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Sample records for acid ph values

  1. [Degradation kinetics of chlorogenic acid, cryptochlorogenic acid, and neochlorogenic acid at neutral and alkaline pH values].

    PubMed

    Zhu, Peng; Miao, Xiao-lei; Chen, Yong

    2016-01-01

    The degradation kinetics of chlorogenic acid (5-CQA), cryptochlorogenic acid (4-CQA), and neochlorogenic acid (3-CQA) in aqueous solution at 37 degrees C and different pH values (7.05, 7.96, 9.25) were investigated in the present work. The results indicated that 3-, 4- and 5-CQA tended to remain stable in acidic pH circumstance, and unstable in neutral and alkaline pH circumstance. With the increase of the alkalinity, the degradation of 3-, 4- and 5-CQA was increased leading to a less amount of total CQA and was satisfactorily described by the Weibull equation. Meanwhile, caffeic acid was not detected after the degradation of CQA. Moreover, the degradation of 3-CQA and 5-CQA tended to be converted to 4-CQA, and the degradation of 4-CQA tended to be converted to 3-CQA rather than 5-CQA. The comparison of the degradation kinetics parameters of 3-, 4- and 5-CQA at neutral and alkaline pH values showed that the orders of the rate constant (k) values were 4-CQA > 3-CQA > 5-CQA, while the orders of the degradation half life (t½) values were 4-CQA < 3-CQA < 5-CQA, indicating the orders of the stabilities of 3-, 4- and 5-CQA at 37 degrees C and neutral and alkaline pH values were 4-CQA < 3-CQA < 5-CQA. PMID:27405173

  2. Optimization of pH values to formulate the bireagent kit for serum uric acid assay.

    PubMed

    Huang, Ya; Chen, Yuanxiang; Yang, Xiaolan; Zhao, Hua; Hu, Xiaolei; Pu, Jun; Liao, Juan; Long, Gaobo; Liao, Fei

    2015-01-01

    A new formulation of the bireagent kit for serum uric acid assay was developed based on the effects of pH on enzyme stability. At 4 °C, half-lives of uricases from Bacillus fastidious and Arthrobacter globiforms were longer than 15 months at pH 9.2, but became shorter at pH below 8.0; half-lives of ascorbate oxidase and peroxidase were comparable at pH 6.5 and 7.0, but became much shorter at pH higher than 7.4. In the new formulation of the bireagent kit, Reagent A contained peroxidase, 4-aminoantipyrine, and ascorbate oxidase in 50 mM phosphate buffer at pH 6.5; Reagent B contained B. fastidious or A. globiforms uricase in 50 mM sodium borate buffer at pH 9.2; Reagents A and B were mixed at 4:1 to produce a final pH from 7.2 to 7.6 for developing a stable color. The new bireagent kit consumed smaller quantities of three enzymes for the same shelf life. With the new bireagent kit, there were linear responses of absorbance at 546 nm to uric acid up to 34 mM in reaction mixtures and a good correlation of uric acid levels in clinical sera with those by a commercial kit, but stronger resistance to ascorbate. Therefore, the new formulation was advantageous.

  3. Lower pH values of weakly acidic refluxes as determinants of heartburn perception in gastroesophageal reflux disease patients with normal esophageal acid exposure.

    PubMed

    de Bortoli, N; Martinucci, I; Savarino, E; Franchi, R; Bertani, L; Russo, S; Ceccarelli, L; Costa, F; Bellini, M; Blandizzi, C; Savarino, V; Marchi, S

    2016-01-01

    Multichannel impedance pH monitoring has shown that weakly acidic refluxes are able to generate heartburn. However, data on the role of different pH values, ranging between 4 and 7, in the generation of them are lacking. The aim of this study was to evaluate whether different pH values of weakly acidic refluxes play a differential role in provoking reflux symptoms in endoscopy-negative patients with physiological esophageal acid exposure time and positive symptom index and symptom association probability for weakly acidic refluxes. One hundred and forty-three consecutive patients with gastroesophageal reflux disease, nonresponders to proton pump inhibitors (PPIs), were allowed a washout from PPIs before undergoing: upper endoscopy, esophageal manometry, and multichannel impedance pH monitoring. In patients with both symptom index and symptom association probability positive for weakly acidic reflux, each weakly acidic reflux was evaluated considering exact pH value, extension, physical characteristics, and correlation with heartburn. Forty-five patients with normal acid exposure time and positive symptom association probability for weakly acidic reflux were identified. The number of refluxes not heartburn related was higher than those heartburn related. In all distal and proximal liquid refluxes, as well as in distal mixed refluxes, the mean pH value of reflux events associated with heartburn was significantly lower than that not associated. This condition was not confirmed for proximal mixed refluxes. Overall, a low pH of weakly acidic reflux represents a determinant factor in provoking heartburn. This observation contributes to better understand the pathophysiology of symptoms generated by weakly acidic refluxes, paving the way toward the search for different therapeutic approaches to this peculiar condition of esophageal hypersensitivity.

  4. [Short-term changes of pH value and Al activity in acid soils after urea fertilization].

    PubMed

    Zeng, Qingru; Liao, Bohan; Jiang, Zhaohui; Zhou, Xihong; Tang, Can; Zhong, Ning

    2005-02-01

    Acidic soils are widely distributed in South China, and their acidity is the major environmental stress factor limiting the growth of most crops. It is well known that soil Al solubilized at low pH is a main toxic factor for plant growth. Our study with three acidic soils showed that soil pH increased quickly, while soil exchangeable Al decreased sharply with the increasing concentrations of applied urea. The time-course experiment revealed that the increase of soil pH was short-lived, with a subsequently slow drop after reached its maximum. Urea fertilization caused a drastic change of soil pH during 2-4 weeks of the experimental period. There was a negative relationship between soil pH and soil exchangeable Al. Biological toxicity test demonstrated that applying urea to acidic soils could obviously decrease the aluminum toxicity of maize in a short-term period.

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

    PubMed

    Oja, M; Maran, U

    2015-01-01

    Absorption in gastrointestinal tract compartments varies and is largely influenced by pH. Therefore, considering pH in studies and analyses of membrane permeability provides an opportunity to gain a better understanding of the behaviour of compounds and to obtain good permeability estimates for prediction purposes. This study concentrates on relationships between the chemical structure and membrane permeability of acidic and basic drugs and drug-like compounds. The membrane permeability of 36 acidic and 61 basic compounds was measured using the parallel artificial membrane permeability assay (PAMPA) at pH 3, 5, 7.4 and 9. Descriptive and/or predictive single-parameter quantitative structure-permeability relationships were derived for all pH values. For acidic compounds, membrane permeability is mainly influenced by hydrogen bond donor properties, as revealed by models with r(2) > 0.8 for pH 3 and pH 5. For basic compounds, the best (r(2) > 0.7) structure-permeability relationships are obtained with the octanol-water distribution coefficient for pH 7.4 and pH 9, indicating the importance of partition properties. In addition to the validation set, the prediction quality of the developed models was tested with folic acid and astemizole, showing good matches between experimental and calculated membrane permeabilities at key pHs. Selected QSAR models are available at the QsarDB repository ( http://dx.doi.org/10.15152/QDB.166 ). PMID:26383235

  6. Bile acids and pH values in total feces and in fecal water from habitually omnivorous and vegetarian subjects.

    PubMed

    van Faassen, A; Hazen, M J; van den Brandt, P A; van den Bogaard, A E; Hermus, R J; Janknegt, R A

    1993-12-01

    Twenty habitually omnivorous subjects and 19 habitually lactoovovegetarian subjects aged 59-65 y collected feces during 4 consecutive days. The concentrations of bile acids in total feces did not differ between the omnivores and vegetarians, but the bile acid concentrations in fecal water were significantly lower in the vegetarians. The concentration of the colorectal cancer-predicting bile acid deoxycholic acid in fecal water was explained by the intake of saturated fat and the daily fecal wet weight (r2 = 0.50). Fecal pH did not differ between the omnivores and vegetarians. This variable was significantly (P < 0.05) explained by the intake of calcium (r2 = 0.30); 24-h fecal wet weight and defecation frequency were significantly higher in the vegetarians. In conclusion, our vegetarian subjects had a lower concentration of deoxycholic acid in fecal water, higher fecal wet weight, and higher defecation frequency than the omnivorous subjects.

  7. Kinetics of an acid-base catalyzed reaction (aspartame degradation) as affected by polyol-induced changes in buffer pH and pK values.

    PubMed

    Chuy, S; Bell, L N

    2009-01-01

    The kinetics of an acid-base catalyzed reaction, aspartame degradation, were examined as affected by the changes in pH and pK(a) values caused by adding polyols (sucrose, glycerol) to phosphate buffer. Sucrose-containing phosphate buffer solutions had a lower pH than that of phosphate buffer alone, which contributed, in part, to reduced aspartame reactivity. A kinetic model was introduced for aspartame degradation that encompassed pH and buffer salt concentrations, both of which change with a shift in the apparent pK(a) value. Aspartame degradation rate constants in sucrose-containing solutions were successfully predicted using this model when corrections (that is, lower pH, lower apparent pK(a) value, buffer dilution from the polyol) were applied. The change in buffer properties (pH, pK(a)) from adding sucrose to phosphate buffer does impact food chemical stability. These effects can be successfully incorporated into predictive kinetic models. Therefore, pH and pK(a) changes from adding polyols to buffer should be considered during food product development.

  8. Influence of nitrogen source and pH value on undesired poly(γ-glutamic acid) formation of a protease producing Bacillus licheniformis strain.

    PubMed

    Meissner, Lena; Kauffmann, Kira; Wengeler, Timo; Mitsunaga, Hitoshi; Fukusaki, Eiichiro; Büchs, Jochen

    2015-09-01

    Bacillus spp. are used for the production of industrial enzymes but are also known to be capable of producing biopolymers such as poly(γ-glutamic acid). Biopolymers increase the viscosity of the fermentation broth, thereby impairing mixing, gas/liquid mass and heat transfer in any bioreactor system. Undesired biopolymer formation has a significant impact on the fermentation and downstream processing performance. This study shows how undesirable poly(γ-glutamic acid) formation of an industrial protease producing Bacillus licheniformis strain was prevented by switching the nitrogen source from ammonium to nitrate. The viscosity was reduced from 32 to 2.5 mPa s. A constant or changing pH value did not influence the poly(γ-glutamic acid) production. Protease production was not affected: protease activities of 38 and 46 U mL(-1) were obtained for ammonium and nitrate, respectively. With the presented results, protease production with industrial Bacillus strains is now possible without the negative impact on fermentation and downstream processing by undesired poly(γ-glutamic acid) formation.

  9. 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 ...

  10. Glucose intolerance in dairy goats with pregnancy toxemia: Lack of correlation between blood pH and beta hydroxybutyric acid values.

    PubMed

    Lima, Miguel S; Cota, João B; Vaz, Yolanda M; Ajuda, Inês G; Pascoal, Rita A; Carolino, Nuno; Hjerpe, Charles A

    2016-06-01

    This study assessed the response to a glucose tolerance test in dairy goats with pregnancy toxemia (PT), in healthy, pregnant, non-lactating dairy goats in the last month of gestation (HP), and in healthy, lactating, non-pregnant, dairy goats in mid-lactation (HL). A 500 mL volume of a 5% glucose solution was administered by the IV route. Blood glucose concentrations returned to pre-infusion levels by 90 min in all 8 HL goats, and by 180 min in all 8 HP goats. In contrast, concentrations of blood glucose were still significantly above pre-infusion levels at 180 min post-infusion in all 8 PT goats. Thus, marked glucose intolerance was demonstrated in the PT goats, and mild intolerance was noted in the HP goats. In 25 goats diagnosed with PT and having blood beta hydroxybutyric acid (BHBA) values ≥ 2.9 mmol/L, the correlation coefficient for BHBA with blood pH was non-significant. PMID:27247464

  11. 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)

  12. Observation of pH Value in Electrokinetic Remediation using various electrolyte (MgSO4, KH2PO4 and Na(NO3)) for Barren Acidic Soil at Ayer Hitam, Johor, Malaysia

    NASA Astrophysics Data System (ADS)

    Norashira, J.; Zaidi, E.; Aziman, M.; Saiful Azhar, A. T.

    2016-07-01

    Barren acidic soil collected at Ayer Hitam, Johor Malaysia was recorded at pH value of 2.36 with relative humidity of 86%. This pH value is not suitable for the growth of any plants especially for the soil stabilization purposes. Gradation weathering within the range of 4 to 6 indicates an incomplete/partial weathering process. The soil grade in this range is known as a black shale mudstone. Beside, this also influences to a factor of the high surface water runoff at this particular soil species. As the acidic pH become a major problem for soil fertilizing hence an appropriate technique was implemented known as using ‘Electrokinetic Remediation’, EKR. This technique has a great potential in changing the soil pH value from acidic to less acidic and also kept maintain the pH at the saturated rate of electrochemical process. This research study presents the monitoring data of pH value due to the effect of various electrolyte consist of 0.5M of MgSO4, KH2PO4, and Na(NO3). Here, the distilled water (DW) was used as reference solution. The electric field was provided by dipping two pieces of identical rectangular aluminum foil as anode and cathode. The EKR was conducted under a constant voltage gradient of 50 V/m across the sample bulk at 0.14 m length measured between both electrodes. The data collection was conducted during the total period of 7 days surveillance. The variation of pH values at the remediation area between anode and cathode for various type of electrolyte indicates that there are a significant saturated value as it reaches 7 days of treatment. During the analysis, it is found that the highest pH value at the remediation area after 7 days treatment using Na(NO3), KH2PO4 and MgSO4 was 3.93, 3.33 and 3.39 respectively. Hence from the last stage of pH value observation, it can be conclude that the best electrolyte for barren soil treatment is Na(NO3) whereby it contribute to highest pH value and turn the soil to be less acidic.

  13. Growth and arginine metabolism of the wine lactic acid bacteria Lactobacillus buchneri and Oenococcus oeni at different pH values and arginine concentrations.

    PubMed

    Mira De Orduña, R; Patchett, M L; Liu, S Q; Pilone, G J

    2001-04-01

    During malolactic fermentation (MLF) in grape must and wine, heterofermentative lactic acid bacteria may degrade arginine, leading to the formation of ammonia and citrulline, among other substances. This is of concern because ammonia increases the pH and thus the risk of growth by spoilage bacteria, and citrulline is a precursor to the formation of carcinogenic ethyl carbamate (EC). Arginine metabolism and growth of Lactobacillus buchneri CUC-3 and Oenococcus oeni strains MCW and Lo111 in wine were investigated. In contrast to L. buchneri CUC-3, both oenococci required a higher minimum pH for arginine degradation, and arginine utilization was delayed relative to the degradation of malic acid, the main aim of MLF. This allows the control of pH increase and citrulline formation from arginine metabolism by carrying out MLF with pure oenococcal cultures and inhibiting cell metabolism after malic acid depletion. MLF by arginine-degrading lactobacilli should be discouraged because arginine degradation may lead to the enhanced formation of acids from sugar degradation. A linear relationship was found between arginine degradation and citrulline excretion rates. From this data, strain-specific arginine-to-citrulline conversion ratios were calculated that ranged between 2.2 and 3.9% (wt/wt), and these ratios can be used to estimate the contribution of citrulline to the EC precursor pool from a given amount of initial arginine. Increasing arginine concentrations led to higher rates of growth of L. buchneri CUC-3 but did not increase the growth yield of either oenococcus. These results suggest the use of non-arginine-degrading oenococci for inducing MLF. PMID:11282618

  14. Unified pH values of liquid chromatography mobile phases.

    PubMed

    Suu, Agnes; Jalukse, Lauri; Liigand, Jaanus; Kruve, Anneli; Himmel, Daniel; Krossing, Ingo; Rosés, Martí; Leito, Ivo

    2015-03-01

    This work introduces a conceptually new approach of measuring pH of mixed-solvent liquid chromatography (LC) mobile phases. Mobile phase pH is very important in LC, but its correct measurement is not straightforward, and all commonly used approaches have deficiencies. The new approach is based on the recently introduced unified pH (pH(abs)) scale, which enables direct comparison of acidities of solutions made in different solvents based on chemical potential of the proton in the solutions. This work represents the first experimental realization of the pH(abs) concept using differential potentiometric measurement for comparison of the chemical potentials of the proton in different solutions (connected by a salt bridge), together with earlier published reference points for obtaining the pH(abs) values (referenced to the gas phase) or pH(abs)(H₂O) values (referenced to the aqueous solution). The liquid junction potentials were estimated in the framework of Izutsu's three-component method. pH(abs) values for a number of common LC and LC-MS mobile phases have been determined. The pH(abs) scale enables for the first time direct comparison of acidities of any LC mobile phases, with different organic additives, different buffer components, etc. A possible experimental protocol of putting this new approach into chromatographic practice has been envisaged and its applicability tested. It has been demonstrated that the ionization behavior of bases (cationic acids) in the mobile phases can be better predicted by using the pH(abs)(H₂O) values and aqueous pKa values than by using the alternative means of expressing mobile phase acidity. Description of the ionization behavior of acids on the basis of pH(abs)(H₂O) values is possible if the change of their pKa values with solvent composition change is taken into account. PMID:25664372

  15. Illumina sequencing-based analyses of bacterial communities during short-chain fatty-acid production from food waste and sewage sludge fermentation at different pH values.

    PubMed

    Cheng, Weixiao; Chen, Hong; Yan, ShuHai; Su, Jianqiang

    2014-09-01

    Short-chain fatty acids (SCFAs) can be produced by primary and waste activated sludge anaerobic fermentation. The yield and product spectrum distribution of SCFAs can be significantly affected by different initial pH values. However, most studies have focused on the physical and chemical aspects of SCFA production by waste activated sludge fermentation at different pH values. Information on the bacterial community structures during acidogenic fermentation is limited. In this study, comparisons of the bacterial communities during the co-substrate fermentation of food wastes and sewage sludge at different pH values were performed using the barcoded Illumina paired-end sequencing method. The results showed that different pH environments harbored a characteristic bacterial community, including sequences related to Lactobacillus, Prevotella, Mitsuokella, Treponema, Clostridium, and Ureibacillus. The most abundant bacterial operational taxonomic units in the different pH environments were those related to carbohydrate-degrading bacteria, which are associated with constituents of co-substrate fermentation. Further analyses showed that during organic matter fermentation, a core microbiota composed of Firmicutes, Proteobacteria, and Bacteroidetes existed. Comparison analyses revealed that the bacterial community during fermentation was significantly affected by the pH, and that the diverse product distribution was related to the shift in bacterial communities.

  16. 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…

  17. Titratable acidity of beverages influences salivary pH recovery.

    PubMed

    Tenuta, Livia Maria Andaló; Fernández, Constanza Estefany; Brandão, Ana Carolina Siqueira; Cury, Jaime Aparecido

    2015-01-01

    A low pH and a high titratable acidity of juices and cola-based beverages are relevant factors that contribute to dental erosion, but the relative importance of these properties to maintain salivary pH at demineralizing levels for long periods of time after drinking is unknown. In this crossover study conducted in vivo, orange juice, a cola-based soft drink, and a 10% sucrose solution (negative control) were tested. These drinks differ in terms of their pH (3.5 ± 0.04, 2.5 ± 0.05, and 5.9 ± 0.1, respectively) and titratable acidity (3.17 ± 0.06, 0.57 ± 0.04 and < 0.005 mmols OH- to reach pH 5.5, respectively). Eight volunteers with a normal salivary flow rate and buffering capacity kept 15 mL of each beverage in their mouth for 10 s, expectorated it, and their saliva was collected after 15, 30, 45, 60, 90, and 120 s. The salivary pH, determined using a mini pH electrode, returned to the baseline value at 30 s after expectoration of the cola-based soft drink, but only at 90 s after expectoration of the orange juice. The salivary pH increased to greater than 5.5 at 15 s after expectoration of the cola drink and at 30 s after expectoration of the orange juice. These findings suggest that the titratable acidity of a beverage influences salivary pH values after drinking acidic beverages more than the beverage pH.

  18. Sector analysis of pH values in the northeastern region of Puerto Rico.

    PubMed

    Peñalber-Ramos, J; Méndez-Tejeda, R; Rodríguez-Rosario, M

    2002-06-01

    Acid rain precipitation has become a major environmental concern. Many long-range projects in the United States and Europe are devoted to the problems associated with acid rain pollution. In Puerto Rico, there has been no formal study on acid rain. The rainfall pH values and the air-mass trajectory of the northeastern part of the island of Puerto Rico on the surface were analyzed from January 1998 to December 2000. The air-mass trajectory was classified in five different sectors, according to where it originates. The mean pH value measured during that period showed a tendency toward acidity. The 80% of the air-mass trajectory that arrived at the station occurred in Sector I, with a pH value of 4.30. The lowest pH value measured was 4.16, and it occurred in Sector V, where the air mass originates in the northwest part of the island.

  19. Some features of the effect the pH value and the physicochemical properties of boric acid have on mass transfer in a VVER reactor's core

    NASA Astrophysics Data System (ADS)

    Gavrilov, A. V.; Kritskii, V. G.; Rodionov, Yu. A.; Berezina, I. G.

    2013-07-01

    Certain features of the effect of boric acid in the reactor coolant of nuclear power installations equipped with a VVER-440 reactor on mass transfer in the reactor core are considered. It is determined that formation of boric acid polyborate complexes begins under field conditions at a temperature of 300°C when the boric acid concentration is equal to around 0.065 mol/L (4 g/L). Operations for decontaminating the reactor coolant system entail a growth of corrosion product concentration in the coolant, which gives rise to formation of iron borates in the zones where subcooled boiling of coolant takes place and to the effect of axial offset anomalies. A model for simulating variation of pressure drop in a VVER-440 reactor's core that has invariable parameters during the entire fuel campaign is developed by additionally taking into account the concentrations of boric acid polyborate complexes and the quantity of corrosion products (Fe, Ni) represented by the ratio of their solubilities.

  20. Notes on the Measurement of pH Values

    SciTech Connect

    Carranza, R M; Rebak, R B

    2005-05-05

    The original definition of pH is: pH = -log a{sub H}. Where a{sub H} is the (relative) hydrogen ion activity. However, a single ion activity cannot be measured. Activities of individual ionic species are necessarily conventional. The pH number, of course, has in itself little absolute significance. As the negative of the logarithm of a product of a concentration (c or m) and an activity coefficient (y or {gamma}), it acquires its magnitude from the numerical scale adopted for the latter. Experimental pH measurements are nonetheless widely applied to the determination of thermodynamic equilibrium data such as pK values, on the assumption that they represent -log a{sub H} (or paH). The single ion activity coefficient approaches unity as the ionic strength goes to zero, so that activity becomes m or c and paH becomes pmH or pcH. pH is therefore defined operationally in terms of the operation or method used to measure it, that is, by means of a cell called an operational cell. The cell is standardized by solutions of assigned pH value (Reference Value pH Standard, Primary pH Standards and Operational Standards). Such standard reference solutions are buffer solutions whose pH values are assigned from measurements on cells with or without liquid junction. It must be emphasized that the definition of pH scale is quite different from the measurement of pH with glass-reference electrode-pH meter assemblies, where several standards are used in order to take into account possible deficiencies in the electrode and meter performance.

  1. Photoproduction of glyoxylic acid in model wine: Impact of sulfur dioxide, caffeic acid, pH and temperature.

    PubMed

    Grant-Preece, Paris; Schmidtke, Leigh M; Barril, Celia; Clark, Andrew C

    2017-01-15

    Glyoxylic acid is a tartaric acid degradation product formed in model wine solutions containing iron and its production is greatly increased by exposure to UV-visible light. In this study, the combined effect of sulfur dioxide, caffeic acid, pH and temperature on the light-induced (⩾300nm) production of glyoxylic acid in model wine containing tartaric acid and iron was investigated using a Box-Behnken experimental design and response surface methodology (RSM). Glyoxylic acid produced in the irradiated model wine was present in free and hydrogen sulfite adduct forms and the measured total, free and percentage free glyoxylic acid values were modeled using RSM. Sulfur dioxide significantly decreased the total amount of glyoxylic acid produced, but could not prevent its production, while caffeic acid showed no significant impact. The interaction between pH and temperature was significant, with low pH values and low temperatures giving rise to higher levels of total glyoxylic acid.

  2. Yogurt made from milk heated at different pH values.

    PubMed

    Ozcan, Tulay; Horne, David S; Lucey, John A

    2015-10-01

    Milk for yogurt manufacture is subjected to high heat treatment to denature whey proteins. Low milk pH values (≤ 6.5) at heating result in most denatured whey proteins becoming associated with casein micelles, whereas high milk pH values (≥ 7.0) at heating result in the formation of mostly soluble (nonmicellar) denatured whey protein complexes. There are conflicting reports on the relative importance of soluble and casein-bound whey protein aggregates on the properties of acid gels. Prior studies investigating the effect of pH of milk at heating used model gels in which milk was acidified by glucono-δ-lactone; in this study, we prepared yogurt gels using commercial starter cultures. Model acid gels can have very different texture and physical properties from those made by fermentation with starter cultures. In this study, we investigated the effects of different pH values of milk at heating on the rheological, light backscatter, and microstructural properties of yogurt gels. Reconstituted skim milk was adjusted to pH values 6.2, 6.7, and 7.2 and heated at 85°C for 30 min. A portion of the heated milk samples was readjusted back to pH 6.7 after heating. Milks were inoculated with 3% (wt/wt) yogurt starter culture and incubated at 40°C until pH 4.6. Gel formation was monitored using dynamic oscillatory rheology, and parameters measured included the storage modulus (G') and loss tangent (LT) values. Light-backscattering properties, such as the backscatter ratio (R) and the first derivative of light backscatter ratio (R'), were also monitored during fermentation. Fluorescence microscopy was used to observe gel microstructure. The G' values at pH 4.6 were highest in gels made from milk heated at pH 6.7 and lowest in milk heated at pH 6.2, with or without pH adjustment after heating. The G' values at pH 4.6 were lower in samples after adjustment back to pH 6.7 after heating. No maximum in the LT parameter was observed during gelation for yogurts made from milk

  3. Yogurt made from milk heated at different pH values.

    PubMed

    Ozcan, Tulay; Horne, David S; Lucey, John A

    2015-10-01

    Milk for yogurt manufacture is subjected to high heat treatment to denature whey proteins. Low milk pH values (≤ 6.5) at heating result in most denatured whey proteins becoming associated with casein micelles, whereas high milk pH values (≥ 7.0) at heating result in the formation of mostly soluble (nonmicellar) denatured whey protein complexes. There are conflicting reports on the relative importance of soluble and casein-bound whey protein aggregates on the properties of acid gels. Prior studies investigating the effect of pH of milk at heating used model gels in which milk was acidified by glucono-δ-lactone; in this study, we prepared yogurt gels using commercial starter cultures. Model acid gels can have very different texture and physical properties from those made by fermentation with starter cultures. In this study, we investigated the effects of different pH values of milk at heating on the rheological, light backscatter, and microstructural properties of yogurt gels. Reconstituted skim milk was adjusted to pH values 6.2, 6.7, and 7.2 and heated at 85°C for 30 min. A portion of the heated milk samples was readjusted back to pH 6.7 after heating. Milks were inoculated with 3% (wt/wt) yogurt starter culture and incubated at 40°C until pH 4.6. Gel formation was monitored using dynamic oscillatory rheology, and parameters measured included the storage modulus (G') and loss tangent (LT) values. Light-backscattering properties, such as the backscatter ratio (R) and the first derivative of light backscatter ratio (R'), were also monitored during fermentation. Fluorescence microscopy was used to observe gel microstructure. The G' values at pH 4.6 were highest in gels made from milk heated at pH 6.7 and lowest in milk heated at pH 6.2, with or without pH adjustment after heating. The G' values at pH 4.6 were lower in samples after adjustment back to pH 6.7 after heating. No maximum in the LT parameter was observed during gelation for yogurts made from milk

  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. PMID:16422525

  5. [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.

  6. Liquid-containing Refluxes and Acid Refluxes May Be Less Frequent in the Japanese Population Than in Other Populations: Normal Values of 24-hour Esophageal Impedance and pH Monitoring

    PubMed Central

    Kawamura, Osamu; Kohata, Yukie; Kawami, Noriyuki; Iida, Hiroshi; Kawada, Akiyo; Hosaka, Hiroko; Shimoyama, Yasuyuki; Kuribayashi, Shiko; Fujiwara, Yasuhiro; Iwakiri, Katsuhiko; Inamori, Masahiko; Kusano, Motoyasu; Hongo, Micho

    2016-01-01

    Background/Aims Twenty-four-hour esophageal impedance and pH monitoring allows detection of all types of reflux episodes and is considered the best technique for identifying gastroesophageal refluxes. However, normative data for the Japanese population are lacking. This multicenter study aimed to establish the normal range of 24-hour esophageal impedance and pH data both in the distal and the proximal esophagus in Japanese subjects. Methods Forty-two healthy volunteers (25 men and 17 women) with a mean ± standard deviation age of 33.3 ± 12.4 years (range: 22–72 years) underwent a combined 24-hour esophageal impedance and pH monitoring. According to the physical and pH properties, distal or proximal esophageal reflux events were categorized. Results Median 45 reflux events occurred in 24 hours, and the 95th percentile was 85 events. Unlike previous reports, liquid-containing reflux events are median 25/24 hours with the 95th percentile of 62/24 hours. Acidic reflux events were median 11/24 hours with the 95th percentile of 39/24 hours. Non-acidic gas reflux events were median 15/24 hours with the 95th percentile of 39/24 hours. Proximal reflux events accounted for 80% of the total reflux events and were mainly non-acidic gas refluxes. About 19% of liquid and mixed refluxes reached the proximal esophagus. Conclusions Unlike previous studies, liquid-containing and acidic reflux events may be less frequent in the Japanese population. Non-acidic gas reflux events may be frequent and a cause of frequent proximal reflux events. This study provides important normative data for 24-hour impedance and pH monitoring in both the distal and the proximal esophagus in the Japanese population. PMID:27247103

  7. 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…

  8. Intracellular pH of acid-tolerant ruminal bacteria.

    PubMed Central

    Russell, J B

    1991-01-01

    Acid-tolerant ruminal bacteria (Bacteroides ruminicola B1(4), Selenomonas ruminantium HD4, Streptococcus bovis JB1, Megasphaera elsdenii B159, and strain F) allowed their intracellular pH to decline as a function of extracellular pH and did not generate a large pH gradient across the cell membrane until the extracellular pH was low (less than 5.2). This decline in intracellular pH prevented an accumulation of volatile fatty acid anions inside the cells. PMID:1781695

  9. Microbiological survey of Adirondack lakes with various pH values

    SciTech Connect

    Boylen, C.W.; Shick, M.O.; Roberts, D.A.

    1983-05-01

    Many of the lakes in the Adirondack region of New York State are particularly sensitive to high H/sup +/ inputs from acidic deposition. Nine high-altitude oligotrophic Adirondack lakes having water of pH 4.3 to 7.0 were surveyed for total bacterial numbers and possible adaptation of the microbial communities to environmental pH. The number of heterotrophic bacteria from water samples recoverable on standard plate count agar were low (10 to 1000 per ml) for most of the lakes. Sediment aerobic heterotrophs recovered on standard plate count agar ranged from 14,000 to 1,300,000 per g of sediment. Low density values were consistent with the oligotrophic nature of all the lakes surveyed. There were no apparent differences in numbers of bacteria originally isolated at pH 5.0 and pH 7.0 between circumneutral lakes (pH 6.0) and acidic lakes (pH 5.0). A chi-square contingency test clearly showed (P 0.005) that two distinct heterotrophic populations had been originally isolated at pH 5.0 and pH 7.0, although there is undoubtedly some overlap between the two populations. 35 references, 5 figures, 3 tables.

  10. [Advances in the effects of pH value of micro-environment on wound healing].

    PubMed

    Tian, Ruirui; Li, Na; Wei, Li

    2016-04-01

    Wound healing is a complex regeneration process, which is affected by lots of endogenous and exogenous factors. Researches have confirmed that acid environment could prevent wound infection and accelerate wound healing by inhibiting bacteria proliferation, promoting oxygen release, affecting keratinocyte proliferation and migration, etc. In this article, we review the literature to identify the potential relationship between the pH value of wound micro-environment and the progress of wound healing, and summarize the clinical application of variation of pH value of micro-environment in wound healing, thereby to provide new treatment strategy for wound healing.

  11. Rhizosphere pH responses to simulated acid rain as measured with glass microelectrodes

    SciTech Connect

    Conkling, B.L.

    1988-01-01

    The objectives of this study were to develop a useful experimental system for studying the rhizosphere of growing roots, and to investigate the effects of bulk soil pH and foliar acid rain application on the rhizosphere pH of alfalfa, corn and soybeans. First, a study was done to compare soil pH measurements made with a standard glass pH electrode with those made using an antimony (Sb) microelectrode. Because of uncertainty with the Sb microelectrodes' response, glass pH-sensitive microelectrodes were made and tested for rhizosphere pH measurements. The influence of soil water pressure gradients in the range of {minus}10 to {minus}1500 kPa in the proximity of the pH and reference electrodes on pH measurements made with microelectrodes was studied. The effect of foliar acid rain application on the rhizosphere pH of alfalfa, corn, and soybean as a function of soil pH were studied. Alfalfa, corn, and soybean were grown into minirhizotrons containing reformed samples of both Seymour A and Bt soil horizons, and the rhizosphere pH measured. The measured in situ bulk soil pH ranged from 4.9 to 6.2 in the A horizon and from 4.0 to 5.7 in the Bt horizon. Plants received acid or non-acid foliar rain applications. Rhizosphere pH was measured using a glass pH-sensitive microelectrode. Acid rain applications caused foliar damage, but had little effect on the rhizosphere pH. The general trend was for the lateral root pH values to be slightly higher than the main root values.

  12. Microbiological Survey of Adirondack Lakes with Various pH Values

    PubMed Central

    Boylen, Charles W.; Shick, Marcy O.; Roberts, Deborah A.; Singer, Robert

    1983-01-01

    Nine high-altitude oligotrophic Adirondack lakes in upstate New York having water of pH 4.3 to 7.0 were surveyed for total bacterial numbers and possible adaptation of the microbial communities to environmental pH. The number of heterotrophic bacteria from water samples recoverable on standard plate count agar were low (101 to 103 per ml) for most of the lakes. Acridine orange direct counts were approximately two orders of magnitude higher than plate counts for each lake. Sediment aerobic heterotrophs recovered on standard plate count agar ranged from 1.4 × 104 to 1.3 × 106 per g of sediment. Direct epifluorescence counts of bacteria in sediment samples ranged from 3.0 × 106 to 1.4 × 107 per g. Low density values were consistent with the oligotrophic nature of all the lakes surveyed. There were no apparent differences in numbers of bacteria originally isolated at pH 5.0 and pH 7.0 between circumneutral lakes (pH > 6.0) and acidic lakes (pH < 5.0). Approximately 1,200 isolates were recultured over a range of pH from 3.0 to 7.0. Regardless of the original isolation pH (pH 5.0 or pH 7.0), less than 10% of the isolates grew at pH < 5.0. Those originally isolated at pH 5.0 also grew at pH 6.0 and 7.0. Those originally isolated at pH 7.0 preferred pH 7.0, with 98% able to grow at pH 6.0 and 44% able to grow at pH 5.0. A chi-square contingency test clearly showed (P < 0.005) that two distinct heterotrophic populations had been originally isolated at pH 5.0 and pH 7.0, although there is undoubtedly some overlap between the two populations. PMID:16346291

  13. Amino acids improve acid tolerance and internal pH maintenance in Bacillus cereus ATCC14579 strain.

    PubMed

    Senouci-Rezkallah, Khadidja; Schmitt, Philippe; Jobin, Michel P

    2011-05-01

    This study investigated the involvement of glutamate-, arginine- and lysine-dependent systems in the Acid Tolerance Response (ATR) of Bacillus cereus ATCC14579 strain. Cells were grown in a chemostat at external pH (pH(e)) 7.0 and 5.5. Population reduction after acid shock at pH 4.0 was strongly limited in cells grown at pH 5.5 (acid-adapted) compared with cells grown at pH 7.0 (unadapted), indicating that B. cereus cells grown at low pH(e) were able to induce a marked ATR. Glutamate, arginine and lysine enhanced the resistance of unadapted cells to pH 4.0 acid shock of 1-log or 2-log populations, respectively. Amino acids had no detectable effect on acid resistance in acid-adapted cells. An acid shock at pH 4.0 resulted in a marked drop in internal pH (pH(i)) in unadapted cells compared with acid-adapted cells. When acid shock was achieved in the presence of glutamate, arginine or lysine, pH(i) was maintained at higher values (6.31, 6.69 or 6.99, respectively) compared with pH(i) in the absence of amino acids (4.88). Acid-adapted cells maintained their pH(i) at around 6.4 whatever the condition. Agmatine (a competitive inhibitor of arginine decarboxylase) had a negative effect on the ability of B. cereus cells to survive and maintain their pH(i) during acid shock. Our data demonstrate that B. cereus is able to induce an ATR during growth at low pH. This adaptation depends on pH(i) homeostasis and is enhanced in the presence of glutamate, arginine and lysine. Hence evaluations of the pathogenicity of B. cereus must take into account its ability to adapt to acid stress.

  14. Negative pH and extremely acidic mine waters from Iron Mountain, California

    SciTech Connect

    Nordstrom, D.K.; Alpers, C.N.; Ptacek, C.J.; Blowes, D.W.

    2000-01-15

    Extremely acidic mine waters with pH values as low as {minus}3.6, total dissolved metal concentrations as high as 200 g/L, and sulfate concentrations as high as 760 g/L, have been encountered underground in the Richmond Mine at Iron Mountain, CA. These are the most acidic waters known. The pH measurements were obtained by using the Pitzer method to define pH for calibration of glass membrane electrodes. The calibration of pH below 0.5 with glass membrane electrodes becomes strongly nonlinear but is reproducible to a pH as low as {minus}4. Numerous efflorescent minerals were found forming from these acid waters. These extreme acid waters were formed primarily by pyrite oxidation and concentration by evaporation with minor effects from aqueous ferrous iron oxidation and efflorescent mineral formation.

  15. Negative pH and extremely acidic mine waters from Iron Mountain, California

    USGS Publications Warehouse

    Nordstrom, D.K.; Alpers, C.N.; Ptacek, C.J.; Blowes, D.W.

    2000-01-01

    Extremely acidic mine waters with pH values as low as -3.6, total dissolved metal concentrations as high as 200 g/L, and sulfate concentrations as high as 760 g/L, have been encountered underground in the Richmond Mine at Iron Mountain, CA. These are the most acidic waters known. The pH measurements were obtained by using the Pitzer method to define pH for calibration of glass membrane electrodes. The calibration of pH below 0.5 with glass membrane electrodes becomes strongly nonlinear but is reproducible to a pH as low as -4. Numerous efflorescent minerals were found forming from these acid waters. These extreme acid waters were formed primarily by pyrite oxidation and concentration by evaporation with minor effects from aqueous ferrous iron oxidation and efflorescent mineral formation.

  16. Effect of pH on corrosion inhibition of steel by polyaspartic acid

    SciTech Connect

    Silverman, D.C.; Kalota, D.J.; Stover, F.S.

    1995-10-01

    Polyaspartic acid, a polymeric form of aspartic acid has been examined as a corrosion inhibitor for steel as a function of pH, temperature, and hydrodynamic conditions. The temperature ranged from 25 C to 95 C and the concentration ranged from less than 1% to about 10% by weight. Experimental procedures included electrochemical impedance spectroscopy, the rotating cylinder electrode, and coupon immersion. At low to neutral pH values, polyaspartic acid increases the corrosion rate of steel. At high pH above about 10, polyaspartic acid is a reasonably robust corrosion inhibitor. Between a pH of 7 and 10, corrosion in the presence of polyaspartic acid is a complex function of temperature, concentration, water quality, and hydrodynamic conditions. By combining corrosion potential measurements with speciation diagrams as obtained by titration, a reasonably cohesive explanation of the behavior has been developed.

  17. Effect of pH on corrosion inhibition of steel by polyaspartic acid

    SciTech Connect

    Silverman, D.C.; Kalota, D.J.; Stover, F.S.

    1995-11-01

    Polyaspartic acid, a polymeric form of aspartic acid (C{sub 4}H{sub 7}NO{sub 4}), was examined as a corrosion inhibitor for steel as a function of pH, temperature, and hydrodynamic conditions. The temperature ranged from 25 C to 95 C, and the concentration ranged from < 1 wt% to {approximately} 10 wt%. Experimental procedures included electrochemical impedance spectroscopy (EIS), the rotating cylinder electrode (RCE), and coupon immersion. At low to neutral pH values, polyaspartic acid increased the corrosion rate of steel. At high pH (< {approximately} 10), polyaspartic acid was a reasonably robust corrosion inhibitor. Between pH 7 and 10, corrosion in the presence of polyaspartic acid was a complex function of temperature concentration, water quality, and hydrodynamic conditions. By combining corrosion potential measurements with speciation diagrams obtained by titration, a reasonably cohesive explanation of the behavior was developed.

  18. Atmospheric methane consumption by forest soils and extracted bacteria at different pH values

    SciTech Connect

    Amaral, J.A.; Ren, T.; Knowles, R.

    1998-07-01

    The effect of pH on atmospheric methane (CH{sub 4}) consumption was studied with slurries of forest soils and with bacteria extracted from the same soils. Soil samples were collected from a mixed hardwood stand in New Hampshire, from jackpine and aspen stands at the BOREAS (Boreal Ecosystem Atmosphere Study) site near Thompson, northern Manitoba, from sites in southern Quebec, including a beech stand and a meadow, and from a site in Ontario. Consumption of atmospheric CH{sub 4} occurred at depths of >5 cm in both acidic and alkaline soils. In slurries of acidic soils, maximum activity occurred at different pH values. Bacteria extracted from these soils by high-speed blending and density gradient centrifugation showed pH responses different from the pH responses of the slurries. In all cases, these bacteria had a methanotrophy pH optimum of 5.8 and exhibited no activity at pH 6.8 to 7.0, the pH optimum range for known methanotrophs. This difference in pH responses could be useful in modifying media currently used for isolation of these organisms. Methanotrophic activity was induced in previously non-CH{sub 4}-consuming soils by preincubation with 5% (vol/vol) CH{sub 4} or by liquid enrichment with 20% CH{sub 4}. The bacteria showed pH responses typical of known methanotrophs and not typical of preexisting consumers of ambient CH{sub 4}. Furthermore, methanotrophs induced by high CH{sub 4} levels were more readily extracted from soil than preexisting ambient CH{sub 4} consumers were. In the alkaline soils, preexisting activity either was destroyed or resisted extraction by the procedure used. The results support the hypothesis that consumers of ambient CH{sub 4} in soils are physiologically distinct from the known methanotrophs.

  19. Stability of superparamagnetic iron oxide nanoparticles at different pH values: experimental and theoretical analysis.

    PubMed

    Park, Yoonjee; Whitaker, Ragnhild D; Nap, Rikkert J; Paulsen, Jeffrey L; Mathiyazhagan, Vidhya; Doerrer, Linda H; Song, Yi-Qiao; Hürlimann, Martin D; Szleifer, Igal; Wong, Joyce Y

    2012-04-17

    The detection of superparamagnetic nanoparticles using NMR logging has the potential to provide enhanced contrast in oil reservoir rock formations. The stability of the nanoparticles is critical because the NMR relaxivity (R(2) ≡ 1/T(2)) is dependent on the particle size. Here we use a molecular theory to predict and validate experimentally the stability of citric acid-coated/PEGylated iron oxide nanoparticles under different pH conditions (pH 5, 7, 9, 11). The predicted value for the critical surface coverage required to produce a steric barrier of 5k(B)T for PEGylated nanoparticles (MW 2000) was 0.078 nm(-2), which is less than the experimental value of 0.143 nm(-2), implying that the nanoparticles should be stable at all pH values. Dynamic light scattering (DLS) measurements showed that the effective diameter did not increase at pH 7 or 9 after 30 days but increased at pH 11. The shifts in NMR relaxivity (from R(2) data) at 2 MHz agreed well with the changes in hydrodynamic diameter obtained from DLS data, indicating that the aggregation behavior of the nanoparticles can be easily and quantitatively detected by NMR. The unexpected aggregation at pH 11 is due to the desorption of the surface coating (citric acid or PEG) from the nanoparticle surface not accounted for in the theory. This study shows that the stability of the nanoparticles can be predicted by the theory and detected by NMR quantitatively, which suggests the nanoparticles to be a possible oil-field nanosensor. PMID:22409538

  20. Atmospheric Methane Consumption by Forest Soils and Extracted Bacteria at Different pH Values.

    PubMed

    Amaral; Ren; Knowles

    1998-07-01

    The effect of pH on atmospheric methane (CH4) consumption was studied with slurries of forest soils and with bacteria extracted from the same soils. Soil samples were collected from a mixed hardwood stand in New Hampshire, from jackpine and aspen stands at the BOREAS (Boreal Ecosystem Atmosphere Study) site near Thompson, northern Manitoba, from sites in southern Québec, including a beech stand and a meadow, and from a site in Ontario (cultivated humisol). Consumption of atmospheric CH4 (concentration, approximately 1.8 ppm) occurred at depths of >5 cm in both acidic (pH 4.5 to 5.2) and alkaline (pH 7.2 to 7.8) soils. In slurries of acidic soils, maximum activity occurred at different pH values (pH 4.0 to 6.5). Bacteria extracted from these soils by high-speed blending and density gradient centrifugation showed pH responses different from the pH responses of the slurries. In all cases, these bacteria had a methanotrophy pH optimum of 5.8 and exhibited no activity at pH 6.8 to 7.0, the pH optimum range for known methanotrophs. This difference in pH responses could be useful in modifying media currently used for isolation of these organisms. Methanotrophic activity was induced in previously non-CH4-consuming soils by preincubation with 5% (vol/vol) CH4 (50,000 µl of CH4 per liter) or by liquid enrichment with 20% CH4. The bacteria showed pH responses typical of known methanotrophs and not typical of preexisting consumers of ambient CH4. Furthermore, methanotrophs induced by high CH4 levels were more readily extracted from soil than preexisting ambient CH4 consumers were. In the alkaline soils, preexisting activity either was destroyed or resisted extraction by the procedure used. The results support the hypothesis that consumers of ambient CH4 in soils are physiologically distinct from the known methanotrophs.

  1. 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

  2. Photoproduction of glyoxylic acid in model wine: Impact of sulfur dioxide, caffeic acid, pH and temperature.

    PubMed

    Grant-Preece, Paris; Schmidtke, Leigh M; Barril, Celia; Clark, Andrew C

    2017-01-15

    Glyoxylic acid is a tartaric acid degradation product formed in model wine solutions containing iron and its production is greatly increased by exposure to UV-visible light. In this study, the combined effect of sulfur dioxide, caffeic acid, pH and temperature on the light-induced (⩾300nm) production of glyoxylic acid in model wine containing tartaric acid and iron was investigated using a Box-Behnken experimental design and response surface methodology (RSM). Glyoxylic acid produced in the irradiated model wine was present in free and hydrogen sulfite adduct forms and the measured total, free and percentage free glyoxylic acid values were modeled using RSM. Sulfur dioxide significantly decreased the total amount of glyoxylic acid produced, but could not prevent its production, while caffeic acid showed no significant impact. The interaction between pH and temperature was significant, with low pH values and low temperatures giving rise to higher levels of total glyoxylic acid. PMID:27542478

  3. The effect of the concentration of citric acid and pH values on the preparation of MgAl{sub 2}O{sub 4} ultrafine powder by citrate sol-gel process

    SciTech Connect

    Zhang Haijun; Jia Xiaolin; Yan Yongjie; Liu Zhanjie; Yang Daoyuan; Li Zhenzhen

    2004-05-05

    Ultrafine MgAl{sub 2}O{sub 4} was synthesized by citrate sol-gel process. A model was presented to evaluate the concentration of species in a citric solution for preparing MgAl{sub 2}O{sub 4} ultrafine powder. The evaluated concentration of species can provide valuable information and help in selecting the optimal condition for preparation of MgAl{sub 2}O{sub 4} powder by citrate sol-gel process. The influence of molar ratio of cations, citric acid and pH on the formation of MgAl{sub 2}O{sub 4} was studied. The spinel precursor gel and the ultrafine MgAl{sub 2}O{sub 4} spinel were characterized by X-ray diffraction (XRD), differential thermal analysis, thermogravimetric (TG-DTA) and scanning electron microscope (SEM). The results show that the MgAl{sub 2}O{sub 4} spinel phase begins to form at 600 deg. C, and most of MgAl{sub 2}O{sub 4} crystals are spherical with a crystal size about 30-50 nm.

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

    PubMed

    Barrette-Ng, Isabelle H

    2011-07-01

    In introductory biochemistry courses, it is often a struggle to teach the basic concepts of acid-base chemistry in a manner that is relevant to biological systems. To help students gain a more intuitive and visual understanding of abstract acid-base concepts, a simple graphical construct called the pH ruler Java applet was developed. The applet allows students to visualize the abundance of different protonation states of diprotic and triprotic amino acids at different pH values. Using the applet, the student can drag a widget on a slider bar to change the pH and observe in real time changes in the abundance of different ionization states of this amino acid. This tool provides a means for developing more complex inquiry-based, active-learning exercises to teach more advanced topics of biochemistry, such as protein purification, protein structure and enzyme mechanism. PMID:21887891

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

    PubMed

    Barrette-Ng, Isabelle H

    2011-07-01

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

  6. Initial pH of medium affects organic acids production but do not affect phosphate solubilization.

    PubMed

    Marra, Leandro M; de Oliveira-Longatti, Silvia M; Soares, Cláudio R F S; de Lima, José M; Olivares, Fabio L; Moreira, Fatima M S

    2015-06-01

    The pH of the culture medium directly influences the growth of microorganisms and the chemical processes that they perform. The aim of this study was to assess the influence of the initial pH of the culture medium on the production of 11 low-molecular-weight organic acids and on the solubilization of calcium phosphate by bacteria in growth medium (NBRIP). The following strains isolated from cowpea nodules were studied: UFLA03-08 (Rhizobium tropici), UFLA03-09 (Acinetobacter sp.), UFLA03-10 (Paenibacillus kribbensis), UFLA03-106 (Paenibacillus kribbensis) and UFLA03-116 (Paenibacillus sp.). The strains UFLA03-08, UFLA03-09, UFLA03-10 and UFLA03-106 solubilized Ca3(PO4)2 in liquid medium regardless of the initial pH, although without a significant difference between the treatments. The production of organic acids by these strains was assessed for all of the initial pH values investigated, and differences between the treatments were observed. Strains UFLA03-09 and UFLA03-10 produced the same acids at different initial pH values in the culture medium. There was no correlation between phosphorus solubilized from Ca3(PO4)2 in NBRIP liquid medium and the concentration of total organic acids at the different initial pH values. Therefore, the initial pH of the culture medium influences the production of organic acids by the strains UFLA03-08, UFLA03-09, UFLA03-10 and UFLA03-106 but it does not affect calcium phosphate solubilization.

  7. Initial pH of medium affects organic acids production but do not affect phosphate solubilization

    PubMed Central

    Marra, Leandro M.; de Oliveira-Longatti, Silvia M.; Soares, Cláudio R.F.S.; de Lima, José M.; Olivares, Fabio L.; Moreira, Fatima M.S.

    2015-01-01

    The pH of the culture medium directly influences the growth of microorganisms and the chemical processes that they perform. The aim of this study was to assess the influence of the initial pH of the culture medium on the production of 11 low-molecular-weight organic acids and on the solubilization of calcium phosphate by bacteria in growth medium (NBRIP). The following strains isolated from cowpea nodules were studied: UFLA03-08 (Rhizobium tropici), UFLA03-09 (Acinetobacter sp.), UFLA03-10 (Paenibacillus kribbensis), UFLA03-106 (Paenibacillus kribbensis) and UFLA03-116 (Paenibacillus sp.). The strains UFLA03-08, UFLA03-09, UFLA03-10 and UFLA03-106 solubilized Ca3(PO4)2 in liquid medium regardless of the initial pH, although without a significant difference between the treatments. The production of organic acids by these strains was assessed for all of the initial pH values investigated, and differences between the treatments were observed. Strains UFLA03-09 and UFLA03-10 produced the same acids at different initial pH values in the culture medium. There was no correlation between phosphorus solubilized from Ca3(PO4)2 in NBRIP liquid medium and the concentration of total organic acids at the different initial pH values. Therefore, the initial pH of the culture medium influences the production of organic acids by the strains UFLA03-08, UFLA03-09, UFLA03-10 and UFLA03-106 but it does not affect calcium phosphate solubilization. PMID:26273251

  8. The pH at the First Equivalence Point in the Titration of a Diprotic Acid

    NASA Astrophysics Data System (ADS)

    Ault, Addison

    2003-12-01

    Some readers will note a similarity between this approach and the one I took in a paper entitled “Do pH in Your Head” (2). In an example in that article the isoelectric pH of glycine (the pH at which the average charge of a glycine molecule is zero), has the value of 6.0, which is exactly half-way between 2.4, the pKa of the carboxyl group of glycine, and 9.6, the pKa of the ammonium group of glycine. This is what one would expect when realizing that a solution of neutral glycine right out of the bottle is equivalent to glycine obtained by titration of the conjugate acid of glycine to the first equivalence point. Those who are interested might want to consider why the isoelectric pH of an “acidic” amino acid, such as alanine, is exactly half-way between the pKa values of the two carboxyl groups, and why the isoelectric pH of a “basic” amino acid such as lysine is exactly half-way between the pKa values of the two ammonium groups.

  9. Physical properties of pregelatinized and granular cold water swelling maize starches at different pH values.

    PubMed

    Hedayati, Sara; Shahidi, Fakhri; Koocheki, Arash; Farahnaky, Asgar; Majzoobi, Mahsa

    2016-10-01

    The aim of this study was to investigate the influence of pH changes (3, 5, 7 and 9) on physical properties of pregelatinized (PG) and granular cold water swelling (GCWS) maize starches. In acidic pH, PG starches were fragmented; however, GCWS starches mainly reserved their granular integrity but were shriveled. For both modified starches the water absorption, cold water viscosity, textural parameters, turbidity and freeze-thaw stability of the samples decreased whereas water solubility increased at pH 3 and 5. On the other hand, alkaline pH did not bring about evident changes on morphology of PG starch but the surface of GCWS starch became smoother. Water absorption, solubility, rheological and mechanical properties, freeze-thaw stability and turbidity of the starch pastes increased at high pH values. Overall, both starches were more stable at alkaline pH compared to acidic pH values and GCWS starch was more resistance to pH changes than PG starch.

  10. The role of low molecular weight organic acids on controlling pH in coastal sea water

    NASA Astrophysics Data System (ADS)

    Ding, H.

    2015-12-01

    Series investigation of the Jiaozhou Bay, China, observed existences of three low molecular weight organic acids (LMWOAs), including lactic acid, acetic acid and formic acid, with high concentration in the sea water. Generally, their amount accounted for about 20% of DOC in the sea water of the bay. Human activities around the bay were considered as the major source of the LMWOAs. Also, long term detection showed that the pH value in the Jiaozhou Bay was lower than that in the adjacent Yellow Sea. On average, the difference of pH values between the bay and the Yellow was about 0.2. Due to higher concentrations of the LMWOAs, their contribution to lower pH value of the bay should not be ignored. To validate the effect of LMWOAs on the pH value of the bay, a new software was developed to calculate the pH value in the sea water samples based on alkalinity by adding three items of the three organic acids in the expression. Compared to the traditional pH calculating software, the new software could improve the calculating results significantly. Our results confirmed that LMWOAs was an important control factor to adjust pH values in coastal area.

  11. Uric acid plasma level and urine pH in rats treated with ambroxol.

    PubMed

    Drewa, Tomasz; Wolski, Zbigniew; Gruszka, Marzena; Misterek, Bartosz; Lysik, Joanna

    2007-01-01

    It was a chance discovery that ambroxol parenteral administration led to urinary bladder stone formation in rats. This study was undertaken to examine the serum uric acid levels and urine pH in rats after ambroxol parenteral treatment. Ambroxol influence on the uric acid level was measured in 5 rats (Rattus sp.) treated with 60 mg/kg (dissolved in injection water, sc, daily) during 2 weeks. Ambroxol influence on urine pH was examined on 45 rats divided into 3 groups. Rats from the 1st and 2nd group received 30 and 60 mg/kg/24h ambroxol, respectively. Urine was collected once daily and measured with strip kit. All values were presented as the means with standard deviations. The Student t test was used to compare the means, p < 0.05 was considered as significant. Dynamics of pH changes was measured in 4 rats treated with 60 mg/kg/24h of ambroxol. Controls received 1 mL of injection water sc. Serum uric acid level increased up to 8.7 +/- 1.0 mg/dL vs. 5.7 +/- 1.0 mg/dL in control (p < 0.002). In the 1st and 2nd group urine pH increased up to 7.5 +/- 0.5 and 7.6 +/- 0.5 vs. 6.7 +/- 0.4 (p < 0.05). Ambroxol withdrawal resulted in sequential urine pH decrease. 11 days after interruption of ambroxol therapy pH reached the starting value. Urine pH changes and possible disturbances in uric acid metabolic pathway may influence on the stone formation in rats after ambroxol parenteral treatment. The influence of ambroxol on urinary tract GAG layer and the balance between xanthine and CaOx in the urine should be checked.

  12. A study on the relationship of pH values in precipitation and weather types in the Taipei area

    SciTech Connect

    Chen, Jin-Shiou

    1996-12-31

    The hourly pH data from an automatic, sequential precipitation collector at a site in the Taipei Metropolitan Area from 1986 to 1988 has been analyzed for this study. In these three years 70% of the pH values were less than 5. In 1986, 8% were less than 4, but a tendency towards less acidity from 1986 to 1988 was evident. The hydrogen ion concentration deduced from the pH is found to be highest in the summer and secondly in the spring. The concentration in winter is the lowest. The pH seasonal variation is similar to that found in the northeastern United States by other investigators. Shower and thunderstorm precipitation types in summer are particularly acidic. The precipitation associated with typhoons in the summer and the north eastern monsoon in the winter less acidic. Typical weather patterns associated with two cases of low pH and two cases of high pH will also be presented here too. Results suggest that long range transport of pollutants from mainland China may influence the pH in the Taipei area quite a lot. However, more thoughtful studies including observations and modeling are needed.

  13. Differential responses of two wetland graminoids to high ammonium at different pH values.

    PubMed

    van Diggelen, J M H; Smolders, A J P; Visser, E J W; Hicks, S; Roelofs, J G M; Lamers, L P M

    2016-03-01

    Enhanced soil ammonium (NH4+) concentrations in wetlands often lead to graminoid dominance, but species composition is highly variable. Although NH4+ is readily taken up as a nutrient, several wetland species are known to be sensitive to high NH4+ concentrations or even suffer toxicity, particularly at low soil pH. More knowledge about differential graminoid responses to high NH4+ availability in relation to soil pH can help to better understand vegetation changes. The responses of two wetland graminoids, Juncus acutiflorus and Carex disticha, to high (2 mmol·l(-1) ) versus control (20 μmol·l(-1) ) NH4+ concentrations were tested in a controlled hydroponic set up, at two pH values (4 and 6). A high NH4+ concentration did not change total biomass for these species at either pH, but increased C allocation to shoots and increased P uptake, leading to K and Ca limitation, depending on pH treatment. More than 50% of N taken up by C. disticha was invested in N-rich amino acids with decreasing C:N ratio, but only 10% for J. acutiflorus. Although both species appeared to be well adapted to high NH4+ loadings in the short term, C. disticha showed higher classic detoxifying responses that are early warning indicators for decreased tolerance in the long term. In general, the efficient aboveground biomass allocation, P uptake and N detoxification explain the competitive strength of wetland graminoids at the expense of overall biodiversity at high NH4+ loading. In addition, differential responses to enhanced NH4+ affect interspecific competition among graminoids and lead to a shift in vegetation composition. PMID:26404423

  14. Differential responses of two wetland graminoids to high ammonium at different pH values.

    PubMed

    van Diggelen, J M H; Smolders, A J P; Visser, E J W; Hicks, S; Roelofs, J G M; Lamers, L P M

    2016-03-01

    Enhanced soil ammonium (NH4+) concentrations in wetlands often lead to graminoid dominance, but species composition is highly variable. Although NH4+ is readily taken up as a nutrient, several wetland species are known to be sensitive to high NH4+ concentrations or even suffer toxicity, particularly at low soil pH. More knowledge about differential graminoid responses to high NH4+ availability in relation to soil pH can help to better understand vegetation changes. The responses of two wetland graminoids, Juncus acutiflorus and Carex disticha, to high (2 mmol·l(-1) ) versus control (20 μmol·l(-1) ) NH4+ concentrations were tested in a controlled hydroponic set up, at two pH values (4 and 6). A high NH4+ concentration did not change total biomass for these species at either pH, but increased C allocation to shoots and increased P uptake, leading to K and Ca limitation, depending on pH treatment. More than 50% of N taken up by C. disticha was invested in N-rich amino acids with decreasing C:N ratio, but only 10% for J. acutiflorus. Although both species appeared to be well adapted to high NH4+ loadings in the short term, C. disticha showed higher classic detoxifying responses that are early warning indicators for decreased tolerance in the long term. In general, the efficient aboveground biomass allocation, P uptake and N detoxification explain the competitive strength of wetland graminoids at the expense of overall biodiversity at high NH4+ loading. In addition, differential responses to enhanced NH4+ affect interspecific competition among graminoids and lead to a shift in vegetation composition.

  15. Effects of saliva on starch-thickened drinks with acidic and neutral pH.

    PubMed

    Hanson, Ben; Cox, Ben; Kaliviotis, Efstathios; Smith, Christina H

    2012-09-01

    Powdered maize starch thickeners are used to modify drink consistency in the clinical management of dysphagia. Amylase is a digestive enzyme found in saliva which breaks down starch. This action is dependent on pH, which varies in practice depending on the particular drink. This study measured the effects of human saliva on the viscosity of drinks thickened with a widely used starch-based thickener. Experiments simulated a possible clinical scenario whereby saliva enters a cup and contaminates a drink. Citric acid (E330) was added to water to produce a controlled range of pH from 3.0 to 7.0, and several commercially available drinks with naturally low pH were investigated. When saliva was added to thickened water, viscosity was reduced to less than 1% of its original value after 10-15 min. However, lowering pH systematically slowed the reduction in viscosity attributable to saliva. At pH 3.5 and below, saliva was found to have no significant effect on viscosity. The pH of drinks in this study ranged from 2.6 for Coca Cola to 6.2 for black coffee. Again, low pH slowed the effect of saliva. For many popular drinks, having pH of 3.6 or less, viscosity was not significantly affected by the addition of saliva. PMID:22210234

  16. Design of smart nanogels that respond to physiologically relevant pH values and temperatures.

    PubMed

    Omura, Tomoyuki; Ebara, Mitsuhiro; Lai, James J; Yin, Xiangchun; Hoffman, Allan S; Stayton, Patrick S

    2014-03-01

    Herein, we report the synthesis and characterization of monodisperse 'smart' nanogels that exhibit a sharp volume phase transition at physiologically relevant temperatures and pH values. The nanogels were prepared by precipitation copolymerization of N-isopropylacrylamide (NIPAAm) and propylacrylic acid (PAA). Briefly, the reaction was performed using a PAA feed of between 0 and 10 mol% in the presence of a crosslinker at 70 degrees C. The size of the nanogel particles was determined as a function of pH and temperature using dynamic light scattering (DLS). At room temperature, the NIPAAm-PAA nanogels were discrete, spherical structures with diameters ranging from 200 to 250 nm. The hydrodynamic diameter of the nanogels decreased to ca. 100-150 nm when the solution temperature was increased to 37 degrees C. At 37 degrees C, when the pKa was below that of the NIPAAm-PAA (ca. 6.0), the gels collapsed and aggregated. However, at 37 degrees C and a physiological pH of 7.4, the nanogels did not fully collapse due to the charge-charge repulsion derived from the ionized carboxyl groups of the PAA. Similar phase transition behavior was observed with the corresponding linear copolymers. Thus, such nanogel particles could be useful for releasing drugs in regions of local acidosis, including sites of infection, tumors, ischemia, and intracellular endosomes.

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

    PubMed

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

    2005-07-01

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

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

    PubMed

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

    2005-07-01

    Organisms growing in acidic environments, pH<3, would be expected to possess fundamentally different molecular structures and physiological controls in comparison with similar species restricted to neutral pH. We begin to investigate this premise by determining the magnitude of the transmembrane electrochemical H+ gradient in an acidophilic Chlamydomonas sp. (ATCC PRA-125) isolated from the Rio Tinto, a heavy metal laden, acidic river (pH 1.7-2.5). This acidophile grows most rapidly at pH 2 but is capable of growth over a wide pH range (1.5-7.0), while Chlamydomonas reinhardtii is restricted to growth at pH>or=3 with optimal growth between pH 5.5 and 8.5. With the fluorescent H+ indicator, 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF), we show that the acidophilic Chlamydomonas maintains an average cytosolic pH of 6.6 in culture medium at both pH 2 and pH 7 while Chlamydomonas reinhardtii maintains an average cytosolic pH of 7.1 in pH 7 culture medium. The transmembrane electric potential difference of Chlamydomonas sp., measured using intracellular electrodes at both pH 2 and 7, is close to 0 mV, a rare value for plants, animals and protists. The 40,000-fold difference in [H+] could be the result of either active or passive mechanisms. Evidence for active maintenance was detected by monitoring the rate of ATP consumption. At the peak, cells consume about 7% more ATP per second in medium at pH 2 than at pH 7. This increased rate of consumption is sufficient to account for removal of H+ entering the cytosol across a membrane with relatively high permeability to H+ (7x10(-8) cm s-1). Our results indicate that the small increase in the rate of ATP consumption can account for maintenance of the transmembrane H+ gradient without the imposition of cell surface H+ barriers. PMID:15961743

  19. Metal Interactions with Microbial Biofilms in Acidic and Neutral pH Environments

    PubMed Central

    Ferris, F. G.; Schultze, S.; Witten, T. C.; Fyfe, W. S.; Beveridge, T. J.

    1989-01-01

    Microbial biofilms were grown on strips of epoxy-impregnated filter paper submerged at four sites in water contaminated with metals from mine wastes. At two sample stations, the water was acidic (pH 3.1); the other sites were in a lake restored to a near neutral pH level by application of a crushed limestone slurry. During a 17-week study period, planktonic bacterial counts increased from 101 to 103 CFU/ml at all sites. Biofilm counts increased rapidly over the first 5 weeks and then leveled to 104 CFU/cm2 in the neutral pH system and 103 CFU/cm2 at the acidic sites. In each case, the biofilms bound Mn, Fe, Ni, and Cu in excess of the amounts adsorbed by control strips covered with nylon filters (pore size, 0.22 μm) to exclude microbial growth; Co bound under neutral conditions but not under acidic conditions. Conditional adsorption capacity constants, obtained graphically from the data, showed that biofilm metal uptake at a neutral pH level was enhanced by up to 12 orders of magnitude over acidic conditions. Similarly, adsorption strength values were usually higher at elevated pH levels. In thin sections of the biofilms, encapsulated bacterial cells were commonly found enmeshed together in microcolonies. The extracellular polymers often contained iron oxide precipitates which generated weak electron diffraction patterns with characteristic reflections for ferrihydrite (Fe2O3 · H2O) at d equaling 0.15 and 0.25 nm. At neutral pH levels, these deposits incorporated trace amounts of Si and exhibited a granular morphology, whereas acicular crystalloids containing S developed under acidic conditions. Images PMID:16347914

  20. Low medium pH value enhances anthocyanin accumulation in Malus crabapple leaves.

    PubMed

    Zhang, Yanchen; Zhang, Jie; Song, Tingting; Li, Jinyan; Tian, Ji; Jin, Kaina; Yao, Yuncong

    2014-01-01

    Anthocyanin is a critical factor involved in coloration of plant tissues, but the mechanism how medium pH values affect anthocyanin accumulation in woody plants is unknown. We analyzed anthocyanin composition and the expression of elements encoding anthocyanin and flavonols biosynthesis underlying different medium pH values by using three different leave color type cultivars. HPLC analysis demonstrated that high medium pH values treatment induced a dramatic decrease in the concentration of cyaniding in crabapple leaves. Conversely, the high medium pH values induced up-regulation of the content of flavones and flavonols, suggesting that low pH treatment-induced anthocyanin accumulation. Quantitative real time PCR experiment showed the expression level of anthocyanidin synthase (McANS) and uridine diphosphate glucose flavonoid 3-O-glucosyltransferase (McUFGT) was up-regulated by low pH values treatment, and high medium pH value treatment up-regulate the transcription level of flavonol synthase (McFLS). Meanwhile, several MYB TFs have been suggested in the regulation of pH responses. These results strongly indicate that the low pH treatment-induced anthocyanin accumulation is mediated by the variation of mRNA transcription of the anthocyanin biosynthetic genes. PMID:24914811

  1. Investigation of pH Influence on Skin Permeation Behavior of Weak Acids Using Nonsteroidal Anti-Inflammatory Drugs.

    PubMed

    Chantasart, Doungdaw; Chootanasoontorn, Siriwan; Suksiriworapong, Jiraphong; Li, S Kevin

    2015-10-01

    As a continuing effort to understand the skin permeation behavior of weak acids and bases, the objectives of the present study were to evaluate skin permeation of nonsteroidal anti-inflammatory drugs (NSAIDs) under the influence of pH, investigate the mechanism of pH effect, and examine a previous hypothesis that the effective skin pH for drug permeation is different from donor solution pH. In vitro permeability experiments were performed in side-by-side diffusion cells with diclofenac, ibuprofen, flurbiprofen, ketoprofen, and naproxen and human skin. The donor solution pH significantly affected skin permeation of NSAIDs, whereas no effect of the receiver pH was observed. Similar to previous observations, the apparent permeability coefficient versus donor solution pH relationships deviated from the predictions (fractions of unionized NSAIDs) according to the acid/base theory. The influences of the viable epidermis barrier, polar pathway transport, ion permeation across skin, and effective skin pH were investigated. The effective pH values for skin permeation determined using the NSAIDs (weak acids) in this study were different from those obtained previously with a weak base at the same donor solution pH conditions, suggesting that the observed permeability-pH relationships could not be explained solely by possible pH differences between skin and donor solution.

  2. Similar bacterial community composition in acidic mining lakes with different pH and lake chemistry.

    PubMed

    Kampe, Heike; Dziallas, Claudia; Grossart, Hans-Peter; Kamjunke, Norbert

    2010-10-01

    As extreme environmental conditions strongly affect bacterial community composition (BCC), we examined whether differences in pH-even at low pH-and in iron and sulfate concentrations lead to changes in BCC of acidic mining lakes. Thereby, we tested the following hypotheses: (1) diversity of the bacterial community in acidic lakes decreases with reducing pH, (2) BCC differs between epilimnion and hypolimnion, and (3) BCC in extremely acidic environments does not vary much over time. Therefore, we investigated the BCC of three acidic lakes with different pH values (2.3, 2.7, and 3.2) by denaturing gradient gel electrophoresis (DGGE) and subsequent sequencing of DGGE bands as well as catalyzed reporter deposition-FISH (CARD-FISH). BCC did not significantly vary among the studied lakes nor differ much between water layers. In contrast, BCC significantly changed over time, which is contradictory to our hypotheses. Bacterial communities were dominated by Alpha-, Beta-, and Gammaproteobacteria, whereas Actino- and Acidobacteria rarely occurred. Cell numbers of both free and attached bacteria were positively related to DOC concentration. Overall, low pH and extreme chemical conditions of the studied lakes led to similar assemblages of bacteria with pronounced temporal differences. This notion indicates that temporal changes in environmental conditions including food web structure also affect unique communities of bacteria thriving at low pH.

  3. [Spectroscopic investigation of 3-hydroxyflavone in different polarity and pH values solutions].

    PubMed

    Ma, Li-na; Nan, Jing-yu; Wu, Feng; Tian, Wei; Chen, Wen-ju; Zhang, Gui-lan

    2009-04-01

    The absorption and fluorescence spectra of 3-hydroxyflavone (3-HF) in different polar solvents were observed with UV-Vis spectrometer and fluorescence spectrometer, respectively. There are three absorption bands in the absorption spectra, wherein two absorption bands with absorption peak at 300 and 345 nm, respectively, are strong, and the other one with absorption peak at 415 nm is weak When the samples in different polar solvents were excited by 345 nm light, there appeared two new fluorescence bands peaked at 400 and 526 nm, respectively. The fluorescence band at 400 nm is attributable to the emission from enol structure and its intensity increases with increasing the polarity of protic solvents; that at 526 nm is attributable to the emission from the isomer structure and its intensity decreases with increasing the polarity of protic solvents. The results show that the increase in the polarity of protic solvents prevents the formation of isomer. When the samples in different polar solvents were excited by 415 nm light, three new fluorescence bands peaked at 440, 471 and 515 nm have not been reported so far. In order to identify the three new fluorescence bands, we prepared the samples with pH value of 5.0, 4.0 and 3.0 through incorporating the different amounts of acetic acid into 3-HF solution. The fluorescence spectra in different pH value solution were observed under excitation of 415 nm light, and it was found that the intensity of two fluorescence bands in the region of shorter wavelength changes with pH values changing. For identifying the fluorescence band of 515 nm peak wavelength, we put sodium hydroxide into 3-HF in ethanol solution and prepared 3-HF samples with pH values of 8.0, 8.5, 9.0, and 10.0. When the samples were excited by the 415 nm light, it was found that two fluorescence bands in the region of shorter wavelength disappeared and the intensity of the fluorescence band of 515 nm was enhanced. Since in sodium hydroxide solution 3-HF forms

  4. The Cytosolic pH of Individual Saccharomyces cerevisiae Cells Is a Key Factor in Acetic Acid Tolerance.

    PubMed

    Fernández-Niño, Miguel; Marquina, Maribel; Swinnen, Steve; Rodríguez-Porrata, Boris; Nevoigt, Elke; Ariño, Joaquín

    2015-11-01

    It was shown recently that individual cells of an isogenic Saccharomyces cerevisiae population show variability in acetic acid tolerance, and this variability affects the quantitative manifestation of the trait at the population level. In the current study, we investigated whether cell-to-cell variability in acetic acid tolerance could be explained by the observed differences in the cytosolic pHs of individual cells immediately before exposure to the acid. Results obtained with cells of the strain CEN.PK113-7D in synthetic medium containing 96 mM acetic acid (pH 4.5) showed a direct correlation between the initial cytosolic pH and the cytosolic pH drop after exposure to the acid. Moreover, only cells with a low initial cytosolic pH, which experienced a less severe drop in cytosolic pH, were able to proliferate. A similar correlation between initial cytosolic pH and cytosolic pH drop was also observed in the more acid-tolerant strain MUCL 11987-9. Interestingly, a fraction of cells in the MUCL 11987-9 population showed initial cytosolic pH values below the minimal cytosolic pH detected in cells of the strain CEN.PK113-7D; consequently, these cells experienced less severe drops in cytosolic pH. Although this might explain in part the difference between the two strains with regard to the number of cells that resumed proliferation, it was observed that all cells from strain MUCL 11987-9 were able to proliferate, independently of their initial cytosolic pH. Therefore, other factors must also be involved in the greater ability of MUCL 11987-9 cells to endure strong drops in cytosolic pH.

  5. Human saliva and taste responses to acids varying in anions, titratable acidity, and pH.

    PubMed

    Norris, M B; Noble, A C; Pangborn, R M

    1984-02-01

    Twenty subjects recorded perceived sourness of solutions of citric + fumaric and of citric + tartaric acids, at pH 3.5 and titratable acidity (TiA) of 4.0 g/l on a moving chart, while parotid saliva flow was recorded via a sialometer . Sourness intensity and flow were greater when citric was the minor acid than when it was dominant. Subjects varied widely in calculated volume of saliva reservoir, but not flow rate (time to 2/3 reservoir vol.). In tartaric-fumaric acid mixtures varying in pH (3.0-3.75) at a constant TiA of 4.0 g/l, and varying in TiA (3.7-4.6 g/l) at a constant pH of 3.5, sourness intensity and parotid flow increased with acidity and decreased with pH. However, eight subjects with a high flow (HF = 1.2 +/- 0.28 g/2 min) and nine subjects with a low flow (LF = 0.43 +/- 0.11 g/2 min) differed widely: (a) In response to variation in stimulus pH and TiA, HF demonstrated marked alteration in flow, but little change in sourness ; LF responded at a lower absolute level, but showed marked changes in sourness and little change in flow; (b) Salivary pH was higher and Na+ was three times greater for the HF than for the LF subjects; and (c) Salivary Ca++ showed a direct relationship with flow and pH among the HF, but an inverse relationship for the LF subjects.

  6. A novel "off-on" colorimetric and fluorescent rhodamine-based pH chemosensor for extreme acidity

    NASA Astrophysics Data System (ADS)

    Tan, Jia-Lian; Zhang, Mu-Xue; Zhang, Fang; Yang, Ting-Ting; Liu, Yu; Li, Zhu-Bo; Zuo, Hua

    2015-04-01

    A novel "off-on" colorimetric and fluorescent rhodamine analogue was synthesized and characterized, and used to monitor extreme acidity (below pH 3.5) via the photophysical response to pH. The colorless spirocyclic structure at high pH (pH ⩾ 7.0) opened to the colored and highly fluorescent form at very low pH (pH < 3.0). This sensitive pH probe was characterized with short response time, good reversibility and no interaction with interfering metal ions, and the quantitative relationship between the fluorescence intensity and pH value was consistent with the equilibrium equation pH = pKa - log[(Imax - I)/(I - Imin)]. The fluorescent response to strong acidity was further verified by fluorescent imaging of bacteria, Escherichia coli, which contributed to the development of more useful colorimetric and fluorescent sensors based on the rhodamine platform for measuring intracellular pH in extremely acidic conditions.

  7. Contributions of Cell Metabolism and H+ Diffusion to the Acidic pH of Tumors1

    PubMed Central

    Schornack, Paul A; Gillies, Robert J

    2003-01-01

    Abstract The tumor microenvironment is hypoxic and acidic. These conditions have a significant impact on tumor progression and response to therapies. There is strong evidence that tumor hypoxia results from inefficient perfusion due to a chaotic vasculature. Consequently, some tumor regions are well oxygenated and others are hypoxic. It is commonly believed that hypoxic regions are acidic due to a stimulation of glycolysis through hypoxia, yet this is not yet demonstrated. The current study investigates the causes of tumor acidity by determining acid production rates and the mechanism of diffusion for H+ equivalents through model systems. Two breast cancer cell lines were investigated with divergent metabolic profiles: nonmetastatic MCF-7/s and highly metastatic MDA-mb-435 cells. Glycolysis and acid production are inhibited by oxygen in MCF-7/s cells, but not in MDA-mb-435 cells. Tumors of MDAmb-435 cells are significantly more acidic than are tumors of MCF-7/s cells, suggesting that tumor acidity is primarily caused by endogenous metabolism, and not the lack of oxygen. Metabolically produced protons are shown to diffuse in association with mobile buffers, in concordance with previous studies. The metabolic and diffusion data were analyzed using a reaction-diffusion model to demonstrate that the consequent pH profiles conform well to measured pH values for tumors of these two cell lines. PMID:12659686

  8. Predicting Thermodynamic Behaviors of Non-Protein Amino Acids as a Function of Temperature and pH

    NASA Astrophysics Data System (ADS)

    Kitadai, Norio

    2016-03-01

    Why does life use α-amino acids exclusively as building blocks of proteins? To address that fundamental question from an energetic perspective, this study estimated the standard molal thermodynamic data for three non-α-amino acids (β-alanine, γ-aminobutyric acid, and ɛ-aminocaproic acid) and α-amino- n-butyric acid in their zwitterionic, negative, and positive ionization states based on the corresponding experimental measurements reported in the literature. Temperature dependences of their heat capacities were described based on the revised Helgeson-Kirkham-Flowers (HKF) equations of state. The obtained dataset was then used to calculate the standard molal Gibbs energies ( ∆G o) of the non-α-amino acids as a function of temperature and pH. Comparison of their ∆G o values with those of α-amino acids having the same molecular formula showed that the non-α-amino acids have similar ∆G o values to the corresponding α-amino acids in physiologically relevant conditions (neutral pH, <100 °C). In acidic and alkaline pH, the non-α-amino acids are thermodynamically more stable than the corresponding α-ones over a broad temperature range. These results suggest that the energetic cost of synthesis is not an important selection pressure to incorporate α-amino acids into biological systems.

  9. Predicting Thermodynamic Behaviors of Non-Protein Amino Acids as a Function of Temperature and pH.

    PubMed

    Kitadai, Norio

    2016-03-01

    Why does life use α-amino acids exclusively as building blocks of proteins? To address that fundamental question from an energetic perspective, this study estimated the standard molal thermodynamic data for three non-α-amino acids (β-alanine, γ-aminobutyric acid, and ε-aminocaproic acid) and α-amino-n-butyric acid in their zwitterionic, negative, and positive ionization states based on the corresponding experimental measurements reported in the literature. Temperature dependences of their heat capacities were described based on the revised Helgeson-Kirkham-Flowers (HKF) equations of state. The obtained dataset was then used to calculate the standard molal Gibbs energies (∆G (o)) of the non-α-amino acids as a function of temperature and pH. Comparison of their ∆G (o) values with those of α-amino acids having the same molecular formula showed that the non-α-amino acids have similar ∆G (o) values to the corresponding α-amino acids in physiologically relevant conditions (neutral pH, <100 °C). In acidic and alkaline pH, the non-α-amino acids are thermodynamically more stable than the corresponding α-ones over a broad temperature range. These results suggest that the energetic cost of synthesis is not an important selection pressure to incorporate α-amino acids into biological systems.

  10. Modeling the combined effects of pH, temperature and ascorbic acid concentration on the heat resistance of Alicyclobacillus acidoterrestis.

    PubMed

    Bahçeci, K Savaş; Acar, Jale

    2007-12-15

    In this study, thermal inactivation parameters (D- and z-values) of Alicyclobacillus acidoterrestris spores in McIlvaine buffers at different pH, apple juice and apple nectar produced with and without ascorbic acid addition were determined. The effects of pH, temperature and ascorbic acid concentration on D-values of A. acidoterrestris spores were also investigated using response surface methodology. A second order polynomial equation was used to describe the relationship between pH, temperature, ascorbic acid concentration and the D-values of A. acidoterrestris spores. Temperature was the most important factor on D-values, and its effect was three times higher than those of pH. Although the statistically significant, heat resistance of A. acidoterrestris spores was not so influenced from the ascorbic acid within the concentration studied. D-values in apple juice and apple nectars were higher than those in buffers as heating medium at similar pH. The D-values ranged from 11.1 (90 degrees C) to 0.7 min (100 degrees C) in apple juice, 14.1 (90 degrees C) to 1.0 min (100 degrees C) in apple nectar produced with ascorbic acid addition, and 14.4 (90 degrees C) to 1.2 min (100 degrees C) in apple nectar produced without ascorbic acid addition. However, no significant difference in z-values was observed among spores in the juices and buffers at different pH, and it was between 8.2 and 9.2 degrees C. The results indicated that the spores of A. acidoterrestris may survive in fruit juices and nectars after pasteurization treatment commonly applied in the food industry.

  11. Effects of urea and acetic acid on the heme axial ligation structure of ferric myoglobin at very acidic pH.

    PubMed

    Droghetti, Enrica; Sumithran, Suganya; Sono, Masanori; Antalík, Marián; Fedurco, Milan; Dawson, John H; Smulevich, Giulietta

    2009-09-01

    The heme iron coordination of ferric myoglobin (Mb) in the presence of 9.0M urea and 8.0M acetic acid at acidic pH values has been probed by electronic absorption, magnetic circular dichroism and resonance Raman spectroscopic techniques. Unlike Mb at pH 2.0, where heme is not released from the protein despite the acid denaturation and the loss of the axial ligand, upon increasing the concentration of either urea or acetic acid, a spin state change is observed, and a novel, non-native six-coordinated high-spin species prevails, where heme is released from the protein.

  12. Effects of urea and acetic acid on the heme axial ligation structure of ferric myoglobin at very acidic pH

    PubMed Central

    Droghetti, Enrica; Sumithran, Suganya; Sono, Masanori; Antalík, Marián; Fedurco, Milan; Dawson, John H.; Smulevich, Giulietta

    2009-01-01

    The heme iron coordination of ferric myoglobin (Mb) in the presence of 9.0 M urea and 8.0 M acetic acid at acidic pH values has been probed by electronic absorption, magnetic circular dichroism and resonance Raman spectroscopic techniques. Unlike Mb at pH 2.0, where heme is not released from the protein despite the acid denaturation and the loss of the axial ligand, upon increasing the concentration of either urea or acetic acid, a spin state change is observed, and a novel, non-native six-coordinated high spin species prevails, where heme is released from the protein. PMID:19622342

  13. 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.

  14. Substituent effects and pH profiles for stability constants of arylboronic acid diol esters.

    PubMed

    Martínez-Aguirre, Mayte A; Villamil-Ramos, Raul; Guerrero-Alvarez, Jorge A; Yatsimirsky, Anatoly K

    2013-05-17

    Stability constants of boronic acid diol esters in aqueous solution have been determined potentiometrically for a series of meta-, para-substituted phenylboronic acids and diols of variable acidity. The constants β(11-1) for reactions between neutral forms of reactants producing the anionic ester plus proton follow the Hammett equation with ρ depending on pKa of diol and varying from 2.0 for glucose to 1.29 for 4-nitrocatechol. Observed stability constants (K(obs)) measured by UV-vis and fluorometric titrations at variable pH for esters of 4,5-dihydroxy-1,3-benzenedisulfonate (Tiron) generally agree with those expected on the basis of β(11-1) values, but the direct fitting of K(obs) vs pH profiles gives shifted pKa values both for boronic acids and diol as a result of significant interdependence of fitting parameters. The subsituent effects on absorption and fluorescence spectra of Tiron arylboronate esters are characterized. The K(obs) for Tiron determined by (11)B NMR titrations are approximately 1 order of magnitude smaller than those determined by UV-vis titrations under identical conditions. A general equation, which makes possible an estimate of β(11-1) for any pair of boronic acid and diol from their pKa values, is proposed on the basis of established Brönsted-type correlation of Hammett parameters for β(11-1) with acidity of diols. The equation allows one to calculate stability constants expected only on basis of acid-base properties of the components, thus permitting more strict evaluation of contributions of additional factors such as steric or charge effects to the ester stability.

  15. [Effects of thiourea on pH and availability of metal ions in acid red soil].

    PubMed

    Yang, Bo; Wang, Wen; Zeng, Qing-Ru; Zhou, Xi-Hong

    2014-03-01

    Through the simulation research, the effects of application of thiourea and urea on pH and availability of metal ions in acid red soil were studied, and the results showed that after applying urea, the soil pH increased in the first experimental stage and then reduced gradually to a low level, however, decreased trends of soil pH values were inhibited by the application of thiourea, especially when the concentration of thiourea reached to 5.0 mmol x kg(-1) dry soil, the soil pH was stable at high level, which exceeded to 6.0. It proved that the application of thiourea could inhibit the soil acidification due to urea application. After applying urea with different concentrations of thiourea, the available contents of Zn and Al decreased with the increasing concentration of thiourea, nevertheless, when the concentration of thiourea reached to 5.0 mmol x kg(-1), the available content of Mn was stable at high level which was over 110 mg x kg(-1). In addition, the results showed a highly significant negative correlation between the soil pH and the available content of Cu, Zn and Al, but for Mn, no discipline was found between the soil pH and the availability after applying thiourea. Moreover, the soil pH became higher after applying urea with thiourea compared to add urea only, which led to the decreasing of available content of Al, and it was benefited for the control of the phytotoxic effect of Al. The available content of Mn in the soil not only depended on soil pH but also the content of thiourea due to its redox and complexing reaction with Mn.

  16. 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

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

    PubMed

    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

  18. Effect of diffusion layer pH and solubility on the dissolution rate of pharmaceutical acids and their sodium salts. II: Salicylic acid, theophylline, and benzoic acid.

    PubMed

    Serajuddin, A T; Jarowski, C I

    1985-02-01

    The pH-solubility profiles of salicylic acid and theophylline, as determined by the addition of HCl or NaOH to their aqueous suspensions, were identical with those of their sodium salts except during phase transitions from acid to salt or vice versa. Supersaturated solutions were formed during phase transitions. Unlike the solubility profiles, the pH-intrinsic dissolution rate profiles of an acid and its salt differed greatly. Good conformity with the Noyes-Whitney equation was demonstrated when the solubility values under pH conditions as the diffusion layer thickness, h, approaches zero (Cs,h = 0) were used rather than solubilities under pH conditions of the bulk media (Cs). The pH when h approaches zero (pHh = 0) was estimated by equilibration of a dissolution medium with an excess of material. Good correlation was shown between the pHh = 0 values of benzoic acid estimated according to this method and the pHh = 0 values reported in the literature. The intrinsic dissolution rate constant, the ratio of the diffusion coefficient to the diffusion layer thickness (D/h), may be assumed constant when comparing the dissolution rates of salicylic acid, theophylline and sodium theophylline. On the other hand, D/h decreased significantly during dissolution of sodium salicylate due to a large increase in Cs,h = 0 and the consequent increase in viscosity in the diffusion layer. A simple method of predicting the dissolution rate of an acid or a salt at different pH values has been developed.

  19. Effects of acetic acid and arginine on pH elevation and growth of Bacillus licheniformis in an acidified cucumber juice medium.

    PubMed

    Yang, Zhenquan; Meng, Xia; Breidt, Frederick; Dean, Lisa L; Arritt, Fletcher M

    2015-04-01

    Bacillus licheniformis has been shown to cause pH elevation in tomato products having an initial pH below 4.6 and metabiotic effects that can lead to the growth of pathogenic bacteria. Because of this, the organism poses a potential risk to acidified vegetable products; however, little is known about the growth and metabolism of this organism in these products. To clarify the mechanisms of pH change and growth of B. licheniformis in vegetable broth under acidic conditions, a cucumber juice medium representative of a noninhibitory vegetable broth was used to monitor changes in pH, cell growth, and catabolism of sugars and amino acids. For initial pH values between pH 4.1 to 6.0, pH changes resulted from both fermentation of sugar (lowering pH) and ammonia production (raising pH). An initial pH elevation occurred, with starting pH values of pH 4.1 to 4.9 under both aerobic and anaerobic conditions, and was apparently mediated by the arginine deiminase reaction of B. licheniformis. This initial pH elevation was prevented if 5 mM or greater acetic acid was present in the brine at the same pH. In laboratory media, under favorable conditions for growth, data indicated that growth of the organism was inhibited at pH 4.6 with protonated acetic acid concentrations of 10 to 20 mM, corresponding to 25 to 50 mM total acetic acid; however, growth inhibition required greater than 300 mM citric acid (10-fold excess of the amount in processed tomato products) products under similar conditions. The data indicate that growth and pH increase by B. licheniformis may be inhibited by the acetic acid present in most commercial acidified vegetable products but not by the citric acid in many tomato products.

  20. 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.

  1. Optical measurement of the pH value of intransparent samples under high pressure

    NASA Astrophysics Data System (ADS)

    Nagel, M.; Wierschem, A.; Rauh, C.; Delgado, A.

    2015-04-01

    We present a method to optically study the pH value of intransparent media under pressure. To this end, we prepare and use immobilized pH-value indicators. The indicators are brought into contact to the medium and their optical signal is read out in reflection with a spectrometer. The pH value and pressure response of the indicator were calibrated with imidazole buffers. As an example for its applicability to foodstuff, we study the pressure-induced pH-value change of fat and meat pastes.

  2. Preferential intracellular pH regulation represents a general pattern of pH homeostasis during acid-base disturbances in the armoured catfish, Pterygoplichthys pardalis.

    PubMed

    Harter, T S; Shartau, R B; Baker, D W; Jackson, D C; Val, A L; Brauner, C J

    2014-08-01

    Preferential intracellular pH (pHi) regulation, where pHi is tightly regulated in the face of a blood acidosis, has been observed in a few species of fish, but only during elevated blood PCO2. To determine whether preferential pHi regulation may represent a general pattern for acid-base regulation during other pH disturbances we challenged the armoured catfish, Pterygoplichthys pardalis, with anoxia and exhaustive exercise, to induce a metabolic acidosis, and bicarbonate injections to induce a metabolic alkalosis. Fish were terminally sampled 2-3 h following the respective treatments and extracellular blood pH, pHi of red blood cells (RBC), brain, heart, liver and white muscle, and plasma lactate and total CO2 were measured. All treatments resulted in significant changes in extracellular pH and RBC pHi that likely cover a large portion of the pH tolerance limits of this species (pH 7.15-7.86). In all tissues other than RBC, pHi remained tightly regulated and did not differ significantly from control values, with the exception of a decrease in white muscle pHi after anoxia and an increase in liver pHi following a metabolic alkalosis. Thus preferential pHi regulation appears to be a general pattern for acid-base homeostasis in the armoured catfish and may be a common response in Amazonian fishes.

  3. Isoelectric focusing of dansylated amino acids in immobilized pH gradients

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  4. Effects of pH adjustment and sodium ions on sour taste intensity of organic acids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Protonated organic acid species have been shown to be the primary stimuli responsible for sour taste of organic acids. However, we have observed that sour taste may be modulated when the pH of acid solutions is raised using sodium hydroxide. Objectives were to evaluate the effect of pH adjustment on...

  5. 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...

  6. The influence of saliva pH value on the retention and durability of bar-clip attachments

    PubMed Central

    Aroso, Carlos; Ustrell, Raul; Braga, Ana Cristina; Mendes, Jose Manuel; Escuin, Tomas

    2015-01-01

    PURPOSE The aim of this study was to compare the durability and retention of 4 types of attachments placed over computer aided design/computer aided manufacturing (CAD/CAM) titanium bars when subjected to different pH conditions. MATERIALS AND METHODS Four commercially available attachments were investigated: Hader Yellow, Hader Red, Ackerman Gold and Ackerman Stainless Steel. These attachments and Ackerman CAD/CAM titanium bars were placed in 2 vessels containing different artificial saliva solutions (pH 7/pH 4) at 37℃ for one month to simulate corrosion conditions, and they were then subjected to mechanical testing (5400 cycles of insertion and removal). RESULTS The results revealed that there were significant differences in the average values of insertion/removal force due to the pH (F (1, 24)=9.207, P<.05) and the type of attachment (F (3, 24)=11.742, P<.05). CONCLUSION More acidic pH values were found to have a negative influence on the retention capacity of the attachments. PMID:25722835

  7. Spontaneous aggregation of humic acid observed with AFM at different pH.

    PubMed

    Colombo, Claudio; Palumbo, Giuseppe; Angelico, Ruggero; Cho, Hyen Goo; Francioso, Ornella; Ertani, Andrea; Nardi, Serenella

    2015-11-01

    Atomic force microscopy in contact (AFM-C) mode was used to investigate the molecular dynamics of leonardite humic acid (HA) aggregate formed at different pH values. HA nanoparticles dispersed at pH values ranging from 2 to 12 were observed on a mica surface under dry conditions. The most clearly resolved and well-resulted AFM images of single particle were obtained at pH 5, where HA appeared as supramolecular particles with a conic shape and a hole in the centre. Those observations suggested that HA formed under these conditions exhibited a pseudo-amphiphilic nature, with secluded hydrophobic domains and polar subunits in direct contact with hydrophilic mica surface. Based on molecular simulation methods, a lignin-carbohydrate complex (LCC) model was proposed to explain the HA ring-like morphology. The LCC model optimized the parameters of β-O-4 linkages between 14 units of 1-4 phenyl propanoid, and resulted in an optimized structure comprising 45-50 linear helical molecules looped spirally around a central cavity. Those results added new insights on the adsorption mechanism of HA on polar surfaces as a function of pH, which was relevant from the point of view of natural aggregation in soil environment. PMID:26295541

  8. Alteration of the phospho- or neutral lipid content and fatty acid composition in Listeria monocytogenes due to acid adaptation mechanisms for hydrochloric, acetic and lactic acids at pH 5.5 or benzoic acid at neutral pH.

    PubMed

    Mastronicolis, Sofia K; Berberi, Anita; Diakogiannis, Ioannis; Petrova, Evanthia; Kiaki, Irene; Baltzi, Triantafillia; Xenikakis, Polydoros

    2010-10-01

    This study provides a first approach to observe the effects on Listeria monocytogenes of cellular exposure to acid stress at low or neutral pH, notably how phospho- or neutral lipids are involved in this mechanism, besides the fatty acid profile alteration. A thorough investigation of the composition of polar and neutral lipids from L. monocytogenes grown at pH 5.5 in presence of hydrochloric, acetic and lactic acids, or at neutral pH 7.3 in presence of benzoic acid, is described relative to cells grown in acid-free medium. The results showed that only low pH values enhance the antimicrobial activity of an acid. We suggest that, irrespective of pH, the acid adaptation response will lead to a similar alteration in fatty acid composition [decreasing the ratio of branched chain/saturated straight fatty acids of total lipids], mainly originating from the neutral lipid class of adapted cultures. Acid adaptation in L. monocytogenes was correlated with a decrease in total lipid phosphorus and, with the exception of cells adapted to benzoic acid, this change in the amount of phosphorus reflected a higher content of the neutral lipid class. Upon acetic or benzoic acid stress the lipid phosphorus proportion was analysed in the main phospholipids present: cardiolipin, phosphatidylglycerol, phosphoaminolipid and phosphatidylinositol. Interestingly only benzoic acid had a dramatic effect on the relative quantities of these four phospholipids.

  9. 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

  10. 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

    2016-12-01

    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 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

  11. Influence of pH, bleaching agents, and acid etching on surface wear of bovine enamel

    PubMed Central

    Soares, Ana Flávia; Bombonatti, Juliana Fraga Soares; Alencar, Marina Studart; Consolmagno, Elaine Cristina; Honório, Heitor Marques; Mondelli, Rafael Francisco Lia

    2016-01-01

    ABSTRACT Development of new materials for tooth bleaching justifies the need for studies to evaluate the changes in the enamel surface caused by different bleaching protocols. Objective The aim of this study was to evaluate the bovine dental enamel wear in function of different bleaching gel protocols, acid etching and pH variation. Material and Methods Sixty fragments of bovine teeth were cut, obtaining a control and test areas. In the test area, one half received etching followed by a bleaching gel application, and the other half, only the bleaching gel. The fragments were randomly divided into six groups (n=10), each one received one bleaching session with five hydrogen peroxide gel applications of 8 min, activated with hybrid light, diode laser/blue LED (HL) or diode laser/violet LED (VHL) (experimental): Control (C); 35% Total Blanc Office (TBO35HL); 35% Lase Peroxide Sensy (LPS35HL); 25% Lase Peroxide Sensy II (LPS25HL); 15% Lase Peroxide Lite (LPL15HL); and 10% hydrogen peroxide (experimental) (EXP10VHL). pH values were determined by a pHmeter at the initial and final time periods. Specimens were stored, subjected to simulated brushing cycles, and the superficial wear was determined (μm). ANOVA and Tukey´s tests were applied (α=0.05). Results The pH showed a slight decrease, except for Group LPL15HL. Group LPS25HL showed the highest degree of wear, with and without etching. Conclusion There was a decrease from the initial to the final pH. Different bleaching gels were able to increase the surface wear values after simulated brushing. Acid etching before bleaching increased surface wear values in all groups. PMID:27008254

  12. The PH gene determines fruit acidity and contributes to the evolution of sweet melons.

    PubMed

    Cohen, Shahar; Itkin, Maxim; Yeselson, Yelena; Tzuri, Galil; Portnoy, Vitaly; Harel-Baja, Rotem; Lev, Shery; Sa'ar, Uzi; Davidovitz-Rikanati, Rachel; Baranes, Nadine; Bar, Einat; Wolf, Dalia; Petreikov, Marina; Shen, Shmuel; Ben-Dor, Shifra; Rogachev, Ilana; Aharoni, Asaph; Ast, Tslil; Schuldiner, Maya; Belausov, Eduard; Eshed, Ravit; Ophir, Ron; Sherman, Amir; Frei, Benedikt; Neuhaus, H Ekkehard; Xu, Yimin; Fei, Zhangjun; Giovannoni, Jim; Lewinsohn, Efraim; Tadmor, Yaakov; Paris, Harry S; Katzir, Nurit; Burger, Yosef; Schaffer, Arthur A

    2014-06-05

    Taste has been the subject of human selection in the evolution of agricultural crops, and acidity is one of the three major components of fleshy fruit taste, together with sugars and volatile flavour compounds. We identify a family of plant-specific genes with a major effect on fruit acidity by map-based cloning of C. melo PH gene (CmPH) from melon, Cucumis melo taking advantage of the novel natural genetic variation for both high and low fruit acidity in this species. Functional silencing of orthologous PH genes in two distantly related plant families, cucumber and tomato, produced low-acid, bland tasting fruit, showing that PH genes control fruit acidity across plant families. A four amino-acid duplication in CmPH distinguishes between primitive acidic varieties and modern dessert melons. This fortuitous mutation served as a preadaptive antecedent to the development of sweet melon cultigens in Central Asia over 1,000 years ago.

  13. [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.

  14. [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. PMID:19968099

  15. Miscibility of Quillaja Saponins with other Co-surfactants under Different pH Values.

    PubMed

    Reichert, Corina L; Salminen, Hanna; Leuenberger, Bruno H; Hinrichs, Jörg; Weiss, Jochen

    2015-11-01

    The miscibility behavior of mixed surfactant systems and the influence of extrinsic parameters are crucial for their application as emulsifiers. Therefore, the objective of this study was to evaluate the miscibility behavior of mixed systems composed of commercial Quillaja saponin and a co-surfactant, namely sodium caseinate, pea protein, rapeseed lecithin, or egg lecithin. These mixtures were evaluated macro- and microscopically at different concentration ratios (maximum concentration 5% w/v) at pH 3, 5, and 7 at 25 °C. The individual ingredients were also assessed for their charge properties and surface hydrophobicity. The results showed that Quillaja saponin-caseinate mixtures were miscible only at pH 7, and showed aggregation and precipitation at lower pH due to increasing electrostatic attraction forces. Rheological measurements showed that Quillaja saponin-pea protein mixtures formed gelled structures at all tested pH values mainly via association of hydrophobic patches. Quillaja saponins mixed with rapeseed lecithin were miscible at all tested pH values due to electrostatic repulsion. Quillaja saponin-egg lecithin mixtures aggregated independent of pH and concentration ratio. The microscopic analysis revealed that the lower the pH and the higher the Quillaja saponin ratio, the denser were the formed Quillaja saponin-egg lecithin aggregates. The results are summarized in ternary phase diagrams that provide a useful tool in selecting a surfactant system for food applications. PMID:26458074

  16. Direct interaction between terbium ion and peroxidase in horseradish at different pH values.

    PubMed

    Wang, Lihong; Zhou, Qing; Huang, Xiaohua

    2014-02-01

    Rare earth elements (REEs) entering plant cells can directly interact with peroxidase in plants, which is the structural basis for the decrease in the activity of peroxidase. Different cellular compartments have different pH values. However, little information is available regarding the direct interaction between REEs and peroxidase in plants at different pH values. Here, we investigated the charge distribution on the surface of horseradish peroxidase (HRP) molecule as well as the interaction of terbium ion (Tb(3+), one type of REEs) and HRP at different pH values. Using the molecular dynamics simulation, we found that when the pH value was from 4.0 to 8.0, a large amount of negative charges were intensively distributed on the surface of HRP molecule, and thus, we speculated that Tb(3+) with positive charges might directly interact with HRP at pH 4.0-8.0. Subsequently, using ultraviolet-visible spectroscopy, we demonstrated that Tb(3+) could directly interact with HRP in the simulated physiological solution at pH 7.0 and did not interact with HRP in other solutions at pH 5.0, pH 6.0 and pH 8.0. In conclusion, we showed that the direct interaction between Tb(3+) and HRP molecule depended on the pH value of cellular compartments.

  17. 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…

  18. Rational design of ratiometric near-infrared fluorescent pH probes with various pKa values, based on aminocyanine.

    PubMed

    Myochin, Takuya; Kiyose, Kazuki; Hanaoka, Kenjiro; Kojima, Hirotatsu; Terai, Takuya; Nagano, Tetsuo

    2011-03-16

    Novel ratiometric, near-infrared fluorescent pH probes with various pK(a) values have been designed and synthesized on the basis of aminocyanine bearing a diamine moiety, and their photochemical properties were evaluated. Under acidic conditions, these pH probes showed a 46- to 83-nm red shift of the absorption maximum. This change is sufficiently large to permit their use as ratiometric pH probes, and is reversible, whereas monoamine-substituted aminocyanines showed irreversible changes because of their instability under acidic conditions. Furthermore, the pK(a) values of these probes can be predicted from the calculated pK(a) values of the diamine moieties, obtained from the SciFinder database. This design strategy is very simple and flexible, and should be applicable to develop NIR pH probes for various applications.

  19. Immobilized pH gradients: new pK values of acrylamido buffers in poly(N-acryloylaminoethoxyethanol) matrices.

    PubMed

    Bossi, A; Righetti, P G; Chiari, M

    1994-01-01

    A novel matrix consisting of N-acryloylaminoethoxyethanol, a hydrophilic monomer extremely resistant to hydrolysis, was recently reported by Chiari et al. (Electrophoresis, 1994, 15, 177-186). When using it as a matrix for grafting immobilized pH gradients for isoelectric focusing, a shift in protein spot position was noticed. This was attributed to a shift in pK values of the Immobiline buffers when changing from the standard poly(acrylamide) to a poly(N-acryloylaminoethoxyethanol) matrix. A series of 1 pH unit gradients was constructed, where a single buffering Immobiline was used and titrated with a counterion having a pK removed by at least 3 pH units from the nearest extreme of the generated pH interval. It was noted that all compounds became weaker acids and bases, with a delta pK ranging from -0.02 to -0.06 for the acids (pK 3.6, 4.4, and 4.6) and a delta pK ranging from -0.12 tp -0.20 for the bases. The new pK values for the seven commercially available buffers are thus pK 3.6-->pK 3.58, pK 4.4-->pK 4.36, pK 4.51-->4.45, pK 6.21-->6.09, pK 7.06-->6.94, pK 8.50-->pK 8.37, and pK 9.59-->pK 9.39. These values refer to 10 degrees C in the gel phase, the first value in poly(acrylamide) and the second in poly(N-acryloylaminoethoxyethanol). PMID:7859716

  20. Visible light absorption of TiO{sub 2} materials impregnated with tungstophosphoric acid ethanol–aqueous solution at different pH values. Evidence about the formation of a surface complex between Keggin anion and TiO{sub 2} surfaces

    SciTech Connect

    Rengifo-Herrera, Julián A. Blanco, Mirta N.; Pizzio, Luis R.

    2014-01-01

    Graphical abstract: - Highlights: • TPA impregnation on TiO{sub 2} particles was done at different initial pH values. • Powders characterization evidenced the possible existence of TPA–TiO{sub 2} complexes. • Keggin anion complexed on TiO{sub 2} would be responsible of visible light absorption. - Abstract: TiO{sub 2} particles prepared by the sol–gel method were impregnated at different pH values (1.0, 2.0, 5.0 and 10.0) with a water–ethanol solution (50% V/V) of tungstophosphoric acid (TPA) (0.012 M). Similar preparation was carried out to synthesize TiO{sub 2} impregnated with [WO{sub 4}]{sup 2−} (TiW). These materials were characterized by different techniques such as UV–vis diffuse reflectance spectroscopy (UV–vis DRS), magic angle spinning nuclear magnetic resonance of {sup 31}P ({sup 31}P MAS NMR), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Fourier transform Raman spectroscopy (FT-Raman). Results revealed that TPA–TiO{sub 2} materials exhibit visible light absorption only when impregnation was done at pH 1.0 (TiTPA1) and 2.0 (TiTPA2). TiW powder did not show visible light absorption. XRD patterns show the presence of peaks at 2θ = 25.4° (1 0 1), 37.9° (0 0 4), 47.8° (2 0 0) and 54.3° associated to the anatase phase. Solid NMR, FT-IR and FT-Raman characterization showed that TiTPA1 and TiTPA2 samples contain Keggin ([PW{sub 12}O{sub 40}]{sup 3−}) and lacunary anions ([PW{sub 11}O{sub 39}]{sup 7−}) respectively. On the other hand, FT-Raman results revealed a blue shifting and broadening of the band at 141 cm{sup −1} corresponding to anatase TiO{sub 2} and moreover, a broadening of bands at 900–1100 cm{sup −1} attributed to Keggin structures of TPA. Both spectral changes could be related to the formation of a surface complex between the Keggin anion of TPA and TiO{sub 2} surfaces. This interaction should be responsible for visible light absorption.

  1. Atmospheric Pressure Plasma Jet in Organic Solution: Spectra, Degradation Effects of Solution Flow Rate and Initial pH Value

    NASA Astrophysics Data System (ADS)

    Chen, Bingyan; Zhu, Changping; Chen, Longwei; Fei, Juntao; Gao, Ying; Wen, Wen; Shan, Minglei; Ren, Zhaoxing

    2014-12-01

    The organic compounds of p-nitrophenol (PNP) solution was treated by the active species generated in a stirred reactor by an atmospheric pressure plasma jet (APPJ). The emission intensities of hydroxyl (OH), oxygen (O), nitric oxide (NO), hydrogen (H) and molecular (N2) were measured by optical emission spectroscopy (OES). The relations between the flow rates of the PNP solution and degradation, the degradation effects and initial pH value of the solution were also investigated. Experimental results show that there exist intense emissions of O (777.1 nm), N2 (337.1 nm), OH (306-310 nm) and NO band (200-290 nm) in the region of plasma. Given the treatment time and gas flow rate, the degradation increased as a function of discharge energy and solution flow rate, respectively. The solution flow rate for the most efficient degradation ranged from 1.414 m/s to 1.702 m/s, and contributed very little when it exceeded 2.199 m/s. This indicates the existence of diffusion-controlled reactions at a low solution flow rate and activation-controlled reactions at a high solution flow rate. Moreover, increasing or decreasing the initial pH value of neutral PNP solution (pH=5.95) could improve the degradation efficiency. Treated by APPJ, the PNP solutions with different initial pH values of 5.95, 7.47 and 2.78 turned more acidic in the end, while the neutral solution had the lowest degradation efficiency. This work clearly demonstrates the close coupling of active species, photolysis of ultraviolet, the organic solution flow rate and the initial pH value, and thus is helpful in the study of the mechanism and application of plasma in wastewater treatment.

  2. Disruption of the transmembrane pH gradient--a possible mechanism for the antibacterial action of azelaic acid in Propionibacterium acnes and Staphylococcus epidermidis.

    PubMed

    Bojar, R A; Cunliffe, W J; Holland, K T

    1994-09-01

    The effect of the topical acne treatment azelaic acid on the transmembrane proton gradient (delta pH) of Propionibacterium acnes and Staphylococcus epidermidis was studied in vitro at external pH values found on human skin (pH 4.0-6.0). Bacteria were grown in defined media using continuous culture and delta pH was estimated by measuring the accumulation of [14C] benzoic by the cells using flow dialysis. In both P. acnes and S. epidermidis the addition of 30 mM azelaic acid and the membrane active inhibitors nigericin (150 microM) and CCCP (150 microM) resulted in a rapid release of [14C] label into the dialysate indicating the dissipation of delta pH between external pH values of 4.0-6.0. The addition of 60 mM NaCl as an iso-osmotic control and 150 microM valinomycin did not induce the release of [14C] label. The addition of 30 mM azelaic acid reduced the delta pH of P. acnes by 44% at external pH 4.0 and 28% at external pH 6.0. In S. epidermidis 30 mM azelaic acid reduced delta pH by 88% at external pH 5.0 and 20% at external pH 6.0. Rapid loss of viability occurred in suspensions of P. acnes and S. epidermidis containing 30 mM azelaic acid at pH 4.0 with no viable cells recovered after 60 min incubation. At pH 6.0 little change in viable numbers of P. acnes and S. epidermidis were observed over a 2 h incubation period. The results indicate that the antibacterial activity of azelaic acid is associated with the perturbation of intracellular pH.

  3. Disruption of the transmembrane pH gradient--a possible mechanism for the antibacterial action of azelaic acid in Propionibacterium acnes and Staphylococcus epidermidis.

    PubMed

    Bojar, R A; Cunliffe, W J; Holland, K T

    1994-09-01

    The effect of the topical acne treatment azelaic acid on the transmembrane proton gradient (delta pH) of Propionibacterium acnes and Staphylococcus epidermidis was studied in vitro at external pH values found on human skin (pH 4.0-6.0). Bacteria were grown in defined media using continuous culture and delta pH was estimated by measuring the accumulation of [14C] benzoic by the cells using flow dialysis. In both P. acnes and S. epidermidis the addition of 30 mM azelaic acid and the membrane active inhibitors nigericin (150 microM) and CCCP (150 microM) resulted in a rapid release of [14C] label into the dialysate indicating the dissipation of delta pH between external pH values of 4.0-6.0. The addition of 60 mM NaCl as an iso-osmotic control and 150 microM valinomycin did not induce the release of [14C] label. The addition of 30 mM azelaic acid reduced the delta pH of P. acnes by 44% at external pH 4.0 and 28% at external pH 6.0. In S. epidermidis 30 mM azelaic acid reduced delta pH by 88% at external pH 5.0 and 20% at external pH 6.0. Rapid loss of viability occurred in suspensions of P. acnes and S. epidermidis containing 30 mM azelaic acid at pH 4.0 with no viable cells recovered after 60 min incubation. At pH 6.0 little change in viable numbers of P. acnes and S. epidermidis were observed over a 2 h incubation period. The results indicate that the antibacterial activity of azelaic acid is associated with the perturbation of intracellular pH. PMID:7829407

  4. Benzimidazole-based ratiometric two-photon fluorescent probes for acidic pH in live cells and tissues.

    PubMed

    Kim, Hyung Joong; Heo, Cheol Ho; Kim, Hwan Myung

    2013-11-27

    Many aspects of cell metabolism are controlled by acidic pH. We report a new family of small molecule and ratiometric two photon (TP) probes derived from benzimidazole (BH1-3 and BH1L) for monitoring acidic pH values. These probes are characterized by a strong two-photon excited fluorescence, a marked blue-to-green emission color change in response to pH, pKa values ranging from 4.9 to 6.1, a distinctive isoemissive point, negligible cytotoxicity, and high photostability, thereby allowing quantitative analysis of acidic pH. Moreover, we show that BH1L optimized as a lysosomal-targeted probe allows for direct, real-time estimation of the pH values inside lysosomal compartments in live cells as well as in living mouse brain tissues through the use of two-photon microscopy. These findings demonstrate that these probes will find useful applications in biomedical research.

  5. A theoretical study on the pH dependence of X-ray emission spectra for aqueous acetic acid

    NASA Astrophysics Data System (ADS)

    Nishida, Naohiro; Tokushima, Takashi; Takahashi, Osamu

    2016-04-01

    We performed theoretical calculations to reproduce the site-selective XES spectra for aqueous acetic acid at the oxygen K-edge. The shape of the experimental XES spectra obtained from aqueous acetic acid drastically changed when the pH value was high. Structure sampling of an aqueous acetic acid cluster model was performed by the ab initio molecular dynamics trajectory. Relative XES peak intensities for the core-hole excited state dynamics simulations were calculated using density functional theory. We found that the theoretical XES spectra reproduced well the experimental spectra and that these calculations gave us electronic and molecular structure information about aqueous acetic acid.

  6. Conformational stability of human erythrocyte transglutaminase. Patterns of thermal unfolding at acid and alkaline pH.

    PubMed

    Bergamini, C M; Dean, M; Matteucci, G; Hanau, S; Tanfani, F; Ferrari, C; Boggian, M; Scatturin, A

    1999-12-01

    Tissue-type transglutaminase is irreversibly inactivated during heat treatment. The rate of inactivation is low at pH 7.5; it increases slightly at acid pH (6.1) but much more at alkaline pH (9.0-9.5), suggesting that specific effects take place in the alkaline range, possibly in relation to decreased stability of the transition-state intermediate as pH is raised above 9.0. Differential scanning calorimetry experiments indicate that thermal unfolding of the protein occurs with two separate transitions, involving independent regions of the enzyme. They are assigned to domains 1 and 2 and domains 3 and 4, respectively, by a combination of calorimetric and spectroscopic techniques. When considering the effects of pH, we noted that transglutaminase was unfolded via different pathways at the different pH values considered. At acid pH, the whole structure of the protein was lost irreversibly, with massive aggregation. At neutral and, even more so, at alkaline pH, aggregation was absent (or very limited at high protein concentration) and the loss of secondary structure was dependent on the ionization state of crucial lysine residues. Unfolding at pH 9.5 apparently chiefly involved the N-terminal region, as testified by changes in protein intrinsic fluorescence. In addition, the C-terminal region was destabilized at each pH value tested during thermal unfolding, as shown by digestion with V8 proteinase, which is inactive on the native protein. Evidence was obtained that the N-terminal and C-terminal regions interact with each other in determining the structure of the native protein. PMID:10561600

  7. ESTIMATED NEPTUNIUM SEDIMENT SORPTION VALUES AS A FUNCTION OF PH AND MEASURED BARIUM AND RADIUM KD VALUES

    SciTech Connect

    Kaplan, D.

    2011-01-13

    The objective of this document is to provide traceability and justification for a select few new geochemical data used in the Special Analysis entitled 'Special Analysis for the Dose Assessment of the Final Inventories in Center Slit Trenches One through Five'. Most values used in the Special Analysis came from the traditional geochemical data package, however, some recent laboratory measurements have made it possible to estimate barium K{sub d} values. Additionally, some recent calculations were made to estimate neptunium K{sub d} values as a function of pH. The assumptions, justifications, and calculations needed to generate these new values are presented in this document, and the values are summarized.

  8. Selective production of lactic acid in continuous anaerobic acidogenesis by extremely low pH operation.

    PubMed

    Itoh, Yuya; Tada, Kiyoshi; Kanno, Tohru; Horiuchi, Jun-Ichi

    2012-11-01

    The selective production of lactic acid by anaerobic acidogenesis with low pH control was examined using a chemostat culture. By decreasing culture pH to 3.5 in a chemostat culture containing mixed microbial populations for anaerobic acidogenesis, heterolactic fermentation became dominant, resulting in the selective production of lactic acid and ethanol. This phenomenon was reversible between the acidic and neutral conditions, and was not affected by the dilution rate. The extremely low pH operation was effective for selective lactic acid production in anaerobic acidogenesis.

  9. pH dependence of methyl phosphonic acid, dipicolinic acid, and cyanide by surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Farquharson, Stuart; Gift, Alan; Maksymiuk, Paul; Inscore, Frank E.; Smith, Wayne W.

    2004-03-01

    U.S. and Coalition forces fighting terrorism in Afghanistan and Iraq must consider a wide range of attack scenarios in addition to car bombings. Among these is the intentional poisoning of water supplies to obstruct military operations. To counter such attacks, the military is developing portable analyzers that can identify and quantify potential chemical agents in water supplies at microgram per liter concentrations within 10 minutes. To aid this effort we have been investigating the value of a surface-enhanced Raman spectroscopy based portable analyzer. In particular we have been developing silver-doped sol-gels to generate SER spectra of chemical agents and their hydrolysis products. Here we present SER spectra of methyl phosphonic acid and cyanide as a function of pH, an important factor affecting quantitation measurements, which to our knowledge has not been examined. In addition, dipicolinic acid, a chemical signature associated with anthrax-causing spores, is also presented.

  10. Effect of pH value on particle morphology and electrochemical properties of LiFePO{sub 4} by hydrothermal method

    SciTech Connect

    Song, Qingzhu; Ou, Xiuqin; Wang, Li; Liang, Guangchuan; Wang, Zuorui

    2011-09-15

    Graphical abstract: The pH value of system is adjusted in the range of 2.5-8.8 by using dilute sulfuric acid and ammonia water. The results indicated that the particle exhibits acute angle diamond flake-like morphology at pH = 2.5. With increase of pH value, the particle gradually becomes to round flake-like and irregular flake-like morphology. The optimal sample synthesized at pH = 6.4 exhibits discharge capacities of 151.8 mAh g{sup -1} at 0.2 C rate and 129.3 mAh g{sup -1} at 3 C rate. Highlights: {yields} The pH value of solution affects greatly on particle morphology. {yields} The solubility product determined the transition of interphases. {yields} The disorder of atoms in crystal is affected by pH value. {yields} LiFePO{sub 4} with high capacity could be synthesized at slight acid or neutral conditions. -- Abstract: Lithium iron phosphate was prepared by hydrothermal synthesis using LiOH.H{sub 2}O, FeSO{sub 4}.7H{sub 2}O and H{sub 3}PO{sub 4} as raw materials. The effects of pH value of reaction solution on particle morphology and electrochemical property were investigated. The pH value of the reaction solution was adjusted in the range of 2.5-8.8 by dilute sulfuric acid and ammonia water. The samples were characterized by field-emission scanning electronic microscope (FE-SEM), X-ray powder diffraction (XRD), constant-current charge/discharge cycling tests and chemical analysis. The results indicated that the particles exhibited acute angle diamond flake-like morphology at pH = 2.5, and as the pH value increased, the particle became hexagon flake-like, round flake-like and irregular flake-like morphology gradually. The optimal sample synthesized at pH = 6.4 exhibited discharge capacities of 151.8 mAh g{sup -1} at 0.2 C rate and 129.3 mAh g{sup -1} at 3 C rate. It was found that pH value affected the morphologies and properties of the product by means of different crystal growth rates.

  11. A smart DNA tetrahedron that isothermally assembles or dissociates in response to the solution pH value changes.

    PubMed

    Liu, Zhiyu; Li, Yingmei; Tian, Cheng; Mao, Chengde

    2013-06-10

    This communication reports a DNA tetrahedron whose self-assembly is triggered by an acidic environment. The key element is the formation/dissociation of a short, cytosine (C)-containing, DNA triplex. As the solution pH value oscillates between 5.0 and 8.0, the DNA triplex will form and dissociate that, in turn, leads to assembly or disassembly of the DNA tetrahedron, which has been demonstrated by native polyacrylamide gel electrophoresis (PAGE). We believe that such environment-responsive behavior will be important for potential applications of DNA nanocages such as on-demand drug release.

  12. Effect of pH value on H2Ti2O5/TiO2 composite nanotubes as Pt catalyst support for methanol oxidation

    NASA Astrophysics Data System (ADS)

    Sui, Xu-Lei; Wang, Zhen-Bo; Li, Cun-Zhi; Zhang, Jing-Jia; Zhao, Lei; Gu, Da-Ming

    2014-12-01

    Hydrogenotitanate/titania composite nanotubes (HTNTs) are synthesized from anatase titania power via hydrothermal process at various pH values of acid treatment. The change of HTNTs components is investigated in detail by X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), which reveal that the products are gradually converted from "H2Ti2O5·H2O" phase to "anatase TiO2" phase with the decrease of pH values. Pt based catalysts are prepared by microwave-assisted ethylene glycol method. The effects of pH values on the performance of Pt/C-HTNTs catalysts have been mainly investigated. It has been found that the distribution and electrocatalytic properties of platinum nanoparticles are sensitive to the pH value of acid treatment. The Pt/C-HTNTs catalyst prepared at the acid treatment pH value of 7 exhibits the better electrochemical activity and stability than other catalysts.

  13. Intermonomer flexibility of Ca- and Mg-actin filaments at different pH values.

    PubMed

    Hild, Gábor; Nyitrai, Miklós; Somogyi, Béla

    2002-02-01

    The fluorescence resonance energy transfer parameter, f, is defined as the efficiency of the energy transfer normalized by the quantum yield of the donor in the presence of acceptor. It is possible to characterize the flexibility of the protein matrix between the appropriate fluorescent probes by monitoring the temperature dependence of f. The intermonomer flexibility of the Ca-actin and Mg-actin filaments was characterized by using this method at pH values of 6.5 and 7.4. The protomers were labeled on Cys374 with donor [N-(((iodoacetyl)amino)ethyl)-5-naphthylamine-1-sulfonate; IAEDANS] or acceptor [5-(iodoacetamido)fluorescein; IAF] molecules. The temperature profile of f suggested that the intermonomer flexibility of actin filaments was larger at pH 7.4 than pH 6.5 in the case of Mg-F-actin while this difference was absent in the case of Ca-F-actin. More rigid intermonomer connection was identified at both pH values between the protomers of Mg-F-actin compared to the Ca-F-actin. The results were further supported by time dependent fluorescence measurements made on IAEDANS and IAF labeled Mg- and Ca-actin filaments at pH 6.5 and 7.4. Our spectroscopic results may suggest that the altered function of muscle following the change of pH within the muscle cells under physiological or pathological conditions might be affected by the modified dynamic properties of the magnesium saturated actin filaments. The change of the intracellular pH does not have an effect on the intermonomer flexibility of the Ca-actin filaments.

  14. Measurement of the pH value in pork meat early postmortem by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Scheier, R.; Schmidt, H.

    2013-05-01

    The pH of a muscle is an accepted parameter to identify normal and deviating meat qualities. In this work, Raman spectroscopy is shown to be suitable for the non-invasive measurement of the early postmortem pH of meat. Raman spectra of ten pork semimembranosus muscles were recorded with a portable handheld device 0.5-24 h postmortem. The spectra were correlated with pH and lactate kinetics measured in parallel. Seven of the muscles were normal, two exhibited accelerated glycolysis and one showed absence of acidification. The pH decline with time could be calculated from the Raman spectra with the Henderson-Hasselbalch equation using only two signals of phosphate vibrations at 980 and 1,080 cm-1 with a close correlation for each muscle, but larger variations between animals. More robust and better correlations for all muscles were obtained with a linear model based on 11 signals from lactate, lactic acid, phosphate, a carbonyl band and nucleotides resulting in R 2 = 0.78 and RMSECV = 0.2 or a partial least-square model using the complete spectrum ( R 2 = 0.94 and RMSECV = 0.2). These results show the potential of Raman spectroscopy for an online detection of the pH and thus meat qualities during meat processing.

  15. [Investigation of apomyoglobin stability depending on urea and temperature at two different pH values].

    PubMed

    Baryshnikova, E N; Sharanov, M G; Kashparov, I A; Il'ina, N B; Bychkova, V E

    2005-01-01

    Equilibrium unfolding of apomyoglobin by urea was investigated in the temperature range from 5 to 25 degrees C at two pH values. The thermodynamic parameters of the apomyoglobin native-unfolded state transition were determined. Conformational changes in the protein structure were monitored by tryptophan fluorescence and far UV circular dichroism. Apomyoglobin preserves its native conformation at pH 5.7 and 6.2 in the temperature range used. It was shown that the apomyoglobin stability and its unfolding cooperativity are substantially lower at 5 degrees C than at other temperatures. This fact should be taken in account at the investigation of apomyoglobin.

  16. Solid-phase microextraction with pH adjustment for the determination of aromatic acids and bases in water.

    PubMed

    van Doorn, H; Grabanski, C B; Miller, D J; Hawthorne, S B

    1998-12-31

    Adjusting the pH of water samples before performing solid-phase microextraction (SPME) analysis can be used to selectively extract organic acids (at pH 2) and bases (at pH 12). Sorption behavior of test organics is predictable based on the acid dissociation constant in water. In general, polyacrylate (PA) and Carbowax-divinylbenzene (CW-DVB) show substantially higher fiber/water sorption coefficients (Kd values) than a polydimethylsiloxane (PDMS) coated fiber. Gas chromatography-flame ionization detection (GC-FID) detection limits with the CW-DVB sorbent are approximately 0.5 to 10 ng/ml in a 2-ml water sample for a variety of aromatic amines, phenols, and chlorinated phenols, and are approximately 1 to 50 ng/ml for the same solutes using the PA sorbent. However, the PA fiber is more selective (depending on the water pH) for the acid or base components than the CW-DVB fiber. With proper pH adjustment, the recovery of spiked aromatic amines and phenols from a surface wetlands water ranged from 73 to 118% of the known values, with a precision (R.S.D.) of approximately 5 to 20%. SPME quantitation of phenols in a coal gasification wastewater using a PA fiber also gave excellent agreement with conventional methylene chloride extraction, although continued use of a single fiber with this wastewater led to poorer precision.

  17. Improvement of physicomechanical properties of carbamazepine by recrystallization at different pH values.

    PubMed

    Javadzadeh, Yousef; Mohammadi, Ameneh; Khoei, Nazaninossadat Seyed; Nokhodchi, Ali

    2009-06-01

    The morphology of crystals has an appreciable impact role on the physicochemical properties of drugs. Drug properties such as flowability, dissolution, hardness and bioavailability may be affected by crystallinity behaviours of drugs. The objective of this study was to achieve an improved physicomechanical property of carbamazepine powder through recrystallization from aqueous solutions at different pH values. For this purpose, carbamazapine was recrystallized from aqueous solutions at different pH values (1, 7, 11). The morphology of crystals was investigated using scanning electron microscopy; X-ray powder diffraction (XRPD) was used to identify polymorphism; thermodynamic properties were analyzed using differential scanning calorimetery (DSC). Dissolution rate was determined using USP dissolution apparatus. Mechanical behavior of recrystallized carbamazepine powders was investigated by making tablets under different compaction pressure and measuring their hardness. SEM studies showed that the carbamazepine crystallization in different media affected the morphology and size of carbamazepine crystals. The shape of carbamazepine crystals changed from flaky or thin plate-like to needle shape. XRPD and DSC results ruled out any crystallinity changes occurring due to the temperature during recrystallization procedure or pH of crystallization media. The crushing strength of tablets indicated that all of the recrystallized carbamazepine samples had better compactiblity than the original carbamazepine powder. In vitro dissolution studies of carbamazepine samples showed a higher dissolution rate for carbamazepine crystals obtained from media with pH 11 and 1. Carbamazepine particles recrystallized from aqueous solutions of different pH values (all media) appeared to have superior mechanical properties to those of the original carbamazepine sample.

  18. 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.

  19. Copper-catalyzed oxidation of a structured lipid-based emulsion containing alpha-tocopherol and citric acid: influence of pH and NaCl.

    PubMed

    Osborn-Barnes, Hannah T; Akoh, Casimir C

    2003-11-01

    The effects of salt and pH on copper-catalyzed lipid oxidation in structured lipid-based emulsions were evaluated. Ten percent oil-in-water emulsions were formulated with a canola oil/caprylic acid structured lipid and stabilized with 0.5% whey protein isolate. alpha-Tocopherol and citric acid were added to the emulsions to determine how changes in pH or the addition of NaCl affected their antioxidant activity. The peroxide values and anisidine values of emulsions stored at 50 degrees C were measured over an 8-day period. Increased lipid oxidation occurred in the pH 7.0 emulsions and when 0.5 M NaCl was added to the pH 3.0 samples. Adding alpha-tocopherol, citric acid, or a combination of the two compounds slowed the formation of hydroperoxides and their subsequent decomposition products in pH 3.0 emulsions.

  20. First-principles calculation of thermodynamic stability of acids and bases under pH environment: A microscopic pH theory

    NASA Astrophysics Data System (ADS)

    Kim, Yong-Hyun; Kim, Kwiseon; Zhang, S. B.

    2012-04-01

    Despite being one of the most important thermodynamic variables, pH has yet to be incorporated into first-principles thermodynamics to calculate stability of acidic and basic solutes in aqueous solutions. By treating the solutes as defects in homogeneous liquids, we formulate a first-principles approach to calculate their formation energies under proton chemical potential, or pH, based on explicit molecular dynamics. The method draws analogy to first-principle calculations of defect formation energies under electron chemical potential, or Fermi energy, in semiconductors. From this, we propose a simple pictorial representation of the general theory of acid-base chemistry. By performing first-principles molecular dynamics of liquid water models with solutes, we apply the formulation to calculate formation energies of various neutral and charged solutes such as H+, OH-, NH3, NH4+, HCOOH, and HCOO- in water. The deduced auto-dissociation constant of water and the difference in the pKa values of NH3 and HCOOH show good agreement with known experimental values. Our first-principles approach can be further extended and applied to other bio- and electro-chemical molecules such as amino acids and redox reaction couples that could exist in aqueous environments to understand their thermodynamic stability.

  1. First-Principles Calculation of Thermodynamic Stability of Acids and Bases under pH Environment: A Microscopic pH Theory

    SciTech Connect

    Kim, Y. H.; Kim, K.; Zhang, S. B.

    2012-04-07

    Despite being one of the most important thermodynamic variables, pH has yet to be incorporated into first-principles thermodynamics to calculate stability of acidic and basic solutes in aqueous solutions. By treating the solutes as defects in homogeneous liquids, we formulate a first-principles approach to calculate their formation energies under proton chemical potential, or pH, based on explicit molecular dynamics. The method draws analogy to first-principle calculations of defect formation energies under electron chemical potential, or Fermi energy, in semiconductors. From this, we propose a simple pictorial representation of the general theory of acid-base chemistry. By performing first-principles molecular dynamics of liquid water models with solutes, we apply the formulation to calculate formation energies of various neutral and charged solutes such as H{sup +}, OH{sup -}, NH{sub 3}, NH{sub 4}{sup +}, HCOOH, and HCOO{sup -} in water. The deduced auto-dissociation constant of water and the difference in the pKa values of NH{sub 3} and HCOOH show good agreement with known experimental values. Our first-principles approach can be further extended and applied to other bio- and electro-chemical molecules such as amino acids and redox reaction couples that could exist in aqueous environments to understand their thermodynamic stability.

  2. First-principles calculation of thermodynamic stability of acids and bases under pH environment: a microscopic pH theory.

    PubMed

    Kim, Yong-Hyun; Kim, Kwiseon; Zhang, S B

    2012-04-01

    Despite being one of the most important thermodynamic variables, pH has yet to be incorporated into first-principles thermodynamics to calculate stability of acidic and basic solutes in aqueous solutions. By treating the solutes as defects in homogeneous liquids, we formulate a first-principles approach to calculate their formation energies under proton chemical potential, or pH, based on explicit molecular dynamics. The method draws analogy to first-principle calculations of defect formation energies under electron chemical potential, or Fermi energy, in semiconductors. From this, we propose a simple pictorial representation of the general theory of acid-base chemistry. By performing first-principles molecular dynamics of liquid water models with solutes, we apply the formulation to calculate formation energies of various neutral and charged solutes such as H(+), OH(-), NH(3), NH(4)(+), HCOOH, and HCOO(-) in water. The deduced auto-dissociation constant of water and the difference in the pKa values of NH(3) and HCOOH show good agreement with known experimental values. Our first-principles approach can be further extended and applied to other bio- and electro-chemical molecules such as amino acids and redox reaction couples that could exist in aqueous environments to understand their thermodynamic stability. PMID:22482545

  3. 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

  4. Total alkalinity versus buffer value (capacity) as a sensitivity indicator for fresh waters receiving acid rain

    SciTech Connect

    Faust, S.D.

    1983-09-01

    The frequently stated idea that total alkalinity is a measure of the buffer capacity of a natural water is refuted. Total alkalinity is a measure of the acid neutralizing capacity, equivalents/liter, of a water. In natural waters, the carbonate system provides most of this neutralizing capacity. In as much as the pH values of natural fresh waters lie below 8.3, the total alkalinity is, for all intents and purposes, the total bicarbonate content. Any contributions of carbonate and hydroxide to total alkalinity are nil. The buffer capacity or buffer value is the relation between the increment of a strong base, or strong acid, that causes a one unit change in the pH value. The values of total alkalinity and pH, considered individually cannot give an accurate assessment of the impact of acid deposition on a natural water. Rather it is necessary to combine the pH and alkalinity values into the beta concept in order to assess accurately and to calculate the capacity of a natural water to resist the impact of acid deposition. An analytical determination of total alkalinity is given with an application of the beta value. 17 references, 2 figures, 4 tables.

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

    PubMed Central

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

    2007-01-01

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

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

    USGS Publications Warehouse

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

    2007-01-01

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

  7. Dual effect of organic acids as a function of external pH in Oenococcus oeni.

    PubMed

    Augagneur, Yoann; Ritt, Jean-François; Linares, Daniel M; Remize, Fabienne; Tourdot-Maréchal, Raphaëlle; Garmyn, Dominique; Guzzo, Jean

    2007-08-01

    In this study we analyzed under various pH conditions including low pH, the effects of L-malic acid and citric acid, combined or not, on the growth, the proton motive force components and the transcription level of selected genes of the heterolactic bacterium Oenococcus oeni. It is shown here that L-malate enhanced the growth yield at pH equal or below 4.5 while the presence of citrate in media led to a complete and unexpected inhibition of the growth at pH 3.2. Nevertheless, whatever the growth conditions, both L-malate and citrate participated in the enhancement of the transmembrane pH gradient, whereas the membrane potential decreased with the pH. These results suggested that it was not citrate that was directly responsible for the inhibition observed in cultures done at low pH, but probably its end products. This was confirmed since, in media containing L-malate, the addition of acetate substantially impaired the growth rate of the bacterium and slightly the membrane potential and pH gradient. Finally, study of the expression of genes involved in the metabolism of organic acids showed that at pH 4.5 and 3.2 the presence of L-malate led to an increased amount of mRNA of mleP encoding a malate transporter.

  8. Retention of ionizable compounds on HPLC. 5. pH scales and the retention of acids and bases with acetonitrile-water mobile phases

    PubMed

    Espinosa; Bosch; Roses

    2000-11-01

    The pH calibration procedures that lead to the different pH scales in acetonitrile-water mixtures used as mobile phases in reversed-phase liquid chromatography are discussed. Appropriate buffers of known pH value in acetonitrile-water mixtures are selected and used to establish the relationship (delta values) between the two rigorous acetonitrile-water pH scales: sspH and wspH (pH measured in acetonitrile-water mixtures and referred to acetonitrile-water or water, respectively, as standard state). These delta values allow one to convert pH values measured in acetonitrile-water with electrode systems calibrated with aqueous buffers (wspH scale) to sspH values, which are directly related to the thermodynamic acid-base constants. This offers an easy way to measure the pH of acetonitrile-water mobile phases and to relate this pH to the chromatographic retention of acids and bases through the thermodynamic acid-base constants. The relationships are tested for the variation of the retention of acids and bases with the pH of the mobile phase at several mobile-phase compositions and favorably compared with the relationships obtained with the common wwpH scale (pH measured in the aqueous buffer before mixing it with the organic modifier). The use of the rigorous sspH and wspH scales allows one to explain the retention behavior of bases, which in many instances cannot be justified from the pH measurement in the ill-founded wwpH scale. PMID:11080863

  9. Retention of ionizable compounds on HPLC. 5. pH scales and the retention of acids and bases with acetonitrile-water mobile phases

    PubMed

    Espinosa; Bosch; Roses

    2000-11-01

    The pH calibration procedures that lead to the different pH scales in acetonitrile-water mixtures used as mobile phases in reversed-phase liquid chromatography are discussed. Appropriate buffers of known pH value in acetonitrile-water mixtures are selected and used to establish the relationship (delta values) between the two rigorous acetonitrile-water pH scales: sspH and wspH (pH measured in acetonitrile-water mixtures and referred to acetonitrile-water or water, respectively, as standard state). These delta values allow one to convert pH values measured in acetonitrile-water with electrode systems calibrated with aqueous buffers (wspH scale) to sspH values, which are directly related to the thermodynamic acid-base constants. This offers an easy way to measure the pH of acetonitrile-water mobile phases and to relate this pH to the chromatographic retention of acids and bases through the thermodynamic acid-base constants. The relationships are tested for the variation of the retention of acids and bases with the pH of the mobile phase at several mobile-phase compositions and favorably compared with the relationships obtained with the common wwpH scale (pH measured in the aqueous buffer before mixing it with the organic modifier). The use of the rigorous sspH and wspH scales allows one to explain the retention behavior of bases, which in many instances cannot be justified from the pH measurement in the ill-founded wwpH scale.

  10. Why Not Replace pH and pOH by Just One Real Acidity Grade, AG?

    NASA Astrophysics Data System (ADS)

    van Lubeck, Henk

    1999-07-01

    The definition of pH according to Sörensen (1909) as pH = -log [H+] offers some striking disadvantages to beginning students in a chemistry course, especially those with no knowledge of logarithms. They will face some puzzling consequences of this definition such as (i) pH of a neutral solution equals 7.0, a value which changes with temperature, and (ii) pH of an acidic solution will rise after dilution. The corresponding disadvantages hold good for pOH in alkaline solutions. These disadvantages disappear after replacing pH and pOH by AG, the acidity grade: AG = log [H+]/[OH-]. AG of neutral solutions equals 0 at all temperatures, whereas AG of acidic solutions is positive and of alkaline solutions, negative. AG offers some other minor advantages as well. Anybody using AG in calculations needs some knowledge of chemical equilibrium, in particular the reversible heterolytic dissociation of water. However, breaking with a long tradition appears to be the major obstacle to an introduction of AG.

  11. Characterization of a recombinant flocculent Saccharomyces cerevisiae strain that co-ferments glucose and xylose: II. influence of pH and acetic acid on ethanol production.

    PubMed

    Matsushika, Akinori; Sawayama, Shigeki

    2012-12-01

    The inhibitory effects of pH and acetic acid on the co-fermentation of glucose and xylose in complex medium by recombinant flocculent Saccharomyces cerevisiae MA-R4 were evaluated. In the absence of acetic acid, the fermentation performance of strain MA-R4 was similar between pH 4.0-6.0, but was negatively affected at pH 2.5. The addition of acetic acid to batch cultures resulted in negligible inhibition of several fermentation parameters at pH 6.0, whereas the interactive inhibition of pH and acetic acid on the maximum cell and ethanol concentrations, and rates of sugar consumption and ethanol production were observed at pH levels below 5.4. The inhibitory effect of acetic acid was particularly marked for the consumption rate of xylose, as compared with that of glucose. With increasing initial acetic acid concentration, the ethanol yield slightly increased at pH 5.4 and 6.0, but decreased at pH values lower than 4.7. Notably, ethanol production was nearly completely inhibited under low pH (4.0) and high acetic acid (150-200 mM) conditions. Together, these results indicate that the inhibitory effects of acetic acid and pH on ethanol fermentation by MA-R4 are highly synergistic, although the inhibition can be reduced by increasing the medium pH. PMID:23076570

  12. Impact of a Glycolic Acid-Containing pH 4 Water-in-Oil Emulsion on Skin pH.

    PubMed

    Behm, Barbara; Kemper, Michael; Babilas, Philipp; Abels, Christoph; Schreml, Stephan

    2015-01-01

    The skin pH is crucial for physiological skin functions. A decline in stratum corneum acidity, as observed in aged or diseased skin, may negatively affect physiological skin functions. Therefore, glycolic acid-containing water-in-oil (W/O) emulsions adjusted to pH 4 were investigated regarding their effect on normal or increased skin pH. A pH 4 W/O emulsion was applied on three areas with pathologically increased skin surface pH in diabetics (n = 10). Further, a 28-day half-side trial (n = 30) was performed to test the long-term efficacy and safety of a pH 4 W/O emulsion (n = 30). In summary, the application of a pH 4 W/O emulsion reduced the skin pH in healthy, elderly and diabetic subjects, which may improve epidermal barrier functions.

  13. Molecular Dynamics Simulations Capture the Misfolding of the Bovine Prion Protein at Acidic pH

    PubMed Central

    Cheng, Chin Jung; Daggett, Valerie

    2014-01-01

    Bovine spongiform encephalopathy (BSE), or mad cow disease, is a fatal neurodegenerative disease that is transmissible to humans and that is currently incurable. BSE is caused by the prion protein (PrP), which adopts two conformers; PrPC is the native innocuous form, which is α-helix rich; and PrPSc is the β-sheet rich misfolded form, which is infectious and forms neurotoxic species. Acidic pH induces the conversion of PrPC to PrPSc. We have performed molecular dynamics simulations of bovine PrP at various pH regimes. An acidic pH environment induced conformational changes that were not observed in neutral pH simulations. Putative misfolded structures, with nonnative β-strands formed in the flexible N-terminal domain, were found in acidic pH simulations. Two distinct pathways were observed for the formation of nonnative β-strands: at low pH, hydrophobic contacts with M129 nucleated the nonnative β-strand; at mid-pH, polar contacts involving Q168 and D178 facilitated the formation of a hairpin at the flexible N-terminus. These mid- and low pH simulations capture the process of nonnative β-strand formation, thereby improving our understanding of how PrPC misfolds into the β-sheet rich PrPSc and how pH factors into the process. PMID:24970211

  14. The cell transmembrane pH gradient in tumors enhances cytotoxicity of specific weak acid chemotherapeutics.

    PubMed

    Kozin, S V; Shkarin, P; Gerweck, L E

    2001-06-15

    The extracellular pH is lower in tumor than in normal tissue, whereas their intracellular pH is similar. In this study, we show that the tumor-specific pH gradient may be exploited for the treatment of cancer by weak acid chemotherapeutics. i.v.-injected glucose substantially decreased the electrode estimated extracellular pH in a xenografted human tumor while its intracellular pH, evaluated by (31)P magnetic resonance spectroscopy, remained virtually unchanged. The resulting increase in the average cell pH gradient caused a parallel increase in tumor growth delay by the weak acid chlorambucil (CHL). Regardless of glucose administration, the effect of CHL was significantly greater in tumors preirradiated with a large dose of ionizing radiation. This suggests that CHL was especially pronounced in radioresistant hypoxic cells possessing a larger transmembrane pH gradient. These results indicate that the naturally occurring cell pH gradient difference between tumor and normal tissue is a major and exploitable determinant of the uptake of weak acids in the complex tumor microenvironment. The use of such drugs may be especially effective in combination with radiation.

  15. Molecular dynamics simulations capture the misfolding of the bovine prion protein at acidic pH.

    PubMed

    Cheng, Chin Jung; Daggett, Valerie

    2014-01-01

    Bovine spongiform encephalopathy (BSE), or mad cow disease, is a fatal neurodegenerative disease that is transmissible to humans and that is currently incurable. BSE is caused by the prion protein (PrP), which adopts two conformers; PrPC is the native innocuous form, which is α-helix rich; and PrPSc is the β-sheet rich misfolded form, which is infectious and forms neurotoxic species. Acidic pH induces the conversion of PrPC to PrPSc. We have performed molecular dynamics simulations of bovine PrP at various pH regimes. An acidic pH environment induced conformational changes that were not observed in neutral pH simulations. Putative misfolded structures, with nonnative β-strands formed in the flexible N-terminal domain, were found in acidic pH simulations. Two distinct pathways were observed for the formation of nonnative β-strands: at low pH, hydrophobic contacts with M129 nucleated the nonnative β-strand; at mid-pH, polar contacts involving Q168 and D178 facilitated the formation of a hairpin at the flexible N-terminus. These mid- and low pH simulations capture the process of nonnative β-strand formation, thereby improving our understanding of how PrPC misfolds into the β-sheet rich PrPSc and how pH factors into the process. PMID:24970211

  16. Thermoluminescence Characteristics of Nanocrystalline LiF Phosphors Synthesized at Different pH Values

    SciTech Connect

    Sharma, A. K.; Dogra, R.; Kumar, Shalendra; Mishra, S. K.; Lochab, S. P.; Kumar, Ravi

    2011-07-15

    Nanocrystalline lithium fluoride (LiF) phosphors have been prepared by the chemical co-precipitation method at different pH values (7.0, 8.0, 9.0). The formation of nanocrystalline structure has been confirmed by X-ray diffraction and transmission electron microscope. The thermolumniscence (TL) properties of LiF phosphors irradiated with gamma rays at different doses have been studied. The analysis of TL glow curve has revealed the existence of two well resolved glow peaks, one low temperature peak at around 145 deg. C and other one at higher temperature around 375 deg. C. The LiF nano-crystallites synthesized at 8.00 pH have been found to show maximum TL intensity at studied gamma doses (0.1 Gy-15 Gy).

  17. Acidic extracellular pH neutralizes the autophagy-inhibiting activity of chloroquine

    PubMed Central

    Pellegrini, Paola; Strambi, Angela; Zipoli, Chiara; Hägg-Olofsson, Maria; Buoncervello, Maria; Linder, Stig; De Milito, Angelo

    2014-01-01

    Acidic pH is an important feature of tumor microenvironment and a major determinant of tumor progression. We reported that cancer cells upregulate autophagy as a survival mechanism to acidic stress. Inhibition of autophagy by administration of chloroquine (CQ) in combination anticancer therapies is currently evaluated in clinical trials. We observed in 3 different human cancer cell lines cultured at acidic pH that autophagic flux is not blocked by CQ. This was consistent with a complete resistance to CQ toxicity in cells cultured in acidic conditions. Conversely, the autophagy-inhibiting activity of Lys-01, a novel CQ derivative, was still detectable at low pH. The lack of CQ activity was likely dependent on a dramatically reduced cellular uptake at acidic pH. Using cell lines stably adapted to chronic acidosis we could confirm that CQ lack of activity was merely caused by acidic pH. Moreover, unlike CQ, Lys-01 was able to kill low pH-adapted cell lines, although higher concentrations were required as compared with cells cultured at normal pH conditions. Notably, buffering medium pH in low pH-adapted cell lines reverted CQ resistance. In vivo analysis of tumors treated with CQ showed that accumulation of strong LC3 signals was observed only in normoxic areas but not in hypoxic/acidic regions. Our observations suggest that targeting autophagy in the tumor environment by CQ may be limited to well-perfused regions but not achieved in acidic regions, predicting possible limitations in efficacy of CQ in antitumor therapies. PMID:24492472

  18. Control of diapause by acidic pH and ammonium accumulation in the hemolymph of Antarctic copepods.

    PubMed

    Schründer, Sabine; Schnack-Schiel, Sigrid B; Auel, Holger; Sartoris, Franz Josef

    2013-01-01

    Life-cycles of polar herbivorous copepods are characterised by seasonal/ontogenetic vertical migrations and diapause to survive periods of food shortage during the long winter season. However, the triggers of vertical migration and diapause are still far from being understood. In this study, we test the hypothesis that acidic pH and the accumulation of ammonium (NH4 (+)) in the hemolymph contribute to the control of diapause in certain Antarctic copepod species. In a recent study, it was already hypothesized that the replacement of heavy ions by ammonium is necessary for diapausing copepods to achieve neutral buoyancy at overwintering depth. The current article extends the hypothesis of ammonium-aided buoyancy by highlighting recent findings of low pH values in the hemolymph of diapausing copepods with elevated ammonium concentrations. Since ammonia (NH3) is toxic to most organisms, a low hemolymph pH is required to maintain ammonium in the less toxic ionized form (NH4 (+)). Recognizing that low pH values are a relevant factor reducing metabolic rate in other marine invertebrates, the low pH values found in overwintering copepods might not only be a precondition for ammonium accumulation, but in addition, it may insure metabolic depression throughout diapause. PMID:24143238

  19. Experimental evaluation of the contribution of acidic pH and Fe concentration to the structure, function and tolerance to metals (Cu and Zn) exposure in fluvial biofilms.

    PubMed

    Luís, Ana Teresa; Bonet, Berta; Corcoll, Natàlia; Almeida, Salomé F P; da Silva, Eduardo Ferreira; Figueira, Etelvina; Guasch, Helena

    2014-09-01

    An indoor channel system was colonised with fluvial biofilms to study the chronic effects of high Fe and SO4(2-) concentrations and acidic pH, the water chemistry in the surrounding streams of Aljustrel mining area (Alentejo, Portugal), and their contribution to community (in)tolerance to metal toxicity by short-term experiments with Cu and Zn. Biofilms were subjected to four different treatments during 8 weeks: high Fe and SO4(2-) concentrations (1 mg Fe l(-1)+ 700 mg SO4(2-) l(-1)) and acidic pH, high Fe and SO4(2-) at alkaline pH; lower Fe and SO4(2-) at acidic pH: and lower Fe and SO4(2-) concentrations at alkaline pH as negative control. During chronic exposure, acidic pH affected growth negatively, based on low values of algal biomass and the autotrophic index, high values of the antioxidant enzyme activities and low diversity diatom communities, dominated by acidophilic species (Pinnularia aljustrelica) in acidic treatments, being the effects more marked with high Fe and SO4(2-). Co-tolerance to metals (Cu and Zn) was also shown in biofilms from the acidic treatments, contrasting with the higher sensitivity observed in the alkaline treatments. We can conclude that the Aljustrel mining area acidic environment limits algal growth and exerts a strong selection pressure on the community composition which is in turn, more tolerant to metal exposure. PMID:25011920

  20. 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. PMID:3681570

  1. 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.

  2. Effect of marination on CIE L* and pH values of chicken breast pectoralis major with different color lightness

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Color lightness (CIE L* values) and pH are widely used as quality indicators for raw poultry breast fillets (pectoralis major). The objective of this study was to evaluate the effects of vacuum-tumbling marination on L* and pH values of raw chicken breast meat with different color lightness. Early ...

  3. Effect of marination on CIE L* and pH values of chicken breast pectoralis major with different color lightness

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Color lightness (CIE L* values) and pH are widely used as quality indicators for raw poultry breast fillets (pectoralis major). The objective of this study was to evaluate the effects of vacuum-tumbling marination on L* and pH values of raw chicken breast meat with different color lightness. Early d...

  4. [Effects of pH value on the adsorption and degradation of 2, 4-DCP by nanoscale zero-valent iron].

    PubMed

    Feng, Li; Ge, Xiao-Peng; Wang, Dong-Sheng; Tang, Hong-Xiao

    2012-01-01

    To evaluate the effect of pH on the degradation of 2,4-DCP by zero-valent iron nanoparticles (with the particle size of 30-40 nm in diameter) samples were taken for TEM, SEM-EDX, and ICP-OES analysis and investigated on the particle morphology changes and 2,4-DCP removal under different pH conditions. It is shown that iron nanoparticles agglomerate from individual particles and tiny clusters into massive aggregate assemblies with their surfaces oxidized and coated by the needle-like rotten iron oxide products (FeOOH) in the degradation process, which will block up a further reaction of 2,4-DCP dechlorination, while the low pH value condition in acidic system can effectively suppress particles aggregation and the surface oxidation, although iron loss in the solid phase is somehow inevitable. Large quantity of Fe2+ ions soaked out from iron nanoparticles significantly promote 2,4-DCP removal by reduction, and the solution pH tends to go up in the reaction process. Acidic conditions facilitate 2,4-DCP dechlorination, and the removal efficiency became higher with the pH reduced, in which 90% of 2,4-DCP removal is reached in 24 h under the pH value of 3.

  5. The absorption of acetylsalicylic acid from the stomach in relation to intragastric pH.

    PubMed

    Dotevall, G; Ekenved, G

    1976-01-01

    A comparative study on the effect of a buffered (pH 6.5) and an unbuffered (pH 2.9) solution of acetylsalicylic acid (ASA) on gastric pH, gastric emptying, and gastric absorption of ASA was performed in 10 healthy volunteers. Gastric pH was recorded using radiotelemetry. Gastric emptying and gastric absorption was studied with an aspiration technique and phenol red as nonabsorbable marker. Administration of the unbuffered solution to the fasting subjects resulted in a gastric pH of about 2 and absorption of ASA from the stomach was found to occur. The buffered solution of ASA increased gastric pH to above 5 and gastric absorption of ASA was found to be significantly less than after the unbuffered solution. The buffered solution was emptied from the stomach more rapidly than the unbuffered one. PMID:12558

  6. Adaptive enhancement of amino acid uptake and exodus by thymic lymphocytes: influence of pH.

    PubMed

    Peck, W A; Rockwell, L H; Lichtman, M A

    1976-11-01

    Entry of certain free amino acids (alpha aminoisobutyric acid (AIB), alanine and proline), but not of leucine into rat thymic lymphocytes increased progressively when the cells were incubated in amino acid deficient medium. Actinomycin D, cycloheximide, or a high concentration of AIB abolished the time-related increase in AIB accumulation, whereas exposure to a high concentration of leucine had no effect. This phenomenon could not be attributed to a progressive alteration in the nature of the incubation medium nor to reduced transinhibition of AIB uptake. The exodus of AIB also increased with time, but to a smaller degree than AIB entry. Initial rates of AIB entry and exodus increased with increases in the pH of the incubation medium over the range 6.5-8.0. The effects of pH on entry and exodus were time-related, increasing progressively oveb nullified the magnified time related increments in AIB transport caused by prolonged incubation at pH 8.0. The influence of a given pH on transport of AIB decreased rapidly when the cells were transferred to medium of another pH, but this tendency diminished the longer the cells were exposed to the initial pH. pH influenced the entry of alanine and proline in the same fashion as that of AIB, but did not affect leucine entry. These results indicate that thymic lymphocytes exhibit adaptive enhancement in the accumulation of free amino acids that are transported largley by the A or alanine-preferring system, and that the adaptive process involves both entry and exodus. Moreover, alterations in pH modify entry and exodus of these same amino acids, profoundly affect the magnitude of time-released increases, and may induce fundamental changes in the mechanism(s) serving amino acid transport.

  7. Toxicity and bioaccumulation of copper in Limnodrilus hoffmeisteri under different pH values: Impacts of perfluorooctane sulfonate.

    PubMed

    Meng, Lingjun; Yang, Shaogui; Feng, Mingbao; Qu, Ruijuan; Li, Yong; Liu, Jiaoqin; Wang, Zunyao; Sun, Cheng

    2016-03-15

    Aquatic oligochaete Limnodrilus hoffmeisteri (L. hoffmeisteri) has been commonly used as a lethal and/or sub-lethal toxicological model organism in ecological risk assessments in contaminated water environments. In this study, experiments were conducted to investigate the potential toxic effects of copper (Cu(II)) with or without perfluorooctane sulfonate (PFOS) under different pH values (6.0, 7.0 and 8.0) on LC50, bioaccumulation, and oxidative stress biomarkers in L. hoffmeisteri after 3 and 7 days. The LC50 values of Cu(II) decreased with the increasing pH and the addition of PFOS. After each exposure, increasing bioaccumulation of Cu(II) in L. hoffmeisteri was observed in the combined exposure treatments, whereas the bioaccumulation of PFOS decreased. Moreover, the activity of superoxide dismutase, the level of glutathione, and the content of malondialdehyde were significantly altered after these exposures, possibly indicating that the bioaccumulation of Cu(II) and PFOS caused adverse effects on antioxidant defenses of L. hoffmeisteri. The integrated biomarker response index, indicates that the combined effect was proposed as synergism, which is coincided with the results of toxic unit. Moreover, this work showed that aquatic environment may become more livable when water conditions changed from acidic to near-neutral or alkaline.

  8. Acidic pH promotes oligomerization and membrane insertion of the BclXL apoptotic repressor.

    PubMed

    Bhat, Vikas; Kurouski, Dmitry; Olenick, Max B; McDonald, Caleb B; Mikles, David C; Deegan, Brian J; Seldeen, Kenneth L; Lednev, Igor K; Farooq, Amjad

    2012-12-01

    Solution pH is believed to serve as an intricate regulatory switch in the induction of apoptosis central to embryonic development and cellular homeostasis. Herein, using an array of biophysical techniques, we provide evidence that acidic pH promotes the assembly of BclXL apoptotic repressor into a megadalton oligomer with a plume-like appearance and harboring structural features characteristic of a molten globule. Strikingly, our data reveal that pH tightly modulates not only oligomerization but also ligand binding and membrane insertion of BclXL in a highly subtle manner. Thus, while oligomerization and the accompanying molten globular content of BclXL is least favorable at pH 6, both of these structural features become more pronounced under acidic and alkaline conditions. However, membrane insertion of BclXL appears to be predominantly favored under acidic conditions. In a remarkable contrast, while ligand binding to BclXL optimally occurs at pH 6, it is diminished by an order of magnitude at lower and higher pH. This reciprocal relationship between BclXL oligomerization and ligand binding lends new insights into how pH modulates functional versatility of a key apoptotic regulator and strongly argues that the molten globule may serve as an intermediate primed for membrane insertion in response to apoptotic cues. PMID:22960132

  9. Microbial degradation of isosaccharinic acid at high pH

    PubMed Central

    Bassil, Naji M; Bryan, Nicholas; Lloyd, Jonathan R

    2015-01-01

    Intermediate-level radioactive waste (ILW), which dominates the radioactive waste inventory in the United Kingdom on a volumetric basis, is proposed to be disposed of via a multibarrier deep geological disposal facility (GDF). ILW is a heterogeneous wasteform that contains substantial amounts of cellulosic material encased in concrete. Upon resaturation of the facility with groundwater, alkali conditions will dominate and will lead to the chemical degradation of cellulose, producing a substantial amount of organic co-contaminants, particularly isosaccharinic acid (ISA). ISA can form soluble complexes with radionuclides, thereby mobilising them and posing a potential threat to the surrounding environment or ‘far field'. Alkaliphilic microorganisms sampled from a legacy lime working site, which is an analogue for an ILW-GDF, were able to degrade ISA and couple this degradation to the reduction of electron acceptors that will dominate as the GDF progresses from an aerobic ‘open phase' through nitrate- and Fe(III)-reducing conditions post closure. Furthermore, pyrosequencing analyses showed that bacterial diversity declined as the reduction potential of the electron acceptor decreased and that more specialised organisms dominated under anaerobic conditions. These results imply that the microbial attenuation of ISA and comparable organic complexants, initially present or formed in situ, may play a role in reducing the mobility of radionuclides from an ILW-GDF, facilitating the reduction of undue pessimism in the long-term performance assessment of such facilities. PMID:25062127

  10. Microbial degradation of isosaccharinic acid at high pH.

    PubMed

    Bassil, Naji M; Bryan, Nicholas; Lloyd, Jonathan R

    2015-02-01

    Intermediate-level radioactive waste (ILW), which dominates the radioactive waste inventory in the United Kingdom on a volumetric basis, is proposed to be disposed of via a multibarrier deep geological disposal facility (GDF). ILW is a heterogeneous wasteform that contains substantial amounts of cellulosic material encased in concrete. Upon resaturation of the facility with groundwater, alkali conditions will dominate and will lead to the chemical degradation of cellulose, producing a substantial amount of organic co-contaminants, particularly isosaccharinic acid (ISA). ISA can form soluble complexes with radionuclides, thereby mobilising them and posing a potential threat to the surrounding environment or 'far field'. Alkaliphilic microorganisms sampled from a legacy lime working site, which is an analogue for an ILW-GDF, were able to degrade ISA and couple this degradation to the reduction of electron acceptors that will dominate as the GDF progresses from an aerobic 'open phase' through nitrate- and Fe(III)-reducing conditions post closure. Furthermore, pyrosequencing analyses showed that bacterial diversity declined as the reduction potential of the electron acceptor decreased and that more specialised organisms dominated under anaerobic conditions. These results imply that the microbial attenuation of ISA and comparable organic complexants, initially present or formed in situ, may play a role in reducing the mobility of radionuclides from an ILW-GDF, facilitating the reduction of undue pessimism in the long-term performance assessment of such facilities. PMID:25062127

  11. Tetramerization of the LexA repressor in solution: implications for gene regulation of the E.coli SOS system at acidic pH.

    PubMed

    Sousa, Francisco J R; Lima, Luis M T R; Pacheco, Ana B F; Oliveira, Cristiano L P; Torriani, Iris; Almeida, Darcy F; Foguel, Debora; Silva, Jerson L; Mohana-Borges, Ronaldo

    2006-06-16

    Structural changes on LexA repressor promoted by acidic pH have been investigated. Intense protein aggregation occurred around pH 4.0 but was not detected at pH values lower than pH 3.5. The center of spectral mass of the Trp increased 400 cm(-1) at pH 2.5 relatively to pH 7.2, an indication that LexA has undergone structural reorganization but not denaturation. The Trp fluorescence polarization of LexA at pH 2.5 indicated that its hydrodynamic volume was larger than its dimer at pH 7.2. 4,4'-Dianilino-1,1'-binaphthyl-5,5'- disulfonic acid (bis-ANS) experiments suggested that the residues in the hydrophobic clefts already present at the LexA structure at neutral pH had higher affinity to it at pH 2.5. A 100 kDa band corresponding to a tetramer was obtained when LexA was subject to pore-limiting native polyacrylamide gel electrophoresis at this pH. The existence of this tetrameric state was also confirmed by small angle X-ray scattering (SAXS) analysis at pH 2.5. 1D 1H NMR experiments suggested that it was composed of a mixture of folded and unfolded regions. Although 14,000-fold less stable than the dimeric LexA, it showed a tetramer-monomer dissociation at pH 2.5 from the hydrostatic pressure and urea curves. Albeit with half of the affinity obtained at pH 7.2 (Kaff of 170 nM), tetrameric LexA remained capable of binding recA operator sequence at pH 2.5. Moreover, different from the absence of binding to the negative control polyGC at neutral pH, LexA bound to this sequence with a Kaff value of 1415 nM at pH 2.5. A binding stoichiometry experiment at both pH 7.2 and pH 2.5 showed a [monomeric LexA]/[recA operator] ratio of 2:1. These results are discussed in relation to the activation of the Escherichia coli SOS regulon in response to environmental conditions resulting in acidic intracellular pH. Furthermore, oligomerization of LexA is proposed to be a possible regulation mechanism of this regulon. PMID:16701697

  12. Fiber optic sensors for an in-situ monitoring of moisture and pH value in reinforced concrete

    NASA Astrophysics Data System (ADS)

    Grahn, Walter; Makedonski, Pavel; Wichern, Juergen; Kowalsky, Wolfgang; Wiese, Stefan

    2002-01-01

    Concrete structures such as social buildings and bridges are important economic goods. Thus, maintenance and preservation of these structures are of major interest. Buildings of reinforced concrete are exposed to a variety of damaging influences. In particular, moisture has an important influence on the lifetime of concrete structures. This is caused by the involvement of free water in corrosion of the steel, and the fact that water acts as transport medium for damaging ions such as chloride, sulfate, carbonate and ammonium. Thus, we designed and developed an integrated fiberoptical sensor system, which allows in-situ non- destructive long-term monitoring of concrete structures. As moisture indicator we use a pyridinium-N-phenolat betainital dye, which shows a strong solvatochromic behavior in the ultraviolet-visible spectral range (UV-VIS). The dye is embedded in a polymer matrix, whose moderate polarity is enhanced by free water diffusing into the sensor. This leads to a continuous hypsochromic shift of the absorption spectrum according to the water concetration. Another appropriate dye is 4-amino-N-methylphthalimid, which shows a similar behavior in its fluorescent spectra, and presently we are developing its derivatives and suitable polymer matrices. The determination of the pH-value of concrete is of major importance for the assessment of acidic attacks which may lead to serious damage in reinforced concrete, as the embedded steel structures exhibit long-term stability (i.e. resistance to corrosion) only at pH-values of 9 or higher. Therefore we have developed a fiberoptical sensor system for the measurement of pH-values in concrete consisting of pH- indicator dyes immobilized in a highly immobilized in a highly hydrophilic polymer matrix. Any change in pH-value of the wet concrete material is indicated by a color change of the dye/polymer system. The sensor system displays long term stability even in aggressive media of pH12 - 13.

  13. Effects of pH adjustment and sodium ions on sour taste intensity of organic acids.

    PubMed

    Neta, E R D; Johanningsmeier, S D; Drake, M A; McFeeters, R F

    2009-01-01

    Protonated organic acid species have been shown to be the primary stimuli responsible for sour taste of organic acids. However, we have observed that sour taste may be modulated when the pH of acid solutions is raised using sodium hydroxide. Objectives were to evaluate the effect of pH adjustment on sour taste of equimolar protonated organic acid solutions and to investigate the potential roles of organic anions and sodium ions on sour taste perception. Despite equal concentrations of protonated acid species, sour taste intensity decreased significantly with increased pH for acetic, lactic, malic, and citric acids (P < 0.05). Total organic anion concentration did not explain the suppression of sour taste in solutions containing a blend of 3 organic acids with constant concentration of protonated organic acid species and hydrogen ions and variable organic anion concentrations (R(2)= 0.480, P = 0.12). Sour taste suppression in these solutions seemed to be more closely related to sodium ions added in the form of NaOH (R(2)= 0.861, P = 0.007). Addition of 20 mM NaCl to acid solutions resulted in significant suppression of sour taste (P = 0.016). However, sour taste did not decrease with further addition of NaCl up to 80 mM. Presence of sodium ions was clearly shown to decrease sour taste of organic acid solutions. Nonetheless, suppression of sour taste in pH adjusted single acid solutions was greater than what would be expected based on the sodium ion concentration alone, indicating an additional suppression mechanism may be involved.

  14. The effect of pH on hydrolysis, cross-linking and barrier properties of starch barriers containing citric acid.

    PubMed

    Olsson, Erik; Menzel, Carolin; Johansson, Caisa; Andersson, Roger; Koch, Kristine; Järnström, Lars

    2013-11-01

    Citric acid cross-linking of starch for e.g. food packaging applications has been intensely studied during the last decade as a method of producing water-insensitive renewable barrier coatings. We managed to improve a starch formulation containing citric acid as cross-linking agent for industrial paper coating applications by adjusting the pH of the starch solution. The described starch formulations exhibited both cross-linking of starch by citric acid as well as satisfactory barrier properties, e.g. fairly low OTR values at 50% RH that are comparable with EVOH. Furthermore, it has been shown that barrier properties of coated papers with different solution pH were correlated to molecular changes in starch showing both hydrolysis and cross-linking of starch molecules in the presence of citric acid. Hydrolysis was shown to be almost completely hindered at solution pH≥4 at curing temperatures≤105 °C and at pH≥5 at curing temperatures≤150 °C, whereas cross-linking still occurred to some extent at pH≤6.5 and drying temperatures as low as 70 °C. Coated papers showed a minimum in water vapor transmission rate at pH 4 of the starch coating solution, corresponding to the point where hydrolysis was effectively hindered but where a significant degree of cross-linking still occurred.

  15. Urea Fertilizer and pH Influence on Sorption Process of Flumetsulam and MCPA Acidic Herbicides in a Volcanic Soil.

    PubMed

    Palma, Graciela; Jorquera, Milko; Demanet, Rolando; Elgueta, Sebastian; Briceño, Gabriela; de la Luz Mora, María

    2016-01-01

    The aim of this study was to evaluate the influence of urea fertilizer and pH on the sorption process of two acidic herbicides, flumetsulam (2',6'-difluoro-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonanilide) and MCPA (4-chloro--tolyloxyacetic acid), on an Andisol. Urea reduced the adsorption of MCPA but not that of flumetsulam. The Freundlich parameter of MCPA decreased from 8.5 to 5.1 mg L kg. This finding could be attributed to an increase in dissolved organic C due to an initial increase in soil pH for urea application. The higher acidic character of MCPA compared with that of flumetsulam produced a greater hydrolysis of urea, leading to a further pH increase. A marked effect of pH on the adsorption of both herbicides was observed. The organic C distribution coefficient () values for flumetsulam were in the range of 74 to 10 L kg, while those of MCPA were in the range of 208 to 45 L kg. In the kinetic studies, the pseudo-second-order model appeared to fit the data best ( > 0.994). The initial adsorption rates () ranged from 20.00 to 4.59 mg kg h for flumetsulam and from 125.00 to 25.60 mg kg hfor MCPA. Both herbicides were adsorbed rapidly during the first stage of the sorption process, and the rates of sorption were dependent on pH. The application of the Elovich and Weber-Morris models led us to conclude that mass transfer through the boundary layer and, to a lesser degree, intraparticle diffusion were influenced by the chemical character of the herbicide. These results suggest that urea application could increase leaching of acid herbicides in soils.

  16. Sensing and adaptation to low pH mediated by inducible amino acid decarboxylases in Salmonella.

    PubMed

    Viala, Julie P M; Méresse, Stéphane; Pocachard, Bérengère; Guilhon, Aude-Agnès; Aussel, Laurent; Barras, Frédéric

    2011-01-01

    During the course of infection, Salmonella enterica serovar Typhimurium must successively survive the harsh acid stress of the stomach and multiply into a mild acidic compartment within macrophages. Inducible amino acid decarboxylases are known to promote adaptation to acidic environments. Three low pH inducible amino acid decarboxylases were annotated in the genome of S. Typhimurium, AdiA, CadA and SpeF, which are specific for arginine, lysine and ornithine, respectively. In this study, we characterized and compared the contributions of those enzymes in response to acidic challenges. Individual mutants as well as a strain deleted for the three genes were tested for their ability (i) to survive an extreme acid shock, (ii) to grow at mild acidic pH and (iii) to infect the mouse animal model. We showed that the lysine decarboxylase CadA had the broadest range of activity since it both had the capacity to promote survival at pH 2.3 and growth at pH 4.5. The arginine decarboxylase AdiA was the most performant in protecting S. Typhimurium from a shock at pH 2.3 and the ornithine decarboxylase SpeF conferred the best growth advantage under anaerobiosis conditions at pH 4.5. We developed a GFP-based gene reporter to monitor the pH of the environment as perceived by S. Typhimurium. Results showed that activities of the lysine and ornithine decarboxylases at mild acidic pH did modify the local surrounding of S. Typhimurium both in culture medium and in macrophages. Finally, we tested the contribution of decarboxylases to virulence and found that these enzymes were dispensable for S. Typhimurium virulence during systemic infection. In the light of this result, we examined the genomes of Salmonella spp. normally responsible of systemic infection and observed that the genes encoding these enzymes were not well conserved, supporting the idea that these enzymes may be not required during systemic infection.

  17. Relationship of Cell Sap pH to Organic Acid Change During Ion Uptake 1

    PubMed Central

    Hiatt, A. J.

    1967-01-01

    Excised roots of barley (Hordeum vulgare, var. Campana) were incubated in KCl, K2SO4, CaCl2, and NaCl solutions at concentrations of 10−5 to 10−2 n. Changes in substrate solution pH, cell sap pH, and organic acid content of the roots were related to differences in cation and anion absorption. The pH of expressed sap of roots increased when cations were absorbed in excess of anions and decreased when anions were absorbed in excess of cations. The pH of the cell sap shifted in response to imbalances in cation and anion uptake in salt solutions as dilute as 10−5 n. Changes in cell sap pH were detectable within 15 minutes after the roots were placed in 10−3 n K2SO4. Organic acid changes in the roots were proportional to expressed sap pH changes induced by unbalanced ion uptake. Changes in organic acid content in response to differential cation and anion uptake appear to be associated with the low-salt component of ion uptake. PMID:16656506

  18. Effect of pH on sulfite oxidation by Thiobacillus thiooxidans cells with sulfurous acid or sulfur dioxide as a possible substrate.

    PubMed

    Takeuchi, T L; Suzuki, I

    1994-02-01

    The oxidation of sulfite by Thiobacillus thiooxidans was studied at various pH values with changing concentrations of potassium sulfite. The optimal pH for sulfite oxidation by cells was a function of sulfite concentrations, rising with increasing substrate concentrations, while that by the cell extracts was unaffected. The sulfite oxidation by cells was inhibited at high sulfite concentrations, particularly at low pH values. The results from kinetic studies show that the fully protonated form of sulfite, sulfurous acid or sulfur dioxide, is the form which penetrates the cells for the oxidation.

  19. Determination of pK(a) Values of Hydrophobic Colorimetric pH Sensitive Probes in Nanospheres.

    PubMed

    Xie, Xiaojiang; Zhai, Jingying; Jarolímová, Zdeňka; Bakker, Eric

    2016-03-15

    A simple and novel method is proposed here for the first time to determine pK(a) values of chromogenic hydrophobic pH sensitive probes directly in nanospheres. pK(a) values can be obtained by measuring the pH response of the nanospheres (containing the probes and ion exchanger) followed by measuring the pH and Na(+) responses of the nanospheres (containing solvatochromic dyes and ion exchanger). The pK(a) values of four chromoionophores were successfully determined. This method is in principle also applicable to characterize colorimetric probes in other water immiscible nanomaterials.

  20. Acidic pH Is a Metabolic Switch for 2-Hydroxyglutarate Generation and Signaling.

    PubMed

    Nadtochiy, Sergiy M; Schafer, Xenia; Fu, Dragony; Nehrke, Keith; Munger, Joshua; Brookes, Paul S

    2016-09-16

    2-Hydroxyglutarate (2-HG) is an important epigenetic regulator, with potential roles in cancer and stem cell biology. The d-(R)-enantiomer (d-2-HG) is an oncometabolite generated from α-ketoglutarate (α-KG) by mutant isocitrate dehydrogenase, whereas l-(S)-2-HG is generated by lactate dehydrogenase and malate dehydrogenase in response to hypoxia. Because acidic pH is a common feature of hypoxia, as well as tumor and stem cell microenvironments, we hypothesized that pH may regulate cellular 2-HG levels. Herein we report that cytosolic acidification under normoxia moderately elevated 2-HG in cells, and boosting endogenous substrate α-KG levels further stimulated this elevation. Studies with isolated lactate dehydrogenase-1 and malate dehydrogenase-2 revealed that generation of 2-HG by both enzymes was stimulated severalfold at acidic pH, relative to normal physiologic pH. In addition, acidic pH was found to inhibit the activity of the mitochondrial l-2-HG removal enzyme l-2-HG dehydrogenase and to stimulate the reverse reaction of isocitrate dehydrogenase (carboxylation of α-KG to isocitrate). Furthermore, because acidic pH is known to stabilize hypoxia-inducible factor (HIF) and 2-HG is a known inhibitor of HIF prolyl hydroxylases, we hypothesized that 2-HG may be required for acid-induced HIF stabilization. Accordingly, cells stably overexpressing l-2-HG dehydrogenase exhibited a blunted HIF response to acid. Together, these results suggest that acidosis is an important and previously overlooked regulator of 2-HG accumulation and other oncometabolic events, with implications for HIF signaling.

  1. Impact of temperature, pH, and salinity changes on the physico-chemical properties of model naphthenic acids.

    PubMed

    Celsie, Alena; Parnis, J Mark; Mackay, Donald

    2016-03-01

    The effects of temperature, pH, and salinity change on naphthenic acids (NAs) present in oil-sands process wastewater were modeled for 55 representative NAs. COSMO-RS was used to estimate octanol-water (KOW) and octanol-air (KOA) partition ratios and Henry's law constants (H). Validation with experimental carboxylic acid data yielded log KOW and log H RMS errors of 0.45 and 0.55 respectively. Calculations of log KOW, (or log D, for pH-dependence), log KOA and log H (or log HD, for pH-dependence) were made for model NAs between -20 °C and 40 °C, pH between 0 and 14, and salinity between 0 and 3 g NaCl L(-1). Temperature increase by 60 °C resulted in 3-5 log unit increase in H and a similar magnitude decrease in KOA. pH increase above the NA pKa resulted in a dramatic decrease in both log D and log HD. Salinity increase over the 0-3 g NaCl L(-1) range resulted in a 0.3 log unit increase on average for KOW and H values. Log KOW values of the sodium salt and anion of the conjugate base were also estimated to examine their potential for contribution to the overall partitioning of NAs. Sodium salts and anions of naphthenic acids are predicted to have on average 4 log units and 6 log units lower log KOW values, respectively, with respect to the corresponding neutral NA. Partitioning properties are profoundly influenced by the by the relative prevailing pH and the substance's pKa at the relevant temperature. PMID:26706930

  2. Influence of acidic pH on hydrogen and acetate production by an electrosynthetic microbiome

    DOE PAGES

    LaBelle, Edward V.; Marshall, Christopher W.; Gilbert, Jack A.; May, Harold D.; Battista, John R.

    2014-10-15

    Production of hydrogen and organic compounds by an electrosynthetic microbiome using electrodes and carbon dioxide as sole electron donor and carbon source, respectively, was examined after exposure to acidic pH (~5). Hydrogen production by biocathodes poised at -600 mV vs. SHE increased>100-fold and acetate production ceased at acidic pH, but ~5–15 mM (catholyte volume)/day acetate and>1,000 mM/day hydrogen were attained at pH ~6.5 following repeated exposure to acidic pH. Cyclic voltammetry revealed a 250 mV decrease in hydrogen overpotential and a maximum current density of 12.2 mA/cm2 at -765 mV (0.065 mA/cm2 sterile control at -800 mV) by the Acetobacterium-dominatedmore » community. Supplying -800 mV to the microbiome after repeated exposure to acidic pH resulted in up to 2.6 kg/m3/day hydrogen (≈2.6 gallons gasoline equivalent), 0.7 kg/m3/day formate, and 3.1 kg/m3/day acetate ( = 4.7 kg CO2 captured).« less

  3. Influence of acidic pH on hydrogen and acetate production by an electrosynthetic microbiome

    SciTech Connect

    LaBelle, Edward V.; Marshall, Christopher W.; Gilbert, Jack A.; May, Harold D.; Battista, John R.

    2014-10-15

    Production of hydrogen and organic compounds by an electrosynthetic microbiome using electrodes and carbon dioxide as sole electron donor and carbon source, respectively, was examined after exposure to acidic pH (~5). Hydrogen production by biocathodes poised at -600 mV vs. SHE increased>100-fold and acetate production ceased at acidic pH, but ~5–15 mM (catholyte volume)/day acetate and>1,000 mM/day hydrogen were attained at pH ~6.5 following repeated exposure to acidic pH. Cyclic voltammetry revealed a 250 mV decrease in hydrogen overpotential and a maximum current density of 12.2 mA/cm2 at -765 mV (0.065 mA/cm2 sterile control at -800 mV) by the Acetobacterium-dominated community. Supplying -800 mV to the microbiome after repeated exposure to acidic pH resulted in up to 2.6 kg/m3/day hydrogen (≈2.6 gallons gasoline equivalent), 0.7 kg/m3/day formate, and 3.1 kg/m3/day acetate ( = 4.7 kg CO2 captured).

  4. 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.

  5. Influence of Acidic pH on Hydrogen and Acetate Production by an Electrosynthetic Microbiome

    PubMed Central

    LaBelle, Edward V.; Marshall, Christopher W.; Gilbert, Jack A.; May, Harold D.

    2014-01-01

    Production of hydrogen and organic compounds by an electrosynthetic microbiome using electrodes and carbon dioxide as sole electron donor and carbon source, respectively, was examined after exposure to acidic pH (∼5). Hydrogen production by biocathodes poised at −600 mV vs. SHE increased>100-fold and acetate production ceased at acidic pH, but ∼5–15 mM (catholyte volume)/day acetate and>1,000 mM/day hydrogen were attained at pH ∼6.5 following repeated exposure to acidic pH. Cyclic voltammetry revealed a 250 mV decrease in hydrogen overpotential and a maximum current density of 12.2 mA/cm2 at −765 mV (0.065 mA/cm2 sterile control at −800 mV) by the Acetobacterium-dominated community. Supplying −800 mV to the microbiome after repeated exposure to acidic pH resulted in up to 2.6 kg/m3/day hydrogen (≈2.6 gallons gasoline equivalent), 0.7 kg/m3/day formate, and 3.1 kg/m3/day acetate ( = 4.7 kg CO2 captured). PMID:25333313

  6. Influence of pH, type of acid and recovery media on the thermal inactivation of Listeria innocua.

    PubMed

    Miller, Fátima A; Ramos, Bárbara; Gil, Maria M; Brandão, Teresa R S; Teixeira, Paula; Silva, Cristina L M

    2009-07-31

    Acidification of foods with organic acids, either by fermentation or by intentional addition, is an important and common mechanism for controlling foodborne pathogens in a diversity of food products. The objective of this work was to study thermal inactivation of Listeria innocua, an acid tolerant microorganism, at 52.5, 60.0 and 65.0 degrees C, at different pH values (4.5, 6.0 and 7.5), using three types of acid (lactic, acetic and hydrochloric) and three different plating media (Tryptic Soy Agar with 0.6% yeast extract-TSAYE; TSAYE plus 5% NaCl-TSAYE+5%NaCl; and Palcam Agar with selective supplement-Palcam Agar), according to a 3(4) factorial experimental design. Survival data experimentally obtained were fitted with a Gompertz-inspired model and kinetic parameters (shoulder, maximum inactivation rate-k(max), and tail) were estimated for all conditions considered. The influence of temperature, pH, type of acid and enumeration media on kinetic parameters was assessed. Results showed that, with the exception of the type of acid, all the remaining factors and their combinations significantly affected the shoulder period and k(max). In relation to tail, temperature and recovery media were the affectable factors. It was concluded that the survival of this bacteria is higher when combining low temperature with neutral pH, and when TSAYE is the enumeration medium. Bigelow-inspired models were successfully developed and describe accurately the temperature and pH effects on the kinetic parameters.

  7. Development of Online Spectroscopic pH Monitoring for Nuclear Fuel Reprocessing Plants: Weak Acid Schemes.

    PubMed

    Casella, Amanda J; Ahlers, Laura R H; Campbell, Emily L; Levitskaia, Tatiana G; Peterson, James M; Smith, Frances N; Bryan, Samuel A

    2015-05-19

    In nuclear fuel reprocessing, separating trivalent minor actinides and lanthanide fission products is extremely challenging and often necessitates tight pH control in TALSPEAK (Trivalent Actinide-Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexes) separations. In TALSPEAK and similar advanced processes, aqueous pH is one of the most important factors governing the partitioning of lanthanides and actinides between an aqueous phase containing a polyaminopolycarboxylate complexing agent and a weak carboxylic acid buffer and an organic phase containing an acidic organophosphorus extractant. Real-time pH monitoring would significantly increase confidence in the separation performance. Our research is focused on developing a general method for online determination of the pH of aqueous solutions through chemometric analysis of Raman spectra. Spectroscopic process-monitoring capabilities, incorporated in a counter-current centrifugal contactor bank, provide a pathway for online, real-time measurement of solution pH. The spectroscopic techniques are process-friendly and can be easily configured for online applications, whereas classic potentiometric pH measurements require frequent calibration/maintenance and have poor long-term stability in aggressive chemical and radiation environments. Raman spectroscopy discriminates between the protonated and deprotonated forms of the carboxylic acid buffer, and the chemometric processing of the Raman spectral data with PLS (partial least-squares) regression provides a means to quantify their respective abundances and therefore determine the solution pH. Interpretive quantitative models have been developed and validated under a range of chemical composition and pH conditions using a lactic acid/lactate buffer system. The developed model was applied to new spectra obtained from online spectral measurements during a solvent extraction experiment using a counter-current centrifugal contactor bank. The model

  8. Vaginal pH and microbicidal lactic acid when lactobacilli dominate the microbiota.

    PubMed

    O'Hanlon, Deirdre E; Moench, Thomas R; Cone, Richard A

    2013-01-01

    Lactic acid at sufficiently acidic pH is a potent microbicide, and lactic acid produced by vaginal lactobacilli may help protect against reproductive tract infections. However, previous observations likely underestimated healthy vaginal acidity and total lactate concentration since they failed to exclude women without a lactobacillus-dominated vaginal microbiota, and also did not account for the high carbon dioxide, low oxygen environment of the vagina. Fifty-six women with low (0-3) Nugent scores (indicating a lactobacillus-dominated vaginal microbiota) and no symptoms of reproductive tract disease or infection, provided a total of 64 cervicovaginal fluid samples using a collection method that avoided the need for sample dilution and rigorously minimized aerobic exposure. The pH of samples was measured by microelectrode immediately after collection and under a physiological vaginal concentration of CO2. Commercial enzymatic assays of total lactate and total acetate concentrations were validated for use in CVF, and compared to the more usual HPLC method. The average pH of the CVF samples was 3.5 ± 0.3 (mean ± SD), range 2.8-4.2, and the average total lactate was 1.0% ± 0.2% w/v; this is a five-fold higher average hydrogen ion concentration (lower pH) and a fivefold higher total lactate concentration than in the prior literature. The microbicidal form of lactic acid (protonated lactic acid) was therefore eleven-fold more concentrated, and a markedly more potent microbicide, than indicated by prior research. This suggests that when lactobacilli dominate the vaginal microbiota, women have significantly more lactic acid-mediated protection against infections than currently believed. Our results invite further evaluations of the prophylactic and therapeutic actions of vaginal lactic acid, whether provided in situ by endogenous lactobacilli, by probiotic lactobacilli, or by products that reinforce vaginal lactic acid.

  9. Enrichment of sulfate-reducing bacteria and resulting mineral formation in media mimicking pore water metal ion concentrations and pH conditions of acidic pit lakes.

    PubMed

    Meier, Jutta; Piva, Angela; Fortin, Danielle

    2012-01-01

    Acid mine drainage sites are extreme environments with high acidity and metal ion concentrations. Under anoxic conditions, microbial sulfate reduction may trigger the formation of secondary minerals as a result of H2S production and pH increase. This process was studied in batch experiments with enrichment cultures from acidic sediments of a pit lake using growth media set at different pH values and containing elevated concentrations of Fe²⁺ and Al³⁺. At initial pH values of 5 and 6, sulfate reduction occurred shortly after inoculation. Sulfate- reducing bacteria affiliated to the genus Desulfosporosinus predominated the microbial communities as shown by 16S rRNA gene analysis performed at the end of the incubation. At initial pH values of 3 and 4, sulfate reduction and cell growth occurred only after an extended lag phase, however, at a higher rate than in the less acidic assays. At the end of the growth phase, enrichments were dominated by Thermodesulfobium spp. suggesting that these sulfate reducers were better adapted to acidic conditions. Iron sulfides in the bulk phase were common in all assays, but specific aluminum precipitates formed in close association with cell surfaces and may function as a detoxification mechanism of dissolved Al species at low pH.

  10. Nestedness in Arbuscular Mycorrhizal Fungal Communities along Soil pH Gradients in Early Primary Succession: Acid-Tolerant Fungi Are pH Generalists

    PubMed Central

    Kawahara, Ai; An, Gi-Hong; Miyakawa, Sachie; Sonoda, Jun

    2016-01-01

    Soil acidity is a major constraint on plant productivity. Arbuscular mycorrhizal (AM) fungi support plant colonization in acidic soil, but soil acidity also constrains fungal growth and diversity. Fungi in extreme environments generally evolve towards specialists, suggesting that AM fungi in acidic soil are acidic-soil specialists. In our previous surveys, however, some AM fungi detected in strongly acidic soils could also be detected in a soil with moderate pH, which raised a hypothesis that the fungi in acidic soils are pH generalists. To test the hypothesis, we conducted a pH-manipulation experiment and also analyzed AM fungal distribution along a pH gradient in the field using a synthesized dataset of the previous and recent surveys. Rhizosphere soils of the generalist plant Miscanthus sinensis were collected both from a neutral soil and an acidic soil, and M. sinensis seedlings were grown at three different pH. For the analysis of field communities, rhizosphere soils of M. sinensis were collected from six field sites across Japan, which covered a soil pH range of 3.0–7.4, and subjected to soil trap culture. AM fungal community compositions were determined based on LSU rDNA sequences. In the pH-manipulation experiment the acidification of medium had a significant impact on the compositions of the community from the neutral soil, but the neutralization of the medium had no effect on those of the community from the acidic soil. Furthermore, the communities in lower -pH soils were subsets of (nested in) those in higher-pH soils. In the field communities a significant nestedness pattern was observed along the pH gradient. These observations suggest that the fungi in strongly acidic soils are pH generalists that occur not only in acidic soil but also in wide ranges of soil pH. Nestedness in AM fungal community along pH gradients may have important implications for plant community resilience and early primary succession after disturbance in acidic soils. PMID

  11. Changes in soil pH across England and Wales in response to decreased acid deposition

    NASA Astrophysics Data System (ADS)

    Kirk, G. J. D.; Bellamy, P. H.

    2009-04-01

    In our recent analysis of data from the National Soil Inventory of England and Wales, we found widespread changes in soil pH across both countries between the two samplings of the Inventory. In general, soil pH increased - i.e. soils became less acid - under all land uses. The Inventory was first sampled in 1978-83 on a 5-km grid over the whole area. This yielded about 6,000 sites of which 5,662 could be sampled for soil. Roughly 40% of the sites were re-sampled at intervals from 12 to 25 years after the original sampling - in 1994/96 for agricultural land and in 2002/03 for non-agricultural. Exactly the same sampling and analytical protocols were used in the two samplings. In arable soils, the increase in pH was right across the range, whereas in grassland soils the main increase was at the acid end of the scale (pH < 5.5) with a small increase above pH 7. Some part of the change is likely to have been due to changes in land management. This includes better targeting of agricultural lime on acid soils; changes in nitrogen fertilizer use; deeper ploughing bringing up more calcareous subsoil on soils on calcareous materials; and so forth. However a major driver appears to have been decreased acid deposition to land. The total amounts of nitrogen compounds deposited were relatively unchanged over the survey period, but the amounts of acidifying sulphur compounds decreased by approximately 50%. We constructed a linear regression model to assess the relation between the rate of change in pH (normalised to an annual basis) and the rate of change in acid deposition, as modified by soil properties (pH, clay content, organic matter content), rainfall and past acid deposition. We used data on rainfall and acid deposition over the survey period on the same 5-km grid as the NSI data. We fitted the model separately for each land use category. The results for arable land showed a significant effect of the change in rate of acid deposition, though a significant part of the

  12. A new boronic acid fluorescent sensor based on fluorene for monosaccharides at physiological pH

    NASA Astrophysics Data System (ADS)

    Hosseinzadeh, Rahman; Mohadjerani, Maryam; Pooryousef, Mona; Eslami, Abbas; Emami, Saeed

    2015-06-01

    Fluorescent boronic acids are very useful fluorescent sensor for detection of biologically important saccharides. Herein we synthesized a new fluorene-based fluorescent boronic acid that shows significant fluorescence changes upon addition of saccharides at physiological pH. Upon addition of fructose, sorbitol, glucose, galactose, ribose, and maltose at different concentration to the solution of 7-(dimethylamino)-9,9-dimethyl-9H-fluoren-2-yl-2-boronic acid (7-DMAFBA, 1), significant decreases in fluorescent intensity were observed. It was found that this boronic acid has high affinity (Ka = 3582.88 M-1) and selectivity for fructose over glucose at pH = 7.4. The sensor 1 showed a linear response toward D-fructose in the concentrations ranging from 2.5 × 10-5 to 4 × 10-4 mol L-1 with the detection limit of 1.3 × 10-5 mol L-1.

  13. X-ray absorption near-edge structure study on the configuration of Cu 2+ /histidine complexes at different pH values

    NASA Astrophysics Data System (ADS)

    Mei-Juan, Yu; Yu, Wang; Wei, Xu

    2016-04-01

    The local configurations around metal ions in metalloproteins are of great significance for understanding their biological functions. Cu2+/histidine (His) is a typical complex existing in many metalloproteins and plays an important role in lots of physiological functions. The three-dimensional (3D) structural configurations of Cu2+/His complexes at different pH values (2.5, 6.5, and 8.5) are quantitatively determined by x-ray absorption near-edge structure (XANES). Generally Cu2+/His complex keeps an octahedral configuration consisting of oxygen atoms from water molecules and oxygen or nitrogen atoms from histidine molecules coordinated around Cu2+. It is proved in this work that the oxygen atoms from water molecules, when increasing the pH value from acid to basic value, are gradually substituted by the Ocarboxyl, Nam, and Nim from hisitidine molecules. Furthermore, the symmetries of Cu2+/His complexes at pH 6.5 and pH 8.5 are found to be lower than at pH 2.5. Project supported by the National Natural Science Foundation of China (Grant No. 11205186).

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

    PubMed Central

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

    2012-01-01

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

  15. A wireless pH sensor using magnetoelasticity for measurement of body fluid acidity.

    PubMed

    Pang, Pengfei; Gao, Xianjuan; Xiao, Xilin; Yang, Wenyue; Cai, Qingyun; Yao, Shouzhuo

    2007-04-01

    The determination of body fluid acidity using a wireless magnetoelastic pH-sensitive sensor is described. The sensor was fabricated by casting a layer of pH-sensitive polymer on a magnetoelastic ribbon. In response to an externally applied time-varying magnetic field, the magnetoelastic sensor mechanically vibrates at a characteristic frequency that is inversely dependent upon the mass of the pH polymer film, which varies as the film swells and shrinks in response to pH. As the magnetoelastic sensor is magnetostrictive, the mechanical vibrations of the sensor launch magnetic flux that can be detected remotely using a pickup coil. The sensor can be used for direct measurements of body fluid acidity without a pretreatment of the sample by using a filtration membrane. A reversible and linear response was obtained between pH 5.0 and 8.0 with a measurement resolution of pH 0.1 and a slope of 0.2 kHz pH(-1). Since there are no physical connections between the sensor and the instrument, the sensor can be applied to in vivo and in situ monitoring of the physiological pH and its fluctuations.

  16. Membrane growth can generate a transmembrane pH gradient in fatty acid vesicles.

    PubMed

    Chen, Irene A; Szostak, Jack W

    2004-05-25

    Electrochemical proton gradients are the basis of energy transduction in modern cells, and may have played important roles in even the earliest cell-like structures. We have investigated the conditions under which pH gradients are maintained across the membranes of fatty acid vesicles, a model of early cell membranes. We show that pH gradients across such membranes decay rapidly in the presence of alkali-metal cations, but can be maintained in the absence of permeable cations. Under such conditions, when fatty acid vesicles grow through the incorporation of additional fatty acid, a transmembrane pH gradient is spontaneously generated. The formation of this pH gradient captures some of the energy released during membrane growth, but also opposes and limits further membrane area increase. The coupling of membrane growth to energy storage could have provided a growth advantage to early cells, once the membrane composition had evolved to allow the maintenance of stable pH gradients.

  17. Dissolved Divalent Metal and pH Effects on Amino Acid Polymerization: A Thermodynamic Evaluation

    NASA Astrophysics Data System (ADS)

    Kitadai, Norio

    2016-06-01

    Polymerization of amino acids is a fundamentally important step for the chemical evolution of life. Nevertheless, its response to changing environmental conditions has not yet been well understood because of the lack of reliable quantitative information. For thermodynamics, detailed prediction over diverse combinations of temperature and pH has been made only for a few amino acid-peptide systems. This study used recently reported thermodynamic dataset for the polymerization of the simplest amino acid "glycine (Gly)" to its short peptides (di-glycine and tri-glycine) to examine chemical and structural characteristics of amino acids and peptides that control the temperature and pH dependence of polymerization. Results showed that the dependency is strongly controlled by the intramolecular distance between the amino and carboxyl groups in an amino acid structure, although the side-chain group role is minor. The polymerization behavior of Gly reported earlier in the literature is therefore expected to be a typical feature for those of α-amino acids. Equilibrium calculations were conducted to examine effects of dissolved metals as a function of pH on the monomer-polymer equilibria of Gly. Results showed that metals shift the equilibria toward the monomer side, particularly at neutral and alkaline pH. Metals that form weak interaction with Gly (e.g., Mg2+) have no noticeable influence on the polymerization, although strong interaction engenders significant decrease of the equilibrium concentrations of Gly peptides. Considering chemical and structural characteristics of Gly and Gly peptides that control their interactions with metals, it can be expected that similar responses to the addition of metals are applicable in the polymerization of neutral α-amino acids. Neutral and alkaline aqueous environments with dissolved metals having high affinity with neutral α-amino acids (e.g., Cu2+) are therefore not beneficial places for peptide bond formation on the primitive

  18. Estimation of water activity from pH and °Brix values of some food products.

    PubMed

    Gabriel, Alonzo A

    2008-06-01

    In this study, a predictive model for the estimation of water activity (aw(25°C)) as a function of pH (1.00-8.00) and °Brix (0-82.00) values of simulated food solutions (SFS) was developed, through response surface methodology. Response fit analyses resulted in a highly significant (pH<0.0001) square root polynomial model that can predict aw(25°C) of SFS in terms of pH and °Brix values within the defined variable ranges. The linear, quadratic and interactive influences of pH and °Brix on aw(25°C) were all significant (pH<0.0001). Model validations in SFS and in a number of actual food systems showed that the model had acceptable predictive performance, as indicated by the calculated accuracy and bias indices. PMID:26065778

  19. Influence of sodium chloride, pH, and lactic acid bacteria on anaerobic lactic acid utilization during fermented cucumber spoilage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cucumbers are preserved commercially by natural fermentations in 5% to 8% sodium chloride (NaCl) brines. Occasionally, fermented cucumbers spoil after the primary fermentation is complete. This spoilage has been characterized by decreases in lactic acid and a rise in brine pH caused by microbial ins...

  20. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Dependence of Nanofluid Viscosity on Particle Size and pH Value

    NASA Astrophysics Data System (ADS)

    Zhao, Jia-Fei; Luo, Zhong-Yang; Ni, Ming-Jiang; Cen, Ke-Fa

    2009-06-01

    We investigate the viscosity of silicon dioxide nanofluid at different particle sizes and pH values considering nanoparticle aggregation. The experimental and simulation results indicate that nanoparticle size is of crucial importance to the viscosity of the nanofluid due to aggregation. As the nanoparticle size decreases, the viscosity becomes much more dependent on the volume fraction. Moreover, when the nanoparticle diameter is smaller than 20 nm, the viscosity is closely related to the pH of the nanofluid, and fluctuates with pH values from 5 and 7.

  1. Acidic pH induced STM1485 gene is essential for intracellular replication of Salmonella.

    PubMed

    Allam, Uday Sankar; Krishna, M Gopala; Sen, Minakshi; Thomas, Rony; Lahiri, Amit; Gnanadhas, Divya Prakash; Chakravortty, Dipshikha

    2012-01-01

    During the course of infection, Salmonella has to face several potentially lethal environmental conditions, one such being acidic pH. The ability to sense and respond to the acidic pH is crucial for the survival and replication of Salmonella. The physiological role of one gene (STM1485) involved in this response, which is upregulated inside the host cells (by 90- to 113-fold) is functionally characterized in Salmonella pathogenesis. In vitro, the ΔSTM1485 neither exhibited any growth defect at pH 4.5 nor any difference in the acid tolerance response. The ΔSTM1485 was compromised in its capacity to proliferate inside the host cells and complementation with STM1485 gene restored its virulence. We further demonstrate that the surface translocation of Salmonella pathogenicity island-2 (SPI-2) encoded translocon proteins, SseB and SseD were reduced in the ΔSTM1485. The increase in co-localization of this mutant with lysosomes was also observed. In addition, the ΔSTM1485 displayed significantly reduced competitive indices (CI) in spleen, liver and mesenteric lymph nodes in murine typhoid model when infected by intra-gastric route. Based on these results, we conclude that the acidic pH induced STM1485 gene is essential for intracellular replication of Salmonella.

  2. Structural and thermotropic properties of calcium-dimyristoylphosphatidic acid complexes at acidic and neutral pH conditions.

    PubMed Central

    Takahashi, H.; Yasue, T.; Ohki, K.; Hatta, I.

    1995-01-01

    Two kinds of calcium-dimyristoylphosphatidic acid (DMPA) complexes at acidic and neutral pH conditions were prepared in the following ways. The complex at pH 4 was obtained by adding Ca2+ to DMPA dispersion in pure water. On the other hand, the complex at pH 7.4 was obtained by adding Ca2+ to DMPA dispersion in the presence of NaOH. The stoichiometries of Ca2+ ion to DMPA molecule are 0.5-0.67 and approximately 1 for the complexes at pH 4 and 7.4, respectively. Static x-ray diffraction shows that the hydrocarbon chains of the Ca(2+)-DMPA complex at pH 4 at 20 degrees C are more tightly packed than those of the complex at pH 7.4 at 20 degrees C. Furthermore, the complex at pH 4 at 20 degrees C gives rise to several reflections that might be related to the ordered arrangement of the Ca2+ ions. These results indicate that the structure of the complex at pH 4 is crystalline-like. In the differential scanning calorimetry (DSC) thermogram, the complex at pH 7.4 undergoes no phase transition in a temperature range between 30 and 80 degrees C. On the other hand, in the DSC thermogram for the complex at pH 4, a peak appears at 65.8 degrees C in the first heating scan. In the successive second heating scan, a transition peak appears at 63.5 degrees C. In connection with the DSC results, the structural changes associated with these phase transitions were studied with temperature-scan x-ray diffraction. In the first heating scan, although a peak appears at 65.80C in the DSC thermogram, the hydrocarbon chain packing gradually converts from an orthorhombic lattice to a hexagonal lattice near 52 degree C, and successively the chain melting phase transition occurs near 670C. In the second heating scan, the hydrocarbon chains are packed in a hexagonal lattice over the whole temperature range and the chain melting phase transition occurs near 63.5 degree C. Therefore,the Ca2+-DMPA complex at pH 4 has a metastable state. The metastable state transforms to a stable state by

  3. Effect of pH value on electromagnetic loss properties of Co-Zn ferrite prepared via coprecipitation method

    NASA Astrophysics Data System (ADS)

    Huang, Xiaogu; Zhang, Jing; Wang, Wei; Sang, Tianyi; Song, Bo; Zhu, Hongli; Rao, Weifeng; Wong, Chingping

    2016-05-01

    In this paper, the cobalt zinc ferrite was prepared by coprecipitation method at different pH conditions. The influence of pH values on the coprecipitation reaction was theoretically analyzed at first. The calculated results showed that the pH values should be controlled in the range of 9-11 to form the stable precipitation. The XRD investigation was used to further confirm the formation of the composite on specific pH values. In addition, the morphological study revealed that the average particle size of the composite decreased from 40 nm to 30 nm when the pH value increased from 9-11. The variation of microstructure plays a critical role in controlling the electromagnetic properties. From the electromagnetic analysis, the dielectric loss factor was 0.02-0.07 and magnetic loss factor was 0.2-0.5 for the composite synthesized at pH of 9, which presents dramatically improved dielectric loss and magnetic loss properties than the samples prepared at pH of 10 and 11. The as-prepared cobalt zinc ferrite are highly promising to be used as microwave absorption materials.

  4. Humic Acid Complexation of Th, Hf and Zr in Ligand Competition Experiments: Metal Loading and Ph Effects

    NASA Technical Reports Server (NTRS)

    Stern, Jennifer C.; Foustoukos, Dionysis I.; Sonke, Jeroen E.; Salters, Vincent J. M.

    2014-01-01

    The mobility of metals in soils and subsurface aquifers is strongly affected by sorption and complexation with dissolved organic matter, oxyhydroxides, clay minerals, and inorganic ligands. Humic substances (HS) are organic macromolecules with functional groups that have a strong affinity for binding metals, such as actinides. Thorium, often studied as an analog for tetravalent actinides, has also been shown to strongly associate with dissolved and colloidal HS in natural waters. The effects of HS on the mobilization dynamics of actinides are of particular interest in risk assessment of nuclear waste repositories. Here, we present conditional equilibrium binding constants (Kc, MHA) of thorium, hafnium, and zirconium-humic acid complexes from ligand competition experiments using capillary electrophoresis coupled with ICP-MS (CE- ICP-MS). Equilibrium dialysis ligand exchange (EDLE) experiments using size exclusion via a 1000 Damembrane were also performed to validate the CE-ICP-MS analysis. Experiments were performed at pH 3.5-7 with solutions containing one tetravalent metal (Th, Hf, or Zr), Elliot soil humic acid (EHA) or Pahokee peat humic acid (PHA), and EDTA. CE-ICP-MS and EDLE experiments yielded nearly identical binding constants for the metal- humic acid complexes, indicating that both methods are appropriate for examining metal speciation at conditions lower than neutral pH. We find that tetravalent metals form strong complexes with humic acids, with Kc, MHA several orders of magnitude above REE-humic complexes. Experiments were conducted at a range of dissolved HA concentrations to examine the effect of [HA]/[Th] molar ratio on Kc, MHA. At low metal loading conditions (i.e. elevated [HA]/[Th] ratios) the ThHA binding constant reached values that were not affected by the relative abundance of humic acid and thorium. The importance of [HA]/[Th] molar ratios on constraining the equilibrium of MHA complexation is apparent when our estimated Kc, MHA values

  5. Autoinducer-2 detection among commensal oral streptococci is dependent on pH and boric acid.

    PubMed

    Cuadra, Giancarlo A; Frantellizzi, Ashley J; Gaesser, Kimberly M; Tammariello, Steven P; Ahmed, Anika

    2016-07-01

    Autoinducer-2, considered a universal signaling molecule, is produced by many species of bacteria; including oral strains. Structurally, autoinducer-2 can exist bound to boron (borated autoinducer-2). Functionally, autoinducer-2 has been linked to important bacterial processes such as virulence and biofilm formation. In order to test production of autoinducer-2 by a given bacterial strain, a bioassay using marine bioluminescent bacteria Vibrio harveyi as a reporter for autoinducer-2 has been designed. We hypothesize that pH adjustment and addition of boron are required for optimal bioluminescence and accurate autoinducer-2 detection. Using this reporter strain we tested autoinducer-2 activity from two oral commensal species, Streptococcus gordonii DL1 and Streptococcus oralis 34. Spent broth was collected and adjusted to pH 7.5 and supplemented with boric acid prior to measuring autoinducer- 2 activity. Results show that low pH inhibits bioluminescence of the reporter strain, but pH 7.5 allows for bioluminescence induction and proper readings of autoinducer-2 activity. Addition of boric acid also has a positive effect on bioluminescence allowing for a more sensitive detection of autoinducer-2 activity. Our data suggests that although autoinducer-2 is present in spent broth, low pH and/or low levels of boric acid become an obstacle for proper autoinducer-2 detection. For proper autoinducer-2 detection, we propose a protocol using this bioassay to include pH adjustment and boric acid addition to spent broth. Studies on autoinducer-2 activity in several bacteria species represent an important area of study as this universal signaling molecule is involved in critical bacterial phenotypes such as virulence and biofilm formation.

  6. Autoinducer-2 detection among commensal oral streptococci is dependent on pH and boric acid.

    PubMed

    Cuadra, Giancarlo A; Frantellizzi, Ashley J; Gaesser, Kimberly M; Tammariello, Steven P; Ahmed, Anika

    2016-07-01

    Autoinducer-2, considered a universal signaling molecule, is produced by many species of bacteria; including oral strains. Structurally, autoinducer-2 can exist bound to boron (borated autoinducer-2). Functionally, autoinducer-2 has been linked to important bacterial processes such as virulence and biofilm formation. In order to test production of autoinducer-2 by a given bacterial strain, a bioassay using marine bioluminescent bacteria Vibrio harveyi as a reporter for autoinducer-2 has been designed. We hypothesize that pH adjustment and addition of boron are required for optimal bioluminescence and accurate autoinducer-2 detection. Using this reporter strain we tested autoinducer-2 activity from two oral commensal species, Streptococcus gordonii DL1 and Streptococcus oralis 34. Spent broth was collected and adjusted to pH 7.5 and supplemented with boric acid prior to measuring autoinducer- 2 activity. Results show that low pH inhibits bioluminescence of the reporter strain, but pH 7.5 allows for bioluminescence induction and proper readings of autoinducer-2 activity. Addition of boric acid also has a positive effect on bioluminescence allowing for a more sensitive detection of autoinducer-2 activity. Our data suggests that although autoinducer-2 is present in spent broth, low pH and/or low levels of boric acid become an obstacle for proper autoinducer-2 detection. For proper autoinducer-2 detection, we propose a protocol using this bioassay to include pH adjustment and boric acid addition to spent broth. Studies on autoinducer-2 activity in several bacteria species represent an important area of study as this universal signaling molecule is involved in critical bacterial phenotypes such as virulence and biofilm formation. PMID:27350615

  7. Sensitization of Listeria monocytogenes to Low pH, Organic Acids, and Osmotic Stress by Ethanol

    PubMed Central

    Barker, Clive; Park, Simon F.

    2001-01-01

    The killing of Listeria monocytogenes following exposure to low pH, organic acids, and osmotic stress was enhanced by the addition of 5% (vol/vol) ethanol. At pH 3, for example, the presence of this agent stimulated killing by more than 3 log units in 40 min of exposure. The rate of cell death at pH 3.0 was dependent on the concentration of ethanol. Thus, while the presence 10% (vol/vol) ethanol at pH 3.0 stimulated killing by more than 3 log units in just 5 min, addition of 1.25% (vol/vol) ethanol resulted in less than 1 log unit of killing in 10 min. The ability of 5% (vol/vol) ethanol to stimulate killing at low pH and at elevated osmolarity was also dependent on the amplitude of the imposed stress, and an increase in the pH from 3.0 to 4.0 or a decrease in the sodium chloride concentration from 25 to 2.5% led to a marked reduction in the effectiveness of 5% (vol/vol) ethanol as an augmentative agent. Combinations of organic acids, low pH, and ethanol proved to be particularly effective bactericidal treatments; the most potent combination was pH 3.0, 50 mM formate, and 5 % (vol/vol) ethanol, which resulted in 5 log units of killing in just 4 min. Ethanol-enhanced killing correlated with damage to the bacterial cytoplasmic membrane. PMID:11282610

  8. Bilayers and wormlike micelles at high pH in fatty acid soap systems.

    PubMed

    Xu, Wenlong; Liu, Huizhong; Song, Aixin; Hao, Jingcheng

    2016-03-01

    Bilayers at high pH in the fatty acid systems of palmitic acid/KOH/H2O, palmitic acid/CsOH/H2O, stearic acid/KOH/H2O and stearic acid/CsOH/H2O can form spontaneously (Xu et al., 2014, 2015). In this work, the bilayers can still be observed at 25°C with an increase of the concentration of fatty acids. We found that wormlike micelles can also be prepared in the fatty acid soap systems at high pH, even though the temperature was increased to be 50°C. The viscoelasticity, apparent viscosity, yield stress of the bilayers were determined by the rheological measurements. Wormlike micelles were identified by cryogenic transmission electron microscopy (cryo-TEM) and emphasized by the rheological characterizations, which are in accordance with the Maxwell fluids with good fit of Cole-Cole plots. The phase transition temperature was determined by differential scanning calorimetry (DSC) and the transition process was recorded. The regulating role of counterions of fatty acids were discussed by (CH3)4N(+), (C2H5)4N(+), (C3H7)4N(+), and (C4H9)4N(+) as comparison, concluding that counterions with appropriate hydrated radius were the vital factor in the formation wormlike micelles.

  9. Fluorescent probes in biology and medicine: measurement of intracellular pH values in individual cells

    NASA Astrophysics Data System (ADS)

    Slavik, Jan; Cimprich, Petr; Gregor, Martin; Smetana, Karel, Jr.

    1997-12-01

    The application possibilities of fluorescent probes have increased dramatically in the last few years. The main areas are as follows (Slavik, 1994, 1996, 1998). Intracellular ionic cell composition: There are selective ion-sensitive dyes for H+, Ca2+, Mg2+, K+, Na+, Fe3+, Cl-, Zn2+, Cd2+, Hg2+, Pb2+, Ba2+, La3+. Membrane potential: Using the so-called slow (Nernstian dyes) or electrochromic dyes one can assess the value of the transmembrane potential. Membrane fluidity: Fluorescent probes inform about the freedom of rotational and translational movement of membrane proteins and lipids. Selective labeling: Almost any object of interest inside the cell or on its surface can be selectively fluorescently labeled. There are dyes specific for DNA, RNA, oligonucleotides (FISH), Golgi, endoplasmic reticulum, mitochondria, vacuoles, cytoskeleton, etc. Using fluorescent dyes specific receptors may be localized, their conformational changes followed and the polarity of corresponding binding sites accessed. The endocytic pathway may be followed, enzymes and their local enzymatic activity localized. For really selective labeling fluorescent labeled antibodies exist. Imaging: One of the main advantages of fluorescence imaging is its versatility. It allow choice among ratio imaging in excitation, ratio imaging in emission and lifetime imaging. These approaches can be applied to both the classical wide-field fluorescence microscopy and to the laser confocal fluorescence microscopy, one day possibly to the scanning near field optical microscopy. Simultaneous application of several fluorescent dyes: The technical progress in both excitation sources and in detectors allows to extend the excitation deeper in the blue and ultraviolet side and the detection further in the NIR and IR. Consequently, up to 6 peaks in excitation and up to 6 peaks in emission can be followed without any substantial difficulties. Application of dyes such with longer fluorescence lifetimes such as rare earth

  10. Recovery of carboxylic acids at pH greater than pK{sub a}

    SciTech Connect

    Tung, L.A.

    1993-08-01

    Economics of producing carboxylic acids by fermentation is often dominated, not by the fermentation cost, but by the cost of recovering and purifying the acids from dilute aqueous solutions. Experiments were performed to measure uptakes of lactic and succinic acids as functions of pH by basic polymeric sorbents; sorbent regeneration was also tested. Performance at pH > pK{sub a} and regenerability depend on sorbent basicity; apparent pK{sub a} and monomer pK{sub a} can be used to predict sorbent performance. Two basic amine extractants, Alamine 336 and Amberlite LA-2, in were also studied; they are able to sustain capacity to higher pH in diluents that stabilize the acid-amine complex through H bonding. Secondary amines perform better than tert-amines in diluents that solvate the additional proton. Competitive sulfate and phosphate, an interference in fermentation, are taken up by sorbents more strongly than by extractants. The third step in the proposed fermentation process, the cracking of the trimethylammonium (TMA) carboxylate, was also examined. Because lactic acid is more soluble and tends to self-esterify, simple thermal cracking does not remove all TMA; a more promising approach is to esterify the TMA lactate by reaction with an alcohol.

  11. Algal and Bacterial Activities in Acidic (pH 3) Strip Mine Lakes

    PubMed Central

    Gyure, Ruth A.; Konopka, Allan; Brooks, Austin; Doemel, William

    1987-01-01

    Reservoir 29 and Lake B are extremely acid lakes (epilimnion pHs of 2.7 and 3.2, respectively), because they receive acidic discharges from coal refuse piles. They differ in that the pH of profundal sediments in Reservoir 29 increased from 2.7 to 3.8 during the period of thermal stratification, whereas permanently anoxic sediments in Lake B had a pH of 6.2. The pH rise in Reservoir 29 sediments was correlated with a temporal increase in H2S concentration in the anaerobic hypolimnion from 0 to >1 mM. The chlorophyll a levels in the epilimnion of Reservoir 29 were low, and the rate of primary production was typical of an oligotrophic system. However, there was a dense 10-cm layer of algal biomass at the bottom of the metalimnion. Production by this layer was low owing to light limitation and possibly H2S toxicity. The specific photosynthetic rates of epilimnetic algae were low, which suggests that nutrient availability is more important than pH in limiting production. The highest photosynthetic rates were obtained in water samples incubated at pH 2.7 to 4. Heterotrophic bacterial activity (measured by [14C]glucose metabolism) was greatest at the sediment/water interface. Bacterial production (assayed by thymidine incorporation) was as high in Reservoir 29 as in a nonacid mesotrophic Indiana lake. PMID:16347430

  12. Algal and bacterial activities in acidic (pH 3) strip mine lakes

    SciTech Connect

    Gyure, R.A.; Konopka, A.; Brooks, A.; Doemel, W.

    1987-09-01

    Reservoir 29 and Lake B are extremely acid lakes (epilimnion pHs of 2.7 and 3.2, respectively), because they receive acidic discharges from coal refuse piles. They differ in that the pH of profundal sediments in Reservoir 29 increased from 2.7 to 3.8 during the period of thermal stratification, whereas permanently anoxic sediments in Lake B had a pH of 6.2. The pH rise in Reservoir 29 sediments was correlated with a temporal increase in H/sub 2/S concentration in the anaerobic hypolimnion from 0 to >1 mM. The chlorophyll a levels in the epilimnion of Reservoir 29 were low, and the rate of primary production was typical of an oligotrophic system. However, there was a dense 10-cm layer of algal biomass at the bottom of the metalimnion. Production by this layer was low owing to light limitation and possibly H/sub 2/S toxicity. The specific photosynthetic rates of epilimnetic algae were low, which suggests that nutrient availability is more important than pH in limiting production. The highest photosynthetic rates were obtained in water samples incubated at pH 2.7 to 4. Heterotrophic bacterial activity (measured by (/sup 14/C)glucose metabolism) was greatest at the sediment/water interface. Bacterial production (assayed by thymidine incorporation) was as high in Reservoir 29 as in a nonacid mesotrophic Indiana lake.

  13. Preparation of acidic and alkaline macrocapsules for pH control.

    PubMed

    Flora, Joseph R V; Baker, Benjamin; Wybenga, Daniel; Zhu, Huiying; Aelion, C Marjorie

    2008-01-01

    A series of experiments was performed to prepare acidic macroencapsulated buffers composed of 20% Ca(H2PO4)(2) and 80% Eudragit S 100 polymer and alkaline macrocapsules composed of 65% K2HPO4 and 35% Eudragit E PO polymer (the powdered form of Eudragit E 100). Eudragit S 100 was shown to be soluble at a pH greater than 7.0, while Eudragit E 100 was soluble at a pH less than 7.0. Both polymers did not impart significant biochemical oxygen demand. The Eudragit E PO polymer solution showed low toxicity (EC50=91%) based on the Microtox Acute Toxicity Test compared to the 0.1mM background phosphate buffer solution (EC50=100%) while the Eudragit S 100 polymer solution showed higher toxicity (EC50=53%). Batch tests showed that the acidic macrocapsules reduced the pH of a 0.1mM phosphate solution from 11 to neutral, while the alkaline macrocapsules increased the pH of a 0.1mM phosphate solution from 3 to neutral. The macrocapsules could potentially be used as an in situ proportional pH controller for groundwater remediation.

  14. Ingested acidic food and liquids may lead to misinterpretation of 24-hour ambulatory pH tests: focus on measurement of extra-esophageal reflux.

    PubMed

    Koskenvuo, Juha W; Pärkkä, Jussi P; Hartiala, Jaakko J; Kinnunen, Ilpo; Peltola, Matti; Sala, Eeva

    2007-07-01

    Normal values of extra-esophageal reflux are difficult to determine owing to variation in the location of the proximal electrode, limited information on the ingestion of acidic food, different exclusion periods for meals, and poor reproducibility of measurement of extra-esophageal reflux. We studied whether ambulatory esophageal pH testing is disturbed by acidic food ingestion. Eighteen healthy subjects were enrolled in standard dual-channel esophageal pH tests (recorder 1). Ten subjects were equipped with another pH device (recorder 2), positioned to measure extra-esophageal reflux. The subjects were exposed to controlled ingestion of different acidic food or liquid for five 1-min periods. The present study showed that acidic food ingestion for 5 min has a significant effect on the outcome of standard dual-channel ambulatory pH testing. Reflux occurs equally on proximal channels during ingestion of acidic food, whether the proximal channel position is normal or 2 cm above the upper esophageal sphincter. We recommend avoiding acidic food intake during esophageal pH testing.

  15. pH-Metric determination of acid values in oilseeds without titration.

    PubMed

    Kuselman, I; Tur'yan, Y I; Burenko, T; Goldfeld, I; Anisimov, B

    1999-07-01

    A new pH-metric method for determination of acid values in oilseeds without titration has been developed in the range 0.6-10 and more mg KOH/g. The method is based on a rapid (1-2 min) selective and complete extraction of free fatty acids from an oilseed test portion into a special reagent A, separation of the solution from the solid oilseed material by centrifugation or filtration, transfer of an aliquot of the solution into a pH-metric cell with reagent B for measurement of conditional pH(1)' of the formed mixture, addition of standard acid (HCl or H(2)SO(4)) and pH(2)' measurement. The reagents are non-toxic, and the method is rapid. Its metrological parameters for Soybean, Canola and Sunflower oilseeds are satisfactory for practical purposes.

  16. Humic Acid Effects on the Transport of Colloidal Particles in Unsaturated Porous Media: Humic Acid Dosage, pH, and Ionic Strength Dependence

    NASA Astrophysics Data System (ADS)

    Morales, V. L.; Gao, B.; Steenhuis, T. S.

    2008-12-01

    Soil colloids and biocolloids can facilitate contaminant transport within the soil profile through the complexation of pollutants previously thought to have limited mobility. Dissolved organic substances are qualitatively known to alter the behavior of colloids and surface chemistry of soil particles in aquatic environments when adsorbed to their surfaces. Specifically, it has been observed that even small amounts of adsorbed humic acids result in a pronounced increase in colloid mobility in saturated porous systems, presumably by a combination of electrostatic and steric stabilization. However, the degree to which adsorbed humic acids stabilize colloidal suspension is highly sensitive to the system's solution chemistry; mainly in terms of pH, ionic strength, and metal ions present. The objective of this study is to expound quantitatively on the role that combined stabilizing and destabilizing solution chemistry components have on humic acid-colloid transport in unsaturated media by isolating experimentally some underlying mechanisms that regulate colloid transport in realistic aquatic systems. We hypothesize that in chemically heterogeneous porous media, with ionic strength values above 0 and pH ranges from 4 to 9, the effect of humic acid on colloid suspensions cannot be simply characterized by increased stability and mobility. That a critical salt concentration must exists for a given humic acid concentration and pH, above which the network of humic acid collapses by forming coordination complexes with other suspended or adsorbed humic acids, thus increasing greatly the retention of colloids in the porous medium by sweep flocculation. In addition, capillary forces in unsaturated media may contribute further to overcome repulsive forces that prevent flocculation of humic acid-colloid complexes. The experimental work in this study will include: jar tests to determine critical solution concentration combinations for desired coagulation/flocculation rates, column

  17. Effect of sampling location on L* values and pH measurements and their relationship in broiler breast fillets

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lightness (CIELAB L*) and pH values are the most widely measured quality indicators for broiler breast fillets (pectoralis major). Measurement of L* values with a spectrophotometer can be done through Specular Component Included (SCI) or Specular Component Excluded (SCE) modes. The intra-fillet loca...

  18. Effects of pH, dissolved oxygen, and ionic strength on the survival of Escherichia coli O157:H7 in organic acid solutions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ability of Escherichia coli O157:H7 to survive in acidified vegetable products is of concern because of previously documented outbreaks associated with fruit juices. A study was conducted to determine the survival of E. coli O157:H7 in organic acids at pH values typical of acidified vegetable pr...

  19. Hydrogel/fiber optic sensor for distributed measurement of humidity and pH value

    NASA Astrophysics Data System (ADS)

    MacLean, Alistair; Michie, W. Craig; Pierce, S. Gareth; Thursby, Graham; Culshaw, Brian; Moran, Chris; Graham, Neil B.

    1998-07-01

    The combination of chemically sensitive, swellable polymer materials with novel optical fiber cable designs to transduce the swelling activity into microbend loss enables a simple yet powerful sensor to be produced. Interrogating such cables with standard optical time domain reflectoctrometry (OTDR) instruments allows particular chemicals of interest to be detected and located along a cable which may extend to several kilometers. We report here on a sensor cable which uses a water swellable material, a hydrogel, to detect positions of water ingress, relative humidity level or pH value. In direct water ingress tests, wet sensor lengths as small as 5 cm in several hundreds of meters have been detected using conventional OTDRs. Following a review of the sensor design, we present the results of an investigation of the mechanical interaction between the hydrogel polymer and the optical fiber within the sensor. The behavior of the sensor is then characterized within environments of different relative humidity levels from 70 percent to 100 percent at temperatures ranging from 0 to 60 degrees C. The sensor was initially designed for applications within civil engineering but can be applied to a much broader range of measurement requirements, for example soil moisture measurement. We will report details on experimental observations on concrete cure within reinforcing tendon ducts and soil humidity measurements within different soil types.

  20. Synthesis and characterization of a pH responsive folic acid functionalized polymeric drug delivery system.

    PubMed

    Li, Xia; McTaggart, Matt; Malardier-Jugroot, Cecile

    2016-01-01

    We report the computational analysis, synthesis and characterization of folate functionalized poly(styrene-alt-maleic anhydride), PSMA for drug delivery purpose. The selection of the proper linker between the polymer and the folic acid group was performed before conducting the synthesis using Density Functional Theory (DFT). The computational results showed the bio-degradable linker 2, 4-diaminobutyric acid, DABA as a good candidate allowing flexibility of the folic acid group while maintaining the pH sensitivity of PSMA, used as a trigger for drug release. The synthesis was subsequently carried out in multi-step experimental procedures. The functionalized polymer was characterized using InfraRed spectroscopy, Nuclear Magnetic Resonance and Dynamic Light Scattering confirming both the chemical structure and the pH responsiveness of PSMA-DABA-Folate polymers. This study provides an excellent example of how computational chemistry can be used in selection process for the functional materials and product characterization. The pH sensitive polymers are expected to be used in delivering anti-cancer drugs to solid tumors with overly expressed folic acid receptors. PMID:27183249

  1. 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

  2. In vivo measurements of changes in pH triggered by oxalic acid in leaf tissue of transgenic oilseed rape.

    PubMed

    Zou, Qiu-Ju; Liu, Sheng-Yi; Dong, Xu-Yan; Bi, Yan-Hua; Cao, Yuan-Cheng; Xu, Qiao; Zhao, Yuan-Di; Chen, Hong

    2007-01-01

    Oxalic acid (OA), a non-host-specific toxin secreted by Sclerotinia sclerotiorum during pathogenesis, has been demonstrated to be a major phytotoxic and pathogenic factor. Oxalate oxidase (OXO) is an enzyme associated with the detoxification of OA, and hence the introduction of an OXO gene into oilseed rape (Brassica napus L.) to break down OA may be an alternative way of increasing the resistance of the plant to Sclerotinia sclerotiorum. In order to investigate the activation of OXO in transgenic oilseed rape, a convenient and accessible method was used to monitor changes in pH in response to stress induced by OA. The pH sensor, a platinum microcylinder electrode modified using polyaniline film, exhibited a linear response within the pH range from 3 to 7, with a Nernst response slope of 70 mV/pH at room temperature. The linear correlation coefficient was 0.9979. Changes induced by OA in the pH values of leaf tissue of different oilseed rape species from Brassica napus L. were monitored in real time in vivo using this electrode. The results clearly showed that the transgenic oilseed rape was more resistant to OA than non-transgenic oilseed rape.

  3. Key role of pH in the photochemical conversion of NO2 to HONO on humic acid

    NASA Astrophysics Data System (ADS)

    Han, Chong; Yang, Wangjin; Wu, Qianqian; Yang, He; Xue, Xiangxin

    2016-10-01

    The heterogeneous photochemical reactions of NO2 with humic acid (HA) were performed using a flow tube reactor coupled to a NOx analyzer. The effects of the pH on the uptake coefficient (γ) of NO2 and HONO and NO yields were investigated in detail. With increasing the pH in the range of 2-12, γ was almost constant with an average value of (4.21 ± 0.46) × 10-6, whereas the HONO yield and NO yield linearly decreased from (81.07 ± 4.07)% and (10.35 ± 3.86)% to (13.87 ± 9.15)% and (1.51 ± 0.94)%, respectively. According to the characterization of HA compositions and possible reaction paths, it can be concluded that the pH may influence the transfer of protons and the equilibrium of HONO with NO2- by varying the contents of carboxyl and phenol groups in HA, which should primarily contribute to the change in the HONO yield with the pH.

  4. Continuous monitoring of salivary flow rate and pH at the surface of the dentition following consumption of acidic beverages.

    PubMed

    Millward, A; Shaw, L; Harrington, E; Smith, A J

    1997-01-01

    Use of a splint-mounted flexible pH electrode has allowed reliable continuous monitoring of pH at the surface of the dentition whilst still enabling subjects to drink normally. pH was monitored at the palatal upper left central incisor and upper right first permanent molar sites after drinking 1% (w/v) citric acid. A maximal decrease in pH to values of 2-3 was observed after 1 min followed by a slower recovery which was above pH 5.5 within 2 min at the former site and in 4-5 min at the latter site. A sharp rise in parotid saliva flow rate was seen at 1 min after drinking the same concentration of citric acid by glass, straw or feeder cup, which returned to resting levels within 6 min although the fall-off of flow rate was slower with the feeder cup. Thus, after dietary acid intake the pH at the surface of the dentition is below the critical pH for enamel dissolution for shorter periods than previously suggested, which is probably a reflection of salivary neutralisation and washing. PMID:8955994

  5. Comparison of the effects of concentration, pH and anion species on astringency and sourness of organic acids.

    PubMed

    Sowalsky, R A; Noble, A C

    1998-06-01

    The separate effects of concentration, pH and anion species on intensity of sourness and astringency of organic acids were evaluated. Judges rated sourness and astringency intensity of lactic, malic, tartaric and citric acid solutions at three levels of constant pH varying in normality and at three levels of constant concentration varying in pH. To assess the comparative sourness and astringency of the organic acid anions of study, binary acid solutions matched in pH and titratable acidity were also rated. As pH was decreased in equinormal solutions, both sourness and astringency increased significantly (P < 0.001). By contrast, as the normality of the equi-pH solutions was increased, only sourness demonstrated significant increases (P < 0.001) while astringency remained constant or decreased slightly. At the lowest normality tested, all solutions were more astringent than sour (P < 0.05). Although lactic acid was found to be significantly more sour than citric acid (P < 0.05), no other sourness or astringency differences among the organic acid anions were noted. This study demonstrates for the first time that astringency elicited by acids is a function of pH and not concentration or anion species, and confirms that sourness is independently influenced by concentration, pH and anion species of the acid.

  6. The impact of the pH value on skin integrity and cutaneous wound healing.

    PubMed

    Schreml, S; Szeimies, R-M; Karrer, S; Heinlin, J; Landthaler, M; Babilas, P

    2010-04-01

    The process of cutaneous wound healing comprises three overlapping major phases: inflammation, proliferation and tissue remodelling. However, while mechanisms are studied scientifically on the cellular and subcellular level, there is still a lack of knowledge concerning basic clinical parameters like wound pH or pO2. It could be proven that wound healing is affected by wound pH changes as they can lead to an inhibition of endogenous and therapeutically applied enzymes. Besides, the conformational structure of proteins and their functionality in wound healing is altered. Furthermore, the likelihood of bacterial colonization, which is a common problem in chronic wound pathogenesis, is affected by wound pH alterations. However, wound pH is rarely taken into account in current wound therapy strategies. A routinely performed monitoring of the wound pH and a subsequently adapted wound therapy would most possibly improve chronic wound therapy.

  7. 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.

  8. 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

  9. Production of Retrovirus-Based Vectors in Mildly Acidic pH Conditions.

    PubMed

    Holic, Nathalie; Fenard, David

    2016-01-01

    Gene transfer vectors based on retroviridae are increasingly becoming a tool of choice for biomedical research and for the development of biotherapies in rare diseases or cancers. To meet the challenges of preclinical and clinical production, different steps of the production process of self-inactivating γ-retroviral (RVs) and lentiviral vectors (LVs) have been improved (e.g., transfection, media optimization, cell culture conditions). However, the increasing need for mass production of such vectors is still a challenge and could hamper their availability for therapeutic use. Recently, we observed that the use of a neutral pH during vector production is not optimal. The use of mildly acidic pH conditions (pH 6) can increase by two- to threefold the production of RVs and LVs pseudotyped with the vesicular stomatitis virus G (VSV-G) or gibbon ape leukemia virus (GALV) glycoproteins. Here, we describe the production protocol in mildly acidic pH conditions of GALVTR- and VSV-G-pseudotyped LVs using the transient transfection of HEK293T cells and the production protocol of GALV-pseudotyped RVs produced from a murine producer cell line. These protocols should help to achieve higher titers of vectors, thereby facilitating experimental research and therapeutic applications. PMID:27317171

  10. Effect of pH and organic acids on nitrogen transformations and metal dissolution in soils

    SciTech Connect

    Fu, Minhong.

    1989-01-01

    The effect of pH (4, 6, and 8) on nitrogen mineralization was evaluated in three Iowa surface soils treated with crop residues (corn (Zea mays L.), soybean (Glycine max (L.) Merr.), and sorghum (Sorghum vulgare Pers.), or alfalfa (Medicago sativa L.)) and incubated in leaching columns under aerobic conditions at 30C for 20 weeks. In general, N mineralization was significantly depressed at soil pH 4, compared with pH 6 or 8. The types of crop residues added influenced the pattern and amount of N mineralization. A study on the effect of 19 trace elements on the nitrate red activity of four Iowa surface soils showed that most trace elements inhibited this enzyme in acid and neutral soils. The trace elements Ag(I), Cd(II), Se(IV), As(V), and W(VI) were the most effective inhibitors, with >75% inhibition. Mn(II) was the least effective inhibitor, with <10% inhibition. Other trace elements included Cu(I), Co(II), Cu(II), Fe(II), Ni(II), Pb(II), Zn(II), Al(III), As(III), Cr(III), Fe(III), V(IV), Mo(VI), and Se(VI). The application of high-performance liquid chromatography (HPLC) showed that, when coupled to a refractive index detector, it is a rapid, sensitive, and accurate method for determining organic acids in soils. Three organic acids, acetic (2-20 mM), propionic (0-3 mM), and n-butyric (0-1.4 mM), were identified with HPLC and confirmed by gas chromatography in crop-residue-treated soils incubated under waterlogged conditions at 25C for 72 h. No organic acids were detected under aerobic conditions. Four mineral acids and 29 organic acids were studied for their effect on N mineralization and metal dissolution in soils incubated under waterlogged conditions at 30C for 10 days.

  11. Chlorogenic acid increased 5-hydroxymethylfurfural formation when heating fructose alone or with aspartic acid at two pH levels.

    PubMed

    Zhang, Zhenhua; Zou, Yueyu; Wu, Taigang; Huang, Caihuan; Pei, Kehan; Zhang, Guangwen; Lin, Xiaohua; Bai, Weibin; Ou, Shiyi

    2016-01-01

    Chlorogenic acid (CGA) is a phenolic acid that ubiquitously exists in fruits. This work aims to investigate whether and how CGA influences HMF formation during heating fructose alone, or with an amino acid. The results showed that that CGA increased 5-hydroxymethylfurfural (HMF) formation. At pH 5.5 and 7.0, the addition of 5.0 μmol/ml CGA increased HMF formation by 49.4% and 25.2%, respectively when heating fructose alone, and by 9.0% and 16.7%, respectively when heating fructose with aspartic acid. CGA significantly increased HMF formation by promoting 3-deoxosone formation, and its conversion to HMF by inhibiting HMF elimination, especially in the Maillard reaction system. A comparison of the catalytic capacity of CGA with its six analogous compounds showed that both its di-hydroxyphenyl and carboxyl groups function in increasing HMF formation.

  12. Flocculation and Membrane Binding of Outer Membrane Protein F, Porin, at Acidic pH

    NASA Astrophysics Data System (ADS)

    Suzuki, Keiko; Nakae, Taiji; Mitaku, Shigeki

    1998-04-01

    Outer membrane protein F (OmpF), porin, of Escherichia coli is an intrinsic membrane protein made of a β-sheet barrel, the amino acid sequence being as hydrophilic as many soluble proteins in spite of its location in the hydrophobic region of membrane. The binding of porin molecules with a lipid membrane and the flocculation of the protein were studied at various pH, using the combination of centrifugation and intrinsic fluorescence measurements. The binding of porin with the lipid membrane occurred in the pH range below 7, whereas the flocculation of porin in the absence of the membrane was observed only at pH below 5. Porin molecules in the pH range between 5 and 7 were stable as a colloid but spontaneously bound with the lipid membrane soon after the addition of lipid vesicles. The possible mechanism of the structural formation of porin in the outer membrane was discussed based on the pH dependence of the membrane binding ability of this protein.

  13. Investigations into aggregate formation with oppositely charged oil-in-water emulsions at different pH values.

    PubMed

    Maier, Christiane; Zeeb, Benjamin; Weiss, Jochen

    2014-05-01

    The pH-dependent formation and stability of food-grade heteroaggregates from oppositely charged oil-in-water (O/W) emulsions was investigated. After screening suitable emulsifiers, 10% (w/w) oil in-water emulsions (d32≈1 μm) were prepared at pH 3-7 using a positively charged emulsifier (Na-lauroyl-l-arginine ethyl ester; LAE) and four negatively charged ones (citric esters of mono- and diglycerides, soy lecithin, sugar beet pectin, and Quillaja saponin). The oppositely charged emulsions were then combined at constant pH values at a volume flow rate ratio of 1:1. Emulsions and heteroaggregates were characterized by their surface charge, particle size distribution and microstructure using dynamic and static light scattering as well as confocal laser scanning microscopy. The emulsifier type was found to greatly influence the type of heteroaggregates formed, as well as the pH value, specifically in combined LAE/Quillaja saponin emulsions. Larger aggregates particularly were formed with increasing pH values (2.71±1.21 to 46.53±4.30 μm from pH 3 to 7, respectively), while LAE/pectin aggregates appeared not to be affected by pH over the full pH range investigated (3.80±2.89 to 3.94±2.78 μm from pH 3 to 7, respectively). Our study thus provides valuable first insights into the mechanism of the formation of food-grade heteroaggregates for later use in food systems.

  14. Investigations into aggregate formation with oppositely charged oil-in-water emulsions at different pH values.

    PubMed

    Maier, Christiane; Zeeb, Benjamin; Weiss, Jochen

    2014-05-01

    The pH-dependent formation and stability of food-grade heteroaggregates from oppositely charged oil-in-water (O/W) emulsions was investigated. After screening suitable emulsifiers, 10% (w/w) oil in-water emulsions (d32≈1 μm) were prepared at pH 3-7 using a positively charged emulsifier (Na-lauroyl-l-arginine ethyl ester; LAE) and four negatively charged ones (citric esters of mono- and diglycerides, soy lecithin, sugar beet pectin, and Quillaja saponin). The oppositely charged emulsions were then combined at constant pH values at a volume flow rate ratio of 1:1. Emulsions and heteroaggregates were characterized by their surface charge, particle size distribution and microstructure using dynamic and static light scattering as well as confocal laser scanning microscopy. The emulsifier type was found to greatly influence the type of heteroaggregates formed, as well as the pH value, specifically in combined LAE/Quillaja saponin emulsions. Larger aggregates particularly were formed with increasing pH values (2.71±1.21 to 46.53±4.30 μm from pH 3 to 7, respectively), while LAE/pectin aggregates appeared not to be affected by pH over the full pH range investigated (3.80±2.89 to 3.94±2.78 μm from pH 3 to 7, respectively). Our study thus provides valuable first insights into the mechanism of the formation of food-grade heteroaggregates for later use in food systems. PMID:24681049

  15. Thermal resistance parameters of acid-adapted and unadapted Escherichia coli O157:H7 in apple-carrot juice blends: effect of organic acids and pH.

    PubMed

    Usaga, Jessie; Worobo, Randy W; Padilla-Zakour, Olga I

    2014-04-01

    Numerous outbreaks involving fresh juices contaminated with Escherichia coli O157:H7 have occurred in the United States and around the world, raising concern for the safety of these products. Until now, only a few studies regarding the thermal tolerance of this pathogen in acidic juices over a wide range of pH values have been published. Therefore, the effect of varying the pH with different organic acids on the thermal inactivation of non-acid-adapted and acid-adapted E. coli O157:H7 (strain C7927) was determined. The decimal reduction times (D-values) and the change in temperature required for the thermal destruction curve to traverse 1 log cycle (z-values) were calculated for non-acid-adapted E. coli in an apple-carrot juice blend (80:20) adjusted to three pH values (3.3, 3.5, and 3.7) by the addition of lactic, malic, or acetic acid and at a pH of 4.5 adjusted with NaOH. Thermal parameters were also determined for acid-adapted cells in juices acidified with malic acid. The effect of the soluble solids content on the thermal tolerance was studied in samples with a pH of 3.7 at 9.4 to 11.5 °Brix. The D-values were determined at 54, 56, and 58 °C, and trials were conducted in triplicate. Non-acid-adapted E. coli exhibited the highest thermal tolerance at pH 4.5 (D-value at 54 °C [D54 °C] of 20 ± 4 min and z-value of 6.2 °C), although on average, the D-values increased significantly (P < 0.01) due to acid adaptation. In acidified juices, the highest tolerance was observed in acid-adapted E. coli in samples adjusted to pH 3.7 with malic acid (D54 °C of 9 ± 2 min and z-value of 5.4 °C) and the lowest in unadapted E. coli at pH 3.3 acidified with acetic acid (D58 °C of 0.03 ± 0.01 min and z-value of 10.4 °C). For juices acidified to the same endpoint pH with different acids, E. coli was found to be more tolerant in samples acidified with malic acid, followed by lactic and acetic acids. Increasing the soluble solids content from 9.4 to 11.5 °Brix showed no

  16. Antimony leaching release from brake pads: Effect of pH, temperature and organic acids.

    PubMed

    Hu, Xingyun; He, Mengchang; Li, Sisi

    2015-03-01

    Metals from automotive brake pads pollute water, soils and the ambient air. The environmental effect on water of antimony (Sb) contained in brake pads has been largely untested. The content of Sb in one abandoned brake pad reached up to 1.62×10(4) mg/kg. Effects of initial pH, temperature and four organic acids (acetic acid, oxalic acid, citric acid and humic acid) on Sb release from brake pads were studied using batch reactors. Approximately 30% (97 mg/L) of the total Sb contained in the brake pads was released in alkaline aqueous solution and at higher temperature after 30 days of leaching. The organic acids tested restrained Sb release, especially acetic acid and oxalic acid. The pH-dependent concentration change of Sb in aqueous solution was best fitted by a logarithmic function. In addition, Sb contained in topsoil from land where brake pads were discarded (average 9×10(3) mg/kg) was 3000 times that in uncontaminated soils (2.7±1 mg/kg) in the same areas. Because potentially high amounts of Sb may be released from brake pads, it is important that producers and environmental authorities take precautions.

  17. Influence of temperature and humidity on rumen pH and fatty acids in dairy cows.

    PubMed

    Gianesella, M; Piccione, G; Cannizzo, C; Casella, S; Morgante, M

    2012-11-01

    The aim of this study was to investigate the variations of rumen pH and fatty acids (acetic acid, propionic acid, iso-butyric acid, n-butyric acid, iso-valerianic acid, n-valerianic, caproic acid and total fatty acids) in 245 early lactating dairy cows under different temperature and humidity conditions. The animals were divided into six groups and rumen fluid was collected by rumenocentesis on 22 dairy cows in April (Group A), 33 in May (Group B), 43 in June (Group C), 48 in July (Group D), 36 in September (Group E) and 60 in October (Group F). One-way analysis of variance (ANOVA), followed by the Bonferroni's test, showed a significant effect of environmental variations on all studied parameters (P < 0.0001). Changes in studied parameters can be explained in relation to the microbial population and shift in the optima for rumen conditions associated with variations of environmental conditions. We can affirm that the microbial assemblages that underlie energy and protein supply to wild ruminant are evident especially in relation to temperature and humidity conditions.

  18. The effects of temperature, pH and redox state on the stability of glutamic acid in hydrothermal fluids

    NASA Astrophysics Data System (ADS)

    Lee, Namhey; Foustoukos, Dionysis I.; Sverjensky, Dimitri A.; Cody, George D.; Hazen, Robert M.

    2014-06-01

    Natural hydrothermal vent environments cover a wide range of physicochemical conditions involving temperature, pH and redox state. The stability of simple biomolecules such as amino acids in such environments is of interest in various fields of study from the origin of life to the metabolism of microbes at the present day. Numerous previous experimental studies have suggested that amino acids are unstable under hydrothermal conditions and decompose rapidly. However, previous studies have not effectively controlled the redox state of the hydrothermal fluids. Here we studied the stability of glutamate with and without reducing hydrothermal conditions imposed by 13 mM aqueous H2 at temperatures of 150, 200 and 250 °C and initial (25 °C) pH values of 6 and 10 in a flow-through hydrothermal reactor with reaction times from 3 to 36 min. We combined the experimental measurements with theoretical calculations to model the in situ aqueous speciation and pH values. As previously observed under hydrothermal conditions, the main reaction involves glutamate cyclizing to pyroglutamate through a simple dehydration reaction. However, the amounts of decomposition products of the glutamate detected, including succinate, formate, carbon dioxide and ammonia depend on the temperature, the pH and particularly the redox state of the fluid. In the absence of dissolved H2, glutamate decomposes in the sequence glutamate, glutaconate, α-hydroxyglutarate, ketoglutarate, formate and succinate, and ultimately to CO2 and micromolar quantities of H2(aq). Model speciation calculations indicate the CO2, formate and H2(aq) are not in metastable thermodynamic equilibrium. However, with 13 mM H2(aq) concentrations, the amounts of decomposition products are suppressed at all temperatures and pH values investigated. The small amounts of CO2 and formate present are calculated to be in metastable equilibrium with the H2. It is further proposed that there is a metastable equilibrium between glutamate

  19. Heat-denaturation and aggregation of quinoa (Chenopodium quinoa) globulins as affected by the pH value.

    PubMed

    Mäkinen, Outi E; Zannini, Emanuele; Koehler, Peter; Arendt, Elke K

    2016-04-01

    The influence of heating (100 °C; 0-15 min) on the relative molecular mass, protein unfolding and secondary structure of quinoa globulins was studied at pH 6.5 (low solubility), 8.5 and 10.5 (high solubility). The patterns of denaturation and aggregation varied with pH. Heating triggered the disruption of the disulfide bonds connecting the acidic and basic chains of the chenopodin subunits at pH 8.5 and 10.5, but not at pH 6.5. Large aggregates unable to enter a 4% SDS-PAGE gel were formed at pH 6.5 and 8.5, which became soluble under reducing conditions. Heating at pH 10.5 lead to a rapid dissociation of the native chenopodin and to the disruption of the subunits, but no SDS-insoluble aggregates were formed. No major changes in secondary structure occurred during a 15 min heating, but an increase in hydrophobicity indicated unfolding of the tertiary structure in all samples.

  20. Heat-denaturation and aggregation of quinoa (Chenopodium quinoa) globulins as affected by the pH value.

    PubMed

    Mäkinen, Outi E; Zannini, Emanuele; Koehler, Peter; Arendt, Elke K

    2016-04-01

    The influence of heating (100 °C; 0-15 min) on the relative molecular mass, protein unfolding and secondary structure of quinoa globulins was studied at pH 6.5 (low solubility), 8.5 and 10.5 (high solubility). The patterns of denaturation and aggregation varied with pH. Heating triggered the disruption of the disulfide bonds connecting the acidic and basic chains of the chenopodin subunits at pH 8.5 and 10.5, but not at pH 6.5. Large aggregates unable to enter a 4% SDS-PAGE gel were formed at pH 6.5 and 8.5, which became soluble under reducing conditions. Heating at pH 10.5 lead to a rapid dissociation of the native chenopodin and to the disruption of the subunits, but no SDS-insoluble aggregates were formed. No major changes in secondary structure occurred during a 15 min heating, but an increase in hydrophobicity indicated unfolding of the tertiary structure in all samples. PMID:26593460

  1. A mathematical model of pH, based on the total stoichiometric concentration of acids, bases and ampholytes dissolved in water.

    PubMed

    Mioni, Roberto; Mioni, Giuseppe

    2015-10-01

    In chemistry and in acid-base physiology, the Henderson-Hasselbalch equation plays a pivotal role in studying the behaviour of the buffer solutions. However, it seems that the general function to calculate the valence of acids, bases and ampholytes, N = f(pH), at any pH, has only been provided by Kildeberg. This equation can be applied to strong acids and bases, pluriprotic weak acids, bases and ampholytes, with an arbitrary number of acid strength constants, pKA, including water. By differentiating this function with respect to pH, we obtain the general equation for the buffer value. In addition, by integrating the titration curve, TA, proposed by Kildeberg, and calculating its Legendre transform, we obtain the Gibbs free energy of pH (or pOH)-dependent titratable acid. Starting from the law of electroneutrality and applying suitable simplifications, it is possible to calculate the pH of the buffer solutions by numerical methods, available in software packages such as Excel. The concept of buffer capacity has also been clarified by Urbansky, but, at variance with our approach, not in an organic manner. In fact, for each set of monobasic, dibasic, tribasic acids, etc., various equations are presented which independently fit each individual acid-base category. Consequently, with the increase in acid groups (pKA), the equations become more and more difficult, both in practice and in theory. Some examples are proposed to highlight the boundary that exists between acid-base physiology and the thermodynamic concepts of energy, chemical potential, amount of substance and acid resistance. PMID:26059505

  2. A mathematical model of pH, based on the total stoichiometric concentration of acids, bases and ampholytes dissolved in water.

    PubMed

    Mioni, Roberto; Mioni, Giuseppe

    2015-10-01

    In chemistry and in acid-base physiology, the Henderson-Hasselbalch equation plays a pivotal role in studying the behaviour of the buffer solutions. However, it seems that the general function to calculate the valence of acids, bases and ampholytes, N = f(pH), at any pH, has only been provided by Kildeberg. This equation can be applied to strong acids and bases, pluriprotic weak acids, bases and ampholytes, with an arbitrary number of acid strength constants, pKA, including water. By differentiating this function with respect to pH, we obtain the general equation for the buffer value. In addition, by integrating the titration curve, TA, proposed by Kildeberg, and calculating its Legendre transform, we obtain the Gibbs free energy of pH (or pOH)-dependent titratable acid. Starting from the law of electroneutrality and applying suitable simplifications, it is possible to calculate the pH of the buffer solutions by numerical methods, available in software packages such as Excel. The concept of buffer capacity has also been clarified by Urbansky, but, at variance with our approach, not in an organic manner. In fact, for each set of monobasic, dibasic, tribasic acids, etc., various equations are presented which independently fit each individual acid-base category. Consequently, with the increase in acid groups (pKA), the equations become more and more difficult, both in practice and in theory. Some examples are proposed to highlight the boundary that exists between acid-base physiology and the thermodynamic concepts of energy, chemical potential, amount of substance and acid resistance.

  3. 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.

  4. Spread mixed monolayers of deoxycholic and dehydrocholic acids at the air-water interface, effect of subphase pH. Characterization by axisymmetric drop shape analysis.

    PubMed

    Messina, Paula V; Fernández-Leyes, Marcos D; Prieto, Gerardo; Ruso, Juan M; Sarmiento, Félix; Schulz, Pablo C

    2008-01-01

    Bile acids (deoxycholic and dehydrocholic acids) spread mixed monolayers behavior at the air/water interface were studied as a function of subphase pH using a constant surface pressure penetration Langmuir balance based on the Axisymmetric Drop Shape Analysis (ADSA). We examined the influence of electrostatic, hydrophobic and hydration forces on the interaction between amphiphilic molecules at the interface by the collapse area values, the thermodynamic parameters and equation of state virial coefficients analysis. The obtained results showed that at neutral (pH=6.7) or basic (pH=10) subphase conditions the collapse areas values are similar to that of cholanoic acid and consistent with the cross-sectional area of the steroid nucleus (approximately 40 A(2)). The Gibbs energy of mixing values (DeltaG(mix)<0) and the first virial coefficients of the equation of state (b(0)<1) indicated that a miscible monolayer with laterally structured microdomains existed. The aggregation number (1/b(0)) was estimated within the order of 6 (pH=6.7) and 3 (pH=10). At pH=3.2, acidic subphase conditions, no phase separation occurs (DeltaG(mix)<0) but a high expanded effect of the monolayer could be noted. The mixed monolayer behavior was no ideal and no aggregates were formed (b(0)> or =1). Such behavior indicates that the polar groups of the molecules interacts each other more strongly by repulsive electrostatic forces than with the more hydrophobic part of the molecule.

  5. Thermodynamic Solubility Profile of Carbamazepine-Cinnamic Acid Cocrystal at Different pH.

    PubMed

    Keramatnia, Fatemeh; Shayanfar, Ali; Jouyban, Abolghasem

    2015-08-01

    Pharmaceutical cocrystal formation is a direct way to dramatically influence physicochemical properties of drug substances, especially their solubility and dissolution rate. Because of their instability in the solution, thermodynamic solubility of cocrystals could not be determined in the common way like other compounds; therefore, the thermodynamic solubility is calculated through concentration of their components in the eutectic point. The objective of this study is to investigate the effect of an ionizable coformer in cocrystal with a nonionizable drug at different pH. Carbamazepine (CBZ), a nonionizable drug with cinnamic acid (CIN), which is an acidic coformer, was selected to prepare CBZ-CIN cocrystal and its thermodynamic solubility was studied in pH range 2-7. Instead of HPLC that is a costly and time-consuming method, a chemometric-based approach, net analyte signal standard addition method, was selected for simultaneous determination of CBZ and CIN in solution. The result showed that, as pH increases, CIN ionization leads to change in CBZ-CIN cocrystal solubility and stability in solution. In addition, the results of this study indicated that there is no significant difference between intrinsic solubility of CBZ and cocrystal despite the higher ideal solubility of cocrystal. This verifies that ideal solubility is not good parameter to predict cocrystal solubility.

  6. SERS spectra of TvNPV-VP influenced by the pH value of Ag hydrosols

    NASA Astrophysics Data System (ADS)

    Bao, PeiDi; Huang, TianQuan; Liu, XinMing; Wu, GuoFeng

    2000-05-01

    Trabala vishnou Nuclear Polyhedrosis Virus is one kind of insect virus. It was found in Chengdu area of southwest China. The surface-enhanced Raman scattering (SERS) spectra of virion protein adsorbed on the silver surface and the SERS spectra influenced by the pH value of silver hydrosols have been obtained and analyzed.

  7. Uranium fate in wetland mesocosms: Effects of plants at two iron loadings with different pH values

    EPA Science Inventory

    Small-scale continuous flow wetland mesocosms (~0.8 L) were used to evaluate how plant roots under different iron loadings affect uranium (U) mobility. When significant concentrations of ferrous iron (Fe) were present at circumneutral pH values, U concentrations in root exposed ...

  8. Acid-induced folding of yeast alcohol dehydrogenase under low pH conditions.

    PubMed

    Le, W P; Yan, S X; Zhang, Y X; Zhou, H M

    1996-04-01

    Under conditions of low pH, the conformational states of holo-YADH and apo-YADH were examined by protein intrinsic fluorescence, ANS fluorescence, and far-UV CD measurements. The results obtained show that a low ionic strength, with the addition of HCl, the holo- and apo- YADH denatured gradually to reach the ultimate unfolded conformation in the vicinity of pH 2.0 and 2.5, respectively. With the decrease of pH from 7.0 to 2.0, the fluorescence emission decreased markedly, with its emission maximum red-shifting from 335 to 355 nm, indicating complete exposure of the buried tryptophan residues to the solvent. The far-UV CD spectra show the loss of the arrayed secondary structure, though the acid-denatured enzyme still maintained a partially arrayed secondary structure. A further decrease in pH by increasing the concentration of HClO4 induced a cooperative folding of the denatured enzyme to a compact conformation with the properties of a molten globule, described previously by Goto et al. [Proc. Natl. Acad. Sci. USA 87, 573-577 (1990)]. More extensive studies showed that although apo-YADH and holo-YADH exhibited similar behavior, the folding cooperative ability of apo-YADH was lower than that of the holo-enzyme. From the above results, it is suggested that the zinc ion plays an important role in the proper folding of YADH and in stabilizing its native conformation.

  9. Resistance of Streptococcus bovis to acetic acid at low pH: Relationship between intracellular pH and anion accumulation

    SciTech Connect

    Russell, J.B. )

    1991-01-01

    Streptococcus bovis JB1, an acid-tolerant ruminal bacterium, was able to grown at pHs from 6.7 to 4.5, and 100 mM acetate had little effect on growth rate or proton motive force across the cell membrane. When S. bovis was grown in glucose-limited chemostats at pH 5.2, the addition of sodium acetate (as much as 100 mM) had little effect on the production of bacterial protein. At higher concentrations of sodium acetate (100 to 360 mM), production of bacterial protein declined, but this decrease could largely be explained by a shift in fermentation products (acetate, formate, and ethanol production to lactate production) and a decline in ATP production (3 ATP per glucose versus 2 ATP per glucose). Y{sub ATP} (grams of cells per mole at ATP) was not decreased significantly even by high concentrations of acetate. Cultures supplemented with 100 mM sodium acetate took up ({sup 14}C)acetate and ({sup 14}C)benzoate in accordance with the Henderson-Hasselbalch equation and gave similar estimates of intracellular pH. As the extracellular pH declined, S. bovis allowed its intracellular pH to decrease and maintained a relatively constant pH gradient across the cell membrane (0.9 unit). The decrease in intracellular pH prevented S. bovis from accumulating large amounts of acetate anion. On the basis of these results it did not appear that acetate was acting as an uncoupler. The sensitivity of other bacteria to volatile fatty acids at low pH is explained most easily by a high transmembrane pH gradient and anion accumulation.

  10. Resistance of Streptococcus bovis to acetic acid at low pH: relationship between intracellular pH and anion accumulation.

    PubMed Central

    Russell, J B

    1991-01-01

    Streptococcus bovis JB1, an acid-tolerant ruminal bacterium, was able to grow at pHs from 6.7 to 4.5, and 100 mM acetate had little effect on growth rate or proton motive force across the cell membrane. When S. bovis was grown in glucose-limited chemostats at pH 5.2, the addition of sodium acetate (as much as 100 mM) had little effect on the production of bacterial protein. At higher concentrations of sodium acetate (100 to 360 mM), production of bacterial protein declined, but this decrease could largely be explained by a shift in fermentation products (acetate, formate, and ethanol production to lactate production) and a decline in ATP production (3 ATP per glucose versus 2 ATP per glucose). YATP (grams of cells per mole of ATP) was not decreased significantly even by high concentrations of acetate. Cultures supplemented with 100 mM sodium acetate took up [14C]acetate and [14C]benzoate in accordance with the Henderson-Hasselbalch equation and gave similar estimates of intracellular pH. As the extracellular pH declined, S. bovis allowed its intracellular pH to decrease and maintained a relatively constant pH gradient across the cell membrane (0.9 unit). The decrease in intracellular pH prevented S. bovis from accumulating large amounts of acetate anion. On the basis of these results it did not appear that acetate was acting as an uncoupler. The sensitivity of other bacteria to volatile fatty acids at low pH is explained most easily by a high transmembrane pH gradient and anion accumulation. PMID:2036013

  11. Microculture model studies on the effect of sorbic acid on Penicillium chrysogenum, Cladosporium cladosporioides and Ulocladium atrum at different pH levels.

    PubMed

    Skirdal, I M; Eklund, T

    1993-02-01

    The minimum growth-inhibitory concentration of sorbic acid has been determined for Penicillium chrysogenum, Cladosporium cladosporioides and Ulocladium atrum at pH 4.1-7.6 by using a microculture technique. This technique had earlier been applied to bacteria and Candida albicans and gave very reliable minimum inhibitory values. This investigation has shown that it is suitable also for determination of mould growth. The minimum inhibitory concentrations of sorbic acid were at the tested pH levels 1-230 mmol l-1 for P. chrysogenum, 0.3-18.0 mmol l-1 for C. cladosporioides and 0.2-33.0 mmol l-1 for U. atrum. A mathematical model for combined inhibition by dissociated and undissociated acid, which gave a good description of the minimum inhibitory concentration data earlier obtained for bacteria and Candida albicans, was suitable also for moulds. Both dissociated and undissociated acid contributed to growth inhibition.

  12. Influence of pH on terminal carbon metabolism in anoxic sediments from a mildly acidic lake

    SciTech Connect

    Phelps, T.J.; Zeikus, J.G.

    1984-12-01

    The carbon and electron flow pathways and the bacterial populations responsible for transformation of H/sub 2/-CO/sub 2/, formate, methanol, methylamine, acetate, glycine, ethanol, and lactate were examined in sediments collected from Knaack Lake, Wisconsin. The sediments were 60% organic matter (pH 6.2) and did not display detectable sulfate-reducing activity, but they contained the following average concentration (in micromoles per liter of sediment) of metabolites and end products: sulfide, 10; methane, 1540; CO/sub 2/, 3950; formate, 25; acetate, 157; ethanol, 174; and lactate, 138. Methane was produced predominately from acetate, and only 4% of the total CH/sub 4/ was derived from CO/sub 2/. Methanogenesis was limited by low environmental temperature and sulfide levels and more importantly by low pH. Increasing in vitro pH to neutral values enhanced total methane production rates and the percentage of CO/sub 2/ transformed to methane but did not alter the amount of /sup 14/CO/sub 2/ produced from (2-/sup 14/C)acetate (approx. 24%). Analysis of both carbon transformation parameters with /sup 14/C-labeled tracers and bacterial trophic group enumerations indicated that methanogenesis from acetate and both heterolactic- and acetic acid-producing fermentations were important to the anaerobic digestion process.

  13. pH-Sensitive Polymeric Micelle-based pH Probe for Detecting and Imaging Acidic Biological Environments

    PubMed Central

    Lee, Young Ju; Kang, Han Chang; Hu, Jun; Nichols, Joseph W.; Jeon, Yong Sun; Bae, You Han

    2012-01-01

    To overcome the limitations of monomeric pH probes for acidic tumor environments, this study designed a mixed micelle pH probe composed of polyethylene glycol (PEG)-b- poly(L-histidine) (PHis) and PEG-b-poly(L-lactic acid) (PLLA), which is well-known as an effective antitumor drug carrier. Unlike monomeric histidine and PHis derivatives, the mixed micelles can be structurally destabilized by changes in pH, leading to a better pH sensing system in nuclear magnetic resonance (NMR) techniques. The acidic pH-induced transformation of the mixed micelles allowed pH detection and pH mapping of 0.2–0.3 pH unit differences by pH-induced “on/off”-like sensing of NMR and magnetic resonance spectroscopy (MRS). The micellar pH probes sensed pH differences in non-biological phosphate buffer and biological buffers such as cell culture medium and rat whole blood. In addition, the pH-sensing ability of the mixed micelles was not compromised by loaded doxorubicin. In conclusion, PHis-based micelles could have potential as a tool to simultaneously treat and map the pH of solid tumors in vivo. PMID:22861824

  14. Putrescine biosynthesis in Lactococcus lactis is transcriptionally activated at acidic pH and counteracts acidification of the cytosol.

    PubMed

    Del Rio, Beatriz; Linares, Daniel; Ladero, Victor; Redruello, Begoña; Fernandez, Maria; Martin, Maria Cruz; Alvarez, Miguel A

    2016-11-01

    Lactococcus lactis subsp. cremoris CECT 8666 is a lactic acid bacterium that synthesizes the biogenic amine putrescine from agmatine via the agmatine deiminase (AGDI) pathway. The AGDI genes cluster includes aguR. This encodes a transmembrane protein that functions as a one-component signal transduction system, the job of which is to sense the agmatine concentration of the medium and accordingly regulate the transcription of the catabolic operon aguBDAC. The latter encodes the proteins necessary for agmatine uptake and its conversion into putrescine. This work reports the effect of extracellular pH on putrescine biosynthesis and on the genetic regulation of the AGDI pathway. Increased putrescine biosynthesis was detected at acidic pH (pH5) compared to neutral pH. Acidic pH induced the transcription of the catabolic operon via the activation of the aguBDAC promoter PaguB. However, the external pH had no significant effect on the activity of the aguR promoter PaguR, or on the transcription of the aguR gene. The transcriptional activation of the AGDI pathway was also found to require a lower agmatine concentration at pH5 than at neutral pH. Finally, the following of the AGDI pathway counteracted the acidification of the cytoplasm under acidic external conditions, suggesting it to provide protection against acid stress.

  15. Binding of sodium dodecyl sulfate with linear and branched polyethyleneimines in aqueous solution at different pH values.

    PubMed

    Wang, Hao; Wang, Yilin; Yan, Haike; Zhang, Jin; Thomas, Robert K

    2006-02-14

    Isothermal titration microcalorimetry (ITC), conductivity, and turbidity measurements have been carried out to study the interaction of sodium dodecyl sulfate (SDS) with polyethyleneimines (PEI) including linear PEI and branched PEI at different pH values of 3, 7, and 10. In all cases, the polymers show a remarkable affinity toward SDS. At pH 3, the polymer PEI is a strong polycation, and the binding is dominated by electrostatic 1:1 charge neutralization with the anionic surfactant. At pH 7, the electrostatic attraction between SDS and PEI is weak, and the hydrophobic interaction becomes stronger. At the natural pH of 10, PEI is essentially nonionic and binds SDS in the form of polymer-bound surfactant aggregates. The charge neutralization concentration (C1) of SDS for the PEI-SDS complex can be derived from the curves of variation of the enthalpy, conductivity, and turbidity with SDS concentration. There is good agreement between the results from the three methods and all show a decrease with increasing pH. The total interaction enthalpies (deltaH(total)) of PEI with SDS are obtained from the observed enthalpy curves and the difference enthalpy (deltaH*) between the total enthalpy of branched PEI with SDS, and the total enthalpy of linear PEI with SDS can be derived from the obtained deltaH(total). The difference deltaH* increases dramatically as pH increases, which indicates that the interactions are different for linear PEI and branched PEI at high pH values. A schematic map of the different states of aggregation is presented.

  16. Technical description of parameters influencing the pH value of suspension absorbent used in flue gas desulfurization systems.

    PubMed

    Głomba, Michał

    2010-08-01

    As a result of the large limestone deposits available in Poland, the low cost of reagent acquisition for the largescale technological use and relatively well-documented processes of flue gas desulfurization (FGD) technologies based on limestone sorbent slurry, wet scrubbing desulfurization is a method of choice in Poland for flue gas treatment in energy production facilities, including power plants and industrial systems. The efficiency of FGD using the above method depends on several technological and kinetic parameters, particularly on the pH value of the sorbent (i.e., ground limestone suspended in water). Consequently, many studies in Poland and abroad address the impact of various parameters on the pH value of the sorbent suspension, such as the average diameter of sorbent particles (related to the limestone pulverization degree), sorbent quality (in terms of pure calcium carbonate [CaCO3] content of the sorbent material), stoichiometric surfeit of CaCO3 in relation to sulfur dioxide (SO2) absorbed from flue gas circulating in the absorption node, time of absorption slurry retention in the absorber tank, chlorine ion concentration in sorbent slurry, and concentration of dissolved metal salts (Na, K, Mg, Fe, Al, and others). This study discusses the results of laboratory-scale tests conducted to establish the effect of the above parameters on the pH value of limestone slurry circulating in the SO2 absorption node. On the basis of the test results, a correlation equation was postulated to help maintain the desirable pH value at the design phase of the wet FGD process. The postulated equation displays good coincidence between calculated pH values and those obtained using laboratory measurements. PMID:20842941

  17. Technical description of parameters influencing the pH value of suspension absorbent used in flue gas desulfurization systems.

    PubMed

    Głomba, Michał

    2010-08-01

    As a result of the large limestone deposits available in Poland, the low cost of reagent acquisition for the largescale technological use and relatively well-documented processes of flue gas desulfurization (FGD) technologies based on limestone sorbent slurry, wet scrubbing desulfurization is a method of choice in Poland for flue gas treatment in energy production facilities, including power plants and industrial systems. The efficiency of FGD using the above method depends on several technological and kinetic parameters, particularly on the pH value of the sorbent (i.e., ground limestone suspended in water). Consequently, many studies in Poland and abroad address the impact of various parameters on the pH value of the sorbent suspension, such as the average diameter of sorbent particles (related to the limestone pulverization degree), sorbent quality (in terms of pure calcium carbonate [CaCO3] content of the sorbent material), stoichiometric surfeit of CaCO3 in relation to sulfur dioxide (SO2) absorbed from flue gas circulating in the absorption node, time of absorption slurry retention in the absorber tank, chlorine ion concentration in sorbent slurry, and concentration of dissolved metal salts (Na, K, Mg, Fe, Al, and others). This study discusses the results of laboratory-scale tests conducted to establish the effect of the above parameters on the pH value of limestone slurry circulating in the SO2 absorption node. On the basis of the test results, a correlation equation was postulated to help maintain the desirable pH value at the design phase of the wet FGD process. The postulated equation displays good coincidence between calculated pH values and those obtained using laboratory measurements.

  18. Rational Design of a Colorimetric pH Sensor from a Soluble Retinoic Acid Chaperone

    PubMed Central

    Berbasova, Tetyana; Nosrati, Meisam; Vasileiou, Chrysoula; Wang, Wenjing; Lee, Kin Sing Stephen; Yapici, Ipek; Geiger, James H.; Borhan, Babak

    2014-01-01

    Reengineering of cellular retinoic acid binding protein II (CRABPII) to be capable of binding retinal as a protonated Schiff base is described. Through rational alterations of the binding pocket, electrostatic perturbations of the embedded retinylidene chromophore that favor delocalization of the iminium charge lead to exquisite control in the regulation of chromophoric absorption properties, spanning the visible spectrum (474–640 nm). The pKa of the retinylidene protonated Schiff base was modulated from 2.4 to 8.1, giving rise to a set of proteins of varying colors and pH sensitivities. These proteins were used to demonstrate a concentration-independent, ratiometric pH sensor. PMID:24059243

  19. Rational design of a colorimetric pH sensor from a soluble retinoic acid chaperone.

    PubMed

    Berbasova, Tetyana; Nosrati, Meisam; Vasileiou, Chrysoula; Wang, Wenjing; Lee, Kin Sing Stephen; Yapici, Ipek; Geiger, James H; Borhan, Babak

    2013-10-30

    Reengineering of cellular retinoic acid binding protein II (CRABPII) to be capable of binding retinal as a protonated Schiff base is described. Through rational alterations of the binding pocket, electrostatic perturbations of the embedded retinylidene chromophore that favor delocalization of the iminium charge lead to exquisite control in the regulation of chromophoric absorption properties, spanning the visible spectrum (474-640 nm). The pKa of the retinylidene protonated Schiff base was modulated from 2.4 to 8.1, giving rise to a set of proteins of varying colors and pH sensitivities. These proteins were used to demonstrate a concentration-independent, ratiometric pH sensor. PMID:24059243

  20. Anacardic acid-mediated changes in membrane potential and pH gradient across liposomal membranes.

    PubMed

    Toyomizu, Masaaki; Okamoto, Katsuyuki; Akiba, Yukio; Nakatsu, Tetsuo; Konishi, Tetsuya

    2002-01-01

    We have previously shown that anacardic acid has an uncoupling effect on oxidative phosphorylation in rat liver mitochondria using succinate as a substrate (Life Sci. 66 (2000) 229-234). In the present study, for clarification of the physicochemical characteristics of anacardic acid, we used a cyanine dye (DiS-C3(5)) and 9-aminoacridine (9-AA) to determine changes of membrane potential (DeltaPsi) and pH difference (DeltapH), respectively, in a liposome suspension in response to the addition of anacardic acid to the suspension. The anacardic acid quenched DiS-C3(5) fluorescence at concentrations higher than 300 nM, with the degree of quenching being dependent on the log concentration of the acid. Furthermore, the K(+) diffusion potential generated by the addition of valinomycin to the suspension decreased for each increase in anacardic acid concentration used over 300 nM, but the sum of the anacardic acid- and valinomycin-mediated quenching was additively increasing. This indicates that the anacardic acid-mediated quenching was not due simply to increments in the K(+) permeability of the membrane. Addition of anacardic acid in the micromolar range to the liposomes with DeltaPsi formed by valinomycin-K(+) did not significantly alter 9-AA fluorescence, but unexpectedly dissipated DeltaPsi. The DeltaPsi preformed by valinomycin-K(+) decreased gradually following the addition of increasing concentrations of anacardic acid. The DeltaPsi dissipation rate was dependent on the pre-existing magnitude of DeltaPsi, and was correlated with the logarithmic concentration of anacardic acid. Furthermore, the initial rate of DeltapH dissipation increased with logarithmic increases in anacardic acid concentration. These results provide the evidence for a unique function of anacardic acid, dissimilar to carbonylcyanide p-trifluoromethoxyphenylhydrazone or valinomycin, in that anacardic acid behaves as both an electrogenic (negative) charge carrier driven by DeltaPsi, and a 'proton

  1. Mycorrhizal Response to Experimental pH and P Manipulation in Acidic Hardwood Forests

    PubMed Central

    Kluber, Laurel A.; Carrino-Kyker, Sarah R.; Coyle, Kaitlin P.; DeForest, Jared L.; Hewins, Charlotte R.; Shaw, Alanna N.; Smemo, Kurt A.; Burke, David J.

    2012-01-01

    Many temperate forests of the Northeastern United States and Europe have received significant anthropogenic acid and nitrogen (N) deposition over the last century. Although temperate hardwood forests are generally thought to be N-limited, anthropogenic deposition increases the possibility of phosphorus (P) limiting productivity in these forest ecosystems. Moreover, inorganic P availability is largely controlled by soil pH and biogeochemical theory suggests that forests with acidic soils (i.e., <pH 5) are particularly vulnerable to P limitation. Results from previous studies in these systems are mixed with evidence both for and against P limitation. We hypothesized that shifts in mycorrhizal colonization and community structure help temperate forest ecosystems overcome an underlying P limitation by accessing mineral and organic P sources that are otherwise unavailable for direct plant uptake. We examined arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) communities and soil microbial activity in an ecosystem-level experiment where soil pH and P availability were manipulated in mixed deciduous forests across eastern Ohio, USA. One year after treatment initiation, AM root biomass was positively correlated with the most available P pool, resin P, while AM colonization was negatively correlated. In total, 15,876 EcM root tips were identified and assigned to 26 genera and 219 operational taxonomic units (97% similarity). Ectomycorrhizal richness and root tip abundance were negatively correlated with the moderately available P pools, while the relative percent of tips colonized by Ascomycetes was positively correlated with soil pH. Canonical correspondence analysis revealed regional, but not treatment, differences in AM communities, while EcM communities had both treatment and regional differences. Our findings highlight the complex interactions between mycorrhizae and the soil environment and further underscore the fact that mycorrhizal communities do not merely

  2. Disruption of bovine oocytes and preimplantation embryos by urea and acidic pH.

    PubMed

    Ocon, O M; Hansen, P J

    2003-04-01

    Feeding cattle diets high in degradable crude protein (CP) or in excess of requirements can reduce fertility and lower uterine pH. Objectives were to determine direct effects of urea and acidic pH during oocyte maturation and embryonic development. For experiment 1, oocytes were matured in medium containing 0, 5, 7.5, or 10 mM urea (0, 14, 21, or 28 mg/dl urea nitrogen, respectively). Cleavage rate was not reduced by any concentration of urea. However, the proportion of oocytes developing to the blastocyst stage at d 8 after insemination was reduced by 7.5 mM urea. In addition, the proportion of cleaved oocytes becoming blastocysts was decreased by 5 and 7.5 mM urea. For experiment 2, putative zygotes were collected -9 h after insemination and cultured in modified Potassium Simplex Optimized Medium (KSOM). Urea did not reduce the proportion of oocytes developing to the blastocyst stage, although 10 mM urea reduced cleavage rate slightly. For experiment 3, dimethadione (DMD), a weak nonmetabolizable acid, was used to decrease culture medium pH. Putative zygotes were cultured in modified KSOM containing 0, 10, 15, or 20 mM DMD for 8 d. DMD reduced cleavage rate at 15 and 20 mM and development to the blastocyst stage at all concentrations. Results support the idea that feeding diets rich in highly degradable CP compromises fertility through direct actions of urea on the oocyte and through diet-induced alterations in uterine pH.

  3. Mycorrhizal response to experimental pH and P manipulation in acidic hardwood forests.

    PubMed

    Kluber, Laurel A; Carrino-Kyker, Sarah R; Coyle, Kaitlin P; DeForest, Jared L; Hewins, Charlotte R; Shaw, Alanna N; Smemo, Kurt A; Burke, David J

    2012-01-01

    Many temperate forests of the Northeastern United States and Europe have received significant anthropogenic acid and nitrogen (N) deposition over the last century. Although temperate hardwood forests are generally thought to be N-limited, anthropogenic deposition increases the possibility of phosphorus (P) limiting productivity in these forest ecosystems. Moreover, inorganic P availability is largely controlled by soil pH and biogeochemical theory suggests that forests with acidic soils (i.e., <pH 5) are particularly vulnerable to P limitation. Results from previous studies in these systems are mixed with evidence both for and against P limitation. We hypothesized that shifts in mycorrhizal colonization and community structure help temperate forest ecosystems overcome an underlying P limitation by accessing mineral and organic P sources that are otherwise unavailable for direct plant uptake. We examined arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) communities and soil microbial activity in an ecosystem-level experiment where soil pH and P availability were manipulated in mixed deciduous forests across eastern Ohio, USA. One year after treatment initiation, AM root biomass was positively correlated with the most available P pool, resin P, while AM colonization was negatively correlated. In total, 15,876 EcM root tips were identified and assigned to 26 genera and 219 operational taxonomic units (97% similarity). Ectomycorrhizal richness and root tip abundance were negatively correlated with the moderately available P pools, while the relative percent of tips colonized by Ascomycetes was positively correlated with soil pH. Canonical correspondence analysis revealed regional, but not treatment, differences in AM communities, while EcM communities had both treatment and regional differences. Our findings highlight the complex interactions between mycorrhizae and the soil environment and further underscore the fact that mycorrhizal communities do not merely

  4. Mycorrhizal response to experimental pH and P manipulation in acidic hardwood forests.

    PubMed

    Kluber, Laurel A; Carrino-Kyker, Sarah R; Coyle, Kaitlin P; DeForest, Jared L; Hewins, Charlotte R; Shaw, Alanna N; Smemo, Kurt A; Burke, David J

    2012-01-01

    Many temperate forests of the Northeastern United States and Europe have received significant anthropogenic acid and nitrogen (N) deposition over the last century. Although temperate hardwood forests are generally thought to be N-limited, anthropogenic deposition increases the possibility of phosphorus (P) limiting productivity in these forest ecosystems. Moreover, inorganic P availability is largely controlled by soil pH and biogeochemical theory suggests that forests with acidic soils (i.e., <pH 5) are particularly vulnerable to P limitation. Results from previous studies in these systems are mixed with evidence both for and against P limitation. We hypothesized that shifts in mycorrhizal colonization and community structure help temperate forest ecosystems overcome an underlying P limitation by accessing mineral and organic P sources that are otherwise unavailable for direct plant uptake. We examined arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) communities and soil microbial activity in an ecosystem-level experiment where soil pH and P availability were manipulated in mixed deciduous forests across eastern Ohio, USA. One year after treatment initiation, AM root biomass was positively correlated with the most available P pool, resin P, while AM colonization was negatively correlated. In total, 15,876 EcM root tips were identified and assigned to 26 genera and 219 operational taxonomic units (97% similarity). Ectomycorrhizal richness and root tip abundance were negatively correlated with the moderately available P pools, while the relative percent of tips colonized by Ascomycetes was positively correlated with soil pH. Canonical correspondence analysis revealed regional, but not treatment, differences in AM communities, while EcM communities had both treatment and regional differences. Our findings highlight the complex interactions between mycorrhizae and the soil environment and further underscore the fact that mycorrhizal communities do not merely

  5. Leaching of organic acids from irradiated EVA plastic as a function of solution pH and polarity.

    PubMed

    Jenke, Dennis; Zietlow, David; Sadain, Salma

    2004-01-01

    The leaching of several target organic acids from an irradiated ethylene vinyl acetate material, such as those used as a solution product container, is examined as a function of solution pH and polarity. The targeted compounds included highly soluble weak acids such as acetic and formic acids, and larger, more lipophillic acids such as myristic, palmitic, and stearic acids. The leaching of these compounds was examined over a pH range of 3 to 11 and in various ethanol/water proportions. While pH and solution polarity had only a modest impact on the accumulation of the acetic and formic acids, the accumulation of the fatty acids was greatly affected by both factors. It is suggested that the accumulation of these leachables at high pH is influenced by two processes. The first process, partitioning, the speciation of the acidic leachables (protonated versus dissociated form) contributes to the pH trends observed. In this case, entities that already exist in the plastic partition themselves between the plastic and solution via migration. A second, more important, contributor to the leaching of these acids is a pH-dependent increase in their availability arising from an unspecified reactive process.

  6. A Lower pH Value Benefits Regeneration of Trichosanthes kirilowii by Somatic Embryogenesis, Involving Rhizoid Tubers (RTBs), a Novel Structure

    PubMed Central

    Xu, Ke-dong; Chang, Yun-xia; Zhang, Ju; Wang, Pei-long; Wu, Jian-xin; Li, Yan-yan; Wang, Xiao-wen; Wang, Wei; Liu, Kun; Zhang, Yi; Yu, De-shui; Liao, Li-bing; Li, Yi; Ma, Shu-ya; Tan, Guang-xuan; Li, Cheng-wei

    2015-01-01

    A new approach was established for the regeneration of Trichosanthes kirilowii from root, stem, and leaf explants by somatic embryogenesis (SE), involving a previously unreported SE structure, rhizoid tubers (RTBs). During SE, special rhizoids were first induced from root, stem, and leaf explants with average rhizoid numbers of 62.33, 40.17, and 11.53 per explant, respectively, on Murashige and Skoog (MS) medium (pH 4.0) supplemented with 1.0 mg/L 1-naphthaleneacetic acid (NAA) under dark conditions. Further, one RTB was formed from each of the rhizoids on MS medium (pH 4.0) supplemented with 20 mg/L thidiazuron (TDZ) under light conditions. In the suitable range (pH 4.0–9.0), a lower pH value increased the induction of rhizoids and RTBs. Approximately 37.77, 33.47, and 31.07% of in vivo RTBs from root, stem, and leaf explants, respectively, spontaneously developed into multiple plantlets on the same MS medium (supplemented with 20 mg/L TDZ) for induction of RTBs, whereas >95.00% of in vitro RTBs from each kind of explant developed into multiple plantlets on MS medium supplemented with 5.0 mg/L 6-benzylaminopurine (BAP). Morphological and histological analyses revealed that RTB is a novel type of SE structure that develops from the cortex cells of rhizoids. PMID:25744384

  7. Intracellular pH regulation by acid-base transporters in mammalian neurons

    PubMed Central

    Ruffin, Vernon A.; Salameh, Ahlam I.; Boron, Walter F.; Parker, Mark D.

    2014-01-01

    Intracellular pH (pHi) regulation in the brain is important in both physiological and physiopathological conditions because changes in pHi generally result in altered neuronal excitability. In this review, we will cover 4 major areas: (1) The effect of pHi on cellular processes in the brain, including channel activity and neuronal excitability. (2) pHi homeostasis and how it is determined by the balance between rates of acid loading (JL) and extrusion (JE). The balance between JE and JL determine steady-state pHi, as well as the ability of the cell to defend pHi in the face of extracellular acid-base disturbances (e.g., metabolic acidosis). (3) The properties and importance of members of the SLC4 and SLC9 families of acid-base transporters expressed in the brain that contribute to JL (namely the Cl-HCO3 exchanger AE3) and JE (the Na-H exchangers NHE1, NHE3, and NHE5 as well as the Na+- coupled HCO3− transporters NBCe1, NBCn1, NDCBE, and NBCn2). (4) The effect of acid-base disturbances on neuronal function and the roles of acid-base transporters in defending neuronal pHi under physiopathologic conditions. PMID:24592239

  8. Injectable pH- and temperature-responsive poly(N-isopropylacrylamide-co-propylacrylic acid) copolymers for delivery of angiogenic growth factors

    PubMed Central

    Garbern, Jessica C.; Hoffman, Allan S.; Stayton, Patrick S.

    2010-01-01

    A new sharply pH- and temperature-responsive hydrogel system was designed for delivering drugs to regions of local acidosis, as found in wound healing, tumor sites, or sites of ischemia. The reversible addition fragmentation chain transfer (RAFT) polymerization technique was used to synthesize copolymers of N-isopropylacrylamide (NIPAAM) and propylacrylic acid (PAA) with feed ratios of PAA between 0 and 20 mol %. The pH-responsive viscoelastic properties of these materials as a function of pH and temperature were quantified by rheometry. At physiologic pH (7.4) and 5 wt %, the polymer did not form gels, but rather remained soluble at temperatures as high as 50 °C. At lower pH values (pH ca. 5.5 and below) the polymer was liquid at 20 °C but exhibited a sol-gel phase transformation with increasing temperature and existed as a physical gel at 37 °C. Incorporation of the hydrophobic monomer, butyl acrylate, into the random copolymer raised the pH of gel formation to greater than 6.0 at 37 °C. Drug loading studies demonstrated that p(NIPAAm-co-PAA) hydrogels are able to maintain the bioactivity of basic fibroblast growth factor following storage in hydrogel for 40 h and can provide sustained pH-dependent release of vascular endothelial growth factor over a period of at least three weeks. This hydrogel system will thus gel at controllable acidic pH values upon injection, and is designed to undergo gradual dissolution as it performs its drug delivery function and the ischemic site returns to physiological pH. PMID:20509687

  9. Rapid 3D Patterning of Poly(acrylic acid) Ionic Hydrogel for Miniature pH Sensors.

    PubMed

    Yin, Ming-Jie; Yao, Mian; Gao, Shaorui; Zhang, A Ping; Tam, Hwa-Yaw; Wai, Ping-Kong A

    2016-02-17

    Poly(acrylic acid) (PAA), as a highly ionic conductive hydrogel, can reversibly swell/deswell according to the surrounding pH conditions. An optical maskless -stereolithography technology is presented to rapidly 3D pattern PAA for device fabrication. A highly sensitive miniature pH sensor is demonstrated by in situ printing of periodic PAA micropads on a tapered optical microfiber.

  10. Influence of five neutralizing products on intra-oral pH after rinsing with simulated gastric acid.

    PubMed

    Lindquist, Birgitta; Lingström, Peter; Fändriks, Lars; Birkhed, Dowen

    2011-08-01

    The aetiology of dental erosion may be of both extrinsic and intrinsic origin. The aim of the present study was to test the ability of various neutralizing products to raise the low intra-oral pH after an erosive exposure, in this case to gastric acid, which was simulated using hydrochloric acid (HCl). Eleven adults participated. They rinsed with 10 ml of 10 mM HCl (pH 2) or 10 ml of 100 mM HCl (pH 1) for 1 min, after which the pH was measured intra-orally for up to 30 min at four sites (two approximal, one buccal, and the dorsum of the tongue). After rinsing with the two acid solutions (pH 1 and pH 2), the following products were used: (i) antacid tablet; (ii) gum arabic lozenge; (iii) mineral water; (iv) milk; and (v) tap water (positive control). The negative control was no product use. The five test products were used for 2 min after the erosive challenge. All the products produced an initially higher pH compared with the negative control. The antacid tablet resulted in the greatest and most rapid increase in pH, followed by the lozenge. In dental practice, the use of any of the neutralizing products tested, especially the antacid tablet, could be recommended in order to increase the intra-oral pH after an erosive challenge. PMID:21726291

  11. Effect of propionate toxicity on methanogen-enriched sludge, Methanobrevibacter smithii, and Methanospirillum hungatii at different pH values.

    PubMed Central

    Barredo, M S; Evison, L M

    1991-01-01

    The effect of propionate toxicity at different pH values (6.5, 7.0, and 8.0) on methanogen-enriched sludge. Methanobrevibacter smithii, and Methanospirillum hungatii was studied. Organisms were grown in Balch medium 3 in Hungate tubes, and toxicity was characterized by a decrease in production of methane and in bacterial numbers. Propionate inhibited bacterial growth and cumulative methane production at concentrations as low as 20 mM. In the absence of propionate, the methanogen-enriched sludge and M. smithii showed better cumulative methane production at pH 6.5 and 7.0 than at pH 8.0. However, in the presence of propionate, these organisms showed better cumulative methane production at pH 8.0. M. hungatii differed in its behavior; the best values of cumulative methane production for this organism occurred at pH 7.0. Bacterial numbers reflected the microbial response to the presence of propionate. The highest counts of methanogenic bacteria were observed at pH 6.5 and 8.0. The numbers of methanogens were affected by the presence of propionate even at concentrations as low as 20 or 30 mM; at propionate concentrations above 80 mM, the methanogen count was affected by at least 2 orders of magnitude. Upon comparison of the responses of the pure cultures and the methanogen-enriched sludge to increasing propionate concentrations, it was found that the sensitivity of the pure cultures was similar to that of the methanogens in the sludge. PMID:1872605

  12. Relative Abundance of Nitrotoga spp. in a Biofilter of a Cold-Freshwater Aquaculture Plant Appears To Be Stimulated by Slightly Acidic pH

    PubMed Central

    Hüpeden, Jennifer; Wegen, Simone; Off, Sandra; Lücker, Sebastian; Bedarf, Yvonne; Daims, Holger; Kühn, Carsten

    2016-01-01

    The functioning of recirculation aquaculture systems (RAS) is essential to maintain water quality for fish health, and one crucial process here is nitrification. The investigated RAS was connected to a rainbow trout production system and operated at an average temperature of 13°C and pH 6.8. Community analyses of the nitrifying biofilm revealed a coexistence of Nitrospira and Nitrotoga, and it is hypothesized that a slightly acidic pH in combination with lower temperatures favors the growth of the latter. Modification of the standard cultivation approach toward lower pH values of 5.7 to 6.0 resulted in the successful enrichment (99% purity) of Nitrotoga sp. strain HW29, which had a 16S rRNA sequence similarity of 99.0% to Nitrotoga arctica. Reference cultures of Nitrospira defluvii and the novel Nitrotoga sp. HW29 were used to confirm differentiation of these nitrite oxidizers in distinct ecological niches. Nitrotoga sp. HW29 revealed pH and temperature optima of 6.8 and 22°C, respectively, whereas Nitrospira defluvii displayed the highest nitrite oxidation rate at pH 7.3 and 32°C. We report here the occurrence of Nitrotoga as one of the main nitrite-oxidizing bacteria in freshwater aquaculture systems and indicate that a slightly acidic pH, in addition to temperatures below 20°C, can be applied as a selective isolation criterion for this microorganism. PMID:26746710

  13. Relative Abundance of Nitrotoga spp. in a Biofilter of a Cold-Freshwater Aquaculture Plant Appears To Be Stimulated by Slightly Acidic pH.

    PubMed

    Hüpeden, Jennifer; Wegen, Simone; Off, Sandra; Lücker, Sebastian; Bedarf, Yvonne; Daims, Holger; Kühn, Carsten; Spieck, Eva

    2016-03-01

    The functioning of recirculation aquaculture systems (RAS) is essential to maintain water quality for fish health, and one crucial process here is nitrification. The investigated RAS was connected to a rainbow trout production system and operated at an average temperature of 13°C and pH 6.8. Community analyses of the nitrifying biofilm revealed a coexistence of Nitrospira and Nitrotoga, and it is hypothesized that a slightly acidic pH in combination with lower temperatures favors the growth of the latter. Modification of the standard cultivation approach toward lower pH values of 5.7 to 6.0 resulted in the successful enrichment (99% purity) of Nitrotoga sp. strain HW29, which had a 16S rRNA sequence similarity of 99.0% to Nitrotoga arctica. Reference cultures of Nitrospira defluvii and the novel Nitrotoga sp. HW29 were used to confirm differentiation of these nitrite oxidizers in distinct ecological niches. Nitrotoga sp. HW29 revealed pH and temperature optima of 6.8 and 22°C, respectively, whereas Nitrospira defluvii displayed the highest nitrite oxidation rate at pH 7.3 and 32°C. We report here the occurrence of Nitrotoga as one of the main nitrite-oxidizing bacteria in freshwater aquaculture systems and indicate that a slightly acidic pH, in addition to temperatures below 20°C, can be applied as a selective isolation criterion for this microorganism. PMID:26746710

  14. Relative Abundance of Nitrotoga spp. in a Biofilter of a Cold-Freshwater Aquaculture Plant Appears To Be Stimulated by Slightly Acidic pH.

    PubMed

    Hüpeden, Jennifer; Wegen, Simone; Off, Sandra; Lücker, Sebastian; Bedarf, Yvonne; Daims, Holger; Kühn, Carsten; Spieck, Eva

    2016-01-08

    The functioning of recirculation aquaculture systems (RAS) is essential to maintain water quality for fish health, and one crucial process here is nitrification. The investigated RAS was connected to a rainbow trout production system and operated at an average temperature of 13°C and pH 6.8. Community analyses of the nitrifying biofilm revealed a coexistence of Nitrospira and Nitrotoga, and it is hypothesized that a slightly acidic pH in combination with lower temperatures favors the growth of the latter. Modification of the standard cultivation approach toward lower pH values of 5.7 to 6.0 resulted in the successful enrichment (99% purity) of Nitrotoga sp. strain HW29, which had a 16S rRNA sequence similarity of 99.0% to Nitrotoga arctica. Reference cultures of Nitrospira defluvii and the novel Nitrotoga sp. HW29 were used to confirm differentiation of these nitrite oxidizers in distinct ecological niches. Nitrotoga sp. HW29 revealed pH and temperature optima of 6.8 and 22°C, respectively, whereas Nitrospira defluvii displayed the highest nitrite oxidation rate at pH 7.3 and 32°C. We report here the occurrence of Nitrotoga as one of the main nitrite-oxidizing bacteria in freshwater aquaculture systems and indicate that a slightly acidic pH, in addition to temperatures below 20°C, can be applied as a selective isolation criterion for this microorganism.

  15. Effect of acidic pH on flow cytometric detection of bacteria stained with SYBR Green I and their distinction from background

    NASA Astrophysics Data System (ADS)

    Baldock, Daniel; Nebe-von-Caron, Gerhard; Bongaerts, Roy; Nocker, Andreas

    2013-12-01

    Unspecific background caused by biotic or abiotic particles, cellular debris, or autofluorescence is a well-known interfering parameter when applying flow cytometry to the detection of microorganisms in combination with fluorescent dyes. We present here an attempt to suppress the background signal intensity and thus to improve the detection of microorganisms using the nucleic acid stain SYBR® Green I. It has been observed that the fluorescent signals from SYBR Green I are greatly reduced at acidic pH. When lowering the pH of pre-stained samples directly prior to flow cytometric analysis, we hypothesized that the signals from particles and cells with membrane damage might therefore be reduced. Signals from intact cells, temporarily maintaining a neutral cytosolic pH, should not be affected. We show here that this principle holds true for lowering background interference, whereas the signals of membrane-compromised dead cells are only affected weakly. Signals from intact live cells at low pH were mostly comparable to signals without acidification. Although this study was solely performed with SYBR® Green I, the principle of low pH flow cytometry (low pH-FCM) might hold promise when analyzing complex matrices with an abundance of non-cellular matter, especially when expanded to non-DNA binding dyes with a stronger pH dependence of fluorescence than SYBR Green I and a higher pKa value.

  16. Basis of antimalarial action: non-weak base effects of chloroquine on acid vesicle pH

    SciTech Connect

    Krogstad, D.J.; Schlesinger, P.H.

    1987-03-01

    Biologically active concentrations of chloroquine increase the pH of the parasite's acid vesicles within 3-5 min. This increase in pH results from two mechanisms, one of which is markedly reduced in chloroquine-resistant parasites. Because chloroquine is a weak base, it increases vesicle pH by that mechanism in chloroquine-susceptible and resistant parasites and mammalian cells (based on its two pKs and on the delta pH between the acid vesicle and the extracellular environment). In chloroquine-susceptible parasites, but not resistant parasites or mammalian cells, chloroquine increases the pH of acid vesicles 700- to 800-fold more than can be accounted for by its properties as a weak base. The increase in acid vesicle pH caused by these non-weak base effects of nanomolar chloroquine in susceptible parasites suggests that chloroquine acts by interfering with acid vesicle functions in the parasite such as the endocytosis and proteolysis of hemoglobin, and the intracellular targeting of lysosomal enzymes. The non-weak base effects of nanomolar chloroquine on parasite vesicle pH are also responsible for its safety because these chloroquine concentrations do not affect mammalian cells.

  17. Ratiometric emission fluorescent pH probe for imaging of living cells in extreme acidity.

    PubMed

    Niu, Weifen; Fan, Li; Nan, Ming; Li, Zengbo; Lu, Dongtao; Wong, Man Shing; Shuang, Shaomin; Dong, Chuan

    2015-03-01

    A novel ratiometric emission fluorescent probe, 1,1-dimethyl-2-[2-(quinolin-4-yl)vinyl]-1H-benzo[e]indole (QVBI), is facilely synthesized via ethylene bridging of benzoindole and quinoline. The probe exhibits ratiometric fluorescence emission (F(522nm)/F(630nm)) characteristics with pKa 3.27 and linear response to extreme-acidity range of 3.8-2.0. Also, its high fluorescence quantum yield (Φ = 0.89) and large Stokes shift (110 nm) are favorable. Moreover, QVBI possesses highly selective response to H(+) over metal ions and some bioactive molecules, good photostability, and excellent reversibility. The probe has excellent cell membrane permeability and is further applied successfully to monitor pH fluctuations in live cells and imaging extreme acidity in Escherichia coli cells without influence of autofluorescence and native cellular species in biological systems. PMID:25664606

  18. Influence of amino acids, buffers, and ph on the γ-irradiation-induced degradation of alginates.

    PubMed

    Ulset, Ann-Sissel T; Mori, Hideki; Dalheim, Marianne Ø; Hara, Masayuki; Christensen, Bjørn E

    2014-12-01

    Alginate-based biomaterials and medical devices are commonly subjected to γ-irradiation as a means of sterilization, either in the dry state or the gel (hydrated) state. In this process the alginate chains degrade randomly in a dose-dependent manner, altering alginates' material properties. The addition of free radical scavenging amino acids such as histidine and phenylalanine protects the alginate significantly against degradation, as shown by monitoring changes in the molecular weight distributions using SEC-MALLS and determining the pseudo first order rate constants of degradation. Tris buffer (0.5 M), but not acetate, citrate, or phosphate buffers had a similar effect on the degradation rate. Changes in pH itself had only marginal effects on the rate of alginate degradation and on the protective effect of amino acids. Contrary to previous reports, the chemical composition (M/G profile) of the alginates, including homopolymeric mannuronan, was unaltered following irradiation up to 10 kGy.

  19. A new method for determining gastric acid output using a wireless ph sensing capsule

    PubMed Central

    Weinstein, D.H.; deRijke, S.; Chow, C. C.; Foruraghi, L.; Zhao, X.; Wright, E.C.; Whatley, M.; Maass-Moreno, R.; Chen, C. C.; Wank, S. A.

    2013-01-01

    BACKGROUND Gastroesophageal reflux disease (GERD) and gastric acid hypersecretion respond well to suppression of gastric acid secretion. However, clinical management and research in diseases of acid secretion have been hindered by the lack of a non-invasive, accurate and reproducible tool to measure gastric acid output (GAO). Thus, symptoms or, in refractory cases, invasive testing may guide acid suppression therapy. AIM To present and validate a novel, non-invasive method of GAO analysis in healthy subjects using a wireless pH sensor, SmartPill® (SP) (SmartPill® Corporation, Buffalo, NY). METHODS Twenty healthy subjects underwent conventional GAO studies with a nasogastric tube. Variables impacting liquid meal-stimulated GAO analysis were assessed by modeling and in vitro verification. Buffering capacity of Ensure Plus® was empirically determined. SP GAO was calculated using the rate of acidification of the Ensure Plus® meal. Gastric emptying scintigraphy and GAO studies with radiolabeled Ensure Plus® and SP assessed emptying time, acidification rate and mixing. Twelve subjects had a second SP GAO study to assess reproducibility. RESULTS Meal stimulated SP GAO analysis was dependent on acid secretion rate and meal buffering capacity but not on gastric emptying time. On repeated studies, SP GAO strongly correlated with conventional BAO (r=0.51, P=0.02), MAO (r=0.72, P=0.0004) and PAO; (r=0.60, P=0.006). The SP sampled the stomach well during meal acidification. CONCLUSIONS SP GAO analysis is a non-invasive, accurate and reproducible method for the quantitative measurement of GAO in healthy subjects. SP GAO analysis could facilitate research and clinical management of GERD and other disorders of gastric acid secretion. PMID:23639004

  20. Association of the pr Peptides with Dengue Virus at Acidic pH Blocks Membrane Fusion

    SciTech Connect

    Yu, I.-M.; Holdaway, H.A.; Chipman, P.R.; Kuhn, R.J.; Rossmann, M.G.; Chen, J.; Purdue

    2010-07-27

    Flavivirus assembles into an inert particle that requires proteolytic activation by furin to enable transmission to other hosts. We previously showed that immature virus undergoes a conformational change at low pH that renders it accessible to furin (I. M. Yu, W. Zhang, H. A. Holdaway, L. Li, V. A. Kostyuchenko, P. R. Chipman, R. J. Kuhn, M. G. Rossmann, and J. Chen, Science 319:1834-1837, 2008). Here we show, using cryoelectron microscopy, that the structure of immature dengue virus at pH 6.0 is essentially the same before and after the cleavage of prM. The structure shows that after cleavage, the proteolytic product pr remains associated with the virion at acidic pH, and that furin cleavage by itself does not induce any major conformational changes. We also show by liposome cofloatation experiments that pr retention prevents membrane insertion, suggesting that pr is present on the virion in the trans-Golgi network to protect the progeny virus from fusion within the host cell.

  1. The effect of pH on the toxicity of fatty acids and fatty acid amides to rainbow trout gill cells.

    PubMed

    Bertin, Matthew J; Voronca, Delia C; Chapman, Robert W; Moeller, Peter D R

    2014-01-01

    Harmful algal blooms (HABs) expose aquatic organisms to multiple physical and chemical stressors during an acute time period. Algal toxins themselves may be altered by water chemistry parameters affecting their bioavailability and resultant toxicity. The purpose of this study was to determine the effects of two abiotic parameters (pH, inorganic metal salts) on the toxicity of fatty acid amides and fatty acids, two classes of lipids produced by harmful algae, including the golden alga, Prymnesium parvum, that are toxic to aquatic organisms. Rainbow trout gill cells were used as a model of the fish gill and exposed to single compounds and mixtures of compounds along with variations in pH level and concentration of inorganic metal salts. We employed artificial neural networks (ANNs) and standard ANOVA statistical analysis to examine and predict the effects of these abiotic parameters on the toxicity of fatty acid amides and fatty acids. Our results demonstrate that increasing pH levels increases the toxicity of fatty acid amides and inhibits the toxicity of fatty acids. This phenomenon is reversed at lower pH levels. Exposing gill cells to complex mixtures of chemical factors resulted in dramatic increases in toxicity compared to tests of single compounds for both the fatty acid amides and fatty acids. These findings highlight the potential of physicochemical factors to affect the toxicity of chemicals released during algal blooms and demonstrate drastic differences in the effect of pH on fatty acid amides and fatty acids. PMID:24240104

  2. Do pH and flavonoids influence hypochlorous acid-induced catalase inhibition and heme modification?

    PubMed

    Krych-Madej, Justyna; Gebicka, Lidia

    2015-09-01

    Hypochlorous acid (HOCl), highly reactive oxidizing and chlorinating species, is formed in the immune response to invading pathogens by the reaction of hydrogen peroxide with chloride catalyzed by the enzyme myeloperoxidase. Catalase, an important antioxidant enzyme, catalyzing decomposition of hydrogen peroxide to water and molecular oxygen, hampers in vitro HOCl formation, but is also one of the main targets for HOCl. In this work we have investigated HOCl-induced catalase inhibition at different pH, and the influence of flavonoids (catechin, epigallocatechin gallate and quercetin) on this process. It has been shown that HOCl-induced catalase inhibition is independent on pH in the range 6.0-7.4. Preincubation of catalase with epigallocatechin gallate and quercetin before HOCl treatment enhances the degree of catalase inhibition, whereas catechin does not affect this process. Our rapid kinetic measurements of absorption changes around the heme group have revealed that heme modification by HOCl is mainly due to secondary, intramolecular processes. The presence of flavonoids, which reduce active catalase intermediate, Compound I to inactive Compound II have not influenced the kinetics of HOCl-induced heme modification. Possible mechanisms of the reaction of hypochlorous acid with catalase are proposed and the biological consequences are discussed.

  3. Do pH and flavonoids influence hypochlorous acid-induced catalase inhibition and heme modification?

    PubMed

    Krych-Madej, Justyna; Gebicka, Lidia

    2015-09-01

    Hypochlorous acid (HOCl), highly reactive oxidizing and chlorinating species, is formed in the immune response to invading pathogens by the reaction of hydrogen peroxide with chloride catalyzed by the enzyme myeloperoxidase. Catalase, an important antioxidant enzyme, catalyzing decomposition of hydrogen peroxide to water and molecular oxygen, hampers in vitro HOCl formation, but is also one of the main targets for HOCl. In this work we have investigated HOCl-induced catalase inhibition at different pH, and the influence of flavonoids (catechin, epigallocatechin gallate and quercetin) on this process. It has been shown that HOCl-induced catalase inhibition is independent on pH in the range 6.0-7.4. Preincubation of catalase with epigallocatechin gallate and quercetin before HOCl treatment enhances the degree of catalase inhibition, whereas catechin does not affect this process. Our rapid kinetic measurements of absorption changes around the heme group have revealed that heme modification by HOCl is mainly due to secondary, intramolecular processes. The presence of flavonoids, which reduce active catalase intermediate, Compound I to inactive Compound II have not influenced the kinetics of HOCl-induced heme modification. Possible mechanisms of the reaction of hypochlorous acid with catalase are proposed and the biological consequences are discussed. PMID:26116387

  4. Acidic pH retards the fibrillization of human islet amyloid polypeptide due to electrostatic repulsion of histidines

    NASA Astrophysics Data System (ADS)

    Li, Yang; Xu, Weixin; Mu, Yuguang; Zhang, John Z. H.

    2013-08-01

    The human Islet Amyloid Polypeptide (hIAPP) is the major constituent of amyloid deposits in pancreatic islets of type-II diabetes. IAPP is secreted together with insulin from the acidic secretory granules at a low pH of approximately 5.5 to the extracellular environment at a neutral pH. The increased accumulation of extracellular hIAPP in diabetes indicates that changes in pH may promote amyloid formation. To gain insights and underlying mechanisms of the pH effect on hIAPP fibrillogenesis, all-atom molecular dynamics simulations in explicit solvent model were performed to study the structural properties of five hIAPP protofibrillar oligomers, under acidic and neutral pH, respectively. In consistent with experimental findings, simulation results show that acidic pH is not conducive to the structural stability of these oligomers. This provides a direct evidence for a recent experiment [L. Khemtemourian, E. Domenech, J. P. F. Doux, M. C. Koorengevel, and J. A. Killian, J. Am. Chem. Soc. 133, 15598 (2011)], 10.1021/ja205007j, which suggests that acidic pH inhibits the fibril formation of hIAPP. In addition, a complementary coarse-grained simulation shows the repulsive electrostatic interactions among charged His18 residues slow down the dimerization process of hIAPP by twofold. Besides, our all-atom simulations reveal acidic pH mainly affects the local structure around residue His18 by destroying the surrounding hydrogen-bonding network, due to the repulsive interactions between protonated interchain His18 residues at acidic pH. It is also disclosed that the local interactions nearby His18 operating between adjacent β-strands trigger the structural transition, which gives hints to the experimental findings that the rate of hIAPP fibril formation and the morphologies of the fibrillar structures are strongly pH-dependent.

  5. Rumen morphometrics and the effect of digesta pH and volume on volatile fatty acid absorption.

    PubMed

    Melo, L Q; Costa, S F; Lopes, F; Guerreiro, M C; Armentano, L E; Pereira, M N

    2013-04-01

    The effects of rumen digesta volume and pH on VFA absorption and its relation to rumen wall morphology were evaluated. Nine rumen cannulated cows formed 3 groups based on desired variation in rumen morphology: The High group was formed by Holsteins yielding 25.9 kg milk/d and fed on a high-grain total mixed ration (TMR); the Medium group by Holstein-Zebu crossbreds yielding 12.3 kg milk/d and fed on corn silage, tropical pasture, and a commercial concentrate; and the Dry group by nonlactating grazing Jerseys fed exclusively on tropical pasture. Within each group, a sequence of 3 ruminal conditions was induced on each cow in 3 × 3 Latin Squares, with 7-d periods: high digesta volume and high pH (HVHP), low volume and high pH (LVHP), and low volume and low pH (LVLP). Rumen mucosa was biopsied on the first day of Period 1. Ruminal morphometric variables evaluated were mitotic index, absorptive surface and papillae number per square centimeter of wall, area per papillae, papillae area as a percentage of absorptive surface, and epithelium, keratinized layer, and nonkeratinized layer thickness. There was marked variation in rumen morphology among the groups of cows. Grazing Jerseys had decreased rumen wall absorptive surface area and basal cells mitotic index, and increased thickness of the epithelium and of the keratin layer compared with cows receiving concentrates. Mean rumen pH throughout the 4 h sampling period was: 6.78 for HVHP, 7.08 for LVHP, and 5.90 for LVLP (P < 0.01). The capacity of the rumen wall to absorb VFA was estimated by the Valerate/CrEDTA technique. The fractional exponential decay rate for the ratio of valeric acid to Cr (k Val/Cr) was determined by rumen digesta sampling at 20-min intervals during 4 h, after the mixing of markers and the return of the evacuated ruminal content. The k Val/Cr values for treatments HVHP, LVHP, and LVLP were, respectively: 19.6, 23.9, and 35.0 %/h (SEM = 2.01; P = 0.21 for contrast HVHP vs. LVHP and P < 0.01 for

  6. Rumen morphometrics and the effect of digesta pH and volume on volatile fatty acid absorption.

    PubMed

    Melo, L Q; Costa, S F; Lopes, F; Guerreiro, M C; Armentano, L E; Pereira, M N

    2013-04-01

    The effects of rumen digesta volume and pH on VFA absorption and its relation to rumen wall morphology were evaluated. Nine rumen cannulated cows formed 3 groups based on desired variation in rumen morphology: The High group was formed by Holsteins yielding 25.9 kg milk/d and fed on a high-grain total mixed ration (TMR); the Medium group by Holstein-Zebu crossbreds yielding 12.3 kg milk/d and fed on corn silage, tropical pasture, and a commercial concentrate; and the Dry group by nonlactating grazing Jerseys fed exclusively on tropical pasture. Within each group, a sequence of 3 ruminal conditions was induced on each cow in 3 × 3 Latin Squares, with 7-d periods: high digesta volume and high pH (HVHP), low volume and high pH (LVHP), and low volume and low pH (LVLP). Rumen mucosa was biopsied on the first day of Period 1. Ruminal morphometric variables evaluated were mitotic index, absorptive surface and papillae number per square centimeter of wall, area per papillae, papillae area as a percentage of absorptive surface, and epithelium, keratinized layer, and nonkeratinized layer thickness. There was marked variation in rumen morphology among the groups of cows. Grazing Jerseys had decreased rumen wall absorptive surface area and basal cells mitotic index, and increased thickness of the epithelium and of the keratin layer compared with cows receiving concentrates. Mean rumen pH throughout the 4 h sampling period was: 6.78 for HVHP, 7.08 for LVHP, and 5.90 for LVLP (P < 0.01). The capacity of the rumen wall to absorb VFA was estimated by the Valerate/CrEDTA technique. The fractional exponential decay rate for the ratio of valeric acid to Cr (k Val/Cr) was determined by rumen digesta sampling at 20-min intervals during 4 h, after the mixing of markers and the return of the evacuated ruminal content. The k Val/Cr values for treatments HVHP, LVHP, and LVLP were, respectively: 19.6, 23.9, and 35.0 %/h (SEM = 2.01; P = 0.21 for contrast HVHP vs. LVHP and P < 0.01 for

  7. Is it possible to produce succinic acid at a low pH?

    PubMed

    Yuzbashev, Tigran V; Yuzbasheva, Evgeniya Y; Laptev, Ivan A; Sobolevskaya, Tatiana I; Vybornaya, Tatiana V; Larina, Anna S; Gvilava, Ilia T; Antonova, Svetlana V; Sineoky, Sergey P

    2011-01-01

    Bio-based succinate is still a matter of special emphasis in biotechnology and adjacent research areas. The vast majority of natural and engineered producers are bacterial strains that accumulate succinate under anaerobic conditions. Recently, we succeeded in obtaining an aerobic yeast strain capable of producing succinic acid at low pH. Herein, we discuss some difficulties and advantages of microbial pathways producing "succinic acid" rather than "succinate." It was concluded that the peculiar properties of the constructed yeast strain could be clarified in view of a distorted energy balance. There is evidence that in an acidic environment, the majority of the cellular energy available as ATP will be spent for proton and anion efflux. The decreased ATP:ADP ratio could essentially reduce the growth rate or even completely inhibit growth. In the same way, the preference of this elaborated strain for certain carbon sources could be explained in terms of energy balance. Nevertheless, the opportunity to exclude alkali and mineral acid waste from microbial succinate production seems environmentally friendly and cost-effective.

  8. High acidity tolerance in lichens with fumarprotocetraric, perlatolic or thamnolic acids is correlated with low pKa1 values of these lichen substances.

    PubMed

    Hauck, Markus; Jürgens, Sascha-René; Huneck, Siegfried; Leuschner, Christoph

    2009-10-01

    The depsidone fumarprotocetraric acid as well as the depsides perlatolic and thamnolic acids are lichen secondary metabolites. Their first dissociation constants (pK(a1)) in methanol were determined to be 2.7 for perlatolic acid and 2.8 for fumarprotocetraric and thamnolic acids by UV spectroscopy. Lower pK(a1) values are, so far, not known from lichen substances. Several lichens producing at least one of these compounds are known for their outstanding tolerance to acidic air pollution. This is demonstrated by evaluating published pH preferences for central European lichens. The low pK(a1) values suggest that strong dissociation of the studied lichen substances is a prerequisite for the occurrence of lichens with these compounds on very acidic substrata, as protonated lichen substances of different chemical groups, but not their conjugated bases, are known to shuttle protons into the cytoplasm and thereby apparently damage lichens.

  9. Novel acidophilic β-galactosidase with high activity at extremely acidic pH region from Teratosphaeria acidotherma AIU BGA-1.

    PubMed

    Chiba, Serina; Yamada, Miwa; Isobe, Kimiyasu

    2015-09-01

    A β-galactosidase exhibiting maximal activity at pH 1.0 was purified from Teratosphaeria acidotherma AIU BGA-1. The enzyme had a molecular mass of 180 kDa and consisted of two heterosubunits of 120 kDa and 66 kDa. The N-terminal amino acid sequence of the large subunit was found to be SPNLQDIVTVDGESY. These physicochemical properties differed from those of other microbial β-galactosidases. At pH values of 1.5 and pH 4.5, the enzyme exhibited its highest activity at temperatures of 70°C and 80°C, respectively. Thus, the enzyme exhibited the lowest optimal pH and highest optimal temperature among the microbial β-galactosidases thus reported. The enzyme retained more than 80% of its original activity in the pH range from 2.0 to 8.0 by incubation at 50°C for 30 min. The enzyme hydrolyzed 4-nitrophenyl-β-D-fucopyranoside, 2-nitrophenyl-β-D-galactopyranoside, and 4-nitrophenyl-β-D-galacto-pyranoside at relative reaction rates of 100, 59, and 24, respectively, at pH 1.5, and its affinity for β-D-galactopyranosides was higher than that for β-D-fucopyranosides. The enzyme also efficiently hydrolyzed lactose in milk and whey from yoghurt at pH 1.5.

  10. Desorption of 137Cs from Brachythecium mildeanum moss using acid solutions with pH 4.60-6.50

    NASA Astrophysics Data System (ADS)

    Čučulović, Ana; Veselinović, Dragan

    2015-12-01

    The desorption of 137Cs from the moss Brachythecium mildeanum (Schimp.) was performed using the following solutions: H2SO4 ( I), HNO3 ( II), H2SO4 + HNO3 ( III) with pH values of 4.60, 5.15, and 5.75, respectively, as well as distilled water (D) with pH 6.50. After five successive desorptions, each lasting 24 h, 20.5-37.6% 137Cs was desorbed from the moss using these solutions, while 30.7% of the starting content was desorbed using distilled water. The first desorption removed the highest percent of the original content of 137Cs in the moss (11.3-18.4%). This was determined by measuring 137Cs activity. If the current results are compared with those obtained earlier it may be concluded that 137Cs desorption from mosses is not species-dependent. The obtained results indicate the necessity of investigating the influence of acid rain, or rather, of H+ ions, on desorption of other ions from biological systems, i.e., the role of H+ ions in spreading other polluting compounds and thus producing secondary environmental pollution. From the results of this study it follows that acid rain will lead, through H+ ion action, to a similar increasing pollution of fallout waters with other ionic compounds which may not be present in the water before the contact with the plants and thus enable the pollution spreading. In the investigated system, the replacement of H+ ions from acid rains by more dangerous radioactive ions occured, increasing the concentration of the radioactive ions in the water, which demonstrates that the same process takes place in fallout water.

  11. Enzymatic characterization of peptidic materials isolated from aqueous solutions of ammonium cyanide (pH 9) and hydrocyanic acid (pH 6) exposed to ionizing radiation.

    PubMed

    Niketic, V; Draganić, Z; Nesković, S; Draganić, I

    1982-01-01

    The enzymatic digestion of some radiolytically produced peptidic materials was examined. The substrates were compounds isolated from 0.1 molar solutions of NH4CN (pH 9) and HCN (pH 6), after their exposure to gamma rays from a 60Co source (15-20 Mrad doses). Commercial proteolytic enzymes pronase and aminopeptidase M were used. The examined materials were of composite nature and proteolytic action was systematically observed after their subsequent purification. In some fractions the effect was found to be positive with up to 30% of peptide bonds cleaved with respect to the amino acid content. These findings support our previous conclusions on the free radical induced formation of peptidic backbones without the intervention of amino acids. Some side effects were also noted which might be of interest in observations on enzymatic cleavage of other composite peptidic materials of abiotic origin. PMID:6124639

  12. Enzymatic characterization of peptidic materials isolated from aqueous solutions of ammonium cyanide (pH 9) and hydrocyanic acid (pH 6) exposed to ionizing radiation.

    PubMed

    Niketic, V; Draganić, Z; Nesković, S; Draganić, I

    1982-01-01

    The enzymatic digestion of some radiolytically produced peptidic materials was examined. The substrates were compounds isolated from 0.1 molar solutions of NH4CN (pH 9) and HCN (pH 6), after their exposure to gamma rays from a 60Co source (15-20 Mrad doses). Commercial proteolytic enzymes pronase and aminopeptidase M were used. The examined materials were of composite nature and proteolytic action was systematically observed after their subsequent purification. In some fractions the effect was found to be positive with up to 30% of peptide bonds cleaved with respect to the amino acid content. These findings support our previous conclusions on the free radical induced formation of peptidic backbones without the intervention of amino acids. Some side effects were also noted which might be of interest in observations on enzymatic cleavage of other composite peptidic materials of abiotic origin.

  13. Design of a Water Soluble Fluorescent 3-Hydroxy-4-Pyridinone Ligand Active at Physiological pH Values.

    PubMed

    Leite, Andreia; Silva, Ana M G; Coutinho, Catarina; Cunha-Silva, Luís; de Castro, Baltazar; Rangel, Maria

    2016-09-01

    In the present work we report the structure and the spectroscopic characterization of a new fluorescent 3-hydroxy-4-pyridinone ligand D-3,4-HPO. The synthesis of the compound was performed in two steps, which involve the reaction of the commercially available fluorophore dansyl chloride with a 3-hydroxy-4-pyridinone chelating unit and further deprotection. The new fluorescent chelator was characterized in the solid state by single-crystal X-ray diffraction and in solution by NMR, MS, absorption and fluorescence spectroscopies. The analysis of the variation of the absorption spectrum with pH allowed the determination of four pK a values (pK a1  = 3.50, pK a2  = 4.50, pK a3  = 9.60, pK a4  = 10.20) and establishment of the corresponding distribution diagram. The study of the fluorescence properties of the ligand show that in the pH range between 4 and 9 the fluorescence intensity is constant and has its maximum value thus allowing its further use at physiological pH values. The interaction of the ligand with copper(II) was accessed by fluorescence spectroscopy in MOPS buffer and the results show that the presence of copper(II) quenches the fluorescence of the ligand in ca 94 % at a ligand: metal ratio of 2:1. The latter result is consistent with the formation of a copper(II) complex with the bidentate ligand, as confirmed by the EPR spectroscopy. Graphical Abstract New water soluble fluorescent ligand active at physiological pH values. PMID:27357392

  14. Design of a Water Soluble Fluorescent 3-Hydroxy-4-Pyridinone Ligand Active at Physiological pH Values.

    PubMed

    Leite, Andreia; Silva, Ana M G; Coutinho, Catarina; Cunha-Silva, Luís; de Castro, Baltazar; Rangel, Maria

    2016-09-01

    In the present work we report the structure and the spectroscopic characterization of a new fluorescent 3-hydroxy-4-pyridinone ligand D-3,4-HPO. The synthesis of the compound was performed in two steps, which involve the reaction of the commercially available fluorophore dansyl chloride with a 3-hydroxy-4-pyridinone chelating unit and further deprotection. The new fluorescent chelator was characterized in the solid state by single-crystal X-ray diffraction and in solution by NMR, MS, absorption and fluorescence spectroscopies. The analysis of the variation of the absorption spectrum with pH allowed the determination of four pK a values (pK a1  = 3.50, pK a2  = 4.50, pK a3  = 9.60, pK a4  = 10.20) and establishment of the corresponding distribution diagram. The study of the fluorescence properties of the ligand show that in the pH range between 4 and 9 the fluorescence intensity is constant and has its maximum value thus allowing its further use at physiological pH values. The interaction of the ligand with copper(II) was accessed by fluorescence spectroscopy in MOPS buffer and the results show that the presence of copper(II) quenches the fluorescence of the ligand in ca 94 % at a ligand: metal ratio of 2:1. The latter result is consistent with the formation of a copper(II) complex with the bidentate ligand, as confirmed by the EPR spectroscopy. Graphical Abstract New water soluble fluorescent ligand active at physiological pH values.

  15. Faecal pH, bile acid and sterol concentrations in premenopausal Indian and white vegetarians compared with white omnivores.

    PubMed

    Reddy, S; Sanders, T A; Owen, R W; Thompson, M H

    1998-06-01

    Faecal bulk, pH, water content, the concentrations of neutral sterols and bile acids and dietary intakes were measured in twenty-two Indian vegetarian, twenty-two white omnivorous and eighteen white vegetarian premenopausal women. Faecal bulk and water content were greater and pH lower in the Indian vegetarians. Total faecal animal sterol and coprostanol concentrations expressed on a dry-weight basis were lower in the vegetarians compared with the omnivores. The faecal sterol concentrations were correlated with dietary cholesterol intake. Primary bile acids were detected in six Indian vegetarians, two white vegetarians and two white omnivores; secondary bile acids were detected in all the white omnivores and vegetarian subjects but not in two of the Indian vegetarians. Total faecal free bile acid and conjugated bile acid concentrations were lower in the white vegetarians compared with the omnivores. Faecal lithocholic acid concentrations were lower in both Indian and white vegetarians. The lithocholic: deoxycholic acid ratio and coprostanol: total animal sterols ratio were significantly lower in the Indian vegetarians compared with the omnivores. Both ratios were positively correlated with faecal pH. Stepwise multiple regression analyses were undertaken in order to identify which nutrients influenced faecal pH, lithocholic and deoxycholic acid concentrations. The intakes of starch and dietary fibre were negatively associated with faecal concentrations of lithocholic and deoxycholic acid. Starch intake alone was negatively associated with faecal pH. The results of this study confirm that diets high in dietary fibre decrease faecal bile acid concentrations and suggest that the complex carbohydrates present in Indian vegetarian diets influence faecal pH and inhibit the degradation of faecal steroids.

  16. Acidic extracellular pH neutralizes the autophagy-inhibiting activity of chloroquine: implications for cancer therapies.

    PubMed

    Pellegrini, Paola; Strambi, Angela; Zipoli, Chiara; Hägg-Olofsson, Maria; Buoncervello, Maria; Linder, Stig; De Milito, Angelo

    2014-04-01

    Acidic pH is an important feature of tumor microenvironment and a major determinant of tumor progression. We reported that cancer cells upregulate autophagy as a survival mechanism to acidic stress. Inhibition of autophagy by administration of chloroquine (CQ) in combination anticancer therapies is currently evaluated in clinical trials. We observed in 3 different human cancer cell lines cultured at acidic pH that autophagic flux is not blocked by CQ. This was consistent with a complete resistance to CQ toxicity in cells cultured in acidic conditions. Conversely, the autophagy-inhibiting activity of Lys-01, a novel CQ derivative, was still detectable at low pH. The lack of CQ activity was likely dependent on a dramatically reduced cellular uptake at acidic pH. Using cell lines stably adapted to chronic acidosis we could confirm that CQ lack of activity was merely caused by acidic pH. Moreover, unlike CQ, Lys-01 was able to kill low pH-adapted cell lines, although higher concentrations were required as compared with cells cultured at normal pH conditions. Notably, buffering medium pH in low pH-adapted cell lines reverted CQ resistance. In vivo analysis of tumors treated with CQ showed that accumulation of strong LC3 signals was observed only in normoxic areas but not in hypoxic/acidic regions. Our observations suggest that targeting autophagy in the tumor environment by CQ may be limited to well-perfused regions but not achieved in acidic regions, predicting possible limitations in efficacy of CQ in antitumor therapies. PMID:24492472

  17. Computer simulation of immobilized pH gradients at acidic and alkaline extremes - A quest for extended pH intervals

    NASA Technical Reports Server (NTRS)

    Mosher, Richard A.; Bier, Milan; Righetti, Pier Giorgio

    1986-01-01

    Computer simulations of the concentration profiles of simple biprotic ampholytes with Delta pKs 1, 2, and 3, on immobilized pH gradients (IPG) at extreme pH values (pH 3-4 and pH 10-11) show markedly skewed steady-state profiles with increasing kurtosis at higher Delta pK values. Across neutrality, all the peaks are symmetric irrespective of their Delta pK values, but they show very high contribution to the conductivity of the background gel and significant alteration of the local buffering capacity. The problems of skewness, due to the exponential conductivity profiles at low and high pHs, and of gel burning due to a strong electroosmotic flow generated by the net charges in the gel matrix, also at low and high pHs, are solved by incorporating in the IPG gel a strong viscosity gradient. This is generated by a gradient of linear polyacrylamide which is trapped in the gel by the polymerization process.

  18. ESTIMATION OF GIARDIA CT VALUES AT HIGH PH FOR THE SURFACE WATER TREATMENT RULE

    EPA Science Inventory

    The U.S. Environmental Protection Agency currently recommends Ct (disinfectant concentration multiplied by the exposure time) values to achieve required levels of inactivation of Giardia lamblia cysts by different disinfectants including free chlorine. Current guidance covers ina...

  19. Ruminant Nutrition Symposium: Role of fermentation acid absorption in the regulation of ruminal pH.

    PubMed

    Aschenbach, J R; Penner, G B; Stumpff, F; Gäbel, G

    2011-04-01

    Highly fermentable diets are rapidly converted to organic acids [i.e., short-chain fatty acids (SCFA) and lactic acid] within the rumen. The resulting release of protons can constitute a challenge to the ruminal ecosystem and animal health. Health disturbances, resulting from acidogenic diets, are classified as subacute and acute acidosis based on the degree of ruminal pH depression. Although increased acid production is a nutritionally desired effect of increased concentrate feeding, the accumulation of protons in the rumen is not. Consequently, mechanisms of proton removal and their quantitative importance are of major interest. Saliva buffers (i.e., bicarbonate, phosphate) have long been identified as important mechanisms for ruminal proton removal. An even larger proportion of protons appears to be removed from the rumen by SCFA absorption across the ruminal epithelium, making efficiency of SCFA absorption a key determinant for the individual susceptibility to subacute ruminal acidosis. Proceeding initially from a model of exclusively diffusional absorption of fermentation acids, several protein-dependent mechanisms have been discovered over the last 2 decades. Although the molecular identity of these proteins is mostly uncertain, apical acetate absorption is mediated, to a major degree, via acetate-bicarbonate exchange in addition to another nitrate-sensitive, bicarbonate-independent transport mechanism and lipophilic diffusion. Propionate and butyrate also show partially bicarbonate-dependent transport modes. Basolateral efflux of SCFA and their metabolites has to be mediated primarily by proteins and probably involves the monocarboxylate transporter (MCT1) and anion channels. Although the ruminal epithelium removes a large fraction of protons from the rumen, it also recycles protons to the rumen via apical sodium-proton exchanger, NHE. The latter is stimulated by ruminal SCFA absorption and salivary Na(+) secretion and protects epithelial integrity. Finally

  20. Volatile fatty acids production from food waste: effects of pH, temperature, and organic loading rate.

    PubMed

    Jiang, Jianguo; Zhang, Yujing; Li, Kaimin; Wang, Quan; Gong, Changxiu; Li, Menglu

    2013-09-01

    The effects of pH, temperature, and organic loading rate (OLR) on the acidogenesis of food waste have been determined. The present study investigated their effects on soluble chemical oxygen demand (SCOD), volatile fatty acids (VFAs), volatile solids (VS), and ammonia nitrogen (NH4(+)-N). Both the concentration and yield of VFAs were highest at pH 6.0, acetate and butyrate accounted for 77% of total VFAs. VFAs concentration and the VFA/SCOD ratio were highest, and VS levels were lowest, at 45 °C, but the differences compared to the values at 35 °C were slight. The concentrations of VFAs, SCOD, and NH4(+)-N increased as OLR increased, whereas the yield of VFAs decreased from 0.504 at 5 g/Ld to 0.306 at 16 g/Ld. Acetate and butyrate accounted for 60% of total VFAs. The percentage of acetate and valerate increased as OLR increased, whereas a high OLR produced a lower percentage of propionate and butyrate.

  1. Efficient interrupting skills of amino acid metallointercalators with DNA at physiological pH: Evaluation of biological assays

    NASA Astrophysics Data System (ADS)

    Raman, Natarajan; Selvaganapathy, Muthusamy; Radhakrishnan, Srinivasan

    2014-06-01

    The 4-aminoantipyrine derivatives (sbnd NO2, sbnd OCH3) and their mixed-ligand complexes with amino acids have been synthesized and investigated for their binding with CT DNA using UV-visible spectroscopy, cyclic voltammetry, and viscosity measurements under physiological conditions of pH (stomach 4.7; blood 7.4). The results from all techniques i.e. binding constant (Kb), and free energy change (ΔG) were in good agreement and inferred spontaneous compound-DNA complexes formation via intercalation. Among all the compounds 1 and 4 showed comparatively greater binding at pH 7.4 as evident from its greater Kb values. All the complexes exhibit oxidative cleavage of supercoiled (SC) pBR322 plasmid DNA in the presence of H2O2 as an activator. It is remarkable that at 25 μM concentration 1 and 4 completely degrade SC DNA into undetectable minor fragments and thus they act as efficient chemical nucleases. Among the new complexes, complexes 1 and 4 have highest potential against all the microorganisms tested. The results of the above biological experiments also reveal that the choice of different metal ions has little influence on the DNA binding, DNA cleavage and antimicrobial assay.

  2. 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...

  3. Comparison of Interstitial Fluid pH, PCO2, PO2 with Venous Blood Values During Repetitive Handgrip Exercise

    NASA Technical Reports Server (NTRS)

    Hagan, Ronald Donald; Soller, Babs R.; Shear, Michael; Walz, Matthias; Landry, Michelle; Heard, Stephen

    2006-01-01

    We evaluated the use of a small, fiber optic sensor to measure pH, PCO2 and PO2 from forearm muscle interstitial fluid (IF) during handgrip dynamometry. PURPOSE: Compare pH, PCO2 and PO2 values obtained from venous blood with those from the IF of the flexor digitorum superficialis (FDS) during three levels of exercise intensity. METHODS: Six subjects (5M/1F), average age 29+/-5 yrs, participated in the study. A venous catheter was placed in the retrograde direction in the antecubital space and a fiber optic sensor (Paratrend, Diametrics Medical, Inc.) was placed through a 22 G catheter into the FDS muscle under ultrasound guidance. After a 45 min rest period, subjects performed three 5-min bouts of repetitive handgrip exercise (2s contraction/1 s relaxation) at attempted levels of 15%, 30% and 45% of maximal voluntary contraction. The order of the exercise bouts was random with the second and third bouts started after blood lactate had returned to baseline. Venous blood was sampled every minute during exercise and analyzed with an I-Stat CG-4+ cartridge, while IF fiber optic sensor measurements were obtained every 2 s. Change from pre-exercise baseline to end of exercise was computed for pH, PCO2 and PO2. Blood and IF values were compared with a paired t-test. RESULTS: Baseline values for pH, PCO2 and PO2 were 7.37+/-0.02, 46+/-4 mm Hg, and 36+/-6 mm Hg respectively in blood and 7.39+/-0.02, 44+/-6 mm Hg, and 35+/-14 mm Hg in IF. Average changes over all exercise levels are noted in the Table below. For each parameter the exercise-induced change was at least twice as great in IF as in blood. In blood and IF, pH and PCO2 increases were directly related to exercise intensity. Change in venous PO2 was unrelated to exercise intensity, while IF PO2 decreased with increases in exercise intensity. CONCLUSIONS: Measurement of IF pH, PCO2 and PO2 is more sensitive to exercise intensity than measurement of the same parameters in venous blood and provides continuous

  4. Influence of pH and diluent on the ion-pair solvent extraction of aromatic carboxylic acids using quaternary ammonium salts

    SciTech Connect

    Kawamura, K.; Takahashi, K.; Okuwaki, A.

    2006-07-01

    The influence of pH and diluent on the ion-pair solvent extraction of benzene polycarboxylic acids have been investigated for the separation of the coal oxidation products, which are formed by the treatment with alkaline solutions at high temperatures. Although the extent of the solvent extraction of benzoic acid (1BE) with a quaternary ammonium reagent (tri-n-octylmethylammonium chloride) into chloroform and benzene did not change at a very acidic and alkaline solutions, those of 1,2-benzenedicarboxylic acid (12BE) and trimellitic acid (124BE) somewhat decreased at very low pH and very high pH. The magnitudes of the equilibrium constants (K{sub ex}) of 1BE using a different diluent decreased in the order benzene {gt} carbontetrachloride {gt} 1,2-dichloroethane {gt} cyclohexane {gt} hexane {gt} chloroform {gt} 1-octanol and those of 12BE decreased in the order benzene {gt} cyclohexane {gt} carbontetrachloride {gt} hexane {gt} 1,2-dichloroethane {gt} chloroform. The inspection of the correlation between the values of K{sub ex} and several parameters of the diluent implies that the magnitude of K{sub ex} can be described by using the dielectric constant and the solubility parameter of diluent.

  5. Measurement of luminal pH of acidic stores as a readout for NAADP action.

    PubMed

    Galione, Antony; Chuang, Kai-Ting; Funnell, Tim M; Davis, Lianne C; Morgan, Anthony J; Ruas, Margarida; Parrington, John; Churchill, Grant C

    2014-10-01

    In addition to mobilizing Ca²⁺, NAADP plays a role in modulating the luminal pH (pHL) of acidic stores of the endolysosomal system. The effects of NAADP on pHL have been most extensively studied in the sea urchin egg, both in the intact egg and in egg homogenates. Related observations have also been made in mammalian systems (e.g., guinea pig atrial myocytes and pancreatic acinar cells). Although the connection between Ca²⁺ mobilization and increase in pHL is not understood, pHL can be a useful parameter to measure when studying NAADP-mediated signaling. This protocol describes the fluorescent measurement of pHL of acidic stores. It relies on the use of acridine orange (AO), a standard dye for pHL. AO selectively accumulates to high concentrations in the lumen of organelles as a function of acidity; at these high concentrations it self-quenches. When pHL increases, some AO is lost from the vesicle. As a result, the lower luminal AO concentration relieves the quenching and fluorescence increases in the lumen.

  6. Total Acid Value Titration of Hydrotreated Biomass Fast Pyrolysis Oil: Determination of Carboxylic Acids and Phenolics with Multiple End-Point Detection

    SciTech Connect

    Christensen, E.; Alleman, T. L.; McCormick, R. L.

    2013-01-01

    Total acid value titration has long been used to estimate corrosive potential of petroleum crude oil and fuel oil products. The method commonly used for this measurement, ASTM D664, utilizes KOH in isopropanol as the titrant with potentiometric end point determination by pH sensing electrode and Ag/AgCl reference electrode with LiCl electrolyte. A natural application of the D664 method is titration of pyrolysis-derived bio-oil, which is a candidate for refinery upgrading to produce drop in fuels. Determining the total acid value of pyrolysis derived bio-oil has proven challenging and not necessarily amenable to the methodology employed for petroleum products due to the different nature of acids present. We presented an acid value titration for bio-oil products in our previous publication which also utilizes potentiometry using tetrabutylammonium hydroxide in place of KOH as the titrant and tetraethylammonium bromide in place of LiCl as the reference electrolyte to improve the detection of these types of acids. This method was shown to detect numerous end points in samples of bio-oil that were not detected by D664. These end points were attributed to carboxylic acids and phenolics based on the results of HPLC and GC-MS studies. Additional work has led to refinement of the method and it has been established that both carboxylic acids and phenolics can be determined accurately. Use of pH buffer calibration to determine half-neutralization potentials of acids in conjunction with the analysis of model compounds has allowed us to conclude that this titration method is suitable for the determination of total acid value of pyrolysis oil and can be used to differentiate and quantify weak acid species. The measurement of phenolics in bio-oil is subject to a relatively high limit of detection, which may limit the utility of titrimetric methodology for characterizing the acidic potential of pyrolysis oil and products.

  7. Interaction of ionic detergent cethyltrimethylammonium bromide with human serum albumin at various values of pH: Spectroscopic study

    NASA Astrophysics Data System (ADS)

    Vlasova, Irina M.; Vlasov, Alexander A.; Saletsky, Alexander M.

    2010-12-01

    The interaction of cationic detergent cethyltrimethylammonium bromide (CTAB) with human serum albumin (HSA) at various values of pH has been studied using steady-state tryptophan fluorescence of HSA, polarized tryptophan fluorescence of HSA, fluorescence of nanomarker eosin in solutions of HSA and CTAB and Raman spectroscopy. By methods of fluorescent analysis the qualitative rearrangements of HSA globules at denaturation under action of CTAB are registered, whereas by Raman spectroscopy the quantitative changes of secondary structure of HSA at CTAB-induced denaturation are determined. It is shown that denaturation of HSA, taking place at interaction of cationic detergent CTAB with HSA, has one-stage character. At interaction of CTAB with HSA the deepest denaturation of HSA is reached at concentration of 4 mM CTAB (in the range of pH 3.5-8.0). More intensive denaturation of HSA under action of CTAB takes place at values of pH, higher than the isoelectric point of HSA (pI 4.7).

  8. Metal accumulation and oxidative stress biomarkers in liver of freshwater fish Carassius auratus following in vivo exposure to waterborne zinc under different pH values.

    PubMed

    Qu, Ruijuan; Feng, Mingbao; Wang, Xinghao; Qin, Li; Wang, Chao; Wang, Zunyao; Wang, Liansheng

    2014-05-01

    In this study, laboratory experiments were conducted to investigate the combined effect of zinc and pH on metal accumulation and oxidative stress biomarkers in Carassius auratus. Fish were exposed to 0.1 and 1.0mg Zn/L at three pH values (5.0, 7.25, 9.0) for 3, 12, and 30 d. After each exposure, the contents of three trace elements (Zn, Fe and Cu) were determined in liver. Generally, longer exposure to zinc (12d and 30 d) increased hepatic Zn and Cu deposition, but decreased Fe content. Increasing accumulation of Zn in the tissue was also observed with increasing zinc concentration in the exposure medium. Moreover, hepatic antioxidant enzyme activities including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), together with the level of glutathione (GSH) were measured to evaluate the oxidative stress status. The decreases in the four measured biochemical parameters after 3d exposure might reflect the failure of the antioxidant defense system in neutralizing the ROS generated during the metabolic process, while the recovery of the antioxidants at days 12 and 30 suggested a possible shift toward a detoxification mechanism. With regard to the influence of pH on zinc toxicity, the general observation was that the living environment became more stressful when the water conditions changed from an acidic state toward a near-neutral or alkaline state. PMID:24632310

  9. Influence of the pH value of a colloidal gold solution on the absorption spectra of an LSPR-assisted sensor

    SciTech Connect

    Zhu, Jin; Li, Wenbin; Zhu, Mao; Zhang, Wei; Niu, Wencheng; Liu, Guohua

    2014-03-15

    The localized surface plasmon resonances (LSPRs) of gold particles assembled on a crystal plate are a powerful tool for biological sensors. Here, we prepare gold colloids in different pH solutions. We monitor the effects of the particle radius and particle coverage on the absorption spectra of AT-cut (r-face dihedral angle of about 3°) crystal plates supporting gold nanoparticles. The surface morphologies were monitored on silicon dioxide substrates using ultraviolet and visible (UV-vis) spectroscopy, and atomic force microscopy (AFM). The results showed that the gold particle coverage decreases with increasing pH value of the gold colloid solution. This phenomenon demonstrates that self-assembled gold surfaces were formed via the electrostatic adsorption of gold particles on the positively charged, ionized amino groups on the crystal plates in the acidic solution. The spectrum of gold nanoparticles with different coverage degree on the crystal plates showed that the LSPR properties are highly dependent on pH.

  10. Metal accumulation and oxidative stress biomarkers in liver of freshwater fish Carassius auratus following in vivo exposure to waterborne zinc under different pH values.

    PubMed

    Qu, Ruijuan; Feng, Mingbao; Wang, Xinghao; Qin, Li; Wang, Chao; Wang, Zunyao; Wang, Liansheng

    2014-05-01

    In this study, laboratory experiments were conducted to investigate the combined effect of zinc and pH on metal accumulation and oxidative stress biomarkers in Carassius auratus. Fish were exposed to 0.1 and 1.0mg Zn/L at three pH values (5.0, 7.25, 9.0) for 3, 12, and 30 d. After each exposure, the contents of three trace elements (Zn, Fe and Cu) were determined in liver. Generally, longer exposure to zinc (12d and 30 d) increased hepatic Zn and Cu deposition, but decreased Fe content. Increasing accumulation of Zn in the tissue was also observed with increasing zinc concentration in the exposure medium. Moreover, hepatic antioxidant enzyme activities including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), together with the level of glutathione (GSH) were measured to evaluate the oxidative stress status. The decreases in the four measured biochemical parameters after 3d exposure might reflect the failure of the antioxidant defense system in neutralizing the ROS generated during the metabolic process, while the recovery of the antioxidants at days 12 and 30 suggested a possible shift toward a detoxification mechanism. With regard to the influence of pH on zinc toxicity, the general observation was that the living environment became more stressful when the water conditions changed from an acidic state toward a near-neutral or alkaline state.

  11. Evaluation of Thiol Raman Activities and pKa Values Using Internally Referenced Raman-Based pH Titration.

    PubMed

    Suwandaratne, Nuwanthi; Hu, Juan; Siriwardana, Kumudu; Gadogbe, Manuel; Zhang, Dongmao

    2016-04-01

    Thiols, including organothiol and thiol-containing biomolecules, are among the most important classes of chemicals that are used broadly in organic synthesis, biological chemistry, and nanosciences. Thiol pKa values are key indicators of thiol reactivity and functionality. Reported herein is an internally referenced Raman-based pH titration method that enables reliable quantification of thiol pKa values for both mono- and dithiols in water. The degree of thiol ionization is monitored directly using the peak intensity of the S-H stretching feature in the 2600 cm(-1) region relative to an internal reference peak as a function of the titration solution's pH. The thiol pKa values and Raman activity relative to its internal reference were then determined by curve fitting the experimental data with equations derived on the basis of the Henderson-Hasselbalch equation. Using this Raman titration method, we determined for the first time the first and second thiol pKa values for 1,2-benzenedithiol in water. This Raman-based method is convenient to implement, and its underlying theory is easy to follow. It should therefore have broad application for thiol pKa determinations and verification.

  12. Evaluation of thiol Raman activities and pKa values using internally referenced Ramanbased pH titration

    NASA Astrophysics Data System (ADS)

    Suwandaratne, Nuwanthi

    Thiols are one of the most important classes of chemicals used broadly in organic synthesis, biological chemistry, and nanosciences. Thiol pKa values are key indicators of thiol reactivity and functionality. This study is an internally-referenced Raman-based pH titration method that enables reliable quantification of thiol pKa values for both mono- and di-thiols in water. The degree of thiol ionization is monitored directly using the peak intensity of the S-H stretching feature relative to an internal reference peak as a function of solution pH. The thiol pKa values and Raman activity relative to its internal reference were then determined by curve-fitting the experimental data with equations derived on the basis of the Henderson-Hasselbalch equation. Using this Raman titration method, first and second thiol pKa values for 1,2-benzenedithol in water were determined for the first time. This method is convenient to implement and its underlying theory is easy to follow.

  13. Aerosol pH buffering in the southeastern US: Fine particles remain highly acidic despite large reductions in sulfate

    NASA Astrophysics Data System (ADS)

    Weber, R. J.; Guo, H.; Russell, A. G.; Nenes, A.

    2015-12-01

    pH is a critical aerosol property that impacts many atmospheric processes, including biogenic secondary organic aerosol formation, gas-particle phase partitioning, and mineral dust or redox metal mobilization. Particle pH has also been linked to adverse health effects. Using a comprehensive data set from the Southern Oxidant and Aerosol Study (SOAS) as the basis for thermodynamic modeling, we have shown that particles are currently highly acidic in the southeastern US, with pH between 0 and 2. Sulfate and ammonium are the main acid-base components that determine particle pH in this region, however they have different sources and their concentrations are changing. Over 15 years of network data show that sulfur dioxide emission reductions have resulted in a roughly 70 percent decrease in sulfate, whereas ammonia emissions, mainly link to agricultural activities, have been largely steady, as have gas phase ammonia concentrations. This has led to the view that particles are becoming more neutralized. However, sensitivity analysis, based on thermodynamic modeling, to changing sulfate concentrations indicates that particles have remained highly acidic over the past decade, despite the large reductions in sulfate. Furthermore, anticipated continued reductions of sulfate and relatively constant ammonia emissions into the future will not significantly change particle pH until sulfate drops to clean continental background levels. The result reshapes our expectation of future particle pH and implies that atmospheric processes and adverse health effects linked to particle acidity will remain unchanged for some time into the future.

  14. Dermal exposure to methamphetamine hydrochloride contaminated residential surfaces: surface pH values, volatility, and in vitro human skin.

    PubMed

    Salocks, Charles B; Hui, Xiaoying; Lamel, Sonia; Qiao, Peter; Sanborn, James R; Maibach, Howard I

    2012-12-01

    This study evaluated pH effects on [(14)C] d-methamphetamine hydrochloride ([(14)C]-meth HCl) percutaneous penetration in vitro and volatility and stability in aqueous solution, on solid surface, or human skin using the finite dose technique and flow through diffusion cells. Results show that when the pH level exceeds 4 or 5, the nonvolatile [(14)C]-meth HCl salt becomes unstable, likely converting to its volatile freebase form. Additionally, contaminated smooth, dense surfaces retain and transfer more [(14)C]-meth HCl than those with rough, loose surfaces, especially under acidic conditions. Skin surface pH is a critical factor affecting the rate and magnitude of dermal absorption. [(14)C]-Meth HCl penetrates into and through the human cadaver skin quickly following exposure. [(14)C]-Meth HCl retained in the skin layer is released into the receptor fluid even if the contact material has been removed. Future exploration of decontaminant and removal procedure efficacies and their effect on dermal penetration of [(14)C]-meth HCl is recommended.

  15. Cadmium availability in rice paddy fields from a mining area: The effects of soil properties highlighting iron fractions and pH value.

    PubMed

    Yu, Huan-Yun; Liu, Chuanping; Zhu, Jishu; Li, Fangbai; Deng, Dong-Mei; Wang, Qi; Liu, Chengshuai

    2016-02-01

    Cadmium (Cd) availability can be significantly affected by soil properties. The effect of pH value on Cd availability has been confirmed. Paddy soils in South China generally contain high contents of iron (Fe). Thus, it is hypothesized that Fe fractions, in addition to pH value, may play an important role in the Cd bioavailability in paddy soil and this requires further investigation. In this study, 73 paired soil and rice plant samples were collected from paddy fields those were contaminated by acid mine drainage containing Cd. The contents of Fe in the amorphous and DCB-extractable Fe oxides were significantly and negatively correlated with the Cd content in rice grain or straw (excluding DCB-extractable Fe vs Cd in straw). In addition, the concentration of HCl-extractable Fe(II) derived from Fe(III) reduction was positively correlated with the Cd content in rice grain or straw. These results suggest that soil Fe redox could affect the availability of Cd in rice plant. Contribution assessment of soil properties to Cd accumulation in rice grain based on random forest (RF) and stochastic gradient boosting (SGB) showed that pH value should be the most important factor and the content of Fe in the amorphous Fe oxides should be the second most important factor in affecting Cd content in rice grain. Overall, compared with the studies from temperate regions, such as Europe and northern China, Fe oxide exhibited its unique role in the bioavailability of Cd in the reddish paddy soil from our study area. The exploration of practical remediation strategies for Cd from the perspective of Fe oxide may be promising. PMID:26629644

  16. Cadmium availability in rice paddy fields from a mining area: The effects of soil properties highlighting iron fractions and pH value.

    PubMed

    Yu, Huan-Yun; Liu, Chuanping; Zhu, Jishu; Li, Fangbai; Deng, Dong-Mei; Wang, Qi; Liu, Chengshuai

    2016-02-01

    Cadmium (Cd) availability can be significantly affected by soil properties. The effect of pH value on Cd availability has been confirmed. Paddy soils in South China generally contain high contents of iron (Fe). Thus, it is hypothesized that Fe fractions, in addition to pH value, may play an important role in the Cd bioavailability in paddy soil and this requires further investigation. In this study, 73 paired soil and rice plant samples were collected from paddy fields those were contaminated by acid mine drainage containing Cd. The contents of Fe in the amorphous and DCB-extractable Fe oxides were significantly and negatively correlated with the Cd content in rice grain or straw (excluding DCB-extractable Fe vs Cd in straw). In addition, the concentration of HCl-extractable Fe(II) derived from Fe(III) reduction was positively correlated with the Cd content in rice grain or straw. These results suggest that soil Fe redox could affect the availability of Cd in rice plant. Contribution assessment of soil properties to Cd accumulation in rice grain based on random forest (RF) and stochastic gradient boosting (SGB) showed that pH value should be the most important factor and the content of Fe in the amorphous Fe oxides should be the second most important factor in affecting Cd content in rice grain. Overall, compared with the studies from temperate regions, such as Europe and northern China, Fe oxide exhibited its unique role in the bioavailability of Cd in the reddish paddy soil from our study area. The exploration of practical remediation strategies for Cd from the perspective of Fe oxide may be promising.

  17. Infectious pancreatic necrosis virus in fish by-products is inactivated with inorganic acid (pH 1) and base (pH 12).

    PubMed

    Myrmel, M; Modahl, I; Nygaard, H; Lie, K M

    2014-04-01

    The aquaculture industry needs a simple, inexpensive and safe method for the treatment of fish waste without heat. Microbial inactivation by inorganic acid (HCl) or base (KOH) was determined using infectious pancreatic necrosis virus (IPNV) as a model organism for fish pathogens. Salmonella and spores of Clostridium perfringens were general hygiene indicators in supplementary examinations. IPNV, which is considered to be among the most chemical- and heat-resistant fish pathogens, was reduced by more than 3 log in 4 h at pH 1.0 and pH 12.0. Salmonella was rapidly inactivated by the same treatment, whereas spores of C. perfringens were hardly affected. The results indicate that low and high pH treatment could be particularly suitable for fish waste destined for biogas production. pH treatment at aquaculture production sites could reduce the spread of fish pathogens during storage and transportation without disturbing the anaerobic digestion process. The treatment could also be an alternative to the current energy-intensive steam pressure sterilization of fish waste to be used by the bioenergy, fertilizer and soil improver industries.

  18. The effect of sugar, amino acid, metal ion, and NaCl on model Maillard reaction under pH control.

    PubMed

    Kwak, E-J; Lim, S-I

    2004-08-01

    The color intensities was determined of Maillard reaction products (MRPs) prepared by heating each of five sugars (maltose, fructose, glucose, arabinose, and xylose) with each of 12 amino acids (aspartic acid, glutamic acid, alanine, leucine, isoleucine, valine, proline, serine, cysteine, phenylalanine, arginine, and lysine). The remaining percentages of glucose and rate of change of color intensity due to the addition of a metal ion and NaCl were monitored for nine MRPs that had been formed between glucose and each of nine amino acids (aspartic acid, glutamic acid, alanine, valine, serine, cysteine, phenylalanine, arginine, and lysine). Model MRPs were prepared in a block heater at 100 degrees C for 1-12 h with the pH value controlled at 6.5. The resulting color intensity of each MRPs formed from the basic amino acids was greater due to the higher reactivity than those from the acidic amino acids. The remaining percentage of glucose in each MRPs from the basic amino acids was lower than those from the acidic amino acids. The MRPs from the nonpolar amino acids showed an intermediate color intensity and remaining percentages of glucose between those formed from the basic and acidic amino acids. Browning tended to be accelerated in the presence of metal ions, especially Fe2+ and Cu2+, although it was affected by the property of the amino acid and heating time as well as by the type of metal ion. On the other hand, browning was greatly inhibited by a high concentration of NaCl.

  19. Tuning Chelation by the Surfactant-Like Peptide A6H Using Predetermined pH Values

    PubMed Central

    2013-01-01

    We examine the self-assembly of a peptide A6H comprising a hexa-alanine sequence A6 with a histidine (H) “head group”, which chelates Zn2+ cations. We study the self-assembly of A6H and binding of Zn2+ ions in ZnCl2 solutions, under acidic and neutral conditions. A6H self-assembles into nanotapes held together by a β-sheet structure in acidic aqueous solutions. By dissolving A6H in acidic ZnCl2 solutions, the carbonyl oxygen atoms in A6H chelate the Zn2+ ions and allow for β-sheet formation at lower concentrations, consequently reducing the onset concentration for nanotape formation. A6H mixed with water or ZnCl2 solutions under neutral conditions produces short sheets or pseudocrystalline tapes, respectively. The imidazole ring of A6H chelates Zn2+ ions in neutral solutions. The internal structure of nanosheets and pseudocrystalline sheets in neutral solutions is similar to the internal structure of A6H nanotapes in acidic solutions. Our results show that it is possible to induce dramatic changes in the self-assembly and chelation sites of A6H by changing the pH of the solution. However, it is likely that the amphiphilic nature of A6H determines the internal structure of the self-assembled aggregates independent from changes in chelation. PMID:24369761

  20. Simultaneous removal of As, Cd, Cr, Cu, Ni and Zn from stormwater using high-efficiency industrial sorbents: Effect of pH, contact time and humic acid.

    PubMed

    Genç-Fuhrman, Hülya; Mikkelsen, Peter S; Ledin, Anna

    2016-10-01

    The effect of contact time, solution pH, and the presence of humic acid (HA) on the combined removal of As, Cd, Cr, Cu, Ni and Zn is investigated in batch tests using alumina, granulated activated carbon (GAC), and bauxsol coated sand (BCS) as sorbents. It is found that the equilibrium time for Cd, Cu, Ni and Zn is about 4h, while no clear equilibrium is observed for As and Cr. It is also found that increasing the pH until pH~8 enhanced Cd, Cu, Ni and Zn removal, but increasing the pH above this point had no major effect. In the cases of As and Cr, higher pH values (i.e. >7) decreased their removal. The presence of both 20 and 100mg/L HA suppressed the heavy metal removal except for Cr, and the suppression was higher at the higher HA concentration. Geochemical simulations suggest that this is due to the formation of dissolved HA-metal complexes preventing effective metal sorption. In the case of Cr, the presence of HA increased the removal when using alumina or BCS, while hindering the removal when using GAC. The findings show that the pH-value of the stormwater to be treated must be in the range of 6-7 in order to achieve removal of the full spectrum of metals. The results also show that natural organic matter may severely influence the removal efficiency, such that, for most metals the removal was reduced to the half, while for Cr it was increased to the double for alumina and BCS. Consequently, a properly working filter set up may not work properly anymore when receiving high loads of natural organic acids during the pollen season in spring or during defoliation in autumn and early winter, and during mixing of runoff with snowmelt having a low pH. PMID:27213673

  1. Reactive solute transport in an acidic stream: Experimental pH increase and simulation of controls on pH, aluminum, and iron

    USGS Publications Warehouse

    Broshears, R.E.; Runkel, R.L.; Kimball, B.A.; McKnight, Diane M.; Bencala, K.E.

    1996-01-01

    Solute transport simulations quantitatively constrained hydrologic and geochemical hypotheses about field observations of a pH modification in an acid mine drainage stream. Carbonate chemistry, the formation of solid phases, and buffering interactions with the stream bed were important factors in explaining the behavior of pH, aluminum, and iron. The precipitation of microcrystalline gibbsite accounted for the behavior of aluminum; precipitation of Fe(OH)3 explained the general pattern of iron solubility. The dynamic experiment revealed limitations on assumptions that reactions were controlled only by equilibrium chemistry. Temporal variation in relative rates of photoreduction and oxidation influenced iron behavior. Kinetic limitations on ferrous iron oxidation and hydrous oxide precipitation and the effects of these limitations on field filtration were evident. Kinetic restraints also characterized interaction between the water column and the stream bed, including sorption and desorption of protons from iron oxides at the sediment-water interface and post-injection dissolution of the precipitated aluminum solid phase.

  2. Influence of amino acids, buffers, and ph on the γ-irradiation-induced degradation of alginates.

    PubMed

    Ulset, Ann-Sissel T; Mori, Hideki; Dalheim, Marianne Ø; Hara, Masayuki; Christensen, Bjørn E

    2014-12-01

    Alginate-based biomaterials and medical devices are commonly subjected to γ-irradiation as a means of sterilization, either in the dry state or the gel (hydrated) state. In this process the alginate chains degrade randomly in a dose-dependent manner, altering alginates' material properties. The addition of free radical scavenging amino acids such as histidine and phenylalanine protects the alginate significantly against degradation, as shown by monitoring changes in the molecular weight distributions using SEC-MALLS and determining the pseudo first order rate constants of degradation. Tris buffer (0.5 M), but not acetate, citrate, or phosphate buffers had a similar effect on the degradation rate. Changes in pH itself had only marginal effects on the rate of alginate degradation and on the protective effect of amino acids. Contrary to previous reports, the chemical composition (M/G profile) of the alginates, including homopolymeric mannuronan, was unaltered following irradiation up to 10 kGy. PMID:25412478

  3. Boronate-Phenolic Network Capsules with Dual Response to Acidic pH and cis-Diols.

    PubMed

    Guo, Junling; Sun, Huanli; Alt, Karen; Tardy, Blaise L; Richardson, Joseph J; Suma, Tomoya; Ejima, Hirotaka; Cui, Jiwei; Hagemeyer, Christoph E; Caruso, Frank

    2015-08-26

    Dual-responsive boronate-phenolic network (BPN) capsules are fabricated by the complexation of phenylborate and phenolic materials. The BPN capsules are stable in the presence of competing carbohydrates, but dissociate at acidic pH or in the presence of competing cis-diols at physiological pH. This engineered capsule system provides a platform for a wide range of biological and biomedical applications.

  4. Lactic acid fermentation from food waste with indigenous microbiota: Effects of pH, temperature and high OLR.

    PubMed

    Tang, Jialing; Wang, Xiaochang; Hu, Yisong; Zhang, Yongmei; Li, Yuyou

    2016-06-01

    The effects of pH, temperature and high organic loading rate (OLR) on lactic acid production from food waste without extra inoculum addition were investigated in this study. Using batch experiments, the results showed that although the hydrolysis rate increased with pH adjustment, the lactic acid concentration and productivity were highest at pH 6. High temperatures were suitable for solubilization but seriously restricted the acidification processes. The highest lactic acid yield (0.46g/g-TS) and productivity (278.1mg/Lh) were obtained at 37°C and pH 6. In addition, the lactic acid concentration gradually increased with the increase in OLR, and the semi-continuous reactor could be stably operated at an OLR of 18g-TS/Ld. However, system instability, low lactic acid yield and a decrease in VS removal were noticed at high OLRs (22g-TS/Ld). The concentrations of volatile fatty acids (VFAs) in the fermentation mixture were relatively low but slightly increased with OLR, and acetate was the predominant VFA component. Using high-throughput pyrosequencing, Lactobacillus from the raw food waste was found to selectively accumulate and become dominant in the semi-continuous reactor.

  5. Microbiological profiles, pH, and titratable acidity of chorizo and salchichón (two Spanish dry fermented sausages) manufactured with ostrich, deer, or pork meat.

    PubMed

    Capita, Rosa; Llorente-Marigómez, Sandra; Prieto, Miguel; Alonso-Calleja, Carlos

    2006-05-01

    Microbial counts, pH, and titratable acidity were determined in 102 Spanish dry fermented sausages (chorizo and salchichón) made with ostrich, deer, or pork meat. Average microbial counts (log CFU per gram) varied from 5.46 +/- 0.24 to 8.25 +/- 0.80 (total viable counts), from 4.79 +/- 0.36 to 7.99 +/- 0.20 (psychrotrophs), from 0.00 +/- 0.00 to 0.99 +/- 1.10 (undetectable values were assumed to be zero) (Enterobacteriaceae), from 0.00 +/- 0.00 to 4.27 +/- 1.47 (enterococci), from 5.15 +/- 1.15 to 8.46 +/- 0.49 (lactic acid bacteria), from 3.08 +/- 0.44 to 6.59 +/- 1.76 (Micrococcaceae), from 2.27 +/- 1.53 to 5.11 +/- 1.81 (molds and yeasts), from 0.00 +/- 0.00 to 2.25 +/- 0.81 (pseudomonads), and from 0.00 +/- 0.00 to 2.78 +/- 0.46 (Brochothrix thermosphacta). Average pH and titratable acidity varied from 5.07 +/- 0.25 to 5.63 +/- 0.51 (pH units) and from 0.30 +/- 0.01 to 0.86 +/- 0.19 (% lactic acid). Both type of sausage (P < 0.05) and species of meat (P < 0.001) influenced microbial counts. Salchich6n samples showed lower average values than chorizo samples for most microbial groups (significant for Enterobacteriaceae, lactic acid bacteria, and B. thermosphacta) and titratable acidity. Sausages made from pork showed the highest microbial loads for total viable counts, psychrotrophs, Enterobacteriaceae, enterococci, lactic acid bacteria, and yeasts and molds. Higher counts were observed only for pseudomonads in ostrich sausages. B. thermosphacta levels were similar for all species of meat. The highest average pH value was observed in sausages made from ostrich meat, and the lowest titratable acidity level was found in pork sausages.

  6. Uranium fate in wetland mesocosms: Effects of plants at two iron loadings with different pH values.

    PubMed

    Koster van Groos, Paul G; Kaplan, Daniel I; Chang, Hyun-Shik; Seaman, John C; Li, Dien; Peacock, Aaron D; Scheckel, Kirk G; Jaffé, Peter R

    2016-11-01

    Small-scale continuous flow wetland mesocosms (∼0.8 L) were used to evaluate how plant roots under different iron loadings affect uranium (U) mobility. When significant concentrations of ferrous iron (Fe) were present at circumneutral pH values, U concentrations in root exposed sediments were an order of magnitude greater than concentrations in root excluded sediments. Micro X-ray absorption near-edge structure (μ-XANES) spectroscopy indicated that U was associated with the plant roots primarily as U(VI) or U(V), with limited evidence of U(IV). Micro X-ray fluorescence (μ-XRF) of plant roots suggested that for high iron loading at circumneutral pH, U was co-located with Fe, perhaps co-precipitated with root Fe plaques, while for low iron loading at a pH of ∼4 the correlation between U and Fe was not significant, consistent with previous observations of U associated with organic matter. Quantitative PCR analyses indicated that the root exposed sediments also contained elevated numbers of Geobacter spp., which are likely associated with enhanced iron cycling, but may also reduce mobile U(VI) to less mobile U(IV) species.

  7. Uranium fate in wetland mesocosms: Effects of plants at two iron loadings with different pH values.

    PubMed

    Koster van Groos, Paul G; Kaplan, Daniel I; Chang, Hyun-Shik; Seaman, John C; Li, Dien; Peacock, Aaron D; Scheckel, Kirk G; Jaffé, Peter R

    2016-11-01

    Small-scale continuous flow wetland mesocosms (∼0.8 L) were used to evaluate how plant roots under different iron loadings affect uranium (U) mobility. When significant concentrations of ferrous iron (Fe) were present at circumneutral pH values, U concentrations in root exposed sediments were an order of magnitude greater than concentrations in root excluded sediments. Micro X-ray absorption near-edge structure (μ-XANES) spectroscopy indicated that U was associated with the plant roots primarily as U(VI) or U(V), with limited evidence of U(IV). Micro X-ray fluorescence (μ-XRF) of plant roots suggested that for high iron loading at circumneutral pH, U was co-located with Fe, perhaps co-precipitated with root Fe plaques, while for low iron loading at a pH of ∼4 the correlation between U and Fe was not significant, consistent with previous observations of U associated with organic matter. Quantitative PCR analyses indicated that the root exposed sediments also contained elevated numbers of Geobacter spp., which are likely associated with enhanced iron cycling, but may also reduce mobile U(VI) to less mobile U(IV) species. PMID:27522183

  8. Temperature and pH responsiveness of poly-(DMAA-co-unsaturated carboxylic acid) hydrogels synthesized by UV-irradiation

    NASA Astrophysics Data System (ADS)

    Kakinoki, Sachiro; Kaetsu, Isao; Nakayama, Masashi; Sutani, Kouichi; Uchida, Kumao; Yukutake, Kouji

    2003-07-01

    Stimuli-responsive polyampholyte hydrogels were synthesized by the copolymerization of dimethylaminoethyl methacrylate (DMAA) and acrylic acid (AAc) or itaconic acid (IAc) by UV-irradiation. Temperature and pH responsiveness of these hydrogels were studied. The temperature responsiveness of poly-(DMAA-co-AAc, IAc) hydrogels shown in change of water content became dull compared to that of DMAA homo-polymer hydrogel. The water content of the poly-(DMAA-co-AAc, IAc) hydrogels showed a minimum at pH 8, and increased in more acidic and alkaline regions. This fact can be attributed to the coexistence of anions and cations in the poly-(DMAA-co-AAc, IAc) hydrogels. The poly-(DMAA-co-AAc, IAc) hydrogels were polyampholyte having both temperature responsiveness and pH responsiveness.

  9. X-ray absorption and resonance raman spectroscopy of human myeloperoxidase at neutral and acid pH.

    PubMed

    Yue, K T; Taylor, K L; Kinkade, J M; Sinclair, R B; Powers, L S

    1997-04-01

    Myeloperoxidase (MPO), an important enzyme in the oxygen-dependent host defense system of human polymorphonuclear leukocytes, utilizes hydrogen peroxide to catalyze the production of hypochlorous acid, an oxidizing bactericidal agent. While MPO shows significant sequence homology with other peroxidases and this homology is particularly striking among the active-site residues, MPO exhibits unusual spectral features and the unique ability to catalyze the oxidation of chloride ions. We have investigated the MPO active-site with X-ray absorption (XAS) and resonance Raman (RRS) spectroscopies at neutral pH and also at the physiological acidic pH (pH approximately 3) and have compared these results with those of horseradish peroxidase (HRP). At pH 7.5, XAS results show that the iron heme active site is 6-coordinate where the distal ligand is likely nitrogen or oxygen, but not sulfur. The heme is distorted compared to HRP, other peroxidases, and heme compounds, but at pH approximately 3, the distal ligand is lost and the heme is less distorted. RRS results under identical pH conditions show that the skeletal core-size sensitive modes and v3 are shifted to higher frequency at pH approximately 3 indicating a 6- to 5-coordination change of high spin ferric heme. In addition, a new band at 270 cm(-1) is observed at pH approximately 3 which is consistent with the loss of the sixth ligand. The higher symmetry of the heme at pH approximately 3 is reflected by a single v4 mode in the (RRS) spectrum. HRP also loses its loosely associated distal water at this pH, but little change in heme distortion is observed. This change suggests that loss of the distal ligand in MPO releases stress on the heme which may facilitate binding of chloride ion.

  10. [Characteristics of soil pH and exchangeable acidity in red soil profile under different vegetation types].

    PubMed

    Ji, Gang; Xu, Ming-gang; Wen, Shi-lin; Wang, Bo-ren; Zhang, Lu; Liu, Li-sheng

    2015-09-01

    The characteristics of soil pH and exchangeable acidity in soil profile under different vegetation types were studied in hilly red soil regions of southern Hunan Province, China. The soil samples from red soil profiles within 0-100 cm depth at fertilized plots and unfertilized plots were collected and analyzed to understand the profile distribution of soil pH and exchangeable acidity. The results showed that, pH in 0-60 cm soil from the fertilized plots decreased as the following sequence: citrus orchard > Arachis hypogaea field > tea garden. As for exchangeable acidity content, the sequence was A. hypogaea field ≤ citrus orchard < tea garden. After tea tree and A. hypogaea were planted for long time, acidification occurred in surface soil (0-40 cm), compared with the deep soil (60-100 cm), and soil pH decreased by 0.55 and 0.17 respectively, but such changes did not occur in citrus orchard. Soil pH in 0-40 cm soil from the natural recovery vegetation unfertilized plots decreased as the following sequence: Imperata cylindrica land > Castanea mollissima garden > Pinus elliottii forest ≥ Loropetalum chinensis forest. As for exchangeable acidity content, the sequence was L cylindrica land < C. mollissima garden < L. chinensis forest ≤ P. elliottii forest. Soil pH in surface soil (0-20 cm) from natural forest plots, secondary forest and Camellia oleifera forest were significantly lower than that from P. massoniana forest, decreased by 0.34 and 0.20 respectively. For exchangeable acidity content in 0-20 cm soil from natural forest plot, P. massoniana forest and secondary forest were significantly lower than C. oleifera forest. Compared with bare land, surface soil acidification in unfertilized plots except I. cylindrica land had been accelerated, and the natural secondary forest was the most serious among them, with surface soil pH decreasing by 0.52. However, the pH increased in deep soils from unfertilized plots except natural secondary forest, and I. cylindrica

  11. [Characteristics of soil pH and exchangeable acidity in red soil profile under different vegetation types].

    PubMed

    Ji, Gang; Xu, Ming-gang; Wen, Shi-lin; Wang, Bo-ren; Zhang, Lu; Liu, Li-sheng

    2015-09-01

    The characteristics of soil pH and exchangeable acidity in soil profile under different vegetation types were studied in hilly red soil regions of southern Hunan Province, China. The soil samples from red soil profiles within 0-100 cm depth at fertilized plots and unfertilized plots were collected and analyzed to understand the profile distribution of soil pH and exchangeable acidity. The results showed that, pH in 0-60 cm soil from the fertilized plots decreased as the following sequence: citrus orchard > Arachis hypogaea field > tea garden. As for exchangeable acidity content, the sequence was A. hypogaea field ≤ citrus orchard < tea garden. After tea tree and A. hypogaea were planted for long time, acidification occurred in surface soil (0-40 cm), compared with the deep soil (60-100 cm), and soil pH decreased by 0.55 and 0.17 respectively, but such changes did not occur in citrus orchard. Soil pH in 0-40 cm soil from the natural recovery vegetation unfertilized plots decreased as the following sequence: Imperata cylindrica land > Castanea mollissima garden > Pinus elliottii forest ≥ Loropetalum chinensis forest. As for exchangeable acidity content, the sequence was L cylindrica land < C. mollissima garden < L. chinensis forest ≤ P. elliottii forest. Soil pH in surface soil (0-20 cm) from natural forest plots, secondary forest and Camellia oleifera forest were significantly lower than that from P. massoniana forest, decreased by 0.34 and 0.20 respectively. For exchangeable acidity content in 0-20 cm soil from natural forest plot, P. massoniana forest and secondary forest were significantly lower than C. oleifera forest. Compared with bare land, surface soil acidification in unfertilized plots except I. cylindrica land had been accelerated, and the natural secondary forest was the most serious among them, with surface soil pH decreasing by 0.52. However, the pH increased in deep soils from unfertilized plots except natural secondary forest, and I. cylindrica

  12. Development of On-Line Spectroscopic pH Monitoring for Nuclear Fuel Reprocessing Plants: Weak Acid Schemes

    SciTech Connect

    Casella, Amanda J.; Hylden, Laura R.; Campbell, Emily L.; Levitskaia, Tatiana G.; Peterson, James M.; Smith, Frances N.; Bryan, Samuel A.

    2015-05-19

    Knowledge of real-time solution properties and composition is a necessity for any spent nuclear fuel reprocessing method. Metal-ligand speciation in aqueous solutions derived from the dissolved commercial spent fuel is highly dependent upon the acid concentration/pH, which influences extraction efficiency and the resulting speciation in the organic phase. Spectroscopic process monitoring capabilities, incorporated in a counter current centrifugal contactor bank, provide a pathway for on-line real-time measurement of solution pH. The spectroscopic techniques are process-friendly and can be easily configured for on-line applications, while classic potentiometric pH measurements require frequent calibration/maintenance and have poor long-term stability in aggressive chemical and radiation environments. Our research is focused on developing a general method for on-line determination of pH of aqueous solutions through chemometric analysis of Raman spectra. Interpretive quantitative models have been developed and validated under the range of chemical composition and pH using a lactic acid/lactate buffer system. The developed model was applied to spectra obtained on-line during solvent extractions performed in a centrifugal contactor bank. The model predicted the pH within 11% for pH > 2, thus demonstrating that this technique could provide the capability of monitoring pH on-line in applications such as nuclear fuel reprocessing.

  13. Acid-extrusion from tissue: the interplay between membrane transporters and pH buffers.

    PubMed

    Hulikova, Alzbeta; Harris, Adrian L; Vaughan-Jones, Richard D; Swietach, Pawel

    2012-01-01

    The acid-base balance of cells is related to the concentration of free H⁺ ions. These are highly reactive, and their intracellular concentration must be regulated to avoid detrimental effects to the cell. H⁺ ion dynamics are influenced by binding to chelator substances ('buffering'), and by the production, diffusion and membrane-transport of free H⁺ ions or of the H⁺-bound chelators. Intracellular pH (pHi) regulation aims to balance this system of diffusion-reaction-transport processes at a favourable steady-state pHi. The ability of cells to regulate pHi may set a limit to tissue growth and can be subject to selection pressures. Cancer cells have been postulated to respond favourably to such selection pressures by evolving a better means of pHi regulation. A particularly important feature of tumour pHi regulation is acid-extrusion, which involves H⁺-extrusion and HCO₃⁻-uptake by membrane-bound transporter-proteins. Extracellular CO₂/HCO₃⁻ buffer facilitates these membrane-transport processes. As a mobile pH-buffer, CO₂/HCO₃⁻ protects the extracellular space from excessive acidification that could otherwise inhibit further acid-extrusion. CO₂/HCO₃⁻ also provides substrate for HCO₃⁻-transporters. However, the inherently slow reaction kinetics of CO₂/HCO₃⁻ can be rate-limiting for acid-extrusion. To circumvent this, cells can express extracellular-facing carbonic anhydrase enzymes to accelerate the attainment of equilibrium between CO₂, HCO₃⁻ and H⁺. The acid-extrusion apparatus has been proposed as a target for anti-cancer therapy. The major targets include H⁺ pumps, Na⁺/H⁺ exchangers and carbonic anhydrases. The effectiveness of such therapy will depend on the correct identification of rate-limiting steps in pHi regulation in a specific type of cancer. PMID:22360560

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

    PubMed

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

    2015-04-01

    In this study, influence of feedwater pH (2-12) was studied for hydrothermal carbonization (HTC) of wheat straw at 200 and 260°C. Acetic acid and KOH were used as acidic and basic medium, respectively. Hydrochars were characterized by elemental and fiber analyses, SEM, surface area, pore volume and size, and ATR-FTIR, while HTC process liquids were analyzed by HPLC and GC. Both hydrochar and HTC process liquid qualities vary with feedwater pH. At acidic pH, cellulose and elemental carbon increase in hydrochar, while hemicellulose and pseudo-lignin decrease. Hydrochars produced at pH 2 feedwater has 2.7 times larger surface area than that produced at pH 12. It also has the largest pore volume (1.1 × 10(-1) ml g(-1)) and pore size (20.2 nm). Organic acids were increasing, while sugars were decreasing in case of basic feedwater, however, phenolic compounds were present only at 260°C and their concentrations were increasing in basic feedwater. PMID:25710573

  15. On the Mechanism by which Alkaline pH Prevents Expression of an Acid-Expressed Gene

    PubMed Central

    Espeso, Eduardo A.; Arst, Herbert N.

    2000-01-01

    Previous work has shown that zinc finger transcription factor PacC mediates the regulation of gene expression by ambient pH in the fungus Aspergillus nidulans. This regulation ensures that the syntheses of molecules functioning in the external environment, such as permeases, secreted enzymes, and exported metabolites, are tailored to the pH of the growth environment. A direct role for PacC in activating the expression of an alkaline-expressed gene has previously been demonstrated, but the mechanism by which alkaline ambient pH prevents the expression of any eukaryotic acid-expressed gene has never been reported. Here we show that a double PacC binding site in the promoter of the acid-expressed gabA gene, encoding γ-aminobutyrate (GABA) permease, overlaps the binding site for the transcriptional activator IntA, which mediates ω-amino acid induction. Using bacterially expressed fusion proteins, we have shown that PacC competes with IntA for DNA binding in vitro at this site. Thus, PacC repression of GABA permease synthesis is direct and occurs by blocking induction. A swap of IntA sites between promoters for gabA and amdS, a gene not subject to pH regulation, makes gabA expression pH independent and amdS acid expressed. PMID:10779325

  16. Metal reduction at low pH by a Desulfosporosinus species: implications for the biological treatment of acidic mine drainage

    SciTech Connect

    Senko, J.M.; Zhang, G.X.; McDonough, J.T.; Bruns, M.A.; Burgos, W.D.

    2009-07-01

    We isolated an acid-tolerant sulfate-reducing bacterium, GBSRB4.2, from coal mine-derived acidic mine drainage (AMD)-derived sediments. Sequence analysis of partial 16S rRNA gene of GBSRB4.2 revealed that it was affiliated with the genus Desulfosporosinus. GBSRB4.2 reduced sulfate, Fe(III) (hydr)oxide, Mn(IV) oxide, and U(VI) in acidic solutions (pH 4.2). Sulfate, Fe(III), and Mn(IV) but not U(VI) bioreduction led to an increase in the pH of acidic solutions and concurrent hydrolysis and precipitation of dissolved Al{sup 3+}. Reduction of Fe(III), Mn(IV), and U(VI) in sulfate-free solutions revealed that these metals are enzymatically reduced by GBSRB4.2. GBSRB4.2 reduced U(VI) in groundwater from a radionuclide-contaminated aquifer more rapidly at pH 4.4 than at pH 7.1, possibly due to the formation of poorly bioreducible Ca-U(VI)-CO{sub 3} complexes in the pH 7.1 groundwater.

  17. Acidic pH and divalent cation sensing by PhoQ are dispensable for systemic salmonellae virulence

    PubMed Central

    Hicks, Kevin G; Delbecq, Scott P; Sancho-Vaello, Enea; Blanc, Marie-Pierre; Dove, Katja K; Prost, Lynne R; Daley, Margaret E; Zeth, Kornelius; Klevit, Rachel E; Miller, Samuel I

    2015-01-01

    Salmonella PhoQ is a histidine kinase with a periplasmic sensor domain (PD) that promotes virulence by detecting the macrophage phagosome. PhoQ activity is repressed by divalent cations and induced in environments of acidic pH, limited divalent cations, and cationic antimicrobial peptides (CAMP). Previously, it was unclear which signals are sensed by salmonellae to promote PhoQ-mediated virulence. We defined conformational changes produced in the PhoQ PD on exposure to acidic pH that indicate structural flexibility is induced in α-helices 4 and 5, suggesting this region contributes to pH sensing. Therefore, we engineered a disulfide bond between W104C and A128C in the PhoQ PD that restrains conformational flexibility in α-helices 4 and 5. PhoQW104C-A128C is responsive to CAMP, but is inhibited for activation by acidic pH and divalent cation limitation. phoQW104C-A128C Salmonella enterica Typhimurium is virulent in mice, indicating that acidic pH and divalent cation sensing by PhoQ are dispensable for virulence. DOI: http://dx.doi.org/10.7554/eLife.06792.001 PMID:26002083

  18. The pH profile for acid-induced elongation of coleoptile and epicotyl sections is consistent with the acid-growth theory

    NASA Technical Reports Server (NTRS)

    Cleland, R. E.; Buckley, G.; Nowbar, S.; Lew, N. M.; Stinemetz, C.; Evans, M. L.; Rayle, D. L.

    1991-01-01

    The acid-growth theory predicts that a solution with a pH identical to that of the apoplast of auxin-treated tissues (4.5.-5.0) should induce elongation at a rate comparable to that of auxin. Different pH profiles for elongation have been obtained, however, depending on the type of pretreatment between harvest of the sections and the start of the pH-incubations. To determine the acid sensitivity under in vivo conditions, oat (Avena sativa L.) coleoptile, maize (Zea mays L.) coleoptile and pea (Pisum sativum L.) epicotyl sections were abraded so that exogenous buffers could penetrate the free space, and placed in buffered solutions of pH 3.5-6.5 without any preincubation. The extension, without auxin, was measured over the first 3 h. Experiments conducted in three laboratories produced similar results. For all three species, sections placed in buffer without pretreatment elongated at least threefold faster at pH 5.0 than at 6.0 or 6.5, and the rate elongation at pH 5.0 was comparable to that induced by auxin. Pretreatment of abraded sections with pH-6.5 buffer or distilled water adjusted to pH 6.5 or above gave similar results. We conclude that the pH present in the apoplast of auxin-treated coleoptile and stems is sufficiently low to account for the initial growth response to auxin.

  19. A Silica-Supported Iron Oxide Catalyst Capable of Activating Hydrogen Peroxide at Neutral pH Values

    PubMed Central

    Pham, Anh Le-Tuan; Lee, Changha; Doyle, Fiona M.; Sedlak, David L.

    2009-01-01

    Iron oxides catalyze the conversion of hydrogen peroxide (H2O2) into oxidants capable of transforming recalcitrant contaminants. Unfortunately, the process is relatively inefficient at circumneutral pH values due to competing reactions that decompose H2O2 without producing oxidants. Silica- and alumina-containing iron oxides prepared by sol-gel processing of aqueous solutions containing Fe(ClO4)3, AlCl3 and tetraethyl orthosilicate efficiently catalyzed the decomposition of H2O2 into oxidants capable of transforming phenol at circumneutral pH values. Relative to hematite, goethite and amorphous FeOOH, the silica-iron oxide catalyst exhibited a stoichiometric efficiency, defined as the number of moles of phenol transformed per mole of H2O2 consumed, that was 10 to 40 times higher than that of the iron oxides. The silica-alumina-iron oxide catalyst had a stoichiometric efficiency that was 50 to 80 times higher than that of the iron oxides. The significant enhancement in oxidant production is attributable to the interaction of Fe with Al and Si in the mixed oxides, which alters the surface redox processes, favoring the production of strong oxidants during H2O2 decomposition. PMID:19943668

  20. A new kind of chelating agent with low pH value applied in the TSV CMP slurry

    NASA Astrophysics Data System (ADS)

    Jiao, Hong; Yuling, Liu; Baoguo, Zhang; Xinhuan, Niu; Liying, Han

    2015-12-01

    TSV (through silicon via) is an emerging technology, which can realize micromation compared with the conventional packaging and extend Moore's law. Chemical mechanical polishing (CMP) is one of the most important steps in the process of TSV manufacture, and it is an enabling technology to extend Moore's law in the past two decades. Low pressure, low abrasive and low pH value are the main requirements for copper interconnection. In this paper, the effect of different kinds of TSV slurry with FA/O II or FA/O IV type chelating agent on CMP are studied. All kinds of slurry used in this study are alkaline with no added inhibitors. From the experiment results, it can be seen that the copper removal rate and surface roughness achieved by using the FA/O IV type chelating agent with a low pH value is superior to using the FA/O II type chelating agent. Project supported by the Major National Science and Technology Special Projects (No. 2009ZX02308), the Fund Project of Hebei Provincial Department of Education, China (No. QN2014208), the Natural Science Foundation of Hebei Province, China (No. E2013202247), and the Colleges and Universities Scientific Research Project of Hebei Province, China (No. Z2014088).

  1. Effect of acid rain pH on leaching behavior of cement stabilized lead-contaminated soil.

    PubMed

    Du, Yan-Jun; Wei, Ming-Li; Reddy, Krishna R; Liu, Zhao-Peng; Jin, Fei

    2014-04-30

    Cement stabilization is a practical approach to remediate soils contaminated with high levels of lead. However, the potential for leaching of lead out of these stabilized soils under variable acid rain pH conditions is a major environmental concern. This study investigates the effects of acid rain on the leaching characteristics of cement stabilized lead contaminated soil under different pH conditions. Clean kaolin clay and the same soil spiked with 2% lead contamination are stabilized with cement contents of 12 and 18% and then cured for 28 days. The soil samples are then subjected to a series of accelerated leaching tests (or semi-dynamic leaching tests) using a simulated acid rain leachant prepared at pH 2.0, 4.0 or 7.0. The results show that the strongly acidic leachant (pH ∼2.0) significantly altered the leaching behavior of lead as well as calcium present in the soil. However, the differences in the leaching behavior of the soil when the leachant was mildly acidic (pH ∼4.0) and neutral (pH ∼7.0) prove to be minor. In addition, it is observed that the lead contamination and cement content levels can have a considerable impact on the leaching behavior of the soils. Overall, the leachability of lead and calcium is attributed to the stability of the hydration products and their consequent influence on the soil buffering capacity and structure.

  2. Anti-biofilm potential of phenolic acids: the influence of environmental pH and intrinsic physico-chemical properties.

    PubMed

    Silva, Sara; Costa, Eduardo M; Horta, Bruno; Calhau, Conceição; Morais, Rui M; Pintado, M Manuela

    2016-09-13

    Phenolic acids are a particular group of small phenolic compounds which have exhibited some anti-biofilm activity, although the link between their activity and their intrinsic pH is not clear. Therefore, the present work examined the anti-biofilm activity (inhibition of biomass and metabolic activity) of phenolic acids in relation to the environmental pH, as well as other physico-chemical properties. The results indicate that, while Escherichia coli was not inhibited by the phenolic acids, both methicillin resistant Staphylococcus aureus and methicillin resistant Staphylococcus epidermidis were susceptible to the action of all phenolic acids, with the pH playing a relevant role in the activity: a neutral pH favored MRSE inhibition, while acidic conditions favored MRSA inhibition. Some links between molecular polarity and size were associated only with their potential as metabolic inhibitors, with the overall interactions hinting at a membrane-based mechanism for MRSA and a cytoplasmic effect for MRSE. PMID:27434592

  3. Effect of acid rain pH on leaching behavior of cement stabilized lead-contaminated soil.

    PubMed

    Du, Yan-Jun; Wei, Ming-Li; Reddy, Krishna R; Liu, Zhao-Peng; Jin, Fei

    2014-04-30

    Cement stabilization is a practical approach to remediate soils contaminated with high levels of lead. However, the potential for leaching of lead out of these stabilized soils under variable acid rain pH conditions is a major environmental concern. This study investigates the effects of acid rain on the leaching characteristics of cement stabilized lead contaminated soil under different pH conditions. Clean kaolin clay and the same soil spiked with 2% lead contamination are stabilized with cement contents of 12 and 18% and then cured for 28 days. The soil samples are then subjected to a series of accelerated leaching tests (or semi-dynamic leaching tests) using a simulated acid rain leachant prepared at pH 2.0, 4.0 or 7.0. The results show that the strongly acidic leachant (pH ∼2.0) significantly altered the leaching behavior of lead as well as calcium present in the soil. However, the differences in the leaching behavior of the soil when the leachant was mildly acidic (pH ∼4.0) and neutral (pH ∼7.0) prove to be minor. In addition, it is observed that the lead contamination and cement content levels can have a considerable impact on the leaching behavior of the soils. Overall, the leachability of lead and calcium is attributed to the stability of the hydration products and their consequent influence on the soil buffering capacity and structure. PMID:24637445

  4. Growth and Metabolism of Lactic Acid Bacteria during and after Malolactic Fermentation of Wines at Different pH

    PubMed Central

    Davis, C. R.; Wibowo, D. J.; Lee, T. H.; Fleet, G. H.

    1986-01-01

    Commercially produced red wines were adjusted to pH 3.0, 3.2, 3.5, 3.7, or 4.0 and examined during and after malolactic fermentation for growth of lactic acid bacteria and changes in the concentrations of carbohydrates, organic acids, amino acids, and acetaldehyde. With one exception, Leuconostoc oenos conducted the malolactic fermentation in all wines and was the only species to occur in wines at pH below 3.5. Malolactic fermentation by L. oenos was accompanied by degradation of malic, citric, and fumaric acids and production of lactic and acetic acids. The concentrations of arginine, histidine, and acetaldehyde also decreased at this stage, but the behavior of hexose and pentose sugars was complicated by other factors. Pediococcus parvulus conducted the malolactic fermentation in one wine containing 72 mg of total sulfur dioxide per liter. Fumaric and citric acids were not degraded during this malolactic fermentation, but hexose sugars were metabolized. P. parvulus and species of Lactobacillus grew after malolactic fermentation in wines with pH adjusted above 3.5. This growth was accompanied by the utilization of wine sugars and production of lactic and acetic acids. PMID:16347015

  5. Retention of ionisable compounds on high-performance liquid chromatography XVIII: pH variation in mobile phases containing formic acid, piperazine, tris, boric acid or carbonate as buffering systems and acetonitrile as organic modifier.

    PubMed

    Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

    2009-03-20

    In the present work dissociation constants of commonly used buffering species, formic acid, piperazine, tris(hydroxymethyl)-aminomethane, boric acid and carbonate, have been determined for several acetonitrile-water mixtures. From these pK(a) values a previous model has been successfully evaluated to estimate pH values in acetonitrile-aqueous buffer mobile phases from the aqueous pH and concentration of the above mentioned buffers up to 60% of acetonitrile, and aqueous buffer concentrations between 0.005 (0.001 mol L(-1) for formic acid-formate) and 0.1 mol L(-1). The relationships derived for the presently studied buffers, together with those established for previously considered buffering systems, allow a general prediction of the pH variation of the most commonly used HPLC buffers when the composition of the acetonitrile-water mobile phase changes during the chromatographic process, such as in gradient elution. Thus, they are an interesting tool that can be easily implemented in general retention models to predict retention of acid-base analytes and optimize chromatographic separations.

  6. Characterization of the acidic and basic limbs of a bell-shaped pH profile in the inhibitory activity of bromelain inhibitor VI.

    PubMed

    Hatano, Ken-ichi; Sawano, Yoriko; Miyakawa, Takuya; Tanokura, Masaru

    2006-03-01

    Bromelain inhibitor VI (BI-VI) is a cysteine proteinase inhibitor from pineapple stem and a unique two-chain inhibitor composed of two distinct domains. BI-VI's inhibitory activity toward the target enzyme bromelain is maximal at pH 4 and shows a bell-shaped pH profile with pKa values of about 2.5 and 5.3. This pH profile is quite different from that of bromelain, which is optimally active around pH 7. In the present article, to characterize the acidic limb, we first expressed the recombinant inhibitors designed to lose two putative hydrogen bonds of Ser7(NH)-Asp28(beta-CO2H) and Lys38(NH)-Asp51(beta-CO2H) and confirmed the existence of the hydrogen bonds by two-dimensional nuclear magnetic resonance (NMR). Moreover, it was revealed that these hydrogen bonds are not the essential electrostatic factor and some ionizable groups would be responsible for the acidic limb in the pH-inhibition profile. On the other hand, to characterize the basic limb, we examined the pH-dependent inhibition using the cysteine proteinase papain, some of whose properties differ from those of bromelain, and compared the data with the corresponding data for bromelain. The result suggests that the basic limb would be affected by some electrostatic factors, probably some carboxyl groups in the target proteinase.

  7. Wavelength-ratiometric near-physiological pH sensors based on 6-aminoquinolinium boronic acid probes.

    PubMed

    Badugu, Ramachandram; Lakowicz, Joseph R; Geddes, Chris D

    2005-04-30

    We describe the pH response of a set of isomeric water-soluble fluorescent probes based on both the 6-aminoquinolinium and boronic acid moieties. These probes show spectral shifts and intensity changes with pH, in a wavelength-ratiometric and colorimetric manner. Subsequently, changes in pH can readily be determined around the physiological level. Although boronic acid containing probes are known to exhibit pH sensitivity along with an ability for saccharide binding/chelating, the new probes reported here are considered to be unique and show an unperturbed pH response, even in the presence of high concentrations of background saccharide, such as with glucose and fructose, allowing for the predominant pH sensitivity. The response of the probes is based on the ability of the boronic acid group to interact with strong bases like OH(-), changing from the neutral form of the boronic acid group, R-B(OH)(2), to the anionic ester, R-B(-)(OH)(3), form, which is an electron donating group. The presence of an electron deficient quaternary heterocyclic nitrogen center and a strong electron donating amino group in the 6-position of the quinolinium backbone, provides for the spectral changes observed upon OH(-) complexation. In addition, by comparing the results obtained with systems separately incorporating 6-methoxy or 6-methyl substituents, the suppressed response towards monosaccharides, such as with glucose and fructose, can clearly be observed for these systems. Finally we compare our results to those of a control compound, BAQ, which does not contain the boronic acid group, allowing a rationale of the spectral changes to be made.

  8. Gallic Acid as a Complexing Agent for Copper Chemical Mechanical Polishing Slurries at Neutral pH

    NASA Astrophysics Data System (ADS)

    Kim, Yung Jun; Kang, Min Cheol; Kwon, Oh Joong; Kim, Jae Jeong

    2011-05-01

    Gallic acid was investigated as a new complexing agent for copper (Cu) chemical mechanical polishing slurries at neutral pH. Addition of 0.03 M gallic acid and 1.12 M H2O2 at pH 7 resulted in a Cu removal rate of 560.73±17.49 nm/min, and the ratio of the Cu removal rate to the Cu dissolution rate was 14.8. Addition of gallic acid improved the slurry performance compared to glycine addition. X-ray photoelectron spectroscopy analysis and contact angle measurements showed that addition of gallic acid enhanced the Cu polishing behavior by suppressing the formation of surface Cu oxide.

  9. Fatty acid fouling of forward osmosis membrane: Effects of pH, calcium, membrane orientation, initial permeate flux and foulant composition.

    PubMed

    Zhao, Pin; Gao, Baoyu; Yue, Qinyan; Liu, Pan; Shon, Ho Kyong

    2016-08-01

    Octanoic acid (OA) was selected to represent fatty acids in effluent organic matter (EOM). The effects of feed solution (FS) properties, membrane orientation and initial permeate flux on OA fouling in forward osmosis (FO) were investigated. The undissociated OA formed a cake layer quickly and caused the water flux to decline significantly in the initial 0.5hr at unadjusted pH3.56; while the fully dissociated OA behaved as an anionic surfactant and promoted the water permeation at an elevated pH of 9.00. Moreover, except at the initial stage, the sudden decline of water flux (meaning the occurrence of severe membrane fouling) occurred in two conditions: 1. 0.5mmol/L Ca(2+), active layer facing draw solution (AL-DS) and 1.5mol/L NaCl (DS); 2. No Ca(2+), active layer-facing FS (AL-FS) and 4mol/L NaCl (DS). This demonstrated that cake layer compaction or pore blocking occurred only when enough foulants were absorbed into the membrane surface, and the water permeation was high enough to compact the deposit inside the porous substrate. Furthermore, bovine serum albumin (BSA) was selected as a co-foulant. The water flux of both co-foulants was between the fluxes obtained separately for the two foulants at pH3.56, and larger than the two values at pH9.00. This manifested that, at pH3.56, BSA alleviated the effect of the cake layer caused by OA, and OA enhanced BSA fouling simultaneously; while at pH9.00, the mutual effects of OA and BSA eased the membrane fouling.

  10. Fatty acid fouling of forward osmosis membrane: Effects of pH, calcium, membrane orientation, initial permeate flux and foulant composition.

    PubMed

    Zhao, Pin; Gao, Baoyu; Yue, Qinyan; Liu, Pan; Shon, Ho Kyong

    2016-08-01

    Octanoic acid (OA) was selected to represent fatty acids in effluent organic matter (EOM). The effects of feed solution (FS) properties, membrane orientation and initial permeate flux on OA fouling in forward osmosis (FO) were investigated. The undissociated OA formed a cake layer quickly and caused the water flux to decline significantly in the initial 0.5hr at unadjusted pH3.56; while the fully dissociated OA behaved as an anionic surfactant and promoted the water permeation at an elevated pH of 9.00. Moreover, except at the initial stage, the sudden decline of water flux (meaning the occurrence of severe membrane fouling) occurred in two conditions: 1. 0.5mmol/L Ca(2+), active layer facing draw solution (AL-DS) and 1.5mol/L NaCl (DS); 2. No Ca(2+), active layer-facing FS (AL-FS) and 4mol/L NaCl (DS). This demonstrated that cake layer compaction or pore blocking occurred only when enough foulants were absorbed into the membrane surface, and the water permeation was high enough to compact the deposit inside the porous substrate. Furthermore, bovine serum albumin (BSA) was selected as a co-foulant. The water flux of both co-foulants was between the fluxes obtained separately for the two foulants at pH3.56, and larger than the two values at pH9.00. This manifested that, at pH3.56, BSA alleviated the effect of the cake layer caused by OA, and OA enhanced BSA fouling simultaneously; while at pH9.00, the mutual effects of OA and BSA eased the membrane fouling. PMID:27521936

  11. Chemical crosslinking of acrylic acid to form biocompatible pH sensitive hydrogel reinforced with cellulose nanocrystals (CNC)

    NASA Astrophysics Data System (ADS)

    Lim, Lim Sze; Ahmad, Ishak; Lazim, Mohd Azwani Shah Mat; Amin, Mohd. Cairul Iqbal Mohd

    2014-09-01

    The purpose of this study is to produce a novel pH and temperature sensitive hydrogel, composed of poly(acrylic acid) (PAA) and cellulose nanocrystal (CNC). CNC was extracted from kenaf fiber through a series of alkali and bleaching treatments followed by acid hydrolysis. The PAA was then subjected to chemical cross-linking using the cross-linking agent (N,N-methylenebisacrylamide) with CNC entrapped in PAA matrix. The mixture was casted onto petri dish to obtain disc shape hydrogel. The effects of reaction conditions such as the ratio of PAA and CNC on the swelling behavior of the hydrogel obtained towards pH and temperature were studied. The obtained hydrogel was further subjected to different tests such swelling test for swelling behaviour at different pH and temperature along with scanning electron microscopy (SEM) for morphology analysis. The hydrogel obtained showed excellent pH sensitivity and obtained maximum swelling at pH 7. Besides that, hydrogel obtained showed significant increase in swelling ratio when temperature of swelling medium was increased from 25°C to 37°C. SEM micrograph showed that the pore size of the hydrogel decreases with increase of CNC content proving that the hydrogel structure became more rigid with addition of CNC. The PAA/CNC hydrogel with such excellent sensitivity towards pH and temperature can be developed further as drug carrier.

  12. Chemical crosslinking of acrylic acid to form biocompatible pH sensitive hydrogel reinforced with cellulose nanocrystals (CNC)

    SciTech Connect

    Lim, Lim Sze; Ahmad, Ishak; Lazim, Mohd Azwani Shah Mat; Amin, Mohd. Cairul Iqbal Mohd

    2014-09-03

    The purpose of this study is to produce a novel pH and temperature sensitive hydrogel, composed of poly(acrylic acid) (PAA) and cellulose nanocrystal (CNC). CNC was extracted from kenaf fiber through a series of alkali and bleaching treatments followed by acid hydrolysis. The PAA was then subjected to chemical cross-linking using the cross-linking agent (N,N-methylenebisacrylamide) with CNC entrapped in PAA matrix. The mixture was casted onto petri dish to obtain disc shape hydrogel. The effects of reaction conditions such as the ratio of PAA and CNC on the swelling behavior of the hydrogel obtained towards pH and temperature were studied. The obtained hydrogel was further subjected to different tests such swelling test for swelling behaviour at different pH and temperature along with scanning electron microscopy (SEM) for morphology analysis. The hydrogel obtained showed excellent pH sensitivity and obtained maximum swelling at pH 7. Besides that, hydrogel obtained showed significant increase in swelling ratio when temperature of swelling medium was increased from 25°C to 37°C. SEM micrograph showed that the pore size of the hydrogel decreases with increase of CNC content proving that the hydrogel structure became more rigid with addition of CNC. The PAA/CNC hydrogel with such excellent sensitivity towards pH and temperature can be developed further as drug carrier.

  13. Buffer Standards for the Biochemical pH of 3-(N-morpholino)-2-hydroxypropanesulfonic Acid from (278.15 to 328.15) K

    PubMed Central

    Roy, Lakshmi N.; Roy, Rabindra N.; Denton, Cole E.; LeNoue, Sean R.; Roy, Chandra N.; Ashkenazi, Shahaf; Fuge, Michael S.; Wollen, Joshua T.; Stegner, Jessica M.; Allen, Kathleen A.; Harmon, Meagan A.

    2009-01-01

    The values of the second dissociation constant pK2 and related thermodynamic quantities of the ampholyte 3-(N-morpholino)-2-hydroxypropanesulfonic acid (MOPSO) have been previously determined at temperatures from (278.15 to 328.15) K. In this study, the pH values of two buffer solutions without NaCl and three buffer solutions with NaCl having ionic strengths (I = 0.16 mol·kg−1) similar to those in blood plasma, have been evaluated at 12 temperatures from (278.15 to 328.15) K using an extended form of the Debye-Hückel equation, since the Bates-Guggenheim convention is valid up to I = 0.1 mol·kg−1. The liquid junction potentials (Ej) between the buffer solutions of MOPSO and saturated KCl solution of the calomel electrode at (298.15 and 310.15) K have been estimated by measurement with a flowing junction cell. These values of Ej have been used to ascertain the operational pH values at (298.15 and 310.15) K. Three buffer solutions of MOPSO are recommended as useful reference solutions for pH measurements in saline media of ionic strength I = 0.16 mol·kg−1. PMID:20160876

  14. Buffer Standards for the Biochemical pH of 3-(N-morpholino)-2-hydroxypropanesulfonic Acid from (278.15 to 328.15) K.

    PubMed

    Roy, Lakshmi N; Roy, Rabindra N; Denton, Cole E; Lenoue, Sean R; Roy, Chandra N; Ashkenazi, Shahaf; Fuge, Michael S; Wollen, Joshua T; Stegner, Jessica M; Allen, Kathleen A; Harmon, Meagan A

    2009-06-11

    The values of the second dissociation constant pK(2) and related thermodynamic quantities of the ampholyte 3-(N-morpholino)-2-hydroxypropanesulfonic acid (MOPSO) have been previously determined at temperatures from (278.15 to 328.15) K. In this study, the pH values of two buffer solutions without NaCl and three buffer solutions with NaCl having ionic strengths (I = 0.16 mol·kg(-1)) similar to those in blood plasma, have been evaluated at 12 temperatures from (278.15 to 328.15) K using an extended form of the Debye-Hückel equation, since the Bates-Guggenheim convention is valid up to I = 0.1 mol·kg(-1). The liquid junction potentials (E(j)) between the buffer solutions of MOPSO and saturated KCl solution of the calomel electrode at (298.15 and 310.15) K have been estimated by measurement with a flowing junction cell. These values of E(j) have been used to ascertain the operational pH values at (298.15 and 310.15) K. Three buffer solutions of MOPSO are recommended as useful reference solutions for pH measurements in saline media of ionic strength I = 0.16 mol·kg(-1).

  15. Modeling growth and bacteriocin production by Lactobacillus amylovorus DCE 471 in response to temperature and pH values used for sourdough fermentations.

    PubMed

    Messens, Winy; Neysens, Patricia; Vansieleghem, Wim; Vanderhoeven, Johan; De Vuyst, Luc

    2002-03-01

    The biokinetics of cell growth of Lactobacillus amylovorus DCE 471 and bacteriocin production by this strain were investigated as a function of the temperatures (28 to 44C) and pH values (pH 4.2 to 6.4) that are characteristic of a sourdough fermentation process. The influence of temperature and pH on microbial behavior is described by using a successfully validated predictive model. PMID:11872497

  16. Modeling Growth and Bacteriocin Production by Lactobacillus amylovorus DCE 471 in Response to Temperature and pH Values Used for Sourdough Fermentations

    PubMed Central

    Messens, Winy; Neysens, Patricia; Vansieleghem, Wim; Vanderhoeven, Johan; De Vuyst, Luc

    2002-01-01

    The biokinetics of cell growth of Lactobacillus amylovorus DCE 471 and bacteriocin production by this strain were investigated as a function of the temperatures (28 to 44°C) and pH values (pH 4.2 to 6.4) that are characteristic of a sourdough fermentation process. The influence of temperature and pH on microbial behavior is described by using a successfully validated predictive model. PMID:11872497

  17. Preservation of glutamic acid-iron chelate into montmorillonite to efficiently degrade Reactive Blue 19 in a Fenton system under sunlight irradiation at neutral pH

    NASA Astrophysics Data System (ADS)

    Huang, Zhujian; Wu, Pingxiao; Gong, Beini; Yang, Shanshan; Li, Hailing; Zhu, Ziao; Cui, Lihua

    2016-05-01

    To further enhance the visible light responsive property and the chemical stability of Fe/clay mineral catalysts, glutamic acid-iron chelate intercalated montmorillonite (G-Fe-Mt) was developed. The physiochemical properties of G-Fe-Mt were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), etc. The results showed that glutamic acid-iron chelates were successfully intercalated into the gallery of montmorillonite and the intercalated glutamic acid-iron chelate molecules were well preserved. The product G-Fe-Mt displayed excellent catalytic performance in heterogeneous photo-Fenton reaction under sunlight irradiation at acidic and neutral pH values. The chelation and the visible light responsiveness of glutamic acid produce a synergistic effect leading to greatly enhanced sunlight-Fenton reaction catalyzed by the heterogeneous G-Fe-Mt under neutral pH. G-Fe-Mt is a promising catalyst for advanced oxidation processes.

  18. Acidic intracellular pH shift during Caenorhabditis elegans larval development

    SciTech Connect

    Wadsworth, W.G.; Riddle, D.L. )

    1988-11-01

    During recovery from the developmentally arrested, nonfeeding dauer stage of the nemotode Caenorhabditis elegans, metabolic activation is accompanied by a decrease in intracellular pH (pH{sub i}). Phosphorus-31 nuclear magnetic resonance ({sup 31}P NMR) analyses of perchloric acid extracts show that inorganic phosphate predominates in dauer larvae, whereas ATP and other high-energy metabolites are abundant within 6 hr after dauer larvae have been placed in food to initiate development. Although metabolic activation has been associated with an alkaline pH{sub i} shift in other organisms, in vivo {sup 31}P NMR analysis of recovering dauer larvae shows a pH{sub i} decrease from {approx} 7.3 to {approx} 6.3 within 3 hr after the animals encounter food. This shift occurs before feeding begins, and it coincides with, or soon follows, the developmental commitment to recover from the dauer stage, suggesting that control of pH{sub i} may be important in the regulation of larval development in nematodes.

  19. On the use of dimensionless parameters in acid-base theory. IV. The pH of water solutions of acids, bases, and simple ampholytes.

    PubMed

    Rilbe, H

    1993-10-01

    Exact relations between pH and concentrations of water solutions of acids, bases, and simple ampholytes are presented in the form of computer-created curves. These are mathematically analysed with respect to linearity and inflexion points. The extreme invariance of pH in the immediate vicinity of the isoelectric points of ampholytes is demonstrated in curves of the logarithm of molarity as a function of the logarithm of magnitude of pH-pI magnitude of. These considerations include a discussion of the suitability of ampholytes as pH standards. PMID:8125066

  20. On the use of dimensionless parameters in acid-base theory. IV. The pH of water solutions of acids, bases, and simple ampholytes.

    PubMed

    Rilbe, H

    1993-10-01

    Exact relations between pH and concentrations of water solutions of acids, bases, and simple ampholytes are presented in the form of computer-created curves. These are mathematically analysed with respect to linearity and inflexion points. The extreme invariance of pH in the immediate vicinity of the isoelectric points of ampholytes is demonstrated in curves of the logarithm of molarity as a function of the logarithm of magnitude of pH-pI magnitude of. These considerations include a discussion of the suitability of ampholytes as pH standards.

  1. Effect of pH on acid production from sorbitol in washed cell suspensions of oral bacteria.

    PubMed

    Kalfas, S; Maki, Y; Birkhed, D; Edwardsson, S

    1990-01-01

    The acid production from sorbitol and glucose was studied under anaerobic conditions in resting cell suspensions of bacteria from the predominant sorbitol-fermenting human dental plaque flora, belonging to the genera Streptococcus, Lactobacillus and Actinomyces. The acid production activity of the bacterial cells was followed by titration with alkali, at environmental pH 7.0, 6.0 and 5.0 after addition of carbohydrate solution. The metabolic end products formed in the suspensions were analyzed thereafter by isotachophoretic and enzymatic methods. The results showed that sorbitol was fermented at a slower rate than glucose. Lowering the environmental pH decreased the acid production activity from the two carbohydrates. Compared with glucose, the catabolism of sorbitol was affected to greater extent by the pH conditions. The total amount of acids formed from sorbitol was considerably less than from glucose. Lactic acid, which was the major end product in glucose-challenged suspensions, was produced only in low concentrations from sorbitol by all strains tested. The ratio strong (formic + lactic)/weak acids was moreover lower for sorbitol than for glucose. The present results further illustrate some of the mechanisms behind the low cariogenic potential of this sugar substitute.

  2. Acid-coated Textiles (pH 5.5-6.5)--a New Therapeutic Strategy for Atopic Eczema?

    PubMed

    Jaeger, Teresa; Rothmaier, Markus; Zander, Holger; Ring, Johannes; Gutermuth, Jan; Anliker, Mark D

    2015-07-01

    Increased transepidermal water loss (TEWL) and decreased skin capacitance are characteristic features of the disturbed epidermal barrier in atopic eczema (AE). The "acid mantle", which is a slightly acidic film on the surface of the skin has led to the development of acidic emollients for skin care. In this context, the effect of citric acid-coated textiles on atopic skin has not been examined to date. A textile carrier composed of cellulose fibres was coated with a citric acid surface layer by esterification, ensuring a constant pH of 5.5-6.5. Twenty patients with AE or atopic diathesis were enrolled in the study. In a double-blind, half-side experiment, patients had to wear these textiles for 12 h a day for 14 days. On day 0 (baseline), 7 and 14, tolerability (erythema, pruritus, eczema, wearing comfort) and efficacy on skin barrier were assessed by TEWL skin hydration (corneometry/capacitance), pH and clinical scoring of eczema (SCORAD). Citric acid-coated textiles were well tolerated and improved eczema and objective parameters of skin physiology, including barrier function and a reduced skin surface pH, with potential lower pathogenic microbial colonisation.

  3. pH dependence and structural interpretation of the reactions of Coprinus cinereus peroxidase with hydrogen peroxide, ferulic acid, and 2,2'-azinobis.

    PubMed

    Abelskov, A K; Smith, A T; Rasmussen, C B; Dunford, H B; Welinder, K G

    1997-08-01

    Steady-state and transient-state analysis of Coprinus cinereus peroxidase, CIP (identical to Arthromyces ramosus peroxidase), was used to characterize the kinetics of the three fundamental steps in heme peroxidase catalysis: compound I (cpd I) formation, cpd I reduction, and compound II (cpd II) reduction. The rate constant k1 for cpd I formation determined by transient-state analysis is (9.9 +/- 0.6) x 10(6) M-1 s-1. The k1 determined by steady-state analysis is (8.8 +/- 0.6) x 10(6) M-1 s-1 in the presence of ferulic acid and (6.7 +/- 0.2) x 10(6) M-1 s-1 in the presence of ABTS. The value of k1 is constant from pH 6 to 11. However, at low pH the value of k1 decreases, corresponding to titration of an enzyme group with a pKa of 5.0. Titration of this group is also detected from cyanide-binding kinetics. Furthermore, titration of this group is linked with marked spectroscopic changes unique to CIP. We ascribe these changes to protonation of proximal His183. A very low pKa is proposed for distal His55 in the resting state of CIP. The rate constants, k2 for cpd I and k3 for cpd II reduction, are very large for both ferulic acid and 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). For ferulic acid, transient-state kinetic analysis shows that the values of k2 and k3 are identical at pH 5-6, and the ratio k2/k3 increases to 10 at pH 10. The similar magnitude of k2 and k3 is unusual for a peroxidase. Both k2 and k3 decrease with increasing pH, and both are influenced by two ionizations: one with a pKa value near 7, assumed to reflect the protonation of His55; and the other with pKa of 9.0 +/- 0.7 for k2 and 8.8 +/- 0.4 for k3, perhaps reflecting the phenol-linked deprotonation of ferulic acid. Steady-state analysis at pH 7.0 gave k2k3/(k2 + k3) = (2.2 +/- 0.1) x 10(7) M-1 s-1 for ferulic acid, and (2.0 +/- 0.7) x 10(7) M-1 s-1 for ABTS and revealed a unimolecular step with ku = 1500 s-1, ascribed to slow ABTS radical product release. From transient

  4. Chemical durability and leaching mechanism of Ce0.5Eu0.5PO4 ceramics: Effects of temperature and pH values

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaofeng; Teng, Yuancheng; Wu, Lang; Huang, Yi; Ma, Jiyan; Wang, Guolong

    2015-11-01

    Ce0.5Eu0.5PO4 ceramics with high relative density were prepared by hot-press (HPS) and pressureless (PLS) sintering. The effects of temperature and pH values on the chemical durability of the ceramics were investigated. The results show that an increase of acidity significantly accelerated the corrosion of the samples. In alkaline leachates, further release elements were prevented by the newborn surface precipitation. The leach rate (Rn) of HPS sample was similar to that of PLS specimen in deionized water, but higher Rn for PLS sample was found in pH = 11 solution. Moreover, apparent activation energy of the dissolution of Eu (40 ± 4 kJ mol-1) is much higher than that of Ce (20 ± 1 kJ mol-1), leading to the higher normalized elemental leach rate of Eu. Both the Eu and Ce elements have low leach rates (10-12-10-9 m d-1) after 42 days in all the leachates studied in this work.

  5. Enzyme-regulated the changes of pH values for assembling a colorimetric and multistage interconnection logic network with multiple readouts.

    PubMed

    Huang, Yanyan; Ran, Xiang; Lin, Youhui; Ren, Jinsong; Qu, Xiaogang

    2015-04-22

    Based on enzymatic reactions-triggered changes of pH values and biocomputing, a novel and multistage interconnection biological network with multiple easy-detectable signal outputs has been developed. Compared with traditional chemical computing, the enzyme-based biological system could overcome the interference between reactions or the incompatibility of individual computing gates and offer a unique opportunity to assemble multicomponent/multifunctional logic circuitries. Our system included four enzyme inputs: β-galactosidase (β-gal), glucose oxidase (GOx), esterase (Est) and urease (Ur). With the assistance of two signal transducers (gold nanoparticles and acid-base indicators) or pH meter, the outputs of the biological network could be conveniently read by the naked eyes. In contrast to current methods, the approach present here could realize cost-effective, label-free and colorimetric logic operations without complicated instrument. By designing a series of Boolean logic operations, we could logically make judgment of the compositions of the samples on the basis of visual output signals. Our work offered a promising paradigm for future biological computing technology and might be highly useful in future intelligent diagnostics, prodrug activation, smart drug delivery, process control, and electronic applications.

  6. Enzyme-regulated the changes of pH values for assembling a colorimetric and multistage interconnection logic network with multiple readouts.

    PubMed

    Huang, Yanyan; Ran, Xiang; Lin, Youhui; Ren, Jinsong; Qu, Xiaogang

    2015-04-22

    Based on enzymatic reactions-triggered changes of pH values and biocomputing, a novel and multistage interconnection biological network with multiple easy-detectable signal outputs has been developed. Compared with traditional chemical computing, the enzyme-based biological system could overcome the interference between reactions or the incompatibility of individual computing gates and offer a unique opportunity to assemble multicomponent/multifunctional logic circuitries. Our system included four enzyme inputs: β-galactosidase (β-gal), glucose oxidase (GOx), esterase (Est) and urease (Ur). With the assistance of two signal transducers (gold nanoparticles and acid-base indicators) or pH meter, the outputs of the biological network could be conveniently read by the naked eyes. In contrast to current methods, the approach present here could realize cost-effective, label-free and colorimetric logic operations without complicated instrument. By designing a series of Boolean logic operations, we could logically make judgment of the compositions of the samples on the basis of visual output signals. Our work offered a promising paradigm for future biological computing technology and might be highly useful in future intelligent diagnostics, prodrug activation, smart drug delivery, process control, and electronic applications. PMID:25819791

  7. Microwave assisted one-pot synthesis of graphene quantum dots as highly sensitive fluorescent probes for detection of iron ions and pH value.

    PubMed

    Zhang, Chunfang; Cui, Yanyan; Song, Li; Liu, Xiangfeng; Hu, Zhongbo

    2016-04-01

    Recently, carbon nanomaterials have received considerable attention as fluorescent probes owing to their low toxicity, water solubility and stable photochemical properties. However, the development of graphene quantum dots (GQDs) is still on its early stage. In this work, GQDs were successfully synthesized by one-step microwave assisted pyrolysis of aspartic acid (Asp) and NH4HCO3 mixture. The as-prepared GQDs exhibited strongly blue fluorescence with high quantum yield up to 14%. Strong fluorescence quenching effect of Fe(3+) on GQDs can be used for its high selectivity detection among of general metal ions. The probe exhibited a wide linear response concentration range (0-50 μM) to Fe(3+) and the limit of detection (LOD) was calculated to be 0.26 μM. In addition, GQDs are also sensitive to the pH value in the range from 2 to 12 indicating a great potential as optical pH sensors. More importantly, the GQDs possess lower cellular toxicity and high photostability and can be directly used as fluorescent probes for cell imaging.

  8. Limitation of tuning the antibody-antigen reaction by changing the value of pH and its consequence for hyperthermia.

    PubMed

    Mleczko, J; Defort, A; Kozioł, J J; Nguyen, T T; Mirończyk, A; Zapotoczny, B; Nowak-Jary, J; Gronczewska, E; Marć, M; Dudek, M R

    2016-04-01

    Distribution of the isoelectric point (pI) was calculated for the hypervariable regions of Fab fragments of the antibody molecules, which structure is annotated in the structural antibody database SabDab. The distribution is consistent with the universal for all organisms dividing the proteome into two sets of acidic and basic proteins. It shows the additional fine structure in a form of the narrow-sized peaks of pI values. This is an explanation why a small change of the environmental pH can have a strong effect on the antibody-antigen affinity. To show this, a typical enzyme-linked immunospecific assay experiment for testing the reaction of goat anti-human IgA antibodies with human IgA immunoglobulins of saliva as antigens was modified in such a way that Fe3O4magnetic nanoparticles were added to PBS buffer. The magnetic nanoparticles were remotely heated by the radio frequency magnetic field providing the local change of temperature and pH. It was observed that short times of the heating were significantly increasing the antibody-antigen binding strength while it was not the case for a longer time. The finding discussed in the study can be useful for biopharmaceuticals using antibodies, the immunoassay techniques as well as for control over the use of hyperthermia.

  9. EFFECTS OF PH, SOLID/SOLUTION RATIO, IONIC STRENGTH, AND ORGANIC ACIDS ON PB AND CD SOPRTION ON KAOLINITE

    EPA Science Inventory

    Potentiometric and ion-selective electrode titrations together with batch sorption/desorption experiments, were performed to explain the aqueous and surface complexation reactions between kaolinite, Pb, Cd and three organic acids. Variables included pH, ionic strength, metal conc...

  10. Significance of pH on the Cytotoxic Potential of the Water Disinfection By-Product Iodoacetic Acid

    EPA Science Inventory

    Significance of pH on the Cytotoxic Potential of the Water Disinfection By-Product Iodoacetic Acid Vicki Richardson1, Susan D. Richardson2, Mary Moyer3, Jane Ellen Simmons1, and Anthony DeAngelo1, 1U.S. Environmental Protection Agency, Research Triangle Park, NC, 2University of...

  11. Rat epididymal luminal fluid acid beta-D-galactosidase optimally hydrolyses glycoprotein substrate at neutral pH.

    PubMed Central

    Skudlarek, M D; Tulsiani, D R; Orgebin-Crist, M C

    1992-01-01

    Several glycosidases, purified and characterized from mammalian tissues, have been shown to be optimally active under acidic conditions when p-nitrophenyl (PNP) or 4-methylumbelliferyl glycosides are used as substrates. Although high levels of the glycosidases are present in the epididymal lumen, their physiological role remains uncertain. To be functional, the glycosidases are expected to be enzymatically active at or near the physiological pH of luminal fluid. In this report, we demonstrate that the rat epididymal luminal fluid beta-D-galactosidase, optimally active toward PNP beta-D-galactoside at pH 3.5, shows maximum activity towards a glycoprotein substrate ([Gal-3H]fetuin) at neutral pH. Several lines of evidence, including immunoprecipitation studies using antibody to the acid beta-D-galactosidase, and substrate competition studies, indicate that PNP galactosidase and [3H]Gal galactosidase activities are caused by a single enzyme, and that the two substrates are probably cleaved by the same catalytic site(s). Competition studies with various disaccharides indicate that this enzyme is capable of cleaving a variety of galactose linkages found in both O- and N-linked oligosaccharides. Molecular-sieve column chromatography of the beta-D-galactosidase of luminal fluid under several conditions of buffer and pH show that, whereas the enzyme eluted as a tetramer (apparent M(r) 320,000) under acidic conditions (pH 3.5-4.3), only dimers and monomers (apparent M(r) 180,000 and 92,000 respectively) were observed in neutral conditions (pH 6.8). This aggregation/dissociation phenomenon is reversible. These studies indicate that beta-D-galactosidase is present in the luminal fluid in dissociated forms, and is therefore optimally active towards glycoprotein substrates at physiological pH. The potential role of the enzyme in modification of sperm surface glycoproteins is discussed. PMID:1417750

  12. Bleb formation is induced by alkaline but not acidic pH in estrogen receptor silenced breast cancer cells.

    PubMed

    Khajah, Maitham A; Mathew, Princy M; Alam-Eldin, Nada S; Luqmani, Yunus A

    2015-04-01

    De novo and acquired resistance to endocrine-based therapies in breast cancer occurs in parallel with epithelial to mesenchymal transition (EMT), which is associated with enhanced proliferative and metastatic potential, and poor clinical outcome. We have established several endocrine insensitive breast cancer lines by shRNA-induced depletion of estrogen receptor (ER) by transfection of MCF7 cells. All of these exhibit EMT. We have previously reported that brief exposure of specifically ER- breast cancer cells, to extracellular alkaline pH, results in cell rounding and segregation, and leads to enhanced invasive potential. In this study we describe more detailed morphological changes and compare these with cell exposure to acidic pH. Morphological changes and localization of various molecules critical for cell adhesion and motility, associated with pH effects, were assessed by live cell microscopy, electron microscopy, and immunofluorescence. Exposure of either ER- or ER+ breast cancer cells to extracellular acidic pH did not induce significant changes in morphological appearance. Conversely, brief exposure of specifically ER silenced cells, to alkaline pH, resulted in cell contractolation and formation of bleb-like actin-rich structures which were evenly distributed on the outer membrane. Integrin α2, FAK, and JAM-1 were found in the cytoplasm streaming into the newly formed blebs. These blebs appear to be related to cell polarity and movement. Pre-treatment with cytochalasin-D or inhibitors of Rho or MLCK prevented both contractolation and bleb formation. Our data suggest that the effect of pH on the microenvironment of endocrine resistant breast cancer cells needs to be more extensively investigated. Alkaline, rather than acidic pH, appears to induce dramatic morphological changes, and enhances their invasive capabilities, through re-organization of cortical actin. PMID:25672508

  13. Denitrification potential in stream sediments impacted by acid mine drainage: Effects of pH, various electron donors, and iron

    USGS Publications Warehouse

    Baeseman, J.L.; Smith, R.L.; Silverstein, J.

    2006-01-01

    Acid mine drainage (AMD) contaminates thousands of kilometers of stream in the western United States. At the same time, nitrogen loading to many mountain watersheds is increasing because of atmospheric deposition of nitrate and increased human use. Relatively little is known about nitrogen cycling in acidic, heavy-metal-laden streams; however, it has been reported that one key process, denitrification, is inhibited under low pH conditions. The objective of this research was to investigate the capacity for denitrification in acidified streams. Denitrification potential was assessed in sediments from several Colorado AMD-impacted streams, ranging from pH 2.60 to 4.54, using microcosm incubations with fresh sediment. Added nitrate was immediately reduced to nitrogen gas without a lag period, indicating that denitrification enzymes were expressed and functional in these systems. First-order denitrification potential rate constants varied from 0.046 to 2.964 day-1. The pH of the microcosm water increased between 0.23 and 1.49 pH units during denitrification. Additional microcosm studies were conducted to examine the effects of initial pH, various electron donors, and iron (added as ferrous and ferric iron). Decreasing initial pH decreased denitrification; however, increasing pH had little effect on denitrification rates. The addition of ferric and ferrous iron decreased observed denitrification potential rate constants. The addition of glucose and natural organic matter stimulated denitrification potential. The addition of hydrogen had little effect, however, and denitrification activity in the microcosms decreased after acetate addition. These results suggest that denitrification can occur in AMD streams, and if stimulated within the environment, denitrification might reduce acidity. ?? Springer Science+Business Media, Inc. 2006.

  14. Photodegradation of gallic acid under UV irradiation: insights regarding the pH effect on direct photolysis and the ROS oxidation-sensitized process of DOM.

    PubMed

    Du, Yingxun; Chen, Hui; Zhang, Yuanyuan; Chang, Yuguang

    2014-03-01

    In this study, the degradation of gallic acid (GA), a model compound for dissolved organic matter (DOM) in controlled UV/N2, UV/air, UV/Fe(3+)/N2, and UV/Fe(3+)/air systems was investigated to elucidate the contribution of direct photolysis and reactive oxygen species (ROS) oxidation to GA degradation at various pH values. In general, the order of the degradation rate of GA in these four systems was as follows: UV/Fe(3+)/air>UV/air>UV/Fe(3+)/N2≈UV/N2. In the UV/N2 system, GA underwent slow direct photolysis, the rate of which decreased with decreasing pH. In the UV/Fe(3+)/air system, the most rapid GA degradation was achieved at pH 5. ROS are mainly derived from two sources. The first source is attributed to the role of DO and the other is attributed to the interaction of Fe(3+) and DO. The contribution of ROS to GA oxidation is much greater (>71%) than that of direct photolysis (<29%) at each pH value and is most obvious at pH 5. H2O2 formation was detected during GA degradation in the UV/air and UV/Fe(3+)/air systems. Using ROS scavengers, it was found that oxidation by OH was the main mechanism of GA degradation in the UV/Fe(3+)/air system. Based on the experimental results, a mechanism for GA degradation and ROS formation involving the effect of pH was proposed. This study furthers our understanding of changes in DOM degradation mechanisms due to global acidification.

  15. Coal ash basin effects (particulates, metals, acidic pH) upon aquatic biota: an eight-year evaluation. [Gambusia affinis; Plathemis lydia; Libellula spp

    SciTech Connect

    Cerry, D.S.; Guthrie, R.K.; Davis, E.M.; Harvey, R.S.

    1984-08-01

    Coal ash effluent effects including particulates, acidic pH excursions, elemental concentrations and bioconcentration in selected organisms have been studied as changes in water quality and densities of benthic macroinvertebrate and mosquitofish (Gambusia affinis) populations in a swanmp drainage system over an eight-year period. Initial density of the aquatic biota was altered severely by heavy ash siltation, followed by acidic pH excursions, and perhaps overall by elemental concentrations and bioaccumulation. Heavy ash siltation, followed by acidic pH excursions after the addition of fly ash to the original settling basin system, had the most profound effect on biota. Dipterans (chironomids) and some odonates (Plathemis lydia and Libellula spp.) were resistant to heavy ash siltation, while mosquitofish, which showed no discernible responses to ash siltation, were absent at acidic pH along with the few previously surviving invertebrate populations. Elemental concentrations of arsenic, cadmium, chromium, copper, selenium, and zinc did not appear to limit aquatic flora and fauna on a short-term, acute basis. Long-chronic elemental exposures may have been instrumental in retarding the recovery of all forms of aquatic life in the receiving system. Elemental concentrations (except for arsenic and selenium) in the receiving system were generally one to two orders of magnitude higher than the Water Quality Criteria set by the US Environmental Protection Agency (1980) for protection of aquatic life for the minimum and 24-hour mean values. By 1978, when the new settling basin systems were operating effectively, invertebrate populations were largely recovered, and mosquito-fish populations recovered within one year afterward.

  16. 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. PMID:20069869

  17. 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.

  18. Embryonic common snapping turtles (Chelydra serpentina) preferentially regulate intracellular tissue pH during acid-base challenges.

    PubMed

    Shartau, Ryan B; Crossley, Dane A; Kohl, Zachary F; Brauner, Colin J

    2016-07-01

    The nests of embryonic turtles naturally experience elevated CO2 (hypercarbia), which leads to increased blood PCO2  and a respiratory acidosis, resulting in reduced blood pH [extracellular pH (pHe)]. Some fishes preferentially regulate tissue pH [intracellular pH (pHi)] against changes in pHe; this has been proposed to be associated with exceptional CO2 tolerance and has never been identified in amniotes. As embryonic turtles may be CO2 tolerant based on nesting strategy, we hypothesized that they preferentially regulate pHi, conferring tolerance to severe acute acid-base challenges. This hypothesis was tested by investigating pH regulation in common snapping turtles (Chelydra serpentina) reared in normoxia then exposed to hypercarbia (13 kPa PCO2 ) for 1 h at three developmental ages: 70% and 90% of incubation, and yearlings. Hypercarbia reduced pHe but not pHi, at all developmental ages. At 70% of incubation, pHe was depressed by 0.324 pH units while pHi of brain, white muscle and lung increased; heart, liver and kidney pHi remained unchanged. At 90% of incubation, pHe was depressed by 0.352 pH units but heart pHi increased with no change in pHi of other tissues. Yearlings exhibited a pHe reduction of 0.235 pH units but had no changes in pHi of any tissues. The results indicate common snapping turtles preferentially regulate pHi during development, but the degree of response is reduced throughout development. This is the first time preferential pHi regulation has been identified in an amniote. These findings may provide insight into the evolution of acid-base homeostasis during development of amniotes, and vertebrates in general. PMID:27091863

  19. Embryonic common snapping turtles (Chelydra serpentina) preferentially regulate intracellular tissue pH during acid-base challenges.

    PubMed

    Shartau, Ryan B; Crossley, Dane A; Kohl, Zachary F; Brauner, Colin J

    2016-07-01

    The nests of embryonic turtles naturally experience elevated CO2 (hypercarbia), which leads to increased blood PCO2  and a respiratory acidosis, resulting in reduced blood pH [extracellular pH (pHe)]. Some fishes preferentially regulate tissue pH [intracellular pH (pHi)] against changes in pHe; this has been proposed to be associated with exceptional CO2 tolerance and has never been identified in amniotes. As embryonic turtles may be CO2 tolerant based on nesting strategy, we hypothesized that they preferentially regulate pHi, conferring tolerance to severe acute acid-base challenges. This hypothesis was tested by investigating pH regulation in common snapping turtles (Chelydra serpentina) reared in normoxia then exposed to hypercarbia (13 kPa PCO2 ) for 1 h at three developmental ages: 70% and 90% of incubation, and yearlings. Hypercarbia reduced pHe but not pHi, at all developmental ages. At 70% of incubation, pHe was depressed by 0.324 pH units while pHi of brain, white muscle and lung increased; heart, liver and kidney pHi remained unchanged. At 90% of incubation, pHe was depressed by 0.352 pH units but heart pHi increased with no change in pHi of other tissues. Yearlings exhibited a pHe reduction of 0.235 pH units but had no changes in pHi of any tissues. The results indicate common snapping turtles preferentially regulate pHi during development, but the degree of response is reduced throughout development. This is the first time preferential pHi regulation has been identified in an amniote. These findings may provide insight into the evolution of acid-base homeostasis during development of amniotes, and vertebrates in general.

  20. Effects of temperature, salinity, light intensity, and pH on the eicosapentaenoic acid production of Pinguiococcus pyrenoidosus

    NASA Astrophysics Data System (ADS)

    Sang, Min; Wang, Ming; Liu, Jianhui; Zhang, Chengwu; Li, Aifen

    2012-06-01

    The effects of temperature, light intensity, salinity, and initial pH on the growth and fatty acid composition of Pinguiococcus pyrenoidosus 2078 were studied for eicosapentaenoic acid (EPA) production potential. The fatty acid composition was assayed by gas chromatography-mass spectrometry, which indicated that the main fatty acids were C14:0, C16:0 and EPA. The highest EPA percentage 20.83% of total fatty acids was obtained at 20°C with the temperature being set at 20, 24, and 28°C. Under different salinities and light intensities, the highest percentages of total polyunsaturated fatty acids (PUFAs) and EPA were 17.82% and 31.37% of total fatty acids, respectively, which were achieved at salinity 30 and 100 μmol photon m-2s-1 illumination. The highest percentages of total PUFAs and EPA were 38.75% and 23.13% of total fatty acids, respectively, which were reached at an initial pH of 6 with the test range being from 5.0 to 9.0.

  1. The effect of acidic pH and presence of metals as parameters in establishing a sulfidogenic process in anaerobic reactor.

    PubMed

    Vieira, Bárbara F; Couto, Pâmela T; Sancinetti, Giselle P; Klein, Bernhard; van Zyl, Dirk; Rodriguez, Renata P

    2016-08-23

    The successful use of anaerobic reactors for bioremediation of acid mine drainage has been shown in systems with neutral pH. However, the choice of an efficient and suitable process for such wastewater must consider the capability of operating at acidic pH and in the presence of metals. This work studies the performance of an anaerobic batch reactor, under conditions of varying initial pH for its efficiencies in sulfate removal and metal precipitation from synthetic acid mine drainage. The chemical oxygen demand/sulfate (COD/SO4(2-)) ratio used was 1.00, with ethanol chosen as the only energy and carbon source. The initial pH of the synthetic drainage was progressively set from 7.0 to 4.0 to make it as close as possible to that of real acid mine drainage. Metals were also added starting with iron, zinc, and finally copper. The effectiveness of sulfate and COD removal from the synthetic acid mine drainage increased as the initial pH was reduced. The sulfate removal increased from 38.5 ± 3.7% to 52.2 ± 3%, while the removal of organic matter started at 91.7 ± 2.4% and ended at 99 ± 1%. These results indicate that the sulfate reducing bacteria (SRB) community adapted to lower pH values. The metal removal observed was 88 ± 7% for iron, 98.0 ± 0.5% for zinc and 99 ± 1% for copper. At this stage, an increase in the sulfate removal was observed, which reaches up to 82.2 ± 5.8%. The kinetic parameters for sulfate removal were 0.22 ± 0.04 h(-1) with Fe, 0.26 ± 0.04 h(-1) with Fe and Zn and 0.44 ± 0.04 h(-1) with Fe, Zn, and Cu. PMID:27222283

  2. Electrochemical oxidation of reverse osmosis concentrate on boron-doped diamond anodes at circumneutral and acidic pH.

    PubMed

    Bagastyo, Arseto Y; Batstone, Damien J; Kristiana, Ina; Gernjak, Wolfgang; Joll, Cynthia; Radjenovic, Jelena

    2012-11-15

    Electrochemical processes have been widely investigated for degrading organic contaminants present in wastewater. This study evaluated the performance of electrochemical oxidation using boron-doped diamond (BDD) electrodes by forming OH() for the treatment of reverse osmosis concentrate (ROC) from secondary-treated wastewater effluents. Since oxidation by OH() and active chlorine species (HClO/ClO(-)) is influenced by pH, the electrochemical oxidation of ROC was evaluated at controlled pH 6-7 and at pH 1-2 (no pH adjustment). A high concentration of chloride ions in the ROC enhanced the oxidation, and 7-11% of Coulombic efficiency for chemical oxygen demand (COD) removal was achieved with 5.2 Ah L(-1) of specific electrical charge. Complete COD removal was observed after 5.2 and 6.6 Ah L(-1), yet the corresponding dissolved organic carbon (DOC) removal was only 48% (at acidic pH) and 59% (at circumneutral pH). Although a higher operating pH seemed to enhance the participation of OH() in oxidation mechanisms, high concentrations of chloride resulted in the formation of significant concentrations of adsorbable organic chlorine (AOCl) after electrochemical oxidation at both pH. While adsorbable organic bromine (AOBr) was degraded at a higher applied electrical charge, a continuous increase in AOCl concentration (up to 0.88 mM) was observed until the end of the experiments (i.e. 10.9 Ah L(-1)). In addition, total trihalomethanes (tTHMs) and total haloacetic acids (tHAAs) were further degraded with an increase in electrical charge under both pH conditions, to final total concentrations of 1 and 4 μM (tTHMs), and 12 and 22 μM (tHAAs), at acidic and circumneutral pH, respectively. In particular, tHAAs were still an order of magnitude above their initial concentration in ROC after further electrooxidation. Where high chloride concentrations are present, it was found to be necessary to separate chloride from ROC prior to electrochemical oxidation in order to

  3. Electrochemical oxidation of reverse osmosis concentrate on boron-doped diamond anodes at circumneutral and acidic pH.

    PubMed

    Bagastyo, Arseto Y; Batstone, Damien J; Kristiana, Ina; Gernjak, Wolfgang; Joll, Cynthia; Radjenovic, Jelena

    2012-11-15

    Electrochemical processes have been widely investigated for degrading organic contaminants present in wastewater. This study evaluated the performance of electrochemical oxidation using boron-doped diamond (BDD) electrodes by forming OH() for the treatment of reverse osmosis concentrate (ROC) from secondary-treated wastewater effluents. Since oxidation by OH() and active chlorine species (HClO/ClO(-)) is influenced by pH, the electrochemical oxidation of ROC was evaluated at controlled pH 6-7 and at pH 1-2 (no pH adjustment). A high concentration of chloride ions in the ROC enhanced the oxidation, and 7-11% of Coulombic efficiency for chemical oxygen demand (COD) removal was achieved with 5.2 Ah L(-1) of specific electrical charge. Complete COD removal was observed after 5.2 and 6.6 Ah L(-1), yet the corresponding dissolved organic carbon (DOC) removal was only 48% (at acidic pH) and 59% (at circumneutral pH). Although a higher operating pH seemed to enhance the participation of OH() in oxidation mechanisms, high concentrations of chloride resulted in the formation of significant concentrations of adsorbable organic chlorine (AOCl) after electrochemical oxidation at both pH. While adsorbable organic bromine (AOBr) was degraded at a higher applied electrical charge, a continuous increase in AOCl concentration (up to 0.88 mM) was observed until the end of the experiments (i.e. 10.9 Ah L(-1)). In addition, total trihalomethanes (tTHMs) and total haloacetic acids (tHAAs) were further degraded with an increase in electrical charge under both pH conditions, to final total concentrations of 1 and 4 μM (tTHMs), and 12 and 22 μM (tHAAs), at acidic and circumneutral pH, respectively. In particular, tHAAs were still an order of magnitude above their initial concentration in ROC after further electrooxidation. Where high chloride concentrations are present, it was found to be necessary to separate chloride from ROC prior to electrochemical oxidation in order to

  4. Effect of the eluent pH and acidic modifiers in high-performance liquid chromatography retention of basic analytes.

    PubMed

    LoBrutto, R; Jones, A; Kazakevich, Y V; McNair, H M

    2001-04-13

    The retention of ionogenic bases in liquid chromatography is strongly dependent upon the pH of the mobile phase. Chromatographic behavior of a series of substituted aniline and pyridine basic compounds has been studied on C18 bonded silica using acetonitrile-water (10:90) as the eluent with different pHs and at various concentrations of the acidic modifier counter anions. The effect of different acidic modifiers on solute retention over a pH range from 1.3 to 8.6 was studied. Ionized basic compounds showed increased retention with a decrease of the mobile phase pH. This increase in retention was attributed to the interaction with counter anions of the acidic modifiers. The increase in retention is dependent on the nature of the counter anion and its concentration in the mobile phase. It was shown that altering the concentration of counter anion of the acidic modifier allows the optimization of the selectivity between basic compounds as well as for neutral and acidic compounds. PMID:11355811

  5. 24-hour esophageal pH-monitoring in children suspected of gastroesophageal reflux disease: Analysis of intraesophageal pH monitoring values recorded in distal and proximal channel at diagnosis

    PubMed Central

    Semeniuk, Janusz; Kaczmarski, Maciej

    2007-01-01

    AIM: To assess values of 24-h esophageal pH-monitoring parameters with dual-channel probe (distal and proximal channel) in children suspected of gastroesophageal reflux disease (GERD). METHODS: 264 children suspected of gastroesophageal reflux (GER) were enrolled in a study (mean age χ = 20.78 ± 17.23 mo). The outcomes of this study, immunoallerrgological tests and positive result of oral food challenge test with a potentially noxious nutrient, enabled to qualify children into particular study groups. RESULTS: 32 (12.1%) infants (group 1) had physiological GER diagnosed. Pathological acid GER was confirmed in 138 (52.3%) children. Primary GER was diagnosed in 76 (28.8%) children (group 2) and GER secondary to allergy to cow milk protein and/or other food (CMA/FA) in 62 (23.5%) children (group 3). 32 (12.1%) of them had CMA/FA (group 4-reference group), and in remaining 62 (23.5%) children neither GER nor CMA/FA was confirmed (group 5). Mean values of pH monitoring parameters measured in distal and proximal channel were analyzed in individual groups. This analysis showed statistically significant differentiation of mean values in the case of: number of episodes of acid GER, episodes of acid GER lasting > 5 min, duration of the longest episode of acid GER in both channels, acid GER index total and supine in proximal channel. Statistically significant differences of mean values among examined groups, especially between group 2 and 3 in the case of total acid GER index (only distal channel) were confirmed. CONCLUSION: 24-h esophageal pH monitoring confirmed pathological acid GER in 52.3% of children with typical and atypical symptoms of GERD. The similar pH-monitoring values obtained in group 2 and 3 confirm the necessity of implementation of differential diagnosis for primary vs secondary cause of GER. PMID:17876877

  6. Effect of pH Value on the Electrochemical and Stress Corrosion Cracking Behavior of X70 Pipeline Steel in the Dilute Bicarbonate Solutions

    NASA Astrophysics Data System (ADS)

    Cui, Z. Y.; Liu, Z. Y.; Wang, L. W.; Ma, H. C.; Du, C. W.; Li, X. G.; Wang, X.

    2015-11-01

    In this work, effects of pH value on the electrochemical and stress corrosion cracking (SCC) behavior of X70 pipeline steel in the dilute bicarbonate solutions were investigated using electrochemical measurements, slow strain rate tensile tests and surface analysis techniques. Decrease of the solution pH from 6.8 to 6.0 promotes the anodic dissolution and cathodic reduction simultaneously. Further decrease of the pH value mainly accelerates the cathodic reduction of X70 pipeline steel. As a result, when the solution pH decreases form 6.8 to 5.5, SCC susceptibility decreases because of the enhancement of the anodic dissolution. When the solution pH decreases from 5.5 to 4.0, SCC susceptibility increases gradually because of the acceleration of cathodic reactions.

  7. Function of aspartic acid residues in optimum pH control of L-arabinose isomerase from Lactobacillus fermentum.

    PubMed

    Xu, Zheng; Li, Sha; Feng, Xiaohai; Zhan, Yijing; Xu, Hong

    2014-05-01

    L-Arabinose isomerase (L-AI) catalyzes the isomerization of L-arabinose to L-ribulose and D-galactose to D-tagatose. Most reported L-AIs exhibit neutral or alkaline optimum pH, which is less beneficial than acidophilic ones in industrial D-tagatose production. Lactobacillus fermentum L-AI (LFAI) is a thermostable enzyme that can achieve a high conversion rate for D-galactose isomerization. However, its biocatalytic activity at acidic conditions can still be further improved. In this study, we report the single- and multiple-site mutagenesis on LFAI targeting three aspartic acid residues (D268, D269, and D299). Some of the lysine mutants, especially D268K/D269K/D299K, exhibited significant optimum pH shifts (from 6.5 to 5.0) and enhancement of pH stability (half-life time increased from 30 to 62 h at pH 6.0), which are more favorable for industrial applications. With the addition of borate, D-galactose was isomerized into D-tagatose by D268K/D269K/D299K at pH 5.0, resulting in a high conversion rate of 62 %. Based on the obtained 3.2-Å crystal structure of LFAI, the three aspartic acid residues were found to be distant from the active site and possibly did not participate in substrate catalysis. However, they were proven to possess similar optimum pH control ability in other L-AI, such as that derived from Escherichia coli. This study sheds light on the essential residues of L-AIs that can be modified for desired optimum pH and better pH stability, which are useful in D-tagatose bioproduction.

  8. Relative effectiveness of various anions on the solubility of acidic Hypoderma lineatum collagenase at pH 7.2.

    PubMed Central

    Carbonnaux, C.; Ries-Kautt, M.; Ducruix, A.

    1995-01-01

    The effects of various anions on decreasing the solubility of acidic Hypoderma lineatum collagenase at pH 7.2 and 18 degrees C were qualitatively defined by replacing the crystallizing agent of known crystallization conditions by various ammonium salts. The solubility curves measured in the presence of the sulfate, phosphate, citrate, and chloride ammonium salts gave the following ranking of anions: HPO4(2-)/H2PO4- > SO4(2-) > citrate 3-/citrate2- >> Cl-. This order is in agreement with the Hofmeister series. In a previous study on the solubility at pH 4.5 of lysozyme, a basic protein, the effectiveness of anions in decreasing the solubility was found to be in the reverse order. This suggests that the effectiveness of anions in the crystallization of proteins is dependent on the net charge of the protein, i.e., depending on whether a basic protein is crystallized at acidic pH or an acidic protein at basic pH. PMID:8535249

  9. [Effects of solution pH and simulated acid rain on the behavior of two sulfonylurea herbicides in soil].

    PubMed

    Zhang, Wei; Wang, Jin-Jun

    2007-03-01

    By the methods of batch equilibration and leaching, this paper studied the effects of solution pH and simulated acid rain on the behavior of bensulfuron-methyl and metsulfuron-methyl in soil. The results showed that the adsorption isotherms of these two herbicides fitted Freundlich equation well, and their adsorbed amounts reduced obviously with the increasing pH of water-soil system, which in turn promoted the translocation of the herbicides in soil. The adsorption coefficient (Kf) was positively correlated with soil organic matter and clay contents, while negatively correlated with soil pH. The higher pH of simulated acid rain had a greater contribution on the leaching of the two sulfonylurea herbicides, and their leached amount was increased with increasing acid rain. There was a close relationship between the leaching of the herbicides and the properties of soil. The soils with higher contents of organic matter and clay had a greater retention capability to the herbicides. PMID:17552202

  10. [Effects of solution pH and simulated acid rain on the behavior of two sulfonylurea herbicides in soil].

    PubMed

    Zhang, Wei; Wang, Jin-Jun

    2007-03-01

    By the methods of batch equilibration and leaching, this paper studied the effects of solution pH and simulated acid rain on the behavior of bensulfuron-methyl and metsulfuron-methyl in soil. The results showed that the adsorption isotherms of these two herbicides fitted Freundlich equation well, and their adsorbed amounts reduced obviously with the increasing pH of water-soil system, which in turn promoted the translocation of the herbicides in soil. The adsorption coefficient (Kf) was positively correlated with soil organic matter and clay contents, while negatively correlated with soil pH. The higher pH of simulated acid rain had a greater contribution on the leaching of the two sulfonylurea herbicides, and their leached amount was increased with increasing acid rain. There was a close relationship between the leaching of the herbicides and the properties of soil. The soils with higher contents of organic matter and clay had a greater retention capability to the herbicides.

  11. Potentiometric pH Measurements of Acidity Are Approximations, Some More Useful than Others

    ERIC Educational Resources Information Center

    de Levie, Robert

    2010-01-01

    A recent article by McCarty and Vitz "demonstrating that it is not true that pH = -log[H+]" is examined critically. Then, the focus shifts to underlying problems with the IUPAC definition of pH. It is shown how the potentiometric method can provide "estimates" of both the IUPAC-defined hydrogen activity "and" the hydrogen ion concentration, using…

  12. Evaluation of Porcine Myofibrillar Protein Gel Functionality as Affected by Microbial Transglutaminase and Red Bean [Vignia angularis] Protein Isolate at Various pH Values.

    PubMed

    Jang, Ho Sik; Lee, Hong Chul; Chin, Koo Bok

    2015-01-01

    This study was investigated to determine the effect of microbial transglutaminase (MTG) with or without red bean protein isolate (RBPI) on the porcine myofibrillar protein (MP) gel functionality at different pH values (pH 5.75-6.5). Cooking yield (CY, %), gel strength (GS, gf), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were determined to measure gel characteristics. Since no differences were observed the interaction between 1% RBPI and pH, data were pooled. CY increased with the addition of 1% RBPI, while it was not affected by pH values. GS increased with increased pH and increased when 1% RBPI was added, regardless of pH. There were distinctive endothermic protein peaks, at 56.55 and 75.02℃ at pH 5.75, and 56.47 and 72.43℃ at pH 6.5 in DSC results, which revealed decreased temperature of the first peak with the addition of 1% RBPI and increased pH. In SEM, a more compact structure with fewer voids was shown with the addition of 1% RBPI and increased pH from 5.75 to 6.5. In addition, the three-dimensional structure was highly dense and hard at pH 6.5 when RBPI was added. These results indicated that the addition of 1% RBPI at pH 6.5 in MTG-mediated MP represent the optimum condition to attain maximum gel-formation and protein gel functionality. PMID:26877645

  13. Evaluation of Porcine Myofibrillar Protein Gel Functionality as Affected by Microbial Transglutaminase and Red Bean [Vignia angularis] Protein Isolate at Various pH Values

    PubMed Central

    2015-01-01

    This study was investigated to determine the effect of microbial transglutaminase (MTG) with or without red bean protein isolate (RBPI) on the porcine myofibrillar protein (MP) gel functionality at different pH values (pH 5.75-6.5). Cooking yield (CY, %), gel strength (GS, gf), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were determined to measure gel characteristics. Since no differences were observed the interaction between 1% RBPI and pH, data were pooled. CY increased with the addition of 1% RBPI, while it was not affected by pH values. GS increased with increased pH and increased when 1% RBPI was added, regardless of pH. There were distinctive endothermic protein peaks, at 56.55 and 75.02℃ at pH 5.75, and 56.47 and 72.43℃ at pH 6.5 in DSC results, which revealed decreased temperature of the first peak with the addition of 1% RBPI and increased pH. In SEM, a more compact structure with fewer voids was shown with the addition of 1% RBPI and increased pH from 5.75 to 6.5. In addition, the three-dimensional structure was highly dense and hard at pH 6.5 when RBPI was added. These results indicated that the addition of 1% RBPI at pH 6.5 in MTG-mediated MP represent the optimum condition to attain maximum gel-formation and protein gel functionality. PMID:26877645

  14. Controlling the pH of acid cheese whey in a two-stage anaerobic digester with sodium hydroxide

    SciTech Connect

    Ghaly, A.E.; Ramkumar, D.R.

    1999-07-01

    Anaerobic digestion of cheese whey offers a two-fold benefit: pollution potential reduction and biogas production. The biogas, as an energy source, could be used to reduce the consumption of traditional fuels in the cheese plant. However, as a result of little or no buffering capacity of whey, the pH of the anaerobic digester drops drastically and the process is inhibited. In this study, the effect of controlling the pH of the second chamber of a two-stage, 150 L anaerobic digester operating on cheese whey on the quality and quantity of biogas and the pollution potential reduction, was investigated using sodium hydroxide. The digester was operated at a temperature of 35 C and a hydraulic retention time of 15 days for three runs (no pH control, pH control with no reseeding, and ph control with reseeding) each lasting 50 days. The results indicated that operating the digester without pH control resulted in a low pH (3.3) which inhibited the methanogenic bacteria. The inhibition was irreversible and the digester did not recover (no methane production) when the pH was restored to 7.0 without reseeding, as the observed increased gas production was a false indication of recovery because the gas was mainly carbon dioxide. The addition of base resulted in a total alkalinity of 12,000 mg/L as CaCO{sub 3}. When the system was reseeded and the pH controlled, the total volatile acid concentration was 15,100 mg/L (as acetic acid), with acetic (28%), propionic (21%), butyric (25%), valeric (8%), and caproic (15%) acids as the major constituents. The biogas production was 62.6 L/d (0.84 m{sup 3}/m{sup 3}/d) and the methane content was 60.7%. Reductions of 27.3, 30.4 and 23.3% in the total solids, chemical oxygen demand and total kjeldahl nitrogen were obtained, respectively. The ammonium nitrogen content increased significantly (140%).

  15. Anaerobic digestion of food waste for volatile fatty acids (VFAs) production with different types of inoculum: effect of pH.

    PubMed

    Wang, Kun; Yin, Jun; Shen, Dongsheng; Li, Na

    2014-06-01

    Food waste anaerobic fermentation was carried out under acidic conditions using inocula based on aerobic activated sludge (Inoculum AE) or anaerobic activated sludge (Inoculum AN) for volatile fatty acids (VFAs) production. The results showed that food waste hydrolysis increased obviously when Inoculum AN was used relative to Inoculum AE at any pH investigated. Hydrolysis at pH 4.0 and uncontrolled pH was higher than that at other pHs when either inoculum was used. Additionally, VFAs production at pH 6.0 was the highest, regardless of the inoculum used. The optimum VFA yields were 0.482g/gVSSremoval with Inoculum AE and 0.918g/gVSSremoval with Inoculum AN, which were observed after 4d and 20d of fermentation, respectively. VFAs composition analysis showed that butyrate acid was the prevalent acid at pH 6.0, followed by acetate acid and propionic acid.

  16. Dissolution kinetics of a lunar glass simulant at 25 degrees C: the effect of pH and organic acids

    NASA Technical Reports Server (NTRS)

    Eick, M. J.; Grossl, P. R.; Golden, D. C.; Sparks, D. L.; Ming, D. W.

    1996-01-01

    The dissolution kinetics of a simulated lunar glass were examined at pH 3, 5, and 7. Additionally, the pH 7 experiments were conducted in the presence of citric and oxalic acid at concentrations of 2 and 20 mM. The organic acids were buffered at pH 7 to examine the effect of each molecule in their dissociated form. At pH 3, 5, and 7, the dissolution of the synthetic lunar glass was observed to proceed via a two-stage process. The first stage involved the parabolic release of Ca, Mg, Al, and Fe, and the linear release of Si. Dissolution was incongruent, creating a leached layer rich in Si and Ti which was verified by transmission electron microscopy (TEM). During the second stage the release of Ca, Mg, Al, and Fe was linear. A coupled diffusion/surface dissolution model was proposed for dissolution of the simulated lunar glass at pH 3, 5, and 7. During the first stage the initial release of mobile cations (i.e., Ca, Mg, Al, Fe) was limited by diffusion through the surface leached layer of the glass (parabolic release), while Si release was controlled by the hydrolysis of the Si-O-Al bonds at the glass surface (linear release). As dissolution continued, the mobile cations diffused from greater depths within the glass surface. A steady-state was then reached where the diffusion rate across the increased path lengths equalled the Si release rate from the surface. In the presence of the organic acids, the dissolution of the synthetic lunar glass proceeded by a one stage process. The release of Ca, Mg, Al, and Fe followed a parabolic relationship, while the release of Si was linear. The relative reactivity of the organic acids used in the experiments was citrate > oxalate. A thinner leached layer rich in Si/Ti, as compared to the pH experiments, was observed using TEM. Rate data suggest that the chemisorption of the organic anion to the surface silanol groups was responsible for enhanced dissolution in the presence of the organic acids. It is proposed that the increased

  17. Dissolution kinetics of a lunar glass simulant at 25 degrees C: the effect of pH and organic acids.

    PubMed

    Eick, M J; Grossl, P R; Golden, D C; Sparks, D L; Ming, D W

    1996-01-01

    The dissolution kinetics of a simulated lunar glass were examined at pH 3, 5, and 7. Additionally, the pH 7 experiments were conducted in the presence of citric and oxalic acid at concentrations of 2 and 20 mM. The organic acids were buffered at pH 7 to examine the effect of each molecule in their dissociated form. At pH 3, 5, and 7, the dissolution of the synthetic lunar glass was observed to proceed via a two-stage process. The first stage involved the parabolic release of Ca, Mg, Al, and Fe, and the linear release of Si. Dissolution was incongruent, creating a leached layer rich in Si and Ti which was verified by transmission electron microscopy (TEM). During the second stage the release of Ca, Mg, Al, and Fe was linear. A coupled diffusion/surface dissolution model was proposed for dissolution of the simulated lunar glass at pH 3, 5, and 7. During the first stage the initial release of mobile cations (i.e., Ca, Mg, Al, Fe) was limited by diffusion through the surface leached layer of the glass (parabolic release), while Si release was controlled by the hydrolysis of the Si-O-Al bonds at the glass surface (linear release). As dissolution continued, the mobile cations diffused from greater depths within the glass surface. A steady-state was then reached where the diffusion rate across the increased path lengths equalled the Si release rate from the surface. In the presence of the organic acids, the dissolution of the synthetic lunar glass proceeded by a one stage process. The release of Ca, Mg, Al, and Fe followed a parabolic relationship, while the release of Si was linear. The relative reactivity of the organic acids used in the experiments was citrate > oxalate. A thinner leached layer rich in Si/Ti, as compared to the pH experiments, was observed using TEM. Rate data suggest that the chemisorption of the organic anion to the surface silanol groups was responsible for enhanced dissolution in the presence of the organic acids. It is proposed that the increased

  18. TiO2 nanoparticles aggregation and disaggregation in presence of alginate and Suwannee River humic acids. pH and concentration effects on nanoparticle stability.

    PubMed

    Loosli, Frédéric; Le Coustumer, Philippe; Stoll, Serge

    2013-10-15

    The behavior of manufactured TiO2 nanoparticles is studied in a systematic way in presence of alginate and Suwannee River humic acids at variable concentrations. TiO2 nanoparticles aggregation, disaggregation and stabilization are investigated using dynamic light scattering and electrophoretic experiments allowing the measurement of z-average hydrodynamic diameters and zeta potential values. Stability of the TiO2 nanoparticles is discussed by considering three pH-dependent electrostatic scenarios. In the first scenario, when pH is below the TiO2 nanoparticle point of zero charge, nanoparticles exhibit a positively charged surface whereas alginate and Suwannee River humic acids are negatively charged. Fast adsorption at the TiO2 nanoparticles occurs, promotes surface charge neutralization and aggregation. By increasing further alginate and Suwannee River humic acids concentrations charge inversion and stabilization of TiO2 nanoparticles are obtained. In the second electrostatic scenario, at the surface charge neutralization pH, TiO2 nanoparticles are rapidly forming aggregates. Adsorption of alginate and Suwannee River humic acids on aggregates leads to their partial fragmentation. In the third electrostatic scenario, when nanoparticles, alginate and Suwannee River humic acids are negatively charged, only a small amount of Suwannee River humic acids is adsorbed on TiO2 nanoparticles surface. It is found that the fate and behavior of individual and aggregated TiO2 nanoparticles in presence of environmental compounds are mainly driven by the complex interplay between electrostatic attractive and repulsive interactions, steric and van der Waals interactions, as well as concentration ratio. Results also suggest that environmental aquatic concentration ranges of humic acids and biopolymers largely modify the stability of aggregated or dispersed TiO2 nanoparticles.

  19. Sorption behavior of 17 phthalic acid esters on three soils: effects of pH and dissolved organic matter, sorption coefficient measurement and QSPR study.

    PubMed

    Yang, Fen; Wang, Meng; Wang, Zunyao

    2013-09-01

    This work studies the sorption behaviors of phthalic acid esters (PAEs) on three soils by batch equilibration experiments and quantitative structure property relationship (QSPR) methodology. Firstly, the effects of soil type, dissolved organic matter and pH on the sorption of four PAEs (DMP, DEP, DAP, DBP) are investigated. The results indicate that the soil organic carbon content has a crucial influence on sorption progress. In addition, a negative correlation between pH values and the sorption capacities was found for these four PAEs. However, the effect of DOM on PAEs sorption may be more complicated. The sorption of four PAEs was promoted by low concentrations of DOM, while, in the case of high concentrations, the influence of DOM on the sorption was complicated. Then the organic carbon content normalized sorption coefficient (logKoc) values of 17 PAEs on three soils were measured, and the mean values ranged from 1.50 to 7.57. The logKoc values showed good correlation with the corresponding logKow values. Finally, two QSPR models were developed with 13 theoretical parameters to get reliable logKoc predictions. The leave-one-out cross validation (CV-LOO) indicated that the internal predictive power of the two models was satisfactory.

  20. Three-dimensional nuclear magnetic resonance structures of mouse epidermal growth factor in acidic and physiological pH solutions.

    PubMed

    Kohda, D; Inagaki, F

    1992-12-01

    The three-dimensional structures of epidermal growth factors (EGF) previously reported were all in acidic solutions (pH 2.0-3.2), at which pHs EGF cannot bind to the receptor. Here we studied the structure of mouse EGF at pH 6.8, where EGF is physiologically active, and compared it with the structure at pH 2.0 by CD and NMR. From pH dependence of CD spectra and a comparison between the chemical shifts of the proton resonances at pH 6.8 and 2.0, the conformations at two pHs were found to be nearly identical except for the C-terminal tail region. The three-dimensional structures at pH 6.8 and 2.0 were determined independently by a combination of two-dimensional 1H NMR and stimulated annealing calculations using the program XPLOR. The calculations were based on 261 distance constraints at pH 6.8 and 355 distance and 24 torsion angle constraints at pH 2.0. The conformational difference of the C-terminal domain (residues 33-50) was detected between the two structures, which were supported by CD and the chemical shift comparison. The positions of the side chains of Leu47, Arg48, Trp49, and Trp50 are changed probably by the effect of the deprotonation of Asp46. Considering the fact that Leu47 is essential in EGF binding to the receptor, this conformational difference may be important in receptor recognition.

  1. Influence of bath PH value on microstructure and corrosion resistance of phosphate chemical conversion coating on sintered Nd-Fe-B permanent magnets

    NASA Astrophysics Data System (ADS)

    Ding, Xia; Xue, Long-fei; Wang, Xiu-chun; Ding, Kai-hong; Cui, Sheng-li; Sun, Yong-cong; Li, Mu-sen

    2016-10-01

    The effect of bath PH value on formation, microstructure and corrosion resistance of the phosphate chemical conversion (PCC) coatings as well as the effect on the magnetic property of the magnets is investigated in this paper. The results show that the coating mass and thickness increase with the decrease of the bath PH value. Scanning electron microscopy observation demonstrates that the PCC coatings are in a blocky structure with different grain size. Transmission electron microscope and X-ray diffractometer tests reveal the coatings are polycomponent and are mainly composed of neodymium phosphate hydrate and praseodymium phosphate hydrate. The electrochemical analysis and static immersion corrosion test show the corrosion resistance of the PCC coatings prepared at bath PH value of 0.52 is worst. Afterwards the corrosion resistance increases first and then decreases with the increasing of the bath PH values. The magnetic properties of all the samples with PCC treatment are decreased. The biggest loss is occurred when the bath PH value is 0.52. Taken together, the optimum PH range of 1.00-1.50 for the phosphate solution has been determined.

  2. Influence of pH on the speciation of copper(II) in reactions with the green tea polyphenols, epigallocatechin gallate and gallic acid.

    PubMed

    Pirker, Katharina F; Baratto, Maria Camilla; Basosi, Riccardo; Goodman, Bernard A

    2012-07-01

    Changes in speciation of copper(II) in reactions with epigallocatechin gallate (EGCG) and gallic acid (GA) as a function of pH have been investigated by multifrequency (X- and S-band) EPR spectroscopy in the fluid and frozen states. The EPR spectra show the formation of three distinct mononuclear species with each of the polyphenols, and these are interpreted in terms of one mono- and two bis-complexes. However, di- or polymeric complexes dominate the Cu(II) speciation in the pH range 4-8, and it is only at alkaline pH values that these mononuclear complexes make appreciable contributions to the metal speciation. Each mononuclear complex displays linewidth anisotropy in fluid solution as a consequence of incomplete averaging of the spin Hamiltonian parameters through molecular motion. Rotational correlation times for the individual complexes have been estimated by analysing the lineshape anisotropy of the fluid solution spectra using parameters determined by simulation of the rigid limit spectra. These show that the molecular masses increase with increasing pH, indicating either coordination of increasing numbers of polyphenol molecules as ligands to the copper or the increasing involvement of polyphenol dimers as ligands in the copper coordination sphere.

  3. pH- and ionic-strength-induced structural changes in poly(acrylic acid)-lipid-based self-assembled materials.

    SciTech Connect

    Crisci, A.; Hay, D. N. T.; Seifert, S.; Firestone, M. A.

    2009-01-01

    The effect of a polyanion introduced as a lipid conjugate (poly(acrylic acid)- dimyristoyl-sn-glycero-3-phosphoethanolamine, PAA-DMPE) on the structure of a self-assembled, biomembrane mimetic has been evaluated using synchrotron small-angle X-ray scattering (SAXS). At high grafting density (8-11 mol.%), the PAA chains were found to produce significant changes in structure in response to changes in pH and electrolyte composition. At low pH and in the absence of salt (NaCl), the neutral PAA chains adopt a coil conformational state that leads to the formation of a swollen lamellar structure. Upon the addition of salt at low to intermediate pH values, two lamellar phases, a collapsed and an expanded structure, coexist. Finally, when the polymer is fully ionized (at high pH), the extended conformation of the polymer generates a cubic phase. The results of this study contribute to an understanding of how polyelectrolytes may ultimately be harnessed for the preparation of self-assembling materials responsive to external stimuli.

  4. Technical Note: Large overestimation of pCO2 calculated from pH and alkalinity in acidic, organic-rich freshwaters

    NASA Astrophysics Data System (ADS)

    Abril, G.; Bouillon, S.; Darchambeau, F.; Teodoru, C. R.; Marwick, T. R.; Tamooh, F.; Ochieng Omengo, F.; Geeraert, N.; Deirmendjian, L.; Polsenaere, P.; Borges, A. V.

    2015-01-01

    Inland waters have been recognized as a significant source of carbon dioxide (CO2) to the atmosphere at the global scale. Fluxes of CO2 between aquatic systems and the atmosphere are calculated from the gas transfer velocity and the water-air gradient of the partial pressure of CO2 (pCO2). Currently, direct measurements of water pCO2 remain scarce in freshwaters, and most published pCO2 data are calculated from temperature, pH and total alkalinity (TA). Here, we compare calculated (pH and TA) and measured (equilibrator and headspace) water pCO2 in a large array of temperate and tropical freshwaters. The 761 data points cover a wide range of values for TA (0 to 14 200 μmol L-1), pH (3.94 to 9.17), measured pCO2 (36 to 23 000 ppmv), and dissolved organic carbon (DOC) (29 to 3970 μmol L-1). Calculated pCO2 were >10% higher than measured pCO2 in 60% of the samples (with a median overestimation of calculated pCO2 compared to measured pCO2 of 2560 ppmv) and were >100% higher in the 25% most organic-rich and acidic samples (with a median overestimation of 9080 ppmv). We suggest these large overestimations of calculated pCO2 with respect to measured pCO2 are due to the combination of two cumulative effects: (1) a more significant contribution of organic acids anions to TA in waters with low carbonate alkalinity and high DOC concentrations; (2) a lower buffering capacity of the carbonate system at low pH, which increases the sensitivity of calculated pCO2 to TA in acidic and organic-rich waters. No empirical relationship could be derived from our data set in order to correct calculated pCO2 for this bias. Owing to the widespread distribution of acidic, organic-rich freshwaters, we conclude that regional and global estimates of CO2 outgassing from freshwaters based on pH and TA data only are most likely overestimated, although the magnitude of the overestimation needs further quantitative analysis. Direct measurements of pCO2 are recommended in inland waters in general

  5. Effects of pH and dissolved oxygen on the photodegradation of 17α-ethynylestradiol in dissolved humic acid solution.

    PubMed

    Ren, Dong; Huang, Bin; Bi, Tingting; Xiong, Dan; Pan, Xuejun

    2016-01-01

    To probe the mechanisms responsible for pH and dissolved oxygen (DO) affecting the photodegradation of 17α-ethynylestradiol (EE2) in dissolved humic acid (HA) solution, EE2 aqueous solutions with pH values ranging from 3.0 to 11.0 and different DO conditions were irradiated by using a 300 W mercury lamp equipped with 290 nm light cutoff filters. In 5.0 mg L(-1) HA solutions (pH 8.0), EE2 was degraded at a rate of 0.0739 h(-1) which was about 4-fold faster than that in Milli-Q water. The degradation of EE2 was mainly caused by the oxidation of photogenerated reactive species (RS), and the contribution of direct photodegradation to EE2 degradation was always lower than 27%. Both the direct and indirect photodegradation of EE2 were closely dependent on the EE2 initial concentration, pH value and DO concentration. The photodegradation rate of EE2 decreased with increased initial concentration of EE2 due to the limitation of photon flux. With pH and DO increasing, the degradation rate of EE2 increased significantly due to the increase in the yields of excited EE2 and RS. Among the photogenerated RS, HO˙ and (3)HA* were determined to be the key contributors, and their global contribution to EE2 photodegradation was about 50%. Although HA could generate more (1)O2 than HO˙, the contribution of (1)O2 to EE2 degradation was lower than 13% due to its low reactivity towards EE2. This study could enlarge our knowledge on the photochemical behaviors of steroid estrogens in natural sunlit waters. PMID:26611276

  6. Retention of ionisable compounds on high-performance liquid chromatography XIX. pH variation in mobile phases containing formic acid, piperazine and tris as buffering systems and methanol as organic modifier.

    PubMed

    Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

    2009-07-10

    In previous works a model to estimate the pH of methanol-aqueous buffer mobile phases from the aqueous pH and concentration of the buffer and the fraction of organic modifier was developed. This model was successfully applied and validated for buffers prepared from ammonia, acetic, phosphoric and citric acids. In the present communication this model has been extended to formic acid, piperazine and tris(hydroxymethyl)aminomethane buffers. Prior to the modelling work, the pK(a) values of the studied buffers at several methanol-water compositions were determined.

  7. A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus

    NASA Astrophysics Data System (ADS)

    Vet, Robert; Artz, Richard S.; Carou, Silvina

    2014-08-01

    Investigating and assessing the chemical composition of precipitation and atmospheric deposition is essential to understanding how atmospheric pollutants contribute to contemporary environmental concerns including ecosystem acidification and eutrophication, loss of biodiversity, air pollution and global climate change. Evidence of the link between atmospheric deposition and these environmental issues is well established. The state of scientific understanding of this link is that present levels of atmospheric deposition of sulfur and nitrogen adversely affect terrestrial and aquatic ecosystems, putting forest sustainability and aquatic biodiversity at risk. Nitrogen and phosphorus loadings are linked to impacts on the diversity of terrestrial and aquatic vegetation through biological cycling, and atmospheric deposition plays a major role in the emission-transport-conversion-loss cycle of chemicals in the atmosphere as well as the formation of particulate matter and ozone in the troposphere. Evidence also shows that atmospheric constituents are changing the earth's climate through direct and indirect atmospheric processes. This Special Issue, comprising a single article titled "A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus", presents a recent comprehensive review of precipitation chemistry and atmospheric deposition at global and regional scales. The information in the Special Issue, including all supporting data sets and maps, is anticipated to be of great value not only to the atmospheric deposition community but also to other science communities including those that study ecosystem impacts, human health effects, nutrient processing, climate change, global and hemispheric modeling and biogeochemical cycling. Understanding and quantifying pollutant loss from the atmosphere is, and will remain, an important component of each of these scientific fields as they

  8. The enzymatic activities of the Escherichia coli basic aliphatic amino acid decarboxylases exhibit a pH zone of inhibition.

    PubMed

    Kanjee, Usheer; Gutsche, Irina; Ramachandran, Shaliny; Houry, Walid A

    2011-11-01

    The stringent response regulator ppGpp has recently been shown by our group to inhibit the Escherichia coli inducible lysine decarboxylase, LdcI. As a follow-up to this observation, we examined the mechanisms that regulate the activities of the other four E. coli enzymes paralogous to LdcI: the constitutive lysine decarboxylase LdcC, the inducible arginine decarboxylase AdiA, the inducible ornithine decarboxylase SpeF, and the constitutive ornithine decarboxylase SpeC. LdcC and SpeC are involved in cellular polyamine biosynthesis, while LdcI, AdiA, and SpeF are involved in the acid stress response. Multiple mechanisms of regulation were found for these enzymes. In addition to LdcI, LdcC and SpeC were found to be inhibited by ppGpp; AdiA activity was found to be regulated by changes in oligomerization, while SpeF and SpeC activities were regulated by GTP. These findings indicate the presence of multiple mechanisms regulating the activity of this important family of decarboxylases. When the enzyme inhibition profiles are analyzed in parallel, a "zone of inhibition" between pH 6 and pH 8 is observed. Hence, the data suggest that E. coli utilizes multiple mechanisms to ensure that these decarboxylases remain inactive around neutral pH possibly to reduce the consumption of amino acids at this pH. PMID:21957966

  9. The enzymatic activities of the Escherichia coli basic aliphatic amino acid decarboxylases exhibit a pH zone of inhibition.

    PubMed

    Kanjee, Usheer; Gutsche, Irina; Ramachandran, Shaliny; Houry, Walid A

    2011-11-01

    The stringent response regulator ppGpp has recently been shown by our group to inhibit the Escherichia coli inducible lysine decarboxylase, LdcI. As a follow-up to this observation, we examined the mechanisms that regulate the activities of the other four E. coli enzymes paralogous to LdcI: the constitutive lysine decarboxylase LdcC, the inducible arginine decarboxylase AdiA, the inducible ornithine decarboxylase SpeF, and the constitutive ornithine decarboxylase SpeC. LdcC and SpeC are involved in cellular polyamine biosynthesis, while LdcI, AdiA, and SpeF are involved in the acid stress response. Multiple mechanisms of regulation were found for these enzymes. In addition to LdcI, LdcC and SpeC were found to be inhibited by ppGpp; AdiA activity was found to be regulated by changes in oligomerization, while SpeF and SpeC activities were regulated by GTP. These findings indicate the presence of multiple mechanisms regulating the activity of this important family of decarboxylases. When the enzyme inhibition profiles are analyzed in parallel, a "zone of inhibition" between pH 6 and pH 8 is observed. Hence, the data suggest that E. coli utilizes multiple mechanisms to ensure that these decarboxylases remain inactive around neutral pH possibly to reduce the consumption of amino acids at this pH.

  10. pH dependence of iron photoreduction in a rocky mountain stream affected by acid mine drainage

    USGS Publications Warehouse

    McKnight, Diane M.; Kimball, B.A.; Runkel, R.L.

    2001-01-01

    The redox speciation of dissolved iron and the transport of iron in acidic, metal-enriched streams is controlled by precipitation and dissolution of iron hydroxides, by photoreduction of dissolved ferric iron and hydrous iron oxides, and by oxidation of the resulting dissolved ferrous iron. We examined the pH dependence of these processes in an acidic mine-drainage stream, St Kevin Gulch, Colorado, by experimentally increasing the pH of the stream from about 4.0 to 6.5 and following the downstream changes in iron species. We used a solute transport model with variable flow to evaluate biogeochemical processes controlling downstream transport. We found that at pH 6.4 there was a rapid and large initial loss of ferrous iron concurrent with the precipitation of aluminium hydroxide. Below this reach, ferrous iron was conservative during the morning but there was a net downstream loss of ferrous iron around noon and in the afternoon. Calculation of net oxidation rates shows that the noontime loss rate was generally much faster than rates for the ferrous iron oxidation at pH 6 predicted by Singer and Stumm (1970. Science 167: 1121). The maintenance of ferrous iron concentrations in the morning is explained by the photoreduction of photoreactive ferric species, which are then depleted by noon. Copyright ?? 2001 John Wiley & Sons, Ltd.

  11. Chemical equilibrium modeling of organic acids, pH, aluminum, and iron in Swedish surface waters.

    PubMed

    Sjöstedt, Carin S; Gustafsson, Jon Petter; Köhler, Stephan J

    2010-11-15

    A consistent chemical equilibrium model that calculates pH from charge balance constraints and aluminum and iron speciation in the presence of natural organic matter is presented. The model requires input data for total aluminum, iron, organic carbon, fluoride, sulfate, and charge balance ANC. The model is calibrated to pH measurements (n = 322) by adjusting the fraction of active organic matter only, which results in an error of pH prediction on average below 0.2 pH units. The small systematic discrepancy between the analytical results for the monomeric aluminum fractionation and the model results is corrected for separately for two different fractionation techniques (n = 499) and validated on a large number (n = 3419) of geographically widely spread samples all over Sweden. The resulting average error for inorganic monomeric aluminum is around 1 µM. In its present form the model is the first internally consistent modeling approach for Sweden and may now be used as a tool for environmental quality management. Soil gibbsite with a log *Ks of 8.29 at 25°C together with a pH dependent loading function that uses molar Al/C ratios describes the amount of aluminum in solution in the presence of organic matter if the pH is roughly above 6.0.

  12. Acid dissociation constants of uridine-5'-diphosphate compounds determined by 31phosphorus nuclear magnetic resonance spectroscopy and internal pH referencing.

    PubMed

    Jancan, Igor; Macnaughtan, Megan A

    2012-10-24

    The acid dissociation constant (pK(a)) of small, biological molecules is an important physical property used for investigating enzyme mechanisms and inhibitor design. For phosphorus-containing molecules, the (31)P nuclear magnetic resonance (NMR) chemical shift is sensitive to the local chemical environment, particularly to changes in the electronic state of the molecule. Taking advantage of this property, we present a (31)P NMR approach that uses inorganic phosphate buffer as an internal pH reference to determine the pK(a) values of the imide and second diphosphate of uridine-5'-diphosphate compounds, including the first reported values for UDP-GlcNAc and UDP-S-GlcNAc. New methods for using inorganic phosphate buffer as an internal pH reference, involving mathematical correction factors and careful control of the chemical shift reference sample, are illustrated. A comparison of the newly determined imide and diphosphate pK(a) values of UDP, UDP-GlcNAc, and UDP-S-GlcNAc with other nucleotide phosphate and thio-analogs reveals the significance of the monosaccharide and sulfur position on the pK(a) values.

  13. Influence of pH on colloidal properties and surface activity of polyglycerol fatty acid ester vesicles.

    PubMed

    Duerr-Auster, N; Eisele, T; Wepf, R; Gunde, R; Windhab, E J

    2008-11-15

    Certain polyglycerol esters of fatty acids (PGE) form dispersions of uni- or multilamellar vesicles in dilute aqueous solution. These self-assembled aggregates reduce the surface-activity of PGE monomers such that interfacial films may take several hours to form. This is undesirable for processes, which rely on rapid surfactant adsorption, for example foaming. In the present work, we study the effect of pH on the colloidal (size distribution, morphology, surface charge) and interfacial (adsorption kinetics) properties of a commercial, non-purified PGE. Using dynamic light scattering, zeta-potential measurements and cryo-SEM, we show that changing the pH of the dispersion media can cause agglomeration and eventually osmotic rupture of PGE vesicles. The change in dispersion state also impacts the adsorption behavior at the water surface. Direct evidence that destabilized vesicle dispersion are more surface-active is provided by comparing the dynamic surface tension of solutions of different pH. The faster adsorption kinetics at low pH correlate with a remarkably increased foaming power. We suggest that an osmotic shock induced by changes in pH causes vesicles to deform and partially open, so that their hydrocarbon core is exposed to the dispersion media. This energetically unfavorable condition promotes the hydrophobically driven adsorption of surfactant monomers at surfaces and hence stimulates the foaming ability.

  14. Short-chain fatty acids and acidic pH upregulate UT-B, GPR41, and GPR4 in rumen epithelial cells of goats.

    PubMed

    Lu, Zhongyan; Gui, Hongbing; Yao, Lei; Yan, Lei; Martens, Holger; Aschenbach, Jörg R; Shen, Zanming

    2015-02-15

    Currently, the mechanism(s) responsible for the regulation of urea transporter B (UT-B) expression levels in the epithelium of the rumen remain unclear. We hypothesized that rumen fermentation products affect ruminal UT-B expression. Therefore, the effects of short-chain fatty acids (SCFA), pH, ammonia, and urea on mRNA and protein levels of UT-B were assayed in primary rumen epithelial cell cultures and in rumen epithelium obtained from intact goats. In vitro, SCFA and acidic pH were found to synergetically stimulate both mRNA and protein expression of UT-B, whereas NH4Cl decreased mRNA and protein levels of UT-B at pH 6.8. Treatment with urea increased both levels at pH 7.4. When goats received a diet rich in nitrogen (N) and nonfiber carbohydrates (NFC), their rumen epithelium had higher levels of UT-B, and the rumen contained higher concentrations of SCFA and NH3-N with a lower pH. An increase in plasma urea-N concentration was also observed compared with the plasma of the goats that received a diet low in N and NFC. In a second feeding trial, goats that received a NFC-rich, but isonitrogenous, diet had higher mRNA and protein levels of UT-B, and higher levels of G protein-coupled receptor (GPR) 41 and GPR4, in their rumen epithelium. The ruminal concentrations of SCFA and NH3-N also increased, while a lower pH was detected. In contrast, the serum urea-N concentrations remained unchanged. These data indicate that ruminal SCFA and pH are key factors, via GPR4 and GPR41, in the dietary regulation of UT-B expression, and they have priority over changes in plasma urea.

  15. Nonideal mixing and phase separation in phosphatidylcholine-phosphatidic acid mixtures as a function of acyl chain length and pH.

    PubMed Central

    Garidel, P; Johann, C; Blume, A

    1997-01-01

    The miscibilities of phosphatidic acids (PAs) and phosphatidylcholines (PCs) with different chain lengths (n = 14, 16) at pH 4, pH 7, and pH 12 were examined by differential scanning calorimetry. Simulation of heat capacity curves was performed using a new approach that incorporates changes of cooperativity of the transition in addition to nonideal mixing in the gel and the liquid-crystalline phase as a function of composition. From the simulations of the heat capacity curves, first estimates for the nonideality parameters for nonideal mixing as a function of composition were obtained, and phase diagrams were constructed using temperatures for onset and end of melting, which were corrected for the broadening effect caused by a decrease in cooperativity. In all cases the composition dependence of the nonideality parameters indicated nonsymmetrical mixing behavior. The phase diagrams were therefore further refined by simulations of the coexistence curves using a four-parameter approximation to account for nonideal and nonsymmetrical mixing in the gel and the liquid-crystalline phase. The mixing behavior was studied at three different pH values to investigate how changes in headgroup charge of the PA influences the miscibility. The experiments showed that at pH 7, where the PA component is negatively charged, the nonideality parameters are in most cases negative, indicating that electrostatic effects favor a mixing of the two components. Partial protonation of the PA component at pH 4 leads to strong changes in miscibility; the nonideality parameters for the liquid-crystalline phase are now in most cases positive, indicating clustering of like molecules. The phase diagram for 1,2-dimyristoyl-sn-glycero-3-phosphatidic acid:1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine mixtures at pH 4 indicates that a fluid-fluid immiscibility is likely. The results show that a decrease in ionization of PAs can induce large changes in mixing behavior. This occurs because of a

  16. Dietary Supplementation of Benzoic Acid and Essential Oil Compounds Affects Buffering Capacity of the Feeds, Performance of Turkey Poults and Their Antioxidant Status, pH in the Digestive Tract, Intestinal Microbiota and Morphology.

    PubMed

    Giannenas, I; Papaneophytou, C P; Tsalie, E; Pappas, I; Triantafillou, E; Tontis, D; Kontopidis, G A

    2014-02-01

    Three trials were conducted to evaluate the effect of supplementation of a basal diet with benzoic acid or thymol or a mixture of essential oil blends (MEO) or a combination of benzoic acid with MEO (BMEO) on growth performance of turkey poults. Control groups were fed a basal diet. In trial 1, benzoic acid was supplied at levels of 300 and 1,000 mg/kg. In trial 2, thymol or the MEO were supplied at levels of 30 mg/kg. In trial 3, the combination of benzoic acid with MEO was evaluated. Benzoic acid, MEO and BMEO improved performance, increased lactic acid bacteria populations and decreased coliform bacteria in the caeca. Thymol, MEO and BMEO improved antioxidant status of turkeys. Benzoic acid and BMEO reduced the buffering capacity compared to control feed and the pH values of the caecal content. Benzoic acid and EOs may be suggested as an effective alternative to AGP in turkeys. PMID:25049947

  17. Dietary Supplementation of Benzoic Acid and Essential Oil Compounds Affects Buffering Capacity of the Feeds, Performance of Turkey Poults and Their Antioxidant Status, pH in the Digestive Tract, Intestinal Microbiota and Morphology

    PubMed Central

    Giannenas, I.; Papaneophytou, C. P.; Tsalie, E.; Pappas, I.; Triantafillou, E.; Tontis, D.; Kontopidis, G. A.

    2014-01-01

    Three trials were conducted to evaluate the effect of supplementation of a basal diet with benzoic acid or thymol or a mixture of essential oil blends (MEO) or a combination of benzoic acid with MEO (BMEO) on growth performance of turkey poults. Control groups were fed a basal diet. In trial 1, benzoic acid was supplied at levels of 300 and 1,000 mg/kg. In trial 2, thymol or the MEO were supplied at levels of 30 mg/kg. In trial 3, the combination of benzoic acid with MEO was evaluated. Benzoic acid, MEO and BMEO improved performance, increased lactic acid bacteria populations and decreased coliform bacteria in the caeca. Thymol, MEO and BMEO improved antioxidant status of turkeys. Benzoic acid and BMEO reduced the buffering capacity compared to control feed and the pH values of the caecal content. Benzoic acid and EOs may be suggested as an effective alternative to AGP in turkeys. PMID:25049947

  18. Continuous measurement of reticuloruminal pH values in dairy cows during the transition period from barn to pasture feeding using an indwelling wireless data transmitting unit.

    PubMed

    Gasteiner, J; Horn, M; Steinwidder, A

    2015-04-01

    This study was performed to investigate the effect of the transition from barn feeding to pasture on the pattern of reticuloruminal pH values in 8 multiparous dairy cows. A indwelling wireless data transmitting system for pH measurement was given to 8 multiparous cows orally. Reticuloruminal pH values were measured every 600 s over a period of 42 days. After 7 days of barn feeding (period 1), all of the animals were pastured with increasing grazing times from 2 to 7 h/day over 7 days (period 2). From day 15 to day 21 (period 3), the cows spent 7 h/day on pasture. Beginning on day 22, the animals had 20 h/day access to pasture (day and night grazing). To study reticuloruminal adaptation to pasture feeding, the phase of day and night grazing was subdivided into another 3 weekly periods (periods 4-6). Despite a mild transition period from barn feeding to pasture, significant effects on reticuloruminal pH values were observed. During barn feeding, the mean reticuloruminal pH value for all of the cows was 6.44 ± 0.14, and the pH values decreased significantly (p < 0.001) during period 2 and 3 to 6.24 ± 0.17 and 6.21 ± 0.19 respectively. During periods 4, 5 and 6, the reticuloruminal pH values increased again (pH 6.25 ± 0.22; pH 6.31 ± 0.17; pH 6.37 ± 0.16). Our results showed that the animals had significantly lowered reticuloruminal pH during the periods of feed transition from barn to pasture feeding. Despite these significant changes, the decrease was not harmful, as indicated by data of feed intake and milk production.

  19. A new hyaluronic acid pH sensitive derivative obtained by ATRP for potential oral administration of proteins.

    PubMed

    Fiorica, Calogero; Pitarresi, Giovanna; Palumbo, Fabio Salvatore; Di Stefano, Mauro; Calascibetta, Filippo; Giammona, Gaetano

    2013-11-30

    Atom transfer radical polymerization (ATRP) has been successfully employed to obtain a new derivative of hyaluronic acid (HA) able to change its solubility as a function of external pH and then to be potentially useful for intestinal release of bioactive molecules, included enzymes and proteins. In particular, a macroinitiator has been prepared by linking 2-bromo-2-methypropionic acid (BMP) to the amino groups of ethylenediamino derivative of tetrabutyl ammonium salt of HA (HA-TBA-EDA). This macroinititor, named HA-TBA-EDA-BMP has been used for the ATRP of sodium methacrylate (MANa) using a complex of Cu(I) and 2,2'-bipyridyl (Byp) as a catalyst. The resulting copolymer, named HA-EDA-BMP-MANa, has been characterized by (1)H NMR and size exclusion chromatography (SEC) analyses. A turbidimetric analysis has showed its pH sensitive behavior, being insoluble in simulated gastric fluid but soluble when pH increases more than 2.5. To confirm the ability of HA-EDA-BMP-MANa in protecting peptides or proteins from denaturation in acidic medium, α-chymotrypsin has been chosen as a model of protein molecule and its activity has been evaluated after entrapment into HA-EDA-BMP-MANa chains and treatment under simulated gastric conditions. Finally, cell compatibility has been evaluated by performing a MTS assay on murine dermal fibroblasts cultured with HA-EDA-BMP-MANa solutions. PMID:24060369

  20. Stereoselective Degradation and Molecular Ecological Mechanism of Chiral Pesticides Beta-Cypermethrin in Soils with Different pH Values.

    PubMed

    Yang, Zhong-Hua; Ji, Guo-Dong

    2015-12-15

    For decades, pesticides have been widely used for agricultural activities around the world, and the environmental problems caused by these compounds have raised widespread concern. However, the different enantioselective behaviors of chiral pesticide enantiomers are often ignored. Here, the selective degradation patterns and mechanisms of chiral pesticide enantiomers were successfully investigated for the first time in the soils of three cultivation areas with different pH values. Beta-cypermethrin was chosen as the target analyte. We found that the degradation rates of the four isomers of beta-cypermethrin were different. We used stepwise regression equations between degradation rates and functional genes to quantitatively study their relationships. Quantitative response analysis revealed that different isomers have different equations even under identical conditions. The results of path analysis showed that a single functional gene can make different direct and indirect contributions to the degradation of different isomers. Finally, the high-throughput technology was used to analysis the genome of the three tested soils and then compared the main microbial communities in them. We have successfully devised a method to investigate the molecular biological mechanisms of the selective degradation behavior of chiral compounds, thus enabling us to better understand these mechanisms.

  1. Technical Note: Large overestimation of pCO2 calculated from pH and alkalinity in acidic, organic-rich freshwaters

    NASA Astrophysics Data System (ADS)

    Abril, G.; Bouillon, S.; Darchambeau, F.; Teodoru, C. R.; Marwick, T. R.; Tamooh, F.; Omengo, F. O.; Geeraert, N.; Deirmendjian, L.; Polsenaere, P.; Borges, A. V.

    2014-07-01

    Inland waters have been recognized as a~significant source of carbon dioxide (CO2) to the atmosphere at the global scale. Fluxes of CO2 between aquatic systems and the atmosphere are calculated from the gas transfer velocity and the water-air gradient of the partial pressure of CO2 (pCO2). Nowadays, direct measurements of water pCO2 remain scarce in freshwaters and most published pCO2 data are calculated from temperature, pH and total alkalinity (TA). Here, we compare calculated (pH and TA) and measured (Equilibrator and headspace) water pCO2 in a large array of temperate and tropical freshwaters. The 761 data points cover a wide range of values for TA (0 to 14.2 mmol L-1), pH (3.94 to 9.17), measured pCO2 (36 to 23 000 ppmv), and dissolved organic carbon (DOC) (29 to 3970 μmol L-1). Calculated pCO2 were > 10% higher than measured pCO2 in 60% of the samples (with a median overestimation of calculated pCO2 compared to measured pCO2 of 2560 ppmv) and were > 100% higher in the 25% most organic-rich and acidic samples (with a median overestimation of 9080 ppmv). We suggest these large overestimations of calculated pCO2 with respect to measured pCO2 are due to the combination of two cumulative effects: (1) a more significant contribution of organic acids anions to TA in waters with low carbonate alkalinity and high DOC concentrations; (2) a lower buffering capacity of the carbonate system at low pH, that increases the sensitivity of calculated pCO2 to TA in acidic and organic-rich waters. We recommend that regional studies on pCO2 should not be based on pH and TA data only, and that direct measurements of pCO2 should become the primary method in inland waters in general, and in particular in acidic, poorly buffered, freshwaters.

  2. Potentiometric investigation of the effect of the pH on the ionic transfer of some amino acids at the interface between two immiscible electrolyte solutions.

    PubMed

    Spătaru, Tanta; Spătaru, Nicolae; Bonciocat, Nicolae; Luca, Constantin

    2004-04-01

    The effect of the pH on the ionic transfer of glycine and beta-alanine at the interface between two immiscible electrolyte solutions (ITIES) was investigated by a simple potentiometric method. Upon addition of small amounts of solution containing the investigated amino acids, a variation of the potential drop across the interface was recorded, which was found to be pH-dependent. This behavior was explained in terms of a preferential orientation of the amino acid molecules at the ITIES, induced by the different lipoficility of the functional groups. The results enabled the measurement of this voltage variation to be used as the basis for a simple and rapid method for determining the isoelectric point of the investigated compounds. The agreement between the pH(i) values thus estimated and those reported in the literature suggests the possibility of using the method for the interpretation of processes occurring at the level of biological membranes. PMID:14990327

  3. The effect of terebinth (Pistacia terebinthus L.) coffee addition on the chemical and physical characteristics, colour values, organic acid profiles, mineral compositions and sensory properties of ice creams.

    PubMed

    Yüksel, Arzu Kavaz; Şat, Ihsan Güngör; Yüksel, Mehmet

    2015-12-01

    The aim of this research was to evaluate the effect of terebinth (Pistacia terebinthus L.) coffee addition (0.5, 1 and 2 %) on the chemical and physical properties, colour values, organic acid profiles, mineral contents and sensory characteristics of ice creams. The total solids, fat, titratable acidity, viscosity, first dripping time and complete melting time values, a (*) and b (*) colour properties, citric, lactic, acetic and butyric acid levels and Ca, Cu, Mg, Fe, K, Zn and Na concentrations of ice creams showed an increase with the increment of terebinth coffee amount, while protein, pH, L (*), propionic acid and orotic acid values decreased. However, Al and malic acid were not detected in any of the samples. The overall acceptability scores of the sensory properties showed that the addition of 1 % terebinth coffee to the ice cream was more appreciated by the panellists.

  4. The effect of terebinth (Pistacia terebinthus L.) coffee addition on the chemical and physical characteristics, colour values, organic acid profiles, mineral compositions and sensory properties of ice creams.

    PubMed

    Yüksel, Arzu Kavaz; Şat, Ihsan Güngör; Yüksel, Mehmet

    2015-12-01

    The aim of this research was to evaluate the effect of terebinth (Pistacia terebinthus L.) coffee addition (0.5, 1 and 2 %) on the chemical and physical properties, colour values, organic acid profiles, mineral contents and sensory characteristics of ice creams. The total solids, fat, titratable acidity, viscosity, first dripping time and complete melting time values, a (*) and b (*) colour properties, citric, lactic, acetic and butyric acid levels and Ca, Cu, Mg, Fe, K, Zn and Na concentrations of ice creams showed an increase with the increment of terebinth coffee amount, while protein, pH, L (*), propionic acid and orotic acid values decreased. However, Al and malic acid were not detected in any of the samples. The overall acceptability scores of the sensory properties showed that the addition of 1 % terebinth coffee to the ice cream was more appreciated by the panellists. PMID:26604374

  5. The PH gene determines fruit acidity and contributes to the evolution of sweet melons

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Acids are one of the three major components of fleshy fruit taste, together with sugars and volatile flavor compounds. However, the molecular-genetic control of acid accumulation in fruit is poorly understood and, to date, no genes responsible for acid accumulation in fleshy fruit have been function...

  6. Corrosion Behavior of E690 High-Strength Steel in Alternating Wet-Dry Marine Environment with Different pH Values

    NASA Astrophysics Data System (ADS)

    Wu, W.; Hao, W. K.; Liu, Z. Y.; Li, X. G.; Du, C. W.; Liao, W. J.

    2015-12-01

    The corrosion behavior and mechanism of E690 high-strength steel in marine environment with different pH values were studied through electrochemical technology and long-term alternating wet-dry cycle experiments combined with SEM and XRD. Results showed that the corrosion current density of E690 high-strength steel gradually increased with decreased pH. After long-term tests in alternating wet-dry marine environment with various pH values, uniform corrosion mainly occurred on E690 steel, accompanied by vast corrosion pitting. Weight loss analysis demonstrated that corrosion rate decreased with increased pH. Moreover, corrosion mechanism varied with pH, and hydrogen-evolution reaction greatly increased the E690 steel corrosion rate at low pH. Meanwhile, the compositions of corrosion products slightly differed with pH; these products consisted of Fe3O4, Fe2O3, α-FeOOH, β-FeOOH, γ-FeOOH, and amorphous substances. However, the rust-layer density varied. Cr in the rust layer promoted the densification of rust layer and improved the decay resistance of E690 steel.

  7. pH and ionic strength effects on the binding constant between a nitrogen-containing polycyclic aromatic compound and humic acid.

    PubMed

    Chang, Kuei-Chen; Lee, Chon-Lin; Hsieh, Ping-Chieh; Brimblecombe, Peter; Kao, Shu-Min

    2015-09-01

    Polycyclic aromatic compounds (PACs) are widespread environmental pollutants with a high potential to act as human carcinogens and mutagens. The behavior of PACs is significantly affected by their interactions with dissolved organic matter (DOM), such as their transport, solubility, bioavailability, and bioaccumulation in the aquatic environment. Being a basic PAC, benzo(h)quinoline (BQ) is the dominant species, as the solution's pH value is higher than BQ's pK a (pK a of BQ = 4.2). In contrast, benzo(h)quinolinium (BQH(+)) is the major species, as the solution's pH value is lower than its pK a. The binding constant (K DOC), measured by fluorescence quenching, between BQ/BQH(+) and Leonardite humic acid (LHA) would decrease 70 to 95 % and 20 to 90 % when increasing the ionic strength in acidic and neutral to basic conditions, respectively. The results can be attributed to the added cation (Na(+) and Mg(2+)), which forms a bridge with LHA and enhances the intramolecular reaction among these functional groups, therefore inducing the coiling up within the LHA molecule. In addition, the decrease of the K DOC with added MgCl2/MgSO4 (75-95 %) is higher than that with added NaCl/Na2SO4 (20-75 %), indicating that the K DOC was affected by the charge density of cations. The fluorescence intensity of BQH(+) in the absence of LHA (F 0) was found to decay only in the acidic solution with Cl(-), suggesting that Cl(-) might be a heavy atom serving as a quencher in an acidic solution. PMID:25940463

  8. An empirical method for estimating instream pre-mining pH and dissolved Cu concentration in catchments with acidic drainage and ferricrete

    USGS Publications Warehouse

    Nimick, D.A.; Gurrieri, J.T.; Furniss, G.

    2009-01-01

    Methods for assessing natural background water quality of streams affected by historical mining are vigorously debated. An empirical method is proposed in which stream-specific estimation equations are generated from relationships between either pH or dissolved Cu concentration in stream water and the Fe/Cu concentration ratio in Fe-precipitates presently forming in the stream. The equations and Fe/Cu ratios for pre-mining deposits of alluvial ferricrete then were used to reconstruct estimated pre-mining longitudinal profiles for pH and dissolved Cu in three acidic streams in Montana, USA. Primary assumptions underlying the proposed method are that alluvial ferricretes and modern Fe-precipitates share a common origin, that the Cu content of Fe-precipitates remains constant during and after conversion to ferricrete, and that geochemical factors other than pH and dissolved Cu concentration play a lesser role in determining Fe/Cu ratios in Fe-precipitates. The method was evaluated by applying it in a fourth, naturally acidic stream unaffected by mining, where estimated pre-mining pH and Cu concentrations were similar to present-day values, and by demonstrating that inflows, particularly from unmined areas, had consistent effects on both the pre-mining and measured profiles of pH and Cu concentration. Using this method, it was estimated that mining has affected about 480 m of Daisy Creek, 1.8 km of Fisher Creek, and at least 1 km of Swift Gulch. Mean values of pH decreased by about 0.6 pH units to about 3.2 in Daisy Creek and by 1-1.5 pH units to about 3.5 in Fisher Creek. In Swift Gulch, mining appears to have decreased pH from about 5.5 to as low as 3.6. Dissolved Cu concentrations increased due to mining almost 40% in Daisy Creek to a mean of 11.7 mg/L and as much as 230% in Fisher Creek to 0.690 mg/L. Uncertainty in the fate of Cu during the conversion of Fe-precipitates to ferricrete translates to potential errors in pre-mining estimates of as much as 0.25 units

  9. Adaptive responses of Bacillus cereus ATCC14579 cells upon exposure to acid conditions involve ATPase activity to maintain their internal pH

    PubMed Central

    Senouci-Rezkallah, Khadidja; Jobin, Michel P; Schmitt, Philippe

    2015-01-01

    This study examined the involvement of ATPase activity in the acid tolerance response (ATR) of Bacillus cereus ATCC14579 strain. In the current work, B. cereus cells were grown in anaerobic chemostat culture at external pH (pHe) 7.0 or 5.5 and at a growth rate of 0.2 h−1. Population reduction and internal pH (pHi) after acid shock at pH 4.0 was examined either with or without ATPase inhibitor N,N’-dicyclohexylcarbodiimide (DCCD) and ionophores valinomycin and nigericin. Population reduction after acid shock at pH 4.0 was strongly limited in cells grown at pH 5.5 (acid-adapted cells) compared with cells grown at pH 7.0 (unadapted cells), indicating that B. cereus cells grown at low pHe were able to induce a significant ATR and Exercise-induced increase in ATPase activity. However, DCCD and ionophores had a negative effect on the ability of B. cereus cells to survive and maintain their pHi during acid shock. When acid shock was achieved after DCCD treatment, pHi was markedly dropped in unadapted and acid-adapted cells. The ATPase activity was also significantly inhibited by DCCD and ionophores in acid-adapted cells. Furthermore, transcriptional analysis revealed that atpB (ATP beta chain) transcripts was increased in acid-adapted cells compared to unadapted cells before and after acid shock. Our data demonstrate that B. cereus is able to induce an ATR during growth at low pH. These adaptations depend on the ATPase activity induction and pHi homeostasis. Our data demonstrate that the ATPase enzyme can be implicated in the cytoplasmic pH regulation and in acid tolerance of B. cereus acid-adapted cells. PMID:25740257

  10. Ecto-alkaline phosphatase activity identified at physiological pH range on intact P19 and HL-60 cells is induced by retinoic acid.

    PubMed

    Scheibe, R J; Kuehl, H; Krautwald, S; Meissner, J D; Mueller, W H

    2000-01-01

    The activity of membrane-bound alkaline phosphatase (ALP) expressed on the external surface of cultured murine P19 teratocarcinoma and human HL-60 myeloblastic leukemia cells was studied at physiological pH using p-nitrophenylphosphate (pNPP) as substrate. The rate of substrate hydrolysis catalyzed by intact viable cells remained constant for eight successive incubations of 30 min and was optimal at micromolar substrate concentrations over the pH range 7.4-8.5. The value of apparent K(m) for pNPP in P19 and HL-60 cells was 120 microM. Hydrolytic activity of the ecto-enzyme at physiological pH decreased by the addition of levamisole, a specific and noncompetitive inhibitor of ALP (K(i) P19 = 57 microM; K(i) HL-60 = 50 microM). Inhibition of hydrolysis was reversed by removal of levamisole within 30 min. Retinoic acid (RA), which promotes the differentiation of P19 and HL-60 cells, induced levamisole-sensitive ecto-phosphohydrolase activity at pH 7.4. After its autophosphorylation by ecto-kinase activity, a 98-kDa membrane protein in P19 cells was found to be sensitive to ecto-ALP, and protein dephosphorylation increased after incubation of cells with RA for 24 h and 48 h. Orthovanadate, an inhibitor of all phosphatase activities, blocked the levamisole-sensitive dephosphorylation of the membrane phosphoproteins, while (R)-(-)-epinephrine reversed the effect by complexation of the inhibitor. The results demonstrate that the levamisole-sensitive phosphohydrolase activity on the cell surface is consistent with ecto-ALP activity degrading both physiological concentrations of exogenously added substrate and endogenous surface phosphoproteins under physiological pH conditions. The dephosphorylating properties of ecto-ALP are induced by RA, suggesting a specific function in differentiating P19 teratocarcinoma and HL-60 myeloblastic leukemia cells. PMID:10649440

  11. Pre-industrial atmospheric pollution: was it important for the pH of acid-sensitive Swedish lakes?

    PubMed

    Bindler, Richard; Korsman, Tom; Renberg, Ingemar; Högberg, Peter

    2002-09-01

    Acid rain has caused extensive surface water acidification in Sweden since the mid-20th century. Sulfur emissions from fossil-fuel burning and metal production were the main sources of acid deposition. In the public consciousness, acid deposition is strongly associated with the industrial period, in particular the last 50 years. However, studies of lake-water pH development and atmospheric pollution, based on analyses of lake sediment deposits, have shown the importance of a long-term perspective. Here, we present a conceptual argument, using the sediment record, that large-scale atmospheric acid deposition has impacted the environment since at least Medieval times. Sulfur sources were the pre-industrial mining and metal industries that produced silver, lead and other metals from sulfide ores. This early excess sulfur deposition in southern Sweden did not cause surface water acidification; on the contrary, it contributed to alkalization, i.e. increased pH and productivity of the lakes. Suggested mechanisms are that the excess sulfur caused enhanced cation exchange in catchment soils, and that it altered iron-phosphorus cycling in the lakes, which released phosphorus and increased lake productivity.

  12. MICROBIAL SULFATE REDUCTION AND METAL ATTENUATION IN PH 4 ACID MINE WATER

    EPA Science Inventory

    Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured for anaerobic bacteria over a range of pH (4 to 7.5). The molecular biology of sediments and cultures was studied to determine whether sulfate-reducing...

  13. More value from food waste: Lactic acid and biogas recovery.

    PubMed

    Kim, Mi-Sun; Na, Jeong-Geol; Lee, Mo-Kwon; Ryu, Hoyoung; Chang, Yong-Keun; Triolo, Jin M; Yun, Yeo-Myeong; Kim, Dong-Hoon

    2016-06-01

    Anaerobic digestion (AD) is one of the traditional technologies for treating organic solid wastes, but its economic benefit is sometimes questioned. To increase the economic feasibility of the treatment process, the aim of this study was to recover not only biogas from food waste but lactic acid (LA) as well. At first, LA fermentation of food waste (FW) was conducted using an indigenous mixed culture. During the operation, temperature was gradually increased from 35 °C to 55 °C, with the highest performance attained at 50 °C. At 50 °C and hydraulic retention time (HRT) of 1.0 d, LA concentration in the broth was 40 kg LA/m(3), corresponding to a yield of 1.6 mol LA/mol hexoseadded. Pyrosequencing results showed that Lactobacillus (97.6% of the total number of sequences) was the predominant species performing LA fermentation of FW. The fermented broth was then centrifuged and LA was extracted from the supernatant by the combined process of nanofiltration and water-splitting electrodialysis. The process could recover highly purified LA by removing 85% of mineral ions such as Na(+), K(+), Mg(2+), and Ca(2+) and 90% of residual carbohydrates. Meanwhile, the solid residue remained after centrifugation was further fermented to biogas by AD. At HRT 40 d (organic loading rate of 7 kg COD/m(3)/d), the highest volumetric biogas production rate of 3.5 m(3)/m(3)/d was achieved with a CH4 yield of 0.25 m(3) CH4/kg COD. The mass flow showed that 47 kg of LA and 54 m(3) of biogas could be recovered by the developed process from 1 ton of FW with COD removal efficiency of 70%. These products have a higher economic value 60 USD/ton FW compared to that of conventional AD (27 USD/ton FW).

  14. Self-assembly of zinc polymers based on a flexible linear ligand at different pH values: Syntheses, structures and fluorescent properties

    NASA Astrophysics Data System (ADS)

    Xu, Yan-Hong; Lan, Ya-Qian; Wang, Xin-Long; Zang, Hong-Ying; Shao, Kui-Zhan; Liao, Yi; Su, Zhong-Min

    2009-03-01

    Five novel coordination polymers, [Zn(imbz) 2] n ( 1), {[Zn(imbz) 2]·H 2O} n ( 2), [Zn(imbz)( μ2-OH)] n ( 3), [Zn 3(imbt) 2( p-bdc) 3] n ( 4), [Zn 4( μ3-OH) 2(imbt) 2( p-bdc) 3] n ( 5), (imbt = 4'-(imidazol-1-ylmethyl)benzonitrile, imbz - = 4'-(imidazol-1-ylmethyl)benzoate and p-bdc = terephthalic acid) have been hydrothermally prepared through systematically changing the pH values of reaction mixture, and structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray crystallography. Compounds 1 and 2 exhibit similar 2D (4,4) grid structures, whereas compound 2 contains a right-handed helix along b-axis. Compound 3 has a distorted diamond framework which was constructed via imbz - ligands and μ2-OH groups linking metal atoms. Compound 4 shows a 2D 6-connected network with trinuclear zinc clusters as secondary building units (SBUs), whereas 5 shows a distorted α-Po with tetranuclear zinc clusters as SBUs, in which p-bdc ligands act as bridges. Moreover, compounds 1- 5 all exhibit strong blue photoluminescence in the solid state at room temperature.

  15. Crystallogenesis of bacteriophage P22 tail accessory factor gp26 at acidic and neutral pH

    SciTech Connect

    Cingolani, Gino Andrews, Dewan; Casjens, Sherwood

    2006-05-01

    The crystallogenesis of bacteriophage P22 tail-fiber gp26 is described. To study possible pH-induced conformational changes in gp26 structure, native trimeric gp26 has been crystallized at acidic pH (4.6) and a chimera of gp26 fused to maltose-binding protein (MBP-gp26) has been crystallized at neutral and alkaline pH (7-10). Gp26 is one of three phage P22-encoded tail accessory factors essential for stabilization of viral DNA within the mature capsid. In solution, gp26 exists as an extended triple-stranded coiled-coil protein which shares profound structural similarities with class I viral membrane-fusion protein. In the cryo-EM reconstruction of P22 tail extracted from mature virions, gp26 forms an ∼220 Å extended needle structure emanating from the neck of the tail, which is likely to be brought into contact with the cell’s outer membrane when the viral DNA-injection process is initiated. To shed light on the potential role of gp26 in cell-wall penetration and DNA injection, gp26 has been crystallized at acidic, neutral and alkaline pH. Crystals of native gp26 grown at pH 4.6 diffract X-rays to 2.0 Å resolution and belong to space group P2{sub 1}, with a dimer of trimeric gp26 molecules in the asymmetric unit. To study potential pH-induced conformational changes in the gp26 structure, a chimera of gp26 fused to maltose-binding protein (MBP-gp26) was generated. Hexagonal crystals of MBP-gp26 were obtained at neutral and alkaline pH using the high-throughput crystallization robot at the Hauptman–Woodward Medical Research Institute, Buffalo, NY, USA. These crystals diffract X-rays to beyond 2.0 Å resolution. Structural analysis of gp26 crystallized at acidic, neutral and alkaline pH is in progress.

  16. Dual fluorescence of N-phenylanthranilic acid: Effect of solvents, pH and β-cyclodextrin

    NASA Astrophysics Data System (ADS)

    Rajendiran, N.; Balasubramanian, T.

    2007-11-01

    Spectral characteristics of N-phenylanthranilic acid (NPAA) have been studied in different solvents, pH and β-cyclodextrin (β-CD) and compared with anthranilic acid (2-aminobenzoic acid, 2ABA). In all solvents a dual fluorescence is observed in NPAA, whereas 2ABA gives single emission. Combining the results observed in the absorption, fluorescence emission and fluorescence excitation spectra, it is found that strong intramolecular hydrogen bonding (IHB) interactions present in NPAA molecule. The inclusion complex of NPAA with β-CD is analysed by UV-vis, fluorimetry, FT-IR, 1H NMR, scanning electron microscope and AM 1 method. The above spectral studies show that NPAA forms a 1:1 inclusion complex with β-CD and COOH group present in the β-CD cavity. A mechanism is proposed to explain the inclusion process.

  17. [pH values in the pharynx of the patients presenting with compromised nasal breathing of inflammatory and non-inflammatory genesis concomitant with gastroesophageal reflux disease].

    PubMed

    Subbotina, M V; Temnikova, I V; Onuchina, E V

    2015-01-01

    The objective of the present study was to estimate the influence of gastroesophageal reflux disease (GERD) on the pH values in the pharynx and nose. It included 87 patients at the age varying from 18 to 81 years admitted to the Irkutsk-based Railway Clinical Hospital and allocated to four groups. Group 1 was comprised of 25 patients presenting with gastroesophageal reflux disease and chronic rhinosinusitis (CRS), group 2 consisted of 29 patients with CRS in the absence of GERD, group 3 included 22 patients with nasal septum deformations (NSD) and GERD, group 4 included 11 patients with NSD and motor rhinitis without GERD. The control group was formed from 10 volunteers. pH was measured by the contact method with the use ofEkokhim indicator paper. Gastroesophageal reflux disease was diagnosed following the recommendations of the Montreal consensus. It was shown that pH values in the pharynx of the patients with compromised nasal breathing of any origin in combination with GERD were lower than in the absence of GERD and in the healthy volunteers. The study groups did not differ in terms of pH values in the nasal cavity. It is concluded that pH values 4 or lower may serve as the criterion for pharyngo-laryngeal reflux (PLR) concomitant with HERD while pH 5 occurs more frequently in the patients with compromised nasal breathing of any etiology, regardless of the presence or absence of GERD.Disordered nasal breathing of any genesis in the patients presenting with gastroesophageal reflux disease was associated with the feeling of the lump in the throat, congestion of the respiratory tract and the nose, pain in the ears, cardialgia, and irregular heartbeat. It isrecommended to use pH measurements as a criterion for diagnostics of pharyngo-laryngeal reflux in the patients presenting with gastroesophageal reflux disease.

  18. Effects of pH and fulvic acids concentration on the stability of fulvic acids--cerium (IV) oxide nanoparticle complexes.

    PubMed

    Oriekhova, Olena; Stoll, Serge

    2016-02-01

    The behavior of cerium (IV) oxide nanoparticles has been first investigated at different pH conditions. The point of zero charge was determined as well as the stability domains using dynamic light scattering, nanoparticle tracking analysis and scanning electron microscopy. A baseline hydrodynamic diameter of 180 nm was obtained indicating that individual CeO2 nanoparticles are forming small aggregates. Then we analyzed the particle behavior at variable concentrations of fulvic acids for three different pH-electrostatic scenarios corresponding to positive, neutral and negative CeO2 surface charges. The presence of fulvic acids was found to play a key role on the CeO2 stability via the formation of electrostatic complexes. It was shown that a small amount of fulvic acids (2 mg L(-1)), representative of environmental fresh water concentrations, is sufficient to stabilize CeO2 nanoparticles (50 mg L(-1)). When electrostatic complexes are formed between negatively charged FAs and positively charged CeO2 NPs the stability of such complexes is obtained with time (up to 7 weeks) as well as in pH changing conditions. Based on zeta potential variations we also found that the fulvic acids are changing the CeO2 acid-base surface properties. Obtained results presented here constitute an important outcome in the domain of risk assessment, transformation and removal of engineered nanomaterials released into the environment. PMID:26347935

  19. Proposal of a New SI Base Unit for Value. An Hedonic Estimation of the Physical Purchasing Power (PhPP) of Money.

    NASA Astrophysics Data System (ADS)

    Defilla, Steivan

    2006-03-01

    Hitherto, the purchasing power of money, i.e. its transaction value, has been measured in terms of inflation index numbers and consumer baskets. Consumer baskets are variable phenomena and their use as measurement units for value confuses the measuring with the measurand. We propose an invariant numeraire, or value unit, based on the market value of a Planck energy (1956 MJ). Planck units form a natural system of units independent of any civilization. The hedonic estimation of the PhPP of a currency differentiates energy by product as well as by thermodynamic quality (exergy). Following SI rules, we propose to name the value unit walras (Wal) in honour of the economist Leon Walras (1834 - 1910). One Wal can also be interpreted as the minimum cost of physiological life of a reference person during one year. The study uses official disaggregated Swiss Producer and Consumer Price Index data and estimates the PhPP of the Swiss franc in 2003.

  20. The toxic effect and bioaccumulation in aquatic oligochaete Limnodrilus hoffmeisteri after combined exposure to cadmium and perfluorooctane sulfonate at different pH values.

    PubMed

    Qu, Ruijuan; Liu, Jiaoqin; Wang, Liansheng; Wang, Zunyao

    2016-06-01

    Cadmium (Cd) and Perfluorooctane sulfonate (PFOS) have been detected in aquatic environment. In this study, we investigated the acute effect, bioaccumulation and oxidative stress status in the aquatic oligocheate Limnodrilus hoffmeisteri after exposure to Cd and PFOS at different pH values. In the studied pH range, acute Cd toxicity was significantly enhanced with pH increasing from 6.2 to 8.0, and the 48h-EC50 of Cd was (significantly) decreased in the presence of PFOS. Bioaccumulation analysis results show that the accumulated Cd/PFOS in single exposure group increased with increasing exposure concentrations, and co-exposure makes internal Cd concentration significantly lowered for Cd(0.1) group at pH 8.0. Significant changes in superoxide dismutase activity, glutathione level and malondialdehyde content were observed in single and combined treatments. Based on IBR value, single Cd and PFOS exposure caused largest damage to the antioxidant defense system at pH 8.0 and pH 6.2, respectively, while the harmful effects of joint exposure were always the "compromise" between single Cd and PFOS exposure. This work could provide useful information for the risk assessment of co-exposure to perfluorinated compounds and heavy metals in natural environment.

  1. Salinity and pH affect Na+-montmorillonite dissolution and amino acid adsorption: a prebiotic chemistry study

    NASA Astrophysics Data System (ADS)

    Farias, Ana Paula S. F.; Tadayozzi, Yasmin S.; Carneiro, Cristine E. A.; Zaia, Dimas A. M.

    2014-06-01

    The adsorption of amino acids onto minerals in prebiotic seas may have played an important role for their protection against hydrolysis and formation of polymers. In this study, we show that the adsorption of the prebiotic amino acids, glycine (Gly), α-alanine (α-Ala) and β-alanine (β-Ala), onto Na+-montmorillonite was dependent on salinity and pH. Specifically, adsorption decreased from 58.3-88.8 to 0-48.9% when salinity was increased from 10 to 100-150% of modern seawater. This result suggests reduced amino acid adsorption onto minerals in prebiotic seas, which may have been even more saline than the tested conditions. Amino acids also formed complexes with metals in seawater, affecting metal adsorption onto Na+-montmorillonite, and amino acid adsorption was enhanced when added before Na+-montmorillonite was exposed to high saline solutions. Also, the dissolution of Na+-montmorillonite was reduced in the presence of amino acids, with β-Ala being the most effective. Thus, prebiotic chemistry experiments should also consider the integrity of minerals in addition to their adsorption capacity.

  2. The renal response to chronic mineral acid feeding: a re-examination of the role of systemic pH.

    PubMed

    Madias, N E; Zelman, S J

    1986-03-01

    It has been widely held that systemic acidemia represents the proximate event signaling the kidney to elicit its acidification response to chronic metabolic acidosis. However, a previous study from this laboratory has cast serious doubt on the validity of this conventional viewpoint. When a large acid load (7 mEq/kg/day) was fed chronically to dogs as HCl, H2SO4 or HNO3, net acid excretion increased similarly in all three groups of animals despite wide variability in the prevailing systemic acid-base composition. Marked or moderate hypobicarbonatemia and acidemia were observed in the HCl- or H2SO4-fed animals respectively, but strikingly, plasma [HCO3-] and pH did not change significantly from the control in the HNO3-fed animals. That study concluded that the renal response to chronic mineral acid feeding appears to be triggered, not by acidemia, but by the interplay of sodium delivery to and sodium avidity of the distal nephron as modulated by the reabsorbability of the "acid" anion. We have re-examined the above provocative conclusion in the light of the observation that the only evidence for a dissociation of the renal response from systemic acidemia in that study was derived from preprandial (8:00 a.m.) blood samples obtained some 23 hr after the ingestion of the daily acid load (administered at 9:00 a.m.). We investigated the diurnal variation of plasma acid-base composition in two groups of dogs fed chronically a large acid load (7 mEq/kg/day) as either HCl or HNO3. Both groups exhibited significant diurnal oscillations of plasma acid-base composition.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3009955

  3. Photonic crystal fiber interferometric pH sensor based on polyvinyl alcohol/polyacrylic acid hydrogel coating.

    PubMed

    Hu, Pengbing; Dong, Xinyong; Wong, Wei Chang; Chen, Li Han; Ni, Kai; Chan, Chi Chiu

    2015-04-01

    We present a simple photonic crystal fiber interferometer (PCFI) that operates in reflection mode for pH measurement. The sensor is made by coating polyvinyl alcohol/polyacrylic acid (PVA/PAA) hydrogel onto the surface of the PCFI, constructed by splicing a stub of PCF at the distal end of a single-mode fiber with its free end airhole collapsed. The experimental results demonstrate a high average sensitivity of 0.9 nm/pH unit for the 11 wt.% PVA/PAA coated sensor in the pH range from 2.5 to 6.5. The sensor also displays high repeatability and stability and low cross-sensitivity to temperature. Fast, reversible rise and fall times of 12 s and 18 s, respectively, are achieved for the sensor time response. PMID:25967171

  4. Interactions of Zn(II) Ions with Humic Acids Isolated from Various Type of Soils. Effect of pH, Zn Concentrations and Humic Acids Chemical Properties

    PubMed Central

    Boguta, Patrycja; Sokołowska, Zofia

    2016-01-01

    The main aim of this study was the analysis of the interaction between humic acids (HAs) from different soils and Zn(II) ions at wide concentration ranges and at two different pHs, 5 and 7, by using fluorescence and FTIR spectroscopy, as well as potentiometric measurements. The presence of a few areas of HAs structures responsible for Zn(II) complexing was revealed. Complexation at α-sites (low humified structures of low-molecular weight and aromatic polycondensation) and β-sites (weakly humified structures) was stronger at pH 7 than 5. This trend was not observed for γ-sites (structures with linearly-condensed aromatic rings, unsaturated bonds and large molecular weight). The amount of metal complexed at pH5 and 7 by α and γ-structures increased with a decrease in humification and aromaticity of HAs, contrary to β-areas where complexation increased with increasing content of carboxylic groups. The stability of complexes was higher at pH 7 and was the highest for γ-structures. At pH 5, stability decreased with C/N increase for α-areas and -COOH content increase for β-sites; stability increased with humification decrease for γ-structures. The stability of complexes at α and β-areas at pH 7 decreased with a drop in HAs humification. FTIR spectra at pH 5 revealed that the most-humified HAs tended to cause bidentate bridging coordination, while in the case of the least-humified HAs, Zn caused bidentate bridging coordination at low Zn additions and bidentate chelation at the highest Zn concentrations. Low Zn doses at pH 7 caused formation of unidentate complexes while higher Zn doses caused bidentate bridging. Such processes were noticed for HAs characterized by high oxidation degree and high oxygen functional group content; where these were low, HAs displayed bidentate bridging or even bidentate chelation. To summarize, the above studies have showed significant impact of Zn concentration, pH and some properties of HAs on complexation reactions of humic

  5. Interactions of Zn(II) Ions with Humic Acids Isolated from Various Type of Soils. Effect of pH, Zn Concentrations and Humic Acids Chemical Properties.

    PubMed

    Boguta, Patrycja; Sokołowska, Zofia

    2016-01-01

    The main aim of this study was the analysis of the interaction between humic acids (HAs) from different soils and Zn(II) ions at wide concentration ranges and at two different pHs, 5 and 7, by using fluorescence and FTIR spectroscopy, as well as potentiometric measurements. The presence of a few areas of HAs structures responsible for Zn(II) complexing was revealed. Complexation at α-sites (low humified structures of low-molecular weight and aromatic polycondensation) and β-sites (weakly humified structures) was stronger at pH 7 than 5. This trend was not observed for γ-sites (structures with linearly-condensed aromatic rings, unsaturated bonds and large molecular weight). The amount of metal complexed at pH5 and 7 by α and γ-structures increased with a decrease in humification and aromaticity of HAs, contrary to β-areas where complexation increased with increasing content of carboxylic groups. The stability of complexes was higher at pH 7 and was the highest for γ-structures. At pH 5, stability decreased with C/N increase for α-areas and -COOH content increase for β-sites; stability increased with humification decrease for γ-structures. The stability of complexes at α and β-areas at pH 7 decreased with a drop in HAs humification. FTIR spectra at pH 5 revealed that the most-humified HAs tended to cause bidentate bridging coordination, while in the case of the least-humified HAs, Zn caused bidentate bridging coordination at low Zn additions and bidentate chelation at the highest Zn concentrations. Low Zn doses at pH 7 caused formation of unidentate complexes while higher Zn doses caused bidentate bridging. Such processes were noticed for HAs characterized by high oxidation degree and high oxygen functional group content; where these were low, HAs displayed bidentate bridging or even bidentate chelation. To summarize, the above studies have showed significant impact of Zn concentration, pH and some properties of HAs on complexation reactions of humic

  6. Interactions of Zn(II) Ions with Humic Acids Isolated from Various Type of Soils. Effect of pH, Zn Concentrations and Humic Acids Chemical Properties.

    PubMed

    Boguta, Patrycja; Sokołowska, Zofia

    2016-01-01

    The main aim of this study was the analysis of the interaction between humic acids (HAs) from different soils and Zn(II) ions at wide concentration ranges and at two different pHs, 5 and 7, by using fluorescence and FTIR spectroscopy, as well as potentiometric measurements. The presence of a few areas of HAs structures responsible for Zn(II) complexing was revealed. Complexation at α-sites (low humified structures of low-molecular weight and aromatic polycondensation) and β-sites (weakly humified structures) was stronger at pH 7 than 5. This trend was not observed for γ-sites (structures with linearly-condensed aromatic rings, unsaturated bonds and large molecular weight). The amount of metal complexed at pH5 and 7 by α and γ-structures increased with a decrease in humification and aromaticity of HAs, contrary to β-areas where complexation increased with increasing content of carboxylic groups. The stability of complexes was higher at pH 7 and was the highest for γ-structures. At pH 5, stability decreased with C/N increase for α-areas and -COOH content increase for β-sites; stability increased with humification decrease for γ-structures. The stability of complexes at α and β-areas at pH 7 decreased with a drop in HAs humification. FTIR spectra at pH 5 revealed that the most-humified HAs tended to cause bidentate bridging coordination, while in the case of the least-humified HAs, Zn caused bidentate bridging coordination at low Zn additions and bidentate chelation at the highest Zn concentrations. Low Zn doses at pH 7 caused formation of unidentate complexes while higher Zn doses caused bidentate bridging. Such processes were noticed for HAs characterized by high oxidation degree and high oxygen functional group content; where these were low, HAs displayed bidentate bridging or even bidentate chelation. To summarize, the above studies have showed significant impact of Zn concentration, pH and some properties of HAs on complexation reactions of humic

  7. An interpretation of differences between field and laboratory pH values reported by the national atmospheric deposition program/national trends network monitoring program

    USGS Publications Warehouse

    Bigelow, D.S.; Sisterson, D.L.; Schroder, L.J.

    1989-01-01

    Differences between field and laboratory pH values reported by the National Atmospheric Deposition Program/National Trends Network (NADP/NTN) monitoring program from 1984 through 1986 are investigated. Median differences in hydrogen ion concentration between laboratory and field pH determinations at sites averaged -4.6 ??equiv/L in natural precipitation samples on an annual basis. The median difference found in external quality assurance samples analyzed during the same time period was -11 ??equiv/L. The results suggest a systematic bias in pH values reported by the NADP/NTN network. The bias appears to have a fixed component of approximately -7 ??equiv/L, which can be attributed to the sampling bucket and lid, and a seasonal and regional component that ranges from +4 to -22 ??equiv/L at the 10th and 90th percentiles. Differences were found to be independent of sample pH and sample volume. The magnitude of the bias has implications for the interpretation of previously published pH and hydrogen ion concentration and deposition values in the western United States.

  8. Poly-dopamine-beta-cyclodextrin: A novel nanobiopolymer towards sensing of some amino acids at physiological pH.

    PubMed

    Hasanzadeh, Mohammad; Sadeghi, Sattar; Bageri, Leyla; Mokhtarzadeh, Ahad; Karimzadeh, Ayub; Shadjou, Nasrin; Mahboob, Soltanali

    2016-12-01

    A novel nanobiopolymer film was electrodeposited on the surface of glassy carbon through cyclic voltammetry from dopamine, β-cyclodextrin, and phosphate buffer solution in physiological pH (7.40). The electrochemical behavior of polydopamine-Beta-cyclodextrin modified glassy carbon electrode was investigated for electro-oxidation and determination of some amino acids (l-Cysteine, l-Tyrosine, l-Glycine, and l-Phenylalanine). The modified electrode was applied for selected amino acid detection at physiological pH using cyclic voltammetry, differential pulse voltammetry and chronoamperometry, chronocoulometery. The linear concentration range of the proposed sensor for the l-Glycine, l-Cysteine, l-Tyrosine, and l-Phenylalanine were 0.2-70, 0.06-0.2, 0.01-0.1, and 0.2-10μM, while low limit of quantifications were 0.2, 0.06, 0.01, and 0.2μM, respectively. The modified electrode shows many advantages as an amino acid sensor such as simple preparation method without using any specific electron transfer mediator or specific reagent, good sensitivity, short response time, and long term stability. PMID:27612722

  9. Poly-dopamine-beta-cyclodextrin: A novel nanobiopolymer towards sensing of some amino acids at physiological pH.

    PubMed

    Hasanzadeh, Mohammad; Sadeghi, Sattar; Bageri, Leyla; Mokhtarzadeh, Ahad; Karimzadeh, Ayub; Shadjou, Nasrin; Mahboob, Soltanali

    2016-12-01

    A novel nanobiopolymer film was electrodeposited on the surface of glassy carbon through cyclic voltammetry from dopamine, β-cyclodextrin, and phosphate buffer solution in physiological pH (7.40). The electrochemical behavior of polydopamine-Beta-cyclodextrin modified glassy carbon electrode was investigated for electro-oxidation and determination of some amino acids (l-Cysteine, l-Tyrosine, l-Glycine, and l-Phenylalanine). The modified electrode was applied for selected amino acid detection at physiological pH using cyclic voltammetry, differential pulse voltammetry and chronoamperometry, chronocoulometery. The linear concentration range of the proposed sensor for the l-Glycine, l-Cysteine, l-Tyrosine, and l-Phenylalanine were 0.2-70, 0.06-0.2, 0.01-0.1, and 0.2-10μM, while low limit of quantifications were 0.2, 0.06, 0.01, and 0.2μM, respectively. The modified electrode shows many advantages as an amino acid sensor such as simple preparation method without using any specific electron transfer mediator or specific reagent, good sensitivity, short response time, and long term stability.

  10. Value of estimating methylamalonic acid excretion in anaemia.

    PubMed

    Green, A E; Pegrum, G D

    1968-09-01

    A rapid technique suitable for routine pathology laboratories has been used to estimate methylmalonic acid excretion in a 24-hour urine collection following a 10g. valine load. Levels above 40 mg./24 hours were found only in patients with vitamin B(12) deficiency. Patients with pernicious anaemia treated more than 24 hours before urine collection and patients with other types of anaemia had methylmalonic acid levels below 25 mg./24 hours.This method of demonstrating vitamin B(12) deficiency can be applied rapidly in debilitated patients so that specific treatment can be instituted within 36 hours of admission.

  11. Whey protein/polysaccharide-stabilized emulsions: Effect of polymer type and pH on release and topical delivery of salicylic acid.

    PubMed

    Combrinck, Johann; Otto, Anja; du Plessis, Jeanetta

    2014-06-01

    Emulsions are widely used as topical formulations in the pharmaceutical and cosmetic industries. They are thermodynamically unstable and require emulsifiers for stabilization. Studies have indicated that emulsifiers could affect topical delivery of actives, and this study was therefore designed to investigate the effects of different polymers, applied as emulsifiers, as well as the effects of pH on the release and topical delivery of the active. O/w emulsions were prepared by the layer-by-layer technique, with whey protein forming the first layer around the oil droplets, while either chitosan or carrageenan was subsequently adsorbed to the protein at the interface. Additionally, the emulsions were prepared at three different pH values to introduce different charges to the polymers. The active ingredient, salicylic acid, was incorporated into the oil phase of the emulsions. Physical characterization of the resulting formulations, i.e., droplet size, zeta potential, stability, and turbidity in the water phase, was performed. Release studies were conducted, after which skin absorption studies were performed on the five most stable emulsions, by using Franz type diffusion cells and utilizing human, abdominal skin membranes. It was found that an increase in emulsion droplet charge could negatively affect the release of salicylic acid from these formulations. Contrary, positively charged emulsion droplets were found to enhance dermal and transdermal delivery of salicylic acid from emulsions. It was hypothesized that electrostatic complex formation between the emulsifier and salicylic acid could affect its release, whereas electrostatic interaction between the emulsion droplets and skin could influence dermal/transdermal delivery of the active.

  12. AN HPLC METHOD WITH UVDETECTION, PH CONTROL, AND REDUCTIVE ASCORBIC ACID FOR CYANURIC ACID ANALYSIS IN WATER

    EPA Science Inventory

    Every year over 250 million pounds of cyanuric acid (CA) and chlorinated isocyanurates are produced industrially. These compounds are standard ingredients in formulations for household bleaches, industrial cleansers, dishwasher compounds, general sanitizers, and chlorine stabiliz...

  13. AN HPLC METHOD WITH UV DETECTION, PH CONTROL, AND REDUCTIVE ASCORBIC ACID FOR CYANURIC ACID ANALYSIS IN WATER

    EPA Science Inventory

    Every year over 250 million pounds of cyanuric acid (CA) and chloroisocyanurates are produced industrially. These compounds are standard ingredients in formulations for household bleaches, industrial cleansers, dishwasher compounds, general sanitizers, and chlorine stabilizers. ...

  14. FIA acid-base titrations with a new flow-through pH detector.

    PubMed

    Kahlert, H; Pörksen, J R; Behnert, J; Scholz, F

    2005-08-01

    A pH-sensitive detector for flow-through potentiometry based on a graphite/quinhydrone composite electrode was applied for flow-injection analysis (FIA) titrations. Hydrochloric acid and acetic acid were titrated by injection of samples into a sodium hydroxide carrier solution. System conditions were optimised by variation of flow rate, injection volume and titrant concentration. The parameters sampling frequency, residence time and dispersion coefficient were determined. The evaluation of peak width (time between the two inflection points on each side of the peak), peak area and slope of the raising edge of the peak lead were studied with respect to their use for calibration. Hydrochloric acid and acetic acid could be titrated down to a concentration of 2 x 10(-4) mol L(-1) using 150-microL injection volumes, which is almost ten times lower than can be achieved using colour indicators and a spectrophotometric detection.

  15. Surviving the Acid Test: Responses of Gram-Positive Bacteria to Low pH

    PubMed Central

    Cotter, Paul D.; Hill, Colin

    2003-01-01

    Gram-positive bacteria possess a myriad of acid resistance systems that can help them to overcome the challenge posed by different acidic environments. In this review the most common mechanisms are described: i.e., the use of proton pumps, the protection or repair of macromolecules, cell membrane changes, production of alkali, induction of pathways by transcriptional regulators, alteration of metabolism, and the role of cell density and cell signaling. We also discuss the reponses of Listeria monocytogenes, Rhodococcus, Mycobacterium, Clostridium perfringens, Staphylococcus aureus, Bacillus cereus, oral streptococci, and lactic acid bacteria to acidic environments and outline ways in which this knowledge has been or may be used to either aid or prevent bacterial survival in low-pH environments. PMID:12966143

  16. Two distinct etiologies of gastric cardia adenocarcinoma: interactions among pH, Helicobacter pylori, and bile acids.

    PubMed

    Mukaisho, Ken-Ichi; Nakayama, Takahisa; Hagiwara, Tadashi; Hattori, Takanori; Sugihara, Hiroyuki

    2015-01-01

    Gastric cancer can be classified as cardia and non-cardia subtypes according to the anatomic site. Although the gastric cancer incidence has decreased steadily in several countries over the past 50 years, the incidence of cardia cancers and esophageal adenocarcinoma (EAC) continue to increase. The etiological factors involved in the development of both cardia cancers and EACs are associated with high animal fat intake, which causes severe obesity. Central obesity plays roles in cardiac-type mucosa lengthening and partial hiatus hernia development. There are two distinct etiologies of cardia cancer subtypes: one associated with gastroesophageal reflux (GER), which predominantly occurs in patients without Helicobacter pylori (H. pylori) infection and resembles EAC, and the other associated with H. pylori atrophic gastritis, which resembles non-cardia cancer. The former can be developed in the environment of high volume duodenal content reflux, including bile acids and a higher acid production in H. pylori-negative patients. N-nitroso compounds, which are generated from the refluxate that includes a large volume of bile acids and are stabilized in the stomach (which has high levels of gastric acid), play a pivotal role in this carcinogenesis. The latter can be associated with the changing colonization of H. pylori from the distal to the proximal stomach with atrophic gastritis because a high concentration of soluble bile acids in an environment of low acid production is likely to act as a bactericide or chemorepellent for H. pylori in the distal stomach. The manuscript introduces new insights in causative factors of adenocarcinoma of the cardia about the role of bile acids in gastro-esophageal refluxate based upon robust evidences supporting interactions among pH, H. pylori, and bile acids. PMID:26029176

  17. Waste activated sludge hydrolysis and short-chain fatty acids accumulation under mesophilic and thermophilic conditions: effect of pH.

    PubMed

    Zhang, Peng; Chen, Yinguang; Zhou, Qi

    2009-08-01

    The effect of pH (4.0-11.0) on waste activated sludge (WAS) hydrolysis and short-chain fatty acids (SCFAs) accumulation under mesophilic and thermophilic conditions were investigated. The WAS hydrolysis increased markedly in thermophilic fermentation compared to mesophilic fermentation at any pH investigated. The hydrolysis at alkaline pHs (8.0-11.0) was greater than that at acidic pHs, but both of the acidic and alkaline hydrolysis was higher than that pH uncontrolled under either mesophilic or thermophilic conditions. No matter in mesophilic or thermophilic fermentation, the accumulation of SCFAs at alkaline pHs was greater than at acidic or uncontrolled pHs. The optimum SCFAs accumulation was 0.298g COD/g volatile suspended solids (VSS) with mesophilic fermentation, and 0.368 with thermophilic fermentation, which was observed respectively at pH 9.0 and fermentation time 5 d and pH 8.0 and time 9 d. The maximum SCFAs productions reported in this study were much greater than that in the literature. The analysis of the SCFAs composition showed that acetic acid was the prevalent acid in the accumulated SCFAs at any pH investigated under both temperatures, followed by propionic acid and n-valeric acid. Nevertheless, during the entire mesophilic and thermophilic fermentation the activity of methanogens was inhibited severely at acid or alkaline pHs, and the highest methane concentration was obtained at pH 7.0 in most cases. The studies of carbon mass balance showed that during WAS fermentation the reduction of VSS decreased with the increase of pH, and the thermophilic VSS reduction was greater than the mesophilic one. Further investigation indicated that most of the reduced VSS was converted to soluble protein and carbohydrate and SCFAs in two fermentations systems, while little formed methane and carbon dioxide.

  18. Production of Value-added Products by Lactic Acid Bacteria

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lactic acid bacteria (LAB) are a group of facultative anaerobic, catalase negative, nonmotile and nonsporeforming–Gram positive bacteria. Most LAB utilize high energy C sources including monomer sugars to produce energy to maintain cellular structure and function. This anaerobic fermentation proce...

  19. Effects of root medium pH on water transport in paper birch (Betula papyrifera) seedlings in relation to root temperature and abscisic acid treatments.

    PubMed

    Kamaluddin, M; Zwiazek, Janusz J

    2004-10-01

    We investigated the effects of root medium pH on water transport in whole-plant and detached roots of paper birch (Betula papyrifera Marsh.). Exposure of seedling roots to pH 4 and 8 significantly decreased root hydraulic conductivity (Lp) and stomatal conductance (gs), compared with pH 6. When roots of solution-culture-grown (pH 6) seedlings were transferred to pH 4 or 8, their steady-state water flow (Qv) declined within minutes, followed by a decline in gs. The root oxygen uptake rates were not significantly affected by the pH treatments. Treatment of roots with mercuric chloride resulted in a large decrease in Qv at pH 6; the extent of this decrease was similar to that brought about by pH 4 and 8. Lowering root temperature from 21 to 4 degrees C decreased Qv irrespective of medium pH. Low root temperatures did not offset the effects of medium pH 4 on Qv and the roots in this treatment had a high activation energy for water flow. Conversely, roots exposed to pH 8 had a low activation energy, similar to that at pH 6. When 2 micro M abscisic acid, (+/-)-cis-trans-ABA, was added to the root medium, Qv increased in roots that were incubated at pH 6. It also increased slightly in roots incubated at pH 4, but not at pH 8. The increase at pH 4 and 6 was temperature-dependent, occurring at 21 degrees C, but not 4 degrees C. We suggest that the pH treatments are responsible for altering root water flow properties through their effects on the activity of water channels. These results support the concept that ABA effects on water channels are modulated by other, possibly metabolic- and pH-dependent factors.

  20. Improving the ratio of monacolin K to citrinin production of Monascus purpureus NTU 568 under dioscorea medium through the mediation of pH value and ethanol addition.

    PubMed

    Lee, Chun-Lin; Hung, Hsi-Kai; Wang, Jyh-Jye; Pan, Tzu-Ming

    2007-08-01

    Using dioscorea root as substrate of Monascus species was found to stimulate monacolin K (cholesterol-lowering agent) formation in our previous study, but the mycotoxin-citrinin has never been studied. This study used dioscorea root as the liquid medium to culture Monascus purpureus NTU 568 using a 6.6 L jar fermentor. Culture pH value, dioscorea concentration, and ethanol concentration were used as the factors of response surface methodology (RSM) to investigate the optimal culture condition for high monacolin K production and low citrinin formation. Monacolin K and citrinin formation of M. purpureus NTU 568 under submerged dioscorea medium were respectively found to be significantly formed by 148% and 147%, as compared to that under submerged rice medium. The reason is due to the pH value (3.5) of dioscorea medium involved in the formation of Monascus cell amount and secondary metabolite. RSM results further indicated that lowering the pH value to 2.5 would result in high monacolin K and citrinin concentrations as well as high biomass in fixed dioscorea amount, implying that pH value may stimulate the formation of monacolin K and citrinin through increasing Monascus cell amount. Lowering dioscorea and ethanol concentration was able to increase the ratio of monacolin K level to citrinin level. The optimal culture condition (pH 5.7, 1% dioscorea concentration, and 0.5% ethanol concentration) would increase monacolin K levels to 27.9 mg/g (by 47%) and decrease citrinin level to 2.15 microg/g (by 54%), as compared to control conditions (pH 3.5, 5% dioscorea, and ethanol free).

  1. [Reference values of folic acid for the Venezuelan population].

    PubMed

    García-Casal, María Nieves; Carias, Diamela; Soto de Sanabria, Ingrid; Victoria López, Ana

    2013-12-01

    The review on folic acid requirements for Venezuela comprise the definitions adopted worldwide known as Dietary Reference Intakes (DRIs) that include Recommended Dietary Allowance (RDA), Estimated Average Requirement (EAR), Adequate Intake (AI) and Tolerable Upper Intake Levels (UL). In contrast with the situation in some countries, that required adjustments in fortification policies in order to avoid excessive folic acid consumption, in Venezuela several studies show an elevated prevalence of deficiency. National evidence at this point is insufficient to establish the recommendation, and as in the 2000 review of the Venezuelan RDAs, the actual recommendations are based on the reported for the United States population. The Recommended Dietary Allowances for Venezuela are 65-80 microg/day for infants less than 1 year old, 150-300 microg/day for children and 400 microg/day for adolescents and adults, increasing to 600 microg/day during pregnancy and to 500 microg/day during lactation. The estimated average requirement is 120-250 microg/day for children, 330 microg/day for adolescents, 320 microg/day for adults, 520 microg/day for pregnancy and 450 microg/day during lactation. The tolerable upper intake levels for folic acid are 300-600 microg/day for children, 800 microg/day for adolescents and 1000 microg/day for adults. During pregnancy and lactation the UL is 800 microg/day for pregnant and lactating women between 14 and 18 years of age, and 1000 microg/day for older pregnant and lactating women. The continuous evaluation of folic acid status is important to design adequate and efficient policies to control both, the deficiency and the excess of folic acid consumption.

  2. Determination and Visualization of pH Values in Anaerobic Digestion of Water Hyacinth and Rice Straw Mixtures Using Hyperspectral Imaging with Wavelet Transform Denoising and Variable Selection

    PubMed Central

    Zhang, Chu; Ye, Hui; Liu, Fei; He, Yong; Kong, Wenwen; Sheng, Kuichuan

    2016-01-01

    Biomass energy represents a huge supplement for meeting current energy demands. A hyperspectral imaging system covering the spectral range of 874–1734 nm was used to determine the pH value of anaerobic digestion liquid produced by water hyacinth and rice straw mixtures used for methane production. Wavelet transform (WT) was used to reduce noises of the spectral data. Successive projections algorithm (SPA), random frog (RF) and variable importance in projection (VIP) were used to select 8, 15 and 20 optimal wavelengths for the pH value prediction, respectively. Partial least squares (PLS) and a back propagation neural network (BPNN) were used to build the calibration models on the full spectra and the optimal wavelengths. As a result, BPNN models performed better than the corresponding PLS models, and SPA-BPNN model gave the best performance with a correlation coefficient of prediction (rp) of 0.911 and root mean square error of prediction (RMSEP) of 0.0516. The results indicated the feasibility of using hyperspectral imaging to determine pH values during anaerobic digestion. Furthermore, a distribution map of the pH values was achieved by applying the SPA-BPNN model. The results in this study would help to develop an on-line monitoring system for biomass energy producing process by hyperspectral imaging. PMID:26901202

  3. Probing the general time scale question of boronic acid binding with sugars in aqueous solution at physiological pH.

    PubMed

    Ni, Nanting; Laughlin, Sarah; Wang, Yingji; Feng, You; Zheng, Yujun; Wang, Binghe

    2012-05-01

    The boronic acid group is widely used in chemosensor design due to its ability to reversibly bind diol-containing compounds. The thermodynamic properties of the boronic acid-diol binding process have been investigated extensively. However, there are few studies of the kinetic properties of such binding processes. In this report, stopped-flow method was used for the first time to study the kinetic properties of the binding between three model arylboronic acids, 4-, 5-, and 8-isoquinolinylboronic acids, and various sugars. With all the boronic acid-diol pairs examined, reactions were complete within seconds. The k(on) values with various sugars follow the order of D-fructose>D-tagatose>D-mannose>D-glucose. This trend tracks the thermodynamic binding affinities for these sugars and demonstrates that the 'on' rate is the key factor determining the binding constant.

  4. Effects of temperature and pH on adsorption of basic brown 1 by the bacterial biopolymer poly(gamma-glutamic acid).

    PubMed

    Inbaraj, B Stephen; Chiu, C P; Ho, G H; Yang, J; Chen, B H

    2008-03-01

    Poly(gamma-glutamic acid) (gamma-PGA), an extracellular polymeric substance (EPS) synthesized by Bacillus species, was explored to study its interaction with the basic brown 1 dye by conducting a systematic batch adsorption study as affected by two critical parameters, temperature and pH. Adsorption isotherms were closely predicted by Temkin equation among the eight isotherm models tested. The rate of adsorption was very rapid attaining equilibrium within 60 min and the kinetics were well described by both modified second-order and pseudo second-order models. Boyd's ion exchange model, which assumes exchanges of ions to be a chemical phenomenon, also fitted the kinetic data precisely. The adsorption rate increased with increasing solution temperature, however, a reversed trend was observed for the adsorption capacity. Changes in enthalpy, entropy and free energy values revealed dye adsorption by gamma-PGA to be an exothermic and spontaneous process involving no structural modification in gamma-PGA, whereas the activation energy of 37.21 kJ/mol indicated dye adsorption to be reaction-controlled. Following a rise in solution pH, the dye adsorption increased and reached a plateau at pH 5, while the maximum release of dye from spent gamma-PGA occurred at pH 1.5, suggesting a possible ion exchange mechanism. Ion exchange adsorption of basic dyes by gamma-PGA was further proved by the presence of two new IR bands at approximately 1600 and 1405.72 cm(-1), representing asymmetric and symmetric stretching vibration of carboxylate anion, for dye-treated gamma-PGA.

  5. Influence on Levels of Information as Presented by Different Technologies on Students' Understanding of Acid, Base, and pH Concepts.

    ERIC Educational Resources Information Center

    Nakhleh, Mary B.; Krajcik, Joseph S.

    1994-01-01

    Involves secondary students in a study designed to allow investigation into how different levels of information presented by various technologies (chemical indicators, pH meters, and microcomputer-based laboratories-MBLs) affected students' understanding of acid, base, and pH concepts. Results showed that students using MBLs exhibited a greater…

  6. [Diagnostic value of lochial pH, pCO2,and pO2 in puerperal endometritis].

    PubMed

    Nikonov, A P; Burlev, V A; Ankirskaia, A S; Sergeev, M V; Lutfullaeva, N A

    1991-06-01

    A new method has been developed for rapid diagnosis of puerperial endometritis, based on measurements of lochial pH, pCO2, and pO2. Endometritis development is associated with acidosis in the uterine cavity (pH 6.8-7.2), elevation of pCO2 to make 40-70 mm Hg, and reduction of pO2 to make 40-80 mm Hg. The degree of these shifts is in direct relationship with the inflammatory process severity. The method is simple, almost noninvasive, and quite reliable. PMID:1951953

  7. Effect of pH(24h), curing salts and muscle types on the oxidative stability, free amino acids profile and vitamin B2, B3 and B6 content of dry-cured ham.

    PubMed

    Gratacós-Cubarsí, M; Sárraga, C; Castellari, M; Valero, A; García Regueiro, J A; Arnau, J

    2013-12-01

    The effects of a curing salt composition (with and without nitrifying salts), and the pH at 24h postmortem (pH24>6.0, 5.5<pH24<6.0 and pH24<5.5) were evaluated in the Semimembranosus (SM) and Biceps femoris (BF) muscles of pork legs for compositional and nutritional attributes at the end of dry-cured ham ageing. The muscles free amino acid profile (FAA) was not influenced by nitrifying salts. The pH24 was the factor which had the greatest consequences on the dry-cured ham characteristics analysed. The increase in nicotinamide and decrease in pyridoxine by curing salts and the decrease in both vitamins by pH24, had no major effect on the nutritional value of the dry-cured ham because the remaining amounts were within the intervals found in the nutritional data base for dry-cured ham. The results obtained suggested a cooperative action of vitamins B3 and B6 and the antioxidant enzyme system against oxidation. Thiobarbituric acid reactive substances (TBARS) were reduced by the addition of curing salts but were low in all cases, suggesting high antioxidant stability in dry-cured ham which was corroborated by the low volatile aldehyde contents.

  8. Influences of heating temperature, pH, and soluble solids on the decimal reduction times of acid-adapted and non-adapted Escherichia coli O157:H7 (HCIPH 96055) in a defined liquid heating medium.

    PubMed

    Gabriel, Alonzo A

    2012-11-01

    The study characterized the influences of various combinations of process and product parameters namely, heating temperature (53, 55, 57.5, 60, 62 °C), pH (2.0, 3.0, 4.5, 6.0, 7.0), and soluble solids (SS) (1.4, 15, 35, 55, 69°Brix) on the thermal inactivation of non-adapted and acid-adapted E. coli O157:H7 (HCIPH 96055) in a defined liquid heating medium (LHM). Acid adaptation was conducted by propagating cells in a gradually acidifying nutrient broth medium, supplemented with 1% glucose. The D values of non-adapted cells ranged from 1.43 s (0.02 min) to 304.89 s (5.08 min). Acid-adapted cells had D values that ranged from 1.33 s (0.02 min) to 2628.57 s (43.81 min). Adaptation did not always result in more resistant cells as indicated by the Log (D(adapted)/D(non-adapted)) values calculated in all combinations tested, with values ranging from -1.10 to 1.40. The linear effects of temperature and pH, and the joint effects of pH and SS significantly influenced the thermal resistance of non-adapted cells. Only the linear and quadratic effects of both pH and SS significantly influenced the D values of acid-adapted cells. Generally, the D values of acid-adapted cells decreased at SS greater than 55 °Brix, suggesting the possible cancelation of thermal cross protection by acid habituation at such SS levels. The relatively wide ranges of LHM pH and SS values tested in the study allowed for better examination of the effects of these factors on the thermal death of the pathogen. The results established in this work may be used in the evaluation, control and improvement of safety of juice products; and of other liquid foods with physicochemical properties that fall within the ranges tested in this work. PMID:23141645

  9. VALUING ACID MINE DRAINAGE REMEDIATION OF IMPAIRED WATERWAYS IN WEST VIRGINIA: A HEDONIC MODELING APPROACH

    EPA Science Inventory

    States with active and abandoned mines face large private and public costs to remediate damage to streams and rivers from acid mine drainage (AMD), the metal rich runoff flowing primarily from abandoned mines and surface deposits of mine waste. AMD can lower stream and river pH ...

  10. Effect of pH and succinic acid on the morphology of α-calcium sulfate hemihydrate synthesized by a salt solution method

    NASA Astrophysics Data System (ADS)

    Li, Fan; Liu, Jianli; Yang, Guangyong; Pan, Zongyou; Ni, Xiao; Xu, Huazi; Huang, Qing

    2013-07-01

    Well-crystallized α-calcium sulfate hemihydrate (α-CSH) powders useful for bone defect filling were synthesized using a salt solution method and their morphologies were effectively modified by adjusting the pH of the reaction solutions or by adding succinic acid. The effect and its mechanism of the pH and the succinic acid on the phase composition and the morphology of the crystals were discussed in detail.

  11. Nickel toxicity to microbes: effect of pH and implications for acid rain

    SciTech Connect

    Babich, H.; Stotzky, G.

    1982-12-01

    A broad spectrum of microorganisms, including eubacteria (nonmarine and marine), actinomycetes, yeasts, and filamentous fungi, were evaluated for their sensitivities to nickel. Wide extremes in sensitivity to Ni were noted among the filamentous fungi, whereas the range of tolerance to Ni of the yeasts, eubacteria, and actinomycetes was narrower. With all microorganisms, the toxicity of Ni has not been defined, although the formation of hydroxylated Ni species with differing toxicities was not involved. The enhanced toxicity of Ni at acidic levels may have implications for the toxicity of Ni in environments stressed by acid precipitation.

  12. Systematics and species-specific response to pH of Oxytricha acidotolerans sp. nov. and Urosomoida sp. (Ciliophora, Hypotricha) from acid mining lakes

    PubMed Central

    Weisse, Thomas; Moser, Michael; Scheffel, Ulrike; Stadler, Peter; Berendonk, Thomas; Weithoff, Guntram; Berger, Helmut

    2013-01-01

    We investigated the morphology, phylogeny of the 18S rDNA, and pH response of Oxytricha acidotolerans sp. nov. and Urosomoida sp. (Ciliophora, Hypotricha) isolated from two chemically similar acid mining lakes (pH ∼ 2.6) located at Langau, Austria, and in Lusatia, Germany. Oxytricha acidotolerans sp. nov. from Langau has 18 frontal-ventral-transverse cirri but a very indistinct kinety 3 fragmentation so that the assignment to Oxytricha is uncertain. The somewhat smaller species from Lusatia has a highly variable cirral pattern and the dorsal kineties arranged in the Urosomoida pattern and is, therefore, preliminary designated as Urosomoida sp. The pH response was measured as ciliate growth rates in laboratory experiments at pH ranging from 2.5 to 7.0. Our hypothesis was that the shape of the pH reaction norm would not differ between these closely related (3% difference in their SSU rDNA) species. Results revealed a broad pH niche for O. acidotolerans, with growth rates peaking at moderately acidic conditions (pH 5.2). Cyst formation was positively and linearly related to pH. Urosomoida sp. was more sensitive to pH and did not survive at circumneutral pH. Accordingly, we reject our hypothesis that similar habitats would harbour ciliate species with virtually identical pH reaction norm. PMID:23021638

  13. Sorption of toluene by humic acids derived from lake sediment and mountain soil at different pH.

    PubMed

    Chang Chien, S W; Chen, C Y; Chang, J H; Chen, S H; Wang, M C; Mannepalli, Madhava Rao

    2010-05-15

    Contamination of soil and groundwater with BTEX compounds (benzene, toluene, ethylbenzene, and xylene) depends on the sorption behavior of these compounds by soil organic matter (SOM) and humic acids (HAs). In this study sorption of toluene by HAs extracted from lake sediment and mountain soil was investigated. HA suspensions were adjusted to pH 4.00, 6.00, or 8.00 and made to the concentration of 200 mg L(-1). Each HA suspension or solution was subjected to particle size analysis using high performance particle sizer (HPPS). The particle size of HA from lake sediment was around 1000-1200 nm while that from mountain soil was 220-320 nm at suspension pH 4.00. Kinetic studies showed that sorption of toluene by the two HAs followed pseudo-first-order and mainly pseudo-zero-order kinetics. At suspension pH 4.00, the sorption of toluene by the two HAs was best described by Langmuir and Temkin adsorption isotherm models. Further, sorption of toluene by the lake sediment HA was significantly greater than that by mountain soil HA. It was thus suggested that the lake sediment HA with larger particle size may develop beneficially chemical conformation for sorption of toluene and related compounds in soil and associated environments.

  14. Identification and thermal stability of purple-fleshed sweet potato anthocyanins in aqueous solutions with various pH values and fruit juices.

    PubMed

    Li, Jie; Li, Xiao-ding; Zhang, Yun; Zheng, Zheng-dong; Qu, Zhi-ya; Liu, Meng; Zhu, Shao-hua; Liu, Shuo; Wang, Meng; Qu, Lu

    2013-02-15

    Thirteen anthocyanins were identified in the purple-fleshed sweet potato cultivar Jihei No. 1. The main anthocyanins were 3-sophoroside-5-glucoside derivatives from cyanidin and peonidin, acylated with p-hydroxybenzoic acid, ferulic acid, or caffeic acid. A unique anthocyanin, delphinidin-3,5-diglucoside was also found. The thermal stability of purple-fleshed sweet potato anthocyanins (PSPAs) followed a first-order kinetics model. Aqueous solutions with various pH (2, 3, 4, 5, and 6) and fruit juices (apple, pear, grapefruit, orange, tangerine, kiwifruit, and lemon) were coloured with PSPAs. The enrichment and degradation kinetics of anthocyanins in these matrices were investigated at 80, 90, and 100°C. A higher stability of anthocyanins was obtained in aqueous solutions with pH 3 and 4 and in apple and pear juices. Moreover, the activation energies for PSPA degradation in aqueous solutions with various pH and fruit juices ranged from 66.56 kJ/mol to 111.57 kJ/mol and 46.76 kJ/mol to 75.68 kJ/mol, respectively.

  15. High-rate volatile fatty acid (VFA) production by a granular sludge process at low pH.

    PubMed

    Tamis, J; Joosse, B M; Loosdrecht, M C M van; Kleerebezem, R

    2015-11-01

    Volatile fatty acids (VFA) are proposed platform molecules for the production of basic chemicals and polymers from organic waste streams. In this study we developed a granular sludge process to produce VFA at high rate, yield and purity while minimizing potential operational costs. A lab-scale anaerobic sequencing batch reactor (ASBR) was fed with 10 g l(-1) glucose as model substrate. Inclusion of a short (2 min) settling phase before effluent discharge enabled effective granulation and very high volumetric conversion rates of 150-300 gCOD l(-1)  d(-1) were observed during glucose conversion. The product spectrum remained similar at the tested pH range with acetate and butyrate as the main products, and a total VFA yield of 60-70% on chemical oxygen demand (COD) basis. The requirement for base addition for pH regulation could be reduced from 1.1 to 0.6 mol OH(-) (mol glucose)(-1) by lowering the pH from 5.5 to 4.5. Solids concentrations in the effluent were 0.6 ± 0.3 g l(-1) but could be reduced to 0.02 ± 0.01 g l(-1) by introduction of an additional settling period of 5 min. The efficient production of VFA at low pH with a virtually solid-free effluent increases the economic feasibility of waste-based chemicals and polymer production. Biotechnol.

  16. Effect of pH, urea, peptide length, and neighboring amino acids on alanine alpha-proton random coil chemical shifts.

    PubMed

    Carlisle, Elizabeth A; Holder, Jessica L; Maranda, Abby M; de Alwis, Adamberage R; Selkie, Ellen L; McKay, Sonya L

    2007-01-01

    Accurate random coil alpha-proton chemical shift values are essential for precise protein structure analysis using chemical shift index (CSI) calculations. The current study determines the chemical shift effects of pH, urea, peptide length and neighboring amino acids on the alpha-proton of Ala using model peptides of the general sequence GnXaaAYaaGn, where Xaa and Yaa are Leu, Val, Phe, Tyr, His, Trp or Pro, and n = 1-3. Changes in pH (2-6), urea (0-1M), and peptide length (n = 1-3) had no effect on Ala alpha-proton chemical shifts. Denaturing concentrations of urea (8M) caused significant downfield shifts (0.10 +/- 0.01 ppm) relative to an external DSS reference. Neighboring aliphatic residues (Leu, Val) had no effect, whereas aromatic amino acids (Phe, Tyr, His and Trp) and Pro caused significant shifts in the alanine alpha-proton, with the extent of the shifts dependent on the nature and position of the amino acid. Smaller aromatic residues (Phe, Tyr, His) caused larger shift effects when present in the C-terminal position (approximately 0.10 vs. 0.05 ppm N-terminal), and the larger aromatic tryptophan caused greater effects in the N-terminal position (0.15 ppm vs. 0.10 C-terminal). Proline affected both significant upfield (0.06 ppm, N-terminal) and downfield (0.25 ppm, C-terminal) chemical shifts. These new Ala correction factors detail the magnitude and range of variation in environmental chemical shift effects, in addition to providing insight into the molecular level interactions that govern protein folding.

  17. Inactivation model equations and their associated parameter values obtained under static acid stress conditions cannot be used directly for predicting inactivation under dynamic conditions.

    PubMed

    Janssen, M; Verhulst, A; Valdramidis, V; Devlieghere, F; Van Impe, J F; Geeraerd, A H

    2008-11-30

    Organic acids (e.g., lactic acid, acetic acid and citric acid) are popular preservatives. In this study, the Listeria innocua inactivation is investigated under dynamic conditions of pH and undissociated lactic acid ([LaH]). A combined primary (Weibull-type) and secondary model developed for the L. innocua inactivation under static conditions [Janssen, M., Geeraerd, A.H., Cappuyns, A., Garcia-Gonzalez, L., Schockaert, G., Van Houteghem, N., Vereecken, K.M., Debevere, J., Devlieghere, F., Van Impe, J.F., 2007. Individual and combined effects of pH and lactic acid concentration on L. innocua inactivation: development of a predictive model and assessment of experimental variability. Applied and Environmental Microbiology 73(5), 1601-1611] was applied to predict the microbial inactivation under dynamic conditions. Because of its non-autonomous character, two approaches were proposed for the application of the Weibull-type model to dynamic conditions. The results quantitatively indicated that the L. innocua cell population was able to develop an induced acid stress resistance under dynamic conditions of pH and [LaH]. From a modeling point of view, it needs to be stressed that (i) inactivation model equations and associated parameter values, derived under static conditions, may not be suitable for use as such under dynamic conditions, and (ii) non-autonomous dynamic models reveal additional technical intricacies in comparison with autonomous models.

  18. pH at the micellar interface: synthesis of pH probes derived from salicylic acid, acid-base dissociation in sodium dodecyl sulfate micelles, and Poisson-Boltzmann simulation.

    PubMed

    Souza, T P; Zanette, D; Kawanami, A E; de Rezende, L; Ishiki, H M; do Amaral, A T; Chaimovich, H; Agostinho-Neto, A; Cuccovia, I M

    2006-05-01

    The study of the H+ concentration at the micellar interface is a convenient system for modeling the distribution of H+ at interfaces. We have synthesized salicylic acid derivatives to analyze the proton dissociation of both the carboxylic and phenol groups of the probes, determining spectrophotometrically the apparent pK(a)'s (pK(ap)) in sodium dodecyl sulfate, SDS, micelles with and without added salt. The synthesized probes were 2-hydroxy-5-(2-trimethylammoniumacetyl)benzoate; 2-hydroxy-5-(2-dimethylhexadecylammoniumacetyl)benzoate; 2-hydroxy-5-(2-dimethylhexadecylammoniumhexanoyl)benzoate; 2-hydroxy-5-(2-dimethylhexadecylammoniumundecanoyl)benzoate; 2-hydroxy-5-acetylbenzoic acid; and 2-hydroxy-5-dodecanoylbenzoic acid. Upon incorporation into SDS micelles the pK(ap)'s of both carboxylic and phenol groups increased by ca. 3 pH units and NaCl addition caused a decrease in the probe-incorporated pK(ap). The experimental results were fitted with a cell model Poisson-Boltzmann (P-B) equation taking in consideration the effect of salt on the aggregation number of SDS and using the distance of the dissociating group as a parameter. The conformations of the probes were analyzed theoretically using two dielectric constants, e.g., 2 and 78. Both the P-B analysis and conformation calculations can be interpreted by assuming that the acid groups dissociate very close to, or at, the interface. Our results are consistent with the assumption that the intrinsic pK(a)'s of both carboxylic and phenol groups of the salicylic acid probes used here can be taken as those in water. Using this assumption the micellar and salt effects on the pK(ap)'s of the (trialkylammonium)benzoate probes were described accurately using a cell model P-B analysis.

  19. Effect of salicylic acid upon trace-metal sorption (Cd, Zn, Co, and Mn) onto alumina, silica, and kaolinite as a function of pH

    SciTech Connect

    Benyahya, L.; Garnier, J.M.

    1999-05-01

    The sorption of four trace metals (Cd, Zn, Co, and Mn) onto alumina, silica, and kaolinite, in the presence or absence of salicylic acid was investigated in batch experiments in the pH range from 4 to 9. The sorption was interpreted in terms of surface complexation using the diffuse layer model (DLM). Equilibrium parameters were optimized using the FITEQL program. The salicylic acid was only significantly sorbed onto the alumina and the sorption was modeled using the anionic monodentate surface complex. In the absence of salicylic acid, the sorption of the trace metals presented different pH edge behaviors, depending on the substrate. Using the cationic monodendate surface complex, the model fitted the experimental data well. In the presence of salicylic acid, at a given pH and depending on the substrate, the sorption of metals was (1) increased, suggesting the occurrence of ternary complexes; (2) reduced (sometimes totally inhibited), due to the complexation with dissolved salicylic acid; or (3) very weakly changed in terms of net effect compared to free-organic-ligand systems. Modeling of the trace-metal sorption in the presence of salicylic acid was performed using ternary surface complexes. In the acidic pH range, this allowed the experimental data to be simulated, but in the alkaline pH range, the model failed to simulate the decrease in sorption. Probable causes of the discrepancies between the experimental data and modeling results are discussed.

  20. Electron transport, uptake of protons, and photophosphorylation in chloroplasts: effects of gramicidin d at various ph values

    SciTech Connect

    Gil'miyarova, S.G.; Blymentel'd, L.A.; Puuge, E.K.; Tikhonov, A.N.

    1986-02-01

    A comparative investigation is presented of the photoinduced uptake of protons by bean chloroplasts, electron transport, and photophosphorylation, with the results of previous work on the subject. The study suggests that the dual nature of the action of gramicidin D--effective uncoupling action at low concentrations and it ''inability'' to suppress proton uptake and the formation of ..delta..ph--may be a consequence of the morphological and functional heterogeneity of the proton acceptor groups localized in the thyalkoid membrane.

  1. Size-controlled dissolution of silver nanoparticles at neutral and acidic pH conditions: kinetics and size changes.

    PubMed

    Peretyazhko, Tanya S; Zhang, Qingbo; Colvin, Vicki L

    2014-10-21

    Silver nanoparticles (Ag(NP)) are widely utilized in increasing number of medical and consumer products due to their antibacterial properties. Once released to aquatic system, Ag(NP) undergoes oxidative dissolution leading to production of toxic Ag(+). Dissolved Ag(+) can have a severe impact on various organisms, including indigenous microbial communities, fungi, alga, plants, vertebrates, invertebrates, and human cells. Therefore, it is important to investigate fate of Ag(NP) and determine physico-chemicals parameters that control Ag(NP) behavior in the natural environment. Nanoparticle size might have a dominant effect on Ag(NP) dissolution in natural waters. In this work, we investigated size-dependent dissolution of AgNP exposed to ultrapure deionized water (pH ≈ 7) and acetic acid (pH 3) and determined changes in nanoparticle size after dissolution. Silver nanoparticles stabilized by thiol functionalized methoxyl polyethylene glycol (PEGSH) of 6 nm (Ag(NP_)6), 9 nm (Ag(NP_)9), 13 nm (Ag(NP_)13), and 70 nm (Ag(NP_)70) were prepared. The results of dissolution experiments showed that the extent of AgNP dissolution in acetic acid was larger than in water. Solubility of Ag(NP) increased with the size decrease and followed the order Ag(NP_)6 > Ag(NP_)9 > Ag(NP_)13 > Ag(NP_)70 in both water and acetic acid. Transmission electron microscopy (TEM) was applied to characterize changes in size and morphology of the AgNP after dissolution in water. Analysis of Ag(NP) by TEM revealed that the particle morphology did not change during dissolution. The particles remained approximately spherical in shape, and no visible aggregation was observed in the samples. TEM analysis also demonstrated that Ag(NP_)6, Ag(NP_)9, and Ag(NP_)13 increased in size after dissolution likely due to Ostwald ripening. PMID:25265014

  2. pH-, Lactic Acid-, and Non-Lactic Acid-Dependent Activities of Probiotic Lactobacilli against Salmonella enterica Serovar Typhimurium

    PubMed Central

    Fayol-Messaoudi, Domitille; Berger, Cédric N.; Coconnier-Polter, Marie-Hélène; Liévin-Le Moal, Vanessa; Servin, Alain L.

    2005-01-01

    The mechanism(s) underlying the antibacterial activity of probiotic Lactobacillus strains appears to be multifactorial and includes lowering of the pH and the production of lactic acid and of antibacterial compounds, including bacteriocins and nonbacteriocin, non-lactic acid molecules. Addition of Dulbecco's modified Eagle's minimum essential medium to the incubating medium delays the killing activity of lactic acid. We found that the probiotic strains Lactobacillus johnsonii La1, Lactobacillus rhamnosus GG, Lactobacillus casei Shirota YIT9029, L. casei DN-114 001, and L. rhamnosus GR1 induced a dramatic decrease in the viability of Salmonella enterica serovar Typhimurium SL1344 mainly attributable to non-lactic acid molecule(s) present in the cell-free culture supernatant (CFCS). These molecules were more active against serovar Typhimurium SL1344 in the exponential growth phase than in the stationary growth phase. We also showed that the production of the non-lactic acid substance(s) responsible for the killing activity was dependent on growth temperature and that both unstable and stable substances with killing activity were present in the CFCSs. We found that t