Strategies to overcome pH-dependent solubility of weakly basic drugs by using different types of alginates.

PubMed

Gutsche, S; Krause, M; Kranz, H

2008-12-01

Weakly basic drugs demonstrate higher solubility at lower pH, thus often leading to faster drug release at lower pH. The objective of this study was to achieve pH-independent release of weakly basic drugs from extended release formulations based on the naturally occurring polymer sodium alginate. Three approaches to overcome the pH-dependent solubility of the weakly basic model drug verapamil hydrochloride were investigated. First, matrix tablets were prepared by direct compression of drug substance with different types of sodium alginate only. Second, pH-modifiers were added to the drug/alginate matrix systems. Third, press-coated tablets consisting of an inner pH-modifier tablet core and an outer drug/sodium alginate coat were prepared. pH-Independent drug release was achieved from matrix tablets consisting of selected alginates and drug substance only. Alginates are better soluble at higher pH. Therefore, they are able to compensate the poor solubility of weakly basic drugs at higher pH as the matrix of the tablets dissolves faster. This approach was successful when using alginates that demonstrated fast hydration and erosion at higher pH. The approach failed for alginates with less-pronounced erosion at higher pH. The addition of fumaric acid to drug/alginate-based matrix systems decreased the microenvironmental pH within the tablets thus increasing the solubility of the weakly basic drug at higher pH. Therefore, pH-independent drug release was achieved irrespective of the type of alginate used. Drug release from press-coated tablets did not provide any further advantages as compound release remained pH-dependent.

Sensitive detection of strong acidic condition by a novel rhodamine-based fluorescent pH chemosensor.

PubMed

Tan, Jia-Lian; Yang, Ting-Ting; Liu, Yu; Zhang, Xue; Cheng, Shu-Jin; Zuo, Hua; He, Huawei

2016-05-01

A novel rhodamine-based fluorescent pH probe responding to extremely low pH values has been synthesized and characterized. This probe showed an excellent photophysical response to pH on the basis that the colorless spirocyclic structure under basic conditions opened to a colored and highly fluorescent form under extreme acidity. The quantitative relationship between fluorescence intensity and pH value (1.75-2.62) was consistent with the equilibrium equation pH = pKa + log[(Imax - I)/(I - Imin)]. This sensitive pH probe was also characterized with good reversibility and no interaction with interfering metal ions, and was successfully applied to image Escherichia coli under strong acidity. Copyright © 2015 John Wiley & Sons, Ltd.

Control of the microstructure and surface chemistry of graphene aerogels via pH and time manipulation by a hydrothermal method.

PubMed

García-Bordejé, E; Víctor-Román, S; Sanahuja-Parejo, O; Benito, A M; Maser, W K

2018-02-15

Three-dimensional graphene aerogels of controlled pore size have emerged as an important platform for several applications such as energy storage or oil-water separation. The aerogels of reduced graphene oxide are mouldable and light weight, with a porosity up to 99.9%, consisting mainly of macropores. Graphene aerogel preparation by self-assembly in the liquid phase is a promising strategy due to its tunability and sustainability. For graphene aerogels prepared by a hydrothermal method, it is known that the pH value has an impact on their properties but it is unclear how pH affects the auto-assembly process leading to the final properties. We have monitored the time evolution of the chemical and morphological properties of aerogels as a function of the initial pH value. In the hydrothermal treatment process, the hydrogel is precipitated earlier and with lower oxygen content for basic pH values (∼13 wt% O) than for acidic pH values (∼20 wt% O). Moreover, ∼7 wt% of nitrogen is incorporated on the graphene nanosheets at basic pH generated by NH 3 addition. To our knowledge, there is no precedent showing that the pH value affects the microstructure of graphene nanosheets, which become more twisted and bent for the more intensive deoxygenation occurring at basic pH. The bent nanosheets attained at pH = 11 reduce the stacking by the basal planes and they connect via the borders, hence leading eventually to higher pore volumes. In contrast, the flatter graphene nanosheets attained under acidic pH entail more stacking and higher oxygen content after a long hydrothermal treatment. The gravimetric absorption capacity of non-polar solvents scales directly with the pore volume. The aerogels have proved to be highly selective, recyclable and robust for the absorption of nonpolar solvents in water. The control of the porous structure and surface chemistry by manipulation of pH and time will also pave the way for other applications such as supercapacitors or batteries.

Quantitative structure-permeability relationships at various pH values for acidic and basic drugs and drug-like compounds.

PubMed

Oja, M; Maran, U

2015-01-01

Absorption in gastrointestinal tract compartments varies and is largely influenced by pH. Therefore, considering pH in studies and analyses of membrane permeability provides an opportunity to gain a better understanding of the behaviour of compounds and to obtain good permeability estimates for prediction purposes. This study concentrates on relationships between the chemical structure and membrane permeability of acidic and basic drugs and drug-like compounds. The membrane permeability of 36 acidic and 61 basic compounds was measured using the parallel artificial membrane permeability assay (PAMPA) at pH 3, 5, 7.4 and 9. Descriptive and/or predictive single-parameter quantitative structure-permeability relationships were derived for all pH values. For acidic compounds, membrane permeability is mainly influenced by hydrogen bond donor properties, as revealed by models with r(2) > 0.8 for pH 3 and pH 5. For basic compounds, the best (r(2) > 0.7) structure-permeability relationships are obtained with the octanol-water distribution coefficient for pH 7.4 and pH 9, indicating the importance of partition properties. In addition to the validation set, the prediction quality of the developed models was tested with folic acid and astemizole, showing good matches between experimental and calculated membrane permeabilities at key pHs. Selected QSAR models are available at the QsarDB repository ( http://dx.doi.org/10.15152/QDB.166 ).

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

Roberts, F. Sloan; Kuhl, Kendra P.; Nilsson, Anders

The activity and selectivity for CO 2/CO reduction over copper electrodes is strongly dependent on the local surface structure of the catalyst and the pH of the electrolyte. Here we investigate a unique, copper nanocube surface (CuCube) as a CO reduction electrode under neutral and basic pH, using online electrochemical mass spectroscopy (OLEMS) to determine the onset potentials and relative intensities of methane and ethylene production. To relate the unique selectivity to the surface structure, the CuCube surface reactivity is compared to polycrystalline copper and three single crystals under the same reaction conditions. Here, we find that the high selectivitymore » for ethylene over the CuCube surface is most comparable to the Cu(100) surface, which has the cubic unit cell. However, the suppression of methane production over CuCube is unique to that particular surface. Basic pH is also shown to enhance ethylene selectivity on all surfaces, again with the CuCube surface being unique.« less

Biodegradation of 2,4,6-trinitrophenol by Rhodococcus sp. isolated from a picric acid-contaminated soil.

PubMed

Shen, Jinyou; Zhang, Jianfa; Zuo, Yi; Wang, Lianjun; Sun, Xiuyun; Li, Jiansheng; Han, Weiqing; He, Rui

2009-04-30

A picric acid-degrading bacterium, strain NJUST16, was isolated from a soil contaminated by picric acid and identified as a member of Rhodococcus sp. based on 16S rRNA sequence. The degradation assays suggested that the strain NJUST16 could utilize picric acid as the sole source of carbon, nitrogen and energy. The isolate grew optimally at 30 degrees C and initial pH 7.0-7.5 in the mineral salts medium supplemented with picric acid. It was basically consistent with degradation of picric acid by the isolate. Addition of nitrogen sources such as yeast extract and peptone accelerated the degradation of picric acid. However, the stimulation was concentration dependent. The degradation was accompanied by release of stoichiometric amount of nitrite and acidification. The degradation of picric acid at relatively high concentrations (>3.93 mM) demonstrated that the degradation was both pH and nitrite dependent. Neutral and slightly basic pH was crucial to achieve high concentrations of picric acid degradation by the NJUST16 strain.

Dissolution-modulating mechanism of pH modifiers in solid dispersion containing weakly acidic or basic drugs with poor water solubility.

PubMed

Tran, Phuong Ha-Lien; Tran, Thao Truong-Dinh; Lee, Kyoung-Ho; Kim, Dong-Jin; Lee, Beom-Jin

2010-05-01

Although the solid dispersion method has been known to increase the dissolution rate of poorly water-soluble drugs by dispersing them in hydrophilic carriers, one obstacle of the solid dispersion method is its limited solubilization capacity, especially for pH-dependent soluble drugs. pH-modified solid dispersion, in which pH modifiers are incorporated, may be a useful method for increasing the dissolution rate of weakly acidic or basic drugs. Sufficient research, including the most recent reports, was undertaken in this review. How could the inclusion of the pH the pH modifiers in the solid dispersion system change drug structural behaviors, molecular interactions, microenvironmental pH, and/or release rate of pH modifiers, relating with the enhanced dissolution of weakly acidic or weakly basic drugs with poor water solubility? These questions have been investigated to determine the dissolution-modulating mechanism of pH modifiers in solid dispersion containing weakly acidic or basic drugs. It is believed that step-by-step mechanistic approaches could provide the ultimate solution for solubilizing several poorly water-soluble drugs with pH-dependent solubility from a solid dispersion system, as well as provide ideas for developing future dosage systems.

Electroreduction of carbon monoxide over a copper nanocube catalyst: Surface structure and pH dependence on selectivity

DOE PAGES

Roberts, F. Sloan; Kuhl, Kendra P.; Nilsson, Anders

2016-02-16

The activity and selectivity for CO 2/CO reduction over copper electrodes is strongly dependent on the local surface structure of the catalyst and the pH of the electrolyte. Here we investigate a unique, copper nanocube surface (CuCube) as a CO reduction electrode under neutral and basic pH, using online electrochemical mass spectroscopy (OLEMS) to determine the onset potentials and relative intensities of methane and ethylene production. To relate the unique selectivity to the surface structure, the CuCube surface reactivity is compared to polycrystalline copper and three single crystals under the same reaction conditions. Here, we find that the high selectivitymore » for ethylene over the CuCube surface is most comparable to the Cu(100) surface, which has the cubic unit cell. However, the suppression of methane production over CuCube is unique to that particular surface. Basic pH is also shown to enhance ethylene selectivity on all surfaces, again with the CuCube surface being unique.« less

Heavy metal removal from waste waters by ion flotation.

PubMed

Polat, H; Erdogan, D

2007-09-05

Flotation studies were carried out to investigate the removal of heavy metals such as copper (II), zinc (II), chromium (III) and silver (I) from waste waters. Various parameters such as pH, collector and frother concentrations and airflow rate were tested to determine the optimum flotation conditions. Sodium dodecyl sulfate and hexadecyltrimethyl ammonium bromide were used as collectors. Ethanol and methyl isobutyl carbinol (MIBC) were used as frothers. Metal removal reached about 74% under optimum conditions at low pH. At basic pH it became as high as 90%, probably due to the contribution from the flotation of metal precipitates.

Effects of Manufacturing Methods on Dissolution and Absorption of Ketoconazole in the Presence of Organic Acid as a pH Modifier.

PubMed

Adachi, Masashi; Hinatsu, Yuta; Kusamori, Kosuke; Katsumi, Hidemasa; Sakane, Toshiyasu; Nakatani, Manabu; Wada, Koichi; Yamamoto, Akira

2017-05-01

Poorly water-soluble compounds have a potential risk of low and variable bioavailability caused by incomplete dissolution. Incorporation of organic acids as pH modifiers is effective method for solubility enhancement of basic compounds and requires no special technique and equipment. The purpose of this study was to evaluate the effect of manufacturing method on the extent of drug solubility enhancement. We successfully prepared the granules and tablets containing ketoconazole (KZ), which is weakly basic, as a model compound and citric acid as a pH modifier using conventional wet and dry granulations. KZ solubility under non-sink condition was enhanced with supersaturation using both wet and dry granulations. High-shear granulation was the most effective method in terms of KZ dissolution enhancement, because both an intimate contact and strong bonding between KZ and incorporated acid were achieved. KZ dissolved amount from the granules prepared by high-shear granulation was about eight times higher than that from the granules without the acid. The granulation involved to suppress a diffusion of acid dissolved, leading to the effectively maintained supersaturation state. The bioavailability of KZ after oral administration to rats was improved by applying high-shear granulation with citric acid independent of gastrointestinal pH. The granules prepared by high-shear granulation showed the bioavailability about 1.7-fold higher than that of the physical mixture in rats with and without neutralization of stomach. As a result, both the dissolution and absorption rates of KZ after oral administration were enhanced using conventional manufacturing technology.

Unusual Fluorescent Responses of Morpholine-functionalized Fluorescent Probes to pH via Manipulation of BODIPY’s HOMO and LUMO Energy Orbitals for Intracellular pH Detection

PubMed Central

Zhang, Jingtuo; Yang, Mu; Mazi, Wafa; Adhikari, Kapil; Fang, Mingxi; Xie, Fei; Valenzano, Loredana; Tiwari, Ashutosh; Luo, Fen-Tair; Liu, Haiying

2016-01-01

Three uncommon morpholine-based fluorescent probes (A, B and C) for pH were prepared by introducing morpholine residues to BODIPY dyes at 4,4’- and 2,6-positions, respectively. In contrast to morpholine-based fluorescent probes for pH reported in literature, these fluorescent probes display high fluorescence in a basic condition while they exhibit very weak fluorescence in an acidic condition. The theoretical calculation confirmed that morpholine is unable to function as either an electron donor or an electron acceptor to quench the BODIPY fluorescence in the neutral and basic condition via photo-induced electron transfer (PET) mechanism because the LUMO energy of morpholine is higher than those of the BODIPY dyes while its HOMO energy is lower than those of the BODIPY dyes. However, the protonation of tertiary amines of the morpholine residues in an acidic environment leads to fluorescence quenching of the BODIPY dyes via d-PET mechanism. The fluorescence quenching is because the protonation effectively decreases the LUMO energy which locates between the HOMO and LUMO energies of the BODIPY dyes. Fluorescent probe C with deep-red emission has been successfully used to detect pH changes in mammalian cells. PMID:27547822

Nanoscale Platelet Formation by Monounsaturated and Saturated Sophorolipids under Basic pH Conditions.

PubMed

Cuvier, Anne-Sophie; Babonneau, Florence; Berton, Jan; Stevens, Christian V; Fadda, Giulia C; Péhau-Arnaudet, Gérard; Le Griel, Patrick; Prévost, Sylvain; Perez, Javier; Baccile, Niki

2015-12-21

The self-assembly behavior of the yeast-derived bolaamphiphile sophorolipid (SL) is generally studied under acidic/neutral pH conditions, at which micellar and fibrillar aggregates are commonly found, according to the (un)saturation of the aliphatic chain: the cis form, which corresponds to the oleic acid form of SL, spontaneously forms micelles, whereas the saturated form, which corresponds to the stearic acid form of SL, preferentially forms chiral fibers. By using small-angle light and X-ray scattering (SLS, SAXS) combined with high-sensitivity transmission electron microscopy imaging under cryogenic conditions (cryo-TEM), the nature of the self-assembled structures formed by these two compounds above pH 10, which is the pH at which they are negatively charged due to the presence of a carboxylate group, has been explored. Under these conditions, these compounds self-assemble into nanoscale platelets, despite the different molecular structures. This work shows that the electrostatic repulsion forces generated by COO(-) mainly drive the self-assembly process at basic pH, in contrast with that found at pH below neutrality, at which self-assembly is driven by van der Waals forces and hydrogen bonding, and thus, is in agreement with previous findings on carbohydrate-based gemini surfactants. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Observed and modeled effects of pH on bioconcentration of diphenhydramine, a weakly basic pharmaceutical, in fathead minnows

EPA Science Inventory

Fathead minnows were exposed to diphenhydramine (DPH), a weakly basic pharmaceutical (pKa = 9.1), to examine pH effects on uptake and accumulation. Fish were exposed to 10 ìg/L DPH in water for up to 96 h at three nominal pH levels: 6.7, 7.7, and 8.7. In each case, an appa...

Role of Self-Association and Supersaturation in Oral Absorption of a Poorly Soluble Weakly Basic Drug.

PubMed

Narang, Ajit S; Badawy, Sherif; Ye, Qingmei; Patel, Dhaval; Vincent, Maria; Raghavan, Krishnaswamy; Huang, Yande; Yamniuk, Aaron; Vig, Balvinder; Crison, John; Derbin, George; Xu, Yan; Ramirez, Antonio; Galella, Michael; Rinaldi, Frank A

2015-08-01

Precipitation of weakly basic drugs in intestinal fluids can affect oral drug absorption. In this study, the implications of self-association of brivanib alaninate in acidic aqueous solution, leading to supersaturation at basic pH condition, on its solubility and oral absorption were investigated. Self-association of brivanib alaninate was investigated by proton NMR spectroscopy, surface tension measurement, dynamic light scattering, isothermal titration calorimetry, and molecular modeling. Drug solubility was determined in various pH media, and its tendency to supersaturate upon pH shift was investigated in buffered and biorelevant aqueous solutions. Pharmacokinetic modeling of human oral drug absorption was utilized for parameter sensitivity analyses of input variables. Brivanib alaninate exhibited continuous, and pH- and concentration-dependent self-association. This phenomenon resulted in positive deviation of drug solubility at acidic pH and the formation of a stable supersaturated drug solution in pH-shift assays. Consistent with the supersaturation phenomenon observed in vitro, oral absorption simulations necessitated invoking long precipitation time in the intestine to successfully predict in vivo data. Self-association of a weakly basic drug in acidic aqueous solution can increase its oral absorption by supersaturation and precipitation resistance at the intestinal pH. This consideration is important to the selection of parameters for oral absorption simulation.

Benzothiazole-Based AIEgen with Tunable Excited-State Intramolecular Proton Transfer and Restricted Intramolecular Rotation Processes for Highly Sensitive Physiological pH Sensing.

PubMed

Li, Kai; Feng, Qi; Niu, Guangle; Zhang, Weijie; Li, Yuanyuan; Kang, Miaomiao; Xu, Kui; He, Juan; Hou, Hongwei; Tang, Ben Zhong

2018-04-23

In this work, a benzothiazole-based aggregation-induced emission luminogen (AIEgen) of 2-(5-(4-carboxyphenyl)-2-hydroxyphenyl)benzothiazole (3) was designed and synthesized, which exhibited multifluorescence emissions in different dispersed or aggregated states based on tunable excited-state intramolecular proton transfer (ESIPT) and restricted intramolecular rotation (RIR) processes. 3 was successfully used as a ratiometric fluorescent chemosensor for the detection of pH, which exhibited reversible acid/base-switched yellow/cyan emission transition. More importantly, the pH jump of 3 was very precipitous from 7.0 to 8.0 with a midpoint of 7.5, which was well matched with the physiological pH. This feature makes 3 very suitable for the highly sensitive detection of pH fluctuation in biosamples and neutral water samples. 3 was also successfully used as a ratiometric fluorescence chemosensor for the detection of acidic and basic organic vapors in test papers.

pH-Dependence of Binding Constants and Desorption Rates of Phosphonate- and Hydroxamate-Anchored [Ru(bpy)3]2+ on TiO2 and WO3.

PubMed

Esarey, Samuel L; Bartlett, Bart M

2018-04-17

The binding constants and rate constants for desorption of the modified molecular dye [Ru(bpy) 3 ] 2+ anchored by either phosphonate or hydroxamate on the bipyridine ligand to anatase TiO 2 and WO 3 have been measured. In aqueous media at pH 1-10, repulsive electrostatic interactions between the negatively charged anchor and the negatively charged surface govern phosphonate desorption under neutral and basic conditions for TiO 2 anatase due to the high acidity of phosphonic acid (p K a,4 = 5.1). In contrast, the lower acidity of hydroxamate (p K a,1 = 6.5, p K a,2 = 9.1) leads to little change in adsorption/desorption properties as a function of pH from 1 to 7. The binding constant for hydroxamate is 10 3 in water, independent of pH in this range. These results are true for WO 3 as well, but are not reported at pH > 4 due to its Arrhenius acidity. Kinetics for desorption as a function of pH are reported, with a proposed mechanism for phosphonate desorption at high pH being the electrostatic repulsion of negative charges between the surface and the anionic anchor. Further, the hydroxamic acid anchor itself is likely the site of quasi-reversible redox activity in [Ru(bpy) 2 (2,2'-bpy-4,4'-(C(O)N(OH)) 2 )] 2+ , which does not lead to any measurable deterioration of the complex within 2 h of dark cyclic voltammogram scans in aqueous media. These results posit phosphonate as the preferred anchoring group under acidic conditions and hydroxamate for neutral/basic conditions.

Photocatalytic degradation of Maxilon C.I. basic dye using CS/CoFe2O4/GONCs as a heterogeneous photo-Fenton catalyst prepared by gamma irradiation.

PubMed

Al-Kahtani, Abdullah A; Abou Taleb, Manal F

2016-05-15

CS/CF/GONCs were synthesized via gamma irradiation cross-linking method with the aid of sonication. The nanocomposites exhibited a photo-Fenton catalytic feature for the degradation of Maxilon C.I. basic dye in aqueous medium using sunlight. The effects of pH, H2O2 concentration, and dosage of the catalyst, on the degradation rates of the dyes were examined. The optimal degradation rate was reached with 10mM H2O2 at pH 9.5. It was verified that the Maxilon C.I. basic dye degradation rate fits a pseudo-first-order kinetics for different initial concentrations of Maxilon C.I. dye. Fourth cyclic tests for Maxilon C.I. degradation showed that the magnetic catalyst was very stable, recoverable, highly active, and easy to separate using an external magnet. Hence, this magnetic catalyst has potential use in organic pollutant removal. Copyright © 2016 Elsevier B.V. All rights reserved.

Pharmacological MRI (phMRI) of the Human Central Nervous System.

PubMed

Lanfermann, H; Schindler, C; Jordan, J; Krug, N; Raab, P

2015-10-01

Pharmacological magnetic resonance imaging (phMRI) of the central nervous system (CNS) addresses the increasing demands in the biopharma industry for new methods that can accurately predict, as early as possible, whether novel CNS agents will be effective and safe. Imaging of physiological and molecular-level function can provide a more direct measure of a drug mechanism of action, enabling more predictive measures of drug activity. The availability of phMRI of the nervous system within the professional infrastructure of the Clinical Research Center (CRC) Hannover as proof of concept center ensures that advances in basic science progress swiftly into benefits for patients. Advanced standardized MRI techniques including quantitative MRI, kurtosis determination, functional MRI, and spectroscopic imaging of the entire brain are necessary for phMRI. As a result, MR scanners will evolve into high-precision measuring instruments for assessment of desirable and undesirable effects of drugs as the basic precondition for individually tailored therapy. The CRC's Imaging Unit with high-end large-scale equipment will allow the following unique opportunities: for example, identification of MR-based biomarkers to assess the effect of drugs (surrogate parameters), establishment of normal levels and reference ranges for MRI-based biomarkers, evaluation of the most relevant MRI sequences for drug monitoring in outpatient care. Another very important prerequisite for phMRI is the MHH Core Facility as the scientific and operational study unit of the CRC partner Hannover Medical School. This unit is responsible for the study coordination, conduction, complete study logistics, administration, and application of the quality assurance system based on required industry standards.

Hydrothermal carbonization (HTC) of wheat straw: influence of feedwater pH prepared by acetic acid and potassium hydroxide.

PubMed

Reza, M Toufiq; Rottler, Erwin; Herklotz, Laureen; Wirth, Benjamin

2015-04-01

In this study, influence of feedwater pH (2-12) was studied for hydrothermal carbonization (HTC) of wheat straw at 200 and 260°C. Acetic acid and KOH were used as acidic and basic medium, respectively. Hydrochars were characterized by elemental and fiber analyses, SEM, surface area, pore volume and size, and ATR-FTIR, while HTC process liquids were analyzed by HPLC and GC. Both hydrochar and HTC process liquid qualities vary with feedwater pH. At acidic pH, cellulose and elemental carbon increase in hydrochar, while hemicellulose and pseudo-lignin decrease. Hydrochars produced at pH 2 feedwater has 2.7 times larger surface area than that produced at pH 12. It also has the largest pore volume (1.1 × 10(-1) ml g(-1)) and pore size (20.2 nm). Organic acids were increasing, while sugars were decreasing in case of basic feedwater, however, phenolic compounds were present only at 260°C and their concentrations were increasing in basic feedwater. Copyright © 2015 Elsevier Ltd. All rights reserved.

Equilibrium and kinetic adsorption study of Basic Yellow 28 and Basic Red 46 by a boron industry waste.

PubMed

Olgun, Asim; Atar, Necip

2009-01-15

In this study, the adsorption characteristics of Basic Yellow 28 (BY 28) and Basic Red 46 (BR 46) onto boron waste (BW), a waste produced from boron processing plant were investigated. The equilibrium adsorption isotherms and kinetics were investigated. The adsorption equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that adsorption behavior of two dyes could be described reasonably well by a generalized isotherm. Kinetic studies indicated that the kinetics of the adsorption of BY 28 and BR 46 onto BW follows a pseudo-second-order model. The result showed that the BW exhibited high-adsorption capacity for basic dyes and the capacity slightly decreased with increasing temperature. The maximum adsorption capacities of BY 28 and BR 46 are reported at 75.00 and 74.73mgg(-1), respectively. The dye adsorption depended on the initial pH of the solution with maximum uptake occurring at about pH 9 and electrokinetic behavior of BW. Activation energy of 15.23kJ/mol for BY 28 and 18.15kJ/mol for BR 46 were determined confirming the nature of the physisorption onto BW. These results indicate that BW could be employed as low-cost material for the removal of the textile dyes from effluents.

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.

Robust analysis of the hydrophobic basic analytes loratadine and desloratadine in pharmaceutical preparations and biological fluids by sweeping-cyclodextrin-modified micellar electrokinetic chromatography.

PubMed

El-Awady, Mohamed; Belal, Fathalla; Pyell, Ute

2013-09-27

The analysis of hydrophobic basic analytes by micellar electrokinetic chromatography (MEKC) is usually challenging because of the tendency of these analytes to be adsorbed onto the inner capillary wall in addition to the difficulty to separate these compounds as they exhibit extremely high retention factors. A robust and reliable method for the simultaneous determination of loratadine (LOR) and its major metabolite desloratadine (DSL) is developed based on cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) with acidic sample matrix and basic background electrolyte (BGE). The influence of the sample matrix on the reachable focusing efficiency is studied. It is shown that the application of a low pH sample solution mitigates problems associated with the low solubility of the hydrophobic basic analytes in aqueous solution while having advantages with regard to on-line focusing. Moreover, the use of a basic BGE reduces the adsorption of these analytes in the separation compartment. The separation of the studied analytes is achieved in less than 7min using a BGE consisting of 10mmolL(-1) disodium tetraborate buffer, pH 9.30 containing 40mmolL(-1) SDS and 20mmolL(-1) hydroxypropyl-β-CD while the sample solution is composed of 10mmolL(-1) phosphoric acid, pH 2.15. A full validation study of the developed method based on the pharmacopeial guidelines is performed. The method is successfully applied to the analysis of the studied drugs in tablets without interference of tablet additives as well as the analysis of spiked human urine without any sample pretreatment. Furthermore, DSL can be detected as an impurity in LOR bulk powder at the stated pharmacopeial limit (0.1%, w/w). The selectivity of the developed method allows the analysis of LOR and DSL in combination with the co-formulated drug pseudoephedrine. It is shown that in CD-MEKC with basic BGE, solute-wall interactions are effectively suppressed allowing the development of efficient and precise methods for the determination of hydrophobic basic analytes, whereas the use of a low pH sample solution has a positive impact on the attainable sweeping efficiency without compromising peak shape and resolution. Copyright © 2013 Elsevier B.V. All rights reserved.

Analytical core loss calculations for magnetic materials used in high frequency high power converter applications. Ph.D. Thesis - Toledo Univ.

NASA Technical Reports Server (NTRS)

Triner, J. E.

1979-01-01

The basic magnetic properties under various operating conditions encountered in the state-of-the-art DC-AC/DC converters are examined. Using a novel core excitation circuit, the basic B-H and loss characteristics of various core materials may be observed as a function of circuit configuration, frequency of operation, input voltage, and pulse-width modulation conditions. From this empirical data, a mathematical loss characteristics equation is developed to analytically predict the specific core loss of several magnetic materials under various waveform excitation conditions.

Effects of gastric pH on oral drug absorption: In vitro assessment using a dissolution/permeation system reflecting the gastric dissolution process.

PubMed

Kataoka, Makoto; Fukahori, Miho; Ikemura, Atsumi; Kubota, Ayaka; Higashino, Haruki; Sakuma, Shinji; Yamashita, Shinji

2016-04-01

The aim of the present study was to evaluate the effects of gastric pH on the oral absorption of poorly water-soluble drugs using an in vitro system. A dissolution/permeation system (D/P system) equipped with a Caco-2 cell monolayer was used as the in vitro system to evaluate oral drug absorption, while a small vessel filled with simulated gastric fluid (SGF) was used to reflect the gastric dissolution phase. After applying drugs in their solid forms to SGF, SGF solution containing a 1/100 clinical dose of each drug was mixed with the apical solution of the D/P system, which was changed to fasted state-simulated intestinal fluid. Dissolved and permeated amounts on applied amount of drugs were then monitored for 2h. Similar experiments were performed using the same drugs, but without the gastric phase. Oral absorption with or without the gastric phase was predicted in humans based on the amount of the drug that permeated in the D/P system, assuming that the system without the gastric phase reflected human absorption with an elevated gastric pH. The dissolved amounts of basic drugs with poor water solubility, namely albendazole, dipyridamole, and ketoconazole, in the apical solution and their permeation across a Caco-2 cell monolayer were significantly enhanced when the gastric dissolution process was reflected due to the physicochemical properties of basic drugs. These amounts resulted in the prediction of higher oral absorption with normal gastric pH than with high gastric pH. On the other hand, when diclofenac sodium, the salt form of an acidic drug, was applied to the D/P system with the gastric phase, its dissolved and permeated amounts were significantly lower than those without the gastric phase. However, the oral absorption of diclofenac was predicted to be complete (96-98%) irrespective of gastric pH because the permeated amounts of diclofenac under both conditions were sufficiently high to achieve complete absorption. These estimations of the effects of gastric pH on the oral absorption of poorly water-soluble drugs were consistent with observations in humans. In conclusion, the D/P system with the gastric phase may be a useful tool for better predicting the oral absorption of poorly water-soluble basic drugs. In addition, the effects of gastric pH on the oral absorption of poorly water-soluble drugs may be evaluated by the D/P system with and without the gastric phase. Copyright © 2016 Elsevier B.V. All rights reserved.

The LHCb Starterkit

NASA Astrophysics Data System (ADS)

Puig, Albert; LHCb Starterkit Team

2017-10-01

The vast majority of high-energy physicists use and produce software every day. Software skills are usually acquired “on the go” and dedicated training courses are rare. The LHCb Starterkit is a new training format for getting LHCb collaborators started in effectively using software to perform their research. The course focuses on teaching basic skills for research computing. Unlike traditional tutorials we focus on starting with basics, performing all the material live, with a high degree of interactivity, giving priority to understanding the tools as opposed to handing out recipes that work “as if by magic”. The LHCb Starterkit was started by two young members of the collaboration inspired by the principles of Software Carpentry, and the material is created in a collaborative fashion using the tools we teach. Three successful entry-level workshops, as well as an advance one, have taken place since the start of the initiative in 2015, and were taught largely by PhD students to other PhD students.

Student understanding of pH: "i don't know what the log actually is, i only know where the button is on my calculator".

PubMed

Watters, Dianne J; Watters, James J

2006-07-01

In foundation biochemistry and biological chemistry courses, a major problem area that has been identified is students' lack of understanding of pH, acids, bases, and buffers and their inability to apply their knowledge in solving acid/base problems. The aim of this study was to explore students' conceptions of pH and their ability to solve problems associated with the behavior of biological acids to understand the source of student difficulties. The responses given by most students are characteristic of an atomistic approach in which they pay no attention to the structure of the problem and concentrate only on juggling the elements together until they get a solution. Many students reported difficulty in understanding what the question was asking and were unable to interpret a simple graph showing the pH activity profile of an enzyme. The most startling finding was the lack of basic understanding of logarithms and the inability of all except one student to perform a simple calculation on logs without a calculator. This deficiency in high school mathematical skills severely hampered their understanding of pH. This study has highlighted a widespread deficiency in basic mathematical skills among first year undergraduates and a fragmented understanding of acids and bases. Implications for the way in which the concepts of pH and buffers are taught are discussed. Copyright © 2006 International Union of Biochemistry and Molecular Biology, Inc.

Observed and modeled effects of pH on bioconcentration of diphenhydramine, a weakly basic pharmaceutical, by fathead minnows

EPA Science Inventory

Understanding the influence of pH on uptake and accumulation of ionizable pharmaceuticals by fish was recently identified as a major research need. In the present study, fathead minnows were exposed to diphenhydramine (DPH), a weakly basic pharmaceutical (pKa = 9.1). Fish were ...

Mouthwatering but erosive? A preliminary assessment of the acidity of a basic sauce used in many Indian dishes.

PubMed

Ghai, Nandini; Burke, F J Trevor

2012-12-01

The aim of this study was to assess whether some types of Indian cuisine may contain erosive components. Indian dishes were prepared by a previously published method and their pH measured using a pH probe. The results indicated: (i) that some components of Indian cooking, such as tomatoes and red chilli powder, had the potential to erode enamel; (ii) that the pH of some foods was reduced with increasing temperature; and (iii) that all the basic masalas made and tested had a pH of less than 4.5. Within the limitations of the study, it may be concluded that the basic sauce/masala used in north Indian dishes may have erosive potential. This information could be considered useful when advising patients who eat Indian curries about causes of acid erosion of their teeth.

How cocrystals of weakly basic drugs and acidic coformers might modulate solubility and stability.

PubMed

Kuminek, G; Rodríguez-Hornedo, N; Siedler, S; Rocha, H V A; Cuffini, S L; Cardoso, S G

2016-04-30

Cocrystals of a weakly basic drug (nevirapine) with acidic coformers are shown to alter the solubility dependence on pH, and to exhibit a pHmax above which a less soluble cocrystal becomes more soluble than the drug. The cocrystal solubility advantage can be dialed up or down by solution pH.

Polymeric Sulfated Amino Acid Surfactants: A New Class of Versatile Chiral Selectors for Micellar Electrokinetic Chromatography (MEKC) and MEKC-MS

PubMed Central

Ali Rizvi, Syed Asad; Zheng, Jie; Apkarian, Robert P.; Dublin, Steven N.; Shamsi, Shahab A.

2008-01-01

In this work, three amino acids derived (L-leucinol, L-isoleucinol and L-valinol) sulfated chiral surfactants are synthesized and polymerized. These chiral sulfated surfactants are thoroughly characterized to determine critical micelle concentration, aggregation number, polarity, optical rotation and partial specific volume. For the first time the morphological behavior of polymeric sulfated surfactants is revealed using cryogenic high-resolution electron microscopy (cryo-HRSEM). The polysodium N-undecenoyl-L-leucine sulfate (poly-L-SUCLS) shows distinct tubular structure, while polysodium N-undecenoyl-L-valine sulfate (poly-L-SUCVS) also shows tubular morphology but without any distinct order of the tubes. On the other hand, polysodium N-undecenoyl-L-isoleucine sulfate (poly-L-SUCILS) displays random distribution of coiled/curved filaments with heavy association of tightly and loosely bound water. All three polymeric sulfated surfactants are compared for enantio-separation of broad range of structurally diverse racemic compounds at very acidic, neutral and basic pH conditions in micellar electrokinetic chromatography (MEKC). A small combinatorial library of 10 structurally related phenylethylamines (PEAs) is investigated for chiral separation under acidic and moderately acidic to neutral pH conditions using an experimental design. In contrast to neutral pH conditions, at acidic pH, significantly enhanced chiral resolution is obtained for class I and class II PEAs due to the compact structure of polymeric sulfated surfactants. It is observed that the presence of hydroxy group on the benzene ring of PEAs resulted in deterioration of enantioseparation. A sensitive MEKC-mass spectrometry (MS) method is developed for one of the PEA (e.g., (±)-pseudoephedrine) in human urine. Very low limit of detection (LOD) is obtained at pH 2.0 (LOD 325 ng/mL), which is ca 16 times better compared to pH 8.0 (LOD 5.2 µg/mL). Other broad range of chiral analytes (β-blockers, phenoxypropionic acid, benzoin derivatives, PTH-amino acids, and benzodiazepinones) studied also provided improved chiral separation at low pH compared to high pH conditions. Among the three polymeric sulfated surfactants, poly-L-SUCILS with two chiral centers on the polymer head group provided overall higher enantioresolution for the investigated acidic, basic and neutral compounds. This work clearly demonstrates for the first time the superiority of chiral separation and sensitive MS detection at low pH over conventional high pH chiral separation and detection employing anionic chiral polymeric surfactants in MEKC and MEKC-MS. PMID:17263313

Effect of n-octanol in the mobile phase on lipophilicity determination by reversed-phase high-performance liquid chromatography on a modified silica column.

PubMed

Benhaim, Deborah; Grushka, Eli

2008-10-31

In this study, we show that the addition of n-octanol to the mobile phase improves the chromatographic determination of lipophilicity parameters of xenobiotics (neutral solutes, acidic, neutral and basic drugs) on a Phenomenex Gemini C18 column. The Gemini C18 column is a new generation hybrid silica-based column with an extended pH range capability. The wide pH range (2-12) afforded the examination of basic drugs and acidic drugs in their neutral form. Extrapolated retention factor values, [Formula: see text] , obtained on the above column with the n-octanol-modified mobile phase were very well correlated (1:1 correlation) with literature values of logP (logarithm of the partition coefficient in n-octanol/water) of neutral compounds and neutral drugs (69). In addition, we found good linear correlations between measured [Formula: see text] values and calculated values of the logarithm of the distribution coefficient at pH 7.0 (logD(7.0)) for ionized acidic and basic drugs (r(2)=0.95). The Gemini C18 phase was characterized using the linear solvation energy relationship (LSER) model of Abraham. The LSER system constants for the column were compared to the LSER constants of n-octanol/water extraction system using the Tanaka radar plots. The comparison shows that the two methods are nearly equivalent.

Influence of surface chemistry of carbon materials on their interactions with inorganic nitrogen contaminants in soil and water.

PubMed

Sumaraj; Padhye, Lokesh P

2017-10-01

Inorganic nitrogen contaminants (INC) (NH 4 + , NO 3 - , NO 2 - , NH 3 , NO, NO 2 , and N 2 O) pose a growing risk to the environment, and their remediation methods are highly sought after. Application of carbon materials (CM), such as biochar and activated carbon, to remediate INC from agricultural fields and wastewater treatment plants has gained a significant interest since past few years. Understanding the role of surface chemistry of CM in adsorption of various INC is highly critical to increase adsorption efficiency as well as to assess the long term impact of using these highly recalcitrant CM for remediation of INC. Critical reviews of adsorption studies related to INC have revealed that carbon surface chemistry (surface functional groups, pH, Eh, elemental composition, and mineral content) has significant influence on adsorption of INC. Compared to basic functional groups, oxygen containing surface functional groups have been found to be more influential for adsorption of INC. However, basic sites on carbon materials still play an important role in chemisorption of anionic INC. Apart from surface functional groups, pH, Eh and pH zpc of CM and elemental and mineral composition of its surface are important properties capable of altering INC interactions with CM. This review summarizes our current understanding of INC interactions with CM's surface through the known chemisorption mechanisms: electrostatic interaction, hydrogen bonding, electron donor-acceptor mechanism, hydrophobic and hydrophilic interaction, chemisorption aided by minerals, and interactions influenced by pH and elemental composition. Change in surface chemistry of CM in soil during aging is also discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

How cocrystals of weakly basic drugs and acidic coformers might modulate solubility and stability

PubMed Central

Kuminek, G.; Rodríguez-Hornedo, N.; Siedler, S.; Rocha, H. V. A.; Cuffini, S. L.; Cardoso, S. G.

2016-01-01

Cocrystals of a weakly basic drug (nevirapine) with acidic coformers are shown to alter the solubility dependence on pH, and to exhibit a pHmax above which a less soluble cocrystal becomes more soluble than the drug. The cocrystal solubility advantage can be dialed up or down by solution pH. PMID:27042997

A basic helix-loop-helix transcription factor, PhFBH4, regulates flower senescence by modulating ethylene biosynthesis pathway in petunia

USDA-ARS?s Scientific Manuscript database

The basic helix-loop-helix (bHLH) transcription factors (TFs) play important roles in regulating multiple biological processes in plants. However, there are few reports about the function of bHLHs in flower senescence. In this study, a bHLH TF, PhFBH4, was found to be dramatically upregulated during...

Parametric and energy consumption optimization of Basic Red 2 removal by electrocoagulation/egg shell adsorption coupling using response surface methodology in a batch system.

PubMed

de Carvalho, Helder Pereira; Huang, Jiguo; Zhao, Meixia; Liu, Gang; Yang, Xinyu; Dong, Lili; Liu, Xingjuan

2016-01-01

In this study, response surface methodology (RSM) model was applied for optimization of Basic Red 2 (BR2) removal using electrocoagulation/eggshell (ES) coupling process in a batch system. Central composite design was used to evaluate the effects and interactions of process parameters including current density, reaction time, initial pH and ES dosage on the BR2 removal efficiency and energy consumption. The analysis of variance revealed high R(2) values (≥85%) indicating that the predictions of RSM models are adequately applicable for both responses. The optimum conditions when the dye removal efficiency of 93.18% and energy consumption of 0.840 kWh/kg were observed were 11.40 mA/cm(2) current density, 5 min and 3 s reaction time, 6.5 initial pH and 10.91 g/L ES dosage.

Electroless Cu Plating on Anodized Al Substrate for High Power LED.

PubMed

Rha, Sa-Kyun; Lee, Youn-Seoung

2015-03-01

Area-selective copper deposition on screen printed Ag pattern/anodized Al/Al substrate was attempted using a neutral electroless plating processes for printed circuit boards (PCBs), according to a range of variation of pH 6.5-pH 8 at 70 °C. The utilized basic electroless solution consisted of copper(II) sulfate pentahydrate, sodium phosphinate monohydrate, sodium citrate tribasic dihydrate, ammonium chloride, and nickel(II) sulfate hexahydrate. The pH of the copper plating solutions was adjusted from pH 6.5 to pH 8 using NH4OH. Using electroless plating in pH 6.5 and pH 7 baths, surface damage to the anodized Al layer hardly occurred; the structure of the plated Cu-rich films was a typical fcc-Cu, but a small Ni component was co-deposited. In electroless plating at pH 8, the surface of the anodized Al layer was damaged and the Cu film was composed of a lot of Ni and P which were co-deposited with Cu. Finally, in a pH 7 bath, we can make a selectively electroless plated Cu film on a PCB without any lithography and without surface damage to the anodized Al layer.

Determination of phenformin hydrochloride using molecular imprinting technology coupled with flow-injection chemiluminescence.

PubMed

Liu, Zhenbo; Jia, Fengyan; Wang, Wenwen; Wang, Cuixia; Liu, Yongming

2012-01-01

A novel method was developed using molecular imprinting technology (MIT) coupled with flow-injection chemiluminescence (FI-CL) for highly sensitive detection of phenformin hydrochloride (PH). The phenformin imprinted polymer was synthesized with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. Newly synthesized molecularly imprinted polymer (MIP) particles were packed into a column as a selective recognition element for determination of PH. A CL method for the determination of PH was developed based on the CL reaction of PH with N-bromosuccinimide sensitized by eosin Y in basic media. The optimization of detection conditions was investigated. The CL intensity responded linearly to the concentration of PH in the range 0.09-2.0 µg/mL, with a correlation coefficient of 0.9920. The detection limit was 0.031 µg/mL. The relative standard deviation for the determination of 1.0 µg/mL PH solution was 1.0% (n = 11). The method was applied to the determination of PH in urine samples, with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.

Crown condition dynamics of oak in southern Sweden 1988-1999.

PubMed

Drobyshev, Igor; Anderson, Stefan; Sonesson, Kerstin

2007-11-01

Crown defoliation of oak (Quercus robur and Q. petraea) was analysed in 808 trees during three forest condition surveys (1988, 1993, and 1999) in the southern Sweden. From 1988 to 1999 crown defoliation increased by more than 20%. Changes in crown defoliation were related to the pH in the upper 20-30 cm of the mineral soils, which was closely connected to other measures of soil fertility (cation exchange capacity, CEC and C/N ratio). Trees growing on soils with a high pH (> or =4.00, in BaCl2 filtrate), high CEC and low C/N ratio had significantly lower crown defoliation than trees growing on more acid soils (pH <4.00), indicating that less favourable soil conditions may further enhance oak decline. Age did not differentiate trees with respect to crown defoliation, indicating that decline in crown condition was not due to an age-related increase in crown transparency. Considering only trees younger than 100 years, a significant interaction was observed between changes in crown defoliation and soil pH. Trees younger than 100 years old growing on more acidic soils had a greater increase in crown transparency than trees on more basic soils between 1988 and 1999. Trees > or =100 years old had significantly higher defoliation on more acidic than on more basic soils, however defoliation dynamics of these trees over 1988-99 was not related to soil acidity. Two biotic agents (insect and fungal leaf infections) evaluated in this study did not prove to be important drivers of defoliation dynamics.

Selective solvent extraction of cellulosic material

DOEpatents

Wang, D.I.C.; Avgerinos, G.C.

1983-07-26

Cellulosic products having a high hemicellulose to lignin weight ratio are obtained by extracting a cellulosic composition with basic ethanol-water solution having a pH between about 12 and about 14 at a temperature between about 15 and about 70 C and for a time period between about 2 and about 80 hours. 6 figs.

Selective solvent extraction of cellulosic material

DOEpatents

Wang, Daniel I. C.; Avgerinos, George C.

1983-01-01

Cellulosic products having a high hemicellulose to lignin weight ratio are obtained by extracting a cellulosic composition with basic ethanol-water solution having a pH between about 12 and about 14 at a temperature between about 15.degree. and about 70.degree. C. and for a time period between about 2 and about 80 hours.

Stability and oxidation products of hydrolysable tannins in basic conditions detected by HPLC/DAD-ESI/QTOF/MS.

PubMed

Tuominen, Anu; Sundman, Terhi

2013-01-01

Hydrolysable tannins occur in plants that are used for food or medicine by humans or herbivores. Basic conditions can alter the structures of tannins, that is, the oxidation of phenolic groups can lead to the formation of toxic quinones. Previously, these labile quinones and other oxidation products have been studied with colorimetric or electron paramagnetic resonance methods, which give limited information about products. To study the stability and oxidation products of hydrolysable tannins in basic conditions using HPLC with a diode-array detector (DAD) combined with electrospray ionisation (ESI) and quadrupole time-of-flight (QTOF) MS. Three galloyl glucoses, four galloyl derivatives with different polyols and three ellagitannins were purified from plants. The incubation reactions of tannins were monitored by HPLC/DAD at five pH values and in reduced oxygen conditions. Reaction products were identified based on UV spectra and mass spectral fragmentation obtained with the high-resolution HPLC/DAD-ESI/QTOF/MS. The use of a base-resistant HPLC column enabled injections without the sample pre-treatment and thus detection of short-lived products. Hydrolysable tannins were unstable in basic conditions and half-lives were mostly less than 10 min at pH 10. Degradation rates were faster at pH 11 but slower at milder pH. The HPLC analyses revealed that various products were formed and identified to be the result of hydrolysis, deprotonation and oxidation. Interestingly, the main hydrolysis product was ellagic acid; it was also formed from galloyl glucoses that do not contain oxidatively coupled galloyl groups in their initial structures. HPLD/DAD-ESI/QTOF/MS was an efficient method for the identification of polyphenol oxidation products and showed how different pH conditions determine the fate of hydrolysable tannins. Copyright © 2013 John Wiley & Sons, Ltd.

The pH-dependent assembly of Chaplin E from Streptomyces coelicolor.

PubMed

Dokouhaki, Mina; Hung, Andrew; Day, Li; Gras, Sally L

2017-05-01

Chaplin E, is one of five self-assembling peptides secreted by Streptomyces coelicolor that assist aerial growth by lowering the surface tension of water. Although the surface activity of a mixture of chaplin peptides has observed to depend on pH, it is unclear how the solvent environment (i.e. pH) influences the structure, assembly and subsequent functionality of these individual peptides. In this study, the conformation and fibril forming propensity of the Chaplin E peptide was assessed as a function of pH using a combination of experimental measurements and molecular dynamics simulations. At an acidic pH of 3.0, Chaplin E retained a random coil structure, whereas at the isoelectric point of 6.7 or a basic pH of 10.0, Chaplin E rapidly formed amyloid fibrils rich in β-sheet structure with high efficiency (>93%). Molecular dynamics simulations indicate the persistence of greater α-helical content at the N-terminus at high pH; this is likely partly due to the lack of electrostatic repulsion between residues His6 and Lys10. Since fibril formation was observed at high but not at low pH, we propose that the presence of an N-terminal α-helix in the monomeric form of Chaplin E is required for aggregation and conversion to β-amyloid fibrils. The pH sensitivity of Chaplin E peptide structure provides a route to control peptide assembly and may be important for the physiological function of this peptide, as a surface active agent in the transition from vegetative to aerial growth and could assist Streptomyces coelicolor in response to environmental fluctuations in pH. Copyright © 2017 Elsevier Inc. All rights reserved.

Noninvasive High-Throughput Single-Cell Analysis of the Intracellular pH of Saccharomyces cerevisiae by Ratiometric Flow Cytometry

PubMed Central

Valkonen, Mari; Mojzita, Dominik; Penttilä, Merja

2013-01-01

The ability of cells to maintain pH homeostasis in response to environmental changes has elicited interest in basic and applied research and has prompted the development of methods for intracellular pH measurements. Many traditional methods provide information at population level and thus the average values of the studied cell physiological phenomena, excluding the fact that cell cultures are very heterogeneous. Single-cell analysis, on the other hand, offers more detailed insight into population variability, thereby facilitating a considerably deeper understanding of cell physiology. Although microscopy methods can address this issue, they suffer from limitations in terms of the small number of individual cells that can be studied and complicated image processing. We developed a noninvasive high-throughput method that employs flow cytometry to analyze large populations of cells that express pHluorin, a genetically encoded ratiometric fluorescent probe that is sensitive to pH. The method described here enables measurement of the intracellular pH of single cells with high sensitivity and speed, which is a clear improvement compared to previously published methods that either require pretreatment of the cells, measure cell populations, or require complex data analysis. The ratios of fluorescence intensities, which correlate to the intracellular pH, are independent of the expression levels of the pH probe, making the use of transiently or extrachromosomally expressed probes possible. We conducted an experiment on the kinetics of the pH homeostasis of Saccharomyces cerevisiae cultures grown to a stationary phase after ethanol or glucose addition and after exposure to weak acid stress and glucose pulse. Minor populations with pH homeostasis behaving differently upon treatments were identified. PMID:24038689

Noninvasive high-throughput single-cell analysis of the intracellular pH of Saccharomyces cerevisiae by ratiometric flow cytometry.

PubMed

Valkonen, Mari; Mojzita, Dominik; Penttilä, Merja; Bencina, Mojca

2013-12-01

The ability of cells to maintain pH homeostasis in response to environmental changes has elicited interest in basic and applied research and has prompted the development of methods for intracellular pH measurements. Many traditional methods provide information at population level and thus the average values of the studied cell physiological phenomena, excluding the fact that cell cultures are very heterogeneous. Single-cell analysis, on the other hand, offers more detailed insight into population variability, thereby facilitating a considerably deeper understanding of cell physiology. Although microscopy methods can address this issue, they suffer from limitations in terms of the small number of individual cells that can be studied and complicated image processing. We developed a noninvasive high-throughput method that employs flow cytometry to analyze large populations of cells that express pHluorin, a genetically encoded ratiometric fluorescent probe that is sensitive to pH. The method described here enables measurement of the intracellular pH of single cells with high sensitivity and speed, which is a clear improvement compared to previously published methods that either require pretreatment of the cells, measure cell populations, or require complex data analysis. The ratios of fluorescence intensities, which correlate to the intracellular pH, are independent of the expression levels of the pH probe, making the use of transiently or extrachromosomally expressed probes possible. We conducted an experiment on the kinetics of the pH homeostasis of Saccharomyces cerevisiae cultures grown to a stationary phase after ethanol or glucose addition and after exposure to weak acid stress and glucose pulse. Minor populations with pH homeostasis behaving differently upon treatments were identified.

Proton triggered emission and selective sensing of picric acid by the fluorescent aggregates of 6,7-dimethyl-2,3-bis-(2-pyridyl)-quinoxaline.

PubMed

Mazumdar, Prativa; Maity, Samir; Shyamal, Milan; Das, Debasish; Sahoo, Gobinda Prasad; Misra, Ajay

2016-03-14

A heteroatom containing organic fluorophore 6,7-dimethyl-2,3-bis-(2-pyridyl)-quinoxaline (BPQ) is weakly emissive in solution but its emission properties are highly enhanced in the aggregated state due to the restriction of intramolecular rotation (RIR) and large amplitude vibrational modes, demonstrating the phenomenon, aggregation induced emission enhancement (AIEE). It has strong proton capture capability, allowing reversible fluorescence switching in basic and acidic medium and the emission color changes from blue to green in the aggregated state through protonation. It has been explained as a competition between intramolecular charge transfers (ICTs) and the AIEE phenomena at a lower pH range (pH ∼1-4). Such behavior enables it as a fluorescent pH sensor for detection in acidic and basic medium. Morphologies of the particles are characterized using optical and field emission scanning electron microscopic (FESEM) studies. The turn off fluorescence properties of aggregated BPQ have been utilized for the selective detection of picric acid and the fluorescence quenching is explained due to ground state complexation with a strong quenching constant, 7.81 × 10(4) M(-1).

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

Kakade, S. G., E-mail: sundipkakade@gmail.com, E-mail: ydk@physics.unipune.ac.in; Department of Physics, Sir Parashurambhau College, Pune-411 030; Kambale, R. C.

Cobalt ferrite (CoFe{sub 2}O{sub 4}) shown to be promising candidate for applications such as high-density magnetic recording, enhanced memory storage, magnetic fluids and catalysts. Utility of ferrite nanoparticles depends on its size, dispersibility in solutions, and magnetic properties. We have investigated the structural properties of synthesized cobalt ferrite nanoparticles synthesized by sol gel auto combustion for uncontrolled, acidic, neutral and basic pH values. X-ray diffraction (XRD) study confirms the cubic spinel phase formation with lattice constant 8.38 Å. In this study, we have optimized the pH value to synthesize homogenous cobalt ferrite nanoparticles with enhanced magnetic behavior. The surface morphologymore » has been investigated by employing SEM images and the confirmation of spinel ferrite was also supported by using IR spectroscopy. Magnetic measurements for CoFe{sub 2}O{sub 4} compositions (with pH <1, pH = 3, 7, 10) were investigated using VSM measurements.« less

SLIP CASTING METHOD

DOEpatents

Allison, A.G.

1959-09-01

S>A process is described for preparing a magnesium oxide slip casting slurry which when used in conjunction with standard casting techniques results in a very strong "green" slip casting and a fired piece of very close dimensional tolerance. The process involves aging an aqueous magnestum oxide slurry, having a basic pH value, until it attains a specified critical viscosity at which time a deflocculating agent is added without upsetting the basic pH value.

Inhibition of Photocatalytic Activity of Basic Blue-41 by ZnO Modified Surface with Amino Silane

NASA Astrophysics Data System (ADS)

Limsapapkasiphon, S.; Sirisaksoontorn, W.; Songsasen, A.

2018-03-01

The reduction of the photo catalytic efficiency of ZnO can be achieved by modifying its surface with amino silane, which synthesized through condensation reaction under basic condition. The pH of solution was varied from 8 to 14 during the synthesis and was found that pH 12 was the most suitable pH for the preparation. All of ZMAS were characterized by Elemental Analysis which showed the highest percentage of nitrogen at 3.1064% and IR technique which indicated the Si-O-Zn bond at about 1000 cm-1. The photodegradation property of ZMAS prepared at pH 8-12 toward basic blue 41 was retarded when compared with the unmodified ZnO. Effect of mole ratio of ZnO:APTES (1:0.1, 1:0.5, 1:1, and 1:2) in the preparation of ZMAS was investigated. The photodegration activity of ZMAS prepared at mole ratio of ZnO:APTES as 1:0.5 to 1:2 toward basic blue 41 was retarded when compared with the unmodified ZnO. The coating of amino silane on ZnO surface did not have much effect on the band gap energy of modified ZnO. The absorption edge of ZMAS was only slightly shifted from 392 to 397 nm.

Influence of humic acids on the adsorption of Basic Yellow 28 dye onto an iron organo-inorgano pillared clay and two hydrous ferric oxides.

PubMed

Zermane, Faiza; Cheknane, Benamar; Basly, Jean Philippe; Bouras, Omar; Baudu, Michel

2013-04-01

Effect of humic acids (HAs), macromolecules from natural organic matter, on the adsorption of Basic Yellow 28 is the aim of the present work. Three adsorbents were investigated in this study: an iron organo-inorgano pillared clay and two synthetic Hydrous Iron Oxide (Goethite and HFO). The surface charge was positive in the pH range of this study for the pillared clay; in contrast, it changes from positive to negative when the pH value increased (pH>9) for the two (oxy)hydroxides. Pseudo-first order kinetic rate constants and adsorption capacities increase from humic acid to BY 28. Adsorption isotherms of BY 28 and HA in single component were analysed using the Freundlich equation. Adsorption capacities increased sharply when the pH value of the dye solution was raised from 3 to 9. Increasing the pH medium from 3 to 9 reduces the HA adsorption capacities onto Fe-SMPM and iron oxyhydroxides, respectively. Fitting between measured and predicted sorption capacities of BY 28 and HA in a binary component system indicates that the Sheindorf-Rebuhn-Sheintuch (SRS) model, an extended Freundlich model, is able to describe the simultaneous adsorption of BY 28 and HA. Humic acids favourably affect the adsorption of BY 28, and a cooperative mechanism could be suggested. The synergetic effect existing between BY 28 and HA is shown by the interaction coefficients η12, which are generally high and increase with pH. Some phenomena have been advanced to explain this mechanism. Copyright © 2012 Elsevier Inc. All rights reserved.

Functionally Similar WRKY Proteins Regulate Vacuolar Acidification in Petunia and Hair Development in Arabidopsis

PubMed Central

de Vries, Michel

2016-01-01

The WD40 proteins ANTHOCYANIN11 (AN11) from petunia (Petunia hybrida) and TRANSPARENT TESTA GLABRA1 (TTG1) from Arabidopsis thaliana and associated basic helix-loop-helix (bHLH) and MYB transcription factors activate a variety of differentiation processes. In petunia petals, AN11 and the bHLH protein AN1 activate, together with the MYB protein AN2, anthocyanin biosynthesis and, together with the MYB protein PH4, distinct genes, such as PH1 and PH5, that acidify the vacuole. To understand how AN1 and AN11 activate anthocyanin biosynthetic and PH genes independently, we isolated PH3. We found that PH3 is a target gene of the AN11-AN1-PH4 complex and encodes a WRKY protein that can bind to AN11 and is required, in a feed-forward loop, together with AN11-AN1-PH4 for transcription of PH5. PH3 is highly similar to TTG2, which regulates hair development, tannin accumulation, and mucilage production in Arabidopsis. Like PH3, TTG2 can bind to petunia AN11 and the Arabidopsis homolog TTG1, complement ph3 in petunia, and reactivate the PH3 target gene PH5. Our findings show that the specificity of WD40-bHLH-MYB complexes is in part determined by interacting proteins, such as PH3 and TTG2, and reveal an unanticipated similarity in the regulatory circuitry that controls petunia vacuolar acidification and Arabidopsis hair development. PMID:26977085

METHOD OF SEPARATING PLUTONIUM

DOEpatents

Heal, H.G.

1960-02-16

BS>A method of separating plutonium from aqueous nitrate solutions of plutonium, uranium. and high beta activity fission products is given. The pH of the aqueous solution is adjusted between 3.0 to 6.0 with ammonium acetate, ferric nitrate is added, and the solution is heated to 80 to 100 deg C to selectively form a basic ferric plutonium-carrying precipitate.

Communities that thrive in extreme conditions captured from a freshwater lake.

PubMed

Low-Décarie, Etienne; Fussmann, Gregor F; Dumbrell, Alex J; Bell, Graham

2016-09-01

Organisms that can grow in extreme conditions would be expected to be confined to extreme environments. However, we were able to capture highly productive communities of algae and bacteria capable of growing in acidic (pH 2), basic (pH 12) and saline (40 ppt) conditions from an ordinary freshwater lake. Microbial communities may thus include taxa that are highly productive in conditions that are far outside the range of conditions experienced in their host ecosystem. The organisms we captured were not obligate extremophiles, but were capable of growing in both extreme and benign conditions. The ability to grow in extreme conditions may thus be a common functional attribute in microbial communities. © 2016 The Author(s).

One-pot integrated biofuel production using low-cost biocompatible protic ionic liquids

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

Sun, Jian; Konda, N. V. S. N. Murthy; Parthasarathi, Ramakrishnan

The transformation of biomass into liquid fuels is of great importance. Previous work has demonstrated the capability of specific ionic liquids (ILs), such as 1-ethyl-3-methylimidazolium acetate ([C(2)C(1)Im][OAc]) and cholinium lysinate ([Ch][Lys]), to be effective biomass pretreatment solvents. Using these ILs for an integrated biomass-to-biofuel configuration is still challenging due to a significant water-wash related to the high toxicity of [C(2)C(1)Im][OAc] and pH adjustment prior to saccharification for the highly basic [Ch][Lys]. In this work, we demonstrate, for the first time, that a one-pot integrated biofuel production is enabled by a low cost (similar to$1 per kg) and biocompatible protic ILmore » (PIL), ethanolamine acetate, without pH adjustments, water-wash and solid-liquid separations. After pretreatment, the whole slurry is directly used for simultaneous saccharification and fermentation (SSF) with commercial enzyme cocktails and wild type yeast strains, generating 70% of the theoretical ethanol yield (based on switchgrass). The structure-performance relationships of PILs in terms of lignin removal, net basicity, and pH value are systematically studied. A technoeconomic analysis (TEA) revealed that an integrated biorefinery concept based on this PIL process could potentially reduce the minimum ethanol selling price by more than 40% compared to scenarios that require pH adjustment prior to SSF. Improvement of the economic performance will be made by reducing the dilution and enzyme loading during SSF as identified by TEA. This study demonstrates the impact of a biocompatible IL in terms of process optimization and conversion efficiency, and opens up avenues for realizing an IL based efficiently integrated biomass conversion technology.« less

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.

Evaluation of effects of pH and ionic strength on colloidal stability of IgG solutions by PEG-induced liquid-liquid phase separation.

PubMed

Thompson, Ronald W; Latypov, Ramil F; Wang, Ying; Lomakin, Aleksey; Meyer, Julie A; Vunnum, Suresh; Benedek, George B

2016-11-14

Colloidal stability of IgG antibody solutions is important for pharmaceutical and medicinal applications. Solution pH and ionic strength are two key factors that affect the colloidal stability of protein solutions. In this work, we use a method based on the PEG-induced liquid-liquid phase separation to examine the effects of pH and ionic strength on the colloidal stability of IgG solutions. We found that at high ionic strength (≥0.25M), the colloidal stability of most of our IgGs is insensitive to pH, and at low ionic strength (≤0.15M), all IgG solutions are much more stable at pH 5 than at pH 7. In addition, the PEG-induced depletion force is less efficient in causing phase separation at pH 5 than at pH 7. In contrast to the native inter-protein interaction of IgGs, the effect of depletion force on phase separation of the antibody solutions is insensitive to ionic strength. Our results suggest that the long-range electrostatic inter-protein repulsion at low ionic strength stabilizes the IgG solutions at low pH. At high ionic strength, the short-range electrostatic interactions do not make a significant contribution to the colloidal stability for most IgGs with a few exceptions. The weaker effect of depletion force at lower pH indicates a reduction of protein concentration in the condensed phase. This work advances our basic understanding of the colloidal stability of IgG solutions and also introduces a practical approach to measuring protein colloidal stability under various solution conditions.

pH tunability and influence of alkali metal basicity on the plasmonic resonance of silver nanoparticles

NASA Astrophysics Data System (ADS)

Yadav, Vijay D.; Akhil Krishnan, R.; Borade, Lalit; Shirolikar, Seema; Jain, Ratnesh; Dandekar, Prajakta

2017-07-01

Localized surface plasmon resonance has been a unique and intriguing feature of silver nanoparticles (AgNPs) that has attracted immense attention. This has led to an array of applications for AgNPs in optics, sensors, plasmonic imaging etc. Although numerous applications have been reported consistently, the importance of buffer and reaction parameters during the synthesis of AgNPs, is still unclear. In the present study, we have demonstrated the influence of parameters like pH, temperature and buffer conditions (0.1 M citrate buffer) on the plasmonic resonance of AgNPs. We found that neutral and basic pH (from alkali metal) provide optimum interaction conditions for nucleation of plasmon resonant AgNPs. Interestingly, this was not observed in the non-alkali metal base (ammonia). Also, when the nanoparticles synthesized from alkali metal base were incorporated in different buffers, it was observed that the nanoparticles dissolved in the acidic buffer and had reduced plasmonic resonance intensity. This, however, was resolved in the basic buffer, increasing the plasmonic resonance intensity and confirming that nucleation of nanoparticles required basic conditions. The above inference has been supported by characterization of AgNPs using UV-Vis spectrophotometer, Fluorimetry analysis, Infrared spectrometer and TEM analysis. The study concluded that the plasmonic resonance of AgNPs occurs due to the interaction of alkali (Na) and transition metal (Ag) salt in basic/neutral conditions, at a specific temperature range, in presence of a capping agent (citric acid), providing a pH tune to the overall system.

Trust Me, I'm a Doctor: A PhD Survival Guide

ERIC Educational Resources Information Center

Deconinck, Koen

2015-01-01

So, you have decided to do a PhD … now what? In this essay, the author provides some advice for beginning PhD students, basically sharing what he would tell his younger self. Doing a PhD is a transformative experience, but the process is challenging, not merely on an intellectual level but also psychologically. To overcome these challenges, one…

One Year of ICTP Diploma Courses On-Line Using the Automated EyA Recording System

ERIC Educational Resources Information Center

Canessa, Enrique; Fonda, Carlo; Zennaro, Marco

2009-01-01

The 12-month pre-Ph.D. ICTP Diploma Courses in the fields of Condensed Matter Physics, High Energy Physics, Mathematics, Earth System Physics and Basics Physics have been recorded using the automated, low cost recording system called EyA developed in-house. We discuss the technical details on how these recordings were implemented, together with…

Liquid permeation and chemical stability of anodic alumina membranes

PubMed Central

Buldakov, Dmitrii A; Tishkin, Alexey A; Lukashin, Alexey V; Eliseev, Andrei A

2017-01-01

A study on the chemical stability of anodic alumina membranes and their performance in long-term water and organic solvent permeation experiments is reported. Anodic alumina possesses high stability for both protonic and aprotonic organic solvents. However, serious degradation of the membrane occurs in pure water, leading to a drastic decrease of permeance (over 20% of the initial value after the passing of 0.250 m3/m2 of pure water). The drying of the membrane induces further permeance drop-off. The rate of membrane degradation strongly depends on the pH of the penetrant solution and increases in basic media. According to 27Al NMR and thermogravimetry results, the degradation of the membranes is associated with the dissolution of water-soluble [Al13O4(OH)24(H2O)12]7+ polyhydroxocomplexes and their further redeposition in the form of [Al(OH)4]−, resulting in channels blocking. This process intensifies in basic pH due to the high positive charge of the anodic alumina surface. An approach for improving anodic aluminum oxide stability towards dissolution in water by carbon CVD coating of the membrane walls is suggested. PMID:28382245

Functionally Similar WRKY Proteins Regulate Vacuolar Acidification in Petunia and Hair Development in Arabidopsis.

PubMed

Verweij, Walter; Spelt, Cornelis E; Bliek, Mattijs; de Vries, Michel; Wit, Niek; Faraco, Marianna; Koes, Ronald; Quattrocchio, Francesca M

2016-03-01

The WD40 proteins ANTHOCYANIN11 (AN11) from petunia (Petunia hybrida) and TRANSPARENT TESTA GLABRA1 (TTG1) from Arabidopsis thaliana and associated basic helix-loop-helix (bHLH) and MYB transcription factors activate a variety of differentiation processes. In petunia petals, AN11 and the bHLH protein AN1 activate, together with the MYB protein AN2, anthocyanin biosynthesis and, together with the MYB protein PH4, distinct genes, such as PH1 and PH5, that acidify the vacuole. To understand how AN1 and AN11 activate anthocyanin biosynthetic and PH genes independently, we isolated PH3. We found that PH3 is a target gene of the AN11-AN1-PH4 complex and encodes a WRKY protein that can bind to AN11 and is required, in a feed-forward loop, together with AN11-AN1-PH4 for transcription of PH5. PH3 is highly similar to TTG2, which regulates hair development, tannin accumulation, and mucilage production in Arabidopsis. Like PH3, TTG2 can bind to petunia AN11 and the Arabidopsis homolog TTG1, complement ph3 in petunia, and reactivate the PH3 target gene PH5. Our findings show that the specificity of WD40-bHLH-MYB complexes is in part determined by interacting proteins, such as PH3 and TTG2, and reveal an unanticipated similarity in the regulatory circuitry that controls petunia vacuolar acidification and Arabidopsis hair development. © 2016 American Society of Plant Biologists. All rights reserved.

[MD PhD programs: Providing basic science education for ophthalmologists].

PubMed

Spaniol, K; Geerling, G

2015-06-01

Enrollment in MD PhD programs offers the opportunity of a basic science education for medical students and doctors. These programs originated in the USA where structured programs have been offered for many years, but now German universities also run MD PhD programs. The MD PhD programs provided by German universities were investigated regarding entrance requirements, structure and financing modalities. An internet and telephone-based search was carried out. Out of 34 German universities 22 offered MD PhD programs. At 15 of the 22 universities a successfully completed course of studies in medicine was required for enrollment, 7 programs admitted medical students in training and 7 programs required a medical doctoral thesis, which had to be completed with at least a grade of magna cum laude in 3 cases. Financing required scholarships in many cases. Several German universities currently offer MD PhD programs; however, these differ considerably regarding entrance requirements, structure and financing. A detailed analysis investigating the success rates of these programs (e.g. successful completion and career paths of graduates) would be of benefit.

Theoretical study on the interactions between chlordecone hydrate and acidic surface groups of activated carbon under basic pH conditions.

PubMed

Melchor-Rodríguez, Kenia; Gamboa-Carballo, Juan José; Ferino-Pérez, Anthuan; Passé-Coutrin, Nady; Gaspard, Sarra; Jáuregui-Haza, Ulises Javier

2018-05-01

A theoretical study of the influence of acidic surface groups (SG) of activated carbon (AC) on chlordecone hydrate (CLDh) adsorption is presented, in order to help understanding the adsorption process under basic pH conditions. A seven rings aromatic system (coronene) with a functional group in the edge was used as a simplified model of AC to evaluate the influence of SG in the course of adsorption from aqueous solution at basic pH conditions. Two SG were modeled in their deprotonated form: carboxyl and hydroxyl (COO - and O - ), interacting with CLDh. In order to model the solvation process, all systems under study were calculated with up to three water molecules. Multiple Minima Hypersurface (MMH) methodology was employed to study the interactions of CLDh with SG on AC using PM7 semiempirical Hamiltonian, to explore the potential energy surfaces of the systems and evaluate their thermodynamic association energies. The re-optimization of representative structures obtained from MMH was done using M06-2X Density Functional Theory. The Quantum Theory of Atoms in Molecules (QTAIM) was used to characterize the interaction types. As result, the association of CLDh with acidic SG at basic pH conditions preferentially occurs between the two alcohol groups of CLDh with COO - and O - groups and by dispersive interactions of chlorine atoms of CLDh with the graphitic surface. On the other hand, the presence of covalent interactions between the negatively charged oxygen of SG and one hydrogen atom of CLDh alcohol groups (O - ⋯HO interactions) without water molecules, was confirmed by QTAIM study. It can be concluded that the interactions of CLDh with acidic SG of AC under basic pH conditions confirms the physical mechanisms of adsorption process. Copyright © 2018 Elsevier Inc. All rights reserved.

Design Strategies for CeO2-MoO3 Catalysts for DeNOx and Hg(0) Oxidation in the Presence of HCl: The Significance of the Surface Acid-Base Properties.

PubMed

Chang, Huazhen; Wu, Qingru; Zhang, Tao; Li, Mingguan; Sun, Xiaoxu; Li, Junhua; Duan, Lei; Hao, Jiming

2015-10-20

A series of CeMoOx catalysts with different surface Ce/Mo ratios was synthesized by a coprecipitation method via changing precipitation pH value. The surface basicity on selective catalytic reduction (SCR) catalysts (CeMoOx and VMo/Ti) was characterized and correlated to the durability and activity of catalyst for simultaneous elimination of NOx and Hg(0). The pH value in the preparation process affected the surface concentrations of Ce and Mo, the Brunauer-Emmett-Teller (BET) specific surface area, and the acid-base properties over the CeMoOx catalysts. The O 1s X-ray photoelectron spectroscopy (XPS) spectra and CO2-temperature programmed desorption (TPD) suggested that the surface basicity increased as the pH value increased. The existence of strong basic sites contributed to the deactivation effect of HCl over the VMo/Ti and CeMoOx catalysts prepared at pH = 12. For the CeMoOx catalysts prepared at pH = 9 and 6, the appearance of surface molybdena species replaced the surface -OH, and the existence of appropriate medium-strength basic sites contributed to their resistance to HCl poisoning in the SCR reaction. Moreover, these sites facilitated the adsorption and activation of HCl and enhanced Hg(0) oxidation. On the other hand, the inhibitory effect of NH3 on Hg(0) oxidation was correlated with the competitive adsorption of NH3 and Hg(0) on acidic surface sites. Therefore, acidic surface sites may play an important role in Hg(0) adsorption. The characterization and balance of basicity and acidity of an SCR catalyst is believed to be helpful in preventing deactivation by acid gas in the SCR reaction and simultaneous Hg(0) oxidation.

The Root Cause of Post-traumatic and Developmental Stress Disorder

DTIC Science & Technology

2011-03-01

traumatic and Developmental Stress Disorder Keith A. Young, PhD 1 MAR 2010 - 28 FEB 2011Annual01-03-2011 Our overarching scientific hypothesis holds that...highly susceptible to the effects of severe stress . We are studying this question using both clinical and basic approaches. New findings from our...experience induce a variation of normal brain anatomy that makes the brain highly susceptible to the effects of severe stress . The new goal of Project 1 is

pH dependent growth of poly( L-lysine)/poly( L-glutamic) acid multilayer films and their cell adhesion properties

NASA Astrophysics Data System (ADS)

Richert, Ludovic; Arntz, Youri; Schaaf, Pierre; Voegel, Jean-Claude; Picart, Catherine

2004-10-01

The short-term interaction of chondrosarcoma cells with (PGA/PLL) polyelectrolyte multilayers was investigated in a serum-containing medium for films built at different pHs and subsequently exposed to the culture medium. The buildup of the films and their stability was first investigated by means of optical waveguide lightmode spectroscopy, quartz crystal microbalance, streaming potential measurements and atomic force microscopy. While film growth is linear at all pHs, after a few layers have been deposited the growth is much larger for the films built at basic pH and even more pronounced for those built at acidic pH. However, these latter films remain stable in the culture medium only if they have been crosslinked prior to the ionic strength and pH jumps. The films built at acidic pH were found to swell in water by about 200% whereas those built at other pHs did not swell in a physiological buffer. For thin films (≈20 nm) built at pH = 7.4, the detachment forces were dependent on the outermost layer, the forces being significantly higher on PLL-ending films than on PGA-ending ones. In contrast, for the thick films built at pH = 4.4 and at pH = 10.4 (thickness of the order of few hundred of nanometers), the detachment forces were independent of the outermost layer of the film. The films built at pH = 10.4, which shrink in contact with salt containing solutions, were highly cell adhesive whereas those built at acidic pH were highly cell resistant. Protein adsorption and film roughness (as measured by AFM) could not explain these striking differences. The high adhesion observed on the film built at pH 10.4 may rather be related to the secondary structure of the film and to its relatively low swellability in water, whereas the cell resistance of the films built at pH 4.4 may be linked to their high swellability. Therefore, for the PGA/PLL films, the cell adhesion properties can be tuned depending on the deposition pH of the polyelectrolyte solutions. This study reveals the importance of the multilayer structure and architecture to control the detachment force of cells onto such films.

Encouraging minority undergraduates to choose science careers: career paths survey results.

PubMed

Villarejo, Merna; Barlow, Amy E L; Kogan, Deborah; Veazey, Brian D; Sweeney, Jennifer K

2008-01-01

To explore the reasons for the dearth of minorities in Ph.D.-level biomedical research and identify opportunities to increase minority participation, we surveyed high-achieving alumni of an undergraduate biology enrichment program for underrepresented minorities. Respondents were asked to describe their career paths and to reflect on the influences that guided their career choices. We particularly probed for attitudes and experiences that influenced students to pursue a research career, as well as factors relevant to their choice between medicine (the dominant career choice) and basic science. In agreement with earlier studies, alumni strongly endorsed supplemental instruction as a mechanism for achieving excellence in basic science courses. Undergraduate research was seen as broadening by many and was transformative for half of the alumni who ultimately decided to pursue Ph.D.s in biomedical research. That group had expressed no interest in research careers at college entry and credits their undergraduate research experience with putting them on track toward a research career. A policy implication of these results is that making undergraduate research opportunities widely available to biology students (including "premed" students) in the context of a structured educational enrichment program should increase the number of minority students who choose to pursue biomedical Ph.D.s.

Electrode effects on temporal changes in electrolyte pH and redox potential for water treatment

PubMed Central

Ciblak, Ali; Mao, Xuhui; Padilla, Ingrid; Vesper, Dorothy; Alshawabkeh, Iyad; Alshawabkeh, Akram N.

2012-01-01

The performance of electrochemical remediation methods could be optimized by controlling the physicochemical conditions of the electrochemical redox system. The effects of anode type (reactive or inert), current density and electrolyte composition on the temporal changes in pH and redox potential of the electrolyte were evaluated in divided and mixed electrolytes. Two types of electrodes were used: iron as a reactive electrode and mixed metal oxide coated titanium (MMO) as an inert electrode. Electric currents of 15, 30, 45 and 60 mA (37.5 mA L−1, 75 mA L−1, 112.5 mA L−1 and 150 mA L−1) were applied. Solutions of NaCl, Na2SO4 and NaHCO3 were selected to mimic different wastewater or groundwater composition. Iron anodes resulted in highly reducing electrolyte conditions compared to inert anodes. Electrolyte pH was dependent on electrode type, electrolyte composition and current density. The pH of mixed-electrolyte was stable when MMO electrodes were used. When iron electrodes were used, the pH of electrolyte with relatively low current density (37.5 mA L−1) did not show significant changes but the pH increased sharply for relatively high current density (150 mA L−1). Sulfate solution showed more basic and relatively more reducing electrolyte condition compared to bicarbonate and chloride solution. The study shows that a highly reducing environment could be achieved using iron anodes in divided or mixed electrolytes and the pH and redox potential could be optimized by using appropriate current and polarity reversal. PMID:22416866

Influence of pH on optoelectronic properties of zinc sulphide thin films prepared using hydrothermal and spin coating method

NASA Astrophysics Data System (ADS)

Choudapur, V. H.; Bennal, A. S.; Raju, A. B.

2018-04-01

The ZnS nanomaterial is synthesized by hydrothermal method under optimized conditions using Zinc acetate and sodium sulphide as precursors. The Zinc Sulphide thin films are obtained by simple spin coating method with high optical transmittance. The prepared thin films are adhesive and uniform. The x-ray diffraction analysis showed that the films are polycrystalline in cubic phase with the preferred orientation along (111) direction. Current-voltage curves were recorded at room temperature using Keithley 617 programmable electrometer and conductivity is calculated for the film coated on ITO by two probe method. The pH of the solution is varied by using ammonia and hydrochloric acid. The comparative studies of effect of pH on the morphology, crystallanity and optoelectronic properties of the films are studied. It is observed that the pH of the solution has large influence on optoelectronic properties. The thin film prepared with neutral pH has higher crystallanity, bandgap and conductivity as compared to the samples prepared in acidic or basic solutions.

pH- and ion-sensitive polymers for drug delivery

PubMed Central

Yoshida, Takayuki; Lai, Tsz Chung; Kwon, Glen S; Sako, Kazuhiro

2013-01-01

Introduction Drug delivery systems (DDSs) are important for effective, safe, and convenient administration of drugs. pH- and ion-responsive polymers have been widely employed in DDS for site-specific drug release due to their abilities to exploit specific pH- or ion-gradients in the human body. Areas covered Having pH-sensitivity, cationic polymers can mask the taste of drugs and release drugs in the stomach by responding to gastric low pH. Anionic polymers responsive to intestinal high pH are used for preventing gastric degradation of drug, colon drug delivery and achieving high bioavailability of weak basic drugs. Tumor-targeted DDSs have been developed based on polymers with imidazole groups or poly(β-amino ester) responsive to tumoral low pH. Polymers with pH-sensitive chemical linkages, such as hydrazone, acetal, ortho ester and vinyl ester, pH-sensitive cell-penetrating peptides and cationic polymers undergoing pH-dependent protonation have been studied to utilize the pH gradient along the endocytic pathway for intracellular drug delivery. As ion-sensitive polymers, ion-exchange resins are frequently used for taste-masking, counterion-responsive drug release and sustained drug release. Polymers responding to ions in the saliva and gastrointestinal fluids are also used for controlled drug release in oral drug formulations. Expert opinion Stimuli-responsive DDSs are important for achieving site-specific and controlled drug release; however, intraindividual, interindividual and intercellular variations of pH should be considered when designing DDSs or drug products. Combination of polymers and other components, and deeper understanding of human physiology are important for development of pH- and ion-sensitive polymeric DDS products for patients. PMID:23930949

A Recyclable Cu-MOF-74 Catalyst for the Ligand-Free O-Arylation Reaction of 4-Nitrobenzaldehyde and Phenol

PubMed Central

Leo, Pedro; Orcajo, Gisela; Briones, David; Calleja, Guillermo; Sánchez-Sánchez, Manuel; Martínez, Fernando

2017-01-01

The activity and recyclability of Cu-MOF-74 as a catalyst was studied for the ligand-free C–O cross-coupling reaction of 4-nitrobenzaldehyde (NB) with phenol (Ph) to form 4-formyldiphenyl ether (FDE). Cu-MOF-74 is characterized by having unsaturated copper sites in a highly porous metal-organic framework. The influence of solvent, reaction temperature, NB/Ph ratio, catalyst concentration, and basic agent (type and concentration) were evaluated. High conversions were achieved at 120 °C, 5 mol % of catalyst, NB/Ph ratio of 1:2, DMF as solvent, and 1 equivalent of K2CO3 base. The activity of Cu-MOF-74 material was higher than other ligand-free copper catalytic systems tested in this study. This catalyst was easily separated and reused in five successive runs, achieving a remarkable performance without significant porous framework degradation. The leaching of copper species in the reaction medium was negligible. The O-arylation between NB and Ph took place only in the presence of Cu-MOF-74 material, being negligible without the solid catalyst. The catalytic advantages of using nanostructured Cu-MOF-74 catalyst were also proven. PMID:28621710

A Recyclable Cu-MOF-74 Catalyst for the Ligand-Free O-Arylation Reaction of 4-Nitrobenzaldehyde and Phenol.

PubMed

Leo, Pedro; Orcajo, Gisela; Briones, David; Calleja, Guillermo; Sánchez-Sánchez, Manuel; Martínez, Fernando

2017-06-16

The activity and recyclability of Cu-MOF-74 as a catalyst was studied for the ligand-free C-O cross-coupling reaction of 4-nitrobenzaldehyde (NB) with phenol (Ph) to form 4-formyldiphenyl ether (FDE). Cu-MOF-74 is characterized by having unsaturated copper sites in a highly porous metal-organic framework. The influence of solvent, reaction temperature, NB/Ph ratio, catalyst concentration, and basic agent (type and concentration) were evaluated. High conversions were achieved at 120 °C, 5 mol % of catalyst, NB/Ph ratio of 1:2, DMF as solvent, and 1 equivalent of K₂CO₃ base. The activity of Cu-MOF-74 material was higher than other ligand-free copper catalytic systems tested in this study. This catalyst was easily separated and reused in five successive runs, achieving a remarkable performance without significant porous framework degradation. The leaching of copper species in the reaction medium was negligible. The O-arylation between NB and Ph took place only in the presence of Cu-MOF-74 material, being negligible without the solid catalyst. The catalytic advantages of using nanostructured Cu-MOF-74 catalyst were also proven.

Adsorption of 6-mercaptopurine and 6-mercaptopurine riboside on silver colloid: a pH dependent surface enhanced Raman spectroscopy and density functional theory study. Part I. 6-Mercaptopurine

NASA Astrophysics Data System (ADS)

Szeghalmi, A. V.; Leopold, L.; Pînzaru, S.; Chis, V.; Silaghi-Dumitrescu, I.; Schmitt, M.; Popp, J.; Kiefer, W.

2005-02-01

Surface enhanced Raman spectroscopy (SERS) on silver colloid has been applied to characterize the interaction of 6-mercaptopurine (6MP), an active drug used in chemotherapy of acute lymphoblastic leukemia, with a model biological substrate at therapeutical concentrations and as function of the pH value. The adsorption active sites and molecular orientation on the metal surface have been determined on the basis of SERS 'surface selection rules' subsequent to a detailed vibrational analysis of the 6MP tautomeric forms. Therefore, DFT calculations (vibrational wavenumbers, Raman scattering activities, partial atomic charges) of the optimized tautomers and potential energy distribution calculations have been performed. Around neutral pH value reorientation of the molecule has been observed. Under basic conditions the 6MP molecule is probably adsorbed on the silver colloid through the N1 atom of the purine ring and possibly the S atom, and adopts a tilted orientation to the surface. A reduction in the number of adsorbed molecules under basic conditions is proposed, since the SERS spectrum recorded at 10-6 M concentration at neutral pH value resembles the SERS spectra obtained under basic conditions at 10-5 M concentration. At acidic pH values a stronger interaction through the N9 and N3 atoms is suggested with an end-on orientation.

Naturally occurring alkaline amino acids function as efficient catalysts on Knoevenagel condensation at physiological pH: a mechanistic elucidation.

PubMed

Li, Weina; Fedosov, Sergey; Tan, Tianwei; Xu, Xuebing; Guo, Zheng

2014-05-01

To maintain biological functions, thousands of different reactions take place in human body at physiological pH (7.0) and mild conditions, which is associated with health and disease. Therefore, to examine the catalytic function of the intrinsically occurring molecules, such as amino acids at neutral pH, is of fundamental interests. Natural basic α-amino acid of L-lysine, L-arginine, and L-histidine neutralized to physiological pH as salts were investigated for their ability to catalyze Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate. Compared with their free base forms, although neutralized alkaline amino acid salts reduced the catalytic activity markedly, they were still capable to perform an efficient catalysis at physiological pH as porcine pancreatic lipase (PPL), one of the best enzymes that catalyze Knoevenagel condensation. In agreement with the fact that the three basic amino acids were well neutralized, stronger basic amino acid Arg and Lys showed more obvious variation in NH bend peak from the FTIR spectroscopy study. Study of ethanol/water system and quantitative kinetic analysis suggested that the microenvironment in the vicinity of amino acid salts and protonability/deprotonability of the amine moiety may determine their catalytic activity and mechanism. The kinetic study of best approximation suggested that the random binding might be the most probable catalytic mechanism for the neutralized alkaline amino acid salt-catalyzed Knoevenagel condensation.

Adsorption of a reactive dye on chemically modified activated carbons--influence of pH.

PubMed

Orfão, J J M; Silva, A I M; Pereira, J C V; Barata, S A; Fonseca, I M; Faria, P C C; Pereira, M F R

2006-04-15

The surface chemistry of a commercial activated carbon with a slightly basic nature was modified by appropriate treatments in order to obtain two additional samples, respectively with acidic and basic properties, without changing its textural parameters significantly. Different techniques (N2 adsorption at 77 K, temperature programmed desorption, and determination of acidity, basicity, and pH at the point of zero charge) were used to characterize the adsorbents. Kinetic and equilibrium adsorption data of a selected textile reactive dye (Rifafix Red 3BN, C.I. reactive red 241) on the mentioned materials were obtained at the pH values of 2, 7, and 12. The kinetic curves are fitted using the second-order model. The respective rate constants seem to diminish progressively with the initial concentration for the more diluted solutions tested, reaching a constant value at higher concentrations, which depends on the experimental system under consideration (adsorbent and pH). In general, the Langmuir model provides the best fit for the equilibrium data. The different uptakes obtained are discussed in relation to the surface chemical properties of the adsorbents. It is shown that the adsorption of the reactive (anionic) dye on the basic sample (prepared by thermal treatment under H2 flow at 700 degrees C) is favored. This conclusion is explained on the basis of the dispersive and electrostatic interactions involved. Moreover, it is also shown that the optimal adsorption condition for all the activated carbons tested corresponds to solution pH values not higher than the pH(pzc) of the adsorbents, which may be interpreted by taking into account the electrostatic forces present.

Tumor cell membrane-targeting pH-dependent electron donor-acceptor fluorescence systems with low background signals.

PubMed

Han, Liang; Liu, Mingming; Ye, Deyong; Zhang, Ning; Lim, Ed; Lu, Jing; Jiang, Chen

2014-03-01

Minimizing the background signal is crucial for developing tumor-imaging techniques with sufficient specificity and sensitivity. Here we use pH difference between healthy tissues and tumor and tumor targeting delivery to achieve this goal. We synthesize fluorophore-dopamine conjugate as pH-dependent electron donor-acceptor fluorescence system. Fluorophores are highly sensitive to electron-transfer processes, which can alter their optical properties. The intrinsic redox properties of dopamine are oxidation of hydroquinone to quinone at basic pH and reduction of quinone to hydroquinone at acidic pH. Quinone can accept electron then quench fluorescence. We design tumor cell membrane-targeting carrier for delivery. We demonstrate quenched fluorophore-quinone can be specially transferred to tumor extracellular environment and tumor-accumulated fluorophore can be activated by acidic pH. These tumor-targeting pH-dependent electron donor-acceptor fluorescence systems may offer new opportunity for developing tumor-imaging techniques. Copyright © 2014 Elsevier Ltd. All rights reserved.

Speedy Alchemy.

ERIC Educational Resources Information Center

Deininger, Rolf A.; Berger, Carl F., Jr.

1983-01-01

Provides instructions for interfacing a pH meter directly to an Apple II microcomputer without an analog-to-digital converter. Includes program listing (with enough remark statements to make it self-documenting) in Integer Basic to display the pH readings. (Author/JN)

Acid-base properties of the alumina surface: influence of the titration procedures on the microcalorimetric results.

PubMed

Morel, Jean-Pierre; Marmier, Nicolas; Hurel, Charlotte; Morel-Desrosiers, Nicole

2009-10-01

The enthalpy changes associated with the protonation and deprotonation of an alumina surface have been determined on the basis of microcalorimetry experiments and acid-base potentiometric titrations at 25 degrees C. It has been shown that the results may vary significantly according to the experimental procedure. In order to do so, the potentiometric and microcalorimetric titrations have been carried out first from an acidic pH to basic pH and second from a pH near the pH(zpc) of alumina to acidic or basic pH. It has been demonstrated that the pK(a) values deduced from the potentiometric titrations are the same whatever the experimental protocol whereas the only way to obtain meaningful enthalpies of proton exchange is to carry out microcalorimetric titrations by starting around the point of zero charge.

Floating lipid beads for the improvement of bioavailability of poorly soluble basic drugs: in-vitro optimization and in-vivo performance in humans.

PubMed

Abouelatta, Samar M; Aboelwafa, Ahmed A; Khalil, Rawia M; ElGazayerly, Omaima N

2015-01-01

The challenge in developing oral drug delivery systems of poorly soluble basic drugs is primarily due to their pH dependent solubility. Cinnarizine (CNZ), a model for a poorly soluble basic drug, has pH dependent solubility; where it dissolves readily at low pH in the stomach and exhibits a very low solubility at pH values greater than 4. It is also characterized by a short half life of 3-6h, which requires frequent daily administration resulting in poor patient compliance. In an attempt to solve these problems, extended release floating lipid beads were formulated. A 2(4) full factorial design was utilized for optimization of the effects of various independent variables; lipid:drug ratio, % Pluronic F-127, % Sterotex, and Gelucire 43/01:Gelucire 50/13 ratio, on the loading efficiency and release of CNZ from the lipid beads. In-vivo pharmacokinetic study of the optimized CNZ-lipid beads compared to Stugeron® (reference standard) was performed in healthy human volunteers. A promising approach for enhancing the bioavailability of the poorly soluble basic drug, CNZ, utilizing novel and simple floating lipid beads was successfully developed. Zero order release profile of CNZ was achieved for 12h. Mean AUC0-24 and AUC0-∞ of the optimized CNZ-loaded lipid beads were 4.23 and 6.04 times that of Stugeron® tablets respectively. Copyright © 2014 Elsevier B.V. All rights reserved.

Stabilization of T4 bacteriophage at acidic and basic pH by adsorption on paper.

PubMed

Meyer, Abigail; Greene, Melissa; Kimmelshue, Chad; Cademartiri, Rebecca

2017-12-01

Bacteriophages find applications in agriculture, medicine, and food safety. Many of these applications can expose bacteriophages to stresses that inactivate them including acidic and basic pH. Bacteriophages can be stabilized against these stresses by materials including paper, a common material in packaging and consumer products. Combining paper and bacteriophages creates antibacterial materials, which can reduce the use of antibiotics. Here we show that adsorption on paper protects T4, T5, and T7 bacteriophage from acidic and basic pH. We added bacteriophages to filter paper functionalized with carboxylic acid (carboxyl methyl cellulose) or amine (chitosan) groups, and exposed them to pH from 5.6 to 14. We determined the number of infective bacteriophages after exposure directly on the paper. All papers extended the lifetime of infective bacteriophage by at least a factor of four with some papers stabilizing bacteriophages for up to one week. The degree of stabilization depended on five main factors (i) the family of the bacteriophage, (ii) the charge of the paper and bacteriophages, (iii) the location of the bacteriophages within the paper, (iv) the ability of the paper to prevent bacteriophage-bacteriophage aggregation, and (v) the sensitivity of the bacteriophage proteins to the tested pH. Even when adsorbed on paper the bacteriophages were able to remove E. coli in milk. Choosing the right paper modification or material will protect bacteriophages adsorbed on that material against detrimental pH and other environmental challenges increasing the range of applications of bacteriophages on materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of pH, temperature, and chemical structure on the stability of S-(purin-6-yl)-L-cysteine: evidence for a novel molecular rearrangement mechanism to yield N-(purin-6-yl)-L-cysteine.

PubMed

Elfarra, A A; Hwang, I Y

1996-01-01

The stability of S-(purin-6-yl)-L-cysteine (SPC), a kidney-selective prodrug of 6-mercaptopurine and a putative metabolite of 6-chloropurine, was investigated under various pH and temperature conditions. At room temperature, the half-life (t 1/2) of SPC at either highly acidic (pH 3.6) or basic conditions (pH 9.6) was longer than at neutral or slightly acidic or basic conditions (pH 5.7-8.75). The primary degradation product, N-(purin-6-yl)-L-cysteine (NPC), was isolated using Sephadex LH-20 chromatography and characterized by 1H NMR and FAB/MS after derivatization with 2-iodoacetic acid. These results reveal novel stability requirements and implicate the cysteinyl amino group and the purinyl N-1 nitrogen in the mechanism of SPC rearrangement to NPC. Further evidence for this hypothesis was provided by the findings that the stability of SPC in phosphate buffer (pH 7.4) at 37 degrees C was similar to that of S-(guanin-6-yl)-L-cysteine, whereas S-(purin-6-yl)-N-acetyl-L-cysteine and S-(purin-6-yl)glutathione which have their cysteine amino groups blocked were much more stable than SPC. S-(Purin-6-yl)-L-homocysteine (SPHC) was also more stable than SPC, possibly because the formation of a 6-membered ring transition state as would be expected with SPHC is kinetically less favored than the formation of a 5-membered ring transition state as would be expected with SPC. These results may explain previous in vivo metabolism results of SPC and its analogs and may contribute to a better understanding of stability of structurally related cysteine S-conjugates.

Phase transition behavior of novel pH-sensitive polyaspartamide derivatives grafted with 1-(3-aminopropyl)imidazole.

PubMed

Seo, Kwangwon; Kim, Dukjoon

2006-09-15

New pH-sensitive polyaspartamide derivatives were synthesized by grafting 1-(3-aminopropyl)imidazole and/or O-(2-aminoethyl)-O'-methylpoly(ethylene glycol) 5000 on polysuccinimide for application in intracellular drug delivery systems. The DS of 1-(3-aminopropyl)imidazole was adjusted by the feed molar ratio, and the structure of the prepared polymer was confirmed using FT-IR and 1H NMR spectroscopy. Their pH-sensitive properties were characterized by light transmittance measurements, and the particle size and its distribution were investigated by dynamic light scattering measurements at varying pH values. The pH-sensitive phase transition was clearly observed in polymer solutions with a high substitution of 1-(3-aminopropyl)imidazole. The prepared polymers showed a high buffering capacity between pH 5 and 7, and this increased with the DS of 1-(3-aminopropyl)imidazole. The pH dependence of the aggregation and de-aggregation behavior was examined using a fluorescence spectrometer. For MPEG/imidazole-g-polyaspartamides with a DS of 1-(3-aminopropyl)imidazole over 82%, self aggregates associated with the hydrophobic interactions of the unprotonated imidazole groups were observed at pH values above 7, and their mean size was over 200 nm, while the aggregates of polymers were dissociated at pH values below 7 by the protonation of imidazole groups. These pH-sensitive polyaspartamide derivatives are potential basic candidates for intracellular drug delivery carriers triggered by small pH changes.

Regulation of Serratia marcescens ompF and ompC porin genes in response to osmotic stress, salicylate, temperature and pH.

PubMed

Begic, Sanela; Worobec, Elizabeth A

2006-02-01

Serratia marcescens is a Gram-negative enterobacterium that has become an important opportunistic pathogen, largely due to its high degree of natural antibiotic resistance. One factor contributing to this natural antibiotic resistance is reduced outer membrane permeability, which is controlled in part by OmpC and OmpF porin proteins. OmpF expression is regulated by micF, an RNA transcript encoded upstream of the ompC gene, which hybridizes with the ompF transcript to inhibit its translation. Regulation of S. marcescens porin gene expression, as well as that of micF, was investigated using beta-galactosidase reporter gene fusions in response to 5, 8 and 10 % sucrose, 1, 5 and 8 mM salicylate, and different pH and temperature values. beta-Galactosidase activity assays revealed that a lower growth temperature (28 degrees C), a more basic pH (pH 8), and an absence of sucrose and salicylate induce the transcription of the ompF gene, whereas the induction of ompC is stimulated at a higher growth temperature (42 degrees C), acidic pH (pH 6), and maximum concentrations of sucrose (10 %) and salicylate (8 mM). In addition, when multiple conditions were tested, temperature had the predominant effect, followed by pH. In this study, it was found that the MicF regulatory mechanism does not play a role in the osmoregulation of the ompF and ompC genes, whereas MicF does repress OmpF expression in the presence of salicylate and high growth temperature, and under low pH conditions.

Highly effective removal of basic fuchsin from aqueous solutions by anionic polyacrylamide/graphene oxide aerogels.

PubMed

Yang, Xiaoxia; Li, Yanhui; Du, Qiuju; Sun, Jiankun; Chen, Long; Hu, Song; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

2015-09-01

Novel anionic polyacrylamide/graphene oxide aerogels were prepared by a freeze drying method and used to remove basic fuchsin from aqueous solutions. These aerogels were sponge-like solid with lightweight, fluffy and porous structure. The batch adsorption experiments were carried out to study the effect of various parameters, such as the solution pH, adsorbent dose, contact time and temperature on adsorption properties of basic fuchsin onto anionic polyacrylamide/graphene oxide aerogels. The kinetics of adsorption corresponded to the pseudo-second-order kinetic model. The Langmuir adsorption isotherm was suitable to describe the equilibrium adsorption process. The maximum adsorption capacity was up to 1034.3 mg/g, which indicated that anionic polyacrylamide/graphene oxide aerogels were promising adsorbents for removing dyes pollutants from aqueous solution. Copyright © 2015 Elsevier Inc. All rights reserved.

Purification and Properties of Streptococcal Competence Factor Isolated from Chemically Defined Medium

PubMed Central

Leonard, C. Gomez; Cole, Roger M.

1972-01-01

A procedure for the isolation and purification of competence factor produced in a defined medium by group H streptococci, strain Challis-6, is presented. Partial characterization and chemical analysis of the product are described. The procedure yields competence factor of high purity, as shown by homogeneity in electrofocusing, by electrophoresis in sodium dodecyl sulfate polyacrylamide gels, and by chemical analysis. The data indicate that competence factor is a small, dialyzable, highly basic compound. It is free from lipids, phosphorus, and carbohydrates, and is colorless and thermoresistant. Its biological activity is destroyed by trypsin but not by deoxyribonuclease, ribonuclease, lipase, or lysozyme. Its high isoelectric point of above pH 11.0 suggests that competence factor may be a protamine or a polymer of basic amino acids. The possibility that a polyamine may be an integral part of the polypeptide molecule has not been excluded. PMID:5018023

Procongopain from Trypanosoma congolense is processed at basic pH: an unusual feature among cathepsin L-like cysteine proteases.

PubMed

Serveau, Carole; Boulangé, Alain; Lecaille, Fabien; Gauthier, Francis; Authié, Edith; Lalmanach, Gilles

2003-06-01

Congopain, the major cysteine protease from Trypanosoma congolense, is synthesized as an inactive zymogen, and further converted into its active form after removal of the proregion, most probably via an autocatalytic mechanism. Processing of recombinant procongopain occurs via an apparent one-step or a multistep mechanism depending on the ionic strength. The auto-activation is pH-dependent, with an optimum at pH 4.0, and no activation observed at pH 6.0. After addition of dextran sulfate (10 microg/ml), an approx. 20-fold increase of processing (expressed as enzymatic activity) is observed. Furthermore, in the presence of dextran sulfate, procongopain can be processed at pH 8.0, an unusual feature among papain-like enzymes. Detection of procongopain and trypanosomal enzymatic activity in the plasma of T. congolense-infected cattle, together with the capacity of procongopain to be activated at weakly basic pH, suggest that procongopain may be extracellularly processed in the presence of blood vessel glycosaminoglycans, supporting the hypothesis that congopain acts as a pathogenic factor in host-parasite relationships.

The pH dependence of silicon-iron interaction in rats.

PubMed

Jia, X; Emerick, R J; Kayongo-Male, H

1997-01-01

A 2 x 2 x 3 factorial experiment was conducted to study the pH dependence of a silicon-iron interaction in vivo. The dietary treatments used in the factorial design were the following (mg/kg of diet): silicon, 0 and 500; iron, 35 and 187; acid-base, ammonium chloride as 0.5% of total diet (acidic), sodium bicarbonate as 1.0% of total diet (basic), or no supplementation of acid or base (control). The supplementation of 500 mg silicon/kg of diet increased plasma-iron concentration in rats fed the acidic or control diets, but not in rats fed the basic diet. A high dietary-iron level suppressed copper absorption and utilization and subsequently imposed a negative effect on its own utilization. An increase in the plasma total-cholesterol concentration caused by high dietary-iron level was likely a consequence of the antagonistic effect of iron on copper absorption and utilization. The use of cupric sulfate pentahydrate as the dietary-copper source in this study resulted in plasma copper concentrations that were approximately twice those obtained in a related study using cupric carbonate. Also, a 42% coefficient of variation (C.V.) for plasma-copper concentrations of rats fed cupric sulfate in this study was greatly reduced from the C.V. = 108% previously associated with the dietary cupric carbonate.

Expression and characterization of plant aspartic protease nepenthesin-1 from Nepenthes gracilis.

PubMed

Kadek, Alan; Tretyachenko, Vyacheslav; Mrazek, Hynek; Ivanova, Ljubina; Halada, Petr; Rey, Martial; Schriemer, David C; Man, Petr

2014-03-01

Carnivorous plants of the genus Nepenthes produce their own aspartic proteases, nepenthesins, to digest prey trapped in their pitchers. Nepenthesins differ significantly in sequence from other aspartic proteases in the animal or even plant kingdoms. This difference, which also brings more cysteine residues into the structure of these proteases, can be a cause of uniquely high temperature and pH stabilities of nepenthesins. Their detailed structure characterization, however, has not previously been possible due to low amounts of protease present in the pitcher fluid and also due to limited accessibility of Nepenthes plants. In the present study we describe a convenient way for obtaining high amounts of nepenthesin-1 from Nepenthes gracilis using heterologous production in Escherichia coli. The protein can be easily refolded in vitro and its characteristics are very close to those described for a natural enzyme isolated from the pitcher fluid. Similarly to the natural enzyme, recombinant nepenthesin-1 is sensitive to denaturing and reducing agents. It also has maximal activity around pH 2.5, shows unusual stability at high pH and its activity is not irreversibly inhibited even after prolonged incubation in the basic pH range. On the other hand, temperature stability of the recombinant enzyme is lower in comparison with the natural enzyme, which can be attributed to missing N-glycosylation in the recombinant protein. Copyright © 2013 Elsevier Inc. All rights reserved.

Comparison between micellar liquid chromatography and capillary zone electrophoresis for the determination of hydrophobic basic drugs in pharmaceutical preparations.

PubMed

Torres-Cartas, S; Martín-Biosca, Y; Sagrado, S; Villanueva-Camañas, R M; Medina-Hernández, M J

2007-01-01

The determination of highly hydrophobic basic compounds by means of conventional reversed-phase liquid chromatographic methods has several drawbacks. Owing to the characteristics of micellar liquid chromatography (MLC) and capillary electrophoresis (CE), these techniques could be advantageous alternatives to reversed-phase chromatographic methods for the determination of these kinds of compounds. The objective of this study was to develop and compare MLC and CE methods for the determination of antipsychotic basic drugs (amitryptiline, haloperidol, perphenazine and thioridazine) in pharmaceutical preparations. The chromatographic determination of the analytes was performed on a Kromasil C(18) analytical column; the mobile phase was 0.04 m cetyltrimethylammonium bromide (CTAB), at pH 3, containing 5% 1-butanol, at a flow rate of 1 mL/min. The CE separation was performed in a fused-silica capillary with a 50 mm tris-(hydroxymethyl)-aminomethane buffer, pH 7, at an applied voltage of 20 kV, using barbital as internal stardard. The proposed methods are suitable for a reliable quantitation of these compounds in the commercial tablets and drops in terms of accuracy and precision and require a very simple pre-treatment of the samples. By comparing the performance characteristics and experimental details of the MLC and CE methods we conclude that CE seems to be slightly better than MLC in the determination of highly hydrophobic compounds in pharmaceuticals in terms of resolution and economy, taking into account that the limits of detection are not a handicap in pharmaceutical samples. Copyright 2006 John Wiley & Sons, Ltd.

Effects of Environmental Stresses and in Vitro Digestion on the Release of Tocotrienols Encapsulated Within Chitosan-Alginate Microcapsules.

PubMed

Tan, Phui Yee; Tan, Tai Boon; Chang, Hon Weng; Tey, Beng Ti; Chan, Eng Seng; Lai, Oi Ming; Sham Baharin, Badlishah; Nehdi, Imededdine Arbi; Tan, Chin Ping

2017-12-06

Considering the health benefits of tocotrienols, continuous works have been done on the encapsulation and delivery of these compounds. In this study, we encapsulated tocotrienols in chitosan-alginate microcapsules and evaluated their release profile. Generally, these tocotrienols microcapsules (TM) displayed high thermal stability. When subjected to pH adjustments (pH 1-9), we observed that the release of tocotrienols was the highest (33.78 ± 0.18%) under basic conditions. The TM were also unstable against the effect of ionic strength, with a high release (70.73 ± 0.04%) of tocotrienols even at a low sodium chloride concentration (50 mM). As for the individual isomers, δ-tocotrienol was the most sensitive to pH and ionic strength. In contrast, β-/γ-tocotrienols were the most ionic-stable isomers but more responsive toward thermal treatment. Simulated gastrointestinal model showed that the chitosan-alginate-based TM could be used to retain tocotrienols in the gastric and subsequently release them in the intestines for possible absorption.

Determinants of the Job Satisfaction of PhD Holders: An Analysis by Gender, Employment Sector, and Type of Satisfaction in Spain

ERIC Educational Resources Information Center

Escardíbul, Josep-Oriol; Afcha, Sergio

2017-01-01

We analyze the determinants of job satisfaction of PhD holders in Spain. Specifically, we consider overall job satisfaction as well as basic and motivational satisfaction, following Herzberg's typology (based on Maslow's hierarchy of needs). Using representative data for Spain's PhD population--collected from the Spanish Survey on Human Resources…

Sensitized terbium(III) macrocyclic-phthalimide complexes as luminescent pH switches.

PubMed

Chen, Gaoyun; Wardle, Nicholas J; Sarris, Jason; Chatterton, Nicholas P; Bligh, S W Annie

2013-10-21

Four new macrocyclic-phthalimide ligands were synthesised via the coupling of N-(3-bromopropyl)phthalimide either to cyclen (1,4,7,10-tetraazacyclododecane) itself or its carboxylate-functionalized analogues, and photophysical studies were carried out on their corresponding Tb(III) complexes in aqueous media as a function of pH. Luminescence intensities of Tb·L1a–Tb·L3a were in ‘switched off’ mode under acidic conditions (pH < 4), and were activated on progression to basic conditions as the phthalimido functions therein were hydrolysed to their corresponding phthalamates Tb·L1b–Tb·L3b. Emission of phthalamate-based macrocyclic Tb(III) complexes Tb·L1b–Tb·L3b was in ‘switched on’ mode between pH 4 and 11, exhibiting high quantum yields (Φ) and long lifetimes (τ) of the order of milliseconds at pH ~ 6. Tb(III) emissions were found to decline with increasing number of chromophores. The values of Φ and τ were 46% and 2.4 ms respectively for Tb·L1b at pH ~ 6 when activated. This is the best pH-dependent sensor based on a Tb(III) complex reported to date, benefiting from the macrocyclic architecture of the ligand.

The effect of synthesis parameters on the geometry and dimensions of mesoporous hydroxyapatite nanoparticles in the presence of 1-dodecanethiol as a pore expander.

PubMed

Bakhtiari, L; Rezaie, H R; Javadpour, J; Erfan, M; Shokrgozar, M A

2015-08-01

Mesoporous hydroxyapatite with different pore diameters and pore volumes were synthesized by the self-assembly method using Cetyltrimethylammonium bromide (CTAB) as the cationic surfactant and 1-dodecanethiol as the pore expander at different micellization pHs, solvent types and surfactant concentrations. Results of field emission scanning electron microscopy (FESEM) showed a decrease in length/diameter ratio of rod-like particles by an increase in micellization pH and also a sphere to rod transition in morphology by an increase in CTAB concentration. Brunauer-Emmett-Teller (BET) surface area and Low angle X-ray diffraction analysis revealed that the optimized mesoporous hydroxyapatite with controlled pore structure can be obtained under basic micellization pH (about 12, pH of complete ionization of 1-dodecanethiol) by using water as the solvent and a high content of cationic surfactant. The results also show that micellization pH has a strong effect on pore structure and changing the pH can shift the mesostructure to a macroporous structure with morphological changes. Copyright © 2015 Elsevier B.V. All rights reserved.

Hydrolysis of Indole-3-Acetic Acid Esters Exposed to Mild Alkaline Conditions 1

PubMed Central

Baldi, Bruce G.; Maher, Barbara R.; Cohen, Jerry D.

1989-01-01

Ester conjugates of indole-3-acetic acid are hydrolyzed easily in basic solutions; however, quantitative data have not been available on the relationship between pH and rate of hydrolysis of the known ester conjugates. The use of basic conditions during extraction or purification of IAA by several laboratories suggested that a more systematic analysis of this process was needed. In this report we present data indicating: (a) that measurable hydrolysis of IAA-glucose (from standard solutions) and IAA-esters (from maize kernel extracts) occurs with only a few hours of treatment at pH 9 or above; (b) that the lability of some ester conjugates is even greater than that of IAA-glucose; and (c) that ester hydrolysis of standard compounds, IAA-glucose and IAA-p-nitrophenol, occurs in the `three phase extraction system' proposed by Liu and Tillberg ([1983] Physiol Plant 57: 441-447). These data indicate that the potential for problems with inadvertent hydrolysis of ester conjugates of IAA exists even at moderate pH values and in the multiphase system where exposure to basic conditions was thought to be limited. PMID:16667049

Multiple response optimization of the coagulation process for upgrading the quality of effluent from municipal wastewater treatment plant

NASA Astrophysics Data System (ADS)

Li, Na; Hu, Yi; Lu, Yong-Ze; Zeng, Raymond J.; Sheng, Guo-Ping

2016-05-01

To meet the high quality standard of receiving water, the coagulation process using polyferric chloride (PFC) was used to further improve the water quality of effluent from wastewater treatment plants. Uniform design (UD) coupled with response surface methodology (RSM) was adopted to assess the effects of the main influence factors: coagulant dosage, pH and basicity, on the removal of total organic carbon (TOC), NH4+-N and PO43--P. A desirability function approach was used to effectively optimize the coagulation process for the comprehensive removal of TOC, NH4+-N and PO43--P to upgrade the effluent quality in practical application. The optimized operating conditions were: dosage 28 mg/L, pH 8.5 and basicity 0.001. The corresponding removal efficiencies for TOC, NH4+-N and PO43--P were 77.2%, 94.6% and 20.8%, respectively. More importantly, the effluent quality could upgrade to surface water Class V of China through coagulation under optimal region. In addition, grey relational analysis (GRA) prioritized these three factors as: pH > basicity > dosage (for TOC), basicity > dosage > pH (for NH4+-N), pH > dosage > basicity (for PO43--P), which would help identify the most important factor to control the treatment efficiency of various effluent quality indexes by PFC coagulation.

Two-step liquid phase microextraction combined with capillary electrophoresis: a new approach to simultaneous determination of basic and zwitterionic compounds.

PubMed

Nojavan, Saeed; Moharami, Arezoo; Fakhari, Ali Reza

2012-08-01

In this work, two-step hollow fiber-based liquid-phase microextraction procedure was evaluated for extraction of the zwitterionic cetirizine (CTZ) and basic hydroxyzine (HZ) in human plasma. In the first step of extraction, the pH of sample was adjusted at 5.0 in order to promote liquid-phase microextraction of the zwitterionic CTZ. In the second step, the pH of sample was increased up to 11.0 for extraction of basic HZ. In this procedure, the extraction times for the first and the second steps were 30 and 20 min, respectively. Owing to the high ratio between the volumes of donor phase and acceptor phase, CTZ and HZ were enriched by factors of 280 and 355, respectively. The linearity of the analytical method was investigated for both compounds in the range of 10-500 ng mL(-1) (R(2) > 0.999). Limit of quantification (S/N = 10) for CTZ and HZ was 10 ng mL(-1) , while the limit of detection was 3 ng mL(-1) for both compounds at a signal to noise ratio of 3:1. Intraday and interday relative standard deviations (RSDs, n = 6) were in the range of 6.5-16.2%. This procedure enabled CTZ and HZ to be analyzed simultaneously by capillary electrophoresis. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of acyl migration in mono- and dicaffeoylquinic acids under aqueous basic, aqueous acidic, and dry roasting conditions.

PubMed

Deshpande, Sagar; Jaiswal, Rakesh; Matei, Marius Febi; Kuhnert, Nikolai

2014-09-17

Acyl migration in chlorogenic acids describes the process of migration of cinnamoyl moieties from one quinic acid alcohol group to another, thus interconverting chlorogenic acid regioisomers. It therefore constitutes a special case of transesterification reaction. Acyl migration constitutes an important reaction pathway in both coffee roasting and brewing, altering the structure of chlorogenic acid initially present in the green coffee bean. In this contribution we describe detailed and comprehensive mechanistic studies comparing inter- and intramolecular acyl migration involving the seven most common chlorogenic acids in coffee. We employe aqueous acidic and basic conditions mimicking the brewing of coffee along with dry roasting conditions. We show that under aqueous basic conditions intramolecular acyl migration is fully reversible with basic hydrolysis competing with acyl migration. 3-Caffeoylquinic acid was shown to be most labile to basic hydrolysis. We additionally show that the acyl migration process is strongly pH dependent with increased transesterification taking place at basic pH. Under dry roasting conditions acyl migration competes with dehydration to form lactones. We argue that acyl migration precedes lactonization, with 3-caffeoylquinic acid lactone being the predominant product.

PhD7Faster: predicting clones propagating faster from the Ph.D.-7 phage display peptide library.

PubMed

Ru, Beibei; 't Hoen, Peter A C; Nie, Fulei; Lin, Hao; Guo, Feng-Biao; Huang, Jian

2014-02-01

Phage display can rapidly discover peptides binding to any given target; thus, it has been widely used in basic and applied research. Each round of panning consists of two basic processes: Selection and amplification. However, recent studies have showed that the amplification step would decrease the diversity of phage display libraries due to different propagation capacity of phage clones. This may induce phages with growth advantage rather than specific affinity to appear in the final experimental results. The peptides displayed by such phages are termed as propagation-related target-unrelated peptides (PrTUPs). They would mislead further analysis and research if not removed. In this paper, we describe PhD7Faster, an ensemble predictor based on support vector machine (SVM) for predicting clones with growth advantage from the Ph.D.-7 phage display peptide library. By using reduced dipeptide composition (ReDPC) as features, an accuracy (Acc) of 79.67% and a Matthews correlation coefficient (MCC) of 0.595 were achieved in 5-fold cross-validation. In addition, the SVM-based model was demonstrated to perform better than several representative machine learning algorithms. We anticipate that PhD7Faster can assist biologists to exclude potential PrTUPs and accelerate the finding of specific binders from the popular Ph.D.-7 library. The web server of PhD7Faster can be freely accessed at http://immunet.cn/sarotup/cgi-bin/PhD7Faster.pl.

Study of human serum albumin structure by dynamic light scattering: two types of reactions under different pH and interaction with physiologically active compounds

NASA Astrophysics Data System (ADS)

Luik, A. I.; Naboka, Yu. N.; Mogilevich, S. E.; Hushcha, T. O.; Mischenko, N. I.

1998-09-01

The effect of pH and binding of ten physiologically active compounds (isoproterenol, yohimbine, propranolol, clonidine, phenylephrine, carbachol, tripeptide fMLP, diphenhydramine, chlorpromazine and atropine) on the molecular structure of human serum albumin (HSA) has been studied using the dynamic light scattering. It was found that albumin globule has the most compact configuration (Stokes diameter 59-62 Å) at physiological pH 7.4. The changes in pH, both increase to 8.0 and decrease to 5.4, result in the growth of globule size to 72-81 Å. At acidic shift of pH an additional peak arises in the correlation spectra caused by the light scattering on the structures with the Stokes diameters of 29-37 Å. Those conform to the sizes of the albumin subdomains. The indicated peak is not displayed at basic shift of pH. The interaction with propranolol, clonidine, phenylephrine, carbachol and tripeptide fMLP which hinder adenylate cyclase (AdC) and activate Ca-polyphosphoinositide (Ca-PPI) signaling system of a cell initiates structural rearrangements similar to acidic transitions. Isoproterenol, yohimbine diphenhydramine, chlorpromazine and atropine, which activate AdC and hinder Ca-PPI, cause conformational changes of HSA similar to basic transitions.

A basic helix-loop-helix transcription factor, PhFBH4, regulates flower senescence by modulating ethylene biosynthesis pathway in petunia.

PubMed

Yin, Jing; Chang, Xiaoxiao; Kasuga, Takao; Bui, Mai; Reid, Michael S; Jiang, Cai-Zhong

2015-01-01

The basic helix-loop-helix (bHLH) transcription factors (TFs) play important roles in regulating multiple biological processes in plants. However, there are few reports about the function of bHLHs in flower senescence. In this study, a bHLH TF, PhFBH4, was found to be dramatically upregulated during flower senescence. Transcription of PhFBH4 is induced by plant hormones and abiotic stress treatments. Silencing of PhFBH4 using virus-induced gene silencing or an antisense approach extended flower longevity, while transgenic petunia flowers with an overexpression construct showed a reduction in flower lifespan. Abundance of transcripts of senescence-related genes (SAG12, SAG29) was significantly changed in petunia PhFBH4 transgenic flowers. Furthermore, silencing or overexpression of PhFBH4 reduced or increased, respectively, transcript abundances of important ethylene biosynthesis-related genes, ACS1 and ACO1, thereby influencing ethylene production. An electrophoretic mobility shift assay showed that the PhFBH4 protein physically interacted with the G-box cis-element in the promoter of ACS1, suggesting that ACS1 was a direct target of the PhFBH4 protein. In addition, ectopic expression of this gene altered plant development including plant height, internode length, and size of leaves and flowers, accompanied by alteration of transcript abundance of the gibberellin biosynthesis-related gene GA2OX3. Our results indicate that PhFBH4 plays an important role in regulating plant growth and development through modulating the ethylene biosynthesis pathway.

Effect of pH and calcium on short-term NO3- fluxes in roots of barley seedlings

NASA Technical Reports Server (NTRS)

Aslam, M.; Travis, R. L.; Huffaker, R. C.

1995-01-01

The effect of pH and Ca2+ on net NO3- uptake, influx, and efflux by intact roots of barley (Hordeum vulgare L.) seedlings was studied. Seedlings were induced with NO3- or NO2-. Net NO3- uptake and efflux, respectively, were determined by following its depletion from, and accumulation in, the external solution. Since roots of both uninduced and NO2(-)-induced seedlings contain little internal NO3- initial net uptake rates are equivalent to influx (M. Aslam, R.L. Travis, R.C. Huffaker [1994] Plant Physiol 106: 1293-1301). NO3-, uptake (influx) by these roots was little affected at acidic pH. In contrast, in NO3(-)-induced roots, which accumulate NO3-, net uptake rates decreased in response to acidic pH. Under these conditions, NO3- efflux was stimulated and was a function of root NO3- concentration. Conversely, at basic pH, NO3- uptake by NO3- and NO2(-)-induced and uninduced roots decreased, apparently because of the inhibition of influx. Calcium had little effect on NO3- uptake (influx) by NO2(-)-induced roots at either pH 3 or 6. However, in NO3(-)-induced roots, lack of Ca2+ at pH 3 significantly decreased net NO3- uptake and stimulated efflux. The results indicate that at acidic pH the decrease in net NO3- uptake is due to the stimulation of efflux, whereas at basic pH, it is due to the inhibition of influx.

Ratiometric Near-Infrared Fluorescent Probes Based On Through-Bond Energy Transfer and π-Conjugation Modulation between Tetraphenylethene and Hemicyanine Moieties for Sensitive Detection of pH Changes in Live Cells.

PubMed

Wang, Jianbo; Xia, Shuai; Bi, Jianheng; Fang, Mingxi; Mazi, Wafa; Zhang, Yibin; Conner, Nathan; Luo, Fen-Tair; Lu, H Peter; Liu, Haiying

2018-04-18

In this paper, we present three ratiometric near-infrared fluorescent probes (A-C) for accurate, ratiometric detection of intracellular pH changes in live cells. Probe A consists of a tetraphenylethene (TPE) donor and near-infrared hemicyanine acceptor in a through-bond energy transfer (TBET) strategy, while probes B and C are composed of TPE and hemicyanine moieties through single and double sp 2 carbon-carbon bond connections in a π-conjugation modulation strategy. The specific targeting of the probes to lysosomes in live cells was achieved by introducing morpholine residues to the hemicyanine moieties to form closed spirolactam ring structures. Probe A shows aggregation-induced emission (AIE) property at neutral or basic pH, while probes B and C lack AIE properties. At basic or neutral pH, the probes only show fluorescence of TPE moieties with closed spirolactam forms of hemicyanine moieties, and effectively avoid blind fluorescence imaging spots, an issue which typical intensity-based pH fluorescent probes encounter. Three probes show ratiometric fluorescence responses to pH changes from 7.0 to 3.0 with TPE fluorescence decreases and hemicyanine fluorescence increases, because acidic pH makes the spirolactam rings open to enhance π-conjugation of hemicyanine moieties. However, probe A shows much more sensitive ratiometric fluorescence responses to pH changes from 7.0 to 3.0 with remarkable ratio increase of TPE fluorescence to hemicyanine fluorescence up to 238-fold than probes B and C because of its high efficiency of energy transfer from TPE donor to the hemicyanine acceptor in the TBET strategy. The probe offers dual Stokes shifts with a large pseudo-Stokes shift of 361 nm and well-defined dual emissions, and allows for colocalization of the imaging readouts of visible and near-infrared fluorescence channels to achieve more precisely double-checked ratiometric fluorescence imaging. These platforms could be employed to develop a variety of novel ratiometric fluorescent probes for accurate detection of different analytes in applications of chemical and biological sensing, imaging, and diagnostics by introducing appropriate sensing ligands to hemicyanine moieties to form on-off spirolactam switches.

Study of the sonophotocatalytic degradation of basic blue 9 industrial textile dye over slurry titanium dioxide and influencing factors.

PubMed

González, Antonia Sandoval; Martínez, Susana Silva

2008-09-01

The sonophotocatalytic degradation of basic blue 9 industrial textile dye has been studied in the presence of ultrasound (20 kHz) over a TiO(2) slurry employing an UV lamp (15 W, 352 nm). It was observed that the color removal efficiency was influenced by the pH of the solution, initial dye concentration and TiO(2) amount. It was found that the dye degradation followed apparent first order kinetics. The rate constant increased by decreasing dye concentration and was affected by the pH of the solution with the highest degradation obtained at pH 7. The first order rate constants obtained with sonophotocatalysis were twofold and tenfold than those obtained under photocatalysis and sonolysis, respectively. The chemical oxygen demand was abated over 80%.

Understanding The Interfacial Structure Of Aqueous Phospholipid Monolayer Films Via External Reflection FT-IR Spectroscopy.

NASA Astrophysics Data System (ADS)

Mitchell, Melody L.; Dluhy, Richard A.

1989-12-01

Monolayer films of dimyristoyl-phosphatidic-acid (DMPA) at neutral and basic pH exhibit first-order phase transitions in their pressure-area curves. In situ external reflection FT-IR studies in the CH, stretching bands over this phase transition region exhibit a --6 cm-1 shift similar to that observed in previous studies of dipalmitoyl-phosphotidylcholine (DPPC)1. The acid form of DMPA at pH 3.0 does not exhibit the first order phase transition, but a ~1cm-1 frequency shift is observed in the liquid condensed phase and is also present in the neutral pH form. A solid-solid phase transition is proposed. Examination of the polar headgroup region (1300-960 cm-1)for acidic, neutral, and basic forms of DMPA give characteristic bands of each protonation state of PO3.

Synthesis and evaluation of porous polymethylsilsesquioxane microspheres as low silanol activity chromatographic stationary phase for basic compound separation.

PubMed

Huo, Zhixia; Wan, Qianhong; Chen, Lei

2018-06-08

Polymethylsilsesquioxanes (PMSQ) are potentially useful materials for liquid chromatography owing to their unique chemical, electrical and mechanical properties. Surprisingly however, no systematic studies on the use of spherical PMSQ particles as chromatographic packing have been reported. Accordingly, we present a comprehensive study aimed to characterize the chromatographic properties of this material in high performance liquid chromatography (HPLC) and to compare them with those observed on methyl (C 1 ) bonded silica phase under comparable conditions. Porous spherical particles were synthesized by a two-step hydrolysis and condensation procedure from methyltrimethoxysilane (MTMS) as a sole precursor. The as-synthesized microspheres possess spherical shape, narrow size distribution, mesoporous structure, high surface area (817 m 2  g -1 ) and reasonable carbon load (16.6%). They can be used directly as the HPLC stationary phase without the need for size classification. The PMSQ phase exhibits typical reversed-phase chromatographic properties with higher methylene selectivity and low silanol activity compared with the C 1 column. The retention mechanism for basic compounds was systematically evaluated by studying the effect of pH, ionic and solvent strength of the mobile phase. Basic compounds displayed lower retention factor and symmetric peak shape on the PMSQ column whereas longer retention and strong tailing peaks were observed on the C 1 column. The difference in retention behavior between the two columns is explained in terms of different principal retention mechanisms. Because of the low silanol activity, retention of basic compounds on the PMSQ column is governed solely by a reversed-phase mechanism. By contrast, multiple interactions including reversed-phase, cation exchange and simultaneous reversed-phase/cationic exchange interaction contribute to the retention on the C 1 column, as previously observed on other silica based reversed-phases. Furthermore, the PMSQ phase exhibited significantly enhanced stability under alkaline conditions compared with its silica-based counterpart. Taken together, the favorable morphology and pore structure combined with the benefits of low silanol activity, high pH stability and prolonged column lifetime make the newly developed PMSQ phase a promising and viable alternative to silica based reversed-phase packings for separation of basic compounds. Copyright © 2018 Elsevier B.V. All rights reserved.

A highly thermostable alkaline cellulase-free xylanase from thermoalkalophilic Bacillus sp. JB 99 suitable for paper and pulp industry: purification and characterization.

PubMed

Shrinivas, Dengeti; Savitha, Gunashekaran; Raviranjan, Kumar; Naik, Gajanan Ramchandra

2010-11-01

A highly thermostable alkaline xylanase was purified to homogeneity from culture supernatant of Bacillus sp. JB 99 using DEAE-Sepharose and Sephadex G-100 gel filtration with 25.7-fold increase in activity and 43.5% recovery. The molecular weight of the purified xylanase was found to be 20 kDA by SDS-PAGE and zymogram analysis. The enzyme was optimally active at 70 °C, pH 8.0 and stable over pH range of 6.0-10.0.The relative activity at 9.0 and 10.0 were 90% and 85% of that of pH 8.0, respectively. The enzyme showed high thermal stability at 60 °C with 95% of its activity after 5 h. The K (m) and V (max) of enzyme for oat spelt xylan were 4.8 mg/ml and 218.6 µM min(-1) mg(-1), respectively. Analysis of N-terminal amino acid sequence revealed that the xylanase belongs to glycosyl hydrolase family 11 from thermoalkalophilic Bacillus sp. with basic pI. Substrate specificity showed a high activity on xylan-containing substrate and cellulase-free nature. The hydrolyzed product pattern of oat spelt xylan on thin-layer chromatography suggested xylanase as an endoxylanase. Due to these properties, xylanase from Bacillus sp. JB 99 was found to be highly compatible for paper and pulp industry.

Two-dimensional RPLC-RPLC system with different pH in two dimensions for separation of alkaloids from Corydalis yanhusuo W. T. Wang.

PubMed

Zhang, Jing; Jin, Yu; Liu, Yanfang; Xiao, Yuansheng; Feng, Jiatao; Xue, Xingya; Zhang, Xiuli; Liang, Xinmiao

2009-06-01

An effective method utilizing the same RP chromatographic column with different pH in first and second LC dimensions has been developed for separation of the basic compounds from traditional Chinese medicines (TCMs). In this work, the alkaloids in Corydalis yanhusuo which is an important TCM were selected as a model to develop the method. The additives and pH values of the mobile phase were optimized in this work. To investigate the feasibility of this method, off-line mode separation was performed in the experiments. According to the UV-absorption intensity, there were eight fractions collected in acidic conditions. All the fractions were analyzed in basic conditions. The results showed that the chromatographic selectivities were significantly different in the separations performed with acidic and alkaline elution systems. Complementary separation was achieved in this work. It is demonstrated that this method would be an effective tool for alkaloids research. Based on the different pH of the mobile phase in this method, it could also be suitable to analyze compounds which were sensible to the pH of the solution.

Urine pH test

MedlinePlus

... 2015:chap 4. Remer T, Manz F. Potential renal acid load of foods and its influence on urine pH. J Am Diet Assoc . 1995;95(7):791-797. PMID: 7797810 www.ncbi.nlm.nih.gov/pubmed/7797810 . Riley RS, McPherson RA. Basic examination of urine. In: McPherson RA, Pincus MR, ...

Generalized model of electromigration with 1:1 (analyte:selector) complexation stoichiometry: part II. Application to dual systems and experimental verification.

PubMed

Müllerová, Ludmila; Dubský, Pavel; Gaš, Bohuslav

2015-03-06

Interactions among analyte forms that undergo simultaneous dissociation/protonation and complexation with multiple selectors take the shape of a highly interconnected multi-equilibrium scheme. This makes it difficult to express the effective mobility of the analyte in these systems, which are often encountered in electrophoretical separations, unless a generalized model is introduced. In the first part of this series, we presented the theory of electromigration of a multivalent weakly acidic/basic/amphoteric analyte undergoing complexation with a mixture of an arbitrary number of selectors. In this work we demonstrate the validity of this concept experimentally. The theory leads to three useful perspectives, each of which is closely related to the one originally formulated for simpler systems. If pH, IS and the selector mixture composition are all kept constant, the system is treated as if only a single analyte form interacted with a single selector. If the pH changes at constant IS and mixture composition, the already well-established models of a weakly acidic/basic analyte interacting with a single selector can be employed. Varying the mixture composition at constant IS and pH leads to a situation where virtually a single analyte form interacts with a mixture of selectors. We show how to switch between the three perspectives in practice and confirm that they can be employed interchangeably according to the specific needs by measurements performed in single- and dual-selector systems at a pH where the analyte is fully dissociated, partly dissociated or fully protonated. Weak monoprotic analyte (R-flurbiprofen) and two selectors (native β-cyclodextrin and monovalent positively charged 6-monodeoxy-6-monoamino-β-cyclodextrin) serve as a model system. Copyright © 2015 Elsevier B.V. All rights reserved.

Basic and Applied Research in the Field of Electronics and Communications

DTIC Science & Technology

1998-02-18

Epitaxy on Semiconductor Surfaces Song, S. Ph.D., 1996 Optical Frequency Metrology Lutwak , R. Ph.D., 1996 Precision Physical Measurements...Systems." J. Opt. Soc. Am. 514(8): 2167-2173 (1997). Lutwak , R., J. Holley, P.P. Chang, S. Paine, D. Kleppner, and T. Ducas. "Circular States of...Domain Analysis of Electromagnetic Interference and Radiation Problems. Ph.D. diss., Dept. of Electr. Eng. and Comput. Sei., MIT, 1995. Lutwak , R

Colorimetric Detection of Thiophenol Based on a Phenolphthalein Derivative and Its Application as a Molecular Logic Gate.

PubMed

Kim, Hyunsu; Swamy, K M K; Kwon, Nahyun; Kim, Yonghee; Park, Sungsu; Yoon, Juyoung

2017-07-05

A phenolphthalein-based colorimetric probe bearing a dinitrobenzene group is reported as a thiophenol (PhSH)-selective chemodosimeter. PhSH can react with chemodosimeter 1 to afford phenolphthalein. The addition of PhSH to the aqueous solution of 1 followed by a change in pH of the resulting solution to basic induces a selective color change from colorless to pink. Furthermore, using PhSH and base as inputs and color change of 1 by naked eye as an output, leads to the construction of an AND logic gate. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Basic Research in Electronics (JSEP).

DTIC Science & Technology

1981-09-30

These antennas can have a low profile or be flush-mounted, are inherently rugged, are simple to fabricate , and can be made conformal to the surface...made in. the " light flash" radiated by the plasma in front of the metal surface. D. High-Power Microwave-Atmosphere Interactions The original model...Scintillation," Ph.D. Thesis , Poly- technic Institute of New York (August 1980); also POLY-MRI Report No. 80-1410. 7. S.R. Barone, "Angular Momentum of Particles

Simulation of stimuli-triggered release of molecular species from halloysite nanotubes

NASA Astrophysics Data System (ADS)

Elumalai, Divya Narayan; Tully, Joshua; Lvov, Yuri; Derosa, Pedro A.

2016-10-01

A Monte Carlo model is used to study the effect of environmental variables (pH and temperature) on the transport and release of dexamethasone molecules from Halloysite Nanotubes (HNTs) in a dielectric fluid medium. The model used for this study was introduced elsewhere and it is based on basic physics interactions without experimental parameters for these interactions. An intermediate phase between the burst and saturation phase is found and explained. Molecules experience a 1-D diffusion process that is different from the diffusion in the burst phase or the surface diffusion experienced by molecules attached to the wall. It is predicted that this phase exists when the molecule-wall interaction is attractive but not always noticeable in the release profile. In this work, it is shown that an agreement with the experiment better than previously reported is obtained when simulated delivery curves are produced by the weighted average of the release profiles from a collection of HNTs with diameters and lengths distributed according to the experimental sample, highlighting the relevance of HNTs' morphology in the release. HNTs are suitable for environment-triggered release and thus the effect of temperature, molecule zeta potential, and pH is studied. It is observed that for temperatures that significantly differ from room temperature (by 100's of degrees), the release profile changes significantly, increasing the delivery speed at high temperature and reducing that speed at low temperature. Finally, it is observed that as the pH becomes more acidic, both the molecule and inner wall surface become more positive (or less negative) with both eventually becoming positive leading to a repulsive interaction; thus, molecules are pushed out by electrostatic repulsion. On the contrary, as the pH becomes more basic, positive molecules become more positive while the wall becomes less negative, but even at pH 12, the wall remains negative and the interaction is attractive. Changes in pH between different regions may act as a trigger for delivery or as a control in the delivery rate.

Pozzolanic filtration/solidification of radionuclides in nuclear reactor cooling water

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

Englehardt, J.D.; Peng, C.

1995-12-31

Laboratory studies to investigate the feasibility of one- and two-step processes for precipitation/coprecipitating radionuclides from nuclear reactor cooling water, filtering with pozzolanic filter aid, and solidifying, are reported in this paper. In the one-step process, ferrocyanide salt and excess lime are added ahead of the filter, and the resulting filter cake solidifies by a pozzolanic reaction. The two-step process involves addition of solidifying agents subsequent to filtration. It was found that high surface area diatomaceous synthetic calcium silicate powders, sold commercially as functional fillers and carriers, adsorb nickel isotopes from solution at neutral and slightly basic pH. Addition of themore » silicates to cooling water allowed removal of the tested metal isotopes (nickel, iron, manganese, cobalt, and cesium) simultaneously at neutral to slightly basic pH. Lime to diatomite ratio was the most influential characteristic of composition on final strength tested, with higher lime ratios giving higher strength. Diatomaceous earth filter aids manufactured without sodium fluxes exhibited higher pozzolanic activity. Pozzolanic filter cake solidified with sodium silicate and a ratio of 0.45 parts lime to 1 part diatomite had compressive strength ranging from 470 to 595 psi at a 90% confidence level. Leachability indices of all tested metals in the solidified waste were acceptable. In light of the typical requirement of removing iron and desirability of control over process pH, a two-step process involving addition of Portland cement to the filter cake may be most generally applicable.« less

Isolation of levoglucosan from pyrolysis oil derived from cellulose

DOEpatents

Moens, Luc

1994-01-01

High purity levoglucosan is obtained from pyrolysis oil derived from cellulose by: mixing pyrolysis oil with water and a basic metal hydroxide, oxide, or salt in amount sufficient to elevate pH values to a range of from about 12 to about 12.5, and adding an amount of the hydroxide, oxide, or salt in excess of the amount needed to obtain the pH range until colored materials of impurities from the oil are removed and a slurry is formed; drying the slurry azeotropically with methyl isobutyl ketone solvent to form a residue, and further drying the residue by evaporation; reducing the residue into a powder; continuously extracting the powder residue with ethyl acetate to provide a levoglucosan-rich extract; and concentrating the extract by removing ethyl acetate to provide crystalline levoglucosan. Preferably, Ca(OH).sub.2 is added to adjust the pH to the elevated values, and then Ca(OH).sub.2 is added in an excess amount needed.

Isolation of levoglucosan from pyrolysis oil derived from cellulose

DOEpatents

Moens, L.

1994-12-06

High purity levoglucosan is obtained from pyrolysis oil derived from cellulose by: mixing pyrolysis oil with water and a basic metal hydroxide, oxide, or salt in amount sufficient to elevate pH values to a range of from about 12 to about 12.5, and adding an amount of the hydroxide, oxide, or salt in excess of the amount needed to obtain the pH range until colored materials of impurities from the oil are removed and a slurry is formed; drying the slurry azeotropically with methyl isobutyl ketone solvent to form a residue, and further drying the residue by evaporation; reducing the residue into a powder; continuously extracting the powder residue with ethyl acetate to provide a levoglucosan-rich extract; and concentrating the extract by removing ethyl acetate to provide crystalline levoglucosan. Preferably, Ca(OH)[sub 2] is added to adjust the pH to the elevated values, and then Ca(OH)[sub 2] is added in an excess amount needed. 3 figures.

Methods of Academic Course Planning for Cancer Biology PhD Students to Enhance Knowledge of Clinical Oncology.

PubMed

Mattes, Malcolm D; Swart, Elizabeth; Markwell, Steven M; Wen, Sijin; Vona-Davis, Linda C

2017-09-15

Little is known about how clinical oncology concepts are taught to PhD students or the most effective methods of doing so. In this study, electronic surveys were sent to faculty and students at PhD training programs, assessing their institution's methods of clinical oncology education and their perspective on optimal approaches to clinical oncology education. Only 40.0% of students reported any clinical oncology component to their institution's training, and only 26.5% had a clinician on their graduate advisory committee. Forty-three percent of students believed that they had a good understanding for translating basic science research into clinical practice, and 77.2% of all participants believed dual degree MD/PhD students were superior to PhD students in this regard. Lectures on clinical oncology research topics were the most valuable type of experience for all participants and were also the most common type of experience utilized. Working with a clinician to develop a clinical trial with correlative endpoints was also highly valued, but was only utilized by approximately 10% of programs. Faculty rated the value of nearly all types of clinical oncology exposure significantly lower than did students. Inclusion of the approaches identified in this study is likely to enhance PhD training in oncology-related disciplines. Cancer Res; 77(18); 4741-4. ©2017 AACR . ©2017 American Association for Cancer Research.

A fluorescent colorimetric pH sensor and the influences of matrices on sensing performances

PubMed Central

Tian, Yanqing; Fuller, Emily; Klug, Summer; Lee, Fred; Su, Fengyu; Zhang, Liqiang; Chao, Shih-hui; Meldrum, Deirdre R.

2013-01-01

A fluorescent colorimetric pH sensor was developed by a polymerization of a monomeric fluorescein based green emitter (SM1) with a monomeric 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran derived red emitter (SM2) in poly(2-hydroxyethyl methacrylate)-co-polyacrylamide (PHEMA-co-PAM) matrices. Polymerized SM1 (PSM1) in the polymer matrices showed bright emissions at basic conditions and weak emissions at acidic conditions. Polymerized SM2 (PSM2) in the polymer matrices exhibited a vastly different response when compared to PSM1. The emissions of PSM2 are stronger under acidic conditions than those under basic conditions. When SM1 and SM2 were polymerized in the same polymer matrix, a dual emission sensor acting as a ratiometric pH sensor (PSM1,2) was successfully developed. Because the PSM1 and PSM2 exhibited different pH responses and separated emission windows, the changes in the emission colors were clearly observed in their dual color sensor of PSM1,2, which changed emission colors dramatically from green at pH 7 to red at pH 4, which was detected visually and/or by using a color camera under an excitation of 488 nm. In addition to the development of the dual color ratiometric pH sensor, we also studied the effects of different matrix compositions, crosslinkers, and charges on the reporting capabilities of the sensors (sensitivity and pKa). PMID:24078772

A fluorescent colorimetric pH sensor and the influences of matrices on sensing performances.

PubMed

Tian, Yanqing; Fuller, Emily; Klug, Summer; Lee, Fred; Su, Fengyu; Zhang, Liqiang; Chao, Shih-Hui; Meldrum, Deirdre R

2013-10-01

A fluorescent colorimetric pH sensor was developed by a polymerization of a monomeric fluorescein based green emitter ( SM1 ) with a monomeric 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran derived red emitter ( SM2 ) in poly(2-hydroxyethyl methacrylate)- co -polyacrylamide (PHEMA-co-PAM) matrices. Polymerized SM1 ( PSM1 ) in the polymer matrices showed bright emissions at basic conditions and weak emissions at acidic conditions. Polymerized SM2 ( PSM2 ) in the polymer matrices exhibited a vastly different response when compared to PSM1 . The emissions of PSM2 are stronger under acidic conditions than those under basic conditions. When SM1 and SM2 were polymerized in the same polymer matrix, a dual emission sensor acting as a ratiometric pH sensor ( PSM1,2 ) was successfully developed. Because the PSM1 and PSM2 exhibited different pH responses and separated emission windows, the changes in the emission colors were clearly observed in their dual color sensor of PSM1,2 , which changed emission colors dramatically from green at pH 7 to red at pH 4, which was detected visually and/or by using a color camera under an excitation of 488 nm. In addition to the development of the dual color ratiometric pH sensor, we also studied the effects of different matrix compositions, crosslinkers, and charges on the reporting capabilities of the sensors (sensitivity and p K a ).

Effect of gastric pH on the pharmacokinetics of a BCS class II compound in dogs: utilization of an artificial stomach and duodenum dissolution model and GastroPlus,™ simulations to predict absorption.

PubMed

Bhattachar, Shobha N; Perkins, Everett J; Tan, Jeffrey S; Burns, Lee J

2011-11-01

Dogs are one of the most commonly used non-rodent species in toxicology studies and are known to have basal stomach pH ranging from 2 to 7 in the fasted state. Thus absorption and resulting plasma exposure of weakly basic compounds administered as crystalline suspensions to dogs are often variable. LY2157299 is a potent and selective transforming growth factor (TGF)-beta receptor type 1 kinase (TGF-βRI) inhibitor that displayed variable absorption in early dog studies. This molecule is a weakly basic Biopharmaceutics Classification System (BCS)Class II compound, and depends on the rate and extent of dissolution to drive oral absorption. An artificial stomach and duodenum (ASD) dissolution model was utilized to evaluate potential effect of gastric pH on the absorption of suspension and buffered solution formulations. GastroPlus™ was also employed to predict the magnitude of gastric pH changes on LY2157299 absorption. The ASD experiments demonstrated that administration of a buffered acidic solution could improve the potential for absorption by normalizing gastric pH and enabling supersaturation in the duodenum. GastroPlus™ modeling suggested that direct modulation of gastric pH could lead to marked changes in bioavailability. Pharmacokinetic experiments were conducted in dogs to evaluate the effect of gastric pH modification on plasma exposure. The data were qualitatively consistent with the predictions. Copyright © 2011 Wiley-Liss, Inc.

Production of edible carbohydrates from formaldehyde in a spacecraft. pH variations in the calcium hydroxide catalyzed formose reaction. Final Report, 1 Jul. 1973 - 30 Jun. 1974. M.S. Thesis

NASA Technical Reports Server (NTRS)

Weiss, A. H.; Kohler, J. T.; John, T.

1974-01-01

The study of the calcium hydroxide catalyzed condensation of formaldehyde was extended to a batch reactor system. Decreases in pH were observed, often in the acid regime, when using this basic catalyst. This observation was shown to be similar to results obtained by others using less basic catalysts in the batch mode. The relative rates of these reactions are different in a batch reactor than in a continuous stirred tank reactor. This difference in relative rates is due to the fact that at any degree of advancement in the batch system, the products have a history of previous products, pH, and dissolved catalyst. The relative rate differences can be expected to yield a different nature of product sugars for the two types of reactors.

Adsorption of Dyes in Studying the Surface Chemistry of Ultradispersed Diamond

NASA Astrophysics Data System (ADS)

Khokhlova, T. D.; Yunusova, G. R.; Lanin, S. N.

2018-05-01

The effect the surface chemistry of ultradispersed diamond (UDD) has on the adsorption of watersoluble dyes is considered. A comparison is made to adsorption on graphitized thermal carbon black (GTCB), which has a homogeneous and nonporous surface. The adsorption isotherms of dyes and the dependence of the adsorption on the pH of solutions are measured. It is found that UDD adsorbs acid (anionic) dyes—acid orange (AO) and acid anthraquinone blue (AAB)—but barely adsorbs a basic (cationic) dye, methylene blue (MB), because of the predominance of positively charged basic groups on the surface of UDD. The maximum adsorption of AO is much lower on UDD than on GTCB, while the maximum adsorption of AAB is similar for both surfaces. The adsorption of AO on UDD depends strongly on the pH of the solution, while the adsorption of AAB is independent of this parameter. It is suggested that the adsorption of AAB is determined not only by ionic and hydrophobic interactions but also by coordination interactions with impurity metal ions on a UDD surface. It is concluded that the adsorption of dyes characterizes the chemistry of a UDD surface with high sensitivity.

Motion-Based pH Sensing Based on the Cartridge-Case-like Micromotor.

PubMed

Su, Yajun; Ge, Ya; Liu, Limei; Zhang, Lina; Liu, Mei; Sun, Yunyu; Zhang, Hui; Dong, Bin

2016-02-17

In this paper, we report a novel cartridge-case-like micromotor. The micromotor, which is fabricated by the template synthesis method, consists of a gelatin shell with platinum nanoparticles decorating its inner surface. Intriguingly, the resulting cartridge-case-like structure exhibits a pH-dependent "open and close" feature, which originates from the pH responsiveness of the gelatin material. On the basis of the catalytic activity of the platinum nanoparticle inside the gelatin shell, the resulting cartridge-case-like structure is capable of moving autonomously in the aqueous solution containing the hydrogen peroxide fuel. More interestingly, we find out that the micromotor can be utilized as a motion-based pH sensor over the whole pH range. The moving velocity of the micromotor increases monotonically with the increase of pH of the analyte solution. Three different factors are considered to be responsible for the proportional relation between the motion speed and pH of the analyte solution: the peroxidase-like and oxidase-like catalytic behavior of the platinum nanoparticle at low and high pH, the volumetric decomposition of the hydrogen peroxide under the basic condition and the pH-dependent catalytic activity of the platinum nanoparticle caused by the swelling/deswelling behavior of the gelatin material. The current work highlights the impact of the material properties on the motion behavior of a micromotor, thus paving the way toward its application in the motion-based sensing field.

Current Concepts in Pediatric Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia

PubMed Central

Bernt, Kathrin M.; Hunger, Stephen P.

2014-01-01

The t(9;22)(q34;q11) or Philadelphia chromosome creates a BCR–ABL1 fusion gene encoding for a chimeric BCR–ABL1 protein. It is present in 3–4% of pediatric acute lymphoblastic leukemia (Ph+ ALL), and about 25% of adult ALL cases. Prior to the advent of tyrosine kinase inhibitors (TKI), Ph+ ALL was associated with a very poor prognosis despite the use of intensive chemotherapy and frequently hematopoietic stem-cell transplantation (HSCT) in first remission. The development of TKIs revolutionized the therapy of Ph+ ALL. Addition of the first generation ABL1 class TKI imatinib to intensive chemotherapy dramatically increased the survival for children with Ph+ ALL and established that many patients can be cured without HSCT. In parallel, the mechanistic understanding of Ph+ ALL expanded exponentially through careful mapping of pathways downstream of BCR–ABL1, the discovery of mutations in master regulators of B-cell development such as IKZF1 (Ikaros), PAX5, and early B-cell factor (EBF), the recognition of the complex clonal architecture of Ph+ ALL, and the delineation of genomic, epigenetic, and signaling abnormalities contributing to relapse and resistance. Still, many important basic and clinical questions remain unanswered. Current clinical trials are testing second generation TKIs in patients with newly diagnosed Ph+ ALL. Neither the optimal duration of therapy nor the optimal chemotherapy backbone are currently defined. The role of HSCT in first remission and post-transplant TKI therapy also require further study. In addition, it will be crucial to continue to dig deeper into understanding Ph+ ALL at a mechanistic level, and translate findings into complementary targeted approaches. Expanding targeted therapies hold great promise to decrease toxicity and improve survival in this high-risk disease, which provides a paradigm for how targeted therapies can be incorporated into treatment of other high-risk leukemias. PMID:24724051

Sodium ion-dependent amino acid transport in membrane vesicles of Bacillus stearothermophilus.

PubMed Central

Heyne, R I; de Vrij, W; Crielaard, W; Konings, W N

1991-01-01

Amino acid transport in membrane vesicles of Bacillus stearothermophilus was studied. A relatively high concentration of sodium ions is needed for uptake of L-alanine (Kt = 1.0 mM) and L-leucine (Kt = 0.4 mM). In contrast, the Na(+)-H(+)-L-glutamate transport system has a high affinity for sodium ions (Kt less than 5.5 microM). Lithium ions, but no other cations tested, can replace sodium ions in neutral amino acid transport. The stimulatory effect of monensin on the steady-state accumulation level of these amino acids and the absence of transport in the presence of nonactin indicate that these amino acids are translocated by a Na+ symport mechanism. This is confirmed by the observation that an artificial delta psi and delta mu Na+/F but not a delta pH can act as a driving force for uptake. The transport system for L-alanine is rather specific. L-Serine, but not L-glycine or other amino acids tested, was found to be a competitive inhibitor of L-alanine uptake. On the other hand, the transport carrier for L-leucine also translocates the amino acids L-isoleucine and L-valine. The initial rates of L-glutamate and L-alanine uptake are strongly dependent on the medium pH. The uptake rates of both amino acids are highest at low external pH (5.5 to 6.0) and decline with increasing pH. The pH allosterically affects the L-glutamate and L-alanine transport systems. The maximal rate of L-glutamate uptake (Vmax) is independent of the external pH between pH 5.5 and 8.5, whereas the affinity constant (Kt) increases with increasing pH. A specific transport system for the basic amino acids L-lysine and L-arginine in the membrane vesicles has also been observed. Transport of these amino acids occurs most likely by a uniport mechanism. PMID:1670936

UPTAKE AND ELIMINATION OF IONIZABLE ORGANIC CHEMICALS AT FISH GILLS: PART I. MODEL FORMULATION, PARAMETERIZATION, AND BEHAVIOR

EPA Science Inventory

Effects of pH and alkalinity on uptake and elimination of ionizable organic chemicals at the gills of large rainbow trout were studied. Increased pH reduced uptake rates of weakly-acidic chlorinated phenols and increased that of weakly-basic 3,4-dichlorobenzylamine, indicating gr...

Reinventing Biostatistics Education for Basic Scientists

PubMed Central

Weissgerber, Tracey L.; Garovic, Vesna D.; Milin-Lazovic, Jelena S.; Winham, Stacey J.; Obradovic, Zoran; Trzeciakowski, Jerome P.; Milic, Natasa M.

2016-01-01

Numerous studies demonstrating that statistical errors are common in basic science publications have led to calls to improve statistical training for basic scientists. In this article, we sought to evaluate statistical requirements for PhD training and to identify opportunities for improving biostatistics education in the basic sciences. We provide recommendations for improving statistics training for basic biomedical scientists, including: 1. Encouraging departments to require statistics training, 2. Tailoring coursework to the students’ fields of research, and 3. Developing tools and strategies to promote education and dissemination of statistical knowledge. We also provide a list of statistical considerations that should be addressed in statistics education for basic scientists. PMID:27058055

Assessment of solubilization characteristics of different surfactants for carvedilol phosphate as a function of pH.

PubMed

Chakraborty, Subhashis; Shukla, Dali; Jain, Achint; Mishra, Brahmeshwar; Singh, Sanjay

2009-07-15

The effect of surfactants on the solubility of a new phosphate salt of carvedilol was investigated at different biorelevent pH to evaluate their solubilization capacity. Solutions of different classes of surfactants viz., anionic-sodium dodecyl sulfate (SDS) and sodium taurocholate (STC), cationic-cetyltrimethylammonium bromide (CTAB) and non-ionic-Tween 80 (T80) were prepared in the concentration range of 5-35 mmol dm(-3) in buffer solutions of pH 1.2, 3.0, 4.5, 5.8, 6.8 and 7.2. The solubility data were used to calculate the solubilization characteristics viz. molar solubilization capacity, water micelle partition coefficient, free energy of solubilization and binding constant. Solubility enhancement in basic pH was in following order: CTAB>T80>SDS>STC. CTAB and T80 showed remarkable solubility enhancement in acidic pH as well. Among the anionic surfactants, solubility in acidic medium was retarded except at pH 1.2 in case of SDS. Cationic and non-ionic surfactants were found to be suitable for enhancing the solubility of CP which can be employed for maintaining the in vitro sink condition in the basic dissolution medium. While anionic surfactants showed solubility retardant behavior which may be exploited in increasing the drug entrapment efficiency of a colloidal drug delivery system formulated by emulsification technique.

Sorption of imazaquin in soils with positive balance of charges.

PubMed

Rocha, Wadson S D; Regitano, Jussara B; Alleoni, Luis R F; Tornisielo, Valdemar L

2002-10-01

The herbicide imazaquin has both an acid and a basic ionizable groups, and its sorption depends upon the pH, the electric potential (psi0), and the oxide and the organic carbon (OC) contents of the soil. Sorption and extraction experiments using 14C-imazaquin were performed in surface and subsurface samples of two acric oxisols (an anionic "rhodic" acrudox and an anionic "xanthic" acrudox) and one non-acric alfisol (a rhodic kandiudalf), treated at four different pH values. Imazaquin showed low to moderate sorption to the soils. Sorption decreased and aqueous extraction increased as pH increased. Up to pH 5.8, sorption was higher in subsurface than in surface layers of the acric soils, due to the positive balance of charges resulted from the high Fe and Al oxide and the low OC contents. It favored electrostatic interactions with anionic molecules of imazaquin. For the subsurface samples of these highly weathered soils, where psi0 was positive and OC was low, it was not possible to predict sorption just by considering imazaquin speciation and its hydrophobic partition to the organic domains of the soil. Moreover, if Koc measured for thesurface samples were assumed to represent the whole profile in predictive models for leaching potential, then it would result in underestimation of sorption potential in subsurface, and consequently result in overestimation of the leaching potential.

Enteric polymers as acidifiers for the pH-independent sustained delivery of a weakly basic drug salt from coated pellets.

PubMed

Körber, Martin; Ciper, Mesut; Hoffart, Valerie; Pearnchob, Nantharat; Walther, Mathias; Macrae, Ross J; Bodmeier, Roland

2011-08-01

Weakly basic drugs and their salts exhibit a decrease in aqueous solubility at higher pH, which can result in pH-dependent or even incomplete release of these drugs from extended release formulations. The objective of this study was to evaluate strategies to set-off the very strong pH-dependent solubility (solubility: 80 mg/ml at pH 2 and 0.02 mg/ml at pH 7.5, factor 4000) of a mesylate salt of weakly basic model drug (pK(a) 6.5), in order to obtain pH-independent extended drug release. Three approaches for pH-independent release were investigated: (1) organic acid addition in the core, (2) enteric polymer addition to the extended release coating and (3) an enteric polymer subcoating below the extended release coating. The layering of aspartic acid onto drug cores as well as the coating of drug cores with an ethylcellulose/Eudragit L (enteric polymer) blend were not effective to avoid the formation of the free base at pH 7.5 and thus failed to significantly improve the completeness of the release compared to standard ethylcellulose/hydroxypropyl cellulose (EC/HPC)-coated drug pellets. Interestingly, the incorporation of an enteric polymer layer underneath the EC/HPC coating decreased the free base formation at pH 7.5 and thus resulted in a more complete release of up to 90% of the drug loading over 18 h. The release enhancing effect was attributed to an extended acidification through the enteric polymer layer. Flexible release patterns with approximately pH-independent characteristics were successfully achieved. Copyright © 2011 Elsevier B.V. All rights reserved.

A functional applied material on recognition of metal ion zinc based on the double azine compound.

PubMed

Wei, Taibao; Liang, Guoyan; Chen, Xiaopeng; Qi, Jin; Lin, Qi; Zhang, Youming; Yao, Hong

2017-05-18

A colorimetric and fluorescent probe L has been designed and synthesized, which bearing the double azine moiety and showing a detection limit of 2.725 × 10 -7  M towards Zn 2+ . Based on the basic recognition mechanism of ESIPT and CHEF effect, the L has high selectivity and sensitivity to only Zn 2+ (not Fe 3+ , Hg 2+ , Ag + , Ca 2+ , Co 2+ , Ni 2+ , Cd 2+ , Pb 2+ , Cr 3+ , and Mg 2+ ) within the physiological pH range (pH = 7.0-8.4) and showed a fluorescence switch. Moreover, this detection progress occured in the DMSO/H 2 O ∼ HEPES buffer (80/20, v/v; pH 7.23) solution which can conveniently used on test strip.

OH radical induced depolymerization of poly(methacrylic acid)

NASA Astrophysics Data System (ADS)

Ulanski, Piotr; Bothe, Eberhard; von Sonntag, Clemens

1999-05-01

Hydroxyl radicals (generated pulse radiolytically in dilute N 2O-saturated aqueous solutions) react with poly(methacrylic acid) producing two kinds of radicals. The primary radical is converted into a secondary one by H-abstraction ( k=3.5 × 10 2 s -1) as monitored by changes in the UV spectrum. Subsequently, the secondary radicals undergo chain scission ( k=1.8 s -1 at pH 7-9). This process has been followed both by spectrophotometry as well as by conductometry. In competition with the bimolecular decay of the radicals the ensuing end-chain radicals undergo efficient depolymerization resulting in the release of monomer. Since the lifetime of the radicals is much longer at high pH, where the polymer attains a rod-like conformation, depolymerization is most efficient in basic solution.

Adsorption of Cu(II) to Bacillus subtilis: A pH-dependent EXAFS and thermodynamic modelling study

NASA Astrophysics Data System (ADS)

Moon, Ellen M.; Peacock, Caroline L.

2011-11-01

Bacteria are very efficient sorbents of trace metals, and their abundance in a wide variety of natural aqueous systems means biosorption plays an important role in the biogeochemical cycling of many elements. We measured the adsorption of Cu(II) to Bacillus subtilis as a function of pH and surface loading. Adsorption edge and XAS experiments were performed at high bacteria-to-metal ratio, analogous to Cu uptake in natural geologic and aqueous environments. We report significant Cu adsorption to B. subtilis across the entire pH range studied (pH ˜2-7), with adsorption increasing with pH to a maximum at pH ˜6. We determine directly for the first time that Cu adsorbs to B. subtilis as a (CuO 5H n) n-8 monodentate, inner-sphere surface complex involving carboxyl surface functional groups. This Cu-carboxyl complex is able to account for the observed Cu adsorption across the entire pH range studied. Having determined the molecular adsorption mechanism of Cu to B. subtilis, we have developed a new thermodynamic surface complexation model for Cu adsorption that is informed by and consistent with EXAFS results. We model the surface electrostatics using the 1p K basic Stern approximation. We fit our adsorption data to the formation of a monodentate, inner-sphere tbnd RCOOCu + surface complex. In agreement with previous studies, this work indicates that in order to accurately predict the fate and mobility of Cu in complex biogeochemical systems, we must incorporate the formation of Cu-bacteria surface complexes in reactive transport models. To this end, this work recommends log K tbnd RCOOCu + = 7.13 for geologic and aqueous systems with generally high B. subtilis-to-metal ratio.

Positively charged mini-protein Zbasic2 as a highly efficient silica binding module: opportunities for enzyme immobilization on unmodified silica supports.

PubMed

Bolivar, Juan M; Nidetzky, Bernd

2012-07-03

Silica is a highly attractive support material for protein immobilization in a wide range of biotechnological and biomedical-analytical applications. Without suitable derivatization, however, the silica surface is not generally usable for attachment of proteins. We show here that Z(basic2) (a three α-helix bundle mini-protein of 7 kDa size that exposes clustered positive charges from multiple arginine residues on one side) functions as highly efficient silica binding module (SBM), allowing chimeras of target protein with SBM to become very tightly attached to underivatized glass at physiological pH conditions. We used two enzymes, d-amino acid oxidase and sucrose phosphorylase, to demonstrate direct immobilization of Z(basic2) protein from complex biological samples with extremely high selectivity. Immobilized enzymes displayed full biological activity, suggesting that their binding to the glass surface had occurred in a preferred orientation via the SBM. We also show that charge complementarity was the main principle of affinity between SBM and glass surface, and Z(basic2) proteins were bound in a very strong, yet fully reversible manner, presumably through multipoint noncovalent interactions. Z(basic2) proteins were immobilized on porous glass in a loading of 30 mg protein/g support or higher, showing that attachment via the SBM combines excellent binding selectivity with a technically useful binding capacity. Therefore, Z(basic2) and silica constitute a fully orthogonal pair of binding module and insoluble support for oriented protein immobilization, and this opens up new opportunities for the application of silica-based materials in the development of supported heterogeneous biocatalysts.

Multiple, simultaneous, independent gradients for a versatile multidimensional liquid chromatography. Part II: Application 2: Computer controlled pH gradients in the presence of urea provide improved separation of proteins: Stability influenced anion and cation exchange chromatography.

PubMed

Hirsh, Allen G; Tsonev, Latchezar I

2017-04-28

This paper details the use of a method of creating controlled pH gradients (pISep) to improve the separation of protein isoforms on ion exchange (IEX) stationary phases in the presence of various isocratic levels of urea. The pISep technology enables the development of computer controlled pH gradients on both cationic (CEX) and anionic (AEX) IEX stationary phases over the very wide pH range from 2 to 12. In pISep, titration curves generated by proportional mixing of the acidic and basic pISep working buffers alone, or in the presence of non-buffering solutes such as the neutral salt NaCl (0-1M), polar organics such as urea (0-8M) or acetonitrile (0-80 Vol%), can be fitted with high fidelity using high order polynomials which, in turn allows construction of a mathematical manifold %A (% acidic pISep buffer) vs. pH vs. [non-buffering solute], permitting precise computer control of pH and the non-buffering solute concentration allowing formation of dual uncoupled liquid chromatographic (LC) gradients of arbitrary shape (Hirsh and Tsonev, 2012 [1]). The separation of protein isoforms examined in this paper by use of such pH gradients in the presence of urea demonstrates the fractionation power of a true single step two dimensional liquid chromatography which we denote as Stability-Influenced Ion Exchange Chromatography (SIIEX). We present evidence that SIIEX is capable of increasing the resolution of protein isoforms difficult to separate by ordinary pH gradient IEX, and potentially simplifying the development of laboratory and production purification strategies involving on-column simultaneous pH and urea unfolding or refolding of targeted proteins. We model some of the physics implied by the dynamics of the observed protein fractionations as a function of both urea concentration and pH assuming that urea-induced native state unfolding competes with native state electrostatic interaction binding to an IEX stationary phase. Implications for in vivo protein-membrane interactions are discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Highly effective degradation of selected groups of organic compounds by cavitation based AOPs under basic pH conditions.

PubMed

Gągol, Michał; Przyjazny, Andrzej; Boczkaj, Grzegorz

2018-07-01

Cavitation has become on the most often applied methods in a number of industrial technologies. In the case of oxidation of organic pollutants occurring in the aqueous medium, cavitation forms the basis of numerous advanced oxidation processes (AOPs). This paper presents the results of investigations on the efficiency of oxidation of the following groups of organic compounds: organosulfur, nitro derivatives of benzene, BTEX, and phenol and its derivatives in a basic model effluent using hydrodynamic and acoustic cavitation combined with external oxidants, i.e., hydrogen peroxide, ozone and peroxone. The studies revealed that the combination of cavitation with additional oxidants allows 100% oxidation of the investigated model compounds. However, individual treatments differed with respect to the rate of degradation. Hydrodynamic cavitation aided by peroxone was found to be the most effective treatment (100% oxidation of all the investigated compounds in 60 min). When using hydrodynamic and acoustic cavitation alone, the effectiveness of oxidation was diversified. Under these conditions, nitro derivatives of benzene and phenol and its derivatives were found to be resistant to oxidation. In addition, hydrodynamic cavitation was found to be more effective in degradation of model compounds than acoustic cavitation. The results of investigations presented in this paper compare favorably with the investigations on degradation of organic contaminants using AOPs under conditions of basic pH published thus far. Copyright © 2018 Elsevier B.V. All rights reserved.

Simultaneous Separation of Acidic and Basic Isoperoxidases in Wounded Potato Tissue by Acrylamide Gel Electrophoresis 1

PubMed Central

Borchert, Rolf; Decedue, Charles J.

1978-01-01

Preparation and use of a newly developed pH 4.3 horizontal thin layer acrylamide gel which permits the simultaneous separation of acidic and basic isoperoxidases in up to 30 samples is described. Use of cytochrome c, horseradish peroxidase, and a purified potato isoperoxidase as internal standards for a range in isoelectric points of peroxidases from pH 3 to 11 is introduced to facilitate comparison of results obtained with different materials and different methods. Distribution of tissue-specific isoperoxidases in different cell layers of wounded potato (Solanum tuberosum L.) tissue is shown and their purification described. Evidence for the in vitro degradation of basic potato isoperoxidases resulting in more acidic forms similar to isoperoxidases occurring in wounded potato tissue is presented. The significance of this observation for the postulated differential function of different isoperoxidases is discussed. ImagesFig. 1-3 PMID:16660608

Gastric reacidification with betaine HCl in healthy volunteers with rabeprazole-induced hypochlorhydria.

PubMed

Yago, Marc R; Frymoyer, Adam R; Smelick, Gillian S; Frassetto, Lynda A; Budha, Nageshwar R; Dresser, Mark J; Ware, Joseph A; Benet, Leslie Z

2013-11-04

Previous studies have demonstrated that increased gastric pH from the use of acid-reducing agents, such as proton-pump inhibitors or H2-receptor antagonists, can significantly impact the absorption of weakly basic drugs that exhibit pH-dependent solubility. Clinically practical strategies to mitigate this interaction have not been developed. This pilot study evaluated the extent and time course of gastric reacidification after a solid oral dosage form of anhydrous betaine HCl in healthy volunteers with pharmacologically induced hypochlorhydria. Six healthy volunteers with baseline normochlorhydria (fasting gastric pH < 4) were enrolled in this single period study. Hypochlorhydria was induced via 20 mg oral rabeprazole twice daily for four days. On the fifth day, an additional 20 mg dose of oral rabeprazole was given and gastric pH was monitored continuously using the Heidelberg pH capsule. After gastric pH > 4 was confirmed for 15 min, 1500 mg of betaine HCl was given orally with 90 mL of water and gastric pH was continuously monitored for 2 h. Betaine HCl significantly lowered gastric pH by 4.5 (± 0.5) units from 5.2 (± 0.5) to 0.6 (± 0.2) (P < 0.001) during the 30 min interval after administration. The onset of effect of betaine HCl was rapid, with a mean time to pH < 3 of 6.3 (± 4.3) min. The reacidification period was temporary with a gastric pH < 3 and < 4 lasting 73 (± 33) and 77 (± 30) min, respectively. Betaine HCl was well tolerated by all subjects. In healthy volunteers with pharmacologically induced hypochlorhydria, betaine HCl was effective at temporarily lowering gastric pH. The rapid onset and relatively short duration of gastric pH reduction gives betaine HCl the potential to aid the absorption of orally administered weakly basic drugs that exhibit pH-dependent solubility when administered under hypochlorhydric conditions.

Gastric Re-acidification with Betaine HCl in Healthy Volunteers with Rabeprazole-Induced Hypochlorhydria

PubMed Central

Yago, Marc Anthony R.; Frymoyer, Adam R.; Smelick, Gillian S.; Frassetto, Lynda A.; Budha, Nageshwar R.; Dresser, Mark J.; Ware, Joseph A.; Benet, Leslie Z.

2013-01-01

Previous studies have demonstrated that increased gastric pH from the use of acid-reducing agents, such as proton-pump inhibitors or H2-receptor antagonists, can significantly impact the absorption of weakly basic drugs that exhibit pH-dependent solubility. Clinically practical strategies to mitigate this interaction have not been developed. This pilot study evaluated the extent and time course of gastric re-acidification after a solid oral dosage form of anhydrous betaine HCl in healthy volunteers with pharmacologically-induced hypochlorhydria. Six healthy volunteers with baseline normochlorhydria (fasting gastric pH < 4) were enrolled in this single period study. Hypochlorhydria was induced via 20 mg oral rabeprazole twice daily for four days. On the fifth day, an additional 20 mg dose of oral rabeprazole was given and gastric pH was monitored continuously using the Heidelberg pH capsule. After gastric pH > 4 was confirmed for 15 minutes, 1500 mg of betaine HCl was given orally with 90 mL of water and gastric pH was continuously monitored for 2 hours. Betaine HCl significantly lowered gastric pH by 4.5 (±0.5) units from 5.2 (±0.5) to 0.6 (±0.2) (P <0.001) during the 30 minute interval after administration. The onset of effect of betaine HCl was rapid, with a mean time to pH < 3 of 6.3 (±4.3) minutes. The re-acidification period was temporary with a gastric pH < 3 and < 4 lasting 73 (±33) and 77 (±30) minutes, respectively. Betaine HCl was well tolerated by all subjects. In healthy volunteers with pharmacologically-induced hypochlorhydria, betaine HCl was effective at temporarily lowering gastric pH. The rapid onset and relatively short duration of gastric pH reduction gives betaine HCl the potential to aid the absorption of orally administered weakly basic drugs that exhibit pH-dependent solubility when administered under hypochlorhydric conditions. PMID:23980906

Influence of exchange group of modified glycidyl methacrylate polymer on phenol removal: A study by batch and continuous flow processes.

PubMed

Aversa, Thiago Muza; da Silva, Carla Michele Frota; da Rocha, Paulo Cristiano Silva; Lucas, Elizabete Fernandes

2016-11-01

Contamination of water by phenol is potentially a serious problem due to its high toxicity and its acid character. In this way some treatment process to remove or reduce the phenol concentration before contaminated water disposal on the environment is required. Currently, phenol can be removed by charcoal adsorption, but this process does not allow easy regeneration of the adsorbent. In contrast, polymeric resins are easily regenerated and can be reused in others cycles of adsorption process. In this work, the interaction of phenol with two polymeric resins was investigated, one of them containing a weakly basic anionic exchange group (GD-DEA) and the other, a strongly basic group (GD-QUAT). Both ion exchange resins were obtained through chemical modifications from a base porous resin composed of glycidyl methacrylate (GMA) and divinyl benzene (DVB). Evaluation tests with resins were carried out with 30 mg/L of phenol in water solution, at pH 6 and 10, employing two distinct processes: (i) batch, to evaluate the effect of temperature, and (ii) continuous flow, to assess the breakthrough of the resins. Batch tests revealed that the systems did not follow the model proposed by Langmuir due to the negative values obtained for the constant b and for the maximum adsorption capacity, Q0. However, satisfactory results for the constants KF and n allowed assuming that the behavior of systems followed the Freundlich model, leading to the conclusion that resin GD-DEA had the best interaction with the phenol when in a solution having pH 10 (phenoxide ions). The continuous flow tests corroborated this conclusion since the performance of GD-DEA in removing phenol was also best at pH 10, indicating that the greater availability of the electron pair in the resin with the weakly basic donor group contributed to enhance the resin's interaction with the phenoxide ions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Recent advances in H-phosphonate chemistry. Part 1. H-phosphonate esters: synthesis and basic reactions.

PubMed

Sobkowski, Michal; Kraszewski, Adam; Stawinski, Jacek

2015-01-01

This review covers recent progress in the preparation of H-phosphonate mono- and diesters, basic studies on mechanistic and stereochemical aspects of this class of phosphorus compounds, and their fundamental chemistry in terms of transformation of P-H bonds into P-heteroatom bonds. Selected recent applications of H-phosphonate derivatives in basic organic phosphorus chemistry and in the synthesis of biologically important phosphorus compounds are also discussed.

Effects of elevated temperature and mobile phase composition on a novel C18 silica column.

PubMed

Lippert, J Andreas; Johnson, Todd M; Lloyd, Jarem B; Smith, Jared P; Johnson, Bryce T; Furlow, Jason; Proctor, Angela; Marin, Stephanie J

2007-05-01

A novel polydentate C18 silica column was evaluated at an elevated temperature under acidic, basic, and neutral mobile phase conditions using ACN and methanol as the mobile phase organic modifier. The temperature range was 40-200 degrees C. The mobile phase compositions were from 0 to 80% organic-aqueous v/v and the mobile phase pH levels were between 2 and 12. The maximum operating temperature of the column was affected by the amount and type of organic modifier used in the mobile phase. Under neutral conditions, the column showed good column thermal stability at temperatures ranging between 120 and 200 degrees C in methanol-water and ACN-water solvent systems. At pH 2 and 3, the column performed well up to about 160 degrees C at two fixed ACN-buffer compositions. Under basic conditions at elevated temperatures, the column material deteriorated more quickly, but still remained stable up to 100 degrees C at pH 9 and 60 degrees C at pH 10. The results of this study indicate that this novel C18 silica-based column represents a significant advancement in RPLC column technology with enhanced thermal and pH stability when compared to traditional bonded phase silica columns.

Great Salt Lake Composition and Rare Earth Speciation Analysis

DOE Data Explorer

Jiao, Yongqin; Lammers, Laura; Brewer, Aaron

2017-04-19

We have conducted aqueous speciation analyses of the Great Salt Lake (GSL) brine sample (Table 1) and a mock geo sample (Table 2) spiked with 1 ppb Tb and 100 ppb Tb. The GSL speciation (Figure 1) aligns with our basic speciation expectations that strong carbonate complexes would form at mid to higher pH's. Although we expected strong aqueous complexes with fluorides at neutral pH and with chlorides, and hydroxides at low pH, we observe that the dominant species in the low to mid pH range to be Tb3+ as a free ion. Still, we do see the presence of fluoride and chloride complexes within the expected low to mid pH range.

Transport and deposition of Suwannee River Humic Acid/Natural Organic Matter formed silver nanoparticles on silica matrices: the influence of solution pH and ionic strength.

PubMed

Akaighe, Nelson; Depner, Sean W; Banerjee, Sarbajit; Sohn, Mary

2013-07-01

The transport and deposition of silver nanoparticles (AgNPs) formed from Ag(+) reduction by Suwannee River Humic Acid (SRHA) and Suwannee River Natural Organic Matter (SRNOM) utilizing a silica matrix is reported. The morphology and stability of the AgNPs was analyzed by transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential measurements. The percentage conversion of the initial [Ag(+)] to [AgNPs] was determined from a combination of atomic absorption (AAS) and UV-Vis spectroscopy, and centrifugation techniques. The results indicate higher AgNP transport and consequently low deposition in the porous media at basic pH conditions and low ionic strength. However, at low acidic pH and high ionic strength, especially with the divalent metallic cations, the mobility of the AgNPs in the porous media was very low, most likely due to NP aggregation. Overall, the results suggest the potential for AgNP contamination of subsurface soils and groundwater aquifers is mostly dependent on their aggregation state, controlled by the soil water and sediment ionic strength and pH. Copyright © 2013 Elsevier Ltd. All rights reserved.

Enhanced Activity and Acid pH Stability of Prussian Blue-type Oxygen Evolution Electrocatalysts Processed by Chemical Etching.

PubMed

Han, Lijuan; Tang, Pengyi; Reyes-Carmona, Álvaro; Rodríguez-García, Bárbara; Torréns, Mabel; Morante, Joan Ramon; Arbiol, Jordi; Galan-Mascaros, Jose Ramon

2016-12-14

The development of upscalable oxygen evolving electrocatalysts from earth-abundant metals able to operate in neutral or acidic environments and low overpotentials remains a fundamental challenge for the realization of artificial photosynthesis. In this study, we report a highly active phase of heterobimetallic cyanide-bridged electrocatalysts able to promote water oxidation under neutral, basic (pH < 13), and acidic conditions (pH > 1). Cobalt-iron Prussian blue-type thin films, formed by chemical etching of Co(OH) 1.0 (CO 3 ) 0.5 ·nH 2 O nanocrystals, yield a dramatic enhancement of the catalytic performance toward oxygen production, when compared with previous reports for analogous materials. Electrochemical, spectroscopic, and structural studies confirm the excellent performance, stability, and corrosion resistance, even when compared with state-of-the-art metal oxide catalysts under moderate overpotentials and in a remarkably large pH range, including acid media where most cost-effective water oxidation catalysts are not useful. The origin of the superior electrocatalytic activity toward water oxidation appears to be in the optimized interfacial matching between catalyst and electrode surface obtained through this fabrication method.

Guidelines for Measuring Changes in Seawater pH and Associated Carbonate Chemistry in Coastal Environments of the Eastern United States

EPA Science Inventory

This report begins with descriptions of the differences between coastal and ocean acidification, factors contributing to acidification on the US east coast, and basic characteristics of the seawater carbonate system and its parameters. A basic survey of available methods and cha...

Doctorate Recipients from United States Universities. Summary Report, 1984.

ERIC Educational Resources Information Center

Coyle, Susan L.; Syverson, Peter D.

A statistical and narrative summary of the results of the 1983-1984 Survey of Earned Doctorates is presented. Basic information, such as sex, field, institution, and year of Ph.D., is presented for all of the 31,253 doctorate recipients; complete questionnaire data are included for the 29,713 Ph.D. recipients who responded to the questionnaire,…

Cyanopyridine Based Bipolar Host Materials for Green Electrophosphorescence with Extremely Low Turn-On Voltages and High Power Efficiencies.

PubMed

Li, Wei; Li, Jiuyan; Liu, Di; Li, Deli; Wang, Fang

2016-08-24

Low driving voltage and high power efficiency are basic requirements when practical applications of organic light emitting diodes (OLEDs) in displays and lighting are considered. Two novel host materials m-PyCNmCP and 3-PyCNmCP incorporating cyanopyridine moiety as electron-transporting unit are developed for use in fac-tris(2-phenylpyridine)iridium(III) (Ir(ppy)3) based green phosphorescent OLEDs (PhOLEDs). Extremely low turn-on voltages of 2.01 and 2.27 V are realized, which are even lower than the theoretical limit of the emitted photon energy (hv)/electron charge (e) (2.37 V) of Ir(ppy)3. High power efficiency of 101.4 lm/W (corresponding to a maximum external quantum efficiency of 18.4%) and 119.3 lm/W (24.7%) are achieved for m-PyCNmCP and 3-PyCNmCP based green PhOLEDs. The excellent EL performance benefits from the ideal parameters of host materials by combining cyano and pyridine to enhance the n-type feature. The energetic favorable alignment of HOMO/LUMO levels of hosts with adjacent layers and the dopant for easy charge injections and direct charge trapping by dopant, their bipolar feature to balance charge transportations, sufficiently high triplet energy and small singlet/triplet energy difference (0.38 and 0.43 eV) combine to be responsible for the extremely low driving voltages and high power efficiencies of the green PhOLEDs.

Pharmacokinetics and absorption of the anticancer agents dasatinib and GDC-0941 under various gastric conditions in dogs--reversing the effect of elevated gastric pH with betaine HCl.

PubMed

Pang, Jodie; Dalziel, Gena; Dean, Brian; Ware, Joseph A; Salphati, Laurent

2013-11-04

Changes in gastric pH can impact the dissolution and absorption of compounds presenting pH-dependent solubility. We assessed, in dogs, the effects of gastric pH-modifying agents on the oral absorption of two weakly basic anticancer drugs, dasatinib and GDC-0941. We also tested whether drug-induced hypochlorhydria could be temporarily mitigated using betaine HCl. Pretreatments with pentagastrin, famotidine, betaine HCl, or combinations of famotidine and betaine HCl were administered orally to dogs prior to drug dosing. The gastric pH was measured under each condition for up to 7 h, and the exposure of the compounds tested was calculated. The average gastric pH in fasted dogs ranged from 1.45 to 3.03. Pentagastrin or betaine HCl treatments lowered the pH and reduced its variability between dogs compared to control animals. In contrast, famotidine treatment maintained gastric pH at values close to 7 for up to 5 h, while betaine HCl transiently reduced the pH to approximately 2 in the famotidine-treated dogs. Famotidine pretreatment lowered GDC-0941 exposure by 5-fold, and decreased dasatinib measurable concentrations 30-fold, compared to the pentagastrin-treated dogs. Betaine HCl restored GDC-0941 AUC in famotidine-treated dogs to levels achieved in control animals, and increased dasatinib AUC to 1.5-fold that measured in control dogs. The results confirmed the negative impact of acid-reducing agents on the absorption of weakly basic drugs. They also suggested that betaine HCl coadministration may be a viable strategy in humans treated with acid-reducing agents in order to temporarily reduce gastric pH and restore drug exposure.

On the Observation of Discrete Fluorine NMR Spectra for Uridine 5′-β,γ-Fluoromethylenetriphosphate Diastereomers at Basic pH

PubMed Central

2015-01-01

Jakeman et al. recently reported the inability to distinguish the diastereomers of uridine 5′-β,γ-fluoromethylenetriphosphate (β,γ-CHF-UTP, 1) by 19F NMR under conditions we previously prescribed for the resolution of the corresponding β,γ-CHF-dGTP spectra, stating further that 1 decomposed under these basic conditions. Here we show that the 19F NMR spectra of 1 (∼1:1 diastereomer mixture prepared by coupling of UMP-morpholidate with fluoromethylenebis(phosphonic acid)) in D2O at pH 10 are indeed readily distinguishable. 1 in this solution was stable for 24 h at rt. PMID:24819695

Competitive adsorption of copper(II), cadmium(II), lead(II) and zinc(II) onto basic oxygen furnace slag.

PubMed

Xue, Yongjie; Hou, Haobo; Zhu, Shujing

2009-02-15

Polluted and contaminated water can often contain more than one heavy metal species. It is possible that the behavior of a particular metal species in a solution system will be affected by the presence of other metals. In this study, we have investigated the adsorption of Cd(II), Cu(II), Pb(II), and Zn(II) onto basic oxygen furnace slag (BOF slag) in single- and multi-element solution systems as a function of pH and concentration, in a background solution of 0.01M NaNO(3). In adsorption edge experiments, the pH was varied from 2.0 to 13.0 with total metal concentration 0.84mM in the single element system and 0.21mM each of Cd(II), Cu(II), Pb(II), and Zn(II) in the multi-element system. The value of pH(50) (the pH at which 50% adsorption occurs) was found to follow the sequence Zn>Cu>Pb>Cd in single-element systems, but Pb>Cu>Zn>Cd in the multi-element system. Adsorption isotherms at pH 6.0 in the multi-element systems showed that there is competition among various metals for adsorption sites on BOF slag. The adsorption and potentiometric titrations data for various slag-metal systems were modeled using an extended constant-capacitance surface complexation model that assumed an ion-exchange process below pH 6.5 and the formation of inner-sphere surface complexes at higher pH. Inner-sphere complexation was more dominant for the Cu(II), Pb(II) and Zn(II) systems.

Fluoride geochemistry of thermal waters in Yellowstone National Park: I. Aqueous fluoride speciation

USGS Publications Warehouse

Deng, Y.; Nordstrom, D. Kirk; McCleskey, R. Blaine

2011-01-01

Thermal water samples from Yellowstone National Park (YNP) have a wide range of pH (1–10), temperature, and high concentrations of fluoride (up to 50 mg/l). High fluoride concentrations are found in waters with field pH higher than 6 (except those in Crater Hills) and temperatures higher than 50 °C based on data from more than 750 water samples covering most thermal areas in YNP from 1975 to 2008. In this study, more than 140 water samples from YNP collected in 2006–2009 were analyzed for free-fluoride activity by ion-selective electrode (ISE) method as an independent check on the reliability of fluoride speciation calculations. The free to total fluoride concentration ratio ranged from <1% at low pH values to >99% at high pH. The wide range in fluoride activity can be explained by strong complexing with H+ and Al3+ under acidic conditions and lack of complexing under basic conditions. Differences between the free-fluoride activities calculated with the WATEQ4F code and those measured by ISE were within 0.3–30% for more than 90% of samples at or above 10−6 molar, providing corroboration for chemical speciation models for a wide range of pH and chemistry of YNP thermal waters. Calculated speciation results show that free fluoride, F−, and major complexes (HF(aq)0">HF(aq)0, AlF2+, AlF2+">AlF2+and AlF30">AlF30) account for more than 95% of total fluoride. Occasionally, some complex species like AlF4-">AlF4-, FeF2+, FeF2+">FeF2+, MgF+ and BF2(OH)2-">BF2(OH)2- may comprise 1–10% when the concentrations of the appropriate components are high. According to the simulation results by PHREEQC and calculated results, the ratio of main fluoride species to total fluoride varies as a function of pH and the concentrations and ratios of F and Al.

Ocean acidification buffering effects of seagrass in Tampa Bay

USGS Publications Warehouse

Yates, Kimberly K.; Moyer, Ryan P.; Moore, Christopher; Tomasko, David A.; Smiley, Nathan A.; Torres-Garcia, Legna; Powell, Christina E.; Chappel, Amanda R.; Bociu, Ioana; Smiley, Nathan; Torres-Garcia, Legna M.; Powell, Christina E.; Chappel, Amanda R.; Bociu, Ioana

2016-01-01

The Intergovernmental Panel on Climate Change has identified ocean acidification as a critical threat to marine and estuarine species in ocean and coastal ecosystems around the world. However, seagrasses are projected to benefit from elevated atmospheric pCO2, are capable of increasing seawater pH and carbonate mineral saturation states through photosynthesis, and may help buffer against the chemical impacts of ocean acidification. Additionally, dissolution of carbonate sediments may also provide a mechanism for buffering seawater pH. Long-term water quality monitoring data from the Environmental Protection Commission of Hillsborough County indicates that seawater pH has risen since the 1980‘s as seagrass beds have continued to recover since that time. We examined the role of seagrass beds in maintaining and elevating pH and carbonate mineral saturation state in northern and southern Tampa Bay where the percent of carbonate sediments is low (<3%) and high (>40%), respectively. Basic water quality and carbonate system parameters (including pH, total alkalinity, dissolved inorganic carbon, partial pressure of CO2, and carbonate mineral saturation state) were measured over diurnal time periods along transects (50-100 m) including dense and sparse Thalassia testudinum. seagrass beds, deep edge seagrass, and adjacent bare sand bottom. Seagrass density and productivity, sediment composition and hydrodynamic parameters were also measured, concurrently. Results indicate that seagrass beds locally elevate pH by up to 0.5 pH unit and double carbonate mineral saturation states relative to bare sand habitats. Thus, seagrass beds in Tampa Bay may provide refuge for marine organisms from the impacts of ocean acidification.

pH and temperature dual-sensitive liposome gel based on novel cleavable mPEG-Hz-CHEMS polymeric vaginal delivery system

PubMed Central

Chen, Daquan; Sun, Kaoxiang; Mu, Hongjie; Tang, Mingtan; Liang, Rongcai; Wang, Aiping; Zhou, Shasha; Sun, Haijun; Zhao, Feng; Yao, Jianwen; Liu, Wanhui

2012-01-01

Background In this study, a pH and temperature dual-sensitive liposome gel based on a novel cleavable hydrazone-based pH-sensitive methoxy polyethylene glycol 2000-hydrazone-cholesteryl hemisuccinate (mPEG-Hz-CHEMS) polymer was used for vaginal administration. Methods The pH-sensitive, cleavable mPEG-Hz-CHEMS was designed as a modified pH-sensitive liposome that would selectively degrade under locally acidic vaginal conditions. The novel pH-sensitive liposome was engineered to form a thermogel at body temperature and to degrade in an acidic environment. Results A dual-sensitive liposome gel with a high encapsulation efficiency of arctigenin was formed and improved the solubility of arctigenin characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry. The dual-sensitive liposome gel with a sol-gel transition at body temperature was degraded in a pH-dependent manner, and was stable for a long period of time at neutral and basic pH, but cleavable under acidic conditions (pH 5.0). Arctigenin encapsulated in a dual-sensitive liposome gel was more stable and less toxic than arctigenin loaded into pH-sensitive liposomes. In vitro drug release results indicated that dual-sensitive liposome gels showed constant release of arctigenin over 3 days, but showed sustained release of arctigenin in buffers at pH 7.4 and pH 9.0. Conclusion This research has shed some light on a pH and temperature dual-sensitive liposome gel using a cleavable mPEG-Hz-CHEMS polymer for vaginal delivery. PMID:22679372

Origin of the Absorption Band of Bromophenol Blue in Acidic and Basic pH: Insight from a Combined Molecular Dynamics and TD-DFT/MM Study.

PubMed

Chattopadhyaya, M; Murugan, N Arul; Rinkevicius, Zilvinas

2016-09-15

We study the linear and nonlinear optical properties of a well-known acid-base indicator, bromophenol blue (BPB), in aqueous solution by employing static and integrated approaches. In the static approach, optical properties have been calculated using time-dependent density functional theory (TD-DFT) on the fully relaxed geometries of the neutral and different unprotonated forms of BPB. Moreover, both closed and open forms of BPB were considered. In the integrated approach, the optical properties have been computed over many snapshots extracted from molecular dynamics simulation using a hybrid time-dependent density functional theory/molecular mechanics approach. The static approach suggests closed neutral ⇒ anionic interconversion as the dominant mechanism for the red shift in the absorption spectra of BPB due to a change from acidic to basic pH. It is found by employing an integrated approach that the two interconversions, namely open neutral ⇒ anionic and open neutral ⇒ dianionic, can contribute to the pH-dependent shift in the absorption spectra of BPB. Even though both static and integrated approaches reproduce the pH-dependent red shift in the absorption spectra of BPB, the latter one is suitable to determine both the spectra and spectral broadening. Finally, the computed static first hyperpolarizability for various protonated and deprotonated forms of BPB reveals that this molecule can be used as a nonlinear optical probe for pH sensing in addition to its highly exploited use as an optical probe.

Recovery and redispersion of gold nanoparticles using the self-assembly of a pH sensitive zwitterionic amphiphile.

PubMed

Morita-Imura, Clara; Imura, Yoshiro; Kawai, Takeshi; Shindo, Hitoshi

2014-11-04

The pH-responsive self-assembly of zwitterionic amphiphile C16CA was expanded to the recovery of gold (Au) nanoparticles for environmentally friendly chemistry applications. Multilayered lamellae at pH ∼ 4 were successfully incorporated into nanoparticles by dispersion. Redispersion of nanoparticles was achieved under basic conditions by the transition of self-assembly.

Adsorption of dyes by ACs prepared from waste tyre reinforcing fibre. Effect of texture, surface chemistry and pH.

PubMed

Acevedo, Beatriz; Rocha, Raquel P; Pereira, Manuel F R; Figueiredo, José L; Barriocanal, Carmen

2015-12-01

This paper compares the importance of the texture and surface chemistry of waste tyre activated carbons in the adsorption of commercial dyes. The adsorption of two commercial dyes, Basic Astrazon Yellow 7GLL and Reactive Rifafix Red 3BN on activated carbons made up of reinforcing fibres from tyre waste and low-rank bituminous coal was studied. The surface chemistry of activated carbons was modified by means of HCl-HNO3 treatment in order to increase the number of functional groups. Moreover, the influence of the pH on the process was also studied, this factor being of great importance due to the amphoteric characteristics of activated carbons. The activated carbons made with reinforcing fibre and coal had the highest SBET, but the reinforcing fibre activated carbon samples had the highest mesopore volume. The texture of the activated carbons was not modified upon acid oxidation treatment, unlike their surface chemistry which underwent considerable modification. The activated carbons made with a mixture of reinforcing fibre and coal experienced the largest degree of oxidation, and so had more acid surface groups. The adsorption of reactive dye was governed by the mesoporous volume, whilst surface chemistry played only a secondary role. However, the surface chemistry of the activated carbons and dispersive interactions played a key role in the adsorption of the basic dye. The adsorption of the reactive dye was more favored in a solution of pH 2, whereas the basic dye was adsorbed more easily in a solution of pH 12. Copyright © 2015 Elsevier Inc. All rights reserved.

Daily and seasonal variability of pH, dissolved oxygen, temperature, and specific conductance in the Colorado River between the forebay of Glen Canyon, Dam and Lees Ferry, northeastern Arizona, 1998-99

USGS Publications Warehouse

Flynn, Marilyn E.; Hart, Robert J.; Marzolf, G. Richard; Bowser, Carl J.

2001-01-01

The productivity of the trout fishery in the tailwater reach of the Colorado River downstream from Glen Canyon Dam depends on the productivity of lower trophic levels. Photosynthesis and respiration are basic biological processes that control productivity and alter pH and oxygen concentration. During 1998?99, data were collected to aid in the documentation of short- and long-term trends in these basic ecosystem processes in the Glen Canyon reach. Dissolved-oxygen, temperature, and specific-conductance profile data were collected monthly in the forebay of Glen Canyon Dam to document the status of water chemistry in the reservoir. In addition, pH, dissolved-oxygen, temperature, and specific-conductance data were collected at five sites in the Colorado River tailwater of Glen Canyon Dam to document the daily, seasonal, and longitudinal range of variation in water chemistry that could occur annually within the Glen Canyon reach.

Enhanced phosphorus removal from wastewater by growing deep-sea bacterium combined with basic oxygen furnace slag.

PubMed

Zhou, Weizhi; Huang, Zhaosong; Sun, Cuiping; Zhao, Haixia; Zhang, Yuzhong

2016-08-01

As one solid waste with potential for phosphorus removal, application of slags in water treatment merits attention. But it was inhibited greatly by alkaline solution (pH>9.5) and cemented clogging generated. To give one solution, phosphorus removal was investigated by combining deep-sea bacterium Alteromonas 522-1 and basic oxygen furnace slag (BOFS). Results showed that by the combination, not only higher phosphorous removal efficiency (>90%) but also neutral solution pH of 7.8-8.0 were achieved at wide ranges of initial solution pH value of 5.0-9.0, phosphorus concentration of 5-30mg/L, salinity of 0.5-3.5%, and temperature of 15-35°C. Moreover, sedimentary property was also improved with lower amount of sludge production and alleviated BOFS cementation with increased porosity and enlarged particle size. These results provided a promising strategy for the phosphorus recovery with slags in large-scale wastewater treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Inhibition of d-xylose isomerase by polyols: atomic details by joint X-ray/neutron crystallography

PubMed Central

Kovalevsky, Andrey; Hanson, B. Leif; Mason, Sax A.; Forsyth, V. Trevor; Fisher, Zoe; Mustyakimov, Marat; Blakeley, Matthew P.; Keen, David A.; Langan, Paul

2012-01-01

d-Xylose isomerase (XI) converts the aldo-sugars xylose and glucose to their keto analogs xylulose and fructose, but is strongly inhibited by the polyols xylitol and sorbitol, especially at acidic pH. In order to understand the atomic details of polyol binding to the XI active site, a 2.0 Å resolution room-temperature joint X-ray/neutron structure of XI in complex with Ni2+ cofactors and sorbitol inhibitor at pH 5.9 and a room-temperature X-ray structure of XI containing Mg2+ ions and xylitol at the physiological pH of 7.7 were obtained. The protonation of oxygen O5 of the inhibitor, which was found to be deprotonated and negatively charged in previous structures of XI complexed with linear glucose and xylulose, was directly observed. The Ni2+ ions occupying the catalytic metal site (M2) were found at two locations, while Mg2+ in M2 is very mobile and has a high B factor. Under acidic conditions sorbitol gains a water-mediated interaction that connects its O1 hydroxyl to Asp257. This contact is not found in structures at basic pH. The new interaction that is formed may improve the binding of the inhibitor, providing an explanation for the increased affinity of the polyols for XI at low pH. PMID:22948921

Conditions affecting the release of phosphorus from surface lake sediments.

PubMed

Christophoridis, Christophoros; Fytianos, Konstantinos

2006-01-01

Laboratory studies were conducted to determine the effect of pH and redox conditions, as well as the effect of Fe, Mn, Ca, Al, and organic matter, on the release of ortho-phosphates in lake sediments taken from Lakes Koronia and Volvi (Northern Greece). Results were evaluated in combination with experiments to determine P fractionation in the sediment. The study revealed the major effect of redox potential and pH on the release of P from lake sediments. Both lakes showed increased release rates under reductive conditions and high pH values. The fractionation experiments revealed increased mobility of the reductive P fraction as well as of the NaOH-P fraction, indicating participation of both fractions in the overall release of sediment-bound P, depending on the prevailing environmental conditions. The results were assessed in combination with the release patterns of Fe, Mn, Ca, Al, and organic matter, enabling the identification of more specific processes of P release for each lake. The basic release patterns included the redox induced reductive dissolution of P-bearing metal oxides and the competitive exchange of phosphate anions with OH- at high pH values. The formation of an oxidized surface microlayer under oxic conditions acted as a protective film, preventing further P release from the sediments of Lake Volvi, while sediments from Lake Koronia exhibited a continuous and increased tendency to release P under various physicochemical conditions, acting as a constant source of internal P loading.

Cationic double-chained surfactant as pseudostationary phase in micellar electrokinetic capillary chromatography for drug separations.

PubMed

Li, Yanqing; Liu, Qian; Yao, Shouzhuo

2008-05-15

The cationic double-chained surfactant didodecyldimethylammonium bromide (DDAB) was used as pseudostationary phase (PSP) in micellar electrokinetic capillary chromatography (MEKC). Its performance on the three kinds of drugs, i.e., basic, acidic, and neutral drugs, was systematically investigated. Nicotine, cotinine, caffeine, lidocaine, and procaine were selected as the model basic drugs. Good baseline separation and high efficiency were obtained under the optimal separation condition that consisted of 50mM phosphate (pH 4.0) and 0.08 mM DDAB. Three basic phenylenediamine isomers can also be well separated with DDAB in buffer. In addition, DDAB can form cationic bilayer on the capillary wall, thus the wall adsorption of basic analytes was greatly suppressed. Compared with commonly used CTAB, the separation of basic drugs was significantly improved with a much lower amount of DDAB present in the buffer. The DDAB-involved MEKC also showed superiority to CTAB upon the separation of acidic drugs, amoxicillin and ampicillin. In the case of neutral compounds, a good separation of resorcinol, 1-naphthol and 2-naphthol was achieved with 0.1mM DDAB and 30% (v/v) acetonitrile (ACN) present in buffer. Hence, it was concluded that the double-chained cationic surfactant DDAB can be a good substitute for traditional single-chained surfactant CTAB in MEKC.

Epinigericin toxicity towards Tetrahymena pyriformis GL; changes in cell volume and intracellular pH.

PubMed

Bamdad, M; David, L; Grolière, C A

1995-12-01

A study of the toxicity of epinigericin, an antibiotic ionophor, towards the ciliate Tetrahymena pyriformis showed that this molecule stopped cell division, increased cell volume and led to a more basic intracellular pH. The action of epinigericin was probably linked to its function as an ionophor. The ionic selectivity of this molecule is still not known. The raising of the intracellular pH of ciliates by this antibiotic may be linked to its toxic action and its iontransport mechanism in Tetrahymena.

Effect of humic acid on ciprofloxacin removal by magnetic multifunctional resins

PubMed Central

Wang, Wei; Cheng, Jiade; Jin, Jing; Zhou, Qing; Ma, Yan; Zhao, Qingqing; Li, Aimin

2016-01-01

Background organic matter significantly influences the removal of emerging contaminants in natural water. In this work, the adsorption of ciprofloxacin (CPX) onto a series of magnetic multifunctional resins (GMA10-GMA90) in the presence and absence of humic acid (HA) was conducted to demonstrate the effect of HA. Both hydrophobic and ion exchange interactions contributed to CPX adsorption. Negative charge-assisted hydrogen bonds also participated in the adsorption process, resulting in the high adsorption amount of anionic CPX onto the negatively charged GMA30 under basic solutions. HA could impact CPX adsorption not only as a competitive adsorbate but also as an additional adsorbent. At pH 5.6, the additional adsorption sites provided by adsorbed HA molecules on the resins dominated and thus facilitated the adsorption process. While at pH 10, HA inhibited the adsorption of CPX by directly competing for ion exchange sites and coexisting with CPX in the solution. The ratio of the amount of CPX adsorbed by dissolved HA to that by the resin reached as high as 1.61 for GMA90. The adsorbed HA molecules onto the resins could provide additional adsorption sites for CPX as proven by the enhanced CPX adsorption in HA-preloading systems at pH 5.6. PMID:27464502

Retention and release of oil-in-water emulsions from filled hydrogel beads composed of calcium alginate: impact of emulsifier type and pH.

PubMed

Zeeb, Benjamin; Saberi, Amir Hossein; Weiss, Jochen; McClements, David Julian

2015-03-21

Delivery systems based on filled hydrogel particles (microgels) can be fabricated from natural food-grade lipids and biopolymers. The potential for controlling release characteristics by modulating the electrostatic interactions between emulsifier-coated lipid droplets and the biopolymer matrix within hydrogel particles was investigated. A multistage procedure was used to fabricate calcium alginate beads filled with lipid droplets stabilized by non-ionic, cationic, anionic, or zwitterionic emulsifiers. Oil-in-water emulsions stabilized by Tween 60, DTAB, SDS, or whey protein were prepared by microfluidization, mixed with various alginate solutions, and then microgels were formed by simple extrusion into calcium solutions. The microgels were placed into a series of buffer solutions with different pH values (2 to 11). Lipid droplets remained encapsulated under acidic and neutral conditions, but were released under highly basic conditions (pH 11) due to hydrogel swelling when the alginate concentration was sufficiently high. Lipid droplet release increased with decreasing alginate concentration, which could be attributed to an increase in the pore size of the hydrogel matrix. These results have important implications for the design of delivery systems to entrap and control the release of lipophilic bioactive components within filled hydrogel particles.

Effect of humic acid on ciprofloxacin removal by magnetic multifunctional resins

NASA Astrophysics Data System (ADS)

Wang, Wei; Cheng, Jiade; Jin, Jing; Zhou, Qing; Ma, Yan; Zhao, Qingqing; Li, Aimin

2016-07-01

Background organic matter significantly influences the removal of emerging contaminants in natural water. In this work, the adsorption of ciprofloxacin (CPX) onto a series of magnetic multifunctional resins (GMA10-GMA90) in the presence and absence of humic acid (HA) was conducted to demonstrate the effect of HA. Both hydrophobic and ion exchange interactions contributed to CPX adsorption. Negative charge-assisted hydrogen bonds also participated in the adsorption process, resulting in the high adsorption amount of anionic CPX onto the negatively charged GMA30 under basic solutions. HA could impact CPX adsorption not only as a competitive adsorbate but also as an additional adsorbent. At pH 5.6, the additional adsorption sites provided by adsorbed HA molecules on the resins dominated and thus facilitated the adsorption process. While at pH 10, HA inhibited the adsorption of CPX by directly competing for ion exchange sites and coexisting with CPX in the solution. The ratio of the amount of CPX adsorbed by dissolved HA to that by the resin reached as high as 1.61 for GMA90. The adsorbed HA molecules onto the resins could provide additional adsorption sites for CPX as proven by the enhanced CPX adsorption in HA-preloading systems at pH 5.6.

Resolution V fractional factorial design for screening of factors affecting weakly basic drugs liposomal systems.

PubMed

Nageeb El-Helaly, Sara; Habib, Basant A; Abd El-Rahman, Mohamed K

2018-07-01

This study aims to investigate factors affecting weakly basic drugs liposomal systems. Resolution V fractional factorial design (2 V 5-1 ) is used as an example of screening designs that would better be used as a wise step before proceeding with detailed factors effects or optimization studies. Five factors probable to affect liposomal systems of weakly basic drugs were investigated using Amisulpride as a model drug. Factors studied were; A: Preparation technique B: Phosphatidyl choline (PhC) amount (mg) C: Cholesterol: PhC molar ratio, D: Hydration volume (ml) and E: Sonication type. Levels investigated were; Ammonium sulphate-pH gradient technique or Transmembrane zinc chelation-pH gradient technique, 200 or 400 mg, 0 or 0.5, 10 or 20 ml and bath or probe sonication for A, B, C, D and E respectively. Responses measured were Particle size (PS) (nm), Zeta potential (ZP) (mV) and Entrapment efficiency percent (EE%). Ion selective electrode was used as a novel method for measuring unentrapped drug concentration and calculating entrapment efficiency without the need for liposomal separation. Factors mainly affecting the studied responses were Cholesterol: PhC ratio and hydration volume for PS, preparation technique for ZP and preparation technique and hydration volume for EE%. The applied 2 V 5-1 design enabled the use of only 16 trial combinations for screening the influence of five factors on weakly basic drugs liposomal systems. This clarifies the value of the use of screening experiments before extensive investigation of certain factors in detailed optimization studies. Copyright © 2018 Elsevier B.V. All rights reserved.

The 3.2 Angstrom Resolution Structure of the Polymorphic Cowpea Chlorotic Mottle Virus Ribonucleoprotein Particle

NASA Astrophysics Data System (ADS)

Speir, Jeffrey Alan

Structural studies of the polymorphic cowpea chlorotic mottle virus have resulted in high resolution structures for two distinct icosahedral ribonucleoprotein particle conformations dependent upon whether acidic or basic pH conditions prevail. CCMV is stable below pH 6.5, however metal-free particles maintain a 10% increase in hydrodynamic volume at pH >=q 7.5. Identification of this swollen' form of CCMV, which can easily be disrupted with 1M NaCl, led to the first reassembly of an icosahedral virus in vitro from purified viral protein and RNA to form infectious particles, and its assembly has been the subject of biochemical and biophysical investigations for over twenty-five years. Under well defined conditions of pH, ionic strength and divalent metal ion concentration, CCMV capsid protein or capsid protein and RNA will reassemble to form icosahedral particles of various sizes, sheets, tubes, rosettes, and a variety of laminar structures which resemble virion structures from non-related virus families. Analysis of native particles at 3.2A resolution and swollen particles at 28A resolution has suggested that the chemical basis for the formation of polymorphic icosahedral and anisometric structures is: (i) hexamers formed of beta-barrel subunits stabilized by an unusual hexameric parallel beta structure made up of their N-termini, (ii) the location of protein-RNA interactions, (iii) divalent metal cation binding sites that regulate quasi-symmetrical subunit associations, (iv) charge repulsion across the same interfaces when lacking divalent metal ions at basic pH, which induces the formation of sixty 20A diameter portals for RNA release, and (v) a novel, C-terminal-based, subunit dimer assembly unit. The use of C- and N-terminal arms in CCMV has not been observed in other icosahedral RNA virus structures determined at near atomic resolution, however, their detailed interactions and roles in stabilizing the quaternary organization of CCMV are related to that found in the atomic structures of the DNA tumor papovaviruses (SV40 and polyoma). The swollen structure is closely similar to the expanded form of tomato bushy stunt virus (TBSV) previously determined at 8A resolution by X-ray crystallography.

"Do-It-Yourself" reliable pH-stat device by using open-source software, inexpensive hardware and available laboratory equipment

PubMed Central

Kragic, Rastislav; Kostic, Mirjana

2018-01-01

In this paper, we present the construction of a reliable and inexpensive pH stat device, by using open-source “OpenPhControl” software, inexpensive hardware (a peristaltic and a syringe pump, Arduino, a step motor…), readily available laboratory devices: a pH meter, a computer, a webcam, and some 3D printed parts. We provide a methodology for the design, development and test results of each part of the device, as well as of the entire system. In addition to dosing reagents by means of a low-cost peristaltic pump, we also present carefully controlled dosing of reagents by an open-source syringe pump. The upgrading of the basic open-source syringe pump is given in terms of pump control and application of a larger syringe. In addition to the basic functions of pH stat, i.e. pH value measurement and maintenance, an improvement allowing the device to be used for potentiometric titration has been made as well. We have demonstrated the device’s utility when applied for cellulose fibers oxidation with 2,2,6,6-tetramethylpiperidine-1-oxyl radical, i.e. for TEMPO-mediated oxidation. In support of this, we present the results obtained for the oxidation kinetics, the consumption of added reagent and experimental repeatability. Considering that the open-source scientific tools are available to everyone, and that researchers can construct and adjust the device according to their needs, as well as, that the total cost of the open-source pH stat device, excluding the existing laboratory equipment (pH meter, computer and glossary) was less than 150 EUR, we believe that, at a small fraction of the cost of available commercial offers, our open-source pH stat can significantly improve experimental work where the use of pH stat is necessary. PMID:29509793

"Do-It-Yourself" reliable pH-stat device by using open-source software, inexpensive hardware and available laboratory equipment.

PubMed

Milanovic, Jovana Z; Milanovic, Predrag; Kragic, Rastislav; Kostic, Mirjana

2018-01-01

In this paper, we present the construction of a reliable and inexpensive pH stat device, by using open-source "OpenPhControl" software, inexpensive hardware (a peristaltic and a syringe pump, Arduino, a step motor…), readily available laboratory devices: a pH meter, a computer, a webcam, and some 3D printed parts. We provide a methodology for the design, development and test results of each part of the device, as well as of the entire system. In addition to dosing reagents by means of a low-cost peristaltic pump, we also present carefully controlled dosing of reagents by an open-source syringe pump. The upgrading of the basic open-source syringe pump is given in terms of pump control and application of a larger syringe. In addition to the basic functions of pH stat, i.e. pH value measurement and maintenance, an improvement allowing the device to be used for potentiometric titration has been made as well. We have demonstrated the device's utility when applied for cellulose fibers oxidation with 2,2,6,6-tetramethylpiperidine-1-oxyl radical, i.e. for TEMPO-mediated oxidation. In support of this, we present the results obtained for the oxidation kinetics, the consumption of added reagent and experimental repeatability. Considering that the open-source scientific tools are available to everyone, and that researchers can construct and adjust the device according to their needs, as well as, that the total cost of the open-source pH stat device, excluding the existing laboratory equipment (pH meter, computer and glossary) was less than 150 EUR, we believe that, at a small fraction of the cost of available commercial offers, our open-source pH stat can significantly improve experimental work where the use of pH stat is necessary.

Silicone adhesive matrix of verapamil hydrochloride to provide pH-independent sustained release.

PubMed

Tolia, Gaurav; Li, S Kevin

2014-02-01

Providing pH-independent oral release of weakly basic drugs with conventional matrix tablets can be challenging because of the pH-dependent solubility characteristics of the drugs and the changing pH environment along the gastrointestinal tract. The aim of the present study was to use a hydrophobic polymer to overcome the issue of pH-dependent release of weakly basic model drug verapamil hydrochloride from matrix tablets without the use of organic buffers in the matrix formulations. Silicone pressure-sensitive adhesive (PSA) polymer was evaluated because of its unique properties of low surface energy, hydrophobicity, low glass transition temperature, high electrical resistance, and barrier to hydrogen ion diffusion. Drug release, hydrogen ion diffusion, tablet contact angle, and internal tablet microenvironment pH with matrix tablets prepared using PSA were compared with those using water-insoluble ethyl cellulose (EC). Silicone PSA films showed higher resistance to hydrogen ion diffusion compared with EC films. Verapamil hydrochloride tablets prepared using silicone PSA showed higher hydrophobicity and lower water uptake than EC tablets. Silicone PSA tablets also showed pH-independent release of verapamil and decreased in dimensions during drug dissolution. By contrast, verapamil hydrochloride tablets prepared using EC did not achieve pH-independent release.

Selectivity differences of water-soluble vitamins separated on hydrophilic interaction stationary phases.

PubMed

Yang, Yuanzhong; Boysen, Reinhard I; Hearn, Milton T W

2013-06-01

In this study, the retention behavior and selectivity differences of water-soluble vitamins were evaluated with three types of polar stationary phases (i.e. an underivatized silica phase, an amide phase, and an amino phase) operated in the hydrophilic interaction chromatographic mode with ESI mass spectrometric detection. The effects of mobile phase composition, including buffer pH and concentration, on the retention and selectivity of the vitamins were investigated. In all stationary phases, the neutral or weakly charged vitamins exhibited very weak retention under each of the pH conditions, while the acidic and more basic vitamins showed diverse retention behaviors. With the underivatized silica phase, increasing the salt concentration of the mobile phase resulted in enhanced retention of the acidic vitamins, but decreased retention of the basic vitamins. These observations thus signify the involvement of secondary mechanisms, such as electrostatic interaction in the retention of these analytes. Under optimized conditions, a baseline separation of all vitamins was achieved with excellent peak efficiency. In addition, the effects of water content in the sample on retention and peak efficiency were examined, with sample stacking effects observed when the injected sample contained a high amount of water. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Release of Hexavalent Chromium by Ash and Soils in Wildfire-Impacted Areas

USGS Publications Warehouse

Wolf, Ruth E.; Morman, Suzette A.; Plumlee, Geoffrey S.; Hageman, Philip L.; Adams, Monique

2008-01-01

The highly oxidizing environment of a wildfire has the potential to convert any chromium present in the soil or in residential or industrial debris to its more toxic form, hexavalent chromium, a known carcinogen. In addition, the highly basic conditions resulting from the combustion of wood and wood products could result in the stabilization of any aqueous hexavalent chromium formed. Samples were collected from the October 2007 wildfires in Southern California and subjected to an array of test procedures to evaluate the potential effects of fire-impacted soils and ashes on human and environmental health. Soil and ash samples were leached using de-ionized water to simulate conditions resulting from rainfall on fire-impacted areas. The resulting leachates were of high pH (10-13) and many, particularly those of ash from burned residential areas, contained elevated total chromium as much as 33 micrograms per liter. Samples were also leached using a near-neutral pH simulated lung fluid to model potential chemical interactions of inhaled particles with fluids lining the respiratory tract. High Performance Liquid Chromatography coupled to Inductively Coupled Plasma Mass Spectrometry was used to separate and detect individual species (for example, Cr+3, Cr+6, As+3, As+5, Se+4, and Se+6). These procedures were used to determine the form of the chromium present in the de-ionized water and simulated lung fluid leachates. The results show that in the de-ionized water leachate, all of the chromium present is in the form of Cr+6, and the resulting high pH tends to stabilize Cr+6 from reduction to Cr+3. Analysis of the simulated lung fluid leachates indicates that the predominant form of chromium present in the near-neutral pH of lung fluid would be Cr+6, which is of concern due to the high possibility of inhalation of the small ash and soil particulates, particularly by fire or restoration crews.

Separation of tricyclic antidepressants by capillary zone electrophoresis with N,N,N',N'-tetramethyl-1,3-butanediamine (TMBD) as an effective electrolyte additive.

PubMed

Dell'Aquila, Caterina

2002-09-05

Five tricyclic antidepressants (TADs), desipramyne, nortriptyline, imipramine, doxepin and amitriptyline, were separated by using the N,N,N',N'-tetramethyl-1,3-butanediamine (TMBD) as additive in the background electrolyte solution. Because the tricyclic antidepressants are similar in structure, mass and pka values, their separation, by capillary zone electrophoresis, requires the careful manipulation of parameters, such as the pH and the composition of the electrolyte solution. As basic drugs, the TADs interact with the silanol groups on the capillary wall giving rise to peak broadening and asymmetry, non reproducible migration times and failing in selectivity. Different concentrations of TMBD (40, 60, 100 and 150 mM) were used at pH 9.5, but only a 100 mM TMBD allowed a good separation and a high efficiency for all the TADs. At this pH the separation was not possible without additive. This result is due to the reduced electroosmotic flow whose mobility is at a value of 10(-9) m(2) V(-1) s(-1).

Halloysite Nanotubes: Controlled Access and Release by Smart Gates.

PubMed

Cavallaro, Giuseppe; Danilushkina, Anna A; Evtugyn, Vladimir G; Lazzara, Giuseppe; Milioto, Stefana; Parisi, Filippo; Rozhina, Elvira V; Fakhrullin, Rawil F

2017-07-28

Hollow halloysite nanotubes have been used as nanocontainers for loading and for the triggered release of calcium hydroxide for paper preservation. A strategy for placing end-stoppers into the tubular nanocontainer is proposed and the sustained release from the cavity is reported. The incorporation of Ca(OH)₂ into the nanotube lumen, as demonstrated using transmission electron microscopy (TEM) imaging and Energy Dispersive X-ray (EDX) mapping, retards the carbonatation, delaying the reaction with CO₂ gas. This effect can be further controlled by placing the end-stoppers. The obtained material is tested for paper deacidification. We prove that adding halloysite filled with Ca(OH)₂ to paper can reduce the impact of acid exposure on both the mechanical performance and pH alteration. The end-stoppers have a double effect: they preserve the calcium hydroxide from carbonation, and they prevent from the formation of highly basic pH and trigger the response to acid exposure minimizing the pH drop-down. These features are promising for a composite nanoadditive in the smart protection of cellulose-based materials.

Synthesis of Mesoporous α-Fe2O3 Nanoparticles by Non-ionic Soft Template and Their Applications to Heavy Oil Upgrading

NASA Astrophysics Data System (ADS)

Park, Chulwoo; Jung, Jinhwan; Lee, Chul Wee; Cho, Joungmo

2016-12-01

This paper reports the synthetic route of 3-D network shape α-Fe2O3 from aqueous solutions of iron precursor using a non-ionic polymeric soft-template, Pluronic P123. During the synthesis of α-Fe2O3, particle sizes, crystal phases and morphologies were significantly influenced by pH, concentrations of precursor and template. The unique shape of worm-like hematite was obtained only when a starting solution was prepared by a weakly basic pH condition and a very specific composition of constituents. The synthesized nanocrystal at this condition had a narrow pore size distribution and high surface area compared to the bulk α-Fe2O3 or the one synthesized from lower pH conditions. The hydrocracking performance was tested over the synthesized iron oxide catalysts with different morphologies. The worm-like shape of iron oxide showed a superior performance, including overall yield of liquid fuel product and coke formation, over the hydrocracking of heavy petroleum oil.

Synthesis of Mesoporous α-Fe2O3 Nanoparticles by Non-ionic Soft Template and Their Applications to Heavy Oil Upgrading

PubMed Central

Park, Chulwoo; Jung, Jinhwan; Lee, Chul Wee; Cho, Joungmo

2016-01-01

This paper reports the synthetic route of 3-D network shape α-Fe2O3 from aqueous solutions of iron precursor using a non-ionic polymeric soft-template, Pluronic P123. During the synthesis of α-Fe2O3, particle sizes, crystal phases and morphologies were significantly influenced by pH, concentrations of precursor and template. The unique shape of worm-like hematite was obtained only when a starting solution was prepared by a weakly basic pH condition and a very specific composition of constituents. The synthesized nanocrystal at this condition had a narrow pore size distribution and high surface area compared to the bulk α-Fe2O3 or the one synthesized from lower pH conditions. The hydrocracking performance was tested over the synthesized iron oxide catalysts with different morphologies. The worm-like shape of iron oxide showed a superior performance, including overall yield of liquid fuel product and coke formation, over the hydrocracking of heavy petroleum oil. PMID:27966663

Synthesis of Mesoporous α-Fe2O3 Nanoparticles by Non-ionic Soft Template and Their Applications to Heavy Oil Upgrading.

PubMed

Park, Chulwoo; Jung, Jinhwan; Lee, Chul Wee; Cho, Joungmo

2016-12-14

This paper reports the synthetic route of 3-D network shape α-Fe 2 O 3 from aqueous solutions of iron precursor using a non-ionic polymeric soft-template, Pluronic P123. During the synthesis of α-Fe 2 O 3 , particle sizes, crystal phases and morphologies were significantly influenced by pH, concentrations of precursor and template. The unique shape of worm-like hematite was obtained only when a starting solution was prepared by a weakly basic pH condition and a very specific composition of constituents. The synthesized nanocrystal at this condition had a narrow pore size distribution and high surface area compared to the bulk α-Fe 2 O 3 or the one synthesized from lower pH conditions. The hydrocracking performance was tested over the synthesized iron oxide catalysts with different morphologies. The worm-like shape of iron oxide showed a superior performance, including overall yield of liquid fuel product and coke formation, over the hydrocracking of heavy petroleum oil.

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

Ertem, Mehmed Zahid; Suna, Yuki; Himeda, Yuichiro

Pentamethylcyclopentadienyl iridium (Cp*Ir) complexes with bidentate ligands consisting of a pyridine ring and an electron-rich diazole ring were prepared. Their catalytic activity towards CO 2 hydrogenation in 2.0 M KHCO 3 aqueous solutions (pH 8.5) at 50 °C, under 1.0 MPa CO 2/H 2 (1:1) have been reported as an alternative to photo- and electrochemical CO 2 reduction. Bidentate ligands incorporating an electron-rich diazole ring improved the catalytic performance of the Ir complexes compared to the bipyridine ligand. Complexes 2, 4 and 6, possessing both a hydroxy group and an uncoordinated NH group, which are proton-responsive and capable of generatingmore » pendent-bases in basic media, recorded high initial TOF values of 1300 h -1, 1550 h -1 and 2000 h -1, respectively. Here, spectroscopic and computational investigations revealed that the reversible deprotonation changes the electronic properties of the complexes and causes interactions between pendent base and substrate and/or solvent water molecules, resulting in the high catalytic performance in basic media.« less

Decolorisation of Basic Textile Dye from Aqueous Solutions using a Biosorbent derived from Thespesia populnea used Biomass

NASA Astrophysics Data System (ADS)

Gunturu, Bhargavi; Rao Palukuri, Nageswara; Sahadevan, Renganathan

2018-03-01

In the present study, the efficiency of a biosorbent derived from seeds of Thespesia populnea was investigated towards the removal of basic textile dye Methylene Blue from an aqueous solution. Adsorption studies were carried out in batch system. Influence of experimental parameters such as adsorbent dosage (0.1g/L-0.3g/L), PH (2-10) and initial dye concentration (50-130mg/L) on adsorption of dye onto biosorbent was investigated. Maximum uptake of dye was observed with 0.1g/L adsorbent dosage at PH 8.0. Equilibrium uptake of methylene blue dye by the adsorbent was analyzed by Langmuir and Freundlich isotherm models. The data fitted best with Freundlich model, suggesting that adsorption of the dye was by multilayer model on the surface of the adsorbent. Experimental results obtained support that the biosorbent used in the present study can be a suitable low cost alternate for the removal of basic textile dyes.

Positional effects of hydroxy groups on catalytic activity of proton-responsive half-sandwich Cp*Iridium(III) complexes

DOE PAGES

Suna, Yuki; Fujita, Etsuko; Ertem, Mehmed Z.; ...

2014-11-12

Proton-responsive half-sandwich Cp*Ir(III) complexes possessing a bipyridine ligand with two hydroxy groups at the 3,3'-, 4,4'-, 5,5'- or 6,6'-positions (3DHBP, 4DHBP, 5DHBP, or 6DHBP) were systematically investigated. UV-vis titration data provided average pK a values of the hydroxy groups on the ligands. Both hydroxy groups were found to deprotonate in the pH 4.6–5.6 range for the 4–6DHBP complexes. One of the hydroxy groups of the 3DHBP complex exhibited the low pK a value of < 0.4 because the deprotonation is facilitated by the strong intramolecular hydrogen bond formed between the generated oxyanion and the remaining hydroxy group, which in turnmore » leads to an elevated pK a value of ~13.6 for the second deprotonation step. The crystal structures of the 4– and 6DHBP complexes obtained from basic aqueous solutions revealed their deprotonated forms. The intramolecular hydrogen bond in the 3DHBP complex was also observed in the crystal structures. The catalytic activities of these complexes in aqueous phase reactions, at appropriate pH, for hydrogenation of carbon dioxide (pH 8.5), dehydrogenation of formic acid (pH 1.8), transfer hydrogenation reactions using formic acid/formate as a hydrogen source (pH 7.2 and 2.6) were investigated to compare the positional effects of the hydroxy groups. The 4– and 6DHBP complexes exhibited remarkably enhanced catalytic activities under basic conditions because of the resonance effect of the strong electrondonating oxyanions, whereas the 5DHBP complex exhibited negligible activity despite the presence of electron-donating groups. The 3DHBP complex exhibited relatively high catalytic activity at low pH owing to the one strong electron-donating oxyanion group stabilized by the intramolecular hydrogen bond. DFT calculations were employed to study the mechanism of CO₂ hydrogenation by the 4DHBP and 6DHBP complexes, and comparison of the activation free energies of the H₂ heterolysis and CO₂ insertion steps indicated that H₂ heterolysis is the rate-determining step for both complexes. The presence of a pendent base in the 6DHBP complex was found to facilitate the rate-determining step, and renders 6DHBP a more effective catalyst for formate production.« less

Characterization of the Adsorption of Nucleic Acid Bases onto Ferrihydrite via Fourier Transform Infrared and Surface-Enhanced Raman Spectroscopy and X-ray Diffractometry.

PubMed

Canhisares-Filho, José E; Carneiro, Cristine E A; de Santana, Henrique; Urbano, Alexandre; da Costa, Antonio C S; Zaia, Cássia T B V; Zaia, Dimas A M

2015-09-01

Minerals could have played an important role in concentration, protection, and polymerization of biomolecules. Although iron is the fourth most abundant element in Earth's crust, there are few works in the literature that describe the use of iron oxide-hydroxide in prebiotic chemistry experiments. In the present work, the interaction of adenine, thymine, and uracil with ferrihydrite was studied under conditions that resemble those of prebiotic Earth. At acidic pH, anions in artificial seawater decreased the pH at the point of zero charge (pHpzc) of ferrihydrite; and at basic pH, cations increased the pHpzc. The adsorption of nucleic acid bases onto ferrihydrite followed the order adenine > uracil > thymine. Adenine adsorption peaked at neutral pH; however, for thymine and uracil, adsorption increased with increasing pH. Electrostatic interactions did not appear to play an important role on the adsorption of nucleic acid bases onto ferrihydrite. Adenine adsorption onto ferrihydrite was higher in distilled water compared to artificial seawater. After ferrihydrite was mixed with artificial seawaters or nucleic acid bases, X-ray diffractograms and Fourier transform infrared spectra did not show any change. Surface-enhanced Raman spectroscopy showed that the interaction of adenine with ferrihydrite was not pH-dependent. In contrast, the interactions of thymine and uracil with ferrihydrite were pH-dependent such that, at basic pH, thymine and uracil lay flat on the surface of ferrihydrite, and at acidic pH, thymine and uracil were perpendicular to the surface. Ferrihydrite adsorbed much more adenine than thymine; thus adenine would have been better protected against degradation by hydrolysis or UV radiation on prebiotic Earth.

Na(+) transport, and the E(1)P-E(2)P conformational transition of the Na(+)/K(+)-ATPase.

PubMed Central

Babes, A; Fendler, K

2000-01-01

We have used admittance analysis together with the black lipid membrane technique to analyze electrogenic reactions within the Na(+) branch of the reaction cycle of the Na(+)/K(+)-ATPase. ATP release by flash photolysis of caged ATP induced changes in the admittance of the compound membrane system that are associated with partial reactions of the Na(+)/K(+)-ATPase. Frequency spectra and the Na(+) dependence of the capacitive signal are consistent with an electrogenic or electroneutral E(1)P <--> E(2)P conformational transition which is rate limiting for a faster electrogenic Na(+) dissociation reaction. We determine the relaxation rate of the rate-limiting reaction and the equilibrium constants for both reactions at pH 6.2-8.5. The relaxation rate has a maximum value at pH 7.4 (approximately 320 s(-1)), which drops to acidic (approximately 190 s(-1)) and basic (approximately 110 s(-1)) pH. The E(1)P <--> E(2)P equilibrium is approximately at a midpoint position at pH 6.2 (equilibrium constant approximately 0.8) but moves more to the E(1)P side at basic pH 8.5 (equilibrium constant approximately 0.4). The Na(+) affinity at the extracellular binding site decreases from approximately 900 mM at pH 6.2 to approximately 200 mM at pH 8.5. The results suggest that during Na(+) transport the free energy supplied by the hydrolysis of ATP is mainly used for the generation of a low-affinity extracellular Na(+) discharge site. Ionic strength and lyotropic anions both decrease the relaxation rate. However, while ionic strength does not change the position of the conformational equilibrium E(1)P <--> E(2)P, lyotropic anions shift it to E(1)P. PMID:11053130

Investigation of pharmaceutical transport in saturated sandy aquifers using column experiments: the effect of pH

NASA Astrophysics Data System (ADS)

Börnick, Hilmar; Boxberger, Norman; Licha, Tobias; Worch, Eckhard

2010-05-01

Due to the development of advanced analytical techniques it is increasingly known that a high number of polar organic trace compounds, particularly residues of pharmaceuticals, occur in the aquatic environment. In contrast to the sources and pathways of such compounds, their impact on ecosystems and their fate in different environmental compartments are comparatively less investigated. Because of the spatial extension and time available, the zone between water and natural solids (e.g. sediments or soil in groundwater zones, bank filtration sites and for soil aquifer treatment) plays an important role in the elimination of anthropogenic trace compounds from water phase. Here, degradation and sorption processes mainly influence the content of trace compounds. Correlations, specific for compound groups, between n-octanol-water distribution coefficients, available from experiment or calculations, and sorption coefficients (e.g. KOC) often allow a suitable prognosis of the transport behavior of organic pollutants in an underground passage. In case of polar, ionizable organic compounds such prediction is problematic and often not possible. Here, besides relatively weak non-polar van der Waals attraction, other interaction mechanisms, such as covalent bonding, complex formation, or ion exchange, can dominate. The latter is closely connected with the type of basic and/or acid groups in a molecule. The degree of protonation could be changed in dependence of type and concentration of other ions and of the acidity constants (pKa) and therefore from pH. Laboratory column studies at different pH value (range from 4 to 8) were carried out using natural sandy sediments from aquifers and model water containing selected pharmaceuticals to investigate the influence of degree of protonation on sorption. Eight different pharmaceuticals were chosen for laboratory column experiments. Their selection was based on the presence of basic/acid functional groups, pKa, high production and consumption rates, and occurrence in environment. The long-term objective of this research is to consider specific interactions such as ion exchange for the improved transport models. Breakthrough experiments show that retardation is significantly influenced by pH for the majority of the selected pharmaceuticals. As a general tendency, it was observed that a decreasing pH caused an enhanced delay. For acidic compounds such as naproxen, this behavior was expected because of the neutral species being the dominating one. The stronger retardation of cationic agents such as atenolol with decreased pH could be explained by additional cation exchange effects. With the exception of atenolol all chosen model compounds show a high stability towards microbial degradation at aerobic conditions. All experiments were repeated at least three times at identical conditions, whereby a good reproducibility was observed. Further experiments are currently performed to characterize pH-depending change of sediment surfaces and to investigate the competitive influence of other presented cations.

Improved dissolution and absorption of ketoconazole in the presence of organic acids as pH-modifiers.

PubMed

Adachi, Masashi; Hinatsu, Yuta; Kusamori, Kosuke; Katsumi, Hidemasa; Sakane, Toshiyasu; Nakatani, Manabu; Wada, Koichi; Yamamoto, Akira

2015-08-30

Formulation development of poorly water-soluble compounds can be challenging because of incomplete dissolution that causes low and variable bioavailability. Enhancing compound solubility is important and many techniques have been investigated to that end, but they require specific materials and machinery. This study investigates the incorporation of a pH-modifier as a method to increase compound solubility and uses ketoconazole (KZ), which is weakly basic (pKa: 6.5), as a model compound. Organic acids are effective pH-modifiers and are generally used in pharmaceutical industries. We successfully obtained granules containing variable organic acids (KZ/acid granule) using a high-shear mixer. Dissolution tests of the KZ/acid granule resulted in highly enhanced solubility under non-sink conditions. Adding water-soluble acids, such as citric acid (CA) and tartaric acid, resulted in more than 8-fold higher dissolution at pH 6.0 compared to that of KZ only. The granules containing citric acid (KZ/CA granule) improved the dissolution of KZ after oral administration to rats under low gastric acid conditions, where the bioavailability of the KZ/CA granules at elevated gastric pH was comparable with that of KZ only at gastric acidic pH. The incorporation of organic acids would result in effective therapeutic outcomes independent of gastric pH in patients. In addition, higher bioavailability of KZ was observed after oral administration of KZ/CA granules under gastric acidic pH conditions than that of KZ alone. Thus, CA improved the dissolution and absorption rate of KZ after oral administration. Copyright © 2015 Elsevier B.V. All rights reserved.

Improvement of the optimum pH of Aspergillus niger xylanase towards an alkaline pH by site-directed mutagenesis.

PubMed

Li, Fei; Xie, Jingcong; Zhang, Xuesong; Zhao, Linguo

2015-01-01

In an attempt to shift the optimal pH of the xylanase B (XynB) from Aspergillus niger towards alkalinity, target mutation sites were selected by alignment between Aspergillus niger xylanase B and other xylanases that have alkalophilic pH optima that highlight charged residues in the eight-residues-longer loop in the alkalophilic xylanase. Multiple engineered XynB mutants were created by site-directed mutagenesis with substitutions Q164K and Q164K+D117N. The variant XynB-117 had the highest optimum pH (at 5.5), which corresponded to a basic 0.5 pH unit shift when compared with the wild-type enzyme. However, the optimal pH of the XynB- 164 mutation was not changed, similar to the wild type. These results suggest that the residues at positions 164 and 117 in the eight-residues-longer loop and the cleft's edge are important in determining the pH optima of XynB from Aspergillus niger.

Hydrogen storage and evolution catalysed by metal hydride complexes.

PubMed

Fukuzumi, Shunichi; Suenobu, Tomoyoshi

2013-01-07

The storage and evolution of hydrogen are catalysed by appropriate metal hydride complexes. Hydrogenation of carbon dioxide by hydrogen is catalysed by a [C,N] cyclometalated organoiridium complex, [Ir(III)(Cp*)(4-(1H-pyrazol-1-yl-κN(2))benzoic acid-κC(3))(OH(2))](2)SO(4) [Ir-OH(2)](2)SO(4), under atmospheric pressure of H(2) and CO(2) in weakly basic water (pH 7.5) at room temperature. The reverse reaction, i.e., hydrogen evolution from formate, is also catalysed by [Ir-OH(2)](+) in acidic water (pH 2.8) at room temperature. Thus, interconversion between hydrogen and formic acid in water at ambient temperature and pressure has been achieved by using [Ir-OH(2)](+) as an efficient catalyst in both directions depending on pH. The Ir complex [Ir-OH(2)](+) also catalyses regioselective hydrogenation of the oxidised form of β-nicotinamide adenine dinucleotide (NAD(+)) to produce the 1,4-reduced form (NADH) under atmospheric pressure of H(2) at room temperature in weakly basic water. In weakly acidic water, the complex [Ir-OH(2)](+) also catalyses the reverse reaction, i.e., hydrogen evolution from NADH to produce NAD(+) at room temperature. Thus, interconversion between NADH (and H(+)) and NAD(+) (and H(2)) has also been achieved by using [Ir-OH(2)](+) as an efficient catalyst and by changing pH. The iridium hydride complex formed by the reduction of [Ir-OH(2)](+) by H(2) and NADH is responsible for the hydrogen evolution. Photoirradiation (λ > 330 nm) of an aqueous solution of the Ir-hydride complex produced by the reduction of [Ir-OH(2)](+) with alcohols resulted in the quantitative conversion to a unique [C,C] cyclometalated Ir-hydride complex, which can catalyse hydrogen evolution from alcohols in a basic aqueous solution (pH 11.9). The catalytic mechanisms of the hydrogen storage and evolution are discussed by focusing on the reactivity of Ir-hydride complexes.

Protein recovery from rainbow trout (Oncorhynchus mykiss) processing byproducts via isoelectric solubilization/precipitation and its gelation properties as affected by functional additives.

PubMed

Chen, Yi-Chen; Jaczynski, Jacek

2007-10-31

Solubility of rainbow trout proteins was determined between pH 1.5 and 13.0 and various ionic strengths (IS). Minimum solubility occurred at pH 5.5; however, when IS = 0.2, the minimum solubility shifted toward more acidic pH. Isoelectric solubilization/precipitation was applied to trout processing byproducts (fish meat left over on bones, head, skin, etc.), resulting in protein recovery yields (Kjeldahl, dry basis) between 77.7% and 89.0%, depending of the pH used for solubilization and precipitation. The recovered protein contained 1.4-2.1% ash (dry basis), while the trout processing byproducts (i.e., starting material) 13.9%. Typical boneless and skinless trout fillets contain 5.5% ash, and therefore, the isoelectric solubilization/precipitation effectively removed impurities such as bones, scales, skin, etc., from the trout processing byproducts. The recovered proteins retained gel-forming ability as assessed with dynamic rheology, torsion test, and texture profile analysis (TPA). However, the recovered proteins failed to gel unless beef plasma protein (BPP) was added. Even with BPP, the recovered protein showed some proteolysis between 40 and 55 degrees C. Addition of potato starch, transglutaminase, and phosphate to the recovered proteins resulted in good texture of trout gels as confirmed by torsion test and TPA. Higher ( P < 0.05) shear stress and strain were measured for gels developed from basic pH treatments than the acidic counterparts. However, proteins recovered from acidic treatments had higher ( P < 0.05) lipid content than the basic treatments. This is probably why the gels from acidic treatments were whiter ( L* - 3 b*) ( P < 0.05) than those from the basic ones. Our study demonstrates that functional proteins can be efficiently recovered from low-value fish processing byproducts using isoelectric solubilization/precipitation and subsequently be used in value-added human foods.

Decreased extracellular pH inhibits osteogenesis through proton-sensing GPR4-mediated suppression of yes-associated protein.

PubMed

Tao, Shi-Cong; Gao, You-Shui; Zhu, Hong-Yi; Yin, Jun-Hui; Chen, Yi-Xuan; Zhang, Yue-Lei; Guo, Shang-Chun; Zhang, Chang-Qing

2016-06-03

The pH of extracellular fluids is a basic property of the tissue microenvironment and is normally maintained at 7.40 ± 0.05 in humans. Many pathological circumstances, such as ischemia, inflammation, and tumorigenesis, result in the reduction of extracellular pH in the affected tissues. In this study, we reported that the osteogenic differentiation of BMSCs was significantly inhibited by decreases in the extracellular pH. Moreover, we demonstrated that proton-sensing GPR4 signaling mediated the proton-induced inhibitory effects on the osteogenesis of BMSCs. Additionally, we found that YAP was the downstream effector of GPR4 signaling. Our findings revealed that the extracellular pH modulates the osteogenic responses of BMSCs by regulating the proton-sensing GPR4-YAP pathway.

Theory and practice in the electrometric determination of pH in precipitation

NASA Astrophysics Data System (ADS)

Brennan, Carla Jo; Peden, Mark E.

Basic theory and laboratory investigations have been applied to the electrometric determination of pH in precipitation samples in an effort to improve the reliability of the results obtained from these low ionic strength samples. The theoretical problems inherent in the measurement of pH in rain have been examined using natural precipitation samples with varying ionic strengths and pH values. The importance of electrode design and construction has been stressed. The proper choice of electrode can minimize or eliminate problems arising from residual liquid junction potentials, streaming potentials and temperature differences. Reliable pH measurements can be made in precipitation samples using commercially available calibration buffers providing low ionic strength quality control solutions are routinely used to verify electrode and meter performance.

pH-modulated self-assembly of colloidal nanoparticles in a dual-droplet inkjet printing process.

PubMed

Al-Milaji, Karam Nashwan; Radhakrishnan, Vinod; Kamerkar, Prajakta; Zhao, Hong

2018-06-05

Interfacial self-assembly has been demonstrated as a powerful driving mechanism for creating various nanostructured assemblies. In this work, we employed a dual-droplet printing process and interfacial self-assembly mechanism to produce deposits with controlled assembly structures of colloidal nanoparticles. We hypothesize that pH modulation of the droplet will influence the interfacial self-assembly through the multibody interactions, e.g. particle-particle, particle-interface, and particle-substrate interactions, correspondingly affecting the deposition morphology of the colloidal nanoparticles. During the dual-droplet printing, a wetting droplet, containing colloidal nanoparticles, was jetted over a supporting droplet that contains water only. pH modulation was carried out to the supporting droplet. The self-assembly of two kinds of functionalized polystyrene (PS) nanoparticles (carboxyl-PS and sulfate-PS) was systematically investigated under various pH conditions. Depending on the pH level of the supporting droplet, deposits of carboxyl-PS particles ranging from clear ring-like patterns to nearly uniform monolayer depositions have been obtained. On the other hand, the sulfate-PS particles, even at extreme basic and acidic environments, successfully assemble into nearly monolayer depositions. The multibody interactions are discussed. Such findings can be harnessed in manufacturing high-performance optical and electronic devices. Copyright © 2018 Elsevier Inc. All rights reserved.

Evaluation of the relation between lipid coat, transepidermal water loss, and skin pH.

PubMed

Algiert-Zielińska, Barbara; Batory, Mirella; Skubalski, Janusz; Rotsztejn, Helena

2017-11-01

The epidermis is an epidermal barrier which accumulates lipid substances and participates in skin moisturizing. An evaluation of the epidermal barrier efficiency can be made, among others, by the measurement of the following values: the lipid coat, the transepidermal water loss (TEWL) index, and pH. The study involved 50 Caucasian, healthy women aged 19-35 years (mean 20.56). Measurements were made using Courage & Khazaka Multi Probe Adapter MPA 580: Tewameter TM 300, pH-Meter PH 905, Sebumeter SM 815. The areas of measurements included forehead, nose, left cheek, right cheek, chin, and thigh. In the T-zone, the lipid coat was in the range between 0 and 270 μg/cm 2 (mean 128 μg/cm 2 ), TEWL between 1 and 55 g/m 2 /h (mean 11.1 g/m 2 /h), and pH 4.0-5.6 (mean 5.39). Lower values of the lipid coat up to 100 μg/cm 2 were accompanied by TEWL greater than 30 g/m 2 /h and less acidic pH of 5.6-9.0. In the U-zone the range of lipid coat was up to 200 μg/cm 2 (mean 65.2 μg/cm 2 ), the skin pH remained 4.0-5.6 (mean 5.47), and TEWL was in the range between 1 and 20 g/m 2 /h (mean 8.7 g/m 2 /h). Lower values of the lipid coat up to 100 μg/cm 2 were accompanied by TEWL between 1 and 20 g/m 2 /h and less acidic pH of 5.6-9.0. High values of the lipid coat between 180 and 200 μg/cm 2 were connected with TEWL of 1-15 g/m 2 /h. On the skin of the thigh, we observed a very thin lipid coat - 35 μg/cm 2 (mean 5.6 μg/cm 2 ), pH (mean 5.37), and TEWL (mean 8.5 g/m 2 /h) were considered by us to be within regular limits. In the T-zone, a thinner lipid coat resulted in relatively high TEWL and pH levels changing toward alkaline. In the U-zone, thinner lipid coat was accompanied by lower TEWL and pH changing toward alkaline. We also observed that lower values of lipid coat up to 100 μg/cm 2 were associated with higher pH values ranging toward the basic character pH 5.6-9.0). © 2017 The International Society of Dermatology.

Two basic bismuth nitrates: [Bi6O6(OH)2](NO3)4 · 2H2O with superior photodegradation activity for rhodamine B and [Bi6O5(OH)3](NO3)5 · 3H2O with ultrahigh adsorption capacity for methyl orange

NASA Astrophysics Data System (ADS)

Pang, Jiawei; Han, Qiaofeng; Liu, Weiqi; Shen, Zichen; Wang, Xin; Zhu, Junwu

2017-11-01

A novel basic bismuth nitrate, [Bi6O6(OH)2](NO3)4·2H2O (denoted as BiON-4N), was easily obtained at room temperature in the existence of 2-methoxyethanol (CH3OCH2CH2OH; 2ME) with a pH value ranging from 4.5 to 7.0. The morphology of BiON-4N could be easily tailored by changing the variety and amount of bases like urea, hexamethylenetetramine (HMTA), NaOH and NH3·H2O. When the solution pH was decreased lower than 4.5, another basic bismuth nitrate, [Bi6O5(OH)3](NO3)5·3H2O (denoted as BiON-5N), could be synthesized. Among those, BiON-4N nanoparticles obtained with 40 mmol of HMTA exhibited superior photocatalytic activity for rhodamine B (RhB) degradation with an efficiency of 100% within 4 min of UV light irradiation, which was much higher than that of commercial TiO2 (P25). The excellent photocatalytic performance of BiON-4N was mainly attributed to higher surface area (13.1 m2 g-1) in comparison with other basic bismuth nitrates. Furthermore, the as-prepared BiON-5N revealed excellent adsorption performance for the anions like methyl orange (MO) and K2Cr2O7, and especially for MO, the maximum adsorption capacity arrived up to 730 mg g-1, which should be relevant to highly positively charged surface. This work provides a new strategy for developing bismuth-based nanomaterials in the big bismuth family as potential photocatalyst and adsorbent for the removal of dyes and contaminants.

The effect of excipients on the stability of levothyroxine sodium pentahydrate tablets.

PubMed

Patel, Himanshu; Stalcup, Apryll; Dansereau, Richard; Sakr, Adel

2003-10-02

Levothyroxine tablets, 50 microg, have been marketed for many decades but have had numerous recalls due to degradation and failure to meet potency. These experiments were devised to study the effects of various excipients on the stability of levothyroxine sodium pentahydrate in aqueous slurries and in formulated tablets. The active alone was found to be stable in the solid state for 6 months at 40 degrees C/75% RH whether stored in open or closed containers, and was found to be non-hygroscopic under normal processing conditions (>30% RH). In aqueous slurries with an excipient, the stability of the active improved as the pH of the slurry was increased from pH 3 to 11. Tablets manufactured with lactose anhydrous, starch, or microcrystalline cellulose failed to meet USP assay requirements at 3 months at 40 degrees C/75% RH. Tablets manufactured with dibasic calcium phosphate or mannitol met USP assay requirements at 3, but not 6 months when stored at 40 degrees C/75% RH. Tablets manufactured with dibasic calcium phosphate and a basic pH modifier, such as sodium carbonate, sodium bicarbonate, or magnesium oxide, met the USP assay requirements at both 3 and 6 months. Thus, the use of basic pH modifiers is a potential technique for improving the stability of levothyroxine sodium pentahydrate tablets.

Capillary gas chromatographic separation of organic bases using a pH-adjusted basic water stationary phase.

PubMed

Darko, Ernest; Thurbide, Kevin B

2016-09-23

The use of a pH-adjusted water stationary phase for analyzing organic bases in capillary gas chromatography (GC) is demonstrated. Through modifying the phase to typical values near pH 11.5, it is found that various organic bases are readily eluted and separated. Conversely, at the normal pH 7 operating level, they are not. Sodium hydroxide is found to be a much more stable base than ammonium hydroxide for altering the pH due to the higher volatility and evaporation of the latter. In the basic condition, such analytes are not ionized and are observed to produce good peak shapes even for injected masses down to about 20ng. By comparison, analyses on a conventional non-polar capillary GC column yield more peak tailing and only analyte masses of 1μg or higher are normally observed. Through carefully altering the pH, it is also found that the selectivity between analytes can be potentially further enhanced if their respective pKa values differ sufficiently. The analysis of different pharmaceutical and petroleum samples containing organic bases is demonstrated. Results indicate that this approach can potentially offer unique and beneficial selectivity in such analyses. Copyright © 2016 Elsevier B.V. All rights reserved.

Optimization of the first dimension for separation by two-dimensional gel electrophoresis of basic proteins from human brain tissue.

PubMed

Pennington, Kyla; McGregor, Emma; Beasley, Clare L; Everall, Ian; Cotter, David; Dunn, Michael J

2004-01-01

A major cause of poor resolution in the alkaline pH range of two-dimensional electrophoresis (2-DE) gels is unsatisfactory separation of basic proteins in the first dimension. We have compared methods for the separation of basic proteins in the isoelectric focusing dimension of human brain proteins. The combined use of anodic cup-loading and the hydroxyethyldisulphide containing solution (DeStreak) produced better resolution in both analytical and micropreparative protein loaded 2-DE gels than the other methods investigated.

Conceptual design project: Accelerator complex for nuclear physics studies and boron neutron capture therapy application at the Yerevan Physics Institute (YerPhI) Yerevan, Armenia

NASA Astrophysics Data System (ADS)

Avagyan, R. H.; Kerobyan, I. A.

2015-07-01

The final goal of the proposed project is the creation of a Complex of Accelerator Facilities at the Yerevan Physics Institute (CAF YerPhI) for nuclear physics basic researches, as well as for applied programs including boron neutron capture therapy (BNCT). The CAF will include the following facilities: Cyclotron C70, heavy material (uranium) target/ion source, mass-separator, LINAC1 (0.15-1.5 MeV/u) and LINAC2 (1.5-10 MeV/u). The delivered by C70 proton beams with energy 70 MeV will be used for investigations in the field of basic nuclear physics and with energy 30 MeV for use in applications.

On-site detection of packaged squid freshness

NASA Astrophysics Data System (ADS)

Ahmad, Noor Azizah; Heng, Lee Yook; Salam, Faridah; Hanifah, Sharina Abu

2018-04-01

The development of indicator label for detection of total volatile basic nitrogen (TVB-N) is described. Dye extract from edible plants containing anthocyanins was immobilized onto iota-carrageenan as polymer matrix. TVB-N detection worked based on pH increase as the basic deterioration volatile amines generated in the package headspace. Results showed that the indicator label has changed color from blue to green after 12 hours of storage at ambient conditions. The TVB-N value was 38.9648 mg /100 g which is exceeded of acceptability level for seafood products. The pH value of squid flesh has also increased during storage. The colour values of L * and a * negative increases while b* negative decrease with increasing storage time. The indicator label is potentially used as freshness indicator for squid at ambient conditions.

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.

Experimental Studies on role of pH, potential and concentration of buffer solution for chemical bath deposition technique

NASA Astrophysics Data System (ADS)

Suresha, B. L.; Sumantha, H. S.; Salman, K. Mohammed; Pramod, N. G.; Abhiram, J.

2018-04-01

The ionization potential is usually found to be less in acid and more in base. The experiment proves that the ionization potential increases on dilution of acid to base and reduces from base to acid. The potential can be tailored according to the desired properties based on our choice of acid or base. The experimental study establishes a direct relationship between pH and electric potential. This work provides theoretical insights on the need for a basic media of pH 10 in chemical thin film growth techniques called Chemical Bath Deposition Techniques.

Using polarizable POSSIM force field and fuzzy-border continuum solvent model to calculate pK(a) shifts of protein residues.

PubMed

Sharma, Ity; Kaminski, George A

2017-01-15

Our Fuzzy-Border (FB) continuum solvent model has been extended and modified to produce hydration parameters for small molecules using POlarizable Simulations Second-order Interaction Model (POSSIM) framework with an average error of 0.136 kcal/mol. It was then used to compute pK a shifts for carboxylic and basic residues of the turkey ovomucoid third domain (OMTKY3) protein. The average unsigned errors in the acid and base pK a values were 0.37 and 0.4 pH units, respectively, versus 0.58 and 0.7 pH units as calculated with a previous version of polarizable protein force field and Poisson Boltzmann continuum solvent. This POSSIM/FB result is produced with explicit refitting of the hydration parameters to the pK a values of the carboxylic and basic residues of the OMTKY3 protein; thus, the values of the acidity constants can be viewed as additional fitting target data. In addition to calculating pK a shifts for the OMTKY3 residues, we have studied aspartic acid residues of Rnase Sa. This was done without any further refitting of the parameters and agreement with the experimental pK a values is within an average unsigned error of 0.65 pH units. This result included the Asp79 residue that is buried and thus has a high experimental pK a value of 7.37 units. Thus, the presented model is capable or reproducing pK a results for residues in an environment that is significantly different from the solvated protein surface used in the fitting. Therefore, the POSSIM force field and the FB continuum solvent parameters have been demonstrated to be sufficiently robust and transferable. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Smart Drug Delivery System-Inspired Enzyme-Linked Immunosorbent Assay Based on Fluorescence Resonance Energy Transfer and Allochroic Effect Induced Dual-Modal Colorimetric and Fluorescent Detection.

PubMed

Miao, Luyang; Zhu, Chengzhou; Jiao, Lei; Li, He; Du, Dan; Lin, Yuehe; Wei, Qin

2018-02-06

Numerous analytical techniques have been undertaken for the detection of protein biomarkers because of their extensive and significant applications in clinical diagnosis, whereas there are few strategies to develop dual-readout immunosensors to achieve more accurate results. To the best of our knowledge, inspired by smart drug delivery system (DDS), a novel pH-responsive modified enzyme-linked immunosorbent assay (ELISA) was innovatively developed for the first time, realizing dual-modal colorimetric and fluorescent detection of cardiac troponin I (cTnI). Curcumin (CUR) was elaborately selected as a reporter molecule, which played the same role of drugs in DDS based on the following considerations: (1) CUR can be used as a kind of pH indicator by the inherited allochroic effect induced by basic pH value; (2) the fluorescence of CUR can be quenched by certain nanocarriers as the acceptor because of the occurrence of fluorescence resonance energy transfer (FRET), while recovered by the stimuli of basic pH value, which can produce "signal-on" fluorescence detection. Three-dimensional MoS 2 nanoflowers (3D-MoS 2 NFs) were employed in immobilizing CUR to constitute a nanoprobe for the determination of cTnI by virtue of good biocompatibility, high absorption capacity, and fluorescence quench efficiency toward CUR. The proposed DDS-inspired ELISA offered dual-modal colorimetric and fluorescent detection of cTnI, thereby meeting the reliable and precise analysis requirements. We believe that the developed dual-readout ELISA will create a new avenue and bring innovative inspirations for biological detections.

Decoupling of the minority PhD talent pool and assistant professor hiring in medical school basic science departments in the US.

PubMed

Gibbs, Kenneth D; Basson, Jacob; Xierali, Imam M; Broniatowski, David A

2016-11-17

Faculty diversity is a longstanding challenge in the US. However, we lack a quantitative and systemic understanding of how the career transitions into assistant professor positions of PhD scientists from underrepresented minority (URM) and well-represented (WR) racial/ethnic backgrounds compare. Between 1980 and 2013, the number of PhD graduates from URM backgrounds increased by a factor of 9.3, compared with a 2.6-fold increase in the number of PhD graduates from WR groups. However, the number of scientists from URM backgrounds hired as assistant professors in medical school basic science departments was not related to the number of potential candidates (R 2 =0.12, p>0.07), whereas there was a strong correlation between these two numbers for scientists from WR backgrounds (R 2 =0.48, p<0.0001). We built and validated a conceptual system dynamics model based on these data that explained 79% of the variance in the hiring of assistant professors and posited no hiring discrimination. Simulations show that, given current transition rates of scientists from URM backgrounds to faculty positions, faculty diversity would not increase significantly through the year 2080 even in the context of an exponential growth in the population of PhD graduates from URM backgrounds, or significant increases in the number of faculty positions. Instead, the simulations showed that diversity increased as more postdoctoral candidates from URM backgrounds transitioned onto the market and were hired.

The effect of pH and concentration upon aggregation transitions in aqueous solutions of poloxamine T701.

PubMed

Armstrong, J K; Chowdhry, B Z; Snowden, M J; Dong, J; Leharne, S A

2001-10-23

Thermally induced aggregation transitions have been investigated for aqueous solutions of the poloxamine block copolymer T701-(OE(4)OP(13))(2)NCH(2)CH(2)N(OP(13)OE(4))(2)-using differential scanning calorimetry. The calorimetric signals obtained were fitted to a mass action model description of aggregation using a previously reported analytical procedure (Patterson et al., Langmuir 13 (1997) 2219). The presence of a central ethylene diamine moiety in the molecular structure renders the T701 molecule basic; this was confirmed and measured by acid/base titration. Basicity is shown to have an important impact upon aggregation. At low pH (2.5), the poloxamine exists in its protonated form and the bulk solution proton concentration is sufficient to suppress de-protonation, aggregation-as a consequence-is shifted to a higher temperature range. Any increase in pH reduces the temperature range over which aggregation occurs. The derived experimental calorimetric parameters, obtained from model fitting procedures, can be used to compute the fraction of poloxamine existing in an aggregated form, at any particular temperature. The data sets obtained were interpolated to show that at human body temperature (310.6 K) the fraction of poloxamine found in its aggregated form is zero at a pH of 2.5. However at a pH of 6.8, the percentage aggregation increases to about 85%. These aggregation characteristics of T701 have important implications for the design of drug delivery systems, which incorporate poloxamines.

Monitoring the Long-Term Degradation Behavior of Biomimetic Bioadhesive using Wireless Magnetoelastic Sensor

PubMed Central

Lin, Meng-Hsien; Anderson, Jonathan; Pinnaratip, Rattapol; Meng, Hao; Konst, Shari; DeRouin, Andrew J.; Rajachar, Rupak

2015-01-01

The degradation behavior of a tissue adhesive is critical to its ability to repair a wound while minimizing prolonged inflammatory response. Traditional degradation tests can be expensive to perform, as they require large numbers of samples. The potential for using magnetoelastic resonant sensors to track bioadhesive degradation behavior was investigated. Specifically, biomimetic poly(ethylene glycol)- (PEG-) based adhesive was coated onto magnetoelastic (ME) sensor strips. Adhesive-coated samples were submerged in solutions buffered at multiple pH levels (5.7, 7.4 and 10.0) at body temperature (37°C) and the degradation behavior of the adhesive was tracked wirelessly by monitoring the changes in the resonant amplitude of the sensors for over 80 days. Adhesive incubated at pH 7.4 degraded over 75 days, which matched previously published data for bulk degradation behavior of the adhesive while utilizing significantly less material (~103 times lower). Adhesive incubated at pH 10.0 degraded within 25 days while samples incubated at pH 5.7 did not completely degrade even after 80 days of incubation. As expected, the rate of degradation increased with increasing pH as the rate of ester bond hydrolysis is higher under basic conditions. As a result of requiring a significantly lower amount of samples compared to traditional methods, the ME sensing technology is highly attractive for fully characterizing the degradation behavior of tissue adhesives in a wide range of physiological conditions. PMID:26087077

Spectral-fluorescent study of the interaction of the polymethine dye probe Cyan 2 with chondroitin-4-sulfate

NASA Astrophysics Data System (ADS)

Tatikolov, Alexander S.; Akimkin, Timofey M.; Panova, Ina G.; Yarmoluk, Sergiy M.

2017-04-01

The noncovalent interaction of the polymethine dye probe 3,3‧,9-trimethylthiacarbocyanine iodide (Cyan 2) with chondroitin-4-sulfate (C4S) in buffer solutions with different pH and in water in the absence of buffers has been studied by spectral-fluorescent methods. It has been shown that in all media studied, at relatively high concentrations, the dye is bound to C4S mainly as a monomer, which is accompanied by a steep rise of fluorescence (the intermediate formation of dye aggregates on the biopolymer is also observed). From the dependence of the fluorescence quantum yield on the concentration of C4S, the parameters of binding of the dye monomer to C4S were obtained: the effective binding constant K, the number of the monomeric C4S units n per one dye monomer bound to C4S, and the fluorescence quantum yield of the bound dye monomer Φfb. The dependence of Φfb (and K) on pH of the medium is not monotonic: it has a minimum in the region of neutral pH and a growth in the regions of acid and basic pH. This can be explained by changing the charge of a C4S macromolecule as a function of pH and related conformational alterations in the biopolymer, which can affect the rigidity of a dye molecule and the energy of its interaction with the biopolymer.

Cycloalkyl-AminoMethylRhodamines: pH Dependent Photophysical Properties Tuned by Cycloalkane Ring Size

PubMed Central

Liu, Chuangjun; Best, Quinn A.; Suarez, Brian; Pertile, Jack; McCarroll, Matthew E.; Scott, Colleen N.

2015-01-01

A series of fluorescent pH probes based on the spiro-cyclic rhodamine core, aminomethylrhodamines (AMR), was synthesized and the effect of cycloalkane ring size on the acid/base properties of the AMR system was explored. The study involved a series of rhodamine 6G (cAMR6G) and rhodamine B (cAMR) pH probes with cycloalkane ring sizes from C-3 to C-6 on the spiro-cyclic amino group. It is known that the pKa value of cycloalkylamines can be tuned by the different ring sizes in accordance with the Baeyer ring strain theory. Smaller ring amines have lower pKa value, i.e. they're less basic, such that the relative order in cycloalkylamine basicity is: cyclohexyl>cyclopentyl>cyclobutyl>cyclopropyl. Herein, it was found that the pKa values of the cAMR and cAMR6G systems can also be predicted by Baeyer ring strain theory. The pKa values for the cAMR6G series were shown to be higher than the cAMR series by a value of approximately 1. PMID:25686771

Removal Enhancement of Basic Blue 41 BY RGO-TiO2 Nanocomposite Synthesized Using Pulsed Laser

NASA Astrophysics Data System (ADS)

Ghasemi, Fatemeh; Kimiagar, Salimeh; Shahbazi, Mozhgan; Vojoudi, Hossein

Graphene oxide (GO) and GO-TiO2 nanocomposite was produced then reduced under pulse laser irradiation (RGO-TiO2). Basic blue 41 (bb41) dye was removed from aqueous solutions by using RGO-TiO2 nanocomposites. The UV-Vis absorption and FTIR analysis were utilized to confirm the reduction of GO-TiO2 to RGO-TiO2. The results showed complete reduction of GO. X-ray diffraction (XRD), Raman spectra and scanning electron microscopy (SEM) analysis were applied to approve the RGO-TiO2 nanocomposite structure. The effect of pH on the bb41 removal by RGO-TiO2 was studied varying the pH from 1 to 11. The optimum pH and adsorbent dosage were found to be 9 and 0.2g/L with 98% efficiency, respectively. The calculated coefficients demonstrated that the Langmuir model was fixed to the experimental data. The results indicated that RGO-TiO2 could be engaged as an exceptional sorbent to remove bb41 dye which is in aqueous solution.

Aging properties of films of plasticized vital wheat gluten cast from acidic and basic solutions.

PubMed

Olabarrieta, Idoia; Cho, Sung-Woo; Gällstedt, Mikael; Sarasua, Jose-Ramon; Johansson, Eva; Hedenqvist, Mikael S

2006-05-01

In order to understand the mechanisms behind the undesired aging of films based on vital wheat gluten plasticized with glycerol, films cast from water/ethanol solutions were investigated. The effect of pH was studied by casting from solutions at pH 4 and pH 11. The films were aged for 120 days at 50% relative humidity and 23 degrees C, and the tensile properties and oxygen and water vapor permeabilities were measured as a function of aging time. The changes in the protein structure were determined by infrared spectroscopy and size-exclusion and reverse-phase high-performance liquid chromatography, and the film structure was revealed by optical and scanning electron microscopy. The pH 11 film was mechanically more stable with time than the pH 4 film, the latter being initially very ductile but turning brittle toward the end of the aging period. The protein solubility and infrared spectroscopy measurements indicated that the protein structure of the pH 4 film was initially significantly less polymerized/aggregated than that of the pH 11 film. The polymerization of the pH 4 film increased during storage but it did not reach the degree of aggregation of the pH 11 film. Reverse-phase chromatography indicated that the pH 11 films were to some extent deamidated and that this increased with aging. At the same time a large fraction of the aged pH 11 film was unaffected by reducing agents, suggesting that a time-induced isopeptide cross-linking had occurred. This isopeptide formation did not, however, change the overall degree of aggregation and consequently the mechanical properties of the film. During aging, the pH 4 films lost more mass than the pH 11 films mainly due to migration of glycerol but also due to some loss of volatile mass. Scanning electron and optical microscopy showed that the pH 11 film was more uniform in thickness and that the film structure was more homogeneous than that of the pH 4 film. The oxygen permeability was also lower for the pH 11 film. The fact that the pH 4 film experienced a larger and more rapid change in its mechanical properties with time than the pH 11 film, as a consequence of a greater loss of plasticizer, was presumably due to its initial lower degree of protein aggregation/polymerization. Consequently, the cross-link density achieved at pH 4 was too low to effectively retain volatiles and glycerol within the matrix.

Decolorization of acid and basic dyes: understanding the metabolic degradation and cell-induced adsorption/precipitation by Escherichia coli.

PubMed

Cerboneschi, Matteo; Corsi, Massimo; Bianchini, Roberto; Bonanni, Marco; Tegli, Stefania

2015-10-01

Escherichia coli strain DH5α was successfully employed in the decolorization of commercial anthraquinone and azo dyes, belonging to the general classes of acid or basic dyes. The bacteria showed an aptitude to survive at different pH values on any dye solution tested, and a rapid decolorization was obtained under aerobic conditions for the whole collection of dyes. A deep investigation about the mode of action of E. coli was carried out to demonstrate that dye decolorization mainly occurred via three different pathways, specifically bacterial induced precipitation, cell wall adsorption, and metabolism, whose weight was correlated with the chemical nature of the dye. In the case of basic azo dyes, an unexpected fast decolorization was observed after just 2-h postinoculation under aerobic conditions, suggesting that metabolism was the main mechanism involved in basic azo dye degradation, as unequivocally demonstrated by mass spectrometric analysis. The reductive cleavage of the azo group by E. coli on basic azo dyes was also further demonstrated by the inhibition of decolorization occurring when glucose was added to the dye solution. Moreover, no residual toxicity was found in the E. coli-treated basic azo dye solutions by performing Daphnia magna acute toxicity assays. The results of the present study demonstrated that E. coli can be simply exploited for its natural metabolic pathways, without applying any recombinant technology. The high versatility and adaptability of this bacterium could encourage its involvement in industrial bioremediation of textile and leather dyeing wastewaters.

Optimised purification and characterisation of lipid transfer protein 1 (LTP1) and its lipid-bound isoform LTP1b from barley malt.

PubMed

Nieuwoudt, Melanie; Lombard, Nicolaas; Rautenbach, Marina

2014-08-15

In beer brewing, brewers worldwide strive to obtain product consistency in terms of flavour, colour and foam. Important proteins contributing to beer foam are lipid transfer proteins (LTPs), in particular LTP1 and its lipid-bound isoform LTP1b, which are known to transport lipids in vivo and prevent lipids from destabilising the beer foam. LTP1 and LTP1b were successfully purified using only five purification steps with a high purified protein yield (160 mg LTP1 and LTP1b from 200 g barley). Circular dichroism of LTP1 and LTP1b confirmed that both proteins are highly tolerant to high temperatures (>90 °C) and are pH stable, particularly at a neutral to a more basic pH. Only LTP1 exhibited antiyeast and thermo-stable lytic activity, while LTP1b was inactive, indicating that the fatty acid moiety compromised the antimicrobial activity of LTP1. This lack in antiyeast activity and the positive foam properties of LTP1b would benefit beer fermentation and quality. Copyright © 2014 Elsevier Ltd. All rights reserved.

Decolorization of basic dye solutions by electrocoagulation: an investigation of the effect of operational parameters.

PubMed

Daneshvar, N; Oladegaragoze, A; Djafarzadeh, N

2006-02-28

Electrocoagulation (EC) is one of the most effective techniques to remove color and organic pollutants from wastewater, which reduces the sludge generation. In this paper, electrocoagulation has been used for the removal of color from solutions containing C. I. Basic Red 46 (BR46) and C. I. Basic Blue 3 (BB3). These dyes are used in the wool and blanket factories for fiber dyeing. The effect of operational parameters such as current density, initial pH of the solution, time of electrolysis, initial dye concentration and solution conductivity were studied in an attempt to reach higher removal efficiency. The findings in this study shows that an increase in the current density up to 60-80 A m(-2) enhanced the color removal efficiency, the electrolysis time was 5 min and the range of pH was determined between 5.5 and 8.5 for two mentioned dye solutions. It was found that for, the initial concentration of dye in solutions should not be higher than 80 mg l(-1) in order to achieve a high color removal percentage. The optimum conductivity was found to be 8 mS cm(-1), which was adjusted using proper amount of NaCl with the dye concentration of 50 mg l(-1). Electrical energy consumption in the above conditions for the decolorization of the dye solutions containing BR46 and BB3 were 4.70 kWh(kgdye removed)(-1) and 7.57 kWh(kgdye removed)(-1), respectively. Also, during the EC process under the optimized conditions, the COD decreased by more than 75% and 99% in dye solutions containing BB3 and BR46, respectively.

A mathematical model for the generation and control of a pH gradient in an immobilized enzyme system involving acid generation.

PubMed

Chen, G; Fournier, R L; Varanasi, S

1998-02-20

An optimal pH control technique has been developed for multistep enzymatic synthesis reactions where the optimal pH differs by several units for each step. This technique separates an acidic environment from a basic environment by the hydrolysis of urea within a thin layer of immobilized urease. With this technique, a two-step enzymatic reaction can take place simultaneously, in proximity to each other, and at their respective optimal pH. Because a reaction system involving an acid generation represents a more challenging test of this pH control technique, a number of factors that affect the generation of such a pH gradient are considered in this study. The mathematical model proposed is based on several simplifying assumptions and represents a first attempt to provide an analysis of this complex problem. The results show that, by choosing appropriate parameters, the pH control technique still can generate the desired pH gradient even if there is an acid-generating reaction in the system. Copyright 1998 John Wiley & Sons, Inc.

Career intentions of PhD students in nursing: A cross-sectional survey.

PubMed

Bai, XiaoLing; Luo, ZhongChen; Lou, Ting; Pang, Jin; Tang, SiYuan

2018-05-01

Despite the rapid growth of Chinese nursing PhD programs, little is known about the career intentions of students in this field. To investigate the career intentions of nursing PhD students. Online cross-sectional survey. Nursing PhD students at Chinese universities. An online questionnaire was designed and the data were analyzed using SPSS. The mean age of the participants was 31.53 ± 4.92 years, and most were female (89.9%), married (74.2%), and had been employed previously (69.7%). Most intended to work in the city where their family lived (34.8%) or near their previous workplace (32.6%). Most (60.7%) desired to work in an educational institution (e.g., a university or college). The most common expected salary was 8000-11,999 RMB/month. The work benefits perceived as indispensable were "Five Insurances and One Fund" (77.5%), good educational resources for children (59.6%), financial allowances for PhD graduates (52.8%), staff dormitories/housing subsidies (50.6%), and tenure (50.6%). Nursing education (75.3%) and research (70.8%) were the most favored fields. The key job characteristics were the opportunity to put strengths to fullest use (79.8%), time to conduct research (60.7%), and work-life balance (51.7%). The key research conditions included a good research incentive mechanism (77.5%), a Basic Scientific Research Foundation (68.5%), opportunity to apply to conduct research projects (66.3%), and the nursing team's atmosphere regarding research (64.0%), and 91.0% were eager to study abroad (e.g., as part of an international exchange). Nursing PhD students would like to work in their hometown or near their previous workplace. Most preferred working in an educational institution, and the most popular fields were nursing education and research (rather than clinical care), despite the high demand of hospital management for nursing PhD graduates. Flexible work, high-quality research conditions, a certain salary, work benefits, and training were key expectations. Copyright © 2018 Elsevier Ltd. All rights reserved.

When America Makes, America Works A Successful Public Private 3D Printing (Additive Manufacturing) Partnership

DTIC Science & Technology

2016-10-01

Additive Manufacturing ) Partnership Jennifer Fielding, Ph.D.  Ed Morris  Rob Gorham  Emily Fehrman Cory, Ph.D.  Scott Leonard Fielding is the...government partners for America Makes and other Manufacturing Innovation Institutes. America Makes is the National Additive Manufactur -ing Innovation Institute...vision for America Makes is to accelerate additive manufacturing (AM) inno-vation to enable widespread adoption by bridging the gap between basic

Lasker Awards Honor Three Researchers.

PubMed

2017-10-01

Three top cancer researchers were among recipients of the prestigious Albert and Mary Lasker Foundation awards. Douglas R. Lowy, MD, and John T. Schiller, PhD, were honored for research leading to the development of the first human papillomavirus vaccine. The prize for basic medical research went to Michael N. Hall, PhD, who discovered the TOR signaling pathway and its role in regulating cell growth and metabolism. ©2017 American Association for Cancer Research.

Properties of PLA/PCL particles as vehicles for oral delivery of the androgen hormone 17α-methyltestosterone.

PubMed

Sacchetin, Priscila Soares Costa; Setti, Rafaela Ferreira; Vieira e Rosa, Paulo de Tarso; Moraes, Ângela Maria

2016-01-01

The aim of this study was to produce PLA (poly(lactic acid)) and PCL (polycaprolactone) oral carriers through the precipitation of the polymer solutions using supercritical CO2 as an antisolvent for the controlled release of the hydrophobic model drug 17α-methyltestosterone (MT). Such drug is a steroidal hormone used orally to develop and sustain primary and secondary male sex characteristics, e.g. for female Nile tilapia sex reversal in aquaculture. The influence of hormone, PLA and PCL concentrations on particle formation was analyzed, showing that high PCL concentrations produced particles with rougher surfaces and greater mean diameters. The incorporation efficiency of MT ranged from 20 to 51%, and its addition resulted in increases in particle mean diameter from 23 to 54 μm. Aggregation was observed for particles incorporating or not MT and high concentrations of MT led to the formation of more amorphous structures, changing the thermal behavior of the particles. The exposure of the PLA/PCL particles to pH conditions simulating gastrointestinal fish conditions showed that hormone release fraction at acidic pH ranged from 8 to 63% (over 2h), while in the basic pH the proportion released varied from 23 to 60% (over 10h), reaching levels adequate for the desired in vivo activity. Copyright © 2015. Published by Elsevier B.V.

Structural studies of n-type nc-Si-QD thin films for nc-Si solar cells

NASA Astrophysics Data System (ADS)

Das, Debajyoti; Kar, Debjit

2017-12-01

A wide optical gap nanocrystalline silicon (nc-Si) dielectric material is a basic requirement at the n-type window layer of nc-Si solar cells in thin film n-i-p structure on glass substrates. Taking advantage of the high atomic-H density inherent to the planar inductively coupled low-pressure (SiH4 + CH4)-plasma, development of an analogous material in P-doped nc-Si-QD/a-SiC:H network has been tried. Incorporation of C in the Si-network extracted from the CH4 widens the optical band gap; however, at enhanced PH3-dilution of the plasma spontaneous miniaturization of the nc-Si-QDs below the dimension of Bohr radius (∼4.5 nm) further enhances the band gap by virtue of the quantum size effect. At increased flow rate of PH3, dopant induced continuous amorphization of the intrinsic crystalline network is counterbalanced by the further crystallization promoted by the supplementary atomic-H extracted from PH3 (1% in H2) in the plasma, eventually holding a moderately high degree of crystallinity. The n-type wide band gap (∼1.93 eV) window layer with nc-Si-QDs in adequate volume fraction (∼52%) could furthermore be instrumental as an effective seed layer for advancing sequential crystallization in the i-layer of nc-Si solar cells with n-i-p structure in superstrate configuration.

Private Philanthropy and Basic Research in Mid-Twentieth Century America: The Hickrill Chemical Research Foundation.

PubMed

Gortler, Leon; Weininger, Stephen J

2017-02-01

The Hickrill Chemical Research Foundation, located north of New York City on the estate of its patrons, Sylvan and Ruth Alice Norman Weil, had a short (1948-59) but productive life. Ruth Alice Weil received a Ph.D. in organic chemistry in 1947, directed by William von Eggers Doering of Columbia University. She intended that Hickrill contribute to cancer chemotherapy while providing resources for Doering's more speculative research. Ultimately, Doering's commitment to theoretical organic chemistry set Hickrill's research agenda. Lawrence Knox, an African American with a Harvard Ph.D., supervised the laboratory's daily activities. Hickrill's two dozen postdoctoral fellows produced path-breaking results in Hückel aromatic theory and reactive intermediate chemistry, fostering the postwar emphasis on "basic science." This essay places the Laboratory's successes in the wider context of postwar politics and scientific priorities. Private philanthropic support of basic science arose because it received little pre-World War II government support. In the immediate postwar period, modest organisations like Hickrill still met a need, but the increasing governmental defence- and non-defence-related support for science eventually rendered them unnecessary.

Sequential cloud-point extraction for toxicological screening analysis of medicaments in human plasma by high pressure liquid chromatography with diode array detector.

PubMed

Madej, Katarzyna; Persona, Karolina; Wandas, Monika; Gomółka, Ewa

2013-10-18

A complex extraction system with the use of cloud-point extraction technique (CPE) was developed for sequential isolation of basic and acidic/neutral medicaments from human plasma/serum, screened by HPLC/DAD method. Eight model drugs (paracetamol, promazine, chlorpromazine, amitriptyline, salicyclic acid, opipramol, alprazolam and carbamazepine) were chosen for the study of optimal CPE conditions. The CPE technique consists in partition of an aqueous sample with addition of a surfactant into two phases: micelle-rich phase with the isolated compounds and water phase containing a surfactant below the critical micellar concentration, mainly under influence of temperature change. The proposed extraction system consists of two chief steps: isolation of basic compounds (from pH 12) and then isolation of acidic/neutral compounds (from pH 6) using surfactant Triton X-114 as the extraction medium. Extraction recovery varied from 25.2 to 107.9% with intra-day and inter-day precision (RSD %) ranged 0.88-1087 and 5.32-17.96, respectively. The limits of detection for the studied medicaments at λ 254nm corresponded to therapeutic or low toxic plasma concentration levels. Usefulness of the proposed CPE-HPLC/DAD method for toxicological drug screening was tested via its application to analysis of two serum samples taken from patients suspected of drug overdosing. Published by Elsevier B.V.

Introduction of agarose gel as a green membrane in electromembrane extraction: An efficient procedure for the extraction of basic drugs with a wide range of polarities.

PubMed

Tabani, Hadi; Asadi, Sakine; Nojavan, Saeed; Parsa, Mitra

2017-05-12

Developing green methods for analyte extraction is one of the most important topics in the field of sample preparation. In this study, for the first time, agarose gel was used as membrane in electromembrane extraction (EME) without using any organic solvent, for the extraction of four model basic drugs (rivastigmine (RIV), verapamil (VER), amlodipine (AML), and morphine (MOR)) with a wide polarity window (log P from 0.43 to 3.7). Different variables playing vital roles in the proposed method were evaluated and optimized. As a driving force, a 25V electrical field was applied to make the analyte migrate from sample solution with pH 7.0, through the agarose gel 3% (w/v) with 5mm thickness, into an acceptor phase (AP) with pH 2.0. The best extraction efficiency was obtained with an extraction duration of 25min. With this new methodology, MOR with high polarity (log P=0.43) was efficiently extracted without using any carrier or ion pair reagents. Limits of detection (LODs) and quantification (LOQs) were in the ranges of 1.5-1.8ngmL -1 and 5.0-6.0ngmL -1 , respectively. Finally, the proposed method was successfully applied to determine concentrations of the model drugs in the wastewater sample. Copyright © 2017 Elsevier B.V. All rights reserved.

Asparagine deamidation dependence on buffer type, pH, and temperature.

PubMed

Pace, Amanda L; Wong, Rita L; Zhang, Yonghua Taylor; Kao, Yung-Hsiang; Wang, Y John

2013-06-01

The deamidation of asparagine into aspartate and isoaspartate moieties is a major pathway for the chemical degradation of monoclonal antibodies (mAbs). It can affect the shelf life of a therapeutic antibody that is not formulated or stored appropriately. A new approach to detect deamidation using ion exchange chromatography was developed that separates papain-digested mAbs into Fc and Fab fragments. From this, deamidation rates of each fragment can be calculated. To generate kinetic parameters useful in setting shelf life, buffers prepared at room temperature and then placed at the appropriate stability temperatures. Solution pH was not adjusted to the same at different temperatures. Deamidation rate at 40°C was faster in acidic buffers than in basic buffers. However, this trend is reversed at 5°C, attributed to the change in hydroxide ion concentration influenced by buffer and temperature. The apparent activation energy was higher for rates generated in an acidic buffer than in a basic buffer. The rate-pH profile for mAb1 can be deconvoluted to Fc and Fab. The Fc deamidation showed a V-shaped profile: deamidation of PENNY peptide is responsible for the rate at high-pH, whereas deamidation of a new site, Asn323, may be responsible for the rate at low-pH. The profile for Fab is a straight line without curvature. Copyright © 2013 Wiley Periodicals, Inc.

The chemical stability of abasic RNA compared to abasic DNA

PubMed Central

Küpfer, Pascal A.; Leumann, Christian J.

2007-01-01

We describe the synthesis of an abasic RNA phosphoramidite carrying a photocleavable 1-(2-nitrophenyl)ethyl (NPE) group at the anomeric center and a triisopropylsilyloxymethyl (TOM) group as 2′-O-protecting group together with the analogous DNA and the 2′-OMe RNA abasic building blocks. These units were incorporated into RNA-, 2′-OMe-RNA- and DNA for the purpose of studying their chemical stabilities towards backbone cleavage in a comparative way. Stability measurements were performed under basic conditions (0.1 M NaOH) and in the presence of aniline (pH 4.6) at 37°C. The kinetics and mechanisms of strand cleavage were followed by High pressure liquid chromotography and ESI-MS. Under basic conditions, strand cleavage at abasic RNA sites can occur via β,δ-elimination and 2′,3′-cyclophosphate formation. We found that β,δ-elimination was 154-fold slower compared to the same mechanism in abasic DNA. Overall strand cleavage of abasic RNA (including cyclophosphate formation) was still 16.8 times slower compared to abasic DNA. In the presence of aniline at pH 4.6, where only β,δ-elimination contributes to strand cleavage, a 15-fold reduced cleavage rate at the RNA abasic site was observed. Thus abasic RNA is significantly more stable than abasic DNA. The higher stability of abasic RNA is discussed in the context of its potential biological role. PMID:17151071

Geochemical study of stream waters affected by mining activities in the SE Spain

NASA Astrophysics Data System (ADS)

Garcia-Lorenzo, Maria Luz; Perez-Sirvent, Carmen; Martinez-Sanchez, Maria Jose; Bech, Jaime

2015-04-01

Water pollution by dissolved metals in mining areas has mainly been associated with the oxidation of sulphide-bearing minerals exposed to weathering conditions, resulting in low quality effluents of acidic pH and containing a high level of dissolved metals. According to transport process, three types of pollution could be established: a) Primary contamination, formed by residues placed close to the contamination sources; b) Secondary contamination, produced as a result of transport out of its production areas; c) Tertiary contamination. The aim of this work was to study trace element in water samples affected by mining activities and to apply the MINTEQ model for calculating aqueous geochemical equilibria. The studied area constituted an important mining centre for more than 2500 years, ceasing activity in 1991. The ore deposits of this zone have iron, lead and zinc as the main metal components. As a result, a lot of contaminations sources, formed by mining steriles, waste piles and foundry residues are present. For this study, 36 surficial water samples were collected after a rain episode in 4 different areas. In these samples, the trace element content was determined by by flame atomic absorption spectrometry (Fe and Zn), electrothermal atomization atomic absorption spectrometry (Pb and Cd), atomic fluorescence spectrometry (As) and ICP-MS for Al. MINTEQA2 is a geochemical equilibrium speciation model capable of computing equilibria among the dissolved, adsorbed, solid, and gas phases in an environmental setting and was applied to collected waters. Zone A: A5 is strongly influenced by tailing dumps and showed high trace element content. In addition, is influenced by the sea water and then showed high bromide, chloride, sodium and magnesium content, together with a basic pH. The MINTEQ model application suggested that Zn and Cd could precipitate as carbonate (hidrocincite, smithsonite and otavite). A9 also showed acid pH and high trace element content; is influenced by tailing dumps and also by waters from gully watercourses, transporting materials from Sierra Minera. The MINTEQ simulation showed that Pb and Ca could precipitate as sulphates (anglesite and gypsum). Waters affected by secondary contamination have been mixed with carbonate materials, present in the zone increasing the pH. Some elements have precipitated, such as Cu and Pb, while Cd, Zn and As are soluble. The MINTEQ model results showed that in A10 and A14, Al could precipitate as diaspore but also carbonates could be formed, particularly dolomite. These model in A12 sample showed that soluble Zn could precipitate as carbonate and Al as oxyhydroxide, similarly than in A13. A2 and A6 waters are affected by tertiary contamination and showed basic pH, soluble carbonates and lower trace element content. Only Zn, Cd and Al are present. The speciation model showed that in A2, Cd and Zn could precipitate as carbonates while Al as oxihydroxide. In A6, the model suggested that soluble Pb could precipitate as carbonate (hidrocerusite and cerusite) or as hydroxide; Al as diaspore, Ca as calcite and Fe as hematite. Zone B: All waters are strongly affected by mining activities and showed acid pH, high trace element content and high content of soluble sulphates. The MINTEQ results showed that in B8, Fe could precipitate as hydroxychloride and in B12 could form alunite. In B9, B10, B13 y B14, the model estimates the precipitation of anglesite, gypsum and Fe hydroxichloride (B9 and B10), diaspore in B13 and B14, and gypsum and Fe hydroxychloride in B13. All the sampling points collected in Zone C are affected by primary contamination, because there are a lot of tailing dumps. C1 showed high trace element content because is a reception point of a lot of tailing dumps. Water samples from C3 to C8 also had acid pH and high trace element content, particularly As, Zn and Cd. In addition, they showed high soluble sulphates. C2 water showed neutral pH, soluble carbonate and low trace element content because is influenced by a stabilised tailing dump. In all samples, except C2, the MINTEQ model showed that a lot of efflorescences could be formed, mainly sulphates. Zone D: All waters collected in this zone showed acid pH and high trace element content, mainly Zn, Cd and As. MINTEQ model results showed that elements could precipitate as jarosite but also anglesite in D8 and gypsum in D9, D11 and D12. D1 is affected by secondary contamination, which showed higher pH (still acid) and lower content in soluble salts and trace elements. The MINTEQ model suggested that Al could precipitate as diaspore, gibbsite and alunite. The applied model is an appropriate tool for the analysis of waters affected by mining activities. The obtained simulations confirm natural attenuation processes.

Mineralogical study of stream waters and efflorescent salts in Sierra Minera, SE Spain

NASA Astrophysics Data System (ADS)

Pérez-Sirvent, Carmen; Garcia-Lorenzo, Maria luz; Martinez-Sanchez, Maria Jose; Hernandez, Carmen; Hernandez-Cordoba, Manuel

2015-04-01

Trace elements contained in the residues from mining and metallurgical operations are often dispersed by wind and/or water after their disposal. These areas have severe erosion problems caused by water run-off in which soil and mine spoil texture, landscape topography and regional and microclimate play an important role. Water pollution by dissolved metals in mining areas has mainly been associated with the oxidation of sulphide-bearing minerals exposed to weathering conditions, resulting in low quality effluents of acidic pH and containing a high level of dissolved metals. The studied area, Sierra Minera, is close to the mining region of La Unión (Murcia, SE Spain). This area constituted an important mining centre for more than 2500 years, ceasing activity in 1991. The ore deposits of this zone have iron, lead and zinc as the main metal components. Studied area showed a lot of contaminations sources, formed by mining steriles, waste piles and foundry residues. As a consequence of the long period of mining activity, large volumes of wastes were generated during the mineral concentration and smelting processes. Historically, these wastes were dumped into watercourses, filling riverbeds and contaminating their surroundings. 40 sediment samples were collected from the area affected by mining exploitations, and at increasing distances from the contamination sources in 4 zones In addition, 36 surficial water samples were collected after a rain episode The Zn and Fe content was determined by flame atomic absorption spectrometry (FAAS). The Pb and Cd content was determined by electrothermal atomization atomic absorption spectrometry (ETAAS). The As content was measured by atomic fluorescence spectrometry using an automated continuous flow hydride generation spectrometer and Al content was determined by ICP-MS. Mineralogical composition of the samples was made by X Ray Diffraction (XRD) analysis using Cu-Kα radiation with a PW3040 Philips Diffractometer. Zone A: Water sample collected in A5 is strongly influenced by a tailing dump, and showed high trace element contents. In addition, is influenced by the sea water and then showed high bromide, chloride, sodium and magnesium content, together with a basic pH.The DRX results of evaporate water showed that halite, hexahydrite and gypsum are present: halite corroborates the sea influence and gypsum and hexahydrite the importance of soluble sulphates. A9 water showed acid pH and high trace elements content; is influenced by the tailing dump and also by waters from El Beal gully watercourse, transporting materials from Sierra Minera Waters affected by secondary contamination are influenced by mining wastes, the sea water and also are affected by agricultural activities (nitrate content). These waters have been mixed with carbonate materials, present in the zone increasing the pH. Some elements have precipitated, such as Cu and Pb, while Cd, Zn and As are soluble. The DRX analysis in the evaporate if A14 showed that halite and gypsum are present: halite confirms the seawater influence and gypsum the relationship between calcium and sulphates A2 and A6 waters are affected by tertiary contamination and showed basic pH, soluble carbonates and lower trace element content. Only Zn, Cd and Al are present. Zone B: All waters are strongly affected by mining activities and showed: acid pH, high trace element content and high content of soluble sulphates. The evaporate of B8 and B12 showed the presence of soluble sulphates: gypsum, halite, bianchite, paracoquimbite, halotrichite and siderotil in B8; gypsum, bianchite, paracoquimbite and coquimbite in B12; gypsum, hexahydrite, carnalite, bianchite, copiapite and sideroti in B10 and polihalite, gypsum, bianchite, coquimbite and paracoquimbite in B14. All the sampling points collected in Zone C are affected by primary contamination, because there are a lot of tailing dumps and sampling points are located close to them. C1 showed high trace element content because is a reception point of a lot of tailing dumps. Water samples from C3 to C8 also had acid pH and high trace element content, particularly As (remains soluble) and Zn and Cd (high mobility). In addition, they showed high soluble sulphates. C2 water showed neutral pH, soluble carbonate and low trace element content because is influenced by a stabilised tailing dump. However, the As remains soluble. Zone D: All waters collected in this zone showed acid pH and high trace element content, mainly Zn, Cd and As. Some differences were found from the high and the low part: samples located in the lower part (D2-D7) showed higher As content while Zn is higher in the high part (D8-D13) The DRX analysis in evaporates suggest that in D4 copiapite, coquimbite, gypsum, bianchite and ferrohexahydrite are formed and in D11 gypsum, bianchite, halotrichite and siderotil. D1 is affected by secondary contamination, which showed higher pH (still acid) and lower content in soluble salts and trace elements.

Influence of molecular weight and pH on adsorption of chitosan at the surface of large and giant vesicles.

PubMed

Quemeneur, Francois; Rinaudo, Marguerite; Pépin-Donat, Brigitte

2008-01-01

This paper describes the mechanisms of adsorption of chitosan, a positively charged polyelectrolyte, on the DOPC lipid membrane of large and giant unilamellar vesicles (respectively, LUVs and GUVs). We observe that the variation of the zeta potential of LUVs as a function of chitosan concentration is independent on the chitosan molecular weight (Mw). This result is interpreted in terms of electrostatic interactions, which induce a flat adsorption of the chitosan on the surface of the membrane. The role of electrostatic interactions is further studied by observing the variation of the zeta potential as a function of the chitosan concentration for two different charge densities tuned by the pH. Results show a stronger chitosan-membrane affinity at pH 6 (lipids are negatively charged, and 40% chitosan amino groups are protonated) than at pH 3.4 (100% of protonated amino groups but zwitterionic lipids are positively charged) which confirms that adsorption is of electrostatic origin. Then, we investigate the stability of decorated LUVs and GUVs in a large range of pH (6.0 < pH < 12.0) in order to complete a previous study made in acidic conditions [Quemeneur et al. Biomacromolecules 2007, 8, 2512-2519]. A comparative study of the variation of the zeta potential as a function of the pH (2.0 < pH < 12.0) reveals a difference in behavior between naked and chitosan-decorated LUVs. This result is further confirmed by a comparative observation by optical microscopy of naked and chitosan-decorated GUVs in basic conditions (6.0 < pH < 12.0): at pH > 10.0, in the absence of chitosan, the vesicles present complex shapes, contrary to the chitosan-decorated vesicles which remain spherical, confirming thus that chitosan remains adsorbed on vesicles in basic conditions up to pH = 12.0. These results, in addition with our previous data, show that the chitosan-decorated vesicles are stable over a very broad range of pH (2.0 < pH < 12.0), which holds promise for their in vivo applications. Finally, the quantification of the chitosan adsorption on a LUV membrane is performed by zeta potential and fluorescence measurements. The fraction of membrane surface covered by chitosan is estimated to be lower than 40 %, which corresponds to the formation of a flat layer of chitosan on the membrane surface on an electrostatic basis.

p-Chlorophenol adsorption on activated carbons with basic surface properties

NASA Astrophysics Data System (ADS)

Lorenc-Grabowska, Ewa; Gryglewicz, Grażyna; Machnikowski, Jacek

2010-05-01

The adsorption of p-chlorophenol (PCP) from aqueous solution on activated carbons (ACs) with basic surface properties has been studied. The ACs were prepared by two methods. The first method was based on the modification of a commercial CWZ AC by high temperature treatment in an atmosphere of ammonia, nitrogen and hydrogen. The second approach comprised the carbonization followed by activation of N-enriched polymers and coal tar pitch using CO 2 and steam as activation agent. The resultant ACs were characterized in terms of porous structure, elemental composition and surface chemistry (pH PZC, acid/base titration, XPS). The adsorption of PCP was carried out from an aqueous solution in static conditions. Equilibrium adsorption isotherm was of L2 type for polymer-based ACs, whereas L3-type isotherm was observed for CWZ ACs series. The Langmuir monolayer adsorption capacity was related to the porous structure and the amount of basic sites. A good correlation was found between the adsorption capacity and the volume of micropores with a width < 1.4 nm for polymer-based ACs. Higher nitrogen content, including that in basic form, did not correspond to the enhanced adsorption of PCP from aqueous solution. The competitive effect of water molecule adsorption on the PCP uptake is discussed.

Mathematical Models for Controlled Drug Release Through pH-Responsive Polymeric Hydrogels.

PubMed

Manga, Ramya D; Jha, Prateek K

2017-02-01

Hydrogels consisting of weakly charged acidic/basic groups are ideal candidates for carriers in oral delivery, as they swell in response to pH changes in the gastrointestinal tract, resulting in drug entrapment at low pH conditions of the stomach and drug release at high pH conditions of the intestine. We have developed 1-dimensional mathematical models to study the drug release behavior through pH-responsive hydrogels. Models are developed for 3 different cases that vary in the level of rigor, which together can be applied to predict both in vitro (drug release from carrier) and in vivo (drug concentration in the plasma) behavior of hydrogel-drug formulations. A detailed study of the effect of hydrogel and drug characteristics and physiological conditions is performed to gain a fundamental insight into the drug release behavior, which may be useful in the design of pH-responsive drug carriers. Finally, we describe a successful application of these models to predict both in vitro and in vivo behavior of docetaxel-loaded micelle in a pH-responsive hydrogel, as reported in a recent experimental study. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Effects of varying the step particle distribution on a probabilistic transport model

NASA Astrophysics Data System (ADS)

Bouzat, S.; Farengo, R.

2005-12-01

The consequences of varying the step particle distribution on a probabilistic transport model, which captures the basic features of transport in plasmas and was recently introduced in Ref. 1 [B. Ph. van Milligen et al., Phys. Plasmas 11, 2272 (2004)], are studied. Different superdiffusive transport mechanisms generated by a family of distributions with algebraic decays (Tsallis distributions) are considered. It is observed that the possibility of changing the superdiffusive transport mechanism improves the flexibility of the model for describing different situations. The use of the model to describe the low (L) and high (H) confinement modes is also analyzed.

Semantic conditioning of salivary pH for communication.

PubMed

Ruf, Carolin A; De Massari, Daniele; Wagner-Podmaniczky, Franziska; Matuz, Tamara; Birbaumer, Niels

2013-10-01

Semantic conditioning of salivary pH was investigated as a new paradigm for binary communication. In a sample of eleven healthy participants, affirmation or negation of presented statements were paired with milk and lemon to condition changes in salivary pH level. Significant differences between the conditioned reactions were found at the group level. However, the analysis of pH changes on single-subject level revealed significant differences between affirmative and negative responses to the presented statements only for isolated samples in few participants. When classifying a change in pH value of more than .01 as correct response to a statement, only responses to affirmative statements reached mean accuracies of more than 60%. Improvements in the paradigm are necessary before testing it with the critical target population of patients to prove its profit for basic yes/no communication in case no other reliable means of communication could be preserved. Copyright © 2013 Elsevier B.V. All rights reserved.

Ph.D. shortage

NASA Astrophysics Data System (ADS)

The late 1990s will see a shortage of Ph.D. graduates, according to the Association of American Universities, Washington, D.C. AAU's new comprehensive study, “The Ph.D. Shortage: The Federal Role,” reports that competition for new Ph.D.s is already intense and can only intensify because demand is greater than supply in both academic and nonacademic markets.Doctoral education plays an increasingly important role in U.S. research and development programs. Students have a pivotal part in doing research and enriching it with new ideas. The AAU report says that graduate students are “major determinants of the creativity and productivity of U.S. academic research, the source of more than 50% of the nation's basic research.’ The market for doctoral education extends beyond the university. In 1985, about 43% of all Ph.D.s employed in this country were working outside higher education; the demand for doctorate recipients in nonacademic sectors continues to grow.

Phenylboronate chromatography selectively separates glycoproteins through the manipulation of electrostatic, charge transfer, and cis-diol interactions.

PubMed

Carvalho, Rimenys J; Woo, James; Aires-Barros, M Raquel; Cramer, Steven M; Azevedo, Ana M

2014-10-01

Phenylboronate chromatography (PBC) has been applied for several years, however details regarding the mechanisms of interactions between the ligand and biomolecules are still scarce. The goal of this work is to investigate the various chemical interactions between proteins and their ligands, using a protein library containing both glycosylated and nonglycosylated proteins. Differences in the adsorption of these proteins over a pH range from 4 to 9 were related to two main properties: charge and presence of glycans. Acidic or neutral proteins were strongly adsorbed below pH 8 although the uncharged trigonal form of phenylboronate (PB) is less susceptible to forming electrostatic and cis-diol interactions with proteins. The glycosylated proteins were only adsorbed above pH 8 when the electrostatic repulsion between the boronate anion and the protein surface was mitigated (at 200 mM NaCl). All basic proteins were highly adsorbed above pH 8 with PB also acting as a cation-exchanger with binding occurring through electrostatic interactions. Batch adsorption performed at acidic conditions in the presence of Lewis base showed that charge-transfer interactions are critical for protein retention. This study demonstrates the multimodal interaction of PBC, which can be a selective tool for separation of different classes of proteins. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stokes-correlometry of polarization-inhomogeneous objects

NASA Astrophysics Data System (ADS)

Ushenko, O. G.; Dubolazov, A.; Bodnar, G. B.; Bachynskiy, V. T.; Vanchulyak, O.

2018-01-01

The paper consists of two parts. The first part presents short theoretical basics of the method of Stokes-correlometry description of optical anisotropy of biological tissues. It was provided experimentally measured coordinate distributions of modulus (MSV) and phase (PhSV) of complex Stokes vector of skeletal muscle tissue. It was defined the values and ranges of changes of statistic moments of the 1st-4th orders, which characterize the distributions of values of MSV and PhSV. The second part presents the data of statistic analysis of the distributions of modulus MSV and PhSV. It was defined the objective criteria of differentiation of samples with urinary incontinence.

Understanding ozone mechanisms to alleviate ceramic membrane fouling

NASA Astrophysics Data System (ADS)

Chu, Irma Giovanna Llamosas

Ceramic membranes are a strong prospect as an advanced treatment in the drinking water domain. But their high capital cost and the lack of specific research on their performance still discourage their application in this field. Thus, knowing that fouling is the main drawback experienced in filtration processes, this bench-scale study was aimed to assess the impact of an ozonation pre-treatment on the alleviation of the fouling of UF ceramic membranes. Preozonation and filtration steps were performed under two different pH and ozone doses. Chosen pH values were at the limits of natural surface waters range (6.5 and 8.5) to keep practicability. Raw water from the Thousand Isle's river at Quebec-Canada was used for the tests. The filtration setup involved an unstirred dead-end filtration cell operated at constant flux. Results showed that pre-oxidation by ozone indeed reduced the fouling degree of the membranes according to the dose applied (up to 60 and 85% for membranes 8 and 50 kDa, respectively). Direct NOM oxidation was found responsible for this effect as the presence of molecular ozone was not essential to achieve these results. In the context of this experiment, however, pH showed to be more effective than the ozonation pre-treatment to keep fouling at low levels: 70% lower at pH 6.5 than at pH 8.5 for un-ozonated waters, which was contrary to most of the literature found on the topic (Changwon, 2013; De Angelis & Fidalgo, 2013; Karnik et al., 2005; S. Lee & Kim, 2014). This behaviour results mainly from the operation mode used in the experiment, the electrical repulsions between MON molecules at basic pH that led to the accumulation of material on the feed side of the membranes (concentration polarisation) and ulterior cake formation. In addition, solution pH showed an influence in the definition of fouling mechanisms. At solution pH 6.5, which was precisely the isoelectric point of the membranes (+/-6.5), the blocking fouling mode was frequently detected before the onset of a cake. These facts put in evidence the important role of electrical charges in filtration processes with ceramic membranes (Chiu, 2011; S. Lee & Kim, 2014; Szymczyk, Fievet, Reggiani, & Pagetti, 1998b). In the ozonation side, it was confirmed that natural waters with high NOM content (>3 mg/L) trigger advanced oxidation processes (Acero & Von Gunten, 2001). It was also found that condition pH 6.5 showed higher NOM decomposition than condition pH 8.5 at the highest ozone dose used.

Development and characterization of a voltammetric carbon-fiber microelectrode pH sensor.

PubMed

Makos, Monique A; Omiatek, Donna M; Ewing, Andrew G; Heien, Michael L

2010-06-15

This work describes the development and characterization of a modified carbon-fiber microelectrode sensor capable of measuring real-time physiological pH changes in biological microenvironments. The reagentless sensor was fabricated under ambient conditions from voltammetric reduction of the diazonium salt Fast Blue RR onto a carbon-fiber surface in aprotic media. Fast-scan cyclic voltammetry was used to probe redox activity of the p-quinone moiety of the surface-bound molecule as a function of pH. In vitro calibration of the sensor in solutions ranging from pH 6.5 to 8.0 resulted in a pH-dependent anodic peak potential response. Flow-injection analysis was used to characterize the modified microelectrode, revealing sensitivity to acidic and basic changes discernible to 0.005 pH units. Furthermore, the modified electrode was used to measure dynamic in vivo pH changes evoked during neurotransmitter release in the central nervous system of the microanalytical model organism Drosophila melanogaster.

Simulating botulinum neurotoxin with constant pH molecular dynamics in Generalized Born implicit solvent

NASA Astrophysics Data System (ADS)

Chen, Yongzhi; Chen, Xin; Deng, Yuefan

2007-07-01

A new method was proposed by Mongan et al. for constant pH molecular dynamics simulation and was implemented in AMBER 8 package. Protonation states are modeled with different charge sets, and titrating residues are sampled from a Boltzmann distribution of protonation states. The simulation periodically adopts Monte Carlo sampling based on Generalized Born (GB) derived energies. However, when this approach was applied to a bio-toxin, Botulinum Neurotoxin Type A (BoNT/A) at pH 4.4, 4.7, 5.0, 6.8 and 7.2, the pK predictions yielded by the method were inconsistent with the experimental values. The systems being simulated were divergent. Furthermore, the system behaviors in a very weak acidic solution (pH 6.8) and in a very weak basic solution (pH 7.2) were significantly different from the neutral case (pH 7.0). Hence, we speculate this method may require further study for modeling large biomolecule.

Development and Characterization of a Voltammetric Carbon-fiber Microelectrode pH Sensor

PubMed Central

Makos, Monique A.; Omiatek, Donna M.; Ewing, Andrew G.; Heien, Michael L.

2010-01-01

This work describes the development and characterization of a modified carbon-fiber microelectrode sensor capable of measuring real-time physiological pH changes in biological microenvironments. The reagentless sensor was fabricated under ambient conditions from voltammetric reduction of the diazonium salt Fast Blue RR onto a carbon-fiber surface in aprotic media. Fast-scan cyclic voltammetry was used to probe redox activity of the p-quinone moiety of the surface-bound molecule as a function of pH. In vitro calibration of the sensor in solutions ranging from pH 6.5 to 8.0 resulted in a pH-dependent anodic peak potential response. Flow-injection analysis was used to characterize the modified microelectrode, revealing sensitivity to acidic and basic changes discernable to 0.005 pH units. Furthermore, the modified electrode was used to measure dynamic in vivo pH changes evoked during neurotransmitter release in the central nervous system of the microanalytical model organism Drosophila melanogaster. PMID:20380393

Stability and activity of lysozyme in stoichiometric and non-stoichiometric protic ionic liquid (PIL)-water systems

NASA Astrophysics Data System (ADS)

Wijaya, Emmy C.; Separovic, Frances; Drummond, Calum J.; Greaves, Tamar L.

2018-05-01

There has been a substantial increase in enzyme applications within the biochemical and pharmaceutical industries, for example, as industrial biocatalysts. However, enzymes have narrow marginal stability which makes them prone to become inactive and/or denature with a slight change in the solvent environment. Typically industrial applications require harsher solvent environments than enzyme native environments, and hence there is a need to understand solvent-protein interactions in order to develop strategies to maintain, or enhance, the enzymatic activity under industrially relevant solvent conditions. Previously we have shown that protic ionic liquids (PILs) with water can have a stabilising effect on lysozyme, with a large variation dependent on which PIL ions are present, and the water concentration [E. C. Wijaya et al., Phys. Chem. Chem. Phys. 18(37), 25926-25936 (2016)]. Here we extend on this work using non-stoichiometric aqueous PIL solvents to investigate, and isolate, the role of pH and ionicity on enzymes. We have used the PILs ethylammonium nitrate (EAN) and ethanolammonium formate (EOAF) since our previous work has identified these as good solvents for lysozyme. Solvent libraries were made from these two PILs with an additional precursor acid or base to modify the acidity/basicity of the neutral stoichiometric PIL, and with water added, to have solutions with 4-17 mol. % of the PIL ions in water. Molar ratios of base:acid were varied between 1:1.05 and 2:1 for EAN and 1:1.25 and 2:1 for EOAF, which enabled from highly basic to highly acidic solutions to be obtained. This was to modify the acidity/basicity of the neutral stoichiometric PILs, without the addition of buffers. The structure and stability of hen egg white lysozyme (HEWL) were explored under these solvent conditions using synchrotron small angle X-ray scattering (SAXS), Fourier transform infrared (FTIR), and activity assays. The radius of gyration and Kratky plots obtained from the SAXS data showed little change with varying ionicity or acid:base ratio. FTIR showed that α-helix was maintained in all, except for the most acidic solvent conditions. The activity data show that HEWL was active between pH 0 and 11 for the EA:N-water system and pH 4.4 and 11 for the EOA:F-water system. This work indicates that ionic liquids have the potential to enable enzymes to maintain activity across a broader range of solvent conditions.

Iridium Complexes with Proton-Responsive Azole-Type Ligands as Effective Catalysts for CO 2 Hydrogenation

DOE PAGES

Ertem, Mehmed Zahid; Suna, Yuki; Himeda, Yuichiro; ...

2017-10-06

Pentamethylcyclopentadienyl iridium (Cp*Ir) complexes with bidentate ligands consisting of a pyridine ring and an electron-rich diazole ring were prepared. Their catalytic activity towards CO 2 hydrogenation in 2.0 M KHCO 3 aqueous solutions (pH 8.5) at 50 °C, under 1.0 MPa CO 2/H 2 (1:1) have been reported as an alternative to photo- and electrochemical CO 2 reduction. Bidentate ligands incorporating an electron-rich diazole ring improved the catalytic performance of the Ir complexes compared to the bipyridine ligand. Complexes 2, 4 and 6, possessing both a hydroxy group and an uncoordinated NH group, which are proton-responsive and capable of generatingmore » pendent-bases in basic media, recorded high initial TOF values of 1300 h -1, 1550 h -1 and 2000 h -1, respectively. Here, spectroscopic and computational investigations revealed that the reversible deprotonation changes the electronic properties of the complexes and causes interactions between pendent base and substrate and/or solvent water molecules, resulting in the high catalytic performance in basic media.« less

The stability of 6-mercaptopurine riboside in neutral and basic medium.

PubMed

Jelińska, A; Magdziarz, M

2000-01-01

The kinetics of hydrolysis of 6-mercaptopurine riboside (R-6-MP) was studied in aqueous solutions over the pH range of 6.11-12.13 at 353 K. The decomposition was investigated by HPLC method. At the pH range from 6.11 to 12.13 hydrolysis of 6-mercaptopurine riboside includes: spontaeous hydrolysis of non-protonated R-6-MP molecules mono- and di-anions R-6-MP molecules under the effect of water.

Modified Activated Carbon Perchlorate Sorbents

DTIC Science & Technology

2007-01-25

Yield 4.64 g. Methyl Chloride Alkylated Activated Carbon Methyl chloride (MeCl) treatment was carried out in a tube furnace generally in...with alkylation agents lowers the solution pH as the basic sites are alkylated . In the case of Me2SO4 treatment , the low slurry pH is believed to be...by Cannon and coworkers, the alkylated carbons are not significantly better. In the case of the SAI carbons, ammonia treatment does not result in a

Formation of 2D-PhCs with missing holes based on Si-layers by EBL

NASA Astrophysics Data System (ADS)

Utkin, D. E.; Shklyev, A. A.; Tsarev, A. V.; Latyshev, A. V.

2017-11-01

The fabrication of the periodic structures, that is two-dimensional photonic crystals (2D PhCs) based on Si-materials by electron beam lithography (EBL) technique has been studied. We have investigated basic lithography processes such as designing, exposition, development, etching and others. The developed top-down approach allows close-packed arrays of elements and holes to be formed in nanometre range. This can be used to produce 2D PhCs with emitting micro-cavities (missing holes) with lateral size parameters with an accuracy of about 2% in the Si (100) substrate and in silicon-on-insulator structures. Such accuracy is expected to be sufficient for obtaining the cavities-coupling radiation interference from large areas of 2D PhCs.

Decoupling of the minority PhD talent pool and assistant professor hiring in medical school basic science departments in the US

PubMed Central

Gibbs, Kenneth D; Basson, Jacob; Xierali, Imam M; Broniatowski, David A

2016-01-01

Faculty diversity is a longstanding challenge in the US. However, we lack a quantitative and systemic understanding of how the career transitions into assistant professor positions of PhD scientists from underrepresented minority (URM) and well-represented (WR) racial/ethnic backgrounds compare. Between 1980 and 2013, the number of PhD graduates from URM backgrounds increased by a factor of 9.3, compared with a 2.6-fold increase in the number of PhD graduates from WR groups. However, the number of scientists from URM backgrounds hired as assistant professors in medical school basic science departments was not related to the number of potential candidates (R2=0.12, p>0.07), whereas there was a strong correlation between these two numbers for scientists from WR backgrounds (R2=0.48, p<0.0001). We built and validated a conceptual system dynamics model based on these data that explained 79% of the variance in the hiring of assistant professors and posited no hiring discrimination. Simulations show that, given current transition rates of scientists from URM backgrounds to faculty positions, faculty diversity would not increase significantly through the year 2080 even in the context of an exponential growth in the population of PhD graduates from URM backgrounds, or significant increases in the number of faculty positions. Instead, the simulations showed that diversity increased as more postdoctoral candidates from URM backgrounds transitioned onto the market and were hired. DOI: http://dx.doi.org/10.7554/eLife.21393.001 PMID:27852433

A wearable fingernail chemical sensing platform: pH sensing at your fingertips.

PubMed

Kim, Jayoung; Cho, Thomas N; Valdés-Ramírez, Gabriela; Wang, Joseph

2016-04-01

This article demonstrates an example of a wearable chemical sensor based on a fingernail platform. Fingernails represent an attractive wearable platform, merging beauty products with chemical sensing, to enable monitoring of our surrounding environment. The new colorimetric pH fingernail sensor relies on coating artificial nails with a recognition layer consisted of pH indicators entrapped in a polyvinyl chloride (PVC) matrix. Such color changing fingernails offer fast and reversible response to pH changes, repeated use, and intense color change detected easily with naked eye. The PVC matrix prevents leaching out of the indicator molecules from the fingernail sensor toward such repeated use. The limited narrow working pH range of a single pH indicator has been addressed by multiplexing three different pH indicators: bromothymol blue (pH 6.0-7.6), bromocresol green (pH 3.8-5.4), and cresol red (pH 7.2-8.8), as demonstrated for analyses of real-life samples of acidic, neutral, and basic character. The new concept of an optical wearable chemical sensor on fingernail platforms can be expanded towards diverse analytes for various applications in connection to the judicious design of the recognition layer. Copyright © 2016 Elsevier B.V. All rights reserved.

Basic mechanism of button battery ingestion injuries and novel mitigation strategies after diagnosis and removal.

PubMed

Jatana, Kris R; Rhoades, Keith; Milkovich, Scott; Jacobs, Ian N

2017-06-01

Button battery (BB) injuries continue to be a significant source of morbidity and mortality, and there is a need to confirm the mechanism of injury for development of additional mitigation strategies. Cadaveric piglet esophageal model. Lithium, silver oxide, alkaline, and zinc-air BBs were placed in thawed sections of cadaveric piglet esophagus, bathed in normal saline. Severity of gross visual burn, pH, and temperature were recorded every 30 minutes for 6 hours. In other esophageal tissue specimens, the lithium BB was removed after 24, 36, and 48 hours and the site was irrigated with either 0.25% or 3% acetic acid. Separately, ReaLemon® juice, orange juice, Coke®, Dasani® water, Pepsi®, and saline were infused over a vertically suspended esophagus with a CR2032 lithium battery every 5 minutes for 2 hours while tissue temperature and pH were measured. A gradual rise in tissue pH and minimal change in temperature was noted for all BBs. ReaLemon® and orange juice applied every 5 minutes were most effective at neutralization of tissue pH with minimal change in tissue temperature. After BB removal (24, 36, 48 hours), irrigation of esophageal tissue specimens with 50-150 mL 0.25% acetic acid neutralized the highly alkaline tissue pH. BB appear to cause an isothermic hydrolysis reaction resulting in an alkaline caustic injury. Potential new mitigation strategies include application of neutralizing weakly acidic solutions that may reduce esophageal injury progression. NA Laryngoscope, 127:1276-1282, 2017. © 2016 The American Laryngological, Rhinological and Otological Society, Inc.

Development of a novel colorimetric sensor based on alginate beads for monitoring rainbow trout spoilage.

PubMed

Majdinasab, Marjan; Hosseini, Seyed Mohammad Hashem; Sepidname, Marziyeh; Negahdarifar, Manizheh; Li, Peiwu

2018-05-01

Alginate is a non-toxic, renewable, and linear copolymer obtained from the brown algae Laminaria digitata that can be easily shaped into beads. Its good gel forming properties have made it useful for entrapping food and pharmaceutical ingredients. In this study, alginate beads were used in a novel application as a colorimetric sensor in food intelligent packaging. Colorimetric sensor was developed through entrapping red cabbage extract as a pH indicator in alginate beads. The pH indicator beads were used in rainbow trout packaging for monitoring fillets spoilage. Color change of beads during fish storage was measured using the CIELab method. The alginate bead colorimetric sensor is validated by measuring total volatile basic nitrogen (TVB-N) levels and microbial populations in fish samples. Moreover, peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) were evaluated during storage. Results indicated that increasing the bacterial population during storage and production of proteolytic enzymes resulted in protein degradation, accumulation of volatile amine compounds, increase in the pH and finally color change of alginate beads. The values of TVB-N, pH, PV and TBARS increased with time of storage. The results of TVB-N and microbial growth were in accordance with color change of beads and CIELab data. Therefore, the proposed system enjoys a high sensitivity to pH variations and is capable of monitoring the spoilage of fish or other protein-rich products through its wide range of color changes. The alginate beads containing the red cabbage extract can, thus, be used as a low-cost colorimetric sensor for intelligent packaging applications.

Identifying across‐system sources of variation in a generalist freshwater fish: Correlates of total and size‐specific abundance of yellow perch

USGS Publications Warehouse

Carey, Michael P.; Mather, M. E.

2009-01-01

Variation in fish abundance across systems presents a challenge to our understanding of fish populations because it limits our ability to predict and transfer basic ecological principles to applied problems. Yellow perch (Perca flavescens) is an ideal species for exploring environmental and biotic correlates across system because it is widely distributed and physiologically tolerant. In 16 small, adjacent systems that span a wide range of environmental and biotic conditions, yellow perch were sampled with a standard suite of gear. Water quality, morphometry, vegetation, invertebrates and fish communities were concurrently measured. Multimodel inference was used to prioritise regressors for the entire yellow perch sample and three size groups (35-80, 81-180, ≥181 mm TL). Across systems, pH and fish richness were identified as the key drivers of yellow perch abundance. At very low pH (<4.0), few fish species and few yellow perch individuals were found. At ponds with moderately low pH (4.0–4.8), numbers of yellow perch increased. Ponds with high pH (>4.8) had many other species and few yellow perch. Similar patterns for pH and fish community were observed for the two largest‐size classes. Negative interactions were observed between the medium‐ and large‐sized yellow perch and between the largest and smallest yellow perch, although interspecific interactions were weaker than expected. This examination of variability for an indicator species and its component‐size classes provides ecological understanding that can help frame the larger‐scale sampling programs needed for the conservation of freshwater fish.

Cottonseed protein derivatives as nutritional and functional supplements in food formulations.

PubMed

Cherry, J P; Berardi, L C; Zarins, Z M; Wadsworth, J I; Vinnett, C H

1978-01-01

Cottonseeds contain protein with desirable food functional and nutritional properties. Storage globulins make up most of the protein stored in cottonseed and can be separated into five fractions by gel filtration chromatography. Each fraction is distinguishable from the other by its amino acid and polyacrylamide gel electrophoretic properties. Proteins of cottonseed contribute greatly to the functional properties of emulsions, co-isolates, and texturized derivatives. For example, increasing the amount of high protein cottonseed flour in wheat suspensions from 2% to 10% improved the capacity (54-97 ml of oil) and viscosity (5,000-100,000+ cps) of emulsions. The 10% suspension formed emulsions with increasing oil capacity (84-100 ml) and viscosity (28,000-100,000+ cps) as the pH was adjusted from 4.5 to 9.5. Consistencies of the products ranged from that of salad dressing (low percent suspensions, or acid pH) to that of mayonnaise (high percent, or basic pH). These data were utilized to derive a multiple regression model to predict optimum use of cottonseed proteins in emulsions of varying consistencies. A coprecipitated isolate containing greater than 94% protein was prepared from a blend of cottonseed and peanut flours. Amino acid content of the co-isolate reflected that of the protein in the two flours of the composite. The co-isolate has lower gossypol level and improved color and functional properties than a cottonseed protein isolate. Storage protein isolate of cottonseed suspended in aqueous solution and heated with constant stirring forms a texturized product; the quality of the product depends on heat, pH, salt, and the quantity of nonstorage proteins. Protein and amino acid content of meat products were improved by the addition of the texturized protein of cottonseed.

Sunlight-assisted Fenton reaction catalyzed by gold supported on diamond nanoparticles as pretreatment for biological degradation of aqueous phenol solutions.

PubMed

Navalon, Sergio; Martin, Roberto; Alvaro, Mercedes; Garcia, Hermenegildo

2011-05-23

Gold nanoparticles supported on Fenton-treated diamond nanoparticles (Au/DNPs) have been reported as one of the most efficient solid catalysts effecting the Fenton reaction, achieving a turnover number (TON) as high as 321,000. However, at room temperature the main limitation for the catalytic activity of Au/DNPs is the pH of the solution, which should be less than 5. In this paper, we report that exposure of Au/DNPs to sunlight enhances the catalytic activity of Au/DNPs up to the point that it can promote the Fenton reaction at room temperature even at slightly basic pH values. Also, in addition to performing a deep Fenton treatment and considering that the excess of H(2)O(2) used in the process should be minimized, we have achieved in our study, using a mild Fenton reaction promoted by Au/DNPs under sunlight irradiation, an optimum in the biodegradability, a minimum in the ecotoxicity, and no toxicity for the Vibrio fischeri test. The results have shown that, by using an H(2)O(2) -to-phenol molar ratio of 5.5 or higher, it is possible to achieve a high biodegradability as well as a complete lack of ecotoxicity and of Vibrio fischeri toxicity. The stability of Au/DNPs was confirmed by analyzing the gold leached to the solution and by performing four consecutive reuses of the catalyst with initial pH values ranging from 4 to 8. It was observed that, after finishing the reaction and exhaustive washings with basic aqueous solutions, the initial reaction rate of the used catalyst is recovered to the value exhibited by the fresh solid. Overall, our study shows that the synergism between catalysis and photocatalysis can overcome the limitations found for dark catalytic reactions and that the reaction parameters can be optimized to effect mild Fenton reactions aimed at increasing biodegradability in biorecalcitrant waste waters. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorption of Cr(III) on ozonised activated carbon. Importance of Cpi-cation interactions.

PubMed

Rivera-Utrilla, J; Sánchez-Polo, M

2003-08-01

The adsorption of Cr(III) in aqueous solution was investigated on a series of ozonised activated carbons, analysing the effect of oxygenated surface groups on the adsorption process. A study was carried out to determine the adsorption isotherms and the influence of the pH on the adsorption of this metal. The adsorption capacity and affinity of the adsorbent for Cr(III) increased with the increase in oxygenated acid groups on the surface of the activated carbon. These findings imply that electrostatic-type interactions predominate in the adsorption process, although the adsorption of Cr(III) on the original (basic) carbon indicates that other forces also participate in the adsorption process. Thus, the ionic exchange of protons in the -Cpi-H3O(+) interaction for Cr(III) accounts for the adsorption of cationic species in basic carbons with positive charge density. Study of the influence of pH on the adsorption of Cr(III) showed that, in each system, the maximum adsorption occurred when the charge of the carbon surface was opposite that of the species of Cr(III) present at the pH of the experiment. These results confirmed that electrostatic interactions predominate in the adsorption process.

Electrospray Ionization Efficiency Is Dependent on Different Molecular Descriptors with Respect to Solvent pH and Instrumental Configuration

PubMed Central

Kiontke, Andreas; Oliveira-Birkmeier, Ariana; Opitz, Andreas

2016-01-01

Over the past decades, electrospray ionization for mass spectrometry (ESI-MS) has become one of the most commonly employed techniques in analytical chemistry, mainly due to its broad applicability to polar and semipolar compounds and the superior selectivity which is achieved in combination with high resolution separation techniques. However, responsiveness of an analytical method also determines its suitability for the quantitation of chemical compounds; and in electrospray ionization for mass spectrometry, it can vary significantly among different analytes with identical solution concentrations. Therefore, we investigated the ESI-response behavior of 56 nitrogen-containing compounds including aromatic amines and pyridines, two compound classes of high importance to both, synthetic organic chemistry as well as to pharmaceutical sciences. These compounds are increasingly analyzed employing ESI mass spectrometry detection due to their polar, basic character. Signal intensities of the peaks from the protonated molecular ion (MH+) were acquired under different conditions and related to compound properties such as basicity, polarity, volatility and molecular size exploring their quantitative impact on ionization efficiency. As a result, we found that though solution basicity of a compound is the main factor initially determining the ESI response of the protonated molecular ion, other factors such as polarity and vaporability become more important under acidic solvent conditions and may nearly outweigh the importance of basicity under these conditions. Moreover, we show that different molecular descriptors may become important when using different types of instruments for such investigations, a fact not detailed so far in the available literature. PMID:27907110

Construction of High Activity Titanium Dioxide Crystal Surface Heterostructures and Characterization of Its Basic Properties

NASA Astrophysics Data System (ADS)

Wang, Chunxiao; Li, DanQi; Shen, Tingting; Lu, Cheng; Sun, Jing; Wang, Xikui

2018-01-01

Heterogeneous photocatalytic materials, which combine the advantages of photocatalytic materials and heterojunction, have been developed rapidly in the field of environmental pollution control. In this paper, TiO2 surface heterojunction catalysts with different catalytic activity were prepared by controlling the amount of HF, and their XRD characterization was also carried out. In addition, the optimum amount of HF was determined by photocatalytic degradation of simulated dye wastewater by methylene blue solution. And the optimal amount of catalyst and the optimal pH reaction conditions for degradation experiments were used to screen the highly reactive titania surface heterojunction system and its optimum application conditions. It provides the possibility of application in the degradation of industrial wastewater and environmental treatment.

Rennin--a Neglected Enzyme?

ERIC Educational Resources Information Center

Gill, John; Saunders, Terry

1987-01-01

Presents investigations to explore the substrate specificity, pH, concentration, and temperature relations of an enzyme with only inexpensive commercial rennet and basic laboratory equipment. Describes how the activities were carried out with a group of 15-year-old students. (CW)

Electromembrane extraction of zwitterionic compounds as acid or base: comparison of extraction behavior at acidic and basic pHs.

PubMed

Nojavan, Saeed; Pourahadi, Ahmad; Hosseiny Davarani, Saied Saeed; Morteza-Najarian, Amin; Beigzadeh Abbassi, Mojtaba

2012-10-01

This study has performed on electromembrane extraction (EME) of some zwitterionic compounds based on their acidic and basic properties. High performance liquid chromatography (HPLC) equipped with UV detection was used for determination of model compounds. Cetirizine (CTZ) and mesalazine (MS) were chosen as model compounds, and each of them was extracted from acidic (as a cation) and basic (as an anion) sample solutions, separately. 1-Octanol and 2-nitrophenyl octylether (NPOE) were used as the common supported liquid membrane (SLM) solvents. EME parameters, such as extraction time, extraction voltage and pH of donor and acceptor solutions were studied in details for cationic and anionic forms of each model compound and obtained results for two ionic forms (cationic and anionic) of each compound were compared together. Results showed that zwitterionic compounds could be extracted in both cationic and anionic forms. Moreover, it was found that the extraction of anionic form of each model compound could be done in low voltages when 1-octanol was used as the SLM solvent. Results showed that charge type was not highly effective on the extraction efficiency of model compounds whereas the position of charge within the molecule was the key parameter. In optimized conditions, enrichment factors (EF) of 27-60 that corresponded to recoveries ranging from 39 to 86% were achieved. Copyright © 2012 Elsevier B.V. All rights reserved.

Effect of peach gum polysaccharides on quality changes of white shrimp.

PubMed

Yao, Xing-Cun; Chang, Cheng-Fei; Wu, Sheng-Jun

2015-01-01

Peach gum polysaccharides (PGPs) have both antibacterial and antioxidant activities. In this study, the retardation effect of the PGPs on the quality changes of white shrimp (Penaeus vannamei) during refrigerated storage was investigated. Shrimp samples were untreated with different concentrations of the PGPs solution and then they were stored under refrigerated conditions for 10 days. During refrigerated storage, shrimp samples were taken periodically and their total viable count, pH value, total volatile basic nitrogen, and overall acceptability score were evaluated. Compared to the control, treatment of the PGPs solution effectively retarded bacterial growth and pH changes, reduced total volatile basic nitrogen, and increased overall acceptability score of white shrimp (P. vannamei) during refrigerated storage. The results indicate that treatment of PGPs could be a promising means to preserve white shrimp (P. vannamei). Copyright © 2014 Elsevier B.V. All rights reserved.

Approach to method development and validation in capillary electrophoresis for enantiomeric purity testing of active basic pharmaceutical ingredients.

PubMed

Sokoliess, Torsten; Köller, Gerhard

2005-06-01

A chiral capillary electrophoresis system allowing the determination of the enantiomeric purity of an investigational new drug was developed using a generic method development approach for basic analytes. The method was optimized in terms of type and concentration of both cyclodextrin (CD) and electrolyte, buffer pH, temperature, voltage, and rinsing procedure. Optimal chiral separation of the analyte was obtained using an electrolyte with 2.5% carboxymethyl-beta-CD in 25 mM NaH2PO4 (pH 4.0). Interchanging the inlet and outlet vials after each run improved the method's precision. To assure the method's suitability for the control of enantiomeric impurities in pharmaceutical quality control, its specificity, linearity, precision, accuracy, and robustness were validated according to the requirements of the International Conference on Harmonization. The usefulness of our generic method development approach for the validation of robustness was demonstrated.

Charge heterogeneity: Basic antibody charge variants with increased binding to Fc receptors.

PubMed

Hintersteiner, Beate; Lingg, Nico; Zhang, Peiqing; Woen, Susanto; Hoi, Kong Meng; Stranner, Stefan; Wiederkum, Susanne; Mutschlechner, Oliver; Schuster, Manfred; Loibner, Hans; Jungbauer, Alois

We identified active isoforms of the chimeric anti-GD2 antibody, ch14.18, a recombinant antibody produced in Chinese hamster ovary cells, which is already used in clinical trials. 1,2,3 We separated the antibody by high resolution ion-exchange chromatography with linear pH gradient elution into acidic, main and basic charge variants on a preparative scale yielding enough material for an in-depth study of the sources and the effects of microheterogeneity. The binding affinity of the charge variants toward the antigen and various cell surface receptors was studied by Biacore. Effector functions were evaluated using cellular assays for antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. Basic charge variants showed increased binding to cell surface receptor FcγRIIIa, which plays a major role in regulating effector functions. Furthermore, increased binding of the basic fractions to the neonatal receptor was observed. As this receptor mediates the prolonged half-life of IgG in human serum, this data may well hint at an increased serum half-life of these basic variants compared to their more acidic counterparts. Different glycoform patterns, C-terminal lysine clipping and N-terminal pyroglutamate formation were identified as the main structural sources for the observed isoform pattern. Potential differences in structural stability between individual charge variant fractions by nano differential scanning calorimetry could not been detected. Our in-vitro data suggests that the connection between microheterogeneity and the biological activity of recombinant antibody therapeutics deserves more attention than commonly accepted.

Observations on the influence of water and soil pH on the persistence of insecticides.

PubMed

Chapman, R A; Cole, C M

1982-01-01

The pH-disappearance rate profiles were determined at ca. 25 degrees C for 24 insecticides at 4 or 5 pH values over the range 4.5 to 8.0 in sterile phosphate buffers prepared in water-ethanol (99:1 v/v). Half-lives measured at pH 8 were generally smaller than at lower pH values. Changes in half lives between pH 8.0 and 4.5 were largest (greater than 1000x) for the aryl carbamates, carbofuran and carbaryl, the oxime carbamate, oxamyl, and the organophosphorus insecticide, trichlorfon. In contrast, half lives of phorate, terbufos, heptachlor, fensulfothion and aldicarb were affected only slightly by pH changes. Under the experimental conditions described half lives at pH8 varied from 1-2 days for trichlorfon and oxamyl to greater than 1 year for fensulfothion and cypermethrin. Insecticide persistence on alumina (acid, neutral and basic), mineral soils amended with aluminum sulfate or calcium hydroxide to different pH values and four natural soils of different pH was examined. No correlation was observed between the measured pH of these solids and the rate of disappearance of selected insecticides applied to them. These observations demonstrate the difficulty of extrapolating the pH dependent disappearance behaviour observed in homogeneous solution to partially solid heterogeneous systems such as soil.

The potential influence of CO2, as an agent for euthanasia, on the pharmacokinetics of basic compounds in rodents.

PubMed

Angus, Derek W; Baker, James A; Mason, Rona; Martin, Iain J

2008-02-01

Rodent tissue distribution and pharmacokinetic studies were performed on basic compounds Org A and Org B in support of central nervous system drug discovery programs. A consistent observation from these studies was that drug concentrations in plasma obtained by cardiac puncture after CO(2) euthanasia were markedly higher compared with those from other sampling methods (serial sampling, isoflurane anesthesia, or cervical dislocation). Further investigations demonstrated that CO(2) euthanasia led to a reduction in blood pH in both rats and mice, which was not observed with the other sampling methods. The use of CO(2) euthanasia resulted in a decrease in the brain/plasma ratio of Org B, largely as a result of increased plasma concentrations. The pharmacokinetics of a basic drug, raloxifene, in rat were also influenced by sampling technique. CO(2) euthanasia before sampling, resulted in a 2- to 3-fold increase in the area under the drug concentration-time curve, a decrease in plasma clearance, and a decrease in the steady-state volume of distribution compared with isoflurane anesthesia. It is proposed that a decrease in the pH of blood relative to that of other tissues, as a consequence of CO(2) exposure, results in a redistribution of basic compounds out of the tissues, leading to higher concentrations in plasma.

[Courses in basic research methodology a valuable asset for clinicians. Twelve years' experiences in southern Sweden].

PubMed

Håkansson, Anders; Lindberg, Eva Pettersson; Henriksson, Karin

2002-03-07

At the Department of Community Medicine at Lund University we have given courses in basic research methodology since 1989. The course has yielded 20 points of university credit, the equivalent of one full-time semester of studies, and it has been run part-time, covering one and a half years. Our aim has been to provide a large number of physicians with basic training in research methods, and to stimulate the engagement of new scientific students from the whole Southern Health Care Region. During the first ten years, 138 general practitioners (20% of the GPs of the region) and 202 specialists completed our courses. Up till now, 19 GPs (14%) and 19 specialists (9%) have begun PhD studies. During the last two years, another 100 physicians from southern Sweden have attended our courses, as well as GPs from Zealand in Denmark. We have been developing our course in basic research methods during a twelve-year period, and it is now well established in our health care region. We feel that we have succeeded in reaching the two goals we had set up: to give a large number of physicians a fundamental knowledge of research methods and to recruit and increase the number of PhD students. We believe that medical research and development must flourish also outside the traditional university settings.

Treatment of waste water by coagulation and flocculation using biomaterials

NASA Astrophysics Data System (ADS)

Muruganandam, L.; Saravana Kumar, M. P.; Jena, Amarjit; Gulla, Sudiv; Godhwani, Bhagesh

2017-11-01

The present study deals with the determination of physical and chemical parameters in the treatment process of waste water by flocculation and coagulation processes using natural coagulants and assessing their feasibility for water treatment by comparing the performance with each other and with a synthetic coagulant. Initial studies were done on the synthetic waste water to determine the optimal pH and dosage, the activity of natural coagulant, followed by the real effluent from tannery waste. The raw tannery effluent was bluish-black in colour, mildly basic in nature, with high COD 4000mg/l and turbidity in the range 700NTU, was diluted and dosed with organic coagulants, AloeVera, MoringaOleifera and Cactus (O.ficus-indica). The study observed that coagulant Moringa Oleifera of 15 mg/L dose at 6 pH gave the best reduction efficiencies for major physicochemical parameters followed by Aloe Vera and Cactus under identical conditions. The study reveals that the untreated tannery effluents can be treated with environmental confirmative naturally occurring coagulants.

Aspects of the "Design Space" in high pressure liquid chromatography method development.

PubMed

Molnár, I; Rieger, H-J; Monks, K E

2010-05-07

The present paper describes a multifactorial optimization of 4 critical HPLC method parameters, i.e. gradient time (t(G)), temperature (T), pH and ternary composition (B(1):B(2)) based on 36 experiments. The effect of these experimental variables on critical resolution and selectivity was carried out in such a way as to systematically vary all four factors simultaneously. The basic element is a gradient time-temperature (t(G)-T) plane, which is repeated at three different pH's of the eluent A and at three different ternary compositions of eluent B between methanol and acetonitrile. The so-defined volume enables the investigation of the critical resolution for a part of the Design Space of a given sample. Further improvement of the analysis time, with conservation of the previously optimized selectivity, was possible by reducing the gradient time and increasing the flow rate. Multidimensional robust regions were successfully defined and graphically depicted. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Precipitation of ammonium from concentrated industrial wastes as struvite: a search for the optimal reagents.

PubMed

Borojovich, Eitan J C; Münster, Meshulam; Rafailov, Gennady; Porat, Ze'ev

2010-07-01

Precipitation of struvite (MgNH4PO4) is a known process for purification of wastewater from high concentrations of ammonium. The optimal conditions for precipitation are basic pH (around 9) and sufficient concentrations of magnesium and phosphate ions. In this work, we accomplished efficient precipitation of ammonium from concentrated industrial waste stream by using magnesium oxide (MgO) both as a source of magnesium ions and as a base. Best results were obtained with technical-grade MgO, which provided 99% removal of ammonium. Moreover, ammonium removal occurred already at pH 7, and the residual ammonium concentration (50 mg/L) remained constant upon addition of more MgO without rising again, as occurs with sodium hydroxide (NaOH). This process may have two other advantages; it also can be relevant for the problem of uncontrolled precipitation of struvite in the supernatant of anaerobic sludge treatment plants, and the precipitate can be used as a fertilizer.

Vacuum investment cast PH13-8Mo corrosion resistant steel. (SAE standard)

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

NONE

1991-07-01

An industry-wide interest has arisen with regards to the properties and capabilities of investment cast PH 13-8Mo corrosion resistant steel. Specifically of interest are the structural applications in the aerospace industry for this product heat treated to the H1000 condition. The objective of this AMEC cooperative test program was to generate and compile useful data for aerospace structural evaluation of investment cast PH 13-8Mo heat treated to H1000. The determination was made of overall mechanical properties, fatigue, fracture toughness, and crack growth data along with basic microstructural evaluation of the investment cast material. The evaluation of mechanical property variations betweenmore » cast and machined tensile specimens and evaluation of microstructural constituents. PH 13-8Mo, H1000 investment castings for use in the aerospace industry is included.« less

Adsorption of leather dyes on activated carbon from leather shaving wastes: kinetics, equilibrium and thermodynamics studies.

PubMed

Manera, Christian; Tonello, Andrezza Piroli; Perondi, Daniele; Godinho, Marcelo

2018-03-23

In this work, the adsorption of Acid Black 210 (AB210) and Acid Red 357 (AR357) onto activated carbon prepared from leather shaving wastes (ACLW) was investigated. The activated carbon presented a surface area of 800.4 m²/g with an average pore size of 1.27 nm. The kinetic study showed that the adsorption of both dyes followed the Elovich kinetic model while the AB210 and AR357 isotherm data were well described by the Langmuir and BET models, respectively. Furthermore, the Boyd plot revealed that the adsorption of the leather dyes on activated carbon was mainly governed by film diffusion. The pH had a strong influence on the adsorption, and the higher amounts of dye adsorbed were obtained at pH 2. The obtained activated carbon exhibited a high monolayer adsorption capacity of 573.9 and 204.4 mg/g for AB210 and AR357, respectively. Its high capacity is mainly attributed to its basicity (0.17 mmol/g) and high surface area. Desorption efficiency of the spent activated carbon was found to be 54.3% and 43.0% for AB210 and AR357, respectively. The spontaneity of the process was demonstrated by the negative values of the Gibbs free energy change.

Diagnostic Value of Vaginal Discharge, Wet Mount and Vaginal pH – An Update on the Basics of Gynecologic Infectiology

PubMed Central

Frobenius, W.; Bogdan, C.

2015-01-01

The majority of uncomplicated vulvovaginal complaints (e.g. bacterial vaginosis, vulvovaginal candidiasis, trichomoniasis) can be detected with uncomplicated basic infectiological tests and can usually be treated effectively without requiring further diagnostic procedures. Tests include measurement of vaginal pH, preparation and assessment of wet mount slides prepared from vaginal or cervical discharge, and the correct clinical and microbiological classification of findings. In Germany, at least in recent years, this has not been sufficiently taught or practiced. As new regulations on specialist gynecologic training in Germany are currently being drawn up, this overview provides basic information on gynecologic infectiology and summarizes clinically relevant aspects of recent microbiological findings on the physiology and pathology of vaginal flora. The clinical signs and symptoms of aerobic vaginitis, the pathogenesis of which is still not completely understood, are also reviewed. Finally, the symptoms, indications and risk factors for pelvic inflammatory disease (PID) are presented. In contrast to the above-listed infections, PID requires immediate culture of the pathogen from samples (e.g. obtained by laparoscopy) with microbiological diagnostic procedures carried out by specialist laboratories. A schematic summary of all pathologies discussed here is presented. PMID:26028693

Modulation of the partition coefficient between octanol and buffer at pH 7.4 and pKa to achieve the optimum balance of blood clearance and volume of distribution for a series of tetrahydropyran histamine type 3 receptor antagonists.

PubMed

Hay, Tanya; Jones, Rhys; Beaumont, Kevin; Kemp, Mark

2009-09-01

The relationship between rat pharmacokinetics and physicochemical parameters [the partition coefficient between octanol and buffer at pH 7.4 (log D((7.4))) and pK(a)] was studied for a series of tetrahydropyran compounds. Sixteen compounds ranging in log D((7.4)) 0.1 to 1.8 were administered intravenously to rats, and the pharmacokinetic parameters were determined from blood concentration time curves. Across the series, a weak correlation was observed between log D((7.4)) and blood clearance, suggesting that log D((7.4)) values less than 0.5 were required to prevent clearance at hepatic blood flow. In terms of the volume of distribution (V(d)), the compounds fell into three distinct subseries characterized by the number of basic centers and differences in ionization of each basic center at physiological pH. These were referred to as the monobasic, weak second base, and strong second base subseries. All the compounds exhibited V(d) greater than body water, as would be expected from their lipophilic and basic nature. For a given clog P, the strong second base subseries showed higher V(d) than the weak second base subseries, which in turn exhibited higher values than the monobasic subseries. In addition, for the weak second base subseries, V(d) could be tuned by modulating the pK(a) of the second basic center. This relationship was rationalized in respect to the interactions of the ionizable centers with phospholipid heads in the cell membrane and/or lysosomal trapping. Compounds in the weak second base subseries showed optimal V(d), and when combined with a log D((7.4)) of 0.1, driving to moderate blood clearance, one compound showed the optimal pharmacokinetic profile.

Formation of metal-nicotianamine complexes as affected by pH, ligand exchange with citrate and metal exchange. A study by electrospray ionization time-of-flight mass spectrometry.

PubMed

Rellán-Alvarez, Rubén; Abadía, Javier; Alvarez-Fernández, Ana

2008-05-01

Nicotianamine (NA) is considered as a key element in plant metal homeostasis. This non-proteinogenic amino acid has an optimal structure for chelation of metal ions, with six functional groups that allow octahedral coordination. The ability to chelate metals by NA is largely dependent on the pK of the resulting complex and the pH of the solution, with most metals being chelated at neutral or basic pH values. In silico calculations using pKa and pK values have predicted the occurrence of metal-NA complexes in plant fluids, but the use of soft ionization techniques (e.g. electrospray), together with high-resolution mass spectrometers (e.g. time-of-flight mass detector), can offer direct and metal-specific information on the speciation of NA in solution. We have used direct infusion electrospray ionization mass spectrometry (time-of-flight) ESI-MS(TOF) to study the complexation of Mn, Fe(II), Fe(III), Ni, Cu by NA. The pH dependence of the metal-NA complexes in ESI-MS was compared to that predicted in silico. Possible exchange reactions that may occur between Fe-NA and other metal micronutrients as Zn and Cu, as well as between Fe-NA and citrate, another possible Fe ligand candidate in plants, were studied at pH 5.5 and 7.5, values typical of the plant xylem and phloem saps. Metal-NA complexes were generally observed in the ESI-MS experiments at a pH value approximately 1-2 units lower than that predicted in silico, and this difference could be only partially explained by the estimated error, approximately 0.3 pH units, associated with measuring pH in organic solvent-containing solutions. Iron-NA complexes are less likely to participate in ligand- and metal-exchange reactions at pH 7.5 than at pH 5.5. Results support that NA may be the ligand chelating Fe at pH values usually found in phloem sap, whereas in the xylem sap NA is not likely to be involved in Fe transport, conversely to what occurs with other metals such as Cu and Ni. Some considerations that need to be addressed when studying metal complexes in plant compartments by ESI-MS are also discussed.

Efficient Electrocatalytic Water Oxidation at Neutral and High pH by Adventitious Nickel at Nanomolar Concentrations.

PubMed

Roger, Isolda; Symes, Mark D

2015-11-04

Electrolytic water oxidation using earth-abundant elements is a key challenge in the quest to develop cheap, large surface area arrays for solar-to-hydrogen conversion. There have been numerous studies in this area in recent years, but there remains an imperative to demonstrate that the current densities reported are indeed due to the species under consideration and not due to the presence of adventitious (yet possibly highly active) contaminants at low levels. Herein, we show that adventitious nickel at concentrations as low as 17 nM can act as a water oxidation catalyst in mildly basic aqueous solutions, achieving stable (tens of hours) current densities of 1 mA cm(-2) at overpotentials as low as 540 mV at pH 9.2 and 400 mV at pH 13. This nickel was not added to the electrolysis baths deliberately, but it was found to be present in the electrolytes as an impurity by ICP-MS. The presence of nickel on anodes from extended-time bulk electrolysis experiments was confirmed by XPS. In showing that such low levels of nickel can perform water oxidation at overpotentials comparable to many recently reported water oxidation catalysts, this work serves to raise the burden of proof required of new materials in this field: contamination by adventitious metal ions at trace loadings must be excluded as a possible cause of any observed water oxidation activity.

Influence of Sulfur Content on the Corrosion Resistance of 17-4PH Stainless Steel

NASA Astrophysics Data System (ADS)

Tavares, S. S. M.; Pardal, J. M.; Martins, T. R. B.; da Silva, M. R.

2017-04-01

According to specification standards, the basic chemical composition of steel 17-4PH for special and critical applications is 15-17% Cr, 3.0-5.0% Ni, 3.0-5.0% Cu, 0.07% C (max) and 0.15-0.45% (Nb + Ta) (wt.%). The maximum sulfur content is 0.030%. However, as it will be shown in this work, this maximum limit for sulfur is too high for services where high corrosion resistance is necessary. Two samples of 17-4PH steel with similar base compositions, but quite different sulfur contents (0.027% and 0.001%S), were compared with respect to pitting corrosion and sensitization. Both materials were heat treated according to commercial treatments A, H900, H1100, H1150 and H1150D (ASTM A-1082). Two corrosion tests were applied to compare the steels. The first one was the double-loop electrochemical potentiodynamic reactivation (DL-EPR) test in 0.25 M H2SO4 + 0.01 KSCN solution, which is used to measure the degree of sensitization. The second test was the anodic polarization in 3.5%NaCl solution, commonly used to evaluate the pitting corrosion resistance. Detailed microstructural characterization by magnetic measurements, light optical and scanning electron microscopy was performed. As main conclusion, despite that both steels have chemical compositions in accordance with the standards, the steel with higher sulfur was much more susceptible to pitting and sensitization.

Arsenic removal using steel manufacturing byproducts as permeable reactive materials in mine tailing containment systems.

PubMed

Ahn, Joo Sung; Chon, Chul-Min; Moon, Hi-Soo; Kim, Kyoung-Woong

2003-05-01

Steel manufacturing byproducts were tested as a means of treating mine tailing leachate with a high As concentration. Byproduct materials can be placed in situ as permeable reactive barriers to control the subsurface release of leachate from tailing containment systems. The tested materials had various compositions of elemental Fe, Fe oxides, Ca-Fe oxides and Ca hydroxides typical of different steel manufacturing processes. Among these materials, evaporation cooler dust (ECD), oxygen gas sludge (OGS), basic oxygen furnace slag (BOFS) and to a lesser degree, electrostatic precipitator dust (EPD) effectively removed both As(V) and As(III) during batch experiments. ECD, OGS and BOFS reduced As concentrations to <0.5mg/l from 25mg/l As(V) or As(III) solution in 72 h, exhibiting higher removal capacities than zero-valent iron. High Ca concentrations and alkaline conditions (pH ca. 12) provided by the dissolution of Ca hydroxides may promote the formation of stable, sparingly soluble Ca-As compounds. When initial pH conditions were adjusted to 4, As reduction was enhanced, probably by adsorption onto iron oxides. The elution rate of retained As from OGS and ECD decreased with treatment time, and increasing the residence time in a permeable barrier strategy would be beneficial for the immobilization of As. When applied to real tailing leachate, ECD was found to be the most efficient barrier material to increase pH and to remove As and dissolved metals.

77 FR 58854 - Office of the Director, National Institutes of Health; Notice of Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-24

... current understanding of the basic biology of the genital tract for HIV prevention. An update will be... Level, Suite T-500, Rockville, MD 20852. Contact Person: Robert Eisinger, Ph.D., Executive Secretary...

CuO-Functionalized Silicon Photoanodes for Photoelectrochemical Water Splitting Devices.

PubMed

Shi, Yuanyuan; Gimbert-Suriñach, Carolina; Han, Tingting; Berardi, Serena; Lanza, Mario; Llobet, Antoni

2016-01-13

One main difficulty for the technological development of photoelectrochemical (PEC) water splitting (WS) devices is the fabrication of active, stable and cost-effective photoelectrodes that ensure high performance. Here, we report the development of a CuO/Silicon based photoanode, which shows an onset potential for the water oxidation of 0.53 V vs SCE at pH 9, that is, an overpotential of 75 mV, and high stability above 10 h. These values account for a photovoltage of 420 mV due to the absorbed photons by silicon, as proven by comparing with analogous CuO/FTO electrodes that are not photoactive. The photoanodes have been fabricated by sputtering a thin film of Cu(0) on commercially available n-type Si wafers, followed by a photoelectrochemical treatment in basic pH conditions. The resulting CuO/Cu layer acts as (1) protective layer to avoid the corrosion of nSi, (2) p-type hole conducting layer for efficient charge separation and transportation, and (3) electrocatalyst to reduce the overpotential of the water oxidation reaction. The low cost, low toxicity, and good performance of CuO-based coatings can be an attractive solution to functionalize unstable materials for solar energy conversion.

Aerobic Oxidation of Xylose to Xylaric acid in Water over Pt Catalysts.

PubMed

Saha, Basudeb; Sadula, Sunitha

2018-05-02

Energy-efficient catalytic conversion of biomass intermediates to functional chemicals can enable bio-products viable. Herein, we report an efficient and low temperature aerobic oxidation of xylose to xylaric acid, a promising bio-based chemical for the production of glutaric acid, over commercial catalysts in water. Among several heterogeneous catalysts investigated, Pt/C exhibits the best activity. Systematic variation of reaction parameters in the pH range of 2.5 to 10 suggests that the reaction is fast at higher temperatures but high C-C scission of intermediate C5-oxidized products to low carbon carboxylic acids undermines xylaric acid selectivity. The C-C cleavage is also high in basic solution. The oxidation at neutral pH and 60 C achieves the highest xylaric acid yield (64%). O2 pressure and Pt-amount have significant influence on the reactivity. Decarboxylation of short chain carboxylic acids results in formation of CO2, causing some carbon loss; however such decarboxylation is slow in the presence of xylose. The catalyst retained comparable activity, in terms of product selectivity, after five cycles with no sign of Pt leaching. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemistry and Photochemistry of Anthocyanins and Related Compounds: A Thermodynamic and Kinetic Approach.

PubMed

Basílio, Nuno; Pina, Fernando

2016-11-10

Anthocyanins are identified by the respective flavylium cation, which is only one species of a multistate of different molecules reversibly interconverted by external inputs such as pH, light and temperature. The flavylium cation (acidic form) is involved in an apparent acid-base reaction, where the basic species is the sum of quinoidal base, hemiketal and cis - and trans -chalcones, their relative fraction depending on the substitution pattern of the flavylium cation. The full comprehension of this complex system requires a thermodynamic and kinetic approach. The first consists in drawing an energy level diagram where the relative positions of the different species are represented as a function of pH. On the other hand, the kinetic approach allows measuring the rates of the reactions that interconnect reversibly the multistate species. The kinetics is greatly dependent on the existence or not of a high cis - trans isomerization barrier. In this work, the procedure to obtain the energy level diagram and the rates of inter-conversion in the multistate in both cases (low or high isomerization barrier) are described. Practical examples of this approach are presented to illustrate the theory, and recently reported applications based on host-guest complexes are reviewed.

Sorption Behavior of Dye Compounds onto Natural Sediment of Qinghe River.

PubMed

Liu, Ruixia; Liu, Xingmin; Tang, Hongxiao; Su, Yongbo

2001-07-15

The objective of this study is to assess the adsorption behavior of C.I. Basic Yellow X-5GL, C.I. Basic Red 13, C.I. Direct Blue 86, C.I. Vat Yellow 2, and C.I. Mordant Black 11 on natural sediment and to identify sediment characteristics that play a predominant role in the adsorption of the dyes. The potentiometric titration experiment is used to investigate acid-base properties of the sediment surface with a constant capacitance surface complexation model. The parameters controlling the sorption such as solution pH and ion strength, as well as the influence of organic carbon and Ca(2+) ion on the adsorption, are evaluated. It is shown that the titration data can be successfully described by the surface protonation and deprotonation model with the least-squares FITEQL program 2.0. The sorption isotherm data are fitted to the Freundlich equation in a nonlinear form (1/n=0.3-0.9) for all tested dyes. With increasing pH value, the sorption of C.I. Mordant Black 11 and C.I. Direct Blue 86 on the sediment decreases, while for C.I. Basic Yellow X-5GL and C.I. Basic Red 13, the extent of sorption slightly increases. In addition, ion strength also exhibits a considerably different effect on the sorption behavior of these dye compounds. The addition of Ca(2+) can greatly reduce the sorption of C.I. Basic Red 13 on the sediment surface, while it enhances the sorption of C.I. Direct Blue 6. The removal of organic carbon decreases the sorption of C.I. Mordant Black 11 and C.I. Direct Blue 86. In contrast, the sorption of C.I. Basic Red 13 and C.I. Basic Yellow X-5GL is obviously enhanced after the removal of organic carbon. The differences in adsorption behavior are mainly attributed to the physicochemical properties of these dye compounds. Copyright 2001 Academic Press.

ZnMoO4:Er3+,Yb3+ phosphor with controlled morphology and enhanced upconversion through alkali ions doping

NASA Astrophysics Data System (ADS)

Luitel, Hom Nath; Chand, Rumi; Watari, Takanori

2018-04-01

A facile hydrothermal method was used to synthesize ZnMoO4:Er3+,Yb3+ nanoparticles. The shapes and sizes of the nanoparticles were well tuned by simply monitoring the pH of the starting solution. Microballs consisting of agglomerated nanograins were observed at strong acidic condition. At mild pH, plates and rectangular particles were realized, while strong basic pH stabilized rods. Further increasing pH to extremely basic conditions (pH > 13), rods changed to fragile hairy structures. The nucleation and growth mechanism of nanograins to form different morphology nanoparticles were studied and illustrated. XRD patterns confirmed well crystalline, triclinic structure despite small amount of aliovalent metal ions doping. Under 980 nm excitation, the ZnMoO4:Er3+,Yb3+ nanophosphor exhibited strong green (centered at 530 and 560 nm) and weak red (centered at 660 nm) upconversion (UC) emissions. Substitution of part of the Zn2+ ions by monovalent alkali ions intensified the UC emission intensities drastically. The order of intensification was K+>Na+>Li+>Rb+>no alkali ion. When Zn2+ ions were substituted with 10 at% K+ ions, the green and red UC emissions intensities increased by more than 50 and 15 folds, respectively. Time dependent measurements confirmed efficient Yb to Er energy transfer in the ZnMoO4:Er3+,Yb3+,K+ nanophosphor. The optimized ZnMoO4:Er3+,Yb3+,K+ phosphor exhibited intense UC emissions with 0.31% quantum yield. The upconverted light is visible to naked eye while pumping by laser of less than 1 mW power and opens door for variety of novel applications.

Interactions between stepwise-eluted sub-fractions of fulvic acids and protons revealed by fluorescence titration combined with EEM-PARAFAC.

PubMed

Song, Fanhao; Wu, Fengchang; Guo, Fei; Wang, Hao; Feng, Weiying; Zhou, Min; Deng, Yanghui; Bai, Yingchen; Xing, Baoshan; Giesy, John P

2017-12-15

In aquatic environments, pH can control environmental behaviors of fulvic acid (FA) via regulating hydrolysis of functional groups. Sub-fractions of FA, eluted using pyrophosphate buffers with initial pHs of 3.0 (FA 3 ), 5.0 (FA 5 ), 7.0 (FA 7 ), 9.0 (FA 9 ) and 13.0 (FA 13 ), were used to explore interactions between the various, operationally defined, FA fractions and protons, by use of EEM-PARAFAC analysis. Splitting of peaks (FA 3 and FA 13 ), merging of peaks (FA 7 ), disappearance of peaks (FA 9 and FA 13 ), and red/blue-shifting of peaks were observed during fluorescence titration. Fulvic-like components were identified from FA 3 -FA 13 , and protein-like components were observed in fractions FA 9 and FA 13 . There primary compounds (carboxylic-like, phenolic-like, and protein-like chromophores) in PARAFAC components were distinguished based on acid-base properties. Dissociation constants (pK a ) for fulvic-like components with proton ranged from 2.43 to 4.13 in an acidic pH and from 9.95 to 11.27 at basic pH. These results might be due to protonation of di-carboxylate and phenolic functional groups. At basic pH, pK a values of protein-like components (9.77-10.13) were similar to those of amino acids. However, at acidic pH, pK a values of protein-like components, which ranged from 3.33 to 4.22, were 1-2units greater than those of amino acids. Results presented here, will benefit understanding of environmental behaviors of FA, as well as interactions of FA with environmental contaminants. Copyright © 2017 Elsevier B.V. All rights reserved.

The Growth Advantage in Stationary-Phase Phenotype Conferred by rpoS Mutations Is Dependent on the pH and Nutrient Environment

PubMed Central

Farrell, Michael J.; Finkel, Steven E.

2003-01-01

Escherichia coli cells that are aged in batch culture display an increased fitness referred to as the growth advantage in stationary phase, or GASP, phenotype. A common early adaptation to this culture environment is a mutant rpoS allele, such as rpoS819, that results in attenuated RpoS activity. However, it is important to note that during long-term batch culture, environmental conditions are in flux. To date, most studies of the GASP phenotype have focused on identifying alleles that render an advantage in a specific environment, Luria-Bertani broth (LB) batch culture. To determine what role environmental conditions play in rendering relative fitness advantages to E. coli cells carrying either the wild-type or rpoS819 alleles, we performed competitions under a variety of culture conditions in which either the available nutrients, the pH, or both were manipulated. In LB medium, we found that while the rpoS819 allele confers a strong competitive fitness advantage at basic pH, it confers a reduced advantage under neutral conditions, and it is disadvantageous under acidic conditions. Similar results were found using other media. rpoS819 conferred its greatest advantage in basic minimal medium in which either glucose or Casamino Acids were the sole source of carbon and energy. In acidic medium supplemented with either Casamino Acids or glucose, the wild-type allele conferred a slight advantage. In addition, populations were dynamic under all pH conditions tested, with neither the wild-type nor mutant rpoS alleles sweeping a culture. We also found that the strength of the fitness advantage gained during a 10-day incubation is pH dependent. PMID:14645263

Structural and surface functionality changes in reticulated vitreous carbon produced from poly(furfuryl alcohol) with sodium hydroxide additions

NASA Astrophysics Data System (ADS)

Oishi, Silvia Sizuka; Botelho, Edson Cocchieri; Rezende, Mirabel Cerqueira; Ferreira, Neidenêi Gomes

2017-02-01

The use of sodium hydroxide to neutralize the acid catalyst increases the storage life of poly(furfuryl alcohol) (PFA) resin avoiding its continuous polymerization. In this work, a concentrated sodium hydroxide solution (NaOH) was added directly to the PFA resin in order to minimize the production of wastes generated when PFA is washed with diluted basic solution. Thus, different amounts of this concentrated basic solution were added to the resin up to reaching pH values of around 3, 5, 7, and 9. From these four types of modified PFA two sample sets of reticulated vitreous carbon (RVC) were processed and heat treated at two different temperatures (1000 and 1700 °C). A correlation among cross-link density of PFA and RVC morphology, structural ordering and surface functionalities was systematically studied using Fourier transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy techniques. The PFA neutralization (pH 7) led to its higher polymerization degree, promoting a crystallinity decrease on RVC treated at 1000 °C as well as its highest percentages of carboxylic groups on surface. A NaOH excess (pH 9) substantially increased the RVC oxygen content, but its crystallinity remained similar to those for samples from pH 3 and 5 treated at 1000 °C, probably due to the reduced presence of carboxylic group and the lower polymerization degree of its cured resin. Samples with pH 3 and 5 heat treated at 1000 and 1700 °C can be considered the most ordered which indicated that small quantities of NaOH may be advantageous to minimize continuous polymerization of PFA resin increasing its storage life and improving RVC microstructure.

Transient removal of proflavine inhibition of bovine beta-trypsin by the bovine basic pancreatic trypsin inhibitor (Kunitz). A case for "chronosteric effects".

PubMed

Antonini, E; Ascenzi, P; Bolognesi, M; Menegatti, E; Guarneri, M

1983-04-25

The formation of the bovine beta-trypsin-bovine basic pancreatic trypsin inhibitor (Kunitz) (BPTI) complex was monitored, making use of three different signals: proflavine displacement, optical density changes in the ultraviolet region, and the loss of the catalytic activity. The rates of the reactions indicated by the three different signals were similar at neutral pH, but diverged at low pH. At pH 3.50, proflavine displacement precedes the optical density changes in the ultraviolet and the loss of enzyme activity by several orders of magnitude in time (Antonini, E., Ascenzi, P., Menegatti, E., and Guarneri, M. (1983) Biopolymers 22, 363-375). These data indicated that the bovine beta-trypsin-BPTI complex formation is a multistage process and led to the prediction that, at pH 3.50, BPTI addition to the bovine beta-trypsin-proflavine complex would remove proflavine inhibition and the enzyme would recover transiently its catalytic activity before being irreversibly inhibited by completion of BPTI binding. The kinetic evidences, by completion of BPTI binding. The kinetic evidences, here shown, verified this prediction, indicating that during the bovine beta-trypsin-BPTI complex formation one transient intermediate occurs, which is not able to bind proflavine but may bind and hydrolyze the substrate. Thus, the observed peculiar catalytic behavior is in line with the proposed reaction mechanism for the bovine beta-trypsin-BPTI complex formation, which postulates a sequence of distinct polar and apolar interactions at the contact area.

Acid-induced exchange of the imino proton in G.C pairs.

PubMed Central

Nonin, S; Leroy, J L; Gueron, M

1996-01-01

Acid-induced catalysis of imino proton exchange in G.C pairs of DNA duplexes is surprisingly fast, being nearly as fast as for the isolated nucleoside, despite base-pair dissociation constants in the range of 10(-5) at neutral or basic pH. It is also observed in terminal G.C pairs of duplexes and in base pairs of drug-DNA complexes. We have measured imino proton exchange in deoxyguanosine and in the duplex (ATATAGATCTATAT) as a function of pH. We show that acid-induced exchange can be assigned to proton transfer from N7-protonated guanosine to cytidine in the open state of the pair. This is faster than transfer from neutral guanosine (the process of intrinsic catalysis previously characterized at neutral ph) due to the lower imino proton pK of the protonated form, 7.2 instead of 9.4. Other interpretations are excluded by a study of exchange catalysis by formiate and cytidine as exchange catalysts. The cross-over pH between the regimes of pH-independent and acid-induced exchange rates is more basic in the case of base pairs than in the mononucleoside, suggestive of an increase by one to two decades in the dissociation constant of the base pair upon N7 protonation of G. Acid-induced catalysis is much weaker in A.T base pairs, as expected in view of the low pK for protonation of thymidine. PMID:8604298

Acid-induced exchange of the imino proton in G.C pairs.

PubMed

Nonin, S; Leroy, J L; Gueron, M

1996-02-15

Acid-induced catalysis of imino proton exchange in G.C pairs of DNA duplexes is surprisingly fast, being nearly as fast as for the isolated nucleoside, despite base-pair dissociation constants in the range of 10(-5) at neutral or basic pH. It is also observed in terminal G.C pairs of duplexes and in base pairs of drug-DNA complexes. We have measured imino proton exchange in deoxyguanosine and in the duplex (ATATAGATCTATAT) as a function of pH. We show that acid-induced exchange can be assigned to proton transfer from N7-protonated guanosine to cytidine in the open state of the pair. This is faster than transfer from neutral guanosine (the process of intrinsic catalysis previously characterized at neutral ph) due to the lower imino proton pK of the protonated form, 7.2 instead of 9.4. Other interpretations are excluded by a study of exchange catalysis by formiate and cytidine as exchange catalysts. The cross-over pH between the regimes of pH-independent and acid-induced exchange rates is more basic in the case of base pairs than in the mononucleoside, suggestive of an increase by one to two decades in the dissociation constant of the base pair upon N7 protonation of G. Acid-induced catalysis is much weaker in A.T base pairs, as expected in view of the low pK for protonation of thymidine.

Multifunctional PHPMA-Derived Polymer for Ratiometric pH Sensing, Fluorescence Imaging, and Magnetic Resonance Imaging.

PubMed

Su, Fengyu; Agarwal, Shubhangi; Pan, Tingting; Qiao, Yuan; Zhang, Liqiang; Shi, Zhengwei; Kong, Xiangxing; Day, Kevin; Chen, Meiwan; Meldrum, Deirdre; Kodibagkar, Vikram D; Tian, Yanqing

2018-01-17

In this paper, we report synthesis and characterization of a novel multimodality (MRI/fluorescence) probe for pH sensing and imaging. A multifunctional polymer was derived from poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) and integrated with a naphthalimide-based-ratiometric fluorescence probe and a gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complex (Gd-DOTA complex). The polymer was characterized using UV-vis absorption spectrophotometry, fluorescence spectrofluorophotometry, magnetic resonance imaging (MRI), and confocal microscopy for optical and MRI-based pH sensing and cellular imaging. In vitro labeling of macrophage J774 and esophageal CP-A cell lines shows the polymer's ability to be internalized in the cells. The transverse relaxation time (T 2 ) of the polymer was observed to be pH-dependent, whereas the spin-lattice relaxation time (T 1 ) was not. The pH probe in the polymer shows a strong fluorescence-based ratiometric pH response with emission window changes, exhibiting blue emission under acidic conditions and green emission under basic conditions, respectively. This study provides new materials with multimodalities for pH sensing and imaging.

Structural phase transition at high temperatures in solid molecular hydrogen and deuterium

NASA Astrophysics Data System (ADS)

Cui, T.; Takada, Y.; Cui, Q.; Ma, Y.; Zou, G.

2001-07-01

We study the effect of temperature up to 1000 K on the structure of dense molecular para-hydrogen (p-H2) and ortho-deuterium (o-D2), using the path-integral Monte Carlo method. We find a structural phase transition from orientationally disordered hexagonal close packed (hcp) to an orthorhombic structure of Cmca symmetry before melting. The transition is basically induced by thermal fluctuations, but quantum fluctuations of protons (deuterons) are important in determining the transition temperature through effectively hardening the intermolecular interaction. We estimate the phase line between hcp and Cmca phases as well as the melting line of the Cmca solid.

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

Wang, Kecheng; Feng, Dawei; Liu, Tian-Fu

A series of mesoporous metalloporphyrin Fe-MOFs, namely PCN-600(M) (M = Mn, Fe, Co, Ni, Cu), have been synthesized using the preassembled [Fe3O(OOCCH3)6] building block. PCN-600 exhibits a one-dimensional channel as large as 3.1 nm and the highest experimental pore volume of 1.80 cm3g–1 among all the reported porphyrinic MOFs. It also shows very high stability in aqueous solutions with pH values ranging from 2–11 and is to our knowledge the only mesoporous porphyrinic MOF stable under basic aqueous conditions. PCN-600(Fe) has been demonstrated as an effective peroxidase mimic to catalyze the co-oxidation reaction.

Effects of copper source and concentration on in vitro phytate phosphorus hydrolysis by phytase.

PubMed

Pang, Yanfang; Applegate, Todd J

2006-03-08

Five copper (Cu) sources were studied at pH 2.5, 5.5, and 6.5 to determine how Cu affects phytate phosphorus (PP) hydrolysis by phytase at concentrations up to 500 mg/kg diet (60 min, 40-41 degrees C). Subsequently, Cu solubility with and without sodium phytate was measured. Adding Cu inhibited PP hydrolysis at pH 5.5 and pH 6.5 (P < 0.05). This inhibition was greater with higher concentrations of Cu. Tri-basic copper chloride and copper lysinate inhibited PP hydrolysis much less than copper sulfate pentahydrate, copper chloride, and copper citrate (P < 0.05). A strong negative relationship was observed between PP hydrolysis and soluble Cu at pH 5.5 (r = -0.76, P < 0.0001) and 6.5 (r = -0.54, P < 0.0001). In conclusion, pH, Cu concentration, and source influenced PP hydrolysis by phytase in vitro and were related to the amount of soluble Cu and the formation of insoluble copper-phytin complexes.

Water chemistry of the secondary circuit at a nuclear power station with a VVER power reactor

NASA Astrophysics Data System (ADS)

Tyapkov, V. F.; Erpyleva, S. F.

2017-05-01

Results of implementation of the secondary circuit organic amine water chemistry at Russian nuclear power plant (NPP) with VVER-1000 reactors are presented. The requirements for improving the reliability, safety, and efficiency of NPPs and for prolonging the service life of main equipment items necessitate the implementation of new technologies, such as new water chemistries. Data are analyzed on the chemical control of power unit coolant for quality after the changeover to operation with the feed of higher amines, such as morpholine and ethanolamine. Power units having equipment containing copper alloy components were converted from the all-volatile water chemistry to the ethanolamine or morpholine water chemistry with no increase in pH of the steam generator feedwater. This enables the iron content in the steam generator feedwater to be decreased from 6-12 to 2.0-2.5 μg/dm3. It is demonstrated that pH of high-temperature water is among the basic factors controlling erosion and corrosion wear of the piping and the ingress of corrosion products into NPP steam generators. For NPP power units having equipment whose construction material does not include copper alloys, the water chemistries with elevated pH of the secondary coolant are adopted. Stable dosing of correction chemicals at these power units maintains pH25 of 9.5 to 9.7 in the steam generator feedwater with a maximum iron content of 2 μg/dm3 in the steam generator feedwater.

Improvement of drug loading onto ion exchange resin by cyclodextrin inclusion complex.

PubMed

Samprasit, Wipada; Rojanarata, Theerasak; Akkaramongkolporn, Prasert; Ngawhirunpat, Tanasait; Sila-on, Warisada; Opanasopit, Praneet

2013-11-01

Ion exchange resins have ability to exchange their counter ions for ionized drug in the surrounding medium, yielding "drug resin complex." Cyclodextrin can be applied for enhancement of drug solubility and stability. Cyclodextrin inclusion complex of poorly water-soluble NSAIDs, i.e. meloxicam and piroxicam, was characterized and its novel application for improving drug loading onto an anionic exchange resin, i.e. Dowex® 1×2, was investigated. β-Cyclodextrin (β-CD) and hydroxypropyl β-cyclodextrin (HP-β-CD) were used for the preparation of inclusion complex with drugs in solution state at various pH. The inclusion complex was characterized by phase solubility, continuous variation, spectroscopic and electrochemistry methods. Then, the drug with and without cyclodextrin were equilibrated with resin at 1:1 and 1:2 weight ratio of drug and resin. Solubility of the drugs was found to increase with increasing cyclodextrin concentration and pH. The increased solubility was explained predominantly due to the formation of inclusion complex at low pH and the increased ionization of drug at high pH. According to characterization studies, the inclusion complex was successfully formed with a 1:1 stoichiometry. The presence of cyclodextrin in the loading solution resulted in the improvement of drug loading onto resin. Enhancing drug loading onto ion-exchange resin via the formation of cyclodextrin inclusion complex is usable in the development of ion-exchange based drug delivery systems, which will beneficially reduce the use of harmful acidic or basic and organic chemicals.

Flue gas adsorption on periodic mesoporous phenylene-silica: a DFT approach.

PubMed

Lourenço, Mirtha A O; Ferreira, Paula; Gomes, José R B

2018-06-20

Periodic mesoporous organosilicas (PMOs) were suggested as potential adsorbents for CO2/CH4 separation because of their large affinities towards CO2 and low interaction with CH4. Herewith, we present a comprehensive computational study on the binding properties of flue gas species with the pore walls of periodic mesoporous phenylene-silica (Ph-PMO) for understanding the possible impact of other gaseous species in the CO2/CH4 separation. The calculations considered three exchange-correlation functionals (PBE, PBE-D2 and M06-2X) based on the density functional theory and the walls of the periodic mesoporous phenylene-silica were modelled within the cluster model approach. The components of the flue gas considered were the diatomic CO, H2, N2, O2 and NO molecules, the triatomic CO2, H2O, H2S and SO2 species, the tetratomic SO3 and NH3 gases and the pentatomic CH4 molecule. The calculated data demonstrate that the presence of H2O, SO2, NH3, H2S and SO3 is a significant threat to CO2 capture by Ph-PMO and suggest that the Ph-PMO material would present high selectivity for CO2 over CH4, CO, H2 or N2 adsorption. The adsorption behaviour of flue gas components in Ph-PMO can be directly related to the experimental proton affinities, basicities or even the polarizabilities of the gaseous molecules.

UV/TiO₂ photocatalytic oxidation of recalcitrant organic matter: effect of salinity and pH.

PubMed

Muthukumaran, Shobha; Song, Lili; Zhu, Bo; Myat, Darli; Chen, Jin-Yuan; Gray, Stephen; Duke, Mikel

2014-01-01

Photocatalytic oxidation processes have interest for water treatment since these processes can remove recalcitrant organic compounds and operate at mild conditions of temperature and pressure. However, performance under saline conditions present in many water resources is not well known. This study aims to explore the basic effects of photocatalysis on the removal of organic matter in the presence of salt. A laboratory-scale photocatalytic reactor system, employing ultraviolet (UV)/titanium dioxide (TiO₂) photocatalysis was evaluated for its ability to remove the humic acid (HA) from saline water. The particle size and zeta potential of TiO₂ under different conditions including solution pH and sodium chloride (NaCl) concentrations were characterized. The overall degradation of organics over the NaCl concentration range of 500-2,000 mg/L was found to be 80% of the non-saline equivalent after 180 min of the treatment. The results demonstrated that the adsorption of HA onto the TiO₂ particles was dependent on both the pH and salinity due to electrostatic interaction and highly unstable agglomerated dispersion. This result supports UV/TiO₂ as a viable means to remove organic compounds, but the presence of salt in waters to be treated will influence the performance of the photocatalytic oxidation process.

A review on applicability of naturally available adsorbents for the removal of hazardous dyes from aqueous waste.

PubMed

Sharma, Pankaj; Kaur, Harleen; Sharma, Monika; Sahore, Vishal

2011-12-01

The effluent water of many industries, such as textiles, leather, paper, printing, cosmetics, etc., contains large amount of hazardous dyes. There is huge number of treatment processes as well as adsorbent which are available for the processing of this effluent water-containing dye content. The applicability of naturally available low cast and eco-friendly adsorbents, for the removal of hazardous dyes from aqueous waste by adsorption treatment, has been reviewed. In this review paper, we have provided a compiled list of low-cost, easily available, safe to handle, and easy-to-dispose-off adsorbents. These adsorbents have been classified into five different categories on the basis of their state of availability: (1) waste materials from agriculture and industry, (2) fruit waste, (3) plant waste, (4) natural inorganic materials, and (5) bioadsorbents. Some of the treated adsorbents have shown good adsorption capacities for methylene blue, congo red, crystal violet, rhodamine B, basic red, etc., but this adsorption process is highly pH dependent, and the pH of the medium plays an important role in the treatment process. Thus, in this review paper, we have made some efforts to discuss the role of pH in the treatment of wastewater.

Roles of pH and the Na+/H+ exchanger NHE1 in cancer: From cell biology and animal models to an emerging translational perspective?

PubMed

Stock, Christian; Pedersen, Stine Falsig

2017-04-01

Acidosis is characteristic of the solid tumor microenvironment. Tumor cells, because they are highly proliferative and anabolic, have greatly elevated metabolic acid production. To sustain a normal cytosolic pH homeostasis they therefore need to either extrude excess protons or to neutralize them by importing HCO 3 - , in both cases causing extracellular acidification in the poorly perfused tissue microenvironment. The Na + /H + exchanger isoform 1 (NHE1) is a ubiquitously expressed acid-extruding membrane transport protein, and upregulation of its expression and/or activity is commonly correlated with tumor malignancy. The present review discusses current evidence on how altered pH homeostasis, and in particular NHE1, contributes to tumor cell motility, invasion, proliferation, and growth and facilitates evasion of chemotherapeutic cell death. We summarize data from in vitro studies, 2D-, 3D- and organotypic cell culture, animal models and human tissue, which collectively point to pH-regulation in general, and NHE1 in particular, as potential targets in combination chemotherapy. Finally, we discuss the possible pitfalls, side effects and cellular escape mechanisms that need to be considered in the process of translating the plethora of basic research data into a clinical setting. Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

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.

Physico-chemical changes of ZnO nanoparticles with different size and surface chemistry under physiological pH conditions.

PubMed

Gwak, Gyeong-Hyeon; Lee, Won-Jae; Paek, Seung-Min; Oh, Jae-Min

2015-03-01

We studied the physico-chemical properties of ZnO nanoparticles under physiological pH conditions (gastric, intestinal and plasma) as functions of their size (20 and 70 nm) and surface chemistry (pristine, L-serine, or citrate coating). ZnO nanoparticles were dispersed in phosphate buffered saline under physiological pH conditions and aliquots were collected at specific time points (0.5, 1, 4, 10 and 24 h) for further characterization. The pH values of the aqueous ZnO colloids at each condition were in the neutral to slightly basic range and showed different patterns depending on the original size and surface chemistry of the ZnO nanoparticles. The gastric pH condition was found to significantly dissolve ZnO nanoparticles up to 18-30 wt%, while the intestinal or plasma pH conditions resulted in much lower dissolution amounts than expected. Based on the X-ray diffraction patterns and X-ray absorption spectra, we identified partial phase transition of the ZnO nanoparticles from wurtzite to Zn(OH)2 under the intestinal and plasma pH conditions. Using scanning electron microscopy, we verified that the overall particle size and morphology of all ZnO nanoparticles were maintained regardless of the pH. Copyright © 2015 Elsevier B.V. All rights reserved.

Optimizing isothiocyanate formation during enzymatic glucosinolate breakdown by adjusting pH value, temperature and dilution in Brassica vegetables and Arabidopsis thaliana

NASA Astrophysics Data System (ADS)

Hanschen, Franziska S.; Klopsch, Rebecca; Oliviero, Teresa; Schreiner, Monika; Verkerk, Ruud; Dekker, Matthijs

2017-01-01

Consumption of glucosinolate-rich Brassicales vegetables is associated with a decreased risk of cancer with enzymatic hydrolysis of glucosinolates playing a key role. However, formation of health-promoting isothiocyanates is inhibited by the epithiospecifier protein in favour of nitriles and epithionitriles. Domestic processing conditions, such as changes in pH value, temperature or dilution, might also affect isothiocyanate formation. Therefore, the influences of these three factors were evaluated in accessions of Brassica rapa, Brassica oleracea, and Arabidopsis thaliana. Mathematical modelling was performed to determine optimal isothiocyanate formation conditions and to obtain knowledge on the kinetics of the reactions. At 22 °C and endogenous plant pH, nearly all investigated plants formed nitriles and epithionitriles instead of health-promoting isothiocyanates. Response surface models, however, clearly demonstrated that upon change in pH to domestic acidic (pH 4) or basic pH values (pH 8), isothiocyanate formation considerably increases. While temperature also affects this process, the pH value has the greatest impact. Further, a kinetic model showed that isothiocyanate formation strongly increases due to dilution. Finally, the results show that isothiocyanate intake can be strongly increased by optimizing the conditions of preparation of Brassicales vegetables.

Proteorhodopsin Photocycle Kinetics Between pH 5 and pH 9.

PubMed

Köhler, Thomas; Weber, Ingrid; Glaubitz, Clemens; Wachtveitl, Josef

2017-05-01

The retinal protein proteorhodopsin is a homolog of the well-characterized light-driven proton pump bacteriorhodopsin. Basic mechanisms of proton transport seem to be conserved, but there are noticeable differences in the pH ranges of proton transport. Proton transport and protonation state of a carboxylic acid side chain, the primary proton acceptor, are correlated. In case of proteorhodopsin, the pK a of the primary proton acceptor Asp-97 (pK a  ≈ 7.5) is unexpectedly close to environmental pH (pH ≈ 8). A significant fraction of proteorhodopsin is possibly inactive at natural pH, in contrast to bacteriorhodopsin. We investigated photoinduced kinetics of proteorhodopsin between pH 5 and pH 9 by time resolved UV/vis absorption spectroscopy. Kinetics is inhomogeneous within that pH region and can be considered as a superposition of two fractions. These fractions are correlated with the Asp-97 titration curve. Beside Asp-97, protonation equilibria of other groups influence kinetics, but the observations do not point toward major differences of primary proton acceptor function in proteorhodopsin and bacteriorhodopsin. The pK a of proteorhodopsin and some of its variants is suspected to be an example of molecular adaptation to the physiology of the original organisms. © 2017 The American Society of Photobiology.

Spatial patterns of soil pH and the factors that influence them in plantation forests of northern China

NASA Astrophysics Data System (ADS)

Hong, Songbai; Liu, Yongwen; Piao, Shilong

2017-04-01

Climate and anthropogenic activities such as afforestation and nitrogen deposition all impact soil pH. Understanding the spatial pattern of soil pH and the factors that influence it can provide basic information for generating appropriate strategies for soil resource management and protection, especially in light of increasing anthropogenic influences and climate change. In this study, we investigated the spatial and vertical pattern of soil pH and evaluated the influence of climate and nitrogen deposition using 1647 soil profiles 1 meter in depth from 549 plots in plantation forests of northern China. We found that soil pH decreased from the southwest to the northeast in the study region and had a similar spatial pattern before and after afforestation. Furthermore, our results show that climate and nitrogen deposition fundamentally influence the pattern of soil pH. Specifically, increasing precipitation significantly decreased soil pH (with a mean rate of 0.3 for every 100 mm rainfall, p<0.001), whereas increasing temperature significantly increased soil pH (0.13 for every degree centigrade, p<0.001). Nitrogen deposition, especially nitrate nitrogen, significantly decreased soil pH (p<0.01). All these factors impact soil pH directly and indirectly through climate-plant-soil interactions. As the risks from both climate change and nitrogen deposition increase, there is an urgent need to further understanding of soil pH dynamics and to develop informed policies to protect soil resources.

Two-Level factorial screening of new plasmid/strain combinations for prodution of recombinant-DNA products.

PubMed

Emborg, C; Jepsen, P K; Biedermann, K

1989-05-01

This article treats the basic problem of selection of experimental conditions for microbiological experiments for evaluation of newly isolated bacterial strains, mutants, or plasmid/strain combinations. For this purpose shake flask experiments in a 2(10-4)confounded factorial design at resolution IV with four blocks of 16 flasks were used. The design was used for testing of two new strain/plasmid combinations (E. coli MT 102/403-SD2 and W 3110/403-SD2) i.e., both strains with the same plasmid 403-SD2. Both strains were integrated in the design, so both strains were tested with nine factors (temperature, aeration, glucose, initial pH, pH regulation, reduced aeration, chloramphenicol, acetate, and glycerol). With both strains the interaction between initial pH and reduced aeration had a significant influence on the yield of the recombinant-DNA product nuclease. There was more than a factor of 10 between lowest and highest yield of product. In this interactive system the strains reacted differently. MT 102/403-SD2 had highest yields at high initial pH (8.4) and no reduction in aeration, whereas W 3110/403-SD2 had highest yields of nuclease at low initial pH (7.4) and reduced aeration (rubber stopper inserted after cultivation for 12 h). These data (and previous work) clearly demonstrate that it is impossible to suggest a simple set of experimental conditions for testing of new plasmid/strain combinations. It is clear that the exclusive application of a standardized growth technique e.g., LB-medium at 37 degrees C at an unspecified and uncontrolled aeration level, may lead to wrong conclusions on properties and potentials of now plasmid/strain combinations and may lead to rejection of useful strains or plasmids.

Effect of the electrostatic surface potential on the oligomerization of full-length human recombinant prion protein at single-molecule level

NASA Astrophysics Data System (ADS)

Wang, Bin; Lou, Zhichao; Zhang, Haiqian; Xu, Bingqian

2016-03-01

The electrostatic surface potential (ESP) of prion oligomers has critical influences on the aggregating processes of the prion molecules. The atomic force microscopy (AFM) and structural simulation were combined to investigate the molecular basis of the full-length human recombinant prion oligomerization on mica surfaces. The high resolution non-intrusive AFM images showed that the prion oligomers formed different patterns on mica surfaces at different buffer pH values. The basic binding units for the large oligomers were determined to be prion momoners (Ms), dimers (Ds), and trimers (Ts). The forming of the D and T units happened through the binding of hydrophobic β-sheets of the M units. In contrast, the α-helices of these M, D, and T units were the binding areas for the formation of large oligomers. At pH 4.5, the binding units M, D, and T showed clear polarized ESP distributions on the surface domains, while at pH 7.0, they showed more evenly distributed ESPs. Based on the conformations of oligomers observed from AFM images, the D and T units were more abundantly on mica surface at pH 4.5 because the ESP re-distribution of M units helped to stabilize these larger oligomers. The amino acid side chains involved in the binding interfaces were stabilized by hydrogen bonds and electrostatic interactions. The detailed analysis of the charged side chains at pH 4.5 indicated that the polarized ESPs induced the aggregations among M, D, and T to form larger oligomers. Therefore, the hydrogen bonds and electrostatic interactions worked together to form the stabilized prion oligomers.

Effect of the electrostatic surface potential on the oligomerization of full-length human recombinant prion protein at single-molecule level

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

Wang, Bin; Xu, Bingqian, E-mail: bxu@engr.uga.edu; Lou, Zhichao

2016-03-21

The electrostatic surface potential (ESP) of prion oligomers has critical influences on the aggregating processes of the prion molecules. The atomic force microscopy (AFM) and structural simulation were combined to investigate the molecular basis of the full-length human recombinant prion oligomerization on mica surfaces. The high resolution non-intrusive AFM images showed that the prion oligomers formed different patterns on mica surfaces at different buffer pH values. The basic binding units for the large oligomers were determined to be prion momoners (Ms), dimers (Ds), and trimers (Ts). The forming of the D and T units happened through the binding of hydrophobicmore » β-sheets of the M units. In contrast, the α-helices of these M, D, and T units were the binding areas for the formation of large oligomers. At pH 4.5, the binding units M, D, and T showed clear polarized ESP distributions on the surface domains, while at pH 7.0, they showed more evenly distributed ESPs. Based on the conformations of oligomers observed from AFM images, the D and T units were more abundantly on mica surface at pH 4.5 because the ESP re-distribution of M units helped to stabilize these larger oligomers. The amino acid side chains involved in the binding interfaces were stabilized by hydrogen bonds and electrostatic interactions. The detailed analysis of the charged side chains at pH 4.5 indicated that the polarized ESPs induced the aggregations among M, D, and T to form larger oligomers. Therefore, the hydrogen bonds and electrostatic interactions worked together to form the stabilized prion oligomers.« less

The pH ruler: a Java applet for developing interactive exercises on acids and bases.

PubMed

Barrette-Ng, Isabelle H

2011-07-01

In introductory biochemistry courses, it is often a struggle to teach the basic concepts of acid-base chemistry in a manner that is relevant to biological systems. To help students gain a more intuitive and visual understanding of abstract acid-base concepts, a simple graphical construct called the pH ruler Java applet was developed. The applet allows students to visualize the abundance of different protonation states of diprotic and triprotic amino acids at different pH values. Using the applet, the student can drag a widget on a slider bar to change the pH and observe in real time changes in the abundance of different ionization states of this amino acid. This tool provides a means for developing more complex inquiry-based, active-learning exercises to teach more advanced topics of biochemistry, such as protein purification, protein structure and enzyme mechanism.

Hydrothermal Reactivity of Amines

NASA Astrophysics Data System (ADS)

Robinson, K.; Shock, E.; Hartnett, H. E.; Williams, L. B.; Gould, I.

2013-12-01

The reactivity of aqueous amines depends on temperature, pH, and redox state [1], all of which are highly variable in hydrothermal systems. Temperature and pH affect the ratio of protonated to unprotonated amines (R-NH2 + H+ = R-NH3+), which act as nucleophiles and electrophiles, respectively. We hypothesize that this dual nature can explain the pH dependence of reaction rates, and predict that rates will approach a maximum at pH = pKa where the ratio of protonated and unprotonated amines approaches one and the two compounds are poised to react with one another. Higher temperatures in hydrothermal systems allow for more rapid reaction rates, readily reversible reactions, and unique carbon-nitrogen chemistry in which water acts as a reagent in addition to being the solvent. In this study, aqueous benzylamine was used as a model compound to explore the reaction mechanisms, kinetics, and equilibria of amines under hydrothermal conditions. Experiments were carried out in anoxic silica glass tubes at 250°C (Psat) using phosphate-buffered solutions to observe changes in reaction rates and product distributions as a function of pH. The rate of decomposition of benzylamine was much faster at pH 4 than at pH 9, consistent with the prediction that benzylamine acts as both nucleophile and an electrophile, and our estimate that the pKa of benzylamine is ~5 at 250°C and Psat. Accordingly, dibenzylamine is the primary product of the reaction of two benzylamine molecules, and this reaction is readily reversible under hydrothermal conditions. Extremely acidic or basic pH can be used to suppress dibenzylamine production, which also suppresses the formation of all other major products, including toluene, benzyl alcohol, dibenzylimine, and tribenzylamine. This suggests that dibenzylamine is the lone primary product that then itself reacts as a precursor to produce the above compounds. Analog experiments performed with ring-substituted benzylamine derivatives and chiral methylbenzylamine suggest an SN2 mechanism for the formation of dibenzylamine. These results show the interdependence of pH and speciation with amine reaction rates. We predict the distribution of primary, secondary, tertiary, and quaternary amines in hydrothermal solutions can be used to solve for the pH of subsurface reaction zones in hydrothermal systems. [1] McCollom, T.M. (2013) The influence of minerals on decomposition of the n-alkyl-α-amino acid norvaline under hydrothermal conditions. Geochim. Cosmochim. Acta, 104, 330-357.

Chemical evolution. XXIX - Pyrimidines from hydrogen cyanide

NASA Technical Reports Server (NTRS)

Ferris, J. P.; Joshi, P. C.; Lawless, J. G.

1978-01-01

Compounds obtained by hydrolysis of HCN oligomers formed by allowing pH 9.2, 0.1 M cyanide to stand at room temperature for 4 to 12 months were analyzed. Hydrolysis of HCN oligomers yielded 4,5-dihydroxypyrimidine and 5-hydroxyuracil; orotic acid was detected after hydrolysis at pH 8.5. A unified pathway from diaminofumaronitrile to the pyrimidines observed is suggested. As purines, pyrimidines and amino acids are released by hydrolysis of HCN oligomers in either acidic or mildly basic aqueous solutions, they could have been formed on the primitive earth in spite of fluctuations in pH. 4,5-dihydroxypyrimidines appear to be likely candidates for incorporation into primitive nucleic acids, as they should undergo Watson-Crick hydrogen bonding with adenine.

Flocculation of Turbid Water Using Polyferric-Based Composite Coagulant

NASA Astrophysics Data System (ADS)

Tan, K. H.; Lai, S. H.

2017-06-01

The flocculation of turbid water using polyferric chloride-polydimethyldiallylammonium chloride (PFC-PDMDAAC) has been studied. Effect of preparation parameters basicity ratio (B ratio) of PFC and PDMDAAC/PFC ratio and operating parameters pH and dosage were investigated. PFC-PDMDAAC displayed maximum turbidity removal of 94.8% at 4.0mg/L when B=0.5 and PDMDAAC/PFC ratio = 7%. The best turbidity removal efficiencies by PFC-PDMDAAC were 84.7% at pH 7.5. These results reveal that PFC-PDMDAAC is efficient for flocculation of turbid water.

Efficient degradation of sulfamethazine in simulated and real wastewater at slightly basic pH values using Co-SAM-SCS /H2O2 Fenton-like system.

PubMed

Cheng, Min; Zeng, Guangming; Huang, Danlian; Lai, Cui; Liu, Yang; Zhang, Chen; Wan, Jia; Hu, Liang; Zhou, Chengyun; Xiong, Weiping

2018-07-01

The presence of antibiotics in aquatic environments has attracted global concern. Fenton process is an attractive yet challenging method for antibiotics degradation, especially when such a reaction can be conducted at neutral pH values. In this study, a novel composite Fe/Co catalyst was synthesized via the modification of steel converter slag (SCS) by salicylic acid-methanol (SAM) and cobalt nitrate (Co(NO 3 ) 2 ). The catalysts were characterized by N 2 -Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results indicated that the Co-SAM-SCS/H 2 O 2 Fenton-like system was very effective for sulfamethazine (SMZ) degradation at a wide pH range. At initial pH of 7.0, the degradation rate of SMZ in Co-SAM-SCS/H 2 O 2 system was 2.48, 3.20, 6.18, and 16.21 times of that in Fe-SAM-SCS/H 2 O 2 , SAM-SCS/H 2 O 2 , Co(NO 3 ) 2 /H 2 O 2 and SCS/H 2 O 2 system, respectively. The preliminary analysis suggested that high surface area of Co-SAM-SCS sample and synergistic effect between introduced Co and SAM-SCS are responsible for the efficient catalytic activity. During the degradation, three main intermediates were identified by high performance liquid chromatography-mass spectrometry (HPLC-MS) analysis. Based on this, a possible degradation pathway was proposed. The SEM images, XRD patterns and XPS spectra before and after the reactions demonstrate that the crystal and chemical structure of Co-SAM-SCS after five cycles are almost unchanged. Besides, the Co-SAM-SCS presented low iron and cobalt leaching (0.17 mg/L and 2.36 mg/L, respectively). The studied Fenton-like process also showed high degradation of SMZ in river water and municipal wastewater. The progress will bring valuable insights to develop high-performance heterogeneous Fenton-like catalysts for environmental remediation. Copyright © 2018 Elsevier Ltd. All rights reserved.

Label-Free Carbon-Dots-Based Ratiometric Fluorescence pH Nanoprobes for Intracellular pH Sensing.

PubMed

Shangguan, Jingfang; He, Dinggeng; He, Xiaoxiao; Wang, Kemin; Xu, Fengzhou; Liu, Jinquan; Tang, Jinlu; Yang, Xue; Huang, Jin

2016-08-02

Measuring pH in living cells is of great importance for better understanding cellular functions as well as providing pivotal assistance for early diagnosis of diseases. In this work, we report the first use of a novel kind of label-free carbon dots for intracellular ratiometric fluorescence pH sensing. By simple one-pot hydrothermal treatment of citric acid and basic fuchsin, the carbon dots showing dual emission bands at 475 and 545 nm under single-wavelength excitation were synthesized. It is demonstrated that the fluorescence intensities of the as-synthesized carbon dots at the two emissions are pH-sensitive simultaneously. The intensity ratio (I475 nm/I545 nm) is linear against pH values from 5.2 to 8.8 in buffer solution, affording the capability as ratiometric probes for intracellular pH sensing. It also displays that the carbon dots show excellent reversibility and photostability in pH measurements. With this nanoprobe, quantitative fluorescence imaging using the ratio of two emissions (I475 nm/I545 nm) for the detection of intracellular pH were successfully applied in HeLa cells. In contrast to most of the reported nanomaterials-based ratiometric pH sensors which rely on the attachment of additional dyes, these carbon-dots-based ratiometric probes are low in toxicity, easy to synthesize, and free from labels.

Introduction to Instrumental Analysis of Water Pollutants. Training Manual.

ERIC Educational Resources Information Center

Office of Water Program Operations (EPA), Cincinnati, OH. National Training and Operational Technology Center.

This course is designed for those requiring an introduction to instruments commonly used in water pollution analyses. Examples are: pH, conductivity, dissolved oxygen meters, spectrophotometers, turbidimeters, carbon analyzer, and gas chromatographs. Students should have a basic knowledge of analytical chemistry. (CO)

Charge heterogeneity: Basic antibody charge variants with increased binding to Fc receptors

PubMed Central

Hintersteiner, Beate; Lingg, Nico; Zhang, Peiqing; Woen, Susanto; Hoi, Kong Meng; Stranner, Stefan; Wiederkum, Susanne; Mutschlechner, Oliver; Schuster, Manfred; Loibner, Hans; Jungbauer, Alois

2016-01-01

ABSTRACT We identified active isoforms of the chimeric anti-GD2 antibody, ch14.18, a recombinant antibody produced in Chinese hamster ovary cells, which is already used in clinical trials.1,2,3 We separated the antibody by high resolution ion-exchange chromatography with linear pH gradient elution into acidic, main and basic charge variants on a preparative scale yielding enough material for an in-depth study of the sources and the effects of microheterogeneity. The binding affinity of the charge variants toward the antigen and various cell surface receptors was studied by Biacore. Effector functions were evaluated using cellular assays for antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. Basic charge variants showed increased binding to cell surface receptor FcγRIIIa, which plays a major role in regulating effector functions. Furthermore, increased binding of the basic fractions to the neonatal receptor was observed. As this receptor mediates the prolonged half-life of IgG in human serum, this data may well hint at an increased serum half-life of these basic variants compared to their more acidic counterparts. Different glycoform patterns, C-terminal lysine clipping and N-terminal pyroglutamate formation were identified as the main structural sources for the observed isoform pattern. Potential differences in structural stability between individual charge variant fractions by nano differential scanning calorimetry could not been detected. Our in-vitro data suggests that the connection between microheterogeneity and the biological activity of recombinant antibody therapeutics deserves more attention than commonly accepted. PMID:27559765

Acid-base responses to feeding and intestinal Cl- uptake in freshwater- and seawater-acclimated killifish, Fundulus heteroclitus, an agastric euryhaline teleost.

PubMed

Wood, Chris M; Bucking, Carol; Grosell, Martin

2010-08-01

Marine teleosts generally secrete basic equivalents (HCO(3)(-)) and take up Na(+) and Cl(-) in the intestine so as to promote absorption of H(2)O. However, neither the integration of these functions with feeding nor the potential role of the gut in ionoregulation and acid-base balance in freshwater have been well studied. The euryhaline killifish (Fundulus heteroclitus) is unusual in lacking both an acid-secreting stomach and a mechanism for Cl(-) uptake at the gills in freshwater. Responses to a satiation meal were evaluated in both freshwater- and seawater-acclimated killifish. In intact animals, there was no change in acid or base flux to the external water after the meal, in accord with the absence of any post-prandial alkaline tide in the blood. Indeed, freshwater animals exhibited a post-prandial metabolic acidosis ('acidic tide'), whereas seawater animals showed no change in blood acid-base status. In vitro gut sac experiments revealed a substantially higher rate of Cl(-) absorption by the intestine in freshwater killifish, which was greatest at 1-3 h after feeding. The Cl(-) concentration of the absorbate was higher in preparations from freshwater animals than from seawater killifish and increased with fasting. Surprisingly, net basic equivalent secretion rates were also much higher in preparations from freshwater animals, in accord with the 'acidic tide'; in seawater preparations, they were lowest after feeding and increased with fasting. Bafilomycin (1 micromol l(-1)) promoted an 80% increase in net base secretion rates, as well as in Cl(-) and fluid absorption, at 1-3 h post-feeding in seawater preparations only, explaining the difference between freshwater and seawater fish. Preparations from seawater animals at 1-3 h post-feeding also acidified the mucosal saline, and this effect was associated with a marked rise in P(CO(2)), which was attenuated by bafilomycin. Measurements of chyme pH from intact animals confirmed that intestinal fluid (chyme) pH and basic equivalent concentration were lowest after feeding in seawater killifish, whereas P(CO(2)) was greatly elevated (80-95 Torr) in chyme from both seawater and freshwater animals but declined to lower levels (13 Torr) after 1-2 weeks fasting. There were no differences in pH, P(CO(2)) or the concentrations of basic equivalents in intestinal fluid from seawater versus freshwater animals at 12-24 h or 1-2 weeks post-feeding. The results are interpreted in terms of the absence of gastric HCl secretion, the limitations of the gills for acid-base balance and Cl(-) transport, and therefore the need for intestinal Cl(-) uptake in freshwater killifish, and the potential for O(2) release from the mucosal blood flow by the high P(CO(2)) in the intestinal fluids. At least in seawater killifish, H(+)-ATPase running in parallel to HCO(3)(-):Cl(-) exchange in the apical membranes of teleost enterocytes might reduce net base secretion and explain the high P(CO(2)) in the chyme after feeding.

The effects of electrolysis on operational solutions in electromembrane extraction: The role of acceptor solution.

PubMed

Kubáň, Pavel; Boček, Petr

2015-06-12

Fundamental operational principle and instrumental set-up of electromembrane extraction (EME) suggest that electrolysis may play an important role in this recently developed micro-extraction technique. In the present study, the effect of electrolysis in EME is described comprehensively for the first time and it is demonstrated that electrolysis considerably influences EME performance. Micro-electromembrane extraction (μ-EME) across free liquid membrane formed by 1-pentanol was utilized for real-time monitoring of the electrolytically induced changes in composition of μ-EME solutions. These changes were visualized with a set of acid-base indicators. Changes in colours of their aqueous solutions revealed serious variations in their pH values, which occurred within seconds to minutes of the μ-EME process. Variations of up to eight pH units were observed for indicator solutions initially prepared in 1, 5 and 10mM hydrochloric acid. No or only negligible pH changes (less than 0.15 pH unit) were observed for indicator solutions prepared in 50 and 100mM acetic acid demonstrating that initial composition of the aqueous solutions was the crucial parameter. These results were also confirmed by theoretical calculations of maximum pH variations in the solutions, which were based on total electric charge transfers measured in the μ-EME systems, and by exact measurements of their pH values after μ-EMEs. Acceptor solutions that, in the current practice, consist predominantly of low concentrations of strong mineral acids or alkali hydroxides may thus not always ensure adequate EME performance, which was manifested by decrease in extraction recoveries of a basic drug papaverine. A suitable remedy to the observed effects is the application of acceptor solutions containing high concentrations of weak acids or bases. These solutions not only eliminate the decrease in recoveries but also serve well as matrices of extracted samples for subsequent analysis by capillary electrophoresis. Copyright © 2015 Elsevier B.V. All rights reserved.

Chem I Supplement: Emphasis on Acids and Bases

ERIC Educational Resources Information Center

Journal of Chemical Education Staff

1977-01-01

Provides supplementary notes on acids and bases suitable for secondary school chemistry instruction, including acidity in solid and natural waters, acidity balance in body chemistry, acid and basic foods, pH values of common fluids, examples of drugs, and commercial preparation of nitric acid. (SL)

pH dependence of the properties of waterborne pressure-sensitive adhesives containing acrylic acid.

PubMed

Wang, Tao; Canetta, Elisabetta; Weerakkody, Tecla G; Keddie, Joseph L; Rivas, Urko

2009-03-01

Polymer colloids are often copolymerized with acrylic acid monomers in order to impart colloidal stability. Here, the effects of the pH on the nanoscale and macroscopic adhesive properties of waterborne poly(butyl acrylate-co-acrylic acid) films are reported. In films cast from acidic colloidal dispersions, hydrogen bonding between carboxylic acid groups dominates the particle-particle interactions, whereas ionic dipolar interactions are dominant in films cast from basic dispersions. Force spectroscopy using an atomic force microscope and macroscale mechanical measurements show that latex films with hydrogen-bonding interactions have lower elastic moduli and are more deformable. They yield higher adhesion energies. On the other hand, in basic latex, ionic dipolar interactions increase the moduli of the dried films. These materials are stiffer and less deformable and, consequently, exhibit lower adhesion energies. The rate of water loss from acidic latex is slower, perhaps because of hydrogen bonding with the water. Therefore, although acid latex offers greater adhesion, there is a limitation in the film formation.

Capillary electrophoretic enantioseparation of basic drugs using a new single-isomer cyclodextrin derivative and theoretical study of the chiral recognition mechanism.

PubMed

Liu, Yongjing; Deng, Miaoduo; Yu, Jia; Jiang, Zhen; Guo, Xingjie

2016-05-01

A novel single-isomer cyclodextrin derivative, heptakis {2,6-di-O-[3-(1,3-dicarboxyl propylamino)-2-hydroxypropyl]}-β-cyclodextrin (glutamic acid-β-cyclodextrin) was synthesized and used as a chiral selector in capillary electrophoresis for the enantioseparation of 12 basic drugs, including terbutaline, clorprenaline, tulobuterol, clenbuterol, procaterol, carvedilol, econazole, miconazole, homatropine methyl bromide, brompheniramine, chlorpheniramine and pheniramine. The primary factors affecting separation efficiency, which include the background electrolyte pH, the concentration of glutamic acid-β-cyclodextrin and phosphate buffer concentration, were investigated. Satisfactory enantioseparations were obtained using an uncoated fused-silica capillary of 50 cm (effective length 40 cm) × 50 μm id with 120 mM phosphate buffer (pH 2.5-4.0) containing 0.5-4.5 mM glutamic acid-β-cyclodextrin as background electrolyte. A voltage of 20 kV was applied and the capillary temperature was kept at 20°C. The results proved that glutamic acid-β-cyclodextrin was an effective chiral selector for studied 12 basic drugs. Moreover, the possible chiral recognition mechanism of brompheniramine, chlorpheniramine and pheniramine on glutamic acid-β-cyclodextrin was investigated using the semi-empirical Parametric Method 3. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optimizing pKa computation in proteins with pH adapted conformations.

PubMed

Kieseritzky, Gernot; Knapp, Ernst-Walter

2008-05-15

pK(A) in proteins are determined by electrostatic energy computations using a small number of optimized protein conformations derived from crystal structures. In these protein conformations hydrogen positions and geometries of salt bridges on the protein surface were determined self-consistently with the protonation pattern at three pHs (low, ambient, and high). Considering salt bridges at protein surfaces is most relevant, since they open at low and high pH. In the absence of these conformational changes, computed pK(A)(comp) of acidic (basic) groups in salt bridges underestimate (overestimate) experimental pK(A)(exp), dramatically. The pK(A)(comp) for 15 different proteins with 185 known pK(A)(exp) yield an RMSD of 1.12, comparable with two other methods. One of these methods is fully empirical with many adjustable parameters. The other is also based on electrostatic energy computations using many non-optimized side chain conformers but employs larger dielectric constants at short distances of charge pairs that diminish their electrostatic interactions. These empirical corrections that account implicitly for additional conformational flexibility were needed to describe the energetics of salt bridges appropriately. This is not needed in the present approach. The RMSD of the present approach improves if one considers only strongly shifted pK(A)(exp) in contrast to the other methods under these conditions. Our method allows interpreting pK(A)(comp) in terms of pH dependent hydrogen bonding pattern and salt bridge geometries. A web service is provided to perform pK(A) computations. 2007 Wiley-Liss, Inc.

Status of soil acidification in North America

USGS Publications Warehouse

Fenn, M.E.; Huntington, T.G.; Mclaughlin, S.B.; Eagar, C.; Gomez, A.; Cook, R.B.

2006-01-01

Forest soil acidification and depletion of nutrient cations have been reported for several forested regions in North America, predominantly in the eastern United States, including the northeast and in the central Appalachians, but also in parts of southeastern Canada and the southern U.S. Continuing regional inputs of nitrogen and sulfur are of concern because of leaching of base cations, increased availability of soil Al, and the accumulation and ultimate transmission of acidity from forest soils to streams. Losses of calcium from forest soils and forested watersheds have now been documented as a sensitive early indicator and a functionally significant response to acid deposition for a wide range of forest soils in North America. For red spruce, a clear link has been established between acidic deposition, alterations in calcium and aluminum supplies and increased sensitivity to winter injury. Cation depletion appears to contribute to sugar maple decline on some soils, specifically the high mortality rates observed in northern Pennsylvania over the last decade. While responses to liming have not been systematically examined in North America, in a study in Pennsylvania, restoring basic cations through liming increased basal area growth of sugar maple and levels of calcium and magnesium in soil and foliage. In the San Bernardino Mountains in southern California near the west coast, the pH of the A horizon has declined by at least 2 pH units (to pH 4.0-4.3) over the past 30 years, with no detrimental effects on bole growth; presumably, because of the Mediterranean climate, base cation pools are still high and not limiting for plant growth.

Smart packaging for the monitoring of fish freshness

NASA Astrophysics Data System (ADS)

Pacquit, Alexis; Lau, King Tong; Diamond, Dermot

2005-06-01

The development of chromo-reactive sensor spots for real time monitoring of fish freshness is described. The on-package sensor spots incorporating an immobilized pH sensitive dye, respond through visible colour change to basic volatile spoilage compounds collectively known as Total Volatile Basic Nitrogen (TVB-N). Trials on fresh fish filets have verified that the sensor can be employed for real time monitoring of fish spoilage. The sensor response can be interrogated with a simple, inexpensive reflectance colorimeter that we have developed based on two LEDs and a photodetector.

A streamlined isolation method and the autoxidation profiles of tuna myoglobin.

PubMed

Nurilmala, Mala; Ushio, Hideki; Watabe, Shugo; Ochiai, Yoshihiro

2018-05-01

Determination of the redox state of myoglobin (Mb) gives useful information for evaluating the quality of tuna meat. To attain this purpose, a fast streamlined method has been established basically based on preparative native gel electrophoresis to isolate Mb from the dark muscle of Pacific bluefin tuna. Crude Mb fraction was prepared from dark muscle by ammonium sulfate saturation fractionation and subsequently Mb was purified by preparative native gel electrophoresis under the isoelectric pH of the Mb, resulting in absorption (or trapping) of all the contaminating proteins in the gel. Purified Mb was converted to oxy form with a trace amount of sodium hydrosulfite, and subsequently dialyzed against 50 mM sodium citrate (pH 5.6) or 50 mM sodium phosphate (pH 6.5). The purified tuna Mb was examined for the temperature and pH dependencies of autoxidation using horse Mb as a reference. Tuna Mb was oxidized 2.5-3 times faster than horse Mb irrespective of the pH conditions examined. The highest autoxidation rates both at 0 and 37 °C were observed at pH 5.6. These data were comparable to those obtained for Mbs isolated by conventional chromatographic methods.

Aggregation and metal-complexation behaviour of THPP porphyrin in ethanol/water solutions as function of pH

NASA Astrophysics Data System (ADS)

Zannotti, Marco; Giovannetti, Rita; Minofar, Babak; Řeha, David; Plačková, Lydie; D'Amato, Chiara A.; Rommozzi, Elena; Dudko, Hanna V.; Kari, Nuerguli; Minicucci, Marco

2018-03-01

The effect of pH change on 5,10,15,20-Tetrakis(4-hydroxyphenyl)-21H,23H-porphine (THPP) with its aggregation as function of water-ethanol mixture was studied with UV-vis, fluorescence, Raman and computational analysis. In neutral pH, THPP was present as free-base and, increasing the water amount, aggregation occurred with the formation of H- and J-aggregates. The aggregation constant and the concentration of dimers were calculated, other information about the dimer aggregation were evaluated by computational study. In acidic pH, by the insertions of two hydrogens in the porphyrin rings, the porphyrin changed its geometry with a ring deformation confirmed by red-shifted spectrum and quenching in fluorescence; at this low pH, increasing the water amount, the acidic form (THPPH2)2 + resulted more stable due to a polar environment with stronger interaction by hydrogen bonding. In basic pH, reached by NH4OH, THPP porphyrin was able to react with alkali metals in order to form sitting-atop complex (M2THPP) confirmed by the typical absorption spectrum of metallo-porphyrin, Raman spectroscopy and by computational analysis.

Structure of the S. aureus PI-specific phospholipase C reveals modulation of active site access by a titratable π-cation latched loop†

PubMed Central

Goldstein, Rebecca; Cheng, Jiongjia; Stec, Boguslaw; Roberts, Mary F.

2012-01-01

Staphylococcus aureus secretes a phosphatidylinositol-specific phospholipase C (PIPLC) as a virulence factor that is unusual in exhibiting higher activity at acidic pH values than other enzymes in this class. We have determined the crystal structure of this enzyme at pH 4.6 and pH 7.5. Under slightly basic conditions, the S. aureus PI-PLC structure closely follows the conformation of other bacterial PI-PLCs. However, when crystallized under acidic conditions, a large section of mobile loop at the αβ-barrel rim in the vicinity of the active site shows ~10 Å shift. This loop displacement at acidic pH is the result of a titratable intramolecular π-cation interaction between His258 and Phe249. This was verified by a structure of the mutant protein H258Y crystallized at pH 4.6, which does not exhibit the large loop shift. The intramolecular π-cation interaction for S. aureus PI-PLC provides an explanation for the activity of the enzyme at acid pH and also suggests how phosphatidylcholine, as a competitor for Phe249, may kinetically activate this enzyme. PMID:22390775

Influence of pH on Drug Absorption from the Gastrointestinal Tract: A Simple Chemical Model

NASA Astrophysics Data System (ADS)

Hickman, Raymond J. S.; Neill, Jane

1997-07-01

A simple model of the gastrointestinal tract is obtained by placing ethyl acetate in contact with water at pH 2 and pH 8 in separate test tubes. The ethyl acetate corresponds to the lipid material lining the tract while the water corresponds to the aqueous contents of the stomach (pH 2) and intestine (pH 8). The compounds aspirin, paracetamol and 3-aminophenol are used as exemplars of acidic, neutral and basic drugs respectively to illustrate the influence which pH has on the distribution of each class of drug between the aqueous and organic phases of the model. The relative concentration of drug in the ethyl acetate is judged by applying microlitre-sized samples of ethyl acetate to a layer of fluorescent silica which, after evaporation of the ethyl acetate, is viewed under an ultraviolet lamp. Each of the three drugs, if present in the ethyl acetate, becomes visible as a dark spot on the silica layer. The observations made in the model system correspond well to the patterns of drug absorption from the gastrointestinal tract described in pharmacology texts and these observations are convincingly explained in terms of simple acid-base chemistry.

Chitosan capped nanoscale Fe-MIL-88B-NH2 metal-organic framework as drug carrier material for the pH responsive delivery of doxorubicin

NASA Astrophysics Data System (ADS)

Sivakumar, P.; Priyatharshni, S.; Nagashanmugam, K. B.; Thanigaivelan, A.; Kumar, K.

2017-08-01

In recent years nanoscale metal-organic frameworks (NMOFs) are contributing as an effective material for use in drug delivery and imaging applications due to their porous surfaces and easy surface modifications. In this work, Fe-MIL-88B-NH2 NMOFs were successfully synthesized on facile hydrothermal route and 2-aminoterephthalic acid (NH2-BDC) was employed as a bridging ligand to activate amine functional groups on the surface. Amine functional groups not only serve as a structure stabilizing agent but also enhance the loading efficiency of the doxorubicin (DOX) anticancer drug. A pH responsive DOX release was realized by introducing a positively charged chitosan (Chi) capping layer. Upon Chi-coating, cleavage was observed in the Fe-MIL-88B-NH2 structure at acidic pH, while gel-like insoluble structure was formed at basic pH. By utilizing this phenomenon, a pH responsive DOX release system was developed by using Chi capped Fe-MIL-88B-NH2 NMOFs under the designed pH (4.0-8.0). The results suggest the Chi capped Fe-MIL-88B-NH2 can be a promising candidate for future pH responsive drug delivery systems.

Development of luminescent pH sensor films for monitoring bacterial growth through tissue.

PubMed

Wang, Fenglin; Raval, Yash; Chen, Hongyu; Tzeng, Tzuen-Rong J; DesJardins, John D; Anker, Jeffrey N

2014-02-01

Although implanted medical devices (IMDs) offer many benefits, they are susceptible to bacterial colonization and infections. Such infections are difficult to treat because bacteria could form biofilms on the implant surface, which reduce antibiotics penetration and generate local dormant regions with low pH and low oxygen. In addition, these infections are hard to detect early because biofilms are often localized on the surface. Herein, an optical sensor film is developed to detect local acidosis on an implanted surface. The film contains both upconverting particles (UCPs) that serve as a light source and a pH indicator that alters the luminescence spectrum. When irradiated with 980 nm light, the UCPs produce deeply penetrating red light emission, while generating negligible autofluorescence in the tissue. The basic form of the pH indicator absorbs more of upconversion luminescence at 661 nm than at 671 nm and consequently the spectral ratio indicates pH. Implanting this pH sensor film beneath 6-7 mm of porcine tissue does not substantially affect the calibration curve because the peaks are closely spaced. Furthermore, growth of Staphylococcus epidermidis on the sensor surface causes a local pH decrease that can be detected non-invasively through the tissue. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Brain pattern of histone H3 phosphorylation after acute amphetamine administration: its relationship to brain c-fos induction is strongly dependent on the particular brain area.

PubMed

Rotllant, David; Armario, Antonio

2012-02-01

Recent evidence strongly suggests a critical role of chromatin remodelling in the acute and chronic effects of addictive drugs. We reasoned that Immunohistochemical detection of certain histone modifications may be a more specific tool than induction of immediate early genes (i.e. c-fos) to detect brain areas and neurons that are critical for the action of addictive drugs. Thus, in the present work we studied in adult male rats the effects of a high dose of amphetamine on brain pattern of histone H3 phosphorylation in serine 10 (pH3S(10)) and c-fos expression. We firstly observed that amphetamine-induced an increase in the number of pH3S(10) positive neurons in a restricted number of brain areas, with maximum levels at 30 min after the drug administration that declined at 90 min in most areas. In a second experiment we studied colocalization of pH3S(10) immunoreactivity (pH3S(10)-IR) and c-fos expression. Amphetamine increased c-fos expression in medial prefrontal cortex (mPFC), dorsal striatum, nucleus accumbens (Acb), major Island of Calleja (ICjM), central amygdala (CeA), bed nucleus of stria terminalis lateral dorsal (BSTld) and paraventricular nucleus of the hypothalamus (PVN). Whereas no evidence for increase in pH3S(10) positive neurons was found in the mPFC and the PVN, in the striatum and the Acb basically all pH3S(10) positive neurons showed colocalization with c-fos. In ICjM, CeA and BSTld a notable degree of colocalization was found, but an important number of neurons expressing c-fos were negative for pH3S(10). The present results give support to the hypothesis that amphetamine-induced pH3S(10)-IR showed a more restricted pattern than brain c-fos induction, being this difference strongly dependent on the particular brain area studied. It is likely that those nuclei and neurons showing pH3S(10)-IR are more specifically associated to important effects of the drug, including neural plasticity. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'. Copyright © 2011 Elsevier Ltd. All rights reserved.

Photodynamic inactivation of bacteria using polyethylenimine-chlorin(e6) conjugates: Effect of polymer molecular weight, substitution ratio of chlorin(e6) and pH.

PubMed

Huang, Liyi; Zhiyentayev, Timur; Xuan, Yi; Azhibek, Dulat; Kharkwal, Gitika B; Hamblin, Michael R

2011-04-01

Antimicrobial photodynamic therapy (APDT) is a novel technique to treat local infections. Previously we reported that the attachment of chlorin(e6) to polyethylenimine (PEI) polymers to form PEI-ce6 conjugates is an effective way to improve ce6 PDT activity against bacteria. The aim of this work was to explore how the polymer molecular weight, substitution ratio (SR) of ce6 and pH value affect the PDT efficacy. We have synthesized PEI-ce6(10) (MW = 60,000, SR = 1) and PEI-ce6(11) (MW = 60,000, SR = 5) and compared these with the previous PEI-ce6(9) (MW = 10,000, SR = 1). We tested the PDT efficacy of these three conjugates against Gram-negative E. coli and Gram-positive bacteria (S. aureus and E. fecalis) at three different pH values (5.0, 7.4, 10.0) that may affect the charge on both the bacterial cells and on the conjugate (that has both basic and acidic groups). PEI-ce6(9) and PEI-ce6(10) were the most effective against these tested bacteria. The PDT effect of all three conjugates depended on pH values. The effective order was pH = 10.0 > pH = 7.4 > pH = 5.0 on E. coli. For S. aureus and E. fecalis the order was pH = 5.0 > pH = 10.0 > pH = 7.4. PEI-ce6(11) PDT activity was worse than PEI-ce6(10) activity which is probably connected to the fact that ce6 molecules are self-quenched within the PEI-ce6(11) molecule. Ce6 quenching within the PEI-ce6 molecules was proved by analyzing fluorescence spectra of PEI-ce6 conjugates at different pH values. There were no differences in bacterial uptake between different pH values in three PEI-ce6 conjugates. We assume high pH (rather than low pH as was hypothesized) disaggregates the conjugates, so the higher pH was more effective than the lower pH against E. coli. But for Gram-positive bacteria, low pH was more effective possibly due to more overall positive charge on the conjugate. Copyright © 2011 Wiley-Liss, Inc.

Hydrothermal synthesis of thiol-capped CdTe nanoparticles and their optical properties.

PubMed

Bu, Hang-Beom; Kikunaga, Hayato; Shimura, Kunio; Takahasi, Kohji; Taniguchi, Taichi; Kim, DaeGwi

2013-02-28

Water soluble nanoparticles (NPs) with a high emission property were synthesized via hydrothermal routes. In this report, we chose thiol ligand N-acetyl-L-cysteine as the ideal stabilizer and have successfully employed it to synthesize readily size-controllable CdTe NPs in a reaction of only one step. Hydrothermal synthesis of CdTe NPs has been carried out in neutral or basic conditions so far. We found out that the pH value of precursor solutions plays an important role in the uniformity of the particle size. Actually, high quality CdTe NPs were synthesized under mild acidic conditions of pH 5. The resultant NPs indicated good visible light-emitting properties and stability. Further, the experimental results showed that the reaction temperature influenced significantly the growth rate and the maximum size of the NPs. The CdTe NPs with a high photoluminescence quantum yield (the highest value: 57%) and narrower half width at half maximum (the narrowest value: 33 nm) were attained in very short time, within 40 minutes, reaching diameters of 2.3 to 4.3 nm. The PL intensity was increased with an increase in the reaction time, reflecting the suppression of nonradiative recombination processes. Furthermore, the formation of CdTe/CdS core-shell structures was discussed from the viewpoint of PL dynamics and X-ray diffraction studies.

Non-basic amino acids in the ROMK1 channels via an appropriate distance modulate PIP2 regulated pHi-gating.

PubMed

Lee, Chien-Hsing; Huang, Po-Tsang; Liou, Horng-Huei; Lin, Mei-Ying; Lou, Kuo-Long; Chen, Chung-Yi

2016-04-22

The ROMK1 (Kir1.1) channel activity is predominantly regulated by intracellular pH (pHi) and phosphatidylinositol 4,5-bisphosphate (PIP2). Although several residues were reported to be involved in the regulation of pHi associated with PIP2 interaction, the detailed molecular mechanism remains unclear. We perform experiments in ROMK1 pHi-gating with electrophysiology combined with mutational and structural analysis. In the present study, non basic residues of C-terminal region (S219, N215, I192, L216 and L220) in ROMK1 channels have been found to mediate channel-PIP2 interaction and pHi gating. Further, our structural results show these residues with an appropriate distance to interact with membrane PIP2. Meanwhile, a cluster of basic residues (R188, R217 and K218), which was previously discovered regarding the interaction with PIP2, exists in this appropriate distance to discriminate the regulation of channel-PIP2 interaction and pHi-gating. This appropriate distance can be observed with high conservation in the Kir channel family. Our results provide insight that an appropriate distance cooperates with the electrostatics interaction of channel-PIP2 to regulate pHi-gating. Copyright © 2016 Elsevier Inc. All rights reserved.

High yield of functional metagenomic library from mangroves constructed in fosmid vector.

PubMed

Gonçalves, A C S; dos Santos, A C F; dos Santos, T F; Pessoa, T B A; Dias, J C T; Rezende, R P

2015-10-02

In the present study, metagenomic technique and fosmid vectors were used to construct a library of clones for exploring the biotechnological potential of mangrove soils by isolation of functional genes encoding hydrolytic enzymes. The library was built with genomic DNA from the soil samples of mangrove sediments and the functional screening of 1824 clones (~64 Mbp) was performed to detect the hydrolytic activity specific for cellulases, amylases (at acidic, neutral and basic pH), lipases/esterases, proteases, and nitrilases. Significant numbers of clones, positive for the tested enzyme activities were obtained. Our results indicate the importance and biotechnological potential of mangrove soils especially when compared to those obtained using other soil metagenomic libraries.

Electrostatic interactions as governing the fouling in protein microfiltration

NASA Astrophysics Data System (ADS)

Ouammou, M.; Tijani, N.; Calvo, J. I.; Palacio, L.; Prádanos, P.; Hernández, A.

2005-03-01

The influence of pH and electrostatic interactions on the fouling mechanism during protein dead-end microfiltration (MF) has been investigated for two charged membranes. Polyethersulfone acidic membranes (ICE-450), being negatively charged, and basic ones (SB-6407), these positively charged, both from Pall Co., have been used in the investigations. BSA and Lysozyme solutions at different pH values (3.0, 5.0, 7.0, 8.5 and 10.0) were microfiltered through the membranes at a constant applied transmembrane pressure. Results have been analysed in terms of usual blocking filtration laws and a substantial change in the fouling behaviour has been observed when solution pH and/or membrane charge as the pressure was changed, this change being clearly related with the specific membrane-protein and protein-protein interactions.

Biosorption of Basic Green 4 from aqueous solution by Ananas comosus (pineapple) leaf powder.

PubMed

Chowdhury, Shamik; Chakraborty, Sagnik; Saha, Papita

2011-06-01

Biosorption characteristics of Ananas comosus (pineapple) leaf powder was investigated for decolorization of Basic Green 4 (BG 4), a cationic dye from its aqueous solutions employing a batch experimental set-up. Parameters that influence the sorption process such as pH, biosorbent dosage, contact time, initial dye concentration and temperature were systematically studied. The optimum conditions for removal of BG 4 were found to be pH 9.0, contact time=150 min, biosorbent dosage=5.0 g L(-1), initial dye concentration=50 mg L(-1). The temperature had a strong influence on the biosorption process. Further, the biosorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Brunauer, Emmett, Teller (BET) surface area and pore size analysis. Experimental biosorption data were modeled by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The biosorption process followed the Langmuir isotherm model with high coefficients of correlation (R(2)>0.99) at different temperatures. The pseudo second order kinetic model fitted well in correlation to the experimental results. Activation energy of the biosorption process (E(a)) was found to be 45.79 kJ mol(-1) by using the Arrhenius equation, indicating chemisorption nature of BG 4 sorption onto pineapple leaf powder. Thermodynamic parameters suggest that the biosorption process is spontaneous and exothermic in nature. Overall, the present findings suggest that this environmentally friendly, efficient and low-cost biosorbent may be useful for the removal of BG 4 from aqueous media. Copyright © 2011 Elsevier B.V. All rights reserved.

A Neutral Thermostable β-1,4-Glucanase from Humicola insolens Y1 with Potential for Applications in Various Industries

PubMed Central

Zhang, Wei; Huang, Huoqing; Shi, Pengjun; Luo, Huiying; Liu, Bo; Zhang, Yuhong; Zhang, Zhifang; Fan, Yunliu; Yao, Bin

2015-01-01

We cloned a new glycoside hydrolase family 6 gene, Hicel6C, from the thermophilic fungus Humicola insolens Y1 and expressed it in Pichia pastoris. Using barley β-glucan as a substrate, recombinant HiCel6C protein exhibited neutral pH (6.5) and high temperature (70°C) optima. Distinct from most reported acidic fungal endo-β-1,4-glucanases, HiCel6C was alkali-tolerant, retaining greater than 98.0, 61.2, and 27.6% of peak activity at pH 8.0, 9.0, and 10.0, respectively, and exhibited good stability over a wide pH range (pH 5.0−11.0) and at temperatures up to 60°C. The K m and V max values of HiCel6C for barley β-glucan were 1.29 mg/mL and 752 μmol/min·mg, respectively. HiCel6C was strictly specific for the β-1,4-glucoside linkage exhibiting activity toward barley β-glucan, lichenan, and carboxy methylcellulose sodium salt (CMC-Na), but not toward laminarin (1,3-β-glucan). HiCel6C cleaved the internal glycosidic linkages of cellooligosaccharides randomly and thus represents an endo-cleaving enzyme. The predominant product of polysaccharide hydrolysis by HiCel6C was cellobiose, suggesting that it functions by an endo-processive mechanism. The favorable properties of HiCel6C make it a good candidate for basic research and for applications in the textile and brewing industries. PMID:25909505

The Effect of Membrane Environment on Surfactant Protein C Stability Studied by Constant-pH Molecular Dynamics.

PubMed

Carvalheda, Catarina A; Campos, Sara R R; Baptista, António M

2015-10-26

Pulmonary surfactant protein C (SP-C) is a small peptide with two covalently linked fatty acyl chains that plays a crucial role in the formation and stabilization of the pulmonary surfactant reservoirs during the compression and expansion steps of the respiratory cycle. Although its function is known to be tightly related to its highly hydrophobic character and key interactions maintained with specific lipid components, much is left to understand about its molecular mechanism of action. Also, although it adopts a mainly helical structure while associated with the membrane, factors as pH variation and deacylation have been shown to affect its stability and function. In this work, the conformational behavior of both the acylated and deacylated SP-C isoforms was studied in a DPPC bilayer under different pH conditions using constant-pH molecular dynamics simulations. Our findings show that both protein isoforms are remarkably stable over the studied pH range, even though the acylated isoform exhibits a labile helix-turn-helix motif rarely observed in the other isoform. We estimate similar tilt angles for the two isoforms over the studied pH range, with a generally higher degree of internalization of the basic N-terminal residues in the deacylated case, and observe and discuss some protonation-conformation coupling effects. Both isoforms establish contacts with the surrounding lipid molecules (preferentially with the sn-2 ester bonds) and have a local effect on the conformational behavior of the surrounding lipid molecules, the latter being more pronounced for acylated SP-C.

Degradation rates of glycerol polyesters at acidic and basic conditions

USDA-ARS?s Scientific Manuscript database

Polyesters prepared from glycerol with mixtures of adipic and citric acids were evaluated in the laboratory to estimate degradation rates over a range of pH conditions. These renewable polymers provide a market for glycerol that is generated during biodiesel production. The polyesters were prepared...

The Rainbow Connection.

ERIC Educational Resources Information Center

Hutton, Bill; Smith, Wayne L.

1984-01-01

Provides materials needed and procedures to illustrate the reversible color changes in certain organic acids on bases due to changes in pH. The technique employs three indicators which are colorless in acidic solution but form primary colors in basic solutions. Also discusses the free energy curve presented in many textbooks. (JM)

Characterization of Chitin and Chitosan Molecular Structure in Aqueous Solution

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

Franca, Eduardo D.; Lins, Roberto D.; Freitas, Luiz C.

Molecular dynamics simulations have been used to characterize the structure of chitin and chitosan fibers in aqueous solutions. Chitin fibers, whether isolated or in the form of a β-chitin nanoparticle, adopt the so-called 2-fold helix with Φ and φ values similar to its crystalline state. In solution, the intramolecular hydrogen bond HO3(n)•••O5(n+1) responsible for the 2-fold helical motif is stabilized by hydrogen bonds with water molecules in a well-defined orientation. On the other hand, chitosan can adopt five distinct helical motifs and its conformational equilibrium is highly dependent on pH. The hydrogen bond pattern and solvation around the O3 atommore » of insoluble chitosan (basic pH) are nearly identical to these quantities in chitin. Our findings suggest that the solubility and conformation of these polysaccharides are related to the stability of the intrachain HO3(n)•••O5(n+1) hydrogen bond, which is affect by the water exchange around the O3-HO3 hydroxyl group.« less

pH-sensitive nanocargo based on smart polymer functionalized graphene oxide for site-specific drug delivery.

PubMed

Kavitha, Thangavelu; Abdi, Syed Izhar Haider; Park, Soo-Young

2013-04-14

Graphene oxide (GO) was functionalized covalently with pH-sensitive poly(2-(diethylamino) ethyl methacrylate) (PDEA) by surface-initiated in situ atom transfer radical polymerization. The structure of the PDEA-grafted GO (GO-PDEA) were examined by Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis and atomic force microscopy. The grafted PDEA endowed the GO sheets with good solubility and stability in physiological solutions. Simple physisorption by π-π stacking and hydrophobic interactions on GO-PDEA can be used to load camptothecin (CPT), a widely used water-insoluble cancer drug. The loaded CPT was released only at the lower (acidic) pH normally found in a tumor environment but not in basic and neutral pH. GO-PDEA did not show practical toxicity to N2a cancer cells but the GO-PDEA-CPT complex exhibited high potency in killing N2a cancer cells in vitro. These results suggest that the GO-PDEA nanocargo carrier might be a promising material for site-specific anticancer drug delivery and controlled release.

Prediction of pH dependent absorption using in vitro, in silico, and in vivo rat models: Early liability assessment during lead optimization.

PubMed

Saxena, Ajay; Shah, Devang; Padmanabhan, Shweta; Gautam, Shashyendra Singh; Chowan, Gajendra Singh; Mandlekar, Sandhya; Desikan, Sridhar

2015-08-30

Weakly basic compounds which have pH dependent solubility are liable to exhibit pH dependent absorption. In some cases, a subtle change in gastric pH can significantly modulate the plasma concentration of the drug and can lead to sub-therapeutic exposure of the drug. Evaluating the risk of pH dependent absorption and potential drug-drug interaction with pH modulators are important aspects of drug discovery and development. In order to assess the risk around the extent of decrease in the systemic exposure of drugs co-administered with pH modulators in the clinic, a pH effect study is carried out, typically in higher species, mostly dog. The major limitation of a higher species pH effect study is the resource and material requirement to assess this risk. Hence, these studies are mostly restricted to promising or advanced leads. In our current work, we have used in vitro aqueous solubility, in silico simulations using GastroPlus™ and an in vivo rat pH effect model to provide a qualitative assessment of the pH dependent absorption liability. Here, we evaluate ketoconazole and atazanavir with different pH dependent solubility profiles and based on in vitro, in silico and in vivo results, a different extent of gastric pH effect on absorption is predicted. The prediction is in alignment with higher species and human pH effect study results. This in vitro, in silico and in vivo (IVISIV) correlation is then extended to assess pH absorption mitigation strategy. The IVISIV predicts pH dependent absorption for BMS-582949 whereas its solubility enhancing prodrug, BMS-751324 is predicted to mitigate this liability. Overall, the material requirement for this assessment is substantially low which makes this approach more practical to screen multiple compounds during lead optimization. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of pH on the structural, optical and morphological properties of Ga-doped ZnO nanoparticles by reflux precipitation method

NASA Astrophysics Data System (ADS)

Ungula, J.; Dejene, B. F.; Swart, H. C.

2018-04-01

Gallium-doped zinc oxide nanoparticles (GZO NPs) were synthesized by the reflux precipitation method at 1, 3, 5, 7 and 8 pH conditions of Ga/Zn precursor solution (Ga/Zn sol.). Analysis of X-ray diffraction (XRD) spectra showed that the diffraction peak intensities of GZO NPs increased and the crystallite sizes varied from 11 to 27 nm with an increase in the pH of the Zn/Ga sol. Scanning electron microscopy micrographs showed agglomerated tiny particles that formed on big slabs of nanorods at the lower pH, but fine and enlarged particles on nano-spherical bases formed at the higher pH values. The photoluminescence exciton peak intensities of the GZO NPs and their respective FWHM increased to a maximum at the 5 pH and then reduced slightly as the solution got more basic. The increase of the deep level peak intensities with the increase in the pH followed the XRD diffraction intensity results. It was observed that both the exciton and DLE peaks emission positions shifted to lower wavelengths up to the 5 pH and then red shifted for a further increase in the pH values. The UV-vis analysis also demonstrated that the optical properties of the GZO NPs improved with the increase Ga/Zn sol. pH, as shown by the blue shift of the absorption edge of the reflectance spectra. The band gap energy was tuned from 3.18 to 3.31 eV with the increase in the pH from 1 to 5. An additional increase in the pH yielded no significant change in the optical properties of the GZO NPs.

Relieving Dry Mouth: Varying Levels of pH Found in Bottled Water.

PubMed

Fisher, Bailey Jean; Spencer, Angela; Haywood, Van; Konchady, Gayathri

2017-07-01

It is estimated that 30% of people older than 60 years suffer from hyposalivation or dry mouth. Drinking water frequently has been recommended as a safe, non-pharmacologic way to combat hyposalivation. The saliva in patients with dry mouth is acidic. Beverages consumed daily may have an erosive potential on teeth. The pH and the mineral content of the beverage determine its erosive potential. An acidic beverage, therefore, may have harmful effects on mineralized tooth structures, causing erosion of enamel, dentin, and cementum. Because bottled water is both convenient and easily available, the authors tested the pH of eight common brands of bottled water. (One brand included two different bottle types, for a total of nine bottled waters tested.) To standardize the pH electrode, pH buffers of 4.7 and 10 were used. The pH was measured using the Denver Instruments basic pH meter. Six recordings were used for each brand and then averaged to report the pH. Two of the bottled water samples tested were below the critical level of 5.2 pH to 5.5 pH, the level at which erosion of enamel occurs. Six of the samples tested were below the critical pH of 6.8, at which erosion of root dentin occurs. The authors conclude that both patients and clinicians incorrectly presume bottled water to be innocuous. Clinicians should be cognizant of the erosive potential of different brands of bottled water to both educate patients and to recommend water with neutral or alkaline pH for patients with symptoms of dry mouth to prevent further deterioration and demineralization of tooth structure.

Characterization of the basic charge variants of a human IgG1

PubMed Central

Lu, Franklin; Derfus, Gayle; Kluck, Brian; Nogal, Bartek; Emery, Craig; Summers, Christie; Zheng, Kai; Bayer, Robert; Amanullah, Ashraf

2011-01-01

We report a case study of an IgG1 with a unique basic charge variant profile caused by C-terminal proline amidation on either one or two heavy chains. The proline amidation was sensitive to copper ion concentration in the production media during cell culture: the higher the Cu2+ ion concentration, the higher the level of proline amidation detected. This conclusion was supported by the analysis of samples that revealed direct correlation between the proline amidation level observed from peptide maps and the level of basic peaks measured by imaged capillary isoelectric focusing and a pH gradient ion-exchange chromatography method. The importance of these observations to therapeutic antibody production is discussed. PMID:22123059

Characterization of the basic charge variants of a human IgG1: effect of copper concentration in cell culture media.

PubMed

Kaschak, Timothy; Boyd, Daniel; Lu, Franklin; Derfus, Gayle; Kluck, Brian; Nogal, Bartek; Emery, Craig; Summers, Christie; Zheng, Kai; Bayer, Robert; Amanullah, Ashraf; Yan, Boxu

2011-01-01

We report a case study of an IgG1 with a unique basic charge variant profile caused by C-terminal proline amidation on either one or two heavy chains. The proline amidation was sensitive to copper ion concentration in the production media during cell culture: the higher the Cu ( 2+) ion concentration, the higher the level of proline amidation detected. This conclusion was supported by the analysis of samples that revealed direct correlation between the proline amidation level observed from peptide maps and the level of basic peaks measured by imaged capillary isoelectric focusing and a pH gradient ion-exchange chromatography method. The importance of these observations to therapeutic antibody production is discussed.

Assessment of spectroscopic parameters of solvated Eu(dmh)3 phen organometallic complex in various basic and acidic solvents.

PubMed

Chitnis, Dipti; Kalyani, N Thejo; Dhoble, Sanjay

2018-05-31

We report on the comprehension of novel europium activated hybrid organic Eu(dmh) 3 phen (Eu: europium, dmh: 2,6-dimethyl-3,5-heptanedione, phen: 1,10 phenanthroline) organo-metallic complexes, synthesized at different pH values by the solution technique. Photo physical properties of these complexes in various basic and acidic solvents were probed by UV-vis optical absorption and photoluminescence (PL) spectra. Minute differences in optical absorption peaks with variable optical densities were encountered with the variation in solvent from basic (chloroform, toluene, tetrahydrofuran) to acidic (acetic acid) media, revealing bathochromic shift in the absorption peaks. The PL spectra of the complex in various acidic and basic organic solvents revealed the position of the emission peak at 613 nm irrespective of the changes in solvents whereas the excitation spectrum almost matched with that of the UV-vis absorption data. The optical density was found to be maximum for the complex with pH 7.0 whereas it gradually decreased when pH was lowered to 6.0 or raised to 8.0 at an interval of 0.5, demonstrating its pH sensitive nature. Several spectroscopic parameters related to probability of transition such as absorbance A(λ), Napierian absorption coefficient α(λ), molecular absorption cross-section σ(λ), radiative lifetime (τ 0 ) and oscillator strength (f) were calculated from UV-vis spectra. The relative intensity ratio (R-ratio), calculated from the emission spectra was found to be almost the same in all the organic solvents. The optical energy gap, calculated for the designed complexes were found to be well in accordance with the ideal acceptance value of energy gap of the emissive materials used for fabrication of red organic light-emitting diode (OLED). The relation between Stoke's shift and solvent polarity function was established by Lippert-Mataga plot. This remarkable independence of the electronic absorption spectra of Eu complexes on the nature of the solvent with unique emission wavelength furnishes its potential to serve as a red light emitter for solution processed OLEDs, display panels and solid-state lighting. Copyright © 2018 John Wiley & Sons, Ltd.

The formation of illite from nontronite by mesophilic and thermophilic bacterial reaction

USGS Publications Warehouse

Jaisi, Deb P.; Eberl, Dennis D.; Dong, Hailiang; Kim, Jinwook

2011-01-01

The formation of illite through the smectite-to-illite (S-I) reaction is considered to be one of the most important mineral reactions occurring during diagenesis. In biologically catalyzed systems, however, this transformation has been suggested to be rapid and to bypass the high temperature and long time requirements. To understand the factors that promote the S-I reaction, the present study focused on the effects of pH, temperature, solution chemistry, and aging on the S-I reaction in microbially mediated systems. Fe(III)-reduction experiments were performed in both growth and non-growth media with two types of bacteria: mesophilic (Shewanella putrefaciens CN32) and thermophilic (Thermus scotoductus SA-01). Reductive dissolution of NAu-2 was observed and the formation of illite in treatment with thermophilic SA-01 was indicated by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). A basic pH (8.4) and high temperature (65°C) were the most favorable conditions for the formation of illite. A long incubation time was also found to enhance the formation of illite. K-nontronite (non-permanent fixation of K) was also detected and differentiated from the discrete illite in the XRD profiles. These results collectively suggested that the formation of illite associated with the biologically catalyzed smectite-to-illite reaction pathway may bypass the prolonged time and high temperature required for the S-I reaction in the absence of microbial activity.

Members of an R2R3-MYB transcription factor family in Petunia are developmentally and environmentally regulated to control complex floral and vegetative pigmentation patterning.

PubMed

Albert, Nick W; Lewis, David H; Zhang, Huaibi; Schwinn, Kathy E; Jameson, Paula E; Davies, Kevin M

2011-03-01

We present an investigation of anthocyanin regulation over the entire petunia plant, determining the mechanisms governing complex floral pigmentation patterning and environmentally induced vegetative anthocyanin synthesis. DEEP PURPLE (DPL) and PURPLE HAZE (PHZ) encode members of the R2R3-MYB transcription factor family that regulate anthocyanin synthesis in petunia, and control anthocyanin production in vegetative tissues and contribute to floral pigmentation. In addition to these two MYB factors, the basic helix-loop-helix (bHLH) factor ANTHOCYANIN1 (AN1) and WD-repeat protein AN11, are also essential for vegetative pigmentation. The induction of anthocyanins in vegetative tissues by high light was tightly correlated to the induction of transcripts for PHZ and AN1. Interestingly, transcripts for PhMYB27, a putative R2R3-MYB active repressor, were highly expressed during non-inductive shade conditions and repressed during high light. The competitive inhibitor PhMYBx (R3-MYB) was expressed under high light, which may provide feedback repression. In floral tissues DPL regulates vein-associated anthocyanin pigmentation in the flower tube, while PHZ determines light-induced anthocyanin accumulation on exposed petal surfaces (bud-blush). A model is presented suggesting how complex floral and vegetative pigmentation patterns are derived in petunia in terms of MYB, bHLH and WDR co-regulators. © 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.

Lack of Dependence of the Sizes of the Mesoscopic Protein Clusters on Electrostatics.

PubMed

Vorontsova, Maria A; Chan, Ho Yin; Lubchenko, Vassiliy; Vekilov, Peter G

2015-11-03

Protein-rich clusters of steady submicron size and narrow size distribution exist in protein solutions in apparent violation of the classical laws of phase equilibrium. Even though they contain a minor fraction of the total protein, evidence suggests that they may serve as essential precursors for the nucleation of ordered solids such as crystals, sickle-cell hemoglobin polymers, and amyloid fibrils. The cluster formation mechanism remains elusive. We use the highly basic protein lysozyme at nearly neutral and lower pH as a model and explore the response of the cluster population to the electrostatic forces, which govern numerous biophysical phenomena, including crystallization and fibrillization. We tune the strength of intermolecular electrostatic forces by varying the solution ionic strength I and pH and find that despite the weaker repulsion at higher I and pH, the cluster size remains constant. Cluster responses to the presence of urea and ethanol demonstrate that cluster formation is controlled by hydrophobic interactions between the peptide backbones, exposed to the solvent after partial protein unfolding that may lead to transient protein oligomers. These findings reveal that the mechanism of the mesoscopic clusters is fundamentally different from those underlying the two main classes of ordered protein solid phases, crystals and amyloid fibrils, and partial unfolding of the protein chain may play a significant role. Copyright © 2015 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Acceptance of a systematic review as a thesis: survey of biomedical doctoral programs in Europe.

PubMed

Puljak, Livia; Sapunar, Damir

2017-12-12

Systematic reviews (SRs) have been proposed as a type of research methodology that should be acceptable for a graduate research thesis. The aim of this study was to analyse whether PhD theses in European biomedical graduate programs can be partly or entirely based on SRs. In 2016, we surveyed individuals in charge of European PhD programs from 105 institutions. The survey asked about acceptance of SRs as the partial or entire basis for a PhD thesis, their attitude towards such a model for PhD theses, and their knowledge about SR methodology. We received responses from 86 individuals running PhD programs in 68 institutions (institutional response rate of 65%). In 47% of the programs, SRs were an acceptable study design for a PhD thesis. However, only 20% of participants expressed a personal opinion that SRs meet the criteria for a PhD thesis. The most common reasons for not accepting SRs as the basis for PhD theses were that SRs are 'not a result of a PhD candidate's independent work, but more of a team effort' and that SRs 'do not produce enough new knowledge for a dissertation'. The majority of participants were not familiar with basic concepts related to SRs; questions about meta-analyses and the type of plots frequently used in SRs were correctly answered by only one third of the participants. Raising awareness about the importance of SRs and their methodology could contribute to higher acceptance of SRs as a type of research that forms the basis of a PhD thesis.

Factors regulating astringency of whey protein beverages.

PubMed

Beecher, J W; Drake, M A; Luck, P J; Foegeding, E A

2008-07-01

A rapidly growing area of whey protein use is in beverages. There are 2 types of whey protein-containing beverages: those at neutral pH and those at low pH. Astringency is very pronounced at low pH. Astringency is thought to be caused by compounds in foods that bind with and precipitate salivary proteins; however, the mechanism of astringency of whey proteins is not understood. The effect of viscosity and pH on the astringency of a model beverage containing whey protein isolate was investigated. Trained sensory panelists (n = 8) evaluated the viscosity and pH effects on astringency and basic tastes of whey protein beverages containing 6% wt/vol protein. Unlike what has been shown for alum and polyphenols, increasing viscosity (1.6 to 7.7 mPa.s) did not decrease the perception of astringency. In contrast, the pH of the whey protein solution had a major effect on astringency. A pH 6.8 whey protein beverage had a maximum astringency intensity of 1.2 (15-point scale), whereas that of a pH 3.4 beverage was 8.8 (15-point scale). Astringency decreased between pH 3.4 and 2.6, coinciding with an increase in sourness. Decreases in astringency corresponded to decreases in protein aggregation as observed by turbidity. We propose that astringency is related to interactions between positively charged whey proteins and negatively charged saliva proteins. As the pH decreased between 3.4 and 2.6, the negative charge on the saliva proteins decreased, causing the interactions with whey proteins to decrease.

76 FR 27653 - National Institute of Environmental Health Sciences; Notice of Closed Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-12

... Southpoint, 7007 Fayetteville Road, Durham, NC 27713. Contact Person: Linda K. Bass, PhD, Scientific Review... Estimation--Health Risks from Environmental Exposures; 93.142, NIEHS Hazardous Waste Worker Health and Safety Training; 93.143, NIEHS Superfund Hazardous Substances--Basic Research and Education; 93.894, Resources and...

Geropsychology Training in a Specialist Geropsychology Doctoral Program

ERIC Educational Resources Information Center

Qualls, Sara Honn; Segal, Daniel L.; Benight, Charles C.; Kenny, Michael P.

2005-01-01

The first PhD specialty program in Geropsychology that launched in fall, 2004 at CU-Colorado Springs is described. Consistent with a scientist-practitioner model, the curriculum sequence builds systematically from basic to complex knowledge and skills across the domains of scientific psychology, research methodology, general clinical,…

BIOSENSOR FOR DIRECT DETERMINATION OF ORGANOPHOSPHATE NERVE AGENTS. 1. POTENTIOMETRIC ENZYME ELECTRODE. (R823663)

EPA Science Inventory

A potentiometric enzyme electrode for the direct measurement of organophosphate (OP)
nerve agents was developed. The basic element of this enzyme electrode was a pH electrode
modified with an immobilized organophosphorus hydrolase (OPH) layer formed by cross-linking
OPH ...

Eliminating cancer stem cells: an interview with CCR’s Steven Hou | Center for Cancer Research

Cancer.gov

Steven Hou, Ph.D., senior investigator in the Basic Research Laboratory at the Center for Cancer Research describes his latest research that has uncovered potential ways to eliminate cancer stem cells and may offer hope to patients with reoccurring tumors.  Learn more...

Primary Events in vision - Investigation of Basic Eye Responses.

DTIC Science & Technology

1983-06-30

Lewis School of Applied & Engineering Physics CORNELL UNIVERSITY Ithaca, NY 30 JUNE 1983 SEF 2 PHASE REPORT Contract No. N62269.62-M-3270 APPROVED FOR...Ph.D. N62269-82-M-3270 9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK School of Applied & Engineering Physics AREA

78 FR 64960 - National Institute on Drug Abuse; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-30

... unwarranted invasion of personal privacy. Name of Committee: National Institute on Drug Abuse Special Emphasis..., Ph.D., Scientific Review Officer, Office of Extramural Affairs, National Institute on Drug Abuse, NIH... . Name of Committee: National Institute on Drug Abuse Special Emphasis Panel; CEBRA: Cutting-Edge Basic...

The Chelate Effect Redefined.

ERIC Educational Resources Information Center

da Silva, J. J. R. Frausto

1983-01-01

Discusses ambiguities of the accepted definition of the chelate effect, suggesting that it be defined in terms of experimental observation rather than mathematical abstraction. Indicates that the effect depends on free energy change in reaction, ligand basicity, pH of medium, type of chelates formed, and concentration of ligands in solution. (JN)

How-to-Do-It: A Simple Demonstration of Fermentation.

ERIC Educational Resources Information Center

Yurkiewicz, William J.; And Others

1989-01-01

Described is a simple demonstration of fermentation. The materials needed, the basic experimental set-up, and various projects are outlined. Included are a diagram of an apparatus for measuring carbon dioxide production and a table showing typical results of the effect of pH on fermentation. (RT)

Micelles for the self-assembly of "off-on-off" fluorescent sensors for pH windows.

PubMed

Diaz-Fernandez, Yuri; Foti, Francesco; Mangano, Carlo; Pallavicini, Piersandro; Patroni, Stefano; Perez-Gramatges, Aurora; Rodriguez-Calvo, Simon

2006-01-11

A micellar approach is proposed to build a series of systems featuring an "off-on-off" fluorescent window response with changes in pH. The solubilizing properties of micelles are used to self-assemble, in water, plain pyrene with lipophilized pyridine and tertiary amine moieties. Since these components are contained in the small volume of the same micelle, pyrene fluorescence is influenced by the basic moieties: protonated pyridines and free tertiary amines behave as quenchers. Accordingly, fluorescence transitions from the "off" to the "on" state, and viceversa, take place when the pH crosses the pK(a) values of the amine and pyridine fragments. To obtain an "off-on-off" fluorescent response in this investigation we use either a set of dibasic lipophilic molecules (containing covalently linked pyridine and tertiary amine groups) or combinations of separate, lipophilic pyridines and tertiary amines. The use of combinations of dibasic and monobasic lipophilic molecules also gives a window-shaped fluorescence response with changes in pH: it is the highest pyridine pK(a) and the lowest tertiary amine pK(a) that determine the window limits. The pK(a) values of all the examined lipophilic molecules were determined in micelles, and compared with the values found for the same molecules in solvent mixtures in which they are molecularly dispersed. The effect of micellization is to significantly lower the observed protonation constants of the lipophilized species. Moreover, the more lipophilic a molecule is, the lower the observed logK value is. Accordingly, changing the substituents on the basic moieties or modifying their structure, tuning the lipophilicity of the mono- or dibases, and choosing among a large set of possible combination of lipophilized mono- and dibases have allowed us to tune, almost at will, both the width and the position along the pH axis of the obtained fluorescent window.

Potentiometric and Conductometric Study of Aqueous Solutions of Lithium and Sodium Salts of Poly(thiophen-3-ylacetic acid).

PubMed

Hostnik, Gregor; Vlachy, Vojko; Bondarev, Dmitrij; Jiří, Vohlídal; Cerar, Janez

2012-09-01

The title polymer, PTAA, practically free of ester groups was obtained by oxidative polymerization of methyl thiophen-3-ylacetate and subsequent basic hydrolysis of primary polymer. Poly(thiophen-3-ylacetic acid) has been thoroughly characterized by NMR, IR, Raman, and UV/Vis spectroscopy. The polyacid behavior during neutralization titrations with lithium and sodium hydroxides, carried out under nitrogen atmosphere, has been studied by conductometry and potentiometry. Henderson-Hasselbach plots of potentiometric titration curves show a break point at pH around 6, where the curve slope drops from 1.8 (at lower pH) to a value from 1.05 to 1.3 (at higher pH values). The UV/Vis spectra monitored during back titration show: (i) monotonous decrease of both λmax and εmax as pH decreases, (ii) the presence of the isosbestic point at 401 nm that can be ascribed to conformational transition of PTAA chains, and (iii) absence of the isosbestic point at 392 nm reported previously by other authors.

New tetrameric forms of the rotavirus NSP4 with antiparallel helices.

PubMed

Kumar, Sushant; Ramappa, Raghavendra; Pamidimukkala, Kiranmayee; Rao, C D; Suguna, K

2018-06-01

Rotavirus nonstructural protein 4, the first viral enterotoxin to be identified, is a multidomain, multifunctional glycoprotein. Earlier, we reported a Ca 2+ -bound coiled-coil tetrameric structure of the diarrhea-inducing region of NSP4 from the rotavirus strains SA11 and I321 and a Ca 2+ -free pentameric structure from the rotavirus strain ST3, all with a parallel arrangement of α-helices. pH was found to determine the oligomeric state: a basic pH favoured a tetramer, whereas an acidic pH favoured a pentamer. Here, we report two novel forms of the coiled-coil region of NSP4 from the bovine rotavirus strains MF66 and NCDV. These crystallized at acidic pH, forming antiparallel coiled-coil tetrameric structures without any bound Ca 2+ ion. Structural and mutational studies of the coiled-coil regions of NSP4 revealed that the nature of the residue at position 131 (Tyr/His) plays an important role in the observed structural diversity.

Testing the stability of magnetic iron oxides/kaolinite nanocomposite under various pH conditions

NASA Astrophysics Data System (ADS)

Tokarčíková, Michaela; Tokarský, Jonáš; Kutláková, Kateřina Mamulová; Seidlerová, Jana

2017-09-01

Magnetically modified clays containing iron oxides nanoparticles (FexOy NPs) are low-cost and environmentally harmless materials suitable for sorption of pollutants from wastewaters. Stability of this smart material was evaluated both experimentally and theoretically using molecular modelling. Original kaolinite and prepared FexOy/kaolinite nanocomposite were characterized using X-ray fluorescence spectroscopy, X-ray powder diffraction, infrared spectroscopy, and transmission electron microscopy, and the stability was studied using leaching tests performed according to the European technical standard EN 12457-2 in deionized water and extraction agents with varying pH (2, 4, 9, and 11). The influence of pH on amount of FexOy NPs released from the composite and amount of the basic elements released from the kaolinite structure was studied using inductively coupled plasma atomic emission spectroscopy. All experiments proved that the magnetic properties of the nanocomposite will not change even after leaching in extraction agents with various pH.

Calculation and affection of pH value of different desulfurization and dehydration rates in the filling station based on Aspen Plus

NASA Astrophysics Data System (ADS)

Lv, J. X.; Wang, B. F.; Nie, L. H.; Xu, R. R.; Zhou, J. Y.; Hao, Y. J.

2018-01-01

The simulation process of the whole CNG filling station are established using Aspen Plus V7.2. The separator (Sep) was used to simulate the desulfurization and dehydration equipment in the gas station, and the flash module separator Flash 2 was used to simulate the gas storage well with proper temperature and environmental pressure. Furthermore, the sensitivity module was used to analyse the behaviour of the dehydration and desulfurization rate, and the residual pH value of the gas storage wells was between 2.2 and 3.3. The results indicated that the effect of water content on pH value is higher than that of hydrogen sulphide in the environment of gas storage wells, and the calculation process of the pH value is feasible. Additionally, the simulation process provides basic data for the subsequent anticorrosive mechanism and work of gas storage well and has great potential for practical applications.

Effects of root medium pH on root water transport and apoplastic pH in red-osier dogwood (Cornus sericea) and paper birch (Betula papyrifera) seedlings.

PubMed

Zhang, W; Zwiazek, J J

2016-11-01

Soil pH is a major factor affecting plant growth. Plant responses to pH conditions widely vary between different species of plants. However, the exact mechanisms of high pH tolerance of plants are largely unknown. In the present study, we compared the pH responses of paper birch (Betula papyrifera) seedlings, a relatively sensitive species to high soil pH, with red-osier dogwood (Cornus sericea), reported to be relatively tolerant of high pH conditions. We examined the hypotheses that tolerance of plants to high root zone pH is linked to effective control of root apoplastic pH to facilitate nutrient and water transport processes In the study, we exposed paper birch and red-osier dogwood seedlings for six weeks to pH 5, 7 and 9 under controlled-environment conditions in hydroponic culture. Then, we measured biomass, gas exchange, root hydraulic conductivity, ferric chelate reductase (FCR) activity, xylem sap pH and the relative abundance of major elements in leaf protoplasts and apoplasts. The study sheds new light on the rarely studied high pH tolerance mechanisms in plants. We found that compared with paper birch, red-osier dogwood showed greater growth, higher gas exchange, and maintained higher root hydraulic conductivity as well as lower xylem sap pH under high pH conditions. The results suggest that the relatively high pH tolerance of dogwood is associated with greater water uptake ability and maintenance of low apoplastic pH. These traits may have a significant impact on the uptake of Fe and Mn by leaf cells. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.

Effect of blueberry agro-industrial waste addition to corn starch-based films for the production of a pH-indicator film.

PubMed

Luchese, Cláudia Leites; Sperotto, Natalia; Spada, Jordana Corralo; Tessaro, Isabel Cristina

2017-11-01

Intelligent packaging is an emerging area of food technology that can provide better preservation and be of further convenience for consumers. It is recommended that biodegradable materials be used to develop low-impact designs for better packaging, which could benefit the environment by simply expanding their use to new areas. In this work, corn starch, glycerol and blueberry powder (with and without prior fruit bleaching) were used to produce films by casting. Blueberry powder, a co-product from juice processing, which is rich in anthocyanins, was added in the films to evaluate its potential as a colorimetric indicator, due to the ability of anthocyanin to change color when placed in an acidic or basic environment. After the films were immersed in different buffer solutions, visual color changes were observed, where the films became reddish at acidic pH and bluish at basic pH. The ΔE* values were greater than 3, suggesting a visually perceptible change to the human eye. The samples with fruit bleaching (CB) were visually darker (lower luminance values), while the samples without bleaching (SB) had a lighter color and higher brightness, represented by larger L* values. These results indicate the potential of blueberry powder as a pH indicator for intelligent food packaging or even for sensing food deterioration. Copyright © 2017 Elsevier B.V. All rights reserved.

Nature of the Charged-Group Effect on the Stability of the C-Peptide Helix

NASA Astrophysics Data System (ADS)

Shoemaker, Kevin R.; Kim, Peter S.; Brems, David N.; Marqusee, Susan; York, Eunice J.; Chaiken, Irwin M.; Stewart, John M.; Baldwin, Robert L.

1985-04-01

The residues responsible for the pH-dependent stability of the helix formed by the isolated C-peptide (residues 1-13 of ribonuclease A) have been identified by chemical synthesis of analogues and measurement of their helix-forming properties. Each of the residues ionizing between pH 2 and pH 8 has been replaced separately by an uncharged residue. Protonation of Glu-2- is responsible for the sharp decrease in helix stability between pH 5 and pH 2, and deprotonation of His-12+ causes a similar decrease between pH 5 and pH 8. Glu-9- is not needed for helix stability. The results cannot be explained by the Zimm-Bragg model and host-guest data for α -helix formation, which predict that the stability of the C-peptide helix should increase when Glu-2- is protonated or when His-12+ is deprotonated. Moreover, histidine+ is a strong helix-breaker in host-guest studies. In proteins, acidic and basic residues tend to occur at opposite ends of α -helices: acidic residues occur preferentially near the NH2-terminal end and basic residues near the COOH-terminal end. A possible explanation, based on a helix dipole model, has been given [Blagdon, D. E. & Goodman, M. (1975) Biopolymers 14, 241-245]. Our results are consistent with the helix dipole model and they support the suggestion that the distribution of charged residues in protein helices reflects the helix-stabilizing propensity of those residues. Because Glu-9 is not needed for helix stability, a possible Glu-9-\\cdots His-12+ salt bridge does not contribute significantly to helix stability. The role of a possible Glu-2-\\cdots Arg-10+ salt bridge has not yet been evaluated. A charged-group effect on α -helix stability in water has also been observed in a different peptide system [Ihara, S., Ooi, T. & Takahashi, S. (1982) Biopolymers 21, 131-145]: block copolymers containing (Ala)20 and (Glu)20 show partial helix formation at low temperatures, pH 7.5, where the glutamic acid residues are ionized. (Glu)20(Ala)20Phe forms a helix that is markedly more stable than (Ala)20(Glu)20Phe. The results are consistent with a helix dipole model.

Reduced gas seepages in serpentinized peridotite complexes: Evidences for multiple origins of the H2-CH4-N2 gas mixtures

NASA Astrophysics Data System (ADS)

Deville, E.; Vacquand, C.; Beaumont, V.; Francois, G.; Sissmann, O.; Pillot, D.; Arcilla, C. A.; Prinzhofer, A.

2017-12-01

A comparative study of reduced gas seepages associated to serpentinized ultrabasic rocks was conducted in the ophiolitic complexes of Oman, the Philippines, Turkey and New Caledonia. This study is based on analyzes of the gas chemical composition, noble gases contents, and stable isotopes of carbon, hydrogen and nitrogen. These gas seepages are mostly made of mixtures of three main components which are H2, CH4 and N2 in various proportions. The relative contents of the three main gas components show 4 distinct families of gas mixtures (H2-rich, N2-rich, N2-H2-CH4 and H2-CH4). These families are interpreted as reflecting different zones of gas generation within or below the ophiolitic complexes. In the H2-rich family associated noble gases display signatures close to the value of air. In addition to the atmospheric component, mantle and crustal contributions are present in the N2-rich, N2-H2-CH4 and H2-CH4 families. H2-bearing gases are either associated to ultra-basic (pH 10-12) spring waters or they seep directly in fracture systems from the ophiolitic rocks. In ophiolitic contexts, ultrabasic rocks provide an adequate environment with available Fe2+ and high pH conditions that favor H2 production. CH4 is produced either directly by reaction of dissolved CO2 with basic-ultrabasic rocks during the serpentinization process or in a second step by H2-CO2 interaction. H2 is present in the gas when no more carbon is available in the system to generate CH4 (conditions of strong carbon restriction). The N2-rich family is associated with relatively high contents of crustal 4He. In this family N2 is interpreted as issued mainly from sediments located below the ophiolitic units.

Release kinetics of vanadium from vanadium titano-magnetite: The effects of pH, dissolved oxygen, temperature and foreign ions.

PubMed

Hu, Xingyun; Yue, Yuyan; Peng, Xianjia

2018-02-01

As part of a broader study of the environmental geochemistry behavior of vanadium (V), the release kinetics of V from the dissolution of natural vanadium titano-magnetite under environmentally relevant conditions was investigated. In both the acidic and basic domains, the V release rate was found to be proportional to fractional powers of hydrogen ion and dissolved oxygen activities. The dependence of the rate on dissolved oxygen can also be described in terms of the Langmuir adsorption model. The empirical rate equation is given by: r [Formula: see text] where, α=0.099-0.265, k'=3.2×10 -6 -1.7×10 -5 , K=2.7×10 4 -3.9×10 4 mol/L in acid solution (pH4.1), and α=-0.494-(-0.527), k'=2.0×10 4 -2.5×10 -11 , and K=4.1×10 3 -6.5×10 3 mol/L in basic solution (pH8.8) at 20°C. Based on the effect of temperature on the release rate of V, the activation energies of minerals at pH8.8 were determined to be 148-235kJ/mol, suggesting that the dissolution of vanadium titano-magnetite is a surface-controlled process. The presence of Na + , Ca 2+ , Mg 2+ , K + , NO 3 - , Cl - , SO 4 2- and CO 3 2- was found to accelerate the V release rates. This study improves the understanding of both the V pollution risk in some mine areas and the fate of V in the environment. Copyright © 2017. Published by Elsevier B.V.

The hydrolysis kinetics of monobasic and dibasic aminoalkyl esters of ketorolac.

PubMed

Qandil, Amjad M; Jamhawi, Noor M; Tashtoush, Bassam M; Al-Ajlouni, Ahmad M; Idkaidek, Nasir M; Obaidat, Aiman A

2013-09-01

Six aminoethyl and aminobutyl esters of ketorolac containing 1-methylpiperazine (MPE and MPB), N-acetylpiperazine (APE and APB) or morpholine (ME and MB), were synthesized and their hydrolysis kinetics were studied. The hydrolysis was studied at pH 1 to 9 (for MPE, APE and ME) and pH 1 to 8 (for MPB, APB and MB) in aqueous phosphate buffer (0.16 M) with ionic strength (0.5 M) at 37°C. Calculation of k(obs), construction of the pH-rate profiles and determination of the rate equations were performed using KaleidaGraph® 4.1. The hydrolysis displays pseudo-first order kinetics and the pH-rate profiles shows that the aminobutyl esters, MPE, APB and MB, are the most stable. The hydrolysis of the ethyl esters MPE, APE and ME, depending on the pH, is either fast and catalyzed by the hydroxide anion or slow and uncatalyzed for the diprotonated, monoprotonated and nonprotonated forms. The hydrolysis of the butyl esters showed a similar profile, albeit it was also catalyzed by hydronium cation. In addition, the hydroxide anion is 105 more effective in catalyzing the hydrolysis than the hydronium cation. The hydrolysis pattern of the aminoethyl esters is affected by the number and pKa of its basic nitrogen atoms. The monobasic APE and ME, show a similar hydrolysis pattern that is different than the dibasic MPE. The length of the side chain and the pKa of the basic nitrogen atoms in the aminoethyl moiety affect the mechanism of hydrolysis as the extent of protonation at a given pH is directly related to the pKa.

Cortlandtitic enclaves associated with calc-alkaline granites from Tapia-Asturias (Hercynian Belt, northwestern Spain)

NASA Astrophysics Data System (ADS)

Galán, G.; Suárez, O.

1989-10-01

Petrographic and mineralogical characteristics of amphibole-olivine- and pyroxene-bearing ultramafic rocks from Asturias (NW Spain) are dealt with in this paper. These rocks are of cortlandtitic type and occur as small rare enclaves in basic rocks related to Hercynian calc-alkaline, post-tectonic epizonal granites, in the northwest of the Iberian Peninsula. These particular ultramafic enclaves are characterized by poikilitic cumulate microtexture. Olivine (Fo 77-81), spinel, from chromite to pleonaste composition, enstatite, subordinated diopside and sulphides are included in large brown calcic amphibole crystals displaying an irregular zonation. Phlogopite and plagioclase are also found, in a much lower proportion, between the large amphibole crystals. Mineral assemblage and chemical composition of minerals indicate formation conditions of 1150°C, 7-8 kbar of Ptotal and PH 2O < Ptotal. These rocks could represent the earlier products of fractional crystallization from a hydrated high-alumina basalt involved in the genesis of the calc-alkaline granites. This basic magma would start crystallizing at a relatively deep level, carrying up the first products of its crystallization during its ascent.

PhOBF1, a petunia ocs element binding factor, plays an important role in antiviral RNA silencing.

PubMed

Sun, Daoyang; Li, Shaohua; Niu, Lixin; Reid, Michael S; Zhang, Yanlong; Jiang, Cai-Zhong

2017-02-01

Virus-induced gene silencing (VIGS) is a common reverse genetics strategy for characterizing the function of genes in plants. The detailed mechanism governing RNA silencing efficiency triggered by viruses is largely unclear. Here, we reveal that a petunia (Petunia hybrida) ocs element binding factor, PhOBF1, one of the basic leucine zipper (bZIP) transcription factors, was up-regulated by Tobacco rattle virus (TRV) infection. Simultaneous silencing of PhOBF1 and a reporter gene, phytoene desaturase (PDS) or chalcone synthase (CHS), by TRV-based VIGS led to a failure of the development of leaf photobleaching or the white-corollas phenotype. PhOBF1 silencing caused down-regulation of RNA silencing-related genes, including RNA-dependent RNA polymerases (RDRs), Dicer-like RNase III enzymes (DCLs), and Argonautes (AGOs). After inoculation with the TRV-PhPDS, PhOBF1-RNAi lines exhibited a substantially impaired PDS silencing efficiency, whereas overexpression of PhOBF1 resulted in a recovery of the silencing phenotype (photobleaching) in systemic leaves. A compromised resistance to TRV and Tobacco mosaic virus was found in PhOBF1-RNAi lines, while PhOBF1-overexpressing lines displayed an enhanced resistance to their infections. Compared with wild-type plants, PhOBF1-silenced plants accumulated lower levels of free salicylic acid (SA), salicylic acid glucoside, and phenylalanine, contrarily to higher levels of those in plants overexpressing PhOBF1. Furthermore, transcripts of a number of genes associated with the shikimate and phenylpropanoid pathways were decreased or increased in PhOBF1-RNAi or PhOBF1-overexpressing lines, respectively. Taken together, the data suggest that PhOBF1 regulates TRV-induced RNA silencing efficiency through modulation of RDRs, DCLs, and AGOs mediated by the SA biosynthesis pathway. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Metabolic Control in Mammalian Fed-Batch Cell Cultures for Reduced Lactic Acid Accumulation and Improved Process Robustness

PubMed Central

Konakovsky, Viktor; Clemens, Christoph; Müller, Markus Michael; Bechmann, Jan; Berger, Martina; Schlatter, Stefan; Herwig, Christoph

2016-01-01

Biomass and cell-specific metabolic rates usually change dynamically over time, making the “feed according to need” strategy difficult to realize in a commercial fed-batch process. We here demonstrate a novel feeding strategy which is designed to hold a particular metabolic state in a fed-batch process by adaptive feeding in real time. The feed rate is calculated with a transferable biomass model based on capacitance, which changes the nutrient flow stoichiometrically in real time. A limited glucose environment was used to confine the cell in a particular metabolic state. In order to cope with uncertainty, two strategies were tested to change the adaptive feed rate and prevent starvation while in limitation: (i) inline pH and online glucose concentration measurement or (ii) inline pH alone, which was shown to be sufficient for the problem statement. In this contribution, we achieved metabolic control within a defined target range. The direct benefit was two-fold: the lactic acid profile was improved and pH could be kept stable. Multivariate Data Analysis (MVDA) has shown that pH influenced lactic acid production or consumption in historical data sets. We demonstrate that a low pH (around 6.8) is not required for our strategy, as glucose availability is already limiting the flux. On the contrary, we boosted glycolytic flux in glucose limitation by setting the pH to 7.4. This new approach led to a yield of lactic acid/glucose (Y L/G) around zero for the whole process time and high titers in our labs. We hypothesize that a higher carbon flux, resulting from a higher pH, may lead to more cells which produce more product. The relevance of this work aims at feeding mammalian cell cultures safely in limitation with a desired metabolic flux range. This resulted in extremely stable, low glucose levels, very robust pH profiles without acid/base interventions and a metabolic state in which lactic acid was consumed instead of being produced from day 1. With this contribution, we wish to extend the basic repertoire of available process control strategies, which will open up new avenues in automation technology and radically improve process robustness in both process development and manufacturing. PMID:28952567

Functional and rheological properties of proteins in frozen turkey breast meat with different ultimate pH.

PubMed

Chan, J T Y; Omana, D A; Betti, M

2011-05-01

Functional and rheological properties of proteins from frozen turkey breast meat with different ultimate pH at 24 h postmortem (pH(24)) have been studied. Sixteen breast fillets from Hybrid Tom turkeys were initially selected based on lightness (L*) values for each color group (pale, normal, and dark), with a total of 48 breast fillets. Further selection of 8 breast samples was made within each class of meat according to the pH(24). The average L* and pH values of the samples were within the following range: pale (L* >52; pH ≤5.7), normal (46 < L* < 52; 5.9 < pH <6.1), and dark (L* <46; pH ≥6.3), referred to as low, normal, and high pH meat, respectively. Ultimate pH did not cause major changes in the emulsifying and foaming properties of the extracted sarcoplasmic and myofibrillar proteins. An SDS-PAGE profile of proteins from low and normal pH meat was similar, which revealed that the extent of protein denaturation was the same. Low pH meat had the lowest water-holding capacity compared with normal and high pH meat as shown by the increase in cooking loss, which can be explained by factors other than protein denaturation. Gel strength analysis and folding test revealed that gel-forming ability was better for high pH meat compared with low and normal pH meat.Dynamic viscoelastic behavior showed that myosin denaturation temperature was independent of pH(24). Normal and high pH meat had similar hardness, springiness, and chewiness values as revealed by texture profile analysis. The results from this study indicate that high pH meat had similar or better functional properties than normal pH meat. Therefore, high pH meat is suitable for further processed products, whereas low pH meat may need additional treatment or ingredient formulations to improve its functionality.

phMRI: methodological considerations for mitigating potential confounding factors

PubMed Central

Bourke, Julius H.; Wall, Matthew B.

2015-01-01

Pharmacological Magnetic Resonance Imaging (phMRI) is a variant of conventional MRI that adds pharmacological manipulations in order to study the effects of drugs, or uses pharmacological probes to investigate basic or applied (e.g., clinical) neuroscience questions. Issues that may confound the interpretation of results from various types of phMRI studies are briefly discussed, and a set of methodological strategies that can mitigate these problems are described. These include strategies that can be employed at every stage of investigation, from study design to interpretation of resulting data, and additional techniques suited for use with clinical populations are also featured. Pharmacological MRI is a challenging area of research that has both significant advantages and formidable difficulties, however with due consideration and use of these strategies many of the key obstacles can be overcome. PMID:25999812

Communication: Quantum molecular dynamics simulation of liquid para-hydrogen by nuclear and electron wave packet approach.

PubMed

Hyeon-Deuk, Kim; Ando, Koji

2014-05-07

Liquid para-hydrogen (p-H2) is a typical quantum liquid which exhibits strong nuclear quantum effects (NQEs) and thus anomalous static and dynamic properties. We propose a real-time simulation method of wave packet (WP) molecular dynamics (MD) based on non-empirical intra- and inter-molecular interactions of non-spherical hydrogen molecules, and apply it to condensed-phase p-H2. The NQEs, such as WP delocalization and zero-point energy, are taken into account without perturbative expansion of prepared model potential functions but with explicit interactions between nuclear and electron WPs. The developed MD simulation for 100 ps with 1200 hydrogen molecules is realized at feasible computational cost, by which basic experimental properties of p-H2 liquid such as radial distribution functions, self-diffusion coefficients, and shear viscosities are all well reproduced.

Constitutive and inducible pectinolytic enzymes from Aspergillus flavipes FP-500 and their modulation by pH and carbon source

PubMed Central

Martínez-Trujillo, Aurora; Aranda, Juan S.; Gómez-Sánchez, Carlos; Trejo-Aguilar, Blanca; Aguilar-Osorio, Guillermo

2009-01-01

Growth and enzymes production by Aspergillus flavipes FP-500 were evaluated on pectin, polygalacturonic acid, galacturonic acid, arabinose, rhamnose, xylose, glycerol and glucose at different initial pH values. We found that the strain produced exopectinases, endopectinases and pectin lyases. Exopectinases and pectin lyase were found to be produced at basal levels as constitutive enzymes and their production was modulated by the available carbon source and pH of culture medium and stimulated by the presence of inducer in the culture medium. Endo-pectinase was basically inducible and was only produced when pectin was used as carbon source. Our results suggest that pectinases in A. flavipes FP-500 are produced in a concerted way. The first enzyme to be produced was exopectinase followed by Pectin Lyase and Endo-pectinase. PMID:24031315

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.

Design and characterization of a plastic optical fiber pH sensor

NASA Astrophysics Data System (ADS)

Ferreira, Licínio; Simões, Pedro; Carvalho, Rui S.; Lopes, Paulo; Ferreira, Mário

2013-11-01

In this paper are present the design and characterization of a pH sensor using plastic optical fiber (POF) technology and a material produced by the sol-gel process with TEOS (tetraethyl orthosilicate) to immobilize universal indicator of pH (comprised of Thymol Blue, Methyl Red, Bromothymol Blue and Phenolphthalein) inside the silica matrix. This matrix is positioned between two extensions of plastic optical fiber tightly positioned at each side with both fibers aligned and sharing a common optical axis. This set will work as a pH sensor since the matrix embedded with indicator and in the presence of a solution (basic or acid solution) will change the optical transmittance properties. The optical source is a superluminescent white LED and the receiver is a photodiode having a good and linear responsivity in the visible spectrum. This pH sensitive matrix has large pores which allow the diffusion of the surrounding fluid molecules into the matrix and thus the close contact of these to the indicator molecules. This contact causes the change of color of the whole matrix allowing proper colorimetric detection by the photodiode. This variation of color associated with the detector wavelength linear response is the base of operation of the proposed device. This pH sensor presents many advantages over the standard and commercial pH meters namely, lightweight, portability and a low cost.

Preparation of Rh/Ag bimetallic nanoparticles as effective catalyst for hydrogen generation from hydrolysis of KBH4

NASA Astrophysics Data System (ADS)

Huang, Liang; Jiao, Chengpeng; Wang, Liqiong; Huang, Zili; Liang, Feng; Liu, Simin; Wang, Yuhua; Zhang, Haijun; Zhang, Shaowei

2018-01-01

ISOBAM-104 protected Rh/Ag bimetallic nanoparticles (NPs) with average diameter less than 3.0 nm were synthesized by a co-reduction method. Ultraviolet-visible spectroscopy, transmission electron microscopy (TEM), high-resolution TEM and x-ray photoelectron spectroscopy (XPS) were employed to characterize the structure, particle size, and electronic structure of the prepared bimetallic NPs. The catalytic activities of prepared bimetallic NPs for hydrogen generation from hydrolysis of a basic KBH4 solution were evaluated in detail. The results indicated that as-prepared Rh/Ag bimetallic NPs showed a higher catalytic activity than corresponding monometallic NPs. Among all the monometallic NPs and bimetallic NPs, Rh80Ag20 bimetallic NPs exhibited the highest catalytic activity with a value of 6010 mol-H2·h-1·mol-catalyst-1 at pH = 12 and 303 K. The high catalytic activities of Rh/Ag bimetallic NPs could be attributed to presence of negatively charged Rh atoms and positively charged Ag atoms, which is supported by the results of XPS and density functional theory calculation. Based on the kinetic study, the apparent activation energy for the hydrolysis reaction of the basic KBH4 solution catalyzed by Rh80Ag20 bimetallic NPs was about 47.0 ± 3.9 kJ mol-1.

Acetic acid bacteria in traditional balsamic vinegar: phenotypic traits relevant for starter cultures selection.

PubMed

Gullo, Maria; Giudici, Paolo

2008-06-30

This review focuses on acetic acid bacteria in traditional balsamic vinegar process. Although several studies are available on acetic acid bacteria ecology, metabolism and nutritional requirements, their activity as well as their technological traits in homemade vinegars as traditional balsamic vinegar is not well known. The basic technology to oxidise cooked grape must to produce traditional balsamic vinegar is performed by the so called "seed-vinegar" that is a microbiologically undefined starter culture obtained from spontaneous acetification of previous raw material. Selected starter cultures are the main technological improvement in order to innovate traditional balsamic vinegar production but until now they are rarely applied. To develop acetic acid bacteria starter cultures, selection criteria have to take in account composition of raw material, acetic acid bacteria metabolic activities, applied technology and desired characteristics of the final product. For traditional balsamic vinegar, significative phenotypical traits of acetic acid bacteria have been highlighted. Basic traits are: ethanol preferred and efficient oxidation, fast rate of acetic acid production, tolerance to high concentration of acetic acid, no overoxidation and low pH resistance. Specific traits are tolerance to high sugar concentration and to a wide temperature range. Gluconacetobacter europaeus and Acetobacter malorum strains can be evaluated to develop selected starter cultures since they show one or more suitable characters.

Stibiconite (Sb3O6OH), senarmontite (Sb2O3) and valentinite (Sb2O3): Dissolution rates at pH 2-11 and isoelectric points

NASA Astrophysics Data System (ADS)

Biver, M.; Shotyk, W.

2013-05-01

Batch reactor experiments were carried out in order to derive rate laws for the proton promoted dissolution of the main natural antimony oxide phases, namely stibiconite (idealized composition SbSb2O6OH), senarmontite (cubic Sb2O3) and (metastable) valentinite (orthorhombic Sb2O3) over the range 2 ⩽ pH ⩽ 11, under standard conditions and ionic strength I = 0.01 mol l-1. The rates of antimony release by stibiconite were r = (2.2 ± 0.2) × 10-9 a(H+)0.11±0.01 mol m-2 s-1 for 2.00 ⩽ pH ⩽ 4.74 and r = (4.3 ± 0.2) × 10-10 a(H+)-0.030±0.003 mol m-2 s-1 for 4.74 ⩽ pH ⩽ 10.54. The rates of dissolution of senarmontite were r = (5.3 ± 2.2) × 10-7 a(H+)0.54±0.05 mol m-2 s-1 for 2.00 ⩽ pH ⩽ 6.93 and r = (1.4 ± 0.3) × 10-14 a(H+)-0.53±0.07 mol m-2 s-1 for 6.93 ⩽ pH ⩽ 10.83. The rates of dissolution of valentinite were r = (6.3 ± 0.2) × 10-8 a(H+)0.052±0.003 mol m-2 s-1 for 1.97 ⩽ pH ⩽ 6.85. Above pH = 6.85, valentinite was found to dissolve at a constant rate of r = (2.79 ± 0.05) × 10-8 mol m-2 s-1. Activation energies were determined at selected pH values in the acidic and basic domain, over the temperature range 25-50 °C. The values for stibiconite are -10.6 ± 1.9 kJ mol-1 (pH = 2.00) and 53 ± 14 kJ mol-1 (pH = 8.7). For senarmontite, we found 46.6 ± 4.7 kJ mol-1 (pH = 3.0) and 68.1 ± 6.1 kJ mol-1 (pH = 9.9) and for valentinite 41.9 ± 1.1 kJ mol-1 (pH = 3.0) and 39.0 ± 4.6 kJ mol-1 (pH = 9.9). These activation energies are interpreted in the text. The solubility of stibiconite at 25 °C in the pH domain from 2 to 10 was determined; solubilities decrease from 452.0 μg l-1 (as Sb) at pH = 2.00 to 153.2 μg l-1 at pH = 7.55 and increase again in the basic region, up to 176.6 μg l-1 at pH = 9.92. A graphical synopsis of all the kinetic results, including those of stibnite (Sb2S3) from earlier work, is presented. This allows an easy comparison between the dissolution rates of stibnite and the minerals examined in the present work. The isoelectric point (i.e.p.) of the minerals was determined electrokinetically, as a proxy for the zero point of charge (pHzpc), which was experimentally inaccessible; the measured i.e.p. do not correspond to the dissolution rate minima. I.e.p. of antimony oxides have not yet been documented in the literature. The geochemical implications for the weathering of antimony oxide minerals and stibnite, with particular reference to the mobilization of antimony in the context of an abandoned antimony mine (Goesdorf, Luxembourg), are discussed.

Computational and theoretical modeling of pH and flow effects on the early-stage non-equilibrium self-assembly of optoelectronic peptides

NASA Astrophysics Data System (ADS)

Mansbach, Rachael; Ferguson, Andrew

Self-assembling π-conjugated peptides are attractive candidates for the fabrication of bioelectronic materials possessing optoelectronic properties due to electron delocalization over the conjugated peptide groups. We present a computational and theoretical study of an experimentally-realized optoelectronic peptide that displays triggerable assembly in low pH to resolve the microscopic effects of flow and pH on the non-equilibrium morphology and kinetics of assembly. Using a combination of molecular dynamics simulations and hydrodynamic modeling, we quantify the time and length scales at which convective flows employed in directed assembly compete with microscopic diffusion to influence assembly. We also show that there is a critical pH below which aggregation proceeds irreversibly, and quantify the relationship between pH, charge density, and aggregate size. Our work provides new fundamental understanding of pH and flow of non-equilibrium π-conjugated peptide assembly, and lays the groundwork for the rational manipulation of environmental conditions and peptide chemistry to control assembly and the attendant emergent optoelectronic properties. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award # DE-SC0011847, and by the Computational Science and Engineering Fellowship from the University of Illinois at Urbana-Champaign.

Properties of the ion-ion hybrid resonator in fusion plasmas

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

Morales, George J.

2015-10-06

The project developed theoretical and numerical descriptions of the properties of ion-ion hybrid Alfvén resonators that are expected to arise in the operation of a fusion reactor. The methodology and theoretical concepts were successfully compared to observations made in basic experiments in the LAPD device at UCLA. An assessment was made of the excitation of resonator modes by energetic alpha particles for burning plasma conditions expected in the ITER device. The broader impacts included the generation of basic insight useful to magnetic fusion and space science researchers, defining new avenues for exploration in basic laboratory experiments, establishing broader contacts betweenmore » experimentalists and theoreticians, completion of a Ph.D. dissertation, and promotion of interest in science through community outreach events and classroom instruction.« less

Further purification of human pituitary-derived chondrocyte growth factor: heparin-binding and cross-reactivity with antiserum to basic FGF.

PubMed

Too, C K; Murphy, P R; Hamel, A M; Friesen, H G

1987-05-14

The previously described human pituitary-derived chondrocyte growth factor (CGF), mitogenic for rabbit fetal chondrocytes, was found to bind to heparin-Sepharose and was eluted with 1.5M NaCl. Further characterization of CGF demonstrated a molecular weight of 18-20 kD and cross-reactivity with antiserum to synthetic bovine basic fibroblast growth factor (FGF1-24). When human pituitaries were homogenized in 0.15 ammonium sulfate (pH 5.5) and the extract chromatographed on heparin-Sepharose, 98% of the mitogenic activity was adsorbed to heparin and eluted with 3M NaCl. These findings indicate that CGF is closely related or identical to basic FGF and that the bulk of mitogenic activity in the human pituitary extracts binds to heparin.

Experimental Evolution of Escherichia coli K-12 at High pH and RpoS Induction.

PubMed

Hamdallah, Issam; Torok, Nadia; Bischof, Katarina M; Majdalani, Nadim; Chadalavada, Sriya; Mdluli, Nonto; Creamer, Kaitlin E; Clark, Michelle; Holdener, Chase; Basting, Preston J; Gottesman, Susan; Slonczewski, Joan L

2018-05-25

Experimental evolution of Escherichia coli K-12 W3110 by serial dilutions for 2,200 generations at high pH extended the range of sustained growth from pH 9.0 to pH 9.3. pH 9.3-adapted isolates showed mutations in DNA-binding regulators and envelope proteins. One population showed an IS1 knockout of phoB (positive regulator of the phosphate regulon). A phoB :: kanR knockout increased growth at high pH. phoB mutants are known to increase production of fermentation acids, which could enhance fitness at high pH. Mutations in pcnB (poly(A) polymerase) also increased growth at high pH. Three out of four populations showed deletions of torI, an inhibitor of TorR, which activates expression of torCAD (trimethylamine N-oxide respiration) at high pH. All populations showed point mutations affecting the stationary-phase sigma RpoS, either in the coding gene or in regulators of RpoS expression. RpoS is required for survival in extreme base. In our microplate assay, rpoS deletion slightly decreased growth at pH 9.1. RpoS protein accumulated faster at pH 9 than at pH 7. The RpoS accumulation at high pH required the presence of one or more antiadapters that block degradation (IraM, IraD, and IraP). Other genes with mutations after high pH evolution encode regulators such as yobG ( mgrB ) (PhoPQ regulator), rpoN (nitrogen starvation sigma), malI , and purR ; as well as envelope proteins ompT and yahO Overall, E. coli evolution at high pH selects for mutations in key transcriptional regulators, including phoB and the stationary-phase sigma RpoS. IMPORTANCE Escherichia coli in its native habitat encounters high pH stress such as that of pancreatic secretions. Experimental evolution over 2,000 generations showed selection for mutations in regulatory factors, such as deletion of the phosphate regulator PhoB and mutations that alter function of the global stress regulator RpoS. RpoS is induced at high pH via multiple mechanisms. Copyright © 2018 American Society for Microbiology.

Growth of plant tissue cultures in simulated lunar soil: Implications for a lunar base CELSS (Controlled Ecological Life Support System)

NASA Technical Reports Server (NTRS)

Venketeswaran, S.

1988-01-01

Experiments were carried out on plant tissue cultures, seed germination, seedling development and plants grown on Simulated Lunar Soil to evaluate the potential of future development of lunar based agriculture. The studies done to determine the effect of the placement of SLS on tissue cultures showed no adverse effect of SLS on tissue cultures. Although statistically insignificant, SLS in suspension showed a comparatively higher growth rate. Observations indicate the SLS, itself cannot support calli growth but was able to show a positive effect on growth rate of calli when supplemented with MS salts. This positive effect related to nutritive value of the SLS was found to have improved at high pH levels, than at the recommended low pH levels for standard media. Results from seed germination indicated that there is neither inhibitory, toxicity nor stimulatory effect of SLS, even though SLS contains high amounts of aluminum compounds compared to earth soil. Analysis of seeding development and growth data showed significant reduction in growth rate indicating that, SLS was a poor growth medium for plant life. This was confirmed by the studies done with embryos and direct plant growth on SLS. Further observations attributed this poor quality of SLS is due to it's lack of essential mineral elements needed for plant growth. By changing the pH of the soil, to more basic conditions, the quality of SLS for plant growth could be improved up to a significant level. Also it was found that the quality of SLS could be improved by almost twice, by external supply of major mineral elements, directly to SLS.

Temperature and pH Dual-Responsive Core-Brush Nanocomposite for Enrichment of Glycoproteins.

PubMed

Jiang, Lingdong; Messing, Maria E; Ye, Lei

2017-03-15

In this report, we present a novel modular approach to the immobilization of a high density of boronic acid ligands on thermoresponsive block copolymer brushes for effective enrichment of glycoproteins via their synergistic multiple covalent binding with the immobilized boronic acids. Specifically, a two-step, consecutive surface-initiated atom transfer radical polymerization (SI-ATRP) was employed to graft a flexible block copolymer brush, pNIPAm-b-pGMA, from an initiator-functionalized nanosilica surface, followed by postpolymerization modification of the pGMA moiety with sodium azide. Subsequently, an alkyne-tagged boronic acid (PCAPBA) was conjugated to the polymer brush via a Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction, leading to a silica-supported polymeric hybrid material, Si@pNIPAm-b-pBA, with a potent glycol binding affinity. The obtained core-brush nanocomposite was systematically characterized with regard to particle size, morphology, organic content, brush density, and number of immobilized boronic acids. We also studied the characteristics of glycoprotein binding of the nanocomposite under different conditions. The nanocomposite showed high binding capacities for ovalbumin (OVA) (98.0 mg g -1 ) and horseradish peroxidase (HRP) (26.8 mg g -1 ) in a basic buffer (pH 9.0) at 20 °C. More importantly, by adjusting the pH and temperature, the binding capacities of the nanocomposite can be tuned, which is meaningful for the separation of biological molecules. In general, the synthetic approach developed for the fabrication of block copolymer brushes in the nanocomposite opened new opportunities for the design of more functional hybrid materials that will be useful in bioseparation and biomedical applications.

Clinical Physiology: A Successful Academic and Clinical Discipline is Threatened in Sweden

ERIC Educational Resources Information Center

Arheden, Hakan

2009-01-01

Clinical physiologists in Sweden are physicians (the majority with a PhD degree) with thorough training in system physiology and pathophysiology. They investigate patients in a functional approach and are engaged in basic and applied physiology teaching and research. In 1954, clinical physiology was founded as an independent academic and clinical…

Steel slag affects pH and Si content of container substrates

USDA-ARS?s Scientific Manuscript database

A substrate representing a typical greenhouse potting mix was prepared using 85% sphagnum peat and 15% perlite. The substrate was filled into 10 cm wide containers. A pulverized steel slag (SS) from a basic oxygen furnace, and dolomitic limestone (DL) were amended to the base substrate at a rate o...

Physician as Scientist: Preparation, Performance, and Prospects

ERIC Educational Resources Information Center

Castle, William B.

1976-01-01

Greatly modifying the present medical curriculum for the future physician-scientist is not recommended. The value of his having a PhD is questioned and the importance of his working in a hospital-based clinical department is stressed. The author contends that emphasizing the interrelationship between basic and applied research will increase public…

Soil Nutrients and pH in Southern Hardwood Nurseries

Treesearch

F. T. Bonner; W. M. Broadfoot

1964-01-01

The rapidly expanding interest in hardwoods in the South has caused many forest nurseries, to begin growing hardwood as well as pine seedlings. Apparently most nurserymen have been able to accomplish this change without great difficulty. Nursery sites and soil conditions suitable for pines should be basically satisfactory for hardwoods also.

Discernment of lint trash in raw cotton using multivariate analysis of excitation-emission luminescence spectra

USDA-ARS?s Scientific Manuscript database

Excitation-Emission luminescence spectra of basic (pH 12.5) phosphate buffer solution extracts were used to distinguish among botanical components of trash within seed cotton. All components were separated from whole plants removed from a field in southern New Mexico. Unfolded Principal Component An...

Cysteine Racemization on IgG Heavy and Light Chains

PubMed Central

Zhang, Qingchun; Flynn, Gregory C.

2013-01-01

Under basic pH conditions, the heavy chain 220-light chain 214 (H220-L214) disulfide bond, found in the flexible hinge region of an IgG1, can convert to a thioether. Similar conditions also result in racemization of the H220 cysteine. Here, we report that racemization occurs on both H220 and L214 on an IgG1 with a λ light chain (IgG1λ) but almost entirely on H220 of an IgGl with a κ light chain (IgG1κ) under similar conditions. Likewise, racemization was detected at significant levels on H220 and L214 on endogenous human IgG1λ but only at the H220 position on IgG1κ. Low but measurable levels of d-cysteines were found on IgG2 cysteines in the hinge region, both with monoclonal antibodies incubated under basic pH conditions and on antibodies isolated from human serum. A simplified reaction mechanism involving reversible β-elimination on the cysteine is presented that accounts for both base-catalyzed racemization and thioether formation at the hinge disulfide. PMID:24142697

Chemical durability of alkali-borosilicate glasses studied by analytical SEM, IBA, isotopic-tracing and SIMS

NASA Astrophysics Data System (ADS)

Trocellier, P.; Djanarthany, S.; Chêne, J.; Haddi, A.; Brass, A. M.; Poissonnet, S.; Farges, F.

2005-10-01

Simple and complex alkali-borosilicate glasses were submitted to aqueous corrosion at room temperature, 60 and 90 °C in solutions with pH ranging between 0 and 12. Analytical scanning electron microscopy (SEM), ion beam analysis (IBA) techniques, isotopic tracing and secondary ion mass-depth profiling (SIMS) have been used to investigate the variations of the surface composition of glass. In acidic medium, the glass surface is generally covered by a thick hydrated silica layer, mobile elements like Li, Na and B and transition elements (Fe, Zr, Mo, etc.) are strongly depleted. Near pH 7, relative enrichments of aluminium, iron and rare earths are shown together with strong Li, Na and B depletions. In basic medium, the glass surface exhibits relative enrichments of the major part of transition metals (from Cr to U) whereas mobile elements seem to be kept close to their nominal concentration level at the glass surface and Si is severely impoverished. Hydrogen incorporated at the glass surface after leaching is much more immobile in neutral and basic media than in acid medium.

Small Angle X-Ray Scattering from Lipid-Bound Myelin Basic Protein in Solution

PubMed Central

Haas, H.; Oliveira, C. L. P.; Torriani, I. L.; Polverini, E.; Fasano, A.; Carlone, G.; Cavatorta, P.; Riccio, P.

2004-01-01

The structure of myelin basic protein (MBP), purified from the myelin sheath in both lipid-free (LF-MBP) and lipid-bound (LB-MBP) forms, was investigated in solution by small angle x-ray scattering. The water-soluble LF-MBP, extracted at pH < 3.0 from defatted brain, is the classical preparation of MBP, commonly regarded as an intrinsically unfolded protein. LB-MBP is a lipoprotein-detergent complex extracted from myelin with its native lipidic environment at pH > 7.0. Under all conditions, the scattering from the two protein forms was different, indicating different molecular shapes. For the LB-MBP, well-defined scattering curves were obtained, suggesting that the protein had a unique, compact (but not globular) structure. Furthermore, these data were compatible with earlier results from molecular modeling calculations on the MBP structure which have been refined by us. In contrast, the LF-MBP data were in accordance with the expected open-coil conformation. The results represent the first direct structural information from x-ray scattering measurements on MBP in its native lipidic environment in solution. PMID:14695288

Simulations of the Viking Gas Exchange Experiment using palagonite and Fe-rich montmorillonite as terrestrial analogs: implications for the surface composition of Mars.

PubMed

Quinn, R; Orenberg, J

1993-10-01

Simulations of the Gas Exchange Experiment (GEX), one of the Viking Lander Biology Experiments, were run using palagonite and Fe-rich montmorillonite as terrestrial analogs of the Martian soil. These terrestrial analogs were exposed to a nutrient solution of the same composition as that of the Viking Landers under humid (no contact with nutrient) and wet (intimate contact) conditions. The headspace gases in the GEX sample cell were sampled and then analyzed by gas chromatography under both humid and wet conditions. Five gases were monitored: CO2, N2, O2, Ar, and Kr. It was determined that in order to simulate the CO2 gas changes of the Viking GEX experiment, the mixture of soil analog mineral plus nutrient medium must be slightly (pH = 7.4) to moderately basic (pH = 8.7). This conclusion suggests constraints upon the composition of terrestrial analogs to the Mars soil; acidic components may be present, but the overall mixture must be basic in order to simulate the Viking GEX results.

Simulations of the Viking gas exchange experiment using palagonite and Fe-rich montmorillonite as terrestrial analogs - Implications for the surface composition of Mars

NASA Astrophysics Data System (ADS)

Quinn, Richard; Orenberg, James

1993-10-01

Simulations of the Gas Exchange Experiment (GEX), one of the Viking Lander Biology Experiments, were run using palagonite and Fe-rich montmorillonite as terrestrial analogs of the Martian soil. These terrestrial analogs were exposed to a nutrient solution of the same composition as that of the Viking Landers under humid (no contact with nutrient) and wet (intimate contact) conditions. The headspace gases in the GEX sample cell were sampled and then analyzed by gas chromatography under both humid and wet conditions. Five gases were monitored: CO2, N2, O2, Ar, and Kr. It was determined that in order to simulate the CO2 gas changes of the Viking GEX experiment, the mixture of soil analog mineral plus nutrient medium must be slightly (pH = 7.4) to moderately basic (pH = 8.7). This conclusion suggests constraints upon the composition of terrestrial analogs of the Mars soil; acidic components may be present, but the overall mixture must be basic in order to simulate the Viking GEX results.

Assessment of the Effects Exerted by Acid and Alkaline Solutions on Bone: Is Chemistry the Answer?

PubMed

Amadasi, Alberto; Camici, Arianna; Porta, Davide; Cucca, Lucia; Merli, Daniele; Milanese, Chiara; Profumo, Antonella; Rassifi, Nabila; Cattaneo, Cristina

2017-09-01

The treatment of corpses with extremely acid or basic liquids is sometimes performed in criminal contexts. A thorough characterization by chemical analysis may provide further help to macroscopic and microscopic analysis; 63 porcine bone samples were treated with solutions at different pH (1-14) for immersion periods up to 70 days, as well as in extremely acidic sulfuric acid solutions (9 M/18 M) and extremely basic sodium hydroxide. Inductively coupled optical emission spectrometry (ICP-OES)/plasma mass spectrometry (ICP-MS), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray analysis (EDX), X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM) showed that only the sulfuric acid solution 18 M was able to completely dissolve the sample. In addition, chemical analysis allowed to recognize the contact between bone and substances. Hydrated calcium sulfate arose from extreme pH. The possibility of detecting the presence of human material within the residual solution was demonstrated, especially with FT-IR, ICP-OES, and EDX. © 2017 American Academy of Forensic Sciences.

Kinetics, isothermal and thermodynamics studies of electrocoagulation removal of basic dye rhodamine B from aqueous solution using steel electrodes

NASA Astrophysics Data System (ADS)

Adeogun, Abideen Idowu; Balakrishnan, Ramesh Babu

2017-07-01

Electrocoagulation was used for the removal of basic dye rhodamine B from aqueous solution, and the process was carried out in a batch electrochemical cell with steel electrodes in monopolar connection. The effects of some important parameters such as current density, pH, temperature and initial dye concentration, on the process, were investigated. Equilibrium was attained after 10 min at 30 °C. Pseudo-first-order, pseudo-second-order, Elovich and Avrami kinetic models were used to test the experimental data in order to elucidate the kinetic adsorption process; pseudo-first-order and Avrami models best fitted the data. Experimental data were analysed using six model equations: Langmuir, Freudlinch, Redlich-Peterson, Temkin, Dubinin-Radushkevich and Sips isotherms and it was found that the data fitted well with Sips isotherm model. The study showed that the process depends on current density, temperature, pH and initial dye concentration. The calculated thermodynamics parameters (Δ G°, Δ H° and Δ S°) indicated that the process is spontaneous and endothermic in nature.

Proton Transports in Pure Liquid Water Characterized by Melted Ice Lattice Model

NASA Astrophysics Data System (ADS)

Jie, Binbin; Sah, Chihtang

Basic water properties have not been understood for 200 years. Our Melted Ice Lattice model accounts for the 2 basic properties of pure water, the ion product (pH) and mobilities. It has HCP primitive unit cells, each with 4H2O, based on the 1933 Bernal-Fowler model, verified by 1935 Pauling residual entropy theory of 1928-1935 Giauque experimental low temperature specific heat measurements. Our 2 ion species are point-mass protons p + and p-, for mass and electricity transport. Three protonic thermal activation energies are obtained from pH and p + and p- mobilities vs T (0-100OC). Proton transport is analyzed in 3 proton-phonon collision steps: proton detrapping by protonic phonon absorption, proton scattering by oxygenic (water) phonons, and proton trapping with protonic phonon emission. Distinction between Potential and Kinetic Energy Bands of protons (Fermions) and phonons (Bosons) is noted. Experimental protonic activation energies are the phonon energies given by the spring-mass vibration frequencies of lattice, wn = (kn/mn)1/2 . n is the proton-mass unit of the synchronized vibrating particles in the primitive unit cells.

Synthesis and Structure of Vanadium Halide Complexes Containing Diphosphine Ligands with Pendant Amines

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

Egbert, Jonathan D.; Labios, Liezel A.; Darmon, Jonathan M.

2016-02-18

A series of vanadium(III) diiodide complexes of the formula CpV(P RN R'P R)I 2 (Cp = 5-C 5H 5; P RN R'P R = (R 2PCH 2) 2N(R)), where R = Et, R = Me (1a), R = Ph (1b); R = Ph, R = Me (1c)) is reported. The corresponding vanadium(II) monoiodide complexes of the formula CpV(P RN R' PR)I, where R = Et, R = Me (2a), R = Ph (2b); R = Ph, R = Me (2c)) were prepared in THF by reduction of 1a-c with Zn powder. The paramagnetic complexes 1a-c and 2a-c are characterized bymore » elemental analysis, 1H NMR spectroscopy, and by cyclic voltammetry for complexes 2b and 4b. Complexes 1c and 2a-c were also characterized in the single crystal by X-ray crystallography. We report the preparation of the vanadium(II) complexes CpV(P Ph 2N Ph 2)I (3) (P Ph 2N Ph 2 = 1,5-diphenyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) and trans-[VCl 2(PEtNMePEt)2] (4a) and trans-[VCl 2(PEtNPhPEt) 2] (4b). These complexes represent initial coordination chemistry of vanadium complexes with P RN R'P R and P Ph 2N Ph 2 diphosphine ligands, which contain a pendant amine in the second coordination sphere. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.« less

Nanoparticle titanium dioxide aqueous interfacial energy can be modified to control phase stability, coarsening, and morphology

NASA Astrophysics Data System (ADS)

Finnegan, Michael Patrick

The effect of solution chemistry on the phase stability, coarsening kinetics and morphology of titanium dioxide (TiO2) nanoparticles is investigated in order to attain efficient production pathways to desired nano-structures with optimal properties. To obtain sample, TiO2 was synthesized via hydrolysis of titanium isopropoxide producing an 85% anatase/15% brookite mixture. The titania was hydrothermally heated in an array of temperatures and pH values for various times. There are distinct phase stability fields for nanoscale titania based on pH alone due to slight interface charging behavior differences among the polymorphs. The mixture transforms to rutile below the pH of zero point of charge (ZPC) and remains anatase above the ZPC. This phenomenon is partially reversible. The solution chemistry also dictates the hydrothermal coarsening mechanism of the anatase polymorph. Ostwald ripening (OR) takes place in basic pH where titania solubility is elevated relative to neutral pH where lower solubility prevents rapid OR but allows for coarsening via oriented attachment (OA) of nanoparticles. This OA event can alter the symmetry of anatase causing unexpected and perhaps technically useful morphologies such as straight and curved nanorods during coarsening.

Eco-Driven Chemical Research in the Boundary Between Academia and Industry. PhD Students' Views on Science and Society

NASA Astrophysics Data System (ADS)

Sjöström, Jesper

2013-10-01

This paper examines and discusses the views on science and society held among PhD students working in two different industrially and environmentally driven research programmes in the broad area of green chemistry. It is based on thirteen in-depth interviews. The analysis shows three main ways of handling the situation as "post-academic" PhD student: (1) the student sees the PhD work mainly as a job and does not reflect about his/her research or the research funding, (2) the student is satisfied with the post-academic situation, accepts the established innovation policy discourse and is sceptical to traditional academic research, and (3) the student sees collaborative research programmes as a way to get funding, which can be used for secretly done basic research. Most PhD students either emphasise usefulness—in line with the dominating research policy discourse—or they adopt the positivistic view of science as objective and independent of the surrounding society. However, there are only a few signs of "double problematisation", that is a critical view where both disciplinary-oriented and industry-dependent research are problematised.

Breakdown of coral colonial form under reduced pH conditions is initiated in polyps and mediated through apoptosis

PubMed Central

Kvitt, Hagit; Kramarsky-Winter, Esti; Maor-Landaw, Keren; Zandbank, Keren; Kushmaro, Ariel; Rosenfeld, Hanna; Fine, Maoz; Tchernov, Dan

2015-01-01

Certain stony corals can alternate between a calcifying colonial form and noncalcifying solitary polyps, supporting the hypothesis that corals have survived through geologic timescale periods of unfavorable calcification conditions. However, the mechanisms enabling this biological plasticity are yet to be identified. Here we show that incubation of two coral species (Pocillopora damicornis and Oculina patagonica) under reduced pH conditions (pH 7.2) simulating past ocean acidification induce tissue-specific apoptosis that leads to the dissociation of polyps from coenosarcs. This in turn leads to the breakdown of the coenosarc and, as a consequence, to loss of coloniality. Our data show that apoptosis is initiated in the polyps and that once dissociation between polyp and coenosarc terminates, apoptosis subsides. After reexposure of the resulting solitary polyps to normal pH (pH 8.2), both coral species regenerated coenosarc tissues and resumed calcification. These results indicate that regulation of coloniality is under the control of the polyp, the basic modular unit of the colony. A mechanistic explanation for several key evolutionarily important phenomena that occurred throughout coral evolution is proposed, including mechanisms that permitted species to survive the third tier of mass extinctions. PMID:25646434

Total enzymatic synthesis of cholecystokinin CCK-5.

PubMed

Xiang, H; Xiang, G Y; Lu, Z M; Guo, L; Eckstein, H

2004-08-01

This paper describes the enzymatic synthesis of the C-terminal fragment H-Gly-Trp-Met-Asp-Phe-NH2 of cholecystokinin. Immobilized enzymes were used for the formation of all peptide bonds except thermolysin. Beginning the synthesis with phenylacetyl (PhAc) glycine carboxamidomethyl ester (OCam) and H-Trp-OMe by using immobilized papain as biocatalyst in buffered ethyl acetate, the dipeptide methyl ester was then coupled directly with Met-OEt.HCl by alpha-chymotrypsin/Celite 545 in a solvent free system. For the 3+2 coupling PhAc-Gly-Trp-Met-OEt had to be converted into its OCam ester. The other fragment H-Asp(OMe)-Phe-NH2 resulted from the coupling of Cbo-Asp(OMe)-OH with H-Phe-NH2.HCl and thermolysin as catalyst, followed by catalytic hydrogenation. Finally PhAc-Gly-Trp-Met-Asp-Phe-NH2 was obtained in a smooth reaction from PhAc-Gly-Trp-Met-OCam and H-Asp(OMe)-Phe-NH2 with alpha-chymotrypsin/Celite 545 in acetonitrile, followed by basic hydrolysis of the beta-methyl ester. The PhAc-group is removed with penicillin G amidase and CCK-5 is obtained in an overall isolated yield of 19.6%.

Optimal Conditions for the Mycelial Growth of Coprinus comatus Strains

PubMed Central

Lee, Yun-Hae; Liu, Jun-Jie; Ju, Young-Cheol

2009-01-01

The principal objective of this study was to acquire basic data regarding the mycelial growth characteristics for the artificial cultivation of Coprinus comatus. 12 URP primers were employed to evaluate the genetic relationships of C. comatus, and the results were divided into three groups. Among six kinds of mushroom media, MYP medium was selected as the most favorable culture medium for C. comatus. The optimal temperature and pH ranges for the mycelial growth of C. comatus were 23~26℃ and pH 6~8, respectively. The carbon and nitrogen sources for optimal mycelial growth were sucrose and tryptone, respectively. PMID:23983517

Corrosion in low dielectric constant Si-O based thin films: Buffer concentration effects

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

Zeng, F. W.; Lane, M. W., E-mail: mlane@ehc.edu; Gates, S. M.

2014-05-15

Organosilicate glass (OSG) is often used as an interlayer dielectric (ILD) in high performance integrated circuits. OSG is a brittle material and prone to stress-corrosion cracking reminiscent of that observed in bulk glasses. Of particular concern are chemical-mechanical planarization techniques and wet cleans involving solvents commonly encountered in microelectronics fabrication where the organosilicate film is exposed to aqueous environments. Previous work has focused on the effect of pH, surfactant, and peroxide concentration on the subcritical crack growth of these films. However, little or no attention has focused on the effect of the conjugate acid/base concentration in a buffer. Accordingly, thismore » work examines the “strength” of the buffer solution in both acidic and basic environments. The concentration of the buffer components is varied keeping the ratio of acid/base and therefore pH constant. In addition, the pH was varied by altering the acid/base ratio to ascertain any additional effect of pH. Corrosion tests were conducted with double-cantilever beam fracture mechanics specimens and fracture paths were verified with ATR-FTIR. Shifts in the threshold fracture energy, the lowest energy required for bond rupture in the given environment, G{sub TH}, were found to shift to lower values as the concentration of the base in the buffer increased. This effect was found to be much larger than the effect of the hydroxide ion concentration in unbuffered solutions. The results are rationalized in terms of the salient chemical bond breaking process occurring at the crack tip and modeled in terms of the chemical potential of the reactive species.« less

The effect of pH, buffer capacity and ionic strength on quetiapine fumarate release from matrix tablets prepared using two different polymeric blends.

PubMed

Hamed, Rania; AlJanabi, Reem; Sunoqrot, Suhair; Abbas, Aiman

2017-08-01

The objective of this study was to investigate the effect of the different physiological parameters of the gastrointestinal (GI) fluid (pH, buffer capacity, and ionic strength) on the in vitro release of the weakly basic BCS class II drug quetiapine fumarate (QF) from two once-a-day matrix tablet formulations (F1 and F2) developed as potential generic equivalents to Seroquel ® XR. F1 tablets were prepared using blends of high and low viscosity grades of hydroxypropyl methylcellulose (HPMC K4M and K100LV, respectively), while F2 tablets were prepared from HPMC K4M and PEGylated glyceryl behenate (Compritol ® HD5 ATO). The two formulations attained release profiles of QF over 24 h similar to that of Seroquel ® XR using the dissolution medium published by the Food and Drug Administration (FDA). A series of solubility and in vitro dissolution studies was then carried out using media that simulate the gastric and intestinal fluids and cover the physiological pH, buffer capacity and ionic strength range of the GIT. Solubility studies revealed that QF exhibits a typical weak base pH-dependent solubility profile and that the solubility of QF increases with increasing the buffer capacity and ionic strength of the media. The release profiles of QF from F1, F2 and Seroquel ® XR tablets were found to be influenced by the pH, buffer capacity and ionic strength of the dissolution media to varying degrees. Results highlight the importance of studying the physiological variables along the GIT in designing controlled release formulations for more predictive in vitro-in vivo correlations.

The Crystallization of Canavalin as a Function of pH and NaCl Concentration

NASA Technical Reports Server (NTRS)

Forsythe, Elizabeth L.; Gorti, Sridhar; Pusey, Marc L.

2004-01-01

We posed the question of what happens to a protein that is known to grow as an n-mer when it is placed in solution conditions where it is monomeric. The trypsin-treated, or cut, form of the protein canavalin (CCAN) has been shown to nucleate and grow crystals as a trimer from neutral to slightly acidic solutions. Under these conditions the solution is composed almost wholly of trimers. The crystalline protein can be readily dissolved by weakly basic solution, which has been proposed to result in a solution that is monomeric. There are three possible outcomes to an attempt at crystallization of the protein under monomeric (high pH) conditions: 1) we will obtain the same crystals as under trimer conditions, but at different protein concentrations governed by the self association equilibria; 2) we will obtain crystals having a different symmetry, based upon a monomeric growth unit; 3) we will not obtain crystals. Obtaining the first result would be indicative that the solution-phase self-association process is critical to the crystal nucleation and growth process. The second result would be less clear, as it may also reflect a pH-dependent shift in the trimer-trimer molecular interactions. The third result, particularly for experiments in the transition pH's between trimeric and monomeric CCAN, would indicate that the monomer does not crystallize, and that solution phase self association is not part of the crystal nucleation and growth path. Results are presented for crystallization experiments of CCAN over the pH 6.4 to 9.6 range. Fluorescence anisotropy, light scattering, and gel filtration experiments show that the solutions are primarily trimers, with association to form larger species occurring as a function of protein concentration.

Factors affecting adsorption characteristics of Zn2+ on two natural zeolites.

PubMed

Oren, Ali Hakan; Kaya, Abidin

2006-04-17

Mining-related and industrial wastes are primary sources of heavy metal contamination in soils and groundwater. The limitation of such waste in drinking water needs to meet government requirements in order to safeguard human health and environment. Zinc, one of the most preponderant pollutants, is difficult to remove from wastewater rather than other heavy metals (i.e. lead, copper and cadmium). This paper investigates Zn2+ adsorption characteristics of two natural zeolites found in the regions of Gordes and Bigadic, in western Turkey. The results show that the Zn2+ adsorption behavior of both zeolites is highly dependent on the pH. Adsorption dependence on lower pH values (pH<4) is explained by the dissolution of crystal structure and the competition of the zinc ions with the H+. Between pH 4 and 6, the basic mechanism is the ion exchange process. The results also showed that decrease in grain size does not increase the adsorption capacity of zeolite from Gordes, yet it increases that of zeolite from Bigadic about 23%. The results also reveal that an increase in the initial concentration of Zn2+ in the system causes an increase in the adsorption capacity to a degree, then it becomes more constant at higher concentrations. With this, the removal efficiency of Gordes zeolite is two times higher than that of Bigadic zeolite. Results show that an increase in slurry concentration results in a lower uptake of Zn2+. In the final part of the paper, we compared the experimental data with the Langmuir and Freundlich isotherms. The results show that there is a good fit between the experimental data and empirical isotherms.

Avian influenza virus (H5N1); effects of physico-chemical factors on its survival

PubMed Central

Shahid, Muhammad Akbar; Abubakar, Muhammad; Hameed, Sajid; Hassan, Shamsul

2009-01-01

Present study was performed to determine the effects of physical and chemical agents on infective potential of highly pathogenic avian influenza (HPAI) H5N1 (local strain) virus recently isolated in Pakistan during 2006 outbreak. H5N1 virus having titer 108.3 ELD50/ml was mixed with sterilized peptone water to get final dilution of 4HA units and then exposed to physical (temperature, pH and ultraviolet light) and chemical (formalin, phenol crystals, iodine crystals, CID 20, virkon®-S, zeptin 10%, KEPCIDE 300, KEPCIDE 400, lifebuoy, surf excel and caustic soda) agents. Harvested amnio-allantoic fluid (AAF) from embryonated chicken eggs inoculated with H5N1 treated virus (0.2 ml/egg) was subjected to haemagglutination (HA) and haemagglutination inhibition (HI) tests. H5N1 virus lost infectivity after 30 min at 56°C, after 1 day at 28°C but remained viable for more than 100 days at 4°C. Acidic pH (1, 3) and basic pH (11, 13) were virucidal after 6 h contact time; however virus retained infectivity at pH 5 (18 h), 7 and 9 (more than 24 h). UV light was proved ineffectual in inactivating virus completely even after 60 min. Soap (lifebuoy®), detergent (surf excel®) and alkali (caustic soda) destroyed infectivity after 5 min at 0.1, 0.2 and 0.3% dilution. All commercially available disinfectants inactivated virus at recommended concentrations. Results of present study would be helpful in implementing bio-security measures at farms/hatcheries levels in the wake of avian influenza virus (AIV) outbreak. PMID:19327163

Quantitative structure-activity relationship for the oxidation of aromatic organic contaminants in water by TAML/H2O2.

PubMed

Su, Hanrui; Yu, Chunyang; Zhou, Yongfeng; Gong, Lidong; Li, Qilin; Alvarez, Pedro J J; Long, Mingce

2018-05-02

Tetra-amido macrocyclic ligand (TAML) activator is a functional analog of peroxidase enzymes, which activates hydrogen peroxide (H 2 O 2 ) to form high valence iron-oxo complexes that selectively degrade persistent aromatic organic contaminants (ACs) in water. Here, we develop quantitative structure-activity relationship (QSAR) models based on measured pseudo first-order kinetic rate coefficients (k obs ) of 29 ACs (e.g., phenols and pharmaceuticals) oxidized by TAML/H 2 O 2 at neutral and basic pH values to gain mechanistic insight on the selectivity and pH dependence of TAML/H 2 O 2 systems. These QSAR models infer that electron donating ability (E HOMO ) is the most important AC characteristic for TAML/H 2 O 2 oxidation, pointing to a rate-limiting single-electron transfer (SET) mechanism. Oxidation rates at pH 7 also depend on AC reactive indices such as f min - and qH + , which respectively represent propensity for electrophilic attack and the most positive net atomic charge on hydrogen atoms. At pH 10, TAML/H 2 O 2 is more reactive towards ACs with a lower hydrogen to carbon atoms ratio (#H:C), suggesting the significance of hydrogen atom abstraction. In addition, lnk obs of 14 monosubstituted phenols is negatively correlated with Hammett constants (σ) and exhibits similar sensitivity to substituent effects as horseradish peroxidase. Although accurately predicting degradation rates of specific ACs in complex wastewater matrices could be difficult, these QSAR models are statistically robust and help predict both relative degradability and reaction mechanism for TAML/H 2 O 2 -based treatment processes. Copyright © 2018 Elsevier Ltd. All rights reserved.

In Vitro Dissolution of Fluconazole and Dipyridamole in Gastrointestinal Simulator (GIS), Predicting in Vivo Dissolution and Drug-Drug Interaction Caused by Acid-Reducing Agents.

PubMed

Matsui, Kazuki; Tsume, Yasuhiro; Amidon, Gregory E; Amidon, Gordon L

2015-07-06

Weakly basic drugs typically exhibit pH-dependent solubility in the physiological pH range, displaying supersaturation or precipitation along the gastrointestinal tract. Additionally, their oral bioavailabilities may be affected by coadministration of acid-reducing agents that elevate gastric pH. The purpose of this study was to assess the feasibility of a multicompartmental in vitro dissolution apparatus, Gastrointestinal Simulator (GIS), in predicting in vivo dissolution of certain oral medications. In vitro dissolution studies of fluconazole, a BCS class I, and dipyridamole, a BCS class II weak bases (class IIb), were performed in the GIS as well as United States Pharmacopeia (USP) apparatus II and compared with the results of clinical drug-drug interaction (DDI) studies. In both USP apparatus II and GIS, fluconazole completely dissolved within 60 min regardless of pH, reflecting no DDI between fluconazole and acid-reducing agents in a clinical study. On the other hand, seven-fold and 15-fold higher concentrations of dipyridamole than saturation solubility were observed in the intestinal compartments in GIS with gastric pH 2.0. Precipitation of dipyridamole was also observed in the GIS, and the percentage of dipyridamole in solution was 45.2 ± 7.0%. In GIS with gastric pH 6.0, mimicking the coadministration of acid-reducing agents, the concentration of dipyridamole was equal to its saturation solubility, and the percentage of drug in solution was 9.3 ± 2.7%. These results are consistent with the clinical DDI study of dipyridamole with famotidine, which significantly reduced the Cmax and area under the curve. An In situ mouse infusion study combined with GIS revealed that high concentration of dipyridamole in the GIS enhanced oral drug absorption, which confirmed the supersaturation of dipyridamole. In conclusion, GIS was shown to be a useful apparatus to predict in vivo dissolution for BCS class IIb drugs.

Apolar Distal Pocket Mutants of Yeast Cytochrome c Peroxidase: Hydrogen Peroxide Reactivity and Cyanide Binding of the TriAla, TriVal, and TriLeu Variants

PubMed Central

Bidwai, Anil K.; Meyen, Cassandra; Kilheeney, Heather; Wroblewski, Damian; Vitello, Lidia B.; Erman, James E.

2012-01-01

Three yeast cytochrome c peroxidase (CcP) variants with apolar distal heme pockets have been constructed. The CcP variants have Arg48, Trp51, and His52 mutated to either all alanines, CcP(triAla), all valines, CcP(triVal), or all leucines, CcP(triLeu). The triple mutants have detectable enzymatic activity at pH 6 but the activity is less than 0.02% that of wild-type CcP. The activity loss is primarily due to the decreased rate of reaction between the triple mutants and H2O2 compared to wild-type CcP. Spectroscopic properties and cyanide binding characteristics of the triple mutants have been investigated over the pH stability region of CcP, pH 4 to 8. The absorption spectra indicate that the CcP triple mutants have hemes that are predominantly five-coordinate, high-spin at pH 5 and six-coordinate, low-spin at pH 8. Cyanide binding to the triple mutants is biphasic indicating that the triple mutants have two slowly-exchanging conformational states with different cyanide affinities. The binding affinity for cyanide is reduced at least two orders of magnitude in the triple mutants compared to wild-type CcP and the rate of cyanide binding is reduced by four to five orders of magnitude. Correlation of the reaction rates of CcP and 12 distal pocket mutants with H2O2 and HCN suggests that both reactions require ionization of the reactants within the distal heme pocket allowing the anion to bind the heme iron. Distal pocket features that promote substrate ionization (basic residues involved in base-catalyzed substrate ionization or polar residues that can stabilize substrate anions) increase the overall rate of reaction with H2O2 and HCN while features that inhibit substrate ionization slow the reactions. PMID:23022490

Nucleation, growth, and repair of a cobalt-based oxygen evolving catalyst.

PubMed

Surendranath, Yogesh; Lutterman, Daniel A; Liu, Yi; Nocera, Daniel G

2012-04-11

The mechanism of nucleation, steady-state growth, and repair is investigated for an oxygen evolving catalyst prepared by electrodeposition from Co(2+) solutions in weakly basic electrolytes (Co-OEC). Potential step chronoamperometry and atomic force microscopy reveal that nucleation of Co-OEC is progressive and reaches a saturation surface coverage of ca. 70% on highly oriented pyrolytic graphite substrates. Steady-state electrodeposition of Co-OEC exhibits a Tafel slope approximately equal to 2.3 × RT/F. The electrochemical rate law exhibits a first order dependence on Co(2+) and inverse orders on proton (third order) and proton acceptor, methylphosphonate (first order for 1.8 mM ≤ [MeP(i)] ≤ 18 mM and second order dependence for 32 mM ≤ [MeP(i)] ≤ 180 mM). These electrokinetic studies, combined with recent XAS studies of catalyst structure, suggest a mechanism for steady state growth at intermediate MeP(i) concentration (1.8-18 mM) involving a rapid solution equilibrium between aquo Co(II) and Co(III) hydroxo species accompanied with a rapid surface equilibrium involving electrolyte dissociation and deprotonation of surface bound water. These equilibria are followed by a chemical rate-limiting step for incorporation of Co(III) into the growing cobaltate clusters comprising Co-OEC. At higher concentrations of MeP(i) ([MeP(i)] ≥ 32 mM), MePO(3)(2-) equilibrium binding to Co(II) in solution is suggested by the kinetic data. Consistent with the disparate pH profiles for oxygen evolution electrocatalysis and catalyst formation, NMR-based quantification of catalyst dissolution as a function of pH demonstrates functional stability and repair at pH values >6 whereas catalyst corrosion prevails at lower pH values. These kinetic insights provide a basis for developing and operating functional water oxidation (photo)anodes under benign pH conditions. © 2012 American Chemical Society

pH : a key control of the nature and distribution of dissolved organic matter and associated trace metals in soil

NASA Astrophysics Data System (ADS)

Pédrot, M.; Dia, A.; Davranche, M.

2009-04-01

Dissolved organic matter is ubiquitous at the Earth's surface and plays a prominent role in controlling metal speciation and mobility from soils to hydrosystems. Humic substances (HS) are usually considered to be the most reactive fraction of organic matter. Humic substances are relatively small and formed by chemically diverse organic molecules, bearing different functional groups that act as binding sites for cations and mineral surfaces. Among the different environmental physicochemical parameters controlling the metal speciation, pH is likely to be the most important one. Indeed, pH affect the dissociation of functional groups, and thus can influence the HS structure, their ability to complex metals, their solubility degree allowing the formation of aggregates at the mineral surface. In this context, soil/water interactions conducted through batch system experiments, were carried out with a wetland organic-rich soil to investigate the effect of pH on the release of dissolved organic carbon (DOC) and associated trace elements. The pH was regulated between 4 and 7.5 using an automatic pH stat titrator. Ultrafiltration experiments were performed to separate the dissolved organic pool following decreasing pore sizes (30 kDa, 5 kDa and 2 kDa with 1 Da = 1 g.mol-1). The pH increase induced a significant DOC release, especially in heavy organic molecules (size >5 kDa) with a high aromaticity (>30 %). These were probably humic acids (HA). This HA release influenced (i) directly the trace element concentrations in soil solution since HA were enriched in several trace elements such as Th, REE, Y, U, Cr and Cu; and (ii) indirectly by the breaking of clay-humic complexes releasing Fe- and Al-rich nanoparticles associated with V, Pb and Ti. By contrast, at acid pH, most HS were complexed onto mineral surfaces. They also sequestered iron nanoparticles. Therefore, at low pH, most part of DOC molecules had a size < 5 kDa and lower aromaticity. Thus, the DOC was mostly composed of simple organic compounds little complexing. Consequently, the soil solution was depleted in trace elements such as Th, REE, Y, U, Cr, Cu, Al, Fe, V, Pb and Ti, but also enriched in Ca, Sr, Ba, Mn, Mg, Co, Zn and in a lesser proportion in Rb, Li and Ni. The aromaticity in the fractions <5 kDa was higher than in the fractions <30 kDa or <0.2 µm. Complementary experiments were performed to understand the HS size distribution and aromaticity according to pH and ionic strength .The molecular size and shape of HS is usually explained by two concepts: (i) the macropolymeric structure with heavy organic molecules considered to be flexible linear polyelectrolytes and (ii) the supramolecular structure with an association of a complex mixture of different molecules held together by dispersive weak forces. Ours results supported the HA supramolecular structure at neutral or basic pH conditions. But, at acid pH, a disruption of the humic supramolecular associations involved the release of small organic molecules with a high aromaticity. Moreover, this aromaticity variation can be due also to the presence of fulvic acids in the fractions <5 kDa and a mixture of heavy organic molecules little complexing in the fractions >5 kDa. These latter molecules displayed a low aromaticity decreasing the global aromaticity of the fractions <30 kDa and <0.2 µm. To summarize, these new data demonstrated that the DOC and trace element concentrations of the soil solutions were strongly controlled by pH. This parameter influenced the nature and the size of the DOC as well as, the trace element concentrations in the soil solutions, with a decreasing contribution of HA when pH decreased. This pH dependence is a key issue of concern since local (human pressure) and/or global (climatic) warning result in pH water changes.

Arginine- and lysine-specific polymers for protein recognition and immobilization.

PubMed

Renner, Christian; Piehler, Jacob; Schrader, Thomas

2006-01-18

Free radical polymerization of methacrylamide-based bisphosphonates turns weak arginine binders into powerful polymeric protein receptors. Dansyl-labeled homo- and copolymers with excellent water solubility are accessible through a simple copolymerization protocol. Modeling studies point to a striking structural difference between the stiff rodlike densely packed homopolymer 1 and the flexible copolymer 2 with spatially separated bisphosphonate units. Fluorescence titrations in buffered aqueous solution (pH = 7.0) confirm the superior affinity of the homopolymer toward oligoarginine peptides reaching nanomolar K(D) values for the Tat peptide. Basic proteins are bound almost equally well by 1 and 2 with micromolar affinities, with the latter producing much more soluble complexes. The Arg selectivity of the monomer is transferred to the polymer, which binds Arg-rich proteins 1 order of magnitude tighter than lysine-rich pendants of comparable pI, size, and (Arg/Lys vs Glu/Asp) ratio. Noncovalent deposition of both polymers on glass substrates via polyethyleneimine layers results in new materials suitable for peptide and protein immobilization. RIfS measurements allow calculation of association constants K(a) as well as dissociation kinetics k(D). They generally confirm the trends already found in free solution. Close inspection of electrostatic potential surfaces suggest that basic domains favor protein binding on the flat surface. The high specificity of the bisphosphonate polymers toward basic proteins is demonstrated by comparison with polyvinyl sulfate, which has almost no effect in RIfS experiments. Thus, copolymerization of few different comonomer units without cross-linking enables surface recognition of basic proteins in free solution as well as their effective immobilization on surfaces.

Peritoneal dialysis: from bench to bedside

PubMed Central

Krediet, Raymond T.

2013-01-01

Peritoneal dialysis was first employed in patients with acute renal failure in the 1940s and since the 1960s for those with end-stage renal disease. Its popularity increased enormously after the introduction of continuous ambulatory peritoneal dialysis in the end of 1970s. This stimulated both clinical and basic research. In an ideal situation, this should lead to cross-fertilization between the two. The present review describes two examples of interactions: one where it worked out very well and another where basic science missed the link with clinical findings. Those on fluid transport are examples of how old physiological findings on absorption of saline and glucose solutions were adopted in peritoneal dialysis by the use of glucose as an osmotic agent. The mechanism behind this in patients was first solved mathematically by the assumption of ultrasmall intracellular pores allowing water transport only. At the same time, basic science discovered the water channel aquaporin-1 (AQP-1), and a few years later, studies in transgenic mice confirmed that AQP-1 was the ultrasmall pore. In clinical medicine, this led to its assessment in patients and the notion of its impairment. Drugs for treatment have been developed. Research on biocompatibility is not a success story. Basic science has focussed on dialysis solutions with a low pH and lactate, and effects of glucose degradation products, although the first is irrelevant in patients and effects of continuous exposure to high glucose concentrations were largely neglected. Industry believed the bench more than the bedside, resulting in ‘biocompatible’ dialysis solutions. These solutions have some beneficial effects, but are evidently not the final answer. PMID:26120456

The physiology of the Tambaqui (Colossoma macropomum) at pH 8.0.

PubMed

Wood, Chris M; Gonzalez, R J; Ferreira, Márcio Soares; Braz-Mota, Susana; Val, Adalberto Luis

2018-05-01

The Tambaqui is a model neotropical teleost which is of great economic and cultural importance in artisanal fisheries and commercial aquaculture. It thrives in ion-poor, often acidic Amazonian waters and exhibits excellent regulation of physiology down to water pH 4.0. Curiously, however, it is reported to perform poorly in aquaculture at pH 8.0, an only slightly alkaline pH which would be benign for most freshwater fish. In initial experiments with Tambaqui of intermediate size (30-50 g), we found that ammonia excretion rate was unchanged at pH 4, 5, 6, and 7, but elevated after 20-24 h at pH 8, exactly opposite the pattern seen in most teleosts. Subsequent experiments with large Tambaqui (150-300 g) demonstrated that only ammonia, and not urea excretion was increased at pH 8.0, and that the elevation was proportional to a general increase in MO 2 . There was an accompanying elevation in net acidic equivalent excretion and/or basic equivalent uptake which occurred mainly at the gills. Net Na + balance was little affected while Cl - balance became negative, implicating a disturbance of Cl - versus base exchange rather than Na + versus acid exchange. Arterial blood pH increased by 0.2 units at pH 8.0, reflecting combined metabolic and respiratory alkaloses. Most parameters recovered to control levels by 18-24 h after return to pH 6.0. With respect to large Tambaqui, we conclude that a physiology adapted to acidic pH performs inappropriately at moderately alkaline pH. In small Tambaqui (4-15 g), the responses were very different, with an initial inhibition of ammonia excretion rate at pH 8.0 followed by a subsequent restoration of control levels. Elevated ammonia excretion rate occurred only after return to pH 6.0. Furthermore, MO 2 , plasma cortisol, and branchial vH + ATPase activities all declined during pH 8.0 exposure in small Tambaqui, in contrast to the responses in larger fish. Overall, small Tambaqui appear to cope better at pH 8.0, a difference that may correlate with their natural history in the wild.

Amino acid sequence of the smaller basic protein from rat brain myelin

PubMed Central

Dunkley, Peter R.; Carnegie, Patrick R.

1974-01-01

1. The complete amino acid sequence of the smaller basic protein from rat brain myelin was determined. This protein differs from myelin basic proteins of other species in having a deletion of a polypeptide of 40 amino acid residues from the centre of the molecule. 2. A detailed comparison is made of the constant and variable regions in a group of myelin basic proteins from six species. 3. An arginine residue in the rat protein was found to be partially methylated. The ratio of methylated to unmethylated arginine at this position differed from that found for the human basic protein. 4. Three tryptic peptides were isolated in more than one form. The differences between the two forms of each peptide are discussed in relation to the electrophoretic heterogeneity of myelin basic proteins, which is known to occur at alkaline pH values. 5. Detailed evidence for the amino acid sequence of the protein has been deposited as Supplementary Publication SUP 50029 at the British Library (Lending Division) (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies may be obtained on the terms given in Biochem. J. (1973) 131, 5. PMID:4141893

pH-Dependent Singlet O2 Oxidation Kinetics of Guanine and 9-Methylguanine: An Online Mass Spectrometry and Spectroscopy Study Combined with Theoretical Exploration.

PubMed

Lu, Wenchao; Sun, Yan; Zhou, Wenjing; Liu, Jianbo

2018-01-11

We report a kinetic and mechanistic study on the title reactions, in which 1 O 2 was generated by the reaction of H 2 O 2 with Cl 2 and bubbled into an aqueous solution of guanine and 9-methylguanine (9MG) at different pH values. Oxidation kinetics and product branching ratios were measured using online electrospray ionization mass spectrometry coupled with absorption and emission spectrophotometry, and product structures were determined by collision-induced dissociation (CID) tandem mass spectrometry. Experiments revealed strong pH dependence of the reactions. The oxidation of guanine is noticeable only in basic solution, while the oxidation of 9MG is weak in acidic solution, increases in neutral solution, and becomes intensive in basic solution. 5-Guanidinohydantoin (Gh) and spiroiminodihydantoin (Sp) were detected as the major oxidation products of guanine and 9MG, and Sp became dominant in basic solution. A reaction intermediate was captured in mass spectra, and assigned to gem-diol on the basis of CID measurements. This intermediate served as the precursor for the formation of Gh. After taking into account solution compositions at each pH, first-order oxidation rate constants were extracted for individual species: that is, 3.2-3.6 × 10 7 M -1 s -1 for deprotonated guanine, and 1.2 × 10 6 and 4.6-4.9 × 10 7 M -1 s -1 for neutral and deprotonated 9MG, respectively. Guided by approximately spin-projected density-functional-theory-calculated reaction potential energy surfaces, the kinetics for the initial 1 O 2 addition to guanine and 9MG was evaluated using transition state theory (TST). The comparison between TST modeling and experiment confirms that 1 O 2 addition is rate-limiting for oxidation, which forms endoperoxide and peroxide intermediates as determined in previous measurements of the same systems in the gas phase.

Investigation of distribution of radioactivity with effects of heavy metals in toothpastes from Penang markets.

PubMed

Salih, Najeba F; Jafri, Zubir M; Jaafar, Mohamad S

2016-12-01

This study was carried out to determine the concentration of 222 Rn, 226 Ra, and 238 U in 25 different toothpastes available in the local market in Penang, Malaysia, using a CR-39 detector. The results showed the maximum concentration of radon/ radium/uranium to be 4197.644 Bq.m -3 , 54.369 Bq.Kgm -1 , and 0.044 ppm in Colgate4; the annual effective dose was found (0.402 mSvy -1 ) in S07. The average concentration of radon (42 %, 3.224 KBq.m -3 ) was higher than the concentration of 214 Po, 218 Po in POS (32 %, 2.415 KBq.m -3 ) and POW (26 %, 1.979 KBq.m -3 ). Also the values of pH of samples ranged from 4.21 (highly acidic) in S04 to 9.97 (highly basic) in S07, with an average of 6.33 which tended towards an acidic behavior; a low or high pH for a long period of time can cause harmful side-effects and enamel erosion. Concentrations of heavy metals varied from the maximum value 56.156 ppm in the Ca elements in the Colgate 4 sample to a minimum value of -0.858 ppm in the Cd elements in Colgate 6 (Ca 56.156 ppm > Cd 51.572 ppm > Zn 41.039 ppm > Mg 11.682 ppm > Pb 11.009 ppm]. Monitoring the accumulation of these metals in toothpaste samples is very important: the average annual effective dose (0.3118 mSvy -1 ) was below the range (3-10 mSvy -1 ) reported by ICRP (1993), and therefore there is no evidence of health problems. Significant strong positive correlations were found (r = 1, Pearson correlation, p < 0.000) in concentration of radon, radium, uranium, annual effective dose, pH, and electrical conductivity.

Influence of succinylation on physicochemical property of yak casein micelles.

PubMed

Yang, Min; Yang, Jitao; Zhang, Yuan; Zhang, Weibing

2016-01-01

Succinylation is a chemical-modification method that affects the physicochemical characteristics and functional properties of proteins. This study assessed the influence of succinylation on the physicochemical properties of yak casein micelles. The results revealed that surface hydrophobicity indices decreased with succinylation. Additionally, denaturation temperature and denaturation enthalpy decreased with increasing succinylation level, except at 82%. The buffering properties of yak casein micelles were affected by succinylation. It was found that chemical modification contributed to a slight shift of the buffering peak towards a lower pH value and a markedly increase of the maximum buffering values of yak casein micelles at pH 4.5-6.0 and pH < 3. Succinylation increased yak casein micellar hydration and whiteness values. The findings obtained from this study will provide the basic information on the physicochemical properties of native and succinylated yak casein micelles. Copyright © 2015 Elsevier Ltd. All rights reserved.

A real-time measurement system for parameters of live biology metabolism process with fiber optics

NASA Astrophysics Data System (ADS)

Tao, Wei; Zhao, Hui; Liu, Zemin; Cheng, Jinke; Cai, Rong

2010-08-01

Energy metabolism is one of the basic life activities of cellular in which lactate, O2 and CO2 will be released into the extracellular environment. By monitoring the quantity of these parameters, the mitochondrial performance will be got. A continuous measurement system for the concentration of O2, CO2 and PH value is introduced in this paper. The system is made up of several small-sized fiber optics biosensors corresponding to the container. The setup of the system and the principle of measurement of several parameters are explained. The setup of the fiber PH sensor based on principle of light absorption is also introduced in detail and some experimental results are given. From the results we can see that the system can measure the PH value precisely suitable for cell cultivation. The linear and repeatable accuracies are 3.6% and 6.7% respectively, which can fulfill the measurement task.

Analysis of pilocarpine and its trans epimer, isopilocarpine, by capillary electrophoresis.

PubMed

Baeyens, W; Weiss, G; Van Der Weken, G; Van Den Bossche, W

1993-05-28

Capillary zone electrophoresis was used for the separation of pilocarpine from its epimer, isopilocarpine, using coated fused-silica capillaries of 20 cm x 25 microm I.D., 8 kV running voltage, migration buffer of 0.1 M sodium dihydrogenphosphate pH 8, detection at 217 nm and injection by electromigration. Injections of aqueous, acid and basic solutions were compared. Linearity of the signal for pilocarpine hydrochloride up to 200 microg ml(-1) in 0.05 M hydrochloric acid was obtained, using naphazoline nitrate as internal standard. Optimization of migration buffer pH using coated silica capillaries of 50 cm x 50 microm I.D. showed that at pH 6.9 pilocarpine can be separated from ++isopilocarpine. Inclusion of beta-cyclodextrin in the buffer allows full baseline separation of both epimers. The method was applied to the analysis of a commercial ophthalmic pilocarpine solution.

Superior magnetic properties of Ni ferrite nanoparticles synthesized by capping agent-free one-step coprecipitation route at different pH values

NASA Astrophysics Data System (ADS)

Iranmanesh, P.; Tabatabai Yazdi, Sh.; Mehran, M.; Saeednia, S.

2018-03-01

In this work, well-dispersed nanoparticles of NiFe2O4 with diameters less than 10 nm and good crystallinity and excellent magnetic properties were synthesized via a simple one-step capping agent-free coprecipitation route from metal chlorides. The ammonia was used as the precipitating agent and also the solution basicity controller. The effect of pH value during the coprecipitation process was investigated by details through microstructural, optical and magnetic characterizations of the synthesized particles using X-ray diffraction, transmission electron microscopy, Fourier transform infrared and UV-vis spectroscopy, and vibrating sample magnetometer. The results showed that the particle size, departure from the inverse spinel structure, the band gap value and the magnetization of Ni ferrite samples increase with pH value from 9 to 11 indicating the more pronounced surface effects in the smaller nanoparticles.

Studying mixing in Non-Newtonian blue maize flour suspensions using color analysis.

PubMed

Trujillo-de Santiago, Grissel; Rojas-de Gante, Cecilia; García-Lara, Silverio; Ballescá-Estrada, Adriana; Alvarez, Mario Moisés

2014-01-01

Non-Newtonian fluids occur in many relevant flow and mixing scenarios at the lab and industrial scale. The addition of acid or basic solutions to a non-Newtonian fluid is not an infrequent operation, particularly in Biotechnology applications where the pH of Non-Newtonian culture broths is usually regulated using this strategy. We conducted mixing experiments in agitated vessels using Non-Newtonian blue maize flour suspensions. Acid or basic pulses were injected to reveal mixing patterns and flow structures and to follow their time evolution. No foreign pH indicator was used as blue maize flours naturally contain anthocyanins that act as a native, wide spectrum, pH indicator. We describe a novel method to quantitate mixedness and mixing evolution through Dynamic Color Analysis (DCA) in this system. Color readings corresponding to different times and locations within the mixing vessel were taken with a digital camera (or a colorimeter) and translated to the CIELab scale of colors. We use distances in the Lab space, a 3D color space, between a particular mixing state and the final mixing point to characterize segregation/mixing in the system. Blue maize suspensions represent an adequate and flexible model to study mixing (and fluid mechanics in general) in Non-Newtonian suspensions using acid/base tracer injections. Simple strategies based on the evaluation of color distances in the CIELab space (or other scales such as HSB) can be adapted to characterize mixedness and mixing evolution in experiments using blue maize suspensions.

A cost and technical efficiency analysis of two alternative models for implementing the basic package of health services in Afghanistan.

PubMed

Blaakman, Aaron Philip; Salehi, Ahmad Shah; Boitard, Romain

2014-01-01

Since 2003, the Afghan Ministry of Public Health (MoPH) and international partners have directed a contracting-out model through which non-governmental organisations (NGOs) deliver the Basic Package of Health Services (BPHS) in 31 of the 34 Afghan provinces. The MoPH also managed health service delivery in three provinces under an alternative initiative entitled Strengthening Mechanisms (SM). In 2011, under the authority of the MoPH and Delegation of the European Union to Afghanistan, EPOS Health Management conducted a cost and technical efficiency study of the contracting-out and SM mechanisms in six provinces to examine economic trade-offs in the provision of the BPHS. The study provides analyses of all resource inputs and primary outputs of the BPHS in the six provinces during 2008 and 2009. The authors examined technical efficiency using Data Envelopment Analysis (DEA) at the BPHS facility level. Cost analysis results indicate that the weighted average cost per BPHS outpatient visit totalled $3.41 in the SM provinces and $5.39 in the NGO-led provinces in 2009. Furthermore, the data envelopment analyses (DEAs) indicate that facilities in the three NGO-led provinces scored 0.168 points higher on the DEA scale (0-1) than SM facilities. The authors conclude that an approximate 60% increase in costs yielded a 16.8% increase in technical efficiency in the delivery of the BPHS during 2009 in the six provinces.

Accurate determination of aldehydes in amine catalysts or amines by 2,4-dinitrophenylhydrazine derivatization.

PubMed

Barman, Bhajendra N

2014-01-31

Carbonyl compounds, specifically aldehydes, present in amine catalysts or amines are determined by reversed-phase liquid chromatography using ultraviolet detection of their corresponding 2,4-dinitrophenylhydrazones. The primary focus has been to establish optimum conditions for determining aldehydes accurately because these add exposure concerns when the amine catalysts are used to manufacture polyurethane products. Concentrations of aldehydes determined by this method are found to vary with the pH of the aqueous amine solution and the derivatization time, the latter being problematic when the derivatization reaction proceeds slowly and not to completion in neutral and basic media. Accurate determination of aldehydes in amines through derivatization can be carried out at an effective solution pH of about 2 and with derivatization time of 20min. Hydrochloric acid has been used for neutralization of an amine. For complete derivatization, it is essential to protonate all nitrogen atoms in the amine. An approach for the determination of an adequate amount of acid needed for complete derivatization has been described. Several 0.2M buffer solutions varying in pH from 4 to 8 have also been used to make amine solutions for carrying out derivatization of aldehydes. These solutions have effective pHs of 10 or higher and provide much lower aldehyde concentrations compared to their true values. Mechanisms for the formation of 2,4-dinitrophenylhydrazones in both acidic and basic media are discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

BSA-coated nanoparticles for improved SERS-based intracellular pH sensing.

PubMed

Zheng, Xiao-Shan; Hu, Pei; Cui, Yan; Zong, Cheng; Feng, Jia-Min; Wang, Xin; Ren, Bin

2014-12-16

Local microenvironment pH sensing is one of the key parameters for the understanding of many biological processes. As a noninvasive and high sensitive technique, surface-enhanced Raman spectroscopy (SERS) has attracted considerable interest in the detection of the local pH of live cells. We herein develop a facile way to prepare Au-(4-MPy)-BSA (AMB) pH nanosensor. The 4-MPy (4-mercaptopyridine) was used as the pH sensing molecule. The modification of the nanoparticles with BSA not only provides a high sensitive response to pH changes ranging from pH 4.0 to 9.0 but also exhibits a high sensitivity and good biocompatibility, stability, and reliability in various solutions (including the solutions of high ionic strength or with complex composition such as the cell culture medium), both in the aggregation state or after long-term storage. The AMB pH nanosensor shows great advantages for reliable intracellular pH analysis and has been successfully used to monitor the pH distribution of live cells and can address the grand challenges in SERS-based pH sensing for practical biological applications.

Identification of novel candidate genes involved in mineralization of dental enamel by genome-wide transcript profiling.

PubMed

Lacruz, Rodrigo S; Smith, Charles E; Bringas, Pablo; Chen, Yi-Bu; Smith, Susan M; Snead, Malcolm L; Kurtz, Ira; Hacia, Joseph G; Hubbard, Michael J; Paine, Michael L

2012-05-01

The gene repertoire regulating vertebrate biomineralization is poorly understood. Dental enamel, the most highly mineralized tissue in mammals, differs from other calcifying systems in that the formative cells (ameloblasts) lack remodeling activity and largely degrade and resorb the initial extracellular matrix. Enamel mineralization requires that ameloblasts undergo a profound functional switch from matrix-secreting to maturational (calcium transport, protein resorption) roles as mineralization progresses. During the maturation stage, extracellular pH decreases markedly, placing high demands on ameloblasts to regulate acidic environments present around the growing hydroxyapatite crystals. To identify the genetic events driving enamel mineralization, we conducted genome-wide transcript profiling of the developing enamel organ from rat incisors and highlight over 300 genes differentially expressed during maturation. Using multiple bioinformatics analyses, we identified groups of maturation-associated genes whose functions are linked to key mineralization processes including pH regulation, calcium handling, and matrix turnover. Subsequent qPCR and Western blot analyses revealed that a number of solute carrier (SLC) gene family members were up-regulated during maturation, including the novel protein Slc24a4 involved in calcium handling as well as other proteins of similar function (Stim1). By providing the first global overview of the cellular machinery required for enamel maturation, this study provide a strong foundation for improving basic understanding of biomineralization and its practical applications in healthcare. Copyright © 2011 Wiley Periodicals, Inc.

One-dimensional filtration of pharmaceutical grade phyllosilicate dispersions.

PubMed

Viseras, C; Cerezo, P; Meeten, G H; Lopez-Galindo, A

2001-04-17

The filtration behaviour of some clay-water dispersions was studied. Two Spanish fibrous phyllosilicates (sepiolite from Vicálvaro and palygorskite from Turón) and a commercial bentonite (Bentopharm UK) with similar sizes and different morphologies (fibrous and/or laminar) were selected as model clays. Sepiolite from Vicálvaro is an almost pure fibrous sample, Bentopharm presents a high amount of laminar particles and palygorskite from Turón is made up of similar percentages of laminar and fibrous particles. The disperse systems were made up using a rotor-stator mixer working at two different mixing rates (1000 and 8000 rpm), for periods of 1 and 10 min. Filtration measurements were taken and the corresponding filtration curves obtained. Finally, the desorptivity (S) of the filtration cakes was calculated and correlated to the textural characteristics of the materials, the solid fraction and mixing conditions. Filtration behaviour of the dispersions depended on all three of these factors. Laminar dispersions presented lower S values than fibrous dispersions. In the 2% w/v dispersions the bridging forces between particles did not permit formation of an interconnected network as in 10% w/v dispersions and, consequently, filtration times increased with the solid fraction (i.e. S values decreased). Regarding stability to pH changes, the results showed that filtration behaviour was highly sensitive to basic pH in the fibrous clay dispersions and almost insensitive in the laminar clay dispersions.

Interfacial and emulsifying properties of designed β-strand peptides.

PubMed

Dexter, Annette F

2010-12-07

The structural and surfactant properties of a series of amphipathic β-strand peptides have been studied as a function of pH. Each nine-residue peptide has a framework of hydrophobic proline and phenylalanine amino acid residues, alternating with acidic or basic amino acids to give a sequence closely related to known β-sheet formers. Surface activity, interfacial mechanical properties, electronic circular dichroism (ECD), droplet sizing and zeta potential measurements were used to gain an overview of the peptide behavior as the molecular charge varied from ±4 to 0 with pH. ECD data suggest that the peptides form polyproline-type helices in bulk aqueous solution when highly charged, but may fold to β-hairpins rather than β-sheets when uncharged. In the uncharged state, the peptides adsorb readily at a macroscopic fluid interface to form mechanically strong interfacial films, but tend to give large droplet sizes on emulsification, apparently due to flocculation at a low droplet zeta potential. In contrast, highly charged peptide states gave a low interfacial coverage, but retained good emulsifying activity as judged by droplet size. Best emulsification was generally seen for intermediate charged states of the peptides, possibly representing a compromise between droplet zeta potential and interfacial binding affinity. The emulsifying properties of β-strand peptides have not been previously reported. Understanding the interfacial properties of such peptides is important to their potential development as biosurfactants.

Extremophiles: from abyssal to terrestrial ecosystems and possibly beyond

NASA Astrophysics Data System (ADS)

Canganella, Francesco; Wiegel, Juergen

2011-04-01

The anthropocentric term "extremophile" was introduced more than 30 years ago to describe any organism capable of living and growing under extreme conditions—i.e., particularly hostile to human and to the majority of the known microorganisms as far as temperature, pH, and salinity parameters are concerned. With the further development of studies on microbial ecology and taxonomy, more "extreme" environments were found and more extremophiles were described. Today, many different extremophiles have been isolated from habitats characterized by hydrostatic pressure, aridity, radiations, elevated temperatures, extreme pH values, high salt concentrations, and high solvent/metal concentrations, and it is well documented that these microorganisms are capable of thriving under extreme conditions better than any other organism living on Earth. Extremophiles have also been investigated as far as the search for life in other planets is concerned and even to evaluate the hypothesis that life on Earth came originally from space. Extremophiles are interesting for basic and applied sciences. Particularly fascinating are their structural and physiological features allowing them to stand extremely selective environmental conditions. These properties are often due to specific biomolecules (DNA, lipids, enzymes, osmolites, etc.) that have been studied for years as novel sources for biotechnological applications. In some cases (DNA polymerase, thermostable enzymes), the search was successful and the final application was achieved, but certainly further exploitations are next to come.

Magnetic- and pH-responsive κ-carrageenan/chitosan complexes for controlled release of methotrexate anticancer drug.

PubMed

Mahdavinia, Gholam Reza; Mosallanezhad, Amirabbas; Soleymani, Moslem; Sabzi, Mohammad

2017-04-01

The aim of the present work was to develop green carriers for methotrexate using κ-carrageenan/chitosan complexes. Magnetic Fe 3 O 4 nanoparticles were first synthesized in the presence of κ-carrageenan through in situ method. Then, the obtained magnetic κ-carrageenan was crosslinked using the polycation chitosan biopolymer. The physical and structural properties of hydrogels were investigated by FTIR, XRD, SEM, TEM, TGA, and VSM techniques. The pH-dependent swelling behavior of hydrogels was examined in various buffer solutions. All of the prepared hydrogels showed a high swelling capacity in basic solutions. The introduction of magnetite nanoparticles into κ-carrageenan/chitosan complexes had a significant effect on the swelling capacity of magnetic hydrogels, as the water absorbency of hydrogels decreased with increasing magnetite content. Methotrexate as an anticancer and model drug was loaded on hydrogels and the release profiles were investigated at pH=7.4 and 5.3. The methotrexate encapsulation efficiency was increased by increasing magnetite and chitosan contents. The results demonstrated that the release of methotrexate from magnetic hydrogels is pH-dependent with a high release content at pH=7.4. The release profiles were analyzed by Peppas's empirical model and the release of drug from hydrogels followed Fickian type of diffusion mechanism at both pHs. Copyright © 2017 Elsevier B.V. All rights reserved.

Natural wrapping paper from banana (Musa paradisiaca Linn) peel waste with additive essential oils

NASA Astrophysics Data System (ADS)

Widiastuti Agustina, E. S.; Elfi Susanti, V. H.

2018-05-01

The research aimed to produce natural wrapping paper from banana (Musa Paradisiaca Linn.) peel waste with additive essentials oils. The method used in this research was alkalization. The delignification process is done with the use of NaOH 4% at the temperature of 100°C for 1.5 hours. Additive materials in the form of essential oils are added as a preservative and aroma agent, namely cinnamon oil, lemon oil, clove oil and lime oil respectively 2% and 3%. Chemical and physical properties of the produced papers are tested included water content (dry-oven method SNI ISO 287:2010), pH (SNI ISO 6588-1.2010), grammage (SNI ISO 536:2010) and brightness (SNI ISO 2470:2010). Testing results of each paper were compared with commercial wrapping paper. The result shows that the natural paper from banana peel waste with additive essential oil meets the standard of ISO 6519:2016 about Basic Paper for Laminated Plastic Wrapping Paper within the parameter of pH and water content. The paper produced also meet the standard of ISO 8218:2015 about Food Paper and Cardboard within the grammage parameter (high-grade grammage), except the paper with 2% lemon oil. The paper which is closest to the characteristic of commercial wrapping paper is the paper with the additive of 2% cinnamon oil, with pH of 6.95, the water content of 7.14%, grammage of 347.6 gram/m2 and the brightness level of 24.68%.

Removal of heavy metal ions from aqueous solution using Fe3O4-SiO2-poly(1,2-diaminobenzene) core-shell sub-micron particles.

PubMed

Zhang, Fan; Lan, Jing; Zhao, Zongshan; Yang, Ye; Tan, Ruiqin; Song, Weijie

2012-12-01

In this work, Fe(3)O(4)-SiO(2)-poly(1,2-diaminobenzene) sub-micron particles (FSPs) with high saturated magnetization of ∼60-70 emu/g were developed and utilized for the removal of As(III), Cu(II), and Cr(III) ions from aqueous solution. The isothermal results fitted well with the Freundlich model and the kinetic results fitted well with the two-site pseudo-second-order model, which indicated that multilayer adsorption of As(III), Cu(II), and Cr(III) ions on FSPs occurred at two sites with different energy of adsorption. The maximum adsorption capacities followed the order of As(III) (84±5 mg/g, pH=6.0)>Cr(III) (77±3 mg/g, pH=5.3)>Cu(II) (65±3 mg/g, pH=6.0). And the chelating interaction was considered as the main adsorption mechanism. The as-prepared materials were chemically stable with low leaching of Fe (≤1.7 wt.%) and poly(1,2-diaminobenzene) (≤4.9 wt.%) in tap water, sea water, and acidic/basic solutions. These metal-loaded FSPs could be easily recovered from aqueous solutions using a permanent magnet within 20s. They could also be easily regenerated with acid. The present work indicates that the FSPs are promising for removal of heavy metal ions in field application. Copyright © 2012 Elsevier Inc. All rights reserved.

The use of detergents and sanitizers in dairy farm sanitation--an updated perspective.

PubMed

Gilbert, P H

1982-06-01

Raw milk quality in South Africa is poor and standard plate counts in the millions per ml are common. This is largely due to inefficient cleaning and sanitizing of dairy equipment. The basic constituents in milk are described and various soils are classified as soluble in water, alkali, acid, solvent or surfactant or as insoluble. The importance of water quality is highlighted and the influence of mineral salts on soil deposition described. Dairy detergents are broadly classified as alkaline or acid, the former being most effective against fatty and proteinaceous soils and the latter effective against mineral salts. Typical detergent ingredients and their properties are described. Chlorine is incorporated into alkaline detergents not as a sanitizing agent, but as a peptizing agent to aid in protein soil removal. At high pH values the antimicrobial activity of chlorine is greatly diminished. The use of a daily acidified rinse (pH 3,0-5,0) is preferred to the periodic acid wash, since the acid rinse prevents mineral deposition rather than removing accumulated milkstone. All cleaning programmes follow the same fundamental steps--Pre-rinse (40-50 degrees C), wash (60-70 degrees C), rinse (pH 3,0-5,0) and sanitize (25 ppm iodine and 100 ppm chlorine). Farms following such a programme are able to achieve Standard Plate Counts of less than 10,000/ml and coliform counts of less than 10/ml for raw milk.

High activity and stability of codon-optimized phosphoenolpyruvate carboxylase from Photobacterium profundum SS9 at low temperatures and its application for in vitro production of oxaloacetate.

PubMed

Park, Soohyun; Hong, Soohye; Pack, Seung Pil; Lee, Jinwon

2014-02-01

Phosphoenolpyruvate carboxylase (PEPC) of Photobacterium profundum SS9 can be expressed and purified using the Escherichia coli expression system. In this study, a codon-optimized PEPC gene (OPPP) was used to increase expression levels. We confirmed OPPP expression and purified it from extracts of recombinant E. coli SGJS117 harboring the OPPP gene. The purified OPPP showed a specific activity value of 80.3 U/mg protein. The OPPP was stable under low temperature (5-30 °C) and weakly basic conditions (pH 8.5-10). The enzymatic ability of OPPP was investigated for in vitro production of oxaloacetate using phosphoenolpyruvate (PEP) and bicarbonate. Only samples containing the OPPP, PEP, and bicarbonate resulted in oxaloacetate production. OPPP production system using E. coli could be a platform technology to produce high yields of heterogeneous gene and provide the PEPC enzyme, which has high enzyme activity.

Halophilic mechanism of the enzymatic function of a moderately halophilic dihydrofolate reductase from Haloarcula japonica strain TR-1.

PubMed

Miyashita, Yurina; Ohmae, Eiji; Ikura, Teikichi; Nakasone, Kaoru; Katayanagi, Katsuo

2017-05-01

Dihydrofolate (DHF) reductase coded by a plasmid of the extremely halophilic archaeon Haloarcula japonica strain TR-1 (HjDHFR P1) shows moderate halophilicity on enzymatic activity at pH 6.0, although there is no significant effect of NaCl on its secondary structure. To elucidate the salt-activation and -inactivation mechanisms of this enzyme, we investigated the effects of pH and salt concentration, deuterium isotope effect, steady-state kinetics, and rapid-phase ligand-binding kinetics. Enzyme activity was increased eightfold by the addition of 500 mM NaCl at pH 6.0, fourfold by 250 mM at pH 8.0, and became independent of salt concentration at pH 10.0. Full isotope effects observed at pH 10.0 under 0-1000 mM NaCl indicated that the rate of hydride transfer, which was the rate-determining step at the basic pH region, was independent of salt concentration. Conversely, rapid-phase ligand-binding experiments showed that the amplitude of the DHF-binding reaction increased and the tetrahydrofolate (THF)-releasing rate decreased with increasing NaCl concentration. These results suggested that the salt-activation mechanism of HjDHFR P1 is via the population change of the anion-unbound and anion-bound conformers, which are binding-incompetent and -competent conformations for DHF, respectively, while that of salt inactivation is via deceleration of the THF-releasing rate, which is the rate-determining step at the neutral pH region.

Dependence of precipitation of trace elements on pH in standard water

NASA Astrophysics Data System (ADS)

Verma, Shivcharan; Mohanty, Biraja P.; Singh, K. P.; Behera, B. R.; Kumar, Ashok

2018-04-01

The present work aimed to study the dependence of precipitation of trace elements on the pH of solution. A standard solution was prepared by using ultrapure deionized water (18.2 MΩ/cm) as the solvent and 11 water-soluble salts having different elements as solutes. Five samples of different pH values (2 acidic, 2 basic, and 1 neutral) were prepared from this standard solution. Sodium-diethyldithiocarbamate was used as the chelating agent to precipitate the metal ions present in these samples of different pH values. The targets were prepared by collecting these precipitates on mixed cellulose esters filter of 0.4 μm pore size by vacuum filtration. Elemental analysis of these targets was performed by particle-induced X-ray emission (PIXE) using 2.7 MeV protons from the single Dee variable energy cyclotron at Panjab University, Chandigarh, India. PIXE data were analyzed using GUPIXWIN software. For most of the elements, except Hg with oxidation state +2, such as Co, Ni, Zn, Ba, and Cd, a general trend of enhancement in precipitation was observed with the increase in pH. However, for other elements such as V, As, Mo, Ag, and Bi, which have oxidation state other than +2, no definite pattern was observed. Precipitation of Ba and As using this method was negligible at all five pH values. From these results, it can be concluded that the precipitation and recovery of elements depend strongly on the pH of the water sample.

Isolation of levoglucosan from lignocellulosic pyrolysis oil derived from wood or waste newsprint

DOEpatents

Moens, Luc

1995-01-01

A method is provided for preparing high purity levoglucosan from lignocellulosic pyrolysis oils derived from wood or waste newsprint. The method includes reducing wood or newsprint to fine particle sizes, treating the particles with a hot mineral acid for a predetermined period of time, and filtering off and drying resulting solid wood or newsprint material; pyrolyzing the dried solid wood or newsprint material at temperatures between about 350.degree. and 375.degree. C. to produce pyrolysis oils; treating the oils to liquid-liquid extraction with methyl isobutyl ketone to remove heavy tar materials from the oils, and to provide an aqueous fraction mixture of the oils containing primarily levoglucosan; treating the aqueous fraction mixtures with a basic metal salt in an amount sufficient to elevate pH values to a range of about 12 to about 12.5 and adding an amount of the salt in excess of the amount needed to obtain the pH range to remove colored materials of impurities from the oil and form a slurry, and freeze-drying the resulting slurry to produce a dry solid residue; and extracting the levoglucosan from the residue using ethyl acetate solvent to produce a purified crystalline levoglucosan.

Isolation of levoglucosan from lignocellulosic pyrolysis oil derived from wood or waste newsprint

DOEpatents

Moens, L.

1995-07-11

A method is provided for preparing high purity levoglucosan from lignocellulosic pyrolysis oils derived from wood or waste newsprint. The method includes reducing wood or newsprint to fine particle sizes, treating the particles with a hot mineral acid for a predetermined period of time, and filtering off and drying resulting solid wood or newsprint material; pyrolyzing the dried solid wood or newsprint material at temperatures between about 350 and 375 C to produce pyrolysis oils; treating the oils to liquid-liquid extraction with methyl isobutyl ketone to remove heavy tar materials from the oils, and to provide an aqueous fraction mixture of the oils containing primarily levoglucosan; treating the aqueous fraction mixtures with a basic metal salt in an amount sufficient to elevate pH values to a range of about 12 to about 12.5 and adding an amount of the salt in excess of the amount needed to obtain the pH range to remove colored materials of impurities from the oil and form a slurry, and freeze-drying the resulting slurry to produce a dry solid residue; and extracting the levoglucosan from the residue using ethyl acetate solvent to produce a purified crystalline levoglucosan. 2 figs.

Combining "Bottom-up" and "Top-down" Approaches to Assess the Impact of Food and Gastric pH on Pictilisib (GDC-0941) Pharmacokinetics.

PubMed

Lu, Tong; Fraczkiewicz, Grazyna; Salphati, Laurent; Budha, Nageshwar; Dalziel, Gena; Smelick, Gillian S; Morrissey, Kari M; Davis, John D; Jin, Jin Y; Ware, Joseph A

2017-11-01

Pictilisib, a weakly basic compound, is an orally administered, potent, and selective pan-inhibitor of phosphatidylinositol 3-kinases for oncology indications. To investigate the significance of high-fat food and gastric pH on pictilisib pharmacokinetics (PK) and enable label recommendations, a dedicated clinical study was conducted in healthy volunteers, whereby both top-down (population PK, PopPK) and bottom-up (physiologically based PK, PBPK) approaches were applied to enhance confidence of recommendation and facilitate the clinical development through scenario simulations. The PopPK model identified food (for absorption rate constant (K a )) and proton pump inhibitors (PPI, for relative bioavailability (F rel ) and K a ) as significant covariates. Food and PPI also impacted the variability of F rel . The PBPK model accounted for the supersaturation tendency of pictilisib, and gastric emptying physiology successfully predicted the food and PPI effect on pictilisib absorption. Our research highlights the importance of applying both quantitative approaches to address critical drug development questions. © 2017 The Authors CPT: Pharmacometrics & Systems Pharmacology published by Wiley Periodicals, Inc. on behalf of American Society for Clinical Pharmacology and Therapeutics.

Effect of Rice Bran and Wheat Fibers on Microbiological and Physicochemical Properties of Fermented Sausages during Ripening and Storage

PubMed Central

Jung, Ji-Taek; Lee, Jin-kyu; Choi, Yeong-Seok; Lee, Ju-Ho; Choi, Jung-Seok; Choi, Yang-Il; Chung, Yoon-Kyung

2018-01-01

Abstract This study investigated the effect of rice bran fiber (RBF) and wheat fibers (WF) on microbiological and physicochemical properties of fermented sausages during ripening and storage. The experimental design included three treatments: Control, no addition; RBF, 1.5%; and WF, 1.5%. During the ripening periods, the addition of dietary fibers rapidly decreased pH and maintained high water activity values of fermented sausages (p<0.05). Lactic acid bacteria were more prevalent in fermented sausages with rice bran fiber than control and sausages with added wheat fiber. During cold storage, lower pH was observed in sausages with dietary fibers (p<0.05), and the water activity and color values were reduced as the storage period lengthened. Fermented sausages containing dietary fibers were higher in lactic acid bacteria counts, volatile basic nitrogen and 2-thiobarbituric acid reactive substance values compared to the control (p<0.05). The results indicate that, the addition of dietary fibers in the fermented sausages promotes the growth of lactic bacteria and fermentation, and suggests that development of functional fermented sausages is possible. PMID:29805280

MnMoO4 nanosheet array: an efficient electrocatalyst for hydrogen evolution reaction with enhanced activity over a wide pH range.

PubMed

Wen, Lulu; Sun, Yiqiang; Zhang, Tao; Bai, Yu; Li, Xinyang; Lyu, Xianjun; Cai, Weiping; Li, Yue

2018-08-17

We report the preparation of MnMoO 4 nanosheet array on nickel foam (MnMoO 4 NSA/NF) as an excellent 3D hydrogen evolution reaction (HER) electrocatalyst with good catalytic performance applied under basic, acidic and neutral conditions. In 0.5 M H 2 SO 4 , this MnMoO 4 NSA/NF electrode needs an overpotential of 89 mV to drive current densities of 10 mA cm -2 , to achieve the same current density, it demands overpotentials of 105 mV in 1.0 M KOH, 161 mV in 1.0 M PBS (pH = 7), respectively. After continuous CV scanning for 1000 cycles under different pH conditions, it also demonstrates an excellent stability with ignorable activity decrease. Such preeminent HER performance may be derived from the synergistic effect between manganese (Mn) and molybdenum (Mo) atoms, exposure of more active sites on the nanosheets and effective electron transport along the nanosheets. This MnMoO 4 NSA/NF electrocatalyst provides us a highly efficient material for water splitting devices for industrial hydrogen production.

Fabrication of luminescent CdS nanoparticles on short-peptide-based hydrogel nanofibers: tuning of optoelectronic properties.

PubMed

Palui, Goutam; Nanda, Jayanta; Ray, Sudipta; Banerjee, Arindam

2009-07-13

The pH-induced self-assembly of three synthetic tripeptides in water medium is used to immobilize luminescent CdS nanoparticles. These peptides form a nanofibrillar network structure upon gelation in aqueous medium at basic pH values (pH 11.0-13.0), and the fabrication of CdS nanoparticles on the gel nanofiber confers the luminescent property to these gels. Atomic force microscopy, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy clearly reveal the presence of CdS nanoparticles in a well-defined array on the gel nanofibers. This is a convenient way to make organic nanofiber-inorganic nanoparticle hybrid nanocomposite systems. The size of the CdS nanoparticles remains almost same before and after deposition on the gel nanofiber. Photoluminescence (PL) measurement of the CdS nanoparticles upon deposition on the gel nanofibers shows a significant blue shift in the emission spectrum of the nanoparticles, and there is a considerable change in the PL gap energy of the CdS nanoparticles after immobilization on different gel nanofibrils. This finding suggests that the optoelectronic properties of CdS nanoparticles can be tuned upon deposition on gel nanofibers without changing the size of the nanoparticles.

Biology, ecology, and biotechnological applications of anaerobic bacteria adapted to environmental stresses in temperature, pH, salinity, or substrates.

PubMed Central

Lowe, S E; Jain, M K; Zeikus, J G

1993-01-01

Anaerobic bacteria include diverse species that can grow at environmental extremes of temperature, pH, salinity, substrate toxicity, or available free energy. The first evolved archaebacterial and eubacterial species appear to have been anaerobes adapted to high temperatures. Thermoanaerobes and their stable enzymes have served as model systems for basic and applied studies of microbial cellulose and starch degradation, methanogenesis, ethanologenesis, acetogenesis, autotrophic CO2 fixation, saccharidases, hydrogenases, and alcohol dehydrogenases. Anaerobes, unlike aerobes, appear to have evolved more energy-conserving mechanisms for physiological adaptation to environmental stresses such as novel enzyme activities and stabilities and novel membrane lipid compositions and functions. Anaerobic syntrophs do not have similar aerobic bacterial counterparts. The metabolic end products of syntrophs are potent thermodynamic inhibitors of energy conservation mechanisms, and they require coordinated consumption by a second partner organism for species growth. Anaerobes adapted to environmental stresses and their enzymes have biotechnological applications in organic waste treatment systems and chemical and fuel production systems based on biomass-derived substrates or syngas. These kinds of anaerobes have only recently been examined by biologists, and considerably more study is required before they are fully appreciated by science and technology. Images PMID:8336675

Carbon dioxide capture using resin-wafer electrodeionization

DOEpatents

Lin, YuPo J.; Snyder, Seth W.; Trachtenberg, Michael S.; Cowan, Robert M.; Datta, Saurav

2015-09-08

The present invention provides a resin-wafer electrodeionization (RW-EDI) apparatus including cathode and anode electrodes separated by a plurality of porous solid ion exchange resin wafers, which when in use are filled with an aqueous fluid. The apparatus includes one or more wafers comprising a basic ion exchange medium, and preferably includes one or more wafers comprising an acidic ion exchange medium. The wafers are separated from one another by ion exchange membranes. The fluid within the acidic and/or basic ion exchange wafers preferably includes, or is in contact with, a carbonic anhydrase (CA) enzyme to facilitate conversion of bicarbonate ion to carbon dioxide within the acidic medium. A pH suitable for exchange of CO.sub.2 is electrochemically maintained within the basic and acidic ion exchange wafers by applying an electric potential across the cathode and anode.

Regulation of gene expression in roots of the pH-sensitive Vaccinium corymbosum and the pH-tolerant Vaccinium arboreum in response to near neutral pH stress using RNA-Seq.

PubMed

Payá-Milans, Miriam; Nunez, Gerardo H; Olmstead, James W; Rinehart, Timothy A; Staton, Margaret

2017-08-07

Blueberries are one of the few horticultural crops adapted to grow in acidic soils. Neutral to basic soil pH is detrimental to all commonly cultivated blueberry species, including Vaccinium corymbosum (VC). In contrast, the wild species V. arboreum (VA) is able to tolerate a wider range of soil pH. To assess the molecular mechanisms involved in near neutral pH stress response, plants from pH-sensitive VC (tetraploid) and pH-tolerant VA (diploid) were grown at near neutral pH 6.5 and at the preferred pH of 4.5. Transcriptome sequencing of root RNA was performed for 4 biological replications per species x pH level interaction, for a total of 16 samples. Reads were mapped to the reference genome from diploid V. corymbosum, transforming ~55% of the reads to gene counts. A quasi-likelihood F test identified differential expression due to pH stress in 337 and 4867 genes in VA and VC, respectively. Both species shared regulation of genes involved in nutrient homeostasis and cell wall metabolism. VA and VC exhibited differential regulation of signaling pathways related to abiotic/biotic stress, cellulose and lignin biosynthesis, and nutrient uptake. The specific responses in VA likely facilitate tolerance to higher soil pH. In contrast, response in VC, despite affecting a greater number of genes, is not effective overcoming the stress induced by pH. Further inspection of those genes with differential expression that are specific in VA may provide insight on the mechanisms towards tolerance.

Hyperplasia vs hypertrophy in tissue regeneration after extensive liver resection.

PubMed

Marongiu, Fabio; Marongiu, Michela; Contini, Antonella; Serra, Monica; Cadoni, Erika; Murgia, Riccardo; Laconi, Ezio

2017-03-14

To address to what extent hypertrophy and hyperplasia contribute to liver mass restoration after major tissue loss. The ability of the liver to regenerate is remarkable on both clinical and biological grounds. Basic mechanisms underlying this process have been intensively investigated. However, it is still debated to what extent hypertrophy and hyperplasia contribute to liver mass restoration after major tissue loss. We addressed this issue using a genetically tagged system. We were able to follow the fate of single transplanted hepatocytes during the regenerative response elicited by 2/3 partial surgical hepatectomy (PH) in rats. Clusters of transplanted cells were 3D reconstructed and their size distribution was evaluated over time after PH. Liver size and liver DNA content were largely recovered 10 d post-PH, as expected ( e.g ., total DNA/liver/100 g b.w. was 6.37 ± 0.21 before PH and returned to 6.10 ± 0.36 10 d after PH). Data indicated that about 2/3 of the original residual hepatocytes entered S-phase in response to PH. Analysis of cluster size distribution at 24, 48, 96 h and 10 d after PH revealed that about half of the remnant hepatocytes completed at least 2 cell cycles. Average size of hepatocytes increased at 24 h (248.50 μm 2 ± 7.82 μm 2 , P = 0.0015), but returned to control values throughout the regenerative process (up to 10 d post-PH, 197.9 μm 2 ± 6.44 μm 2 , P = 0.11). A sizeable fraction of the remnant hepatocyte population does not participate actively in tissue mass restoration. Hyperplasia stands as the major mechanism contributing to liver mass restoration after PH, with hypertrophy playing a transient role in the process.

HNO and NO release from a primary amine-based diazeniumdiolate as a function of pH

PubMed Central

Salmon, Debra J.; Torres de Holding, Claudia L.; Thomas, Lynta; Peterson, Kyle V.; Goodman, Gens P.; Saavedra, Joseph E.; Srinivasan, Aloka; Davies, Keith M.; Keefer, Larry K.; Miranda, Katrina M.

2011-01-01

The growing evidence that nitroxyl (HNO) has a rich pharmacological potential that differs from that of nitric oxide (NO) has intensified interest in HNO donors. Recently, the diazeniumdiolate (NONOate) based on isopropylamine (IPA/NO; Na[(CH3)2CHNH(N(O)NO)]) was demonstrated to function under physiological conditions as an organic analogue to the commonly used HNO donor Angeli’s salt (Na2N2O3). The decomposition mechanism of Angeli’s salt is dependent on pH, with transition from an HNO to an NO donor occurring abruptly near pH 3. Here, pH is shown to also affect product formation from IPA/NO. Chemical analysis of HNO and NO production led to refinement of an earlier, quantum mechanically based prediction of the pH-dependent decomposition mechanisms of primary amine NONOates such as IPA/NO. Under basic conditions, the amine proton of IPA/NO is able to initiate decomposition to HNO by tautomerization to the nitroso nitrogen (N2). At lower pH, protonation activates a competing pathway to NO production. At pH 8, the donor properties of IPA/NO and Angeli’s salt are demonstrated to be comparable, suggesting that at or above this pH, IPA/NO is primarily an HNO donor. Below pH 5, NO is the major product, while IPA/NO functions as a dual donor of HNO and NO at intermediate pH. This pH-dependent variability in product formation may prove useful in examination of the chemistry of NO and HNO. Furthermore, primary amine NONOates may serve as a tunable class of nitrogen oxide donor. PMID:21405089

pH shift protein recovery with organic acids on texture and color of cooked gels.

PubMed

Paker, Ilgin; Beamer, Sarah; Jaczynski, Jacek; Matak, Kristen E

2015-01-01

Isoelectric solubilization and precipitation (ISP) processing uses pH shifts to separate protein from fish frames, which may increase commercial interest for silver carp. Texture and color properties of gels made from silver carp protein recovered at different pH strategies and organic acid types were compared. ISP was applied to headed gutted silver carp using 10 mol L(-1) sodium hydroxide (NaOH) and either glacial acetic acid (AA) or a (1:1) formic and lactic acid combination (F&L). Protein gels were made with recovered protein and standard functional additives. Texture profile analysis and the Kramer shear test showed that protein gels made from protein solubilized at basic pH values were firmer, harder, more cohesive, gummier and chewier (P < 0.05) than proteins solubilized under acidic conditions. Acidic solubilization led to whiter (P < 0.05) gels, and using F&L during ISP yielded whiter gels under all treatments (P < 0.05). Gels made from ISP-recovered silver carp protein using organic acids show potential for use as a functional ingredient in restructured foods. © 2014 Society of Chemical Industry.

Dynamic oligomeric conversions of the cytoplasmic RCK domains mediate MthK potassium channel activity.

PubMed

Kuo, Mario Meng-Chiang; Baker, Kent A; Wong, Lee; Choe, Senyon

2007-02-13

The crystal structure of the RCK-containing MthK provides a molecular framework for understanding the ligand gating mechanisms of K+ channels. Here we examined the macroscopic currents of MthK in enlarged Escherichia coli membrane by patch clamp and rapid perfusion techniques and showed that the channel undergoes desensitization in seconds after activation by Ca2+ or Cd2+. Additionally, MthK is inactivated by slightly acidic pH only from the cytoplasmic side. Examinations of isolated RCK domain by size-exclusion chromatography, static light scattering, analytical sedimentation, and stopped-flow spectroscopy show that Ca2+ rapidly converts isolated RCK monomers to multimers at alkaline pH. In contrast, the RCK domain at acidic pH remains firmly dimeric regardless of Ca2+ but restores predominantly to multimer or monomer at basic pH with or without Ca2+, respectively. These functional and biochemical analyses correlate the four functional states of the MthK channel with distinct oligomeric states of its RCK domains and indicate that the RCK domains undergo oligomeric conversions in modulating MthK activities.

Stability studies on diloxanide furoate: effect of pH, temperature, gastric and intestinal fluids.

PubMed

Gadkariem, E A; Belal, F; Abounassif, M A; El-Obeid, H A; E E Ibrahim, K

2004-04-01

The degradation of the amoebicide diloxanide furoate in alkaline medium at different temperatures was investigated using both a spectrophotometric and a developed HPLC method. In solutions, the drug was found to undergo decomposition, i.e., temperature and pH dependent. The pH-rate profile at pH between 7.6 and 9.6 indicated a first-order dependence of Kobs on [-OH]. Arrhenius plot obtained at pH 8 was linear between 40 and 63 degrees C. The estimated activation energy of hydrolysis was found to be 18.25 kcal degree.mol(-1). The effect of simulated gastric and intestinal fluids on the drug was also investigated. A new thin-layer chromatographic (TLC) procedure for the fractionation of the drug and its alkaline hydrolysis products has been developed and was found to compare favorably with that of the British Pharmacopoeia. Three hydrolysis products of a basic methanolic solution of the drug, namely furoic acid, diloxanide and methylfuroate could be identified by the use of TLC, HPLC, infrared and mass spectrometry.

Sorption influenced transport of ionizable pharmaceuticals onto a natural sandy aquifer sediment at different pH.

PubMed

Schaffer, Mario; Boxberger, Norman; Börnick, Hilmar; Licha, Tobias; Worch, Eckhard

2012-04-01

The pH-dependent transport of eight selected ionizable pharmaceuticals was investigated by using saturated column experiments. Seventy-eight different breakthrough curves on a natural sandy aquifer material were produced and compared for three different pH levels at otherwise constant conditions. The experimentally obtained K(OC) data were compared with calculated K(OC) values derived from two different logK(OW)-logK(OC) correlation approaches. A significant pH-dependence on sorption was observed for all compounds with pK(a) in the considered pH range. Strong retardation was measured for several compounds despite their hydrophilic character. Besides an overall underestimation of K(OC), the comparison between calculated and measured values only yields meaningful results for the acidic and neutral compounds. Basic compounds retarded much stronger than expected, particularly at low pH when their cationic species dominated. This is caused by additional ionic interactions, such as cation exchange processes, which are insufficiently considered in the applied K(OC) correlations. Copyright © 2011 Elsevier Ltd. All rights reserved.

Personnel Needs and Training for Biomedical and Behavioral Research.

ERIC Educational Resources Information Center

National Academy of Sciences - National Research Council, Washington, DC. Commission on Human Resources.

The fourth in a series of annual reports assessing the role of and need for federal training programs in the biomedical and behavioral sciences is presented. Highlights of this 1978 report include: (1) the results of surveys of the chairpersons of 1,324 basic biomedical science departments and 474 behavioral science departments in Ph.D.-granting…

Building Infrastructure to Accelerate Transfer of Basic Research in Spinal Cord Injury (SCI) to Clinical Practice: North American Clinical Trials Network

DTIC Science & Technology

2013-08-01

RISCIS trial. 2. Participation by NACTN sites in the Novartis clinical trial of the monoclonal antibody to Nogo. Martin Schwab, PhD...Martha Horn and Simone Hirsch at Traumacenter, Murnau; Kristin Lorenz and Petra Schatz at Hohe Warte, Bayreuth. 8 Neurorehabilitation and Neural Repair

Basic Research in Orbital Debris Detection and Estimation

NASA Technical Reports Server (NTRS)

Culp, Robert D.

1999-01-01

The research conducted under NASA Research Grant has been reported periodically throughout the duration of this grant. This research has been coordinated with the work supported by NASA Graduate Student Research Grant awarded to further the graduate doctoral program of Kira Jorgensen. This work will continue through the completion of Kira Jorgensen's Ph.D. program in May, 2000.

A Comparison Study between a Traditional and Experimental Program.

ERIC Educational Resources Information Center

Dogan, Hamide

This paper is part of a dissertation defended in January 2001 as part of the author's Ph.D. requirement. The study investigated the effects of use of Mathematica, a computer algebra system, in learning basic linear algebra concepts, It was done by means of comparing two first year linear algebra classes, one traditional and one Mathematica…

1969 & 1980 Science and Engineering Doctorate Supply and Utilization.

ERIC Educational Resources Information Center

National Science Foundation, Washington, DC.

This study is limited to science and engineering doctorates (both PhD and Doctor of Arts) and spans the period 1969 to 1980--a period for which most of the factors likely to have a significant effect on the supply and utilization of doctorates are known or can be reasonably anticipated. The basic methodology involves statistically projecting past…

Doctoral and Postdoctoral Education in Science and Engineering: Europe in the International Competition

ERIC Educational Resources Information Center

MOGUEROU, PHILIPPE

2005-01-01

In this article, we discuss the recent evolutions of science and engineering doctoral and postdoctoral education in Europe. Indeed, Ph.Ds are crucial to the conduct of research and innovation in the national innovation systems, as they provide a large amount of input into creating the competitive advantage, notably through basic research. First,…

Use of ENSO forecasts to select nitrogen fertilizer application strategies for winter

USDA-ARS?s Scientific Manuscript database

El Niño Southern Oscillation (ENSO) has a strong impact on winter crops in Alabama (AL). Wheat is basically grown during winter as cash crop and sometimes also as fodder or grain crop in AL. Thus, it is very necessary to understand the impact of variability in climate factors due to the different ph...

Randomized, Controlled Trial of CBT Training for PTSD Providers

DTIC Science & Technology

2013-10-01

and Therapy, 47, 902-909. Shapiro, F. (2001). Eye movement desensitization and reprocessing ( EMDR ): Basic principles...Hopper, E. K., Korn, D. L., & Simpson, W. B. (2007). A randomized clinical trial of eye movement desensitization and reprocessing ( EMDR ), fluoxetine...Josef Ruzek, Ph.D. CONTRACTING ORGANIZATION: Palo Alto Institute for Research and Education Palo Alto, CA 94304 REPORT

Understanding the Differences Between Cocrystal and Salt Aqueous Solubilities.

PubMed

Cavanagh, Katie L; Maheshwari, Chinmay; Rodríguez-Hornedo, Naír

2018-01-01

This work challenges the popular notion that pharmaceutical salts are more soluble than cocrystals. There are cocrystals that are more soluble than salt forms of a drug and vice-versa. It all depends on the interplay between the chemistry of both the solid and solution phases. Aqueous solubility, pH max , and supersaturation index (SA = S CC /S D or S salt /S D ) of cocrystals and salts of a basic drug, lamotrigine (LTG), were determined, and mathematical models that predict the influence of cocrystal/salt K sp and K a were derived. K sp and SA followed the order LTG-nicotinamide cocrystal (18) > LTG-HCl salt (12) > LTG-saccharin salt (5) > LTG-methylparaben cocrystal (1) > LTG-phenobarbital cocrystal (0.2). The values in parenthesis represent SA under nonionizing conditions. Cocrystal/salt solubility and thermodynamic stability are determined by pH and will drastically change with a single unit change in pH. pH max values ranged from 5.0 (saccharin salt) to 6.4 (methylparaben cocrystal) to 9.0 (phenobarbital cocrystal). Cocrystal/salt pH max dependence on pK sp and pK a shows that cocrystals and salts exhibit different behavior. Solubility and pH max are as important as supersaturation index in assessing the stability and risks associated with conversions of supersaturating forms. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Nanoparticle-based luminescent probes for intracellular sensing and imaging of pH.

PubMed

Schäferling, Michael

2016-05-01

Fluorescence imaging microscopy is an essential tool in biomedical research. Meanwhile, various fluorescent probes are available for the staining of cells, cell membranes, and organelles. Though, to monitor intracellular processes and dysfunctions, probes that respond to ubiquitous chemical parameters determining the cellular function such as pH, pO2 , and Ca(2+) are required. This review is focused on the progress in the design, fabrication, and application of photoluminescent nanoprobes for sensing and imaging of pH in living cells. The advantages of using nanoprobes carrying fluorescent pH indicators compared to single molecule probes are discussed as well as their limitations due to the mostly lysosomal uptake by cells. Particular attention is paid to ratiometric dual wavelength nanosensors that enable intrinsic referenced measurements. Referencing and proper calibration procedures are basic prerequisites to carry out reliable quantitative pH determinations in complex samples such as living cells. A variety of examples will be presented that highlight the diverseness of nanocarrier materials (polymers, micelles, silica, quantum dots, carbon dots, gold, photon upconversion nanocrystals, or bacteriophages), fluorescent pH indicators for the weak acidic range, and referenced sensing mechanisms, that have been applied intracellularly up to now. WIREs Nanomed Nanobiotechnol 2016, 8:378-413. doi: 10.1002/wnan.1366 For further resources related to this article, please visit the WIREs website. © 2015 Wiley Periodicals, Inc.

Remediation of TCE-contaminated groundwater using acid/BOF slag enhanced chemical oxidation.

PubMed

Tsai, T T; Kao, C M; Wang, J Y

2011-04-01

The objective of this study was to evaluate the potential of applying acid/H(2)O(2)/basic oxygen furnace slag (BOF slag) and acid/S(2)O(8)(2-)/BOF slag systems to enhance the chemical oxidation of trichloroethylene (TCE)-contaminated groundwater. Results from the bench-scale study indicate that TCE oxidation via the Fenton-like oxidation process can be enhanced with the addition of BOF slag at low pH (pH=2-5.2) and neutral (pH=7.1) conditions. Because the BOF slag has iron abundant properties (14% of FeO and 6% of Fe(2)O(3)), it can be sustainably reused for the supplement of iron minerals during the Fenton-like or persulfate oxidation processes. Results indicate that higher TCE removal efficiency (84%) was obtained with the addition of inorganic acid for the activation of Fenton-like reaction compared with the experiments with organic acids addition (with efficiency of 10-15% lower) (BOF slag=10gL(-1); initial pH=5.2). This could be due to the fact that organic acids would compete with TCE for available oxidants. Results also indicate that the pH value had a linear correlation with the observed first-order decay constant of TCE, and thus, lower pH caused a higher TCE oxidation rate. Copyright © 2011 Elsevier Ltd. All rights reserved.

Highly Sensitive and Selective Uranium Detection in Natural Water Systems Using a Luminescent Mesoporous Metal-Organic Framework Equipped with Abundant Lewis Basic Sites: A Combined Batch, X-ray Absorption Spectroscopy, and First Principles Simulation Investigation.

PubMed

Liu, Wei; Dai, Xing; Bai, Zhuanling; Wang, Yanlong; Yang, Zaixing; Zhang, Linjuan; Xu, Lin; Chen, Lanhua; Li, Yuxiang; Gui, Daxiang; Diwu, Juan; Wang, Jianqiang; Zhou, Ruhong; Chai, Zhifang; Wang, Shuao

2017-04-04

Uranium is not only a strategic resource for the nuclear industry but also a global contaminant with high toxicity. Although several strategies have been established for detecting uranyl ions in water, searching for new uranium sensor material with great sensitivity, selectivity, and stability remains a challenge. We introduce here a hydrolytically stable mesoporous terbium(III)-based MOF material compound 1, whose channels are as large as 27 Å × 23 Å and are equipped with abundant exposed Lewis basic sites, the luminescence intensity of which can be efficiently and selectively quenched by uranyl ions. The detection limit in deionized water reaches 0.9 μg/L, far below the maximum contamination standard of 30 μg/L in drinking water defined by the United States Environmental Protection Agency, making compound 1 currently the only MOF material that can achieve this goal. More importantly, this material exhibits great capability in detecting uranyl ions in natural water systems such as lake water and seawater with pH being adjusted to 4, where huge excesses of competing ions are present. The uranyl detection limits in Dushu Lake water and in seawater were calculated to be 14.0 and 3.5 μg/L, respectively. This great detection capability originates from the selective binding of uranyl ions onto the Lewis basic sites of the MOF material, as demonstrated by synchrotron radiation extended X-ray adsorption fine structure, X-ray adsorption near edge structure, and first principles calculations, further leading to an effective energy transfer between the uranyl ions and the MOF skeleton.

Anthocyanins: Model Compounds for Learning about More than pH

NASA Astrophysics Data System (ADS)

Curtright, Robert; Rynearson, James A.; Markwell, John

1996-04-01

We have all experienced anthocyanins as a part of the natural beauty of the plant world. Anthocyanins provide a startling contrast to an otherwise green world producing the beauty of garden-variety flowers, wildflowers, and the blazing colors of many trees, bushes, and berries. We believe that anthocyanins deserve a more prominent role as models for engaging student interest in basic chemical principles. In recent years it has become common to use anthocyanins as pH indicators. We believe that chemistry teachers can capitalize further on the natural interest of students in anthocyanin pigments to design meaningful lessons involving chromatography and hydrolysis. This article focuses on the use of anthocyanins in chromatography and hydrolysis.

A new approach to evaluate natural zeolite ability to sorb lead (Pb) from aqueous solutions

NASA Astrophysics Data System (ADS)

Drosos, Evangelos I. P.; Karapanagioti, Hrissi K.

2013-04-01

Lead (Pb) is a hazardous pollutant commonly found in aquatic ecosystems. Among several methods available, the addition of sorbent amendments to soils or sediments is attractive, since its application is relatively simple, while it can also be cost effective when a low cost and re-usable sorbent is used; e.g. natural zeolites. Zeolites are crystalline aluminosilicates with a three-dimensional structure composed of a set of cavities occupied by large ions and water molecules. Zeolites can accommodate a wide variety of cations, such as Na+, K+, Ca2+, Mg2+, which are rather loosely held and can readily be exchanged for others in an aqueous solution. Natural zeolites are capable of removing cations, such as lead, from aqueous solutions by ion exchange. There is a wide variation in the cation exchange capacity (CEC) of natural zeolites because of the different nature of various zeolites cage structures, natural structural defects, adsorbed ions, and their associated gangue minerals. Naturally occurring zeolites are rarely pure and are contaminated to varying degrees by other minerals, such as clays and feldspars, metals, quartz, or other zeolites as well. These impurities affect the CEC even for samples originated from the same region but from a different source. CEC of the material increases with decreasing impurity content. Potentially exchangeable ions in such impurities do not necessarily participate in ion exchange mechanism, while, in some cases, impurities may additionally block the access to active sites. For zeoliferous rocks having the same percentage of a zeolitic phase, the CEC increases with decreasing Si/Al ratio, as the more Si ions are substituted by Al ions, the more negative the valence of the matrix becomes. Sodium seems to be the most effective exchangeable ion for lead. On the contrary, it is unlikely that the potassium content of the zeolite would be substituted. A pretreatment with high concentration solutions of Na, such as 2 M NaCl, can significantly improve zeolite CEC by bringing the material to near homoionic form. pH and temperature are the critical parameters for using natural zeolites as sorbents. Zeolites should not be used in extremely acidic, neither in extremely basic pH conditions, except for very short times. The exchange of Pb, requires low solution pH, to avoid precipitation but not too low because the H+ are competitive ions for ion exchange; as a result the zeolite CEC related to Pb removal may be downgraded. If pH enters the basic range (e.g. pH>8), more aquatic complexes with lower positive valence than those prevailing in lower pH are produced; these complexes are less attracted by the negative charged zeolitic matrix. Pb uptake is favored at higher temperatures as ion exchange (including the diffusion of exchangeable ions inside the material and the medium, and vice versa) is an endothermic process. With the increase of temperature there is a decrease in hydration of all available exchangeable cations that eases the movement within the channels of the solid matrix. Additionally, the mobility of the potassium ions, present in the zeolitic material, also increases with the temperature resulting in enhanced CEC.

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.

Single step, pH induced gold nanoparticle chain formation in lecithin/water system.

PubMed

Sharma, Damyanti

2013-07-01

Gold nanoparticle (AuNP) chains have been formed by a single step method in a lecithin/water system where lecithin itself plays the role of a reductant and a template for AuNP chain formation. Two preparative strategies were explored: (1) evaporating lecithin solution with aqueous gold chloride (HAuCl4) at different pHs and (2) dispersing lecithin vesicles in aqueous HAuCl4 solutions of various pHs in the range of 2.5-11.3. In method 1, at initial pH 2.5, 20-50 nm AuNPs are found attached to lecithin vesicles. When pH is raised to 5.5 there are no vesicles present and 20 nm monodisperse particles are found aggregating. Chain formation of fine nanoparticles (3-5 nm) is observed from neutral to basic pH, between 6.5-10.3 The chains formed are hundreds of nanometers to micrometer long and are usually 2-3 nanoparticles wide. On further increasing pH to 11.3, particles form disk-like or raft-like structures. When method (ii) was used a little chain formation was observed. Most of the nanoparticles formed were found either sitting together as raft like structures or scattered on lecithin structures. Copyright © 2013 Elsevier B.V. All rights reserved.

pH sensing by lipids in membranes: The fundamentals of pH-driven migration, polarization and deformations of lipid bilayer assemblies.

PubMed

Angelova, Miglena I; Bitbol, Anne-Florence; Seigneuret, Michel; Staneva, Galya; Kodama, Atsuji; Sakuma, Yuka; Kawakatsu, Toshihiro; Imai, Masayuki; Puff, Nicolas

2018-03-06

Most biological molecules contain acido-basic groups that modulate their structure and interactions. A consequence is that pH gradients, local heterogeneities and dynamic variations are used by cells and organisms to drive or regulate specific biological functions including energetic metabolism, vesicular traffic, migration and spatial patterning of tissues in development. While the direct or regulatory role of pH in protein function is well documented, the role of hydrogen and hydroxyl ions in modulating the properties of lipid assemblies such as bilayer membranes is only beginning to be understood. Here, we review approaches using artificial lipid vesicles that have been instrumental in providing an understanding of the influence of pH gradients and local variations on membrane vectorial motional processes: migration, membrane curvature effects promoting global or local deformations, crowding generation by segregative polarization processes. In the case of pH induced local deformations, an extensive theoretical framework is given and an application to a specific biological issue, namely the structure and stability of mitochondrial cristae, is described. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo. Copyright © 2018 Elsevier B.V. All rights reserved.

Assessment of polyelectrolyte coating stability under dynamic buffer conditions in CE.

PubMed

Swords, Kyleen E; Bartline, Peter B; Roguski, Katherine M; Bashaw, Sarah A; Frederick, Kimberley A

2011-09-01

Dynamic buffer conditions are present in many electrophoretically driven separations. Polyelectrolyte multilayer coatings have been employed in CE because of their chemical and physical stability as well as their ease of application. The goal of this study is to measure the effect of dynamic changes in buffer pH on flow using a real-time method for measuring EOF. Polyelectrolyte multilayers (PEMs) were composed of pairs of strong or completely ionized polyelectrolytes including poly(diallyldimethylammonium) chloride and poly(styrene sulfonate) and weak or ionizable polyelectrolytes including poly(allylamine) and poly(methacrylic acid). Polyelectrolyte multilayers of varying thicknesses (3, 4, 7, 8, 15, or 16 layers) were also studied. While the magnitude of the EOF was monitored every 2 s, the buffer pH was exchanged from a relatively basic pH (7.1) to increasingly acidic pHs (6.6, 6.1, 5.5, and 5.1). Strong polyelectrolytes responded minimally to changes in buffer pH (<1%), whereas substantial (>10%) and sometimes irreversible changes were measured with weak polyelectrolytes. Thicker coatings resulted in a similar magnitude of response but were more likely to degrade in response to buffer pH changes. The most stable coatings were formed from thinner layers of strong polyelectrolytes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Glycolytic potential and activity of adenosine monophosphate kinase (AMPK), glycogen phosphorylase (GP) and glycogen debranching enzyme (GDE) in steer carcasses with normal (<5.8) or high (>5.9) 24h pH determined in M. longissimus dorsi.

PubMed

Apaoblaza, A; Galaz, A; Strobel, P; Ramírez-Reveco, A; Jeréz-Timaure, N; Gallo, C

2015-03-01

Muscle glycogen concentration (MGC) and lactate (LA), activity of glycogen debranching enzyme (GDE), glycogen phosphorylase (GP) and adenosine monophosphate kinase (AMPK) were determined at 0.5h (T0) and 24h (T24) post-mortem in Longissimus dorsi samples from 38 steers that produced high pH (>5.9) and normal pH (<5.8) carcasses at 24h postmortem. MGC, LA and glycolytic potential were higher (P<0.05) in normal pH carcasses. GDE activity was similar (P>0.05) in both pH categories. GP activity increased between T0 and T24 only in normal pH carcasses. AMPK activity was four times higher in normal pH v/s high pH carcasses, without changing its activity over time. Results reinforce the idea that differences in postmortem glycogenolytic/glycolytic flow in L. dorsi of steers showing normal v/s high muscle pH at 24h, could be explained not only by the higher initial MGC in normal pH carcasses, but also by a high and sustained activity of AMPK and an increased GP activity at 24h postmortem. Copyright © 2014 Elsevier Ltd. All rights reserved.

Synthesis and evaluation of thiophenyl derivatives as inhibitors of alkaline phosphatase.

PubMed

Chang, Lei; Duy, Do Le; Mébarek, Saida; Popowycz, Florence; Pellet-Rostaing, Stéphane; Lemaire, Marc; Buchet, René

2011-04-15

Pathological calcifications induced by deposition of basic phosphate crystals or hydroxyapatite (HA) on soft tissues are a large family of diseases comprising of ankylosing spondylitis (AS), end-stage osteoarthritis (OA) and vascular calcification. High activity of tissue non-specific alkaline phosphatase (TNAP) is a hallmark of pathological calcifications induced by HA deposition. The use of TNAP inhibitor is a possible therapeutic option to address calcific diseases produced by HA deposition on soft tissues. We report the synthesis of a series of thiopheno-imidazo[2,1-b]thiazole derivatives which were evaluated as potential inhibitors of TNAP displaying a large range of IC(50) at pH 10.4 (from 42±13 μM to more than 800 μM). Copyright © 2011. Published by Elsevier Ltd.

The chitosan affects severely the carbon metabolism in mango (Mangifera indica L. cv. Palmer) fruit during storage.

PubMed

Cosme Silva, Gláucia Michelle; Silva, Willian Batista; Medeiros, David B; Salvador, Acácio Rodrigues; Cordeiro, Maria Helena Menezes; da Silva, Natália Martins; Santana, Diederson Bortolini; Mizobutsi, Gisele Polete

2017-12-15

Mango is a highly perishable fruit with a short post-harvest time due to the intense metabolic activity after harvesting. In attempt to evaluate the effects of chitosan in mango fruits, it was treated with 0%, 1%, 2% or 3% of chitosan solutions, placed into plastic trays, and stored at room temperature. Changes in physical and chemical parameters were evaluated. Chitosan delayed the climacteric peak, water loss and firmness. Further, few changes in soluble solid content, titratable acidity, pH of the pulp as well as in sugar content and decreased starch degradation were observed. Altogether, our results suggest chitosan edible coating effectively prolongs the quality attributes, affecting basic mitochondrial respiration and starch degradation rate. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

Arieen, A.; Goigoux, C.; Baquey, C.

Factors affecting liposome transport to the blood compartment after oral administration to rats were evaluated. A high entrapment of calcitonin (CT) was obtained when the vesicles were prepared by sonication and were composed of egg phosphatidylcholine, cholesterol and stearylamine. In vitro tests showed that the liposomes were stable in light acidic or basic buffers, but that they were partly lysed in pH 2.5, 10 mM bile salts and pancreatin. Oral administration of liposomes entrapping calcitonin in fasting rats showed that the vesicles facilitate transport of the hormone to the general circulation and that they increase the lifetime of [sup 125]I-CTmore » in blood. Oral administration of liposomes entrapping radioactive indium in fasting rats did not induce radioactivity in blood. This could be explained by disruption of most of the vesicles in the enterocytes.« less

Toxicity of Pb and of Pb/Cd combination on the springtail Folsomia candida in natural soils: reproduction, growth and bioaccumulation as indicators.

PubMed

Bur, T; Crouau, Y; Bianco, A; Gandois, L; Probst, A

2012-01-01

The toxicity of Pb and Cd+Pb was assessed on the Collembola F. candida in two cultivated soils (SV and AU) with low organic matter (OM) content and circumneutral to basic pH, and an acid forested soil (EPC) with high OM content. Collembola reproduction and growth as well as metal content in Collembola body, in soil, exchangeable fraction and soil solutions, pH and DOC were investigated. Pb and Cd+Pb were the highest in exchangeable fraction and soil solution of the acidic soils. Soil solution pH decreased after metal spiking in every soil due to metal adsorption, which was similar for Cd and the highest in AU for Pb. With increasing Pb and Cd+Pb, the most important reproduction decrease was in EPC soil. The LOEC for reproduction after metal addition was 2400 (Pb) and 200/2400 (Cd/Pb), 1200 and 100/1200, 300 and 100/1200 μg g(-1) for AU, SV and EPC, respectively. The highest and the lowest Pb toxicity was observed for EPC and AU bulk soil, respectively. The metal in Collembola increased with increasing soil concentration, except in AU, but the decreasing BF(solution) with increasing concentrations indicates a limited metal transfer to Collembola or an increased metal removal. Loading high Pb concentrations decreases Cd absorption by the Collembola, but the reverse was not true. The highest Pb toxicity in EPC can be explained by pH and OM content. Because of metal complexation, OM might have a protective role but its ingestion by Collembola lead to higher toxicity. Metal bioavailability in Collembola differs from soil solution indicating that soil solution is not sufficient to evaluate toxicity in soil organisms. The toxicity as a whole decreased when metals were combined, except for Pb in AU, due to adsorption competition between Cd and Pb on clay particles and OM sites in AU and EPC soils, respectively. Copyright © 2011 Elsevier B.V. All rights reserved.

Geochemical behavior and dissolved species control in acid sand pit lakes, Sepetiba sedimentary basin, Rio de Janeiro, SE - Brazil

NASA Astrophysics Data System (ADS)

Marques, Eduardo D.; Sella, Sílvia M.; Bidone, Edison D.; Silva-Filho, Emmanoel V.

2010-12-01

This work shows the influence of pluvial waters on dissolved components and mineral equilibrium of four sand pit lakes, located in the Sepetiba sedimentary basin, SE Brazil. The sand mining activities promote sediment oxidation, lowering pH and increasing SO 4 contents. The relatively high acidity of these waters, similar to ore pit lakes environment and associated acid mine drainage, increases weathering rate, especially of silicate minerals, which produces high Al concentrations, the limiting factor for fish aquaculture. During the dry season, basic cations (Ca, Mg, K and Na), SiO 2 and Al show their higher values due to evapoconcentration and pH are buffered. In the beginning of the wet season, the dilution factor by rainwater increases SO 4 and decreases pH values. The aluminum monomeric forms (Al(OH) 2+ and Al(OH) 2+), the most toxic species for aquatic organisms, occur during the dry season, while AlSO 4+ species predominate during the wet season. Gibbsite, allophane, alunite and jurbanite are the reactive mineral phases indicated by PHREEQC modeling. During the dry season, hydroxialuminosilicate allophane is the main phase in equilibrium with the solution, while the sulphate salts alunite and jurbanite predominate in the rainy season due to the increasing of SO 4 values. Gibbsite is also in equilibrium with sand pit lakes waters, pointing out that hydrolysis reaction is a constant process in the system. Comparing to SiO 2, sulphate is the main Al retriever in the pit waters because the most samples (alunite and jurbanite) are in equilibrium with the solution in both seasons. This Al hydrochemical control allied to some precaution, like pH correction and fertilization of these waters, allows the conditions for fishpond culture. Equilibrium of the majority samples with kaolinite (Ca, Mg, Na diagrams) and primary minerals (K diagram) points to moderate weathering rate in sand pit sediments, which cannot be considered for the whole basin due to the anomalous acidification of the studied waters.

Incorporation of lysosomal sequestration in the mechanistic model for prediction of tissue distribution of basic drugs.

PubMed

Assmus, Frauke; Houston, J Brian; Galetin, Aleksandra

2017-11-15

The prediction of tissue-to-plasma water partition coefficients (Kpu) from in vitro and in silico data using the tissue-composition based model (Rodgers & Rowland, J Pharm Sci. 2005, 94(6):1237-48.) is well established. However, distribution of basic drugs, in particular into lysosome-rich lung tissue, tends to be under-predicted by this approach. The aim of this study was to develop an extended mechanistic model for the prediction of Kpu which accounts for lysosomal sequestration and the contribution of different cell types in the tissue of interest. The extended model is based on compound-specific physicochemical properties and tissue composition data to describe drug ionization, distribution into tissue water and drug binding to neutral lipids, neutral phospholipids and acidic phospholipids in tissues, including lysosomes. Physiological data on the types of cells contributing to lung, kidney and liver, their lysosomal content and lysosomal pH were collated from the literature. The predictive power of the extended mechanistic model was evaluated using a dataset of 28 basic drugs (pK a ≥7.8, 17 β-blockers, 11 structurally diverse drugs) for which experimentally determined Kpu data in rat tissue have been reported. Accounting for the lysosomal sequestration in the extended mechanistic model improved the accuracy of Kpu predictions in lung compared to the original Rodgers model (56% drugs within 2-fold or 88% within 3-fold of observed values). Reduction in the extent of Kpu under-prediction was also evident in liver and kidney. However, consideration of lysosomal sequestration increased the occurrence of over-predictions, yielding overall comparable model performances for kidney and liver, with 68% and 54% of Kpu values within 2-fold error, respectively. High lysosomal concentration ratios relative to cytosol (>1000-fold) were predicted for the drugs investigated; the extent differed depending on the lysosomal pH and concentration of acidic phospholipids among cell types. Despite this extensive lysosomal sequestration in the individual cells types, the maximal change in the overall predicted tissue Kpu was <3-fold for lysosome-rich tissues investigated here. Accounting for the variability in cellular physiological model input parameters, in particular lysosomal pH and fraction of the cellular volume occupied by the lysosomes, only partially explained discrepancies between observed and predicted Kpu data in the lung. Improved understanding of the system properties, e.g., cell/organelle composition is required to support further development of mechanistic equations for the prediction of drug tissue distribution. Application of this revised mechanistic model is recommended for prediction of Kpu in lysosome-rich tissue to facilitate the advancement of physiologically-based prediction of volume of distribution and drug exposure in the tissues. Copyright © 2017 Elsevier B.V. All rights reserved.