain-tolerant crop, the injury threshold value of acid rain was likely between pH 1.0 and pH 2.0, and normal corn and waxy corn would be prioritized for planting in acid rain-stricken area.

Net community calcification and production rates from Palmyra Atoll using a boundary layer gradient flux approach

NASA Astrophysics Data System (ADS)

Takeshita, Y.; McGillis, W. R.; Martz, T. R.; Price, N.; Smith, J.; Donham, E. M.

2016-02-01

Coral reefs are a highly dynamic system, where large variability in environmental conditions (e.g. pH) occurs on timescales of minutes to hours. Yet, techniques that are capable of monitoring reef calcification rates without artificial confinement on the same frequency are scarce. Here, we present a 2 week time series of sub-hourly, in situ benthic net community production (Pnet) and net community calcification (Gnet) rates from a reef terrace at Palmyra Atoll using the Benthic Ecosystem and Acidification Monitoring System (BEAMS). The net metabolism rates reported here are measured under natural conditions, without any alterations to the environment (e.g. light, flow, pH). The BEAMS measures the chemical gradient and the current velocity profile in the benthic boundary layer using autonomous sensors to calculate the chemical flux from the benthos. The O2 and total alkalinity (TA) fluxes were used to calculate Pnet and Gnet, respectively; TA gradients were calculated from pH and O2 measurements. Gnet can be constrained to better than 3 mmol CaCO3 m-2 hr-1 using this approach, based on three simultaneous BEAMS deployments. A clear diel cycle of Gnet was observed, where the peak day time Gnet and average nighttime Gnet were 14 and 1 mmol CaCO3 m-2 hr-1, respectively. Integrated daily Gnet ranged from 76 to 219 mmol CaCO3 m-2 d-1, with an average of 107 ± 14 mmol CaCO3 m-2 d-1. Light had the strongest control over Gnet, with current velocity having a smaller yet noticeable effect. During the deployment, pH varied by 0.16 (ranged between 7.92 and 8.08), and a significant positive relationship was observed between pH and Gnet. However, pH was also positively correlated with current velocity and Pnet, making it difficult to determine if natural variability in pH was significantly affecting Gnet on the timescale of days to weeks.

Average rainwater pH, concepts of atmospheric acidity, and buffering in open systems

NASA Astrophysics Data System (ADS)

Liljestrand, Howard M.

The system of water equilibrated with a constant partial pressure of CO 2, as a reference point for pH acidity-alkalinity relationships, has nonvolatile acidity and alkalinity components as conservative quantities, but not [H +]. Simple algorithms are presented for the determination of the average pH for combinations of samples both above and below pH 5.6. Averaging the nonconservative quantity [H +] yields erroneously low mean pH values. To extend the open CO 2 system to include other volatile atmospheric acids and bases distributed among the gas, liquid and particulate matter phases, a theoretical framework for atmospheric acidity is presented. Within certain oxidation-reduction limitations, the total atmospheric acidity (but not free acidity) is a conservative quantity. The concept of atmospheric acidity is applied to air-water systems approximating aerosols, fogwater, cloudwater and rainwater. The buffer intensity in hydrometeors is described as a function of net strong acidity, partial pressures of acid and base gases and the water to air ratio. For high liquid to air volume ratios, the equilibrium partial pressures of trace acid and base gases are set by the pH or net acidity controlled by the nonvolatile acid and base concentrations. For low water to air volume ratios as well as stationary state systems such as precipitation scavenging with continuous emissions, the partial pressures of trace gases (NH 3, HCl, HNO 3, SO 2 and CH 3COOH) appear to be of greater or equal importance as carbonate species as buffers in the aqueous phase.

Analysis of Small RNAs in Streptococcus mutans under Acid Stress-A New Insight for Caries Research.

PubMed

Liu, Shanshan; Tao, Ye; Yu, Lixia; Zhuang, Peilin; Zhi, Qinghui; Zhou, Yan; Lin, Huancai

2016-09-14

Streptococcus mutans (S. mutans) is the major clinical pathogen responsible for dental caries. Its acid tolerance has been identified as a significant virulence factor for its survival and cariogenicity in acidic conditions. Small RNAs (sRNAs) are recognized as key regulators of virulence and stress adaptation. Here, we constructed three libraries of sRNAs with small size exposed to acidic conditions for the first time, followed by verification using qRT-PCR. The levels of two sRNAs and target genes predicted to be bioinformatically related to acid tolerance were further evaluated under different acid stress conditions (pH 7.5, 6.5, 5.5, and 4.5) at three time points (0.5, 1, and 2 h). Meanwhile, bacterial growth characteristics and vitality were assessed. We obtained 1879 sRNAs with read counts of at least 100. One hundred and ten sRNAs were perfectly mapped to reported msRNAs in S. mutans. Ten out of 18 sRNAs were validated by qRT-PCR. The survival of bacteria declined as the acid was increased from pH 7.5 to 4.5 at each time point. The bacteria can proliferate under each pH except pH 4.5 with time. The levels of sRNAs gradually decreased from pH 7.5 to 5.5, and slightly increased in pH 4.5; however, the expression levels of target mRNAs were up-regulated in acidic conditions than in pH 7.5. These results indicate that some sRNAs are specially induced at acid stress conditions, involving acid adaptation, and provide a new insight into exploring the complex acid tolerance for S. mutans.

Acidogenic digestion of food waste in a thermophilic leach bed reactor: Effect of pH and leachate recirculation rate on hydrolysis and volatile fatty acid production.

PubMed

Hussain, Abid; Filiatrault, Mélissa; Guiot, Serge R

2017-12-01

The effect of pH control (4, 5, 6, 7) on volatile fatty acids (VFA) production from food waste was investigated in a leach bed reactor (LBR) operated at 50°C. Stabilisation of pH at 7 resulted in hydrolysis yield of 530g soluble chemical oxygen demand (sCOD)/kg total volatile solids (TVS) added and VFA yield of 247gCOD/kg TVS added, which were highest among all pH tested. Butyric acid dominated the VFA mix (49-54%) at pH of 7 and 6, while acetate composed the primary VFA (41-56%) at pH of 4 and 5. A metabolic shift towards lactic acid production was observed at pH of 5. Improving leachate recirculation rate further improved the hydrolysis and degradation efficiency by 10-16% and the acidification yield to 340gCOD/kgTVS added. The butyric acid concentration of 16.8g/L obtained at neutral pH conditions is among the highest reported in literature. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Potential mechanism of corpus-predominant gastritis after PPI therapy in Helicobacter pylori-positive patients with GERD.

PubMed

Mukaisho, Ken-ichi; Hagiwara, Tadashi; Nakayama, Takahisa; Hattori, Takanori; Sugihara, Hiroyuki

2014-09-14

The long-term use of proton pump inhibitors (PPIs) exacerbates corpus atrophic gastritis in patients with Helicobacter pylori (H. pylori) infection. To identify a potential mechanism for this change, we discuss interactions between pH, bile acids, and H. pylori. Duodenogastric reflux, which includes bile, occurs in healthy individuals, and bile reflux is increased in patients with gastroesophageal reflux disease (GERD). Diluted human plasma and bile acids have been found to be significant chemoattractants and chemorepellents, respectively, for the bacillus H. pylori. Although only taurine conjugates, with a pKa of 1.8-1.9, are soluble in an acidic environment, glycine conjugates, with a pKa of 4.3-5.2, as well as taurine-conjugated bile acids are soluble in the presence of PPI therapy. Thus, the soluble bile acid concentrations in the gastric contents of patients with GERD after continuous PPI therapy are considerably higher than that in those with intact acid production. In the distal stomach, the high concentration of soluble bile acids is likely to act as a bactericide or chemorepellent for H. pylori. In contrast, the mucous layer in the proximal stomach has an optimal bile concentration that forms chemotactic gradients with plasma components required to direct H. pylori to the epithelial surface. H. pylori may then colonize in the stomach body rather than in the pyloric antrum, which may explain the occurrence of corpus-predominant gastritis after PPI therapy in H. pylori-positive patients with GERD.

Influence of sodium chloride, pH, and lactic acid bacteria on anaerobic lactic acid utilization during fermented cucumber spoilage.

PubMed

Johanningsmeier, Suzanne D; Franco, Wendy; Perez-Diaz, Ilenys; McFeeters, Roger F

2012-07-01

Cucumbers are preserved commercially by natural fermentations in 5% to 8% sodium chloride (NaCl) brines. Occasionally, fermented cucumbers spoil after the primary fermentation is complete. This spoilage has been characterized by decreases in lactic acid and a rise in brine pH caused by microbial instability. Objectives of this study were to determine the combined effects of NaCl and pH on fermented cucumber spoilage and to determine the ability of lactic acid bacteria (LAB) spoilage isolates to initiate lactic acid degradation in fermented cucumbers. Cucumbers fermented with 0%, 2%, 4%, and 6% NaCl were blended into slurries (FCS) and adjusted to pH 3.2, 3.8, 4.3, and 5.0 prior to centrifugation, sterile-filtration, and inoculation with spoilage organisms. Organic acids and pH were measured initially and after 3 wk, 2, 6, 12, and 18 mo anaerobic incubation at 25 °C. Anaerobic lactic acid degradation occurred in FCS at pH 3.8, 4.3, and 5.0 regardless of NaCl concentration. At pH 3.2, reduced NaCl concentrations resulted in increased susceptibility to spoilage, indicating that the pH limit for lactic acid utilization in reduced NaCl fermented cucumbers is 3.2 or lower. Over 18 mo incubation, only cucumbers fermented with 6% NaCl to pH 3.2 prevented anaerobic lactic acid degradation by spoilage bacteria. Among several LAB species isolated from fermented cucumber spoilage, Lactobacillus buchneri was unique in its ability to metabolize lactic acid in FCS with concurrent increases in acetic acid and 1,2-propanediol. Therefore, L. buchneri may be one of multiple organisms that contribute to development of fermented cucumber spoilage. Microbial spoilage of fermented cucumbers during bulk storage causes economic losses for producers. Current knowledge is insufficient to predict or control these losses. This study demonstrated that in the absence of oxygen, cucumbers fermented with 6% sodium chloride to pH 3.2 were not subject to spoilage. However, lactic acid was degraded by spoilage microorganisms in reduced salt, even with pH as low as 3.2. Efforts to reduce salt in commercial brining operations will need to include control measures for this increased susceptibility to spoilage. Lactobacillus buchneri was identified as a potential causative agent and could be used as a target in development of such control measures. Journal of Food Science © 2012 Institute of Food Technologists® No claim to original US government works.

A single pH fluorescent probe for biosensing and imaging of extreme acidity and extreme alkalinity.

PubMed

Chao, Jian-Bin; Wang, Hui-Juan; Zhang, Yong-Bin; Li, Zhi-Qing; Liu, Yu-Hong; Huo, Fang-Jun; Yin, Cai-Xia; Shi, Ya-Wei; Wang, Juan-Juan

2017-07-04

A simple tailor-made pH fluorescent probe 2-benzothiazole (N-ethylcarbazole-3-yl) hydrazone (Probe) is facilely synthesized by the condensation reaction of 2-hydrazinobenzothiazole with N-ethylcarbazole-3-formaldehyde, which is a useful fluorescent probe for monitoring extremely acidic and alkaline pH, quantitatively. The pH titrations indicate that Probe displays a remarkable emission enhancement with a pK a of 2.73 and responds linearly to minor pH fluctuations within the extremely acidic range of 2.21-3.30. Interestingly, Probe also exhibits strong pH-dependent characteristics with pK a 11.28 and linear response to extreme-alkalinity range of 10.41-12.43. In addition, Probe shows a large Stokes shift of 84 nm under extremely acidic and alkaline conditions, high selectivity, excellent sensitivity, good water-solubility and fine stability, all of which are favorable for intracellular pH imaging. The probe is further successfully applied to image extremely acidic and alkaline pH values fluctuations in E. coli cells. Copyright © 2017 Elsevier B.V. All rights reserved.

Change of pH during excess sludge fermentation under alkaline, acidic and neutral conditions.

PubMed

Yuan, Yue; Peng, Yongzhen; Liu, Ye; Jin, Baodan; Wang, Bo; Wang, Shuying

2014-12-01

The change in pH during excess sludge (ES) fermentation of varying sludge concentrations was investigated in a series of reactors at alkaline, acidic, and neutral pHs. The results showed that the changes were significantly affected by fermentative conditions. Under different conditions, pH exhibited changing profiles. When ES was fermented under alkaline conditions, pH decreased in a range of (10±1). At the beginning of alkaline fermentation, pH dropped significantly, at intervals of 4h, 4h, and 5h with sludge concentrations of 8665.6mg/L, 6498.8mg/L, and 4332.5mg/L, then it would become moderate. However, under acidic conditions, pH increased from 4 to 5. Finally, under neutral conditions pH exhibited a decrease then an increase throughout entire fermentation process. Further study showed short-chain fatty acids (SCFAs), ammonia nitrogen and cations contributed to pH change under various fermentation conditions. This study presents a novel strategy based on pH change to predict whether SCFAs reach their stable stage. Copyright © 2014 Elsevier Ltd. All rights reserved.

Imaging of pH in vivo using hyperpolarized 13C-labelled zymonic acid

PubMed Central

Düwel, Stephan; Hundshammer, Christian; Gersch, Malte; Feuerecker, Benedikt; Steiger, Katja; Buck, Achim; Walch, Axel; Haase, Axel; Glaser, Steffen J.; Schwaiger, Markus; Schilling, Franz

2017-01-01

Natural pH regulatory mechanisms can be overruled during several pathologies such as cancer, inflammation and ischaemia, leading to local pH changes in the human body. Here we demonstrate that 13C-labelled zymonic acid (ZA) can be used as hyperpolarized magnetic resonance pH imaging sensor. ZA is synthesized from [1-13C]pyruvic acid and its 13C resonance frequencies shift up to 3.0 p.p.m. per pH unit in the physiological pH range. The long lifetime of the hyperpolarized signal enhancement enables monitoring of pH, independent of concentration, temperature, ionic strength and protein concentration. We show in vivo pH maps within rat kidneys and subcutaneously inoculated tumours derived from a mammary adenocarcinoma cell line and characterize ZA as non-toxic compound predominantly present in the extracellular space. We suggest that ZA represents a reliable and non-invasive extracellular imaging sensor to localize and quantify pH, with the potential to improve understanding, diagnosis and therapy of diseases characterized by aberrant acid-base balance. PMID:28492229

Evidence for the identity and some comparative properties of alpha-ketoglutarate and 2-keto-4-hydroxyglutarate dehydrogenase activity.

PubMed

Gupta, S C; Dekker, E E

1980-02-10

Enzyme preparations of pig heart and Escherichia coli are shown to catalyze a NAD+- and CoASH-dependent oxidation of 2-keto-4-hydroxyglutarate. Several independent lines of evidence support the conclusion that this hydroxyketo acid is a substrate for the well known alpha-ketoglutarate dehydrogenase complex of the citric acid cycle. The evidence includes (a) a constant ratio of specific activity values for the two substrates through several steps of purification, (b) identical elution profiles from a calcium phosphate gel-cellulose column and a constant ratio of specific activity toward the two substrates throughout the activity peak, (c) identical inactivation curves in controlled heat denaturation studies, (d) the same pH activity curves, (e) no effect on the oxidation of either keto acid by repeated freezing and thawing of dehydrogenase preparations, and (f) the same activity pattern when the E. coli complex is distributed into several fractions by sucrose density gradient centrifugation. Additionally, the same cofactors are required for maximal activity and glyoxylate inhibits the oxidation of either substrate noncompetitively. Ferricyanide-linked oxidation of 2-keto-4-hydroxyglutarate yields malate as the product and a 1:2:1 stoichiometric relationship is obtained between the amount of hydroxyketo acid oxidized, ferricyanide reduced, and malate formed.

QSAR, QSPR and QSRR in Terms of 3-D-MoRSE Descriptors for In Silico Screening of Clofibric Acid Analogues.

PubMed

Di Tullio, Maurizio; Maccallini, Cristina; Ammazzalorso, Alessandra; Giampietro, Letizia; Amoroso, Rosa; De Filippis, Barbara; Fantacuzzi, Marialuigia; Wiczling, Paweł; Kaliszan, Roman

2012-07-01

A series of 27 analogues of clofibric acid, mostly heteroarylalkanoic derivatives, have been analyzed by a novel high-throughput reversed-phase HPLC method employing combined gradient of eluent's pH and organic modifier content. The such determined hydrophobicity (lipophilicity) parameters, log kw , and acidity constants, pKa , were subjected to multiple regression analysis to get a QSRR (Quantitative StructureRetention Relationships) and a QSPR (Quantitative Structure-Property Relationships) equation, respectively, describing these pharmacokinetics-determining physicochemical parameters in terms of the calculation chemistry derived structural descriptors. The previously determined in vitro log EC50 values - transactivation activity towards PPARα (human Peroxisome Proliferator-Activated Receptor α) - have also been described in a QSAR (Quantitative StructureActivity Relationships) equation in terms of the 3-D-MoRSE descriptors (3D-Molecule Representation of Structures based on Electron diffraction descriptors). The QSAR model derived can serve for an a priori prediction of bioactivity in vitro of any designed analogue, whereas the QSRR and the QSPR models can be used to evaluate lipophilicity and acidity, respectively, of the compounds, and hence to rational guide selection of structures of proper pharmacokinetics. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A comparative study of monosaccharide composition analysis as a carbohydrate test for biopharmaceuticals.

PubMed

Harazono, Akira; Kobayashi, Tetsu; Kawasaki, Nana; Itoh, Satsuki; Tada, Minoru; Hashii, Noritaka; Ishii, Akiko; Arato, Teruyo; Yanagihara, Shigehiro; Yagi, Yuki; Koga, Akiko; Tsuda, Yuriko; Kimura, Mikiko; Sakita, Masashi; Kitamura, Satoshi; Yamaguchi, Hideto; Mimura, Hisashi; Murata, Yoshimi; Hamazume, Yasuki; Sato, Takayuki; Natsuka, Shunji; Kakehi, Kazuaki; Kinoshita, Mitsuhiro; Watanabe, Sakie; Yamaguchi, Teruhide

2011-05-01

The various monosaccharide composition analysis methods were evaluated as monosaccharide test for glycoprotein-based pharmaceuticals. Neutral and amino sugars were released by hydrolysis with 4-7N trifluoroacetic acid. The monosaccharides were N-acetylated if necessary, and analyzed by high-performance liquid chromatography (HPLC) with fluorometric or UV detection after derivatization with 2-aminopyridine, ethyl 4-aminobenzoate, 2-aminobenzoic acid or 1-phenyl-3-methyl-5-pyrazolone, or high pH anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Sialic acids were released by mild acid hydrolysis or sialidase digestion, and analyzed by HPLC with fluorometric detection after derivatization with 1,2-diamino-4,5-methylenedioxybenzene, or HPAEC-PAD. These methods were verified for resolution, linearity, repeatability, and accuracy using a monosaccharide standard solution, a mixture of epoetin alfa and beta, and alteplase as models. It was confirmed that those methods were useful for ensuring the consistency of glycosylation. It is considered essential that the analytical conditions including desalting, selection of internal standards, release of monosaccharides, and gradient time course should be determined carefully to eliminate interference of sample matrix. Various HPLC-based monosaccharide analysis methods were evaluated as a carbohydrate test for glycoprotein pharmaceuticals by an inter-laboratory study. Copyright © 2011 The International Association for Biologicals. Published by Elsevier Ltd. All rights reserved.

The chemistry, physiology and pathology of pH in cancer.

PubMed

Swietach, Pawel; Vaughan-Jones, Richard D; Harris, Adrian L; Hulikova, Alzbeta

2014-03-19

Cell survival is conditional on the maintenance of a favourable acid-base balance (pH). Owing to intensive respiratory CO2 and lactic acid production, cancer cells are exposed continuously to large acid-base fluxes, which would disturb pH if uncorrected. The large cellular reservoir of H(+)-binding sites can buffer pH changes but, on its own, is inadequate to regulate intracellular pH. To stabilize intracellular pH at a favourable level, cells control trans-membrane traffic of H(+)-ions (or their chemical equivalents, e.g. ) using specialized transporter proteins sensitive to pH. In poorly perfused tumours, additional diffusion-reaction mechanisms, involving carbonic anhydrase (CA) enzymes, fine-tune control extracellular pH. The ability of H(+)-ions to change the ionization state of proteins underlies the exquisite pH sensitivity of cellular behaviour, including key processes in cancer formation and metastasis (proliferation, cell cycle, transformation, migration). Elevated metabolism, weakened cell-to-capillary diffusive coupling, and adaptations involving H(+)/H(+)-equivalent transporters and extracellular-facing CAs give cancer cells the means to manipulate micro-environmental acidity, a cancer hallmark. Through genetic instability, the cellular apparatus for regulating and sensing pH is able to adapt to extracellular acidity, driving disease progression. The therapeutic potential of disturbing this sequence by targeting H(+)/H(+)-equivalent transporters, buffering or CAs is being investigated, using monoclonal antibodies and small-molecule inhibitors.

Neutralizing salivary pH by mouthwashes after an acidic challenge.

PubMed

Dehghan, Mojdeh; Tantbirojn, Daranee; Kymer-Davis, Emily; Stewart, Colette W; Zhang, Yanhui H; Versluis, Antheunis; Garcia-Godoy, Franklin

2017-05-01

The aim of the present study was to test the neutralizing effect of mouthwashes on salivary pH after an acidic challenge. Twelve participants were recruited for three visits, one morning per week. Resting saliva was collected at baseline and after 2-min swishing with 20 mL orange juice as an acidic challenge. Participants then rinsed their mouth for 30 s with 20 mL water (control), an over-the-counter mouthwash (Listerine), or a two-step mouthwash, randomly assigned for each visit. Saliva was collected immediately, 15, and 45 min after rinsing. The pH values of the collected saliva were measured and analyzed with anova, followed by Student-Newman-Keuls post-hoc test (significance level: 0.05). Orange juice significantly lowered salivary pH. Immediately after rinsing, Listerine and water brought pH back to baseline values, with the pH significantly higher in the Listerine group. The two-step mouthwash raised pH significantly higher than Listerine and water, and higher than the baseline value. Salivary pH returned to baseline and was not significantly different among groups at 15 and 45 min post-rinsing. Mouth rinsing after an acidic challenge increased salivary pH. The tested mouthwashes raised pH higher than water. Mouthwashes with a neutralizing effect can potentially reduce tooth erosion from acid exposure. © 2015 Wiley Publishing Asia Pty Ltd.

Acid-catalysed xylose dehydration into furfural in the presence of kraft lignin.

PubMed

Lamminpää, Kaisa; Ahola, Juha; Tanskanen, Juha

2015-02-01

In this study, the effects of kraft lignin (Indulin AT) on acid-catalysed xylose dehydration into furfural were studied in formic and sulphuric acids. The study was done using D-optimal design. Three variables in both acids were included in the design: time (20-80 min), temperature (160-180°C) and initial lignin concentration (0-20 g/l). The dependent variables were xylose conversion, furfural yield, furfural selectivity and pH change. The results showed that the xylose conversion and furfural yield decreased in sulphuric acid, while in formic acid the changes were minor. Additionally, it was showed that lignin has an acid-neutralising capacity, and the added lignin increased the pH of reactant solutions in both acids. The pH rise was considerably lower in formic acid than in sulphuric acid. However, the higher pH did not explain all the changes in conversion and yield, and thus lignin evidently inhibits the formation of furfural. Copyright © 2014 Elsevier Ltd. All rights reserved.

The sensitivity of particle pH to NH3: Can high NH3 cause London Fog conditions?

NASA Astrophysics Data System (ADS)

Weber, R. J.; Guo, H.; Nenes, A.

2017-12-01

High ammonia emissions from agriculture or other sources have been suggested to elevate ambient particle pH levels to near neutral acidity (pH=7), a condition that promotes rapid SO2 oxidation by NO2 to form aerosol sulfate concentration consistent with "London fog" levels. This mechanism has been used to explain pollution haze events in China. Predicted pH for locations in the US and Europe show fine particles are highly acidic with pH typically less than 2. The results are consistent with measured ammonia and nitric acid gas-particle partitioning, validating predicted pH levels. Using these data sets from representative sites around the world we conduct a thermodynamic analysis of aerosol pH and its sensitivity to ammonia levels. We find that particle pH, regardless of ammonia levels, is always acidic even for the unusually high ammonia levels found in highly polluted Asian cities, Beijing (pH=4.5) and Xi'an (pH=5), locations where sulfate production from NOx is proposed. These results indicate that sulfur dioxide oxidation through a NO2-mediated pathway is not likely in China, nor any other region of the world (e.g., US, Mediterranean) since the fine aerosol is consistently acidic. The mildly acidic conditions would, however, permit rapid oxidation of sulfur dioxide through transition metal chemistry. The limited alkalinity from the carbonate buffer in dust and seasalt can provide the only likely set of conditions where NO2-mediated oxidation of SO2 outcompetes with other well-established pathways.

Oxidative stability of egg and soy lecithin as affected by transition metal ions and pH in emulsion.

PubMed

Wang, Guang; Wang, Tong

2008-12-10

Oxidative stability of egg and soy lecithin in emulsion was evaluated with two transition metal ions, cupric and ferric ion, at two concentration levels (50 and 500 microM). The effect of pH on lipid oxidation was also examined under these two concentrations for each ion. Egg lecithin (EL) had similar peroxide value (PV) development pattern as soy lecithin (SL) when treated with cupric ion under both acidic and neutral pH. Acidic pH of 3 accelerated oxidation of both EL and SL, especially under high concentration of copper. When treated with ferric ion, EL oxidized much faster than SL did. EL had higher value of thiobarbituric acid-reactive substances (TBARS) than SL, possibly because of its higher content of long-chain polyunsaturated fatty acids (PUFA). Acidic pH accelerated TBARS development for both EL and SL, but EL had more significantly increased values. Cupric ion was more powerful than ferric in catalyzing oxidation of both EL and SL under both acidic and neutral pH conditions as measured by PV and TBARS. Linoleic acid may contribute to higher PV production, however, arachidonic acid and docosahexaenoic acid may have contributed more to TBARS production. Overall, SL showed better oxidative stability than EL under the experimental conditions. This study also suggests that using multiple methods is necessary in properly evaluating lipid oxidative stability.

Estimated net acid excretion inversely correlates with urine pH in vegans, lacto-ovo vegetarians, and omnivores.

PubMed

Ausman, Lynne M; Oliver, Lauren M; Goldin, Barry R; Woods, Margo N; Gorbach, Sherwood L; Dwyer, Johanna T

2008-09-01

Diet affects urine pH and acid-base balance. Both excess acid/alkaline ash (EAA) and estimated net acid excretion (NAE) calculations have been used to estimate the effects of diet on urine pH. This study's goal was to determine if free-living vegans, lacto-ovo vegetarians, and omnivores have increasingly acidic urine, and to assess the ability of EAA and estimated NAE calculations to predict urine pH. This study used a cross-sectional design. This study assessed urine samples of 10 vegan, 16 lacto-ovo vegetarian, and 16 healthy omnivorous women in the Boston metropolitan area. Six 3-day food records from each dietary group were analyzed for EAA content and estimated NAE, and correlations with measured urine pH were calculated. The mean (+/- SD) urine pH was 6.15 +/- 0.40 for vegans, 5.90 +/- 0.36 for lacto-ovo vegetarians, and 5.74 +/- 0.21 for omnivores (analysis of variance, P = .013). Calculated EAA values were not significantly different among the three groups, whereas mean estimated NAE values were significantly different: 17.3 +/- 14.5 mEq/day for vegans, 31.3 +/- 8.5 mEq/day for lacto-ovo vegetarians, and 42.6 +/- 13.2 mEq/day for omnivores (analysis of variance, P = .01). The average deattenuated correlation between urine pH and EAA was 0.333; this value was -0.768 for estimated NAE and urine pH, with a regression equation of pH = 6.33 - 0.014 NAE (P = .02, r = -0.54). Habitual diet and estimated NAE calculations indicate the probable ranking of urine pH by dietary groups, and may be used to determine the likely acid-base status of an individual; EAA calculations were not predictive of urine pH.

Changes in composition and enamel demineralization inhibition activities of gallic acid at different pH values.

PubMed

Zhang, Jingyang; Huang, Xuelian; Huang, Shengbin; Deng, Meng; Xie, Xincheng; Liu, Mingdong; Liu, Hongling; Zhou, Xuedong; Li, Jiyao; Ten Cate, Jacob Martien

2015-01-01

Gallic acid (GA) has been shown to inhibit demineralization and enhance remineralization of enamel; however, GA solution is highly acidic. This study was to investigate the stability of GA solutions at various pH and to examine the resultant effects on enamel demineralization. The stability of GA in H2O or in phosphate buffer at pH 5.5, pH 7.0 and pH 10.0 was evaluated qualitatively by ultraviolet absorption spectra and quantified by high performance liquid chromatography with diode array detection (HPLC-DAD). Then, bovine enamel blocks were subjected to a pH-cycling regime of 12 cycles. Each cycle included 5 min applications with one of the following treatments: 1 g/L NaF (positive control), 4 g/L GA in H2O or buffered at pH 5.5, pH 7.0 and pH 10.0 and buffers without GA at the same pH (negative control), followed by a 60 min application with pH 5.0 acidic buffers and a 5 min application with neutral buffers. The acidic buffers were analysed for dissolved calcium. GA was stable in pure water and acidic condition, but was unstable in neutral and alkaline conditions, in which ultraviolet spectra changed and HPLC-DAD analysis revealed that most of the GA was degraded. All the GA groups significantly inhibited demineralization (p < 0.05) and there was no significant difference of the inhibition efficacy among different GA groups (p > 0.05). GA could inhibit enamel demineralization and the inhibition effect is not influenced by pH. GA could be a useful source as an anti-cariogenic agent for broad practical application.

Microfluidic device having an immobilized pH gradient and PAGE gels for protein separation and analysis

DOEpatents

Sommer, Gregory J.; Hatch, Anson V.; Singh, Anup K.; Wang, Ying-Chih

2012-12-11

Disclosed is a novel microfluidic device enabling on-chip implementation of a two-dimensional separation methodology. Previously disclosed microscale immobilized pH gradients (IPG) are combined with perpendicular polyacrylamide gel electrophoresis (PAGE) microchannels to achieve orthogonal separations of biological samples. Device modifications enable inclusion of sodium dodecyl sulfate (SDS) in the second dimension. The device can be fabricated to use either continuous IPG gels, or the microscale isoelectric fractionation membranes we have also previously disclosed, for the first dimension. The invention represents the first all-gel two-dimensional separation microdevice, with significantly higher resolution power over existing devices.

Microfluidic device having an immobilized pH gradient and page gels for protein separation and analysis

DOEpatents

Sommer, Gregory J; Hatch, Anson V; Singh, Anup K; Wang, Ying-Chih

2014-05-20

Disclosed is a novel microfluidic device enabling on-chip implementation of a two-dimensional separation methodology. Previously disclosed microscale immobilized pH gradients (IPG) are combined with perpendicular polyacrylamide gel electrophoresis (PAGE) microchannels to achieve orthogonal separations of biological samples. Device modifications enable inclusion of sodium dodecyl sulfate (SDS) in the second dimension. The device can be fabricated to use either continuous IPG gels, or the microscale isoelectric fractionation membranes we have also previously disclosed, for the first dimension. The invention represents the first all-gel two-dimensional separation microdevice, with significantly higher resolution power over existing devices.

Urine alkalization facilitates uric acid excretion

PubMed Central

2010-01-01

Background Increase in the incidence of hyperuricemia associated with gout as well as hypertension, renal diseases and cardiovascular diseases has been a public health concern. We examined the possibility of facilitated excretion of uric acid by change in urine pH by managing food materials. Methods Within the framework of the Japanese government's health promotion program, we made recipes which consist of protein-rich and less vegetable-fruit food materials for H+-load (acid diet) and others composed of less protein but vegetable-fruit rich food materials (alkali diet). Healthy female students were enrolled in this consecutive 5-day study for each test. From whole-day collected urine, total volume, pH, organic acid, creatinine, uric acid and all cations (Na+,K+,Ca2+,Mg2+,NH4+) and anions (Cl-,SO42-,PO4-) necessary for the estimation of acid-base balance were measured. Results Urine pH reached a steady state 3 days after switching from ordinary daily diets to specified regimens. The amount of acid generated ([SO42-] +organic acid-gut alkai) were linearly related with those of the excretion of acid (titratable acidity+ [NH4+] - [HCO3-]), indicating that H+ in urine is generated by the metabolic degradation of food materials. Uric acid and excreted urine pH retained a linear relationship, where uric acid excretion increased from 302 mg/day at pH 5.9 to 413 mg/day at pH 6.5, despite the fact that the alkali diet contained a smaller purine load than the acid diet. Conclusion We conclude that alkalization of urine by eating nutritionally well-designed food is effective for removing uric acid from the body. PMID:20955624

The effect of pH on the toxicity of fatty acids and fatty acid amides to rainbow trout gill cells.

PubMed

Bertin, Matthew J; Voronca, Delia C; Chapman, Robert W; Moeller, Peter D R

2014-01-01

Harmful algal blooms (HABs) expose aquatic organisms to multiple physical and chemical stressors during an acute time period. Algal toxins themselves may be altered by water chemistry parameters affecting their bioavailability and resultant toxicity. The purpose of this study was to determine the effects of two abiotic parameters (pH, inorganic metal salts) on the toxicity of fatty acid amides and fatty acids, two classes of lipids produced by harmful algae, including the golden alga, Prymnesium parvum, that are toxic to aquatic organisms. Rainbow trout gill cells were used as a model of the fish gill and exposed to single compounds and mixtures of compounds along with variations in pH level and concentration of inorganic metal salts. We employed artificial neural networks (ANNs) and standard ANOVA statistical analysis to examine and predict the effects of these abiotic parameters on the toxicity of fatty acid amides and fatty acids. Our results demonstrate that increasing pH levels increases the toxicity of fatty acid amides and inhibits the toxicity of fatty acids. This phenomenon is reversed at lower pH levels. Exposing gill cells to complex mixtures of chemical factors resulted in dramatic increases in toxicity compared to tests of single compounds for both the fatty acid amides and fatty acids. These findings highlight the potential of physicochemical factors to affect the toxicity of chemicals released during algal blooms and demonstrate drastic differences in the effect of pH on fatty acid amides and fatty acids. Published by Elsevier B.V.

Acid-rain induced changes in streamwater quality during storms on Catoctin Mountain, Maryland

USGS Publications Warehouse

Rice, Karen C.; Bricker, O.P.

1992-01-01

Catoctin Mountain receives some of the most acidic (lowest pH) rain in the United States. In 1990, the U.S. Geological Survey (USGS), in cooperation with the Maryland Department of the Environment (MDE) and the Maryland Department of Natural Resources (DNR), began a study of the effects of acid rain on the quality of streamwater on the part of Catoctin Mountain within Cunningham Falls State Park, Maryland (fig. 1). Samples of precipitation collected on the mountain by the USGS since 1982 have been analyzed for acidity and concentration of chemical constituents. During 1982-91, the volume-weighted average pH of precipitation was 4.2. (Volume weighting corrects for the effect of acids being washed out of the atmosphere at the beginning of rainfall). The pH value is measured on a logarithmic scale, which means that for each whole number change, the acidity changes by a factor of 10. Thus rain with a pH of 4.2 is more than 10 times as acidic as uncontaminated rain, which has a pH of about 5.6. The acidity of rain during several rainstorms on Catoctin Mountain was more than 100 times more acidic than uncontaminated rain.

The acid tolerance response and pH adaptation of Enterococcus faecalis in extract of lime Citrus aurantiifolia from Aceh Indonesia.

PubMed

Mubarak, Zaki; Soraya, Cut

2018-01-01

Background:  The objective of the present study was to evaluate the acid tolerance response and pH adaptation when Enterococcus faecalis interacted with extract of lime ( Citrus aurant iifolia ). Methods : We used E. faecalis ATCC 29212 and lime extract from Aceh, Indonesia. The microbe was analyzed for its pH adaptation, acid tolerance response, and adhesion assay using a light microscope with a magnification of x1000. Further, statistical tests were performed to analyze both correlation and significance of the acid tolerance and pH adaptation as well as the interaction activity. Results : E. faecalis was able to adapt to a very acidic environment (pH 2.9), which was characterized by an increase in its pH (reaching 4.2) at all concentrations of the lime extract (p < 0.05). E. faecalis was also able to provide acid tolerance response to lime extract based on spectrophotometric data (595 nm) (p < 0.05). Also, the interaction activity of E. faecalis in different concentrations of lime extract was relatively stable within 6 up to 12 hours (p < 0.05), but it became unstable within 24-72 hours (p > 0.05) based on the mass profiles of its interaction activity. Conclusions : E. faecalis can adapt to acidic environments (pH 2.9-4.2); it is also able to tolerate acid generated by Citrus auranti ifolia extract, revealing a stable interaction in the first 6-12 hours.

Estimating iron and aluminum content of acid mine discharge from a north-central Pennsylvania coal field by use of acidity titration curves

USGS Publications Warehouse

Ott, A.N.

1986-01-01

Determination of acidity provides a value that denotes the quantitative capacity of the sample water to neutralize a strong base to a particular pH. However, much additional information can be obtained from this determination if a titration curve is constructed from recorded data of titrant increments and their corresponding pH values. The curve can be used to identify buffer capabilities, the acidity with respect to any pH value within the curve limit, and, in the case of acid mine drainage from north-central Pennsylvania, the identification and estimation of the concentration of dissolved ferrous iron, ferric iron, and aluminum. Through use of titration curves, a relationship was observed for the acid mine drainage between: (1) the titratable acidity (as milligrams per liter calcium carbonate) to pH 4.0 and the concentration of dissolved ferric iron; and (2) the titratable acidity (as milligrams per liter calcium carbonate) from pH 4.0 to 5.0 and the concentration of dissolved aluminum. The presence of dissolved ferrous iron can be detected by the buffering effect exhibited in the area between pH 5.5 to 7.5. The concentration of ferrous iron is estimated by difference between the concentrations of ferric iron in an oxidized and unoxidized sample. Interferences in any of the titrations from manganese, magnesium, and aluminate, appear to be negligible within the pH range of interest.

Determination of Acidity in Donor Milk.

PubMed

Escuder-Vieco, Diana; Vázquez-Román, Sara; Sánchez-Pallás, Juan; Ureta-Velasco, Noelia; Mosqueda-Peña, Rocío; Pallás-Alonso, Carmen Rosa

2016-11-01

There is no uniformity among milk banks on milk acceptance criteria. The acidity obtained by the Dornic titration technique is a widely used quality control in donor milk. However, there are no comparative data with other acidity-measuring techniques, such as the pH meter. The objective of this study was to assess the correlation between the Dornic technique and the pH measure to determine the pH cutoff corresponding to the Dornic degree limit value used as a reference for donor milk quality control. Fifty-two human milk samples were obtained from 48 donors. Acidity was measured using the Dornic method and pH meter in triplicate. Statistical data analysis to estimate significant correlations between variables was carried out. The Dornic acidity value that led to rejecting donor milk was ≥ 8 Dornic degrees (°D). In the evaluated sample size, Dornic acidity measure and pH values showed a statistically significant negative correlation (τ = -0.780; P = .000). A pH value of 6.57 corresponds to 8°D and of 7.12 to 4°D. Donor milk with a pH over 6.57 may be accepted for subsequent processing in the milk bank. Moreover, the pH measurement seems to be more useful due to certain advantages over the Dornic method, such as objectivity, accuracy, standardization, the lack of chemical reagents required, and the fact that it does not destroy the milk sample.

Interaction of melanin with proteins--the importance of an acidic intramelanosomal pH.

PubMed

Mani, I; Sharma, V; Tamboli, I; Raman, G

2001-06-01

Melanin is a highly irregular heteropolymer consisting of monomeric units derived from the enzymatic oxidation of the amino acid tyrosine. The process of melanin formation takes place in specialized acidic organelles (melanosomes) in melanocytes. The process of melanin polymerization requires an alkaline pH in vitro, and therefore, the purpose of an acidic environment in vivo remains a mystery. It is known that melanin is always bound to protein in vivo. It is also seen that polymerization in vitro at an acidic pH necessarily requires the presence of proteins. The effect of various model proteins on melanin synthesis and their interaction with melanin was studied. It was seen that many proteins could increase melanin synthesis at an acidic pH, and that different proteins resulted in the formation of different states of melanin, i.e., a precipitate or a soluble, protein-bound form. We also present evidence to show that soluble protein-bound melanin is present in vivo (in B16 cells as well as in B16 melanoma tissue). An acidic pH appeared to be necessary to ensure the formation of a uniform, very high molecular weight melano-protein complex. The interaction between melanin and proteins appears to be largely charge-dependent as evidenced by zeta potential measurements, and this interaction is also increased in an acidic pH. Thus, it appears that an acidic intramelanosomal pH is essential to ensure maximum interaction between protein and melanin, and also to ensure that all the melanin formed is protein-bound.

In vitro effects of hydrochloric acid and various concentrations of acetic, propionic, butyric, or valeric acids on bioelectric properties of equine gastric squamous mucosa.

PubMed

Andrews, Frank M; Buchanan, Benjamin R; Smith, Sionagh H; Elliott, Sarah B; Saxton, Arnold M

2006-11-01

To compare the effects of hydrochloric acid (HCl) and various concentrations of volatile fatty acids (VFAs) on tissue bioelectric properties of equine stomach nonglandular (NG) mucosa. Gastric tissues obtained from 48 adult horses. NG gastric mucosa was studied by use of Ussing chambers. Short-circuit current (Isc) and potential difference (PD) were measured and electrical resistance (R) and conductance calculated for tissues after addition of HCl and VFAs (5, 10, 20, and 40 mM) in normal Ringer's solution (NRS). Mucosa exposed to HCl in NRS (pH of 1.5 and, to a lesser extent, 4.0) had a significant decrease in Isc, PD, and R, whereas tissues exposed to acetic acid at a pH of < 4.0, propionic and butyric acids at a pH of

In situ changes of tropical crustose coralline algae along carbon dioxide gradients

NASA Astrophysics Data System (ADS)

Fabricius, K. E.; Kluibenschedl, A.; Harrington, L.; Noonan, S.; de'Ath, G.

2015-04-01

Crustose coralline algae (CCA) fulfill important ecosystem functions in coral reefs, including reef framework stabilization and induction of larval settlement. To investigate in situ the effects of high carbon dioxide on CCA communities, we deployed settlement tiles at three tropical volcanic CO2 seeps in Papua New Guinea along gradients spanning from 8.1 to 7.4 pH. After 5 and 13 months deployment, there was a steep transition from CCA presence to absence around pH 7.8 (660 μatm pCO2): 98% of tiles had CCA at pH > 7.8, whereas only 20% of tiles had CCA at pH <= 7.8. As pH declined from 8.0 to 7.8, the least and most sensitive CCA species lost 43% and 85% of cover, respectively. Communities on upward facing surfaces exposed to high light and high grazing pressure showed less steep losses than those on shaded surfaces with low grazing. Direct CO2 effects on early life stages were the main mechanisms determining CCA cover, rather than competitive interactions with other benthic groups. Importantly, declines were steepest at near-ambient pH, suggesting that CCA may have already declined in abundance due to the recent seawater pH decline of 0.1 units, and that future severe losses are likely with increasing ocean acidification.

Reversibly extracellular pH controlled cellular uptake and photothermal therapy by PEGylated mixed-charge gold nanostars.

PubMed

Wang, Shouju; Teng, Zhaogang; Huang, Peng; Liu, Dingbin; Liu, Ying; Tian, Ying; Sun, Jing; Li, Yanjun; Ju, Huangxian; Chen, Xiaoyuan; Lu, Guangming

2015-04-17

Shielding nanoparticles from nonspecific interactions with normal cells/tissues before they reach and after they leave tumors is crucial for the selective delivery of NPs into tumor cells. By utilizing the reversible protonation of weak electrolytic groups to pH changes, long-chain amine/carboxyl-terminated polyethylene glycol (PEG) decorated gold nanostars (GNSs) are designed, exhibiting reversible, significant, and sensitive response in cell affinity and therapeutic efficacy to the extracellular pH (pHe) gradient between normal tissues and tumors. This smart nanosystem shows good dispersity and unimpaired photothermal efficacy in complex bioenvironment at pH 6.4 and 7.4 even when their surface charge is neutral. One PEGylated mixed-charge GNSs with certain surface composition, GNS-N/C 4, exhibits high cell affinity and therapeutic efficacy at pH 6.4, and low affinity and almost "zero" damage to cells at pH 7.4. Remarkably, this significant and sensitive response in cell affinity and therapeutic efficacy is reversible as local pH alternated. In vivo, GNS-N/C 4 shows higher accumulation in tumors and improved photothermal therapeutic efficacy than pH-insensitive GNSs. This newly developed smart nanosystem, whose cell affinity reversibly transforms in response to pHe gradient with unimpaired biostability, provides a novel effective means of tumor-selective therapy. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Differences in soil micro-eukaryotic communities over soil pH gradients are strongly driven by parasites and saprotrophs.

PubMed

Dupont, A Ö C; Griffiths, R I; Bell, T; Bass, D

2016-06-01

A recent large-scale assessment of bacterial communities across a range of UK soil types showed that bacterial community structure was strongly determined by soil pH. We analysed a data set of eukaryotic 454 sequencing 18S rDNA from the surveyed samples and showed significant differences in eukaryotic assemblages according to pH class, mostly between low pH and higher pH soils. Soil eukaryote communities (per sample) differed most at the taxonomic rank approximating to order level. Taxonomies assigned with the Protist Ribosomal Reference and the Silva 119 databases were taxonomically inconsistent, mostly due to differing 18S annotations, although general structure and composition according to pH were coherent. A relatively small number of lineages, mostly putative parasitic protists and fungi, drive most differences between pH classes, with weaker contributions from bacterivores and autotrophs. Overall, soil parasites included a large diversity of alveolates, in particular apicomplexans. Phylogenetic analysis of alveolate lineages demonstrates a large diversity of unknown gregarines, novel perkinsids, coccidians, colpodellids and uncharacterized alveolates. Other novel and/or divergent lineages were revealed across the eukaryote tree of life. Our study provides an in-depth taxonomic evaluation of micro-eukaryotic diversity, and reveals novel lineages and insights into their relationships with environmental variables across soil gradients. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

Monitoring of biogenic amines and drugs of various therapeutic groups in urine samples with use of HPLC.

PubMed

Baranowska, Irena; Płonka, Joanna

2016-04-01

A high-performance liquid chromatography method for simultaneous separation and determination of biogenic amines [dopamine, epinephrine, serotonin and its six metabolites (normetanephrine, metanephrine, 3,4-dihydroxyphenylacetic acid, 4-hydroxy-3-methoxyphenylglycol, homovanilic acid and 5-hydroxyindoloacetic acid)] with drugs from different therapeutically groups [analgesics (paracetamol, metamizol), diuretics (furosemide) and antibiotics (cefazolin, fluconazole)] was developed. A chromatographic column with pre-column with octadecylsilane phase (C18e ) and two detectors - diode array serial connected and fluorescence - was used. Gradient elution of mixture of acetate buffer (pH 4.66) and methanol as a mobile phase was applied. The limit of detection (LOD) of 8-10 ng/mL and limit of quantitation (LOQ) of 24-30 ng/mL for biogenic amines, as well as the LOD of 50-100 ng/mL and the LOQ of 150-300 ng/mL for drugs, were determined. The applied sample preparation method allowed recoveries of 93% for the biogenic amines and 92% for the drugs to be achieved. The developed procedure has been applied to simultaneous determination of the examined compounds in urine samples and could be used in clinical analysis. Copyright © 2015 John Wiley & Sons, Ltd.

Development of a precolumn derivatization HPLC method with diode-array detection for the determination of amino sugars in peat and soil humic acids.

PubMed

Beňo, Erik; Góra, Róbert; Hutta, Milan

2018-02-01

The work is focused on the development of a high-performance liquid chromatography method with diode-array detection for the separation and quantitation of the three most abundant amino sugars; d-glucosamine, d-galactosamine, and d-mannosamine. The high-performance liquid chromatography separation was carried out by reversed-phase chromatography on Chromolith Performance RP-18e monolithic column after acid hydrolysis (5 M HCl) and precolumn derivatization of samples using diethyl ethoxymethylenemalonate. Gradient elution and a mobile phase composed of ammonium formate buffer solution (10 mmol/L, pH 3.60) and methanol with flow rate of 1.0 mL/min were used. The monitoring wavelength was set at 280 nm. The limits of detection and quantitation for analytes ranged from 0.017 to 0.122 mg/L and from 0.057 to 0.407 mg/L, respectively. The proposed method was successfully applied for the determination of amino sugars in samples of humic acids isolated from different soils and peat. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparative effects of simulated acid rain of different ratios of SO42- to NO3- on fine root in subtropical plantation of China.

PubMed

Liu, Xin; Zhao, Wenrui; Meng, Miaojing; Fu, Zhiyuan; Xu, Linhao; Zha, Yan; Yue, Jianmin; Zhang, Shuifeng; Zhang, Jinchi

2018-03-15

The influence of acid rain on forest trees includes direct effects on foliage as well as indirect soil-mediated effects that cause a reduction in fine-root growth. In addition, the concentration of NO 3 - in acid rain increases with the rapidly growing of nitrogen deposition. In this study, we investigated the impact of simulated acid rain with different SO 4 2- /NO 3 - (S/N) ratios, which were 5:1 (S), 1:1 (SN) and 1:5 (N), on fine-root growth from March 2015 to February 2016. Results showed that fine roots were more sensitive to the effects of acid rain than soils in the short-term. Both soil pH and fine root biomass (FRB) significantly decreased as acid rain pH decreased, and also decreased with the percentage of NO 3 - increased in acid rain. Acid rain pH significantly influenced soil total carbon and available potassium in summer. Higher acidity level (pH=2.5), especially of the N treatments, had the strongest inhibitory impact on soil microbial activity after summer. The structural equation modelling results showed that acid rain S/N ratio and pH had stronger direct effects on FRB than indirect effects via changed soil and fine root properties. Fine-root element contents and antioxidant enzymes activities were significantly affected by acid rain S/N ratio and pH during most seasons. Fine-root Al ion content, Ca/Al, Mg/Al ratios and catalase activity were used as better indicators than soil parameters for evaluating the effects of different acid rain S/N ratios and pH on forests. Our results suggest that the ratio of SO 4 2- to NO 3 - in acid rain is an important factor which could affect fine-root growth in subtropical forests of China. Copyright © 2017. Published by Elsevier B.V.