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Sample records for alkaline ph ph

  1. Alkaline pH sensor molecules.

    PubMed

    Murayama, Takashi; Maruyama, Ichiro N

    2015-11-01

    Animals can survive only within a narrow pH range. This requires continual monitoring of environmental and body-fluid pH. Although a variety of acidic pH sensor molecules have been reported, alkaline pH sensor function is not well understood. This Review describes neuronal alkaline pH sensors, grouped according to whether they monitor extracellular or intracellular alkaline pH. Extracellular sensors include the receptor-type guanylyl cyclase, the insulin receptor-related receptor, ligand-gated Cl- channels, connexin hemichannels, two-pore-domain K+ channels, and transient receptor potential (TRP) channels. Intracellular sensors include TRP channels and gap junction channels. Identification of molecular mechanisms underlying alkaline pH sensing is crucial for understanding how animals respond to environmental alkaline pH and how body-fluid pH is maintained within a narrow range.

  2. Low pH alkaline chemical formulations

    SciTech Connect

    French, T.R.; Peru, D.A.; Thornton, S.D.

    1989-01-01

    This report describes the development of a surfactant-enhanced alkaline flooding system that is applicable to specific reservoir conditions in Wilmington (California) field. The cost of the chemicals for an ASP (alkali/surfactant/polymer) flood is calculated to be $3.90/bbl of oil produced, with 78% of that cost attributable to polymer. This research included phase behavior tests, oil displacement tests, mineral dissolution tests, and adsorption measurements. It was discovered that consumption of low pH alkalis is low enough in the Wilmington field to be acceptable. In addition, alkali dramatically reduced surfactant adsorption and precipitation. A mixture of NaHCO3 and Na2CO3 was recommended for use as a preflush and in the ASP formulation. Research was also conducted on the synergistic effect that occurs when a mixture of alkali and synthetic surfactant contacts crude oil. It appears that very low IFT is predominantly a result of the activation of the natural surfactants present in the Wilmington oil, and the sustained low IFT is primarily the result of the synthetic surfactant. It also appears that removal of acids from the crude oil by the alkali renders the oil more interfacially reactive to synthetic surfactant. These phenomena help to explain the synergism that results from combining alkali and synthetic surfactant into a single oil recovery formulation. 19 refs., 24 figs., 10 tabs.

  3. Field measurement of alkalinity and pH

    USGS Publications Warehouse

    Barnes, Ivan

    1964-01-01

    The behavior of electrometric pH equipment under field conditions departs from the behavior predicted from Nernst's law. The response is a linear function of pH, and hence measured pH values may be corrected to true pH if the instrument is calibrated with two reference solutions for each measurement. Alkalinity titrations may also be made in terms of true pH. Standard methods, such as colorimetric titrations, were rejected as unreliable or too cumbersome for rapid field use. The true pH of the end point of the alkalinity titration as a function of temperature, ionic strength, and total alkalinity has been calculated. Total alkalinity in potable waters is the most important factor influencing the end point pH, which varies from 5.38 (0 ? C, 5 ppm (parts per million) HC0a-) to 4.32 (300 ppm HC0a-,35 ? C), for the ranges of variables considered. With proper precautions, the pH may be determined to =i:0.02 pH and the alkalinity to =i:0.6 ppm HCO3- for many naturally occurring bodies of fresh water.

  4. Alkaline pH Homeostasis in Bacteria: New Insights

    PubMed Central

    Padan, Etana; Bibi, Eitan; Ito, Masahiro; Krulwich, Terry A.

    2011-01-01

    The capacity of bacteria to survive and grow at alkaline pH values is of widespread importance in the epidemiology of pathogenic bacteria, in remediation and industrial settings, as well as in marine, plant-associated and extremely alkaline ecological niches. Alkali-tolerance and alkaliphily, in turn, strongly depend upon mechanisms for alkaline pH homeostasis, as shown in pH shift experiments and growth experiments in chemostats at different external pH values. Transcriptome and proteome analyses have recently complemented physiological and genetic studies, revealing numerous adaptations that contribute to alkaline pH homeostasis. These include elevated levels of transporters and enzymes that promote proton capture and retention (e.g. the ATP synthase and monovalent cation/proton antiporters), metabolic changes that lead to increased acid production, and changes in the cell surface layers that contribute to cytoplasmic proton retention. Targeted studies over the past decade have followed up the long-recognized importance of monovalent cations in active pH homeostasis. These studies show the centrality of monovalent cation/proton antiporters in this process while microbial genomics provides information about the constellation of such antiporters in individual strains. A comprehensive phylogenetic analysis of both eukaryotic and prokaryotic genome databases has identified orthologes from bacteria to humans that allow better understanding of the specific functions and physiological roles of the antiporters. Detailed information about the properties of multiple antiporters in individual strains is starting to explain how specific monovalent cation/proton antiporters play dominant roles in alkaline pH homeostasis in cells that have several additional antiporters catalyzing ostensibly similar reactions. New insights into the pH-dependent Na+/H+ antiporter NhaA that plays an important role in Escherichia coli have recently emerged from the determination of the structure

  5. Biochemical Stabilization of Glucagon at Alkaline pH

    PubMed Central

    Jackson, Melanie A.; Castle, Jessica R.; El Youssef, Joseph; Bakhtiani, Parkash A.; Bergstrom, Colin P.; Carroll, Julie M.; Breen, Matthew E.; Leonard, Gerald L.; David, Larry L.; Roberts, Charles T.; Ward, W. Kenneth

    2014-01-01

    Abstract Background: For patients with type 1 diabetes mellitus, a bihormonal artificial endocrine pancreas system utilizing glucagon and insulin has been found to stabilize glycemic control. However, commercially available formulations of glucagon cannot currently be used in such systems because of physical instability characterized by aggregation and chemical degradation. Storing glucagon at pH 10 blocks protein aggregation but results in chemical degradation. Reductions in pH minimize chemical degradation, but even small reductions increase protein aggregation. We hypothesized that common pharmaceutical excipients accompanied by a new excipient would inhibit glucagon aggregation at an alkaline pH. Methods and Results: As measured by tryptophan intrinsic fluorescence shift and optical density at 630 nm, protein aggregation was indeed minimized when glucagon was formulated with curcumin and albumin. This formulation also reduced chemical degradation, measured by liquid chromatography with mass spectrometry. Biological activity was retained after aging for 7 days in an in vitro cell-based bioassay and also in Yorkshire swine. Conclusions: Based on these findings, a formulation of glucagon stabilized with curcumin, polysorbate-80, l-methionine, and albumin at alkaline pH in glycine buffer may be suitable for extended use in a portable pump in the setting of a bihormonal artificial endocrine pancreas. PMID:24968220

  6. The Alkaline Diet: Is There Evidence That an Alkaline pH Diet Benefits Health?

    PubMed Central

    Schwalfenberg, Gerry K.

    2012-01-01

    This review looks at the role of an alkaline diet in health. Pubmed was searched looking for articles on pH, potential renal acid loads, bone health, muscle, growth hormone, back pain, vitamin D and chemotherapy. Many books written in the lay literature on the alkaline diet were also reviewed and evaluated in light of the published medical literature. There may be some value in considering an alkaline diet in reducing morbidity and mortality from chronic diseases and further studies are warranted in this area of medicine. PMID:22013455

  7. The alkaline diet: is there evidence that an alkaline pH diet benefits health?

    PubMed

    Schwalfenberg, Gerry K

    2012-01-01

    This review looks at the role of an alkaline diet in health. Pubmed was searched looking for articles on pH, potential renal acid loads, bone health, muscle, growth hormone, back pain, vitamin D and chemotherapy. Many books written in the lay literature on the alkaline diet were also reviewed and evaluated in light of the published medical literature. There may be some value in considering an alkaline diet in reducing morbidity and mortality from chronic diseases and further studies are warranted in this area of medicine.

  8. Interpretation of pH, acidity, and alkalinity in fisheries and aquaculture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Measurements of pH, acidity, and alkalinity are commonly used to describe water quality. The three variables are interrelated and are sometimes confused. The pH of water is an intensity factor, while the acidity and alkalinity of waters are capacity factors. More precisely, acidity and alkalinity ar...

  9. Decision making in C. elegans chemotaxis to alkaline pH

    PubMed Central

    Murayama, Takashi; Maruyama, Ichi N

    2013-01-01

    Monitoring of environmental and tissue pH is critical for animal survival. The nematode, Caenorhabditis elegans (C. elegans), is attracted to mildly alkaline pH, but avoids strongly alkaline pH. However, little is known about how the behavioral switching or decision making occurs. Genetic dissection and Ca2+ imaging have previously demonstrated that ASEL and ASH are the major sensory neurons responsible for attraction and repulsion, respectively. Here we report that unlike C. elegans wild type, mutants deficient in ASEL or ASH were repelled by mildly alkaline pH, or were attracted to strongly alkaline pH, respectively. These results suggest that signals through ASEL and ASH compete to determine the animal’s alkaline-pH chemotaxis. Furthermore, mutants with 2 ASEL neurons were more efficiently attracted to mildly alkaline pH than the wild type with a single ASEL neuron, indicating that higher activity of ASEL induces stronger attraction to mildly alkaline pH. This stronger attraction was overridden by normal activity of ASH, suggesting that ASH-mediated avoidance dominates ASEL-mediated attraction. Thus, C. elegans chemotactic behaviors to alkaline pH seems to be determined by signal strengths from the sensory neurons ASEL and ASH, and the behavior decision making seems to be the result of competition between the 2 sensory neurons. PMID:24563708

  10. SIMPLE WAYS TO IMPROVE PH AND ALKALINITY MEASUREMENTS FOR WATER UTILITIES AND LABORATORIES

    EPA Science Inventory

    Both pH and total alkalinity determinations are critical in characterizing chemical properties of water, being important to implementing good process control, determining corrosivity and other water quality properties, and assessing changes in water characteristics. Poor charac...

  11. Change of pH during excess sludge fermentation under alkaline, acidic and neutral conditions.

    PubMed

    Yuan, Yue; Peng, Yongzhen; Liu, Ye; Jin, Baodan; Wang, Bo; Wang, Shuying

    2014-12-01

    The change in pH during excess sludge (ES) fermentation of varying sludge concentrations was investigated in a series of reactors at alkaline, acidic, and neutral pHs. The results showed that the changes were significantly affected by fermentative conditions. Under different conditions, pH exhibited changing profiles. When ES was fermented under alkaline conditions, pH decreased in a range of (10±1). At the beginning of alkaline fermentation, pH dropped significantly, at intervals of 4h, 4h, and 5h with sludge concentrations of 8665.6mg/L, 6498.8mg/L, and 4332.5mg/L, then it would become moderate. However, under acidic conditions, pH increased from 4 to 5. Finally, under neutral conditions pH exhibited a decrease then an increase throughout entire fermentation process. Further study showed short-chain fatty acids (SCFAs), ammonia nitrogen and cations contributed to pH change under various fermentation conditions. This study presents a novel strategy based on pH change to predict whether SCFAs reach their stable stage.

  12. An alkaline active xylanase: insights into mechanisms of high pH catalytic adaptation.

    PubMed

    Mamo, Gashaw; Thunnissen, Marjolein; Hatti-Kaul, Rajni; Mattiasson, Bo

    2009-09-01

    The alkaliphilic bacterium, Bacillus halodurans S7, produces an alkaline active xylanase (EC 3.2.1.8), which differs from many other xylanases in being operationally stable under alkaline conditions as well as at elevated temperature. Compared to non-alkaline active xylanases, this enzyme has a high percent composition of acidic amino acids which results in high ratio of negatively to positively charged residues. A positive correlation was observed between the charge ratio and the pH optima of xylanases. The recombinant xylanase was crystallized using a hanging drop diffusion method. The crystals belong to the space group P2(1)2(1)2(1) and the structure was determined at a resolution of 2.1 A. The enzyme has the common eight-fold TIM-barrel structure of family 10 xylanases; however, unlike non-alkaline active xylanases, it has a highly negatively charged surface and a deeper active site cleft. Mutational analysis of non-conserved amino acids which are close to the acid/base residue has shown that Val169, Ile170 and Asp171 are important to hydrolyze xylan at high pH. Unlike the wild type xylanase which has optimum pH at 9-9.5, the triple mutant xylanase (V169A, I170F and D171N), which was constructed using sequence information of alkaline sensitive xylanses was optimally active around pH 7. Compared to non-alkaline active xylanases, the alkaline active xylanases have highly acidic surfaces and fewer solvent exposed alkali labile residues. Based on these results obtained from sequence, structural and mutational analysis, the possible mechanisms of high pH stability and catalysis are discussed. This will provide useful information to understand the mechanism of high pH adaptation and engineering of enzymes that can be operationally stable at high pH.

  13. Cementitious porous pavement in stormwater quality control: pH and alkalinity elevation.

    PubMed

    Kuang, Xuheng; Sansalone, John

    2011-01-01

    A certain level of alkalinity acts as a buffer and maintains the pH value in a stable range in water bodies. With rapid urban development, more and more acidic pollutants flow to watersheds with runoff and drop alkalinity to a very low level and ultimately degrade the water environment. Cementitious porous pavement is an effective tool for stormwater acidic neutralization. When stormwater infiltrates cement porous pavement (CPP) materials, alkalinity and pH will be elevated due to the basic characteristics of cement concrete. The elevated alkalinity will neutralize acids in water bodies and maintain the pH in a stable level as a buffer. It is expected that CPP materials still have a certain capability of alkalinity elevation after years of service, which is important for CPP as an effective tool for stormwater management. However, few previous studies have reported on how CPP structures would elevate runoff alkalinity and pH after being exposed to rainfall-runoff for years. In this study, three groups of CPP specimens, all exposed to rainfall-runoff for 3 years, were used to test the pH and alkalinity elevation properties. It was found that runoff pH values were elevated from 7.4 to the range of 7.8-8.6 after infiltrating through the uncoated specimens, and from 7.4 to 8.5-10.7 after infiltrating through aluminum-coated specimens. Runoff alkalinity elevation efficiencies are 11.5-14.5% for uncoated specimens and 42.2% for coated specimens. The study shows that CPP is an effective passive unit operation for stormwater acid neutralization in our built environment.

  14. Improved volatile fatty acids anaerobic production from waste activated sludge by pH regulation: Alkaline or neutral pH?

    PubMed

    Ma, Huijun; Chen, Xingchun; Liu, He; Liu, Hongbo; Fu, Bo

    2016-02-01

    In this study, the anaerobic fermentation was carried out for volatile fatty acids (VFAs) production at different pH (between 7.0 and 10.0) conditions with untreated sludge and heat-alkaline pretreated waste activated sludge. In the fermentation with untreated sludge, the extent of hydrolysis of organic matters and extent of acidification at alkaline pH are 54.37% and 30.37%, respectively, resulting in the highest VFAs yield at 235.46mg COD/gVS of three pH conditions. In the fermentation with heat-alkaline pretreated sludge, the acidification rate and VFAs yield at neutral pH are 30.98% and 240.14mg COD/gVS, respectively, which are higher than that at other pH conditions. With the glucose or bovine serum albumin as substrate for VFAs production, the neutral pH showed a higher VFAs concentration than the alkaline pH condition. The results of terminal restriction fragment length polymorphism (T-RFLP) analysis indicated that the alkaline pH caused low microbial richness. Based on the results in this study, we demonstrated that the alkaline pH is favor of hydrolysis of organic matter in sludge while neutral pH improved the acidogenesis for the VFAs production from sludge. Our finding is obvious different to the previous research and helpful for the understanding of how heat-alkaline pretreatment and alkaline fermentation influence the VFAs production, and beneficial to the development of VFAs production process.

  15. Method of determining pH by the alkaline absorption of carbon dioxide

    DOEpatents

    Hobbs, David T.

    1992-01-01

    A method for measuring the concentration of hydroxides in alkaline solutions in a remote location using the tendency of hydroxides to absorb carbon dioxide. The method includes the passing of carbon dioxide over the surface of an alkaline solution in a remote tank before and after measurements of the carbon dioxide solution. A comparison of the measurements yields the absorption fraction from which the hydroxide concentration can be calculated using a correlation of hydroxide or pH to absorption fraction.

  16. pH neutralization and zonation in alkaline-saline tank waste plumes.

    PubMed

    Wan, Jiamin; Larsen, Joern T; Tokunaga, Tetsu K; Zheng, Zuoping

    2004-03-01

    At the Hanford Site in Washington State, the pH values of contaminant plumes resulting from leaking of initially highly alkaline-saline radioactive waste solutions into the subsurface are now found to be substantially neutralized. However, the nature of plume pH neutralization has not previously been understood. As a master geochemical variable, pH needs to be understood in order to predict the fate and transport of contaminants carried by the waste plumes. Through this laboratory study, we found that the plume pH values spanned a broad range from 14 (within the near-source region) down to the value of 7 (lower than the pH value of the initial soil solution) while the plume was still connected to an actively leaking source. We defined two zones within a plume: the silicate dissolution zone (SDZ, pH 14-10) and the neutralized zone (NZ, pH 10-7). Quartz dissolution at elevated temperature and precipitation of secondary silicates (including sodium metasilicate, cancrinite, and zeolites) are the key reactions responsible for the pH neutralization within the SDZ. The rapid and thorough cation exchange of Na+ replacing Ca2+/Mg2+, combined with transport, resulted in a dynamic Ca2+/Mg2+-enriched plume front. Subsequent precipitation of calcite, sodium silicate, and possibly talc led to dramatically reduced pH within the plume front and the neutralized zone. During aging (after the plume source became inactive), continued quartz dissolution and the secondary silicate precipitation drove the pH value lower, toward pH 11 at equilibrium within the SDZ, whereas the pH values in the NZ remained relatively unchanged with time. A pH profile of 11 from the plume source to pH 7 at the plume front is expected for a historical plume. This laboratory-based study provided realistic plume pH profiles (consistent with that measured from borehole samples) and identified underlying mechanisms responsible for pH evolution.

  17. Specific molten globule conformation of stem bromelain at alkaline pH.

    PubMed

    Dave, Sandeep; Mahajan, Sahil; Chandra, Vemika; Dkhar, H Kitdorlang; Sambhavi; Gupta, Pawan

    2010-07-01

    Stem bromelain (SBM), a therapeutic protein, is rapidly absorbed across the gut epithelium. Because SBM encounters an alkaline pH at its principal site of absorption, we investigated the alkaline-induced denaturation of SBM. From pH 7 to 10, the protein's secondary structure remained the same, although a slight loss of tertiary structure was observed. Above pH 10, there was a significant and irreversible loss of secondary and tertiary structure. At pH 10, SBM showed enhanced tryptophan fluorescence, however, the number of accessible tryptophans remained the same. The thermodynamics of temperature transition at pH 7 and 10 were strikingly different, with the former showing a two-phase transition endotherm, and the latter a broad non-two-state transition. At pH 10, SBM showed a significant increase in 8-anilino-1-naphthalene-sulfonate binding relative to the native state, suggestive of a specific molten globule (SMG) state. These studies suggest a distinct conformational rearrangement in SBM, at the protein's isoelectric point.

  18. Design of stability at extreme alkaline pH in streptococcal protein G.

    PubMed

    Palmer, Benjamin; Angus, Katy; Taylor, Linda; Warwicker, Jim; Derrick, Jeremy P

    2008-04-30

    Protein G (PrtG) is widely used as an affinity-based ligand for the purification of IgG. It would be desirable to improve the resistance of affinity chromatography ligands, such as PrtG, to commercial cleaning-in-place procedures using caustic alkali (0.5 M NaOH). It has been shown that Asn residues are the most susceptible at extreme alkaline pH: here, we show that replacement of all three Asn residues within the IgG-binding domain of PrtG only improves stability towards caustic alkali by about 8-fold. Study of the effects of increasing pH on PrtG by fluorescence and CD shows that the protein unfolds progressively between pH 11.5 and 13.0. Calculation of the variation in electrostatic free energy with pH indicated that deprotonation of Tyr, Lys and Arg side-chains at high pH would destabilize PrtG. Introduction of the triple mutation Y3F/T16I/T18I into PrtG stabilized it by an extra 6.8 kcal/mol and the unfolding of the protein occurred at a pH of about 13, or 1.5 pH units higher than wild type. The results show that strategies for the stabilization of proteins at extreme alkaline pH should consider thermodynamic stabilization that will retain the tertiary structure of the protein and modification of surface electrostatics, as well as mutation of alkali-susceptible residues.

  19. Extremely alkaline (pH > 12) ground water hosts diverse microbial community.

    PubMed

    Roadcap, George S; Sanford, Robert A; Jin, Qusheng; Pardinas, José R; Bethke, Craig M

    2006-01-01

    Chemically unusual ground water can provide an environment for novel communities of bacteria to develop. Here, we describe a diverse microbial community that inhabits extremely alkaline (pH > 12) ground water from the Lake Calumet area of Chicago, Illinois, where historic dumping of steel slag has filled in a wetland. Using microbial 16S ribosomal ribonucleic acid gene sequencing and microcosm experiments, we confirmed the presence and growth of a variety of alkaliphilic beta-Proteobacteria, Bacillus, and Clostridium species at pH up to 13.2. Many of the bacterial sequences most closely matched those of other alkaliphiles found in more moderately alkaline water around the world. Oxidation of dihydrogen produced by reaction of water with steel slag is likely a primary energy source to the community. The widespread occurrence of iron-oxidizing bacteria suggests that reduced iron serves as an additional energy source. These results extend upward the known range of pH tolerance for a microbial community by as much as 2 pH units. The community may provide a source of novel microbes and enzymes that can be exploited under alkaline conditions.

  20. Method of determining pH by the alkaline absorption of carbon dioxide

    DOEpatents

    Hobbs, D.T.

    1992-10-06

    A method is described for measuring the concentration of hydroxides in alkaline solutions in a remote location using the tendency of hydroxides to absorb carbon dioxide. The method includes the passing of carbon dioxide over the surface of an alkaline solution in a remote tank before and after measurements of the carbon dioxide solution. A comparison of the measurements yields the absorption fraction from which the hydroxide concentration can be calculated using a correlation of hydroxide or pH to absorption fraction. 2 figs.

  1. Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities

    PubMed Central

    Rout, Simon P.; Charles, Christopher J.; Doulgeris, Charalampos; McCarthy, Alan J.; Rooks, Dave J.; Loughnane, J. Paul; Laws, Andrew P.; Humphreys, Paul N.

    2015-01-01

    One design concept for the long-term management of the UK’s intermediate level radioactive wastes (ILW) is disposal to a cementitious geological disposal facility (GDF). Under the alkaline (10.0<pH>13.0) anoxic conditions expected within a GDF, cellulosic wastes will undergo chemical hydrolysis. The resulting cellulose degradation products (CDP) are dominated by α- and β-isosaccharinic acids (ISA), which present an organic carbon source that may enable subsequent microbial colonisation of a GDF. Microcosms established from neutral, near-surface sediments demonstrated complete ISA degradation under methanogenic conditions up to pH 10.0. Degradation decreased as pH increased, with β-ISA fermentation more heavily influenced than α-ISA. This reduction in degradation rate was accompanied by a shift in microbial population away from organisms related to Clostridium sporosphaeroides to a more diverse Clostridial community. The increase in pH to 10.0 saw an increase in detection of Alcaligenes aquatilis and a dominance of hydrogenotrophic methanogens within the Archaeal population. Methane was generated up to pH 10.0 with acetate accumulation at higher pH values reflecting a reduced detection of acetoclastic methanogens. An increase in pH to 11.0 resulted in the accumulation of ISA, the absence of methanogenesis and the loss of biomass from the system. This study is the first to demonstrate methanogenesis from ISA by near surface microbial communities not previously exposed to these compounds up to and including pH 10.0. PMID:26367005

  2. Transcriptome Profiling of Shewanella oneidensis Gene Expressionfollowing Exposure to Acidic and Alkaline pH

    SciTech Connect

    Leaphart, Adam B.; Thompson, Dorothea K.; Huang, Katherine; Alm,Eric; Wan, Xiu-Feng; Arkin, Adam P.; Brown, Steven D.; Wu, Liyou; Yan,Tingfen; Liu, Xueduan; Wickham, Gene S.; Zhou, Jizhong

    2007-04-02

    The molecular response of Shewanella oneidensis MR-1 tovariations in extracellular pH was investigated based on genomewide geneexpression profiling. Microarray analysis revealed that cells elicitedboth general and specific transcriptome responses when challenged withenvironmental acid (pH 4) or base (pH 10) conditions over a 60-minperiod. Global responses included the differential expression of genesfunctionally linked to amino acid metabolism, transcriptional regulationand signal transduction, transport, cell membrane structure, andoxidative stress protection. Response to acid stress included theelevated expression of genes encoding glycogen biosynthetic enzymes,phosphate transporters, and the RNA polymerase sigma-38 factor (rpoS),whereas the molecular response to alkaline pH was characterized byupregulation of nhaA and nhaR, which are predicted to encode an Na+/H+antiporter and transcriptional activator, respectively, as well assulfate transport and sulfur metabolism genes. Collectively, theseresults suggest that S. oneidensis modulates multiple transporters, cellenvelope components, and pathways of amino acid consumption and centralintermediary metabolism as part of its transcriptome response to changingexternal pH conditions.

  3. The Effects of Alkaline pH on Microleakage of Mineral Trioxide Aggregate and Calcium Enriched Mixture Apical Plugs

    PubMed Central

    Mirhadi, Hossein; Moazzami, Fariborz; Rangani Jahromi, Saeed; Safarzade, Sareh

    2016-01-01

    Statement of the Problem Alkaline pH can affect the physical and chemical properties and sealing ability of apical plug material. Calcium hydroxide is used as an intracanal medication to complete disinfection of root canals. It raises the pH of environment to alkaline value. Purpose The aim of this in vitro study was to evaluate and compare the effect of alkaline pH on the sealing ability of calcium-enriched mixture (CEM) cement and mineral trioxide aggregate (MTA) apical plugs. Materials and Method Seventy single-rooted human maxillary anterior teeth were randomly divided to two experimental groups for Angelus MTA and CEM cement (n=30) and two control groups (n=5). Each group was divided into two subgroups of 15 for neutral and alkaline pH, and 1 negative and 1 positive control groups of 5. The root canals were cleaned and shaped by using ProTaper rotary system (Dentsply Maillefer; Ballaigues, Switzerland) and the terminal 3mm of the roots were resected. Then, MTA and CEM cement were condensed in apical region with 3mm thickness. The samples were exposed to two environments with different pH values of 13 and 7.4. The leakage was assessed by using the fluid filtration technique at 1, 7, 14, 30 days intervals. Data were analyzed by the repeated measures MANOVA. Results There was no statistically significant difference in the rate of microleakage between neutral and alkaline pH of CEM cement and MTA (p> 0.05). The sealing ability of MTA in an alkaline pH of 13 was significantly less than CEM cement in this pH (p< 0.05). Conclusion An environment with alkaline pH had no adverse effect on the sealing ability of MTA and CEM cement used as apical plugs. CEM cement had better sealing ability in alkaline pH. PMID:26966703

  4. Uranium(VI) Diffusion in Sodium-Montmorillonite at Alkaline pH Conditions

    NASA Astrophysics Data System (ADS)

    Tinnacher, R. M.; Davis, J. A.; Tournassat, C.; Birkholzer, J. T.

    2015-12-01

    Diffusive transport of uranium(VI) in montmorillonite clay and bentonite has important implications for uranium(VI) mobility in engineered barrier systems or host rocks in high level radioactive waste repositories, and clay-rich soils and sediments in the environment. The prediction of uranium(VI) adsorption and diffusion in clay-rich media, however, is complicated by (1) the complexity of the mineralogical structure of montmorillonite, in terms of its pore-size distributions and available surface site types, and (2) the complex uranium(VI) solution speciation, which can include cationic, uncharged, and anionic complexes, depending on solution conditions. For instance, a partial or full exclusion of anions from negatively charged clay interlayer spaces could change the effective 'anion-accessible' porosity and decrease the diffusive flux of these solutes under steady state conditions. In contrast, weak cation exchange reactions can result in 'surface diffusion' of adsorbed cations, such as UO2OH+, in addition to diffusion in the liquid phase, resulting in greater diffusive fluxes at steady state. In order to investigate these complex interactions, we performed two, lab-scale uranium(VI) through-diffusion experiments in lightly compacted Na-montmorillonite at slightly different, alkaline pH conditions (average pH values of 8.69 and 8.87). Observed uranium(VI) diffusive fluxes were decreased by approximately an order of magnitude in comparison to a tritium tracer. This indicates a relevance of 'anion exclusion' effects, the full or partial exclusion of anionic U(VI)-carbonato species from clay interlayer spaces. In addition, uranium(VI) sorption reactions were shown to be relevant in the diffusion experiments, even at alkaline pH values of around 8.7 and 8.9, where uranium(VI) sorption is low compared to other pH conditions. Despite the similarity of pH conditions, different degrees of uranium(VI) retardation were determined for the two systems. Additionally, we

  5. Carbon dioxide addition to microbial fuel cell cathodes maintains sustainable catholyte pH and improves anolyte pH, alkalinity, and conductivity.

    PubMed

    Fornero, Jeffrey J; Rosenbaum, Miriam; Cotta, Michael A; Angenent, Largus T

    2010-04-01

    Bioelectrochemical system (BES) pH imbalances develop due to anodic proton-generating oxidation reactions and cathodic hydroxide-ion-generating reduction reactions. Until now, workers added unsustainable buffers to reduce the pH difference between the anode and cathode because the pH imbalance contributes to BES potential losses and, therefore, power losses. Here, we report that adding carbon dioxide (CO(2)) gas to the cathode, which creates a CO(2)/bicarbonate buffered catholyte system, can diminish microbial fuel cell (MFC) pH imbalances in contrast to the CO(2)/carbonate buffered catholyte system by Torres, Lee, and Rittmann [Environ. Sci. Technol. 2008, 42, 8773]. We operated an air-cathode and liquid-cathode MFC side-by-side. For the air-cathode MFC, CO(2) addition resulted in a stable catholyte film pH of 6.61 +/- 0.12 and a 152% increase in steady-state power density. By adding CO(2) to the liquid-cathode system, we sustained a steady catholyte pH (pH = 5.94 +/- 0.02) and a low pH imbalance (DeltapH = 0.65 +/- 0.18) over a 2-week period without external salt buffer addition. By migrating bicarbonate ions from the cathode to the anode (with an anion-exchange membrane), we increased the anolyte pH (DeltapH = 0.39 +/- 0.31), total alkalinity (494 +/- 6 to 582 +/- 6 as mg CaCO(3)/L), and conductivity (1.53 +/- 0.49 to 2.16 +/- 0.03 mS/cm) relative to the feed properties. We also verified with a phosphate-buffered MFC that our reaction rates were limited mainly by the reactor configuration rather than limitations due to the bicarbonate buffer.

  6. 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.

  7. Use of natural mordenite to remove chromium (III) and to neutralize pH of alkaline waste waters.

    PubMed

    Córdova-Rodríguez, Valduvina; Rodríguez-Iznaga, Inocente; Acosta-Chávez, Raquel María; Chávez-Rivas, Fernando; Petranovskii, Vitalii; Pestryakov, Alexey

    2016-01-01

    The natural mordenite from Palmarito de Cauto deposit (PZ), Cuba, was studied in this work as an ion exchanger to remove Cr(3+) cations from alkaline aqueous solutions at different pH and chromium concentrations. The mordenite stability under cyclic treatment processes with alkaline solutions and its capacity to decrease the pH of the solutions was also analyzed. It was shown that PZ removes Cr(3+) ions from alkaline solutions, and it happens independently of the starting chromium concentration and the pH of the exchange solution used. This material has an important neutralizing effect on alkaline solutions, expressed in a significant pH decrease from the early stages of the treatments. For solutions with initial pH equal to 11, it decreases to a value of around seven. The stability of this material is not affected significantly after continuous cyclic treatment with NaOH solution, which shows that mordenite, in particular from Palmarito de Cauto deposit, has high stability in alkaline solutions. The results are important as they suggest that natural zeolites may be of interest in treatments of alkaline industrial waste effluents.

  8. Improved methane production from waste activated sludge with low organic content by alkaline pretreatment at pH 10.

    PubMed

    Feng, L Y; Yang, L Q; Zhang, L X; Chen, H L; Chen, J

    2013-01-01

    Sludge with low organic content always results in an unsatisfactory performance, even failure of anaerobic digestion. The alkaline pretreatment effect on anaerobic digestion of sludge with low organic content has seldom been studied although it gives many benefits for sludge with high organic content. In this study the influence of alkaline pretreatment (pH 10, an effective alkaline pH) on the solubilization and methane production from waste activated sludge (WAS) with low organic content was investigated. Results from biochemical methane potential (BMP) experiments showed that anaerobic biodegradability of WAS was greatly improved by alkaline pretreatment at pH 10. Methane production from the current WAS under conditions of pretreatment time 4 h and digestion time 15 d was 139.6 mL/g VS (volatile solids), much higher than that from the unpretreated WAS with digestion time of 20 d (75.2 mL/g VS). Also, the solubilization of WAS was significantly accelerated by alkaline pretreatment. Mechanism exploration indicated that the general activities of anaerobic microorganisms, specific activities of key enzymes and the amounts of methanogens were enhanced by alkaline pretreatment at pH 10, showing good agreement with methane production.

  9. Low temperature alkaline pH hydrolysis of oxygen-free Titan tholins

    NASA Astrophysics Data System (ADS)

    Brassé, C.; Buch, A.; Raulin, F.; Coll, P.; Poch, O.; Ramirez, S.

    2013-09-01

    Titan, the largest moon of Saturn, is known for its dense and nitrogen-rich atmosphere. The organic aerosols which are produced in Titan's atmosphere are objects of astrobiological interest. In this paper we focus on their potential chemical evolution when they reach the surface and interact with putative ammonia-water cryomagma[1]. In this context we have studied the evolution of alkaline pH hydrolysis of Titan tholins (produced by an experimental setup using a plasma DC discharge named PLASMA) at ambient and low temperature. However, we identified oxygenated molecules in non-hydrolyzed tholins meaning that oxygen gets in the PLASMA reactor during the tholins synthesis [2]. Following this preliminary study the synthesis protocol has been improved by isolating the whole device in a specially designed glove box which protect the PLASMA experiment from the laboratory atmosphere. After confirming the non-presence of oxygen in tholins produced with this new experimental setup, the study of oxygen-free tholins' evolution has been carried out. A recent study shows that the subsurface ocean may contain a lower fraction of ammonia (about 5wt% or less [3]), as previously described by other teams [2,4]. Thus new hydrolysis experiments will take this lower value into account. Additionally, a new report [5] provides upper and lower limits for the bulk content of Titan's interior for various gas species. It also shows that most of them are likely stored and dissolved in the subsurface water ocean. But considering the plausible acido-alkaline properties of the ammonia-water ocean, additional species could be dissolved in the ocean and present in the magma. They were also included in our hydrolysis experiments. Taking into account these new data, four different hydrolysis have been applied to oxygen-free tholins. For each type of hydrolysis, we also follow the influence of the hydrolysis temperature on the organic molecules production. The preliminary qualitative and quantitative

  10. Effect of pH alkaline salts of fatty acids on the inhibition of bacteria associated with poultry processing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The agar diffusion assay was used to examine the effect of pH on the ability of alkaline salts of three fatty acids (FA) to inhibit growth of bacteria associated with poultry processing. FA solutions were prepared by dissolving 0.5 M concentrations of caprylic, capric, or lauric acid in separate ali...

  11. Quaternary structure of partially liganded intermediates of sheep carbon monoxide hemoglobin at alkaline pH.

    PubMed

    Gray, R D

    1975-01-25

    A rapid change in absorbance was observed in the Soret region during the interval between photolysis of sheep carbon monoxide hemoglobin and the subsequent reassociation of CO in the dark. The rate constant for this spectral change was about 4000 s--1 at 20 degrees in 0.05 M solium borate, pH 9.3. The wavelength dependence of the amplitude of the absorbance change is similar to that observed when deoxygenated alpha and theta chains are allowed to recombine (Brunori, M., Antonini, E., Wyman, J., and Anderson, S. R. (1968) J. Mol. Biol. 34, 357-359), and therefore reflects changes in the quanternary structure of the hemoglobin tetramer induced by ligand displacement. The amplitude of this conformation-dependent spectral change was not a linear function of the fraction of bound CO removed by photolysis. The results suggest that of the possible intermediate species present after partial photolysis, only Hb4 and Hb4(CO) change from the ligand-bound to the ligand-free sturcture prior to CO reassociation under these alkaline conditions.

  12. Low temperature alkaline pH hydrolysis of oxygen-free Titan tholins

    NASA Astrophysics Data System (ADS)

    Brassé, Coralie; Buch, Arnaud; Raulin, François; Coll, Patrice; Poch, Olivier; Ramirez, Sandra

    2014-05-01

    The largest moon of Saturn, Titan, is known for its dense, nitrogen-rich atmosphere. The organic aerosols which are produced in Titan's atmosphere are of great astrobiological interest, particularly because of their potential evolution when they reach the surface and may interact with putative ammonia-water cryomagma[1]. In this context we have followed the evolution of alkaline pH hydrolysis (25wt% ammonia-water) of Titan tholins (produced by an experimental setup using a plasma DC discharge named PLASMA) at low temperature. Urea has been identified as one of the main product of tholins hydrolysis along with several amino acids (alanine, glycine and aspartic acid). However, those molecules have also been detected in non-hydrolyzed tholins. One explanation is a possible oxygen leak in the PLASMA reactor during the tholins synthesis[2]. Following this preliminary study the synthesis protocol has been improved by isolating the whole device in a specially designed glove box which protect the PLASMA experiment from the laboratory atmosphere. Once we confirmed the non-presence of oxygen in tholins, we performed alkaline pH hydrolysis of oxygen-free tholins. Then we verify that the organic compounds cited above are still produced in-situ. Moreover, a recent study shows that the subsurface ocean may contain a lower fraction of ammonia (about 5wt% or less[3]), than the one used until now in this kind of experimental study[2, 4]. Thus, we have carried out new hydrolysis experiments which take this lower value into account. Additional studies have provided new highlights on the bulk composition of Titan for various gas species. Indeed, the observed Saturn's atmosphere enrichment constrains the composition of the planetesimals present in the feeding zone of Saturn. The enrichment in volatiles in Saturn's atmosphere has been reproduced by assuming the presence of specific gas species[5, 6], in particular CO2 and H2S. In the present study we assume that those gas species have

  13. Sewage sludge pretreatment by microwave irradiation combined with activated carbon fibre at alkaline pH for anaerobic digestion.

    PubMed

    Sun, Dedong; Guo, Sixiao; Ma, Nina; Wang, Guowen; Ma, Chun; Hao, Jun; Xue, Mang; Zhang, Xinxin

    2016-01-01

    This research focuses on the effects of microwave-assisted activated carbon fibre (ACF) (MW-ACF) treatment on sewage sludge at alkaline pH. The disintegration and biodegradability of sewage sludge were studied. It was found that the MW-ACF process at alkaline pH provided a rapid and efficient process to disrupt the microbial cells in the sludge. The results suggested that when irradiated at 800 W MW for 110 s with a dose of 1.0 g ACF/g solid concentration (SS) at pH 10.5, the MW-ACF pretreatment achieved 55% SS disintegration, 23% greater than the value of MW alone (32%). The concentration of total nitrogen, total phosphorus, supernatant soluble chemical oxygen demand, protein, and polysaccharide increased by 60%, 144%, 145%, 74%, and 77%, respectively. An increase in biogas production by 63.7% was achieved after 20 days of anaerobic digestion (AD), compared to the control. The results indicated that the MW-ACF pretreatment process at alkaline pH provides novel sludge management options in disintegration of sewage sludge for further AD.

  14. Abiotic Synthesis of Methane Under Alkaline Hydrothermal Conditions: the Effect of pH in Heterogeneous Catalysis

    NASA Astrophysics Data System (ADS)

    Foustoukos, D. I.; Qi, F.; Seyfried, W. E.

    2004-12-01

    Abiotic formation of methane in hydrothermal reaction zones at mid-ocean ridges likely occurs by Fischer-Tropsch catalytic processes involving reaction of CO2-bearing fluids with mineral surfaces. The elevated concentrations of dissolved methane and low molecular weight hydrocarbons observed in high temperature vent fluids issuing from ultramafic-hosted hydrothermal systems, in particular, suggest that Fe and Cr-bearing mineral phases attribute as catalysts, enhancing abiotic production of alkanes. The chemi-adsorption of dissolved CO2 on the catalytic mineral surface, however, might be influenced by a pH dependent surface electron charge developed within the mineral-fluid interface. Thus, a series of experiments was conducted to evaluate the role of pH on rates of carbon reduction in fluids coexisting with Fe-oxides at 390 degree C and 400 bars. At two distinct pH conditions, acidic (pH = 5) and alkaline (pH = 8.8), the abiotic production of isotopically labelled CH4(aq) was monitored during FeO reaction with aqueous NaCl-NaHCO3-H2-bearing fluid (0.56 mol/kg NaCl, 0.03 mol/kg NaH13CO3). Despite the lower H2(aq) concentrations (120 mmol/kg) in the high pH system, concentrations of abiogenic methane attained values of 195 umol/kg and 120 umol/kg respectively, suggesting enhanced catalytic properties of mineral under moderately high pH. X-ray photoelectron spectroscopy (XPS), performed on unreacted and final solid products, reveal the significantly greater abundances of alkyl (C-C-) groups on the surface of FeO oxidized at elevated pH, in comparison with mineral reacted at low pH conditions. Thus, enhanced adsorption of dissolved CO2 and the resulting Fischer-Tropsch formation of alkyl groups likely contributes to methane production observed at alkaline conditions. Introducing the effect of pH in the Fischer-Tropsch mechanism of alkane formation has important implications for the recently discovered Lost City ultramafic-hosted hydrothermal system, where elevated pH

  15. Carbon Dioxide Addition to Microbial Fuel Cell Cathodes Maintains Sustainable Catholyte pH and Improves Anolyte pH, Alkalinity, and Conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bioelectrochemical system (BES) pH imbalances develop due to anodic proton-generating oxidation reactions and cathodic hydroxide-ion-generating reduction reactions. Until now, workers added unsustainable buffers to reduce the pH difference between the anode and cathode because the pH imbalance cont...

  16. Tendency for oxidation of annelid hemoglobin at alkaline pH and dissociated states probed by redox titration.

    PubMed

    Bispo, Jose Ailton Conceicao; Landini, Gustavo Fraga; Santos, Jose Luis Rocha; Norberto, Douglas Ricardo; Bonafe, Carlos Francisco Sampaio

    2005-08-01

    The redox titration of extracellular hemoglobin of Glossoscolex paulistus (Annelidea) was investigated in different pH conditions and after dissociation induced by pressure. Oxidation increased with increasing pH, as shown by the reduced amount of ferricyanide necessary for the oxidation of hemoglobin. This behavior was the opposite of that of vertebrate hemoglobins. The potential of half oxidation (E1/2) changed from -65.3 to +146.8 mV when the pH increased from 4.50 to 8.75. The functional properties indicated a reduction in the log P50 from 1.28 to 0.28 in this pH range. The dissociation at alkaline pH or induced by high pressure, confirmed by HPLC gel filtration, suggested that disassembly of the hemoglobin could be involved in the increased potential for oxidation. These results suggest that the high stability and prolonged lifetime common to invertebrate hemoglobins is related to their low tendency to oxidize at acidic pH, in contrast to vertebrate hemoglobins.

  17. Upper ocean carbon cycling inferred from direct pH observations made by profiling floats and estimated alkalinity

    NASA Astrophysics Data System (ADS)

    Johnson, K. S.; Plant, J. N.; Jannasch, H. W.; Coletti, L. J.; Elrod, V.; Sakamoto, C.; Riser, S.

    2015-12-01

    The annual cycle of dissolved inorganic carbon (DIC) is a key tracer of net community production and carbon export in the upper ocean. In particular, the DIC concentration is much less sensitive to air-sea gas exchange, when compared to oxygen, another key tracer of upper ocean metabolism. However, the annual DIC cycle is observed with a seasonal resolution at only a few time-series stations in the open ocean. Here, we consider the annual carbon cycle that has been observed using profiling floats equipped with pH sensors. Deep-Sea DuraFET pH sensors have been deployed on profiling floats for over three years and they can provide temporal and spatial resolution of 5 to 10 days and 5 to 10 m in the upper ocean over multi-year periods. In addition to pH, a second carbon system parameter is required to compute DIC. Total alkalinity can be derived from the float observations of temperature, salinity and oxygen using equations in these variables that are fitted to shipboard observations of alkalinity obtained in the global repeat hydrography programs (e.g., Juranek et al., GRL, doi:10.1029/2011GL048580, 2011), as the relationships should be stable in time in the open ocean. Profiling floats with pH have been deployed from Hawaii Ocean Time-series (HOT) cruises since late 2012 and an array of floats with pH have been deployed since early 2014 in the Southern Ocean as part of the SOCCOM program. The SOCCOM array should grow to nearly 200 floats over the next 5 years. The sensor data was quality controlled and adjusted by comparing observations at 1500 m depth to the deep climatology of pH (derived from DIC and alkalinity) computed with the GLODAP data set. After adjustment, the surface DIC concentrations were calculated from pH and alkalinity. This yields a data set that is used to examine annual net community production in the oligotrophic North Pacific and in the South Pacific near 150 West from 40 South to 65 South.

  18. The immobilization of all spermatozoa in vitro by bitter lemon drink and the effect of alkaline pH.

    PubMed

    Nwoha, P U

    1992-12-01

    Researchers at Obafemi Awolowo University in Ile-Ife, Nigeria, collected semen samples from 7 healthy men 25-30 years old who had abstained from sex for at least 5 days in order to examine the spermicidal action of 4 soft drinks (Krest bitter lemon, Afri-Cola, Coca-Cola, and Pepsi-Cola), the effect of increased temperature of the drinks on spermicidal action, and the effect of changing the soft drinks from an acid, as it comes from the factory, (ph 2.4) to an alkaline (pH 7.5). Increasing the temperature of the soft drinks from room temperature (22 degrees Celsius) to body temperatures (37 degrees Celsius) did not significantly change the spermicidal action any of the soft drinks. All soft drinks with an acid pH, except Coca-Cola, had a significantly lower percent of sperm motility than those with an alkaline pH (0-42.3% vs. 20-52.1%; p .001). In fact, Krest bitter lemon in its factory form (acid pH) completely immobilized all spermatozoa within 1 minute after the researchers diluted the semen with the soft drink. Alkaline Coca-Cola had a significantly lower percent of sperm motility than did acid Coca-Cola (35.8% vs. 46.5%; p .001). Other than Krest bitter lemon, the significant decreases in sperm motility were not enough to prevent pregnancy. These findings indicated that researchers should test Krest bitter lemon for effectiveness as a postcoital contraceptive. If indeed it proves effective, it has great potential as such a contraceptive among the poor in the densely population developed countries since it is readily available and inexpensive.

  19. Evaluation of pH, alkalinity and temperature during air stripping process for ammonia removal from landfill leachate.

    PubMed

    Campos, Juacyara Carbonelli; Moura, Denise; Costa, Ana Paula; Yokoyama, Lidia; Araujo, Fabiana Valeria da Fonseca; Cammarota, Magali Christe; Cardillo, Luigi

    2013-01-01

    The objective of this research was to evaluate the air stripping technology for the removal of ammonia from landfill leachates. In this process, pH, temperature, airflow rate and operation time were investigated. Furthermore, the relationship between the leachate alkalinity and the ammonia removal efficiency during the process was studied. The leachate used in the tests was generated in the Gramacho Municipal Solid Waste Landfill (Rio de Janeiro State, Brazil). The best results were obtained with a temperature of 60(o)C, and they were independent of the pH value for 7 h of operation (the ammonia nitrogen removal was greater than 95%). A strong influence of the leachate alkalinity on the ammonia nitrogen removal was observed; as the alkalinity decreased, the ammonia concentration also decreased because of prior CO2 removal, which increased the pH and consequently favored the NH3 stripping. The air flow rate, in the values evaluated (73, 96 and 120 L air.h(-1).L(-1) of leachate), did not influence the results.

  20. Proteolytic Activity at Alkaline pH in Oat Leaves, Isolation of an Aminopeptidase 1

    PubMed Central

    Casano, Leonardo M.; Desimone, Marcelo; Trippi, Victorio S.

    1989-01-01

    Proteolytic activity in oat leaf extracts was measured with both azocasein and ribulose bisphosphate carboxylase (Rubisco) as substrates over a wide range of pH (3.0-9.2). With either azocasein or Rubisco activity peaks appeared at pH 4.8, 6.6, and 8.4. An aminopeptidase (AP) which hydrolyzes leucine-nitroanilide was partially purified. Purification consisted of a series of six steps which included ammonium sulfate precipitation, gel filtration, and two ionic exchange chromatographies. The enzyme was purified more than 100-fold. The apparent Km for leucine-nitroanilide is 0.08 millimolar at its pH optimum of 8.4. AP may be a cystein protease since it is inhibited by heavy metals and activated by 2-mercaptoethanol. Isolated chloroplasts were also able to hydrolyze leucine-nitroanilide at a pH optimum of 8.4, indicating that AP could be localized inside the photosynthetic organelles. PMID:16667194

  1. Isolation of a Sulfur-oxidizing Bacterium That can Grow under Alkaline pH, from Corroded Concrete.

    PubMed

    Maeda, T; Negishi, A; Oshima, Y; Nogami, Y; Kamimura, K; Sugio, T

    1998-01-01

    To study the early stages of concrete corrosion by bacteria, sulfur-oxidizing bacterium strain RO-1, which grows in an alkaline thiosulfate medium (pH 10.0) was isolated from corroded concreate and characterized. Strain RO-1 was a Gram negative, rod-shaped bacterium (0.5-0.6×0.9-1.5 μm). The mean G+C content of the DNA of strain RO-1 was 65.0 mol%. Optimum pH and temperature for growth were 8.0. and 30-37°C, respectively. When grown in thiosulfate medium with pH 10.0, growth rate of the strain was 48% of that observed at the optimum pH for growth. Strain RO-1 used sulfide, thiosulfate, and glucose, but not elemental sulfur or tetrathionate, as a sole energy source. Strain RO-1 grew under anaerobic conditions in pepton-NO3 (-) medium containing sodium nitrate as an electron acceptor, and had enzyme activities that oxidized sulfide, elemental sulfur, thiosulfate, sulfite, and glucose, but not tetrathionate. The bacterium had an activity to assimilate (14)CO2 into the cells when thiosulfate was used as an energy source. These results suggest that strain RO-1 is Thiobacillus versutus. Strain RO-1 exuded Ca(2+) from concrete blocks added to thiosulfate medium with pH 9.0 and the pH of the medium decreased from 9.0 to 5.5 after 22 days of cultivation. In contrast, Thiobacillus thiooxidans strain NB1-3 could not exude Ca(2+) in the same thiosulfate medium, suggesting that strain RO-1, but not T. thiooxidans NB1-3, is involved in the early stage of concrete corrosion because concrete structures just after construction contain calcium hydroxide and have a pH of 12-13.

  2. Effect of Alkaline pH on Polishing and Etching of Single and Polycrystalline Silicon

    NASA Astrophysics Data System (ADS)

    Venkatesh, R. Prasanna; Prasad, Y. Nagendra; Kwon, Tae-Young; Kang, Young-Jae; Park, Jin-Goo

    2012-07-01

    In this paper, the polishing and etching behavior of single and polycrystalline silicon were studied. Prior to chemical mechanical polishing (CMP) process, the surfaces were treated with dilute hydrofluoric acid (DHF) to remove native oxides. The surface analysis shows that the poly contains trace amount of oxygen even after DHF treatment. The static and dynamic etch rates, and removal rates were measured as a function of slurry pH. The single silicon showed a higher static etch rate than the poly. After static etch rate measurements, poly showed higher surface roughness and more hydrophilic which indicates that the surface of poly is different from single crystal silicon. The friction force between pad and substrate and pad temperature was also measured as a function of pH during polishing in order to get more understanding of polishing process. At all the pH values being investigated, poly showed lower dynamic and removal rates, higher friction force and higher temperature. This indicates that the removal of poly in CMP is predominantly by mechanical actions. Also, these results, suggest a mechanism in which the oxygen present in the poly grain boundaries strongly influences the etching and removal mechanism.

  3. Metabolic flux modeling of detoxification of acetic acid by Ralstonia eutropha at slightly alkaline pH levels.

    PubMed

    Yu, J; Wang, J

    2001-06-20

    Ralstonia eutropha grows on and produces polyhydroxyalkanoates (PHAs) from fermentation acids. Acetic acid, one major organic acid from acidogenesis of organic wastes, has an inhibitory effect on the bacterium at slightly alkaline pH (6 g HAc/L at pH 8). The tolerance of R. eutropha to acetate, however, was increased significantly up to 15 g/L at the slightly alkaline pH level with high cell mass concentration. A metabolic cell model with five fluxes is proposed to depict the detoxification mechanism including mass transfer and acetyl-CoA formation of acetic acid and the formation of three final metabolic products, polyhydroxybutyrate (PHB), active biomass, and CO(2). The fluxes were measured under different conditions such as cell mass concentration, acetic acid concentration, and medium composition. The experimental results indicate that the acetate detoxification by high cell mass concentration is attributed to the increased fluxes at high extracellular acetate concentrations. The fluxes could be doubled to reduce and hence detoxify the accumulated intracellular acetate anions.

  4. Comparison of Salivary pH, Buffering Capacity and Alkaline Phosphatase in Smokers and Healthy Non-Smokers

    PubMed Central

    Ahmadi-Motamayel, Fatemeh; Falsafi, Parisa; Goodarzi, Mohammad T.; Poorolajal, Jalal

    2016-01-01

    Objectives: Saliva contains alkaline phosphatase (ALP)—a key intracellular enzyme related to destructive processes and cellular damage—and has buffering capacity (BC) against acids due to the presence of bicarbonate and phosphate ions. Smoking may have deleterious effects on the oral environment due to pH changes which can affect ALP activity. This study aimed to evaluate the salivary pH, BC and ALP activity of male smokers and healthy non-smokers. Methods: This retrospective cohort study took place between August 2012 and December 2013. A total of 251 healthy male non-smokers and 259 male smokers from Hamadan, Iran, were selected. Unstimulated whole saliva was collected from each participant and pH and BC were determined using a pH meter. Salivary enzymes were measured by spectrophotometric assay. Results: Mean salivary pH (7.42 ± 0.48 and 7.52 ± 0.43, respectively; P = 0.018) and BC (3.41 ± 0.54 and 4.17 ± 0.71; P = 0.001) was significantly lower in smokers compared to non-smokers. Mean ALP levels were 49.58 ± 23.33 IU/L among smokers and 55.11 ± 27.85 IU/L among non-smokers (P = 0.015). Conclusion: Significantly lower pH, BC and ALP levels were observed among smokers in comparison to a healthy control group. These salivary alterations could potentially be utilised as biochemical markers for the evaluation of oral tissue function and side-effects among smokers. Further longitudinal studies are recommended to evaluate the effects of smoking on salivary components. PMID:27606111

  5. Contrasting pH buffering patterns in neutral-alkaline soils along a 3600 km transect in northern China

    NASA Astrophysics Data System (ADS)

    Luo, W.; Nelson, P. N.; Li, M.-H.; Cai, J.; Zhang, Y.; Zhang, Y.; Shan, Y.; Wang, R.; Han, X.; Jiang, Y.

    2015-08-01

    Soil pH buffering capacity (pHBC) plays a crucial role in predicting acidification rates, yet its large-scale patterns and controls are poorly understood, especially for neutral-alkaline soils. Here, we evaluated the spatial patterns and drivers of pHBC along a 3600 km long transect (1900 km sub-transect with carbonate containing soils and 1700 km sub-transect with non-carbonate containing soils) across northern China. Soil pHBC was greater in the carbonate containing soils than in the non-carbonate containing soils. Acid addition decreased soil pH in the non-carbonate containing soils more markedly than in the carbonate containing soils. Within the carbonate soil sub-transect, soil pHBC was positively correlated with cation exchange capacity (CEC), carbonate content and exchangeable sodium (Na) concentration, but negatively correlated with initial pH and clay content, and not correlated with soil organic carbon (SOC) content. Within the non-carbonate sub-transect, soil pHBC was positively related to initial pH, clay content, CEC and exchangeable Na concentration, but not related to SOC content. Carbonate content was the primary determinant of pHBC in the carbonate containing soils and CEC was the main determinant of buffering capacity in the non-carbonate containing soils. Soil pHBC was positively related to aridity index and carbonate content across the carbonate containing soil sub-transect. Our results indicated that mechanisms controlling pHBC differ among neutral-alkaline soils of northern China, especially between carbonate and non-carbonate containing soils, leading to different rates, risks, and impacts of acidification. This understanding should be incorporated into the acidification risk assessment and landscape management in a changing world.

  6. Contrasting pH buffering patterns in neutral-alkaline soils along a 3600 km transect in northern China

    NASA Astrophysics Data System (ADS)

    Luo, W. T.; Nelson, P. N.; Li, M.-H.; Cai, J. P.; Zhang, Y. Y.; Zhang, Y. G.; Yang, S.; Wang, R. Z.; Wang, Z. W.; Wu, Y. N.; Han, X. G.; Jiang, Y.

    2015-12-01

    Soil pH buffering capacity (pHBC) plays a crucial role in predicting acidification rates, yet its large-scale patterns and controls are poorly understood, especially for neutral-alkaline soils. Here, we evaluated the spatial patterns and drivers of pHBC along a 3600 km long transect (1900 km sub-transect with carbonate-containing soils and 1700 km sub-transect with non-carbonate-containing soils) across northern China. Soil pHBC was greater in the carbonate-containing soils than in the non-carbonate-containing soils. Acid addition decreased soil pH in the non-carbonate-containing soils more markedly than in the carbonate-containing soils. Within the carbonate soil sub-transect, soil pHBC was positively correlated with cation exchange capacity (CEC), carbonate content and exchangeable sodium (Na) concentration, but negatively correlated with initial pH and clay content, and not correlated with soil organic carbon (SOC) content. Within the non-carbonate sub-transect, soil pHBC was positively related to initial pH, clay content, CEC and exchangeable Na concentration, but not related to SOC content. Carbonate content was the primary determinant of pHBC in the carbonate-containing soils and CEC was the main determinant of buffering capacity in the non-carbonate-containing soils. Along the transect, soil pHBC was different in regions with different aridity index. Soil pHBC was positively related to aridity index and carbonate content across the carbonate-containing soil sub-transect. Our results indicated that mechanisms controlling pHBC differ among neutral-alkaline soils of northern China, especially between carbonate- and non-carbonate-containing soils. This understanding should be incorporated into the acidification risk assessment and landscape management in a changing world.

  7. Computational Design of a pH Stable Enzyme: Understanding Molecular Mechanism of Penicillin Acylase's Adaptation to Alkaline Conditions

    PubMed Central

    Suplatov, Dmitry; Panin, Nikolay; Kirilin, Evgeny; Shcherbakova, Tatyana; Kudryavtsev, Pavel; Švedas, Vytas

    2014-01-01

    Protein stability provides advantageous development of novel properties and can be crucial in affording tolerance to mutations that introduce functionally preferential phenotypes. Consequently, understanding the determining factors for protein stability is important for the study of structure-function relationship and design of novel protein functions. Thermal stability has been extensively studied in connection with practical application of biocatalysts. However, little work has been done to explore the mechanism of pH-dependent inactivation. In this study, bioinformatic analysis of the Ntn-hydrolase superfamily was performed to identify functionally important subfamily-specific positions in protein structures. Furthermore, the involvement of these positions in pH-induced inactivation was studied. The conformational mobility of penicillin acylase in Escherichia coli was analyzed through molecular modeling in neutral and alkaline conditions. Two functionally important subfamily-specific residues, Gluβ482 and Aspβ484, were found. Ionization of these residues at alkaline pH promoted the collapse of a buried network of stabilizing interactions that consequently disrupted the functional protein conformation. The subfamily-specific position Aspβ484 was selected as a hotspot for mutation to engineer enzyme variant tolerant to alkaline medium. The corresponding Dβ484N mutant was produced and showed 9-fold increase in stability at alkaline conditions. Bioinformatic analysis of subfamily-specific positions can be further explored to study mechanisms of protein inactivation and to design more stable variants for the engineering of homologous Ntn-hydrolases with improved catalytic properties. PMID:24959852

  8. Computational design of a pH stable enzyme: understanding molecular mechanism of penicillin acylase's adaptation to alkaline conditions.

    PubMed

    Suplatov, Dmitry; Panin, Nikolay; Kirilin, Evgeny; Shcherbakova, Tatyana; Kudryavtsev, Pavel; Svedas, Vytas

    2014-01-01

    Protein stability provides advantageous development of novel properties and can be crucial in affording tolerance to mutations that introduce functionally preferential phenotypes. Consequently, understanding the determining factors for protein stability is important for the study of structure-function relationship and design of novel protein functions. Thermal stability has been extensively studied in connection with practical application of biocatalysts. However, little work has been done to explore the mechanism of pH-dependent inactivation. In this study, bioinformatic analysis of the Ntn-hydrolase superfamily was performed to identify functionally important subfamily-specific positions in protein structures. Furthermore, the involvement of these positions in pH-induced inactivation was studied. The conformational mobility of penicillin acylase in Escherichia coli was analyzed through molecular modeling in neutral and alkaline conditions. Two functionally important subfamily-specific residues, Gluβ482 and Aspβ484, were found. Ionization of these residues at alkaline pH promoted the collapse of a buried network of stabilizing interactions that consequently disrupted the functional protein conformation. The subfamily-specific position Aspβ484 was selected as a hotspot for mutation to engineer enzyme variant tolerant to alkaline medium. The corresponding Dβ484N mutant was produced and showed 9-fold increase in stability at alkaline conditions. Bioinformatic analysis of subfamily-specific positions can be further explored to study mechanisms of protein inactivation and to design more stable variants for the engineering of homologous Ntn-hydrolases with improved catalytic properties.

  9. Two pore channel 2 (TPC2) inhibits autophagosomal-lysosomal fusion by alkalinizing lysosomal pH.

    PubMed

    Lu, Yingying; Hao, Bai-Xia; Graeff, Richard; Wong, Connie W M; Wu, Wu-Tian; Yue, Jianbo

    2013-08-16

    Autophagy is an evolutionarily conserved lysosomal degradation pathway, yet the underlying mechanisms remain poorly understood. Nicotinic acid adenine dinucleotide phosphate (NAADP), one of the most potent Ca(2+) mobilizing messengers, elicits Ca(2+) release from lysosomes via the two pore channel 2 (TPC2) in many cell types. Here we found that overexpression of TPC2 in HeLa or mouse embryonic stem cells inhibited autophagosomal-lysosomal fusion, thereby resulting in the accumulation of autophagosomes. Treatment of TPC2 expressing cells with a cell permeant-NAADP agonist, NAADP-AM, further induced autophagosome accumulation. On the other hand, TPC2 knockdown or treatment of cells with Ned-19, a NAADP antagonist, markedly decreased the accumulation of autophagosomes. TPC2-induced accumulation of autophagosomes was also markedly blocked by ATG5 knockdown. Interestingly, inhibiting mTOR activity failed to increase TPC2-induced autophagosome accumulation. Instead, we found that overexpression of TPC2 alkalinized lysosomal pH, and lysosomal re-acidification abolished TPC2-induced autophagosome accumulation. In addition, TPC2 overexpression had no effect on general endosomal-lysosomal degradation but prevented the recruitment of Rab-7 to autophagosomes. Taken together, our data demonstrate that TPC2/NAADP/Ca(2+) signaling alkalinizes lysosomal pH to specifically inhibit the later stage of basal autophagy progression.

  10. Characterization of steady-state activities of cytochrome c oxidase at alkaline pH: mimicking the effect of K-channel mutations in the bovine enzyme.

    PubMed

    Riegler, David; Shroyer, Lois; Pokalsky, Christine; Zaslavsky, Dmitry; Gennis, Robert; Prochaska, Lawrence J

    2005-01-07

    The cytochrome c oxidase activity of the bovine heart enzyme decreases substantially at alkaline pH, from 650 s(-1) at pH 7.0 to less than 10 s(-1) at pH 9.75. In contrast, the cytochrome c peroxidase activity of the enzyme shows little or no pH dependence (30-50 s(-1)) at pH values greater than 8.5. Under the conditions employed, it is demonstrated that the dramatic decrease in oxidase activity at pH 9.75 is fully reversible and not due to a major alkaline-induced conformational change in the enzyme. Furthermore, the Km values for cytochrome c interaction with the enzyme were also not significantly different at pH 7.8 and pH 9.75, suggesting that the pH dependence of the activity is not due to an altered interaction with cytochrome c at alkaline pH. However, at alkaline pH, the steady-state reduction level of the hemes increased, consistent with a slower rate of electron transfer from heme a to heme a3 at alkaline pH. Since it is well established that the rate of electron transfer from heme a to heme a3 is proton-coupled, it is reasonable to postulate that at alkaline pH, proton uptake becomes rate-limiting. The fact that this is not observed when hydrogen peroxide is used as a substrate in place of O2 suggests that the rate-limiting step is proton uptake via the K-channel associated with the reduction of the heme a3/CuB center prior to the reaction with O2. This step is not required for the reaction with H2O2, as shown previously in the examination of mutants of bacterial oxidases in which the K-channel was blocked. It is concluded that at pH values near 10, the delivery of protons via the K-channel becomes the rate-limiting step in the catalytic cycle with O2, so that the behavior of the bovine enzyme resembles that of the K-channel mutants in the bacterial enzymes.

  11. Dissociation energies of PH and PH+.

    NASA Astrophysics Data System (ADS)

    Reddy, R. R.; Nazeer Ahammed, Y.; Srinivasa Rao, A.; Rao, T. V. R.

    1995-12-01

    Dissociation energies for the ground electronic states of diatomic PH and PH+ are determined by fitting empirical potential functions to the respective RKRV curves using correlation coefficients. The estimated ground state dissociation energies of PH and PH+ are 3.10 and 3.20 eV respectively by the curve fitting procedure using the Lippincott potential function. The computed values are in good agreement with experimental values.

  12. The Aspergillus PacC zinc finger transcription factor mediates regulation of both acid- and alkaline-expressed genes by ambient pH.

    PubMed Central

    Tilburn, J; Sarkar, S; Widdick, D A; Espeso, E A; Orejas, M; Mungroo, J; Peñalva, M A; Arst, H N

    1995-01-01

    The pH regulation of gene expression in Aspergillus nidulans is mediated by pacC, whose 678 residue-derived protein contains three putative Cys2His2 zinc fingers. Ten pacCc mutations mimicking growth at alkaline pH remove between 100 and 214 C-terminal residues, including a highly acidic region containing an acidic glutamine repeat. Nine pacC+/- mutations mimicking acidic growth conditions remove between 299 and 505 C-terminal residues. Deletion of the entire pacC coding region mimics acidity but leads additionally to poor growth and conidiation. A PacC fusion protein binds DNA with the core consensus GCCARG. At alkaline ambient pH, PacC activates transcription of alkaline-expressed genes (including pacC itself) and represses transcription of acid-expressed genes. pacCc mutations obviate the need for pH signal transduction. Images PMID:7882981

  13. Catalytically active alkaline molten globular enzyme: Effect of pH and temperature on the structural integrity of 5-aminolevulinate synthase.

    PubMed

    Stojanovski, Bosko M; Breydo, Leonid; Hunter, Gregory A; Uversky, Vladimir N; Ferreira, Gloria C

    2014-12-01

    5-Aminolevulinate synthase (ALAS), a pyridoxal-5'phosphate (PLP)-dependent enzyme, catalyzes the first step of heme biosynthesis in mammals. Circular dichroism (CD) and fluorescence spectroscopies were used to examine the effects of pH (1.0-3.0 and 7.5-10.5) and temperature (20 and 37°C) on the structural integrity of ALAS. The secondary structure, as deduced from far-UV CD, is mostly resilient to pH and temperature changes. Partial unfolding was observed at pH2.0, but further decreasing pH resulted in acid-induced refolding of the secondary structure to nearly native levels. The tertiary structure rigidity, monitored by near-UV CD, is lost under acidic and specific alkaline conditions (pH10.5 and pH9.5/37°C), where ALAS populates a molten globule state. As the enzyme becomes less structured with increased alkalinity, the chiral environment of the internal aldimine is also modified, with a shift from a 420nm to 330nm dichroic band. Under acidic conditions, the PLP cofactor dissociates from ALAS. Reaction with 8-anilino-1-naphthalenesulfonic acid corroborates increased exposure of hydrophobic clusters in the alkaline and acidic molten globules, although the reaction is more pronounced with the latter. Furthermore, quenching the intrinsic fluorescence of ALAS with acrylamide at pH1.0 and 9.5 yielded subtly different dynamic quenching constants. The alkaline molten globule state of ALAS is catalytically active (pH9.5/37°C), although the kcat value is significantly decreased. Finally, the binding of 5-aminolevulinate restricts conformational fluctuations in the alkaline molten globule. Overall, our findings prove how the structural plasticity of ALAS contributes to reaching a functional enzyme.

  14. Diversity and food web structure of nematode communities under high soil salinity and alkaline pH.

    PubMed

    Salamún, Peter; Kucanová, Eva; Brázová, Tímea; Miklisová, Dana; Renčo, Marek; Hanzelová, Vladimíra

    2014-10-01

    A long-term and intensive magnesium (Mg) ore processing in Slovenské Magnezitové Závody a.s. in Jelšava has resulted in a high Mg content and alkaline pH of the soil environment, noticeable mainly in the close vicinity of the smelter. Nematode communities strongly reacted to the contamination mostly by a decrease in abundance of the sensitive groups. Nematodes from c-p 1 group and bacterivores, tolerant to pollution played a significant role in establishing the dominance at all sites. With increasing distance from the pollution source, the nematode communities were more structured and complex, with an increase in proportion of sensitive c-p 4 and 5 nematodes, composed mainly of carnivores and omnivores. Various ecological indices (e.g. MI2-5, SI, H') indicated similar improvement of farther soil ecosystems.

  15. Coordinate responses to alkaline pH stress in budding yeast

    PubMed Central

    Serra-Cardona, Albert; Canadell, David; Ariño, Joaquín

    2015-01-01

    Alkalinization of the medium represents a stress condition for the budding yeast Saccharomyces cerevisiae to which this organism responds with profound remodeling of gene expression. This is the result of the modulation of a substantial number of signaling pathways whose participation in the alkaline response has been elucidated within the last ten years. These regulatory inputs involve not only the conserved Rim101/PacC pathway, but also the calcium-activated phosphatase calcineurin, the Wsc1-Pkc1-Slt2 MAP kinase, the Snf1 and PKA kinases and oxidative stress-response pathways. The uptake of many nutrients is perturbed by alkalinization of the environment and, consequently, an impact on phosphate, iron/copper and glucose homeostatic mechanisms can also be observed. The analysis of available data highlights cases in which diverse signaling pathways are integrated in the gene promoter to shape the appropriate response pattern. Thus, the expression of different genes sharing the same signaling network can be coordinated, allowing functional coupling of their gene products. PMID:28357292

  16. High-resolution Imaging of pH in Alkaline Sediments and Water Based on a New Rapid Response Fluorescent Planar Optode

    NASA Astrophysics Data System (ADS)

    Han, Chao; Yao, Lei; Xu, Di; Xie, Xianchuan; Zhang, Chaosheng

    2016-05-01

    A new dual-lumophore optical sensor combined with a robust RGB referencing method was developed for two-dimensional (2D) pH imaging in alkaline sediments and water. The pH sensor film consisted of a proton-permeable polymer (PVC) in which two dyes with different pH sensitivities and emission colors: (1) chloro phenyl imino propenyl aniline (CPIPA) and (2) the coumarin dye Macrolex® fluorescence yellow 10 GN (MFY-10 GN) were entrapped. Calibration experiments revealed the typical sigmoid function and temperature dependencies. This sensor featured high sensitivity and fast response over the alkaline working ranges from pH 7.5 to pH 10.5. Cross-sensitivity towards ionic strength (IS) was found to be negligible for freshwater when IS <0.1 M. The sensor had a spatial resolution of approximately 22 μm and aresponse time of <120 s when going from pH 7.0 to 9.0. The feasibility of the sensor was demonstrated using the pH microelectrode. An example of pH image obtained in the natrual freshwater sediment and water associated with the photosynthesis of Vallisneria spiral species was also presented, suggesting that the sensor held great promise for the field applications.

  17. High-resolution Imaging of pH in Alkaline Sediments and Water Based on a New Rapid Response Fluorescent Planar Optode

    PubMed Central

    Han, Chao; Yao, Lei; Xu, Di; Xie, Xianchuan; Zhang, Chaosheng

    2016-01-01

    A new dual-lumophore optical sensor combined with a robust RGB referencing method was developed for two-dimensional (2D) pH imaging in alkaline sediments and water. The pH sensor film consisted of a proton-permeable polymer (PVC) in which two dyes with different pH sensitivities and emission colors: (1) chloro phenyl imino propenyl aniline (CPIPA) and (2) the coumarin dye Macrolex® fluorescence yellow 10 GN (MFY-10 GN) were entrapped. Calibration experiments revealed the typical sigmoid function and temperature dependencies. This sensor featured high sensitivity and fast response over the alkaline working ranges from pH 7.5 to pH 10.5. Cross-sensitivity towards ionic strength (IS) was found to be negligible for freshwater when IS <0.1 M. The sensor had a spatial resolution of approximately 22 μm and aresponse time of <120 s when going from pH 7.0 to 9.0. The feasibility of the sensor was demonstrated using the pH microelectrode. An example of pH image obtained in the natrual freshwater sediment and water associated with the photosynthesis of Vallisneria spiral species was also presented, suggesting that the sensor held great promise for the field applications. PMID:27199163

  18. Strategies for regulation of hemolymph pH in acidic and alkaline water by the larval mosquito Aedes aegypti (L.) (Diptera; Culicidae).

    PubMed

    Clark, Thomas M; Vieira, Marcus A L; Huegel, Kara L; Flury, Dawn; Carper, Melissa

    2007-12-01

    The responses of larval Aedes aegypti to media of pH 4, 7 and 11 provide evidence for pH regulatory strategies. Drinking rates in pH 4 media were elevated 3- to 5-fold above those observed in pH 7 or 11. Total body water was elevated during acute exposure to acidic media. During chronic exposure, total body water was decreased and Malpighian tubule mitochondrial luminosity, quantified using Mitotracker Green FM, increased. Malpighian tubule secretion rates and energy demands thus appear to increase dramatically during acid exposure. In alkaline media, drinking rates were quite low. Larvae in pH 11 media excreted net acid (0.12 nequiv H(+) g(-1) h(-1)) and the pH indicators azolitmin and bromothymol blue revealed that the rectal lumen is acidic in vivo at all ambient pH values. The anal papillae (AP) were found to be highly permeant to acid-base equivalents. Ambient pH influenced the length, and the mass-specific length, of the AP in the presence of NaCl (59.9 mmol l(-1)). In contrast, the length and mass-specific length of AP were not influenced by ambient pH in low NaCl conditions. Mitochondrial luminosity was reduced in AP of larvae reared in acidic media, and was not elevated in alkaline media, relative to that of larvae reared in neutral media. These data suggest that the AP may compromise acid-base balance in acidic media, and may also be an important site of trade-offs between H(+) homeostasis and NaCl uptake in dilute, acidic media.

  19. Irrigation water acidification to neutralize alkalinity for nursery crop production: Substrate pH, electrical conductivity, and nutrient concentrations; and plant nutrition and growth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Liming agents (LA) in irrigation water, typically associated with carbonates and bicarbonates of calcium (Ca) and magnesium (Mg), contribute to water alkalinity. Repeated application of LA to container crops can cause media-solution pH to rise overtime, that uncorrected, can lead to a nutrient avail...

  20. High pH (and not free ammonia) is responsible for Anammox inhibition in mildly alkaline solutions with excess of ammonium.

    PubMed

    Puyol, D; Carvajal-Arroyo, J M; Li, G B; Dougless, A; Fuentes-Velasco, M; Sierra-Alvarez, R; Field, J A

    2014-10-01

    Ammonium is a substrate of the anaerobic ammonium oxidation (Anammox) process but it has been suggested as a substrate-inhibitor because of the action of its unionized form, free ammonia. High pH of the medium is also an important limiting factor of the Anammox bacteria. Both effects are difficult to discriminate. In this work the inhibitory effects of high pH, total ammonia (TA) and NH3 on the Anammox process were investigated simultaneously. Results confirmed that TA caused no inhibition and high pH is a much more important inhibiting factor than NH3 in mildly alkaline conditions, based on a multi-factorial analysis. Values of pH higher than 7.6 caused Anammox inhibition >10 % and should be avoided during the application of the Anammox process in practice.

  1. Application of a fluidized bed reactor charged with aragonite for control of alkalinity, pH and carbon dioxide in marine recirculating aquaculture systems

    USGS Publications Warehouse

    Paul S Wills, PhD; Pfeiffer, Timothy; Baptiste, Richard; Watten, Barnaby J.

    2016-01-01

    Control of alkalinity, dissolved carbon dioxide (dCO2), and pH are critical in marine recirculating aquaculture systems (RAS) in order to maintain health and maximize growth. A small-scale prototype aragonite sand filled fluidized bed reactor was tested under varying conditions of alkalinity and dCO2 to develop and model the response of dCO2 across the reactor. A large-scale reactor was then incorporated into an operating marine recirculating aquaculture system to observe the reactor as the system moved toward equilibrium. The relationship between alkalinity dCO2, and pH across the reactor are described by multiple regression equations. The change in dCO2 across the small-scale reactor indicated a strong likelihood that an equilibrium alkalinity would be maintained by using a fluidized bed aragonite reactor. The large-scale reactor verified this observation and established equilibrium at an alkalinity of approximately 135 mg/L as CaCO3, dCO2 of 9 mg/L, and a pH of 7.0 within 4 days that was stable during a 14 day test period. The fluidized bed aragonite reactor has the potential to simplify alkalinity and pH control, and aid in dCO2 control in RAS design and operation. Aragonite sand, purchased in bulk, is less expensive than sodium bicarbonate and could reduce overall operating production costs.

  2. Alkaline pH Is a signal for optimal production and secretion of the heat labile toxin, LT in enterotoxigenic Escherichia coli (ETEC).

    PubMed

    Gonzales, Lucia; Ali, Zahra Bagher; Nygren, Erik; Wang, Zhiyun; Karlsson, Stefan; Zhu, Baoli; Quiding-Järbrink, Marianne; Sjöling, Åsa

    2013-01-01

    Enterotoxigenic Escherichia coli (ETEC) cause secretory diarrhea in children and travelers to endemic areas. ETEC spreads through the fecal-oral route. After ingestion, ETEC passes through the stomach and duodenum before it colonizes the lower part of the small intestine, exposing bacteria to a wide range of pH and environmental conditions. This study aimed to determine the impact of external pH and activity of the Cyclic AMP receptor protein (CRP) on the regulation of production and secretion of heat labile (LT) enterotoxin. ETEC strain E2863wt and its isogenic mutant E2863ΔCRP were grown in LBK media buffered to pH 5, 7 and 9. GM1 ELISA, cDNA and cAMP analyses were carried out on bacterial pellet and supernatant samples derived from 3 and 5 hours growth and from overnight cultures. We confirm that CRP is a repressor of LT transcription and production as has been shown before but we show for the first time that CRP is a positive regulator of LT secretion both in vitro and in vivo. LT secretion increased at neutral to alkaline pH compared to acidic pH 5 where secretion was completely inhibited. At pH 9 secretion of LT was optimal resulting in 600 percent increase of secreted LT compared to unbuffered LBK media. This effect was not due to membrane leakage since the bacteria were viable at pH 9. The results indicate that the transition to the alkaline duodenum and/or exposure to high pH close to the epithelium as well as activation of the global transcription factor CRP are signals that induce secretion of the LT toxin in ETEC.

  3. Combined effects of carbonate alkalinity and pH on survival, growth and haemocyte parameters of the Venus clam Cyclina sinensis.

    PubMed

    Lin, Tingting; Lai, Qifang; Yao, Zongli; Lu, Jianxue; Zhou, Kai; Wang, Hui

    2013-08-01

    Carbonate alkalinity (CA) and pH are considered to be two important stress factors that determine the response of aquatic animals to sudden transfers into saline-alkaline water. To evaluate the potential for aquaculture production of Venus clams (Cyclina sinensis) farmed in saline-alkaline water, the combined effects of CA (2.5 (control), 10.0, 20.0 and 40.0 meq/l) and pH (8.0 (control), 8.5, 9.0 and 9.5) on survival rate was monitored every day for 10 days. Length gain rate (LGR) and weight gain rate (WGR) were also monitored for two months, and total haemocyte count (THC), phagocytic rate (PR) and haemocyte mortality (HM) were measured for 3, 6, 12 and 24 days under the same water temperature (20 °C) and salinity (15‰) conditions. The results showed that survival rates in treatments of CA ≤ 20.0, combined with pH ≤ 9.0, were 100%. LGR and WGR in treatments of CA 2.5 & pH 8.0 (control), CA 2.5 & pH 8.5 and CA 10.0 & pH 8.0 exhibited the largest values (P > 0.05), while in other treatments, they showed a decreasing trend with an increase in either CA or pH or both (P < 0.05). Similarly, for THC, PR and HM, no significant differences were observed among the fast growth treatments during the entire experimental period (P > 0.05), however, in other treatments, they presented significant differences, especially on day 3 and 6 (P < 0.05), most notably with increases in CA or pH, but returned to control levels on day 12. In conclusion, in this study, a strong interaction between CA and pH was observed. Additionally, it was ascertained that the Venus clam C. sinensis can withstand the stress of CA 20.0 combined pH 9.0, although individuals grows slowly and may take approximately 12 days to recover to the unstressed condition.

  4. High external pH enables more efficient secretion of alkaline α-amylase AmyK38 by Bacillus subtilis

    PubMed Central

    2012-01-01

    Background Bacillus subtilis genome-reduced strain MGB874 exhibits enhanced production of exogenous extracellular alkaline cellulase Egl-237 and subtilisin-like alkaline protease M-protease. Here, we investigated the suitability of strain MGB874 for the production of α-amylase, which was anticipated to provoke secretion stress responses involving the CssRS (Control secretion stress Regulator and Sensor) system. Results Compared to wild-type strain 168, the production of a novel alkaline α-amylase, AmyK38, was severely decreased in strain MGB874 and higher secretion stress responses were also induced. Genetic analyses revealed that these phenomena were attributable to the decreased pH of growth medium as a result of the lowered expression of rocG, encoding glutamate dehydrogenase, whose activity leads to NH3 production. Notably, in both the genome-reduced and wild-type strains, an up-shift of the external pH by the addition of an alkaline solution improved AmyK38 production, which was associated with alleviation of the secretion stress response. These results suggest that the optimal external pH for the secretion of AmyK38 is higher than the typical external pH of growth medium used to culture B. subtilis. Under controlled pH conditions, the highest production level (1.08 g l-1) of AmyK38 was obtained using strain MGB874. Conclusions We demonstrated for the first time that RocG is an important factor for secretory enzyme production in B. subtilis through its role in preventing acidification of the growth medium. As expected, a higher external pH enabled a more efficient secretion of the alkaline α-amylase AmyK38 in B. subtilis. Under controlled pH conditions, the reduced-genome strain MGB874 was demonstrated to be a beneficial host for the production of AmyK38. PMID:22681752

  5. Improving the expression of recombinant proteins in E. coli BL21 (DE3) under acetate stress: an alkaline pH shift approach.

    PubMed

    Wang, Hengwei; Wang, Fengqing; Wang, Wei; Yao, Xueling; Wei, Dongzhi; Cheng, Hairong; Deng, Zixin

    2014-01-01

    Excess acetate has long been an issue for the production of recombinant proteins in E. coli cells. Recently, improvements in acetate tolerance have been achieved through the use of genetic strategies and medium supplementation with certain amino acids and pyrimidines. The aim of our study was to evaluate an alternative to improve the acetate tolerance of E. coli BL21 (DE3), a popular strain used to express recombinant proteins. In this work we reported the cultivation of BL21 (DE3) in complex media containing acetate at high concentrations. In the presence of 300 mM acetate, compared with pH 6.5, pH 7.5 improved cell growth by approximately 71%, reduced intracellular acetate by approximately 50%, and restored the expression of glutathione S-transferase (GST), green fluorescent protein (GFP) and cytochrome P450 monooxygenase (CYP). Further experiments showed that alkaline pHs up to 8.5 had little inhibition in the expression of GST, GFP and CYP. In addition, the detrimental effect of acetate on the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) by the cell membrane, an index of cellular metabolic capacity, was substantially alleviated by a shift to alkaline pH values of 7.5-8.0. Thus, we suggest an approach of cultivating E. coli BL21 (DE3) at pH 8.0 ± 0.5 to minimize the effects caused by acetate stress. The proposed strategy of an alkaline pH shift is a simple approach to solving similar bioprocessing problems in the production of biofuels and biochemicals from sugars.

  6. Hydrolysis and volatile fatty acids accumulation of waste activated sludge enhanced by the combined use of nitrite and alkaline pH.

    PubMed

    Huang, Cheng; Liu, Congcong; Sun, Xiuyun; Sun, Yinglu; Li, Rui; Li, Jiansheng; Shen, Jinyou; Han, Weiqing; Liu, Xiaodong; Wang, Lianjun

    2015-12-01

    Volatile fatty acids (VFAs) production from anaerobic digestion of waste activated sludge (WAS) is often limited by the slow hydrolysis and/or poor substrate availability. Increased attention has been given to enhance the hydrolysis and acidification of WAS recently. This study presented an efficient and green strategy based on the combined use of nitrite pretreatment and alkaline pH to stimulate hydrolysis and VFA accumulation from WAS. Results showed that both proteins and polysaccharides increased in the presence of nitrite, indicating the enhancement of sludge solubilization and hydrolysis processes. Mechanism investigations showed that nitrite pretreatment could disintegrate the sludge particle and disperse extracellular polymeric substances (EPS). Then, anaerobic digestion tests demonstrated VFA production increased with nitrite treatment. The maximal VFA accumulation was achieved with 0.1 g N/L nitrite dosage and pH 10.0 at a sludge retention time (SRT) of 7 days, which was much higher VFA production in comparison with the blank, sole nitrite pretreatment, or sole pH 10. The potential analysis suggested that the combined nitrite pretreatment and alkaline pH is capable of enhancing WAS digestion with a great benefit for biological nutrient removal (BNR).

  7. The Effect of Carbonate and pH on Hydrogen Oxidation and Oxygen Reduction on Pt-Based Electrocatalysts in Alkaline Media

    DOE PAGES

    John, Samuel St.; Atkinson, Robert W.; Roy, Asa; ...

    2016-01-11

    In this paper, we investigated the performance of several carbon-supported RuxPty electrocatalysts for their alkaline hydrogen oxidation and oxygen reduction performance in the presence of carbonate and compared their performance with monometallic, carbon-supported Pt. Our results indicate a strong dependence of HOR upon pH for the monometallic Pt catalysts (22 mV/pH) and a weak dependence upon pH for the Ru-containing electrocatalysts (3.7, 2.5, and 4.7 mV/pH on Ru0.2Pt0.8, Ru0.4Pt0.6, and Ru0.8Pt0.2, respectively). These results are consistent with our previous findings that illustrate a change in rds from electron transfer (on monometallic Pt) to dissociative hydrogen adsorption (on RuxPty catalysts). Analysismore » of the kinetic currents to determine the rate-determining step via Tafel slope analysis provides additional data supporting this conclusion. There is no difference in the performance at comparable pH values in the presence or absence of carbonate on monometallic Pt indicating that water/hydroxide is the primary proton acceptor for alkaline HOR in 0.1 M KOH aqueous electrolyte. Finally, we observe no pH or carbonate dependence for the ORR on monometallic Pt.« less

  8. Microprofiles of oxygen, redox potential, and pH, and microbial fermentation products in the highly alkaline gut of the saprophagous larva of Penthetria holosericea (Diptera: Bibionidae).

    PubMed

    Šustr, Vladimír; Stingl, Ulrich; Brune, Andreas

    2014-08-01

    The saprophagous larvae of bibionid flies harbor bacteria in their alkaline intestinal tracts, but little is known about the contribution of the gut microbiota to the digestion of their recalcitrant diet. In this study, we measured oxygen and hydrogen partial pressure, redox potential and pH in the midgut, gastric caeca and hindgut of larvae of the bibionid fly Penthetria holosericea with Clark-type O2 and H2 microsensors, platinum redox microelectrodes, and LIX-type pH microelectrodes. The center of the midgut lumen was anoxic, whereas gastric caeca and hindgut were hypoxic. However, redox potential profiles indicated oxidizing conditions throughout the gut, with lowest values in the midgut (+20 to +60mV). Hydrogen production was not detected. The midgut was extremely alkaline (pH around 11), whereas hindgut and gastric caeca were neutral to slightly alkaline. While HPLC analysis showed high concentrations of glucose in the midgut (15mM) and gastric caeca (27mM), the concentrations of microbial fermentation products such as lactate (2-4mM), acetate (<1mM) and succinate (<0.5mM) were low in all gut regions, suggesting that the contribution of microorganisms to the digestive process, particularly in the alkaline midgut, is only of minor importance. We conclude that the digestive strategy of the saprophytic larva of P. holosericea, which feeds selectively on decomposed leaves and its own microbe-rich faeces, differs fundamentally from those of detritivorous and humivorous insects, which host a highly active, fermentative microbiota in their alkaline midgut or hindgut compartments.

  9. Pho4 Is Essential for Dissemination of Cryptococcus neoformans to the Host Brain by Promoting Phosphate Uptake and Growth at Alkaline pH

    PubMed Central

    Kaufman-Francis, Keren; Desmarini, Desmarini; Juillard, Pierre G.; Li, Cecilia; Stifter, Sebastian A.; Feng, Carl G.; Sorrell, Tania C.; Grau, Georges E. R.; Bahn, Yong-Sun

    2017-01-01

    ABSTRACT Phosphate acquisition by fungi is regulated by the phosphate-sensing and acquisition (PHO) signaling pathway. Cryptococcus neoformans disseminates from the lung to the brain and is the commonest cause of fungal meningitis worldwide. To investigate the contribution of PHO signaling to cryptococcal dissemination, we characterized a transcription factor knockout strain (hlh3Δ/pho4Δ) defective in phosphate acquisition. Despite little similarity with other fungal Pho4 proteins, Hlh3/Pho4 functioned like a typical phosphate-responsive transcription factor in phosphate-deprived cryptococci, accumulating in nuclei and triggering expression of genes involved in phosphate acquisition. The pho4Δ mutant strain was susceptible to a number of stresses, the effect of which, except for alkaline pH, was alleviated by phosphate supplementation. Even in the presence of phosphate, the PHO pathway was activated in wild-type cryptococci at or above physiological pH, and under these conditions, the pho4Δ mutant had a growth defect and compromised phosphate uptake. The pho4Δ mutant was hypovirulent in a mouse inhalation model, where dissemination to the brain was reduced dramatically, and markedly hypovirulent in an intravenous dissemination model. The pho4Δ mutant was not detected in blood, nor did it proliferate significantly when cultured with peripheral blood monocytes. In conclusion, dissemination of infection and the pathogenesis of meningitis are dependent on cryptococcal phosphate uptake and stress tolerance at alkaline pH, both of which are Pho4 dependent. IMPORTANCE Cryptococcal meningitis is fatal without treatment and responsible for more than 500,000 deaths annually. To be a successful pathogen, C. neoformans must obtain an adequate supply of essential nutrients, including phosphate, from various host niches. Phosphate acquisition in fungi is regulated by the PHO signaling cascade, which is activated when intracellular phosphate decreases below a critical

  10. The Effect of Carbonate and pH on Hydrogen Oxidation and Oxygen Reduction on Pt-Based Electrocatalysts in Alkaline Media

    SciTech Connect

    John, Samuel St.; Atkinson, Robert W.; Roy, Asa; Unocic, Raymond R.; Papandrew, Alexander B.; Zawodzinski, Thomas A.

    2016-01-11

    In this paper, we investigated the performance of several carbon-supported RuxPty electrocatalysts for their alkaline hydrogen oxidation and oxygen reduction performance in the presence of carbonate and compared their performance with monometallic, carbon-supported Pt. Our results indicate a strong dependence of HOR upon pH for the monometallic Pt catalysts (22 mV/pH) and a weak dependence upon pH for the Ru-containing electrocatalysts (3.7, 2.5, and 4.7 mV/pH on Ru0.2Pt0.8, Ru0.4Pt0.6, and Ru0.8Pt0.2, respectively). These results are consistent with our previous findings that illustrate a change in rds from electron transfer (on monometallic Pt) to dissociative hydrogen adsorption (on RuxPty catalysts). Analysis of the kinetic currents to determine the rate-determining step via Tafel slope analysis provides additional data supporting this conclusion. There is no difference in the performance at comparable pH values in the presence or absence of carbonate on monometallic Pt indicating that water/hydroxide is the primary proton acceptor for alkaline HOR in 0.1 M KOH aqueous electrolyte. Finally, we observe no pH or carbonate dependence for the ORR on monometallic Pt.

  11. pH. Agricultural Lesson Plans.

    ERIC Educational Resources Information Center

    Southern Illinois Univ., Carbondale. Dept. of Agricultural Education and Mechanization.

    This lesson plan is intended for use in conducting classes on the effect of pH on plant growth. Presented first are an attention step/problem statement and a series of questions and answers designed to convey general information about soil pH and its effect on plants. The following topics are among those discussed: acidity and alkalinity; the…

  12. Plant Habitat (PH)

    NASA Technical Reports Server (NTRS)

    Onate, Bryan

    2016-01-01

    The International Space Station (ISS) will soon have a platform for conducting fundamental research of Large Plants. Plant Habitat (PH) is designed to be a fully controllable environment for high-quality plant physiological research. PH will control light quality, level, and timing, temperature, CO2, relative humidity, and irrigation, while scrubbing ethylene. Additional capabilities include leaf temperature and root zone moisture and oxygen sensing. The light cap will have red (630 nm), blue (450 nm), green (525 nm), far red (730 nm) and broad spectrum white LEDs. There will be several internal cameras (visible and IR) to monitor and record plant growth and operations.

  13. Halotolerant cyanobacterium Aphanothece halophytica contains NapA-type Na+/H+ antiporters with novel ion specificity that are involved in salt tolerance at alkaline pH.

    PubMed

    Wutipraditkul, Nuchanat; Waditee, Rungaroon; Incharoensakdi, Aran; Hibino, Takashi; Tanaka, Yoshito; Nakamura, Tatsunosuke; Shikata, Masamitsu; Takabe, Tetsuko; Takabe, Teruhiro

    2005-08-01

    Aphanothece halophytica is a halotolerant alkaliphilic cyanobacterium which can grow at NaCl concentrations up to 3.0 M and at pH values up to 11. The genome sequence revealed that the cyanobacterium Synechocystis sp. strain PCC 6803 contains five putative Na+/H+ antiporters, two of which are homologous to NhaP of Pseudomonas aeruginosa and three of which are homologous to NapA of Enterococcus hirae. The physiological and functional properties of NapA-type antiporters are largely unknown. One of NapA-type antiporters in Synechocystis sp. strain PCC 6803 has been proposed to be essential for the survival of this organism. In this study, we examined the isolation and characterization of the homologous gene in Aphanothece halophytica. Two genes encoding polypeptides of the same size, designated Ap-napA1-1 and Ap-napA1-2, were isolated. Ap-NapA1-1 exhibited a higher level of homology to the Synechocystis ortholog (Syn-NapA1) than Ap-NapA1-2 exhibited. Ap-NapA1-1, Ap-NapA1-2, and Syn-NapA1 complemented the salt-sensitive phenotypes of an Escherichia coli mutant and exhibited strongly pH-dependent Na+/H+ and Li+/H+ exchange activities (the highest activities were at alkaline pH), although the activities of Ap-NapA1-2 were significantly lower than the activities of the other polypeptides. Only one these polypeptides, Ap-NapA1-2, complemented a K+ uptake-deficient E. coli mutant and exhibited K+ uptake activity. Mutagenesis experiments suggested the importance of Glu129, Asp225, and Asp226 in the putative transmembrane segment and Glu142 in the loop region for the activity. Overexpression of Ap-NapA1-1 in the freshwater cyanobacterium Synechococcus sp. strain PCC 7942 enhanced the salt tolerance of cells, especially at alkaline pH. These findings indicate that A. halophytica has two NapA1-type antiporters which exhibit different ion specificities and play an important role in salt tolerance at alkaline pH.

  14. On the effect of alkaline pH and cofactor availability in the conformational and oligomeric state of Escherichia coli glutamate decarboxylase.

    PubMed

    Giovannercole, F; Mérigoux, C; Zamparelli, C; Verzili, D; Grassini, G; Buckle, M; Vachette, P; De Biase, D

    2017-01-05

    Escherichia coli glutamate decarboxylase (EcGad) is a homohexameric pyridoxal 5'-phosphate (PLP)-dependent enzyme. It is the structural component of the major acid resistance system that protects E. coli from strong acid stress (pH < 3), typically encountered in the mammalian gastrointestinal tract. In fact EcGad consumes one proton/catalytic cycle while yielding γ-aminobutyrate and carbon dioxide from the decarboxylation of l-glutamate. Two isoforms of Gad occur in E. coli (GadA and GadB) that are 99% identical in sequence. GadB is the most intensively investigated. Prompted by the observation that some transcriptomic and proteomic studies show EcGad to be expressed in conditions far from acidic, we investigated the structural organization of EcGadB in solution in the pH range 7.5-8.6. Small angle X-ray scattering, combined with size exclusion chromatography, and analytical ultracentrifugation analysis show that the compact and entangled EcGadB hexameric structure undergoes dissociation into dimers as pH alkalinizes. When PLP is not present, the dimeric species is the most abundant in solution, though evidence for the occurrence of a likely tetrameric species was also obtained. Trp fluorescence emission spectra as well as limited proteolysis studies suggest that PLP plays a key role in the acquisition of a folding necessary for the canonical catalytic activity.

  15. Catalysis and stability of an alkaline protease from a haloalkaliphilic bacterium under non-aqueous conditions as a function of pH, salt and temperature.

    PubMed

    Pandey, Sandeep; Rakholiya, Kalpna D; Raval, Vikram H; Singh, Satya P

    2012-09-01

    A haloalkaliphilic bacterium, isolated from Coastal Gujarat (India) was identified as Oceanobacillus sp. (GQ162111) based on 16S rRNA gene sequence. The organism grew and secreted extra cellular protease in presence of various organic solvents. At 30% (v/v) concentration of hexane, heptane, isooctane, dodecane and decane, significant growth and protease production was evident. The alkaline protease was purified in a single step on phenyl sepharose 6 FF with 28% yield. The molecular mass as judged by SDS-PAGE was 30 kDa. The temperature optimum of protease was 50°C and the enzyme retained 70% activity in 10% (v/v) isooctane. Effect of salt and pH was investigated in combination to assess the effect of isooctane. In organic solvents, the enzyme was considerably active at pH 8-11, with optimum activity at pH 10. Salt at 2 M was optimum for activity and enzyme maintained significant stability up to 18 h even at 3 M salt concentration. Patters of growth, protease production, catalysis and stability of the enzyme are presented. The study resumes significance as limited information is available on the interaction of haloalkaliphilic bacteria and their enzymes with organic solvents.

  16. Chemical equilibrium model for interfacial activity of crude oil in aqueous alkaline solution: the effects of pH, alkali and salt

    SciTech Connect

    Chan, M.; Yen, T.F.

    1980-11-01

    A chemical equilibrium model for interfacial activity of crude in aqueous alkaline solution is proposed. The model predicts the observed effects of pH and concentrations of alkali and salt on the interfacial tension (IFT). The model proposed was shown to describe the observed effects of acid content, pH, and sodium ions on the interfacial activity of crude oil in water. Once the pH of the interface reaches the pKa of the acids, sometimes with the help of addition of some salt, the IFT experiences a sudden steep drop to the range of 10/sup -2/ dynes/cm. After that, further addition of sodium either in the form of NaOH or NaCl is going to increase the IFT due to a shift of equilibriumn to the formation of undissociated soap. This was confirmed by the difference in the observed effect of sodium on the IFT of the extracted soap molecules which are dissociated easily and those which are associated highly and precipitated easily. These soap molecules have dissociation constant values ranging from below 10/sup -2/ to above one. 13 references.

  17. Growth of Leuconostoc mesenteroides NRRL-B523 in an alkaline medium: suboptimal pH growth inhibition of a lactic acid bacterium.

    PubMed

    Wolf, Barry F; Fogler, H Scott

    2005-01-05

    Bacterial profile modification (BPM), a form of tertiary oil recovery, diverts water from the water-flooded high-permeability zone into the oil-bearing low-permeability zone. During field use, exopolymer-producing bacteria plug the high-permeability zone only in the immediate vicinity of the injection point (the near-well bore region). For effective BPM the plug must penetrate far into the formation. Slowing the specific growth rate, lengthening the lag phase, and slowing the polymerization rate are techniques that can prolong the onset of biopolymer gelation and extend the depth of the biological plug. In batch experiments, the growth of Leuconostoc mesenteroides NRRL-B523 was inhibited by the synergistic effects of high substrate loading and an alkaline pH. Exponential growth was delayed up to 190 h. It was observed that cell division was significantly retarded until the medium pH, reduced by the acid byproducts of fermentation, reached a critical value of 6.79 +/- 0.06. A mathematical model was developed to describe the relationship between specific growth rate, lag time, and medium pH.

  18. pH Basics

    ERIC Educational Resources Information Center

    Lunelli, Bruno; Scagnolari, Francesco

    2009-01-01

    The exposition of the pervasive concept of pH, of its foundations and implementation as a meaningful quantitative measurement, in nonspecialist university texts is often not easy to follow because too many of its theoretical and operative underpinnings are neglected. To help the inquiring student we provide a concise introduction to the depth just…

  19. pH optrode

    DOEpatents

    Northrup, M. Allen; Langry, Kevin C.

    1993-01-01

    A process is provided for forming a long-lasting, stable, pH-sensitive dye-acrylamide copolymer useful as a pH-sensitive material for use in an optrode or other device sensitive to pH. An optrode may be made by mechanically attaching the copolymer to a sensing device such as an optical fiber.

  20. 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.

  1. Extracellular pH alkalinization by Cl-/HCO3- exchanger is crucial for TASK2 activation by hypotonic shock in proximal cell lines from mouse kidney.

    PubMed

    L'Hoste, S; Barriere, H; Belfodil, R; Rubera, I; Duranton, C; Tauc, M; Poujeol, C; Barhanin, J; Poujeol, P

    2007-02-01

    We have previously shown that K(+)-selective TASK2 channels and swelling-activated Cl(-) currents are involved in a regulatory volume decrease (RVD; Barriere H, Belfodil R, Rubera I, Tauc M, Lesage F, Poujeol C, Guy N, Barhanin J, Poujeol P. J Gen Physiol 122: 177-190, 2003; Belfodil R, Barriere H, Rubera I, Tauc M, Poujeol C, Bidet M, Poujeol P. Am J Physiol Renal Physiol 284: F812-F828, 2003). The aim of this study was to determine the mechanism responsible for the activation of TASK2 channels during RVD in proximal cell lines from mouse kidney. For this purpose, the patch-clamp whole-cell technique was used to test the effect of pH and the buffering capacity of external bath on Cl(-) and K(+) currents during hypotonic shock. In the presence of a high buffer concentration (30 mM HEPES), the cells did not undergo RVD and did not develop outward K(+) currents (TASK2). Interestingly, the hypotonic shock reduced the cytosolic pH (pH(i)) and increased the external pH (pH(e)) in wild-type but not in cftr (-/-) cells. The inhibitory effect of DIDS suggests that the acidification of pH(i) and the alkalinization of pH(e) induced by hypotonicity in wild-type cells could be due to an exit of HCO(3)(-). In conclusion, these results indicate that Cl(-) influx will be the driving force for HCO(3)(-) exit through the activation of the Cl(-)/HCO(3)(-) exchanger. This efflux of HCO(3)(-) then alkalinizes pH(e), which in turn activates TASK2 channels.

  2. A low-temperature-active alkaline pectate lyase from Xanthomonas campestris ACCC 10048 with high activity over a wide pH range.

    PubMed

    Yuan, Peng; Meng, Kun; Wang, Yaru; Luo, Huiying; Shi, Pengjun; Huang, Huoqing; Tu, Tao; Yang, Peilong; Yao, Bin

    2012-11-01

    Alkaline pectate lyases are favorable for the textile industry. Here, we report the gene cloning and expression of a low-temperature-active alkaline pectate lyase (PL D) from Xanthomonas campestris ACCC 10048. Deduced PL D consists of a putative 27-residue signal peptide and a catalytic domain of 320 residues belonging to family PF09492. Recombinant PL D (r-PL D) produced in Escherichia coli was purified to electrophoretic homogeneity with a single step of Ni(2+)-NTA affinity chromatography and showed an apparent molecular weight of ~38 kDa. The pH and temperature optima of r-PL D were found to be 9.0 °C and 30 °C, respectively. Compared with its microbial counterparts, r-PL D had higher activity over a wide pH range (>45 % of the maximum activity at pH 3.0-12.0) and at lower temperatures (>35 % of activity even at 0 °C). The K(m) and V(max) values of r-PL D for polygalacturonic acid were 4.9 gl(-1) and 30.1 μmolmin(-1) mg(-1), respectively. Compared with the commercial compound pectinase from Novozymes, r-PL D showed similar efficacy in reducing the intrinsic viscosity of polygalacturonic acid (35.1 % vs. 36.5 %) and in bioscouring of jute (10.25 % vs. 10.82 %). Thus, r-PL D is a valuable additive candidate for the textile industry.

  3. Rhesus glycoprotein and urea transporter genes in rainbow trout embryos are upregulated in response to alkaline water (pH 9.7) but not elevated water ammonia.

    PubMed

    Sashaw, Jessica; Nawata, Michele; Thompson, Sarah; Wood, Chris M; Wright, Patricia A

    2010-03-01

    Recent studies have shown that genes for the putative ammonia transporter, Rhesus glycoproteins (Rh) and the facilitated urea transporter (UT) are expressed before hatching in rainbow trout (Oncorhychus mykiss Walbaum) embryos. We tested the hypothesis that Rh and UT gene expressions are regulated in response to environmental conditions that inhibit ammonia excretion during early life stages. Eyed-up embryos (22 days post-fertilization (dpf)) were exposed to control (pH 8.3), high ammonia (1.70 mmol l(-1) NH4HCO3) and high pH (pH 9.7) conditions for 48h. With exposure to high water ammonia, ammonia excretion rates were reversed, tissue ammonia concentration was elevated by 9-fold, but there were no significant changes in mRNA expression relative to control embryos. In contrast, exposure to high water pH had a smaller impact on ammonia excretion rates and tissue ammonia concentrations, whereas mRNA levels for the Rhesus glycoprotein Rhcg2 and urea transporter (UT) were elevated by 3.5- and 5.6-fold, respectively. As well, mRNAs of the genes for H+ATPase and Na+/H+ exchanger (NHE2), associated with NH3 excretion, were also upregulated by 7.2- and 13-fold, respectively, in embryos exposed to alkaline water relative to controls. These results indicate that the Rhcg2, UT and associated transport genes are regulated in rainbow trout embryos, but in contrast to adults, there is no effect of high external ammonia at this stage of development.

  4. Effect of Treatment pH on the End Products of the Alkaline Hydrolysis of TNT and RDX

    DTIC Science & Technology

    2007-06-01

    Comparison of final TOC of TNT alkaline hydrolysis solutions at three pHs........................19 Table 7. Results of ion chromatographic analysis ...25 Table 12. Results of ion chromatographic analysis of unlabeled RDX solutions following extended alkaline hydrolysis at three...8330 explo- sives analysis TOC IC Lime Control ERDC/EL TR-07-4 7 3 Materials and Methods Chemicals Chemicals used in this study included

  5. Development of a selective enterococcus medium based on manganese ion deficiency, sodium azide, and alkaline pH.

    PubMed

    Efthymiou, C J; Joseph, S W

    1974-09-01

    Rogosa broth, without its salt supplement and dissolved in deionized water, was adapted for the selective isolation and enumeration of enterococci. This medium supported good growth of enterococci, but it suppressed growth of other lactic acid bacteria. The sensitivity and specificity of the medium were tested after addition of various increasing concentrations of NaN(3) against known strains of enterococci and other bacteria. Many strains of Streptococcus faecium showed low azide tolerance; optimal growth was obtained at a concentration of 0.01% NaN(3), which totally or partially inhibited unrelated species of lactic acid bacteria. The selectivity of the medium was further increased by pH adjustment to 9.6. Carbonate and Tween 80 were added to overcome partial inhibition of enterococcal growth by the new combination of selective conditions. The final medium was evaluated in agar form in isolations from human and animal feces, polluted water, meat, and dairy products. Counts were obtained after 16 to 17 h of incubation at 37 C. The isolates satisfactorily conformed to the group characteristics of enterococci.

  6. Development of a Selective Enterococcus Medium Based on Manganese Ion Deficiency, Sodium Azide, and Alkaline pH

    PubMed Central

    Efthymiou, C. J.; Joseph, S. W.

    1974-01-01

    Rogosa broth, without its salt supplement and dissolved in deionized water, was adapted for the selective isolation and enumeration of enterococci. This medium supported good growth of enterococci, but it suppressed growth of other lactic acid bacteria. The sensitivity and specificity of the medium were tested after addition of various increasing concentrations of NaN3 against known strains of enterococci and other bacteria. Many strains of Streptococcus faecium showed low azide tolerance; optimal growth was obtained at a concentration of 0.01% NaN3, which totally or partially inhibited unrelated species of lactic acid bacteria. The selectivity of the medium was further increased by pH adjustment to 9.6. Carbonate and Tween 80 were added to overcome partial inhibition of enterococcal growth by the new combination of selective conditions. The final medium was evaluated in agar form in isolations from human and animal feces, polluted water, meat, and dairy products. Counts were obtained after 16 to 17 h of incubation at 37 C. The isolates satisfactorily conformed to the group characteristics of enterococci. Images PMID:4214072

  7. Enhanced production of heterologous proteins by the filamentous fungus Trichoderma reesei via disruption of the alkaline serine protease SPW combined with a pH control strategy.

    PubMed

    Zhang, Guoxiu; Zhu, Yao; Wei, Dongzhi; Wang, Wei

    2014-01-01

    The filamentous fungus Trichoderma reesei has received attention as a host for heterologous protein production because of its high secretion capacity and eukaryotic post-translational modifications. However, the heterologous production of proteins in T. reesei is limited by its high expression of proteases. The pH control strategies have been proposed for eliminating acidic, but not alkaline, protease activity. In this study, we verified the expression of a relatively major extracellular alkaline protease (GenBank accession number: EGR49466.1, named spw in this study) from 20 candidates through real-time polymerase chain reaction. The transcriptional level of spw increased about 136 times in response to bovine serum albumin as the sole nitrogen source. Additionally, extracellular protease activity was reduced by deleting the spw gene. Therefore, using this gene expression system, we observed enhanced production and stability of the heterologous alkaline endoglucanase EGV from Humicola insolens using the Δspw strain as compared to the parental strain RUT-C30.

  8. Roles of alkaline phosphatase and labile internal mineral in matrix vesicle-mediated calcification. Effect of selective release of membrane-bound alkaline phosphatase and treatment with isosmotic pH 6 buffer.

    PubMed

    Register, T C; McLean, F M; Low, M G; Wuthier, R E

    1986-07-15

    The roles of alkaline phosphatase and labile internal mineral in matrix vesicle-mediated mineralization have been studied by selectively releasing the enzyme from a wide variety of matrix vesicle preparations using treatment with a bacterial phosphatidylinositol-specific phospholipase C and by demineralization of the vesicles using isosmotic pH 6 buffer. Following depletion of 50-90% of the alkaline phosphatase activity or treatment with citrate buffer, the vesicles were tested for their ability to accumulate 45Ca2+ and 32Pi from a synthetic cartilage lymph. Removal of alkaline phosphatase by phospholipase C treatment caused two principal effects, depending on the matrix vesicle preparation. In rapidly mineralizing vesicle fractions which did not require organic phosphate esters (Po) to accumulate mineral ions, release of alkaline phosphatase had only a minor effect. In slowly mineralizing vesicles preparations or those dependent on Po substrates for mineral ion uptake, release of alkaline phosphatase caused significant loss of mineralizing activity. The activity of rapidly calcifying vesicles was shown to be dependent on the presence of labile internal mineral, as demonstrated by major loss in activity when the vesicles were decalcified by various treatments. Ion uptake by demineralized vesicles or those fractionated on sucrose step gradients required Po and was significantly decreased by alkaline phosphatase depletion. Uptake of Pi, however, was not coupled with hydrolysis of the Po substrate. These findings argue against a direct role for alkaline phosphatase as a porter in matrix vesicle Pi uptake, contrary to previous postulates. The results emphasize the importance of internal labile mineral in rapid uptake of mineral ions by matrix vesicles.

  9. Eukaryotic diversity at pH extremes

    PubMed Central

    Amaral-Zettler, Linda A.

    2013-01-01

    Extremely acidic (pH < 3) and extremely alkaline (pH > 9) environments support a diversity of single-cell and to a lesser extent, multicellular eukaryotic life. This study compared alpha and beta diversity in eukaryotic communities from seven diverse aquatic environments with pH values ranging from 2 to 11 using massively-parallel pyrotag sequencing targeting the V9 hypervariable region of the 18S ribosomal RNA (rRNA) gene. A total of 946 operational taxonomic units (OTUs) were recovered at a 6% cut-off level (94% similarity) across the sampled environments. Hierarchical clustering of the samples segregated the communities into acidic and alkaline groups. Similarity percentage (SIMPER) analysis followed by indicator OTU analysis (IOA) and non-metric multidimensional scaling (NMDS) were used to determine which characteristic groups of eukaryotic taxa typify acidic or alkaline extremes and the extent to which pH explains eukaryotic community structure in these environments. Spain's Rio Tinto yielded the fewest observed OTUs while Nebraska Sandhills alkaline lakes yielded the most. Distinct OTUs, including metazoan OTUs, numerically dominated pH extreme sites. Indicator OTUs included the diatom Pinnularia and unidentified opisthokonts (Fungi and Filasterea) in the extremely acidic environments, and the ciliate Frontonia across the extremely alkaline sites. Inferred from NMDS, pH explained only a modest fraction of the variation across the datasets, indicating that other factors influence the underlying community structure in these environments. The findings from this study suggest that the ability for eukaryotes to adapt to pH extremes over a broad range of values may be rare, but further study of taxa that can broadly adapt across diverse acidic and alkaline environments, respectively present good models for understanding adaptation and should be targeted for future investigations. PMID:23335919

  10. 17-4 PH and 15-5 PH

    NASA Technical Reports Server (NTRS)

    Johnson, Howard T.

    1995-01-01

    17-4 PH and 15-5 PH are extremely useful and versatile precipitation-hardening stainless steels. Armco 17-4 PH is well suited for the magnetic particle inspection requirements of Aerospace Material Specification. Armco 15-5 PH and 17-4 PH are produced in billet, plate, bar, and wire. Also, 15-5 PH is able to meet the stringent mechanical properties required in the aerospace and nuclear industries. Both products are easy to heat treat and machine, making them very useful in many applications.

  11. Alkaline Cytosolic pH and High Sodium Hydrogen Exchanger 1 (NHE1) Activity in Th9 Cells.

    PubMed

    Singh, Yogesh; Zhou, Yuetao; Shi, Xiaolong; Zhang, Shaqiu; Umbach, Anja T; Salker, Madhuri S; Lang, Karl S; Lang, Florian

    2016-11-04

    CD4(+) T helper 9 (Th9) cells are a newly discovered Th cell subset that produce the pleiotropic cytokine IL-9. Th9 cells can protect against tumors and provide resistance against helminth infections. Given their pivotal role in the adaptive immune system, understanding Th9 cell development and the regulation of IL-9 production could open novel immunotherapeutic opportunities. The Na(+)/H(+) exchanger 1 (NHE1; gene name Slc9α1)) is critically important for regulating intracellular pH (pHi), cell volume, migration, and cell survival. The pHi influences cytokine secretion, activities of membrane-associated enzymes, ion transport, and other effector signaling molecules such as ATP and Ca(2+) levels. However, whether NHE1 regulates Th9 cell development or IL-9 secretion has not yet been defined. The present study explored the role of NHE1 in Th9 cell development and function. Th cell subsets were characterized by flow cytometry and pHi was measured using 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein-acetoxymethyl ester (BCECF-AM) dye. NHE1 functional activity was estimated from the rate of realkalinization following an ammonium pulse. Surprisingly, in Th9 cells pHi and NHE1 activity were significantly higher than in all other Th cell subsets (Th1/Th2/Th17 and induced regulatory T cells (iTregs)). NHE1 transcript levels and protein abundance were significantly higher in Th9 cells than in other Th cell subsets. Inhibition of NHE1 by siRNA-NHE1 or with cariporide in Th9 cells down-regulated IL-9 and ATP production. NHE1 activity, Th9 cell development, and IL-9 production were further blunted by pharmacological inhibition of protein kinase Akt1/Akt2. Our findings reveal that Akt1/Akt2 control of NHE1 could be an important physiological regulator of Th9 cell differentiation, IL-9 secretion, and ATP production.

  12. Quantification of the dissolved inorganic carbon species and of the pH of alkaline solutions exposed to CO2 under pressure: a novel approach by Raman scattering.

    PubMed

    Beuvier, Thomas; Calvignac, Brice; Bardeau, Jean-François; Bulou, Alain; Boury, Frank; Gibaud, Alain

    2014-10-07

    Dissolved inorganic carbon (DIC) content of aqueous systems is a key function of the pH, of the total alkanility (TA), and of the partial pressure of CO2. However, common analytical techniques used to determine the DIC content in water are unable to operate under high CO2 pressure. Here, we propose to use Raman spectroscopy as a novel alternative to discriminate and quantitatively monitor the three dissolved inorganic carbon species CO2(aq), HCO3(-), and CO3(2-) of alkaline solutions under high CO2 pressure (from P = 0 to 250 bar at T = 40 °C). In addition, we demonstrate that the pH values can be extracted from the molalities of CO2(aq) and HCO3(-). The results are in very good agreement with those obtained from direct spectrophotometric measurements using colored indicators. This novel method presents the great advantage over high pressure conventional techniques of not using breakable electrodes or reference additives and appears of great interest especially in marine biogeochemistry, in carbon capture and storage and in material engineering under high CO2 pressure.

  13. Determination of the equilibrium formation constants of two U(VI)-peroxide complexes at alkaline pH.

    PubMed

    Meca, S; Martínez-Torrents, A; Martí, V; Giménez, J; Casas, I; de Pablo, J

    2011-08-21

    The formation of uranyl-peroxide complexes was studied at alkaline media by using UV-Visible spectrophotometry and the STAR code. Two different complexes were found at a H(2)O(2)/U(VI) ratio lower than 2. A graphical method was used in order to obtain the formation constants of such complexes and the STAR program was used to refine the formation constants values because of its capacity to treat multiwavelength absorbance data and refining equilibrium constants. The values obtained for the two complexes identified were: UO(2)(2+) + H(2)O(2) + 4OH(-) <−> UO(2)(O(2))(OH)(2)(2-) + 2H(2)O: log β°(1,1,4) = 28.1 ± 0.1 (1). UO(2)(2+) + 2H(2)O(2) + 6OH(-) <−> UO(2)(O(2))(2)(OH)(2)(4-) + 4H(2)O: log β°(1,2,6) = 36.8 ± 0.2 (2). At hydrogen peroxide concentrations higher than 10(-5) mol dm(-3), and in the absence of carbonate, the UO(2)(O(2))(2)(OH)(2)(4-) complex is predominant in solution, indicating the significant peroxide affinity of peroxide ions for uranium and the strong complexes of uranium(VI) with peroxide.

  14. High-resolution kinetics of transferrin acidification in BALB/c 3T3 cells: exposure to pH 6 followed by temperature-sensitive alkalinization during recycling.

    PubMed

    Sipe, D M; Murphy, R F

    1987-10-01

    The kinetics of acidification of diferric human transferrin in BALB/c mouse 3T3 cells were determined by flow cytometry using a modification of the fluorescein-rhodamine fluorescence ratio technique. For cells labeled at 0 degrees C and warmed to 37 degrees C, the minimum pH observed was 6.1 +/- 0.2, occurring 5 min after warmup. This step was followed by a slower alkalinization to the pH of the external medium, occurring with a half-time of 5 min. Warmup to 24 degrees C or 17 degrees C resulted in slowing of the time of onset of acidification such that the minimum pH was 6.3 +/- 0.2, attained 15 and 25 min after warmup, respectively; the alkalinization step was completely blocked. The limited acidification observed for transferrin corresponds to the initial phase of acidification normally observed for other (nonrecycled) ligands. Since transferrin is not further acidified, the results confirm the existence of two phases of acidification during endocytosis. Measurements of transferrin dissociation at neutral pH after exposure to mildly acidic pH support the conclusion that the transferrin cycle may be completed without exposure of transferrin to a pH below 6. The mildly acidic pH of the endocytic compartments involved in recycling may play a role in regulating enzymatic processing of endocytosed material.

  15. Continuous bioproduction of short-chain fatty acids from sludge enhanced by the combined use of surfactant and alkaline pH.

    PubMed

    Chen, Yinguang; Liu, Kun; Su, Yinglong; Zheng, Xiong; Wang, Qin

    2013-07-01

    This work reported the enhancement of continuous SCFA production from sludge by the combined use of surfactant (sodium dodecylbenzene sulfonate (SDBS)) and pH 10 (i.e., SDBS & pH 10). The maximal SCFA production (2056 mg COD/L) was achieved under the SDBS & pH 10 condition at a sludge retention time (SRT) of 12d, which was much higher than that of the blank, sole SDBS, or pH 10. The mechanisms investigation showed that the combined strategy had greater sludge solubilization, higher protein hydrolysis, and lower activity of methanogens. Fluorescence in situ hybridization analysis revealed that the abundance of bacteria was increased, whereas that of archaea was decreased by SDBS & pH 10. The excitation emission matrix fluorescence spectroscopy assay further suggested that SBDS caused protein structure change, which benefited protein hydrolysis.

  16. Energy separations for the electronic states of PH -2,PH 2 and PH +2

    NASA Astrophysics Data System (ADS)

    Balasubramanian, K.

    1993-03-01

    All-electron complete-active space multi-configuration self-consistent field (CASSCF) followed by second-order configuration interaction (SOCI) calculations in conjunction with large P(13s10p3d2flg/7s6p3d2flg) and H (10s5p1d/8s5p1d) basis sets are made on the electronic states of PH -2, PH 2 and PH +2. We compute the adiabatic electron affinities of PH 2 and PH. The 3B 1-X 1A 1, 1B 1-X 1A 1 energy separations of PH +2 and the 2A 1-X 2B 1 energy separation of PH 2 are computed.

  17. Escherichia coli YqjA, a Member of the Conserved DedA/Tvp38 Membrane Protein Family, Is a Putative Osmosensing Transporter Required for Growth at Alkaline pH

    PubMed Central

    Kumar, Sujeet

    2015-01-01

    ABSTRACT The ability to persist and grow under alkaline conditions is an important characteristic of many bacteria. In order to survive at alkaline pH, Escherichia coli must maintain a stable cytoplasmic pH of about 7.6. Membrane cation/proton antiporters play a major role in alkaline pH homeostasis by catalyzing active inward proton transport. The DedA/Tvp38 family is a highly conserved membrane protein family of unknown function present in most sequenced genomes. YqjA and YghB are members of the E. coli DedA family with 62% amino acid identity and partially redundant functions. We have shown that E. coli with ΔyqjA and ΔyghB mutations cannot properly maintain the proton motive force (PMF) and is compromised in PMF-dependent drug efflux and other PMF-dependent functions. Furthermore, the functions of YqjA and YghB are dependent upon membrane-embedded acidic amino acids, a hallmark of several families of proton-dependent transporters. Here, we show that the ΔyqjA mutant (but not ΔyghB) cannot grow under alkaline conditions (ranging from pH 8.5 to 9.5), unlike the parent E. coli. Overexpression of yqjA restores growth at alkaline pH, but only when more than ∼100 mM sodium or potassium is present in the growth medium. Increasing the osmotic pressure by the addition of sucrose enhances the ability of YqjA to support growth under alkaline conditions in the presence of low salt concentrations, consistent with YqjA functioning as an osmosensor. We suggest that YqjA possesses proton-dependent transport activity that is stimulated by osmolarity and that it plays a significant role in the survival of E. coli at alkaline pH. IMPORTANCE The ability to survive under alkaline conditions is important for many species of bacteria. Escherichia coli can grow at pH 5.5 to 9.5 while maintaining a constant cytoplasmic pH of about 7.6. Under alkaline conditions, bacteria rely upon proton-dependent transporters to maintain a constant cytoplasmic pH. The DedA/Tvp38 protein family

  18. Snow leopard (Panthera uncia) spermatozoa are sensitive to alkaline pH, but motility in vitro is not influenced by protein or energy supplements.

    PubMed

    Roth, T L; Swanson, W F; Collins, D; Burton, M; Garell, D M; Wildt, D E

    1996-01-01

    To better understand the biology of snow leopard spermatozoa and to facilitate developing assisted reproduction, a series of studies was conducted to: 1) identify the component(s) of complex culture media responsible for the detrimental effect on sperm survival in vitro, 2) optimize medium for supporting sperm viability, and 3) evaluate sperm capacitation in vitro. Constituents of complex media were added systematically to phosphate-buffered saline (PBS) to isolate the factor(s) influencing snow leopard sperm motility in vitro. Sperm capacitation was also assessed following incubation in PBS with bovine serum albumin (BSA), fetal calf serum (FCS), or heparin. For maintaining sperm motility, there was no benefit (P > or = 0.05) to supplementing PBS with low (5%) or high (20%) concentrations of snow leopard serum (SLS) versus FCS or BSA. Likewise, adding supplemental energy substrates (pyruvate, glucose, lactate, or glutamine) did not enhance or hinder (P > or = 0.05) sperm motility. However, motility rapidly decreased (P < 0.05) with the addition of NaHCO3 to PBS or Ham's F10 nutrient mixture. Surprisingly, Ham's F10 with no buffering component or with both NaHCO3 and N-Z-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) maintained sperm motility at levels similar (P > or = 0.05) to PBS. Although sperm motility in all treatments decreased with time, there was a strong inverse relationship (P < 0.01; r = 0.90) between motility and sample pH at 6 hours. Spermatozoa incubated in PBS containing FCS, BSA, or heparin did not undergo the acrosome reaction when exposed to calcium ionophore. In summary, alkaline pH has a profound detrimental effect on snow leopard sperm motility, and capacitation does not occur under conditions that normally promote this event in other felid species. These results clearly demonstrate a high degree of interspecific variation among felids in fundamental sperm function, and they provide evidence for the necessity of basic research when

  19. The pH Game.

    ERIC Educational Resources Information Center

    Chemecology, 1996

    1996-01-01

    Describes a game that can be used to teach students about the acidity of liquids and substances around their school and enable them to understand what pH levels tell us about the environment. Students collect samples and measure the pH of water, soil, plants, and other natural material. (DDR)

  20. Urine pH test

    MedlinePlus

    ... pubmed/7797810 . Read More Acid loading test (pH) Acute kidney failure Alkalosis Chronic obstructive pulmonary disease Diabetic ketoacidosis Diarrhea - overview Distal renal tubular acidosis Gastric suction Interstitial nephritis Kidney stones ...

  1. Exercise and Pulmonary Hypertension (PH)

    MedlinePlus

    ... Process: Some First Steps Adoption Success Story Watch Classroom Recordings Empowered Patient Online Toolkit Tab 1: Very ... Kathy Groebner Education Programs Patients and Caregivers PHA Classroom PHA on the Road: PH Patients and Families ...

  2. Esophageal pH monitoring

    MedlinePlus

    ... test can also be done during upper GI endoscopy by clipping a pH monitor to the lining of the esophagus. ... esophagitis : Barium swallow Esophagogastroduodenoscopy (also called upper GI endoscopy)

  3. PhEDEx Data Service

    NASA Astrophysics Data System (ADS)

    Egeland, Ricky; Wildish, Tony; Huang, Chih-Hao

    2010-04-01

    The PhEDEx Data Service provides access to information from the central PhEDEx database, as well as certificate-authenticated managerial operations such as requesting the transfer or deletion of data. The Data Service is integrated with the "SiteDB" service for fine-grained access control, providing a safe and secure environment for operations. A plug-in architecture allows server-side modules to be developed rapidly and easily by anyone familiar with the schema, and can automatically return the data in a variety of formats for use by different client technologies. Using HTTP access via the Data Service instead of direct database connections makes it possible to build monitoring web-pages with complex drill-down operations, suitable for debugging or presentation from many aspects. This will form the basis of the new PhEDEx website in the near future, as well as providing access to PhEDEx information and certificate-authenticated services for other CMS dataflow and workflow management tools such as CRAB, WMCore, DBS and the dashboard. A PhEDEx command-line client tool provides one-stop access to all the functions of the PhEDEx Data Service interactively, for use in simple scripts that do not access the service directly. The client tool provides certificate-authenticated access to managerial functions, so all the functions of the PhEDEx Data Service are available to it. The tool can be expanded by plug-ins which can combine or extend the client-side manipulation of data from the Data Service, providing a powerful environment for manipulating data within PhEDEx.

  4. Programmable pH buffers

    DOEpatents

    Gough, Dara Van; Huber, Dale L.; Bunker, Bruce C.; Roberts, Mark E.

    2017-01-24

    A programmable pH buffer comprises a copolymer that changes pK.sub.a at a lower critical solution temperature (LCST) in water. The copolymer comprises a thermally programmable polymer that undergoes a hydrophobic-to-hydrophilic phase change at the LCST and an electrolytic polymer that exhibits acid-base properties that are responsive to the phase change. The programmable pH buffer can be used to sequester CO.sub.2 into water.

  5. Evaluating the role of metal ions in the bathochromic and hyperchromic responses of cyanidin derivatives in acidic and alkaline pH.

    PubMed

    Sigurdson, G T; Robbins, R J; Collins, T M; Giusti, M M

    2016-10-01

    In many food products, colorants derived from natural sources are increasingly popular due to consumer demand. Anthocyanins are one class of versatile and abundant naturally occurring chromophores that produce different hues in nature, especially with metal ions and other copigments assisting. The effects of chelation of metal ions (Mg(2+), Al(3+), Cr(3+), Fe(3+), and Ga(3+)) in factorial excesses to anthocyanin concentration (0-500×) on the spectral characteristics (380-700nm) of cyanidin and acylated cyanidin derivatives were evaluated to better understand the color evolution of anthocyanin-metal chelates in pH 3-8. In all pH, anthocyanins exhibited bathochromic and hyperchromic shifts. Largest bathochromic shifts most often occurred in pH 6; while largest hyperchromic shifts occurred in pH 5. Divalent Mg(2+) showed no observable effect on anthocyanin color while trivalent metal ions caused bathochromic shifts and hue changes. Generally, bathochromic shifts on anthocyanins were greatest with more electron rich metal ions (Fe(3+)≈Ga(3+)>Al(3+)>Cr(3+)).

  6. Effect of pH and temperature on stability and kinetics of novel extracellular serine alkaline protease (70 kDa).

    PubMed

    Bhunia, Biswanath; Basak, Bikram; Mandal, Tamal; Bhattacharya, Pinaki; Dey, Apurba

    2013-03-01

    A novel extracellular serine protease (70 kDa by SDS-PAGE) was purified and characterized. This enzyme retained more than 93% of its initial activity after preincubation for 30 min at 37 °C in the presence of 25% (v/v) tested organic solvents and showed feather degradation activity. The purified enzyme was deactivated at various combinations of pH and temperature to examine the interactive effect of them on enzyme activity. The deactivation process was modeled as first-order kinetics and the deactivation rate constant (k(d)) was found to be minimum at pH 9 and 37 °C. The kinetic analysis of enzyme over a range of pH values indicated two pK values at 6.21 and at 10.92. The lower pK value was likely due to the catalytic histidine in the free enzyme and higher pK value likely reflected deprotonation of the proline moiety of the substrate but ionization of the active site serine is another possibility. Inhibition kinetic showed that enzyme is serine protease because enzyme was competitively inhibited by antipain and aprotinin as these compounds are known to be competitive inhibitors of serine protease. The organic solvent, thermal and pH tolerances of enzyme suggested that it may have potential for use as a biocatalyst in industry.

  7. Deletions of endocytic components VPS28 and VPS32 affect growth at alkaline pH and virulence through both RIM101-dependent and RIM101-independent pathways in Candida albicans.

    PubMed

    Cornet, Muriel; Bidard, Frédérique; Schwarz, Patrick; Da Costa, Grégory; Blanchin-Roland, Sylvie; Dromer, Françoise; Gaillardin, Claude

    2005-12-01

    Ambient pH signaling involves a cascade of conserved Rim or Pal products in ascomycetous yeasts or filamentous fungi, respectively. Recent evidences in the fungi Aspergillus nidulans, Saccharomyces cerevisiae, Yarrowia lipolytica, and Candida albicans suggested that components of endosomal sorting complexes required for transport (ESCRT) involved in endocytic trafficking were needed for signal transduction along the Rim pathway. In this study, we confirm these findings with C. albicans and show that Vps28p (ESCRT-I) and Vps32p/Snf7p (ESCRT-III) are required for the transcriptional regulation of known targets of the Rim pathway, such as the PHR1 and PHR2 genes encoding cell surface proteins, which are expressed at alkaline and acidic pH, respectively. We additionally show that deletion of these two VPS genes, particularly VPS32, has a more drastic effect than a RIM101 deletion on growth at alkaline pH and that this effect is only partially suppressed by expression of a constitutively active form of Rim101p. Finally, in an in vivo mouse model, both vps null mutants were significantly less virulent than a rim101 mutant, suggesting that VPS28 and VPS32 gene products affect virulence both through Rim-dependent and Rim-independent pathways.

  8. Intragastric pH Monitoring,

    DTIC Science & Technology

    1993-10-01

    disposable sensor.. hnt Care 13. Peterson WL. GI bleeding. In: Sleisenger MH, Fordtran IS, Med 1988;14:232-5. ,. eds. Gastrointestinal disease: pathophysiology ... diagnosis and 27. Fimmel CL, Etienne A, Cilluffo T, et al. Long-term ambu- management, Vol I. 4th ed. Philadelphia: WB Saunders, latory gastric pH

  9. Making pH Tangible.

    ERIC Educational Resources Information Center

    McIntosh, Elizabeth; Moss, Robert

    1995-01-01

    Presents a laboratory exercise in which students test the pH of different substances, study the effect of a buffer on acidic solutions by comparing the behavior of buffered and unbuffered solutions upon the addition of acid, and compare common over-the-counter antacid remedies. (MKR)

  10. Isolated secretion granules from parotid glands of chronically stimulated rats possess an alkaline internal pH and inward-directed H/sup +/ pump activity

    SciTech Connect

    Arvan, P.; Castle, J.D.

    1986-10-01

    Secretion granules have been isolated from the parotid glands of rats that have been chronically stimulated with the ..beta..-adrenergic agonist, isoproterenol. These granules are of interest because they package a quantitatively different set of secretory proteins in comparison with granules from the normal gland. Polypeptides enriched in proline, glycine, and glutamine, which are known to have pI's >10, replace ..cap alpha..-amylase (pI's = 6.8) as the principal content species. The internal pH of granules from the treated rats changes from 7.8 in a potassium sulfate medium to 6.9 in a choline chloride medium. The increased pH over that of normal parotid granules (approx.6.8) appears to protect the change in composition of the secretory contents. Whereas normal mature parotide granules have practically negligible levels of H/sup +/ pumping ATPase activity, the isolated granules from isoproterenol-treated rats undergo a time-dependent internal acidification that requires the presence of ATP and is abolished by an H/sup +/ ionophore. Additionally, an inside-positive granule transmembrane potential develops after ATP addition that depends upon ATP hydrolysis. Two independent methods have been used that exclude the possibility that contaminating organelles are the source of the H/sup +/-ATPase activity. Together these data provide clear evidence for the presence of an H/sup +/ pump in the membranes of parotid granules from chronically stimulated rats. However, despite the presence of H/sup +/-pump activity, fluorescence microscopy with the weak base, acridine orange, reveals that the intragranular pH in live cells is greater than that of the cytoplasm.

  11. Organelle pH in the Arabidopsis endomembrane system.

    PubMed

    Shen, Jinbo; Zeng, Yonglun; Zhuang, Xiaohong; Sun, Lei; Yao, Xiaoqiang; Pimpl, Peter; Jiang, Liwen

    2013-09-01

    The pH of intracellular compartments is essential for the viability of cells. Despite its relevance, little is known about the pH of these compartments. To measure pH in vivo, we have first generated two pH sensors by combining the improved-solubility feature of solubility-modified green fluorescent protein (GFP) (smGFP) with the pH-sensing capability of the pHluorins and codon optimized for expression in Arabidopsis. PEpHluorin (plant-solubility-modified ecliptic pHluorin) gradually loses fluorescence as pH is lowered with fluorescence vanishing at pH 6.2 and PRpHluorin (plant-solubility-modified ratiomatric pHluorin), a dual-excitation sensor, allowing for precise measurements. Compartment-specific sensors were generated by further fusing specific sorting signals to PEpHluorin and PRpHluorin. Our results show that the pH of cytosol and nucleus is similar (pH 7.3 and 7.2), while peroxisomes, mitochondrial matrix, and plastidial stroma have alkaline pH. Compartments of the secretory pathway reveal a gradual acidification, spanning from pH 7.1 in the endoplasmic reticulum (ER) to pH 5.2 in the vacuole. Surprisingly, pH in the trans-Golgi network (TGN) and multivesicular body (MVB) is, with pH 6.3 and 6.2, quite similar. The inhibition of vacuolar-type H(+)-ATPase (V-ATPase) with concanamycin A (ConcA) caused drastic increase in pH in TGN and vacuole. Overall, the PEpHluorin and PRpHluorin are excellent pH sensors for visualization and quantification of pH in vivo, respectively.

  12. Effects of alkalinity on ammonia removal, carbon dioxide stripping, and system pH in semi-commercial scale water recirculating aquaculture systems operated with moving bed bioreactors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    When operating water recirculating systems (RAS) with high make-up water flushing rates in locations that have low alkalinity in the raw water, such as Norway, knowledge about the required RAS alkalinity concentration is important. Flushing RAS with make-up water containing low alkalinity washes out...

  13. Proton Transport and pH Control in Fungi.

    PubMed

    Kane, Patricia M

    2016-01-01

    Despite diverse and changing extracellular environments, fungi maintain a relatively constant cytosolic pH and numerous organelles of distinct lumenal pH. Key players in fungal pH control are V-ATPases and the P-type proton pump Pma1. These two proton pumps act in concert with a large array of other transporters and are highly regulated. The activities of Pma1 and the V-ATPase are coordinated under some conditions, suggesting that pH in the cytosol and organelles is not controlled independently. Genomic studies, particularly in the highly tractable S. cerevisiae, are beginning to provide a systems-level view of pH control, including transcriptional responses to acid or alkaline ambient pH and definition of the full set of regulators required to maintain pH homeostasis. Genetically encoded pH sensors have provided new insights into localized mechanisms of pH control, as well as highlighting the dynamic nature of pH responses to the extracellular environment. Recent studies indicate that cellular pH plays a genuine signaling role that connects nutrient availability and growth rate through a number of mechanisms. Many of the pH control mechanisms found in S. cerevisiae are shared with other fungi, with adaptations for their individual physiological contexts. Fungi deploy certain proton transport and pH control mechanisms not shared with other eukaryotes; these regulators of cellular pH are potential antifungal targets. This review describes current and emerging knowledge proton transport and pH control mechanisms in S. cerevisiae and briefly discusses how these mechanisms vary among fungi.

  14. pH distributions in spontaneous and isotransplanted rat tumours.

    PubMed Central

    Kallinowski, F.; Vaupel, P.

    1988-01-01

    Spontaneous mammary tumours of the rat with various degrees of malignancy exhibit similar tissue pH distributions. The mean pH (+/- s.d.) of dysplasia is 7.05 +/- 0.20. In benign tumours the mean pH is 6.95 +/- 0.19 and in malignant tumours it is 6.94 +/- 0.19. In contrast, tumours with the same degree of malignancy but different histologies show different pH distributions. Benign tumours with a higher percentage of fibrous tissue exhibit less acidic pH values than those with larger portions of epithelial cells (delta pH = 0.38 pH units). The pH distribution in the benign tumours is independent of the tumour wet weight up to stages of very advanced growth. In the malignant tumours, a trend towards more acidic pH values is observed as the tumour mass enlarges. However, in tissue areas within a malignant tumour with gross, long-established necrosis the pH distribution is shifted towards more alkaline pH values. The pH distributions in spontaneous rat tumours are not significantly different from those obtained in isotransplanted Yoshida sarcomas (6.87 +/- 0.21). In the Yoshida sarcomas, mean pH values do not correlate with tumour size. However, a pH gradient from the rim to the centre of the tumours is found which coincides with the development of small, disseminated necroses in the tumour centre. It is concluded that pathology-related variations of tumour pH may be more important than the mode of tumour origin or the degree of malignancy. PMID:3179183

  15. Anaerobic methanethiol degradation and methanogenic community analysis in an alkaline (pH 10) biological process for liquefied petroleum gas desulfurization.

    PubMed

    van Leerdam, Robin C; Bonilla-Salinas, Monica; de Bok, Frank A M; Bruning, H; Lens, Piet N L; Stams, Alfons J M; Janssen, Albert J H

    2008-11-01

    Anaerobic methanethiol (MT) degradation by mesophilic (30 degrees C) alkaliphilic (pH 10) communities was studied in a lab-scale Upflow Anaerobic Sludge Bed (UASB) reactor inoculated with a mixture of sediments from the Wadden Sea (The Netherlands), Soap Lake (Central Washington), and Russian soda lakes. MT degradation started after 32 days of incubation. During the first 252 days, complete degradation was achieved till a volumetric loading rate of 7.5 mmol MT/L/day, and sulfide, methane, and carbon dioxide were the main reaction products. Temporary inhibition of MT degradation occurred after MT peak loads and in the presence of dimethyl disulfide (DMDS), which is the autooxidation product of MT. From day 252 onwards, methanol was dosed to the reactor as co-substrate at a loading rate of 3-6 mmol/L/day to stimulate growth of methylotrophic methanogens. Methanol was completely degraded and also a complete MT degradation was achieved till a volumetric loading rate of 13 mmol MT/L/day (0.77 mmol MT/gVSS/day). However, from day 354 till the end of the experimental run (day 365), acetate was formed and MT was not completely degraded anymore, indicating that methanol-degrading homoacetogenic bacteria had partially outcompeted the methanogenic MT-degrading archea. The archeal community in the reactor sludge was analyzed by DGGE and sequencing of 16S rRNA genes. The methanogenic archea responsible for the degradation of MT in the reactor were related to Methanolobus oregonensis. A pure culture, named strain SODA, was obtained by serial dilutions in medium containing both trimethyl amine and dimethyl sulfide (DMS). Strain SODA degraded MT, DMS, trimethyl amine, and methanol. Flow sheet simulations revealed that for sufficient MT removal from liquefied petroleum gas, the extraction and biological degradation process should be operated above pH 9.

  16. Nitrification Enhancement through pH Control with Rotating Biological Contactors

    DTIC Science & Technology

    1981-09-01

    Inst. of Sew. Purif., 130 (1964). 31. Engel, M. S. and M. Alexander, " Growth and Autotrophic Metabolism of Nitrosomonas Europaea ," Jour. Bact., 76, 217...relative effectiveness of four different alkaline chemicals on enhancing the nitrifying process under optimum pH conditions was evaluated in Phase II...111 6.12 Relative RBC Heterotrophic Bacteria Growth Under pH Conditions from pH 7.0 to pH 8.5 ....... ............. .. 112 6.13 Batch Alkalinity

  17. The fluorescence properties of the phenylated fullerenes C 70Ph 4, C 70Ph 6, C 70Ph 8, and C 70Ph 10 in room temperature solutions

    NASA Astrophysics Data System (ADS)

    Schwell, Martin; Gustavsson, Thomas; Marguet, Sylvie; Vaissière, Benoı̂t de La; Wachter, Norbert K.; Birkett, Paul R.; Mialocq, Jean-Claude; Leach, Sydney

    2001-12-01

    The emission and excitation spectra of four phenylated [70] fullerenes, C 70Ph 4, C 70Ph 6, C 70Ph 8, and C 70Ph 10 in cyclohexane and toluene solutions have been measured. The fluorescence spectra and related excited state properties are found to depend strongly on the number of attached phenyl groups, but with no systematic trends. Quantum yields and fluorescence lifetimes were measured for C 70Ph 6, C 70Ph 8, and C 70Ph 10, allowing the determination of S1 → S0 radiative transition rates kR. It is found that kR for C 70Ph 10 is about six times larger than for the other compounds. This is consistent with measured absorbtivities for these compounds. The particular character of C 70Ph 10 is also manifested by its higher intersystem crossing rate kISC.

  18. The pH of Enceladus' ocean

    NASA Astrophysics Data System (ADS)

    Glein, Christopher R.; Baross, John A.; Waite, J. Hunter

    2015-08-01

    Saturn's moon, Enceladus, is a geologically active waterworld. The prevailing paradigm is that there is a subsurface ocean that erupts to the surface, which leads to the formation of a plume of vapor and ice above the south polar region. The chemistry of the ocean is just beginning to be understood, but is of profound geochemical and astrobiological interest. Here, we determine the pH of the ocean using a thermodynamic model of carbonate speciation. Observational data from the Cassini spacecraft are used to make a chemical model of ocean water on Enceladus. The model suggests that Enceladus' ocean is a Na-Cl-CO3 solution with an alkaline pH of ∼11-12. The dominance of aqueous NaCl is a feature that Enceladus' ocean shares with terrestrial seawater, but the ubiquity of dissolved Na2CO3 suggests that soda lakes are more analogous to the Enceladus ocean. The high pH implies that the hydroxide ion should be relatively abundant, while divalent metals should be present at low concentrations owing to buffering by carbonates and phyllosilicates on the ocean floor. Carboxyl groups in dissolved organic species would be negatively charged, while amino groups would exist predominately in the neutral form. Knowledge of the pH improves our understanding of geochemical processes in Enceladus' ocean. The high pH is interpreted to be a key consequence of serpentinization of chondritic rock, as predicted by prior geochemical reaction path models; although degassing of CO2 from the ocean may also play a role depending on the efficiency of mixing processes in the ocean. Serpentinization leads to the generation of H2, a geochemical fuel that can support both abiotic and biological synthesis of organic molecules such as those that have been detected in Enceladus' plume. Serpentinization and H2 generation should have occurred on Enceladus, like on the parent bodies of aqueously altered meteorites; but it is unknown whether these critical processes are still taking place, or if

  19. Dipstick Spot urine pH does not accurately represent 24 hour urine PH measured by an electrode

    PubMed Central

    Omar, Mohamed; Sarkissian, Carl; Jianbo, Li; Calle, Juan; Monga, Manoj

    2016-01-01

    ABSTRACT Objectives To determine whether spot urine pH measured by dipstick is an accurate representation of 24 hours urine pH measured by an electrode. Materials and Methods We retrospectively reviewed urine pH results of patients who presented to the urology stone clinic. For each patient we recorded the most recent pH result measured by dipstick from a spot urine sample that preceded the result of a 24-hour urine pH measured by the use of a pH electrode. Patients were excluded if there was a change in medications or dietary recommendations or if the two samples were more than 4 months apart. A difference of more than 0.5 pH was considered an inaccurate result. Results A total 600 patients were retrospectively reviewed for the pH results. The mean difference in pH between spot urine value and the 24 hours collection values was 0.52±0.45 pH. Higher pH was associated with lower accuracy (p<0.001). The accuracy of spot urine samples to predict 24-hour pH values of <5.5 was 68.9%, 68.2% for 5.5 to 6.5 and 35% for >6.5. Samples taken more than 75 days apart had only 49% the accuracy of more recent samples (p<0.002). The overall accuracy is lower than 80% (p<0.001). Influence of diurnal variation was not significant (p=0.588). Conclusions Spot urine pH by dipstick is not an accurate method for evaluation of the patients with urolithiasis. Patients with alkaline urine are more prone to error with reliance on spot urine pH. PMID:27286119

  20. The pH of antiseptic cleansers

    PubMed Central

    Kulthanan, Kanokvalai; Varothai, Supenya; Nuchkull, Piyavadee

    2014-01-01

    Background Daily bathing with antiseptic cleansers are proposed by some physicians as an adjunctive management of atopic dermatitis (AD). As atopic skin is sensitive, selection of cleansing products becomes a topic of concern. Objective Our purpose is to evaluate the pH of various antiseptic body cleansers to give an overview for recommendation to patients with AD. Methods Commonly bar and liquid cleansers consisted of antiseptic agents were measured for pH using pH meter and pH-indicator strips. For comparison, mild cleansers and general body cleansers were also measured. Results All cleansing bars had pH 9.8-11.3 except syndet bar that had neutral pH. For liquid cleansers, three cleansing agents had pH close to pH of normal skin, one of antiseptic cleansers, one of mild cleansers and another one of general cleansers. The rest of antiseptic cleansers had pH 8.9-9.6 while mild cleansers had pH 6.9-7.5. Syndet liquid had pH 7 and general liquid cleansers had pH 9.6. Conclusion The pH of cleanser depends on composition of that cleanser. Adding antiseptic agents are not the only factor determining variation of pH. Moreover, benefit of antiseptic properties should be considered especially in cases of infected skin lesions in the selection of proper cleansers for patients with AD. PMID:24527408

  1. Fetal scalp pH testing

    MedlinePlus

    Fetal scalp blood; Scalp pH testing; Fetal blood testing - scalp; Fetal distress - fetal scalp testing; Labor - fetal scalp testing ... a baby. In these cases, testing the scalp pH can help the doctor decide whether the fetus ...

  2. Acid loading test (pH)

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/003615.htm Acid loading test (pH) To use the sharing features on this page, please enable JavaScript. The acid loading test (pH) measures the ability of the ...

  3. Solar light (hv) and H2O2/hv photo-disinfection of natural alkaline water (pH 8.6) in a compound parabolic collector at different day periods in Sahelian region.

    PubMed

    Ndounla, J; Pulgarin, C

    2015-11-01

    The photo-disinfection of natural alkaline surface water (pH 8.6 ± 0.3) for drinking purposes was carried out under solar radiation treatments. The enteric bacteria studied were the wild total coliforms/Escherichia coli (10(4) CFU/ml) and Salmonella spp. (10(4) CFU/ml) naturally present in the water. The photo-disinfection of a 25-l water sample was carried out in a solar compound parabolic collector (CPC) in the absence and in the presence of hydrogen peroxide (H2O2). The addition of H2O2 (10 mg/L) to the sample water was sufficient to enhance the photo-disinfection and ensure an irreversible lethal action on the wild enteric bacteria contents of the sample. The inactivation kinetic of the system was significantly enhanced compared to the one carried out without H2O2 addition. The effect of the solar radiation parameters on the efficiency of the photo-disinfection were assessed. The pH has increased during the treatment in all the photo-disinfection processes (hv and H2O2/hv). The Salmonella spp strain has shown the best effective inactivate time in alkaline water than the one recorded under acidic or near-neutral conditions. The evolution of some physico-chemical parameters of the water (turbidity, NO2(-), NO3(-), NH4(+), HPO4(2-), and bicarbonate (HCO3(-))) was monitored during the treatment. Finally, the possible mechanistic process involved during the enteric bacteria inactivation was suggested.

  4. Intracellular pH and the Control of Multidrug Resistance

    NASA Astrophysics Data System (ADS)

    Simon, Sanford; Roy, Deborshi; Schindler, Melvin

    1994-02-01

    Many anticancer drugs are classified as either weak bases or molecules whose binding to cellular structures is pH dependent. Accumulation of these drugs within tumor cells should be affected by transmembrane pH gradients. Indeed, development of multidrug resistance (MDR) in tumor cells has been correlated with an alkaline shift of cytosolic pH. To examine the role of pH in drug partitioning, the distribution of two drugs, doxorubicin and daunomycin, was monitored in fibroblasts and myeloma cells. In both cell types the drugs rapidly accumulated within the cells. The highest concentrations were measured in the most acidic compartments-e.g., lysosomes. Modifying the cellular pH in drug-sensitive cells to mimic reported shifts in MDR caused an immediate change in the cellular drug concentration. Drug accumulation was enhanced by acidic shifts and reversed by alkaline shifts. All of these effects were rapid and reversible. These results demonstrate that the alkaline shift observed in MDR is sufficient to prevent the accumulation of chemotherapeutic drugs independent of active drug efflux.

  5. Intracellular pH and the control of multidrug resistance.

    PubMed Central

    Simon, S; Roy, D; Schindler, M

    1994-01-01

    Many anticancer drugs are classified as either weak bases or molecules whose binding to cellular structures is pH dependent. Accumulation of these drugs within tumor cells should be affected by transmembrane pH gradients. Indeed, development of multidrug resistance (MDR) in tumor cells has been correlated with an alkaline shift of cytosolic pH. To examine the role of pH in drug partitioning, the distribution of two drugs, doxorubicin and daunomycin, was monitored in fibroblasts and myeloma cells. In both cell types the drugs rapidly accumulated within the cells. The highest concentrations were measured in the most acidic compartments--e.g., lysosomes. Modifying the cellular pH in drug-sensitive cells to mimic reported shifts in MDR caused an immediate change in the cellular drug concentration. Drug accumulation was enhanced by acidic shifts and reversed by alkaline shifts. All of these effects were rapid and reversible. These results demonstrate that the alkaline shift observed in MDR is sufficient to prevent the accumulation of chemotherapeutic drugs independent of active drug efflux. Images PMID:8302842

  6. Variation of ocean pH in the Indonesia waters

    NASA Astrophysics Data System (ADS)

    Putri, Mutiara Rachmat; Setiawan, Agus; Safitri, Mediana

    2015-09-01

    The variation of ocean acidity (pH) in the Indonesia waters is strongly influenced by monsoon. Since the climate change tends to potentially change monsoonal variation over the Indonesian region, it will give also implication to the ocean pH variation. Moreover, changes of ocean pH will give effects to the marine lifes and their environment. In order to investigate this issue, we tried to calculate monthly variation of sea surface pH in the Indonesia waters based on monthly average temperature and salinity over past 18 years data. Temperature and salinity data used in this study were taken from the hydrodynamic model of Hamburg Shelf Ocean Model (HAMSOM), while alkalinity and dissolved inorganic carbon (DIC) were from World Ocean Atlas 2009 (WOA 2009). Algorithm from Ocean Carbon Model Intercomparison Project-version.3 (OCMIP-3) was used to calculate the pH. The estimation results indicate that pH variation in the Indonesia waters changes insignificantly over 18 years. El Nino Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) contribute to physical changes of seawater, but did not affect the pH significantly. The average pH of seawater is higher during northwest monsoon than during southeast monsoon.

  7. Functional photoacoustic microscopy of pH

    NASA Astrophysics Data System (ADS)

    Chatni, M. Rameez; Yao, Junjie; Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin I.; Wang, Lihong V.

    2012-02-01

    pH is a tightly regulated indicator of metabolic activity. In mammalian systems, imbalance of pH regulation may result from or result in serious illness. Even though the regulation system of pH is very robust, tissue pH can be altered in many diseases such as cancer, osteoporosis and diabetes mellitus. Traditional high-resolution optical imaging techniques, such as confocal microscopy, routinely image pH in cells and tissues using pH sensitive fluorescent dyes, which change their fluorescence properties with the surrounding pH. Since strong optical scattering in biological tissue blurs images at greater depths, high-resolution pH imaging is limited to penetration depths of 1mm. Here, we report photoacoustic microscopy (PAM) of commercially available pH-sensitive fluorescent dye in tissue phantoms. Using both opticalresolution photoacoustic microscopy (OR-PAM), and acoustic resolution photoacoustic microscopy (AR-PAM), we explored the possibility of recovering the pH values in tissue phantoms. In this paper, we demonstrate that PAM was capable of recovering pH values up to a depth of 2 mm, greater than possible with other forms of optical microscopy.

  8. Extracellular pH modulates GABAergic neurotransmission in rat hypothalamus.

    PubMed

    Chen, Z L; Huang, R Q

    2014-06-20

    Changes in extracellular pH have a modulatory effect on GABAA receptor function. It has been reported that pH sensitivity of the GABA receptor is dependent on subunit composition and GABA concentration. Most of previous investigations focused on GABA-evoked currents, which only reflect the postsynaptic receptors. The physiological relevance of pH modulation of GABAergic neurotransmission is not fully elucidated. In the present studies, we examined the influence of extracellular pH on the GABAA receptor-mediated inhibitory neurotransmission in rat hypothalamic neurons. The inhibitory postsynaptic currents (IPSCs), tonic currents, and the GABA-evoked currents were recorded with whole-cell patch techniques on the hypothalamic slices from Sprague-Dawley rats at 15-26 postnatal days. The amplitude and frequency of spontaneous GABA IPSCs were significantly increased while the external pH was changed from 7.3 to 8.4. In the acidic pH (6.4), the spontaneous GABA IPSCs were reduced in amplitude and frequency. The pH induced changes in miniature GABA IPSCs (mIPSCs) similar to that in spontaneous IPSCs. The pH effect on the postsynaptic GABA receptors was assessed with exogenously applied varying concentrations of GABA. The tonic currents and the currents evoked by sub-saturating concentration of GABA ([GABA]) (10 μM) were inhibited by acidic pH and potentiated by alkaline pH. In contrast, the currents evoked by saturating [GABA] (1mM) were not affected by pH changes. We also investigated the influence of pH buffers and buffering capacity on pH sensitivity of GABAA receptors on human recombinant α1β2γ2 GABAA receptors stably expressed in HEK 293 cells. The pH influence on GABAA receptors was similar in HEPES- and MES-buffered media, and not dependent on protonated buffers, suggesting that the observed pH effect on GABA response is a specific consequence of changes in extracellular protons. Our data suggest that the hydrogen ions suppress the GABAergic neurotransmission

  9. Improved reliability of pH measurements.

    PubMed

    Spitzer, Petra; Werner, Barbara

    2002-11-01

    Measurements of pH are performed on a large scale at laboratory level, and in industry. To meet the quality-control requirements and other technical specifications there is a need for traceability in measurement results. The prerequisite for the international acceptance of analytical data is reliability. To measure means to compare. Comparability entails use of recognised references to which the standard buffer solutions used for calibration of pH meter-electrode assemblies can be traced. The new recommendation on the measurement of pH recently published as a provisional document by the International Union on Pure and Applied Chemistry (IUPAC) enables traceability for measured pH values to a conventional reference frame which is recognised world-wide. The primary method for pH will be described. If analytical data are to be accepted internationally it is necessary to demonstrate the equivalence of the national traceability structures, including national measurement standards. For the first time key comparisons for pH have been performed by the Consultative Committee for Amount of Substance (CCQM, set up by the International Bureau of Weights and Measures, BIPM) to assess the equivalence of the national measurement procedures used to determine the pH of primary standard buffer solutions. The results of the first key comparison on pH CCQM-K9, and other international initiatives to improve the consistency of the results of measurement for pH, are reported.

  10. pH Meter probe assembly

    DOEpatents

    Hale, C.J.

    1983-11-15

    An assembly for mounting a pH probe in a flowing solution, such as a sanitary sewer line, which prevents the sensitive glass portion of the probe from becoming coated with grease, oil, and other contaminants, whereby the probe gives reliable pH indication over an extended period of time. The pH probe assembly utilizes a special filter media and a timed back-rinse feature for flushing clear surface contaminants of the filter. The flushing liquid is of a known pH and is utilized to check performance of the probe. 1 fig.

  11. pH Meter probe assembly

    DOEpatents

    Hale, Charles J.

    1983-01-01

    An assembly for mounting a pH probe in a flowing solution, such as a sanitary sewer line, which prevents the sensitive glass portion of the probe from becoming coated with grease, oil, and other contaminants, whereby the probe gives reliable pH indication over an extended period of time. The pH probe assembly utilizes a special filter media and a timed back-rinse feature for flushing clear surface contaminants of the filter. The flushing liquid is of a known pH and is utilized to check performance of the probe.

  12. A variable stoichiometry model for pH homeostasis in bacteria.

    PubMed Central

    Macnab, R M; Castle, A M

    1987-01-01

    The composition of the proton-motive force of a hypothetical bacterial cell of wide pH tolerance is analyzed according to a model whereby the electron transport chain and various proton-linked sodium and potassium ion transporting modes are responsible for the development of the membrane potential and the chemical potentials of the three cations. Simultaneous use of two or more modes employing the same metal cation, but at a different stoichiometric ratio with respect to protons, produces nonintegral stoichiometry; the modes could represent either different devices or different states of a single device. Cycling of the cation, driven by proton-motive force, results. The relative conductances of the various modes are postulated to be pH-dependent. The pattern of potentials that results is qualitatively in accord with current knowledge and may reflect the mechanism of pH homeostasis in bacteria. The membrane potential is outwardly directed (positive inside) at extremely acid pH, becoming inwardly directed as the pH increases; the pH gradient across the membrane is large and inwardly directed (alkaline inside) at acid pH, becoming smaller and eventually inverting at alkaline pH values; the transmembrane potassium gradient is outwardly directed (high concentration inside) at all pH values; the transmembrane sodium gradient is inwardly directed at all pH values, following the pH gradient from acid through neutral pH, but then diverging at alkaline pH. PMID:3676443

  13. Low pH increases the yield of exosome isolation.

    PubMed

    Ban, Jae-Jun; Lee, Mijung; Im, Wooseok; Kim, Manho

    2015-05-22

    Exosomes are the extracellular vesicles secreted by various cells. Exosomes mediate intercellular communication by delivering a variety of molecules between cells. Cancer cell derived exosomes seem to be related with tumor progression and metastasis. Tumor microenvironment is thought to be acidic and this low pH controls exosome physiology, leading to tumor progression. Despite the importance of microenvironmental pH on exosome, most of exosome studies have been performed without regard to pH. Therefore, the difference of exosome stability and yield of isolation by different pH need to be studied. In this research, we investigated the yield of total exosomal protein and RNA after incubation in acidic, neutral and alkaline conditioned medium. Representative exosome markers were investigated by western blot after incubation of exosomes in different pH. As a result, the concentrations of exosomal protein and nucleic acid were significantly increased after incubation in the acidic medium compared with neutral medium. The higher levels of exosome markers including CD9, CD63 and HSP70 were observed after incubation in an acidic environment. On the other hand, no exosomal protein, exosomal RNA and exosome markers have been detected after incubation in an alkaline condition. In summary, our results indicate that the acidic condition is the favorable environment for existence and isolation of exosomes.

  14. pH [Measure of Acidity].

    ERIC Educational Resources Information Center

    Henderson, Paula

    This autoinstructional program deals with the study of the pH of given substances by using litmus and hydrion papers. It is a learning activity directed toward low achievers involved in the study of biology at the secondary school level. The time suggested for the unit is 25-30 minutes (plus additional time for further pH testing). The equipment…

  15. Middle School and pH?

    ERIC Educational Resources Information Center

    Herricks, Susan

    2007-01-01

    A local middle school requested that the Water Center of Advanced Materials for Purification of Water With Systems (WaterCAMPWS), a National Science Foundation Science and Technology Center, provide an introduction to pH for their seventh-grade water-based service learning class. After sorting through a multitude of information about pH, a…

  16. Inexpensive and Disposable pH Electrodes

    ERIC Educational Resources Information Center

    Goldcamp, Michael J.; Conklin, Alfred; Nelson, Kimberly; Marchetti, Jessica; Brashear, Ryan; Epure, Emily

    2010-01-01

    Inexpensive electrodes for the measurement of pH have been constructed using the ionophore tribenzylamine for sensing H[superscript +] concentrations. Both traditional liquid-membrane electrodes and coated-wire electrodes have been constructed and studied, and both exhibit linear, nearly Nernstian responses to changes in pH. Measurements of pH…

  17. Determination Of Ph Including Hemoglobin Correction

    DOEpatents

    Maynard, John D.; Hendee, Shonn P.; Rohrscheib, Mark R.; Nunez, David; Alam, M. Kathleen; Franke, James E.; Kemeny, Gabor J.

    2005-09-13

    Methods and apparatuses of determining the pH of a sample. A method can comprise determining an infrared spectrum of the sample, and determining the hemoglobin concentration of the sample. The hemoglobin concentration and the infrared spectrum can then be used to determine the pH of the sample. In some embodiments, the hemoglobin concentration can be used to select an model relating infrared spectra to pH that is applicable at the determined hemoglobin concentration. In other embodiments, a model relating hemoglobin concentration and infrared spectra to pH can be used. An apparatus according to the present invention can comprise an illumination system, adapted to supply radiation to a sample; a collection system, adapted to collect radiation expressed from the sample responsive to the incident radiation; and an analysis system, adapted to relate information about the incident radiation, the expressed radiation, and the hemoglobin concentration of the sample to pH.

  18. Endoscopic sensing of alveolar pH

    PubMed Central

    Choudhury, D.; Tanner, M. G.; McAughtrie, S.; Yu, F.; Mills, B.; Choudhary, T. R.; Seth, S.; Craven, T. H.; Stone, J. M.; Mati, I. K.; Campbell, C. J.; Bradley, M.; Williams, C. K. I.; Dhaliwal, K.; Birks, T. A.; Thomson, R. R.

    2016-01-01

    Previously unobtainable measurements of alveolar pH were obtained using an endoscope-deployable optrode. The pH sensing was achieved using functionalized gold nanoshell sensors and surface enhanced Raman spectroscopy (SERS). The optrode consisted of an asymmetric dual-core optical fiber designed for spatially separating the optical pump delivery and signal collection, in order to circumvent the unwanted Raman signal generated within the fiber. Using this approach, we demonstrate a ~100-fold increase in SERS signal-to-fiber background ratio, and demonstrate multiple site pH sensing with a measurement accuracy of ± 0.07 pH units in the respiratory acini of an ex vivo ovine lung model. We also demonstrate that alveolar pH changes in response to ventilation. PMID:28101415

  19. Metal/Metal Oxide Differential Electrode pH Sensors

    NASA Technical Reports Server (NTRS)

    West, William; Buehler, Martin; Keymeulen, Didier

    2007-01-01

    Solid-state electrochemical sensors for measuring the degrees of acidity or alkalinity (in terms of pH values) of liquid solutions are being developed. These sensors are intended to supplant older electrochemical pH sensors that include glass electrode structures and reference solutions. The older sensors are fragile and subject to drift. The present developmental solid-state sensors are more rugged and are expected to be usable in harsh environments. The present sensors are based on a differential-electrode measurement principle. Each sensor includes two electrodes, made of different materials, in equilibrium with the solution of interest.

  20. Molecular Basis of pH and Ca2+ Regulation of Aquaporin Water Permeability

    PubMed Central

    Németh-Cahalan, Karin L.; Kalman, Katalin; Hall, James E.

    2004-01-01

    Aquaporins facilitate the diffusion of water across cell membranes. We previously showed that acid pH or low Ca2+ increase the water permeability of bovine AQP0 expressed in Xenopus oocytes. We now show that external histidines in loops A and C mediate the pH dependence. Furthermore, the position of histidines in different members of the aquaporin family can “tune” the pH sensitivity toward alkaline or acid pH ranges. In bovine AQP0, replacement of His40 in loop A by Cys, while keeping His122 in loop C, shifted the pH sensitivity from acid to alkaline. In the killifish AQP0 homologue, MIPfun, with His at position 39 in loop A, alkaline rather than acid pH increased water permeability. Moving His39 to His40 in MIPfun, to mimic bovine AQP0 loop A, shifted the pH sensitivity back to the acid range. pH regulation was also found in two other members of the aquaporin family. Alkaline pH increased the water permeability of AQP4 that contains His at position 129 in loop C. Acid and alkaline pH sensitivity was induced in AQP1 by adding histidines 48 (in loop A) and 130 (in loop C). We conclude that external histidines in loops A and C that span the outer vestibule contribute to pH sensitivity. In addition, we show that when AQP0 (bovine or killifish) and a crippled calmodulin mutant were coexpressed, Ca2+ sensitivity was lost but pH sensitivity was maintained. These results demonstrate that Ca2+ and pH modulation are separable and arise from processes on opposite sides of the membrane. PMID:15078916

  1. Exhaled breath condensate pH assays.

    PubMed

    Davis, Michael D; Hunt, John

    2012-08-01

    Airway pH is central to the physiologic function and cellular biology of the airway. The causes of airway acidification include (1) hypopharyngeal gastric acid reflux with or without aspiration through the vocal cords, (2) inhalation of acid fog or gas (such as chlorine), and (3) intrinsic airway acidification caused by altered airway pH homeostasis in infectious and inflammatory disease processes. The recognition that relevant airway pH deviations occur in lung diseases is opening doors to new simple and inexpensive therapies. This recognition has resulted partly from the ability to use exhaled breath condensate as a window on airway acid-base balance.

  2. Coral calcifying fluid pH is modulated by seawater carbonate chemistry not solely seawater pH.

    PubMed

    Comeau, S; Tambutté, E; Carpenter, R C; Edmunds, P J; Evensen, N R; Allemand, D; Ferrier-Pagès, C; Tambutté, S; Venn, A A

    2017-01-25

    Reef coral calcification depends on regulation of pH in the internal calcifying fluid (CF) in which the coral skeleton forms. However, little is known about calcifying fluid pH (pHCF) regulation, despite its importance in determining the response of corals to ocean acidification. Here, we investigate pHCF in the coral Stylophora pistillata in seawater maintained at constant pH with manipulated carbonate chemistry to alter dissolved inorganic carbon (DIC) concentration, and therefore total alkalinity (AT). We also investigate the intracellular pH of calcifying cells, photosynthesis, respiration and calcification rates under the same conditions. Our results show that despite constant pH in the surrounding seawater, pHCF is sensitive to shifts in carbonate chemistry associated with changes in [DIC] and [AT], revealing that seawater pH is not the sole driver of pHCF Notably, when we synthesize our results with published data, we identify linear relationships of pHCF with the seawater [DIC]/[H(+)] ratio, [AT]/ [H(+)] ratio and [[Formula: see text

  3. Stabilization of Mercury in High pH Tank Sludges

    SciTech Connect

    Spence, R.; Barton, J.

    2003-02-24

    DOE complex contains many tank sludges contaminated with mercury. The high pH of these tank sludges typically fails to stabilize the mercury, resulting in these radioactive wastes also being characteristically hazardous or mixed waste. The traditional treatment for soluble inorganic mercury species is precipitation as insoluble mercuric sulfide. Sulfide treatment and a commercial mercury-stabilizing product were tested on surrogate sludges at various alkaline pH values. Neither the sulfide nor the commercial product stabilized the mercury sufficiently at the high pH of the tank sludges to pass the Toxicity Characteristic Leach Procedure (TCLP) treatment standards of the Resource Conservation and Recovery Act (RCRA). The commercial product also failed to stabilize the mercury in samples of the actual tank sludges.

  4. Molecular Components of the Neurospora crassa pH Signaling Pathway and Their Regulation by pH and the PAC-3 Transcription Factor

    PubMed Central

    Virgilio, Stela; Cupertino, Fernanda Barbosa; Bernardes, Natália Elisa; Freitas, Fernanda Zanolli; Takeda, Agnes Alessandra Sekijima; Fontes, Marcos Roberto de Mattos; Bertolini, Maria Célia

    2016-01-01

    Environmental pH induces a stress response triggering a signaling pathway whose components have been identified and characterized in several fungi. Neurospora crassa shares all six components of the Aspergillus nidulans pH signaling pathway, and we investigate here their regulation during an alkaline pH stress response. We show that the N. crassa pal mutant strains, with the exception of Δpal-9, which is the A. nidulans palI homolog, exhibit low conidiation and are unable to grow at alkaline pH. Moreover, they accumulate the pigment melanin, most likely via regulation of the tyrosinase gene by the pH signaling components. The PAC-3 transcription factor binds to the tyrosinase promoter and negatively regulates its gene expression. PAC-3 also binds to all pal gene promoters, regulating their expression at normal growth pH and/or alkaline pH, which indicates a feedback regulation of PAC-3 in the pal gene expression. In addition, PAC-3 binds to the pac-3 promoter only at alkaline pH, most likely influencing the pac-3 expression at this pH suggesting that the activation of PAC-3 in N. crassa results from proteolytic processing and gene expression regulation by the pH signaling components. In N. crassa, PAC-3 is proteolytically processed in a single cleavage step predominately at alkaline pH; however, low levels of the processed protein can be observed at normal growth pH. We also demonstrate that PAC-3 preferentially localizes in the nucleus at alkaline pH stress and that the translocation may require the N. crassa importin-α since the PAC-3 nuclear localization signal (NLS) has a strong in vitro affinity with importin-α. The data presented here show that the pH signaling pathway in N. crassa shares all the components with the A. nidulans and S. cerevisiae pathways; however, it exhibits some properties not previously described in either organism. PMID:27557053

  5. Molecular Components of the Neurospora crassa pH Signaling Pathway and Their Regulation by pH and the PAC-3 Transcription Factor.

    PubMed

    Virgilio, Stela; Cupertino, Fernanda Barbosa; Bernardes, Natália Elisa; Freitas, Fernanda Zanolli; Takeda, Agnes Alessandra Sekijima; Fontes, Marcos Roberto de Mattos; Bertolini, Maria Célia

    2016-01-01

    Environmental pH induces a stress response triggering a signaling pathway whose components have been identified and characterized in several fungi. Neurospora crassa shares all six components of the Aspergillus nidulans pH signaling pathway, and we investigate here their regulation during an alkaline pH stress response. We show that the N. crassa pal mutant strains, with the exception of Δpal-9, which is the A. nidulans palI homolog, exhibit low conidiation and are unable to grow at alkaline pH. Moreover, they accumulate the pigment melanin, most likely via regulation of the tyrosinase gene by the pH signaling components. The PAC-3 transcription factor binds to the tyrosinase promoter and negatively regulates its gene expression. PAC-3 also binds to all pal gene promoters, regulating their expression at normal growth pH and/or alkaline pH, which indicates a feedback regulation of PAC-3 in the pal gene expression. In addition, PAC-3 binds to the pac-3 promoter only at alkaline pH, most likely influencing the pac-3 expression at this pH suggesting that the activation of PAC-3 in N. crassa results from proteolytic processing and gene expression regulation by the pH signaling components. In N. crassa, PAC-3 is proteolytically processed in a single cleavage step predominately at alkaline pH; however, low levels of the processed protein can be observed at normal growth pH. We also demonstrate that PAC-3 preferentially localizes in the nucleus at alkaline pH stress and that the translocation may require the N. crassa importin-α since the PAC-3 nuclear localization signal (NLS) has a strong in vitro affinity with importin-α. The data presented here show that the pH signaling pathway in N. crassa shares all the components with the A. nidulans and S. cerevisiae pathways; however, it exhibits some properties not previously described in either organism.

  6. Coping with PH over the Long Term

    MedlinePlus

    ... Process: Some First Steps Adoption Success Story Watch Classroom Recordings Empowered Patient Online Toolkit Tab 1: Very ... Kathy Groebner Education Programs Patients and Caregivers PHA Classroom PHA on the Road: PH Patients and Families ...

  7. Effect of two mouthwashes on salivary ph.

    PubMed

    Belardinelli, Paola A; Morelatto, Rosana A; Benavidez, Tomás E; Baruzzi, Ana M; López de Blanc, Silvia A

    2014-01-01

    To analyze the effect of two mouthwashes on salivary pH and correlate it with age, buffer capacity and saliva flow rate in healthy volunteers, a crossover phase IV clinical study involving three age-based groups was designed. Two commercial mouthwashes (MW), Cool Mint ListerineR (MWa) and Periobacter R (MWb) were used. The unstimulated saliva of each individual was first characterized by measuring flow rate, pH, and buffer capacity. Salivary pH was evaluated before rinsing with a given MW, immediately after rinsing, 5 minutes later, and then every 10 min (at 15, 25, 35 min) until the baseline pH was recovered. Paired t-test, ANOVA with a randomized block design, and Pearson correlation tests were used. Averages were 0.63 mL/min, 7.06, and 0.87 for flow rate, pH, and buffer capacity, respectively. An immediate significant increase in salivary pH was observed after rinsing, reaching average values of 7.24 (MWb) and 7.30 (MWa), which declined to an almost stable value 15 minutes. The great increase in salivary pH, after MW use shows that saliva is a dynamic system, and that the organism is capable of responding to a stimulus with changes in its composition. It is thus evident that pH of the external agent alone is not a good indicator for its erosive potential because biological systems tend to neutralize it. The results of this study enhance the importance of in vivo measurements and reinforce the concept of the protective action of saliva.

  8. [Photohemolysis sensitized by psoralen: dependence on pH].

    PubMed

    Potapenko, A Ia; Belichenko, I V; Mamedov, I S; Zhuravel', N N; Kiagova, A A; Beijersbergen van Henegouwen, G M J; De Vries, Ch

    2007-01-01

    The effect of pH on the hemolysis of erythrocytes photosensitized (366 nm, 23 Wt/m2) by psoralen has been studied. The dependence of the photohemolysis rate (V) on irradiation dose (D) was described by the equation V = Vo + kD, where Vo is the rate of hemolysis without irradiation (dark), and k is the constant. The index of the power at dose x was approximately equal to 2, and its value did not change as the pH of the erythrocyte suspension was changed. It was found that changes in pH led to a sharp change in the value of coefficient k and correspondingly V. The lowest rate of photohemolysis was observed in the pH range from 8.0 to 8.4. As pH was changed from 3.4 to 9.0 or from 8.0 to 7.4, the V value increased approximately twofold. At pH below 7.4, an abrupt increase (approximately fourfold) in V was observed, with the pK value being equal to 7.3. The psoralen molecule lacks titratable acidic and basic groups; therefore, the effects of pH can hardly be assigned to changes in the photophysical properties of the sensitizer. The increase in V in the alkaline region is prohably related to the acceleration of photooxidation of reduced glutathione, whereas the jump of V at pH of about 7.3 may be due to the titration of the product of psoralen photooxidation. The latter assumption is confirmed by the data of hign performance liquid chromatography. In these experiments, psoralen was oxidized in ethanol and mixed with the phosphate buffer at different pH values followed by a qualitative and quantitative analysis by high performance liquid chromatography of photoproducts. Several photoproducts of psoralen have been identified whose content depended on pH. The curve of titration of one photoproduct was similar in shape to the pH dependence of psoralen-photosensitized hemolysis.

  9. Relation of pH to toxicity of lampricide TFM in the laboratory

    USGS Publications Warehouse

    Bills, T.D.; Marking, L.L.; Howe, G.E.; Rach, J.J.

    1988-01-01

    In the control of larval sea lamprey (Petromyzon marinus ) with 3-trifluoromethyl-4-nitrophenol (TFM) in tributaries of the Great Lakes, occasional kills of other fishes have caused concern about the effects of the chemical on non-target organisms. Stream treatment rates have been based on previous application rates, alkalinity measurements, results of on-site toxicity tests, or combinations of these. Laboratory studies in 1987 showed that pH is the primary factor that affects the toxicity of TFM (the lower the pH, the greater the toxicity): even small changes in pH alter the toxicity, whereas substantial changes in alkalinity have little effect. In 12-h exposures, the 96-h LC50 for TFM to rainbow trout (Salmo gairdneri ) ranged from about 0.9 mg/L at pH 6.5 to > 100 mg/L at pH 9.5, but (at pH 7.5) the LC50's differed little at total alkalinities of about 18 mg/L and 207 mg/L. Decreases in pH as small as 0.5 pH unit caused nontoxic solutions to become toxic to rainbow trout. Some kills of non-target fish during stream treatments were reportedly caused by decreases in pH, and (conversely) that some stream treatments for sea lampreys were ineffective because pH increased.

  10. A ph sensor based on a flexible substrate

    NASA Astrophysics Data System (ADS)

    Huang, Wen-Ding

    pH sensor is an essential component used in many chemical, food, and bio-material industries. Conventional glass electrodes have been used to construct pH sensors, however, have some disadvantages. Glass electrodes are easily affected by alkaline or HF solution, they require a high input impedance pH meter, they often exhibit a sluggish response. In some specific applications, it is also difficult to use glass electrodes for in vivo biomedical or food monitoring applications due to the difficulty of size miniaturization, planarization and polymerization based on current manufacturing technologies. In this work, we have demonstrated a novel flexible pH sensor based on low-cost sol-gel fabrication process of iridium oxide (IrOx) sensing film (IROF). A pair of flexible miniature IrOx/AgCl electrode generated the action potential from the solution by electrochemical mechanism to obtain the pH level of the reagent. The fabrication process including sol-gel, thermal oxidation, and the electro-plating process of the silver chloride (AgCl) reference electrode were reported in the work. The IrOx film was verified and characterized using electron dispersive analysis (EDAX), scanning electron microscope (SEM), and x-ray diffraction (XRD). The flexible pH sensor's performance and characterization have been investigated with different testing parameters such as sensitivity, response time, stability, reversibility, repeatability, selectivity and temperature dependence. The flexible IrOx pH sensors exhibited promising sensing performance with a near-Nernstian response of sensitivity which is between --51.1mV/pH and --51.7mV/pH in different pH levels ranging from 1.5 to 12 at 25°C. Two applications including gastroesophageal reflux disease (GERD) diagnosis and food freshness wireless monitoring using our micro-flexible IrOx pH sensors were demonstrated. For the GERD diagnosing system, we embedded the micro flexible pH sensor on a 1.2cmx3.8cm of the capsule size of wireless sensor

  11. Effects of pH on aquatic biodegradation processes

    NASA Astrophysics Data System (ADS)

    Krachler, R. F.; Krachler, R.; Stojanovic, A.; Wielander, B.; Herzig, A.

    2009-01-01

    To date, little is known about the pH-stimulated mineralization of organic matter in aquatic environments. In this study, we investigated biodegradation processes in alkaline waters. Study site is a large shallow soda lake in Central Europe (Neusiedler See/Ferto). The decomposition rate of plant litter was measured as a function of pH by incubating air-saturated lake-water samples in contact with Phragmites litter (leaves) from the littoral vegetation. All samples showed high decomposition rates (up to 32% mass loss within 35 days) and a characteristic two-step degradation mechanism. During the degradation process, the solid plant litter was dissolved forming humic colloids. Subsequently, the humic colloids were mineralized to CO2 in the water column. The decomposition rate was linearly related to pH. Increasing pH values accelerated significantly the leaching of humic colloids as well as the final degradation process. The observed two-step mechanism controls the wetland/lake/air carbon fluxes, since large quantities of humic colloids are currently produced in the reed belt, exported through wind-driven circulations and incorporated into the open lake foodweb. At present, the lake is rapidly shrinking due to peat deposition in the littoral zone, whereas it has been resistant to silting-up processes for thousands of years. In order to investigate the cause of this abrupt change, the chemical composition of the lake-water was measured during 1995-2007. A thorough analysis of these data revealed that major lake-water discharges through the lake's artificial outlet channel led to a decline in salinity and alkalinity. According to our estimates, the lake's original salinity and alkalinity was 70-90% higher compared to the present conditions, with the consequence of substantially lower pH values in the present lake. The observed pH dependence of reed litter biodegradation rates points to a causal connection between low pH values and accumulation of peat in the lake basin

  12. pH sensitivity of ammonium transport by Rhbg

    PubMed Central

    Abdulnour-Nakhoul, Solange M.; Schmidt, Eric; Doetjes, Rienk; Rabon, Edd; Hamm, L. Lee

    2010-01-01

    Rhbg is a membrane glycoprotein that is involved in NH3/NH4+ transport. Several models have been proposed to describe Rhbg, including an electroneutral NH4+/H+ exchanger, a uniporter, an NH4+ channel, or even a gas channel. In this study, we characterized the pH sensitivity of Rhbg expressed in Xenopus oocytes. We used two-electrode voltage clamp and ion-selective microelectrodes to measure NH4+-induced [and methyl ammonium (MA+)] currents and changes in intracellular pH (pHi), respectively. In oocytes expressing Rhbg, 5 mM NH4Cl (NH3/NH4+) at extracellular pH (pHo) of 7.5 induced an inward current, decreased pHi, and depolarized the cell. Raising pHo to 8.2 significantly enhanced the NH4+-induced current and pHi changes, whereas decreasing bath pH to 6.5 inhibited these changes. Lowering pHi (decreased by butyrate) also inhibited the NH4+-induced current and pHi decrease. In oocytes expressing Rhbg, 5 mM methyl amine hydrochloride (MA/MA+), often used as an NH4Cl substitute, induced an inward current, a pHi increase (not a decrease), and depolarization of the cell. Exposing the oocyte to MA/MA+ at alkaline bath pH (8.2) enhanced the MA+-induced current, whereas lowering bath pH to 6.5 inhibited the MA+ current completely. Exposing the oocyte to MA/MA+ at low pHi abolished the MA+-induced current and depolarization; however, pHi still increased. These data indicate that 1) transport of NH4+ and MA/MA+ by Rhbg is pH sensitive; 2) electrogenic NH4+ and MA+ transport are stimulated by alkaline pHo but inhibited by acidic pHi or pHo; and 3) electroneutral transport of MA by Rhbg is likely but is less sensitive to pH changes. PMID:20810915

  13. pH sensitivity of ammonium transport by Rhbg.

    PubMed

    Nakhoul, Nazih L; Abdulnour-Nakhoul, Solange M; Schmidt, Eric; Doetjes, Rienk; Rabon, Edd; Hamm, L Lee

    2010-12-01

    Rhbg is a membrane glycoprotein that is involved in NH(3)/NH(4)(+) transport. Several models have been proposed to describe Rhbg, including an electroneutral NH(4)(+)/H(+) exchanger, a uniporter, an NH(4)(+) channel, or even a gas channel. In this study, we characterized the pH sensitivity of Rhbg expressed in Xenopus oocytes. We used two-electrode voltage clamp and ion-selective microelectrodes to measure NH(4)(+)-induced [and methyl ammonium (MA(+))] currents and changes in intracellular pH (pH(i)), respectively. In oocytes expressing Rhbg, 5 mM NH(4)Cl (NH(3)/NH(4)(+)) at extracellular pH (pH(o)) of 7.5 induced an inward current, decreased pH(i), and depolarized the cell. Raising pH(o) to 8.2 significantly enhanced the NH(4)(+)-induced current and pH(i) changes, whereas decreasing bath pH to 6.5 inhibited these changes. Lowering pH(i) (decreased by butyrate) also inhibited the NH(4)(+)-induced current and pH(i) decrease. In oocytes expressing Rhbg, 5 mM methyl amine hydrochloride (MA/MA(+)), often used as an NH(4)Cl substitute, induced an inward current, a pH(i) increase (not a decrease), and depolarization of the cell. Exposing the oocyte to MA/MA(+) at alkaline bath pH (8.2) enhanced the MA(+)-induced current, whereas lowering bath pH to 6.5 inhibited the MA(+) current completely. Exposing the oocyte to MA/MA(+) at low pH(i) abolished the MA(+)-induced current and depolarization; however, pH(i) still increased. These data indicate that 1) transport of NH(4)(+) and MA/MA(+) by Rhbg is pH sensitive; 2) electrogenic NH(4)(+) and MA(+) transport are stimulated by alkaline pH(o) but inhibited by acidic pH(i) or pH(o); and 3) electroneutral transport of MA by Rhbg is likely but is less sensitive to pH changes.

  14. Effect of initial solution pH on photo-induced reductive decomposition of perfluorooctanoic acid.

    PubMed

    Qu, Yan; Zhang, Chao-Jie; Chen, Pei; Zhou, Qi; Zhang, Wei-Xian

    2014-07-01

    The effects of initial solution pH on the decomposition of perfluorooctanoic acid (PFOA) with hydrated electrons as reductant were investigated. The reductive decomposition of PFOA depends strongly on the solution pH. In the pH range of 5.0-10.0, the decomposition and defluorination rates of PFOA increased with the increase of the initial solution pH. The rate constant was 0.0295 min(-1) at pH 10.0, which was more than 49.0 times higher than that at pH 5.0. Higher pH also inhibits the generation of toxic intermediates during the PFOA decomposition. For example, the short-chain PFCAs reached a lower maximum concentration in shorter reaction time as pH increasing. The peak areas of accumulated fluorinated and iodinated hydrocarbons detected by GC/MS under acidic conditions were nearly 10-100 times more than those under alkaline conditions. In short, alkaline conditions were more favorable for photo-induced reduction of PFOA as high pH promoted the decomposition of PFOA and inhibited the accumulation of intermediate products. The concentration of hydrated electron, detected by laser flash photolysis, increased with the increase of the initial pH. This was the main reason why the decomposition of PFOA in the UV-KI system depended strongly on the initial pH.

  15. Interrelationship between growth factor-induced pH changes and intracellular Ca/sup 2 +/

    SciTech Connect

    Ives, H.E.; Daniel, T.O.

    1987-04-01

    Many mitogens cause rapid changes in intracellular pH and Ca/sup 2 +/. The authors studied the patterns of pH and Ca/sup 2 +/ changes after exposure of murine fibroblasts to platelet-derived growth factor (PDGF), bombesin, phorbol 12-myristate 13-acetate (PMA), and the vasoactive peptide bradykinin. Intracellular pH and Ca/sup 2 +/ were measured by using the fluorescent dyes 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein and fura-2. Three distinct patterns of intracellular pH change were observed. (i) PDGF and bombesin caused a rapid cytoplasmic acidification of 0.03 pH unit followed by a slower alkalinization of approx. = 0.11 pH unit above the resting pH of 6.88. (ii) PMA caused alkalinization without causing the early acidification. (iii) Bradykinin caused rapid acidification without the slower net alkalinization. All acidification responses were amiloride resistant. Patterns of intracellular Ca/sup 2 +/ response were also determined for each agent. In Ca/sup 2 +/-buffered cells, PDGF, bombesin, bradykinin, and ionomycin failed to induce cellular acidification, but alkalinization responses to PDGF, bombesin, and PMA persisted. They propose that the transient acidification seen with PDGF, bombesin, and other agents is the result of increased intracellular Ca/sup 2 +/. However, growth factor-induced alkalinization via the Na/sup +//H/sup +/ exchanger is independent of changes in Ca/sup 2 +/.

  16. A Nanocrystal-based Ratiometric pH Sensor for Natural pH Ranges.

    PubMed

    Somers, Rebecca C; Lanning, Ryan M; Snee, Preston T; Greytak, Andrew B; Jain, Rakesh K; Bawendi, Moungi G; Nocera, Daniel G

    A ratiometric fluorescent pH sensor based on CdSe/CdZnS nanocrystal quantum dots (NCs) has been designed for biological pH ranges. The construct is formed from the conjugation of a pH dye (SNARF) to NCs coated with a poly(amido amine) (PAMAM) dendrimer. The sensor exhibits a well-resolved ratio response at pH values between 6 and 8 under linear or two-photon excitation, and in the presence of a 4% bovine serum albumin (BSA) solution.

  17. A Nanocrystal-based Ratiometric pH Sensor for Natural pH Ranges

    PubMed Central

    Somers, Rebecca C.; Lanning, Ryan M.; Snee, Preston T.; Greytak, Andrew B.; Jain, Rakesh K.

    2014-01-01

    Summary A ratiometric fluorescent pH sensor based on CdSe/CdZnS nanocrystal quantum dots (NCs) has been designed for biological pH ranges. The construct is formed from the conjugation of a pH dye (SNARF) to NCs coated with a poly(amido amine) (PAMAM) dendrimer. The sensor exhibits a well–resolved ratio response at pH values between 6 and 8 under linear or two–photon excitation, and in the presence of a 4% bovine serum albumin (BSA) solution. PMID:26413260

  18. Thermally programmable pH buffers.

    PubMed

    Van Gough, Dara; Bunker, Bruce C; Roberts, Mark E; Huber, Dale L; Zarick, Holly F; Austin, Mariah J; Wheeler, Jill S; Moore, Diana; Spoerke, Erik D

    2012-11-01

    Many reactions in both chemistry and biology rely on the ability to precisely control and fix the solution concentrations of either protons or hydroxide ions. In this report, we describe the behavior of thermally programmable pH buffer systems based on the copolymerization of varying amounts of acrylic acid (AA) groups into N-isopropylacrylamide polymers. Because the copolymers undergo phase transitions upon heating and cooling, the local environment around the AA groups can be reversibly switched between hydrophobic and hydrophilic states affecting the ionization behavior of the acids. Results show that moderate temperature variations can be used to change the solution pH by two units. However, results also indicate that the nature of the transition and its impact on the pH values are highly dependent on the AA content and the degree of neutralization.

  19. Fiber-Optic pH Sensor

    NASA Astrophysics Data System (ADS)

    Ganesh, A. Balaji; Radhakrishnan, T. K.

    The new enhancement in the determination of pH using optical fiber system is described here. This work uses the membrane made of cellulose acetate membrane for reagent immobilization and congo red (pKa 3.7) and neutral red (pKa 7.2) as pH indicators. An effective covalent chemical binding procedure is used to immobilize the indicatorsE The response time, reversibility, linear range, reproducibility, and long-term stability of fiber optic sensor with congo red as well as neutral red have been determined. The linear range measured for the sensor based on the congo red and neutral red is 4.2-6.3 and 4.1-9.0, respectively. The response time of sensor membrane is measured by varying the substance pH values between 11.0 and 2.0.

  20. Differential genotoxicity of diphenyl diselenide (PhSe)2 and diphenyl ditelluride (PhTe)2.

    PubMed

    Meinerz, Daiane Francine; Allebrandt, Josiane; Mariano, Douglas O C; Waczuk, Emily P; Soares, Felix Antunes; Hassan, Waseem; Rocha, João Batista T

    2014-01-01

    Organoselenium compounds have been pointed out as therapeutic agents. In contrast, the potential therapeutic aspects of tellurides have not yet been demonstrated. The present study evaluated the comparative toxicological effects of diphenyl diselenide (PhSe)2 and diphenyl ditelluride (PhTe)2 in mice after in vivo administration. Genotoxicity (as determined by comet assay) and mutagenicicity were used as end-points of toxicity. Subcutaneous administration of high doses of (PhSe)2 or (PhTe)2 (500 µmol/kg) caused distinct genotoxicity in mice. (PhSe)2 significantly decreased the DNA damage index after 48 and 96 h of its injection (p < 0.05). In contrast, (PhTe) caused a significant increase in DNA damage (p < 0.05) after 48 and 96 h of intoxication. (PhSe)2 did not cause mutagenicity but (PhTe)2 increased the micronuclei frequency, indicating its mutagenic potential. The present study demonstrated that acute in vivo exposure to ditelluride caused genotoxicity in mice, which may be associated with pro-oxidant effects of diphenyl ditelluride. In addition, the use of this compound and possibly other related tellurides must be carefully controlled.

  1. Evaluation of fluorimetric pH sensors for bioprocess monitoring at low pH.

    PubMed

    Janzen, Nils H; Schmidt, Michael; Krause, Christian; Weuster-Botz, Dirk

    2015-09-01

    Optical chemical sensors are the standard for pH monitoring in small-scale bioreactors such as microtiter plates, shaking flasks or other single-use bioreactors. The dynamic pH range of the so far commercially available fluorescent pH sensors applied in small-scale bioreactors is restricted to pH monitoring around neutral pH, although many fermentation processes are performed at pH < 6 on industrial scale. Thus, two new prototype acidic fluorescence pH sensors immobilized in single-use stirred-tank bioreactors, one with excitation at 470 nm and emission at 550 nm (sensor 470/550) and the other with excitation at 505 nm and emission at 600 nm (sensor 505/600), were characterized with respect to dynamic ranges and operational stability in representative fermentation media. Best resolution and dynamic range was observed with pH sensor 505/600 in mineral medium (dynamic range of 3.9 < pH < 7.2). Applying the same pH sensors to complex medium results in a drastic reduction of resolution and dynamic ranges. Yeast extract in complex medium was found to cause background fluorescence at the sensors' operating wavelength combinations. Optical isolation of the sensor by adding a black colored polymer layer above the sensor spot and fixing an aperture made of adhesive photoresistant foil between the fluorescence reader and the transparent bottom of the polystyrene reactors enabled full re-establishment of the sensor's characteristics. Reliability and operational stability of sensor 505/600 was shown by online pH monitoring (4.5 < pH < 5.8) of parallel anaerobic batch fermentations of Clostridium acetobutylicum for the production of acetone, butanol and ethanol (ABE) with offline pH measurements with a standard glass electrode as reference.

  2. What My Ph.D. Taught Me

    ERIC Educational Resources Information Center

    Levenstein, Jessica

    2013-01-01

    The author started in the Ph.D. program in comparative literature at Princeton in 1992, a year after she graduated from college. She fell in love with mythology and the classical traditions and find herself teaching literature. In the remainder of her time at Princeton, she precepted for four or five more classes, got the chance to join the…

  3. The Economic Contribution of PhDs

    ERIC Educational Resources Information Center

    Casey, Bernard H.

    2009-01-01

    This paper looks at what the value of a doctorate is, both to employers in particular and to society and the economy at large. Given the emphasis many universities and funding agencies/governments are putting upon the development of PhD programmes, this is an issue deserving attention. The paper tries to show how two separate but interrelated…

  4. PH Sensitive WO3-Based Microelectrochemical Transistors.

    DTIC Science & Technology

    1986-09-22

    a WO3 target. The cyclic voltammetry of these microelectrodes indicates that WO3 connects individual microelectrodes, since the voltammogram of a...transistor that is sensitive to pH. The cyclic voltammetry is pH-dependent and consistent with pH-dependent transistor characteristics, which indicate that the

  5. Development of sulfonamide AKT PH domain inhibitors.

    PubMed

    Ahad, Ali Md; Zuohe, Song; Du-Cuny, Lei; Moses, Sylvestor A; Zhou, Li Li; Zhang, Shuxing; Powis, Garth; Meuillet, Emmanuelle J; Mash, Eugene A

    2011-03-15

    Disruption of the phosphatidylinositol 3-kinase/AKT signaling pathway can lead to apoptosis in cancer cells. Previously we identified a lead sulfonamide that selectively bound to the pleckstrin homology (PH) domain of AKT and induced apoptosis when present at low micromolar concentrations. To examine the effects of structural modification, a set of sulfonamides related to the lead compound was designed, synthesized, and tested for binding to the expressed PH domain of AKT using a surface plasmon resonance-based competitive binding assay. Cellular activity was determined by means of an assay for pAKT production and a cell killing assay using BxPC-3 cells. The most active compounds in the set are lipophilic and possess an aliphatic chain of the proper length. Results were interpreted with the aid of computational modeling. This paper represents the first structure-activity relationship (SAR) study of a large family of AKT PH domain inhibitors. Information obtained will be used in the design of the next generation of inhibitors of AKT PH domain function.

  6. Teaching Physics Using PhET Simulations

    ERIC Educational Resources Information Center

    Wieman, C. E.; Adams, W. K.; Loeblein, P.; Perkins, K. K.

    2010-01-01

    PhET Interactive Simulations (sims) are now being widely used in teaching physics and chemistry. Sims can be used in many different educational settings, including lecture, individual or small group inquiry activities, homework, and lab. Here we will highlight a few ways to use them in teaching, based on our research and experiences using them in…

  7. Ph.D.'s and the Marketplace.

    ERIC Educational Resources Information Center

    Harvey, James

    Throughout the last decade, Ph.D. recipients were accustomed to a job market in which demand for their services far exceeded supply. During the same period, manpower experts predicted this situation would continue in the foreseeable future. However, when the 60's ended, the employment illusion had been rudely dispelled by frantic reports of a…

  8. Optoelectronic pH Meter: Further Details

    NASA Technical Reports Server (NTRS)

    Jeevarajan, Antony S.; Anderson, Mejody M.; Macatangay, Ariel V.

    2009-01-01

    A collection of documents provides further detailed information about an optoelectronic instrument that measures the pH of an aqueous cell-culture medium to within 0.1 unit in the range from 6.5 to 7.5. The instrument at an earlier stage of development was reported in Optoelectronic Instrument Monitors pH in a Culture Medium (MSC-23107), NASA Tech Briefs, Vol. 28, No. 9 (September 2004), page 4a. To recapitulate: The instrument includes a quartz cuvette through which the medium flows as it is circulated through a bioreactor. The medium contains some phenol red, which is an organic pH-indicator dye. The cuvette sits between a light source and a photodetector. [The light source in the earlier version comprised red (625 nm) and green (558 nm) light-emitting diodes (LEDs); the light source in the present version comprises a single green- (560 nm)-or-red (623 nm) LED.] The red and green are repeatedly flashed in alternation. The responses of the photodiode to the green and red are processed electronically to obtain the ratio between the amounts of green and red light transmitted through the medium. The optical absorbance of the phenol red in the green light varies as a known function of pH. Hence, the pH of the medium can be calculated from the aforesaid ratio.

  9. pH & Rate of Enzymatic Reactions.

    ERIC Educational Resources Information Center

    Clariana, Roy B.

    1991-01-01

    A quantitative and inexpensive way to measure the rate of enzymatic reaction is provided. The effects of different pH levels on the reaction rate of an enzyme from yeast are investigated and the results graphed. Background information, a list of needed materials, directions for preparing solutions, procedure, and results and discussion are…

  10. The Ph.D. Value Proposition

    ERIC Educational Resources Information Center

    Cooper, Kenneth J.

    2012-01-01

    Atlanta University launched its doctor of arts in humanities (DAH) programs almost 40 years ago, and, since the 1988 merger with Clark College, Clark Atlanta University has continued to award the degrees. This fall, for the first time, its students will be able to earn Ph.D.s in humanities instead. In DAH programs around the country, there's been…

  11. Monitoring fetal pH by telemetry

    NASA Technical Reports Server (NTRS)

    Blum, A.; Donahoe, T.; Jhabvala, M. D.; Ryan, W.

    1980-01-01

    Telemetry unit has been developed for possible use in measuring scalp-tissue pH and heart rate of unborn infant. Unit radius data to receiver as much as 50 ft. away. Application exists during hours just prior to childbirth to give warning of problems that might require cesarean delivery.

  12. Catalytic gold nanoparticle driven pH specific chemical locomotion.

    PubMed

    Dey, Krishna Kanti; Panda, Biswa Ranjan; Paul, Anumita; Basu, Saurabh; Chattopadhyay, Arun

    2010-08-15

    Gold nanoparticle (Au NP) catalyzed decomposition of alkaline hydrogen peroxide has been utilized in driving chemical locomotives in a liquid. Au NPs deposited on spherical micron sized polymer resin beads catalyzed the decomposition of H(2)O(2) in the pH range 9.1-10.8. The O(2) gas bubbles produced in the decomposition moved the beads upward with average velocities that depended on the pH of the solution. The measured average velocity of the bead increased with the increase in pH in the range 9.1-10.8. Above this pH, the self-decomposition of H(2)O(2) produced sufficient bubbles in the medium that made the motion haphazard and thus prevented a clear measurement of the velocity. The observed accelerated motion of the locomotive has been explained by considering the time-dependent growth of O(2) gas bubbles on the polymer, while taking into consideration desorption and other factors.

  13. Determination of pH in regions of the midguts of acaridid mites.

    PubMed

    Erban, Tomas; Hubert, Jan

    2010-01-01

    The pH of the guts of mites strongly affects their digestive processes. This study was carried out to determine the pH in the guts of 12 species of stored product and house dust mites. Eighteen pH indicators were chosen and offered to the mites in the feeding biotest. Based on the color changes of the indicators, the gut contents of acaridid mites were determined to be within a pH range of 4 to neutral. The gut contents showed a gradient in pH from the anterior to the posterior part. The anterior midgut (ventriculus and caeca) of most species had a pH ranging from 4.5 to 5, or slightly more alkaline for most of the species, while the middle midgut (intercolon/colon) had a pH of 5 to 6. Finally, the pH of the posterior midgut (postcolon) was between 5.5 and 7. Except for Dermatophagoides spp., no remarkable differences in the pH of the gut were observed among the tested species. Dermatophagoides spp. had a more acidic anterior midgut (a pH of 4 to 5) and colon (a pH of 5) with postcolon (a pH of below 6). The results characterizing in vivo conditions in the mite gut offer useful information to study the activity of mite digestive enzymes including their inhibitors and gut microflora.

  14. pH adjustment schedule for the amide local anesthetics.

    PubMed

    Ikuta, P T; Raza, S M; Durrani, Z; Vasireddy, A R; Winnie, A P; Masters, R W

    1989-01-01

    Several studies have indicated that the addition of sodium bicarbonate to solutions of local anesthetics to raise the pH closer to the pKa shortens the latency, increases the intensity, and prolongs the duration of the resultant neural blockade. However, the addition of too much bicarbonate will cause precipitation, and this may result in the injection of particulate free base along with the solution. The present study was carried out to determine the maximal amount of sodium bicarbonate that can be added to each of the amide local anesthetics without the formation of a precipitate, and, thus, to construct a pH adjustment schedule to simplify the alkalinization of local anesthetics in clinical practice.

  15. Effect of pH on fecal recovery of energy derived from volatile fatty acids.

    PubMed

    Kien, C L; Liechty, E A

    1987-01-01

    We assessed the effect of pH on volatilization of short-chain fatty acids during lyophilization. Acetic, propionic, valeric, and butyric acids were added to a fecal homogenate in amounts sufficient to raise the energy density by 18-27%. Fecal homogenate samples were either acidified (pH 2.8-3.2), alkalinized (pH 7.9-8.7), or left unchanged (4.0-4.8) prior to lyophilization and subsequent bomb calorimetry. Alkalinizing the fecal samples prevented the 20% loss of energy derived from each of these volatile fatty acids observed in samples either acidified or without pH adjustment. These data suggest that in energy balance studies involving subjects with active colonic fermentation, fecal samples should be alkalinized prior to lyophilization and bomb calorimetry.

  16. Interacting effects of pH acclimation, and pH and heavy metals on acute and chronic toxicity to Ceriodaphnia dubia (Cladocera)

    SciTech Connect

    Belanger, S.E.; Cherry, D.S. )

    1990-05-01

    Understanding the factors that modify the sensitivity of the zooplankton Ceriodaphnia dubia to toxicants is important to the interpretation of chronic toxicity data generated for granting industrial permits. Early reports of high sensitivity of Ceriodaphnia to brief pH excursions led toxicologists to question the use of C. dubia as a test organism. Acute and chronic toxicity of pH and heavy metals, pH acclimation to acidic and alkaline conditions and the role of pH in modifying heavy metal (copper and zinc) toxicities were investigated. Ceriodaphnia dubia acclimated near neutral pH had acute (48-hr) lethal concentrations of 4.6 and 10.3 SU. Reproduction and mortality were not impaired between pH 6.14-8.99 regardless of pH acclimation history. Reproduction was significantly impaired beyond these extremes. Acute exposures to both heavy metals at pH 6, 8 and 9 and in water hardness of 180, 110 and 100 mg/L showed C dubia was consistently most sensitive in low pH and low hardness waters. Reproduction and mortality were not so affected by pH in chronic exposures. Similar concentrations of metals at all pH levels resulted in equivalent reductions in offspring per female. The results strongly suggest that effluent guidelines for pH at 6-9 are sound, and that toxicant activity in chronic time frames is directed primarily by concentration and water hardness, not by pH. 34 refs., 2 figs., 8 tabs.

  17. pH control in biological systems using calcium carbonate.

    PubMed

    Salek, S S; van Turnhout, A G; Kleerebezem, R; van Loosdrecht, M C M

    2015-05-01

    Due to its abundance, calcium carbonate (CaCO3) has high potentials as a source of alkalinity for biotechnological applications. The application of CaCO3 in biological systems as neutralizing agent is, however, limited due to potential difficulties in controlling the pH. The objective of the present study was to determine the dominant processes that control the pH in an acid-forming microbial process in the presence of CaCO3. To achieve that, a mathematical model was made with a minimum set of kinetically controlled and equilibrium reactions that was able to reproduce the experimental data of a batch fermentation experiment using finely powdered CaCO3. In the model, thermodynamic equilibrium was assumed for all speciation, complexation and precipitation reactions whereas, rate limited reactions were included for the biological fatty acid production, the mass transfer of CO2 from the liquid phase to the gas phase and the convective transport of CO2 out of the gas phase. The estimated pH-pattern strongly resembled the measured pH, suggesting that the chosen set of kinetically controlled and equilibrium reactions were establishing the experimental pH. A detailed analysis of the reaction system with the aid of the model revealed that the pH establishment was most sensitive to four factors: the mass transfer rate of CO2 to the gas phase, the biological acid production rate, the partial pressure of CO2 and the Ca(+2) concentration in the solution. Individual influences of these factors on the pH were investigated by extrapolating the model to a continuously stirred-tank reactor (CSTR) case. This case study indicates how the pH of a commonly used continuous biotechnological process could be manipulated and adjusted by altering these four factors. Achieving a better insight of the processes controlling the pH of a biological system using CaCO3 as its neutralizing agent can result in broader applications of CaCO3 in biotechnological industries.

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

    PubMed

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

    2013-10-01

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

  19. 21 CFR 876.1400 - Stomach pH electrode.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Stomach pH electrode. 876.1400 Section 876.1400...) MEDICAL DEVICES GASTROENTEROLOGY-UROLOGY DEVICES Diagnostic Devices § 876.1400 Stomach pH electrode. (a) Identification. A stomach pH electrode is a device used to measure intragastric and intraesophageal pH...

  20. 21 CFR 876.1400 - Stomach pH electrode.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Stomach pH electrode. 876.1400 Section 876.1400...) MEDICAL DEVICES GASTROENTEROLOGY-UROLOGY DEVICES Diagnostic Devices § 876.1400 Stomach pH electrode. (a) Identification. A stomach pH electrode is a device used to measure intragastric and intraesophageal pH...

  1. 21 CFR 876.1400 - Stomach pH electrode.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Stomach pH electrode. 876.1400 Section 876.1400...) MEDICAL DEVICES GASTROENTEROLOGY-UROLOGY DEVICES Diagnostic Devices § 876.1400 Stomach pH electrode. (a) Identification. A stomach pH electrode is a device used to measure intragastric and intraesophageal pH...

  2. 21 CFR 876.1400 - Stomach pH electrode.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Stomach pH electrode. 876.1400 Section 876.1400...) MEDICAL DEVICES GASTROENTEROLOGY-UROLOGY DEVICES Diagnostic Devices § 876.1400 Stomach pH electrode. (a) Identification. A stomach pH electrode is a device used to measure intragastric and intraesophageal pH...

  3. PH DEPENDENT TOXICITY OF FIVE METALS TO THREE MARINE ORGANISMS

    EPA Science Inventory

    The pH of natural marine systems is relatively stable; this may explain why metal toxicity changes with pH have not been well documented. However, changes in metal toxicity with pH in marine waters are of concern in toxicity testing. During porewater toxicity testing pH can chang...

  4. 21 CFR 876.1400 - Stomach pH electrode.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Stomach pH electrode. 876.1400 Section 876.1400...) MEDICAL DEVICES GASTROENTEROLOGY-UROLOGY DEVICES Diagnostic Devices § 876.1400 Stomach pH electrode. (a) Identification. A stomach pH electrode is a device used to measure intragastric and intraesophageal pH...

  5. What Is a pH Probe Study?

    MedlinePlus

    What is a pH Probe Study ? What is pH a probe study? M easuring the pH in the esophagus helps determine whether or not acid is coming up from the stomach. A pH probe study is usually done in patients where ...

  6. [Measurement of intracellular pH].

    PubMed

    Hanaoka, K; Imai, M; Yoshitomi, K

    1992-09-01

    Since various cellular processes depend on changes in pH, the regulation of intracellular pH (pHi) is important both for the individual cell and for the organism. The mechanisms of the regulation of pHi can be investigated by monitoring pHi. In this report, we discuss the four major techniques available for measuring pHi, which are 1) Distribution of weak acids and bases, 2) pH-sensitive microelectrodes, 3) pH-sensitive dyes, and 4) Nuclear magnetic resonance. Among four techniques, the advantage of the microelectrode approach is that it can monitor membrane potential at the same time and be applied to a single cell. The dye technique is a relative new developing technique, which has lots of advantages. It is easy to use, and is capable of monitoring rapid pHi changes, and being applied to a smaller cell, or a single cell.

  7. Not Your Father's Ph.D.

    ERIC Educational Resources Information Center

    Withrow, Brandon G.

    2008-01-01

    This article describes how the author, a devoted blogger, confronts his fear that his virtual life is damaging his career prospects in academe. As a new Ph.D. in religious studies, the author has every reason to believe he will find a tenure-track job. He has read the numbers and know that, on average, job candidates spend two to five years in…

  8. Complexation Key to a pH Locked Redox Reaction

    ERIC Educational Resources Information Center

    Rizvi, Masood Ahmad; Dangat, Yuvraj; Shams, Tahir; Khan, Khaliquz Zaman

    2016-01-01

    An unfavorable pH can block a feasible electron transfer for a pH dependent redox reaction. In this experiment, a series of potentiometric titrations demonstrate the sequential loss in feasibility of iron(II) dichromate redox reaction over a pH range of 0-4. The pH at which this reaction failed to occur was termed as a pH locked reaction. The…

  9. Growth of water hyacinth in municipal landfill leachate with different pH.

    PubMed

    El-Gendy, A S; Biswas, N; Bewtra, J K

    2004-07-01

    Batch experiments were conducted to investigate the effect of municipal landfill leachate pH on the growth of water hyacinth (Eichhornia crassipes). These experiments were carried out in a green house environment on leachate samples collected from Essex-Windsor Regional Landfill, Windsor, Ontario, Canada. It was found that water hyacinth plants survived in a pH range of 4.0 to 8.0. Both alkaline pH (above 8.0) and highly acidic pH (below 4.0) had inhibitory effect on the growth of plants. The pH range, for optimum growth of the water hyacinth plants was found to be 5.8 to 6.0. At optimum growth, water hyacinth had an average mean relative growth rate of 0.043 d-1. It was found that nitrogen compounds underwent different transformations depending on the pH of leachate. Plant uptake, nitrification and volatilization were among these transformations.

  10. Analysis of individual versus group behavior of zebrafish: a model using pH sublethal effects.

    PubMed

    Magalhães, Danielly de Paiva; Buss, Daniel Forsin; da Cunha, Rodolfo Armando; Linde-Arias, Ana Rosa; Baptista, Darcilio Fernandes

    2012-06-01

    An image analysis biomonitoring system was used to evaluate sublethal effects of pH on the mean swimming velocity of zebrafish. Responses to stress were tested comparing individual and group responses. Group analysis indicated no effect for all acid pH and for pH 9.0-9.5. Individual analysis indicated behavioral differences for most acid pH and higher than 9.5. Sensitivity to sublethal pH was best assessed when using individual analysis. Zebrafish decreased hyperactivity and increased hypoactivity with more acid or alkaline pH. Individual approach allowed to determine hyperactivity or hypoactivity and the species' thresholds of exposure, which is critical for the management of impairments.

  11. The Added Value of a PhD in Medicine--PhD Students' Perceptions of Acquired Competences

    ERIC Educational Resources Information Center

    Anttila, Henrika; Lindblom-Ylänne, Sari; Lonka, Kristi; Pyhältö, Kirsi

    2015-01-01

    PhD in the field of medicine is more common than in any other domain. Many medical doctors are driven towards PhD, but also students with other backgrounds (usually MSc) are conducting a PhD in medical schools. Higher education has invested a lot in developing generic and research competences. Still little is known about how PhD students…

  12. The Influence of pH on Prokaryotic Cell Size and Temperature

    NASA Astrophysics Data System (ADS)

    Sundararajan, D.; Gutierrez, F.; Heim, N. A.; Payne, J.

    2015-12-01

    The pH of a habitat is essential to an organism's growth and success in its environment. Although most organisms maintain a neutral internal pH, their environmental pH can vary greatly. However, little research has been done concerning an organism's environmental pH across a wide range of taxa. We studied pH tolerance in prokaryotes and its relationship with biovolume, taxonomic classification, and ideal temperature. We had three hypotheses: pH and temperature are not correlated; pH tolerance is similar within taxonomic groups; and extremophiles have small cell sizes. To test these hypotheses, we used pH, size, and taxonomic data from The Prokaryotes. We found that the mean optimum external pH was neutral for prokaryotes as a whole and when divided by domain, phylum, and class. Using ANOVA to test for pH within and among group variances, we found that variation of pH in domains, phyla, classes, and families was greater than between them. pH and size did not show much of a correlation, except that the largest and smallest sized prokaryotes had nearly neutral pH. This seems significant because extremophiles need to divert more of their energy from growth to maintain a neutral internal pH. Acidophiles showed a larger range of optimum pH values than alkaliphiles. A similar result was seen with the minimum and maximum pH values of acidophiles and alkaliphiles. While acidophiles were spread out and had some alkaline maximum values, alkaliphiles had smaller ranges, and unlike some acidophiles that had pH minimums close to zero, alkaliphile pH maximums did not go beyond a pH of 12. No statistically significant differences were found between sizes of acidophiles and alkaliphiles. However, optimum temperatures of acidophiles and alkaliphiles did have a statistically significant difference. pH and temperature had a negative correlation. Therefore, pH seems to have a correlation with cell size, temperature, and taxonomy to some extent.

  13. Cervical length versus vaginal PH in the second trimester as preterm birth predictor

    PubMed Central

    Foroozanfard, Fatemeh; Tabasi, Zohreh; Mesdaghinia, Elaheh; Sehat, Mojtaba; Mehrdad, Mahdian

    2015-01-01

    Objective: To evaluate diagnostic value of vaginal pH and cervical length measurement in the second trimester of pregnancy as a preterm labor (PTL) predictor. Methods: During a prospective cohort study 438 uncomplicated singleton pregnant women between 18 and 24 weeks of gestation were assessed regarding vaginal PH and cervical length. Vaginal pH was measured using Ph-indicator strips and cervical length was determined using transvaginal ultrasound. The cut-off values for vaginal PH and cervical length were defined as 5 and <30 mm respectively. Results: Vaginal pH of 5 and above was found in 162/438 women (37%) while cervical length <30mm was found in 38/438 (8.7%). The incidence of PTL < 37 weeks was 87/438 (19.9%) while the incidence of early (PTL <34 weeks) was 51/438 (11.6%). Predictive value of higher vaginal PH was significantly more (31%) than vaginal PH<5 (13%) in predicting PTL. As a result, alkaline vaginal PH significantly increases the odds of preterm labor (OR=3.06). Shortened cervical length is better predictor of PTL than higher vaginal PH with positive predictive value of 71% and negative predictive value of 85%. Cervical length less than 30 mm nearly 14-fold increases odds of preterm birth (OR=13.9). Conclusion: Compared to alkaline vaginal PH, shortened cervical length has better value to predict PTL overall. However, regarding early or late PTL, vaginal PH is more accurate to predict late PTL, while cervical length measurement is more appropriate to predict early PTL (<34 weeks). PMID:26101494

  14. TASK-2 Channels Contribute to pH Sensitivity of Retrotrapezoid Nucleus Chemoreceptor Neurons

    PubMed Central

    Wang, Sheng; Benamer, Najate; Zanella, Sébastien; Kumar, Natasha N.; Shi, Yingtang; Bévengut, Michelle; Penton, David; Guyenet, Patrice G.; Lesage, Florian

    2013-01-01

    Phox2b-expressing glutamatergic neurons of the retrotrapezoid nucleus (RTN) display properties expected of central respiratory chemoreceptors; they are directly activated by CO2/H+ via an unidentified pH-sensitive background K+ channel and, in turn, facilitate brainstem networks that control breathing. Here, we used a knock-out mouse model to examine whether TASK-2 (K2P5), an alkaline-activated background K+ channel, contributes to RTN neuronal pH sensitivity. We made patch-clamp recordings in brainstem slices from RTN neurons that were identified by expression of GFP (directed by the Phox2b promoter) or β-galactosidase (from the gene trap used for TASK-2 knock-out). Whereas nearly all RTN cells from control mice were pH sensitive (95%, n = 58 of 61), only 56% of GFP-expressing RTN neurons from TASK-2−/− mice (n = 49 of 88) could be classified as pH sensitive (>30% reduction in firing rate from pH 7.0 to pH 7.8); the remaining cells were pH insensitive (44%). Moreover, none of the recorded RTN neurons from TASK-2−/− mice selected based on β-galactosidase activity (a subpopulation of GFP-expressing neurons) were pH sensitive. The alkaline-activated background K+ currents were reduced in amplitude in RTN neurons from TASK-2−/− mice that retained some pH sensitivity but were absent from pH-insensitive cells. Finally, using a working heart–brainstem preparation, we found diminished inhibition of phrenic burst amplitude by alkalization in TASK-2−/− mice, with apneic threshold shifted to higher pH levels. In conclusion, alkaline-activated TASK-2 channels contribute to pH sensitivity in RTN neurons, with effects on respiration in situ that are particularly prominent near apneic threshold. PMID:24107938

  15. Acidic Food pH Increases Palatability and Consumption and Extends Drosophila Lifespan12

    PubMed Central

    Deshpande, Sonali A; Yamada, Ryuichi; Mak, Christine M; Hunter, Brooke; Obando, Alina Soto; Hoxha, Sany; Ja, William W

    2015-01-01

    Background: Despite the prevalent use of Drosophila as a model in studies of nutrition, the effects of fundamental food properties, such as pH, on animal health and behavior are not well known. Objectives: We examined the effect of food pH on adult Drosophila lifespan, feeding behavior, and microbiota composition and tested the hypothesis that pH-mediated changes in palatability and total consumption are required for modulating longevity. Methods: We measured the effect of buffered food (pH 5, 7, or 9) on male gustatory responses (proboscis extension), total food intake, and male and female lifespan. The effect of food pH on germfree male lifespan was also assessed. Changes in fly-associated microbial composition as a result of food pH were determined by 16S ribosomal RNA gene sequencing. Male gustatory responses, total consumption, and male and female longevity were additionally measured in the taste-defective Pox neuro (Poxn) mutant and its transgenic rescue control. Results: An acidic diet increased Drosophila gustatory responses (40–230%) and food intake (5–50%) and extended survival (10–160% longer median lifespan) compared with flies on either neutral or alkaline pH food. Alkaline food pH shifted the composition of fly-associated bacteria and resulted in greater lifespan extension (260% longer median survival) after microbes were eliminated compared with flies on an acidic (50%) or neutral (130%) diet. However, germfree flies lived longer on an acidic diet (5–20% longer median lifespan) compared with those on either neutral or alkaline pH food. Gustatory responses, total consumption, and longevity were unaffected by food pH in Poxn mutant flies. Conclusions: Food pH can directly influence palatability and feeding behavior and affect parameters such as microbial growth to ultimately affect Drosophila lifespan. Fundamental food properties altered by dietary or drug interventions may therefore contribute to changes in animal physiology, metabolism, and

  16. The panacea toolbox of a PhD biomedical student.

    PubMed

    Skaik, Younis

    2014-01-01

    Doing a PhD (doctor of philosophy) for the sake of contribution to knowledge should give the student an immense enthusiasm through the PhD period. It is the time in one's life that one spends to "hit the nail on the head" in a specific area and topic of interest. A PhD consists mostly of hard work and tenacity; however, luck and genius might also play a little role. You can pass all PhD phases without having both luck and genius. The PhD student should have pre-PhD and PhD toolboxes, which are "sine quibus non" for getting successfully a PhD degree. In this manuscript, the toolboxes of the PhD student are discussed.

  17. Influence of pH on yeast immobilization on polystyrene surfaces modified by energetic ion bombardment.

    PubMed

    Tran, Clara T H; Kondyurin, Alexey; Chrzanowski, Wojciech; Bilek, Marcela M M; McKenzie, David R

    2013-04-01

    Plasma immersion ion implantation (PIII) treatment is a novel method for immobilizing yeast on polymer surfaces by covalent linkage. This study of the immobilization of Saccharomyces cerevisiae in both rehydrated and cultured forms showed that the density of cell attachment on PIII treated polystyrene (PS) was strongly dependent on the pH of the incubation medium and was higher for rehydrated yeast. A study of the surface charge was undertaken to explain this result. A high density of cell attachment occurs in acidic conditions (pH 3-5) and a significantly reduced cell density occurs in neutral and alkaline buffers (pH 6-10) for both types of yeast. Force measurements using atomic force microscopy show that a negative charge is present on polystyrene after PIII treatment. The charge is close to zero at pH 3 to pH 5 and increasingly negative from pH 6 to pH 10. Both rehydrated yeast and cultured yeast have negative electrophoretic mobility in the pH range studied. The repulsive forces are weak in acidic buffers and stronger in neutral and alkaline buffers, in good agreement with the cell densities observed. Rehydrated yeast cells are found to be more hydrophobic than cultured yeasts in the same buffer. The higher hydrophobicity explains the higher attachment of rehydrated yeast compared to cultured yeast.

  18. Recent Ph.D.s; Honors

    NASA Astrophysics Data System (ADS)

    2005-04-01

    Recent Ph.D.s. Atmospheric Sciences. A study of atmospheric ammonia in coastal ecosystems utilizing relaxed eddy accumulation techniques and ion mobility spectrometry, LaToya Myles, Florida A&M University, December 2004, Advisor: Larry Robinson. Honors. Rana A. Fine has been awarded the 2005 Provost Award for Scholarly Activity, presented by the University of Miami. The award ``recognizes faculty for extraordinary research and scholarly pursuits.'' Charles David Keeling and Lonnie G. Thompson will receive the 2005 Tyler Prize for Environmental Achievement. The prize is given to individuals whose accomplishments in environmental science, policy, energy, and medicine confer great benefit upon mankind.

  19. Intracellular pH in sperm physiology.

    PubMed

    Nishigaki, Takuya; José, Omar; González-Cota, Ana Laura; Romero, Francisco; Treviño, Claudia L; Darszon, Alberto

    2014-08-01

    Intracellular pH (pHi) regulation is essential for cell function. Notably, several unique sperm ion transporters and enzymes whose elimination causes infertility are either pHi dependent or somehow related to pHi regulation. Amongst them are: CatSper, a Ca(2+) channel; Slo3, a K(+) channel; the sperm-specific Na(+)/H(+) exchanger and the soluble adenylyl cyclase. It is thus clear that pHi regulation is of the utmost importance for sperm physiology. This review briefly summarizes the key components involved in pHi regulation, their characteristics and participation in fundamental sperm functions such as motility, maturation and the acrosome reaction.

  20. Polypeptide micelles with dual pH activatable dyes for sensing cells and cancer imaging

    NASA Astrophysics Data System (ADS)

    Gong, Ping; Yang, Yueting; Yi, Huqiang; Fang, Shengtao; Zhang, Pengfei; Sheng, Zonghai; Gao, Guanhui; Gao, Duyang; Cai, Lintao

    2014-04-01

    pH is an important control parameter for maintenance of cell viability and tissue functions. pH monitoring provides valuable information on cell metabolic processes and the living environment. In this study, we prepared dual pH-sensitive, fluorescent dye-loaded polypeptide nanoparticles (DPNs) for ratiometric sensing of pH changes in living cells. DPNs contain two types of dyes: N-(rhodamine B) lactam cystamine (RBLC), an acid activatable fluorescent dye with increased fluorescence in an acidic environment, and fluorescein isothiocyanate (FITC), a base activatable fluorescent dye with enhanced fluorescence in an alkaline environment. Hence, DPNs exhibited a dual response signal with strong red fluorescence and weak green fluorescence under acidic conditions; in contrast, they showed strong green fluorescence and almost no red fluorescence under alkaline and neutral conditions. The favorable inverse pH responses of the two fluorescent dyes resulted in ratiometric pH determination for DPNs with an optimized pH-sensitive range of pH 4.5-7.5. Quantitative analysis of the intracellular pH of intact MCF-7 cells has been successfully demonstrated with our nanosensor. Moreover, single acid activatable fluorescent dye doped polypeptide nanoparticles that only contained RBLC can distinguish tumor tissue from normal tissue by monitoring the acidic extracellular environment.pH is an important control parameter for maintenance of cell viability and tissue functions. pH monitoring provides valuable information on cell metabolic processes and the living environment. In this study, we prepared dual pH-sensitive, fluorescent dye-loaded polypeptide nanoparticles (DPNs) for ratiometric sensing of pH changes in living cells. DPNs contain two types of dyes: N-(rhodamine B) lactam cystamine (RBLC), an acid activatable fluorescent dye with increased fluorescence in an acidic environment, and fluorescein isothiocyanate (FITC), a base activatable fluorescent dye with enhanced fluorescence

  1. Nanomechanical DNA Origami pH Sensors

    PubMed Central

    Kuzuya, Akinori; Watanabe, Ryosuke; Yamanaka, Yusei; Tamaki, Takuya; Kaino, Masafumi; Ohya, Yuichi

    2014-01-01

    Single-molecule pH sensors have been developed by utilizing molecular imaging of pH-responsive shape transition of nanomechanical DNA origami devices with atomic force microscopy (AFM). Short DNA fragments that can form i-motifs were introduced to nanomechanical DNA origami devices with pliers-like shape (DNA Origami Pliers), which consist of two levers of 170-nm long and 20-nm wide connected at a Holliday-junction fulcrum. DNA Origami Pliers can be observed as in three distinct forms; cross, antiparallel and parallel forms, and cross form is the dominant species when no additional interaction is introduced to DNA Origami Pliers. Introduction of nine pairs of 12-mer sequence (5′-AACCCCAACCCC-3′), which dimerize into i-motif quadruplexes upon protonation of cytosine, drives transition of DNA Origami Pliers from open cross form into closed parallel form under acidic conditions. Such pH-dependent transition was clearly imaged on mica in molecular resolution by AFM, showing potential application of the system to single-molecular pH sensors. PMID:25325338

  2. The pH of Mars

    NASA Technical Reports Server (NTRS)

    Plumb, R. C.; Bishop, J. L.; Edwards, J. O.

    1993-01-01

    The Viking labeled release (LR) experiments provided data that can be used to determine the acid-base characteristics of the regolith. Constraints on the acid-base properties and redox potentials of the Martian surface material would provide additional information for determining what reactions are possible and defining formation conditions for the regolith. Calculations devised to determine the pH of Mars must include the amount of soluble acid species or base species present in the LR regolith sample and the solubility product of the carbonate with the limiting solubility. This analysis shows that CaCO3, either as calcite or aragonite, has the correct K(sub sp) to have produced the Viking LR successive injection reabsorption effects. Thus CaCO3 or another MeCO3 with very similar solubility characteristics must have been present on Mars. A small amount of soluble acid, but no more than 4 micro-mol per sample, could also have been present. It is concluded that the pH of the regolith is 7.2 +/- 0.1.

  3. Constant pH simulations of pH responsive polymers

    NASA Astrophysics Data System (ADS)

    Sharma, Arjun; Smith, J. D.; Walters, Keisha B.; Rick, Steven W.

    2016-12-01

    Polyacidic polymers can change structure over a narrow range of pH in a competition between the hydrophobic effect, which favors a compact state, and electrostatic repulsion, which favors an extended state. Constant pH molecular dynamics computer simulations of poly(methacrylic acid) reveal that there are two types of structural changes, one local and one global, which make up the overall response. The local structural response depends on the tacticity of the polymer and leads to different cooperative effects for polymers with different stereochemistries, demonstrating both positive and negative cooperativities.

  4. The pH sensitivity of Aqp0 channels in tetraploid and diploid teleosts

    PubMed Central

    Chauvigné, François; Zapater, Cinta; Stavang, Jon Anders; Taranger, Geir Lasse; Cerdà, Joan; Finn, Roderick Nigel

    2015-01-01

    Water homeostasis and the structural integrity of the vertebrate lens is partially mediated by AQP0 channels. Emerging evidence indicates that external pH may be involved in channel gating. Here we show that a tetraploid teleost, the Atlantic salmon, retains 4 aqp0 genes (aqp0a1, -0a2, -0b1, and -0b2), which are highly, but not exclusively, expressed in the lens. Functional characterization reveals that, although each paralog permeates water efficiently, the permeability is respectively shifted to the neutral, alkaline, or acidic pH in Aqp0a1, -0a2, and -0b1, whereas that of Aqp0b2 is not regulated by external pH. Mutagenesis studies demonstrate that Ser38, His39, and His40 residues in the extracellular transmembrane domain of α-helix 2 facing the water pore are critical for the pH modulation of water transport. To validate these findings, we show that both zebrafish Aqp0a and -0b are functional water channels with respective pH sensitivities toward alkaline or acid pH ranges and that an N-terminal allelic variant (Ser19) of Aqp0b exists that abolishes water transport in Xenopus laevis oocytes. The data suggest that the alkaline pH sensitivity is a conserved trait in teleost Aqp0 a-type channels, whereas mammalian AQP0 and some teleost Aqp0 b-type channels display an acidic pH permeation preference.—Chauvigné, F., Zapater, C., Stavang, J. A., Taranger, G. L., Cerdà, J., Finn, R. N. The pH sensitivity of Aqp0 channels in tetraploid and diploid teleosts. PMID:25667219

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

    PubMed Central

    2012-01-01

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

  6. [Spatiotemporal variation of soil pH in Guangdong Province of China in past 30 years].

    PubMed

    Guo, Zhi-Xing; Wang, Jing; Chai, Min; Chen, Ze-Peng; Zhan, Zhen-Shou; Zheng, Wu-Ping; Wei, Xiu-Guo

    2011-02-01

    Based on the 1980s' soil inventory data and the 2002-2007 soil pH data of Guangdong Province, the spatiotemporal variation of soil pH in the Province in past 30 years was studied. In the study period, the spatial distribution pattern of soil pH in the Province had less change (mainly acidic), except that in Pearl River Delta and parts of Qingyuan and Shaoguan (weak alkaline). The overall variation of soil pH was represented as acidification, with the average pH value changed from 5.70 to 5.44. Among the soil types in the Province, alluvial soil had an increased pH, lateritic red soil, paddy soil, and red soil had a large decrement of pH value, and lime soil was most obvious in the decrease of pH value and its area percentage. The soil acidification was mainly induced by soil characteristics, some natural factors such as acid rain, and human factors such as unreasonable fertilization and urbanization. In addition, industrialization and mining increased the soil pH in some areas.

  7. Effect of environment pH on the photophysics of fisetin in solid lipid nanoparticles.

    PubMed

    Das, Shrabanti; Maity, Arnab; Purkayastha, Pradipta

    2015-12-01

    Photophysical modulation of fisetin has been extensively studied in bulk aqueous as well as solid lipid nanoparticles (SLN) by varying the pH of the medium. The solution pH was varied from 5 to 9 to mimic biological environments. Neutral and anionic forms of fisetin coexist in ground state in both acidic and alkaline conditions. However, in the excited state and at low pH, the anionic form of fisetin predominates over the proton transferred form, whereas in SLNs, the proton transferred form is the major emitting species. Higher pH showed enhancement in anionic emission to different extent in the two types of environments. Limited percolation of H(+) and OH(-) ions inside the SLNs that host fisetin molecules controls their photophysics. The experimental results encourage usage of fisetin as a drug depending on the ratio of the neutral and anionic as well as the proton transferred forms under various pH conditions.

  8. The effect of pH on phosphorus availability and speciation in an aquaponics nutrient solution.

    PubMed

    Cerozi, Brunno da Silva; Fitzsimmons, Kevin

    2016-11-01

    The interaction between the main ions in aquaponics nutrient solutions affects chemical composition and availability of nutrients, and nutrient uptake by plant roots. This study determined the effect of pH on phosphorus (P) speciation and availability in an aquaponics nutrient solution and used Visual MINTEQ to simulate P species and P activity. In both experimental and simulated results, P availability decreased with increase in pH of aquaponics nutrient solutions. According to simulations, P binds to several cations leaving less free phosphate ions available in solution. High pH values resulted in the formation of insoluble calcium phosphate species. The study also demonstrated the importance of organic matter and alkalinity in keeping free phosphate ions in solution at high pH ranges. It is recommended though that pH in aquaponics systems is maintained at a 5.5-7.2 range for optimal availability and uptake by plants.

  9. Ian Douglass Coulter, PhD

    PubMed Central

    Brown, Douglas M

    2004-01-01

    This paper focuses on Dr. Ian Coulter’s accomplishments from the time he became Executive Vice-President of CMCC in 1981, until he ended his presidency with a year’s administrative leave in 1990. Annual planning initiatives, pedagogy, scholarship, conflicts, and the quest for university affiliation are discussed as well as his legacy to the College and the chiropractic profession. The term “adventurous” was first attributed to Coulter by Oswald Hall, PhD, Professor Emeritus, University of Toronto who had worked closely with Coulter in a major investigation of the chiropractic profession from 1976 to 1979. Throughout this article the author tries to capture the spirit of daring, innovation and intellect that permeated Coulter’s presidency, enthralling his advocates and confounding his detractors. PMID:17549218

  10. Intracellular pH in Sperm Physiology

    PubMed Central

    Nishigaki, Takuya; José, Omar; González-Cota, Ana Laura; Romero, Francisco; Treviño, Claudia L.; Darszon, Alberto

    2014-01-01

    Intracellular pH (pHi) regulation is essential for cell function. Notably, several unique sperm ion transporters and enzymes whose elimination causes infertility are either pHi dependent or somehow related to pHi regulation. Amongst them are: CatSper, a Ca2+ channel; Slo3, a K+ channel; the sperm-specific Na+/H+ exchanger and the soluble adenylyl cyclase. It is thus clear that pHi regulation is of the utmost importance for sperm physiology. This review briefly summarizes the key components involved in pHi regulation, their characteristics and participation in fundamental sperm functions such as motility, maturation and the acrosome reaction. PMID:24887564

  11. Barrett's oesophagus: pH profile.

    PubMed

    Gillen, P; Keeling, P; Byrne, P J; Hennessy, T P

    1987-09-01

    Twenty-four patients with a columnar-lined (Barrett's) oesophagus underwent oesophageal manometry and 24 h ambulatory oesophageal pH monitoring. The results were compared with 25 patients with oesophagitis studied in the same fashion. No significant difference in lower oesophageal sphincter pressure was demonstrated between the two groups. The Barrett's patients demonstrated significantly greater acid exposure in the distal oesophagus than oesophagitis patients. Clearance or refluxed acid was poorer in Barrett's patients than oesophagitis patients. Twelve of the Barrett's patients presented with complications of the condition, i.e. ulceration or stricture. No significant difference in acid exposure was demonstrated between Barrett's patients with or without complications. These results suggest that patients with columnar-lined (Barrett's) oesophagus have greater acid exposure than patients with oesophagitis. The development of complications of a Barrett's oesophagus may not be dependent on acid reflux alone.

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

    PubMed

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

    2016-11-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  14. Polypeptide micelles with dual pH activatable dyes for sensing cells and cancer imaging.

    PubMed

    Gong, Ping; Yang, Yueting; Yi, Huqiang; Fang, Shengtao; Zhang, Pengfei; Sheng, Zonghai; Gao, Guanhui; Gao, Duyang; Cai, Lintao

    2014-05-21

    pH is an important control parameter for maintenance of cell viability and tissue functions. pH monitoring provides valuable information on cell metabolic processes and the living environment. In this study, we prepared dual pH-sensitive, fluorescent dye-loaded polypeptide nanoparticles (DPNs) for ratiometric sensing of pH changes in living cells. DPNs contain two types of dyes: N-(rhodamine B) lactam cystamine (RBLC), an acid activatable fluorescent dye with increased fluorescence in an acidic environment, and fluorescein isothiocyanate (FITC), a base activatable fluorescent dye with enhanced fluorescence in an alkaline environment. Hence, DPNs exhibited a dual response signal with strong red fluorescence and weak green fluorescence under acidic conditions; in contrast, they showed strong green fluorescence and almost no red fluorescence under alkaline and neutral conditions. The favorable inverse pH responses of the two fluorescent dyes resulted in ratiometric pH determination for DPNs with an optimized pH-sensitive range of pH 4.5-7.5. Quantitative analysis of the intracellular pH of intact MCF-7 cells has been successfully demonstrated with our nanosensor. Moreover, single acid activatable fluorescent dye doped polypeptide nanoparticles that only contained RBLC can distinguish tumor tissue from normal tissue by monitoring the acidic extracellular environment.

  15. Effect of pH on Metal Lability in Drinking Water Treatment Residuals.

    PubMed

    Wang, Changhui; Yuan, Nannan; Pei, Yuansheng

    2014-01-01

    Drinking water treatment residuals (WTRs), by-products generated during treatment of drinking water, can be reused as environmental amendments to remediate contamination. However, this beneficial reuse may be hampered by the potential release of toxic contaminants (e.g., metals) in the WTRs. In present study, batch tests and then fractionation, in vitro digestion, and the toxicity characteristic leaching procedure were used to investigate the release and extractability of metals in the Fe/Al hydroxides comprised WTRs under differing pH. The results demonstrated that significant release from WTRs for Ba, Be, Ca, Cd, Co, Cr, Fe, Mg, Mn, Pb, Sr, and Zn occurred under low pH (acid condition); for As, Mo, and V under high pH (alkaline condition); and for Al, Cu, and Ni under both conditions. In comparison, most metals in the WTRs were more easily released under low pH, but the release was stable at a relatively low level between pH 6 and 9, especially under alkaline conditions. Further analysis indicated that the chemical extractability and bioaccessibility of many metals was found to increase in the WTRs after being leached, even though the leached WTRs could still be considered nonhazardous. These results demonstrated that pH had a substantial effect on the lability of metals in WTRs. Overall, caution should be used when considering pH conditions during WTRs reuse to avoid potential metal pollution.

  16. Acid Rain, pH & Acidity: A Common Misinterpretation.

    ERIC Educational Resources Information Center

    Clark, David B.; Thompson, Ronald E.

    1989-01-01

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

  17. Steel slag raises pH of greenhouse substrates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dolomitic lime (DL) is the primary liming agent used for increasing pH in peatmoss-based substrates. Steel slag (SS) is a byproduct of the steel manufacturing industry that has been used to elevate field soil pH. The objective of this research was to determine the pH response of a peatmoss-based g...

  18. High temperature pH measurements using novel pH electrodes. Final report

    SciTech Connect

    Macdonald, D.D.; Song, H.; Hettiarachchi, S.

    1995-12-01

    Researchers used three pH sensors: (1) a yttria-stabilized zirconia, (2) tungsten/tungsten oxide, and (3) platinum hydrogen electrodes to measure the pH in concentrated solutions heated to temperatures from 125-300 C in autoclaves. The studies indicated measurements of pH for solutions containing sodium hydroxide, sodium sulfate, sodium chloride, boric acid, ferrous sulfate, nickel sulfate, and chromous sulfate in various compositions. The solution composition and pH was then calculated by MULTEQ at the experimental conditions. These calculations compared well with the experimental measurements for binary and quaternary systems at temperatures to 300 C and concentrations to 1 molal. The agreement was also excellent for the metal sulfate systems but was poor for chromous sulfate. The agreement for boric acid solutions was adequate for low concentrations of boric acid but was poor for concentrated borate solutions where polyborate ions likely exist. It is not known whether the lack of agreement under these conditions is due to deficiencies in MULTEQ or the experimental measurements.

  19. Understanding Non-Traditional PhD Students Habitus--Implications for PhD Programmes

    ERIC Educational Resources Information Center

    Naidoo, Devika

    2015-01-01

    Against the background of vast changes in doctoral education and the emergence of non-traditional doctoral programmes, this paper investigates the habitus of non-traditional PhD students at a South African university. Bourdieu's conceptual tool of habitus informed the study. In-depth and open-ended interviews were conducted with 10 non-traditional…

  20. Comparison of Rumen Fluid pH by Continuous Telemetry System and Bench pH Meter in Sheep with Different Ranges of Ruminal pH

    PubMed Central

    Reis, Leonardo F.; Minervino, Antonio H. H.; Araújo, Carolina A. S. C.; Sousa, Rejane S.; Oliveira, Francisco L. C.; Rodrigues, Frederico A. M. L.; Meira-Júnior, Enoch B. S.; Barrêto-Júnior, Raimundo A.; Mori, Clara S.; Ortolani, Enrico L.

    2014-01-01

    We aimed to compare the measurements of sheep ruminal pH using a continuous telemetry system or a bench pH meter using sheep with different degrees of ruminal pH. Ruminal lactic acidosis was induced in nine adult crossbred Santa Ines sheep by the administration of 15 g of sucrose per kg/BW. Samples of rumen fluid were collected at the baseline, before the induction of acidosis (T0) and at six, 12, 18, 24, 48, and 72 hours after the induction for pH measurement using a bench pH meter. During this 72-hour period, all animals had electrodes for the continuous measurement of pH. The results were compared using the Bland-Altman analysis of agreement, Pearson coefficients of correlation and determination, and paired analysis of variance with Student's t-test. The measurement methods presented a strong correlation (r = 0.94, P < 0.05) but the rumen pH that was measured continuously using a telemetry system resulted in lower values than the bench pH meter (overall mean of 5.38 and 5.48, resp., P = 0.0001). The telemetry system was able to detect smaller changes in rumen fluid pH and was more accurate in diagnosing both subacute ruminal lactic acidosis and acute ruminal lactic acidosis in sheep. PMID:24967422

  1. Solubilization of matrix protein M1/M from virions occurs at different pH for orthomyxo- and paramyxoviruses.

    PubMed

    Zhirnov, O P

    1990-05-01

    Enveloped viruses, of which the orthomyxo- and paramyxoviruses are members, are known to be uncoated by nonionic detergents in a salt concentration-dependent manner. In this study we have shown that detergent uncoating of myxoviruses depends not only on salt concentration but also on pH. Treatment of orthomyxoviruses with Nonidet-P40 or Triton N-101 at low salt concentrations results in solubilization of surface virion glycopolypeptides in alkaline and neutral pH (9.0-6.5), but in acidic pH (6.0-5.0) the viral matrix protein M1 is also removed, and the viral ribonucleoprotein complex is released. Conversely, the paramyxovirus matrix protein M is more completely solubilized in alkaline pH (pH 9.0) than in neutral and acidic pH 7.4-5.0. The described pH-dependent differences are discussed in terms of orthomyxo- and paramyxovirus uncoating in target cells.

  2. PhD Students' Work Conditions and Study Environment in University- and Industry-Based PhD Programmes

    ERIC Educational Resources Information Center

    Kolmos, A.; Kofoed, L. B.; Du, X. Y.

    2008-01-01

    During the last 10 years, new models of funding and training PhD students have been established in Denmark in order to integrate industry into the entire PhD education. Several programmes have been conducted where it is possible to co-finance PhD scholarships or to become an employee as an industrial PhD in a company. An important question is what…

  3. The effects of pH on the growth of Chlorella vulgaris and its interactions with cadmium toxicity.

    PubMed

    Rachlin, J W; Grosso, A

    1991-05-01

    The effects of pH alone, and in combination with exposure to 0.89 microM cadmium, on the growth response of the green alga Chlorella vulgaris were evaluated. Acidic (3.0-6.2) and alkaline (8.3-9.0) pH values retarded the growth of this alga. Optimal growth occurred when the pH of the medium was adjusted to values of 7.5 and 8.0. When the cells were exposed to pH adjusted medium plus the presence of 0.89 microM Cd, a value known to reduce population growth by 50% at the control pH of 6.9, the affects were additive at the acidic (3.0-5.0) pH ranges. At alkaline pH values of 8.3-9.0 all toxicity responses could be explained by pH adjustment alone, indicating that additional cadmium toxicity was absent. At pH values of 7.5 and 8.0, cadmium toxicity was mitigated against, and resultant growth at pH 8.0 was at the same enhanced rate as this pH without cadmium.

  4. The Role of pH Regulation in Cancer Progression.

    PubMed

    McIntyre, Alan; Harris, Adrian L

    Frequently observed phenotypes of tumours include high metabolic activity, hypoxia and poor perfusion; these act to produce an acidic microenvironment. Cellular function depends on pH homoeostasis, and thus, tumours become dependent on pH regulatory mechanisms. Many of the proteins involved in pH regulation are highly expressed in tumours, and their expression is often of prognostic significance. The more acidic tumour microenvironment also has important implications with regard to chemotherapeutic and radiotherapeutic interventions. In addition, we review pH-sensing mechanisms, the role of pH regulation in tumour phenotype and the use of pH regulatory mechanisms as therapeutic targets.

  5. Continuous intra-arterial pH measurement.

    PubMed

    Oeseburg, B; Kwant, G; Schut, J K; Veenstra, J

    1980-07-01

    A flexible glass electrode catheter with a diameter of 3 mm has been developed for pH measurement in the arterial system of dogs. In combination with a galvanically isolated amplifier, an undisturbed pH signal could be obtained from the aorta. The system was fast enough to truly record pH changes synchronous with respiration and was shown to be insensitive to variations in blood flow velocity. Good agreement was found between pH catheter readings nd pH values of simultaneously taken arterial samples as measured with a conventional capillary glass electrode.

  6. Time course of pH change in plant epidermis using microscopic pH imaging system

    NASA Astrophysics Data System (ADS)

    Dan, Risako; Shimizu, Megumi; Kazama, Haruko; Sakaue, Hirotaka

    2010-11-01

    We established a microscopic pH imaging system to track the time course of pH change in plant epidermis in vivo. In the previous research, we have found out that anthocyanin containing cells have higher pH. However, it was not clear whether the anthocyanin increased the pH or anthocyanin was synthesized result from the higher pH. Therefore, we further investigated the relationship between anthocyanin and pH change. To track the time course of pH change in plant epidermis, we established a system using luminescent imaging technique. We used HPTS (8-Hydroxypyrene-1,3,6-Trisulfonate) as pH indicator and applied excitation ratio imaging method. Luminescent image was converted to a pH distribution by obtained in vitro calibration using known pH solution. Cellular level observation was enabled by merging microscopic color picture of the same region to the pH change image. The established system was applied to epidermal cells of red-tip leaf lettuce, Lactuca Sativa L. and the time course was tracked in the growth process. We would discuss about the relationship between anthocyanin and pH change in plant epidermis.

  7. Effects of ph, carbonate, orthophosphate, and redox potential on cuprosolvency

    SciTech Connect

    Schock, M.R.; Lytle, D.A.; Clement, J.A.

    1995-12-01

    A comprehensive solubility model for copper in drinking water has been developed, that is consistent with available data for copper dissolution and passivation in drinking water systems. Copper solubility (cuprosolvency) is greatly affected by the redox conditions of the systems. The concentration of Cu(I) is dominated by Cu{sub 2}O(s) or CuOH(s) solid phases, plus soluble aqueous ammonia and chloride complexes. In new piping, the concentration of Cu(II) is mainly governed by Cu(OH){sub 2}(s) (cupric hydroxide), rather than CuO(s) (tenorite) or Cu{sub 2}(OH){sub 2}CO{sub 3}(s)(malachite). Complexation of Cu(II) by DIC and hydroxide ion is extremely important. Increases in DIC are predicted to cause significant increases in copper solubility in the pH range of 7.5--10. Utilities may trade off increasing cuprosolvency by DIC addition for ensuring adequate buffering intensity in the finished water. Sufficient dosages of orthophosphate in the pH range of 6.5 to 7.5 may reduce cuprosolvency under oxidizing conditions. Sulfate may decrease cuprosolvency under some conditions, or may interfere with the formation of cupric hydroxide films under mildly alkaline conditions. Dissolved oxygen and chlorine residual play complicated roles in determining copper concentrations after various standing times. Frequently, 48--72 hours are necessary to reach equilibrium levels of copper in disinfected systems.

  8. Histidine oxidation photosensitized by pterin: pH dependent mechanism.

    PubMed

    Castaño, Carolina; Oliveros, Esther; Thomas, Andrés H; Lorente, Carolina

    2015-12-01

    Aromatic pterins accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder, due to the oxidation of tetrahydrobiopterin, the biologically active form of pterins. In this work, we have investigated the ability of pterin, the parent compound of aromatic pterins, to photosensitize the oxidation of histidine in aqueous solutions under UV-A irradiation. Histidine is an α-amino acid with an imidazole functional group, and is frequently present at the active sites of enzymes. The results highlight the role of the pH in controlling the competition between energy and electron transfer mechanisms. It has been previously demonstrated that pterins participate as sensitizers in photosensitized oxidations, both by type I (electron-transfer) and type II mechanisms (singlet oxygen ((1)O2)). By combining different analytical techniques, we could establish that a type I photooxidation was the prevailing mechanism at acidic pH, although a type II mechanism is also present, but it is more important in alkaline solutions.

  9. Adaptation of Ustilago maydis to extreme pH values: A transcriptomic analysis.

    PubMed

    Cervantes-Montelongo, Juan Antonio; Aréchiga-Carvajal, Elva Teresa; Ruiz-Herrera, José

    2016-11-01

    Fungi are capable to adapt to environments with different pH values. Here we used microarrays to analyze the transcriptomic response of the Basidiomycota Ustilago maydis when transferred from a neutral pH medium to acidic, or alkaline media. Yeast and hyphal monomorphic mutants were used as controls, permitting the identification of 301 genes differentially regulated during the transfer from neutral to an acidic medium, of which 162 were up-regulated and 139 down-regulated. When cells were transferred to an alkaline medium, we identified 797 differentially regulated genes, 335 up-regulated, and 462 down-regulated. The category showing the highest number of regulated genes during the change to either pH, besides "unclassified," was "metabolism," indicating that a very important factor for adaptation is a change in the metabolic machinery. These data reveal that adaptation of U. maydis to environments with different pH involves a severe modification of the transcription machinery to cope with the new conditions, and that the stress by an alkaline environment is more drastic than a change to an acidic medium. The data also revealed that only a minor proportion of the identified genes are under the apparent control of the Pal/Rim pathway, indicating that pH adaptation of this fungus involves other than this cannonical pathway.

  10. Attributing seasonal pH variability in surface ocean waters to governing factors

    NASA Astrophysics Data System (ADS)

    Hagens, M.; Middelburg, J. J.

    2016-12-01

    On-going ocean acidification and increasing availability of high-frequency pH data have stimulated interest to understand seasonal pH dynamics in surface waters. Here we show that it is possible to accurately reproduce observed pH values by combining seasonal changes in temperature (T), dissolved inorganic carbon (DIC), and total alkalinity (TA) from three time series stations with novel pH sensitivity factors. Moreover, we quantify the separate contributions of T, DIC, and TA changes to winter-to-summertime differences in pH, which are in the ranges of -0.0334 to -0.1237, 0.0178 to 0.1169, and -0.0063 to 0.0234, respectively. The effects of DIC and temperature are therefore largely compensatory, and are slightly tempered by changes in TA. Whereas temperature principally drives pH seasonality in low-latitude to midlatitude systems, winter-to-summer DIC changes are most important at high latitudes. This work highlights the potential of pH sensitivity factors as a tool for quantifying the driving mechanisms behind pH changes.

  11. Effect of pH and metal ions on the decomposition rate of S-nitrosocysteine.

    PubMed

    Gu, Jun; Lewis, Randy S

    2007-09-01

    S-nitrosothiols (RSNOs) have many biological functions including platelet deactivation, immunosupression, neurotransmission, and host defense. Most of the functions are attributed to nitric oxide (NO) release during S-nitrosothiol decomposition. As the simplest biologically occurring S-nitrosothiol, S-nitrosocysteine (CySNO) has been widely used as an NO donor and has also been incorporated into biomedical polymers. Knowledge of the CySNO decomposition rate is important for assessing the impact of CySNO on various bioengineering applications or biological systems. In this work, spectrophotometer measurements of CySNO decomposition in the presence of metal ions showed that the decomposition rate is highly susceptible to the pH. The maximum decomposition occurs near physiological pH (near 7.4) while in the acidic (pH < 6) and alkaline (pH > 9) condition CySNO is very stable. This demonstrates that blood provides an optimized environment for the decomposition of CySNO leading to the release of NO. The CySNO decomposition rate can also be affected by buffers with different purity levels in the presence and absence of metal ion chelators-although all buffers show the same pH phenomenon of maximizing near physiological pH. An equilibrium model of metal ions as a function of pH provides a plausible explanation for the pH dependence on the experimental decomposition rate.

  12. Improvement of the Performance of an Electrocoagulation Process System Using Fuzzy Control of pH.

    PubMed

    Demirci, Yavuz; Pekel, Lutfiye Canan; Altinten, Ayla; Alpbaz, Mustafa

    2015-12-01

    The removal efficiencies of electrocoagulation (EC) systems are highly dependent on the initial value of pH. If an EC system has an acidic influent, the pH of the effluent increases during the treatment process; conversely, if such a system has an alkaline influent, the pH of the effluent decreases during the treatment process. Thus, changes in the pH of the wastewater affect the efficiency of the EC process. In this study, we investigated the dynamic effects of pH. To evaluate approaches for preventing increases in the pH of the system, the MATLAB/Simulink program was used to develop and evaluate an on-line computer-based system for pH control. The aim of this work was to study Proportional-Integral-Derivative (PID) control and fuzzy control of the pH of a real textile wastewater purification process using EC. The performances and dynamic behaviors of these two control systems were evaluated based on determinations of COD, colour, and turbidity removal efficiencies.

  13. Activity and stability trends of perovskite oxides for oxygen evolution catalysis at neutral pH.

    PubMed

    Han, Binghong; Risch, Marcel; Lee, Yueh-Lin; Ling, Chen; Jia, Hongfei; Shao-Horn, Yang

    2015-09-21

    Perovskite oxides (ABO3) have been studied extensively to promote the kinetics of the oxygen evolution reaction (OER) in alkaline electrolytes. However, developing highly active catalysts for OER at near-neutral pH is desirable for many photoelectrochemical/electrochemical devices. In this paper, we systematically studied the activity and stability of well-known perovskite oxides for OER at pH 7. Previous activity descriptors established for perovskite oxides at pH 13, such as having an eg occupancy close to unity or having an O p-band center close to Fermi level, were shown to scale with OER activity at pH 7. Stability was a greater challenge at pH 7 than at pH 13, where two different modes of instability were identified from combined transmission electron microscopy and density functional theory analyses. Perovskites with O p-band close to Fermi level showed leaching of A-site atoms and surface amorphization under all overpotentials examined at pH 7, while those with O p-band far from Fermi level were stable under low OER current/potential but became unstable at high current/potential accompanied by leaching of B-site atoms. Therefore, efforts are needed to enhance the activity and stability of perovskites against A-site or B-site loss if used at neutral pH.

  14. Accurate transport properties for O(3P)-H and O(3P)-H2

    NASA Astrophysics Data System (ADS)

    Dagdigian, Paul J.; Kłos, Jacek; Warehime, Mick; Alexander, Millard H.

    2016-10-01

    Transport properties for collisions of oxygen atoms with hydrogen atoms and hydrogen molecules have been computed by means of time-independent quantum scattering calculations. For the O(3P)-H(2S) interaction, potential energy curves for the four OH electronic states emanating from this asymptote were computed by the internally-contracted multi-reference configuration interaction method, and the R-dependent spin-orbit matrix elements were taken from Parlant and Yarkony [J. Chem. Phys. 110, 363 (1999)]. For the O(3P)-H2 interaction, diabatic potential energy surfaces were derived from internally contracted multi-reference configuration interaction calculations. Transport properties were computed for these two collision pairs and compared with those obtained with the conventional approach that employs isotropic Lennard-Jones (12-6) potentials.

  15. To PhET or Not To PhET: That Is the Question

    NASA Astrophysics Data System (ADS)

    Casao, Robert

    2008-10-01

    The investigation examined use of a Physics Education Technology (PhET) simulation versus a hands-on lab activity on student's conceptual understanding of physics content. Topics of study included vectors, projectile motion, direct current (DC) circuits, and the photoelectric effect. Participants consisted of high school juniors and seniors enrolled in a physics course. Assessment instruments consisted of questions taken from the Vector Evaluation Test, the Electric Circuits Concept Evaluation test, textbook test banks, or written to address concepts under evaluation. Data collection consisted of a pre-test score, a post-test score, and a gain score. The conceptual understanding of the experimental and the control groups did not significantly differ for vectors and DC circuits. The conceptual understanding of the experimental and control groups did significantly differ for projectile motion. The results indicated a conceptual gain for students using the photoelectric effect simulation. Student attitudes towards the PhET simulations were positive.

  16. Combined M.D./Ph.D. and Ph.D. Training Program in Breast Cancer Prevention

    DTIC Science & Technology

    2005-07-01

    of trainees, and the development of courses for the program. In the sixth year, we recruited Ms. Anne Miermont and Mr. Mark Markowski . Ms. Miermont...Baltimore County. Mr. Markowski , an MD/PhD student received his BS in Biochemistry and Mathematics from Georgetown University. Ms. Miermont is...currently working in the lab of her Thesis Mentor, Dr. Priscilla Furth. Mr. Markowski is currently working in the lab of Thesis Mentor Dr. Edward Gelmann

  17. Italia-Netherland PhD Program: the I.O. PhD Research Program.

    PubMed

    Bellissima, Valentina; Borghesi, Alessandro; Bozzetti, Valentina; Dessì, Angelica; Fabiano, Adele; Risso, Francesco M; Salvo, Vincenzo; Satriano, Angela; Silvagni, Davide; Varrica, Alessandro; van Bel, Frank; Visser, Gerard H A; Vles, Hans Js; Zimmermann, Luc J I; Gavilanes, Antonio D W; Gazzolo, Diego

    2011-10-01

    In the framework of long-term scientific collaboration among the founder members coming from Holland and Italy there was a growing consensus to activate a philosophical doctorate (PhD) program, involving young Italian researchers in the field of perinatal medicine, neonatology and pediatrics. The aims were to promote excellence in research, offering to young Italian physicians the opportunity to maturate an International research experience leading to PhD degree, and to promote human and technological improvement energies in perinatal, neonatal and pediatrics research. Thus, an official collaboration among the Dutch Universities from Maastricht and Utrecht and the Italian Children's Hospital from Alessandria, has been activated on March 1st 2010, finalized to the PhD program. The experimental phase included the selection of projects and relative candidates after an interview-selection focusing on their scientific attitudes and the availability on their research projects. Candidates' selection started on May 2010 and on September 29th ten projects and candidates have been approved by the scientific commission. Research topics included: perinatal asphyxia, aging and the origin of adulthood neurodegenerative disease, neuroprotective strategies, biochemical pulmonology, intrauterine growth retardation and perinatal teratology. To date, all projects have been approved by local Ethics Committee from the University/Hospital of origin of the candidates. Five manuscripts have been published and/or submitted to international Journals regarding pneumology, perinatal asphyxia and teratology, whilst about 60-70% of data regarding clinical studies have already been collected.

  18. The effect of pH on the survival of leptospires in water*

    PubMed Central

    Smith, C. E. Gordon; Turner, L. H.

    1961-01-01

    One of the factors on which the incidence of leptospirosis is dependent is the survival time of shed leptospires in surface water or soil water, and this time is in turn affected by the acidity or alkalinity of the water. The authors have therefore studied the survival of four leptospiral serotypes in buffered distilled water at pH's ranging from 5.3 to 8.0. All survived longer in alkaline than in acid water, and significant differences between the serotypes were found in response to pH. Survival at pH's under 7.0 ranged from 10 to 117 days and at pH's over 7.0 from 21 to 152 days. Survival was also studied in aqueous extracts of soil samples from different areas in Malaya; no correlation was found between pH and survival time. It was also noted that in a group of Malayan ricefields a low incidence of leptospirosis in man was accompanied by a high infection rate among rodents, and when it was found that this phenomenon could not be explained by pH or salinity, attention was turned to the soil. Bentonite clay, similar to the montmorrillonite clay of the ricefields, was found to adsorb about half the leptospires in suspension. The authors recommend that field study of this laboratory observation be undertaken. PMID:20604084

  19. The effect of pH on anaerobic fermentation of primary sludge at room temperature.

    PubMed

    Wu, Haiyan; Yang, Dianhai; Zhou, Qi; Song, Zhoubing

    2009-12-15

    The effect of pH in the range of 3.0-11.0 on anaerobic fermentation of primary sludge (PS) was investigated at room temperature. The experimental results showed that the concentrations of soluble chemical oxygen demands (SCOD), soluble protein and carbohydrate and short-chain fatty acids (SCFAs) under alkaline conditions were significantly higher than those under other pHs. At fermentation time of 5 days, the average SCFAs concentration increased from 968 to 3511mg COD/L with the increase of pH from 3.0 to 10.0. However, further increasing pH to 11.0 resulted in the decrease of SCFAs. At pH 10.0, acetic, propionic and iso-valeric acids were the three main products, and the volatile suspended solids (VSS) reduction reached 38%. It was also observed that at any pH value investigated, there were obvious ammonia and phosphorus releases during fermentation. According to this study it is obvious that alkaline pH benefited the soluble organic carbon production from PS.

  20. A neutral ceramidase homologue from Dictyostelium discoideum exhibits an acidic pH optimum.

    PubMed Central

    Monjusho, Hatsumi; Okino, Nozomu; Tani, Motohiro; Maeda, Mineko; Yoshida, Motonobu; Ito, Makoto

    2003-01-01

    The nucleotide sequence reported for the Dictyostelium discoideum ceramidase is available on the DNA Data Bank of Japan (DDBJ). Ceramidases (CDases) are currently classified into three categories (acid, neutral and alkaline) based on their optimal pHs and primary structures. Here, we report the first exception to this rule. We cloned the CDase cDNA, consisting of 2142 nucleotides encoding 714 amino-acid residues, from the slime mould, Dictyostelium discoideum. The putative amino-acid sequence indicates 32-42% identity with various neutral CDases, but does not show any similarity to the acid and alkaline CDases, indicating the enzyme should be classified as a neutral CDase. However, overexpression of the cDNA in D. discoideum resulted in increased CDase activity at an acidic, but not a neutral pH range. Knockout of the gene in slime mould eliminated CDase activity at acidic pH. The recombinant enzyme expressed in the slime mould was purified and then characterized. Consequently, the purified CDase was found to exhibit the maximal activity at approx. pH 3.0. The singular pH dependency of slime mould CDase is not derived from the specific post-translational modification in the slime mould, because the enzyme showed an acidic pH optimum even when expressed in Chinese hamster ovary cells, whereas rat neutral-CDase exhibited a neutral pH optimum when expressed in slime mould. PMID:12943537

  1. In vitro synthesis and purification of PhIP-deoxyguanosine and PhIP-DNA oligomer covalent complexes

    SciTech Connect

    Freeman, J.

    1994-12-01

    2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a heterocyclic amine compound formed when meats are cooked at high temperatures. PhIP damages DNA by forming covalent complexes with DNA carcinogen. In an effort to understand how the binding of PhIP to DNA may cause cancer, it is important to characterize the structures of PhIP-damaged DNA molecules. Our HPLC data support fluorescence and {sup 32}P Post-labeling studies which indicate the formation of several species of 2{prime}deoxyguanosine-(dG) or oligodeoxynucleotide-PhIP adducts. The reaction of PhIP with dG resulted in a reddish precipitate that was likely the major adduct, N-(deoxyguanosin-8-yl)-PhIP (dG-C8-PhIP) adduct, with a more polar adduct fraction remaining in the supernatant. Reversed-phase HPLC analysis of the adducts in the supernatant revealed the existence of species of much shorter retention times than the dG-C8-PhIP adduct, confirming that these species are more polar than dG-C8-PhIP. At least four adducts were formed in the reaction of PhIP with DNA oligomer. HPLC analysis of the PhIP-DNA oligomer supernatant after butanol extractions revealed four unresolved peaks which spectra had maximum wavelengths between 340 and 360 nm. Though adduct peaks were not completely resolved, there was {approximately}3 minutes interval between the DNA oligomer peak and the adduct peaks. Furthermore, fluorescence emission data of the DNA oligomer-PhIP adduct solution show heterogeneous binding. The more polar PhIP adducts were fraction-collected and their structures will be solved by nuclear magnetic resonance or x-ray crystallography.

  2. [Modeling research on impact of pH on metals leaching behavior of air pollution control residues from MSW incinerator].

    PubMed

    Zhang, Hua; He, Pin-Jing; Li, Xin-Jie; Shao, Li-Ming

    2008-01-01

    Metals leaching behavior of air pollution control residues (APC residues) from municipal solid waste incinerator (MSWI) is greatly dependent on the leachate pH. pH-varying leaching tests and Visual MINTEQ modeling were conducted to investigate the mechanism of pH effect on the metals leaching characteristics from MSWI APC residues. Results show that, under acidic environment (for Cd, Zn, and Ni, pH < 8; for Pb, Cu, and Cr, pH < 6; for Al, pH < 4), leaching concentrations of metals increase greatly with the decrease of pH. Release of amphoteric metals, Pb and Zn, can be induced in strong alkaline leachate, reaching to 42 and 2.4 mg x L(-1) at pH 12.5 respectively. The equilibrium modeling results are well in agreement with the analyzed leaching concentrations. Variation of leachate pH changes the metals speciation in the leaching system, thus influencing their leaching concentrations. Speciation and leaching behavior of Pb, Zn, Cu, Ca, and Al mainly depend on their dissolution/precipitation reactions under different leachate pH. Leachability of Cd, Cr, and Ni can be lowered under acidic and neutral leachate pH due to HFO adsorption, while under alkaline conditions, the effect of adsorption is not significant and dissolution/precipitation becomes the major reactions controlling the leaching toxicity of these heavy metals.

  3. Structural Insight into and Mutational Analysis of Family 11 Xylanases: Implications for Mechanisms of Higher pH Catalytic Adaptation

    PubMed Central

    Bai, Wenqin; Zhou, Cheng; Zhao, Yueju; Wang, Qinhong; Ma, Yanhe

    2015-01-01

    To understand the molecular basis of higher pH catalytic adaptation of family 11 xylanases, we compared the structures of alkaline, neutral, and acidic active xylanases and analyzed mutants of xylanase Xyn11A-LC from alkalophilic Bacillus sp. SN5. It was revealed that alkaline active xylanases have increased charged residue content, an increased ratio of negatively to positively charged residues, and decreased Ser, Thr, and Tyr residue content relative to non-alkaline active counterparts. Between strands β6 and β7, alkaline xylanases substitute an α-helix for a coil or turn found in their non-alkaline counterparts. Compared with non-alkaline xylanases, alkaline active enzymes have an inserted stretch of seven amino acids rich in charged residues, which may be beneficial for xylanase function in alkaline conditions. Positively charged residues on the molecular surface and ionic bonds may play important roles in higher pH catalytic adaptation of family 11 xylanases. By structure comparison, sequence alignment and mutational analysis, six amino acids (Glu16, Trp18, Asn44, Leu46, Arg48, and Ser187, numbering based on Xyn11A-LC) adjacent to the acid/base catalyst were found to be responsible for xylanase function in higher pH conditions. Our results will contribute to understanding the molecular mechanisms of higher pH catalytic adaptation in family 11 xylanases and engineering xylanases to suit industrial applications. PMID:26161643

  4. Histidine-proline-rich glycoprotein as a plasma pH sensor. Modulation of its interaction with glycosaminoglycans by ph and metals.

    PubMed

    Borza, D B; Morgan, W T

    1998-03-06

    The middle domain of plasma histidine-proline-rich glycoprotein (HPRG) contains unusual tandem pentapeptide repeats (consensus G(H/P)(H/P)PH) and binds heparin and transition metals. Unlike other proteins that interact with heparin via lysine or arginine residues, HPRG relies exclusively on histidine residues for this interaction. To assess the consequences of this unusual requirement, we have studied the interaction between human plasma HPRG and immobilized glycosaminoglycans (GAGs) using resonant mirror biosensor techniques. HPRG binding to immobilized heparin was strikingly pH-sensitive, producing a titration curve with a midpoint at pH 6.8. There was little binding of HPRG to heparin at physiological pH in the absence of metals, but the interaction was promoted by nanomolar concentrations of free zinc and copper, and its pH dependence was shifted toward alkaline pH by zinc. The affinity of HPRG for various GAGs measured in a competition assay decreased in the following order: heparin > dermatan sulfate > heparan sulfate > chondroitin sulfate A. Binding of HPRG to immobilized dermatan sulfate had a midpoint at pH 6.5, was less influenced by zinc, and exhibited cooperativity. Importantly, plasminogen interacted specifically with GAG-bound HPRG. We propose that HPRG is a physiological pH sensor, interacting with negatively charged GAGs on cell surfaces only when it acquires a net positive charge by protonation and/or metal binding. This provides a mechanism to regulate the function of HPRG (the local pH) and rationalizes the role of its unique, conserved histidine-proline-rich domain. Thus, under conditions of local acidosis (e.g. ischemia or hypoxia), HPRG can co-immobilize plasminogen at the cell surface as well as compete for heparin with other proteins such as antithrombin.

  5. Modeling CO2 degassing and pH in a stream-aquifer system

    USGS Publications Warehouse

    Choi, J.; Hulseapple, S.M.; Conklin, M.H.; Harvey, J.W.

    1998-01-01

    Pinal Creek, Arizona receives an inflow of ground water with high dissolved inorganic carbon (57-75 mg/l) and low pH (5.8-6.3). There is an observed increase of in-stream pH from approximately 6.0-7.8 over the 3 km downstream of the point of groundwater inflow. We hypothesized that CO2 gas-exchange was the most important factor causing the pH increase in this stream-aquifer system. An existing transport model, for coupled ground water-surface water systems (OTIS), was modified to include carbonate equilibria and CO2 degassing, used to simulate alkalinity, total dissolved inorganic carbon (C(T)), and pH in Pinal Creek. Because of the non-linear relation between pH and C(T), the modified transport model used the numerical iteration method to solve the non-linearity. The transport model parameters were determined by the injection of two tracers, bromide and propane. The resulting simulations of alkalinity, C(T) and pH reproduced, without fitting, the overall trends in downstream concentrations. A multi-parametric sensitivity analysis (MPSA) was used to identify the relative sensitivities of the predictions to six of the physical and chemical parameters used in the transport model. MPSA results implied that C(T) and pH in stream water were controlled by the mixing of ground water with stream water and CO2 degassing. The relative importance of these two processes varied spatially depending on the hydrologic conditions, such as stream flow velocity and whether a reach gained or lost stream water caused by the interaction with the ground water. The coupled transport model with CO2 degassing and generalized sensitivity analysis presented in this study can be applied to evaluate carbon transport and pH in other coupled stream-ground water systems.An existing transport model for coupled groundwater-surface water systems was modified to include carbonate equilibria and CO2 degassing. The modified model was used to simulate alkalinity, total dissolved inorganic carbon (CT) and

  6. Effect of Ca2+ and K+ on the intracellular pH of an Escherichia coli L-form.

    PubMed

    Onoda, T; Oshima, A; Fukunaga, N; Nakatani, A

    1992-06-01

    The L-form NC7, derived from Escherichia coli K12, grew in a complex medium containing 0.2 M-CaCl2 as osmotic stabilizer, but not at pH values above 7.8. The cessation of growth at alkaline pH was not due to cell death. In complex media containing K+ or Na+, the L-form grew ove a wide pH range. Growth at alkaline pH was inhibited by 1 mM-amiloride, indicating that Na+/H+ antiport activity was required for growth at alkaline pH. The internal pH (pHi) of the L-form in media containing K+, Na+ or Ca2+ was constant at about 7.8 to 8.0 at external pH (pHo) values of 7.2 and 8.2. The rates of O2 consumption by intact cells, lactate oxidation by membrane vesicles from cells grown in Ca(2+)-containing medium, and cell division were all strongly repressed under alkaline conditions.

  7. Synergistic and Antagonistic Effects of Salinity and pH on Germination in Switchgrass (Panicum virgatum L.)

    PubMed Central

    Liu, Yuan; Wang, Quanzhen; Zhang, Yunwei; Cui, Jian; Chen, Guo; Xie, Bao; Wu, Chunhui; Liu, Haitao

    2014-01-01

    The effects of salt-alkaline mixed stress on switchgrass were investigated by evaluating seed germination and the proline, malondialdehyde (MDA) and soluble sugar contents in three switchgrass (Panicum virgatum L.) cultivars in order to identify which can be successfully produced on marginal lands affected by salt-alkaline mixed stress. The experimental conditions consisted of four levels of salinity (10, 60, 110 and 160 mM) and four pH levels (7.1, 8.3, 9.5 and 10.7). The effects of salt-alkaline mixed stress with equivalent coupling of the salinity and pH level on the switchgrass were explored via model analyses. Switchgrass was capable of germinating and surviving well in all treatments under low-alkaline pH (pH≤8.3), regardless of the salinity. However, seed germination and seedling growth were sharply reduced at higher pH values in conjunction with salinity. The salinity and pH had synergetic effects on the germination percentage, germination index, plumular length and the soluble sugar and proline contents in switchgrass. However, these two factors exhibited antagonistic effects on the radicular length of switchgrass. The combined effects of salinity and pH and the interactions between them should be considered when evaluating the strength of salt-alkaline mixed stress. PMID:24454834

  8. Cell wall pH and auxin transport velocity

    NASA Technical Reports Server (NTRS)

    Hasenstein, K. H.; Rayle, D.

    1984-01-01

    According to the chemiosmotic polar diffusion hypothesis, auxin pulse velocity and basal secretion should increase with decreasing cell wall pH. Experiments were designed to test this prediction. Avena coleoptile sections were preincubated in either fusicoccin (FC), cycloheximide, pH 4.0, or pH 8.0 buffer and subsequently their polar transport capacities were determined. Relative to controls, FC enhanced auxin (IAA) uptake while CHI and pH 8.0 buffer reduced IAA uptake. Nevertheless, FC reduced IAA pulse velocity while cycloheximide increased velocity. Additional experiments showed that delivery of auxin to receivers is enhanced by increased receiver pH. This phenomenon was overcome by a pretreatment of the tissue with IAA. Our data suggest that while acidic wall pH values facilitate cellular IAA uptake, they do not enhance pulse velocity or basal secretion. These findings are inconsistent with the chemiosmotic hypothesis for auxin transport.

  9. pH measurement of low-conductivity waters

    USGS Publications Warehouse

    Busenberg, Eurybiades; Plummer, L.N.

    1987-01-01

    pH is an important and commonly measured parameter of precipitation and other natural waters. The various sources of errors in pH measurement were analyzed and procedures for improving the accuracy and precision of pH measurements in natural waters with conductivities of < 100 uS/cm at 25 C are suggested. Detailed procedures are given for the preparation of dilute sulfuric acid standards to evaluate the performance of pH electrodes in low conductivity waters. A daily check of the pH of dilute sulfuric acid standards and deionized water saturated with a gas mixture of low carbon dioxide at partial pressure (air) prior to the measurement of the pH of low conductivity waters is suggested. (Author 's abstract)

  10. Chapter A6. Section 6.4. pH

    USGS Publications Warehouse

    Wilde, Franceska D.; Busenberg, Eurybiades; Radtke, Dean B.

    2006-01-01

    Measurement of pH is critical to the understanding of the viability and vulnerability of environmental waters and is considered a master variable in determining the aqueous geochemistry of an aqueous system. pH is a measure that represents the hydrogen-ion concentration (activity) of a solution. This section of the National Field Manual (NFM) describes U.S. Geological Survey (USGS) guidance and protocols for measurement of pH in ground and surface waters.

  11. Ratiometric Imaging of Extracellular pH in Dental Biofilms.

    PubMed

    Schlafer, Sebastian; Dige, Irene

    2016-03-09

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

  12. Quantum dot photoluminescence lifetime-based pH nanosensor.

    PubMed

    Ruedas-Rama, Maria J; Orte, Angel; Hall, Elizabeth A H; Alvarez-Pez, Jose M; Talavera, Eva M

    2011-03-14

    The first CdSe/ZnS quantum dot photoluminescence lifetime-based pH nanosensor has been developed. The average lifetime of mercaptopropionic acid-capped QD nanosensors showed a linear response in the pH range of 5.2-6.9. These nanosensors have been satisfactorily applied for pH estimation in simulated intracellular media, with high sensitivity and high selectivity toward most of the intracellular components.

  13. Nanosensor aided photoacoustic measurement of pH in vivo

    NASA Astrophysics Data System (ADS)

    Ray, Aniruddha; Yoon, Hyung Ki; Kopelman, Raoul; Wang, Xueding

    2013-03-01

    pH plays a critical role in many aspects of cell and tissues physiology. Lower pH is also a typical characteristic of arthritic joints and tumor tissues. These pH anomalies are also exploited in different drug delivery mechanisms. Here we present, a new method of pH sensing in vivo using spectroscopic photoacoustic measurements facilitated by pH sensitive nanosensors. The nanosensors consist of Seminaphtharhodafluor (SNARF), a pH sensitive dye, encapsulated in a specially designed polyacrylamide hydrogel matrix with a hydrophobic core. The photoacoustic intensity ratio between the excitation wavelengths of 585nm and 565nm increases in the pH range from 6.0 to 8.0 and is used to determine the pH of the local environment. These nanosensors are biodegradable, biocompatible, have a long plasma lifetime and can be targeted to any type of cells or tissues by surface modification using proper targeting moieties. The encapsulation of the dye prevents the interaction of the dye with proteins in plasma and also reduces the dye degradation. The SNARF dye in its free form loses 90% of its absorbance in presence of albumin, a protein found in abundance in plasma, and this has severely limited its adaptation to in vivo environments. In comparison, the SNARF nanosensors lose only 16% of their absorbance in the same environment. We employ these nanosensors to demonstrate the feasibility of pH sensing in vivo through photoacoustic measurements on a rat joint model.

  14. pH inactivation of phosphofructokinase arrests postmortem glycolysis.

    PubMed

    England, Eric M; Matarneh, Sulaiman K; Scheffler, Tracy L; Wachet, Céline; Gerrard, David E

    2014-12-01

    Fresh meat quality development is influenced by pH decline that results from muscle glycolyzing energy substrates postmortem. The exact reason why glycolysis stops in the presence of residual glycogen remains unclear. We hypothesized that a critical glycolytic enzyme loses activity near the ultimate pH of meat. Porcine longissimus muscle samples were subjected to an in vitro system that mimics postmortem anaerobic metabolism at buffered pH values (7.0, 6.5, 6.0, 5.5 or 5.0). At pH7.0, 6.5, and 6.0, glycogenolysis and glycolysis proceeded normally while pH5.5 stopped lactate formation. Additional experimentation indicated that phosphofructokinase lost activity at pH5.5 while all other glycolytic enzymes remained active. A similar inactivation of phosphofructokinase was observed when using chicken and beef muscle. Elevated temperature hastened pH decline and phosphofructokinase activity loss. Thus, pH inactivates phosphofructokinase and arrests postmortem glycolysis, which may explain the similar ultimate pH across meat of different species.

  15. Cytoplasmic pH and human erythrocyte shape.

    PubMed Central

    Gedde, M M; Davis, D K; Huestis, W H

    1997-01-01

    Altered external pH transforms human erythrocytes from discocytes to stomatocytes (low pH) or echinocytes (high pH). The mechanism of this transformation is unknown. The preceding companion study (Gedde and Huestis) demonstrated that these shape changes are not mediated by changes in membrane potential, as has been reported. The aim of this study was to identify the physiological properties that mediate this shape change. Red cells were placed in a wide range of physiological states by manipulation of buffer pH, chloride concentration, and osmolality. Morphology and four potential predictor properties (cell pH, membrane potential, cell water, and cell chloride concentration) were assayed. Analysis of the data set by stratification and nonlinear multivariate modeling showed that change in neither cell water nor cell chloride altered the morphology of normal pH cells. In contrast, change in cell pH caused shape change in normal-range membrane potential and cell water cells. The results show that change in cytoplasmic pH is both necessary and sufficient for the shape changes of human erythrocytes equilibrated in altered pH environments. PMID:9138569

  16. Effects of pH and Temperature on the Stability of Fumonisins in Maize Products

    PubMed Central

    Bryła, Marcin; Waśkiewicz, Agnieszka; Szymczyk, Krystyna; Jędrzejczak, Renata

    2017-01-01

    This paper is a study of the stability of fumonisins in dough based on maize flour prepared in a phosphate buffer with a pH of 3.5, 5.5 or 7.5 and baked at a temperature within the range of 100–250 °C. Buffers with various pH values were tested, since it is well-known that pH may significantly influence interactions of fumonisins with other substances. A standard analytical procedure was used to determine the concentration of free fumonisins. Hydrolysis in an alkaline medium was then applied to reveal the hidden forms, while the total fumonisins concentations was determined in another measurement. The total concentration of fumonisins was statistically higher in pH = 3.5 and pH = 5.5 than the concentration of free fumonisins; no similar difference was found at pH = 7.5. The applied phosphate buffer pH 7.5 may enhance solubility of fumonisins, which would increase extraction efficiency of free analytes, thereby decreasing the difference between concentrations of total and free fumonisins. Hydrolysed B1 fumonisin (HFB1) and partially hydrolysed B1 fumonisin (isomers a and b: PHFB1a and PHFB1b, respectively) were the main investigated substances. For baking temperatures below 220 °C, fumonisins were slightly more stable for pH = 5.5 than for pH = 3.5 and pH = 7.5. In both of these latter cases, the concentration of partially hydrolysed fumonisins grew initially (up to 200 °C) with an increase in the baking temperature, and then dropped. Similar behaviour was observed for free HFB1, which may suggest the following fumonisin degradation mechanism: initially, the tricarballylic acid (TCA) groups are removed from the molecules, and next, the HFB1 molecules disintegrate. PMID:28257053

  17. [Effect of pH on precipitate composition during phosphorus recovery as struvite from swine wastewater].

    PubMed

    Bao, Xiao-Dan; Ye, Zhi-Long; Ma, Jian-Hua; Chen, Shao-Hua; Lin, Li-Feng; Yan, Yi-Jun

    2011-09-01

    Phosphorus recovery as struvite from swine wastewater was carried out. Fourier transform infrared spectroscopy (FTIR), Xray diffraction (XRD) and mass balance analysis were utilized to analyze the species of precipitated minerals under different pH conditions. Results showed that increasing pH from 8.0 to 9.0 resulted in the increase of phosphorus removal efficiency from 85% to 94%. A relatively stable phosphorus removal at 94% was observed at pH 9.0-11.0, whereas a drastic decline to 70% was detected when pH increased to 12.0. The minerals precipitated in the deposits were struvite (MgNH4PO4 x 6H2O), K-struvite (MgKPO4 x 6H2O), amorphous calcium phosphate [Ca3 (PO4 )2 (x) xH2O, ACP] and Mg (OH)2. Struvite was the dominant species in the precipitate at pH 8.0-9.0. Enhancing pH from 9.0 to 10.0 resulted in struvite decline and gave rise to K-struvite and ACP steadily. With regard to highly alkaline conditions at pH above 10, drastic decrease of struvite and rapid increase of ACP and Mg(OH)2 were observed. Maximum concentration of K-struvite was obtained at pH 11.0, following a sharp decline to pH 12.0. Controlling pH between 8.0 and 9.0 could inhibit other minerals formation and obtain the highly pure struvite crystal product.

  18. Dynamics of pH modification of an acidic protein bait used for tropical fruit flies (Diptera: Tephritidae).

    PubMed

    Heath, Robert R; Vazquez, Aime; Schnell, Elena Q; Villareal, Janett; Kendra, Paul E; Epsky, Nancy D

    2009-12-01

    Several species of Anastrepha and Bactrocera fruit flies (Diptera: Tephritidae) are captured in traps baited with the protein bait NuLure combined with borax (sodium tetraborate decahydrate) in an aqueous solution, typically 9% NuLure (vol:vol) with 3% borax (wt:vol). NuLure is an acid hydrolysate of corn and has an acidic pH. Addition of borax makes the solution more alkaline, and increase in alkalinity results in increase of ammonia release from the bait solution. This is a very dynamic system, with resultant pH affected by factors such as the amount of borax added, the pH of the water used for preparation, the age of the bait solution, and the development of microbial growth. Problems with borax include amount needed to increase alkalinity of NuLure solutions, which creates difficulties in disposing of spent bait in fruit fly trapping programs. Therefore, research was conducted to evaluate NaOH as an alternative method to increase alkalinity of NuLure solutions. Laboratory experiments compared effect of NaOH versus borax for pH modification on changes in pH and ammonia content of NuLure solutions over time. Although NuLure/NaOH solutions could be adjusted to a more alkaline pH than NuLure/borax solutions, borax plays a critical role in pH stability over time. However, the pH of NuLure/NaOH is stabilized when propylene glycol (10% vol:vol) was used to prepare the bait solution. The use of NaOH can provide an alternative to the use of borax to increase bait solution alkalinity.

  19. Natural skin surface pH is on average below 5, which is beneficial for its resident flora.

    PubMed

    Lambers, H; Piessens, S; Bloem, A; Pronk, H; Finkel, P

    2006-10-01

    Variable skin pH values are being reported in literature, all in the acidic range but with a broad range from pH 4.0 to 7.0. In a multicentre study (N = 330), we have assessed the skin surface pH of the volar forearm before and after refraining from showering and cosmetic product application for 24 h. The average pH dropped from 5.12 +/- 0.56 to 4.93 +/- 0.45. On the basis of this pH drop, it is estimated that the 'natural' skin surface pH is on average 4.7, i.e. below 5. This is in line with existing literature, where a relatively large number of reports (c. 50%) actually describes pH values below 5.0; this is in contrast to the general assumption, that skin surface pH is on average between 5.0 and 6.0. Not only prior use of cosmetic products, especially soaps, have profound influence on skin surface pH, but the use of plain tap water, in Europe with a pH value generally around 8.0, will increase skin pH up to 6 h after application before returning to its 'natural' value of on average below 5.0. It is demonstrated that skin with pH values below 5.0 is in a better condition than skin with pH values above 5.0, as shown by measuring the biophysical parameters of barrier function, moisturization and scaling. The effect of pH on adhesion of resident skin microflora was also assessed; an acid skin pH (4-4.5) keeps the resident bacterial flora attached to the skin, whereas an alkaline pH (8-9) promotes the dispersal from the skin.

  20. Predicting thermal inactivation in media of different pH of Salmonella grown at different temperatures.

    PubMed

    Mañas, Pilar; Pagán, Rafael; Raso, Javier; Condón, Santiago

    2003-10-15

    The influence of the growth temperature and the pH of the heating medium on the heat resistance at different temperatures of Salmonella typhimurium ATCC 13311 was studied and described mathematically. The shift of the growth temperature from 10 to 37 degrees C increased heat resistance of S. typhimurium fourfold. The pH of the heating medium at which heat resistance was maximum was pH 6 for cells grown at 37 degrees C, but changed with growth temperature. The alkalinization of the heating medium from pH 6 to pH 7.7 decreased the heat resistance of cells grown at 37 degrees C by a factor of 3. Neither the growth temperature nor the pH modified the z values significantly (4.9 degrees C). The decimal reduction times at different treatment temperatures, in buffers of different pH of cells of S. typhimurium grown at different temperatures, were accurately described by a mathematical equation (correlation coefficient of 0.97). This equation was also tested for Salmonella senftenberg 775W (ATCC 43845) and Salmonella enteritidis ATCC 13076, strains in which the correlation coefficients between the observed and the theoretically calculated values were 0.91 and 0.98, respectively.

  1. Influence of pH of spray solution on optoelectronic properties of cadmium oxide thin films

    NASA Astrophysics Data System (ADS)

    Hodlur, R. M.; Rabinal, M. K.

    2015-03-01

    Highly conducting transparent cadmium oxide thin films were prepared by the conventional spray pyrolysis technique. The pH of the spray solution is varied by adding ammonia/hydrochloric acid. The effect of pH on the morphology, crystallinity and optoelectronic properties of these films is studied. The structural analysis showed all the films in the cubic phase. For the films with pH < 7 (acidic condition), the preferred orientation is along the (111) direction and for those with pH >7 (alkaline condition), the preferred orientation is along the (200) direction. A lowest resistivity of 9.9 × 10-4 Ω·cm (with carrier concentration = 5.1 × 1020 cm-3, mobility = 12.4 cm2/(V·s)) is observed for pH ≈ 12. The resistivity is tuned almost by three orders of magnitude by controlling the bath pH with optical transmittance more than 70%. Thus, the electrical conductivity of CdO films could be easily tuned by simply varying the pH of the spray solution without compromising the optical transparency.

  2. Hydrolyzed polyacrylamide grafted maize starch based microbeads: application in pH responsive drug delivery.

    PubMed

    Setty, C Mallikarjuna; Deshmukh, Anand S; Badiger, Aravind M

    2014-09-01

    The present study details the synthesis, characterization and pharmaceutical application of hydrolysed polyacrylamide grafted maize starch (HPam-g-MS) as promising polymeric material for the development of pH responsive microbeads. Different grades of graft copolymer were synthesized by changing the net microwave irradiation time, while keeping all other factors constant. Acute oral toxicity study performed in rodents ensured the bio-safety of graft copolymer for clinical application. Various batches of aceclofenac loaded microbeads were prepared by ionic gelation method using synthesized graft copolymers and evaluated for formulation parameters. FTIR spectroscopy confirmed the chemical compatibility between drug and graft copolymer. Results of in vitro release study (USP type-II) carried out in two different pH media (pH 1.2 acid buffer and pH 7.4 phosphate buffer) showed that release rate of drug from developed microbeads was a function of both: (a) surrounding pH and (b) the matrix composition. The drug release was relatively higher at alkaline pH as compared to acidic pH and this feature is desirable from viewpoint of site specific drug delivery. A direct correlation was observed between percentage grafting and microbeads performance and it presents a scope for further research on application and optimization of HPam-g-MS based microbeads as drug delivery carriers.

  3. Influence of pH on wound-healing: a new perspective for wound-therapy?

    PubMed

    Schneider, Lars Alexander; Korber, Andreas; Grabbe, Stephan; Dissemond, Joachim

    2007-02-01

    Wound healing is a complex regeneration process, which is characterised by intercalating degradation and re-assembly of connective tissue and epidermal layer. The pH value within the wound-milieu influences indirectly and directly all biochemical reactions taking place in this process of healing. Interestingly it is so far a neglected parameter for the overall outcome. For more than three decades the common assumption amongst physicians was that a low pH value, such as it is found on normal skin, is favourable for wound healing. However, investigations have shown that in fact some healing processes such as the take-rate of skin-grafts require an alkaline milieu. The matter is thus much more complicated than it was assumed. This review article summarises the existing literature dealing with the topic of pH value within the wound-milieu, its influence on wound healing and critically discusses the currently existing data in this field. The conclusion to be drawn at present is that the wound pH indeed proves to be a potent influential factor for the healing process and that different pH ranges are required for certain distinct phases of wound healing. Further systematic data needs to be collected for a better understanding of the pH requirements under specific circumstances. This is important as it will help to develop new pH targeted therapeutic strategies.

  4. Immunomodulatory effects of temperature and pH of water in an Indian freshwater sponge.

    PubMed

    Mukherjee, Soumalya; Bhunia, Anindya Sundar; Bhunia, Niladri Sekhar; Ray, Mitali; Ray, Sajal

    2016-07-01

    Eunapius carteri, a freshwater sponge of India, inhabits the ponds and lakes and experiences variations of temperature and pH of water throughout the year. Sponges bear evolutionary and ecological importance with limited information on their immunological attribute and adaptational resilience in a changing environment. This paper reports temperature and pH specific responses of immune related parameters in sponge maintained in the experimental conditions of laboratory. Innate immunological parameters like phagocytosis and generation of cytotoxic molecules like superoxide anion, nitric oxide and phenoloxidase activity were estimated in E. carteri at different environmentally realistic water temperatures (10, 20, 30 and 40°C) and pH (6.4, 7.4 and 8.4). Phagocytosis and cytotoxicity are established as important immune parameters of invertebrates. Calalase, an antioxidant enzyme and phosphatases are involved in pathogen destruction and are considered as components of innate immunity. Activities of catalase, acid and alkaline phosphatases were estimated in E. carteri at different thermal regimes and pH. Modulation of phagocytic and cytotoxic responses and the activities of catalase and phosphatases at different water temperatures and pH indicated temperature and pH specific immunological status of E. carteri. Present investigation deals with the effects of selected hydrological parameters on the fundamental immune related parameters in sponge indicating its adaptational plasticity. Immunological resilience of this species in the face of variation of water temperature and pH is thought to be a special adaptive feature of sponge, a reported "living fossil".

  5. Regulation of neuronal connexin-36 channels by pH.

    PubMed

    González-Nieto, Daniel; Gómez-Hernández, Juan M; Larrosa, Belén; Gutiérrez, Cristina; Muñoz, María D; Fasciani, Ilaria; O'Brien, John; Zappalà, Agata; Cicirata, Federico; Barrio, Luis C

    2008-11-04

    Neurotransmission through electrical synapses plays an important role in the spike synchrony among neurons and oscillation of neuronal networks. Indeed, electrical transmission has been implicated in the hypersynchronous electrical activity of epilepsy. We have investigated the influence of intracellular pH on the strength of electrical coupling mediated by connexin36 (Cx36), the principal gap junction protein in the electrical synapses of vertebrates. In striking contrast to other connexin isoforms, the activity of Cx36 channels decreases following alkalosis rather than acidosis when it is expressed in Xenopus oocytes and N2A cells. This uncoupling of Cx36 channels upon alkalinization occurred in the vertebrate orthologues analyzed (human, mouse, chicken, perch, and skate). While intracellular acidification caused a mild or moderate increase in the junctional conductance of virtually all these channels, the coupling of the skate Cx35 channel was partially blocked by acidosis. The mutational analysis suggests that the Cx36 channels may contain two gating mechanisms operating with opposing sensitivity to pH. One gate, the dominant mechanism, closes for alkalosis and it probably involves an interaction between the C- and N-terminal domains, while a secondary acid sensing gate only causes minor, albeit saturating, changes in coupling following acidosis and alkalosis. Thus, we conclude that neuronal Cx36 channels undergo unique regulation by pH(i) since their activity is inhibited by alkalosis rather than acidosis. These data provide a novel basis to define the relevance and consequences of the pH-dependent modulation of Cx36 synapses under physiological and pathological conditions.

  6. Physiological effects of pH gradients on Escherichia coli during plasmid DNA production.

    PubMed

    Cortés, José T; Flores, Noemí; Bolívar, Francisco; Lara, Alvaro R; Ramírez, Octavio T

    2016-03-01

    A two-compartment scale-down system was used to mimic pH heterogeneities that can occur in large-scale bioreactors. The system consisted of two interconnected stirred tank reactors (STRs) where one of them represented the conditions of the bulk of the fluid and the second one the zone of alkali addition for pH control. The working volumes ratio of the STRs was set to 20:1 in order to simulate the relative sizes of the bulk and alkali addition zones, respectively, in large-scale bioreactors. Residence times (tR ) in the alkali addition STR of 60, 120, 180, and 240 s were simulated during batch cultures of an engineered Escherichia coli strain that produced plasmid DNA (pDNA). pH gradients of up to 0.9 units, between the two compartments, were attained. The kinetic, stoichiometric, and pDNA topological changes due to the pH gradients were studied and compared to cultures at constant pH of 7.2 and 8.0. As the tR increased, the pDNA and biomass yields, as well as pDNA final titer decreased, whereas the accumulation of organic acids increased. Furthermore, the transcriptional response of 10 selected genes to alkaline stress (pH 8.0) and pH gradients was monitored at different stages of the cultures. The selected genes coded for ion transporters, amino acids catabolism enzymes, and transcriptional regulators. The transcriptional response of genes coding for amino acids catabolism, in terms of relative transcription level and stage of maximal expression, was different when the alkaline stress was constant or transient. This suggests the activation of different mechanisms by E. coli to cope with pH fluctuations compared to constant alkaline pH. Moreover, the transcriptional response of genes related to negative control of DNA synthesis did not correlate with the lower pDNA yields. This is the first study that reports the effects of pH gradients on pDNA production by E. coli cultures. The information presented can be useful for the design of better bioreactor scale

  7. Mapping Soil pH Buffering Capacity of Selected Fields

    NASA Technical Reports Server (NTRS)

    Weaver, A. R.; Kissel, D. E.; Chen, F.; West, L. T.; Adkins, W.; Rickman, D.; Luvall, J. C.

    2003-01-01

    Soil pH buffering capacity, since it varies spatially within crop production fields, may be used to define sampling zones to assess lime requirement, or for modeling changes in soil pH when acid forming fertilizers or manures are added to a field. Our objective was to develop a procedure to map this soil property. One hundred thirty six soil samples (0 to 15 cm depth) from three Georgia Coastal Plain fields were titrated with calcium hydroxide to characterize differences in pH buffering capacity of the soils. Since the relationship between soil pH and added calcium hydroxide was approximately linear for all samples up to pH 6.5, the slope values of these linear relationships for all soils were regressed on the organic C and clay contents of the 136 soil samples using multiple linear regression. The equation that fit the data best was b (slope of pH vs. lime added) = 0.00029 - 0.00003 * % clay + 0.00135 * % O/C, r(exp 2) = 0.68. This equation was applied within geographic information system (GIS) software to create maps of soil pH buffering capacity for the three fields. When the mapped values of the pH buffering capacity were compared with measured values for a total of 18 locations in the three fields, there was good general agreement. A regression of directly measured pH buffering capacities on mapped pH buffering capacities at the field locations for these samples gave an r(exp 2) of 0.88 with a slope of 1.04 for a group of soils that varied approximately tenfold in their pH buffering capacities.

  8. The Semen pH Affects Sperm Motility and Capacitation.

    PubMed

    Zhou, Ji; Chen, Li; Li, Jie; Li, Hongjun; Hong, Zhiwei; Xie, Min; Chen, Shengrong; Yao, Bing

    2015-01-01

    As the chemical environment of semen can have a profound effect on sperm quality, we examined the effect of pH on the motility, viability and capacitation of human sperm. The sperm in this study was collected from healthy males to avoid interference from other factors. The spermatozoa cultured in sperm nutrition solution at pH 5.2, 6.2, 7.2 and 8.2 were analyzed for sperm total motility, progressive motility (PR), hypo-osmotic swelling (HOS) rate, and sperm penetration. Our results showed that these parameters were similar in pH 7.2 and 8.2 sperm nutrition solutions, but decreased in pH 5.2 and 6.2 solutions. The HOS rate exhibited positive correlation with the sperm total motility and PR. In addition, the sperm Na(+)/K(+)-ATPase activity at different pHs was measured, and the enzyme activity was significantly lower in pH 5.2 and 6.2 media, comparing with that in pH 8.2 and pH 7.2 solutions. Using flow cytometry (FCM) and laser confocal scanning microscopy (LCSM) analysis, the intracellular Ca2(+ )concentrations of sperm cultured in sperm capacitation solution at pH 5.2, 6.2, 7.2 and 8.2 were determined. Compared with that at pH 7.2, the mean fluorescence intensity of sperm in pH 5.2 and 6.2 media decreased significantly, while that of pH 8.2 group showed no difference. Our results suggested that the declined Na(+)/K(+)-ATPase activity at acidic pHs result in decreased sperm movement and capacitation, which could be one of the mechanisms of male infertility.

  9. Biomedical PhD education--an international perspective.

    PubMed

    Mulvany, Michael J

    2013-05-01

    The PhD, otherwise known as the doctor of philosophy or Dr. Phil., is an internationally recognized degree, indicating that the PhD graduate has received training in research under supervision. Traditionally, the PhD was the route to an academic career, with most successful PhD graduates receiving tenured university positions. However, over the past 20-30 years, and particularly the past 10 years, the situation has changed dramatically. Governments in many countries have invested massively in PhD education, believing that trained researchers will contribute to the 'knowledge society', and thus increase the competitiveness of their countries in the future economies of the world. Thus, only a small fraction of PhD graduates now end up in academic research. Yet, the PhD remains a research degree, and indeed, institutions have become heavily dependent on PhD students for their research output. The situation has thus created a paradox. On the one hand, it has become essential for institutions to have many PhD students and for the research performed to be of the highest level. On the other hand, the careers of PhD students are not necessarily going to be directly related to the research performed during their PhD studies. The purpose of this article is to explore how this seeming paradox is being addressed in biomedicine and to show that far from being inconsistent that the two aspects are in fact complementary. The article is based on the author's experience as Head of Aarhus Graduate School of Health Sciences 2002-2011 and his work with graduate schools across Europe and internationally through the organization ORPHEUS.

  10. Macroalgae contribute to nested mosaics of pH variability in a subarctic fjord

    NASA Astrophysics Data System (ADS)

    Krause-Jensen, D.; Duarte, C. M.; Hendriks, I. E.; Meire, L.; Blicher, M. E.; Marbà, N.; Sejr, M. K.

    2015-08-01

    The Arctic Ocean is considered the most vulnerable ecosystem to ocean acidification, and large-scale assessments of pH and the saturation state for aragonite (Ωarag) have led to the notion that the Arctic Ocean is already close to a corrosive state. In high-latitude coastal waters the regulation of pH and Ωarag is, however, far more complex than offshore because increased biological activity and input of glacial meltwater affect pH. Effects of ocean acidification on calcifiers and non-calcifying phototrophs occupying coastal habitats cannot be derived from extrapolation of current and forecasted offshore conditions, but they require an understanding of the regimes of pH and Ωarag in their coastal habitats. To increase knowledge of the natural variability in pH in the Arctic coastal zone and specifically to test the influence of benthic vegetated habitats, we quantified pH variability in a Greenland fjord in a nested-scale approach. A sensor array logging pH, O2, PAR, temperature and salinity was applied on spatial scales ranging from kilometre scale across the horizontal extension of the fjord; to 100 m scale vertically in the fjord, 10-100 m scale between subtidal habitats with and without kelp forests and between vegetated tidal pools and adjacent vegetated shores; and to centimetre to metre scale within kelp forests and millimetre scale across diffusive boundary layers of macrophyte tissue. In addition, we assessed the temporal variability in pH on diurnal and seasonal scales. Based on pH measurements combined with point samples of total alkalinity, dissolved inorganic carbon and relationships to salinity, we also estimated variability in Ωarag. Results show variability in pH and Ωarag of up to 0.2-0.3 units at several scales, i.e. along the horizontal and vertical extension of the fjord, between seasons and on a diel basis in benthic habitats and within 1 m3 of kelp forest. Vegetated intertidal pools exhibited extreme diel pH variability of > 1.5 units and

  11. Characterization of an invertase with pH tolerance and truncation of its N-terminal to shift optimum activity toward neutral pH.

    PubMed

    Du, Liqin; Pang, Hao; Wang, Zilong; Lu, Jian; Wei, Yutuo; Huang, Ribo

    2013-01-01

    Most invertases identified to date have optimal activity at acidic pH, and are intolerant to neutral or alkaline environments. Here, an acid invertase named uninv2 is described. Uninv2 contained 586 amino acids, with a 100 amino acids N-terminal domain, a catalytic domain and a C-terminal domain. With sucrose as the substrate, uninv2 activity was optimal at pH 4.5 and at 45°C. Removal of N-terminal domain of uninv2 has shifted the optimum pH to 6.0 while retaining its optimum temperaure at 45°C. Both uninv2 and the truncated enzyme retained highly stable at neutral pH at 37°C, and they were stable at their optimum pH at 4°C for as long as 30 days. These characteristics make them far superior to invertase from Saccharomyces cerevisiae, which is mostly used as industrial enzyme.

  12. Effects of pH on the chlorination process of phenols in drinking water.

    PubMed

    Ge, Fei; Zhu, Lizhong; Chen, Hairong

    2006-05-20

    Toxic organic compounds detected generally in source water could combine with chlorine and contribute significantly to chlorination disinfection by-products (CDBPs). The effects of pH on species distribution of CDBPs and the kinetics of chlorination were investigated using phenol as a model of ionizable toxic organic compounds in the pH range of 6.0-9.0. It was found that five chlorination products including 2-monochlorophenol (2-MCP), 4-monochlorophenol (4-MCP), 2,6-dichlorophenol (2,6-DCP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (TCP) were produced by successive chlorination substitution. MCP (2-MCP and 4-MCP) were the dominant products and phenol partly remained in acid media, while TCP and DCP (2,6-DCP and 2,4-DCP) were the main components in neutral and alkaline media. A steady equilibrium of phenol and its chlorination products was reached in 20-30 min in acid-, neutral- and slightly alkaline media, and was delayed to 60-180 min in alkaline media. The difference in properties between phenols and phenolates, and those between HOCl and ClO(-) should be considered simultaneously in explaining the effects of pH on the chlorination process with the theory of electrophilic substitution. These results show that pH plays an important regulating role in the species distribution of CDBPs and the kinetics of chlorination for ionizable toxic organic compounds in chlorination.

  13. Wide pH range tolerance in extremophiles: towards understanding an important phenomenon for future biotechnology.

    PubMed

    Dhakar, Kusum; Pandey, Anita

    2016-03-01

    Microorganisms that inhabit the extreme pH environments are classified as acidophiles and alkaliphiles. A number of studies emerged from extreme high (hot springs, hydrothermal vents) as well as low temperature (arctic and antarctic regions, sea water, ice shelf, marine sediments, cold deserts, glaciers, temperate forests, and plantations) environments have highlighted the occurrence of microorganisms (thermophiles/psychrophiles) with the ability to tolerate wide pH range, from acidic to alkaline (1.5-14.0 in some cases), under laboratory conditions. However, the sampling source (soil/sediment) of these microorganisms showed the pH to be neutral or slightly acidic/alkaline. The aim of the present review is to discuss the phenomenon of wide pH range tolerance possessed by these microorganisms as a hidden character in perspective of their habitats, possible mechanisms, phylogeny, ecological and biotechnological relevance, and future perspectives. It is believed that the genome is a probable reservoir of the hidden variations. The extremophiles have the ability to adapt against the environmental change that is probably through the expression/regulation of the specific genes that were already present in the genome. The phenomenon is likely to have broad implications in biotechnology, including both environmental (such as bioremediation, biodegradation, and biocontrol), and industrial applications (as a source of novel extremozymes and many other useful bioactive compounds with wide pH range tolerance).

  14. Effect of pH on the thermal gelation of carob protein isolate.

    PubMed

    Bengoechea, Carlos; Ortiz, Sara E Molina; Guerrero, Antonio; Puppo, María C

    2017-01-01

    The specific aim of this work was to study the capability of a carob protein isolate (CPI) to produce self-supporting gels when subjected to a thermal treatment. CPI aqueous dispersions (10, 20 and 30 wt% protein basis) at three different pH values (2, 6 and 10) were subjected to a heating/cooling process (95 °C-30 min/4 °C-24 h) leading to the formation of self-supporting gels. Those gels were characterized for dynamic rheological properties; water holding capacity (WHC); textural properties; extractability in different media; scanning electron microscopy; and SDS-PAGE profiles of the soluble proteins. The results demonstrated that self-supporting CPI gels can only be obtained at concentrations higher than 20 wt%, being favoured at extreme pH values, especially at alkaline pH. At pH 10, gels with higher dynamic elastic and hardness properties and appropriate WHC were formed due to the promotion of disulphide bonds formation. Thus, if higher rheological properties and hardness are required for thermally treated CPI gels, alkaline pH conditions that favour hydrophobic interactions and disulphide bonding should be selected.

  15. Roles of the pH signaling transcription factor PacC in Wangiella (Exophiala) dermatitidis

    PubMed Central

    Wang, Qin; Szaniszlo, Paul J.

    2009-01-01

    To study the function of the PacC transcription factor in Wangiella dermatitidis, a black, polymorphic fungal pathogen of humans with yeast-phase predominance, the PACC gene was cloned, sequenced, disrupted and expressed. Three zinc finger DNA-binding motifs were found at the N-terminus, and a signaling protease cleavage site at the C-terminus. PACC was more expressed at neutral-alkaline pH than at acidic pH. Truncation at about 40 residues of the coding sequence upstream of the conserved protease processing cleavage site of PacC affected growth on a nutrient-rich medium, increased sensitivity to Na+ stress, decreased yeast growth at neutral-alkaline pH, and repressed hyphal growth on a nutrient-poor medium at 25°C.Truncation at the coding sequence for the conserved signaling protease box of PacC impaired growth and reduced RNA expression of the class II chitin synthase gene at acidic pH. The results suggested that PacC is important not only for the adaptation of W. dermatitidis to different ambient pH conditions and Na+ stress conditions, but also for influencing yeast-hyphal transitions in this agent of phaeohyphomycosis. PMID:19501183

  16. The Ph.D. Surplus - Realities and Illusions.

    ERIC Educational Resources Information Center

    Hansen, Harold P.

    Every 6 years the number of Ph.D.'s produced doubles. At this point about 1 percent of the babies born 27 years ago gets a Ph.D. This production rate will probably increase to 6 percent of the adult population. With the present situation in higher education, which includes an average retirement after 40 years of service, the supply already…

  17. Tracking the PhD Students' Daily Computer Use

    ERIC Educational Resources Information Center

    Sim, Kwong Nui; van der Meer, Jacques

    2015-01-01

    This study investigated PhD students' computer activities in their daily research practice. Software that tracks computer usage (Manic Time) was installed on the computers of nine PhD students, who were at their early, mid and final stage in doing their doctoral research in four different discipline areas (Commerce, Humanities, Health Sciences and…

  18. Effect of pH on biological phosphorus uptake.

    PubMed

    Serralta, J; Ferrer, J; Borrás, L; Seco, A

    2006-12-05

    An anaerobic aerobic laboratory scale sequencing batch reactor (SBR) was operated to study the effect of pH on enhanced biological phosphorus removal. Seven steady states were achieved under different operating conditions. In all of them, a slight variation in the pH value was observed during anaerobic phase. However, pH rose significantly during aerobic phase. The increase observed was due to phosphorus uptake and carbon dioxide stripping. When pH was higher than 8.2-8.25 the phosphorus uptake rate clearly decreased. The capability of Activated Sludge Model No. 2d (ASM2d) and Biological Nutrient Removal Model No. 1 (BNRM1) to simulate experimental results was evaluated. Both models successfully characterized the enhanced biological phosphorus removal performance of the SBR. Furthermore, BNRM1 also reproduced the pH variations observed and the decrease in the phosphorus uptake rate. This model includes a switch function in the kinetic expressions to represent the pH inhibition in biological processes. The pH inhibition constants related to polyphosphate storage process were obtained by adjusting model predictions to measured phosphorus concentrations. On the other hand, pH inhibition should be included in ASM2d to accurately simulate experimental phosphorus evolution observed in an A/O SBR.

  19. Research Collaboration and Commercialization: The PhD Candidate Perspective

    ERIC Educational Resources Information Center

    Dooley, Lawrence; Kenny, Breda

    2015-01-01

    This paper explores PhD students' perceptions of their entrepreneurial and commercial capabilities, their attitude towards university supports and the extent to which they engage in external collaboration. The study concentrated on current PhD researchers at one university in Ireland as a unit of analysis and provides encouraging evidence from the…

  20. Factors associated with ruminal pH at herd level.

    PubMed

    Geishauser, T; Linhart, N; Neidl, A; Reimann, A

    2012-08-01

    The objective of this study was to evaluate factors associated with ruminal pH at herd level. Four hundred and thirty-two cows of a Thuringian dairy herd were sampled before claw trimming using a rumen fluid scoop. Volume and pH of the rumen sample were measured, and lactation number, percentage of concentrates in the ration, days in milk (DIM), time of day, and daily milk yield were recorded. Rumen sampling was successful in 99.8% of the cows. The average sample volume was 25 mL. Rumen sample pH decreased with increasing percentage of concentrates in the ration. Ruminal pH decreased from calving to 77 DIM, and grew subsequently to 330 DIM. During the day, rumen pH followed a sinus curve, with maxima in the morning (0915 h) and afternoon (1533 h), and a minimum around noon (1227 h). Ruminal pH decreased with increasing daily milk yield. Lactation number interacted with daily milk yield on rumen pH. The percentage of concentrates in the ration, DIM, time of day, and daily milk yield were significant factors affecting ruminal pH at the herd level.

  1. Consideration of Factors Affecting Strip Effluent PH and Sodium Content

    SciTech Connect

    Peters, T.

    2015-07-29

    A number of factors were investigated to determine possible reasons for why the Strip Effluent (SE) can sometimes have higher than expected pH values and/or sodium content, both of which have prescribed limits. All of the factors likely have some impact on the pH values and Na content.

  2. International Mobility of French Ph.D.s

    ERIC Educational Resources Information Center

    Bonnard, Claire; Calmand, Julien; Giret, Jean-François

    2017-01-01

    This research investigates the determinants of international mobility of Ph.D.s upon graduation. It is based on a survey of 400 young Ph.D.s who graduated in France between 2003 and 2008, half of whom were still abroad more than six years after graduating. The impacts of personal, occupational and scientific characteristics on the successive…

  3. The PhD Viva: A Space for Academic Development

    ERIC Educational Resources Information Center

    Share, Michelle

    2016-01-01

    This study examined the viva experiences of 87 social science PhD graduates from three Irish higher education institutions through a questionnaire that assessed outcome, preparation, conduct and post-viva. The majority were awarded their PhD with minor corrections, considered their viva as a summative assessment, and emphasised its purpose as…

  4. The Undergraduate Origins of PhD Economists Revisited

    ERIC Educational Resources Information Center

    Stock, Wendy A.; Siegfried, John J.

    2015-01-01

    The authors update prior analyses of the undergraduate origins of individuals who earn a PhD in economics in the United States. They include the list of the top institutions worldwide graduating the largest number of undergraduates who subsequently earn an economics PhD from a U.S. university and lists of American institutions with the largest…

  5. A Renaissance in Engineering PhD Education

    ERIC Educational Resources Information Center

    Akay, Adnan

    2008-01-01

    This paper addresses the role of engineering PhD education and its relationship to innovation and technology, and the need to reconsider how we educate PhD engineers. Much of the effort on engineering education in the last two decades focused on undergraduate education with a few exceptions that relate to master degree programs. Doctoral education…

  6. The Importance of Having a Ph.D., Career Advice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A presentation on the importance of having a PhD to motivate Initiative to Maximize Student Diversity Program (IMSD) undergrads towards conducting research, pursuing careers in the biomedical field, applying to grad school, and getting a Ph.D., based upon ARS scientist's experiences as a student, a ...

  7. Can Community Colleges Survive the PhD Glut?

    ERIC Educational Resources Information Center

    Taylor, Anita

    The impact of the current employment situation on hiring faculty for community college teaching is examined. It is concluded that prospects for improving the quality of learning in community colleges are not particularly enhanced by the apparently growing surplus of new PhDs in our field. On the contrary, it is suggested that hiring PhDs for…

  8. PhDs in Australia, from the Beginning

    ERIC Educational Resources Information Center

    Dobson, Ian R.

    2012-01-01

    The Australian PhD is a relatively recent phenomenon, the first three being awarded in 1948. Before that, most Australian scholars typically went to Britain (predominantly) or the USA to undertake their doctoral studies. The aim of this research note is to provide a brief statistical history of the Australian PhD, noting changes over time between…

  9. Sugar sensing based on induced pH changes.

    PubMed

    Kim, Youngmi; Hilderbrand, Scott A; Weissleder, Ralph; Tung, Ching-Hsuan

    2007-06-14

    A sensory assembly consisting of a pH sensitive NIR dye and an arylboronic acid shows ratiometric absorption changes with increased fluorescence intensity upon addition of sugar in aqueous media; this demonstrates a new signal transduction mechanism for the detection of sugar based on pH changes induced in the microenvironment of the sensory assembly.

  10. Evanescent-wave spectroscopic fiber optic pH sensor

    NASA Astrophysics Data System (ADS)

    Egami, C.; Takeda, K.; Isai, M.; Ogita, M.

    1996-02-01

    We demonstrate a new type of fiber optic pH sensor, which is the application of evanescent-wave spectroscopic technique. A methyl red (MR)-doped-poly(methyl methacrylate) (PMMA) film that coated as part of cladding does function as a pH sensor probe. In this system MR doped in PMMA is used as indicator dye for pH measurement. The absorption spectrum shift in wavelength of indicator dye enables us to get the pH value. The sensor probe is immersed in water solution containing a small proportion of acetic acid over the wide pH range of 5.0 to 7.0. The chemical interaction between MR in sensor probe and hydrogen ion in the water solution causes a change in the dipole moment of MR, that is, the absorption spectrum macroscopically. The evanescent-wave spectroscopic technique provides the measurement of the absorption spectrum shift over a broad range of visible wavelength. The result of experiment was that MR absorption spectrum shifted by 40 nm every increase of 1.0 in pH. The small change in the pH value can be sensed as a large wavelength shift of pH indicator absorption spectrum.

  11. Rethinking PhD Learning Incorporating Communities of Practice

    ERIC Educational Resources Information Center

    Shacham, Miri; Od-Cohen, Yehudit

    2009-01-01

    This paper grows from research which focuses on the learning characteristics of PhD students, incorporating communities of practice both during their studies and beyond completion of their PhD, and drawing on theories of adult learning and lifelong learning. It shows how professional discourse enhances academic discourse through student engagement…

  12. The Early Development of Electronic pH Meters

    ERIC Educational Resources Information Center

    Hines, Wallis G.; de Levie, Robert

    2010-01-01

    A 19-year-old undergraduate at the University of Chicago, Kenneth Goode, in 1921 came up with the idea of an electronic pH meter, worked out some of its initial problems, and set in motion an international scientific effort that culminated in the current, wide availability of electronic pH meters. Except for the replacement of vacuum tubes by…

  13. Ambulatory pH Monitoring: New Advances and Indications

    PubMed Central

    Lutsi, Brant

    2006-01-01

    Ambulatory pH monitoring is currently used to objectively demonstrate abnormal degrees of esophageal acid exposure in patients with suspected gastroesophageal reflux disease. The development of wireless pH capsule recording has improved the tolerability and increased the duration of pH recording. Use of symptom-reflux correlation measures and pH testing, combining periods off and on PPI therapy, serves to optimize the performance of conventional pH testing. On the other hand, devices that measure bile reflux as well as nonacid reflux (esophageal impedance testing) have broadened the definition of gastroesophageal reflux and present potential explanations for patients with continued symptoms despite high-dose PPI therapy. These advances and their current and future clinical applications are reviewed

  14. ['Sandwich PhD': considerations for a successful experience abroad].

    PubMed

    Salvetti, Marina de Goes; Bueno, Mariana; Gastaldo, Denise; Kimura, Amélia Fumiko; Pimenta, Cibele Andrucioli de Mattos

    2013-03-01

    International PhD internship, named "Sandwich PhD" in Brazil is an opportunity to improve research abilities, to become known in academic area and to establish and/or increase work opportunities in an international context. In this article, we describe key factors regarding the planning and development of the "Sandwich PhD" as experienced by professors and students involved in the collaboration between the School of Nursing, University of São Paulo and Lawrence S. Bloomberg Faculty of Nursing, University of Toronto, Canada. We also present the participation of PhD students' network as an alternative to the "Sandwich PhD". An international experience, when well-planned and developed correctly, promotes students' personal and professional development and favors the internationalization of Brazilian graduate programs and research groups.

  15. The entomopathogenic fungus Metarhizium anisopliae alters ambient pH, allowing extracellular protease production and activity.

    PubMed

    St Leger, R J; Nelson, J O; Screen, S E

    1999-10-01

    Ambient pH regulates the expression of virulence genes of Metarhizium anisopliae, but it was unknown if M. anisopliae can regulate ambient pH. Mutants of M. anisopliae altered in production of oxalic acid were evaluated for the interrelationship of ambient pH, buffering capacity added to media, growth, and generation of extracellular proteases and ammonia. Wild-type and acid-overproducing mutants [Acid(+)] grew almost as well at pH 8 as at pH 6, but acid-non-producing [Acid(-)] mutants showed limited growth at pH 8, indicating that acid production is linked to the ability to grow at higher pH. Production of ammonia by M. anisopliae was strongly stimulated by low levels of amino acids in the medium when cells were derepressed for nitrogen and carbon. Likewise, although Aspergillus fumigatus and Neurospora crassa produced some ammonia in minimal media, addition of low levels of amino acids enhanced production. Ammonia production by A. fumigatus, N. crassa and M. anisopliae increased the pH of the medium and allowed production of subtilisin proteases, whose activities are observed only at basic pH. In contrast, protease production by the Acid(+) mutants of M. anisopliae was greatly reduced because of the acidification of the medium. This suggests that alkalinization by ammonia production is adaptive by facilitating the utilization of proteinaceous nutrients. Collectively, the data imply that ammonia may have functions related to regulation of the microenvironment and that it represents a previously unconsidered virulence factor in diverse fungi with the potential to harm tissues and disturb the host's immune system.

  16. pH dependent unfolding characteristics of DLC8 dimer: Residue level details from NMR.

    PubMed

    Mohan, P M Krishna; Hosur, Ramakrishna V

    2008-11-01

    Environment dependence of folding and unfolding of a protein is central to its function. In the same vein, knowledge of pH dependence of stability and folding/unfolding is crucial for many biophysical equilibrium and kinetic studies designed to understand protein folding mechanisms. In the present study we investigated the guanidine induced unfolding transition of dynein light chain protein (DLC8), a cargo adaptor of the dynein complex in the pH range 7-10. It is observed that while the protein remains a dimer in the entire pH range, its stability is somewhat reduced at alkaline pH. Global unfolding features monitored using fluorescence spectroscopy revealed that the unfolding transition of DLC8 at pH 7 is best described by a three-state model, whereas, that at pH 10 is best described by a two-state model. Chemical shift perturbations due to pH change provided insights into the corresponding residue level structural perturbations in the DLC8 dimer. Likewise, backbone (15)N relaxation measurements threw light on the corresponding motional changes in the dimeric protein. These observations have been rationalized on the basis of expected changes with increasing pH in the protonation states of the titratable residues on the structure of the protein. These, in turn provide an explanation for the change from three-state to two-state guanidine induced unfolding transition as the pH is increased from 7 to 10. All these results exemplify and highlight the role of environment vis-à-vis the sequence and structure of a given protein in dictating its folding/unfolding characteristics.

  17. Are salivary amylase and pH – Prognostic indicators of cancers?

    PubMed Central

    Ramya, Atmakuri Shanmukha; Uppala, Divya; Majumdar, Sumit; Surekha, Ch.; Deepak, K.G.K.

    2015-01-01

    Background Saliva, “Mirror of body's health” has long been of particular interest as a substitute for blood for disease diagnosis and monitoring. The radiation effects on salivary glands are of particular interest in which salivary amylase is a good indicator of salivary glands function. Thus, estimation of these parameters represents a reasonable approach in evaluation of patient's risk for disease occurrence, intensity and prognosis. Aim of study To evaluate and compare the pH and amylase levels in saliva of cancer patients prior to treatment, patients during treatment. Materials and methods Saliva samples of 90 individuals were taken which were divided into 3 groups - 30 individuals without cancer, 30 cancer patients prior treatment and 30 cancer patients during treatment. Materials used were pH strips and pH meter, Salivary Amylase assay. Results Statistical analysis – ANOVA with post-hoc Tukey's test. 1) Significant decrease in salivary amylase levels – in cancer patients, during treatment when compared to others. 2) Significant decrease in salivary pH levels in newly diagnosed cancer patients prior to treatment. Conclusion To conclude, pH strips and pH meter showed to be a useful tool in the measurement of pH of saliva in individuals with and without cancer. This study showed that cancer patients without treatment have a lower pH of saliva. Treatment increased the pH of the saliva to a more alkaline level whereas amylase levels decreased in those subjects. Therefore those parameters can be an area of further research with an increased sample size, which in-turn may help in opening the doors for new dimension in non invasive prognostic markers. PMID:26258019

  18. Effect of Different pH Values on the Compressive Strength of Calcium-Enriched Mixture Cement

    PubMed Central

    Sobhnamayan, Fereshte; Sahebi, Safoora; Alborzi, Ali; Ghorbani, Saeed; Shojaee, Nooshin Sadat

    2015-01-01

    Introduction: The aim of this study was to evaluate the compressive strength of calcium-enriched mixture (CEM) cement in contact with acidic, neutral and alkaline pH values. Methods and Materials: The cement was mixed according to the manufacturer’s instructions, it was then condensed into fourteen split molds with five 4×6 mm holes. The specimens were randomly divided into 7 groups (n=10) and were then exposed to environments with pH values of 4.4, 5.4, 6.4, 7.4, 8.4, 9.4 and 10.4 in an incubator at 37° C for 4 days. After removing the samples from the molds, cement pellets were compressed in a universal testing machine. The exact forces required for breaking of the samples were recorded. The data were analyzed with the Kruskal-Wallis and Dunn tests for individual and pairwise comparisons, respectively. The level of significance was set at 0.05. Results: The greatest (48.59±10.36) and the lowest (9.67±3.16) mean compressive strength values were observed after exposure to pH value of 9.4 and 7.4, respectively. Alkaline environment significantly increased the compressive strength of CEM cement compared to the control group. There was no significant difference between the pH values of 9.4 and 10.4 but significant differences were found between pH values of 9.4, 8.4 and 7.4. The acidic environment showed better results than the neutral environment, although the difference was not significant for the pH value of 6.4. Alkaline pH also showed significantly better results than acidic and neutral pH. Conclusion: The compressive strength of CEM cement improved in the presence of acidic and alkaline environments but alkaline environment showed the best results. PMID:25598805

  19. Antioxidant Defense System of Tadpoles (Eupemphix nattereri) Exposed to Changes in Temperature and pH.

    PubMed

    Freitas, Juliane S; Almeida, Eduardo A

    2016-04-01

    Amphibians are highly susceptible to environmental changes, mainly at the larval stage during which they are restricted to small and ephemeral aquatic habitats, which are subject to large fluctuations of abiotic parameters, such as temperature and pH. Consequently, tadpoles experience changes in biochemical, physiological, and molecular processes related to the maintenance of homeostasis, which may lead them to an oxidative stress state. In the present study, we investigated the effects of stress caused by changes in temperature and pH on the antioxidant enzymes catalase (CAT), glucose-6-phosphate dehydrogenase (G6PDH), glutathione reductase (GR) and glutathione-S-transferase (GST) in tadpoles of Eupemphix nattereri. The results show that changes in temperature and pH conditions induce an antioxidant response in tadpoles. GST and GR showed temperature-dependent activities; GST activity was higher in tadpoles exposed to 28°C, whereas GR exhibited increased activity in response to 28°C and 36°C. At 32°C, both GST and GR had the lowest activity. CAT was induced by treatments with acidic (pH 5.0) and alkaline (pH 8.5) pH. Tadpoles exposed to acidic pH also had increased GR activity. The G6PDH was not changed in either experiment. Our data demonstrate that E. nattereri possesses an efficient antioxidant defense system for coping with the damaging effects of heat and acidity/alkalinity conditions in water. The alterations in antioxidant enzymes are probably a result of immediate physiological adaptation of individuals in response to increased production of ROS under environmental stress conditions.

  20. Mitochondrial nitric oxide synthase regulates mitochondrial matrix pH.

    PubMed

    Ghafourifar, P; Richter, C

    1999-01-01

    Nitric oxide (nitrogen monoxide, NO) exerts a wide profile of its biological activities via regulation of respiration and respiration-dependent functions. The presence of nitric oxide synthase (NOS) in mitochondria (mtNOS) was recently reported by us (Ghafourifar and Richter, FEBS Lett. 418, 291-296, 1997) and others (Giulivi et al., J. Biol. Chem. 273, 11038-11043, 1998). Here we report that NO, provided by an NO donor as well as by mtNOS stimulation, regulates mitochondrial matrix pH, transmembrane potential and Ca2+ buffering capacity. Exogenously-added NO causes a dose-dependent matrix acidification. Also mtNOS stimulation, induced by loading mitochondria with Ca2+, causes mitochondrial matrix acidification and a drop in mitochondrial transmembrane potential. Inhibition of mtNOS's basal activity causes mitochondrial matrix alkalinization and provides a resistance to the sudden drop of mitochondrial transmembrane potential induced by mitochondrial Ca2+ uptake. We conclude that mtNOS plays a critical role in regulating mitochondrial delta(pH).

  1. Ventilatory regulation of arterial H(+) (pH) during exercise.

    PubMed

    Wasserman, Karlman; Cox, Timothy A; Sietsema, Kathy E

    2014-01-01

    We hypothesized that exercise ventilation and arterial H(+) ([H(+)]a) are mutually interactive, [H(+)]a stimulating V(E) and V(E) regulating [H(+)]a increase. Fifty-five patients were studied, 10 normal and 45 with cardio-respiratory disorders. Each patient underwent cardiopulmonary exercise testing with simultaneous serial arterial blood gas and pH measurements. Subsequently, they were classified into one of 7 clinical groups: (1) normal, (2) exercise-induced hypoxemia (PaO2<50mmHg), (3) exercise-induced myocardial ischemia, (4) heart failure, (5) COPD, (6) interstitial lung disease, and (7) pulmonary vasculopathy. The average resting pHa was 7.42 or 7.43 for each group. At anaerobic (lactic acidosis) threshold (AT), [H(+)]a increased due to PaCO2 increase (+2mmHg), primarily. At peak exercise, [H(+)]a increased further due to arterial HCO3(-) decrease. In summary, [H(+)]a appears to be closely regulated at rest to AT and further to peak exercise by CO2 elimination from the venous return. No evidence was observed for over-ventilation of CO2, causing the arterial blood to become more alkaline during exercise in the patient groups studied.

  2. Carbon System Measurements and Potential Climatic Drivers at a Site of Rapidly Declining Ocean pH

    PubMed Central

    Wootton, J. Timothy; Pfister, Catherine A.

    2012-01-01

    We explored changes in ocean pH in coastal Washington state, USA, by extending a decadal-scale pH data series, by reporting independent measures of dissolved inorganic carbon (DIC), spectrophotometric pH, and total alkalinity (TA), by exploring pH patterns over larger spatial scales, and by probing for long-term trends in environmental variables reflecting potentially important drivers of pH. We found that pH continued to decline in this area at a rapid rate, that pH exhibited high natural variability within years, that our measurements of pH corresponded well to spectrophotometric pH measures and expected pH calculated from DIC/TA, and that TA estimates based on salinity predicted well actual alkalinity. Multiple datasets reflecting upwelling, including water temperature, nutrient levels, phytoplankton abundance, the NOAA upwelling index, and data on local wind patterns showed no consistent trends over the period of our study. Multiple datasets reflecting precipitation change and freshwater runoff, including precipitation records, local and regional river discharge, salinity, nitrate and sulfate in rainwater, and dissolved organic carbon (DOC) in rivers also showed no consistent trends over time. Dissolved oxygen did not decline over time, indicating that long-term changes did not result from shifts in contributions of respiration to pH levels. These tests of multiple potential drivers of the observed rapid rate of pH decline indicate a primary role for inorganic carbon and suggest that geochemical models of coastal ocean carbon fluxes need increased investigation. PMID:23285290

  3. High-Resolution pH Imaging of Living Bacterial Cells To Detect Local pH Differences

    PubMed Central

    Morimoto, Yusuke V.; Kami-ike, Nobunori; Miyata, Tomoko; Kawamoto, Akihiro; Kato, Takayuki

    2016-01-01

    ABSTRACT Protons are utilized for various biological activities such as energy transduction and cell signaling. For construction of the bacterial flagellum, a type III export apparatus utilizes ATP and proton motive force to drive flagellar protein export, but the energy transduction mechanism remains unclear. Here, we have developed a high-resolution pH imaging system to measure local pH differences within living Salmonella enterica cells, especially in close proximity to the cytoplasmic membrane and the export apparatus. The local pH near the membrane was ca. 0.2 pH unit higher than the bulk cytoplasmic pH. However, the local pH near the export apparatus was ca. 0.1 pH unit lower than that near the membrane. This drop of local pH depended on the activities of both transmembrane export components and FliI ATPase. We propose that the export apparatus acts as an H+/protein antiporter to couple ATP hydrolysis with H+ flow to drive protein export. PMID:27923921

  4. Thermal processing of acidified foods with pH 4.1 to pH 4.6

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shelf-stable acidified foods with a pH at or below 4.6 must be processed to achieve a 5-log reduction for vegetative bacterial pathogens. Published research does not exist to adequately support the Food and Drug Administration process filings for products with pH 4.1–4.6 or to define critical limits...

  5. Continuous pH monitoring in a perfused bioreactor system using an optical pH sensor

    NASA Technical Reports Server (NTRS)

    Jeevarajan, Antony S.; Vani, Sundeep; Taylor, Thomas D.; Anderson, Melody M.

    2002-01-01

    Monitoring and regulating the pH of the solution in a bioprocess is one of the key steps in the success of bioreactor operation. An in-line optical pH sensor, based on the optical absorption properties of phenol red present in the medium, was developed and tested in this work for use in NASA space bioreactors based on a rotating wall-perfused vessel system supporting a baby hamster kidney (BHK-21) cell culture. The sensor was tested over three 30-day and one 124-day cell runs. The pH sensor initially was calibrated and then used during the entire cell culture interval. The pH reported by the sensor was compared to that measured by a fiber optically coupled Shimadzu spectrophotometer and a blood gas analyzer. The maximum standard error of prediction for all the four cell runs for development pH sensor against BGA was +/-0.06 pH unit and for the fiber optically coupled Shimadzu spectrophotometer against the blood gas analyzer was +/-0.05 pH unit. The pH sensor system performed well without need of recalibration for 124 days. Copyright 2002 Wiley Periodicals, Inc.

  6. Physiological pH. Effects on posthypoxic proximal tubular injury.

    PubMed

    Zager, R A; Schimpf, B A; Gmur, D J

    1993-04-01

    After O2 deprivation, tissue acidosis rapidly self-corrects. This study assessed the effect of this pH correction on the induction, and pathways, of posthypoxic proximal tubular injury. In addition, ways to prevent the resultant injury were explored. Isolated rat proximal tubular segments (PTSs) were subjected to hypoxia/reoxygenation (50/30 or 30/50 minutes) under the following incubation conditions: 1) continuous pH 7.4, 2) continuous pH 6.8, or 3) hypoxia at pH 6.8 and reoxygenation at pH 7.4 (NaHCO3 or Tris base addition). Continuously oxygenated PTSs maintained under these same pH conditions served as controls. Lethal cell injury was assessed by lactate dehydrogenase (LDH) release. pH effects on several purported pathways of hypoxia/reoxygenation injury were also assessed (ATP depletion, lipid peroxidation, and membrane deacylation). Acidosis blocked hypoxic LDH release (pH 7.4, 50 +/- 2%; pH 6.8, 6 +/- 1%) without mitigating membrane deacylation or ATP depletion. During reoxygenation, minimal LDH was released (3-5%) if pH was held constant. However, if posthypoxic pH was corrected, immediate (< or = 5 minutes) and marked cell death (e.g., 55 +/- 3% with Tris) occurred. This was dissociated from lipid peroxidation or new deacylation, and it was preceded by a depressed ATP/ADP ratio (suggesting an acidosis-associated defect in hypoxic/posthypoxic cell energetics). Realkalinization injury was not inevitable, since it could be substantially blocked by 1) posthypoxic glycine addition, 2) transient posthypoxic hypothermia, or 3) allowing a 10-minute reoxygenation (cell recovery) period before base addition. Neither mannitol nor graded buffer Ca2+ deletion conferred protection. Acute pH correction caused no injury to continuously oxygenated PTSs. Conclusions are as follows: 1) Posthypoxic "pH shock" causes virtually immediate cell death, not by causing de novo injury but, rather, by removing the cytoprotective effect of acidosis. 2) This injury can be prevented by a

  7. Influence of Urinary pH on the Pharmacokinetics of Cinoxacin in Humans and on Antibacterial Activity In Vitro

    PubMed Central

    Barbhaiya, Rashmi H.; Gerber, Andreas U.; Craig, William A.; Welling, Peter G.

    1982-01-01

    The impact of acidification and alkalinization of the urine on the pharmacokinetics of cinoxacin was examined after single 500-mg oral doses were administered to nine healthy male volunteers. Acidic and alkaline conditions were achieved by repeated oral doses of ammonium chloride or sodium bicarbonate, respectively. Plasma cinoxacin levels in all subjects were adequately described in terms of one-compartment-model kinetics with first-order absorption and elimination. Acidification and alkalinization treatment had no effect on cinoxacin absorption or distribution. The mean elimination half-life of cinoxacin in plasma was 1.1, 2.0, and 0.6 h in control subjects and with acidification and alkalinization of urine, respectively. Recovery of intact cinoxacin in samples of urine collected 0 to 36 h after cinoxacin administration represented 65% of the dose in control subjects and urine acidification and 80% of the dose with alkalinization of urine. The mean renal clearance of cinoxacin was 76, 118, and 278 ml/min with acidification, control, and alkalinization, respectively, and renal clearance was highly correlated with urinary pH. Urine concentrations of cinoxacin were significantly higher with alkalinization compared with control values during the first 4 h after drug administration. Urine cinoxacin concentrations were reduced somewhat by acidification, but these tended not to be significantly different from control values. Changes in cinoxacin elimination owing to urine pH are less pronounced in humans than in dogs. The antibacterial activity of cinoxacin against some common urinary tract pathogens was pH dependent. A four- to eightfold reduction in cinoxacin activity was generally observed at pH 8 compared with lower pH values. However, in view of the high levels of cinoxacin which are obtained in both acidic and basic urine, the impact of urine pH on cinoxacin antibacterial efficacy would be of minor clinical importance. PMID:7103450

  8. Effect of soil pH on as hyperaccumulation capacity in fern species, Pityrogramma calomelanos.

    PubMed

    Anh, B T Kim; Kim, D D; Kuschk, P; Tua, T V; Hue, N T; Minh, N N

    2013-03-01

    Arsenic uptake by hyperaccumulator plant species depends on many different environmental factors. Soil pH is one of the most important factors due to its combined effect on both chemical and biological processes. In greenhouse experiment, the effect of pH (within the pH range 3.6 - 8.9) on As uptake as well as biomass of Pityrogramma calomelanos was evaluated. The plants were grown in mining soil containing 645.6 mg As kg(-1) for 14 weeks. Within this time, the plant biomass growth was 3.78 - 8.64 g d. wt. per plant and the removal amounted 6.3-18.4 mg As per plant. Translocation factor (ratio of As in fronds to roots) of the fern was 3.6 - 9.7, indicating its potential in phytoremediation of As contaminated soil. Influence of pH on As bioavailability was visible as the available As concentration was higher in acidic soil compared to alkaline soil. Furthermore, it was found that As accumulation by Pityrogramma calomelanos was optimum in the soil of pH 3.6. Nevertheless, the results of this study demonstrate that remediation of As-contaminated mining soils, by this fern, can be improved by changing the soil pH from 4.6 to 6.8.

  9. Cell culturability of Pseudomonas protegens CHA0 depends on soil pH.

    PubMed

    Mascher, Fabio; Hase, Carsten; Bouffaud, Marie-Lara; Défago, Geneviève; Moënne-Loccoz, Yvan

    2014-02-01

    Pseudomonas inoculants may lose colony-forming ability in soil, but soil properties involved are poorly documented. Here, we tested the hypothesis that soil acidity could reduce persistence and cell culturability of Pseudomonas protegens CHA0. At 1 week in vitro, strain CHA0 was found as culturable cells at pH 7, whereas most cells at pH 4 and all cells at pH 3 were noncultured. In 21 natural soils of contrasted pH, cell culturability loss of P. protegens CHA0 took place in all six very acidic soils (pH < 5.0) and in three of five acidic soils (5.0 < pH < 6.5), whereas it was negligible in the neutral and alkaline soils at 2 weeks and 2 months. No correlation was found between total cell counts of P. protegens CHA0 and soil composition data, whereas colony counts of the strain correlated with soil pH. Maintenance of cell culturability in soils coincided with a reduction in inoculant cell size. Some of the noncultured CHA0 cells were nutrient responsive in Kogure's viability test, both in vitro and in soil. Thus, this shows for the first time that the sole intrinsic soil composition factor triggering cell culturability loss in P. protegens CHA0 is soil acidity.

  10. pH dominates variation in tropical soil archaeal diversity and community structure.

    PubMed

    Tripathi, Binu M; Kim, Mincheol; Lai-Hoe, Ang; Shukor, Nor A A; Rahim, Raha A; Go, Rusea; Adams, Jonathan M

    2013-11-01

    Little is known of the factors influencing soil archaeal community diversity and composition in the tropics. We sampled soils across a range of forest and nonforest environments in the equatorial tropics of Malaysia, covering a wide range of pH values. DNA was PCR-amplified for the V1-V3 region of the 16S rRNA gene, and 454-pyrosequenced. Soil pH was the best predictor of diversity and community composition of Archaea, being a stronger predictor than land use. Archaeal OTU richness was highest in the most acidic soils. Overall archaeal abundance in tropical soils (determined by qPCR) also decreased at higher pH. This contrasts with the opposite trend previously found in temperate soils. Thaumarcheota group 1.1b was more abundant in alkaline soils, whereas group 1.1c was only detected in acidic soils. These results parallel those found in previous studies in cooler climates, emphasizing niche conservatism among broad archaeal groups. Among the most abundant operational taxonomic units (OTUs), there was clear evidence of niche partitioning by pH. No individual OTU occurred across the entire range of pH values. Overall, the results of this study show that pH plays a major role in structuring tropical soil archaeal communities.

  11. Effect of carbon dioxide and ammonium removal on pH changes in polishing ponds.

    PubMed

    Cavalcanti, P F F; van Haandel, A; Lettinga, G

    2002-01-01

    If nutrient removal is to be obtained in ponds treating sewage, the pH must be raised so that ammonia can desorb and phosphates can precipitate. In this paper it is shown that the pH increase in ponds can be predicted quantitatively from simple stoichiometry, taking into consideration physical and biological carbon dioxide removal, ammonia stripping and calcium carbonate precipitation. Biological CO2 removal by photosynthesis is identified as the main process to effect pH increase in ponds. The rate of pH increase and consequently the required retention time depend on the net rate of CO2 consumption, the extent of ammonium stripping, the characteristics of the influent (alkalinity and pH) as well as factors concerning the environment (temperature) and dimensions (depth) of the pond. A high pH (range 9 to 10) can be obtained in about 5 days if digested sewage is used (low organic material concentration), climate conditions are favourable and the pond is shallow (< 0.5 m deep).

  12. [Effect of pH for the electrochemical oxidation products and oxidation pathways of ammonia].

    PubMed

    Chen, Jin-luan; Shi, Han-chang; Xu, Li-li

    2008-08-01

    The electrochemical oxidation of ammonia in wastewater was investigated in a flow electrochemical cell. The effect of pH on ammonia removal efficiency, oxidation products and oxidation pathways was elucidated. The experimental results indicated that, the higher production efficiency of free chlorine and hydroxyl radical can be obtained under the moderate alkaline condition, and the electrochemical oxidation rate of ammonia was higher in this condition. In existence of chloride ions, chloramines produced during the electrolysis of ammonia. The constituent of chloramines related with the pH of reaction system. When pH was higher than 9, monochloramine was dominant; When pH was equal to 7, monochloramine and dichloramine existed at the same time and the concentration of the two chloramines was an approximation of the same; When pH was smaller than 5, most of the production was dichloramine. The production of nitrogen trichloride can be avoided when pH was higher than 5. Under the current density of 20 mA/cm2, the concentration of hydroxyl radical produced by electrolysis was smaller than 5 x 10(-15) mol/L. The indirect oxidation was the dominant reaction in the two pathways of electrochemical oxidation of ammonia.

  13. Effect of altitude on brain intracellular pH and inorganic phosphate levels

    PubMed Central

    Shi, Xian-Feng; Carlson, Paul J.; Kim, Tae-Suk; Sung, Young-Hoon; Hellem, Tracy L.; Fiedler, Kristen K.; Kim, Seong-Eun; Glaeser, Breanna; Wang, Kristina; Zuo, Chun S.; Jeong, Eun-Kee; Renshaw, Perry F.; Kondo, Douglas G.

    2015-01-01

    Normal brain activity is associated with task-related pH changes. Although central nervous system syndromes associated with significant acidosis and alkalosis are well understood, the effects of less dramatic and chronic changes in brain pH are uncertain. One environmental factor known to alter brain pH is the extreme, acute change in altitude encountered by mountaineers. However, the effect of long-term exposure to moderate altitude has not been studied. The aim of this two-site study was to measure brain intracellular pH and phosphate-bearing metabolite levels at two altitudes in healthy volunteers, using phosphorus-31 magnetic resonance spectroscopy (31P-MRS). Increased brain pH and reduced inorganic phosphate (Pi) levels were found in healthy subjects who were long-term residents of Salt Lake City, UT (4720 ft/1438 m), compared with residents of Belmont, MA (20 ft/6 m). Brain intracellular pH at the altitude of 4720 ft was more alkaline than that observed near sea level. In addition, the ratio of inorganic phosphate to total phosphate signal also shifted toward lower values in the Salt Lake City region compared with the Belmont area. These results suggest that long-term residence at moderate altitude is associated with brain chemical changes. PMID:24768210

  14. Effect of altitude on brain intracellular pH and inorganic phosphate levels.

    PubMed

    Shi, Xian-Feng; Carlson, Paul J; Kim, Tae-Suk; Sung, Young-Hoon; Hellem, Tracy L; Fiedler, Kristen K; Kim, Seong-Eun; Glaeser, Breanna; Wang, Kristina; Zuo, Chun S; Jeong, Eun-Kee; Renshaw, Perry F; Kondo, Douglas G

    2014-06-30

    Normal brain activity is associated with task-related pH changes. Although central nervous system syndromes associated with significant acidosis and alkalosis are well understood, the effects of less dramatic and chronic changes in brain pH are uncertain. One environmental factor known to alter brain pH is the extreme, acute change in altitude encountered by mountaineers. However, the effect of long-term exposure to moderate altitude has not been studied. The aim of this two-site study was to measure brain intracellular pH and phosphate-bearing metabolite levels at two altitudes in healthy volunteers, using phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS). Increased brain pH and reduced inorganic phosphate (Pi) levels were found in healthy subjects who were long-term residents of Salt Lake City, UT (4720ft/1438m), compared with residents of Belmont, MA (20ft/6m). Brain intracellular pH at the altitude of 4720ft was more alkaline than that observed near sea level. In addition, the ratio of inorganic phosphate to total phosphate signal also shifted toward lower values in the Salt Lake City region compared with the Belmont area. These results suggest that long-term residence at moderate altitude is associated with brain chemical changes.

  15. Optical fibre PH sensor based on immobilized indicator

    NASA Astrophysics Data System (ADS)

    Cai, Defu; Cao, Qiang; Han, JingHong; Cai, Jine; Li, YaTing; Zhu, ZeMin; Fan, Jie; Gao, Ning

    1991-08-01

    An optical fiber pH sensor which has the immobilized pH sensitive indicator dye reagents on the tip of the optical fiber has been studied. The probe is made by covalently immobilizing the phenol red, bromine phenol blue, or bromothymol blue on the polyacrylamide microsphere fixed by polyterafluoroethylene (PTFE) film. A gap between the dye and optical fiber was used to make the diffusion of the hydrogen ions easier. The parameters of the optical fiber pH sensor have been given completely. The ranges of measurement are 3.0 - 5.0 pH, 7.0 - 8.5 pH, and 8.0 - 10.0 pH for bromine phenol blue, phenol red, and bromothymol blue, respectively. The sensitivity is 66.6 mV/pH. The probe has a precision of better than 0.55 pH. The linear correlation coefficient is 0.999. The response time is 1 - 2 min. The hysteresis is 0.52%. The repeatability is 0.013 mV, while the stability is 0.015 pH/h.

  16. Improved granular activated carbon for the stabilization of wastewater PH

    SciTech Connect

    Farmer, R.W.; Dussert, B.W.; Kovacic, S.L.

    1996-12-31

    Laboratory studies have identified the cause of the pH rise, which occurs during water treatment with activated carbon, as an interaction between the naturally occurring anions and protons in the water and the carbon surface. The interaction can be described as an ion exchange type of phenomenon, in which the carbon surface sorbs the anions and corresponding hydronium ions from the water. These studies have shown that the anion sorption and resulting pH increase is independent of the raw material used for the activated carbon production, e.g. bituminous or subbituminous coal, peat, wood or coconut. Also, the pH excursions occur with virgin, reactivated, and acid washed granular carbons. Current pH control technologies focus on adjustment of the wastewater pH prior to discharge or recycle of the initial effluent water until the pH increase abates. However, improved water pH control options have been realized by altering the carbon surface through controlled oxidation rather than the water chemistry or extended preprocessing at the treatment site.

  17. Implications of pH manipulation methods for metal toxicity: not all acidic environments are created equal.

    PubMed

    Esbaugh, A J; Mager, E M; Brix, K V; Santore, R; Grosell, M

    2013-04-15

    The toxicity of many metals is impacted by environmental pH, through both competition and complexation by hydroxide and carbonate ions. To establish safe environmental regulation it is important to properly define the relationship between pH and metal toxicity, a process that involves manipulating the pH of test water in the lab. The current study compares the effects of the three most common pH manipulation methods (carbon dioxide, acid-base addition, and chemical buffers) on acute Pb toxicity of a model fish species, Pimephales promelas. Acidification of test water revealed that the Pb and Pb(2+) LC50 values were impacted by the pH manipulation method, with the following order of effects: HClpH was alkalinized using MOPS or NaOH. The different impacts of pH manipulation methods on Pb toxicity are likely due to different physiological stresses resulting from the respective methods; the physiological implications of each method are discussed. The results suggest that when studying the impacts of pH on metal toxicity it is important to properly replicate the ambient conditions of interest as artificial buffering using CO2 environments or organic buffers significantly affects the physiology of the test organisms above and beyond what is expected from pH alone. Thus, using CO2 and organic buffers overestimates the impact of acid pH on Pb toxicity.

  18. Axillary pH and influence of deodorants.

    PubMed

    Stenzaly-Achtert, S.; Schölermann, A.; Schreiber, J.; Diec, K. H.; Rippke, F.; Bielfeldt, S.

    2000-05-01

    BACKGROUND/AIMS: In moist intertriginous regions, such as the armpit, the pH value is physiologically higher than in other skin regions. The regulation of the axillary pH-value was examined in an open study with 48 subjects in three groups with n=16 each. METHODS: In the first 10 days (run-in) the subjects received a standard treatment in the axilla with shaving, cleansing and application of a pH-neutral deodorant. This was followed by a 5 day treatment period with the three test products (pH5 Eucerin(R) Deodorant Roll-on, Deodorant Balsam Spray, Deodorant Cream). The study was concluded by a wash-out period with procedures identical to the run-in phase. The pH was measured with a calibrated pH-meter. RESULTS: A significant pH reduction was shown during the treatment period when compared to the run-in phase. The Deodorant Roll-on induced a reduction of the mean pH values from 6.1 to 5.3, the Deodorant Balsam Spray from 6.5 to 5.7 and the Deodorant Cream from 6.2 to 5.3. During the wash-out period all pH values returned to baseline. CONCLUSION: All of the deodorants tested demonstrated a significant reduction in axillary pH. There is evidence that a high skin pH promotes the growth of several microorganisms that produce malodor. Therefore, the regulation of pH may contribute to the deodorant efficacy of the test products.

  19. Near Infrared Spectral Determination of Human Tissue pH.

    DTIC Science & Technology

    1995-10-01

    Continuous Tissue pH Monitory in the Human Fetus During Labor", Obstet . Gynecol ., 55:523, 1980. 23. [Lemer 82] Lemer, H., et al., "Measurement of Glucose...Umbilical Blood pH", Am. J. Obstet . Gynecol ., 128: 901-903, 1977. 38. [Weyer 85] Weyer, L G., "Near Infrared Spectroscopy of Organic Substances," Applied...Patterns and Tissue pH in the Human Fetus", Am. J. Obstet . Gynecol ., 134:685-690, 1979. 24 Appendix I An Estimation Extension of the FKNN Algorithm In

  20. pH sensor based on boron nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Huang, Q.; Bando, Y.; Zhao, L.; Zhi, C. Y.; Golberg, D.

    2009-10-01

    A submicrometer-sized pH sensor based on biotin-fluorescein-functionalized multiwalled BN nanotubes with anchored Ag nanoparticles is designed. Intrinsic pH-dependent photoluminescence and Raman signals in attached fluorescein molecules enhanced by Ag nanoparticles allow this novel nanohybrid to perform as a practical pH sensor. It is able to work in a submicrometer-sized space. For example, the sensor may determine the environmental pH of sub-units in living cells where a traditional optical fiber sensor fails because of spatial limitations.

  1. Imaging pH with hyperpolarized 13C.

    PubMed

    Gallagher, Ferdia A; Kettunen, Mikko I; Brindle, Kevin M

    2011-10-01

    pH is a fundamental physiological parameter that is tightly controlled by endogenous buffers. The acid-base balance is altered in many disease states, such as inflammation, ischemia and cancer. Despite the importance of pH, there are currently no routine methods for imaging the spatial distribution of pH in humans. The enormous gain in sensitivity afforded by dynamic nuclear polarization (DNP) has provided a novel way in which to image tissue pH using MR, which has the potential to be translated into the clinic. This review explores the advantages and disadvantages of current pH imaging techniques and how they compare with DNP-based approaches for the measurement and imaging of pH with hyperpolarized (13)C. Intravenous injection of hyperpolarized (13)C-labeled bicarbonate results in the rapid production of hyperpolarized (13)CO(2) in the reaction catalyzed by carbonic anhydrase. As this reaction is close to equilibrium in the body and is pH dependent, the ratio of the (13)C signal intensities from H(13)CO(3)(-) and (13)CO(2), measured using MRS, can be used to calculate pH in vivo. The application of this technique to a murine tumor model demonstrated that it measured predominantly extracellular pH and could be mapped in the animal using spectroscopic imaging techniques. A second approach has been to use the production of hyperpolarized (13)CO(2) from hyperpolarized [1-(13)C]pyruvate to measure predominantly intracellular pH. In tissues with a high aerobic capacity, such as the heart, the hyperpolarized [1-(13)C]pyruvate undergoes rapid oxidative decarboxylation, catalyzed by intramitochondrial pyruvate dehydrogenase. Provided that there is sufficient carbonic anhydrase present to catalyze the rapid equilibration of the hyperpolarized (13)C label between CO(2) and bicarbonate, the ratio of their resonance intensities may again be used to estimate pH, which, in this case, is predominantly intracellular. As both pyruvate and bicarbonate are endogenous molecules they

  2. Method for producing rapid pH changes

    DOEpatents

    Clark, John H.; Campillo, Anthony J.; Shapiro, Stanley L.; Winn, Kenneth R.

    1981-01-01

    A method of initiating a rapid pH change in a solution by irradiating the solution with an intense flux of electromagnetic radiation of a frequency which produces a substantial pK change to a compound in solution. To optimize the resulting pH change, the compound being irradiated in solution should have an excited state lifetime substantially longer than the time required to establish an excited state acid-base equilibrium in the solution. Desired pH changes can be accomplished in nanoseconds or less by means of picosecond pulses of laser radiation.

  3. Method for producing rapid pH changes

    DOEpatents

    Clark, J.H.; Campillo, A.J.; Shapiro, S.L.; Winn, K.R.

    A method of initiating a rapid pH change in a solution comprises irradiating the solution with an intense flux of electromagnetic radiation of a frequency which produces a substantial pK change to a compound in solution. To optimize the resulting pH change, the compound being irradiated in solution should have an excited state lifetime substantially longer than the time required to establish an excited state acid-base equilibrium in the solution. Desired pH changes can be accomplished in nanoseconds or less by means of picosecond pulses of laser radiation.

  4. A pH dependent Raman and surface enhanced Raman spectroscopic studies of citrazinic acid aided by theoretical calculations.

    PubMed

    Sarkar, Sougata; Chowdhury, Joydeep; Dutta, Soumen; Pal, Tarasankar

    2016-12-05

    A pH dependent normal Raman scattering (NRS) and surface enhanced Raman scattering (SERS) spectral patterns of citrazinic acid (CZA), a biologically important molecule, have been investigated. The acid, with different pKa values (~4 and ~11) for the two different functional groups (-COOH and -OH groups), shows interesting range of color changes (yellow at pH~14 and brown at pH~2) with the variation in solution pH. Thus, depending upon the pH of the medium, CZA molecule can exist in various protonated and/or deprotonated forms. Here we have prescribed the existence different possible forms of CZA at different pH (Forms "C", "H" and "Dprot" at pH~14 and Forms "A", "D", and "P" at pH~2 respectively). The NRS spectra of these solutions and their respective SERS spectra over gold nanoparticles were recorded. The spectra clearly differ in their spectral profiles. For example the SERS spectra recorded with the CZA solution at pH~2 shows blue shift for different bands compared to its NRS window e.g. 406 to 450cm(-1), 616 to 632cm(-1), 1332 to 1343cm(-1) etc. Again, the most enhanced peak at ~1548cm(-1) in NRS while in the SERS window this appears at ~1580cm(-1). Similar observation was also made for CZA at pH~14. For example, the 423cm(-1) band in the NRS profile experience a blue shift and appears at ~447cm(-1) in the SERS spectrum as well as other bands at ~850, ~1067 and ~1214cm(-1) in the SERS window are markedly enhanced. It is also worth noting that the SERS spectra at the different pH also differ from each other. These spectral differences indicate the existence of various adsorptive forms of the CZA molecule depending upon the pH of the solution. Therefore based on the experimental findings we propose different possible molecular forms of CZA at different pH (acidic and alkaline) conditions. For example forms 'A', 'D' and 'P' existing in acidic pH (pH~2) and three other deprotonated forms 'C', 'H' and 'Dprot' in alkaline pH (pH~14). The DFT calculations for these

  5. A pH dependent Raman and surface enhanced Raman spectroscopic studies of citrazinic acid aided by theoretical calculations

    NASA Astrophysics Data System (ADS)

    Sarkar, Sougata; Chowdhury, Joydeep; Dutta, Soumen; Pal, Tarasankar

    2016-12-01

    A pH dependent normal Raman scattering (NRS) and surface enhanced Raman scattering (SERS) spectral patterns of citrazinic acid (CZA), a biologically important molecule, have been investigated. The acid, with different pKa values (~ 4 and ~ 11) for the two different functional groups (-COOH and -OH groups), shows interesting range of color changes (yellow at pH ~ 14 and brown at pH ~ 2) with the variation in solution pH. Thus, depending upon the pH of the medium, CZA molecule can exist in various protonated and/or deprotonated forms. Here we have prescribed the existence different possible forms of CZA at different pH (Forms "C", "H" and "Dprot" at pH ~ 14 and Forms "A", "D", and "P" at pH ~ 2 respectively). The NRS spectra of these solutions and their respective SERS spectra over gold nanoparticles were recorded. The spectra clearly differ in their spectral profiles. For example the SERS spectra recorded with the CZA solution at pH ~ 2 shows blue shift for different bands compared to its NRS window e.g. 406 to 450 cm- 1, 616 to 632 cm- 1, 1332 to 1343 cm- 1 etc. Again, the most enhanced peak at ~ 1548 cm- 1 in NRS while in the SERS window this appears at ~ 1580 cm- 1. Similar observation was also made for CZA at pH ~ 14. For example, the 423 cm- 1 band in the NRS profile experience a blue shift and appears at ~ 447 cm- 1 in the SERS spectrum as well as other bands at ~ 850, ~ 1067 and ~ 1214 cm- 1 in the SERS window are markedly enhanced. It is also worth noting that the SERS spectra at the different pH also differ from each other. These spectral differences indicate the existence of various adsorptive forms of the CZA molecule depending upon the pH of the solution. Therefore based on the experimental findings we propose different possible molecular forms of CZA at different pH (acidic and alkaline) conditions. For example forms 'A', 'D' and 'P' existing in acidic pH (pH ~ 2) and three other deprotonated forms 'C', 'H' and 'Dprot' in alkaline pH (pH ~ 14). The DFT

  6. [Phosphatase activity in Amoeba proteus at pH 9.0].

    PubMed

    Sopina, V A

    2007-01-01

    In the free-living amoeba Amoeba proteus (strain B), after PAAG disk-electrophoresis of the homogenate supernatant, at using 1-naphthyl phosphate as a substrate and pH 9.0, three forms of phosphatase activity were revealed; they were arbitrarily called "fast", "intermediate", and "slow" phosphatases. The fast phosphatase has been established to be a fraction of lysosomal acid phosphatase that preserves some low activity at alkaline pH. The question as to which particular class the intermediate phosphatase belongs to has remained unanswered: it can be both acid phosphatase and protein tyrosine phosphatase (PTP). Based on data of inhibitor analysis, large substrate specificity, results of experiments with reactivation by Zn ions after inactivation with EDTA, other than in the fast and intermediate phosphatases localization in the amoeba cell, it is concluded that only slow phosphatase can be classified as alkaline phosphatase (EC 3.1.3.1).

  7. Strain-specific variation in a soilborne phytopathogenic fungus for the expression of genes involved in pH signal transduction pathway, pathogenesis and saprophytic survival in response to environmental pH changes.

    PubMed

    Daval, Stéphanie; Lebreton, Lionel; Gracianne, Cécile; Guillerm-Erckelboudt, Anne-Yvonne; Boutin, Morgane; Marchi, Muriel; Gazengel, Kévin; Sarniguet, Alain

    2013-12-01

    The soilborne fungus Gaeumannomyces graminis var. tritici (Ggt) causes take-all, a wheat root disease. In an original strain-specific way, a previous study indicates that inside the Ggt species, some strains grow preferentially at acidic pH and other strains at neutral/alkaline pH. The most important mechanism for a fungal response to the environmental pH is the Pal pathway which integrates the products of the six pal genes and the transcription factor PacC. To evaluate whether the Ggt strain-specific growth in function of the ambient pH is mediated via the Pal pathway, a transcriptional study of the genes encoding this pathway was carried out. This study provided the first evidence that the pH signalling pathway similar to those described in other fungi operated in Ggt. The pacC gene was induced at neutral pH whatever the strain. In an original way, the expression of Ggt genes coding for the different Pal proteins depended on the strain and on the ambient pH. In the strain growing better at acidic pH, few pal genes were pH-regulated, and some were overexpressed at neutral pH when regulated. In the strain growing better at neutral pH, underexpression of most of the pal genes at neutral pH occurred. The strains displayed higher gene expression in the ambient pH that unfavoured their growth as if it was a compensation system. All pH taken together, a globally weaker Pal transcript level occurred in the strains that were less sensitive to acidic pH, and on the contrary, the strain growing better on neutral pH showed higher Pal mRNA levels. The expression of genes involved in pathogenesis and saprophytic growth was also regulated by the ambient pH and the strain: each gene displayed a specific pH-regulation that was similar between strains. But all pH taken together, the global transcript levels of four out of six genes were higher in the strain growing better on neutral pH. Altogether, for the first time, the results show that inside a species, conditions affecting

  8. The Na+ /H+ -exchanger (NHE1) generates pH nanodomains at focal adhesions.

    PubMed

    Ludwig, Florian Timo; Schwab, Albrecht; Stock, Christian

    2013-06-01

    Many tumor cells are characterized by an increased net acid production. They extrude the excess protons mainly through the Na(+) /H(+) -exchanger NHE1. An increased NHE1 activity elevates the metastatic potential of tumor cells. Cell migration, a key step in the metastatic cascade, requires the formation and release of integrin-mediated cell-matrix contacts (focal adhesions). As NHE1 has been localized to focal adhesion sites, the present study tests the hypothesis that NHE1 generates measurable pH nanodomains right at focal adhesions. In order to ratiometrically measure pH close to the plasma membrane, we established a novel application of the total internal reflection fluorescence microscopy (TIRFM). Human melanoma cells were transfected with DsRed2-paxillin to identify focal adhesion sites. The pH-sensitive dyes BCECF and WGA-fluorescein were used to measure the submembranous cytosolic and the pericellular pH, respectively. Distinct pH nanodomains were found at focal adhesions, particularly at those located at the cell front, where NHE1 was concentrated. These sites featured a remarkably alkaline cytosolic and an acidic pericellular pH and thus a much steeper proton gradient across the plasma membrane compared to the rest of the cell. The generation of pH nanodomains could be assigned to NHE1-mediated H(+) export because such pH domains could not be detected in NHE1-deficient cells. Given that both integrin avidity and mechanisms contributing to adhesion turnover are pH-sensitive, we propose that pH nanodomains at focal adhesions, locally created and maintained by NHE1 activity especially at the cell front, modulate adhesion dynamics in migrating cells.

  9. Role of pH on antioxidants production by Spirulina (Arthrospira) platensis.

    PubMed

    Ismaiel, Mostafa Mahmoud Sami; El-Ayouty, Yassin Mahmoud; Piercey-Normore, Michele

    2016-01-01

    Algae can tolerate a broad range of growing conditions but extreme conditions may lead to the generation of highly dangerous reactive oxygen species (ROS), which may cause the deterioration of cell metabolism and damage cellular components. The antioxidants produced by algae alleviate the harmful effects of ROS. While the enhancement of antioxidant production in blue green algae under stress has been reported, the antioxidant response to changes in pH levels requires further investigation. This study presents the effect of pH changes on the antioxidant activity and productivity of the blue green alga Spirulina (Arthrospira) platensis. The algal dry weight (DW) was greatly enhanced at pH 9.0. The highest content of chlorophyll a and carotenoids (10.6 and 2.4mg/g DW, respectively) was recorded at pH 8.5. The highest phenolic content (12.1mg gallic acid equivalent (GAE)/g DW) was recorded at pH 9.5. The maximum production of total phycobiliprotein (159mg/g DW) was obtained at pH 9.0. The antioxidant activities of radical scavenging activity, reducing power and chelating activity were highest at pH 9.0 with an increase of 567, 250 and 206% compared to the positive control, respectively. Variation in the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) was also reported. While the high alkaline pH may favor the overproduction of antioxidants, normal cell metabolism and membrane function is unaffected, as shown by growth and chlorophyll content, which suggests that these conditions are suitable for further studies on the harvest of antioxidants from S. platensis.

  10. Impact of pH on zinc oxide particle size by using sol-gel process

    NASA Astrophysics Data System (ADS)

    Lee, Keanchuan; Guan, Beh Hoe; Zaid, Hasnah Mohd.; Soleimani, Hassan; Ching, Dennis Ling Chuan

    2016-11-01

    Zinc oxide (ZnO) nanoparticles were prepared and synthesized via sol-gel method, by using citric acid as a precursor. The annealing temperature was fixed at 600 °C. The impact of pH on the particle size was investigated. Based on the results from the Thermogravimetric Analysis (TGA), three different pH for the precursor which is 3.0, 5.0 and 1.01 were chosen followed by the characterization of the ZnO nanoparticle by using Powder X-Ray Diffraction (PXRD), Transmission Electron Microscopy (TEM) and Field Emission Scanning Electron Microscopy (FESEM). Results showed that the crystallite size estimated from PXRD increased with the pH value which was hexagonal structure for ZnO. TEM further revealed the same tendency which the Zn NPs size also increased with the alkalinity of the precursor.

  11. Preparing MD-PhD students for clinical rotations: navigating the interface between PhD and MD training.

    PubMed

    Goldberg, Charles; Insel, Paul A

    2013-06-01

    Many aspects of MD-PhD training are not optimally designed to prepare students for their future roles as translational clinician-scientists. The transition between PhD research efforts and clinical rotations is one hurdle that must be overcome. MD-PhD students have deficits in clinical skills compared with those of their MD-only colleagues at the time of this transition. Reimmersion programs (RPs) targeted to MD-PhD students have the potential to help them navigate this transition.The authors draw on their experience creating and implementing an RP that incorporates multiple types of activities (clinical exam review, objective structured clinical examination, and supervised practice in patient care settings) designed to enhance the participants' skills and readiness for clinical efforts. On the basis of this experience, they note that MD-PhD students' time away from the clinical environment negatively affects their clinical skills, causing them to feel underprepared for clinical rotations. The authors argue that participation in an RP can help students feel more comfortable speaking with and examining patients and decrease their anxiety regarding clinical encounters. The authors propose that RPs can have positive outcomes for improving the transition from PhD to clinical MD training in dual-degree programs. Identifying and addressing this and other transitions need to be considered to improve the educational experience of MD-PhD students.

  12. Loss on drying, calcium concentration and pH of fluoride dentifrices

    PubMed Central

    Brito, Arella Cristina Muniz; Dantas, Lívia Rocha; De Brito, André Luiz Fiquene; Muniz, Ana Cristina Silva; Ramos, Ianny Alves; Cardoso, Andreia Medeiros Rodrigues; Xavier, Alidianne Fábia Cabral; Cavalcanti, Alessandro Leite

    2015-01-01

    Introduction: Fluoride dentifrices containing calcium carbonate have advantages such as control of dental plaque and progression of dental caries, also contributing to oral hygiene, represent most dentifrices marketed in Brazil. Aim: To evaluate the physicochemical properties of seven fluoride dentifrices containing calcium carbonate in relation to hydrogen potential (pH), loss on drying and calcium concentration. Materials and Methods: Data collection was performed using the potentiometric method for pH ranges, gravimetric analysis for loss on drying and atomic absorption spectrometry for the concentration of calcium ions. All tests were performed in triplicate and the analysis was performed entirely at random according to one-way analysis of variance at 5% significance level. Results: The pH values were alkaline and ranged from 8.67 (Oral-B 123®) to 10.03 (Colgate Máxima Proteção Anticáries®). The results of loss on drying ranged from 33.81% (Oral-B 123®) to 61.13% (Close Up®), with significant differences between brands tested. In relation to the calcium content, the highest and lowest concentrations were found in dentifrices Even® (155.55 g/kg) and Colgate Ultra Branco® (129 g/kg), respectively, with significant difference (P < 0.05). Conclusion: Fluoride dentifrices analyzed showed alkaline pH and high levels of loss on drying and calcium concentration. However, these physicochemical characteristics differed according to the different brands tested. PMID:25821380

  13. Modeling carbon dioxide, pH, and un-ionized ammonia relationships in serial reuse systems

    USGS Publications Warehouse

    Colt, J.; Watten, B.; Rust, M.

    2009-01-01

    In serial reuse systems, excretion of metabolic carbon dioxide has a significant impact on ambient pH, carbon dioxide, and un-ionized ammonia concentrations. This impact depends strongly on alkalinity, water flow rate, feeding rate, and loss of carbon dioxide to the atmosphere. A reduction in pH from metabolic carbon dioxide can significantly reduce the un-ionized ammonia concentration and increase the carbon dioxide concentrations compared to those parameters computed from influent pH. The ability to accurately predict pH in serial reuse systems is critical to their design and effective operation. A trial and error solution to the alkalinity-pH system was used to estimate important water quality parameters in serial reuse systems. Transfer of oxygen and carbon dioxide across the air-water interface, at overflow weirs, and impacts of substrate-attached algae and suspended bacteria were modeled. Gas transfer at the weirs was much greater than transfer across the air-water boundary. This simulation model can rapidly estimate influent and effluent concentrations of dissolved oxygen, carbon dioxide, and un-ionized ammonia as a function of water temperature, elevation, water flow, and weir type. The accuracy of the estimates strongly depends on assumed pollutional loading rates and gas transfer at the weirs. The current simulation model is based on mean daily loading rates; the impacts of daily variation loading rates are discussed. Copies of the source code and executable program are available free of charge.

  14. Important electromigration effects of carbon dioxide in capillary electrophoresis at high pH.

    PubMed

    Malá, Zdena; Gebauer, Petr; Boček, Petr

    2011-06-01

    This paper deals with unwanted effects of carbonate in capillary zone electrophoretic analyses of anions in alkaline BGEs with indirect UV absorption and conductivity detection. Computer simulations and experimental study of selected model systems have shown that carbon dioxide absorbed from air into BGEs and samples induce important electrophoretic effects like formation of new additional zones and/or boundaries that may further induce strong and pronounced temporary changes in the migration of analytes. Examples are reduction of the pH of alkaline BGEs around pH 11 by up to 1 unit or formation of a pronounced detectable carbon dioxide peak comparable with peaks of analytes at 1 mM level. The higher the pH of the BGE, the stronger these effects and the broader their spectrum, involving (i) changes of effective mobilities and selectivity due to changes in pH of the BGE, (ii) occurrence of additional system zones appearing in form of peaks, dips or more complex disturbances in the detection signal, (iii) temporary interactions with the sample components and subsequent modification of the separation process and of its result. This paper reveals all these effects and brings the knowledge necessary to prevent problems with qualitative and quantitative evaluation of the analysis results.

  15. pH dependence of the dissociation of multimeric hemoglobin probed by high hydrostatic pressure.

    PubMed

    Bispo, Jose A C; Santos, Jose L R; Landini, Gustavo F; Goncalves, Juliana M; Bonafe, Carlos F S

    2007-02-01

    We investigated the thermodynamic features of the classic alkaline dissociation of multimeric hemoglobin (3.1 MDa) from Glossoscolex paulistus (Annelidea) using high hydrostatic pressure. Light scattering measurements up to microscopic thermodynamic equilibrium indicated a high pH dependency of dissociation and association. Electron microscopy and gel filtration corroborated these findings. The volume change of dissociation decreased in absolute values from -48.0 mL/mol of subunit at pH 6.0 to -19.2 mL/mol at pH 9.0, suggesting a lack of protein interactions under alkaline conditions. Concomitantly, an increase in pH reduced the Gibbs free energy of dissociation from 37.7 to 27.5 kJ/mol of subunit. The stoichiometry of proton release calculated from the pressure-induced dissociation curves was +0.602 mol of H(+)/mol of subunit. These results provide a direct quantification of proton participation in stabilizing the aggregated state of the hemoglobin, and contribute to our understanding of protein-protein interactions and of the surrounding conditions that modulate the process of aggregation.

  16. Meet EPA Ecologist Paul Mayer, Ph.D.

    EPA Pesticide Factsheets

    EPA ecologist Paul Mayer, Ph.D. works in EPA's Groundwater and Ecosystem Restoration division where he studies riparian zones (the area along rivers and streams where the habitats are influenced by both the land and water) and stream restoration

  17. Meet EPA Scientist Heriberto Cabezas, Ph.D.

    EPA Pesticide Factsheets

    Heriberto Cabezas, Ph.D. is currently the Senior Science Advisor to the Sustainable Technology Division in EPA's National Risk Management Research Lab, where he works to advance the application of science and technologies to address sustainability.

  18. Meet EPA Microbiologist Eric Villegas, Ph.D.

    EPA Pesticide Factsheets

    Eric Villegas, Ph.D. is a research microbiologist in EPA's Office of Research and Development. His recent work focuses on next generation sequencing technology to better understand risks associated with waterborne parasites.

  19. Brenda K. Edwards, PhD | DCCPS/NCI/NIH

    Cancer.gov

    Brenda K. Edwards, PhD, has been with the Surveillance Research Program (SRP) and its predecessor organizations at the National Cancer Institute (NCI) since 1989, serving as SRP’s Associate Director from 1990-2011.

  20. Thermodynamic, Kinetic, Structural, and Computational Studies of the Ph3Sn-H, Ph3Sn-SnPh3, and Ph3Sn-Cr(CO)3C5Me5 Bond Dissociation Enthalpies.

    PubMed

    Cai, Xiaochen; Majumdar, Subhojit; Fortman, George C; Koppaka, Anjaneyulu; Serafim, Leonardo; Captain, Burjor; Temprado, Manuel; Hoff, Carl D

    2016-10-05

    The kinetics of the reaction of Ph3SnH with excess •Cr(CO)3C5Me5 = •Cr, producing HCr and Ph3Sn-Cr, was studied in toluene solution under 2-3 atm CO pressure in the temperature range of 17-43.5 °C. It was found to obey the rate equation d[Ph3Sn-Cr]/dt = k[Ph3SnH][•Cr] and exhibit a normal kinetic isotope effect (kH/kD = 1.12 ± 0.04). Variable-temperature studies yielded ΔH(‡) = 15.7 ± 1.5 kcal/mol and ΔS(‡) = -11 ± 5 cal/(mol·K) for the reaction. These data are interpreted in terms of a two-step mechanism involving a thermodynamically uphill hydrogen atom transfer (HAT) producing Ph3Sn• and HCr, followed by rapid trapping of Ph3Sn• by excess •Cr to produce Ph3Sn-Cr. Assuming an overbarrier of 2 ± 1 kcal/mol in the HAT step leads to a derived value of 76.0 ± 3.0 kcal/mol for the Ph3Sn-H bond dissociation enthalpy (BDE) in toluene solution. The reaction enthalpy of Ph3SnH with excess •Cr was measured by reaction calorimetry in toluene solution, and a value of the Sn-Cr BDE in Ph3Sn-Cr of 50.4 ± 3.5 kcal/mol was derived. Qualitative studies of the reactions of other R3SnH compounds with •Cr are described for R = (n)Bu, (t)Bu, and Cy. The dehydrogenation reaction of 2Ph3SnH → H2 + Ph3SnSnPh3 was found to be rapid and quantitative in the presence of catalytic amounts of the complex Pd(IPr)(P(p-tolyl)3). The thermochemistry of this process was also studied in toluene solution using varying amounts of the Pd(0) catalyst. The value of ΔH = -15.8 ± 2.2 kcal/mol yields a value of the Sn-Sn BDE in Ph3SnSnPh3 of 63.8 ± 3.7 kcal/mol. Computational studies of the Sn-H, Sn-Sn, and Sn-Cr BDEs are in good agreement with experimental data and provide additional insight into factors controlling reactivity in these systems. The structures of Ph3Sn-Cr and Cy3Sn-Cr were determined by X-ray crystallography and are reported. Mechanistic aspects of oxidative addition reactions in this system are discussed.

  1. Allosteric properties of PH domains in Arf regulatory proteins.

    PubMed

    Roy, Neeladri Sekhar; Yohe, Marielle E; Randazzo, Paul A; Gruschus, James M

    2016-01-01

    Pleckstrin Homology (PH) domains bind phospholipids and proteins. They are critical regulatory elements of a number enzymes including guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) for Ras-superfamily guanine nucleotide binding proteins such as ADP-ribosylation factors (Arfs). Recent studies have indicated that many PH domains may bind more than one ligand cooperatively. Here we discuss the molecular basis of PH domain-dependent allosteric behavior of 2 ADP-ribosylation factor exchange factors, Grp1 and Brag2, cooperative binding of ligands to the PH domains of Grp1 and the Arf GTPase-activating protein, ASAP1, and the consequences for activity of the associated catalytic domains.

  2. Meet EPA Biologist Laura Jackson, Ph.D.

    EPA Pesticide Factsheets

    Research Biologist Laura Jackson, Ph.D., has worked for the EPA for 22 years, leading research initiatives in a diversity of disciplines, including environmental monitoring, land use planning, and the impacts that urbanization has on an area's ecology

  3. Meet EPA Natural Resource Economist Marisa Mazzotta, Ph.D.

    EPA Pesticide Factsheets

    Marisa Mazzotta, Ph.D. currently works as an Economist at EPA's Atlantic Ecology Division. Her research focuses on the public's valuation and prioritization of natural resources, and the relationship between ecological changes and economic benefits.

  4. Meet EPA Scientist Susan Yee, Ph.D.

    EPA Pesticide Factsheets

    Susan Yee, Ph.D., is an ecologist at EPA's Gulf Ecology Division. She is working on the Puerto Rico Sustainable Communities program, developing decision support tools to evaluate how alternative decisions impact coastal ecosystem goods and services

  5. Meet EPA Scientist Jordan West, Ph.D.

    EPA Pesticide Factsheets

    Jordan West, Ph.D. is an aquatic ecologist at EPA. Her areas of expertise include freshwater & marine ecology, climate change impacts and adaptation, resilience and threshold theory, environmental risk assessment, expert elicitation & stakeholder processes

  6. Meet EPA Biologist Mitch Kostich, Ph.D.

    EPA Pesticide Factsheets

    EPA biologist, Mitch Kostich, Ph.D., conducts research to identify risks from exposures to chemical contaminants in water. His research uses technologies to prioritize contaminants in the environment based on the potential risks they pose to life

  7. Meet EPA Scientist Tim Shafer, Ph.D.

    EPA Pesticide Factsheets

    Tim Shafer earned his bachelor’s degree in biology and chemistry from Hope College in Holland, MI, in 1986 and his Ph.D. in pharmacology and environmental toxicology from Michigan State University in 1991.

  8. Meet EPA Chemist Quincy Teng, Ph.D.

    EPA Pesticide Factsheets

    EPA research chemist Quincy Teng, Ph.D., focuses on the application of metabolomics—a relatively new, specialized field of biochemistry focused on studying small molecules known as metabolites—on environmental and life sciences.

  9. Ashley Felix, Ph.D., M.P.H.

    Cancer.gov

    NCI Cancer Prevention Fellowship Program (CPFP) alumna, Ashley Felix, Ph.D., M.P.H., details her transition from pre-med student to an epidemiologist who focuses on studying the causes and prevention of disease.

  10. Meet EPA Environmental Engineer Terra Haxton, Ph.D.

    EPA Pesticide Factsheets

    EPA Environmental Engineer Terra Haxton, Ph.D., uses computer simulation models to protect drinking water. She investigates approaches to help water utilities be better prepared to respond to contamination incidents in their distribution systems.

  11. Frequently Asked Questions for Parents of Children with PH

    MedlinePlus

    ... Process: Some First Steps Adoption Success Story Watch Classroom Recordings Empowered Patient Online Toolkit Tab 1: Very ... Kathy Groebner Education Programs Patients and Caregivers PHA Classroom PHA on the Road: PH Patients and Families ...

  12. Colorimetric pH measurement of animal cell culture media.

    PubMed

    Jang, Juno; Moon, Soo-Jin; Hong, Sung-Hwan; Kim, Ik-Hwan

    2010-11-01

    Most animal cell culture media can be buffered using bicarbonate and high pressure CO(2) in a closed system. However, in an open system, the pH of the culture media increases continuously due to the marked difference in CO(2) pressure between the culture media and the atmosphere. Therefore, it is important to measure the exact pH of the culture media in an intact closed system. In this study, a pH measurement method was developed using visible light. The pH was calculated from light absorbance by the cells and by the culture media. This method was successfully applied to both suspension and anchorage-dependent cell cultures.

  13. pH Effects on Electrospray Ionization Efficiency

    NASA Astrophysics Data System (ADS)

    Liigand, Jaanus; Laaniste, Asko; Kruve, Anneli

    2017-03-01

    Electrospray ionization efficiency is known to be affected by mobile phase composition. In this paper, a detailed study of analyte ionization efficiency dependence on mobile phase pH is presented. The pH effect was studied on 28 compounds with different chemical properties. Neither p K a nor solution phase ionization degree by itself was observed to be sufficient at describing how aqueous phase pH affects the ionization efficiency of the analyte. Therefore, the analyte behavior was related to various physicochemical properties via linear discriminant analyses. Distinction between pH-dependent and pH-independent compounds was achieved using two parameters: number of potential charge centers and hydrogen bonding acceptor capacity (in the case of 80% acetonitrile) or polarity of neutral form of analyte and p K a (in the case of 20% acetonitrile). It was also observed that decreasing pH may increase ionization efficiency of a compound by more than two orders of magnitude.

  14. Commentary: PhDs in biochemistry education-5 years later.

    PubMed

    Offerdahl, Erika G; Momsen, Jennifer L; Osgood, Marcy

    2014-01-01

    In this commentary, the discussion of PhDs in biochemistry education research is expanded to explore a number of diverse pathways leading to a competitive research program in biochemistry education research.

  15. Commentary: PhDs in Biochemistry Education--5 Years Later

    ERIC Educational Resources Information Center

    Offerdahl, Erika G.; Momsen, Jennifer L.; Osgood, Marcy

    2014-01-01

    In this commentary, the discussion of PhDs in biochemistry education research is expanded to explore a number of diverse pathways leading to a competitive research program in biochemistry education research.

  16. Meet EPA Scientist Dermont Bouchard, Ph.D.

    EPA Pesticide Factsheets

    EPA Scientist Dermont Bouchard, Ph.D., is working to better understand how tiny nanomaterials might be released into the environment. His research helps regulators and other decision-makers lower risks and better protect human health and the environment

  17. The Training and Work of Ph.D. Physical Scientists

    NASA Astrophysics Data System (ADS)

    Smith, S. J.; Schweitzer, A. E.

    2003-05-01

    Doctoral education has often been viewed as the pinnacle of the formal education system. How useful is doctoral training in one's later career? In an NSF-funded project, we set out to perform a study of the training, careers, and work activities of Ph.D. physical scientists. The study included both in-depth interviews and a survey sent out to a sample of Ph.D. holders 4-8 years after graduation. Come and find out the results of this study: What skills are most Ph.D. physical scientists using? What should graduate programs be teaching? Are Ph.D.'s who are working in their specific field of training happier than their counterparts working different jobs? What skills and preparation lead to future job satisfaction, perhaps the most important indicator of the "success" of graduate education? A preprint and further details can be found at the project web site at: spot.colorado.edu/ phdcarer.

  18. Meet EPA Scientist Valerie Zartarian, Ph.D.

    EPA Pesticide Factsheets

    Senior exposure scientist and research environmental engineer Valerie Zartarian, Ph.D. helps build computer models and other tools that advance our understanding of how people interact with chemicals.

  19. Meet EPA Scientist Jody Shoemaker, Ph.D.

    EPA Pesticide Factsheets

    EPA research chemist Jody Shoemaker, Ph.D., works to support Agency efforts to protect drinking water. She helps develop methods for analyzing organic chemicals on the Drinking Water Contaminant Candidate List (CCL).

  20. Meet EPA Engineer Shawn Ryan, Ph.D.

    EPA Pesticide Factsheets

    Shawn Ryan, Ph.D. is a chemical engineer at EPA's National Homeland Security Research Center. He has worked at EPA for 12 years, nine of which have been devoted to leading research to support decontamination and consequence management.

  1. Meet EPA Chemist Linda Sheldon, Ph.D.

    EPA Pesticide Factsheets

    Environmental chemist Linda Sheldon, Ph.D, is the Associate Director for Human Heath in the National Exposure Research Laboratory. She studies environmental exposure, particularly focusing on children's environments and their contact with chemicals.

  2. Meet EPA Scientist Jeff Szabo, Ph.D.

    EPA Pesticide Factsheets

    EPA scientist Jeff Szabo, Ph.D., has worked for the EPA’s National Homeland Security Research Center since 2005. He conducts and manages water security research projects at EPA’s Test and Evaluation facility.

  3. Meet EPA Scientist Blake Schaeffer, Ph.D.

    EPA Pesticide Factsheets

    EPA research ecologist Blake Schaeffer, Ph.D. focuses on ways to use satellite remote sensing technology to monitor water quality. His research interests broadly include deriving water quality parameters in coasts, estuaries, and lakes using satellites

  4. Meet EPA Scientist Michael Nye, Ph.D.

    EPA Pesticide Factsheets

    Michael Nye, Ph.D., is a social scientist who studies natural risk, socio-demographic change and sustainable behavior. Prior to joining EPA, he worked for the UK Environment Agency in flood risk management and emergency preparedness

  5. The PhD in Writing Accompanied by an Exegesis

    ERIC Educational Resources Information Center

    Arnold, Josie

    2005-01-01

    The position of this paper is to further the discussion on what constitutes academic assessment in the PhD by artefact and exegesis. In doing so, it explores some of the ideas that arose in setting up the PhD in creative writing at Swinburne University of Technology. Thus, I: (1) survey some of the questions that arise about the journeys made by…

  6. Mouthguard and sports drinks on tooth surface pH.

    PubMed

    Maeda, Y; Yang, T-C; Miyanaga, H; Tanaka, Y; Ikebe, K; Akimoto, N

    2014-09-01

    The influence of sports drinks and mouthguards on the pH level of tooth surface was examined. A custom-made mouthguard was fabricated for each subject. The pH level was measured by electric pH meter with sensitivity of 0.01 up to 30 min. Sports drinks (pH=3.75) containing 9.4% sugar were used in this study. Measurements were performed on a cohort of 23 female subjects without a mouthguard (control), wearing a mouthguard only (MG), wearing a mouthguard after 30 ml sports drink intake (SD+MG), wearing a mouthguard during a 5-min jogging exercise (MG+EX) and wearing a mouthguard during jogging after sports drink intake (SD+MG+EX). For 7 male subjects, the same measurements were performed while a sports drink was taken over the mouthguard (MG+SD, MD+EX+SD). MG showed statistically higher pH level than control (p<0.05). SD+MG exhibited a significant decrease in pH level, and SD+MG+EX exhibited even below the critical level of pH 5.5 in some subjects. When sports drinks were taken over the mouthguard, no significant differences in pH level were observed among the different conditions.Within the limitations of this study, it was suggested that wearing a mouthguard during exercise is in itself not a possible risk factor for dental caries, while wearing a mouthguard after consuming sports drinks is.

  7. Teaching Human Digestion and pH Using Technology

    ERIC Educational Resources Information Center

    Kim, Hanna

    2008-01-01

    Testing the pH of various liquids is one of the most popular activities in 5th- through 8th-grade classrooms. The author presents an extensive pH-testing lesson based on a 5E (engagement, exploration, explanation, extension, and evaluation) teaching model. The activity provides students with the opportunity to learn about pH and how it relates to…

  8. MD-PhD training: looking back and looking forward.

    PubMed

    Bonham, Ann C

    2014-01-01

    MD-PhD programs provide rigorous, integrated training for physician-scientists, enabling them to frame scientific questions in unique ways and to apply clinical insight to fundamental science. Few would question the influential contributions of MD-PhD physician-scientists in advancing medical science. In this issue of Academic Medicine, Jeffe et al affirm high levels of excellence in educational outcomes from MD-PhD training programs at U.S. MD-granting medical schools, especially programs that receive funding from the NIH Medical Scientist Training Program (MSTP). The author of this commentary observes that, in the face of current economic pressures, comprehensive, longitudinal national outcomes data from MSTP- and non-MSTP-funded MD-PhD programs will help verify the value provided by MD-PhD physician-scientists. She proposes that MD-PhD programs should better prepare the next generation of physician-scientists for future research environments, which will provide new technologies, venues, and modalities. These research environments will be more closely integrated within health care delivery systems, extend into diverse communities and regions, and employ complex technologies. MD-PhD physician-scientists also will train and gain expertise in broadening areas of research, such as health policy, health economics, clinical epidemiology, and medical informatics. Program leaders are ideally situated to foster innovative learning environments and methodologies. By sharing their innovations, they can help ensure production of a diverse MD-PhD physician-scientist workforce, prepared to engage in myriad research opportunities to meet patient and population needs in a new environment.

  9. Automated high precision secondary pH measurements

    NASA Astrophysics Data System (ADS)

    Bastkowski, F.; Jakobsen, P. T.; Stefan, F.; Kristensen, H. B.; Jensen, H. D.; Kawiecki, R.; Wied, C. E.; Kauert, A.; Seidl, B.; Spitzer, P.; Eberhardt, R.; Adel, B.

    2013-04-01

    A new setup for high precision, automated secondary pH measurements together with a reference measurement procedure has been developed and tested in interlaboratory comparisons using buffers pH 4.005, pH 7.000, and pH 10.012 at 25 °C and 37 °C. Using primary buffers as standards, a standard uncertainty in pH better than 0.005 can be reached. The central measuring device is a one piece, thermostatted cell of PFA (perfluoroalkoxy) with a built-in Hamilton® Single Pore™ Glass electrode. Due to its flow-through principle this device allows pH measurements with low consumption of measurement solutions. The very hydrophobic and smooth PFA as construction material facilitates complete emptying of the cell. Furthermore, the tempering unit affords very precise temperature control and hence contributes to the low target uncertainty of the produced secondary buffer solutions. Use of a symmetric measurement sequence and the two point calibration was sufficient to reach high precision and accuracy.

  10. Monitoring pH and ORP in a SHARON reactor.

    PubMed

    Claros, J; Serralta, J; Seco, A; Ferrer, J; Aguado, D

    2011-01-01

    This paper analyses the valuable information provided by the on-line measurements of pH and oxidation reduction potential (ORP) in a continuous single high ammonia removal over nitrite (SHARON) reactor. A laboratory-scale SHARON reactor equipped with pH, ORP, electric conductivity and dissolved oxygen (DO) probes has been operated for more than one year. Nitrogen removal over nitrite has been achieved by adding methanol at the beginning of anoxic stages. Time evolution of pH and ORP along each cycle allows identifying the decrease in nitritation rate when ammonia is consumed during the aerobic phase and the end of the denitrification process during the anoxic phase. Therefore, monitoring pH and ORP can be used to develop a real-time control system aimed at optimizing the length of both aerobic and anoxic stages. Real-time control of methanol addition can be carried out by using the information provided by these probes: excessive methanol addition in the anoxic stage is clearly detected in the ORP profile of the following aerobic phase, while a deficit of methanol is detected in both pH and ORP profiles of that anoxic phase. Moreover, other valuable information such as the amount of ammonia nitrified, failures in DO measurements, excessive stirring during the anoxic stage and methanol dosage in the aerobic phase was also provided by the pH and ORP profiles.

  11. Structure of human saposin A at lysosomal pH

    SciTech Connect

    Hill, Chris H.; Read, Randy J.; Deane, Janet E.

    2015-06-27

    A 1.8 Å resolution structure of the sphingolipid activator protein saposin A has been determined at pH 4.8, the physiologically relevant lysosomal pH for hydrolase enzyme activation and lipid-transfer activity. The saposins are essential cofactors for the normal lysosomal degradation of complex glycosphingolipids by acid hydrolase enzymes; defects in either saposin or hydrolase function lead to severe metabolic diseases. Saposin A (SapA) activates the enzyme β-galactocerebrosidase (GALC), which catalyzes the breakdown of β-d-galactocerebroside, the principal lipid component of myelin. SapA is known to bind lipids and detergents in a pH-dependent manner; this is accompanied by a striking transition from a ‘closed’ to an ‘open’ conformation. However, previous structures were determined at non-lysosomal pH. This work describes a 1.8 Å resolution X-ray crystal structure determined at the physiologically relevant lysosomal pH 4.8. In the absence of lipid or detergent at pH 4.8, SapA is observeed to adopt a conformation closely resembling the previously determined ‘closed’ conformation, showing that pH alone is not sufficient for the transition to the ‘open’ conformation. Structural alignments reveal small conformational changes, highlighting regions of flexibility.

  12. Data collection and analysis strategies for phMRI.

    PubMed

    Mandeville, Joseph B; Liu, Christina H; Vanduffel, Wim; Marota, John J A; Jenkins, Bruce G

    2014-09-01

    Although functional MRI traditionally has been applied mainly to study changes in task-induced brain function, evolving acquisition methodologies and improved knowledge of signal mechanisms have increased the utility of this method for studying responses to pharmacological stimuli, a technique often dubbed "phMRI". The proliferation of higher magnetic field strengths and the use of exogenous contrast agent have boosted detection power, a critical factor for successful phMRI due to the restricted ability to average multiple stimuli within subjects. Receptor-based models of neurovascular coupling, including explicit pharmacological models incorporating receptor densities and affinities and data-driven models that incorporate weak biophysical constraints, have demonstrated compelling descriptions of phMRI signal induced by dopaminergic stimuli. This report describes phMRI acquisition and analysis methodologies, with an emphasis on data-driven analyses. As an example application, statistically efficient data-driven regressors were used to describe the biphasic response to the mu-opioid agonist remifentanil, and antagonism using dopaminergic and GABAergic ligands revealed modulation of the mesolimbic pathway. Results illustrate the power of phMRI as well as our incomplete understanding of mechanisms underlying the signal. Future directions are discussed for phMRI acquisitions in human studies, for evolving analysis methodologies, and for interpretative studies using the new generation of simultaneous PET/MRI scanners. This article is part of the Special Issue Section entitled 'Neuroimaging in Neuropharmacology'.

  13. Data Collection and Analysis Strategies for phMRI

    PubMed Central

    Mandeville, Joseph B.; Liu, Christina H.; Vanduffel, Wim; Marota, John J.A.; Jenkins, Bruce G.

    2014-01-01

    Although functional MRI traditionally has been applied mainly to study changes in task-induced brain function, evolving acquisition methodologies and improved knowledge of signal mechanisms have increased the utility of this method for studying responses to pharmacological stimuli, a technique often dubbed “phMRI”. The proliferation of higher magnetic field strengths and the use of exogenous contrast agent have boosted detection power, a critical factor for successful phMRI due to the restricted ability to average multiple stimuli within subjects. Receptor-based models of neurovascular coupling, including explicit pharmacological models incorporating receptor densities and affinities and data-driven models that incorporate weak biophysical constraints, have demonstrated compelling descriptions of phMRI signal induced by dopaminergic stimuli. This report describes phMRI acquisition and analysis methodologies, with an emphasis on data-driven analyses. As an example application, statistically efficient data-driven regressors were used to describe the biphasic response to the mu-opioid agonist remifentanil, and antagonism using dopaminergic and GABAergic ligands revealed modulation of the mesolimbic pathway. Results illustrate the power of phMRI as well as our incomplete understanding of mechanisms underlying the signal. Future directions are discussed for phMRI acquisitions in human studies, for evolving analysis methodologies, and for interpretative studies using the new generation of simultaneous PET/MRI scanners. PMID:24613447

  14. Macroalgae contribute to nested mosaics of pH variability in a sub-Arctic fjord

    NASA Astrophysics Data System (ADS)

    Krause-Jensen, D.; Duarte, C. M.; Hendriks, I. E.; Meire, L.; Blicher, M. E.; Marbà, N.; Sejr, M. K.

    2015-03-01

    The Arctic Ocean is considered the most vulnerable ecosystem to ocean acidification (OA) and large-scale assessments of pH and the saturation state for aragonite (Ωarag) indicate that it is already close to corrosive states (Ωarag < 1). In high-latitude coastal waters the regulation of pH and Ωarag is far more complex than offshore because increased biological activity and input of glacial meltwater affect pH. As most calcifiers occupy coastal habitats, the assessment of risks from OA to these vulnerable organisms cannot be derived from extrapolation of current and forecasted offshore conditions, but requires an understanding of the regimes of pH and Ωarag in their coastal habitats. To increase knowledge of the natural variability of pH in the Arctic coastal zone and specifically to test the influence of benthic vegetated habitats, we quantified pH-variability in a Greenland fjord in a nested scale approach. A sensor array logging pH, O2, PAR, temperature and salinity was applied on spatial scales ranging from km-scale across the horizontal extension of the fjord, over 100 m scale vertically in the fjord, 10-100 m scale between subtidal habitats with and without kelp forests and between vegetated tidal pools and adjacent vegetated shores, to cm-m scale within kelp forests and mm-scale across boundary layers of macrophyte tissue. In addition, we assessed the temporal variability in pH on diurnal and seasonal scales. Based on pH-measurements combined with relationships between salinity, total alkalinity and dissolved inorganic carbon we also estimated variability of Ωarag. Results show variability in pH and Ωarag of up to 0.2-0.3 units at several scales, i.e. along the horizontal and vertical extension of the fjord, between seasons and on a diel basis in benthic habitats and within 1 m3 of kelp forest. Vegetated intertidal pools exhibited extreme diel pH variability of > 1.5 units and macrophyte boundary layers a pH-range of up to 0.8 units. Overall, Ωarag was

  15. Evaluation of the 5 and 8 pH point titration methods for monitoring anaerobic digesters treating solid waste.

    PubMed

    Vannecke, T P W; Lampens, D R A; Ekama, G A; Volcke, E I P

    2015-01-01

    Simple titration methods certainly deserve consideration for on-site routine monitoring of volatile fatty acid (VFA) concentration and alkalinity during anaerobic digestion (AD), because of their simplicity, speed and cost-effectiveness. In this study, the 5 and 8 pH point titration methods for measuring the VFA concentration and carbonate system alkalinity (H2CO3*-alkalinity) were assessed and compared. For this purpose, synthetic solutions with known H2CO3*-alkalinity and VFA concentration as well as samples from anaerobic digesters treating three different kind of solid wastes were analysed. The results of these two related titration methods were verified with photometric and high-pressure liquid chromatography measurements. It was shown that photometric measurements lead to overestimations of the VFA concentration in the case of coloured samples. In contrast, the 5 pH point titration method provides an accurate estimation of the VFA concentration, clearly corresponding with the true value. Concerning the H2CO3*-alkalinity, the most accurate and precise estimations, showing very similar results for repeated measurements, were obtained using the 8 pH point titration. Overall, it was concluded that the 5 pH point titration method is the preferred method for the practical monitoring of AD of solid wastes due to its robustness, cost efficiency and user-friendliness.

  16. Comparing Metal Leaching and Toxicity from High pH, Low pH, and High Ammonia Fly Ash

    SciTech Connect

    Palumbo, Anthony Vito; Phillips, Jana Randolph; Fagan, Lisa Anne; Drake, Meghan M; Ruther, Rose Emily; Fisher, L. Suzanne; Amonette, J. E.

    2007-01-01

    Previous work with both class F and class C fly ash indicated minimal leaching from most fly ashes tested. However, the addition of NOx removal equipment might result in higher levels of ammonia in the fly ash. We have recently been testing fly ash with a wide range of pH (3.7-12.4) originating from systems with NOx removal equipment. Leaching experiments were done using dilute CaCl2 solutions in batch and columns and a batch nitric acid method. All methods indicated that the leaching of heavy metals was different in the highest ammonia sample tested and the high pH sample. However, toxicity testing with the Microtox system has indicated little potential toxicity in leachates except for the fly ash at the highest pH (12.4). When the leachate from the high pH fly ash was neutralized, toxicity was eliminated.

  17. Comparing metal leaching and toxicity from high pH, low pH, and high ammonia fly ash

    SciTech Connect

    Palumbo, Anthony V.; Tarver, Jana R.; Fagan, Lisa A.; McNeilly, Meghan S.; Ruther, Rose; Fisher, L. S.; Amonette, James E.

    2007-07-01

    Previous work with both class F and class C fly ash indicated minimal leaching from most fly ashes tested. However, the addition of NOx removal equipment might result in higher levels of ammonia in the fly ash. We have recently been testing fly ash with a wide range of pH (3.7–12.4) originating from systems with NOx removal equipment. Leaching experiments were done using dilute CaCl2 solutions in batch and columns and a batch nitric acid method. All methods indicated that the leaching of heavy metals was different in the highest ammonia sample tested and the high pH sample. However, toxicity testing with the Microtox* system has indicated little potential toxicity in leachates except for the fly ash at the highest pH (12.4). When the leachate from the high pH fly ash was neutralized, toxicity was eliminated.

  18. Saliva and tongue coating pH before and after use of mouthwashes and relationship with parameters of halitosis

    PubMed Central

    TOLENTINO, Elen de Souza; CHINELLATO, Luiz Eduardo Montenegro; TARZIA, Olinda

    2011-01-01

    Objectives The aim of this work was to evaluate saliva and tongue coating pH in oral healthy patients with morning bad breath before and after use of different oral mouthrinses. Material and Methods aliva and tongue coating pH of 50 patients allocated in 5 groups were measured respectively by a digital pHmeter and color pH indicators, before, immediately after and 30 min after rinsing 5 different mouthrinses: cetilpiridine chloride associated with sodium chloride, triclosan, enzymatic solution, essential oil and distilled water. Results Only triclosan and essential oil increased salivary pH immediately after rising. The enzymatic solution decreased salivary and tongue coating pH immediately after rinsing. Conclusion Salivary pH tended to be acidic while tongue coating pH tended to be alkaline, even after rising. Triclosan and essential oil mouthrinses increased salivary pH immediately after rinsing. Enzymatic solution decreased saliva and tongue coating pH immediately after rising. PMID:21552707

  19. Effect of initial pH on anaerobic co-digestion of kitchen waste and cow manure.

    PubMed

    Zhai, Ningning; Zhang, Tong; Yin, Dongxue; Yang, Gaihe; Wang, Xiaojiao; Ren, Guangxin; Feng, Yongzhong

    2015-04-01

    This study investigated the effects of different initial pH (6.0, 6.5, 7.0, 7.5 and 8.0) and uncontrolled initial pH (CK) on the lab-scale anaerobic co-digestion of kitchen waste (KW) with cow manure (CM). The variations of pH, alkalinity, volatile fatty acids (VFAs) and total ammonia nitrogen (NH4(+)-N) were analyzed. The modified Gompertz equation was used for selecting the optimal initial pH through comprehensive evaluation of methane production potential, degradation of volatile solids (VS), and lag-phase time. The results showed that CK and the fermentation with initial pH of 6.0 failed. The pH values of the rest treatments reached 7.7-7.9 with significantly increased methane production. The predicted lag-phase times of treatments with initial pH of 6.5 and 7.5 were 21 and 22 days, which were 10 days shorter than the treatments with initial pH of 7.0 and 8.0, respectively. The maximum methane production potential (8579 mL) and VS degradation rate (179.8 mL/g VS) were obtained when the initial pH was 7.5, which is recommended for co-digestion of KW and CM.

  20. [Phosphatase activity in Amoeba proteus at low pH].

    PubMed

    Sopina, V A

    2009-01-01

    In free-living Amoeba proteus (strain B), three forms of tartrate-sensitive phosphatase were revealed using PAGE of the supernatant of ameba homogenates obtained with 1% Triton X-100 or distilled water and subsequent staining of gels with 2-naphthyl phosphate as substrate (pH 4.0). The form with the highest mobility in the ameba supernatant was sensitive to all tested phosphatase activity modulators. Two other forms with the lower mobilities were completely or significantly inactivated not only by sodium L-(+)-tartrate, but also by L-(+)-tartaric acid, sodium orthovanadate, ammonium molybdate, EDTA, EGTA, o-phospho-L-tyrosine, DL-dithiotreitol, H2O2, 2-mercaptoethanol, and ions of heavy metals - Fe2+, Fe3+, and Cu2+. Based on results of inhibitory analysis, lysosome location in the ameba cell, and wide substrate specificity of these two forms, it has been concluded that they belong to nonspecific acid phosphomonoesterases (AcP, EC 3.1.3.2). This AcP is suggested to have both phosphomonoesterase and phosphotyrosyl-protein phosphatase activitis. Two ecto-phosphatases were revealed in the culture medium, in which amebas were cultivated. One of them was inhibited by the same reagents as the ameba tartrate-sensitive AcP and seems to be the AcP released into the culture medium in the process of exocytosis of the content of food vacuoles. In the culture medium, apart from this AcP, another phosphatase was revealed, which was not inhibited by any tested inhibitors of AcP and alkaline phosphatase. It cannot be ruled out that this phosphatase belong to the ecto-ATPases found in many protists; however, its ability to hydrolyze ATP has not yet been proven.

  1. Characterisation and deployment of an immobilised pH sensor spot towards surface ocean pH measurements.

    PubMed

    Clarke, Jennifer S; Achterberg, Eric P; Rérolle, Victoire M C; Abi Kaed Bey, Samer; Floquet, Cedric F A; Mowlem, Matthew C

    2015-10-15

    The oceans are a major sink for anthropogenic atmospheric carbon dioxide, and the uptake causes changes to the marine carbonate system and has wide ranging effects on flora and fauna. It is crucial to develop analytical systems that allow us to follow the increase in oceanic pCO2 and corresponding reduction in pH. Miniaturised sensor systems using immobilised fluorescence indicator spots are attractive for this purpose because of their simple design and low power requirements. The technology is increasingly used for oceanic dissolved oxygen measurements. We present a detailed method on the use of immobilised fluorescence indicator spots to determine pH in ocean waters across the pH range 7.6-8.2. We characterised temperature (-0.046 pH/°C from 5 to 25 °C) and salinity dependences (-0.01 pH/psu over 5-35), and performed a preliminary investigation into the influence of chlorophyll on the pH measurement. The apparent pKa of the sensor spots was 6.93 at 20 °C. A drift of 0.00014 R (ca. 0.0004 pH, at 25 °C, salinity 35) was observed over a 3 day period in a laboratory based drift experiment. We achieved a precision of 0.0074 pH units, and observed a drift of 0.06 pH units during a test deployment of 5 week duration in the Southern Ocean as an underway surface ocean sensor, which was corrected for using certified reference materials. The temperature and salinity dependences were accounted for with the algorithm, R=0.00034-0.17·pH+0.15·S(2)+0.0067·T-0.0084·S·1.075. This study provides a first step towards a pH optode system suitable for autonomous deployment. The use of a short duration low power illumination (LED current 0.2 mA, 5 μs illumination time) improved the lifetime and precision of the spot. Further improvements to the pH indicator spot operations include regular application of certified reference materials for drift correction and cross-calibration against a spectrophotometric pH system. Desirable future developments should involve novel

  2. pH measurement and a rational and practical pH control strategy for high throughput cell culture system.

    PubMed

    Zhou, Haiying; Purdie, Jennifer; Wang, Tongtong; Ouyang, Anli

    2010-01-01

    The number of therapeutic proteins produced by cell culture in the pharmaceutical industry continues to increase. During the early stages of manufacturing process development, hundreds of clones and various cell culture conditions are evaluated to develop a robust process to identify and select cell lines with high productivity. It is highly desirable to establish a high throughput system to accelerate process development and reduce cost. Multiwell plates and shake flasks are widely used in the industry as the scale down model for large-scale bioreactors. However, one of the limitations of these two systems is the inability to measure and control pH in a high throughput manner. As pH is an important process parameter for cell culture, this could limit the applications of these scale down model vessels. An economical, rapid, and robust pH measurement method was developed at Eli Lilly and Company by employing SNARF-4F 5-(-and 6)-carboxylic acid. The method demonstrated the ability to measure the pH values of cell culture samples in a high throughput manner. Based upon the chemical equilibrium of CO(2), HCO(3)(-), and the buffer system, i.e., HEPES, we established a mathematical model to regulate pH in multiwell plates and shake flasks. The model calculates the required %CO(2) from the incubator and the amount of sodium bicarbonate to be added to adjust pH to a preset value. The model was validated by experimental data, and pH was accurately regulated by this method. The feasibility of studying the pH effect on cell culture in 96-well plates and shake flasks was also demonstrated in this study. This work shed light on mini-bioreactor scale down model construction and paved the way for cell culture process development to improve productivity or product quality using high throughput systems.

  3. Deletion of pH Regulator pac-3 Affects Cellulase and Xylanase Activity during Sugarcane Bagasse Degradation by Neurospora crassa

    PubMed Central

    Campos Antoniêto, Amanda Cristina; Ramos Pedersoli, Wellington; dos Santos Castro, Lílian; da Silva Santos, Rodrigo; Cruz, Aline Helena da Silva; Nogueira, Karoline Maria Vieira; Silva-Rocha, Rafael; Rossi, Antonio

    2017-01-01

    Microorganisms play a vital role in bioethanol production whose usage as fuel energy is increasing worldwide. The filamentous fungus Neurospora crassa synthesize and secrete the major enzymes involved in plant cell wall deconstruction. The production of cellulases and hemicellulases is known to be affected by the environmental pH; however, the regulatory mechanisms of this process are still poorly understood. In this study, we investigated the role of the pH regulator PAC-3 in N. crassa during their growth on sugarcane bagasse at different pH conditions. Our data indicate that secretion of cellulolytic enzymes is reduced in the mutant Δpac-3 at alkaline pH, whereas xylanases are positively regulated by PAC-3 in acidic (pH 5.0), neutral (pH 7.0), and alkaline (pH 10.0) medium. Gene expression profiles, evaluated by real-time qPCR, revealed that genes encoding cellulases and hemicellulases are also subject to PAC-3 control. Moreover, deletion of pac-3 affects the expression of transcription factor-encoding genes. Together, the results suggest that the regulation of holocellulase genes by PAC-3 can occur as directly as in indirect manner. Our study helps improve the understanding of holocellulolytic performance in response to PAC-3 and should thereby contribute to the better use of N. crassa in the biotechnology industry. PMID:28107376

  4. Deletion of pH Regulator pac-3 Affects Cellulase and Xylanase Activity during Sugarcane Bagasse Degradation by Neurospora crassa.

    PubMed

    Campos Antoniêto, Amanda Cristina; Ramos Pedersoli, Wellington; Dos Santos Castro, Lílian; da Silva Santos, Rodrigo; Cruz, Aline Helena da Silva; Nogueira, Karoline Maria Vieira; Silva-Rocha, Rafael; Rossi, Antonio; Silva, Roberto Nascimento

    2017-01-01

    Microorganisms play a vital role in bioethanol production whose usage as fuel energy is increasing worldwide. The filamentous fungus Neurospora crassa synthesize and secrete the major enzymes involved in plant cell wall deconstruction. The production of cellulases and hemicellulases is known to be affected by the environmental pH; however, the regulatory mechanisms of this process are still poorly understood. In this study, we investigated the role of the pH regulator PAC-3 in N. crassa during their growth on sugarcane bagasse at different pH conditions. Our data indicate that secretion of cellulolytic enzymes is reduced in the mutant Δpac-3 at alkaline pH, whereas xylanases are positively regulated by PAC-3 in acidic (pH 5.0), neutral (pH 7.0), and alkaline (pH 10.0) medium. Gene expression profiles, evaluated by real-time qPCR, revealed that genes encoding cellulases and hemicellulases are also subject to PAC-3 control. Moreover, deletion of pac-3 affects the expression of transcription factor-encoding genes. Together, the results suggest that the regulation of holocellulase genes by PAC-3 can occur as directly as in indirect manner. Our study helps improve the understanding of holocellulolytic performance in response to PAC-3 and should thereby contribute to the better use of N. crassa in the biotechnology industry.

  5. Development of pH Sensitive Nanoparticles for Intestinal Drug Delivery Using Chemically Modified Guar Gum Co-Polymer

    PubMed Central

    Varma, Vegesna Naga Sravan Kumar; Shivakumar, Hosakote Gurumalappa; Balamuralidhara, Veerna; Navya, Manne; Hani, Umme

    2016-01-01

    The aim of the research work was to chemically modify guargum (GG) as a pH sensitive co-polymer and formulating intestinal targeting ESO nanoparticles (NPs) using the synthesized co-polymer. Poly acrylamide-grafted-guar gum (PAAm-g-GG) co-polymer was synthesized by free radical polymerization. Chemical modification of PAAm-g-GG by alkaline hydrolysis results in formation of a pH-sensitive co-polymer. The effect of GG and acryl amide (AAm) on grafting was studied. Esomeprazole magnesium (ESO) loaded pH sensitive NPs were prepared by nano-emulsification polymer crosslinking method and characterized. Sixteen formulations were prepared and the concentration of process variables wasvaried to obtain nanoparticles of 200-600 nm. The NPs were found to be homogenous in size distribution. The encapsulation efficiency and drug loading ranged from 33.2% to 50.1% and 12.2% to 17.2% respectively. Particle size, encapsulation efficiency and drug loading increasedalong with co-polymer concentration. In-vitro release studies at pH 1.2 for 2 h, followed by pH 6.8 showed that environment pH significantly affected the drug release. SEM has shown that NPsare spherical with smooth surface. The pH sensitive PAAm-g-GGNPs resisted the initial release of the drug from the drug loaded NPs in acidic pH and delayed the release process to a longer period in alkaline environment. PMID:27610149

  6. Use of limestone for pH control in autotrophic denitrification: continuous flow experiments in pilot-scale packed bed reactors.

    PubMed

    Koenig, A; Liu, L H

    2002-10-23

    The sulfur-utilizing autotrophic denitrification process consumes about 4 g alkalinity (as CaCO(3)) per g NO(3)-N reduced resulting in a decrease of pH. Using limestone as an alkalinity source to control the pH, autotrophic denitrification of synthetic wastewater with varying alkalinity to NO(3)-N ratios was evaluated in pilot-scale packed bed reactors operating in the upflow mode, which contained limestone and sulfur granules in different volumetric ratios. The results demonstrated that limestone supplies effective buffering capacity, if the initial alkalinity of the wastewater is insufficient for complete denitrification. The alkalinity supplied by limestone is a function of hydraulic retention time and the pH, which in turn depends on the extent of biological denitrification and the initial alkalinity to NO(3)-N ratio in the wastewater. The dissolution rate of limestone is inversely proportional to pH for pH values lower than 7.1. It was found that the ratio of influent alkalinity to theoretically required alkalinity in the wastewater should not be lower than 0.5 in order to prevent a decrease in nitrate removal performance. Based on the established chemical-biological interactive relationships, a multilayer approach was proposed to determine the optimum sulfur:limestone ratio for nitrate removal under steady state conditions, taking into account the characteristics of the influent wastewater.

  7. High Ph, Ammonia Toxicity, and the Search for Life on the Jovian Planets

    NASA Technical Reports Server (NTRS)

    Deal, P. H.; Souza, K. A.; Mack, H. M.

    1975-01-01

    The effects of pH and ammonia concentration were studied separately, where possible, on a variety of organisms, including some isolated from natural environments of high pH and/or ammonia concentration. Escherichia coli and Bacillus subtilis are both extremely sensitive to ammonia. An aerobic organism (growth up to pH 11.4) from an alkaline spring is more resistant, but exhibits a toxic response to ammonia at a pH much lower than its maximum for growth. The greatest ammonia resistance has been found in an unidentified organism growing at near neutral pH. Even in this case, however, urvival at ammonia concentrations reasonably expected on the Jovian planets is measured in hours. This is two to three orders of magnitude longer than for E. coli. Results support the tentative conclusion that contamination of the Jovian planets with terrestrial organisms that can grow is unlikely. However, the range of toxic response noted, coupled with the observation that terrestrial life has not been exposed to high ammonia concentrations for millions of years, suggests that adaptation to greater ammonia tolerance may be possible.

  8. Assessing mine drainage pH from the color and spectral reflectance of chemical precipitates

    USGS Publications Warehouse

    Williams, D.J.; Bigham, J.M.; Cravotta, C.A.; Traina, S.J.; Anderson, J.E.; Lyon, J.G.

    2002-01-01

    The pH of mine impacted waters was estimated from the spectral reflectance of resident sediments composed mostly of chemical precipitates. Mine drainage sediments were collected from sites in the Anthracite Region of eastern Pennsylvania, representing acid to near neutral pH. Sediments occurring in acidic waters contained primarily schwertmannite and goethite while near neutral waters produced ferrihydrite. The minerals comprising the sediments occurring at each pH mode were spectrally separable. Spectral angle difference mapping was used to correlate sediment color with stream water pH (r2=0.76). Band-center and band-depth analysis of spectral absorption features were also used to discriminate ferrihydrite and goethite and/or schwertmannite by analyzing the 4T1??? 6A1 crystal field transition (900-1000 nm). The presence of these minerals accurately predicted stream water pH (r2=0.87) and provided a qualitative estimate of dissolved SO4 concentrations. Spectral analysis results were used to analyze airborne digital multispectral video (DMSV) imagery for several sites in the region. The high spatial resolution of the DMSV sensor allowed for precise mapping of the mine drainage sediments. The results from this study indicate that airborne and space-borne imaging spectrometers may be used to accurately classify streams impacted by acid vs. neutral-to-alkaline mine drainage after appropriate spectral libraries are developed.

  9. Pathway and mechanism of pH dependent human hemoglobin tetramer-dimer-monomer dissociations.

    PubMed

    Huang, Yao-Xiong; Wu, Zheng-Jie; Huang, Bao-Tian; Luo, Man

    2013-01-01

    Hemoglobin dissociation is of great interest in protein process and clinical medicine as well as in artificial blood research. However, the pathway and mechanisms of pH-dependent human Hb dissociation are not clear, whether Hb would really dissociate into monomers is still a question. Therefore, we have conducted a multi-technique investigation on the structure and function of human Hb versus pH. Here we demonstrate that tetramer hemoglobin can easily dissociate into dimer in abnormal pH and the tetramer → dimer dissociation is reversible if pH returns to normal physiological value. When the environmental pH becomes more acidic (<6.5) or alkaline (>8.0), Hb can further dissociate from dimer to monomer. The proportion of monomers increases while the fraction of dimers decreases as pH declines from 6.2 to 5.4. The dimer → monomer dissociation is accompanied with series changes of protein structure thus it is an irreversible process. The structural changes in the dissociated Hbs result in some loss of their functions. Both the Hb dimer and monomer cannot adequately carry and release oxygen to the tissues in circulation. These findings provide a comprehensive understanding on the pH-dependent protein transitions of human Hb, give guideline to explain complex protein processes and the means to control protein dissociation or re-association reaction. They are also of practical value in clinical medicine, blood preservation and blood substitute development.

  10. pH modeling for maximum dissolved organic matter removal by enhanced coagulation.

    PubMed

    Xie, Jiankun; Wang, Dongsheng; van Leeuwen, John; Zhao, Yanmei; Xing, Linan; Chow, Christopher W K

    2012-01-01

    Correlations between raw water characteristics and pH after enhanced coagulation to maximize dissolved organic matter (DOM) removal using four typical coagulants (FeCl3, Al2(SO4)3, polyaluminum chloride (PACl) and high performance polyaluminum chloride (HPAC)) without pH control were investigated. These correlations were analyzed on the basis of the raw water quality and the chemical and physical fractionations of DOM of thirteen Chinese source waters over three seasons. It was found that the final pH after enhanced coagulation for each of the four coagulants was influenced by the content of removable DOM (i.e. hydrophobic and higher apparent molecular weight (AMW) DOM), the alkalinity and the initial pH of raw water. A set of feed-forward semi-empirical models relating the final pH after enhanced coagulation for each of the four coagulants with the raw water characteristics were developed and optimized based on correlation analysis. The established models were preliminarily validated for prediction purposes, and it was found that the deviation between the predicted data and actual data was low. This result demonstrated the potential for the application of these models in practical operation of drinking water treatment plants.

  11. Effect of systemic pH on pH sub i and lactic acid generation in exhaustive forearm exercise

    SciTech Connect

    Hood, V.L.; Schubert, C.; Keller, U.; Mueller, S. Univ. of Vermont College of Medicine, Burlington )

    1988-09-01

    To investigate whether changes in systemic pH affect intracellular pH (pH{sub i}), energy-rich phosphates, and lactic acid generation in muscle, eight normal volunteers performed exhaustive forearm exercise with arterial blood flow occluded for 2 min on three occasions. Subjects ingested 4 mmol/kg NH{sub 4}Cl (acidosis; A) or NaHCO{sub 3} (alkalosis; B) or nothing (control; C) 3 h before the exercise. Muscle pH{sub i} and phosphocreatine (PCr) content were measured with {sup 31}P-nuclear magnetic resonance ({sup 31}P-NMR) spectroscopy during exercise and recovery. Lactate output during 0.5-7 min of recovery was calculated as deep venous-arterial concentration differences times forearm blood flow. Before exercise, blood pH and bicarbonate were lower in acidosis than alkalosis and intermediate in control. Lactic acid output during recovery was less with A than B and intermediate in C. PCr utilization and resynthesis were not affected by extracellular pH changes. pH{sub i} did not differ before exercise or at its end. Hence systemic acidosis inhibited and alkalosis stimulated lactic acid output. These findings suggest that systemic pH regulates cellular acid production, protecting muscle pH, at the expense of energy availability.

  12. Ligand accessibility and bioactivity of a hormone–dendrimer conjugate depend on pH and pH history

    SciTech Connect

    Kim, Sung Hoon; Madak-Erdogan, Zeynep; Bae, Sung Chul; Carlson, Kathryn E.; Mayne, Christopher G.; Granick, Steve; Katzenellenbogen, Benita S.; Katzenellenbogen, John A.

    2015-07-17

    Estrogen conjugates with a polyamidoamine (PAMAM) dendrimer have shown remarkably selective regulation of the nongenomic actions of estrogens in target cells in this paper. In response to pH changes, however, these estrogen–dendrimer conjugates (EDCs) display a major morphological transition that alters the accessibility of the estrogen ligands that compromises the bioactivity of the EDC. A sharp break in dynamic behavior near pH 7 occurs for three different ligands on the surface of a PAMAM-G6 dendrimer: a fluorophore (tetramethylrhodamine [TMR]) and two estrogens (17α-ethynylestradiol and diphenolic acid). Collisional quenching and time-resolved fluorescence anisotropy experiments with TMR–PAMAM revealed high ligand shielding above pH 7 and low shielding below pH 7. Furthermore, when the pH was cycled from 8.5 (conditions of ligand–PAMAM conjugation) to 4.5 (e.g., endosome/lysosome) and through 6.5 (e.g., hypoxic environment) back to pH 8.5, the 17α-ethynylestradiol– and diphenolic acid–PAMAM conjugates experienced a dramatic, irreversible loss in cell stimulatory activity; dynamic NMR studies indicated that the hormonal ligands had become occluded within the more hydrophobic core of the PAMAM dendrimer. Thus, the active state of these estrogen–dendrimer conjugates appears to be metastable. Finally, this pH-dependent irreversible masking of activity is of considerable relevance to the design of drug conjugates with amine-bearing PAMAM dendrimers.

  13. pH Signaling in Sclerotinia sclerotiorum: Identification of a pacC/RIM1 Homolog

    PubMed Central

    Rollins, Jeffrey A.; Dickman, Martin B.

    2001-01-01

    Sclerotinia sclerotiorum acidifies its ambient environment by producing oxalic acid. This production of oxalic acid during plant infection has been implicated as a primary determinant of pathogenicity in this and other phytopathogenic fungi. We found that ambient pH conditions affect multiple processes in S. sclerotiorum. Exposure to increasing alkaline ambient pH increased the oxalic acid accumulation independent of carbon source, sclerotial development was favored by acidic ambient pH conditions but inhibited by neutral ambient pH, and transcripts encoding the endopolygalacturonase gene pg1 accumulated maximally under acidic culture conditions. We cloned a putative transcription factor-encoding gene, pac1, that may participate in a molecular signaling pathway for regulating gene expression in response to ambient pH. The three zinc finger domains of the predicted Pac1 protein are similar in sequence and organization to the zinc finger domains of the A. nidulans pH-responsive transcription factor PacC. The promoter of pac1 contains eight PacC consensus binding sites, suggesting that this gene, like its homologs, is autoregulated. Consistent with this suggestion, the accumulation of pac1 transcripts paralleled increases in ambient pH. Pac1 was determined to be a functional homolog of PacC by complementation of an A. nidulans pacC-null strain with pac1. Our results suggest that ambient pH is a regulatory cue for processes linked to pathogenicity, development, and virulence and that these processes may be under the molecular regulation of a conserved pH-dependent signaling pathway analogous to that in the nonpathogenic fungus A. nidulans. PMID:11133430

  14. Effects of pH amendment on metal working fluid wastewater biological treatment using a defined bacterial consortium.

    PubMed

    van der Gast, Christopher J; Thompson, Ian P

    2005-02-05

    The aim of this study was to determine whether pH amendment of a highly alkaline metal working fluid (MWF) wastewater would improve biological treatment in a bioreactor system following introduction of a bacterial inoculum (comprised of the following strains: Agrobacterium radiobacter, Comamonas testosteroni, Methylobacterium mesophilicum, Microbacterium esteraromaticum, and Microbacterium saperdae). The pH values tested were 6, 7, 8, and 9. Three replicate batch mode bioreactors inoculated with the bacterial inoculum (plus an abiotic control bioreactor) were operated for each of the four pH conditions. After 14 days, the final mean chemical oxygen demand (COD) reduction at pH 9 was 50 +/- 1.4%; at pH 8, 58 +/- 1.4%; pH 7, 65 +/- 1.0%; and pH 6, 75 +/- 2.7% of the initial COD (approximately 10,000 mg L(-1)), respectively. Interestingly, within 5 days, the pH in all inoculated bioreactors progressed toward pH 8. However, all abiotic control bioreactors remained at the pH at which they were amended. The fate of the inoculum, determined by denaturing gradient gel electrophoresis (DGGE) and by cluster analysis of the resulting DGGE profiles, revealed that the inocula survived throughout operation of all pH-amended bioreactors. Length-heterogeneity polymerase chain reaction (PCR) was used to track the population dynamics of individual strains. After 7 days of operation, M. esteraromaticum was the most abundant population in all bioreactors, regardless of pH. From our findings, it appears necessary to adjust the MWF wastewater from pH 9 to between 6 and 7, to achieve optimal biological treatment rates.

  15. PH5 for integrating and archiving different data types

    NASA Astrophysics Data System (ADS)

    Azevedo, Steve; Hess, Derick; Beaudoin, Bruce

    2016-04-01

    PH5 is IRIS PASSCAL's file organization of HDF5 used for seismic data. The extensibility and portability of HDF5 allows the PH5 format to evolve and operate on a variety of platforms and interfaces. To make PH5 even more flexible, the seismic metadata is separated from the time series data in order to achieve gains in performance as well as ease of use and to simplify user interaction. This separation affords easy updates to metadata after the data are archived without having to access waveform data. To date, PH5 is currently used for integrating and archiving active source, passive source, and onshore-offshore seismic data sets with the IRIS Data Management Center (DMC). Active development to make PH5 fully compatible with FDSN web services and deliver StationXML is near completion. We are also exploring the feasibility of utilizing QuakeML for active seismic source representation. The PH5 software suite, PIC KITCHEN, comprises in-field tools that include data ingestion (e.g. RefTek format, SEG-Y, and SEG-D), meta-data management tools including QC, and a waveform review tool. These tools enable building archive ready data in-field during active source experiments greatly decreasing the time to produce research ready data sets. Once archived, our online request page generates a unique web form and pre-populates much of it based on the metadata provided to it from the PH5 file. The data requester then can intuitively select the extraction parameters as well as data subsets they wish to receive (current output formats include SEG-Y, SAC, mseed). The web interface then passes this on to the PH5 processing tools to generate the requested seismic data, and e-mail the requester a link to the data set automatically as soon as the data are ready. PH5 file organization was originally designed to hold seismic time series data and meta-data from controlled source experiments using RefTek data loggers. The flexibility of HDF5 has enabled us to extend the use of PH5 in several

  16. Noninvasive Ph-telemetric Measurement of Gastrointestinal Function

    NASA Technical Reports Server (NTRS)

    Tietze, Karen J.

    1991-01-01

    The purpose of this study was to gain experience with and validate the Heidelberg pH-telemetric methodology in order to determine if the pH-telemetric methodology would be a useful noninvasive measure of gastrointestinal transit time for future ground-based and in-flight drug evaluation studies. The Heidelberg pH metering system is a noninvasive, nonradioactive telemetric system that, following oral ingestion, continuously measures intraluminal pH of the stomach, duodenum, small bowel, ileocecal junction, and large bowel. Gastrointestinal motility profiles were obtained in normal volunteers using the lactulose breath-hydrogen and Heidelberg pH metering techniques. All profiles were obtained in the morning after an overnight fast. Heidelberg pH profiles were obtained in the fasting and fed states; lactulose breath-hydrogen profiles were obtained after a standard breakfast. Mouth-to-cecum transit time was measured as the interval from administration of lactulose (30 ml; 20 g) to a sustained increase in breath-hydrogen of 10 ppm or more. Gastric emptying time was measured as the interval from the administration of the Heidelberg capsule to a sustained increase in pH of three units or more.

  17. The Production Rate and Employment of Ph.D. Astronomers

    NASA Astrophysics Data System (ADS)

    Metcalfe, Travis S.

    2008-02-01

    In an effort to encourage self-regulation of the astronomy job market, I examine the supply of, and demand for, astronomers over time. On the supply side, I document the production rate of Ph.D. astronomers from 1970 to 2006 using the UMI Dissertation Abstracts database, along with data from other independent sources. I compare the long-term trends in Ph.D. production with federal astronomy research funding over the same time period, and I demonstrate that additional funding is correlated with higher subsequent Ph.D. production. On the demand side, I monitor the changing patterns of employment using statistics about the number and types of jobs advertised in the AAS Job Register from 1984 to 2006. Finally, I assess the sustainability of the job market by normalizing this demand by the annual Ph.D. production. The most recent data suggest that there are now annual advertisements for about one postdoctoral job, half a faculty job, and half a research/support position for every new domestic Ph.D. recipient in astronomy and astrophysics. The average new astronomer might expect to hold up to 3 jobs before finding a steady position.

  18. Interfacial pH during mussel adhesive plaque formation

    PubMed Central

    Rodriguez, Nadine R. Martinez; Das, Saurabh; Kaufman, Yair; Israelachvili, Jacob N.; Waite, J. Herbert

    2015-01-01

    Mussel (Mytilus californianus) adhesion to marine surfaces involves an intricate and adaptive synergy of molecules and spatio-temporal processes. Although the molecules, such as mussel foot proteins (mfps), are well characterized, deposition details remain vague and speculative. Developing methods for the precise surveillance of conditions that apply during mfp deposition would aid both in understanding mussel adhesion and translating this adhesion into useful technologies. To probe the interfacial pH at which mussels buffer the local environment during mfp deposition, a lipid bilayer with tethered pH-sensitive fluorochromes was assembled on mica. The interfacial pH during foot contact with modified mica ranged from 2.2−3.3, which is well below the seawater pH of ~8. The acidic pH serves multiple functions: it limits mfp-Dopa oxidation, thereby enabling the catecholic functionalities to adsorb to surface oxides by H-bonding and metal ion coordination, and provides a solubility switch for mfps, most of which aggregate at pH ≥ 7-8. PMID:25875963

  19. PhIN: A Protein Pharmacology Interaction Network Database

    PubMed Central

    Wang, Z; Li, J; Dang, R; Liang, L; Lin, J

    2015-01-01

    Network pharmacology is a new and hot concept in drug discovery for its ability to investigate the complexity of polypharmacology, and becomes more and more important in drug development. Here we report a protein pharmacology interaction network database (PhIN), aiming to assist multitarget drug discovery by providing comprehensive and flexible network pharmacology analysis. Overall, PhIN contains 1,126,060 target–target interaction pairs in terms of shared compounds and 3,428,020 pairs in terms of shared scaffolds, which involve 12,419,700 activity data, 9,414 targets, 314 viral targets, 652 pathways, 1,359,400 compounds, and 309,556 scaffolds. Using PhIN, users can obtain interacting target networks within or across human pathways, between human and virus, by defining the number of shared compounds or scaffolds under an activity cutoff. We expect PhIN to be a useful tool for multitarget drug development. PhIN is freely available at http://cadd.pharmacy.nankai.edu.cn/phin/. PMID:26225242

  20. Ocean Acidification: Euphausia Pacifica's Response to Decreasing pH

    NASA Astrophysics Data System (ADS)

    Weber, H. N.; Cooper, H.

    2014-12-01

    The increasing rate of CO2 accumulating in Earth's oceans creates a threat to organisms that can lead to disturbances in their reproduction, survival and growth. Euphausia pacifica is the dominant species of krill in Monterey Bay, CA, and a keystone species in the bay's food web. Previous work on the effects of ocean acidification on the survival, growth and molting of E. pacifica have shown they are fairly tolerant to increased CO2 concentrations. However, less is known about energy costs associated with maintaining their internal pH levels which could affect food consumption, swimming behavior or growth activity. We hypothesized that krill exposed to high CO2 will increase their feeding rate on local species of phytoplankton to account for increased energy costs of pH buffering activity. We exposed experimental E. pacifica to waters of pH 7.6 (the expected pH surface waters in year 2100), and pH 8.0 (control) periods.test for acclimation or longer term stress. Feeding rates were calculated as changes in phytoplankton counts over 24 hours of feeding using Frost's equations (Frost 1972). Understanding the way E. pacifica is affected by ocean acidification is important because of the role they play as the primary food source for a variety of predators necessary to maintain the Pacific's ecology.

  1. Reduction of dehydroascorbic acid at low pH.

    PubMed

    Wechtersbach, Luka; Cigić, Blaz

    2007-08-01

    Ascorbic acid and dehydroascorbic acid are unstable in aqueous solution in the presence of copper and iron ions, causing problems in the routine analysis of vitamin C. Their stability can be improved by lowering the pH below 2, preferably with metaphosphoric acid. Dehydroascorbic acid, an oxidised form of vitamin C, gives a relatively low response on the majority of chromatographic detectors, and is therefore routinely determined as the increase of ascorbic acid formed after reduction. The reduction step is routinely performed at a pH that is suboptimal for the stability of both forms. In this paper, the reduction of dehydroascorbic acid with tris-[2-carboxyethyl] phosphine (TCEP) at pH below 2 is evaluated. Dehydroascorbic acid is fully reduced with TCEP in metaphosphoric acid in less than 20 min, and yields of ascorbic acid are the same as at higher pH. TCEP and ascorbic acid formed by reduction, are more stable in metaphosphoric acid than in acetate or citrate buffers at pH 5, in the presence of redox active copper ions. The simple experimental procedure and low probability of artefacts are major benefits of this method, over those currently applied in a routine assay of vitamin C, performed on large number of samples.

  2. Kinetics of biological perchlorate reduction and pH effect.

    PubMed

    Wang, Chao; Lippincott, Lee; Meng, Xiaoguang

    2008-05-01

    Batch experiments were conducted to investigate the kinetics of perchlorate reduction by heterotrophic and mixed perchlorate-reducing bacteria. Substrate-utilizing and cellular maintenance models were employed to fit the experimental data for microbial perchlorate reduction. The half saturation constant, K(s), obtained in this study was below 0.1mg/L, which indicated that perchlorate-reducing bacteria are effective at utilizing low concentrations of perchlorate. The effect of pH on the kinetics of microbial perchlorate reduction was also studied. Perchlorate reduction occurred throughout the pH range from 5.0 to 9.0. Nevertheless, the rates of perchlorate removal by a unit mass of bacteria were significantly different at various pHs with a maximum rate at pH 7.0. The variation of q(max) with pH was described well with a Gaussian peak equation. This equation is expected to be applicable for practical purposes when pH effects need to be considered.

  3. pH responsive graft copolymers of chitosan.

    PubMed

    Yilmaz, Elvan; Yalinca, Zulal; Yahya, Kovan; Sirotina, Uliana

    2016-09-01

    Grafting suitable polymers onto chitosan can produce cationic or polyampholyte polymers or hydrogels that are potential smart biomedical materials. Chitosan-graft-[poly(diethylamino)ethyl methacrylate] has been prepared in three different physical forms as linear free chains in solution, chemical gels crosslinked with glutaraldehyde, and poly(diethylamino)ethyl methacrylate] grafted onto chitosan tripolyphosphate gel beads. In addition to chemical structure, the graft copolymers were characterized with respect to their dissolution and swelling behavior in aqueous solution. It has been established that solubility of the products is controlled by the grafting yield. While pH sensitive polymers, which collapse at a given pH value are obtained at lower grafting yields, hydrogels form at higher grafting yields with pH responsive swelling behavior. Glutaraldehyde crosslinked chitosan-graft-[poly(diethylamino)ethyl methacrylate] gels and chitosan tripolyphosphate gel beads grafted with poly[(diethylamino)ethyl methacrylate] exhibit pH sensitive swelling with highest equilibrium swelling capacity at pH=1.2.

  4. Near-infrared noninvasive spectroscopic determination of pH

    DOEpatents

    Alam, Mary K.; Robinson, Mark R.

    1998-08-11

    Methods and apparatus for, preferably, determining noninvasively and in vitro pH in a human. The non-invasive method includes the steps of: generating light at three or more different wavelengths in the range of 1000 nm to 2500 nm; irradiating blood containing tissue; measuring the intensities of the wavelengths emerging from the blood containing tissue to obtain a set of at least three spectral intensities v. wavelengths; and determining the unknown values of pH. The determination of pH is made by using measured intensities at wavelengths that exhibit change in absorbance due to histidine titration. Histidine absorbance changes are due to titration by hydrogen ions. The determination of the unknown pH values is performed by at least one multivariate algorithm using two or more variables and at least one calibration model. The determined pH values are within the physiological ranges observed in blood containing tissue. The apparatus includes a tissue positioning device, a source, at least one detector, electronics, a microprocessor, memory, and apparatus for indicating the determined values.

  5. Interfacial pH during mussel adhesive plaque formation.

    PubMed

    Martinez Rodriguez, Nadine R; Das, Saurabh; Kaufman, Yair; Israelachvili, Jacob N; Waite, J Herbert

    2015-01-01

    Mussel (Mytilus californianus) adhesion to marine surfaces involves an intricate and adaptive synergy of molecules and spatio-temporal processes. Although the molecules, such as mussel foot proteins (mfps), are well characterized, deposition details remain vague and speculative. Developing methods for the precise surveillance of conditions that apply during mfp deposition would aid both in understanding mussel adhesion and translating this adhesion into useful technologies. To probe the interfacial pH at which mussels buffer the local environment during mfp deposition, a lipid bilayer with tethered pH-sensitive fluorochromes was assembled on mica. The interfacial pH during foot contact with modified mica ranged from 2.2 to 3.3, which is well below the seawater pH of ~ 8. The acidic pH serves multiple functions: it limits mfp-Dopa oxidation, thereby enabling the catecholic functionalities to adsorb to surface oxides by H-bonding and metal ion coordination, and provides a solubility switch for mfps, most of which aggregate at pH ≥ 7-8.

  6. [Effects of simulated acid rain on respiration rate of cropland system with different soil pH].

    PubMed

    Zhu, Xue-zhu; Zhang, Gao-chuan; Li, Hui

    2009-10-15

    To evaluate the effects of acid rain on the respiration rate of cropland system, an outdoor pot experiment was conducted with paddy soils of pH 5.48 (S1), pH 6.70 (S1) and pH 8.18 (S3) during the 2005-2007 wheat-growing seasons. The cropland system was exposed to acid rain by spraying the wheat foliage and irrigating the soil with simulated rainwater of T1 (pH 6.0), T2 (pH 6.0, ionic concentration was twice as rainwater T1), and T3 (pH 4.4, ionic concentration was twice as rainwater T1), respectively. The static opaque chamber-gas chromatograph method was used to measure CO2 fluxes from cropland system. The results showed that acid rain affected the respiration rate of cropland system through crop plant, and the cropland system could adapt to acid rain. Acid rainwater significantly increased the average respiration rate in alkaline soil (S3) cropland system, while it had no significant effects on the average respiration rate in neutral soil (S2) and acidic soil (S1) cropland systems. During 2005-2006, after the alkaline soil cropland system was treated with rainwater T3, the average respiration rate was 23.6% and 27.6% higher than that of alkaline soil cropland system treated with rainwater T1 and T2, respectively. During March to April, the respiration rate was enhanced with the increase of rainwater ionic concentration, while it was dropped with the decrease of rainwater pH value in acidic soil cropland system. It was demonstrated that soil pH and crop plant played important roles on the respiration rate of cropland system.

  7. The effects of temperature, pH, and ammonia concentration on the inactivation of Ascaris eggs in sewage sludge.

    PubMed

    Pecson, Brian M; Barrios, José Antonio; Jiménez, Blanca Elena; Nelson, Kara L

    2007-07-01

    The reported inactivation of Ascaris eggs during alkaline sludge stabilization is highly variable. The objective of our research was to better understand the sources of this variability by quantifying the effects of temperature, pH, and ammonia concentration on the inactivation of indigenous Ascaris eggs in wastewater sludge. Primary sludge was supplemented with ammonia (0, 1000, and 5000 mg/l NH(3)-N) and Ca(OH)(2) and incubated in sealed bottles across the range of temperatures (20, 30, 40, and 50 degrees C) and pH (7 and 12) that may be encountered during treatment. Changes in egg viability over time were fit to a two-parameter kinetic model (shoulder and first-order region); to compare treatment conditions, the time for 99% inactivation (t(99)) was also calculated. Each 10 degrees C increase in temperature caused a significant decrease in t(99) at every pH and ammonia concentration tested. At 50 degrees C, the effect of temperature was dominant, such that no effect of pH or ammonia was observed. At 30 and 40 degrees C, raising the pH from 7 to 12 decreased t(99), but at 20 degrees C no pH effect was seen over 80 d (very little inactivation occurred). At 20, 30, and 40 degrees C, the addition of ammonia dramatically decreased t(99). The effect of pH could not be completely separated from that of ammonia, as the unamended sludge samples contained 100-200mg/l indigenous ammonia. Because temperature, pH, and ammonia all contributed to Ascaris egg inactivation, it is essential that these parameters are measured and accounted for when assessing the effectiveness of alkaline stabilization. Furthermore, inactivation by ammonia could be exploited to improve the effectiveness of alkaline sludge stabilization.

  8. THE INFLUENCE OF pH UPON THE CONCENTRATION POTENTIALS ACROSS THE SKIN OF THE FROG.

    PubMed

    Amberson, W R; Klein, H

    1928-07-20

    The production of concentration P.D.'s across the skin of the frog is very intimately related to the pH of the applied solutions. On the alkaline side of an isoelectric point the dilute solution is electropositive; on the acid side this solution becomes electronegative. When the pH is suddenly lowered from a value more alkaline than this isoelectric point to one considerably more acid the change in polarity may occur within a few seconds. The effect is reversible. When a series of unbuffered solutions at different pH values are applied reversal curves may be obtained. When the concentration gradient is .1 N-.001 N KCl the reversal points lie between pH 4.1 and 4.8. When studied in acetate buffers this electromotive reversal is found to be closely correlated with the electrical charge upon the membrane, as determined by electroendosmosis through it. Reversal occurs between pH 4.9 and 5.2. It is concluded that the electromotive behavior of this material is controlled by some ampholyte, or group of ampholytes, within the membrane. This ampholyte is probably a protein. On both sides of their isoelectric point these membranes, in common with protein membranes, behave as if they retarded or prevented the movement through them of ions of the same electrical sign as they themselves bear, while permitting the movement of ions of the opposite sign. It is suggested that this correlation arises because of electrostatic effects between the charged surfaces and ions in the solution.

  9. ALKALINITY, PH, AND COPPER CORROSION BY-PRODUCT RELEASE

    EPA Science Inventory

    Contrary to expectations, higher bicarbonate concentrations exacerbate copper corrosion rates and by-product release. In fact, as illustrated by monitoring experiences of large utilities and by laboratory data, the concentration of copper corrosion by-products in drinking water i...

  10. Epidermal growth factor elevates intracellular pH in chicken granulosa cells.

    PubMed

    Li, M; Morley, P; Asem, E K; Tsang, B K

    1991-08-01

    Many bioregulators, such as epidermal growth factor (EGF), induce intracellular alkalinization by activating a membrane bound Na+/H+ antiporter. The present studies were designed to examine the influence of EGF on intracellular pH (pHi) in chicken granulosa cells. pHi in granulosa cells from the two largest preovulatory follicles of hens was determined spectrofluorometrically using the dye 2',7'-bis(carboxyethyl-5(6)-carboxyfluorescein. The resting pHi was 6.81 +/- 0.006 (n = 30) when the extracellular pH and sodium concentration (Na+o) were 7.3 and 144 mM, respectively. EGF (5-100 ng/ml) induced a concentration-dependent increase in pHi, which reached a maximum of 0.217 +/- 0.009 pH units at a concentration of 100 ng/ml EGF. Cytosolic alkalinization was observed within 10 min of the addition of EGF and lasted over the 60 min observation period. The increase in pHi was dependent upon the presence of Na+o, since the EGF effect was attenuated when Na+o was substituted with equimolar concentrations of nonpermeant choline chloride. The EGF-induced pHi change was also inhibited by amiloride, dimethyl amiloride, and ethylisopropyl amiloride, inhibitors of the Na+/H+ antiporter. The alkalinization effect of EGF was mimicked by transforming growth factor-alpha but not by insulin, insulin-like growth factor-I, or transforming growth factor-beta. These studies suggest for the first time that intracellular alkalinization resulting from activation of the Na+/H+ antiporter may be a part of the transmembrane signaling pathway in the action of EGF on chicken granulosa cells.

  11. Hydrothermal and oceanic pH conditions of possible relevance to the origin of life.

    PubMed

    MacLeod, G; McKeown, C; Hall, A J; Russell, M J

    1994-02-01

    Because of the continuous focusing of thermal and chemical energy, ancient submarine hot springs are contenders as sites for the origin of life. But it is generally assumed that these would be of the acid and high-temperature 'black smoker' variety (Corliss et al., 1981). In fact today the greater part of the ocean circulates through off-ridge springs where it issues after modification at temperatures of around 40 degrees C or so but with the potential to reach 200 degrees C. Such offridge or ridge-flank springs remind us that there are other candidate sites for the origin of life. Although there is no firm indication of the pH of these off-ridge springs we have argued that the solutions are likely to be alkaline rather than acid, We test the feasibility of this idea using EQ geochemical water-rock interaction modelling codes (Wolery 1983) and find that for a range of possible initial chemistries of Hadean seawater, the pH of issuing solutions at around 200 degrees C is around one or more units alkaline. Such pH values hold for interaction with both basaltic and komatiitic crust. The robustness of this result suggests to us that alkaline submarine springs of moderate temperature, carrying many hundreds of ppm HS to the ocean basins, are also serious contenders as sites for the origin of life, particularly as Hadean seawater was probably slightly acid, with a dissolved iron concentration approaching 100 ppm. On mixing of these solutions, supersaturation, especially of iron sulphide, would lead to the precipitation of colloidal gels. In our view iron sulphide was the likely substance of, or contributor to, the first vesicle membranes which led to life, as the supply organic molecules would have been limited in the Hadean. Such a membrane would have bid catalytic properties, expansivity, and would have maintained the natural chemiosmotic gradient, a consequence of the acid ocean and the alkaline interior to the vesicles.

  12. The pH dependent Raman spectroscopic study of caffeine

    NASA Astrophysics Data System (ADS)

    Kang, Jian; Gu, Huaimin; Zhong, Liang; Hu, Yongjun; Liu, Fang

    2011-02-01

    First of all the surface enhanced Raman spectroscopy (SERS) and normal Raman spectra of caffeine aqueous solution were obtained at different pH values. In order to obtain the detailed vibrational assignments of the Raman spectroscopy, the geometry of caffeine molecule was optimized by density functional theory (DFT) calculation. By comparing the SERS of caffeine with its normal spectra at different pH values; it is concluded that pH value can dramatically affect the SERS of caffeine, but barely affect the normal Raman spectrum of caffeine aqueous solution. It can essentially affect the reorientation of caffeine molecule to the Ag colloid surface, but cannot impact the vibration of functional groups and chemical bonds in caffeine molecule.

  13. Designing pH induced fold switch in proteins.

    PubMed

    Baruah, Anupaul; Biswas, Parbati

    2015-05-14

    This work investigates the computational design of a pH induced protein fold switch based on a self-consistent mean-field approach by identifying the ensemble averaged characteristics of sequences that encode a fold switch. The primary challenge to balance the alternative sets of interactions present in both target structures is overcome by simultaneously optimizing two foldability criteria corresponding to two target structures. The change in pH is modeled by altering the residual charge on the amino acids. The energy landscape of the fold switch protein is found to be double funneled. The fold switch sequences stabilize the interactions of the sites with similar relative surface accessibility in both target structures. Fold switch sequences have low sequence complexity and hence lower sequence entropy. The pH induced fold switch is mediated by attractive electrostatic interactions rather than hydrophobic-hydrophobic contacts. This study may provide valuable insights to the design of fold switch proteins.

  14. PH and Electrochemical Responsive Materials for Corrosion Smart Coating Applications

    NASA Technical Reports Server (NTRS)

    Li, Wenyan; Calle, Luz M.

    2008-01-01

    Corrosion is a costly issue for military operations and civil industries. While most corrosion initiates from localized corrosion form, such as pitting, failure directly caused by localized corrosion is the most dangerous kind, because it is difficult to anticipate and prevent, occurs very suddenly and can be catastrophic. One way of preventing these failures is with a coating that can detect and heal localized corrosion. pH and other electrochemical changes are often associated with localized corrosion, so it is expected that materials that are pH or otherwise electrochemical responsive can be used to detect and control corrosion. This paper will review various pH and electrochemical responsive materials and their potential applications in corrosion smart coatings. Current research results in this field will also be reported.

  15. IMPACT OF WATER PH ON ZEBRA MUSSEL MORTALITY

    SciTech Connect

    Daniel P. Molloy

    2002-10-15

    The experiments conducted this past quarter have suggested that the bacterium Pseudomonas fluorescens strain CL0145A is effective at killing zebra mussels throughout the entire range of pH values tested (7.2 to 8.6). Highest mortality was achieved at pH values characteristic of preferred zebra mussel waterbodies, i.e., hard waters with a range of 7.8 to 8.6. In all water types tested, however, ranging from very soft to very hard, considerable mussel kill was achieved (83 to 99% mean mortality), suggesting that regardless of the pH or hardness of the treated water, significant mussel kill can be achieved upon treatment with P. fluorescens strain CL0145A. These results further support the concept that this bacterium has significant potential for use as a zebra mussel control agent in power plant pipes receiving waters with a wide range of physical and chemical characteristics.

  16. Photonic porous silicon as a pH sensor.

    PubMed

    Pace, Stephanie; Vasani, Roshan B; Zhao, Wei; Perrier, Sébastien; Voelcker, Nicolas H

    2014-01-01

    Chronic wounds do not heal within 3 months, and during the lengthy healing process, the wound is invariably exposed to bacteria, which can colonize the wound bed and form biofilms. This alters the wound metabolism and brings about a change of pH. In this work, porous silicon photonic films were coated with the pH-responsive polymer poly(2-diethylaminoethyl acrylate). We demonstrated that the pH-responsive polymer deposited on the surface of the photonic film acts as a barrier to prevent water from penetrating inside the porous matrix at neutral pH. Moreover, the device demonstrated optical pH sensing capability visible by the unaided eye.

  17. Photonic porous silicon as a pH sensor

    NASA Astrophysics Data System (ADS)

    Pace, Stephanie; Vasani, Roshan B.; Zhao, Wei; Perrier, Sébastien; Voelcker, Nicolas H.

    2014-08-01

    Chronic wounds do not heal within 3 months, and during the lengthy healing process, the wound is invariably exposed to bacteria, which can colonize the wound bed and form biofilms. This alters the wound metabolism and brings about a change of pH. In this work, porous silicon photonic films were coated with the pH-responsive polymer poly(2-diethylaminoethyl acrylate). We demonstrated that the pH-responsive polymer deposited on the surface of the photonic film acts as a barrier to prevent water from penetrating inside the porous matrix at neutral pH. Moreover, the device demonstrated optical pH sensing capability visible by the unaided eye.

  18. Controllable dissociations of PH3 molecules on Si(001)

    NASA Astrophysics Data System (ADS)

    Liu, Qin; Lei, Yanhua; Shao, Xiji; Ming, Fangfei; Xu, Hu; Wang, Kedong; Xiao, Xudong

    2016-04-01

    We demonstrate for the first time to our knowledge that controllable dissociation of PH3 adsorption products PH x (x = 2, 1) can be realized by STM (scanning tunneling microscope) manipulation techniques at room temperature. Five dissociative products and their geometric structures are identified via combining STM experiments and first-principle calculations and simulations. In total we realize nine kinds of controllable dissociations by applying a voltage pulse among the PH3-related structures on Si(001). The dissociation rates of the five most common reactions are measured by the I-t spectrum method as a function of voltage. The suddenly increased dissociation rate at 3.3 V indicates a transition from multivibrational excitation to single-step excitation induced by inelastic tunneling electrons. Our studies prove that selectively breaking the chemical bonds of a single molecule on semiconductor surface by STM manipulation technique is feasible.

  19. An analysis of Ph.D. examiners' reports in engineering

    NASA Astrophysics Data System (ADS)

    Prieto, Elena; Holbrook, Allyson; Bourke, Sid

    2016-03-01

    In recent years, there have been increasing calls for an overall transformation of the nature of engineering Ph.D. programs and the way theses are assessed. There exists a need to understand the examination process to ensure the best quality outcome for candidates in engineering. The work we present in this paper uses data collected between 2003 and 2010 for a total of 1220 Australian Ph.D. theses by analysing examiner reports. Our analysis indicates that Ph.D. theses in engineering, N = 106, differ considerably from those in other fields in areas such as gender of candidates and examiners and the examiners' geographical location. We also found that assessment areas such as significance and contribution of the thesis, publications arising from the thesis, breadth, depth and recency of the literature review and communication and editorial correctness are areas in which the proportion of text of engineering examiners' comments differs significantly from other fields.

  20. Nanocrystalline hydroxyapatite prepared under various pH conditions.

    PubMed

    Palanivelu, R; Mary Saral, A; Ruban Kumar, A

    2014-10-15

    Hydroxyapatite (HAP) has sovereign biomedical application due to its excellent biocompatibility, chemical and crystallographic similitude with natural human bone. In this present work, we discussed about the role of pH in the synthesis of calcium phosphate compound using calcium nitrate tetrahydrate and di-ammonium hydrogen phosphate as starting materials by chemical precipitation method assisted with ultrasonic irradiation technique. 5% polyethylene glycol (PEG600) is added along with the precursors under various pH condition of 7, 9 and 11 respectively. The functional group analysis, crystallized size and fraction of crystallized size are confirmed using Fourier Transformation Infra-Red spectroscopy and X-ray diffraction pattern. Morphological observations are done by scanning electron microscope. The results revealed the presence of nanocrystalline hydroxyapatite at pH above 9.

  1. Mid-Career PhD Physicists: Academia & Beyond

    NASA Astrophysics Data System (ADS)

    White, Susan

    2017-01-01

    What jobs do mid-career PhD physicists hold? In a first-ever study, we collected data in 2011 from over 1,500 physics PhD recipients from the classes of 1996, 1997, 2000, and 2001. About 45% of the physics PhD recipients in these classes immediately took jobs that were not temporary, and over 40% accepted postdocs. How does taking a postdoc affect mid-career employment? What is the relationship between first job (after any postdocs) and mid-career employment? How do physicists' actual jobs compare with what they thought they would be doing when they graduated? Using our initial employment and mid-career data, I will answer these questions and more.

  2. The respiratory burst activity and expression of catalase in white shrimp, Litopenaeus vannamei, during long-term exposure to pH stress.

    PubMed

    Wang, Wei-Na; Li, Bao-Sheng; Liu, Jin-Jian; Shi, Lei; Alam, M J; Su, Shi-Juan; Wu, Juan; Wang, Lei; Wang, An-Li

    2012-08-01

    In this study, changes of reactive oxygen species (ROS) and the mRNA expression of catalase of the Pacific white shrimp, Litopenaeus vannamei, exposed to pH (5.4, 6.7, 8.0, and 9.3) stress was investigated at different stress time (24, 48, 72, 96, and 120 h). Level of malondialdehyde (MDA) in shrimp also were assessed. The results revealed that acidic (pH 5.4 and 6.7) or alkaline exposure (pH 9.3) induced production of ROS hemocytes and increase of MDA level in shrimp. Moreover, the catalase mRNA expression in hepatopancreas of L. vannamei was up-regulated in 24 h at pH 5.4, in 72 h at pH 6.7 and in 48 h at pH 9.3, whereas was down-regulated significantly after 72 h acidic (pH 5.4 and 6.7) or alkaline (pH 9.4) exposure. In the present study, there was the relationship between ROS and catalase mRNA expression under normal acidic and alkaline conditions. At pH 8, the increase of catalase transcripts due to up-regulation by ROS, whereas MDA level did not significantly change, suggesting activation of corresponding protective mechanisms of detoxifying ROS is essential for the proper functioning of cells and the survival of shrimps.

  3. Bicarbonate Increases Tumor pH and Inhibits Spontaneous Metastases

    PubMed Central

    Robey, Ian F.; Baggett, Brenda K.; Kirkpatrick, Nathaniel D.; Roe, Denise J.; Dosescu, Julie; Sloane, Bonnie F.; Hashim, Arig Ibrahim; Morse, David L.; Raghunand, Natarajan; Gatenby, Robert A.; Gillies, Robert J.

    2010-01-01

    The external pH of solid tumors is acidic as a consequence of increased metabolism of glucose and poor perfusion. Acid pH has been shown to stimulate tumor cell invasion and metastasis in vitro and in cells before tail vein injection in vivo. The present study investigates whether inhibition of this tumor acidity will reduce the incidence of in vivo metastases. Here, we show that oral NaHCO3 selectively increased the pH of tumors and reduced the formation of spontaneous metastases in mouse models of metastatic breast cancer. This treatment regimen was shown to significantly increase the extracellular pH, but not the intracellular pH, of tumors by 31P magnetic resonance spectroscopy and the export of acid from growing tumors by fluorescence microscopy of tumors grown in window chambers. NaHCO3 therapy also reduced the rate of lymph node involvement, yet did not affect the levels of circulating tumor cells, suggesting that reduced organ metastases were not due to increased intravasation. In contrast, NaHCO3 therapy significantly reduced the formation of hepatic metastases following intrasplenic injection, suggesting that it did inhibit extravasation and colonization. In tail vein injections of alternative cancer models, bicarbonate had mixed results, inhibiting the formation of metastases from PC3M prostate cancer cells, but not those of B16 melanoma. Although the mechanism of this therapy is not known with certainty, low pH was shown to increase the release of active cathepsin B, an important matrix remodeling protease. PMID:19276390

  4. Harvard College Observatory: Shapley's Factory for PhD Degrees?

    NASA Astrophysics Data System (ADS)

    Welther, B. L.

    2000-12-01

    When Harlow Shapley assumed the Directorship of Harvard College Observatory in 1921, there was no program in place there to train the next generation of astronomers. In 1923, using the Pickering Fund for women assistants, Shapley hired a young English woman, Cecilia Payne, to work on stellar spectra. Just two short years later, Payne completed her research and wrote a celebrated thesis on stellar atmospheres. Because Harvard University was not prepared to confer a PhD degree on a woman at that time, Payne presented her thesis to Radcliffe College. Thus, in 1925 she became the first person to receive a PhD in astronomy for a research project at HCO. By 1933, a PhD in Astronomy had been conferred on eight graduate students who had undertaken research projects at HCO: four men who received their degree from Harvard, and four women, from Radcliffe. In subsequent years, however, the equal distribution of degrees for men and women quickly changed. When the 30th degree was bestowed in 1943, only 10 of the candidates were women. By 1955, when the 60th degree was conferred, only 14 women had received a PhD. In just two decades, then, the ratio of women astronomers had steadily dropped from a solid 50% at the height of the Shapley era to slightly less than 25% at his retirement. Also, until the mid-1960s, the women astronomers still had to apply to Radcliffe for their PhD degrees. This paper will briefly examine the funding and research topics of some of the HCO PhD candidates in the Shapley Era (1921-1955). It will also highlight some of their subsequent contributions to 20th-century American Astronomy.

  5. pH sensitive quantum dot-anthraquinone nanoconjugates

    NASA Astrophysics Data System (ADS)

    Ruedas-Rama, Maria Jose; Hall, Elizabeth A. H.

    2014-05-01

    Semiconductor quantum dots (QDs) have been shown to be highly sensitive to electron or charge transfer processes, which may alter their optical properties. This feature can be exploited for different sensing applications. Here, we demonstrate that QD-anthraquinone conjugates can function as electron transfer-based pH nanosensors. The attachment of the anthraquinones on the surface of QDs results in the reduction of electron hole recombination, and therefore a quenching of the photoluminescence intensity. For some anthraquinone derivatives tested, the quenching mechanism is simply caused by an electron transfer process from QDs to the anthraquinone, functioning as an electron acceptor. For others, electron transfer and energy transfer (FRET) processes were found. A detailed analysis of the quenching processes for CdSe/ZnS QD of two different sizes is presented. The photoluminescence quenching phenomenon of QDs is consistent with the pH sensitive anthraquinone redox chemistry. The resultant family of pH nanosensors shows pKa ranging ˜5-8, being ideal for applications of pH determination in physiological samples like blood or serum, for intracellular pH determination, and for more acidic cellular compartments such as endosomes and lysosomes. The nanosensors showed high selectivity towards many metal cations, including the most physiologically important cations which exist at high concentration in living cells. The reversibility of the proposed systems was also demonstrated. The nanosensors were applied in the determination of pH in samples mimicking the intracellular environment. Finally, the possibility of incorporating a reference QD to achieve quantitative ratiometric measurements was investigated.

  6. Bicarbonate increases tumor pH and inhibits spontaneous metastases.

    PubMed

    Robey, Ian F; Baggett, Brenda K; Kirkpatrick, Nathaniel D; Roe, Denise J; Dosescu, Julie; Sloane, Bonnie F; Hashim, Arig Ibrahim; Morse, David L; Raghunand, Natarajan; Gatenby, Robert A; Gillies, Robert J

    2009-03-15

    The external pH of solid tumors is acidic as a consequence of increased metabolism of glucose and poor perfusion. Acid pH has been shown to stimulate tumor cell invasion and metastasis in vitro and in cells before tail vein injection in vivo. The present study investigates whether inhibition of this tumor acidity will reduce the incidence of in vivo metastases. Here, we show that oral NaHCO(3) selectively increased the pH of tumors and reduced the formation of spontaneous metastases in mouse models of metastatic breast cancer. This treatment regimen was shown to significantly increase the extracellular pH, but not the intracellular pH, of tumors by (31)P magnetic resonance spectroscopy and the export of acid from growing tumors by fluorescence microscopy of tumors grown in window chambers. NaHCO(3) therapy also reduced the rate of lymph node involvement, yet did not affect the levels of circulating tumor cells, suggesting that reduced organ metastases were not due to increased intravasation. In contrast, NaHCO(3) therapy significantly reduced the formation of hepatic metastases following intrasplenic injection, suggesting that it did inhibit extravasation and colonization. In tail vein injections of alternative cancer models, bicarbonate had mixed results, inhibiting the formation of metastases from PC3M prostate cancer cells, but not those of B16 melanoma. Although the mechanism of this therapy is not known with certainty, low pH was shown to increase the release of active cathepsin B, an important matrix remodeling protease.

  7. Manganese toxicity to fungi: influence of pH

    SciTech Connect

    Babich, H.; Stotzky, G.

    1981-10-01

    The effects of Mn on mycelial proliferation of fungi and the effect of pH on Mn toxicity were evaluated. Results indicated that the fungi exhibited wide differences in their sensitivities to Mn. Incipient inhibition (i.e., the level of Mn at which growth inhibition was noted initially, P < 0.05) for Scopulariopsis brevicaulis and Aspergillus giganteus occurred at 100 ppM Mn; for Rhizopus stolonifer, Arthrobotrys conoides, Aspergillus niger, Aspergillus flavus, Trichoderma viride, and Penicillium vermiculatum at 500 ppM Mn; for Cephalosporium sp. at 1000 ppM Mn; and for Gliocladium sp. at 1000 to 1500 ppM Mn; growth of Aspergillus clavatus was not inhibited even at 2000 ppM Mn. No growth of S. brevicaulis occurred at 500 ppM Mn and of R. stolonifer at 1500 ppM Mn. The levels of Mn causing incipient and/or total inhibition of mycelial growth of the fungi studied were comparable to the levels reported to inhibit mycelial proliferation of some phylloplane fungi. Only A. conoides showed significant (P < 0.5) stimulation of mycelial growth by Mn; 10, 50, and 100 ppM Mn increased growth rates over control (0 ppM Mn) values. There was no consistent trend in the effect of pH on Mn toxicity to the fungi. However, each fungus showed a definitive response to Mn at the different pH levels. Thus, increasing the pH from 5.5 to 8.5 did not significantly affect the toxicity of Mn to Gliocladium sp., P. vermiculatum, or A. niger. The toxicity of Mn to R. stolonifer and T. viride was not different at pH 5.5 and 6.5, but increasing the pH to 7.5 or 8.5 significantly enhanced the toxicity.

  8. Cytoplasmic pH mediates pH taxis and weak-acid repellent taxis of bacteria.

    PubMed

    Kihara, M; Macnab, R M

    1981-03-01

    Bacteria migrate away from an acid pH and from a number of chemicals, including organic acids such as acetate; the basis for detection of these environmental cues has not been demonstrated. Membrane-permeant weak acids caused prolonged tumbling when added to Salmonella sp. or Escherichia coli cells at pH 5.5. Tethered Salmonella cells went from a prestimulus behavior of 14% clockwise rotation to 80% clockwise rotation when 40 mM acetate was added and remained this way for more than 30 min. A low external pH in the absence of weak acid did not markedly affect steady-state tumbling frequency. Among the weak acids tested, the rank for acidity (salicylate greater than benzoate greater than acetate greater than 5,5-dimethyl-2,4-oxazolidinedione) was the same as the rank for the ability to collapse the transmembrane pH gradient and to cause tumbling. At pH 7.0, the tumbling responses caused by the weak acids were much briefer. Indole, a non-weak-acid repellent, did not cause prolonged tumbling at low pH. Two chemotaxis mutants (a Salmonella mutant defective in the chemotaxis methylesterase and an E. coli mutant defective in the methyl-accepting protein in MCP I) showed inverse responses of enhanced counterclockwise rotation in the first 1 min after acetate addition. The latter mutant had been found previously to be defective in the sensing of gradients of extracellular pH and (at neutral pH) of acetate. We conclude (i) that taxes away from acid pH and membrane-permeant weak acids are both mediated by a pH-sensitive component located either in the cytoplasm or on the cytoplasmic side of the membrane, rather than by an external receptor (as in the case of the attractants), and (ii) that both of these taxes involve components of the chemotaxis methylation system, at least in the early phase of the response.

  9. Seasonal pH variability in the Saronikos Gulf: A year-study using a new photometric pH sensor

    NASA Astrophysics Data System (ADS)

    González-Dávila, Melchor; Santana-Casiano, J. Magdalena; Petihakis, George; Ntoumas, Manolis; Suárez de Tangil, Miguel; Krasakopoulou, Evangelia

    2016-10-01

    Long-term determination of carbon dioxide data is a priority requirement to ensure a realistic picture of how ocean seawater properties change as the result of atmospheric evolution. Due to the extreme daily and seasonal variability of the carbonate system characteristics, constant autonomous measurements are a necessity when seeking to provide total spatial-temporal coverage of inorganic carbon data. We present here results of a one-year study in the Eastern Mediterranean Aegean Sea by using a new spectrophotometric pH-based system, applicable in long time deployments. The manifold has proved to be capable of providing sea-surface temperature and salinity together with highly accurate pH values determined each 6 h over the period between September 2013 and October 2014. The average seasonal temperature difference of 12.4 °C, determined from March to September, can be correlated to the seasonal pH decrease of 0.2 pH units, from 8.18 to 7.98. The area also presented a maximum seasonal change in partial pressure of CO2 of 208 μatm, computed from the salinity-based total alkalinity values. The Saronikos area in the Aegean Sea was characterized to be a thermodynamically controlled region, since it is oligotrophic, acting as a source of CO2 into the atmosphere of 0.20 mol m- 2 yr- 1.

  10. Effects of pH and temperature on the chromatographic performance and stability of immobilized poly(methyloctylsiloxane) stationary phases.

    PubMed

    Borges, Endler M; Collins, Carol H

    2012-03-02

    The effects of mobile phase pH, temperature, buffer type and buffer concentration on the selectivity and stability of four stationary phases, with different PMOS loadings, prepared by the thermal immobilization of poly(methyloctylsiloxane) on to silica (PMOS-SiO₂), were evaluated with both hydrophobic and hydrophilic basic solutes. These solutes show longer retention times at near neutral pH, where both the silanols and the basic solutes are partially ionized, and shorter retention times in more alkaline pH, where the silanols are mostly ionized and the basic solutes are not ionized. Increases in temperature and buffer concentration also result in shorter retention times. These PMOS-SiO₂ stationary phases are quite stable at low pH and are also stable at ambient temperature (23 °C) using pH 7 phosphate. The PMOS-SiO₂ stationary phases are more stable at higher pH using triethylamine (pH 11) and borate (pH 10) buffers than with phosphate and carbonate buffers. Temperature increases stationary phase degradation, while buffer concentration has a minimal effect on stationary phase degradation, indicating that these PMOS-SiO₂ stationary phases have stabilities similar to the equivalent chemically bonded phases.

  11. Trpac1, a pH response transcription regulator, is involved in cellulase gene expression in Trichoderma reesei.

    PubMed

    He, Ronglin; Ma, Lijuan; Li, Chen; Jia, Wendi; Li, Demao; Zhang, Dongyuan; Chen, Shulin

    2014-12-01

    Fungi grow over a relatively wide pH range and adapt to extracellular pH through a genetic regulatory system mediated by a key component PacC, which is a pH transcription regulator. The cellulase production of the filamentous fungi Trichoderma reesei is sensitive to ambient pH. To investigate the connection between cellulase expression regulation and ambient pH, an ortholog of Aspergillus nidulans pacC, Trpac1, was identified and functionally characterized using a target gene deletion strategy. Deleting Trpac1 dramatically increased the cellulase production and the transcription levels of the major cellulase genes at neutral pH, which suggested Trpac1 is involved in the regulation of cellulase production. It was further observed that the expression levels of transcription factors xyr1 and ace2 also increased in the ΔTrpac1 mutant at neutral pH. In addition, the ΔTrpac1 mutant exhibited conidiation defects under neutral and alkaline pH. These results implied that Trpac1 in involved in growth and development process and cellulase gene expression in T. reesei.

  12. Suitability of the isolated chicken eye test for classification of extreme pH detergents and cleaning products.

    PubMed

    Cazelle, Elodie; Eskes, Chantra; Hermann, Martina; Jones, Penny; McNamee, Pauline; Prinsen, Menk; Taylor, Hannah; Wijnands, Marcel V W

    2015-04-01

    A.I.S.E. investigated the suitability of the regulatory adopted ICE in vitro test method (OECD TG 438) with or without histopathology to identify detergent and cleaning formulations having extreme pH that require classification as EU CLP/UN GHS Category 1. To this aim, 18 extreme pH detergent and cleaning formulations were tested covering both alkaline and acidic extreme pHs. The ICE standard test method following OECD Test Guideline 438 showed good concordance with in vivo classification (83%) and good and balanced specificity and sensitivity values (83%) which are in line with the performances of currently adopted in vitro test guidelines, confirming its suitability to identify Category 1 extreme pH detergent and cleaning products. In contrast to previous findings obtained with non-extreme pH formulations, the use of histopathology did not improve the sensitivity of the assay whilst it strongly decreased its specificity for the extreme pH formulations. Furthermore, use of non-testing prediction rules for classification showed poor concordance values (33% for the extreme pH rule and 61% for the EU CLP additivity approach) with high rates of over-prediction (100% for the extreme pH rule and 50% for the additivity approach), indicating that these non-testing prediction rules are not suitable to predict Category 1 hazards of extreme pH detergent and cleaning formulations.

  13. Doping of germanium nanowires grown in presence of PH3

    NASA Astrophysics Data System (ADS)

    Tutuc, E.; Chu, J. O.; Ott, J. A.; Guha, S.

    2006-12-01

    The authors study the Au-catalyzed chemical vapor growth of germanium (Ge) nanowires in the presence of phosphine (PH3), used as a dopant precursor. The device characteristics of the ensuing nanowire field effect transistors (FETs) indicate n-type, highly doped nanowires. Using a combination of different nanowire growth sequences and their FET characteristics, the authors determine that phosphorus incorporates predominately via the conformal growth, which accompanies the acicular, nanowire growth. As such, the Ge nanowires grown in the presence of PH3 contain a phosphorus doped shell and an undoped core. The authors determine the doping level in the shell to be ≃(1-4)×1019cm-3.

  14. Physiological carbon dioxide, bicarbonate, and pH sensing

    PubMed Central

    Tresguerres, Martin; Buck, Jochen

    2010-01-01

    In biological systems, carbon dioxide exists in equilibrium with bicarbonate and protons. The individual components of this equilibrium (i.e., CO2, HCO3−, and H+), which must be sensed to be able to maintain cellular and organismal pH, also function as signals to modulate multiple physiological functions. Yet, the molecular sensors for CO2/HCO3−/pH remained unknown until recently. Here, we review recent progress in delineating molecular and cellular mechanisms for sensing CO2, HCO3−, and pH. PMID:20683624

  15. Developing imidazoles as CEST MRI pH sensors

    PubMed Central

    Yang, Xing; Song, Xiaolei; Banerjee, Sangeeta Ray; Li, Yuguo; Byun, Youngjoo; Liu, Guanshu; Bhujwalla, Zaver M.; Pomper, Martin G.; McMahon, Michael T.

    2016-01-01

    A series of intra-molecular hydrogen bonded imidazoles and related heterocyclic compounds were screened for their N–H chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) contrast properties. Of the compounds, imidazole-4,5-dicarboxamides (I45DCs) were found to provide the strongest contrast, with the contrast produced at a large chemical shift from water (7.8 ppm) and strongly dependent on pH. We have tested several probes based on this scaffold, and demonstrated that these probes could be applied for in vivo detection of kidney pH after intravenous administration. PMID:27071959

  16. Physiological carbon dioxide, bicarbonate, and pH sensing.

    PubMed

    Tresguerres, Martin; Buck, Jochen; Levin, Lonny R

    2010-11-01

    In biological systems, carbon dioxide exists in equilibrium with bicarbonate and protons. The individual components of this equilibrium (i.e., CO₂, HCO₃⁻, and H(+)), which must be sensed to be able to maintain cellular and organismal pH, also function as signals to modulate multiple physiological functions. Yet, the molecular sensors for CO₂/HCO₃⁻/pH remained unknown until recently. Here, we review recent progress in delineating molecular and cellular mechanisms for sensing CO₂, HCO₃⁻, and pH.

  17. Measurement and control of pH in hydrothermal solutions

    SciTech Connect

    Wesolowski, D.J.; Palmer, D.A.; Mesmer, R.E.

    1995-12-31

    Hydrogen-electrode concentration cells with liquid junction are routinely used to measure the pH of aqueous solutions from 0 to 300 C. Results include the dissociation constants of common acids and bases and the hydrolysis and complexation of metal ions in aqueous electrolytes over a wide range of salinities. Recently, we have utilized these cells to examine the sorption of H{sup +} on mineral surfaces, the solubility of minerals with continuous in situ pH measurement, and the thermal decompositon rates of organic acids.

  18. Measuring Phagosomal pH by Fluorescence Microscopy.

    PubMed

    Canton, Johnathan; Grinstein, Sergio

    2017-01-01

    Dual wavelength ratiometric imaging has become a powerful tool for the study of pH in intracellular compartments. It allows for the dynamic imaging of live cells while accounting for changes in the focal plane, differential loading of the fluorescent probe, and photobleaching caused by repeated image acquisitions. Ratiometric microscopic imaging has the added advantage over whole population methods of being able to resolve individual cells and even individual organelles. In this chapter we provide a detailed discussion of the basic principles of ratiometric imaging and its application to the measurement of phagosomal pH, including probe selection, the necessary instrumentation, and calibration methods.

  19. Stress corrosion cracking properties of 15-5PH steel

    NASA Technical Reports Server (NTRS)

    Rosa, Ferdinand

    1993-01-01

    Unexpected occurrence of failures, due to stress corrosion cracking (SCC) of structural components, indicate a need for improved characterization of materials and more advanced analytical procedures for reliably predicting structures performance. Accordingly, the purpose of this study was to determine the stress corrosion susceptibility of 15-5PH steel over a wide range of applied strain rates in a highly corrosive environment. The selected environment for this investigation was a highly acidified sodium chloride (NaCl) aqueous solution. The selected alloy for the study was a 15-5PH steel in the H900 condition. The slow strain rate technique was selected to test the metals specimens.

  20. Evolution of extreme stomach pH in bilateria inferred from gastric alkalization mechanisms in basal deuterostomes.

    PubMed

    Stumpp, Meike; Hu, Marian Y; Tseng, Yung-Che; Guh, Ying-Jeh; Chen, Yi-Chih; Yu, Jr-Kai; Su, Yi-Hsien; Hwang, Pung-Pung

    2015-06-08

    The stomachs of most vertebrates operate at an acidic pH of 2 generated by the gastric H(+)/K(+)-ATPase located in parietal cells. The acidic pH in stomachs of vertebrates is believed to aid digestion and to protect against environmental pathogens. Little attention has been placed on whether acidic gastric pH regulation is a vertebrate character or a deuterostome ancestral trait. Here, we report alkaline conditions up to pH 10.5 in the larval digestive systems of ambulacraria (echinoderm + hemichordate), the closest relative of the chordate. Microelectrode measurements in combination with specific inhibitors for acid-base transporters and ion pumps demonstrated that the gastric alkalization machinery in sea urchin larvae is mainly based on direct H(+) secretion from the stomach lumen and involves a conserved set of ion pumps and transporters. Hemichordate larvae additionally utilized HCO3(-) transport pathways to generate even more alkaline digestive conditions. Molecular analyses in combination with acidification experiments supported these findings and identified genes coding for ion pumps energizing gastric alkalization. Given that insect larval guts were also reported to be alkaline, our discovery raises the hypothesis that the bilaterian ancestor utilized alkaline digestive system while the vertebrate lineage has evolved a strategy to strongly acidify their stomachs.

  1. Evolution of extreme stomach pH in bilateria inferred from gastric alkalization mechanisms in basal deuterostomes

    PubMed Central

    Stumpp, Meike; Hu, Marian Y.; Tseng, Yung-Che; Guh, Ying-Jeh; Chen, Yi-Chih; Yu, Jr-Kai; Su, Yi-Hsien; Hwang, Pung-Pung

    2015-01-01

    The stomachs of most vertebrates operate at an acidic pH of 2 generated by the gastric H+/K+-ATPase located in parietal cells. The acidic pH in stomachs of vertebrates is believed to aid digestion and to protect against environmental pathogens. Little attention has been placed on whether acidic gastric pH regulation is a vertebrate character or a deuterostome ancestral trait. Here, we report alkaline conditions up to pH 10.5 in the larval digestive systems of ambulacraria (echinoderm + hemichordate), the closest relative of the chordate. Microelectrode measurements in combination with specific inhibitors for acid-base transporters and ion pumps demonstrated that the gastric alkalization machinery in sea urchin larvae is mainly based on direct H+ secretion from the stomach lumen and involves a conserved set of ion pumps and transporters. Hemichordate larvae additionally utilized HCO3− transport pathways to generate even more alkaline digestive conditions. Molecular analyses in combination with acidification experiments supported these findings and identified genes coding for ion pumps energizing gastric alkalization. Given that insect larval guts were also reported to be alkaline, our discovery raises the hypothesis that the bilaterian ancestor utilized alkaline digestive system while the vertebrate lineage has evolved a strategy to strongly acidify their stomachs. PMID:26051042

  2. [Effect of pH and fermentation time on yield and optical purity of lactic acid from kitchen wastes fermentation].

    PubMed

    Zhang, Bo; He, Pin-Jing; Shao, Li-Ming

    2007-04-01

    Batch experiments were carried out to analyze the effect of pH and fermentation time on the yield of total lactic acid and the distribution of L- and D-lactic acid among total lactic acid during the non-sterilized fermentation of kitchen wastes. The results show that the concentration of reduced sugar (calculated as organic carbon) is low, and its concentration was higher at neutral and alkali conditions (pH 6 - 8) than at acidic conditions (non-controlled pH and pH = 5). The maximum total lactic acid production rate and yield is 0.59 g x (L x h)(-1) and 0.62 g per gram VS at pH 7, respectively. The proportion of lactic acid (calculated as organic carbon) among the TOC reaches 78% and 89% at controlled pH 7 and 8, respectively. The L-lactic acid is the predominant isomer form at pH 8. Lactic acid concentration depends on pH, fermentation time and interaction from the response surface analysis. pH and fermentation time have a significant effect on the optical purity of lactic acid. At acidic conditions, the ratio of L-lactic acid to the total lactic acid increases with the fermentation time before 120 h, and the ratio reaches 0.9 at 120 h. At alkaline conditions, the ratio keeps at above 0.86 in the whole experimental fermentation time and reachs the maximum value (0.93) at 48 h. It decreases with fermentation time at pH 7. To obtain high lactic acid yield and optical purity simultaneously, it is suggested that pH should be contralled at 8.

  3. Vibrational investigation on the copper(II) binding mode of carcinine and its pH dependence

    NASA Astrophysics Data System (ADS)

    Torreggiani, Armida; Reggiani, Matteo; Manco, Immacolata; Tinti, Anna

    2007-05-01

    A comparative FT-Raman and FT-IR study of Carcinine (Carc), a natural imidazole dipeptide, and its complexes with Cu(II) ions was performed at different pH's. Both Raman and IR spectra present marker bands useful for the identification of the predominant complexes; in particular, Raman spectroscopy appears useful for identifying the metal-coordination site of the imidazole ring (N π or N τ atoms) of Carc. Free Carc shows a strong network of H-bonds and tautomer I (N τ-H) is the preferred form of the imidazolic ring (bands at 1578, 1292 and 988 cm -1). The presence of Cu(II) does not affect the tautomeric equilibrium at pH 7, whereas the deprotonation of both N-imidazolic nitrogens is strongly induced at higher pH. Under neutral and alkaline conditions the primary amino group takes part to the Cu(II) chelation, whereas all the peptidic moieties are involved in coordination only at pH 7. Thus, Carc acts as a tri-dentate ligand at neutral pH, mainly giving a monomeric complex, [CuLH -1], containing tautomer I, whereas an oligonuclear complex, probably [Cu 4L 4H -8], where metal-imidazolate ions connect different ligand molecules, predominates at alkaline pH.

  4. The constitutive production of pectinase by the CT1 mutant of Penicillium occitainis is modulated by pH.

    PubMed

    Romdhane, Zamen Ben; Tounsi, Hajer; Hadj-Sassi, Azza; Hadj-Taieb, Noomen; Gargouri, Ali

    2013-01-01

    The aim of the present study was to investigate pectinases production by CT1 mutant of Penicillium occitanis on glucose based media. Two main groups of pectinases were followed: lyases (pectin and pectate lyases) and hydrolases (polygalacturonases and polymethylgalacturonases). When cultivated in different liquid media, where either the starting glucose concentration or the nature of nitrogen sources used was varied, the CT1 mutant secreted either lyases or hydrolases. In fact, the pH of these various media seemed to correlate with the activity produced: The lyases were highly and exclusively produced at neutral or alkaline ambient pH, whereas hydrolases were highly produced on acidic ambient pH. Such conclusion was confirmed by following pectinase production in the same culture medium (with the same glucose concentration and the same nitrogen source) set at two initial pH of 4 and 7. Altogether, these results suggest that the pectinases control by PacC signaling pathway of P. occitanis should resemble to that of Aspergillus and its ability to "activate the expression of alkaline-expressed genes and repress acid-expressed genes" remains intact in the CT1 over-producing and constitutive strain. Enzymes produced at acidic pH (hydrolases) and at neutral pH (lyases) were applied in the hydrolysis of orange peel and gave results comparable to commercial enzymes.

  5. X-ray Diffraction Analysis of ProRoot Mineral Trioxide Aggregate Hydrated at Different pH Values

    PubMed Central

    Akhavan, Hengameh; Mohebbi, Pooneh; Firouzi, Amir; Noroozi, Mehdi

    2016-01-01

    Introduction: The aim of this study was to compare the chemical compounds of white ProRoot mineral trioxide aggregate (WMTA) hydrated at different pH environments. Methods and Materials: Mixed samples of WMTA were kept in acidic (pH=5.4), neutral (pH=7.4) and alkaline (pH=9.4) environments for 48 h. Then, X-ray diffraction (XRD) analysis was performed for both hydrated and powder forms of WMTA. Portlandite crystalline structures of environments were compared from three aspects: intensity (height of the peak, corresponding to the concentration), crystallinity (peak area/total area) and crystal size (full-width at half-maximum of the peak). Results: After matching the peaks of each sample with those of the International Center for Diffraction Data (ICDD) database, the main constituent of all set cements and powder form was found to be bismuth oxide. Acidic environment exhibited lower intensity and crystallinity of portlandite in comparison with neutral environment. Conclusion: The highest concentration and crystallinity of portlandite were observed in WMTA samples hydrated at neutral pH and the highest crystal size was detected after hydration in alkaline pH. PMID:27141218

  6. Excipient hydrolysis and ester formation increase pH in a parenteral solution over aging.

    PubMed

    Hirakura, Yutaka; Nakamura, Mitsuhiro; Wakasawa, Tatsuyoshi; Ban, Kazutoshi; Yokota, Shoji; Kitamura, Satoshi

    2006-11-15

    Recently, the number of drug substances that are poorly water-soluble has increased dramatically. This makes improving solubility one of the most critical tasks in pharmaceutical development today. In this study, the physicochemical stability of an injectable solution of conivaptan hydrochloride salt was investigated. Because its free form is hydrophobic, the drug substance was solubilized in a co-solvent system, 40% of which was composed of different alcohols. Since the free form is also alkaline, lactic acid was added to the co-solvent system to further improve its solubility. Remarkably, the pH of the solution was found to increase gradually over time. Considering the physicochemical nature of the drug substance, uncontrolled increases in pH would pose a potential threat of reducing solubility and forming precipitates. For this reason, a risk evaluation was performed. The evaluation revealed that the pH increase was caused by the hydrolysis of lactic acid oligomers as well as by the ester formation occurring between lactic acid and the alcohols. High concentrations of lactic acid supplied as an excipient usually contain lactic acid oligomers, which are hydrolyzed into lactic acid monomers upon dilution with water. Commercial software was used to determine the pK(a) values of the lactic acid oligomers, which were found to be lower than that of lactic acid monomers. This indicates that hydrolysis causes the pH to increase. Ester formation consumes the acid, which also causes the pH to increase. However, both hydrolysis and ester formation equilibrated by the 16-month time point when stored at 25 degrees C. This information allowed the upper limit of the pH increase to be determined molecularly, thereby ensuring product quality through the prevention of precipitate formation due to reduced solubility. Increased awareness of the importance of risk evaluation in pharmaceutical development is critical as these kinds of chemical reactions between excipients constitute

  7. Molecular Details of the PH Domain of ACAP1(BAR-PH) Protein Binding to PIP-Containing Membrane.

    PubMed

    Chan, Kevin Chun; Lu, Lanyuan; Sun, Fei; Fan, Jun

    2017-02-03

    ACAP1 proteins were previously reported to specifically bind PIP2-containing cell membranes and form well-structured protein lattices in order to conduct membrane tubulation. We carried out molecular dynamics simulations to characterize orientation of the PH domains with respect to the BAR domains inside the protein dimer. Followed by molecular dynamics simulations, we present a comprehensive orientation analysis of PH domain under different states including unbound and bound with lipids. We have examined two binding pockets on the PH domain and present PMF profiles of the two pockets to account for their preference to PIP2 lipids. Combining orientation analysis and studies of binding pockets, our simulations results reveal valuable molecular basis for protein-lipid interactions of ACAP1 proteins during membrane remodeling process.

  8. Antikaliuretic action of trimethoprim is minimized by raising urine pH.

    PubMed

    Schreiber, M; Schlanger, L E; Chen, C B; Lessan-Pezeshki, M; Halperin, M L; Patnaik, A; Ling, B N; Kleyman, T R

    1996-01-01

    This study was designed to test the hypothesis that the antikaliuresis caused by trimethoprim could be diminished by alkalinizing the luminal fluid in the CCD, thereby converting trimethoprim from its cationic, active form to an electroneutral, inactive, form. Trimethoprim-induced inhibition of transepithelial Na+ transport was examined in A6 distal nephron cells by analysis of short circuit current. The voltage-dependence of the trimethoprim-induced block of Na+ channels was examined with patch clamp recordings of A6 cells. The antikaliuretic effect of trimethoprim was examined in vivo in rats pretreated with deoxycorticosterone and with NH4Cl to lower urine pH, and in rats also receiving acetazolamide to raise urine pH. We found that the concentration of trimethoprim required to inhibit the amiloride sensitive component of short circuit current by 50% (IC50) was 340 microM (at pH 8.2) and 50 microM (at pH 6.3). The IC50S of protonated trimethoprim were similar (34 microM at pH 8.2 and 45 microM at pH 6.3). The mean time open for the high selectivity, Na+ channel was reduced from 1679 +/- 387 msec to 502 +/- 98 msec with addition of 10-5 M trimethoprim to patch pipette solution at the resting membrane potential (-Vpipette = 0 mV). further decreases in mean time open were observed as -Vpipette was reduced (that is, apical membrane hyperpolarization) to -40 mV (mean time open = 217 +/- 85 msec) and to -80 mV (mean time open = 69 +/- 13 msec). In vivo, trimethoprim caused a > 50% reduction in potassium (K+) excretion due primarily to a fall in the [K+] in the lumen of the terminal CCD. This effect of trimethoprim was markedly attenuated in an alkaline urine induced by acetazolamide. We conclude that it is the charged, protonated species of trimethoprim which blocks epithelial Na+ channels. Increasing urinary pH decreases the concentration of the charged species of trimethoprim and minimizes its antikaliuretic effect.

  9. Ligand accessibility and bioactivity of a hormone–dendrimer conjugate depend on pH and pH history

    DOE PAGES

    Kim, Sung Hoon; Madak-Erdogan, Zeynep; Bae, Sung Chul; ...

    2015-07-17

    Estrogen conjugates with a polyamidoamine (PAMAM) dendrimer have shown remarkably selective regulation of the nongenomic actions of estrogens in target cells in this paper. In response to pH changes, however, these estrogen–dendrimer conjugates (EDCs) display a major morphological transition that alters the accessibility of the estrogen ligands that compromises the bioactivity of the EDC. A sharp break in dynamic behavior near pH 7 occurs for three different ligands on the surface of a PAMAM-G6 dendrimer: a fluorophore (tetramethylrhodamine [TMR]) and two estrogens (17α-ethynylestradiol and diphenolic acid). Collisional quenching and time-resolved fluorescence anisotropy experiments with TMR–PAMAM revealed high ligand shielding abovemore » pH 7 and low shielding below pH 7. Furthermore, when the pH was cycled from 8.5 (conditions of ligand–PAMAM conjugation) to 4.5 (e.g., endosome/lysosome) and through 6.5 (e.g., hypoxic environment) back to pH 8.5, the 17α-ethynylestradiol– and diphenolic acid–PAMAM conjugates experienced a dramatic, irreversible loss in cell stimulatory activity; dynamic NMR studies indicated that the hormonal ligands had become occluded within the more hydrophobic core of the PAMAM dendrimer. Thus, the active state of these estrogen–dendrimer conjugates appears to be metastable. Finally, this pH-dependent irreversible masking of activity is of considerable relevance to the design of drug conjugates with amine-bearing PAMAM dendrimers.« less

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

    PubMed

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

    2012-08-01

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

  11. Meet EPA Ecologist Michael Murrell, Ph.D.

    EPA Pesticide Factsheets

    Michael Murrel, Ph.D., is a EPA research ecologist working on the Gulf of Mexico Hypoxia Project, helping develop models of the northern Gulf to quantify the links between freshwater flowing into the Gulf from the land, nutrients, and hypoxia—“dead zones”

  12. Promoting Creativity in PhD Supervision: Tensions and Dilemmas

    ERIC Educational Resources Information Center

    Whitelock, Denise; Faulkner, Dorothy; Miell, Dorothy

    2008-01-01

    In this paper we argue that the processes of collaborative creativity are just as important within the sociocultural context of PhD supervisory practice, as they are in other organizational and educational settings. In order to test this claim a series of interviews with supervisors and students were undertaken to uncover the pedagogic processes…

  13. Vance Berger, PhD | Division of Cancer Prevention

    Cancer.gov

    Dr. Vance Berger completed his PhD in statistics at Rutgers University in 1995, and then began working at the FDA. This is where he developed his research focus on biases and threats to the validity of medical studies, especially clinical trials. In 1999, Dr. Berger joined the NCI, and has remained ever since. |

  14. Measures for Ph.D. Evaluation: The Recruitment Process

    ERIC Educational Resources Information Center

    D'Agostino, Antonella; Fruzzetti, Stefania; Ghellini, Giulio; Neri, Laura

    2011-01-01

    In the last years the quality of Higher Education (HE) system and its evaluation have been key issues of the political and scientific debate on education policies all over Europe. In the wide landscape that involves the entire HE system we draw attention on the third level of its organization, i.e. the Ph.D. In particular, this paper discusses the…

  15. The PhD Project: How Successful Is It?

    ERIC Educational Resources Information Center

    Schwartz, Bill N.; Williams, Satina V.; Walden, W. Darrell

    2011-01-01

    The PhD Project's mission to diversify the work force by increasing the diversity of business school faculty is quite admirable, but is the Project successful? To gather insights toward responding to that question and to offer suggestions, we reviewed three of the Project's objectives that relate most closely to minority doctoral students and…

  16. Annotation of Fusarium graminearum (PH-1) Version 5.0

    PubMed Central

    Hammond-Kosack, Kim E.

    2017-01-01

    ABSTRACT Fusarium graminearum floral infections are a major risk to the global supply of safe cereal grains. We report updates to the PH-1 reference genome and significant improvements to the annotation. Changes include introduction of legacy annotation identifiers, new gene models, secretome and effectorP predictions, and inclusion of extensive untranslated region (UTR) annotations. PMID:28082505

  17. Carbon Nanotube Chemiresistor for Wireless pH Sensing

    NASA Astrophysics Data System (ADS)

    Gou, Pingping; Kraut, Nadine D.; Feigel, Ian M.; Bai, Hao; Morgan, Gregory J.; Chen, Yanan; Tang, Yifan; Bocan, Kara; Stachel, Joshua; Berger, Lee; Mickle, Marlin; Sejdić, Ervin; Star, Alexander

    2014-03-01

    The ability to accurately measure real-time pH fluctuations in-vivo could be highly advantageous. Early detection and potential prevention of bacteria colonization of surgical implants can be accomplished by monitoring associated acidosis. However, conventional glass membrane or ion-selective field-effect transistor (ISFET) pH sensing technologies both require a reference electrode which may suffer from leakage of electrolytes and potential contamination. Herein, we describe a solid-state sensor based on oxidized single-walled carbon nanotubes (ox-SWNTs) functionalized with the conductive polymer poly(1-aminoanthracene) (PAA). This device had a Nernstian response over a wide pH range (2-12) and retained sensitivity over 120 days. The sensor was also attached to a passively-powered radio-frequency identification (RFID) tag which transmits pH data through simulated skin. This battery-less, reference electrode free, wirelessly transmitting sensor platform shows potential for biomedical applications as an implantable sensor, adjacent to surgical implants detecting for infection.

  18. Structure of human saposin A at lysosomal pH.

    PubMed

    Hill, Chris H; Read, Randy J; Deane, Janet E

    2015-07-01

    The saposins are essential cofactors for the normal lysosomal degradation of complex glycosphingolipids by acid hydrolase enzymes; defects in either saposin or hydrolase function lead to severe metabolic diseases. Saposin A (SapA) activates the enzyme β-galactocerebrosidase (GALC), which catalyzes the breakdown of β-D-galactocerebroside, the principal lipid component of myelin. SapA is known to bind lipids and detergents in a pH-dependent manner; this is accompanied by a striking transition from a `closed' to an `open' conformation. However, previous structures were determined at non-lysosomal pH. This work describes a 1.8 Å resolution X-ray crystal structure determined at the physiologically relevant lysosomal pH 4.8. In the absence of lipid or detergent at pH 4.8, SapA is observeed to adopt a conformation closely resembling the previously determined `closed' conformation, showing that pH alone is not sufficient for the transition to the `open' conformation. Structural alignments reveal small conformational changes, highlighting regions of flexibility.

  19. Online Ph.D. Program Delivery Models and Student Success

    ERIC Educational Resources Information Center

    Jorissen, Shari L.; Keen, James P.; Riedel, Eric S.

    2015-01-01

    The purpose of this study was to provide information to an online university that offers Ph.D. programs in three formats: knowledge area modules (or KAM, a type of faculty-led, self-directed doctoral study), course-based model, and mixed model (a combination of the KAM and course-based models). The investigators sought to determine why students…

  20. Gender Differences in Research Patterns among PhD Economists

    ERIC Educational Resources Information Center

    Barbezat, Debra A.

    2006-01-01

    This study is based on a 1996 survey of PhD economists working in the academic and nonacademic sectors since 1989. Despite a raw gender difference in all types of research output, the male dummy variable proves statistically significant in predicting only one publication measure. In a full sample and faculty subsample, number of years since…

  1. Earth and Space Science PhDs: Class of 2000

    NASA Astrophysics Data System (ADS)

    Giesler, J.

    2001-12-01

    The American Geophysical Union (AGU) and the American Geological Institute (AGI) have been collecting data on recent PhDs in the geosciences for 5 years (1996-2000). Over these years continual improvement has been recorded in the job market through indicators such as time to find employment and starting salaries. As these indicators continue to improve, so too does the perception of the job market in general. There are several characteristics that are unique to PhDs in the geosciences. Unlike physical science graduates, there is a significant number who have been working full-time at least one year prior to earning their PhD. Recent graduates employed prior to graduation are heavily concentrated in Solid Earth Geology (41%) followed by Atmospheric Sciences (19%) and Oceanography (12%). A second distinguishable feature of Earth & space science PhDs is their age. Each year there is a higher percentage of recent graduates over the age of 40: 16% in 1998, 20% in 1999, and 23% in 2000. In 2000, the average time between earning a B.S. and starting a graduate program was 4.6 years. Both 1999 and 2000 show a drop in the overall numbers of postdoctoral appointments. This suggests that greater than 50% of the recent graduates are finding full-time permanent employment. Of the geoscience subfields, oceanography has greatest number of people obtaining employment outside the field.

  2. The Production Rate and Employment of Ph.D. Astronomers

    NASA Astrophysics Data System (ADS)

    Metcalfe, Travis S.

    2007-05-01

    As in many sciences, the production rate of new Ph.D. astronomers is decoupled from the global demand for trained scientists. As noted by Thronson (1991, PASP, 103, 90), overproduction appears to be built into the system, making the mathematical formulation of surplus astronomer production similar to that for industrial pollution models -- an unintended side effect of the process. Following Harris (1994, ASP Conf., 57, 12), I document the production of Ph.D. astronomers from 1990 to 2005 using the online Dissertation Abstracts database. To monitor the changing patterns of employment, I examine the number of postdoctoral, tenure-track, and other jobs advertised in the AAS Job Register during this same period. Although the current situation is clearly unsustainable, it was much worse a decade ago with nearly 7 new Ph.D. astronomers in 1995 for every new tenure-track job. While the number of new permanent positions steadily increased throughout the late 1990's, the number of new Ph.D. recipients gradually declined. After the turn of the century, the production of new astronomers leveled off, but new postdoctoral positions grew dramatically. There has also been recent growth in the number of non-tenure-track lecturer, research, and support positions. This is just one example of a larger cultural shift to temporary employment that is happening throughout society -- it is not unique to astronomy.

  3. Engineering a pH responsive pore forming protein.

    PubMed

    Kisovec, Matic; Rezelj, Saša; Knap, Primož; Cajnko, Miša Mojca; Caserman, Simon; Flašker, Ajda; Žnidaršič, Nada; Repič, Matej; Mavri, Janez; Ruan, Yi; Scheuring, Simon; Podobnik, Marjetka; Anderluh, Gregor

    2017-02-08

    Listeriolysin O (LLO) is a cytolysin capable of forming pores in cholesterol-rich lipid membranes of host cells. It is conveniently suited for engineering a pH-governed responsiveness, due to a pH sensor identified in its structure that was shown before to affect its stability. Here we introduced a new level of control of its hemolytic activity by making a variant with hemolytic activity that was pH-dependent. Based on detailed structural analysis coupled with molecular dynamics and mutational analysis, we found that the bulky side chain of Tyr406 allosterically affects the pH sensor. Molecular dynamics simulation further suggested which other amino acid residues may also allosterically influence the pH-sensor. LLO was engineered to the point where it can, in a pH-regulated manner, perforate artificial and cellular membranes. The single mutant Tyr406Ala bound to membranes and oligomerized similarly to the wild-type LLO, however, the final membrane insertion step was pH-affected by the introduced mutation. We show that the mutant toxin can be activated at the surface of artificial membranes or living cells by a single wash with slightly acidic pH buffer. Y406A mutant has a high potential in development of novel nanobiotechnological applications such as controlled release of substances or as a sensor of environmental pH.

  4. [Regulation effects of tourmaline on seawater pH value].

    PubMed

    Xia, Meisheng; Zhang, Hongmei; Hu, Caihong; Xu, Zirong

    2005-10-01

    In this paper, chemical analysis, X-ray diffraction and atomic force microscopy were employed to examine the characteristics of tourmaline produced in east Inner Mongolia Autonomous Region, and batch experiments were conducted to study its regulation effects on seawater pH value. The factors affecting the regulation, such as the dosage of tourmaline and the salinity and initial pH value of seawater, were also studied. The results showed that tourmaline could regulate the seawater pH value from its initial 3 and 10 to 7.1 and 8.9, respectively, and the regulation effect was greater in the seawater with lower salinity, e.g., after 120 minutes treatment, the initial pH value (5.0) of the seawater with a salinity of 5, 10, 15, 20 and 35 was increased by 3.24, 3.16, 3.06, 2.99 and 2.85 unit, respectively. Tourmaline had little effect on seawater conductivity. This study would provide an experimental base for the application of tourmaline in aquaculture.

  5. DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING

    EPA Science Inventory

    Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb, and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

  6. Miniaturized metal oxide pH sensors for bacteria detection.

    PubMed

    Uria, Naroa; Abramova, Natalia; Bratov, Andrey; Muñoz-Pascual, Francesc-Xavier; Baldrich, Eva

    2016-01-15

    It is well known that the metabolic activity of some microorganisms results in changes of pH of the culture medium, a phenomenon that can be used for detection and quantification of bacteria. However, conventional glass electrodes that are commonly used for pH measurements are bulky, fragile and expensive, which hinders their application in miniaturized systems and encouraged to the search for alternatives. In this work, two types of metal oxide pH sensors have been tested to detect the metabolic activity of the bacterium Escherichia coli (E. coli). These pH sensors were produced on silicon chips with platinum metal contacts, onto which thin layers of IrOx or Ta2O5 were incorporated by two different methods (electrodeposition and e-beam sputtering, respectively). In order to facilitate measurement in small sample volumes, an Ag/AgCl pseudo-reference was also screen-printed in the chip and was assayed in parallel to an external Ag/AgCl reference electrode. As it is shown, the developed sensors generated results indistinguishable from those provided by a conventional glass pH-electrode but could be operated in significantly smaller sample volumes. After optimization of the detection conditions, the metal oxide sensors are successfully applied for detection of increasing concentrations of viable E. coli, with detection of less than 10(3)cfu mL(-1) in undiluted culture medium in just 5h.

  7. PhDs by Publications: An "Easy Way Out"?

    ERIC Educational Resources Information Center

    Niven, Penelope; Grant, Carolyn

    2012-01-01

    PhDs by publications are a relatively new model for doctoral research, especially in the context of the Humanities or Education. This paper describes two writers' experiences of conducting doctoral studies in this genre and in these faculties. Each discover alternative ways of employing a body of published research papers in development of an…

  8. Karl Krueger, PhD | Division of Cancer Prevention

    Cancer.gov

    Dr. Karl Krueger received a PhD in biochemistry from Vanderbilt University and continued his research training at NIH as a postdoctoral fellow before joining the faculty at Georgetown University School of Medicine. His research throughout this period focused on different aspects of drug receptors and their role in the nervous system. |

  9. Vaginal pH: Home-Use Tests

    MedlinePlus

    ... the pH paper to the color on the chart provided with the test kit. The number on the chart for the color that best matches the color ... Medical Devices Radiation-Emitting Products Vaccines, Blood & Biologics Animal & Veterinary Cosmetics Tobacco Products

  10. Modulation of autophagic activity by extracellular pH.

    PubMed

    Xu, Teng; Su, Hang; Ganapathy, Suthakar; Yuan, Zhi-Min

    2011-11-01

    Reprogramming energy metabolism from oxidative phosphorylation to aerobic glycolysis, a common feature of human cancer, is associated with a relative acidic tumor microenvironment which can sometimes be further accentuated by hypoxia operating within most solid tumors. We found that alteration of extracellular pH induces marked and rapid changes of autophagic activity. Interestingly, acidic and basic conditions induced completely opposite effect on autophagy, with its activity suppressed at lower pH whereas stimulated at higher pH. Gene knockdown experiments indicated that pH induced-autophagy requires Beclin 1, Vps34 and Atg5, key components of the autophagy pathway. Of note, an acidic condition not only inhibits the basal but also blocks the starvation-induced autophagy activity. Significantly, examination of different areas of tumor mass revealed a lower autophagic activity within the inner region than the outer region. These findings have important implications on the connections between autophagy and cancer as well as a wide range of other physiological and pathological processes.

  11. Richard Mazurchuk, PhD | Division of Cancer Prevention

    Cancer.gov

    Dr. Richard Mazurchuk received a BS in Physics and MS and PhD in Biophysics from SUNY Buffalo. His research focused on developing novel multi-modality imaging techniques, contrast (enhancing) agents and methods to assess the efficacy of experimental therapeutics. |

  12. An Analysis of Ph.D. Examiners' Reports in Engineering

    ERIC Educational Resources Information Center

    Prieto, Elena; Holbrook, Allyson; Bourke, Sid

    2016-01-01

    In recent years, there have been increasing calls for an overall transformation of the nature of engineering Ph.D. programs and the way theses are assessed. There exists a need to understand the examination process to ensure the best quality outcome for candidates in engineering. The work we present in this paper uses data collected between 2003…

  13. Engineering a pH responsive pore forming protein

    PubMed Central

    Kisovec, Matic; Rezelj, Saša; Knap, Primož; Cajnko, Miša Mojca; Caserman, Simon; Flašker, Ajda; Žnidaršič, Nada; Repič, Matej; Mavri, Janez; Ruan, Yi; Scheuring, Simon; Podobnik, Marjetka; Anderluh, Gregor

    2017-01-01

    Listeriolysin O (LLO) is a cytolysin capable of forming pores in cholesterol-rich lipid membranes of host cells. It is conveniently suited for engineering a pH-governed responsiveness, due to a pH sensor identified in its structure that was shown before to affect its stability. Here we introduced a new level of control of its hemolytic activity by making a variant with hemolytic activity that was pH-dependent. Based on detailed structural analysis coupled with molecular dynamics and mutational analysis, we found that the bulky side chain of Tyr406 allosterically affects the pH sensor. Molecular dynamics simulation further suggested which other amino acid residues may also allosterically influence the pH-sensor. LLO was engineered to the point where it can, in a pH-regulated manner, perforate artificial and cellular membranes. The single mutant Tyr406Ala bound to membranes and oligomerized similarly to the wild-type LLO, however, the final membrane insertion step was pH-affected by the introduced mutation. We show that the mutant toxin can be activated at the surface of artificial membranes or living cells by a single wash with slightly acidic pH buffer. Y406A mutant has a high potential in development of novel nanobiotechnological applications such as controlled release of substances or as a sensor of environmental pH. PMID:28176876

  14. Christos Patriotis, PhD | Division of Cancer Prevention

    Cancer.gov

    Dr. Christos Patriotis obtained his MSc in Biochemistry from the University of Sofia, Bulgaria in 1985 and his PhD in Molecular Biology from the Bulgarian Academy of Sciences in 1990. Postdoctoral training focused on signal transduction and tumor cell biology. |

  15. Robert Shoemaker, PhD | Division of Cancer Prevention

    Cancer.gov

    Dr. Robert Shoemaker obtained his PhD in human genetics from the Graduate School of Public Health of the University of Pittsburgh in 1975. Following postdoctoral experience at the Armed Forces Institute of Pathology he moved to the Children's Hospital Medical Center of Akron. His research on pediatric tumors led to an interest in the genetics of drug resistance and new drug discovery. |

  16. Asad Umar, DVM, PhD | Division of Cancer Prevention

    Cancer.gov

    Dr. Asad Umar received his PhD in Biochemistry and Immunology at the Johns Hopkins University in Baltimore, MD, in 1993. He conducted his postdoctoral training in the laboratories of Patricia Gearhart in Baltimore, MD and Thomas Kunkel at the National Institutes of Environmental Health Sciences in Research Triangle Park, NC. Dr. |

  17. Engineering a pH responsive pore forming protein

    NASA Astrophysics Data System (ADS)

    Kisovec, Matic; Rezelj, Saša; Knap, Primož; Cajnko, Miša Mojca; Caserman, Simon; Flašker, Ajda; Žnidaršič, Nada; Repič, Matej; Mavri, Janez; Ruan, Yi; Scheuring, Simon; Podobnik, Marjetka; Anderluh, Gregor

    2017-02-01

    Listeriolysin O (LLO) is a cytolysin capable of forming pores in cholesterol-rich lipid membranes of host cells. It is conveniently suited for engineering a pH-governed responsiveness, due to a pH sensor identified in its structure that was shown before to affect its stability. Here we introduced a new level of control of its hemolytic activity by making a variant with hemolytic activity that was pH-dependent. Based on detailed structural analysis coupled with molecular dynamics and mutational analysis, we found that the bulky side chain of Tyr406 allosterically affects the pH sensor. Molecular dynamics simulation further suggested which other amino acid residues may also allosterically influence the pH-sensor. LLO was engineered to the point where it can, in a pH-regulated manner, perforate artificial and cellular membranes. The single mutant Tyr406Ala bound to membranes and oligomerized similarly to the wild-type LLO, however, the final membrane insertion step was pH-affected by the introduced mutation. We show that the mutant toxin can be activated at the surface of artificial membranes or living cells by a single wash with slightly acidic pH buffer. Y406A mutant has a high potential in development of novel nanobiotechnological applications such as controlled release of substances or as a sensor of environmental pH.

  18. pH Effects on Electrospray Ionization Efficiency

    NASA Astrophysics Data System (ADS)

    Liigand, Jaanus; Laaniste, Asko; Kruve, Anneli

    2016-12-01

    Electrospray ionization efficiency is known to be affected by mobile phase composition. In this paper, a detailed study of analyte ionization efficiency dependence on mobile phase pH is presented. The pH effect was studied on 28 compounds with different chemical properties. Neither pK a nor solution phase ionization degree by itself was observed to be sufficient at describing how aqueous phase pH affects the ionization efficiency of the analyte. Therefore, the analyte behavior was related to various physicochemical properties via linear discriminant analyses. Distinction between pH-dependent and pH-independent compounds was achieved using two parameters: number of potential charge centers and hydrogen bonding acceptor capacity (in the case of 80% acetonitrile) or polarity of neutral form of analyte and pK a (in the case of 20% acetonitrile). It was also observed that decreasing pH may increase ionization efficiency of a compound by more than two orders of magnitude.

  19. Peer Mentorship and Transformational Learning: PhD Student Experiences

    ERIC Educational Resources Information Center

    Preston, Jane P.; Ogenchuk, Marcella J.; Nsiah, Joseph K.

    2014-01-01

    The purpose of the paper is to describe our peer mentorship experiences and explain how these experiences fostered transformational learning during our PhD graduate program in educational administration. As a literature backdrop, we discuss characteristics of traditional forms of mentorship and depict how our experiences of peer mentorship was…

  20. Supervising the PhD: A Guide to Success.

    ERIC Educational Resources Information Center

    Delamont, Sara; Atkinson, Paul; Parry, Odette

    This handbook is a practical guide for the novice and experienced supervisor of Ph.D. students focusing on the British system. The book is organized to follow the progress of a student from starting out to a career after the viva voce examination. The chapters are: (1) "A Most Persuasive Piece of Argument"; (2) "Caught and Held by a…

  1. Improved pH buffering agent for sodium hypochlorite

    NASA Technical Reports Server (NTRS)

    Nash, J. R.; Veeder, L. N.

    1969-01-01

    Sodium citrate/citric acid was found to be an effective buffer for pH control when used with sodium hypochlorite. The mixture does not corrode aluminum. The buffer appears to form a type of conversion coating that may provide corrosion-resistant properties to aluminum in other applications.

  2. Trends and drivers in global surface ocean pH over the past 3 decades

    NASA Astrophysics Data System (ADS)

    Lauvset, S. K.; Gruber, N.; Landschützer, P.; Olsen, A.; Tjiputra, J.

    2015-03-01

    We report global long-term trends in surface ocean pH using a new pH data set computed by combining fCO2 observations from the Surface Ocean CO2 Atlas (SOCAT) version 2 with surface alkalinity estimates based on temperature and salinity. Trends were determined over the periods 1981-2011 and 1991-2011 for a set of 17 biomes using a weighted linear least squares method. We observe significant decreases in surface ocean pH in ~70% of all biomes and a mean rate of decrease of 0.0018 ± 0.0004 yr-1 for 1991-2011. We are not able to calculate a global trend for 1981-2011 because too few biomes have enough data for this. In half the biomes, the rate of change is commensurate with the trends expected based on the assumption that the surface ocean pH change is only driven by the surface ocean CO2 chemistry remaining in a transient equilibrium with the increase in atmospheric CO2. In the remaining biomes, deviations from such equilibrium may reflect that the trend of surface ocean fCO2 is not equal to that of the atmosphere, most notably in the equatorial Pacific Ocean, or may reflect changes in the oceanic buffer (Revelle) factor. We conclude that well-planned and long-term sustained observational networks are key to reliably document the ongoing and future changes in ocean carbon chemistry due to anthropogenic forcing.

  3. Acidic pH increases airway surface liquid viscosity in cystic fibrosis

    PubMed Central

    Tang, Xiao Xiao; Ostedgaard, Lynda S.; Hoegger, Mark J.; Moninger, Thomas O.; Karp, Philip H.; McMenimen, James D.; Choudhury, Biswa; Varki, Ajit; Stoltz, David A.; Welsh, Michael J.

    2016-01-01

    Cystic fibrosis (CF) disrupts respiratory host defenses, allowing bacterial infection, inflammation, and mucus accumulation to progressively destroy the lungs. Our previous studies revealed that mucus with abnormal behavior impaired mucociliary transport in newborn CF piglets prior to the onset of secondary manifestations. To further investigate mucus abnormalities, here we studied airway surface liquid (ASL) collected from newborn piglets and ASL on cultured airway epithelia. Fluorescence recovery after photobleaching revealed that the viscosity of CF ASL was increased relative to that of non-CF ASL. CF ASL had a reduced pH, which was necessary and sufficient for genotype-dependent viscosity differences. The increased viscosity of CF ASL was not explained by pH-independent changes in HCO3– concentration, altered glycosylation, additional pH-induced disulfide bond formation, increased percentage of nonvolatile material, or increased sulfation. Treating acidic ASL with hypertonic saline or heparin largely reversed the increased viscosity, suggesting that acidic pH influences mucin electrostatic interactions. These findings link loss of cystic fibrosis transmembrane conductance regulator–dependent alkalinization to abnormal CF ASL. In addition, we found that increasing Ca2+ concentrations elevated ASL viscosity, in part, independently of pH. The results suggest that increasing pH, reducing Ca2+ concentration, and/or altering electrostatic interactions in ASL might benefit early CF. PMID:26808501

  4. pH dependence of listeriolysin O aggregation and pore-forming ability.

    PubMed

    Bavdek, Andrej; Kostanjšek, Rok; Antonini, Valeria; Lakey, Jeremy H; Dalla Serra, Mauro; Gilbert, Robert J C; Anderluh, Gregor

    2012-01-01

    Listeriolysin O (LLO) is the major factor implicated in the escape of Listeria monocytogenes from the phagolysosome. It is the only representative of cholesterol-dependent cytolysins that exhibits pH-dependent activity. Despite intense studies of LLO pH-dependence, this feature of the toxin still remains incompletely explained. Here we used fluorescence and CD spectroscopy to show that the structure of LLO is not detectably affected by pH at room temperature. We observed slightly altered haemolytic and permeabilizing activities at different pH values, which we relate to reduced binding of LLO to the lipid membranes. However, alkaline pH and elevated temperatures caused rapid denaturation of LLO. Aggregates of the toxin were able to bind Congo red and Thioflavin T dyes and were visible under transmission electron microscopy as large, amorphous, micrometer-sized assemblies. The aggregates had the biophysical properties of amyloid. Analytical ultracentrifugation indicated dimerization of the protein in acidic conditions, which protects the protein against premature denaturation in the phagolysosome, where toxin activity takes place. We therefore suggest that LLO spontaneously aggregates at the neutral pH found in the host cell cytosol and that this is a major mechanism of LLO inactivation.

  5. Metabolic Microenvironmental Control by Photosynthetic Biofilms under Changing Macroenvironmental Temperature and pH Conditions▿ †

    PubMed Central

    Bissett, Andrew; Reimer, Andreas; de Beer, Dirk; Shiraishi, Fumito; Arp, Gernot

    2008-01-01

    Ex situ microelectrode experiments, using cyanobacterial biofilms from karst water creeks, were conducted under various pH, temperature, and constant-alkalinity conditions to investigate the effects of changing environmental parameters on cyanobacterial photosynthesis-induced calcification. Microenvironmental chemical conditions around calcifying sites were controlled by metabolic activity over a wide range of photosynthesis and respiration rates, with little influence from overlying water conditions. Regardless of overlying water pH levels (from 7.8 to 8.9), pH at the biofilm surface was approximately 9.4 in the light and 7.8 in the dark. The same trend was observed at various temperatures (4°C and 17°C). Biological processes control the calcium carbonate saturation state (Ω) in these and similar systems and are able to maintain Ω at approximately constant levels over relatively wide environmental fluctuations. Temperature did, however, have an effect on calcification rate. Calcium flux in this system is limited by its diffusion coefficient, resulting in a higher calcium flux (calcification and dissolution) at higher temperatures, despite the constant, biologically mediated pH. The ability of biological systems to mitigate the effects of environmental perturbation is an important factor that must be considered when attempting to predict the effects of increased atmospheric partial CO2 pressure on processes such as calcification and in interpreting microfossils in the fossil record. PMID:18689512

  6. Modeling Carbon Dioxide, pH and Un-Ionized Ammonia Relationships in Serial Reuse Systems

    USGS Publications Warehouse

    Watten, Barnaby J.; Rust, Michael; Colt, John

    2009-01-01

    In serial reuse systems, excretion of metabolic carbon dioxide has a significant impact on ambient pH, carbon dioxide, and un-ionized ammonia concentrations. This impact depends strongly on alkalinity, water flow rate, feeding rate, and loss of carbon dioxide to the atmosphere. A reduction in pH from metabolic carbon dioxide can significantly reduce the un-ionized ammonia concentration and increase the carbon dioxide concentrations compared to those parameters computed from influent pH. The ability to accurately predict pH in serial reuse systems is critical to their design and effective operation. A trial and error solution to the alkalinity–pH system was used to estimate important water quality parameters in serial reuse systems. Transfer of oxygen and carbon dioxide across the air–water interface, at overflow weirs, and impacts of substrate-attached algae and suspended bacteria were modeled. Gas transfer at the weirs was much greater than transfer across the air–water boundary. This simulation model can rapidly estimate influent and effluent concentrations of dissolved oxygen, carbon dioxide, and un-ionized ammonia as a function of water temperature, elevation, water flow, and weir type. The accuracy of the estimates strongly depends on assumed pollutional loading rates and gas transfer at the weirs. The current simulation model is based on mean daily loading rates; the impacts of daily variation loading rates are discussed. Copies of the source code and executable program are available free of charge.

  7. Stability and solubility of trans-resveratrol are strongly influenced by pH and temperature.

    PubMed

    Zupančič, Špela; Lavrič, Zoran; Kristl, Julijana

    2015-06-01

    Recently trans-resveratrol (trans-RSV) has received great attention due to its prophylactic and therapeutic properties. Its limited bioavailability provides compelling evidence of the need for more suitable formulations in order to attain better clinical effectiveness. Some physicochemical properties of trans-RSV are still unknown or research findings are contradictory. Therefore, this paper presents newly determined trans-RSV solubility and stability at various pH and temperatures, and the importance of such data for the studies of novel trans-RSV-loaded nanofibers. In acidic pH trans-RSV was stable, whereas its degradation started to increase exponentially above pH 6.8. Consequently, it is worthwhile to note that special consideration has to be dedicated to long dissolution testing or biological assays on cell lines in order to obtain relevant data. Measurements were done by validated UV/VIS spectroscopy, HPLC, and newly developed UPLC methods. Specificity was confirmed for HPLC and UPLC method, whereas UV/VIS spectroscopy resulted in false higher trans-RSV concentrations in conditions under which it was not stable (alkaline pH, light, increased temperature). The study is of interest because it draws attention to the importance of careful selected experimental conditions, their influence on the trans-RSV stability and the implications this has for formulation development, storage, and maintenance of therapeutic doses.

  8. Targeting pH regulating proteins for cancer therapy-Progress and limitations.

    PubMed

    Parks, Scott K; Pouysségur, Jacques

    2017-01-27

    Tumour acidity induced by metabolic alterations and incomplete vascularisation sets cancer cells apart from normal cellular physiology. This distinguishing tumour characteristic has been an area of intense study, as cellular pH (pHi) disturbances disrupt protein function and therefore multiple cellular processes. Tumour cells effectively utilise pHi regulating machinery present in normal cells with enhancements provided by additional oncogenic or hypoxia induced protein modifications. This overall improvement of pH regulation enables maintenance of an alkaline pHi in the continued presence of external acidification (pHe). Considerable experimentation has revealed targets that successfully disrupt tumour pHi regulation in efforts to develop novel means to weaken or kill tumour cells. However, redundancy in these pH-regulating proteins, which include Na(+)/H(+) exchangers (NHEs), carbonic anhydrases (CAs), Na(+)/HCO3(-) co-transporters (NBCs) and monocarboxylate transporters (MCTs) has prevented effective disruption of tumour pHi when individual protein targeting is performed. Here we synthesise recent advances in understanding both normoxic and hypoxic pH regulating mechanisms in tumour cells with an ultimate focus on the disruption of tumour growth, survival and metastasis. Interactions between tumour acidity and other cell types are also proving to be important in understanding therapeutic applications such as immune therapy. Promising therapeutic developments regarding pH manipulation along with current limitations are highlighted to provide a framework for future research directives.

  9. Acidic pH increases airway surface liquid viscosity in cystic fibrosis.

    PubMed

    Tang, Xiao Xiao; Ostedgaard, Lynda S; Hoegger, Mark J; Moninger, Thomas O; Karp, Philip H; McMenimen, James D; Choudhury, Biswa; Varki, Ajit; Stoltz, David A; Welsh, Michael J

    2016-03-01

    Cystic fibrosis (CF) disrupts respiratory host defenses, allowing bacterial infection, inflammation, and mucus accumulation to progressively destroy the lungs. Our previous studies revealed that mucus with abnormal behavior impaired mucociliary transport in newborn CF piglets prior to the onset of secondary manifestations. To further investigate mucus abnormalities, here we studied airway surface liquid (ASL) collected from newborn piglets and ASL on cultured airway epithelia. Fluorescence recovery after photobleaching revealed that the viscosity of CF ASL was increased relative to that of non-CF ASL. CF ASL had a reduced pH, which was necessary and sufficient for genotype-dependent viscosity differences. The increased viscosity of CF ASL was not explained by pH-independent changes in HCO3- concentration, altered glycosylation, additional pH-induced disulfide bond formation, increased percentage of nonvolatile material, or increased sulfation. Treating acidic ASL with hypertonic saline or heparin largely reversed the increased viscosity, suggesting that acidic pH influences mucin electrostatic interactions. These findings link loss of cystic fibrosis transmembrane conductance regulator-dependent alkalinization to abnormal CF ASL. In addition, we found that increasing Ca2+ concentrations elevated ASL viscosity, in part, independently of pH. The results suggest that increasing pH, reducing Ca2+ concentration, and/or altering electrostatic interactions in ASL might benefit early CF.

  10. Cytoplasmic pH influences cytoplasmic calcium in MC3T3-E1 osteoblast cells

    NASA Technical Reports Server (NTRS)

    Lin, H. S.; Hughes-Fulford, M.; Kumegawa, M.; Pitts, A. C.; Snowdowne, K. W.

    1993-01-01

    We found that the cytoplasmic concentration of calcium (Cai) of MC3T3-E1 osteoblasts was influenced by the type of pH buffer we used in the perfusing medium, suggesting that intracellular pH (pHi) might influence Cai. To study this effect, the Cai and pHi were monitored as we applied various experimental conditions known to change pHi. Exposure to NH4Cl caused a transient increase in both pHi and Cai without a change in extracellular pH (pHo). Decreasing pHo and pHi by lowering the bicarbonate concentration of the medium decreased Cai, and increasing pHi by the removal of 5% CO2 increased Cai. Clamping pHi to known values with 10 microM nigericin, a potassium proton ionophore, also influenced Cai: acid pHi lowered Cai, whereas alkaline pHi increased it. The rise in Cai appears to be very sensitive to the extracellular concentration of calcium, suggesting the existence of a pH-sensitive calcium influx mechanism. We conclude that physiologic changes in pH could modulate Cai by controlling the influx of calcium ions and could change the time course of the Cai transient associated with hormonal activation.

  11. Metabolic microenvironmental control by photosynthetic biofilms under changing macroenvironmental temperature and pH conditions.

    PubMed

    Bissett, Andrew; Reimer, Andreas; de Beer, Dirk; Shiraishi, Fumito; Arp, Gernot

    2008-10-01

    Ex situ microelectrode experiments, using cyanobacterial biofilms from karst water creeks, were conducted under various pH, temperature, and constant-alkalinity conditions to investigate the effects of changing environmental parameters on cyanobacterial photosynthesis-induced calcification. Microenvironmental chemical conditions around calcifying sites were controlled by metabolic activity over a wide range of photosynthesis and respiration rates, with little influence from overlying water conditions. Regardless of overlying water pH levels (from 7.8 to 8.9), pH at the biofilm surface was approximately 9.4 in the light and 7.8 in the dark. The same trend was observed at various temperatures (4 degrees C and 17 degrees C). Biological processes control the calcium carbonate saturation state (Omega) in these and similar systems and are able to maintain Omega at approximately constant levels over relatively wide environmental fluctuations. Temperature did, however, have an effect on calcification rate. Calcium flux in this system is limited by its diffusion coefficient, resulting in a higher calcium flux (calcification and dissolution) at higher temperatures, despite the constant, biologically mediated pH. The ability of biological systems to mitigate the effects of environmental perturbation is an important factor that must be considered when attempting to predict the effects of increased atmospheric partial CO(2) pressure on processes such as calcification and in interpreting microfossils in the fossil record.

  12. pH Regulation of ammonia secretion by Colletotrichum gloeosporioides and its effect on appressorium formation and pathogenicity.

    PubMed

    Miyara, Itay; Shafran, Hadas; Davidzon, Maayan; Sherman, Amir; Prusky, Dov

    2010-03-01

    Host-tissue alkalinization via ammonia accumulation is key to Colletotrichum spp. colonization. Using macroarrays carrying C. gloeosporioides cDNAs, we monitored gene expression during the alkalinization process. A set of genes involved in synthesis and catabolism of ammonia accumulation were identified. Expression of NAD(+)-specific glutamate dehydrogenase (GDH2, encoding ammonia synthesis) and the ammonia exporter AMET were induced at pH 4.0 to 4.5. Conversely, ammonia uptake and transcript activation of the ammonia and glutamate importers (MEP and GLT, respectively) and glutamine synthase (GS1) were higher at pH 6.0 to 7.0. Accumulated ammonia in the wild-type mycelium decreased during ambient alkalinization, concurrent with increased GS1 expression. Deltapac1 mutants of C. gloeosporioides, which are sensitive to alkaline pH changes, showed upregulation of the acid-expressed GDH2 and downregulation of the alkaline-expressed GS1, resulting in 60% higher ammonia accumulation inside the mycelium. Deltagdh2 strains of C. gloeosporioides, impaired in ammonia production, showed 85% inhibition in appressorium formation followed by reduced colonization on avocado fruit (Persea americana cv. Fuerte) pericarp, while exogenic ammonia addition restored appressoria formation. Thus the modulation of genes involved in ammonia metabolism and catabolism by C. gloeosporioides is ambient pH-dependent. Aside from its contribution to necrotrophic stages, ammonia accumulation by germinating spores regulates appressorium formation and determines the initiation of biotrophic stages of avocado-fruit colonization by Colletotrichum spp.

  13. Habit-associated salivary pH changes in oral submucous fibrosis–A controlled cross-sectional study

    PubMed Central

    Donoghue, Mandana; Basandi, Praveen S; Adarsh, H; Madhushankari, GS; Selvamani, M; Nayak, Prachi

    2015-01-01

    Context: Oral submucous fibrosis (OSF) is a multi-causal inflammatory reaction to the chemical or mechanical trauma caused due to exposure to arecanut containing products with or without tobacco (ANCP/T). Arecanut and additional components such as lime and chewing tobacco render ANCP/T highly alkaline. Fibrosing repair is a common reaction to an alkaline exposure in the skin. OSF may be related to the alkaline exposure by ANCP/T in a similar manner. Aims: The study was aimed at establishing the relationship of habit-associated salivary pH changes and OSF. Settings and Design: The study design was controlled cross-sectional. Materials and Methods: Base line salivary pH (BLS pH), salivary pH after chewing the habitual ANCP/T substance, post chew salivary pH (PCSpH) for 2 min and salivary pH recovery time (SpHRT) were compared in 30 OSF patients and 30 sex-matched individuals with ANCP/T habits and apparently healthy oral mucosa. Results: The group's mean BLSpH values were similar and within normal range and representative of the population level values. The average PCSpH was significantly higher (P ˂ 0.0001) than the average BLSpH in both groups. There was no significant difference (P = 0.09) between PCSpH of OSF patients and controls. OSF patients had a significantly longer (P = 0.0076) SpHRT than controls. Factors such as age, daily exposure, cumulative habit years, BLSpH and PCSpH, had varying effects on the groups. Conclusions: Chewing ANCP/T causes a significant rise in salivary pH of all individuals. SpHRT has a significant association with OSF. The effect of salivary changes in OSF patients differs with those in healthy controls. PMID:26604493

  14. Role of ammonia secretion and pH modulation on pathogenicity of Colletotrichum coccodes on tomato fruit.

    PubMed

    Alkan, N; Fluhr, R; Sherman, A; Prusky, D

    2008-08-01

    Colletotrichum coccodes was found to alkalinize the decaying tissue of tomato fruit via accumulation and secretion of ammonia. Alkalinization dynamics caused by ammonia secretion from growing hyphae was examined microscopically using the pH-sensitive fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Values of pH of 7.9 observed in the host tissue close to the hyphal tips declined to pH 6.0 at 10 mm away from the hyphal tip, which was a value that was still higher than that detected in the healthy tissue, pH 4.2. Ammonia accumulation at the infection site depended on the initial environmental pH. Treatments with low (4.0) pH buffer at the infection site resulted in high levels of ammonia secretion and increased virulence of C. coccodes compared with similar treatments with buffer at pH 7.0. Significantly, mutants of C. coccodes defective in nitrogen utilization, nit-, and areA- were impaired in ammonia secretion and showed reduced decay development. The reduced infection rate of nit- mutants could be complemented by adding glutamine at the infection site. Thus, ammonia accumulation is a critical factor contributing to C. coccodes pathogenicity on tomato fruit. The results show that the initial acidic pH of the fruit is conducive to ammonia secretion and the subsequent alkalinization of the infection site, and facilitates fungal virulence and the transformation from the quiescent-biotrophic to active-necrotrophic state.

  15. Nitric oxide and pH modulation in gynaecological cancer.

    PubMed

    Sanhueza, Carlos; Araos, Joaquín; Naranjo, Luciano; Barros, Eric; Subiabre, Mario; Toledo, Fernando; Gutiérrez, Jaime; Chiarello, Delia I; Pardo, Fabián; Leiva, Andrea; Sobrevia, Luis

    2016-12-01

    Nitric oxide plays several roles in cellular physiology, including control of the vascular tone and defence against pathogen infection. Neuronal, inducible and endothelial nitric oxide synthase (NOS) isoforms synthesize nitric oxide. Cells generate acid and base equivalents, whose physiological intracellular concentrations are kept due to membrane transport systems, including Na(+) /H(+) exchangers and Na(+) /HCO3(-) transporters, thus maintaining a physiological pH at the intracellular (~7.0) and extracellular (~7.4) medium. In several pathologies, including cancer, cells are exposed to an extracellular acidic microenvironment, and the role for these membrane transport mechanisms in this phenomenon is likely. As altered NOS expression and activity is seen in cancer cells and because this gas promotes a glycolytic phenotype leading to extracellular acidosis in gynaecological cancer cells, a pro-inflammatory microenvironment increasing inducible NOS expression in this cell type is feasible. However, whether abnormal control of intracellular and extracellular pH by cancer cells regards with their ability to synthesize or respond to nitric oxide is unknown. We, here, discuss a potential link between pH alterations, pH controlling membrane transport systems and NOS function. We propose a potential association between inducible NOS induction and Na(+) /H(+) exchanger expression and activity in human ovary cancer. A potentiation between nitric oxide generation and the maintenance of a low extracellular pH (i.e. acidic) is proposed to establish a sequence of events in ovarian cancer cells, thus preserving a pro-proliferative acidic tumour extracellular microenvironment. We suggest that pharmacological therapeutic targeting of Na(+) /H(+) exchangers and inducible NOS may have benefits in human epithelial ovarian cancer.

  16. Regulation of Vacuolar pH in Citrus limon

    SciTech Connect

    Lincoln Taiz

    2005-06-22

    The primary objective of this grant was to characterize the vacuolar V-ATPase of lemon fruits. Lemon fruit vacuoles have an internal pH of about 2.5. Since a typical plant vacuole has a luminal pH of around 5.5, the lemon fruit V-APTase must have special properties which allow it to acidify the lumen to such a low pH: (1) it might have a different structure; (2) it might have a different H{sup +}/ATP stoichiometry; and (3) it might be regulated differently. During the course of the investigations (which began in 1996) they characterized these aspects of the V-ATPases of both lemon fruits and lime fruits. They examined lime fruits because of the availability of both acidic limes with a low vacuolar pH and sweet limes, which have a much higher vacuolar pH. The existence of two types of lime fruits allowed a comparison of the V-ATPases of the two varieties. In this report they are including two publications from 1996 and 1997 as background for the later publications. A review article with Heven Sze on V-ATPase nomenclature was also generated during the funding period. In addition to the studies on citrus fruit vacuoles, they also initiated studies in two new areas: polar auxin transport and the regulation of stomatal opening by UV-B irradiation. These studies were intended to serve as a basis of future separate grants, but the proposals they submitted on these topics were not funded.

  17. Sulfate reduction at low pH to remediate acid mine drainage.

    PubMed

    Sánchez-Andrea, Irene; Sanz, Jose Luis; Bijmans, Martijn F M; Stams, Alfons J M

    2014-03-30

    Industrial activities and the natural oxidation of metallic sulfide-ores produce sulfate-rich waters with low pH and high heavy metals content, generally termed acid mine drainage (AMD). This is of great environmental concern as some heavy metals are highly toxic. Within a number of possibilities, biological treatment applying sulfate-reducing bacteria (SRB) is an attractive option to treat AMD and to recover metals. The process produces alkalinity, neutralizing the AMD simultaneously. The sulfide that is produced reacts with the metal in solution and precipitates them as metal sulfides. Here, important factors for biotechnological application of SRB such as the inocula, the pH of the process, the substrates and the reactor design are discussed. Microbial communities of sulfidogenic reactors treating AMD which comprise fermentative-, acetogenic- and SRB as well as methanogenic archaea are reviewed.

  18. Modeling the Role of pH on Baltic Sea Cyanobacteria

    PubMed Central

    Hinners, Jana; Hofmeister, Richard; Hense, Inga

    2015-01-01

    We simulate pH-dependent growth of cyanobacteria with an ecosystem model for the central Baltic Sea. Four model components—a life cycle model of cyanobacteria, a biogeochemical model, a carbonate chemistry model and a water column model—are coupled via the framework for aquatic biogeochemical models. The coupled model is forced by the output of a regional climate model, based on the A1B emission scenario. With this coupled model, we perform simulations for the period 1968–2098. Our simulation experiments suggest that in the future, cyanobacteria growth is hardly affected by the projected pH decrease. However, in the simulation phase prior to 1980, cyanobacteria growth and N2-fixation are limited by the relatively high pH. The observed absence of cyanobacteria before the 1960s may thus be explained not only by lower eutrophication levels, but also by a higher alkalinity. PMID:25830591

  19. An ester derivative of the drug gabapentin: pH dependent crystal stability

    NASA Astrophysics Data System (ADS)

    André, Vânia; Marques, M. Matilde; da Piedade, M. F. Minas; Duarte, M. Teresa

    2010-06-01

    Gabapentin solutions with different pHs were prepared and slow crystallization was allowed to occur. Different crystalline forms were obtained at pHs up to 7, whereas alkaline media (pH 9) gave rise to an amorphous product. A new crystal structure of an ethyl ester derivative, obtained at pH 2 under Fischer esterification conditions, is described herein. Esterification blocked the supramolecular interactions typically observed through the carboxyl group of gabapentin, which resulted in a dramatic change in the solid-state structure. As it is known, this change could have a marked influence on the physiological absorption characteristics of the drug, which supports the search for ester-based gabapentin prodrugs as a means of improving the limited bioavailability of the drug.

  20. [Raman spectra of different kinds of thalassemia erythrocytes with the effect of pH].

    PubMed

    Wu, Zheng-Jie; Wang, Cheng; Lin, Zheng-Chun

    2013-04-01

    Thalassemia is a kind of blood diseases which has high morbidity and large influence. Previous methods for diagnosis are all very cumbersome and time consuming. By comparing Raman spectra of different kinds of thalassemia and normal erythrocytes at acid or alkaline pH, it was found that beta-thalassemia and alpha-thalassemia erythrocytes have dissimilar Raman spectra in the acidic environment, such as the Raman spectra of beta-thalassemia erythrocytes showed higher intensity at the characteristic bands assigned to oxyhemoglobin, and the characteristic bands assigned to deoxyhemoglobin were even completely replaced; beta-thalassemia erythrocytes membrane has a smaller chain interaction between the transverse order parameters than normal erythrocytes, and the S(lat) values are different for different stages of anemia, while the S(lat) values are similar between alpha-thalassemia and normal erythrocytes, indicating that based on the effect of pH it is possible to diagnose thalassemia more quickly by using Raman spectra.