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Sample records for acid buffer ph

  1. 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.

  2. Matching phosphate and maleate buffer systems for dissolution of weak acids: Equivalence in terms of buffer capacity of bulk solution or surface pH?

    PubMed

    Cristofoletti, Rodrigo; Dressman, Jennifer B

    2016-06-01

    The development of in vitro dissolution tests able to anticipate the in vivo fate of drug products has challenged pharmaceutical scientists over time, especially in the case of ionizable compounds. In the seminal model proposed by Mooney et al. thirty-five years ago, the pH at the solid-liquid interface (pH0) was identified as a key parameter in predicting dissolution rate. In the current work it is demonstrated that the in vitro dissolution of the weak acid ibuprofen in maleate and phosphate buffer systems is a function of the pH0, which in turn is affected by properties of the drug and the medium. The reported pH0 for ibuprofen dissolution in bicarbonate buffer, the predominant buffer species in the human small intestine under fasting conditions, can be achieved by reducing the phosphate buffer concentration to 5.0mM or the maleate buffer concentration to 2.2mM. Using this approach to identify the appropriate buffer/buffer capacity combination for in vitro experiments in FaSSIF-type media, it would be possible to increase the physiological relevance of this important biopharmaceutics tool. However, the necessity of monitoring and adjusting the bulk pH during the experiments carried out in 5.0mM phosphate or 2.2mM maleate buffers must also be taken into consideration. PMID:27032508

  3. Matching phosphate and maleate buffer systems for dissolution of weak acids: Equivalence in terms of buffer capacity of bulk solution or surface pH?

    PubMed

    Cristofoletti, Rodrigo; Dressman, Jennifer B

    2016-06-01

    The development of in vitro dissolution tests able to anticipate the in vivo fate of drug products has challenged pharmaceutical scientists over time, especially in the case of ionizable compounds. In the seminal model proposed by Mooney et al. thirty-five years ago, the pH at the solid-liquid interface (pH0) was identified as a key parameter in predicting dissolution rate. In the current work it is demonstrated that the in vitro dissolution of the weak acid ibuprofen in maleate and phosphate buffer systems is a function of the pH0, which in turn is affected by properties of the drug and the medium. The reported pH0 for ibuprofen dissolution in bicarbonate buffer, the predominant buffer species in the human small intestine under fasting conditions, can be achieved by reducing the phosphate buffer concentration to 5.0mM or the maleate buffer concentration to 2.2mM. Using this approach to identify the appropriate buffer/buffer capacity combination for in vitro experiments in FaSSIF-type media, it would be possible to increase the physiological relevance of this important biopharmaceutics tool. However, the necessity of monitoring and adjusting the bulk pH during the experiments carried out in 5.0mM phosphate or 2.2mM maleate buffers must also be taken into consideration.

  4. 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

  5. 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

  6. 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.

  7. An evaluation of MES (2(N-Morpholino)ethanesulfonic acid) and Amberlite IRC-50 as pH buffers for nutrient solution studies

    NASA Technical Reports Server (NTRS)

    Bugbee, B. G.; Salisbury, F. B.

    1985-01-01

    All buffering agents used to stabilize pH in hydroponic research have disadvantages. Inorganic buffers are absorbed and may become phytotoxic. Solid carbonate salts temporarily mitigate decreasing pH but provide almost no protection against increasing pH, and they alter nutrient absorption. Exchange resins are more effective, but we find that they remove magnesium and manganese from solution. We have tested 2(N-Morpholino)ethanesulfonic acid (MES) as a buffering agent at concentrations of 1 and 10 mol m-3 (1 and 10 mM) with beans, corn, lettuce, tomatoes, and wheat. MES appears to be biologically inert and does not interact significantly with other solution ions. Relative growth rates among controls and MES treatments were nearly identical for each species during the trial period. The pH was stabilized by 1 mol m-3 MES. This buffer warrants further consideration in nutrient research.

  8. Improved pH buffering agent for sodium hypochlorite

    NASA Technical Reports Server (NTRS)

    Nash, J. R.; Veeder, L. N.

    1969-01-01

    Sodium citrate/citric acid was found to be an effective buffer for pH control when used with sodium hypochlorite. The mixture does not corrode aluminum. The buffer appears to form a type of conversion coating that may provide corrosion-resistant properties to aluminum in other applications.

  9. 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.

  10. 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.

  11. 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

  12. 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).

  13. 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.

  14. Mapping Soil pH Buffering Capacity of Selected Fields

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  15. Peak shapes of acids and bases under overloaded conditions in reversed-phase liquid chromatography, with weakly buffered mobile phases of various pH: a thermodynamic interpretation.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2009-01-01

    We measured overloaded band profiles for a series of nine compounds (phenol, caffeine, 3-phenyl 1-propanol, 2-phenylbutyric acid, amphetamine, aniline, benzylamine, p-toluidine, and procainamidium chloride) on columns packed with four different C(18)-bonded packing materials: XTerra-C(18), Gemini-C(18), Luna-C(18)(2), and Halo-C(18), using buffered methanol-water mobile phases. The pHWS of the mobile phase was increased from 2.6 to 11.3. The buffer concentration (either phosphate, acetate, or carbonate buffers) was set constant at values below the maximum concentration of the sample in the band. The influence of the surface chemistry of the packing material on the retention and the shape of the peaks was investigated. Adsorbents having a hybrid inorganic/organic structure tend to give peaks exhibiting moderate or little tailing. The retention and the shape of the band profiles can easily be interpreted at pHsWS that are well above or well below the pKWS(a) of the compound studied. In contrast, the peak shapes in the intermediary pH range (i.e., close to the compound pKWS(a)) have rarely been studied. These shapes reveal the complexity of the competitive adsorption behavior of couples of acido-basic conjugated compounds at pHsWS that are close to their pKWS(a). They also reveal the role of the buffer capacity on the resulting peak shape. With increasing pHWS, the overloaded profiles are first langmuirian (isotherm type I) at low pHsWS, they become S-shaped (isotherm type II), then anti-langmuirian (isotherm type III), S-shaped again at intermediate pHsWS, and finally return to a langmuirian shape at high pHsWS. A new general adsorption isotherm model that takes into account the dissociation equilibrium of conjugated acidic and basic species in the bulk mobile phase accounts for these transient band shapes. An excellent agreement was achieved between experimental profiles and those calculated with a two-sites adsorption isotherm model at all pHsWS. The neutral

  16. Ionizable drugs and pH oscillators: buffering effects.

    PubMed

    Misra, Gauri P; Siegel, Ronald A

    2002-09-01

    It has been proposed that chemical pH oscillators may form a basis for periodic, pulsed drug delivery of weak acids and bases across lipophilic membranes. However, drugs have been shown to interfere with the ability of the chemical systems to oscillate, and rhythmic delivery of drugs by this means has been demonstrated only under constrained circumstances. Herein, we provide evidence that low concentrations of acidic drugs can attenuate and ultimately quench chemical pH oscillators, by a simple buffering mechanism. A model system consisting of the bromate-sulfite-marble pH oscillator in a continuous stirred tank reactor is used, along with acidic drugs of varying concentration and acid dissociation constant, pK(D). A published kinetic model for this oscillator is modified to account for the presence of acidic drug, and the results of this model are in qualitative agreement with the experimental results. PMID:12210047

  17. Rapid demineralization in acidic buffers.

    PubMed

    Eggert, F M; Germain, J P

    1979-01-22

    The demineralization of routine histological specimens in buffers of weakly ionized organic acids, unbuffered formic acid, and EDTA was investigated. The rate of demineralization was measured by a chemical method and from radiographs. Lactate-containing buffers and buffers of formic acid with its potassium salt were more rapid in effect than any other agent. Acidic buffers and unbuffered formic acid produced rapid diffuse demineralization with secondary precipitation of calcium salts. Preservation of dental enamel in such buffers resulted from the significantly slower rate of enamel demineralization than that for bone and dentine. In rapid demineralizing agents the secondary salts were quickly redissolved while in slow buffers these salts persisted. Multivalent ions such as citrate and maleate slowed the rate of demineralization, and a citrate-containing buffer was the slowest of all the agents tested. Demineralization in EDTA exhibited a different pattern with the establishment of a well-defined front of demineralization without apparent reprecipitation. EDTA attacked enamel, bone and dentine at the same rate. An attempt was made to relate the observed rates of demineralization to current theories of the demineralization process.

  18. Peak shapes of acids and bases under overloaded conditions in reversed-phase liquid chromatography, with weakly buffered mobile phases of various pH: A thermodynamic interpretation

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2009-01-01

    We measured overloaded band profiles for a series of nine compounds (phenol, caffeine, 3-phenyl 1-propanol, 2-phenylbutyric acid, amphetamine, aniline, benzylamine, p-toluidine, and procainamidium chloride) on columns packed with four different C{sub 18}-bonded packing materials: XTerra-C{sub 18}, Gemini-C{sub 18}, Luna-C{sub 18}(2), and Halo-C{sub 18}, using buffered methanol-water mobile phases. The {sub W}{sup S}pH of the mobile phase was increased from 2.6 to 11.3. The buffer concentration (either phosphate, acetate, or carbonate buffers) was set constant at values below the maximum concentration of the sample in the band. The influence of the surface chemistry of the packing material on the retention and the shape of the peaks was investigated. Adsorbents having a hybrid inorganic/organic structure tend to give peaks exhibiting moderate or little tailing. The retention and the shape of the band profiles can easily be interpreted at {sub W}{sup S}pHs that are well above or well below the {sub W}{sup S}pK{sub a} of the compound studied. In contrast, the peak shapes in the intermediary pH range (i.e., close to the compound {sub W}{sup S}pK{sub a}) have rarely been studied. These shapes reveal the complexity of the competitive adsorption behavior of couples of acido-basic conjugated compounds at {sub W}{sup S}pHs that are close to their {sub W}{sup S}pK{sub a}. They also reveal the role of the buffer capacity on the resulting peak shape. With increasing {sub W}{sup S}pH, the overloaded profiles are first langmuirian (isotherm type I) at low {sub W}{sup S}pHs, they become S-shaped (isotherm type II), then anti-langmuirian (isotherm type III), S-shaped again at intermediate {sub W}{sup S}pHs, and finally return to a langmuirian shape at high {sub W}{sup S}pHs. A new general adsorption isotherm model that takes into account the dissociation equilibrium of conjugated acidic and basic species in the bulk mobile phase accounts for these transient band shapes. An

  19. Comparison of Buffer Effect of Different Acids During Sandstone Acidizing

    NASA Astrophysics Data System (ADS)

    Umer Shafiq, Mian; Khaled Ben Mahmud, Hisham; Hamid, Mohamed Ali

    2015-04-01

    The most important concern of sandstone matrix acidizing is to increase the formation permeability by removing the silica particles. To accomplish this, the mud acid (HF: HCl) has been utilized successfully for many years to stimulate the sandstone formations, but still it has many complexities. This paper presents the results of laboratory investigations of different acid combinations (HF: HCl, HF: H3PO4 and HF: HCOOH). Hydrofluoric acid and fluoboric acid are used to dissolve clays and feldspar. Phosphoric and formic acids are added as a buffer to maintain the pH of the solution; also it allows the maximum penetration of acid into the core sample. Different tests have been performed on the core samples before and after the acidizing to do the comparative study on the buffer effect of these acids. The analysis consists of permeability, porosity, color change and pH value tests. There is more increase in permeability and porosity while less change in pH when phosphoric and formic acids were used compared to mud acid. From these results it has been found that the buffer effect of phosphoric acid and formic acid is better than hydrochloric acid.

  20. Biochar contribution to soil pH buffer capacity

    NASA Astrophysics Data System (ADS)

    Tonutare, Tonu; Krebstein, Kadri; Utso, Maarius; Rodima, Ako; Kolli, Raimo; Shanskiy, Merrit

    2014-05-01

    Biochar as ecologically clean and stable form of carbon has complex of physical and chemical properties which make it a potentially powerful soil amendment (Mutezo, 2013). Therefore during the last decade the biochar application as soil amendment has been a matter for a great number of investigations. For the ecological viewpoint the trend of decreasing of soil organic matter in European agricultural land is a major problem. Society is faced with the task to find possibilities to stabilize or increase soil organic matter content in soil and quality. The availability of different functional groups (e.g. carboxylic, phenolic, acidic, alcoholic, amine, amide) allows soil organic matter to buffer over a wide range of soil pH values (Krull et al. 2004). Therefore the loss of soil organic matter also reduces cation exchange capacity resulting in lower nutrient retention (Kimetu et al. 2008). Biochar can retain elements in soil directly through the negative charge that develops on its surfaces, and this negative charge can buffer acidity in the soil. There are lack of investigations about the effect of biochar to soil pH buffering properties, The aim of our investigation was to investigate the changes in soil pH buffer capacity in a result of addition of carbonizated material to temperate region soils. In the experiment different kind of softwood biochars, activated carbon and different soil types with various organic matter and pH were used. The study soils were Albeluvisols, Leptosols, Cambisols, Regosols and Histosols . In the experiment the series of the soil: biochar mixtures with the biochar content 0 to 100% were used. The times of equiliberation between solid and liquid phase were from 1 to 168 hours. The suspension of soil: biochar mixtures was titrated with HCl solution. The titration curves were established and pH buffer capacities were calculated for the pH interval from 3.0 to 10.0. The results demonstrate the dependence of pH buffer capacity from soil type

  1. Ruminal buffers: temporal effects on buffering capacity and pH of ruminal fluid from cows fed a high concentrate diet.

    PubMed

    Le Ruyet, P; Tucker, W B

    1992-04-01

    In vitro characteristics of several buffers and alkalinizing agents commonly utilized to reduce ruminal acid load were evaluated. Ruminal fluid was collected from five cows consuming a diet containing concentrate and sorghum silage in a 68:32 ratio (DM basis). This fluid was incubated with either NaHCO3, a natural sodium sesquicarbonate, a multielement buffer or MgO (7.1 g/L of ruminal fluid), or no buffer for 48 h; flasks were removed and analyzed for pH, buffering capacity, and buffer value index every 12 h during the 48-h incubation. The buffer value index accounts simultaneously for alterations in pH and buffering capacity. Compared with the unbuffered control, all buffering compounds increased ruminal fluid buffer value index. However, the buffer value index separated these buffering compounds into two categories. The NaH-CO3 and sodium sesquicarbonate exhibited similar buffer value indexes; both were markedly higher than those for the multielement buffer and MgO. Although NaHCO3 and sodium sesquicarbonate each increased both ruminal fluid pH and buffering capacity sharply, the multielement buffer only increased pH and buffering capacity moderately. The increase in buffer value index for MgO primarily was due to an increase in pH. Both NaHCO3 and sodium sesquicarbonate were fully active within the first 12 h of incubation; activity of multielement buffer and MgO reached a plateau at 24 h. Compared with the multielement buffer and MgO, NaHCO3 and sodium sesquicarbonate should be more beneficial in preventing short-term postprandial increases in ruminal fluid hydrogen ion concentration; because of their slower release rates, the multielement buffer and MgO should help stabilize ruminal acid-base status, but efficacy might be reduced because of passage out of the rumen. PMID:1315810

  2. 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

  3. 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

  4. Buffer Standards for the Biological pH of the Amino Acid N-[2 hydroxyethyl]piperazine-N’-[3-propanesulfonic acid], HEPPS, From (278.15 to 328.15) K

    PubMed Central

    Roy, Lakshmi N.; Roy, Rabindra N.; Wollen, Joshua T.; Harmon, Meagan A.; Stegner, Jessica M.; Shah, Ankita A.; Henson, Isaac B.

    2011-01-01

    For the HEPPS buffer under investigation, there are seven buffer solutions without NaCl and eight buffer solutions that contain Cl− and have an ionic strength (I = 0.16 mol·kg−1), which is similar to that of blood plasma. These buffer solutions have been evaluated in the temperature range of (278.15 to 328.15) K using the extended Debye- Hückel equation and the Bates-Guggenheim convention. The previously determined Ej values have been used to determine the operational pH values of HEPPS buffer solutions at (298.15 and 310.15) K. These are recommended as secondary standard reference solutions for pH measurements in saline media with an isotonic ionic strength of I = 0.16 mol·kg−1. PMID:22096257

  5. Buffer Standards for the Biological pH of the Amino Acid N-[2 hydroxyethyl]piperazine-N'-[3-propanesulfonic acid], HEPPS, From (278.15 to 328.15) K.

    PubMed

    Roy, Lakshmi N; Roy, Rabindra N; Wollen, Joshua T; Harmon, Meagan A; Stegner, Jessica M; Shah, Ankita A; Henson, Isaac B

    2011-01-01

    For the HEPPS buffer under investigation, there are seven buffer solutions without NaCl and eight buffer solutions that contain Cl(-) and have an ionic strength (I = 0.16 mol·kg(-1)), which is similar to that of blood plasma. These buffer solutions have been evaluated in the temperature range of (278.15 to 328.15) K using the extended Debye- Hückel equation and the Bates-Guggenheim convention. The previously determined E(j) values have been used to determine the operational pH values of HEPPS buffer solutions at (298.15 and 310.15) K. These are recommended as secondary standard reference solutions for pH measurements in saline media with an isotonic ionic strength of I = 0.16 mol·kg(-1).

  6. Measurement of pH by NMR Spectroscopy in Concentrated Aqueous Fluoride Buffers

    PubMed Central

    Gerken, James B.

    2010-01-01

    An NMR spectroscopic technique has been developed to give rapid, accurate pH measurements on tenth-milliliter samples of concentrated acidic aqueous solutions buffered by fluoride ion in the pH 1.5 – 4.5 range. The fluoride 19F chemical shift has been calibrated as a function of pH at 0.1 and 1.0 M concentration by reference to an internal 3-fluoropyridine standard. Subsequent measurements of fluoride buffer pH required no additives and only two NMR spectra in the presence of an external reference standard. PMID:21278857

  7. Application of Good's buffers to pH imaging using hyperpolarized (13)C MRI.

    PubMed

    Flavell, Robert R; von Morze, Cornelius; Blecha, Joseph E; Korenchan, David E; Van Criekinge, Mark; Sriram, Renuka; Gordon, Jeremy W; Chen, Hsin-Yu; Subramaniam, Sukumar; Bok, Robert A; Wang, Zhen J; Vigneron, Daniel B; Larson, Peder E; Kurhanewicz, John; Wilson, David M

    2015-09-25

    N-(2-Acetamido)-2-aminoethanesulfonic acid (ACES), one of Good's buffers, was applied to pH imaging using hyperpolarized (13)C magnetic resonance spectroscopy. Rapid NMR- and MRI-based pH measurements were obtained by exploiting the sensitive pH-dependence of its (13)C chemical shift within the physiologic range.

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

    PubMed

    Andrés, Axel; Rosés, Martí; Bosch, Elisabeth

    2015-03-13

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

  9. Macroreticulate buffers: a novel approach to pH control in living systems.

    PubMed

    Righetti, P G; Chiari, M; Crippa, L

    1991-02-01

    It is possible to control the pH of growing living systems in vitro by adding, to the growth media, macroreticulate buffers, i.e. amphoteric resins made with buffering and titrant groups simultaneously affixed to the matrix. Such beads possess a very precise isoelectric point (pI) and are able to maintain the solutions' pH close to their pI values for extended growth periods. These pearls are made of a neutral polyacrylamide backbone containing up to 200 mM grafted weak acrylamido acids and bases. It is possible to produce such buffers with any desired pH value in the pH 2.5-11 scale. An example is given of conditioning the pH of endive plants grown hydroponically. PMID:1366985

  10. An automated system for monitoring and regulating the pH of bicarbonate buffers.

    PubMed

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

    2013-06-01

    The bicarbonate buffer is considered as the most biorelevant buffer system for the simulation of intestinal conditions. However, its use in dissolution testing of solid oral dosage forms is very limited. The reason for this is the thermodynamic instability of the solution containing hydrogen carbonate ions and carbonic acid. The spontaneous loss of carbon dioxide (CO(2)) from the solution results in an uncontrolled increase of the pH. In order to maintain the pH on the desired level, either a CO(2) loss must be completely avoided or the escaped CO(2) has to be replaced by quantitative substitution, i.e. feeding the solution with the respective amount of gas, which re-acidifies the buffer after dissociation. The present work aimed at the development of a device enabling an automatic pH monitoring and regulation of hydrogen carbonate buffers during dissolution tests.

  11. Volatile buffers can override the "pH memory" of subtilisin catalysis in organic media.

    PubMed

    Zacharis, E; Halling, P J; Rees, D G

    1999-02-16

    The protonation state and activity of enzymes in low-water media are affected by the aqueous pH before drying ("pH memory"). However, both protonation and activity will change if buffer ions can be removed as volatile or organic-extractable weak acids or bases. With NH4OOCH buffers, in which both ions can be removed, pH memory disappears completely for subtilisin-catalyzed transesterification in hexane. Only weak pH memory is found with buffers having one volatile component, NH4-phosphate and NaOOCH. The changes in ionization state result from proton exchanges like Protein-COO-NH4+ --> Protein-COOH + NH3 (g) and Protein-NH3+HCOO- --> Protein-NH2 + HOOCH (g). An equivalent, complementary picture is that net charges on the protein and buffer ions must remain equal and opposite. With NaOOCH buffers, loss of some HCOO- ions gives a more negative net charge on the protein, balanced by the excess Na+. With NH4-phosphate buffers, loss of NH3 gives protein with a more positive net charge. The resulting catalytic activities were high and low, respectively, similar to those after drying from Na-phosphate buffers of optimal (8.5) and acid pH. All of the above effects have been demonstrated for both covalently immobilized subtilisin and the lyophilized free enzyme. Subtilisin lyophilized from NH4OOCH buffers gave pH approximately 4 after redissolution in water, probably because removal of HCOO- counterions remains incomplete. The resulting catalytic activity was low. The effects are discussed in relation to the possible locations, in low-dielectric media, of the positive charge that balances the net negative catalytic triad in active subtilisin. PMID:9990001

  12. Zinc(II) complexation by some biologically relevant pH buffers.

    PubMed

    Wyrzykowski, D; Tesmar, A; Jacewicz, D; Pranczk, J; Chmurzyński, L

    2014-12-01

    The isothermal titration calorimetry (ITC) technique supported by potentiometric titration data was used to study the interaction of zinc ions with pH buffer substances, namely 2-(N-morpholino)ethanesulfonic acid (Mes), piperazine-N,N'-bis(2-ethanesulfonic acid) (Pipes), and dimethylarsenic acid (Caco). The displacement ITC titration method with nitrilotriacetic acid as a strong, competitive ligand was applied to determine conditional-independent thermodynamic parameters for the binding of Zn(II) to Mes, Pipes, and Caco. Furthermore, the relationship between the proposed coordination mode of the buffers and the binding enthalpy has been discussed.

  13. Single pH buffer refolding screen for protein from inclusion bodies.

    PubMed

    Coutard, Bruno; Danchin, Etienne G J; Oubelaid, Rachid; Canard, Bruno; Bignon, Christophe

    2012-04-01

    We previously reported the set up of an automated test for screening the refolding of recombinant proteins expressed as inclusion bodies in Escherichia coli[1]. The screen used 96 refolding buffers and was validated with 24 proteins, 70% of which remained soluble in at least one buffer. In the present paper, we have analyzed in more detail these experimental data to see if the refolding process can be driven by general rules. Notably, we found that proteins with an acidic isoelectric point (pI) refolded in buffers the average pH of which was alkaline and conversely. In addition, the number of refolding buffers wherein a protein remained soluble increased with the difference between its pI and the average pH of the buffers in which it refolded. A trend analysis of the other variables (ionic strength, detergents, etc.) was also performed. On the basis of this analysis, we devised and validated a new refolding screen made of a single buffer for acidic proteins and a single buffer for alkaline proteins. PMID:22343064

  14. Single pH buffer refolding screen for protein from inclusion bodies.

    PubMed

    Coutard, Bruno; Danchin, Etienne G J; Oubelaid, Rachid; Canard, Bruno; Bignon, Christophe

    2012-04-01

    We previously reported the set up of an automated test for screening the refolding of recombinant proteins expressed as inclusion bodies in Escherichia coli[1]. The screen used 96 refolding buffers and was validated with 24 proteins, 70% of which remained soluble in at least one buffer. In the present paper, we have analyzed in more detail these experimental data to see if the refolding process can be driven by general rules. Notably, we found that proteins with an acidic isoelectric point (pI) refolded in buffers the average pH of which was alkaline and conversely. In addition, the number of refolding buffers wherein a protein remained soluble increased with the difference between its pI and the average pH of the buffers in which it refolded. A trend analysis of the other variables (ionic strength, detergents, etc.) was also performed. On the basis of this analysis, we devised and validated a new refolding screen made of a single buffer for acidic proteins and a single buffer for alkaline proteins.

  15. The potential effects of pH and buffering capacity on dental erosion.

    PubMed

    Owens, Barry M

    2007-01-01

    Soft drink pH (initial pH) has been shown to be a causative factor--but not necessarily the primary initiating factor--of dental erosion. The titratable acidity or buffering capacity has been acknowledged as playing a significant role in the etiology of these lesions. This in vitro study sought to evaluate five different soft drinks (Coca-Cola Classic, Diet Coke, Gatorade sports drink, Red Bull high-energy drink, Starbucks Frappucino coffee drink) and tap water (control) in terms of initial pH and buffering capacity. Initial pH was measured in triplicate for the six beverages. The buffering capacity of each beverage was assessed by measuring the weight (in grams) of 0.10 M sodium hydroxide necessary for titration to pH levels of 5.0, 6.0, 7.0, and 8.3. Coca-Cola Classic produced the lowest mean pH, while Starbucks Frappucino produced the highest pH of any of the drinks except for tap water. Based on statistical analysis using ANOVA and Fisher's post hoc tests at a P < 0.05 level of significance, Red Bull had the highest mean buffering capacity (indicating the strongest potential for erosion of enamel), followed by Gatorade, Coca-Cola Classic, Diet Coke, and Starbucks Frappucino. PMID:18050578

  16. The potential effects of pH and buffering capacity on dental erosion.

    PubMed

    Owens, Barry M

    2007-01-01

    Soft drink pH (initial pH) has been shown to be a causative factor--but not necessarily the primary initiating factor--of dental erosion. The titratable acidity or buffering capacity has been acknowledged as playing a significant role in the etiology of these lesions. This in vitro study sought to evaluate five different soft drinks (Coca-Cola Classic, Diet Coke, Gatorade sports drink, Red Bull high-energy drink, Starbucks Frappucino coffee drink) and tap water (control) in terms of initial pH and buffering capacity. Initial pH was measured in triplicate for the six beverages. The buffering capacity of each beverage was assessed by measuring the weight (in grams) of 0.10 M sodium hydroxide necessary for titration to pH levels of 5.0, 6.0, 7.0, and 8.3. Coca-Cola Classic produced the lowest mean pH, while Starbucks Frappucino produced the highest pH of any of the drinks except for tap water. Based on statistical analysis using ANOVA and Fisher's post hoc tests at a P < 0.05 level of significance, Red Bull had the highest mean buffering capacity (indicating the strongest potential for erosion of enamel), followed by Gatorade, Coca-Cola Classic, Diet Coke, and Starbucks Frappucino.

  17. Buffer standards for the physiological pH of the zwitterionic compound of 3-(N-morpholino)propanesulfonic acid (MOPS) from T = (278.15 to 328.15) K.

    PubMed

    Roy, Lakshmi N; Roy, Rabindra N; Allen, Kathleen A; Mehrhoff, Casey J; Henson, Isaac B; Stegner, Jessica M

    2012-04-01

    This paper reports the pH values of five NaCl-free buffer solutions and eleven buffer compositions containing NaCl at I = 0.16 mol·kg(-1). Conventional pa(H) values are reported for sixteen buffer solutions with and without NaCl salt. The operational pH values have been calculated for five buffer solutions and are recommended as pH standards at T = (298.15 and 310.15) K after correcting the liquid junction potentials. For buffer solutions with the composition m(1) = 0.04 mol·kg(-1), m(2) = 0.08 mol·kg(-1), m(3) = 0.08 mol·kg(-1) at I = 0.16 mol·kg(-1), the pH at 310.15 K is 7.269, which is close to 7.407, the pH of blood serum. It is recommended as a pH standard for biological specimens.

  18. Buffer standards for the physiological pH of the zwitterionic compound of 3-(N-morpholino)propanesulfonic acid (MOPS) from T = (278.15 to 328.15) K

    PubMed Central

    Roy, Lakshmi N.; Roy, Rabindra N.; Allen, Kathleen A.; Mehrhoff, Casey J.; Henson, Isaac B.; Stegner, Jessica M.

    2011-01-01

    This paper reports the pH values of five NaCl-free buffer solutions and eleven buffer compositions containing NaCl at I = 0.16 mol·kg−1. Conventional paH values are reported for sixteen buffer solutions with and without NaCl salt. The operational pH values have been calculated for five buffer solutions and are recommended as pH standards at T = (298.15 and 310.15) K after correcting the liquid junction potentials. For buffer solutions with the composition m1 = 0.04 mol·kg−1, m2 = 0.08 mol·kg−1, m3 = 0.08 mol·kg−1 at I = 0.16 mol·kg−1, the pH at 310.15 K is 7.269, which is close to 7.407, the pH of blood serum. It is recommended as a pH standard for biological specimens. PMID:22247568

  19. pH- and concentration-programmable electrodialytic buffer generator.

    PubMed

    Chen, Yongjing; Edwards, Brian L; Dasgupta, Purnendu K; Srinivasan, Kannan

    2012-01-01

    We have presented in a companion paper a suppressor-based electrodialytic buffer generator (EBG) that can produce programmable pH gradients. Here we demonstrate a three-electrode EBG. In this three-compartment flow-through device, the central compartment is separated from the outer compartments with a cation-exchange membrane (CEM) and an anion-exchange membrane (AEM), respectively. One platinum electrode is disposed in each compartment. The flows through each compartment are independent. With appropriate solutions in each compartment, independent potentials are applied to the CEM and AEM electrodes with respect to the grounded central electrode. The CEM current and the AEM current can be independently manipulated to generate buffers with variable concentration and pH in the central compartment. Both the CEM and AEM currents can be positive or negative. For the CEM, a positive current (i(cat)(in)) indicates that cations are coming in from the CEM channel to the center. A negative current (i(cat)(out)) takes cations out of the center to the CEM channel. Similarly for the AEM, currents governing anion transport into the center channel from the AEM channel (AEM electrode negative) or the reverse (AEM electrode positive) are respectively denoted by i(an)(in) or i(an)(out). Most examples herein involve inward ion transport, referred to as the additive mode. Depending on whether i(cat)(in) i(an)(in), H(+)/O(2) and OH(-)/H(2) are respectively produced at the central electrode to maintain electroneutrality. Any gas formed is subsequently removed by a gas removal device. The pH of the central channel effluent is related to the ratio of the currents through the two membranes, while the generated concentration is controlled by the absolute value of the currents. The buffer concentration and pH can be varied in a controlled predictable manner. A pH span of 3-12 was attained and a phosphate buffer concentration up to 140 mM was generated. We

  20. Buffer Standards for pH Measurement of N-(2-Hydroxyethyl)piperazine-N’-2-ethanesulfonic Acid (HEPES) for I = 0.16 mol·kg−1 from 5 to 55°C

    PubMed Central

    Roy, Rabindra N.; Roy, Lakshmi N.; Ashkenazi, Shahaf; Wollen, Joshua T.; Dunseth, Craig D.; Fuge, Michael S.; Durden, Jared L.; Roy, Chandra N.; Hughes, Hannah M.; Morris, Brett T.; Cline, Kevin L.

    2009-01-01

    The values of the second dissociation constant, pK2 of N-(2-hydroxyethyl) piperazine-N’-2-ethanesulfonic acid (HEPES) have been reported at 12 temperatures over the temperature range 5 to 55°C, including 37°C. This paper reports the results for the paH of eight isotonic saline buffer solutions with an I = 0.16 mol•kg−1 including compositions: (a) HEPES (0.01 mol•kg−1) + NaHEPES (0.01 mol•kg−1) + NaCl (0.15 mol•kg−1); (b) HEPES (0.02 mol•kg−1) + NaHEPES (0.02 mol•kg−1) + NaCl (0.14 mol•kg−1); (c) HEPES (0.03 mol•kg−1) + NaHEPES (0.03 mol•kg−1) + NaCl (0.13 mol•kg−1); (d) HEPES (0.04 mol•kg−1) + NaHEPES (0.04 mol•kg−1) + NaCl (0.12 mol•kg−1); (e) HEPES (0.05 mol•kg−1) + NaHEPES (0.05 mol•kg−1) + NaCl (0.11 mol•kg−1); (f) HEPES (0.06 mol•kg−1) + NaHEPES (0.06 mol•kg−1) + NaCl (0.10 mol•kg−1); (g) HEPES (0.07 mol•kg−1) + NaHEPES (0.07 mol•kg−1) + NaCl (0.09 mol•kg−1); and (h) HEPES (0.08 mol•kg−1) + NaHEPES (0.08 mol•kg−1) + NaCl (0.08 mol•kg−1). Conventional paH values, for all eight buffer solutions from 5 to 55°C have been calculated. The operational pH values with liquid junction corrections, at 25 and 37°C have been determined based on the NBS/NIST standard between the physiological phosphate standard and four buffer solutions. These are recommended as pH standards for physiological fluids in the range of pH 7.3 to 7.5 at I = 0.16 mol•kg−1. PMID:20161485

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

    PubMed

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

    2013-06-01

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

  2. The influences of the buffer capacity of various substances on pH changes in dental plaque.

    PubMed

    Shibasaki, K; Sano, H; Matsukubo, T; Takaesu, Y

    1994-02-01

    This study clarified the suitable pKa value for buffering substances against plaque pH fall in vitro and simultaneously estimated the effect of low molecular chitosan (LMCS) on plaque pH lowered by metabolized acids in vitro and in vivo. Five buffering substances with different pKa, aspartame (pKa: 7.8), phosphate buffer (7.1), LMCS (6.4), maleate buffer (6.2), and monofluorophosphate (4.8), were tested in this study. In the method using S. mutans cells, phosphate inhibited the pH fall from an initial pH of over 7.0, but phosphate exhibited no effect when the initial pH was 6.0. By the addition with lactic acid, LMCS and maleate exhibited more effective inhibition of the pH-fall than the others. These observations imply that pKa value is an important indicator of the ability of a buffering substance to reduce pH fall in dental plaque and that the optimum pKa value may be around pH 6.3. In the plaque pH measurement using ISFET electrode, LMCS showed an additional effect in inhibiting plaque pH fall following direct application of the glucose solution. The findings indicate that LMCS may be useful as a food additive to decrease the cariogenicity of foods.

  3. Reductive dechlorination of carbon tetrachloride using buffered alkaline ascorbic acid.

    PubMed

    Lin, Ya-Ting; Liang, Chenju

    2015-10-01

    Alkaline ascorbic acid (AA) was recently discovered as a novel in-situ chemical reduction (ISCR) reagent for remediating chlorinated solvents in the subsurface. For this ISCR process, the maintenance of an alkaline pH is essential. This study investigated the possibility of the reduction of carbon tetrachloride (CT) using alkaline AA solution buffered by phosphate and by NaOH. The results indicated that CT was reduced by AA, and chloroform (CF) was a major byproduct at a phosphate buffered pH of 12. However, CT was completely reduced by AA in 2M NaOH without CF formation. In the presence of iron/soil minerals, iron could be reduced by AA and Fe(2+) tends to precipitate on the mineral surface to accelerate CT degradation. A simultaneous transfer of hydrogenolysis and dichloroelimination would occur under phosphate buffered pH 12. This implies that a high alkaline environment is a crucial factor for maintaining the dominant pathway of two electron transfer from dianionic AA to dehydroascorbic acid, and to undergo dichloroelimination of CT. Moreover, threonic acid and oxalic acid were identified to be the major AA decomposition products in alkaline solutions.

  4. Influence of phosphate ions on buffer capacity of soil humic acids

    NASA Astrophysics Data System (ADS)

    Boguta, P.; Sokołowska, Z.

    2012-02-01

    The object of this study was to determine change of natural buffer capacity of humic acids by strong buffering agents, which were phosphate ions. Studies were carried out on the humic acids extracted from peat soils. Additional information was obtained by determination of water holding capacity, density, ash and pH for peats and optical parameter Q4/6 for humic acids. Humic acid suspensions exhibited the highest buffer properties at low pH and reached maximum at pH ~ 4. Phosphates possessed buffer properties in the pH range from 4.5 to 8.0. The maximum of buffering was at pH~6.8 and increased proportionally with an increase in the concentration of phosphate ions. The study indicated that the presence of phosphate ions may strongly change natural buffer capacity of humic acids by shifting buffering maximum toward higher pH values. Significant correlations were found for the degree of the secondary transformation with both the buffer capacity and the titrant volume used during titration.

  5. Effect of temperature, pH and buffer presence on ethanol production from synthesis gas by "Clostridium ragsdalei".

    PubMed

    Kundiyana, Dimple K; Wilkins, Mark R; Maddipati, Prasanth; Huhnke, Raymond L

    2011-05-01

    Fermentation pH, incubation temperature, and presence or absence of media buffer can alter the activity of microorganisms. For instance, carbon monoxide and hydrogen components of syngas show decreased solubility with increasing temperature, Clostridium species preferentially switch from acetogenesis to solventogenesis phase at pH below 5.0, and morpholinoethanesulfonic acid (MES) added as media buffer has been shown to increase lag time for ethanol production. The objective of the present study was to determine the effects of temperature, pH and MES buffer on ethanol production by "Clostridium ragsdalei". This study showed syngas fermentation using "Clostridium ragsdalei" at 32°C with media without buffer was associated with higher ethanol concentration and reduced lag time in switching to solventogenesis. Temperature above 40°C and pH below 5.0 were outside the optimal range for growth and metabolism of the bacteria.

  6. Internal acid buffering in San Joaquin Valley fog drops and its influence on aerosol processing

    NASA Astrophysics Data System (ADS)

    Collett, Jeffrey L.; Hoag, Katherine J.; Rao, Xin; Pandis, Spyros N.

    Although several chemical pathways exist for S(IV) oxidation in fogs and clouds, many are self-limiting: as sulfuric acid is produced and the drop pH declines, the rates of these pathways also decline. Some of the acid that is produced can be buffered by uptake of gaseous ammonia. Additional internal buffering can result from protonation of weak and strong bases present in solution. Acid titrations of high pH fog samples (median pH=6.49) collected in California's San Joaquin Valley reveal the presence of considerable internal acid buffering. In samples collected at a rural location, the observed internal buffering could be nearly accounted for based on concentrations of ammonia and bicarbonate present in solution. In samples collected in the cities of Fresno and Bakersfield, however, significant additional, unexplained buffering was present over a pH range extending from approximately four to seven. The additional buffering was found to be associated with dissolved compounds in the fogwater. It could not be accounted for by measured concentrations of low molecular weight ( C1- C3) carboxylic acids, S(IV), phosphate, or nitrophenols. The amount of unexplained buffering in individual fog samples was found to correlate strongly with the sum of sample acetate and formate concentrations, suggesting that unmeasured organic species may be important contributors. Simulation of a Bakersfield fog episode with and without the additional, unexplained buffering revealed a significant impact on the fog chemistry. When the additional buffering was included, the simulated fog pH remained 0.3-0.7 pH units higher and the amount of sulfate present after the fog evaporated was increased by 50%. Including the additional buffering in the model simulation did not affect fogwater nitrate concentrations and was found to slightly decrease ammonium concentrations. The magnitude of the buffering effect on aqueous sulfate production is sensitive to the amount of ozone present to oxidize S

  7. Thermophysical properties of carboxylic and amino acid buffers at subzero temperatures: relevance to frozen state stabilization.

    PubMed

    Sundaramurthi, Prakash; Suryanarayanan, Raj

    2011-06-01

    Macromolecules and other thermolabile biologicals are often buffered and stored in frozen or dried (freeze-dried) state. Crystallization of buffer components in frozen aqueous solutions and the consequent pH shifts were studied in carboxylic (succinic, malic, citric, tartaric acid) and amino acid (glycine, histidine) buffers. Aqueous buffer solutions were cooled from room temperature (RT) to -25 °C and the pH of the solution was measured as a function of temperature. The thermal behavior of frozen solutions was investigated by differential scanning calorimetry (DSC), and the crystallized phases were identified by X-ray diffractometry (XRD). Based on the solubility of the neutral species of each buffer system over a range of temperatures, it was possible to estimate its degree of supersaturation at the subambient temperature of interest. This enabled us to predict its crystallization propensity in frozen systems. The experimental and the predicted rank orderings were in excellent agreement. The malate buffer system was robust with no evidence of buffer component crystallization and hence negligible pH shift. In the citrate and tartrate systems, at initial pH < pK(a)(2), only the most acidic buffer component (neutral form) crystallized on cooling, causing an increase in the freeze-concentrate pH. In glycine buffer solutions, when the initial pH was ∼3 units < isoelectric pH (pI = 5.9), β-glycine crystallization caused a small decrease in pH, while a similar effect but in the opposite direction was observed when the initial pH was ∼3 units > pI. In the histidine buffer system, depending on the initial pH, either histidine or histidine HCl crystallized.

  8. Buffer Standards for the Physiological pH of the Zwitterionic Compound, DIPSO from 5 to 55°C

    PubMed Central

    Roy, Lakshmi N.; Roy, Rabindra N.; LeNoue, Sean R.; Denton, Cole E.; Fuge, Michael S.; Dunseth, Craig D.; Roy, Chandra N.; Hayden, Shawn M.; Wollen, Joshua T.; Sreepada, Kripa

    2009-01-01

    The values of the second dissociation constant, pK2, and related thermodynamic quantities of 3-[N,N-bis (2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) have already been reported over the temperature range 5 to 55°C including 37°C. This paper reports the pH values of four NaCl-free buffer solutions and four buffer composition containing NaCl salt at I = 0.16 mol·kg−1. Conventional paH values are reported for all eight buffer solutions. The operational pH values have been calculated for four buffer solutions recommended as pH standards, at 25 and 37°C after correcting the liquid junction potentials with the flowing junction cell. PMID:20160870

  9. Buffer Standards for the Physiological pH of the Zwitterionic Compound, DIPSO from 5 to 55 degrees C.

    PubMed

    Roy, Lakshmi N; Roy, Rabindra N; Lenoue, Sean R; Denton, Cole E; Fuge, Michael S; Dunseth, Craig D; Roy, Chandra N; Hayden, Shawn M; Wollen, Joshua T; Sreepada, Kripa

    2009-04-01

    The values of the second dissociation constant, pK(2), and related thermodynamic quantities of 3-[N,N-bis (2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) have already been reported over the temperature range 5 to 55 degrees C including 37 degrees C. This paper reports the pH values of four NaCl-free buffer solutions and four buffer composition containing NaCl salt at I = 0.16 mol.kg(-1). Conventional pa(H) values are reported for all eight buffer solutions. The operational pH values have been calculated for four buffer solutions recommended as pH standards, at 25 and 37 degrees C after correcting the liquid junction potentials with the flowing junction cell.

  10. Salivary pH and Buffering Capacity as Risk Markers for Early Childhood Caries: A Clinical Study

    PubMed Central

    Ganesan, S

    2015-01-01

    ABSTRACT Background: The diagnostic utility of saliva is currently being explored in various branches of dentistry, remarkably in the field of caries research. This study was aimed to determine if assessment of salivary pH and buffering capacity would serve as reliable tools in risk prediction of early childhood caries (ECC). Materials and methods: Paraffin-stimulated salivary samples were collected from 50 children with ECC (group I) and 50 caries free children (group II). Salivary pH and buffering capacity (by titration with 0.1 N hydrochloric acid) were assessed using a handheld digital pH meter in both groups. The data obtained were subjected to statistical analysis. Results: Statistically, no significant difference was observed between both the groups for all salivary parameters assessed, except for the buffering capacity level at 150 μl titration of 0.1 N hydrochloric acid (p = 0.73; significant at 1% level). Conclusion: Salivary pH and buffering capacity may not serve as reliable markers for risk prediction of ECC. How to cite this article: Jayaraj D, Ganesan S. Salivary pH and Buffering Capacity as Risk Markers for Early Childhood Caries: A Clinical Study. Int J Clin Pediatr Dent 2015;8(3):167-171. PMID:26628849

  11. Optimizing buffering chemistry to maintain near neutral pH of broiler feed during pre-enrichment for Salmonella.

    PubMed

    Berrang, M E; Cosby, D E; Cox, N A; Cason, J A; Richardson, K E

    2015-12-01

    Salmonella is a human pathogen that can accompany live broilers to the slaughter plant, contaminating fully processed carcasses. Feed is one potential source of Salmonella to growing broilers. Monitoring feed for the presence of Salmonella is part of good agricultural practice. The first step in culturing feed for Salmonella (which may be at low numbers and sub-lethally stressed) is to add it to a pre-enrichment broth which is incubated for 24 h. During the course of pre-enrichment, extraneous bacteria metabolize carbohydrates in some feed and excrete acidic byproducts, causing the pH to drop dramatically. An acidic pre-enrichment pH can injure or kill Salmonella resulting in a failure to detect, even if it is present and available to infect chickens. The objective of this study was to test an array of buffering chemistries to prevent formation of an injurious acidic environment during pre-enrichment of feed in peptone water. Five grams of feed were added to 45 mL of peptone water buffered with carbonate, Tris pH 8, and phosphate buffering ingredients individually and in combination. Feed was subjected to a pre-enrichment at 35°C for 24 h; pH was measured at 0, 18, and 24 h. Standard phosphate buffering ingredients at concentrations up to 4 times the normal formulation were unable to fully prevent acidic conditions. Likewise, carbonate and Tris pH 8 were not fully effective. The combination of phosphate, carbonate, and Tris pH 8 was the most effective buffer tested. It is recommended that a highly buffered pre-enrichment broth be used to examine feed for the presence of Salmonella.

  12. [pH buffering capacity of landfill leachate contaminated aquifer sediments in different redox zones].

    PubMed

    Dong, Jun; Zhao, Yong-Sheng; Hong, Mei; Zhu, Zhi-Guo

    2009-09-15

    A simulated column filled with fine sand was constructed to investigate pH buffering capacity of aquifer sediments and its variation in different redox zones. Experimental results indicated that background pH buffering capacity of sediments was 324.93 pH(-1) mmol/kg, and the buffering capacities of cation exchange, calcium carbonate, silicate and secondary were 41.77 x pH(-1), 86.53 pH(-1), 47.33 pH(-1) and 149.31 x pH(-1) mmol/kg, respectively. pH buffering capacity increased 12.4%, 10.8%, 19.8% and 11.1% in MGZ/SRZ, IRZ, NRZ and ORZ, respectively. Cation exchange capacity (CEC) and base exchangeable cation (BEC) content of sediments in redox zones were lower than background content which was 11.59 x pH(-1) and 8.52 x pH(-1) mmol/kg, respectively. Base cation saturation was increasing first and then then decreasing, and it was higher than background of 63.47%. Therefore, the aquifer sediments have high pH buffering capacity. Research on the pH buffering capacity of landfill leachate polluted aquifer sediments in redox zones could provide theoretical evidences for remediation of polluted sites.

  13. Secular decline of seawater calcium increases seawater buffering and pH

    NASA Astrophysics Data System (ADS)

    Hain, M.; Sigman, D. M.; Higgins, J. A.; Haug, G. H.

    2015-12-01

    Reconstructed changes in seawater calcium and magnesium concentration ([Ca2+], [Mg2+]) predictably affect the ocean's acid/base and carbon chemistry. Yet inaccurate formulations of chemical equilibrium "constants" are currently in use to account for these changes. Here we develop an efficient implementation of the MIAMI Ionic Interaction Model (Millero and Pierrot, 1998) to predict all chemical equilibrium constants required for carbon chemistry calculations under variable [Ca2+] and [Mg2+] (Hain et al., 2015). We investigate the impact of [Ca2+] and [Mg2+] on the relationships among the ocean's pH, CO2, dissolved inorganic carbon (DIC), saturation state of CaCO3 (Ω), and buffer capacity. Increasing [Ca2+] and/or [Mg2+] enhances "ion pairing," which increases seawater buffering by increasing the concentration ratio of total to "free" (uncomplexed) carbonate ion. An increase in [Ca2+], however, also causes a decline in carbonate ion to maintain a given Ω, thereby overwhelming the ion pairing effect and decreasing seawater buffering. Given the reconstructions of Eocene [Ca2+] and [Mg2+] ([Ca2+]~20mM; [Mg2+]~30 mM), Eocene seawater would have required essentially the same DIC as today to simultaneously explain a similar-to-modern Ω and the estimated Eocene atmospheric CO2 of ~1000 ppm. During the Cretaceous, at ~4 times modern [Ca2+], ocean buffering would have been at a minimum. Overall, during times of high seawater [Ca2+], CaCO3 saturation, pH, and atmospheric CO2 were more susceptible to perturbations of the global carbon cycle. For example, given both Eocene and Cretaceous seawater [Ca2+] and [Mg2+], a doubling of atmospheric CO2 would require less carbon addition to the ocean/atmosphere system than under modern seawater composition. Moreover, increase in seawater buffering since the Cretaceous may have been a driver of evolution by raising energetic demands of biologically controlled calcification and CO2 concentration mechanisms that aid photosynthesis.

  14. Towards biochemical filters with a sigmoidal response to pH changes: buffered biocatalytic signal transduction

    NASA Astrophysics Data System (ADS)

    Pita, Marcos; Privman, Vladimir; Arugula, Mary A.; Melnikov, Dmitriy; Bocharova, Vera; Katz, Evgeny

    We realize a biochemical filtering process by introducing a buffer in a biocatalytic signal-transduction logic system based on the function of an enzyme, esterase. The input, ethyl butyrate, is converted into butyric acid-the output signal, which in turn is measured by the drop in the pH value. The developed approach offers a versatile "network element" for increasing the complexity of biochemical information processing systems. Evaluation of an optimal regime for quality filtering is accomplished in the framework of a kinetic rate-equation model.

  15. [Soil pH buffer capacity of tea garden with different planting years].

    PubMed

    Su, You-Jian; Wang, Ye-Jun; Zhang, Yong-Li; Luo, Yi; Sun, Li; Song, Li; Liao, Wan-You

    2014-10-01

    In order to investigate the effects of long-term tea planting on soil pH buffer capacity (pHBC), the variation of pHBC and its influence factors were investigated in tea gardens of 10, 15, 20, 25 and 30 years in Langxi and Qimen of Anhui Province. The results showed that the acid-base titration method was suitable for the determination of soil pHBC of tea gardens. The amount of acid-base added had approximate linear relationship with soil pH value in specific section (pH 4.0-6.0) of acid-base titration curves, so the soil pHBC could be calculated by linear regression equation. Soil pHBC in the tea gardens from the two regions showed a downward trend with increasing the planting years, which decreased at rates of 0.10 and 0.06 mmol · kg(-1) · a(-1) in Langxi and Qimen tea gardens, respectively. Soil pHBC had significant positive correlation with CEC, soil organic matter, base saturation and physical clay content, and significant negative correlation with exchangeable acid and exchange H+. PMID:25796900

  16. [Soil pH buffer capacity of tea garden with different planting years].

    PubMed

    Su, You-Jian; Wang, Ye-Jun; Zhang, Yong-Li; Luo, Yi; Sun, Li; Song, Li; Liao, Wan-You

    2014-10-01

    In order to investigate the effects of long-term tea planting on soil pH buffer capacity (pHBC), the variation of pHBC and its influence factors were investigated in tea gardens of 10, 15, 20, 25 and 30 years in Langxi and Qimen of Anhui Province. The results showed that the acid-base titration method was suitable for the determination of soil pHBC of tea gardens. The amount of acid-base added had approximate linear relationship with soil pH value in specific section (pH 4.0-6.0) of acid-base titration curves, so the soil pHBC could be calculated by linear regression equation. Soil pHBC in the tea gardens from the two regions showed a downward trend with increasing the planting years, which decreased at rates of 0.10 and 0.06 mmol · kg(-1) · a(-1) in Langxi and Qimen tea gardens, respectively. Soil pHBC had significant positive correlation with CEC, soil organic matter, base saturation and physical clay content, and significant negative correlation with exchangeable acid and exchange H+.

  17. Application of acetate buffer in pH adjustment of sorghum mash and its influence on fuel ethanol fermentation.

    PubMed

    Zhao, Renyong; Bean, Scott R; Crozier-Dodson, Beth Ann; Fung, Daniel Y C; Wang, Donghai

    2009-01-01

    A 2 M sodium acetate buffer at pH 4.2 was tried to simplify the step of pH adjustment in a laboratory dry-grind procedure. Ethanol yields or conversion efficiencies of 18 sorghum hybrids improved significantly with 2.0-5.9% (3.9% on average) of relative increases when the method of pH adjustment changed from traditional HCl to the acetate buffer. Ethanol yields obtained using the two methods were highly correlated (R (2) = 0.96, P < 0.0001), indicating that the acetate buffer did not influence resolution of the procedure to differentiate sorghum hybrids varying in fermentation quality. Acetate retarded the growth of Saccharomyces cerevisiae, but did not affect the overall fermentation rate. With 41-47 mM of undissociated acetic acid in mash of a sorghum hybrid at pH 4.7, rates of glucose consumption and ethanol production were inhibited during exponential phase but promoted during stationary phase. The maximum growth rate constants (mu(max)) were 0.42 and 0.32 h(-1) for cells grown in mashes with pH adjusted by HCl and the acetate buffer, respectively. Viable cell counts of yeast in mashes with pH adjusted by the acetate buffer were 36% lower than those in mashes adjusted by HCl during stationary phase. Coupled to a 5.3% relative increase in ethanol, a 43.6% relative decrease in glycerol was observed, when the acetate buffer was substituted for HCl. Acetate helped to transfer glucose to ethanol more efficiently. The strain tested did not use acetic acid as carbon source. It was suggested that decreased levels of ATP under acetate stress stimulate glycolysis to ethanol formation, increasing its yield at the expense of biomass and glycerol production.

  18. Diffusion of ionizable solutes across planar lipid bilayer membranes: boundary-layer pH gradients and the effect of buffers.

    PubMed

    Xiang, T X; Anderson, B D

    1993-11-01

    The diffusion of weak acids or bases across planar lipid bilayer membranes results in aqueous boundary layer pH gradients. If not properly taken into account, such pH gradients will lead to errors in estimated membrane permeability coefficients, Pm. The role of the permeant concentration, the buffer capacity, and the physicochemical properties of both permeant and buffer on the magnitude and impact of such pH gradients have been explored. A theoretical model has been developed to describe the diffusion of both permeant and buffer species. Significant pH gradients develop depending on solution pH and the pKa's, concentrations, and Pm values of both permeant and buffer. The relative error in experimentally determined Pm values was calculated as the ratio, r, between apparent Pm values (obtained from flux measurements using an equation which neglected boundary layer pH gradients) and its true value. Simulated r values ranged from 1 (0% error) to < 0.01 (> 100% error) for weak acids, decreasing with decreasing buffer capacity and increasing solute flux. The buffer capacity required for an r > 0.95 was calculated versus pH for permeants varying in pKa and Pm. Membrane-permeable buffers significantly reduce boundary layer pH gradients through a feedback effect due to buffer cotransport. Apparent Pm values of p-hydroxymethyl benzoic acid across lecithin bilayer membranes at 25 degrees C were obtained as a function of permeant concentration in various buffers [glycolic, 2-(N-morpholino)ethane-sulfonic, and formic acids]. Predictions agreed closely with experimental fluxes. PMID:8290481

  19. Calorimetric and Diffractometric Evidence for the Sequential Crystallization of Buffer Components and the Consequential pH Swing in Frozen Solutions

    SciTech Connect

    Sundaramurthi, Prakash; Shalaev, Evgenyi; Suryanarayanan, Raj

    2010-06-22

    Sequential crystallization of succinate buffer components in the frozen solution has been studied by differential scanning calorimetry and X-ray diffractometry (both laboratory and synchrotron sources). The consequential pH shifts were monitored using a low-temperature electrode. When a solution buffered to pH < pK{sub a2} was cooled from room temperature (RT), the freeze-concentrate pH first increased and then decreased. This was attributed to the sequential crystallization of succinic acid, monosodium succinate, and finally disodium succinate. When buffered to pH > pK{sub a2}, the freeze-concentrate pH first decreased and then increased due to the sequential crystallization of the basic (disodium succinate) followed by the acidic (monosodium succinate and succinic acid) buffer components. XRD provided direct evidence of the crystallization events in the frozen buffer solutions, including the formation of disodium succinate hexahydrate [Na{sub 2}(CH{sub 2}COO){sub 2} {center_dot} 6H{sub 2}O]. When the frozen solution was warmed in a differential scanning calorimeter, multiple endotherms attributable to the melting of buffer components and ice were observed. When the frozen solutions were dried under reduced pressure, ice sublimation was followed by dehydration of the crystalline hexahydrate to a poorly crystalline anhydrate. However, crystalline succinic acid and monosodium succinate were retained in the final lyophiles. The pH and the buffer salt concentration of the prelyo solution influenced the crystalline salt content in the final lyophile. The direction and magnitude of the pH shift in the frozen solution depended on both the initial pH and the buffer concentration. In light of the pH-sensitive nature of a significant fraction of pharmaceuticals (especially proteins), extreme care is needed in both the buffer selection and its concentration.

  20. The Effect of Crystallizing and Non-crystallizing Cosolutes on Succinate Buffer Crystallization and the Consequent pH Shift in Frozen Solutions

    SciTech Connect

    Sundaramurthi, Prakash; Suryanarayanan, Raj

    2011-09-06

    To effectively inhibit succinate buffer crystallization and the consequent pH changes in frozen solutions. Using differential scanning calorimetry (DSC) and X-ray diffractometry (XRD), the crystallization behavior of succinate buffer in the presence of either (i) a crystallizing (glycine, mannitol, trehalose) or (ii) a non-crystallizing cosolute (sucrose) was evaluated. Aqueous succinate buffer solutions, 50 or 200 mM, at pH values 4.0 or 6.0 were cooled from room temperature to -25 C at 0.5 C/min. The pH of the solution was measured as a function of temperature using a probe designed to function at low temperatures. The final lyophiles prepared from these solutions were characterized using synchrotron radiation. When the succinic acid solution buffered to pH 4.0, in the absence of a cosolute, was cooled, there was a pronounced shift in the freeze-concentrate pH. Glycine and mannitol, which have a tendency to crystallize in frozen solutions, remained amorphous when the initial pH was 6.0. Under this condition, they also inhibited buffer crystallization and prevented pH change. At pH 4.0 (50 mM initial concentration), glycine and mannitol crystallized and did not prevent pH change in frozen solutions. While sucrose, a non-crystallizing cosolute, did not completely prevent buffer crystallization, the extent of crystallization was reduced. Sucrose decomposition, based on XRD peaks attributable to {beta}-D-glucose, was observed in frozen buffer solutions with an initial pH of 4.0. Trehalose completely inhibited crystallization of the buffer components when the initial pH was 6.0 but not at pH 4.0. At the lower pH, the crystallization of both trehalose dihydrate and buffer components was evident. When retained amorphous, sucrose and trehalose effectively inhibited succinate buffer component crystallization and the consequent pH shift. However, when trehalose crystallized or sucrose degraded to yield a crystalline decomposition product, crystallization of buffer was

  1. Role of bicarbonate as a pH buffer and electron sink in microbial dechlorination of chloroethenes

    PubMed Central

    2012-01-01

    Background Buffering to achieve pH control is crucial for successful trichloroethene (TCE) anaerobic bioremediation. Bicarbonate (HCO3−) is the natural buffer in groundwater and the buffer of choice in the laboratory and at contaminated sites undergoing biological treatment with organohalide respiring microorganisms. However, HCO3− also serves as the electron acceptor for hydrogenotrophic methanogens and hydrogenotrophic homoacetogens, two microbial groups competing with organohalide respirers for hydrogen (H2). We studied the effect of HCO3− as a buffering agent and the effect of HCO3−-consuming reactions in a range of concentrations (2.5-30 mM) with an initial pH of 7.5 in H2-fed TCE reductively dechlorinating communities containing Dehalococcoides, hydrogenotrophic methanogens, and hydrogenotrophic homoacetogens. Results Rate differences in TCE dechlorination were observed as a result of added varying HCO3− concentrations due to H2-fed electrons channeled towards methanogenesis and homoacetogenesis and pH increases (up to 8.7) from biological HCO3− consumption. Significantly faster dechlorination rates were noted at all HCO3− concentrations tested when the pH buffering was improved by providing 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) as an additional buffer. Electron balances and quantitative PCR revealed that methanogenesis was the main electron sink when the initial HCO3− concentrations were 2.5 and 5 mM, while homoacetogenesis was the dominant process and sink when 10 and 30 mM HCO3− were provided initially. Conclusions Our study reveals that HCO3− is an important variable for bioremediation of chloroethenes as it has a prominent role as an electron acceptor for methanogenesis and homoacetogenesis. It also illustrates the changes in rates and extent of reductive dechlorination resulting from the combined effect of electron donor competition stimulated by HCO3− and the changes in pH exerted by methanogens and

  2. Acid loading test (pH)

    MedlinePlus

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

  3. Retention of ionisable compounds on high-performance liquid chromatography XVII. Estimation of the pH variation of aqueous buffers with the change of the methanol fraction of the mobile phase.

    PubMed

    Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

    2007-01-01

    The use of methanol-aqueous buffer mobile phases in HPLC is a common election when performing chromatographic separations of ionisable analytes. The addition of methanol to the aqueous buffer to prepare such a mobile phase changes the buffer capacity and the pH of the solution. In the present work, the variation of these buffer properties is studied for acetic acid-acetate, phosphoric acid-dihydrogenphosphate-hydrogenphosphate, citric acid-dihydrogencitrate-hydrogencitrate-citrate, and ammonium-ammonia buffers. It is well established that the pH change of the buffers depends on the initial concentration and aqueous pH of the buffer, on the percentage of methanol added, and on the particular buffer used. The proposed equations allow the pH estimation of methanol-water buffered mobile phases up to 80% in volume of organic modifier from initial aqueous buffer pH and buffer concentration (before adding methanol) between 0.001 and 0.01 mol L(-1). From both the estimated pH values of the mobile phase and the estimated pKa of the ionisable analytes, it is possible to predict the degree of ionisation of the analytes and therefore, the interpretation of acid-base analytes behaviour in a particular methanol-water buffered mobile phase.

  4. Pain perception with pH buffered peribulbar anaesthesia: a pilot study

    PubMed Central

    Minasian, M.; Ionides, A.; Fernando, R.; Davey, C.

    2000-01-01

    AIMS—To determine the relation between pH of anaesthetic solutions and patient perception of pain with peribulbar injection of local anaesthesia.
METHODS—This prospective randomised controlled double blind pilot study involved 60 consecutive patients who received a peribulbar block with either a standard acidic local anaesthetic of 5 ml 2% lignocaine and 5 ml of 0.5% bupivacaine (solution A), or an alkalinised solution composed of the same anaesthetic agents but with a pH of 7.44 (solution B). Before surgery patients were asked to grade the pain of both the preoperative dilating drops and the peribulbar injection using a visual analogue scale.
RESULTS—The mean pain scores were similar in the two treatment groups—slightly higher (4.97) in group B who received the buffered solution, compared with group A (4.84) who received the plain solution. The small difference (−0.13, 95% confidence limits −1.6 and +1.3) was not significant. There was, however, a highly significant association between pain threshold ("drop pain") and injection pain levels (p<0.0001).
CONCLUSION—This study showed no difference in the reduction in the pain experienced by patients undergoing peribulbar anaesthesia with pH buffered local anaesthetic. The study suggests the importance of "pain threshold" as a confounder and also showed the considerable pain felt by some patients on instillation of the preoperative dilating drops.

 PMID:10966962

  5. Macrophyte and pH buffering updates to the Klamath River water-quality model upstream of Keno Dam, Oregon

    USGS Publications Warehouse

    Sullivan, Annett B.; Rounds, Stewart A.; Asbill-Case, Jessica R.; Deas, Michael L.

    2013-01-01

    A hydrodynamic, water temperature, and water-quality model of the Link River to Keno Dam reach of the upper Klamath River was updated to account for macrophytes and enhanced pH buffering from dissolved organic matter, ammonia, and orthophosphorus. Macrophytes had been observed in this reach by field personnel, so macrophyte field data were collected in summer and fall (June-October) 2011 to provide a dataset to guide the inclusion of macrophytes in the model. Three types of macrophytes were most common: pondweed (Potamogeton species), coontail (Ceratophyllum demersum), and common waterweed (Elodea canadensis). Pondweed was found throughout the Link River to Keno Dam reach in early summer with densities declining by mid-summer and fall. Coontail and common waterweed were more common in the lower reach near Keno Dam and were at highest density in summer. All species were most dense in shallow water (less than 2 meters deep) near shore. The highest estimated dry weight biomass for any sample during the study was 202 grams per square meter for coontail in August. Guided by field results, three macrophyte groups were incorporated into the CE-QUAL-W2 model for calendar years 2006-09. The CE-QUAL-W2 model code was adjusted to allow the user to initialize macrophyte populations spatially across the model grid. The default CE-QUAL-W2 model includes pH buffering by carbonates, but does not include pH buffering by organic matter, ammonia, or orthophosphorus. These three constituents, especially dissolved organic matter, are present in the upper Klamath River at concentrations that provide substantial pH buffering capacity. In this study, CE-QUAL-W2 was updated to include this enhanced buffering capacity in the simulation of pH. Acid dissociation constants for ammonium and phosphoric acid were taken from the literature. For dissolved organic matter, the number of organic acid groups and each group's acid dissociation constant (Ka) and site density (moles of sites per mole of

  6. Light adaptation of invertebrate photoreceptors: influence of intracellular pH buffering capacity.

    PubMed Central

    Bolsover, S R; Brown, J E

    1982-01-01

    1. The possible role of pH changes in mediating light adaptation in Limulus ventral photoreceptor cells was studied by intracellular injection of zwitterionic pH buffers. The intracellular concentration of buffer was estimated by inclusion of a radioactive marker in the injection solution. 2. The light-induced increase of intracellular Ca2+ concentration was monitored by intracellular aequorin. The light-induced increase of Ca2+ concentration was not markedly altered by injection of pH buffer to an intracellular concentration of about 200 mM. 3. The progressive decrease in responsiveness during intracellular ionophoretic injection of Ca2+ was not markedly altered by injection of pH buffer to an intracellular concentration of about 200 mM. 4. Photoreceptors of both Limulus and Balanus were impaled with two micropipettes and voltage clamped. Membrane current induced by a prolonged steady illumination declined from an early transient to a plateau. This delayed decline of current indicates a light-induced reduction of sensitivity (i.e. light adaptation). The wave forms were similar before and after injection of pH buffer to an intracellular concentration of about 200 mM. 5. We conclude that it is unlikely that a light-induced change of cytosolic pH mediates light adaptation in Limulus (and Balanus) photoreceptors. PMID:7175745

  7. Aluminum elution and precipitation in glass vials: effect of pH and buffer species.

    PubMed

    Ogawa, Toru; Miyajima, Makoto; Wakiyama, Naoki; Terada, Katsuhide

    2015-02-01

    Inorganic extractables from glass vials may cause particle formation in the drug solution. In this study, the ability of eluting Al ion from borosilicate glass vials, and tendencies of precipitation containing Al were investigated using various pHs of phosphate, citrate, acetate and histidine buffer. Through heating, all of the buffers showed that Si and Al were eluted from glass vials in ratios almost the same as the composition of borosilicate glass, and the amounts of Al and Si from various buffer solutions at pH 7 were in the following order: citrate > phosphate > acetate > histidine. In addition, during storage after heating, the Al concentration at certain pHs of phosphate and acetate buffer solution decreased, suggesting the formation of particles containing Al. In citrate buffer, Al did not decrease in spite of the high elution amount. Considering that the solubility profile of aluminum oxide and the Al eluting profile of borosilicate glass were different, it is speculated that Al ion may be forced to leach into the buffer solution according to Si elution on the surface of glass vials. When Al ions were added to the buffer solutions, phosphate, acetate and histidine buffer showed a decrease of Al concentration during storage at a neutral range of pHs, indicating the formation of particles containing Al. In conclusion, it is suggested that phosphate buffer solution has higher possibility of forming particles containing Al than other buffer solutions.

  8. Report of key comparison SIM.QM-K91 pH of phthalate buffer (nominal pH ~4.01 at 25 °C)

    NASA Astrophysics Data System (ADS)

    Gonzaga, F. B.; Dias, J. C.; Pratt, K. W.; Waters, J.; Dimitrova, L.; Delgado, M.; Canaza, G. T.; Cristancho, R. O.; Chavarro, L. A.; Fajardo, S.; Rodruangthum, P.; Tangpaisarnkul, N.; Gavrilkin, V.; Nagibin, S.; Petrenko, A.; Manska, A.

    2015-01-01

    At the SIM meeting in Buenos Aires, from 30 May to 1 June 2012, it was decided a RMO key comparison on pH measurement coordinated by INMETRO would be performed, named SIM.QM-K91, in order to investigate the degrees of equivalence of measurement procedures for the pH determination of a phthalate buffer solution (nominal pH around 4.01 at 25 °C). Phthalate buffer is widely used to calibrate pH electrodes in the acid range. A buffer solution of 0.05 mol kg-1 potassium hydrogen phthalate, KHC8H4O4, is one of the primary pH reference buffer solutions recommended by IUPAC. It was only allowed to participate in this comparison by using a differential cell or a glass electrode, instead of primary cells, if the highest metrological standard in the institute or if the CMCs are based on the type of cell to be used. The results obtained by INMETRO and NIST (who also participated in CCQM-K91 comparison) were used to link the results from the other institutes to the key comparison reference value of CCQM-K91. In this comparison, pH measurements were performed at 25 °C, and optionally also at 15 °C and 37 °C. Nine institutes took part in the comparison and the results are presented in this report. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  9. Ability of subsoils to buffer extremely acidic simulated coal-pile leachates

    SciTech Connect

    Zelmanowitz, S.; Boyle, W.C.; Armstrong, D.E.; Park, J.K.

    1995-11-01

    Coal piles stored directly on soil surfaces may pose a risk of ground-water contamination, particularly when extremely acidic coal-pile leachates, which contain elevated concentrations of heavy metals, are generated. Soil-column experiments were run to evaluate the ability of a sand, a silt loam, and a silt loam amended with 4% CaCO{sub 3} to buffer dilute H{sub 2}SO{sub 4} solutions (pH 3.5 and 1.5) and a synthetic coal-pile leachate (a pH 1.5 H{sub 2}SO{sub 4} solution containing metal sulfate salts). Both silt-loam soils were able to buffer the pH 3.5 H{sub 2}SO{sub 4} solution for the entire leaching period (more than 50 pore volumes), but the sand was not. The buffering capacities of all three soils were insufficient to neutralize pH 1.5 acid and synthetic coal-pile leachates. The sand exhibited the least buffering, and the silt loam at a low flow rate and the silt loam amended with CaCO{sub 3} showed the greatest buffering. The buffering capacities of both silt loam soils were exhausted more rapidly when leached with synthetic coal-pile leachate rather than pH 1.5 H{sub 2}SO{sub 4} solution. This suggests that soil-buffering studies using pure acid solutions may underpredict contamination due to coal-pile leachates. The results indicate that there is a potential for ground-water contamination due to coal-pile storage, particularly where leachates are acidic ad coarse textured soils exist. Coal storage practices should be adopted that protect soils and ground water from acidification and metals contamination.

  10. Predicting the crystallization propensity of carboxylic acid buffers in frozen systems--relevance to freeze-drying.

    PubMed

    Sundaramurthi, Prakash; Suryanarayanan, Raj

    2011-04-01

    Selective crystallization of buffer components in frozen solutions is known to cause pronounced pH shifts. Our objective was to study the crystallization behavior and the consequent pH shift in frozen aqueous carboxylic acid buffers. Aqueous carboxylic acid buffers were cooled to -25°C and the pH of the solution was measured as a function of temperature. The thermal behavior of solutions during freezing and thawing was investigated by differential scanning calorimetry. The crystallized phases in frozen solution were identified by X-ray diffractometry. The malate buffer system was robust with no evidence of buffer component crystallization and hence negligible pH shift. In the citrate and tartarate systems, at initial pH acidic buffer component (neutral form) crystallized on cooling, causing an increase in the freeze-concentrate pH. Carboxylic acid buffers were rank ordered based on their propensity to crystallize in frozen solutions. From the aqueous solubility values of these carboxylic acids, which have been reported over a range of temperatures, it was also possible to estimate the degree of supersaturation at the subambient temperature of interest. This enabled us to predict their crystallization propensity in frozen systems. The experimental and the predicted rank orderings were in excellent agreement.

  11. The effect of pH and buffer concentration on anode biofilms of Thermincola ferriacetica.

    PubMed

    Lusk, Bradley G; Parameswaran, Prathap; Popat, Sudeep C; Rittmann, Bruce E; Torres, Cesar I

    2016-12-01

    We assessed the effects of pH and buffer concentration on current production and growth of biofilms of Thermincola ferriacetica - a thermophilic, Gram-positive, anode-respiring bacterium (ARB) - grown on anodes poised at a potential of -0.06V vs. SHE in microbial electrolysis cells (MECs) at 60°C. T. ferriacetica generated current in the pH range of 5.2 to 8.3 with acetate as the electron donor and 50mM bicarbonate buffer. Maximum current density was reduced by ~80% at pH5.2 and ~14% at 7.0 compared to pH8.3. Increasing bicarbonate buffer concentrations from 10mM to 100mM resulted in an increase in the current density by 40±6%, from 6.8±1.1 to 11.2±2.7Am(-2), supporting that more buffer alleviated pH depression within T. ferriacetica biofilms. Confocal laser scanning microscopy (CLSM) images indicated that higher bicarbonate buffer concentrations resulted in larger live biofilm thicknesses: from 68±20μm at 10mM bicarbonate to >150μm at 100mM, supporting that buffer availability was a strong influence on biofilm thickness. In comparison to mesophilic Geobacter sulfurreducens biofilms, the faster transport rates at higher temperature and the ability to grow at relatively lower pH allowed T. ferriacetica to produce higher current densities with lower buffer concentrations.

  12. The effect of pH and buffer concentration on anode biofilms of Thermincola ferriacetica.

    PubMed

    Lusk, Bradley G; Parameswaran, Prathap; Popat, Sudeep C; Rittmann, Bruce E; Torres, Cesar I

    2016-12-01

    We assessed the effects of pH and buffer concentration on current production and growth of biofilms of Thermincola ferriacetica - a thermophilic, Gram-positive, anode-respiring bacterium (ARB) - grown on anodes poised at a potential of -0.06V vs. SHE in microbial electrolysis cells (MECs) at 60°C. T. ferriacetica generated current in the pH range of 5.2 to 8.3 with acetate as the electron donor and 50mM bicarbonate buffer. Maximum current density was reduced by ~80% at pH5.2 and ~14% at 7.0 compared to pH8.3. Increasing bicarbonate buffer concentrations from 10mM to 100mM resulted in an increase in the current density by 40±6%, from 6.8±1.1 to 11.2±2.7Am(-2), supporting that more buffer alleviated pH depression within T. ferriacetica biofilms. Confocal laser scanning microscopy (CLSM) images indicated that higher bicarbonate buffer concentrations resulted in larger live biofilm thicknesses: from 68±20μm at 10mM bicarbonate to >150μm at 100mM, supporting that buffer availability was a strong influence on biofilm thickness. In comparison to mesophilic Geobacter sulfurreducens biofilms, the faster transport rates at higher temperature and the ability to grow at relatively lower pH allowed T. ferriacetica to produce higher current densities with lower buffer concentrations. PMID:27450427

  13. Influences of biochar addition on vegetable soil nitrogen balance and pH buffering capacity

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Odindo, AO; Xue, L.; Yang, L.

    2016-08-01

    Leaching is a major path for chemical nitrogen fertilizer loss from in vegetable soil, which would destroy soil pH buffering capacity soil and result in acidification. It has been a common phenomenon in Tai Lake Region, China. However, few study focused on the change soil pH buffering capacity, especially the effect of soil amendment on pH buffering capacity. In this study, a pot experiment was conducted to research the effects of biochar addition to a vegetable soil on nitrogen leaching and pH buffering capacity with pakchoi (B.chinensis L.) growth as the experimental crop. The results showed that biochar could significantly increase the pakchoi nitrogen utilization efficiency, decrease 48%-65% nitrogen loss from leaching under the urea continuous applied condition. Biochar also could effectively maintain the content of soil organic matter and base cations. Therefore, it rose up soil pH buffering capacity by 9.4%-36.8% and significantly slowed down acidification rate. It was suggested that 1%-2% addition ratio was recommended from this study when used as similar soil condition.

  14. Reaction of nerve agents with phosphate buffer at pH 7.

    PubMed

    Creasy, William R; Fry, Roderick A; McGarvey, David J

    2012-07-12

    Chemical weapon nerve agents, including isopropyl methylphosphonofluoridate (GB or Sarin), pinacolyl methylphosphonofluoridate (GD or Soman), and S-(2-diisopropylaminoethyl) O-ethyl methylphosphonothioate (VX), are slow to react in aqueous solutions at midrange pH levels. The nerve agent reactivity increases in phosphate buffer at pH 7, relative to distilled water or acetate buffer. Reactions were studied using (31)P NMR. Phosphate causes faster reaction to the corresponding alkyl methylphosphonic acids, and produces a mixed phosphate/phosphonate compound as an intermediate reaction product. GB has the fastest reaction rate, with a bimolecular rate constant of 4.6 × 10(-3) M(-1)s(-1)[PO(4)(3-)]. The molar product branching ratio of GB acid to the pyro product (isopropyl methylphosphonate phosphate anhydride) is 1:1.4, independent of phosphate concentration, and the pyro product continues to react much slower to form GB acid. The pyro product has two doublets in the (31)P NMR spectrum. The rate of reaction for GD is slower than GB, with a rate constant of 1.26 × 10(-3) M(-1)s(-1) [PO(4)(3-)]. The rate for VX is considerably slower, with a rate constant of 1.39 × 10(-5) M(-1)s(-1) [PO(4)(3-)], about 2 orders of magnitude slower than the rate for GD. The rate constant of the reaction of GD with pyrophosphate at pH 8 is 2.04 × 10(-3) min(-1) at a concentration of 0.0145 M. The rate of reaction for diisopropyl fluorophosphate is 2.84 × 10(-3) min(-1) at a concentration of 0.153 M phosphate, a factor of 4 slower than GD and a factor of 15 slower than GB, and there is no detectable pyro product. The half-lives of secondary reaction of the GB pyro product in 0.153 and 0.046 M solution of phosphate are 23.8 and 28.0 h, respectively, which indicates little or no dependence on phosphate. PMID:22667763

  15. Continuous-flow electrophoresis: Membrane-associated deviations of buffer pH and conductivity

    NASA Technical Reports Server (NTRS)

    Smolka, A. J. K.; Mcguire, J. K.

    1978-01-01

    The deviations in buffer pH and conductivity which occur near the electrode membranes in continuous-flow electrophoresis were studied in the Beckman charged particle electrophoresis system and the Hanning FF-5 preparative electrophoresis instrument. The nature of the membranes separating the electrode compartments from the electrophoresis chamber, the electric field strength, and the flow rate of electrophoresis buffer were all found to influence the formation of the pH and conductivity gradients. Variations in electrode buffer flow rate and the time of electrophoresis were less important. The results obtained supported the hypothesis that a combination of Donnan membrane effects and the differing ionic mobilities in the electrophoresis buffer was responsible for the formation of the gradients. The significance of the results for the design and stable operation of continuous-flow electrophoresis apparatus was discussed.

  16. The Determination of the pH of Standard Buffer Solution: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Harris, K. R.

    1985-01-01

    Describes an experiment which shows: (1) how measurements of the reaction electromotive force for the cell (Pt/glass/NaCl(aq,m),buffer/AgCl/Ag/Pt) can be utilized in determining the absolute pH of the buffer; and (2) the demonstration of the use of the Debye-Huckel model of an electrolyte solution in solving an important electrochemical problem.…

  17. The dependence of the lipid bilayer membrane: buffer partition coefficient of pentobarbitone on pH and lipid composition.

    PubMed Central

    Miller, K W; Yu, S C

    1977-01-01

    1 The membrane/buffer partition coefficient of [14C]-pentobarbitone has been determined as a function of the lipid composition of bilayer membranes. 2 A new technique based on ultrafiltration gave comparable results to conventional techniques but required less time for equilbration. 3 The membrane/buffer coefficient was independent of pentobarbitone concentration in the range studies. 4 The apparent partition coefficient varied with pH and was a linear function of the degree of dissociation of pentobarbition. 5 Both the charged and uncharged forms of pentobarbitone partitioned into the membrane, the latter to a much greater extent than the former. 6 At low pH the highest partition coefficient observed was in egg phosphatidylcholine bilayer membranes. 7 Incorporation of cholesterol or phosphatidic acid into phosphatidylcholine membranes greatly reduced the partition coefficient. 8 High pressures do not greatly change these partition coefficients. PMID:21013

  18. 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)

  19. Preliminary assessment of alginic acid as a factor buffering triethanolamine interacting with artificial skin sebum.

    PubMed

    Musiał, Witold; Kubis, Aleksander

    2003-03-01

    Triethanolamine is an ethanolamine used as counter-ion for fatty acid soaps. Interaction between triethanolamine and free fatty acids is suggested to be useful for cleansing sebaceous follicles in acne prevention. This study describes the preliminary assessment of alginic acid as a factor buffering triethanolamine interacting with stearic acid--a compound of artificial skin sebum. Penetration of triethanolamine into artificial sebum, induced by the above mentioned interaction, was measured using a specific optical method. The values of the penetration depth amounted to 0.07-5.74 mm. pH values were measured. The value of pH is reduced from 10.06 for pure 1.49% (w/w) aqueous triethanolamine solution to 6.61 with the increase of the alginic acid to triethanolamine ratio in the preparations. The data of this in vitro research will support further study on other anionic polymers as factors buffering ethanolamines penetrating artificial skin sebum.

  20. Influence of ignored and well-known zone distortions on the separation performance of proteins in capillary free zone electrophoresis with special reference to analysis in polyacrylamide-coated fused silica capillaries in various buffers. II. Experimental studies at acidic pH with on-line enrichment.

    PubMed

    Mohabbati, Sheila; Hjertén, Stellan; Westerlund, Douglas

    2004-10-22

    The separation of acidic and basic model proteins was studied in capillary free zone electrophoresis in a polyacrylamide-coated, electroosmosis-free capillary at pH below their isoelectric points (pI) using various buffers at pH 2.7-4.8 with UV detection at 200 nm. The separation performance was significantly dependent on the coating quality, which may even differ within the same batch of capillaries. In addition, a washing step with 2 M HCl and the storage of the capillary in distilled water was essential for the performance. For high efficiency and resolution the choice of buffer constituents was extremely important which is discussed in quantitative terms in Part I. The most promising buffers were ammonium acetate and ammonium hydroxyacetate at pH 4 (ionic strengths: 0.12 and 0.15 M, respectively) with plate numbers up to 1,700,000 plates/m, corresponding to a zone width (2sigma) of only 1 mm in a capillary with 40 cm effective length, when the injected samples were dissolved in a 10-fold diluted background electrolyte (BGE), a zone even narrower than those obtained in polyacrylamide gel electrophoresis, the characteristic feature of which is remarkably thin zones. In the experiment giving this plate number, the calculated variance for longitudinal diffusion was larger than all the other calculated variances (those for the width of the starting zone, Joule heating, sedimentation and the curvature of the capillary). Interestingly, the effect of capillary curvature was significant. In addition, the sum of all other imaginable variances (corresponding to various types of slow on/off kinetics and hyper-sharp peaks) was in the most successful experiments only 28-50% of the variance for longitudinal diffusion. One hundred- to two hundred-fold dilution of the BGE improved the detection limits and provided high precision in both migration times and peak areas with ammonium hydroxyacetate and ammonium acetate as background electrolytes. However, that high dilution

  1. Saliva flow rate, buffer capacity, and pH of autistic individuals.

    PubMed

    Bassoukou, Ivy Haralambos; Nicolau, José; dos Santos, Maria Teresa

    2009-03-01

    The objective of the study was to evaluate saliva flow rate, buffer capacity, pH levels, and dental caries experience (DCE) in autistic individuals, comparing the results with a control group (CG). The study was performed on 25 noninstitutionalized autistic boys, divided in two groups. G1 composed of ten children, ages 3-8. G2 composed of 15 adolescents ages 9-13. The CG was composed of 25 healthy boys, randomly selected and also divided in two groups: CG3 composed of 14 children ages 4-8, and CG4 composed of 11 adolescents ages 9-14. Whole saliva was collected under slight suction, and pH and buffer capacity were determined using a digital pHmeter. Buffer capacity was measured by titration using 0.01 N HCl, and the flow rate expressed in ml/min, and the DCE was expressed by decayed, missing, and filled teeth (permanent dentition [DMFT] and primary dentition [dmft]). Data were plotted and submitted to nonparametric (Kruskal-Wallis) and parametric (Student's t test) statistical tests with a significance level less than 0.05. When comparing G1 and CG3, groups did not differ in flow rate, pH levels, buffer capacity, or DMFT. Groups G2 and CG4 differ significantly in pH (p = 0.007) and pHi = 7.0 (p = 0.001), with lower scores for G2. In autistic individuals aged 3-8 and 9-13, medicated or not, there was no significant statistical difference in flow rate, pH, and buffer capacity. The comparison of DCE among autistic children and CG children with deciduous (dmft) and mixed/permanent decayed, missing, and filled teeth (DMFT) did not show statistical difference (p = 0.743). Data suggest that autistic individuals have neither a higher flow rate nor a better buffer capacity. Similar DCE was observed in both groups studied. PMID:18594879

  2. Effect of a low-moisture buffer block on ruminal pH in lactating dairy cattle induced with subacute ruminal acidosis.

    PubMed

    Krause, K M; Dhuyvetter, D V; Oetzel, G R

    2009-01-01

    The objective of this study was to evaluate the effect of a low-moisture buffer block on ruminal pH and milk production in cows induced with subacute ruminal acidosis (SARA). Sixteen ruminally cannulated cows were randomly assigned to treatment (access to buffer blocks) or control (no buffer blocks). Ruminal pH was recorded each minute; dry matter intake (DMI), milk yield, and milk composition were measured daily. The experiment lasted 12 d and consisted of a 3-d pre-SARA period (without access to buffer blocks; d 1 to 3), after which 8 cows were given access to buffer blocks and 8 cows continued without access to buffer blocks. The next 4 d (d 4 to 7) were for evaluating the response to buffer blocks. On d 8, cows were restricted to 50% of previous DMI, and on d 9 SARA was induced (addition of 4 kg of wheat/barley pellet to pre-SARA total mixed ration (TMR). Cows were then monitored for a 3-d recovery period (d 10 to 12). The SARA challenge was successful in decreasing mean ruminal pH and time and area below pH 5.6. Intake of buffer blocks averaged 0.33 kg of DM/cow per day and was greatest on d 4 and d 8. Total DMI (TMR plus buffer block) and yields of milk and milk components were not affected by treatment. Although there was no overall effect of treatment on any of the ruminal pH variables measured, there were significant treatment by period interactions for several ruminal pH variables. Cows on the control treatment tended to experience a greater decrease in mean ruminal pH when induced with SARA than cows with access to buffer blocks (-0.55 vs. -0.20 pH units). Cows on the control treatment also experienced a greater increase in time (9.7 vs. 4.1 h/d) and area (249 vs. 83 min x pH units/d) below pH 5.6 compared with cows with access to buffer blocks. Ruminal volatile fatty acids, lactate, ethanol, and succinate concentrations during the SARA challenge did not differ between treatments. Eating behavior was not affected by treatment. Size of the first meal of

  3. Laboratory sand column study of encapsulated buffer release for potential in situ pH control.

    PubMed

    Rust, Christine M; Aelion, C Marjorie; Flora, Joseph R V

    2002-01-01

    Encapsulation technology is being investigated as a method for controlling pH in situ at contaminated groundwater sites where pH may limit remediation of organic contaminants. This study examined the effectiveness of using KH2PO4 buffer encapsulated in a pH-sensitive coating to neutralize pH in laboratory sand columns (1.5-1) under a simulated groundwater flow rate and characterized the pattern of capsule release in the flow-through system. Denitrification was used in the columns to increase the pH of the pore water. Each of three columns was equipped with three miniature mesh wells to allow contact of the buffer with column pore water, but capsules (15 g) were inserted into only one column (amended). The two other columns served as amendment (no buffer) and abiotic (no denitrification) controls. Oxidation-reduction potential, dissolved organic and inorganic carbon, NH4+, NO3- +NO2-, PO(4)3-, and pH were measured in the influent, two side ports, and effluent of the columns over time. Near complete conversion of 80 mg N/1 of nitrate and 152 mg/l of ethanol per day resulted in a mean pH increase from 6.2 to 8.2 in the amendment control column. The amended column maintained the target pH of 7.0 +/- 0.2 for 4 weeks until the capsules began to be depleted, after which time the pH slowly started to increase. The capsules exhibited pulses of buffer release, and were effectively dissolved after 7.5 weeks of operation. Base-neutralizing capacity contributed by the encapsulated buffer over the entire study period, calculated as cation equivalents, was 120 mM compared to 8 mM without buffer. This study demonstrates the potential for this technology to mediate pH changes and provides the framework for future studies in the laboratory and in the field, in which pH is controlled in order to enhance organic contaminant remediation by pH-sensitive systems.

  4. Oxygen permeability of soft contact lenses in different pH, osmolality and buffering solution

    PubMed Central

    Lee, Se Eun; Kim, So Ra; Park, Mijung

    2015-01-01

    AIM To determine the effect of pH, osmolality, and buffering system on the oxygen permeability (Dk) of soft contact lenses. METHODS Two hydrogel lenses (nelfilcon A and etafilcon A) and 2 silicone hydrogel lenses (lotrafilcon A and balafilcon A) were used in the study. These lenses were incubated in phosphate-buffered saline (PBS) and borate-buffered saline (BBS) solutions adjusted by 0.8 pH increments to a pH in the range of 5.8-9.0 or in hypotonic (280 mOsmol/kg), isotonic (310 mOsmol/kg) and hypertonic (380 mOsmol/kg) PBS solutions. Polarographic method was used for measuring the Dk and lenses were stacked as 4 layers to correct the boundary effect. RESULTS Dk values of all contact lenses measured in BBS solutions were more stable than those in PBS solutions. Especially the etafilcon A lens showed a relative big change compared with other types of contact lenses at the same conditions. When the osmolality of PBS solution increased from hypotonic to hypertonic, Dk of all contact lenses decreased. Variations in Dk existed depending on lens materials, etafilcon A lens was the most affected and nelfilcon A was the least affected by osmolality. CONCLUSION From the result obtained, it is revealed that Dk of contact lenses is changed by the pH, osmolality, and buffering condition of tear. Thus, Dk of contact lens can be varied by the lens wearers' physiological and/or pathological conditions. PMID:26558223

  5. Buffer capacities of fresh water lakes sensitive to acid rain deposition

    SciTech Connect

    Faust, S.D.; McIntosh, A.

    1983-01-01

    The Van Slyke definition of buffer capacity, the increment of a strong base or strong acid that causes an incremental change in the pH value of water, is better than total alkalinity for defining a water's resistance to acid rain. This Van Slyke value, designated by beta, shows a peak at pH 6.3 for the bicarbonate-carbonate pair, indicating that the effect of acid rain on the pH and alkalinity of natural waters is not deleterious until this peak is traversed. A beta value of zero indicates a dead water with no capacity to neutralize acid. The beta values, pH and total alkalinity of lakes, reservoirs, and streams in New Jersey are given. Data clearly show that pH and alkalinity alone cannot determine buffer capacity. For example: Fairview Lake (pH of 5.5 and alkalinity of 10.2 mg per liter) has a beta value 11 times that of Clyde Potts Reservoir (pH of 7.3, alkalinity of 8.1 mg per liter). 3 references, 1 figure, 1 table.

  6. THE KINETICS OF SAPONIFICATION OF IODOACETIC ACID BY SODIUM HYDROXIDE AND BY CERTAIN ALKALINE BUFFER SOLUTIONS.

    PubMed

    Brdicka, R

    1936-07-20

    1. The rate of the saponification of iodoacetic acid in sodium hydroxide and alkaline buffer solutions yielding glycollic acid was measured by means of Heyrovský's polarographic method. 2. From the bimolecular velocity constants, increasing with the ionic strength of the solution, the Brönsted factor, F, which characterizes the primary salt effect, was calculated. 3. In the borate buffer solutions the monomolecular constants of the saponification were determined which, at values above the pH of neutralization of boric acid, show a proportionality to the concentration of hydroxyl anions. Below the pH of neutralization of boric acid, they are proportional to the concentration of borate anions.

  7. 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

  8. Defining the buffering process by a triprotic acid without relying on Stewart-electroneutrality considerations.

    PubMed

    Nguyen, Minhtri K; Kao, Liyo; Kurtz, Ira

    2011-01-01

    Upon the addition of protons to an aqueous solution, a component of the H+ load will be bound i.e. buffered. In an aqueous solution containing a triprotic acid, H+ can be bound to three different states of the acid as well as to OH- ions that are derived from the auto-ionization of H2O. In quantifying the buffering process of a triprotic acid, one must define the partitioning of H+ among the three states of the acid and also the OH- ions in solution in order to predict the equilibrium pH value. However, previous quantitative approaches that model triprotic acid titration behaviour and used to predict the equilibrium pH rely on the mathematical convenience of electroneutrality/charge balance considerations. This fact has caused confusion in the literature, and has led to the assumption that charge balance/electroneutrality is a causal factor in modulating proton buffering (Stewart formulation). However, as we have previously shown, although charge balance can be used mathematically as a convenient tool in deriving various formulae, electroneutrality per se is not a fundamental physicochemical parameter that is mechanistically involved in the underlying buffering and proton transfer reactions. The lack of distinction between a mathematical tool, and a fundamental physicochemical parameter is in part a reason for the current debate regarding the Stewart formulation of acid-base analysis. We therefore posed the following question: Is it possible to generate an equation that defines and predicts the buffering of a triprotic acid that is based only on H+ partitioning without incorporating electroneutrality in the derivation? Towards this goal, we derived our new equation utilizing: 1) partitioning of H+ buffering; 2) conservation of mass; and 3) acid-base equilibria. In validating this model, we compared the predicted equilibrium pH with the measured pH of an aqueous solution consisting of Na2HPO4 to which HCl was added. The measured pH values were in excellent agreement

  9. Defining the buffering process by a triprotic acid without relying on Stewart-electroneutrality considerations.

    PubMed

    Nguyen, Minhtri K; Kao, Liyo; Kurtz, Ira

    2011-08-17

    Upon the addition of protons to an aqueous solution, a component of the H+ load will be bound i.e. buffered. In an aqueous solution containing a triprotic acid, H+ can be bound to three different states of the acid as well as to OH- ions that are derived from the auto-ionization of H2O. In quantifying the buffering process of a triprotic acid, one must define the partitioning of H+ among the three states of the acid and also the OH- ions in solution in order to predict the equilibrium pH value. However, previous quantitative approaches that model triprotic acid titration behaviour and used to predict the equilibrium pH rely on the mathematical convenience of electroneutrality/charge balance considerations. This fact has caused confusion in the literature, and has led to the assumption that charge balance/electroneutrality is a causal factor in modulating proton buffering (Stewart formulation). However, as we have previously shown, although charge balance can be used mathematically as a convenient tool in deriving various formulae, electroneutrality per se is not a fundamental physicochemical parameter that is mechanistically involved in the underlying buffering and proton transfer reactions. The lack of distinction between a mathematical tool, and a fundamental physicochemical parameter is in part a reason for the current debate regarding the Stewart formulation of acid-base analysis. We therefore posed the following question: Is it possible to generate an equation that defines and predicts the buffering of a triprotic acid that is based only on H+ partitioning without incorporating electroneutrality in the derivation? Towards this goal, we derived our new equation utilizing: 1) partitioning of H+ buffering; 2) conservation of mass; and 3) acid-base equilibria. In validating this model, we compared the predicted equilibrium pH with the measured pH of an aqueous solution consisting of Na2HPO4 to which HCl was added. The measured pH values were in excellent agreement

  10. 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.

  11. Application of Acetate Buffer in pH Adjustment of Mash and its Influence on Fuel Ethanol Fermentation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A 2M sodium acetate buffer at pH 4.2 was used to adjust pH of liquefied mashes in a simultaneous saccharification and fermentation (SSF) procedure. Although 5 mL of the buffer did not bring the pH values of the mashes (~100 mL) from a sorghum hybrid to 4.2, it kept the system stable (pH from 4.7 to ...

  12. An Efficient Protocol for the Oxidative Hydrolysis of Ketone SAMP Hydrazones Employing SeO(2) and H(2)O(2) under Buffered (pH 7) Conditions.

    PubMed

    Smith, Amos B; Liu, Zhuqing; Simov, Vladimir

    2009-06-01

    An effective oxidative protocol for the liberation of ketones from SAMP hydrazones employing peroxyselenous acid under aqueous buffered conditions (pH 7) has been developed. The procedure proceeds without epimerization of adjacent stereocenters or dehydration, respectively, in representative SAMP alkylation and aldol reaction adducts. PMID:20657727

  13. 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.

  14. Positively charged and pH self-buffering quantum dots for efficient cellular uptake by charge mediation and monitoring cell membrane permeability

    NASA Astrophysics Data System (ADS)

    Wang, Suhua; Song, Haipeng; Ong, Wei Yi; Han, Ming Yong; Huang, Dejian

    2009-10-01

    Positively charged and pH self-buffering quantum dots (Tren-QDs) were achieved by surface functionalization with tris(2-aminoethyl)amine (Tren) derivatives, which are attached to the inorganic cores of QDs through bidentate chelating of dithiocarbamates. The Tren-QDs exhibit pH buffering capability by absorbing or releasing protons due to the surface polyamine groups as the surrounding pH fluctuates. Such self-buffering capability stabilizes the photoluminescence of the Tren-QDs against acid. The Tren-QDs bear positive charges through protonation of the surface polyamine groups under physiological conditions and the surface positive charges improve their cellular uptake efficiency by charge mediation, which has been demonstrated by BV-2 microglia cells. The photoluminescence of Tren-QDs shows a selective Stern-Volmer response to copper ions and this property has been preliminarily evaluated for investigating the BV-2 cell membrane structure by monitoring the photoluminescence of intracellular Tren-QDs.

  15. Modelling study on buffering pH and retaining U using a simplified uranium mill tailings pile example

    NASA Astrophysics Data System (ADS)

    Jacques, Diederik; Simunek, Jirka

    2014-05-01

    The hypothetical problem that is presented here considers the release and migration of uranium from a simplified uranium mill tailings pile towards a river. The modeling exercise with the coupled reactive transport model HP2 illustrates the effect of the geochemical conceptual model for sorption on (i) the buffering of the pH in the soil/aquifer system and (ii) the retention of U in the soil. The HP2 module, which couples the PHREEQC geochemical code with HYDRUS (2D/3D), is a two-dimensional equivalent of the one-dimensional HP1 program that was first released in 2005 (Jacques et al., 2008), and used successfully in many applications. Sorption of U is described using a multi-site cation exchange model (see Jacques et al., 2008). This sorption model also buffers the acid pH due to proton exchange. Two scenarios are considered: a soil with a relatively low (8.1 × 10-3 mol/kg) and relatively high (8.1 × 10-2 mol/kg) sorption capacity. In the third scenario, specific sorption of U and other cations and anions on Fe-oxides is described using a non-electrostatic surface complexation model with a very low capacity (8.1 × 10-4 mol/kg), in addition to low exchange complexation. Proton exchange on the cation exchanger buffers the acidity by replacing calcium with protons on the exchanger; the spatial extent of the pH-perturbed region is smaller in the scenario with the higher exchange capacity. Specific sorption has only a small effect on the pH-perturbed zone, although it is important to note that its capacity is one order of magnitude lower than in the scenario with the low sorption capacity. U reaches the river system within 1000 d in scenarios with low and high exchange capacities. Only in the scenario with specific sorption, U migration within the ground water system is retarded, compared to the other two cases. The results of the three scenarios do not seem to be intuitive, especially the equally fast movement of U in the scenario with a high exchange capacity

  16. Acid-base buffering of soils in transitional and transitional-accumulative positions of undisturbed southern-taiga landscapes

    NASA Astrophysics Data System (ADS)

    Rusakova, E. S.; Ishkova, I. V.; Tolpeshta, I. I.; Sokolova, T. A.

    2012-05-01

    The method of continuous potentiometric titration (CPT) of soil water suspensions was used to evaluate the acid-base buffering of samples from the major genetic horizons of podzolic soils on a slope and soddy gley soils on the adjacent floodplain of a rivulet. In the soils of the slope, the buffering to acid upon titration from the pH of the initial titration point (ITP) to pH 3 in all the horizons was 1.5-2.0 times lower than that in the podzolic soils of the leveled interfluve, which could be due to the active leaching of exchangeable bases and oxalate-soluble aluminum and iron compounds with the later soil flows. In the soddy gley soils, the buffering to acid in the mineral horizons was 2-10 times higher than that in the podzolic soils. A direct dependence of the soil buffering to acid on the total content of exchangeable bases and on the content of oxalate-soluble aluminum compounds was found. A direct dependence of the buffering to basic upon titration from the ITP to pH 10 on the contents of the oxalate-soluble aluminum and organic matter was observed in the mineral horizons of all the studied soils. The soil treatment with Tamm's reagent resulted in the decrease of the buffering to acid in the soddy gley soils of the floodplain, as well as in the decrease of the buffering to basic in the soils on the slopes and in the soddy gley soils. It was also found that the redistribution of the mobile aluminum compounds between the eluvial, transitional, and transitional-accumulative positions in the undisturbed southern taiga landscapes leads to significant spatial differentiation of the acid-base buffering of the mineral soil horizons with a considerable increase in the buffer capacity of the soils within the transitional-accumulative terrain positions.

  17. 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

  18. Effect of pH on sporicidal and microbicidal activity of buffered mixtures of alcohol and sodium hypochlorite.

    PubMed Central

    Death, J E; Coates, D

    1979-01-01

    The effect of pH on the activity of buffered sodium hypochlorite solution, and a buffered methanol/sodium hypochlorite mixture, against Bacillus subtilis spores was investigated. The best results, considering both sporicidal activity and stability, were achieved in the pH range 7.6--8.1. The sporicidal activity and stability of five alcohol/hypochlorite mixtures, each containing a different alcohol and buffered to pH 7.6 and of hypochlorite alone buffered to pH 7.6, were compared. The mixtures were marginally more sporicidal than hypochlorite alone when fresh but were much less stable. An unbuffered methanol/hypochlorite mixture, a methanol/hypochlorite mixture buffered to pH 7.6, and hypochlorite alond buffered to pH 7.6 were all found to be effective against six vegetative organisms and spores of B. subtilis and Clostridium sporogenes. By buffering alcohol/hypochlorite mixtures or hypochlorite solution alone in the pH range 7.6--8.1, high sporicidal activity can be achieved with low concentrations of alcohol and hypochlorite. Such formulations show promise for the disinfection of heat-sensitive medical equipment. PMID:35554

  19. Effect of pH on the Electrochemical Behavior of Tantalum in Borate Buffer Solutions

    NASA Astrophysics Data System (ADS)

    Attarzadeh, F. R.; Attarzadeh, N.; Vafaeian, S.; Fattah-Alhosseini, A.

    2016-08-01

    In this research, various electrochemical methods were used to investigate the electrochemical behavior of tantalum in borate buffer solutions of various pH values, ranging from 9.0 to 6.5. Potentiodynamic polarization curves revealed that tantalum showed excellent passive behavior in borate buffer solutions. The potentiodynamic polarization and electrochemical impedance spectroscopy results showed that the passive film formed on tantalum offered its best protective behavior when the pH is 8.0, with the passivity undergoing a drastic change as the pH moved toward higher values. The semiconductive behavior of the passive films formed on tantalum was investigated by employing Mott-Schottky analysis in conjunction with a point defect model. The results indicated that the passive film exhibited n-type semiconductive behavior and that donor densities were in the range of 1.958-7.242 × 1020 cm-3. Moreover, this analysis showed that the donor density and flat band potential were quite sensitive to the pH.

  20. Effect of pH on the Electrochemical Behavior of Tantalum in Borate Buffer Solutions

    NASA Astrophysics Data System (ADS)

    Attarzadeh, F. R.; Attarzadeh, N.; Vafaeian, S.; Fattah-Alhosseini, A.

    2016-10-01

    In this research, various electrochemical methods were used to investigate the electrochemical behavior of tantalum in borate buffer solutions of various pH values, ranging from 9.0 to 6.5. Potentiodynamic polarization curves revealed that tantalum showed excellent passive behavior in borate buffer solutions. The potentiodynamic polarization and electrochemical impedance spectroscopy results showed that the passive film formed on tantalum offered its best protective behavior when the pH is 8.0, with the passivity undergoing a drastic change as the pH moved toward higher values. The semiconductive behavior of the passive films formed on tantalum was investigated by employing Mott-Schottky analysis in conjunction with a point defect model. The results indicated that the passive film exhibited n-type semiconductive behavior and that donor densities were in the range of 1.958-7.242 × 1020 cm-3. Moreover, this analysis showed that the donor density and flat band potential were quite sensitive to the pH.

  1. pH buffering of single rat skeletal muscle fibers in the in vivo environment.

    PubMed

    Tanaka, Yoshinori; Inagaki, Tadakatsu; Poole, David C; Kano, Yutaka

    2016-05-15

    Homeostasis of intracellular pH (pHi) has a crucial role for the maintenance of cellular function. Several membrane transporters such as lactate/H(+) cotransporter (MCT), Na(+)/H(+) exchange transporter (NHE), and Na(+)/HCO3 (-) cotransporter (NBC) are thought to contribute to pHi regulation. However, the relative importance of each of these membrane transporters to the in vivo recovery from the low pHi condition is unknown. Using an in vivo bioimaging model, we pharmacologically inhibited each transporter separately and all transporters together and then evaluated the pHi recovery profiles following imposition of a discrete H(+) challenge loaded into single muscle fibers by microinjection. The intact spinotrapezius muscle of adult male Wistar rats (n = 72) was exteriorized and loaded with the fluorescent probe 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein-acetoxymethyl ester (10 μM). A single muscle fiber was then loaded with low-pH solution [piperazine-N,N'-bis(2-ethanesulfonic acid) buffer, pH 6.5, ∼2.33 × 10(-3) μl] by microinjection over 3 s. The rats were divided into groups for the following treatments: 1) no inhibitor (CONT), 2) MCT inhibition (by α-Cyano-4-hydroxyciannamic acid; 4 mM), 3) NHE inhibition (by ethylisopropyl amiloride; 0.5 mM), 4) NBC inhibition (by DIDS; 1 mM), and 5) MCT, NHE, and NBC inhibition (All blockade). The fluorescence ratio (F500 nm/F445 nm) was determined from images captured during 1 min (60 images/min) and at 5, 10, 15, and 20 min after injection. The pHi at 1-2 s after injection significantly decreased from resting pHi (ΔpHi = -0.73 ± 0.03) in CONT. The recovery response profile was biphasic, with an initial rapid and close-to-exponential pHi increase (time constant, τ: 60.0 ± 7.9 s). This initial rapid profile was not affected by any pharmacological blockade but was significantly delayed by carbonic anhydrase inhibition. In contrast, the secondary, more gradual, return toward baseline that restored CONT pHi to

  2. Thermodynamic characteristics of the interaction between nicotinic acid and phenylalanine in an aqueous buffer solution at 298 K

    NASA Astrophysics Data System (ADS)

    Badelin, V. G.; Tyunina, E. Yu.; Mezhevoi, I. N.; Tarasova, G. N.

    2013-08-01

    The interaction between L-phenylalanine and nicotinic acid is studied by solution calorimetry in an aqueous buffer solution (pH 7.35) at different ratios of the reagents. Experimental data on the enthalpy of dissolution of amino acid in the buffer solution of nicotinic acid at 298.15 K are calculated. The values of thermodynamic parameters for the complexation of L-phenylalanine with nicotinic acid are calculated. It is shown that the formation of a 1: 2 molecular complex is stabilized by the entropy factor due to the dominant role of the dehydration effect of initial reagents.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  4. Key comparison on pH of an unknown phosphate buffer

    NASA Astrophysics Data System (ADS)

    Bastkowski, F.; Spitzer, P.; Sander, B.; Máriássy, M.; Dimitrova, L.; Reyes, A.; Rodríguez, A.; Manzano, V. Lara; Vospelova, A.; Jakobsen, P. T.; Pawlina, M.; Korol, M.; Kozlowski, W.; Delgado, M.; Ticona Canaza, G.; Dias, J. C.; Gonzaga, F. B.; Nagyné Szilágyi, Z.; Jakusovszky, B.; Nongluck, T.; Waters, J.; Pratt, K. W.; Asakai, T.; Maksimov, I.; Hankova, Z.; Uysal, E.; Gavrilkin, V.; Prokunin, S. V.; Ferreira, E.; Fajardo, S.

    2016-01-01

    Results of CCQM-K99 key comparison on unknown phosphate buffer pH ~ 7.5 at 5 °C, 15 °C, 25 °C, 37 °C and 50 °C are reported. Good agreement is found between the majority of participants. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  5. Enamel erosion by some soft drinks and orange juices relative to their pH, buffering effect and contents of calcium phosphate.

    PubMed

    Larsen, M J; Nyvad, B

    1999-01-01

    The capability of a soft drink or a juice to erode dental enamel depends not only on the pH of the drink, but also on its buffering effect. As the latter is the ability of the drink to resist a change of pH it may add to the effects of the actual pH. The aim of the present study was to compare the pH and the buffering effect of various soft drinks with their erosive effects and the solubility of apatite. In 18 soft drinks, mineral waters and juices available on the Danish market, pH and the concentrations of calcium, phosphate and fluoride were determined. The buffering effect was determined by titration with NaOH. Human teeth (n = 54) covered with nail varnish except for 3x4-mm windows were exposed to 1.5 liters of the drink for either 7 days or 24 h under constant agitation. The depth of the erosions was assessed in longitudinal sections. The depth was found to vary greatly from 3 mm eroded by the most acidic drinks and fresh orange juice to only slightly affected surfaces by most of the mineral waters. The dissolution of enamel increased logarithmically inversely with the pH of the drink and parallel with the solubility of enamel apatite. Orange juice, pH 4.0, supplemented with 40 mmol/l calcium and 30 mmol/l phosphate did not erode the enamel as the calcium and phosphate saturated the drink with respect to apatite. Generally, the lower the pH the more NaOH was necessary to bring the pH to neutrality. In particular the buffering effect of the juice was high. For all drinks, no effect of their low fluoride concentrations was observed.

  6. Poly(N-vinylimidazole) gels as insoluble buffers that neutralize acid solutions without dissolving.

    PubMed

    Horta, Arturo; Piérola, Inés F

    2009-04-01

    Typical buffers are solutions containing weak acids or bases. If these groups were anchored to insoluble gels, what would be their behavior? Simple thermodynamics is used to calculate the pH in two-phase systems that contain the weak acid or base fixed to only one of the phases and is absent in the other. The experimental reference of such systems are pH sensitive hydrogels and heterogeneous systems of biological interest. It is predicted that a basic hydrogel immersed in slightly acidic solutions should absorb the acid and leave the external solution exactly neutral (pH 7). This is in accordance with experimental results of cross-linked poly(N-vinylimidazole). The pH 7 cannot be obtained if the system were homogeneous; the confinement of the weak base inside the gel phase is a requisite for this neutral pH in the external solution. The solution inside the gel is regulated to a much higher pH, which has important implications in studies on chemical reactions and physical processes taking place inside a phase insoluble but in contact with a solution. PMID:19245223

  7. Acid-base and respiratory properties of a buffered bovine erythrocyte perfusion medium.

    PubMed

    Lindinger, M I; Heigenhauser, G J; Jones, N L

    1986-05-01

    Current research in organ physiology often utilizes in situ or isolated perfused tissues. We have characterized a perfusion medium associated with excellent performance characteristics in perfused mammalian skeletal muscle. The perfusion medium consisting of Krebs-Henseleit buffer, bovine serum albumin, and fresh bovine erythrocytes was studied with respect to its gas-carrying relationships and its response to manipulation of acid-base state. Equilibration of the perfusion medium at base excess of -10, -5, 0, 5, and 10 mmol X L-1 to humidified gas mixtures varying in their CO2 and O2 content was followed by measurements of perfusate hematocrit, hemoglobin concentration, pH, Pco2, Cco2, Po2, and percent oxygen saturation. The oxygen dissociation curve was similar to that of mammalian bloods, having a P50 of 32 Torr (1 Torr = 133.3 Pa), Hill's constant n of 2.87 +/- 0.15, and a Bohr factor of -0.47, showing the typical Bohr shifts with respect to CO2 and pH. The oxygen capacity was calculated to be 190 mL X L-1 blood. The carbon dioxide dissociation curve was also similar to that of mammalian blood. The in vitro nonbicarbonate buffer capacity (delta [HCO3-] X delta pH-1) at zero base excess was -24.6 and -29.9 mmol X L-1 X pH-1 for the perfusate and buffer, respectively. The effects of reduced oxygen saturation on base excess and pH of the medium were quantified. The data were used to construct an acid-base alignment diagram for the medium, which may be used to quantify the flux of nonvolatile acid or base added to the venous effluent during tissue perfusions.

  8. Importance of the pH buffering capacity - comparison of various methods to estimate the pH properties of a waste material

    SciTech Connect

    Baeverman, C.

    1997-12-01

    The final pH of the leach water controls the leaching of many metals from MSWI ash in construction materials and landfills. The buffering properties of the ash determines the final pH of the leachate and is therefore one of the most important properties of a waste material. In this study three different methods to investigate the pH buffering capacity of ashes have been compared; two batch methods and one flow-through method. The results of this study showed that the MSWI bottom ash used here had a large buffering capacity in the pH region where the solubility of most pH-sensitive metals is lowest, around pH 8. The buffering reactions are slow. The duration of an experiment should therefore be about 50 days if all material should have time to react. A comparison of the results of the experiments showed that at least 50% of the buffering capacity in a batch system comes from dissolved constituents, that would not buffer in a flow-through system.

  9. Retention of ionisable compounds on high-performance liquid chromatography. XV. Estimation of the pH variation of aqueous buffers with the change of the acetonitrile fraction of the mobile phase.

    PubMed

    Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

    2004-12-01

    The most commonly used mobile phases in reversed-phase high-performance liquid chromatography (RP-HPLC) are hydro-organic mixtures of an aqueous buffer and an organic modifier. The addition of this organic solvent to buffered aqueous solutions involves a variation of the buffer properties (pH and buffer capacity). In this paper, the pH variation is studied for acetic acid-acetate, phosphoric acid-dihydrogenphosphate-hydrogenphosphate, citric acid-dihydrogencitrate-citrate, and ammonium-ammonia buffers. The proposed equations allow pH estimation of acetonitrile-water buffered mobile phases up to 60% (v/v) of organic modifier and initial aqueous buffer concentrations between 0.001 and 0.1 mol L(-1), from the initial aqueous pH. The estimated pH variation of the mobile phase and the pKa variation of the analytes allow us to predict the degree of ionisation of the analytes and from this and analyte hydrophobicities, to interpret the relative retention and separation of analyte mixtures.

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  12. Use of pH 9.5 Tris-HCl buffer containing 5% urea for antigen retrieval immunohistochemistry.

    PubMed

    Shi, S R; Cote, R J; Young, L; Imam, S A; Taylor, C R

    1996-07-01

    Successful antigen retrieval (AR) immunohistochemistry is dependent on the temperature, heating time, and pH value of the AR solutions. There is no single standardized AR solution, however, that is suitable for all antibodies "routinely" used in surgical pathology for immunostaining archival tissue sections. We tested a variety of AR solutions varying in pH value, chemical composition, and molarity. Based upon preliminary results, we compared three AR solutions: 0.1 M Tris-HCl buffer, pH 9.5, containing 5% urea, 0.1 M Tris-HCl buffer pH 9.5 without urea, and citrate buffer, pH 6.0. Each AR solution was tested with a panel of 34 antibodies using microwave heating for antigen retrieval. The heating conditions were standardized at 10 min and an automated stainer was used to standardize the immunostaining method. The Tris-HCl containing urea was superior to pH 6.0 citrate buffer for 22 antibodies. In 12 cases, Tris-HCl with urea was also superior to Tris-HCl alone. In 12 cases, the intensity was similar for all three retrieval solutions. The staining obtained with Tris-HCl with urea was equal to or better than with pH 6.0 citrate buffer in all cases. The Tris-HCl with urea solution is satisfactory for AR of most antibodies employed in routine surgical pathology.

  13. Responses of soil buffering capacity to acid treatment in three typical subtropical forests.

    PubMed

    Jiang, Jun; Wang, Ying-Ping; Yu, Mengxiao; Li, Kun; Shao, Yijing; Yan, Junhua

    2016-09-01

    Elevated anthropogenic acid deposition can significantly affect forest ecosystem functioning by changing soil pH, nutrient balance, and chemical leaching and so on. These effects generally differ among different forests, and the dominant mechanisms for those observed responses often vary, depending on climate, soil conditions and vegetation types. Using soil monoliths (0-40cm) from pine forest (pioneer), coniferous and broadleaved mixed forest (transitional) and broadleaved forest (mature) in southern China, we conducted a leaching experiment with acid treatments at different pH levels (control: pH≈4.5; pH=3.5; pH=2.5). We found that pH3.5 treatment significantly reduced dissolved organic carbon (DOC) concentrations in leachate from the pioneer forest soil. pH2.5 treatment significantly increased concentrations of NO3(-), SO4(2-), Ca(2+), Mg(2+), Al(3+), Fe(3+) and DOC in leachate from the pioneer forest soil, and also concentrations of NO3(-), SO4(2-), Mg(2+), Al(3+), Fe(3+) and DOC in leachate from the transitional forest soil. All acid treatments had no significant effects on concentrations of these chemicals in leachate from the mature forest soil. The responses can be explained by the changes in soil pH, acid neutralizing capacity (ANC) and concentrations of Al and Fe. Our results showed that acid buffering capacity of the pioneer or transitional forest soil was lower than that of the mature forest soil. Therefore preserving mature forests in southern China is important for reducing the adverse impacts of high acid deposition on stream water quality at present and into the future. PMID:27185346

  14. Dissolution properties of co-amorphous drug-amino acid formulations in buffer and biorelevant media.

    PubMed

    Heikkinen, A T; DeClerck, L; Löbmann, K; Grohganz, H; Rades, T; Laitinen, R

    2015-07-01

    Co-amorphous formulations, particularly binary drug-amino acid mixtures, have been shown to provide enhanced dissolution for poorly-soluble drugs and improved physical stability of the amorphous state. However, to date the dissolution properties (mainly intrinsic dissolution rate) of the co-amorphous formulations have been tested only in buffers and their supersaturation ability remain unexplored. Consequently, dissolution studies in simulated intestinal fluids need to be conducted in order to better evaluate the potential of these systems in increasing the oral bioavailability of biopharmaceutics classification system class II drugs. In this study, solubility and dissolution properties of the co-amorphous simvastatin-lysine, gibenclamide-serine, glibenclamide-threonine and glibenclamide-serine-threonine were studied in phosphate buffer pH 7.2 and biorelevant media (fasted and fed state simulated intestinal fluids (FaSSIF and FeSSIF, respectively)). The co-amorphous formulations were found to provide a long-lasting supersaturation and improve the dissolution of the drugs compared to the crystalline and amorphous drugs alone in buffer. Similar improvement, but in lesser extent, was observed in biorelevant media suggesting that a dissolution advantage observed in aqueous buffers may overestimate the advantage in vivo. However, the results show that, in addition to stability advantage shown earlier, co-amorphous drug-amino acid formulations provide dissolution advantage over crystalline drugs in both aqueous and biorelevant conditions.

  15. On the use of dimensionless parameters in acid-base theory. V. Buffers composed of binary mixtures of monovalent weak acids and bases.

    PubMed

    Rilbe, H

    1993-12-01

    A general theory for buffers consisting of one weak acid and one weak base is developed, particular interest being devoted to the special case of doubly weak salts. The pH course as it varies with the acid/base concentration ratio is presented in equations and graphs. The influence of delta pK' = pK'b-pK'a, which can be negative as well as positive, is discussed and visualized in graphs. The buffer capacity is deduced as a function of pH. The buffer range is, at a maximum, 2.67 times that of a monovalent weak protolyte for delta pK' = 2.7 pH units. The buffer capacity curve has two maxima for delta pK' values bigger than 0.77. For negative delta pK' values the buffer capacity curve has only one maximum, and the buffer range is not better than that of a monovalent protolyte. A general equation for the ionic concentrations is deduced, and as a corollary the degree of hydrolysis of the doubly weak salt is obtained as a function of delta pK'. For solutions of this salt, the relation between concentration and pH is elucidated by equations and graphs. PMID:8137789

  16. Comparison of peak shape in hydrophilic interaction chromatography using acidic salt buffers and simple acid solutions.

    PubMed

    Heaton, James C; Russell, Joseph J; Underwood, Tim; Boughtflower, Robert; McCalley, David V

    2014-06-20

    The retention and peak shape of neutral, basic and acidic solutes was studied on hydrophilic interaction chromatography (HILIC) stationary phases that showed both strong and weak ionic retention characteristics, using aqueous-acetonitrile mobile phases containing either formic acid (FA), ammonium formate (AF) or phosphoric acid (PA). The effect of organic solvent concentration on the results was also studied. Peak shape was good for neutrals under most mobile phase conditions. However, peak shapes for ionised solutes, particularly for basic compounds, were considerably worse in FA than AF. Even neutral compounds showed deterioration in performance with FA when the mobile phase water concentration was reduced. The poor performance in FA cannot be entirely attributed to the negative impact of ionic retention on ionised silanols on the underlying silica base materials, as results using PA at lower pH (where their ionisation is suppressed) were inferior to those in AF. Besides the moderating influence of the salt cation on ionic retention, it is likely that salt buffers improve peak shape due to the increased ionic strength of the mobile phase and its impact on the formation of the water layer on the column surface.

  17. Effects of pH and buffer concentration on the thermal stability of etanercept using DSC and DLS.

    PubMed

    Kim, Nam Ah; An, In Bok; Lim, Dae Gon; Lim, Jun Yeul; Lee, Sang Yeol; Shim, Woo Sun; Kang, Nae-Gyu; Jeong, Seong Hoon

    2014-01-01

    The protein size, electrical interaction, and conformational stability of etanercept (marketed as Enbrel®) were examined by thermodynamic and light scattering methods with changing pH and buffer concentration. As pH of etanercept increased from pH 6.6 to 8.6, electrical repulsion in the solution increased, inducing a decrease in protein size. However, the size changed less in high buffer concentration and irreversible aggregation issues were not observed; in contrast, aggregates of about 1000 nm were observed in low buffer concentration at the pH range. Three significant unfolding transitions (Tm) were observed by differential scanning calorimetry (DSC). Unlikely to Tm1, Tm2 and Tm3 were increased as the pH increased. Higher Tm at high buffer concentration was observed, indicating increased conformational stability. The apparent activation energy of unfolding was further investigated since continuous increase of Tm2 and Tm3 was not sufficient to determine optimal conditions. A higher energy barrier was calculated at Tm2 than at Tm3. In addition, the energy barriers were the highest at pH from 7.4 to 7.8 where higher Tm1 was also observed. Therefore, the conformational stability of protein solution significantly changed with pH dependent steric repulsion of neighboring protein molecules. An optimized pH range was obtained that satisfied the stability of all three domains. Electrostatic circumstances and structural interactions resulted in irreversible aggregation at low buffer concentrations and were suppressed by increasing the concentration. Therefore, increased buffer concentration is recommended during protein formulation development, even in the earlier stages of investigation, to avoid protein instability issues.

  18. Buffer capacity, pH, and flow rate in saliva of children aged 2-60 months with Down syndrome.

    PubMed

    Siqueira, Walter Luiz; Bermejo, Patrícia Rota; Mustacchi, Zan; Nicolau, José

    2005-03-01

    This study measured the flow rate, pH, and buffer capacity of saliva from children with Down syndrome aged 2-60 months. We compared 25 children with Down syndrome with 21 children without Down syndrome. The whole saliva was collected under slight suction and the pH and the buffer capacity were determined using a digital pHmeter. The buffer capacity was measured by titration with 0.01 N HCl. The Down syndrome group demonstrated higher buffer capacity than the control group in the pH ranges of 6.9-6.0, 5.9-5.0, and 4.9-4.0. The flow rate was low in the Down syndrome group. Boys from the Down syndrome group demonstrated higher buffer capacity in the pH ranges 6.9-6.0, 5.9-5.0, and 4.9-4.0 than controls, while girls from the Down syndrome group showed no difference compared with controls. Girls with Down syndrome demonstrated significant difference only in the range of pHi-pH 7.0. Conclusion. These data suggest that the Down syndrome persons present a better buffer capacity, supporting the results observed in several studies which found the low dental caries in persons with Down syndrome. PMID:15378405

  19. Fluctuations in surface pH of maturing rat incisor enamel are a result of cycles of H(+)-secretion by ameloblasts and variations in enamel buffer characteristics.

    PubMed

    Damkier, Helle H; Josephsen, Kaj; Takano, Yoshiro; Zahn, Dirk; Fejerskov, Ole; Frische, Sebastian

    2014-03-01

    It is disputed if ameloblasts in the maturation zone of the enamel organ mainly buffer protons released by hydroxyapatite (HA) crystal growth or if they periodically secrete protons to create alternating acidic and alkaline conditions. The latter hypothesis predicts alternating pH regimes in maturing enamel, which would be affected by pharmacological interference with ameloblast H(+)-secretion. This study tests these predictions. Colorimetric pH-indicators and ratiometric fluorometry were used to measure surface pH in maturation zone enamel of rat incisors. Alternating acidic (down to pH6.24±0.06) and alkaline zones (up to pH7.34±0.08) were found along the tooth coinciding with ameloblast morphological cycles. Underlying the cyclic pattern, a gradual decrease in pH towards the incisal edge was seen. Vinblastine or FR167356 (H(+)-ATPase-inhibitor) disturbed ameloblast acid-secretion, especially in the early parts of acidic zones. Enamel surface pH reflects the titration state of surface PO4(3-)-ions. At the pH-values observed, PO4(3-) would be protonated (pKa>12) and HA dissolved. However, by molecular dynamics simulations we estimate the pKa of HPO4(2-) at an ideal HA surface to be 4.3. The acidic pH measured at the enamel surface may thus only dissolve non-perfect domains of HA crystals in which PO4(3-) is less electrostatically shielded. During repeated alkaline/acidic cycles, near-perfect HA-domains may therefore gradually replace less perfect HA-domains resulting in near-perfect HA-crystals. In conclusion, cyclic changes in ameloblast H(+)-secretion and the degree of enamel maturation determine enamel surface pH. This is in accordance with a hypothesis implicating H(+)-ATPase mediated acid-secretion by ameloblasts.

  20. Electrogenerated chemiluminescence of tris(2,2' bipyridine)ruthenium(II) using common biological buffers as co-reactant, pH buffer and supporting electrolyte.

    PubMed

    Kebede, Noah; Francis, Paul S; Barbante, Gregory J; Hogan, Conor F

    2015-11-01

    A series of aliphatic tertiary amines (HEPES, POPSO, EPPS and BIS-TRIS) commonly used to buffer the pH in biological experiments, were examined as alternative, non-toxic co-reactants for the electrogenerated chemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium(ii) ([Ru(bpy)3](2+)). These were found to be very attractive as "multi-tasking" reagents, serving not only as co-reactants, but also fulfiling the roles of pH buffer and supporting electrolyte within an aqueous environment; thus significantly simplifying the overall ECL analysis. Sub-nanomolar detection limits were obtained for [Ru(bpy)3](2+) in the presence of BIS-TRIS, making this species an valuable option for co-reactant ECL-based bioanalytical applications. PMID:26347905

  1. Electrogenerated chemiluminescence of tris(2,2' bipyridine)ruthenium(II) using common biological buffers as co-reactant, pH buffer and supporting electrolyte.

    PubMed

    Kebede, Noah; Francis, Paul S; Barbante, Gregory J; Hogan, Conor F

    2015-11-01

    A series of aliphatic tertiary amines (HEPES, POPSO, EPPS and BIS-TRIS) commonly used to buffer the pH in biological experiments, were examined as alternative, non-toxic co-reactants for the electrogenerated chemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium(ii) ([Ru(bpy)3](2+)). These were found to be very attractive as "multi-tasking" reagents, serving not only as co-reactants, but also fulfiling the roles of pH buffer and supporting electrolyte within an aqueous environment; thus significantly simplifying the overall ECL analysis. Sub-nanomolar detection limits were obtained for [Ru(bpy)3](2+) in the presence of BIS-TRIS, making this species an valuable option for co-reactant ECL-based bioanalytical applications.

  2. Analysis of Natural Buffer Systems and the Impact of Acid Rain

    ERIC Educational Resources Information Center

    Powers, David C.; Yoder, Claude H.; Higgs, Andrew T.; Obley, Matt L.; Hess, Kenneth R.; Leber, Phyllis A.

    2005-01-01

    The environmental significance of acid rain on water systems of different buffer capacities is discussed. The most prevalent natural buffer system is created by the equilibrium between carbonate ions and carbon dioxide.

  3. Stacking and determination of phenazine-1-carboxylic acid with low pKa in soil via moving reaction boundary formed by alkaline and double acidic buffers in capillary electrophoresis.

    PubMed

    Sun, Chong; Yang, Xiao-Di; Fan, Liu-Yin; Zhang, Wei; Xu, Yu-Quan; Cao, Cheng-Xi

    2011-04-01

    As shown herein, a normal moving reaction boundary (MRB) formed by an alkaline buffer and a single acidic buffer had poor stacking to the new important plant growth promoter of phenazine-1-carboxylic acid (PCA) in soil due to the leak induced by its low pK(a). To stack the PCA with low pK(a) efficiently, a novel stacking system of MRB was developed, which was formed by an alkaline buffer and double acidic buffers (viz., acidic sample and blank buffers). With the novel system, the PCA leaking into the blank buffer from the sample buffer could be well stacked by the prolonged MRB formed between the alkaline buffer and blank buffer. The relevant mechanism of stacking was discussed briefly. The stacking system, coupled with sample pretreatment, could achieve a 214-fold increase of PCA sensitivity under the optimal conditions (15 mM (pH 11.5) Gly-NaOH as the alkaline buffer, 15 mM (pH 3.0) Gly-HCl-acetonitrile (20%, v/v) as the acidic sample buffer, 15 mM (pH 3.0) Gly-HCl as the blank buffer, 3 min 13 mbar injection of double acidic buffers, benzoic acid as the internal standard, 75 μm i.d. × 53 cm (44 cm effective length) capillary, 25 kV and 248 nm). The limit of detection of PCA in soil was decreased to 17 ng/g, the intra-day and inter-day precision values (expressed as relative standard deviations) were 3.17-4.24% and 4.17-4.87%, respectively, and the recoveries of PCA at three concentration levels changed from 52.20% to 102.61%. The developed method could be used for the detection of PCA in soil at trace level.

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  5. Base excess or buffer base (strong ion difference) as measure of a non-respiratory acid-base disturbance.

    PubMed

    Siggaard-Andersen, O; Fogh-Andersen, N

    1995-01-01

    Stewart in 1983 (Can J Physiol Pharmacol 1983: 61: 1444) reintroduced plasma buffer base under the name "strong ion difference" (SID). Buffer base was originally introduced by Singer and Hastings in 1948 (Medicine (Baltimore) 1948: 27: 223). Plasma buffer base, which is practically equal to the sum of bicarbonate and albuminate anions, may be increased due to an excess of base or due to an increased albumin concentration. Singer and Hastings did not consider changes in albumin as acid-base disorders and therefore used the base excess, i.e., the actual buffer base minus the buffer base at normal pH and pCO2, as measure of a non-respiratory acid-base disturbance. Stewart and followers, however, consider changes in albumin concentration to be acid-base disturbances: a patient with normal pH, pCO2, and base excess but with increased plasma buffer base due to increased plasma albumin concentration get the diagnoses metabolic (strong ion) alkalosis (because plasma buffer base is increased) combined with metabolic hyperalbuminaemic acidosis. Extrapolating to whole blood, anaemia and polycytaemia should represent types of metabolic alkalosis and acidosis, respectively. This reveals that the Stewart approach is absurd and anachronistic in the sense that an increase or decrease in any anion is interpreted as indicating an excess or deficit of a specific acid. In other words, a return to the archaic definitions of acids and bases as being the same as anions and cations. We conclude that the acid-base status (the hydrogen ion status) of blood and extracellular fluid is described in terms of the arterial pH, the arterial pCO2, and the extracellular base excess. It is measured with a modern pH-blood gas analyser. The electrolyte status of the plasma is a description of the most important electrolytes, usually measured in venous blood with a dedicated electrolyte analyser, i.e., Na+, Cl-, HCO3-, and K+. Albumin anions contribute significantly to the anions, but calculation

  6. [Effects of long-term fertilization on pH buffer system of sandy loam calcareous fluvor-aquic soil].

    PubMed

    Wang, Ji-Dong; Qi, Bing-Jie; Zhang, Yong-Chun; Zhang, Ai-Jun; Ning, Yun-Wang; Xu, Xian-Ju; Zhang, Hui; Ma, Hong-Bo

    2012-04-01

    Soil samples (0-80 cm) were collected from a 30-year fertilization experimental site in Xuzhou, Jiangsu Province of East China to study the variations of the pH, calcium carbonate and active calcium carbonate contents, and pH buffer capacity of sandy loam calcareous fluvor-aquic soil under different fertilization treatments. Thirty-year continuous application of different fertilizers accelerated the acidification of topsoil (0-20 cm), with the soil pH decreased by 0.41-0.70. Under different fertilization, the soil pH buffer capacity (pHBC) varied from 15.82 to 21.96 cmol x kg(-1). As compared with no fertilization, single N fertilization decreased the pHBC significantly, but N fertilization combined with organic fertilization could significantly increase the pHBC. The soil pHBC had significant positive correlations with soil calcium carbonate and active calcium carbonate contents, but less correlation with soil organic matter content and soil cation exchange capacity, suggesting that after a long-term fertilization, the sandy loam calcareous fluvor-aquic soil was still of an elementary calcium carbonate buffer system, and soil organic matter and cation exchange capacity contributed little to the buffer system. The soil calcium carbonate and active calcium carbonate contents were greater in 0-40 cm than in 40-80 cm soil layer. Comparing with soil calcium carbonate, soil active calcium carbonate was more sensitive to reflect the changes of soil physical and chemical properties, suggesting that the calcium carbonate buffer system could be further classified as soil active calcium carbonate buffer system.

  7. Control of groundwater pH during bioremediation: Improvement and validation of a geochemical model to assess the buffering potential of ground silicate minerals

    NASA Astrophysics Data System (ADS)

    Lacroix, Elsa; Brovelli, Alessandro; Holliger, Christof; Barry, D. A.

    2014-05-01

    Accurate control of groundwater pH is of critical importance for in situ biological treatment of chlorinated solvents. The use of ground silicate minerals mixed with groundwater is an appealing buffering strategy as silicate minerals may act as long-term sources of alkalinity. In a previous study, we developed a geochemical model for evaluation of the pH buffering capacity of such minerals. The model included the main microbial processes driving groundwater acidification as well as mineral dissolution. In the present study, abiotic mineral dissolution experiments were conducted with five silicate minerals (andradite, diopside, fayalite, forsterite, nepheline). The goal of the study was to validate the model and to test the buffering capacity of the candidate minerals identified previously. These five minerals increased the pH from acidic to neutral and slightly basic values. The model was revised and improved to represent better the experimental observations. In particular, the experiments revealed the importance of secondary mineral precipitation on the buffering potential of silicates, a process not included in the original formulation. The main secondary phases likely to precipitate were identified through model calibration, as well as the degree of saturation at which they formed. The predictions of the revised geochemical model were in good agreement with the observations, with a correlation coefficient higher than 0.9 in most cases. This study confirmed the potential of silicates to act as pH control agents and showed the reliability of the geochemical model, which can be used as a design tool for field applications.

  8. 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.

  9. Numerical Study on the Effects of pH Buffering Minerals for CO2 Sequestration in Geology by CMS Technology

    NASA Astrophysics Data System (ADS)

    Miyoshi, S.; Suzuki, K.

    2014-12-01

    Among the technical alternatives of CCS, Koide and Xue (2009) proposed the technology, CO2 Microbubble Storage (CMS). In CMS, CO2 is injected into shallow geology as microbubbles in water. Suzuki et al. (2012) studied on the legal, economic, and effective operation of CMS and showed an appropriate one as follows. CO2 microbubbles are injected in a vertical injection well with water withdrawn from the surrounding wells. When the microbubbles are mixed with water, the water is quickly saturated with CO2 because of the large surface area of the bubbles. As a result, CO2 is injected into geology as the solute, mostly bicarbonate ion. The cost efficiency of this operation is reasonbale. There is an issue that should be assessed when CO2 dissolved water is injected in shallow geology. That is the migration of low pH groundwater. The low pH pore solution might have impacts on the underground environment. Here the preliminary numerical study on the pH buffering capacity for CMS was done. In the numerical study, groundwater migration dominated by Darcy law, the advective and dispersive transport of the ions, and the reaction between pore water and minerals were considered. One dimensional geology model was used. There are various mechanisms that bring pH buffering effect in an underground circumstance. Here calcite dissolution by low pH groundwater was considered because it is one of the most casual phenomena that can bring pH buffering effect. The results of the case studies where the different mass fractions of calcite in the model layer were supposed show that the pore solution in the case with calcite was neutralized and that in the case without calcite was not. They also showed that the mass fraction of calcite does not change much the pH buffering effect. Those results were brought by the principle that the pH of the pore solution is controlled by the equilibrium constant of the reaction between minerals and the pore solution. That is, the excess portion of calcite is

  10. The effects of buffers and pH on the thermal stability, unfolding and substrate binding of RecA.

    PubMed

    Metrick, Michael A; Temple, Joshua E; MacDonald, Gina

    2013-12-31

    The Escherichia coli protein RecA is responsible for catalysis of the strand transfer reaction used in DNA repair and recombination. Previous studies in our lab have shown that high concentrations of salts stabilize RecA in a reverse-anionic Hofmeister series. Here we investigate how changes in pH and buffer alter the thermal unfolding and cofactor binding. RecA in 20mM HEPES, MES, Tris and phosphate buffers was studied in the pH range from 6.5 to 8.5 using circular dichroism (CD), infrared (IR) and fluorescence spectroscopies. The results show all of the buffers studied stabilize RecA up to 50°C above the Tris melting temperature and influence RecA's ability to nucleate on double-stranded DNA. Infrared and CD spectra of RecA in the different buffers do not show that secondary structural changes are associated with increased stability or decreased ability to nucleate on dsDNA. These results suggest the differences in stability arise from decreasing positive charge and/or buffer interactions.

  11. In Vivo Predictive Dissolution: Comparing the Effect of Bicarbonate and Phosphate Buffer on the Dissolution of Weak Acids and Weak Bases.

    PubMed

    Krieg, Brian J; Taghavi, Seyed Mohammad; Amidon, Gordon L; Amidon, Gregory E

    2015-09-01

    Bicarbonate is the main buffer in the small intestine and it is well known that buffer properties such as pKa can affect the dissolution rate of ionizable drugs. However, bicarbonate buffer is complicated to work with experimentally. Finding a suitable substitute for bicarbonate buffer may provide a way to perform more physiologically relevant dissolution tests. The dissolution of weak acid and weak base drugs was conducted in bicarbonate and phosphate buffer using rotating disk dissolution methodology. Experimental results were compared with the predicted results using the film model approach of (Mooney K, Mintun M, Himmelstein K, Stella V. 1981. J Pharm Sci 70(1):22-32) based on equilibrium assumptions as well as a model accounting for the slow hydration reaction, CO2 + H2 O → H2 CO3 . Assuming carbonic acid is irreversible in the dehydration direction: CO2 + H2 O ← H2 CO3 , the transport analysis can accurately predict rotating disk dissolution of weak acid and weak base drugs in bicarbonate buffer. The predictions show that matching the dissolution of weak acid and weak base drugs in phosphate and bicarbonate buffer is possible. The phosphate buffer concentration necessary to match physiologically relevant bicarbonate buffer [e.g., 10.5 mM (HCO3 (-) ), pH = 6.5] is typically in the range of 1-25 mM and is very dependent upon drug solubility and pKa . PMID:25980464

  12. In Vivo Predictive Dissolution: Comparing the Effect of Bicarbonate and Phosphate Buffer on the Dissolution of Weak Acids and Weak Bases.

    PubMed

    Krieg, Brian J; Taghavi, Seyed Mohammad; Amidon, Gordon L; Amidon, Gregory E

    2015-09-01

    Bicarbonate is the main buffer in the small intestine and it is well known that buffer properties such as pKa can affect the dissolution rate of ionizable drugs. However, bicarbonate buffer is complicated to work with experimentally. Finding a suitable substitute for bicarbonate buffer may provide a way to perform more physiologically relevant dissolution tests. The dissolution of weak acid and weak base drugs was conducted in bicarbonate and phosphate buffer using rotating disk dissolution methodology. Experimental results were compared with the predicted results using the film model approach of (Mooney K, Mintun M, Himmelstein K, Stella V. 1981. J Pharm Sci 70(1):22-32) based on equilibrium assumptions as well as a model accounting for the slow hydration reaction, CO2 + H2 O → H2 CO3 . Assuming carbonic acid is irreversible in the dehydration direction: CO2 + H2 O ← H2 CO3 , the transport analysis can accurately predict rotating disk dissolution of weak acid and weak base drugs in bicarbonate buffer. The predictions show that matching the dissolution of weak acid and weak base drugs in phosphate and bicarbonate buffer is possible. The phosphate buffer concentration necessary to match physiologically relevant bicarbonate buffer [e.g., 10.5 mM (HCO3 (-) ), pH = 6.5] is typically in the range of 1-25 mM and is very dependent upon drug solubility and pKa .

  13. Pharmacokinetic study of a new oral buffered acetylsalicylic acid (ASA) formulation in comparison with plain ASA in healthy volunteers.

    PubMed

    Viganò, G; Garagiola, U; Gaspari, F

    1991-01-01

    A single-blind, randomized, crossover pharmacokinetic study was carried out to investigate the bioavailability of a new oral buffered 325 mg acetylsalicylic acid (ASA) formulation (ASPIRINA 03) in comparison with a 325 mg plain tablet. Twelve healthy volunteers of both sexes, aged between 20 and 37 years, received buffered or plain ASA on two separate occasions with a wash-out interval of at least two weeks. ASA and salicylic acid (SA) plasma levels were determined by a chromatographic method. The results showed no difference between the area under concentration time curve (AUC0-infinity) ASA values of both formulations (p = 0.19), and buffered ASA relative bioavailability was 102.49% (= bioequivalence). A significant difference was found between the AUC0-30 min ASA values: 90.5 micrograms. min/ml with buffered and 67.7 micrograms. min/ml with the plain tablet (p less than 0.05). The buffered ASA time of maximum concentration was shorter (28 +/- 8 min) than the plain one (38 +/- 19 min, p less than 0.05). The plasma concentrations and pharmacokinetic parameters of SA were not significantly different after the administration of the two ASA formulations. The plain ASA tablet had a significantly lower (p less than 0.05) dissolution rate than buffered ASA tablet. Moreover, the buffered ASA tablet significantly (p less than 0.01) increased the pH by 0.5 units. In conclusion, the bioavailability of the new oral buffered ASA was equivalent to that of plain ASA, but the plasma concentration peak was reached in a shorter time. PMID:1809699

  14. An investigation using atomic force microscopy nanoindentation of dental enamel demineralization as a function of undissociated acid concentration and differential buffer capacity

    NASA Astrophysics Data System (ADS)

    Barbour, Michele E.; Shellis, R. Peter

    2007-02-01

    Acidic drinks and foodstuffs can demineralize dental hard tissues, leading to a pathological condition known as dental erosion, which is of increasing clinical concern. The first step in enamel dissolution is a demineralization of the outer few micrometres of tissue, which results in a softening of the structure. The primary determinant of dissolution rate is pH, but the concentration of undissociated acid, which is related to buffer capacity, also appears to be important. In this study, atomic force microscopy nanoindentation was used to measure the first initial demineralization (softening) induced within 1 min by exposure to solutions with a range of undissociated acid concentration and natural pH of 3.3 or with an undissociated acid concentration of 10 mmol l-1 and pH adjusted to 3.3. The results indicate that differential buffering capacity is a better determinant of softening than undissociated acid concentration. Under the conditions of these experiments, a buffer capacity of >3 mmol l-1 pH-1 does not have any further effect on dissolution rate. These results imply that differential buffering capacity should be used for preference over undissociated acid concentration or titratable acidity, which are more commonly employed in the literature.

  15. Tested Demonstrations: Buffer Capacity of Various Acetic Acid-Sodium Acetate Systems: A Lecture Experiment.

    ERIC Educational Resources Information Center

    Donahue, Craig J.; Panek, Mary G.

    1985-01-01

    Background information and procedures are provided for a lecture experiment which uses indicators to illustrate the concept of differing buffer capacities by titrating acetic acid/sodium acetate buffers with 1.0 molar hydrochloric acid and 1.0 molar sodium hydroxide. A table with data used to plot the titration curve is included. (JN)

  16. Comparison and trend study on acidity and acidic buffering capacity of particulate matter in China

    NASA Astrophysics Data System (ADS)

    Ren, Lihong; Wang, Wei; Wang, Qingyue; Yang, XiaoYang; Tang, Dagang

    2011-12-01

    The acidity of about 2000 particulate matter samples from aircraft and ground-based monitoring is analyzed by the method similar to soil acidity determination. The ground-based samples were collected at about 50 urban or background sites in northern and southern China. Moreover, the acidic buffering capacity of those samples is also analyzed by the method of micro acid-base titration. Results indicate that the acidity level is lower in most northern areas than those in the south, and the acidic buffering capacity showed inverse tendency, correspondingly. This is the most important reason why the pollution of acidic-precipitation is much more serious in Southern China than that in Northern China. The acidity increases and the acidic buffering capacity drops with the decreasing of the particle sizes, indicating that fine particle is the main influencing factor of the acidification. The ionic results show that Ca salt is the main alkaline substance in particulate matter, whereas the acidification of particulate matter is due to the SO 2 and NO x emitted from the fossil fuel burning. And among of them, coal burning is the main contributor of SO 2, however the contribution of NO x that emitted from fuel burning of motor vehicles has increased in recent years. By comparison of the experimental results during the past 20 years, it can be concluded that the acid precipitation of particulate matter has not been well controlled, and it even shows an increasing tendency in China lately. The acid precipitation of particulate matter has begun to frequently attack in part of the northern areas. Multiple regression analysis indicates that coefficient value of the ions is the lowest at the urban sites and the highest at the regional sites, whereas the aircraft measurement results are intermediate between those two kinds of sites.

  17. Controlled release of acidic drugs in compendial and physiological hydrogen carbonate buffer from polymer blend-coated oral solid dosage forms.

    PubMed

    Wulff, R; Rappen, G-M; Koziolek, M; Garbacz, G; Leopold, C S

    2015-09-18

    The objective of this study was to investigate the suitability of "Eudragit® RL/Eudragit® L55" (RL/L55) blend coatings for a pH-independent release of acidic drugs. A coating for ketoprofen and naproxen mini tablets was developed showing constant drug release rate under pharmacopeial two-stage test conditions for at least 300 min. To simulate drug release from the mini tablets coated with RL/L55 blends in the gastrointestinal (GI) tract, drug release profiles in Hanks buffer pH 6.8 were recorded and compared with drug release profiles in compendial media. RL/L55 blend coatings showed increased drug permeability in Hanks buffer pH 6.8 compared to phosphate buffer pH 6.8 due to its higher ion concentration. However, drug release rates of acidic drugs were lower in Hanks buffer pH 6.8 because of the lower buffer capacity resulting in reduced drug solubility. Further dissolution tests were performed in Hanks buffer using pH sequences simulating the physiological pH conditions in the GI tract. Drug release from mini tablets coated with an RL/L55 blend (8:1) was insensitive to pH changes of the medium within the pH range of 5.8-7.5. It was concluded that coatings of RL/L55 blends show a high potential for application in coated oral drug delivery systems with a special focus on pH-independent release of acidic drugs.

  18. Influence of solid-state acidity on the decomposition of sucrose in amorphous systems II (effect of buffer).

    PubMed

    Alkhamis, Khouloud A

    2009-04-01

    It was of interest to investigate the solid-state acidity using indicator probe molecules and sucrose degradation. Amorphous samples containing lactose, sucrose, buffers (citrate, malate, tartarate, or phosphate) with different pH values, and sodium chloride (to adjust the ionic strength) were prepared by freeze-drying. The lyophiles were characterized using powder X-ray diffraction, differential scanning calorimetry, and Karl Fischer titrimetry. The solid-state acidity of all lyophiles was measured using diffuse reflectance spectroscopy and suitable indicators (thymol blue or bromophenol blue). Selected lyophiles were subjected to a temperature of 60 degrees C and were analyzed for sucrose degradation using the Trinder kit. The results obtained from this study have shown that good correlation can be obtained between the solid-state acidity and the molar ratio of the salt and the acid in solution. The degradation of sucrose in the lyophiles is extremely sensitive to the solid-state acidity and might be able to provide a better estimate for the acidity than the indicator probe molecules. The Hammett acidity-rate profile for sucrose degradation in the lyophiles (using four different buffers) was also obtained. The profile showed similarity to the pH-rate profile in solution, and no buffer catalysis for sucrose degradation was detected in this study. PMID:19016102

  19. Buffer-free production of gamma-aminobutyric acid using an engineered glutamate decarboxylase from Escherichia coli.

    PubMed

    Kang, Taek Jin; Ho, Ngoc Anh Thu; Pack, Seung Pil

    2013-08-15

    Escherichia coli glutamate decarboxylase (GAD) converts glutamate into γ-aminobutyric acid (GABA) through decarboxylation using proton as a co-substrate. Since GAD is active only at acidic conditions even though pH increases as the reaction proceeds, the conventional practice of using this enzyme involved the use of relatively high concentration of buffers, which might complicate the downstream purification steps. Here we show by simulation and experiments that the free acid substrate, glutamic acid, rather than its monosodium salt can act as a substrate and buffer at the same time. This yielded the buffer- and salt-free synthesis of GABA conveniently in a batch mode. Furthermore, we engineered GAD to hyper active ones by extending or reducing the length of the enzyme by just one residue at its C-terminus. Through the buffer-free reaction with engineered GAD, we could synthesize 1M GABA in 3h, which can be translated into a space-time yield of 34.3g/L/h.

  20. 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.

  1. 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…

  2. 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

  3. 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

  4. The effect of buffering dairy cow diets with limestone, calcareous marine algae, or sodium bicarbonate on ruminal pH profiles, production responses, and rumen fermentation.

    PubMed

    Cruywagen, C W; Taylor, S; Beya, M M; Calitz, T

    2015-08-01

    Six ruminally cannulated Holstein cows were used to evaluate the effect of 2 dietary buffers on rumen pH, milk production, milk composition, and rumen fermentation parameters. A high concentrate total mixed ration [35.2% forage dry matter (DM)], formulated to be potentially acidotic, was used to construct 3 dietary treatments in which calcareous marine algae (calcified remains of the seaweed Lithothamnium calcareum) was compared with limestone (control) and sodium bicarbonate plus limestone. One basal diet was formulated and the treatment diets contained either 0.4% of dietary DM as Acid Buf, a calcified marine algae product (AB treatment), or 0.8% of dietary DM as sodium bicarbonate and 0.37% as limestone (BC treatment), or 0.35% of dietary DM as limestone [control (CON) treatment]. Cows were randomly allocated to treatments according to a double 3×3 Latin square design, with 3 treatments and 3 periods. The total experimental period was 66 d during which each cow received each treatment for a period of 15 d before the data collection period of 7 d. Rumen fluid was collected to determine volatile fatty acids, lactic acid, and ammonia concentrations. Rumen pH was monitored every 10min for 2 consecutive days using a portable data logging system fitted with in-dwelling electrodes. Milk samples were analyzed for solid and mineral contents. The effect of treatment on acidity was clearly visible, especially from the period from midday to midnight when rumen pH dropped below 5.5 for a longer period of time (13 h) in the CON treatment than in the BC (8.7 h) and AB (4 h) treatments. Daily milk, 4% fat-corrected milk, and energy-corrected milk yields differed among treatments, with AB being the highest, followed by BC and CON. Both buffers increased milk fat content. Treatment had no effect on milk protein content, but protein yield was increased in the AB treatment. Total rumen volatile fatty acids and acetate concentrations were higher and propionate was lower in the AB

  5. Acidification due to microbial dechlorination near a trichloroethene DNAPL is overcome with pH buffer or formate as electron donor: experimental demonstration in diffusion-cells.

    PubMed

    Philips, Jo; Maes, Nele; Springael, Dirk; Smolders, Erik

    2013-04-01

    Acidification due to microbial dechlorination of trichloroethene (TCE) can limit the bio-enhanced dissolution of TCE dense non-aqueous phase liquid (DNAPL). This study related the dissolution enhancement of a TCE DNAPL to the pH buffer capacity of the medium and the type of electron donor used. In batch systems, dechlorination was optimal at pH7.1-7.5, but was completely inhibited below pH6.2. In addition, dechlorination in batch systems led to a smaller pH decrease at an increasing pH buffer capacity or with the use of formate instead of lactate as electron donor. Subsequently, bio-enhanced TCE DNAPL dissolution was quantified in diffusion-cells with a 5.5 cm central sand layer, separating a TCE DNAPL layer from an aqueous top layer. Three different pH buffer capacities (2.9 mM-17.9 mM MOPS) and lactate or formate as electron donor were applied. In the lactate fed diffusion-cells, the DNAPL dissolution enhancement factor increased from 1.5 to 2.2 with an increase of the pH buffer capacity. In contrast, in the formate fed diffusion-cells, the DNAPL dissolution enhancement factor (2.4±0.3) was unaffected by the pH buffer capacity. Measurement of the pore water pH confirmed that the pH decreased less with an increased pH buffer capacity or with formate instead of lactate as electron donor. These results suggest that the significant impact of acidification on bio-enhanced DNAPL dissolution can be overcome by the amendment of a pH buffer or by applying a non acidifying electron donor like formate.

  6. The erosion kinetics of conventional and resin-modified glass-ionomer luting cements in acidic buffer solutions.

    PubMed

    Hazar-Yoruc, Binnaz; Bavbek, Andac Barkin; Özcan, Mutlu

    2012-01-01

    This study investigated the erosion kinetics of conventional and resin-modified glass-ionomer luting cements in acidic buffer solutions as a function of time. Disc shaped specimens were prepared from conventional (Ketac-Cem: KTC) and resin-modified glass ionomer cements (Fuji Plus: FP) and immersed in three acidic buffer solutions (0.01 M) namely, acetic acid/sodium acetate (AA(B)), lactic acid/sodium lactate (LA(B)) and citric acid/sodium citrate (CA(B)) with a constant pH of 4.1 and stored for 1, 8, 24, 48, 80, 120 and 168 h. F concentration was determined using ion-specific electrode. Si, Ca and Al concentrations were determined by atomic absorption spectroscopy. Ca, Al, Si and F solubility rates in both FP and KTC were the highest in CA(B) solution. The erosion rates of both FP and KTC in all buffer solutions increased as a function of immersion time. The amount of F eluted from FP was more than that of KTC. The total amount of elements released from FP was less than KTC in all solutions. PMID:23207217

  7. Improving impurities clearance by amino acids addition to buffer solutions for chromatographic purifications of monoclonal antibodies.

    PubMed

    Ishihara, Takashi; Hosono, Mareto

    2015-07-15

    The performance of amino acids in Protein A affinity chromatography, anion exchange chromatography and cation exchange chromatography for monoclonal antibody purification was investigated. Glycine, threonine, arginine, glutamate, and histidine were used as buffer components in the equilibration, washing, and elution steps of these chromatographies. Improved clearance of impurity, high molecular weight species (HMW) and host cell proteins (HCP) was observed in the purification processes when using the amino acids as base-buffer constituents, additives or eluents compared with that of buffers without these amino acids. In addition, we designed a buffer system in which the mobile phases were composed of only a single amino acid, histidine, and applied it to the above three chromatographies. Effective HMW and HCP clearance was also obtained in this manner. These results suggest that amino acids may enhance impurity clearance during the purification of monoclonal antibodies. PMID:26057847

  8. 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.

  9. Buffer Therapy for Cancer

    PubMed Central

    Ribeiro, Maria de Lourdes C; Silva, Ariosto S.; Bailey, Kate M.; Kumar, Nagi B.; Sellers, Thomas A.; Gatenby, Robert A.; Ibrahim-Hashim, Arig; Gillies, Robert J.

    2013-01-01

    Oral administration of pH buffers can reduce the development of spontaneous and experimental metastases in mice, and has been proposed in clinical trials. Effectiveness of buffer therapy is likely to be affected by diet, which could contribute or interfere with the therapeutic alkalinizing effect. Little data on food pH buffering capacity was available. This study evaluated the pH and buffering capacity of different foods to guide prospective trials and test the effect of the same buffer (lysine) at two different ionization states. Food groups were derived from the Harvard Food Frequency Questionnaire. Foods were blended and pH titrated with acid from initial pH values until 4.0 to determine “buffering score”, in mmol H+/pH unit. A “buffering score” was derived as the mEq H+ consumed per serving size to lower from initial to a pH 4.0, the postprandial pH of the distal duodenum. To differentiate buffering effect from any metabolic byproduct effects, we compared the effects of oral lysine buffers prepared at either pH 10.0 or 8.4, which contain 2 and 1 free base amines, respectively. The effect of these on experimental metastases formation in mice following tail vein injection of PC-3M prostate cancer cells were monitored with in vivo bioluminescence. Carbohydrates and dairy products’ buffering score varied between 0.5 and 19. Fruits and vegetables showed a low to zero buffering score. The score of meats varied between 6 and 22. Wine and juices had negative scores. Among supplements, sodium bicarbonate and Tums® had the highest buffering capacities, with scores of 11 and 20 per serving size, respectively. The “de-buffered” lysine had a less pronounced effect of prevention of metastases compared to lysine at pH 10. This study has demonstrated the anti-cancer effects of buffer therapy and suggests foods that can contribute to or compete with this approach to manage cancer. PMID:24371544

  10. The acid-base buffer capacity of podzolic soils and its changes under the impact of treatment with the Mehra-Jackson and Tamm reagents

    NASA Astrophysics Data System (ADS)

    Maksimova, Yu. G.; Maryakhina, N. N.; Tolpeshta, I. I.; Sokolova, T. A.

    2010-10-01

    The acid-base buffer capacity before and after the treatment with the Mehra-Jackson and Tamm reagents was assessed by continuous potentiometric titration for the main genetic horizons of two profiles of podzolic soils in the Central Forest State Reserve. The total buffer capacity was calculated in the pH range from the initial titration point (ITP) to 3 for the acid titration and from the ITP to 10 for the base titration, as well as the buffer capacities in the pH intervals of 0.25. It was found that both treatments abruptly decreased the base buffer capacity, which reached 70-90% in the E horizons. The high direct linear correlation of the difference between the total base buffer capacities before and after each treatment with the content of Fe in the Tamm extract was revealed. From the results obtained, a conclusion was drawn that finely dispersed Fe hydroxides were the main solid-phase constituents ensuring the base buffer capacity, and the deprotonation of hydroxyl groups on the surface of Fe hydroxides was the essential buffer reaction during the base titration.

  11. 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

  12. 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.

  13. Evaluation of different approaches to quantify strong organic acidity and acid-base buffering of organic-rich surface waters in Sweden.

    PubMed

    Köhler, Stephan; Hruska, Jakub; Jönsson, Jörgen; Lövgren, Lars; Lofts, Stephen

    2002-11-01

    The role of organic acids in buffering pH in surface waters has been studied using a small brownwater stream (26mg L(-1) TOC) draining a forested catchment in Northern Sweden. Under the conditions of elevated pressure of CO2 stream field pH was changed between 3.5 and 6.1 during the acidification and alkalinization experiment. Acid-base characteristics of the natural organic matter were also determined using a high precision potentiometric method for a concentrated sample from the same stream. We compared the predictions from the Windermere Humic Aqueous Model (WHAM Model V), a model derived from the potentiometric titration (diprotic/monoprotic acid model) and a previously derived triprotic acid model which only uses alkalinity and TOC as input variables. The predicted buffering characteristics of all three models are very similar in the pH range 4.5-7 which suggests that during routine analysis alkalinity and TOC are sufficient to give a good estimate of organic acid anion charge contribution in a large range of surface waters. A slightly adjusted version of WHAM V successfully describes the organic charge contribution in a large number of sampled surface water lakes, which were previously used to calibrate the triprotic model.

  14. 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

  15. Kinetic buffers.

    PubMed

    Alibrandi, Giuseppe; Fabbrizzi, Luigi; Licchelli, Maurizio; Puglisi, Antonio

    2015-01-12

    This paper proposes a new type of molecular device that is able to act as an inverse proton sponge to slowly decrease the pH inside a reaction vessel. This makes the automatic monitoring of the concentration of pH-sensitive systems possible. The device is a composite formed of an alkyl chloride, which kinetically produces acidity, and a buffer that thermodynamically modulates the variation in pH value. Profiles of pH versus time (pH-t plots) have been generated under various experimental conditions by computer simulation, and the device has been tested by carrying out automatic spectrophotometric titrations, without using an autoburette. To underline the wide variety of possible applications, this new system has been used to realize and monitor HCl uptake by a di-copper(II) bistren complex in a single run, in a completely automatic experiment.

  16. Effect of coexisting Al(III) ions on Pb(II) sorption on biochars: Role of pH buffer and competition.

    PubMed

    Yang, Yuxi; Zhang, Weihua; Qiu, Hao; Tsang, Daniel C W; Morel, Jean-Louis; Qiu, Rongliang

    2016-10-01

    Biochar is being widely considered as a promising amendment agent for immobilizing heavy metals in contaminated acidic soils, where plenty of soluble Al(III) ions exist. In view of uncertain significance of the effects of coexisting Al(III) on Pb(II) sorption by biochars, this study used kenaf core biochar (KB550; high carbon, low ash) and sewage sludge biochar (SB550; low carbon, high ash) pyrolyzed at 550 °C to elucidate the influence of coexisting Al(III) species and biochars' mineral components on Pb(II) immobilization conducted in aqueous solution with initial pHs of 3.0-4.5. Results showed that Al(III) reduced Pb(II) sorption on KB550 primarily via pH buffering against biochar alkalinity, thus inhibiting lead carbonate formation. In contrast, the reduction on SB550 mainly resulted from direct competition for sorption sites, especially on Fe-rich phengite 2M1 and metakaolinite. Because of Pb-P precipitation and Pb-K interlayer exchange, the residual Pb(II) adsorption capacity resistant to coexisting Al(III) was 3-5 times higher on SB550 than on KB550. The Pb-K interlayer exchange was enhanced by lower pH and coexisting Al(III), while Pb-P precipitation was the dominant Pb(II) sorption mechanism on SB550 resistant to Al(III) buffering and competition at higher pH. Application of these two biochars as amendments confirmed that the mineral-rich SB550 was more suitable for Pb(II) immobilization in acidic soils with high levels of extractable Al(III). PMID:27454898

  17. Effect of coexisting Al(III) ions on Pb(II) sorption on biochars: Role of pH buffer and competition.

    PubMed

    Yang, Yuxi; Zhang, Weihua; Qiu, Hao; Tsang, Daniel C W; Morel, Jean-Louis; Qiu, Rongliang

    2016-10-01

    Biochar is being widely considered as a promising amendment agent for immobilizing heavy metals in contaminated acidic soils, where plenty of soluble Al(III) ions exist. In view of uncertain significance of the effects of coexisting Al(III) on Pb(II) sorption by biochars, this study used kenaf core biochar (KB550; high carbon, low ash) and sewage sludge biochar (SB550; low carbon, high ash) pyrolyzed at 550 °C to elucidate the influence of coexisting Al(III) species and biochars' mineral components on Pb(II) immobilization conducted in aqueous solution with initial pHs of 3.0-4.5. Results showed that Al(III) reduced Pb(II) sorption on KB550 primarily via pH buffering against biochar alkalinity, thus inhibiting lead carbonate formation. In contrast, the reduction on SB550 mainly resulted from direct competition for sorption sites, especially on Fe-rich phengite 2M1 and metakaolinite. Because of Pb-P precipitation and Pb-K interlayer exchange, the residual Pb(II) adsorption capacity resistant to coexisting Al(III) was 3-5 times higher on SB550 than on KB550. The Pb-K interlayer exchange was enhanced by lower pH and coexisting Al(III), while Pb-P precipitation was the dominant Pb(II) sorption mechanism on SB550 resistant to Al(III) buffering and competition at higher pH. Application of these two biochars as amendments confirmed that the mineral-rich SB550 was more suitable for Pb(II) immobilization in acidic soils with high levels of extractable Al(III).

  18. Buffer capacity of biologics--from buffer salts to buffering by antibodies.

    PubMed

    Karow, Anne R; Bahrenburg, Sven; Garidel, Patrick

    2013-01-01

    Controlling pH is essential for a variety of biopharmaceutical process steps. The chemical stability of biologics such as monoclonal antibodies is pH-dependent and slightly acidic conditions are favorable for stability in a number of cases. Since control of pH is widely provided by added buffer salts, the current study summarizes the buffer characteristics of acetate, citrate, histidine, succinate, and phosphate buffers. Experimentally derived values largely coincide with values calculated from a model that had been proposed in 1922 by van Slyke. As high concentrated protein formulations become more and more prevalent for biologics, the self-buffering potential of proteins becomes of relevance. The current study provides information on buffer characteristics for pH ranges down to 4.0 and up to 8.0 and shows that a monoclonal antibody at 50 mg/mL exhibits similar buffer capacity as 6 mM citrate or 14 mM histidine (pH 5.0-6.0). Buffer capacity of antibody solutions scales linearly with protein concentration up to more than 200 mg/mL. At a protein concentration of 220 mg/mL, the buffer capacity resembles the buffer capacity of 30 mM citrate or 50 mM histidine (pH 5.0-6.0). The buffer capacity of monoclonal antibodies is practically identical at the process relevant temperatures 5, 25, and 40°C. Changes in ionic strength of ΔI=0.15, in contrast, can alter the buffer capacity up to 35%. In conclusion, due to efficient self-buffering by antibodies in the pH range of favored chemical stability, conventional buffer excipients could be dispensable for pH stabilization of high concentrated protein solutions.

  19. Separation of oligonucleotides of identical size, but different base composition, by free zone capillary electrophoresis in strongly acidic, isoelectric buffers.

    PubMed

    Perego, M; Gelfi, C; Stoyanov, A V; Righetti, P G

    1997-12-01

    A novel method for analyzing oligonucleotides of the same length, but bearing a single base substitution, is reported, based on free zone capillary electrophoresis (CZE) under rather acidic pH values. For this purpose, a set of four 18-mers of fairly random base composition has been synthesized, bearing, in nucleotide 9, the following bases: T, C, G or A. Theoretical predictions, based on titration curves of single free nucleotides, allowed us to predict that the simultaneous separation of a mixture of all four oligonucleotides could be possible in a pH 3-4 window. In fact, electrophoresis at pH 5.7 gave a single, asymmetric peak, whereas CZE at pH 4.8 could resolve three out of four species (the T9 and G9 oligonucleotides co-migrating into a single zone). A unique separation power could be obtained at pH 3.3 in a buffer comprising an amphoteric species (isoelectric iminodiacetic acid, IDA) and 7 M urea. Although IDA exhibited a pI of 2.23 (for a 100 mM solution), the addition of 7 M urea (necessary to denature the oligonucleotides) raised the apparent pH of the solution to 3.3. PMID:9504830

  20. The Effects of pH on the Growth and Aspect Ratio of Chicken Egg White Lysozyme Crystals Prepared in Different Buffers

    NASA Technical Reports Server (NTRS)

    Gibson, U. J.; Horrell, E. E.; Kou, Y.; Pusey, Marc

    2000-01-01

    We have measured the nucleation and aspect ratio of CEWL crystals grown by vapor diffusion in acetate, butyrate, carbonate, succinate, and phosphate buffers in a range of pH spanning the pK(sub a) of these buffers. The nucleation numbers drop off significantly in the vicinity of pK(sub a) for each of the buffers except the phosphate system, in which we used only the pH range around the second titration point(pK2). There is a concomitant increase in the sizes of the crystals. Some typical nucleation number results are shown. These data support and extend other observations. In addition, we have examined changes in aspect ratio which accompany the suppression of nucleation within each buffer system. The length of the face in the [001] direction was measured, and compared to the width of the (110) face in the [110] type directions. We find that while the aspect ratio of the crystals is affected by pH, it is dominated by a correlation with the size of the crystals. Small crystals are longer in the [0011 direction than crystals that are larger (higher pH within a buffer system). This relationship is found to hold independent of the choice of buffer. These results are consistent with those of Judge et al, who used a batch process which resulted in uniform sizing of crystals at each pH. In these experiments, we specifically avoid agitating the protein/salt buffer mixture when combining the two. This permits the formation of a range of sizes at a given pH. The results for a .05 M acetate 5% NaCl buffer are also shown. We will discuss these results in light of a growth model.

  1. Structural transitions in polycytidylic acid: proton buffer capacity data.

    PubMed

    Zarudnaya, Margarita I; Samijlenko, Svitlana P; Potyahaylo, Andriy L; Hovorun, Dmytro M

    2002-01-01

    The pH-dependences of proton buffer capacity of poly(C) were computed on the basis of the literature data. In these curves there were observed four peaks: two narrow and two wide ones. The first narrow peak reflects the process of cooperative formation of double helices, which is induced by protonation of the N3 atom of nucleotide bases. The first wide peak is assigned to noncooperative process of poly(C) double helices protonation at the N3 nitrogen atom. It is proposed that the second wide peak corresponds to noncooperative protonation of the neutral cytosine bases at the oxygen atom. This reaction causes cooperative dissociation of the poly(C) double helices. The second narrow peak reflects the dissociation process. PMID:11991140

  2. Exciton-blocking phosphonic acid-treated anode buffer layers for organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Zimmerman, Jeramy D.; Song, Byeongseop; Griffith, Olga; Forrest, Stephen R.

    2013-12-01

    We demonstrate significant improvements in power conversion efficiency of bilayer organic photovoltaics by replacing the exciton-quenching MoO3 anode buffer layer with an exciton-blocking benzylphosphonic acid (BPA)-treated MoO3 or NiO layer. We show that the phosphonic acid treatment creates buffers that block up to 70% of excitons without sacrificing the hole extraction efficiency. Compared to untreated MoO3 anode buffers, BPA-treated NiO buffers exhibit a ˜ 25% increase in the near-infrared spectral response in diphenylanilo functionalized squaraine (DPSQ)/C60-based bilayer devices, increasing the power conversion efficiency under 1 sun AM1.5G simulated solar illumination from 4.8 ± 0.2% to 5.4 ± 0.3%. The efficiency can be further increased to 5.9 ± 0.3% by incorporating a highly conductive exciton blocking bathophenanthroline (BPhen):C60 cathode buffer. We find similar increases in efficiency in two other small-molecule photovoltaic systems, indicating the generality of the phosphonic acid-treated buffer approach to enhance exciton blocking.

  3. Implementing bacterial acid resistance into cell-free protein synthesis for buffer-free expression and screening of enzymes.

    PubMed

    Kim, Ho-Cheol; Kim, Kwang-Soo; Kang, Taek-Jin; Choi, Jong Hyun; Song, Jae Jun; Choi, Yun Hee; Kim, Byung-Gee; Kim, Dong-Myung

    2015-12-01

    Cell-free protein synthesis utilizes translational machinery isolated from the cells for in vitro expression of template genes. Because it produces proteins without gene cloning and cell cultivation steps, cell-free protein synthesis can be used as a versatile platform for high-throughput expression of enzyme libraries. Furthermore, the open nature of cell-free protein synthesis allows direct integration of enzyme synthesis with subsequent screening steps. However, the presence of high concentration of chemical buffers in the conventional reaction mixture makes it difficult to streamline cell-free protein synthesis with pH-based assay of the synthesized enzymes. In this study, we have implemented an enzyme-assisted bacterial acid resistance mechanism into an Escherichia coli (E.coli) extract-based cell-free protein synthesis system in place of chemical buffers. When deployed in the reaction mixture for cell-free synthesis of enzymes, through proton-consuming conversion of glutamate into γ-aminobutyric acid (GABA), an engineered glutamate decarboxylase (GADβ) was able to maintain the pH of reaction mixture during enzyme synthesis. Because the reaction mixture becomes free of buffering capacity upon the depletion of glutamate, synthesized enzyme could be directly assayed without purification steps. The designed method was successfully applied to the screening of mutant library of sialyltransferase genes to identify mutants with improved enzymatic activity.

  4. In situ ellipsometric investigation of stainless steel corrosion behavior in buffered solutions with amino acids

    NASA Astrophysics Data System (ADS)

    Vinnichenko, M. V.; Pham, M. T.; Chevolleau, T.; Poperenko, L. V.; Maitz, M. F.

    2003-02-01

    The corrosion of metals is associated both with a release of ions and changes in optical surface properties. In this study, these two effects were correlated by a potentiodynamic corrosion test and in situ probing of the surface by ellipsometry. The studies were carried out with stainless steel (SS) AISI 304 and 316 in phosphate buffered saline (PBS) and in Dulbecco's modified minimal essential medium (DMEM) at pH 7.4. In both media, 304 steel is more susceptible to corrosion than 316 grade. The 316 steel shows a higher corrosion potential and higher corrosion current density in PBS than in DMEM, for 304 steel this behavior is vice versa. Ellipsometry demonstrated a higher sensitivity than potentiodynamics to surface modification in the cathodic area. In DMEM the removal of a surface layer at negative potential and a further repassivation with increasing potential was characteristic. In PBS a surface layer started to grow immediately. X-ray photoelectron spectra of this layer formed in PBS are consistent with iron phosphate. Its formation is inhibited in DMEM; the presence of amino acids is discussed as the reason.

  5. Thermodynamical characteristics of the reaction of pyridoxal-5'-phosphate with L-amino acids in aqueous buffer solution

    NASA Astrophysics Data System (ADS)

    Barannikov, V. P.; Badelin, V. G.; Venediktov, E. A.; Mezhevoi, I. N.; Guseinov, S. S.

    2011-01-01

    The reaction of pyridoxal-5'-phosphate with L-isomers of alanine, lysine, arginine, aspartic acid, glutamic acid, and glycine in phosphate buffer solution was studied by absorption spectroscopy and the calorimetry of dissolution at physiological acidity of the medium (pH 7.35). The formation constants of Schiff bases during reactions and changes in Gibbs energy, enthalpy, and entropy were determined. It was shown that the formation constant of the Schiff base and its spectral properties depend on the nature of the bound amino acid. The progress of the reaction with a majority of amino acids is governed by the entropy factor due to the predominant role of the dehydration effect of the reaction center of amino acids during chemical reactions. The intramolecular electrostatic interaction of an ionized phosphate group with the positively charged amino group on the end of the chain of amino acid residue stabilizes the Schiff bases formed by lysine and arginine. The extinction coefficient of the base, equilibrium constant, and the exothermic effect of the reaction then increase. The excess negative charge on the end of the chain of amino acid residues of aspartic and glutamic acids destabilizes the molecule of the Schiff base. In this case, the equilibrium constant decreases and the endothermic effect of the reaction increases.

  6. DNA adsorption to and elution from silica surfaces: influence of amino acid buffers.

    PubMed

    Vandeventer, Peter E; Mejia, Jorge; Nadim, Ali; Johal, Malkiat S; Niemz, Angelika

    2013-09-19

    Solid phase extraction and purification of DNA from complex samples typically requires chaotropic salts that can inhibit downstream polymerase amplification if carried into the elution buffer. Amino acid buffers may serve as a more compatible alternative for modulating the interaction between DNA and silica surfaces. We characterized DNA binding to silica surfaces, facilitated by representative amino acid buffers, and the subsequent elution of DNA from the silica surfaces. Through bulk depletion experiments, we found that more DNA adsorbs to silica particles out of positively compared to negatively charged amino acid buffers. Additionally, the type of the silica surface greatly influences the amount of DNA adsorbed and the final elution yield. Quartz crystal microbalance experiments with dissipation monitoring (QCM-D) revealed multiphasic DNA adsorption out of stronger adsorbing conditions such as arginine, glycine, and glutamine, with DNA more rigidly bound during the early stages of the adsorption process. The DNA film adsorbed out of glutamate was more flexible and uniform throughout the adsorption process. QCM-D characterization of DNA elution from the silica surface indicates an uptake in water mass during the initial stage of DNA elution for the stronger adsorbing conditions, which suggests that for these conditions the DNA film is partly dehydrated during the prior adsorption process. Overall, several positively charged and polar neutral amino acid buffers show promise as an alternative to methods based on chaotropic salts for solid phase DNA extraction.

  7. 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.

  8. Influence of the acid buffering capacity of different types of Technosols on the chemistry of their leachates.

    PubMed

    Yao, F X; Macías, F; Santesteban, A; Virgel, S; Blanco, F; Jiang, X; Camps Arbestain, M

    2009-01-01

    The preparation of tailor-made Technosols from wastes may be a novel and prospective option for the re-use of wastes and restoration of degraded areas. A two-month study with pilot columns was conducted to evaluate the influence of the acid buffering capacity of different Technosols on the chemistry of their leachates. The Technosols were made from mixtures of organic and inorganic wastes at a ratio of 56:44 (w/w). The organic components used were an anaerobic (AN) and an aerobic (AE) sewage sludge. The inorganic wastes used--referred to as "conditioners"--were Linz-Donowitz slag (LD) and foundry sand (FS). A mixture of the two conditioners at a ratio of 50:50 (w/w) was made to provide a third type of conditioner (LD+FS). Controls consisted of columns filled with organic waste only (either AN or AE sludges). Changes in pH, electrical conductivity, concentrations of major ions and dissolved organic carbon in the leachates were evaluated periodically. The main processes determining the pH of the systems were nitrification and leaching, but organic matter decomposition and carbonation may also have had an influence. Nitrification was strongly retarded in the AN sludge (attributed to the probable absence of nitrifiers in this waste after the AN wastewater treatment) and was impeded in those mixtures in which LD was used as a component (due to the liming effect). Final pH values ranged from 5.0 and 5.4 (in AE and AE+FS, respectively) to 11.1 (in AN+LD). The pH of the other mixtures finally ranged between 7 and 8. In formulating mixtures of wastes, their acid buffering capacity should be taken into account in addition to the nutrient contents and the limits of contaminants established by local regulations. PMID:19026435

  9. Acid neutralizing processes in an alpine watershed front range, Colorado, U.S.A.-1: Buffering capacity of dissolved organic carbon in soil solutions

    USGS Publications Warehouse

    Iggy, Litaor M.; Thurman, E.M.

    1988-01-01

    Soil interstitial waters in the Green Lakes Valley, Front Range, Colorado were studied to evaluate the capacity of the soil system to buffer acid deposition. In order to determine the contribution of humic substances to the buffering capacity of a given soil, dissolved organic carbon (DOC) and pH of the soil solutions were measured. The concentration of the organic anion, Ai-, derived from DOC at sample pH and the concentration of organic anion, Ax- at the equivalence point were calculated using carboxyl contents from isolated and purified humic material from soil solutions. Subtracting Ax- from Ai- yields the contribution of humic substances to the buffering capacity (Aequiv.-). Using this method, one can evaluate the relative contribution of inorganic and organic constituents to the acid neutralizing capacity (ANC) of the soil solutions. The relative contribution of organic acids to the overall ANC was found to be extremely important in the alpine wetland (52%) and the forest-tundra ecotone (40%), and somewhat less important in the alpine tundra sites (20%). A failure to recognize the importance of organic acids in soil solutions to the ANC will result in erroneous estimates of the buffering capacity in the alpine environment of the Front Range, Colorado. ?? 1988.

  10. Leaching with Penicillium simplicissimum: Influence of metals and buffers on proton extrusion and citric acid production

    SciTech Connect

    Franz, A.; Burgstaller, W.; Schinner, F. )

    1991-03-01

    In the presence of insoluble metal oxides (industrial filter dust, zinc oxide, synthetic mixture of metal oxides), Penicillium simplicissimum developed the ability to excrete considerable amounts of citric acid (>100 mM). Parallel with the increase of citric acid concentration in the culture broth, zinc was solubilized from zinc oxide. The adsorption of filter dust onto the mycelium (the pellets formed were less than 1 mm in diameter) was required for not only the citric acid excretion but also the leaching of zinc. When the filter dust was replaced with a synthetic mixture of metal oxides or with zinc oxide in combination with trace elements, levels of adsorption and citric acid production were observed to be similar to those in experiments where industrial filter dust was used. The two most important properties of the filter dust were its heavy-metal content and its buffering capacity. These properties were simulated by adding heavy metals in soluble form (as chlorides, sulfates, or nitrates) or soluble buffers to the medium. Both heavy metals and buffers were not able to induce a citric acid efflux. As with citric acid production by Aspergillus niger, the addition of manganese lowered citric acid excretion (by 40% with metal oxide-induced citric acid efflux and by 100% with urea-induced citric acid efflux). Copper antagonized the effect of manganese. The mechanism for the bulk of citric acid excretion by P. simplicissimum, however, seemed to be different from that described for citric acid accumulation by A. niger. Because of the inefficiency of metals in solubilized form and of soluble buffers to induce a strong citric acid efflux, adsorption of an insoluble metal compound (zinc oxide) turned out to be essential.

  11. Preparation of Buffers. An Experiment for Quantitative Analysis Laboratory

    NASA Astrophysics Data System (ADS)

    Buckley, P. T.

    2001-10-01

    In our experience, students who have a solid grounding in the theoretical aspects of buffers, buffer preparation, and buffering capacity are often at a loss when required to actually prepare a buffer in a research setting. However, there are very few published laboratory experiments pertaining to buffers. This laboratory experiment for the undergraduate quantitative analysis lab gives students hands-on experience in the preparation of buffers. By preparing a buffer to a randomly chosen pH value and comparing the theoretical pH to the actual pH, students apply their theoretical understanding of the Henderson-Hasselbalch equation, activity coefficients, and the effect of adding acid or base to a buffer. This experiment gives students experience in buffer preparation for research situations and helps them in advanced courses such as biochemistry where a fundamental knowledge of buffer systems is essential.

  12. 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

  13. Dependence of buffer acidity and surfactant chain-length on electro-osmotic mobility in thermoplastic microchannels.

    PubMed

    Wang, Shau-Chun; Lee, Chia-Yu; Chen, Hsiao-Ping

    2005-04-15

    In this paper, we report the dependence of buffer pH and coating surfactant chain-length on electro-osmotic (EO) mobility in co-polyester microchannels. Thermoplastics co-polyester hydrolyzes to anionic functionality to create electrical double layer on the micro-channel walls. These negatively charged sites are partially or completely screened when long-chain surfactants are added into the buffer. This ancillary technique to modify surface charge polarity to avoid analyte adsorption is known as dynamic coating. We develop a theory to predict the EO mobility tendency on buffer acidity considering the combination of pH-dependent surfactant aggregation and surface dissociation. Our findings of pH-dependent EO mobility in coated channels, using three types of quaternary ammonium surfactants, lauryltrimethyammonium bromide (LTAB), trimethyl (tetradecyl) ammonium bromide (TTAB), and cetyltrimethyammonium bromide (CTAB), agree with our theoretical prediction. We also explain the chain-length dependence of mobility with a collaborative adsorption mechanism of surfactant aggregates.

  14. Ligand-enhanced electrokinetic remediation of metal-contaminated marine sediments with high acid buffering capacity.

    PubMed

    Masi, Matteo; Iannelli, Renato; Losito, Gabriella

    2016-06-01

    The suitability of electrokinetic remediation for removing heavy metals from dredged marine sediments with high acid buffering capacity was investigated. Laboratory-scale electrokinetic remediation experiments were carried out by applying two different voltage gradients to the sediment (0.5 and 0.8 V/cm) while circulating water or two different chelating agents at the electrode compartments. Tap water, 0.1 M citric acid and 0.1 M ethylenediaminetetraacetic acid (EDTA) solutions were used respectively. The investigated metals were Zn, Pb, V, Ni and Cu. In the unenhanced experiment, the acid front could not propagate due to the high acid buffering capacity of the sediments; the production of OH(-) ions at the cathode resulted in a high-pH environment causing the precipitation of CaCO3 and metal hydroxides. The use of citric acid prevented the formation of precipitates, but solubilisation and mobilisation of metal species were not sufficiently achieved. Metal removal was relevant when EDTA was used as the conditioning agent, and the electric potential was raised up to 0.8 V/cm. EDTA led to the formation of negatively charged complexes with metals which migrated towards the anode compartment by electromigration. This result shows that metal removal from sediments with high acid buffering capacity may be achieved by enhancing the electrokinetic process by EDTA addition when the acidification of the medium is not economically and/or environmentally sustainable. PMID:26490900

  15. Photodegradation of Mercaptopropionic Acid- and Thioglycollic Acid-Capped CdTe Quantum Dots in Buffer Solutions.

    PubMed

    Miao, Yanping; Yang, Ping; Zhao, Jie; Du, Yingying; He, Haiyan; Liu, Yunshi

    2015-06-01

    CdTe quantum dots (QDs) were synthesized by 3-mercaptopropionic acid (MPA) and thioglycollic acid (TGA) as capping agents. It is confirmed that TGA and MPA molecules were attached on the surface of the QDs using Fourier transform infrared (FT-IR) spectra. The movement of the QDs in agarose gel electrophoresis indicated that MPA-capped CdTe QDs had small hydrodynamic diameter. The photoluminescence (PL) intensity of TGA-capped QDs is higher than that of MPA-capped QDs at same QD concentration because of the surface passivation of TGA. To systemically investigate the photodegradation, CdTe QDs with various PL peak wavelengths were dispersed in phosphate buffered saline (PBS) and Tris-borate-ethylenediaminetetraacetic acid (TBE) buffer solutions. It was found that the PL intensity of the QDs in PBS decreased with time. The PL peak wavelengths of the QDs in PBS solutions remained unchanged. As for TGA-capped CdTe QDs, the results of PL peak wavelengths in TBE buffer solutions indicated that S(2-) released by TGA attached to Cd(2+) and formed CdS-like clusters layer on the surface of aqueous CdTe QDs. In addition, the number of TGA on the CdTe QDs surface was more than that of MPA. When the QDs were added to buffer solutions, agents were removed from the surface of CdTe QDs, which decreased the passivation of agents thus resulted in photodegradation of CdTe QDs in buffer solutions.

  16. Evaluation of pH, buffering capacity, viscosity and flow rate levels of saliva in caries-free, minimal caries and nursing caries children: An in vivo study

    PubMed Central

    Animireddy, Dwitha; Reddy Bekkem, Venkata Thimma; Vallala, Pranitha; Kotha, Sunil Babu; Ankireddy, Swetha; Mohammad, Noorjahan

    2014-01-01

    Background and Aim: The present study was undertaken to evaluate the pH, buffering capacity, viscosity and flow rate of saliva in caries free, minimal caries and nursing caries children and to evaluate the relationship of these on the caries activity of children. Materials and Methods: A total of 75 school children of age group between 4 and 12 years were selected and divided into three equal groups: Group I, Group II and Group III, consisting of 25 subjects each. Group I included caries-free subjects, Group II included subjects with minimal caries and Group III included subjects with nursing caries. Saliva samples were collected from all subjects and were estimated for flow rate, pH, buffering capacity and viscosity. Results: There was a significant decrease in the mean salivary flow rate, salivary ph and salivary buffer capacity and a significant increase in the salivary viscosity among caries-free subjects, subjects with minimal caries and subjects with nursing caries. Conclusion: The physicochemical properties of saliva, such as salivary flow rate, pH, buffering capacity and viscosity, has a relation with caries activity in children and act as markers of caries activity. PMID:25191067

  17. Salivary Parameters (Salivary Flow, pH and Buffering Capacity) in Stimulated Saliva of Mexican Elders 60 Years Old and Older

    PubMed Central

    Islas-Granillo, H; Borges-Yañez, SA; Medina-Solís, CE; Galan-Vidal, CA; Navarrete-Hernández, JJ; Escoffié-Ramirez, M; Maupomé, G

    2014-01-01

    ABSTRACT Objective: To compare a limited array of chewing-stimulated saliva features (salivary flow, pH and buffer capacity) in a sample of elderly Mexicans with clinical, sociodemographic and socio-economic variables. Subjects and Methods: A cross-sectional study was carried out in 139 adults, 60 years old and older, from two retirement homes and a senior day care centre in the city of Pachuca, Mexico. Socio-demographic, socio-economic and behavioural variables were collected through a questionnaire. A trained and standardized examiner obtained the oral clinical variables. Chewing-stimulated saliva (paraffin method) was collected and the salivary flow rate, pH and buffer capacity were measured. The analysis was performed using non-parametric tests in Stata 9.0. Results: Mean age was 79.1 ± 9.8 years. Most of the subjects included were women (69.1%). Mean chewing-stimulated salivary flow was 0.75 ± 0.80 mL/minute, and the pH and buffer capacity were 7.88 ± 0.83 and 4.20 ± 1.24, respectively. Mean chewing-stimulated salivary flow varied (p < 0.05) across type of retirement home, tooth brushing frequency, number of missing teeth and use of dental prostheses. pH varied across the type of retirement home (p < 0.05) and marginally by age (p = 0.087); buffer capacity (p < 0.05) varied across type of retirement home, tobacco consumption and the number of missing teeth. Conclusions: These exploratory data add to the body of knowledge with regard to chewing-stimulated salivary features (salivary flow rate, pH and buffer capacity) and outline the variability of those features across selected sociodemographic, socio-economic and behavioural variables in a group of Mexican elders. PMID:25867562

  18. Accelerating the dissolution of enteric coatings in the upper small intestine: evolution of a novel pH 5.6 bicarbonate buffer system to assess drug release.

    PubMed

    Varum, Felipe J O; Merchant, Hamid A; Goyanes, Alvaro; Assi, Pardis; Zboranová, Veronika; Basit, Abdul W

    2014-07-01

    Despite rapid dissolution in compendial phosphate buffers, gastro resistant (enteric coated) products can take up to 2 h to disintegrate in the human small intestine, which clearly highlights the inadequacy of the in vitro test method to predict in vivo behaviour of these formulations. The aim of this study was to establish the utility of a novel pH 5.6 bicarbonate buffer, stabilized by an Auto pH™ System, as a better surrogate of the conditions of the proximal small intestine to investigate the dissolution behaviour of standard and accelerated release enteric double coating formulations. Prednisolone tablets were coated with 3 or 5 mg/cm(2) of partially neutralized EUDRAGIT(®) L 30 D-55, HP-55 or HPMC adjusted to pH 6 or 8. An outer layer of EUDRAGIT(®) L 30 D-55 was applied at 5mg/cm(2). For comparison purposes, a standard single layer of EUDRAGIT(®) L 30 D-55 was applied to the tablets. Dissolution was carried out using USP II apparatus in 0.1 M HCl for 2 h, followed by pH 5.6 bicarbonate buffer. EUDRAGIT(®) L 30 D-55 single-coated tablets showed a slow drug release with a lag time of 75 min in buffer, whereas release from the EUDRAGIT(®) L 30 D-55 double-coated tablets was accelerated. These in vitro lag times closely match the in vivo disintegration times for these coated tablets reported previously. Drug release was further accelerated from modified double coatings, particularly in the case of coatings with a thinner inner layer of HP-55 or HPMC (pH 8 and KH2PO4). This study confirms that the pH 5.6 bicarbonate buffer system offers significant advantages during the development of dosage forms designed to release the drug in the upper small intestine.

  19. Thermodynamic characteristics of molecular interactions between L-tryptophan and nicotinic acid and uracyl in aqueous buffer solutions at 298 K

    NASA Astrophysics Data System (ADS)

    Badelin, V. G.; Tyunina, E. Yu.; Mezhevoi, I. N.; Tarasova, G. N.

    2015-12-01

    The interaction between L-tryptophan (Trp) and nicotinic acid (NA) and uracyl (Ur) in aqueous buffer solutions (pH 7.35) at different ratios of reagents is studied via the calorimetry of dissolution. The enthalpies of dissolution of the amino acid in the buffer solutions of the ligands at 298.15 K are obtained. The stoichiometric compositions of the complexes being formed and binding constants have been determined. The values of the thermodynamic characteristics for the complex formation of L-tryptophan with nicotinic acid and uracyl are calculated. It is shown that the formation of molecular complexes with 1 : 2 composition is stabilized by the entropy factor for the Trp-NA system, and by the enthalpy factor for the Trp-Ur system.

  20. Making pH Tangible.

    ERIC Educational Resources Information Center

    McIntosh, Elizabeth; Moss, Robert

    1995-01-01

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

  1. 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

  2. Identification and quantification of redox and pH buffering processes in a heterogeneous, low carbonate aquifer during managed aquifer recharge

    NASA Astrophysics Data System (ADS)

    Seibert, Simone; Atteia, Olivier; Ursula Salmon, S.; Siade, Adam; Douglas, Grant; Prommer, Henning

    2016-05-01

    Managed aquifer recharge of aerobic water into deep aquifers often induces the oxidation of pyrite, which can lead to groundwater acidification and metal mobilization. As circumneutral pH is often maintained by the dissolution of sedimentary calcite or high injectant alkalinity little attention is generally paid to potential alternative pH buffering processes. In contrast, this study analyzed water quality evolution from a 2 year long groundwater replenishment trial in an anaerobic, mostly carbonate free aquifer. While injection of aerobic, very low salinity water triggered pyrite oxidation, the comprehensive field data showed that in many aquifer zones pH was buffered without substantial release of inorganic carbon. A numerical analysis was performed to test and evaluate different conceptual models and suggested that either proton buffering or the dissolution of aluminosilicates, or a combination thereof, can explain the observed, rapid buffering at locations where carbonates were absent. In contrast to many previous managed aquifer recharge [MAR) studies, the oxidation of sedimentary pyrite by nitrate was found to be of minor importance or negligible. The study also highlights that the depositional history of the aquifer, and the associated differences in mineralogy and geochemistry, need to be considered when estimating groundwater quality evolution during the injection of various water types for aquifer replenishment or other management purposes.

  3. Mechanisms of buffer therapy resistance.

    PubMed

    Bailey, Kate M; Wojtkowiak, Jonathan W; Cornnell, Heather H; Ribeiro, Maria C; Balagurunathan, Yoganand; Hashim, Arig Ibrahim; Gillies, Robert J

    2014-04-01

    Many studies have shown that the acidity of solid tumors contributes to local invasion and metastasis. Oral pH buffers can specifically neutralize the acidic pH of tumors and reduce the incidence of local invasion and metastatic formation in multiple murine models. However, this effect is not universal as we have previously observed that metastasis is not inhibited by buffers in some tumor models, regardless of buffer used. B16-F10 (murine melanoma), LL/2 (murine lung) and HCT116 (human colon) tumors are resistant to treatment with lysine buffer therapy, whereas metastasis is potently inhibited by lysine buffers in MDA-MB-231 (human breast) and PC3M (human prostate) tumors. In the current work, we confirmed that sensitive cells utilized a pH-dependent mechanism for successful metastasis supported by a highly glycolytic phenotype that acidifies the local tumor microenvironment resulting in morphological changes. In contrast, buffer-resistant cell lines exhibited a pH-independent metastatic mechanism involving constitutive secretion of matrix degrading proteases without elevated glycolysis. These results have identified two distinct mechanisms of experimental metastasis, one of which is pH-dependent (buffer therapy sensitive cells) and one which is pH-independent (buffer therapy resistant cells). Further characterization of these models has potential for therapeutic benefit.

  4. 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

  5. High-quality fiber fabrication in buffered hydrofluoric acid solution with ultrasonic agitation.

    PubMed

    Zhong, Nianbing; Liao, Qiang; Zhu, Xun; Wang, Yongzhong; Chen, Rong

    2013-03-01

    An etching method for preparing high-quality fiber-optic sensors using a buffered etchant with ultrasonic agitation is proposed. The effects of etching conditions on the etch rate and surface morphology of the etched fibers are investigated. The effect of surface roughness is discussed on the fibers' optical properties. Linear etching behavior and a smooth fiber surface can be repeatedly obtained by adjusting the ultrasonic power and etchant pH. The fibers' spectral quality is improved as the ratio of the pit depth to size decreases, and the fibers with smooth surfaces are more sensitive to a bacterial suspension than those with rough surfaces.

  6. 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

  7. 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.

  8. 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.

  9. Visualization of Buffer Capacity with 3-D "Topo" Surfaces: Buffer Ridges, Equivalence Point Canyons and Dilution Ramps

    ERIC Educational Resources Information Center

    Smith, Garon C.; Hossain, Md Mainul

    2016-01-01

    BufCap TOPOS is free software that generates 3-D topographical surfaces ("topos") for acid-base equilibrium studies. It portrays pH and buffer capacity behavior during titration and dilution procedures. Topo surfaces are created by plotting computed pH and buffer capacity values above a composition grid with volume of NaOH as the x axis…

  10. 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

  11. 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.

  12. An exploratory study into students' conceptual understanding of acid/base principles associated with chemical buffer systems

    NASA Astrophysics Data System (ADS)

    MacGowan, Catherine Elizabeth

    The overall objective of this research project was to provide an insight into students' conceptual understanding of acid/base principles as it relates to the comprehension and correct application of scientific concepts during a problem-solving activity. The difficulties experienced learning science and in developing appropriate problem-solving strategies most likely are predetermined by students' existing conceptual and procedural knowledge constructs; with the assimilation of newly acquired knowledge hindering or aiding the learning process. Learning chemistry requires a restructuring of content knowledge which will allow the individual to assemble and to integrate his/her own perception of science with instructional knowledge. The epistemology of constructivism, the theoretical grounding for this research project, recognizes the student's role as an active participant in the learning process. The study's design was exploratory in nature and descriptive in design. The problem-solving activity, the preparation of a chemical buffer solution at pH of 9, was selected and modified to reflect and meet the study's objective. Qualitative research methods (i.e., think aloud protocols, retrospective interviews, survey questionnaires such as the Scale of Intellectual Development (SID), and archival data sources) were used in the collection and assessment of data. Given its constructivist grounding, simplicity, and interpretative view of knowledge acquisition and learning of collegiate aged individuals, the Perry Intellectual and Ethical Development Model (1970) was chosen as the applied model for evaluation student cognition. The study's participants were twelve traditional college age students from a small, private liberal arts college. All participants volunteered for the project and had completed or were completing a general college chemistry course at the time of the project. Upon analysis of the data the following observations and results were noted: (1) students

  13. Preliminary observations of lung injury produced by instillation of HF in acidic and neutral buffer

    SciTech Connect

    Brainard, J.R.; Kinkead, S.A.; Kober, E.M.; Sebring, R.J.; Stavert, D.M.; Lehnert, B.E.

    1990-01-01

    Perfluoroisobutylene (PFIB) is an extremely toxic organofluoride that can be produced during pyrolysis of tetrafluoroethylene polymers, including Teflon{reg sign}. Inhalation of PFIB at very low concentrations causes acute lung injury, the hallmark of which is pulmonary edema. Several lines of evidence have suggested that hydrolysis of PFIB and resulting production of hydrofluoric acid may be responsible for pulmonary damage. In order to investigate the potential involvement of hydrofluoric acid in producing lung injury and its relationship to the mechanism of fluorocarbon toxicity, we have compared the pulmonary injury produced by PFIB, by dissociated (H{sup +} and F{sup {minus}}), and by undissociated (HF) hydrofluoric acid in the deep lung. By delivering hydrofluoric acid by intratracheal instillation in neutral buffer, we demonstrate that F{sup {minus}} produces no significant pulmonary injury as assessed by increased in lung weight and ultrastructural changes. Similarly, instillation of acid buffer alone demonstrated that H{sup +} did not produce detectable lung injury. Instillation of HF produced changes in lung weight and ultrastructure similar to those observed in PFIB-treated rats. However, the ultrastructural studies show that in contrast to inhalation of PFIB, which produces both endothelial and epithelial cell damage, instillation of HF appears to exert its injurious effects only upon epithelial cells. 9 refs., 1 fig.

  14. A biogeochemical comparison of two well-buffered catchments with contrasting histories of acid deposition

    USGS Publications Warehouse

    Shanley, J.B.; Kram, P.; Hruska, J.; Bullen, T.D.

    2004-01-01

    Much of the biogeochemical cycling research in catchments in the past 25 years has been driven by acid deposition research funding. This research has focused on vulnerable base-poor systems; catchments on alkaline lithologies have received little attention. In regions of high acid loadings, however, even well-buffered catchments are susceptible to forest decline and episodes of low alkalinity in streamwater. As part of a collaboration between the Czech and U.S. Geological Surveys, we compared biogeochemical patterns in two well-studied, well-buffered catchments: Pluhuv Bor in the western Czech Republic, which has received high loading of atmospheric acidity, and Sleepers River Research Watershed in Vermont, U.S.A., where acid loading has been considerably less. Despite differences in lithology, wetness, forest type, and glacial history, the catchments displayed similar patterns of solute concentrations and flow. At both catchments, base cation and alkalinity diluted with increasing flow, whereas nitrate and dissolved organic carbon increased with increasing flow. Sulfate diluted with increasing flow at Sleepers River, while at Pluhuv Bor the sulfate-flow relation shifted from positive to negative as atmospheric sulfur (S) loadings decreased and soil S pools were depleted during the 1990s. At high flow, alkalinity decreased to near 100 ??eq L-1 at Pluhuv Bor compared to 400 ??eq L-1 at Sleepers River. Despite the large amounts of S flushed from Pluhuv Bor soils, these alkalinity declines were caused solely by dilution, which was greater at Pluhuv Bor relative to Sleepers River due to greater contributions from shallow flow paths at high flow. Although the historical high S loading at Pluhuv Bor has caused soil acidification and possible forest damage, it has had little effect on the acid/base status of streamwater in this well-buffered catchment. ?? 2004 Kluwer Academic Publishers.

  15. 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.

  16. Effect of N-tris (Hydroxymethyl) Methylglycine and N-2-Hydroxyethyl-piperazine-N′-2-Ethanesulfonic Acid Buffers on Linolenic Acid as a Substrate for Flaxseed Lipoxidase

    PubMed Central

    Zimmerman, Don C.

    1968-01-01

    The delay in, or loss of, flaxseed lipoxidase activity in N-tris (hydroxymethyl) methylglycine and N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid buffers with linolenic acid as a substrate appears due to an alteration of the lipid micelle. Flaxseed lipoxidase activity is dependent on the ionic strength of the assay solution. These effects are not observed with linoleic acid as substrate. The influence of these 2 buffers on linolenic acid micelles may have a direct bearing on recent reports of chloroplast structure and activity in these buffers. PMID:16656951

  17. 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.

  18. 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

  19. Contributions of separate reactions to the acid-base buffering of soils in brook floodplains (Central Forest State Reserve)

    NASA Astrophysics Data System (ADS)

    Sokolova, T. A.; Tolpeshta, I. I.; Rusakova, E. S.

    2016-04-01

    The acid-base buffering of gleyic gray-humus soils developed in brook floodplains and undisturbed southern-taiga landscapes has been characterized by the continuous potentiometric titration of soil water suspensions. During the interaction with an acid, the major amount of protons (>80%) is consumed for the displacement of exchangeable bases and the dissolution of Ca oxalates. In the O and AY horizons, Mn compounds make the major contribution (2-15%) to the acid buffering. The buffer reactions with the participation of Al compounds make up from 0.5 to 1-2% of the total buffering capacity, and the protonation of the surface OH groups of kaolinite consumes 2-3% of the total buffering capacity. The deprotonation of OH groups on the surface of Fe hydroxides (9-43%), the deprotonation of OH groups on the surface of illite crystals (3-19%), and the dissolution of unidentified aluminosilicates (9-14%) are the most significant buffer reactions whose contributions have been quantified during the interaction with a base. The contribution of the deprotonation of OH groups on the surface of kaolinite particles is lower (1-5%) because of the small specific surface area of this mineral, and that of the dissolution of Fe compounds is insignificant. In the AY horizon, the acid and base buffering of soil in the rhizosphere is higher than beyond the rhizosphere because of the higher contents of organic matter and nonsilicate Fe and Al compounds.

  20. Relative contribution of ruminal buffering systems to pH regulation in feedlot cattle fed either low- or high-forage diets.

    PubMed

    Chibisa, G E; Beauchemin, K A; Penner, G B

    2016-07-01

    The relative contribution of ruminal short-chain fatty acid (SCFA) absorption and salivary buffering to pH regulation could potentially change under different dietary conditions. Therefore, the objective of this study was to investigate the effects of altering the ruminal supply of rapidly fermentable carbohydrate (CHO) on absorptive function and salivation in beef cattle. Eight heifers (mean BW±SD=410±14 kg) were randomly allocated to two treatments in a crossover design with 37-day periods. Dietary treatments were barley silage at 30% low forage (LF) or 70% high forage (HF) of dietary dry matter (DM), with the remainder of the diet consisting of barley grain (65% or 25% on a DM basis) and a constant level (5%) of supplement. The LF and HF diets contained 45.3% and 30.9% starch, and 4.1% and 14.0% physically effective fiber (DM basis), respectively. Ruminal pH was continuously measured from day 17 to day 23, whereas ruminal fluid was collected on day 23 to determine SCFA concentration. Ruminal liquid passage rate was determined on day 23 using Cr-ethylenediaminetetraacetic acid. Eating or resting salivation was measured by collecting masticate (days 28 and 29) or saliva samples (days 30 and 31) at the cardia, respectively. On days 30 and 31, the temporarily isolated and washed reticulo-rumen technique was used to measure total, and Cl--competitive (an indirect measure of protein-mediated transport) absorption of acetate, propionate and butyrate. As a result of the higher dietary starch content and DM intake, the ruminal supply of rapidly fermentable CHO, total ruminal SCFA concentration (118 v. 95 mM; P<0.001) and osmolality (330 v. 306 mOsm/kg; P=0.018) were greater in cattle fed LF compared with HF. In addition, feeding LF resulted in a longer duration (2.50 v. 0.09 h/day; P=0.02) and a larger area (0.44 v. 0.01 (pH×h)/day; P=0.050) that pH was below 5.5. There was no diet effect on total and Cl--competitive absorption (mmol/h and %/h) of acetate, propionate

  1. Relative contribution of ruminal buffering systems to pH regulation in feedlot cattle fed either low- or high-forage diets.

    PubMed

    Chibisa, G E; Beauchemin, K A; Penner, G B

    2016-07-01

    The relative contribution of ruminal short-chain fatty acid (SCFA) absorption and salivary buffering to pH regulation could potentially change under different dietary conditions. Therefore, the objective of this study was to investigate the effects of altering the ruminal supply of rapidly fermentable carbohydrate (CHO) on absorptive function and salivation in beef cattle. Eight heifers (mean BW±SD=410±14 kg) were randomly allocated to two treatments in a crossover design with 37-day periods. Dietary treatments were barley silage at 30% low forage (LF) or 70% high forage (HF) of dietary dry matter (DM), with the remainder of the diet consisting of barley grain (65% or 25% on a DM basis) and a constant level (5%) of supplement. The LF and HF diets contained 45.3% and 30.9% starch, and 4.1% and 14.0% physically effective fiber (DM basis), respectively. Ruminal pH was continuously measured from day 17 to day 23, whereas ruminal fluid was collected on day 23 to determine SCFA concentration. Ruminal liquid passage rate was determined on day 23 using Cr-ethylenediaminetetraacetic acid. Eating or resting salivation was measured by collecting masticate (days 28 and 29) or saliva samples (days 30 and 31) at the cardia, respectively. On days 30 and 31, the temporarily isolated and washed reticulo-rumen technique was used to measure total, and Cl--competitive (an indirect measure of protein-mediated transport) absorption of acetate, propionate and butyrate. As a result of the higher dietary starch content and DM intake, the ruminal supply of rapidly fermentable CHO, total ruminal SCFA concentration (118 v. 95 mM; P<0.001) and osmolality (330 v. 306 mOsm/kg; P=0.018) were greater in cattle fed LF compared with HF. In addition, feeding LF resulted in a longer duration (2.50 v. 0.09 h/day; P=0.02) and a larger area (0.44 v. 0.01 (pH×h)/day; P=0.050) that pH was below 5.5. There was no diet effect on total and Cl--competitive absorption (mmol/h and %/h) of acetate, propionate

  2. In silico prediction of drug dissolution and absorption with variation in intestinal pH for BCS class II weak acid drugs: ibuprofen and ketoprofen.

    PubMed

    Tsume, Yasuhiro; Langguth, Peter; Garcia-Arieta, Alfredo; Amidon, Gordon L

    2012-10-01

    The FDA Biopharmaceutical Classification System guidance allows waivers for in vivo bioavailability and bioequivalence studies for immediate-release solid oral dosage forms only for BCS class I. Extensions of the in vivo biowaiver for a number of drugs in BCS class III and BCS class II have been proposed, in particular, BCS class II weak acids. However, a discrepancy between the in vivo BE results and in vitro dissolution results for BCS class II acids was recently observed. The objectives of this study were to determine the oral absorption of BCS class II weak acids via simulation software and to determine if the in vitro dissolution test with various dissolution media could be sufficient for in vitro bioequivalence studies of ibuprofen and ketoprofen as models of carboxylic acid drugs. The oral absorption of these BCS class II acids from the gastrointestinal tract was predicted by GastroPlus™. Ibuprofen did not satisfy the bioequivalence criteria at lower settings of intestinal pH of 6.0. Further the experimental dissolution of ibuprofen tablets in a low concentration phosphate buffer at pH 6.0 (the average buffer capacity 2.2 mmol l (-1) /pH) was dramatically reduced compared with the dissolution in SIF (the average buffer capacity 12.6 mmol l (-1) /pH). Thus these predictions for the oral absorption of BCS class II acids indicate that the absorption patterns depend largely on the intestinal pH and buffer strength and must be considered carefully for a bioequivalence test. Simulation software may be a very useful tool to aid the selection of dissolution media that may be useful in setting an in vitro bioequivalence dissolution standard.

  3. Effects of pH and dissolved oxygen on the reduction of hexavalent chromium by dissolved ferrous iron in poorly buffered aqueous systems.

    PubMed

    Schlautman, M A; Han, I

    2001-04-01

    The effects of pH and dissolved oxygen (DO) on the reduction of Cr(VI) by dissolved Fe(II) were investigated for aqueous solutions having relatively low buffering capacities. All solutions were maintained at a constant ionic strength (generally 0.05 M) and temperature (23 +/- 2 degrees C). For the majority of the experiments conducted, initial concentrations of Fe(II) and Cr(VI) were 50 and 20 microM, respectively, representing a deficient amount of Fe(II) (i.e. nonstoichiometric conditions). Experiments conducted in the absence and presence of DO were performed in an anaerobic chamber and in vessels open to the atmosphere, respectively. Specific initial pH values were obtained by adjusting the pH of Cr(VI) and Fe(II) stock solutions prior to their mixing or by spiking Cr(VI)-Fe(II) systems with strong base to rapidly increase the pH in situ. Consistent with previous reports, Cr(VI) reduction rates for our systems increased with increasing pH (pH ranges of 3.5-6 and 3.5-7.2 for oxic and anoxic experiments, respectively). Because of our poorly buffered experimental systems, pH values decreased over the course of the reactions which, in turn, caused decreases in the reduction rates with time. Spiking some experimental systems with NaOH to rapidly raise the pH resulted in faster rates of Cr(VI) reduction than when the pH was adjusted prior to mixing the stock solutions together; this observation is likely due to the presence of microenvironments in the reactors for which local, short-term pH values greatly exceed the equilibrium value (i.e. mixing is slower than the reduction reaction in these high pH microenvironments). The molar ratios of Fe(II) oxidized to Cr(VI) reduced were close to the expected stoichiometric value of 3 for the majority of our experimental systems, which shows that DO will not cause a serious interference in most applications using Fe(II) to reduce Cr(VI).

  4. The effects of secular calcium and magnesium concentration changes on the thermodynamics of seawater acid/base chemistry: Implications for Eocene and Cretaceous ocean carbon chemistry and buffering

    NASA Astrophysics Data System (ADS)

    Hain, Mathis P.; Sigman, Daniel M.; Higgins, John A.; Haug, Gerald H.

    2015-05-01

    Reconstructed changes in seawater calcium and magnesium concentration ([Ca2+], [Mg2+]) predictably affect the ocean's acid/base and carbon chemistry. Yet inaccurate formulations of chemical equilibrium "constants" are currently in use to account for these changes. Here we develop an efficient implementation of the MIAMI Ionic Interaction Model to predict all chemical equilibrium constants required for carbon chemistry calculations under variable [Ca2+] and [Mg2+]. We investigate the impact of [Ca2+] and [Mg2+] on the relationships among the ocean's pH, CO2, dissolved inorganic carbon (DIC), saturation state of CaCO3 (Ω), and buffer capacity. Increasing [Ca2+] and/or [Mg2+] enhances "ion pairing," which increases seawater buffering by increasing the concentration ratio of total to "free" (uncomplexed) carbonate ion. An increase in [Ca2+], however, also causes a decline in carbonate ion to maintain a given Ω, thereby overwhelming the ion pairing effect and decreasing seawater buffering. Given the reconstructions of Eocene [Ca2+] and [Mg2+] ([Ca2+]~20 mM; [Mg2+]~30 mM), Eocene seawater would have required essentially the same DIC as today to simultaneously explain a similar-to-modern Ω and the estimated Eocene atmospheric CO2 of ~1000 ppm. During the Cretaceous, at ~4 times modern [Ca2+], ocean buffering would have been at a minimum. Overall, during times of high seawater [Ca2+], CaCO3 saturation, pH, and atmospheric CO2 were more susceptible to perturbations of the global carbon cycle. For example, given both Eocene and Cretaceous seawater [Ca2+] and [Mg2+], a doubling of atmospheric CO2 would require less carbon addition to the ocean/atmosphere system than under modern seawater composition. Moreover, increasing seawater buffering since the Cretaceous may have been a driver of evolution by raising energetic demands of biologically controlled calcification and CO2 concentration mechanisms that aid photosynthesis.

  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. Plasma levels of acetylsalicylic acid and salicylic acid after oral ingestion of plain and buffered acetylsalicylic acid in relation to bleeding time and thrombocyte function.

    PubMed

    Proost, J H; Van Imhoff, G W; Wesseling, H

    1983-02-25

    Buffered acetylsalicylic acid (Alka Seltzer, B-ASA) and plain aspirin (P-ASA) tablets were compared as to their effects on bleeding time and platelet function in eight healthy male volunteers. Two doses (500 and 1000 mg) of each preparation were investigated in a cross-over design, each volunteer being his own control in each dose group (n=4). Both preparations disturbed platelet aggregation to the same extent. Bleeding time increased after both preparations, though significantly more after the buffered preparation than after plain acetylsalicylic acid, irrespective of the dosage. The 1000 mg dose prolonged bleeding time significantly more than the 500 mg dose, irrespective of the preparation. Kinetic analysis showed that B-ASA gave higher peak plasma levels of acetylsalicylic acid (ASA) and accordingly salicylic acid peak levels were also higher after the buffered preparation. It is concluded that B-ASA in equi-analgesic doses prolongs bleeding time more than the plain preparation. Since it is less agressive on the gastro-intestinal mucosa, its use may be advantageous in situations where acetylsalicylic acid induced loss of platelet aggregation is desired. However, the risk of prolonged bleeding--e.g. after tooth extractions--is probably higher after the buffered preparation. PMID:6844122

  7. Studies of a weak polyampholyte at the air-buffer interface: The effect of varying pH and ionic strength

    NASA Astrophysics Data System (ADS)

    Cicuta, Pietro; Hopkinson, Ian

    2001-05-01

    We have carried out experiments to probe the static and dynamic interfacial properties of β-casein monolayers spread at the air-buffer interface, and analyzed these results in the context of models of weak polyampholytes. Measurements have been made systematically over a wide range of ionic strength and pH. In the semidilute regime of surface concentration a scaling exponent, which can be linked to the degree of chain swelling, is found. This shows that at pH close to the isoelectric point, the protein is compact. At pH away from the isoelectric pH the protein is extended. The transition between compact and extended states is continuous. As a function of increasing ionic strength, we observe swelling of the protein at the isoelectric pH but contraction of the protein at pH values away from it. These behaviors are typical of a those predicted theoretically for a weak polyampholyte. Dilational moduli measurements, made as a function of surface concentration exhibit maxima that are linked to the collapse of hydrophilic regions of the protein into the subphase. Based on this data we present a configuration map of the protein configuration in the monolayer. These findings are supported by strain (surface pressure) relaxation measurements and surface quasielastic light scattering measurements which suggest the existence of loops and tails in the subphase at higher surface concentrations.

  8. A Novel Mechanism of pH Buffering in C. elegans Glia: Bicarbonate Transport via the Voltage-Gated ClC Cl− Channel CLH-1

    PubMed Central

    Grant, Jeff; Matthewman, Cristina

    2015-01-01

    An important function of glia is the maintenance of the ionic composition and pH of the synaptic microenvironment. In terms of pH regulation, HCO3− buffering has been shown to be important in both glia and neurons. Here, we used in vivo fluorescent pH imaging and RNA sequencing of the amphid sheath glia of Caenorhabditis elegans to reveal a novel mechanism of cellular HCO3− uptake. While the classical mechanism of HCO3− uptake involves Na+/HCO3− cotransporters, here we demonstrate that the C. elegans ClC Cl− channel CLH-1 is highly permeable to HCO3− and mediates HCO3− uptake into amphid sheath glia. CLH-1 has homology and electrophysiological properties similar to the mammalian ClC-2 Cl− channel. Our data suggest that, in addition to maintaining synaptic Cl− concentration, these channels may also be involved in maintenance of synaptic pH via HCO3− flux. These findings provide an exciting new facet of study regarding how pH is regulated in the brain. SIGNIFICANCE STATEMENT Maintenance of pH is essential for the physiological function of the nervous system. HCO3− is crucial for pH regulation and is transported into the cell via ion transporters, including ion channels, the molecular identity of which remains unclear. In this manuscript, we describe our discovery that the C. elegans amphid sheath glia regulate intracellular pH via HCO3− flux through the voltage-gated ClC channel CLH-1. This represents a novel function for ClC channels, which has implications for their possible role in mammalian glial pH regulation. This discovery may also provide a novel therapeutic target for pathologic conditions, such as ischemic stroke where acidosis leads to widespread death of glia and subsequently neurons. PMID:26674864

  9. 3-D Surface Visualization of pH Titration "Topos": Equivalence Point Cliffs, Dilution Ramps, and Buffer Plateaus

    ERIC Educational Resources Information Center

    Smith, Garon C.; Hossain, Md Mainul; MacCarthy, Patrick

    2014-01-01

    3-D topographic surfaces ("topos") can be generated to visualize how pH behaves during titration and dilution procedures. The surfaces are constructed by plotting computed pH values above a composition grid with volume of base added in one direction and overall system dilution on the other. What emerge are surface features that…

  10. Isolation and characterization of Chinese standard fulvic acid sub-fractions separated from forest soil by stepwise elution with pyrophosphate buffer.

    PubMed

    Bai, Yingchen; Wu, Fengchang; Xing, Baoshan; Meng, Wei; Shi, Guolan; Ma, Yan; Giesy, John P

    2015-01-01

    XAD-8 adsorption technique coupled with stepwise elution using pyrophosphate buffers with initial pH values of 3, 5, 7, 9, and 13 was developed to isolate Chinese standard fulvic acid (FA) and then separated the FA into five sub-fractions: FApH3, FApH5, FApH7, FApH9 and FApH13, respectively. Mass percentages of FApH3-FApH13 decreased from 42% to 2.5%, and the recovery ratios ranged from 99.0% to 99.5%. Earlier eluting sub-fractions contained greater proportions of carboxylic groups with greater polarity and molecular mass, and later eluting sub-fractions had greater phenolic and aliphatic content. Protein-like components, as well as amorphous and crystalline poly(methylene)-containing components were enriched using neutral and basic buffers. Three main mechanisms likely affect stepwise elution of humic components from XAD-8 resin with pyrophosphate buffers including: 1) the carboxylic-rich sub-fractions are deprotonated at lower pH values and eluted earlier, while phenolic-rich sub-fractions are deprotonated at greater pH values and eluted later. 2) protein or protein-like components can be desorbed and eluted by use of stepwise elution as progressively greater pH values exceed their isoelectric points. 3) size exclusion affects elution of FA sub-fractions. Successful isolation of FA sub-fractions will benefit exploration of the origin, structure, evolution and the investigation of interactions with environmental contaminants. PMID:25735451

  11. Isolation and characterization of Chinese standard fulvic acid sub-fractions separated from forest soil by stepwise elution with pyrophosphate buffer.

    PubMed

    Bai, Yingchen; Wu, Fengchang; Xing, Baoshan; Meng, Wei; Shi, Guolan; Ma, Yan; Giesy, John P

    2015-03-04

    XAD-8 adsorption technique coupled with stepwise elution using pyrophosphate buffers with initial pH values of 3, 5, 7, 9, and 13 was developed to isolate Chinese standard fulvic acid (FA) and then separated the FA into five sub-fractions: FApH3, FApH5, FApH7, FApH9 and FApH13, respectively. Mass percentages of FApH3-FApH13 decreased from 42% to 2.5%, and the recovery ratios ranged from 99.0% to 99.5%. Earlier eluting sub-fractions contained greater proportions of carboxylic groups with greater polarity and molecular mass, and later eluting sub-fractions had greater phenolic and aliphatic content. Protein-like components, as well as amorphous and crystalline poly(methylene)-containing components were enriched using neutral and basic buffers. Three main mechanisms likely affect stepwise elution of humic components from XAD-8 resin with pyrophosphate buffers including: 1) the carboxylic-rich sub-fractions are deprotonated at lower pH values and eluted earlier, while phenolic-rich sub-fractions are deprotonated at greater pH values and eluted later. 2) protein or protein-like components can be desorbed and eluted by use of stepwise elution as progressively greater pH values exceed their isoelectric points. 3) size exclusion affects elution of FA sub-fractions. Successful isolation of FA sub-fractions will benefit exploration of the origin, structure, evolution and the investigation of interactions with environmental contaminants.

  12. Isolation and Characterization of Chinese Standard Fulvic Acid Sub-fractions Separated from Forest Soil by Stepwise Elution with Pyrophosphate Buffer

    NASA Astrophysics Data System (ADS)

    Bai, Yingchen; Wu, Fengchang; Xing, Baoshan; Meng, Wei; Shi, Guolan; Ma, Yan; Giesy, John P.

    2015-03-01

    XAD-8 adsorption technique coupled with stepwise elution using pyrophosphate buffers with initial pH values of 3, 5, 7, 9, and 13 was developed to isolate Chinese standard fulvic acid (FA) and then separated the FA into five sub-fractions: FApH3, FApH5, FApH7, FApH9 and FApH13, respectively. Mass percentages of FApH3-FApH13 decreased from 42% to 2.5%, and the recovery ratios ranged from 99.0% to 99.5%. Earlier eluting sub-fractions contained greater proportions of carboxylic groups with greater polarity and molecular mass, and later eluting sub-fractions had greater phenolic and aliphatic content. Protein-like components, as well as amorphous and crystalline poly(methylene)-containing components were enriched using neutral and basic buffers. Three main mechanisms likely affect stepwise elution of humic components from XAD-8 resin with pyrophosphate buffers including: 1) the carboxylic-rich sub-fractions are deprotonated at lower pH values and eluted earlier, while phenolic-rich sub-fractions are deprotonated at greater pH values and eluted later. 2) protein or protein-like components can be desorbed and eluted by use of stepwise elution as progressively greater pH values exceed their isoelectric points. 3) size exclusion affects elution of FA sub-fractions. Successful isolation of FA sub-fractions will benefit exploration of the origin, structure, evolution and the investigation of interactions with environmental contaminants.

  13. Iron buffer system in the water column and partitioning in the sediments of the naturally acidic Lake Caviahue, Neuquén, Argentina

    NASA Astrophysics Data System (ADS)

    Cabrera, J. M.; Diaz, M. M.; Schultz, S.; Temporetti, P.; Pedrozo, F.

    2016-05-01

    Sedimentary iron partitioning was studied for five sediment strata (16 cm depth) at three sampling sites of the naturally-occurring acidic Lake Caviahue (Patagonia, Argentina). Additionally, water column iron was modeled based on five-year period input loadings to study a possible iron buffer system. The partition coefficient between the water column and the total iron content of the sediments was also addressed. Sedimentary iron was found to be distributed, on average, in the following forms: exchangeable (6%), iron oxides (4%), pyrite and reactive organic matter (38%) and residual (non-andesitic) materials with a high content of humic acids (52%). Furthermore, we found that the dissolved iron in the lake was nearly constant throughout the five year period we studied. This is consistent with the existence of an iron buffer system in the lake at pH between 2.0 and 3.0, which may cause differential iron precipitation at the delta of the volcanic river with respect to the deeper northern and southern arms. Sedimentary iron measurements taken at the delta further support the existence of a buffer system, where it was found that the iron content in the sub-superficial stratum (2 cm) was double that of the remainder of the vertical profile at the same site.

  14. 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.

  15. 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

  16. Artificially MoO3 graded ITO anodes for acidic buffer layer free organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Lee, Hye-Min; Kim, Seok-Soon; Kim, Han-Ki

    2016-02-01

    We report characteristics of MoO3 graded ITO anodes prepared by a RF/DC graded sputtering for acidic poly(3,4-ethylene dioxylene thiophene):poly(styrene sulfonic acid) (PEDOT:PSS)-free organic solar cells (OSCs). Graded sputtering of the MoO3 buffer layer on top of the ITO layer produced MoO3 graded ITO anodes with a sheet resistance of 12.67 Ω/square, a resistivity of 2.54 × 10-4 Ω cm, and an optical transmittance of 86.78%, all of which were comparable to a conventional ITO anode. In addition, the MoO3 graded ITO electrode showed a greater work function of 4.92 eV than that (4.6 eV) of an ITO anode, which is beneficial for hole extraction from an organic active layer. Due to the high work function of MoO3 graded ITO electrodes, the acidic PEDOT:PSS-free OSCs fabricated on the MoO3 graded ITO electrode exhibited a power conversion efficiency 3.60% greater than that of a PEDOT:PSS-free OSC on the conventional ITO anode. The successful operation of PEDOT:PSS-free OSCs indicates simpler fabrication steps for cost-effective OSCs and elimination of interfacial reactions caused by the acidic PEDOT:PSS layer for reliable OSCs.

  17. The adsorption/desorption of phosphorus in freshwater sediments from buffer zones: the effects of sediment concentration and pH.

    PubMed

    Zhang, Liang; Du, Yun; Du, Chao; Xu, Meng; Loáiciga, Hugo A

    2016-01-01

    Riparian buffer zones adjacent to reservoirs and lakes protect aquatic ecosystems from polluted surface runoff. Sediments, collected from the buffer zones of Danjiangkou Reservoir (SR) and Honghu Lake (SL) in an ecologically fragile region in central China, were evaluated to reveal their phosphorus-adsorbing/desorbing properties and storage capacities. A nonlinear regression method was used to fit the pseudo-second-order kinetic and the modified crossover-type Langmuir isotherm models to the experimental data. It is shown that the adsorption of phosphorus onto the studied sediments followed the pseudo-second-order kinetic expression. The modified crossover-type Langmuir isotherm model was found to be a suitable method for describing adsorption/desorption processes in the experimental sediments. The maximum adsorption capacities (Q m), partitioning coefficients (K p), native adsorbed exchangeable phosphorus (NAP), and equilibrium phosphorus concentration (EPC0) were subsequently obtained for the experimental sediments. The effects of sediment concentration and pH were also investigated by batch experiments and Fourier transformation infrared and scanning electron microscopy analyses. The adsorption/desorption characteristics of different phosphate species on the sediments from reservoir and lake buffer zones were identified.

  18. Evaluation of an electrochemical model of erythrocyte pH buffering using 31P nuclear magnetic resonance data

    PubMed Central

    1990-01-01

    When erythrocytes are suspended in a solution of known composition the resultant values of such basic cell parameters as volume and pH are difficult to predict. To facilitate such predictions, we developed a mathematical model describing the passive transmembrane distribution of permeant species; three simultaneous equations were produced. Certain essential data required for the model were determined experimentally; these included the pH dependence of the charge on the hemoglobin molecule and the variation of the osmotic coefficient of hemoglobin with cell volume. Finally, cells were added to various solutions, and then titrated to produce a wide pH range (pH 6-8). We measured the resultant cell volume, cellular and extracellular pH using both conventional and 31P NMR methods. The expected equilibrium values of these electrochemical parameters were also calculated by solving (numerically) the three model equations. The accuracy of the model simulations was evaluated by direct comparison of calculated and experimentally determined values. PMID:2374002

  19. 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...

  20. 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...

  1. Simultaneous pollutant removal and electricity generation in denitrifying microbial fuel cell with boric acid-borate buffer solution.

    PubMed

    Chen, Gang; Zhang, Shaohui; Li, Meng; Wei, Yan

    2015-01-01

    A double-chamber denitrifying microbial fuel cell (MFC), using boric acid-borate buffer solution as an alternative to phosphate buffer solution, was set up to investigate the influence of buffer solution concentration, temperature and external resistance on electricity generation and pollutant removal efficiency. The result revealed that the denitrifying MFC with boric acid-borate buffer solution was successfully started up in 51 days, with a stable cell voltage of 205.1 ± 1.96 mV at an external resistance of 50 Ω. Higher concentration of buffer solution favored nitrogen removal and electricity generation. The maximum power density of 8.27 W/m(3) net cathodic chamber was obtained at a buffer solution concentration of 100 mmol/L. An increase in temperature benefitted electricity generation and nitrogen removal. A suitable temperature for this denitrifying MFC was suggested to be 25 °C. Decreasing the external resistance favored nitrogen removal and organic matter consumption by exoelectrogens. PMID:25768227

  2. Simultaneous pollutant removal and electricity generation in denitrifying microbial fuel cell with boric acid-borate buffer solution.

    PubMed

    Chen, Gang; Zhang, Shaohui; Li, Meng; Wei, Yan

    2015-01-01

    A double-chamber denitrifying microbial fuel cell (MFC), using boric acid-borate buffer solution as an alternative to phosphate buffer solution, was set up to investigate the influence of buffer solution concentration, temperature and external resistance on electricity generation and pollutant removal efficiency. The result revealed that the denitrifying MFC with boric acid-borate buffer solution was successfully started up in 51 days, with a stable cell voltage of 205.1 ± 1.96 mV at an external resistance of 50 Ω. Higher concentration of buffer solution favored nitrogen removal and electricity generation. The maximum power density of 8.27 W/m(3) net cathodic chamber was obtained at a buffer solution concentration of 100 mmol/L. An increase in temperature benefitted electricity generation and nitrogen removal. A suitable temperature for this denitrifying MFC was suggested to be 25 °C. Decreasing the external resistance favored nitrogen removal and organic matter consumption by exoelectrogens.

  3. [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

  4. Comparative Evaluation of Shear Bond Strength of Luting Cements to Different Core Buildup Materials in Lactic Acid Buffer Solution

    PubMed Central

    Patil, Siddharam M.; Desai, Raviraj G.; Arabbi, Kashinath C.; Prakash, Ved

    2015-01-01

    Aim and Objectives The core buildup material is used to restore badly broken down tooth to provide better retention for fixed restorations. The shear bond strength of a luting agent to core buildup is one of the crucial factors in the success of the cast restoration. The aim of this invitro study was to evaluate and compare the shear bond strength of luting cements with different core buildup materials in lactic acid buffer solution. Materials and Methods Two luting cements {Traditional Glass Ionomer luting cement (GIC) and Resin Modified Glass Ionomer luting cement (RMGIC)} and five core buildup materials {Silver Amalgam, Glass ionomer (GI), Glass Ionomer Silver Reinforced (GI Silver reinforced), Composite Resin and Resin Modified Glass Ionomer(RMGIC)} were selected for this study. Total 100 specimens were prepared with 20 specimens for each core buildup material using a stainless steel split metal die. Out of these 20 specimens, 10 specimens were bonded with each luting cement. All the bonded specimens were stored at 370c in a 0.01M lactic acid buffer solution at a pH of 4 for 7days. Shear bond strength was determined using a Universal Testing Machine at a cross head speed of 0.5mm/min. The peak load at fracture was recorded and shear bond strength was calculated. The data was statistically analysed using Two-way ANOVA followed by HOLM-SIDAK method for pair wise comparison at significance level of p<0.05. Results Two-Way ANOVA showed significant differences in bond strength of the luting cements (p<0.05) and core materials (p<0.05) and the interactions (p<0.05). Pairwise comparison of luting cements by HOLM-SIDAK test, showed that the RMGIC luting cement had higher shear bond strength values than Traditional GIC luting cement for all the core buildup materials. RMGIC core material showed higher bond strength values followed by Composite resin, GI silver reinforced, GI and silver amalgam core materials for both the luting agents. Conclusion Shear bond strength of

  5. Effect of Ethephon, Indole Butyric Acid, and Treatment Solution pH on Rooting and on Ethylene Levels within Mung Bean Cuttings.

    PubMed

    Mudge, K W; Swanson, B T

    1978-02-01

    Light-grown mung bean (Phaseolus aureus Roxb.) cuttings were treated with buffered and nonbuffered solutions of Ethephon, indole butyric acid (IBA), and the combination of both. Ethephon treatment resulted in increased tissue ethylene levels with increasing solution pH, but had no effect on rooting. IBA treatment had no effect on tissue ethylene levels, but strongly promoted rooting. Combinations of Ethephon and IBA had no effect on rooting of mung bean cuttings beyond that obtained by IBA alone. PMID:16660274

  6. 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

  7. 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.

  8. Effect of heavy metals on pH buffering capacity and solubility of Ca, Mg, K, and P in non-spiked and heavy metal-spiked soils.

    PubMed

    Najafi, Sarvenaz; Jalali, Mohsen

    2016-06-01

    In many parts of the world, soil acidification and heavy metal contamination has become a serious concern due to the adverse effects on chemical properties of soil and crop yield. The aim of this study was to investigate the effect of pH (in the range of 1 to 3 units above and below the native pH of soils) on calcium (Ca), magnesium (Mg), potassium (K), and phosphorus (P) solubility in non-spiked and heavy metal-spiked soil samples. Spiked samples were prepared by cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) as chloride salts and incubating soils for 40 days. The pH buffering capacity (pHBC) of each sample was determined by plotting the amount of H(+) or OH(-) added (mmol kg(-1)) versus the related pH value. The pHBC of soils ranged from 47.1 to 1302.5 mmol kg(-1) for non-spiked samples and from 45.0 to 1187.4 mmol kg(-1) for spiked soil samples. The pHBC values were higher in soil 2 (non-spiked and spiked) which had higher calcium carbonate content. The results indicated the presence of heavy metals in soils generally decreased the solution pH and pHBC values in spiked samples. In general, solubility of Ca, Mg, and K decreased with increasing equilibrium pH of non-spiked and spiked soil samples. In the case of P, increasing the pH to about 7, decreased the solubility in all soils but further increase of pH from 7, enhanced P solubility. The solubility trends and values for Ca, Mg, and K did not differed significantly in non-spiked and spiked samples. But in the case of P, a reduction in solubility was observed in heavy metal-spiked soils. The information obtained in this study can be useful to make better estimation of the effects of soil pollutants on anion and cation solubility from agricultural and environmental viewpoints. PMID:27168329

  9. Effect of heavy metals on pH buffering capacity and solubility of Ca, Mg, K, and P in non-spiked and heavy metal-spiked soils.

    PubMed

    Najafi, Sarvenaz; Jalali, Mohsen

    2016-06-01

    In many parts of the world, soil acidification and heavy metal contamination has become a serious concern due to the adverse effects on chemical properties of soil and crop yield. The aim of this study was to investigate the effect of pH (in the range of 1 to 3 units above and below the native pH of soils) on calcium (Ca), magnesium (Mg), potassium (K), and phosphorus (P) solubility in non-spiked and heavy metal-spiked soil samples. Spiked samples were prepared by cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) as chloride salts and incubating soils for 40 days. The pH buffering capacity (pHBC) of each sample was determined by plotting the amount of H(+) or OH(-) added (mmol kg(-1)) versus the related pH value. The pHBC of soils ranged from 47.1 to 1302.5 mmol kg(-1) for non-spiked samples and from 45.0 to 1187.4 mmol kg(-1) for spiked soil samples. The pHBC values were higher in soil 2 (non-spiked and spiked) which had higher calcium carbonate content. The results indicated the presence of heavy metals in soils generally decreased the solution pH and pHBC values in spiked samples. In general, solubility of Ca, Mg, and K decreased with increasing equilibrium pH of non-spiked and spiked soil samples. In the case of P, increasing the pH to about 7, decreased the solubility in all soils but further increase of pH from 7, enhanced P solubility. The solubility trends and values for Ca, Mg, and K did not differed significantly in non-spiked and spiked samples. But in the case of P, a reduction in solubility was observed in heavy metal-spiked soils. The information obtained in this study can be useful to make better estimation of the effects of soil pollutants on anion and cation solubility from agricultural and environmental viewpoints.

  10. 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.

  11. [Impact of a simultaneous application of anionic salts and rumen buffer on acid-base-balance and mineral metabolism in dairy cows].

    PubMed

    Gelfert, Carl-Christian; Hauser, Simone; Löptien, Antje; Montag, Nicole; Passmann, Mareike; Baumgartner, Walter; Staufenbiel, Rudolf

    2006-01-01

    In this study, the influence of simultaneous application of anionic salts (AS) and rumen buffer (RB) on the metabolism of dairy cows was examined. Eleven rumen fistulated, non-pregnant and non-lactating dairy cows received equal amounts of one AS (CaCl2 or CaSO4) and one RB (NaHCO3 or KHCO3) via rumen cannula during feeding time over a period of eight days. Before the first application of AS and RB and on day eight of the treatment period, blood, urine and rumen fluid samples were taken. The following parameters were measured: whole blood: pH, base excess, bicarbonate; serum: sodium, potassium, chloride, calcium; urine: pH, net acid base excretion, sodium, potassium, chloride, calcium; rumen fluid: pH. The changes of each parameter were compared via ANOVA. The changes in acid-base balance on day eight were very small, although significant. But p-values showed that the statistical evidence was low. The most changes occurred when NaHCO3 was fed in combination with one of the AS used. In this case a small acidogenic load was seen in blood (p < 0.05), and calcium concentrations increased slightly (p < 0.05). No alkalotic reaction could be detected when any combination of AS and RB were given to the cows. Simultaneous application of AS and RB results in a loss of effectivity of AS. Neither an adequate acidification of blood nor an activation of calcium metabolism occurred. In feed ration for cows in the last weeks of pregnancy, rumen buffer must not be fed, if anionic salts are given for prevention of parturient paresis.

  12. The hydrophilicity vs. ion interaction selectivity plot revisited: The effect of mobile phase pH and buffer concentration on hydrophilic interaction liquid chromatography selectivity behavior.

    PubMed

    Iverson, Chad D; Gu, Xinyun; Lucy, Charles A

    2016-08-01

    This work systematically investigates the selectivity changes on many HILIC phases from w(w)pH 3.7-6.8, at 5 and 25mM buffer concentrations. Hydrophilicity (kcytosine/kuracil) vs. ion interaction (kBTMA/kuracil) selectivity plots developed by Ibrahim et al. (J. Chromatogr. A 1260 (2012) 126-131) are used to investigate the effect of mobile phase changes on the selectivity of 18 HILIC columns from various classes. "Selectivity change plots" focus on the change in hydrophilicity and ion interaction that the columns exhibit upon changing mobile phase conditions. In general, the selectivity behavior of most HILIC columns is dominated by silanol activity. Minimal changes in selectivity are observed upon changing pH between w(w)pH 5 and 6.8. However, a reduction in ionic interaction is observed when the buffer concentration is increased at w(w)pH≥5.0 due to ionic shielding. Reduction of the w(w)pH to<5.0 results in decreasing cation exchange activity due to silanol protonation. Under all eluent conditions, the majority of phases show little change in their hydrophilicity.

  13. Inhibition of potato polyphenol oxidase by anions and activity in various carboxylate buffers (pH 4.8) at constant ionic strength.

    PubMed

    Malkin, B D; Thickman, K R; Markworth, C J; Wilcox, D E; Kull, F J

    2001-01-01

    The activity of potato polyphenol oxidase (tyrosinase) toward DL-3,4-dihydroxyphenylalanine (K(M) 5.39 mM) was studied using a variety of carboxylate buffers at a common pH and ionic strength. Enzyme activity, greatest in citrate and least in oxalate, correlated with increasing carboxyl concentration and molecular mass. The lower activity in oxalate was attributed to more effective chelation of a copper(II) form of the enzyme by the oxalate dianion. Sodium halide salts inhibited the enzyme. Although there was little difference in inhibition between sodium and potassium salts, the degree and type of inhibition was anion dependent; K(is), values for NaCl and KCl, (competitive inhibitors) were 1.82 and 1.62 mM, whereas Na(2) SO(4) and K(2) SO(4) (mixed inhibitors) had K(is) and K(ii) values in the 250 to 450 mM range. PMID:11342282

  14. Internal Active Thermal Control System (IATCS) Sodium Bicarbonate/Carbonate Buffer in an Open Aqueous Carbon Dioxide System and Corollary Electrochemical/Chemical Reactions Relative to System pH Changes

    NASA Technical Reports Server (NTRS)

    Stegman, Thomas W.; Wilson, Mark E.; Glasscock, Brad; Holt, Mike

    2014-01-01

    The International Space Station (ISS) Internal Active Thermal Control System (IATCS) experienced a number of chemical changes driven by system absorption of CO2 which altered the coolant’s pH. The natural effects of the decrease in pH from approximately 9.2 to less than 8.4 had immediate consequences on system corrosion rates and corrosion product interactions with specified coolant constituents. The alkalinity of the system was increased through the development and implementation of a carbonate/bicarbonate buffer that would increase coolant pH to 9.0 – 10.0 and maintain pH above 9.0 in the presence of ISS cabin concentrations of CO2 up to twenty times higher than ground concentrations. This paper defines how a carbonate/bicarbonate buffer works in an open carbon dioxide system and summarizes the analyses performed on the buffer for safe and effective application in the on-orbit system. The importance of the relationship between the cabin environment and the IATCS is demonstrated as the dominant factor in understanding the system chemistry and pH trends before and after addition of the carbonate/bicarbonate buffer. The paper also documents the corollary electrochemical and chemical reactions the system has experienced and the rationale for remediation of these effects with the addition of the carbonate/bicarbonate buffer.

  15. 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%).

  16. Simultaneous analysis of several antiretroviral nucleosides in rat-plasma by high-performance liquid chromatography with UV using acetic acid/hydroxylamine buffer Test of this new volatile medium-pH for HPLC-ESI-MS/MS.

    PubMed

    Bezy, Vincent; Morin, Philippe; Couerbe, Philippe; Leleu, Ghislaine; Agrofoglio, Luigi

    2005-07-25

    Zalcitabine (ddC), lamivudine (3TC), didanosine (ddI), stavudine (d4T), carbovir (CBV), zidovudine (AZT), tenofovir (PMPA) and its administrated form (tenofovir diisoproxyl fumarate, TDF), are nucleosides currently approved in HIV therapy. To facilitate pharmacokinetics studies, a specific reversed-phase high-performance liquid chromatography (HPLC) method was developed for their analysis in rat plasma. The method involved a quantitative recovery of these drugs from rat plasma by solid-phase extraction on Oasis HLB Waters cartridges followed by optimised HPLC separation on an Atlantis dC18 column with acetic acid-hydroxylamine buffer (ionic strength 5mM, pH 7)-acetonitrile elution gradient. Quantitation was performed by HPLC/UV at 260 nm. Linear calibration curves were obtained within a 30-10,000 ng/mL plasma concentration range. Correlation coefficients (r2) greater than 0.992 were obtained by least-squares regression and limits of quantification were in 30-90 ng/mL concentration range. Quantitative parameters (accuracy, intra-day repeatability and inter-day reproducibility) yielded satisfactory results. Finally, a new buffer, obtained with acetic acid and hydroxylamine, has been tested in HPLC/ESI-MS/MS and appears to be an efficient volatile buffer in the medium 5-7 pH range. Indeed, at pH 7 and low ionic strength (5 mM), its buffer capacity is one hundred times higher to that obtained for the usual acetic acid/ammonia buffer.

  17. Estimation of salivary flow rate, pH, buffer capacity, calcium, total protein content and total antioxidant capacity in relation to dental caries severity, age and gender

    PubMed Central

    Pandey, Pallavi; Reddy, N. Venugopal; Rao, V. Arun Prasad; Saxena, Aditya; Chaudhary, C. P.

    2015-01-01

    Purpose: The aim of the study was to evaluate salivary flow rate, pH, buffering capacity, calcium, total protein content and total antioxidant capacity in relation to dental caries, age and gender. Materials and Methods: The study population consisted of 120 healthy children aged 7–15 years that was further divided into two groups: 7–10 years and 11–15 years. In this 60 children with DMFS/dfs = 0 and 60 children with DMFS/dfs ≥5 were included. The subjects were divided into two groups; Group A: Children with DMFS/dfs = 0 (caries-free) Group B: Children with DMFS/dfs ≥5 (caries active). Unstimulated saliva samples were collected from all groups. Flow rates were determined, and samples analyzed for pH, buffer capacity, calcium, total protein and total antioxidant status. Salivary antioxidant activity is measured with spectrophotometer by an adaptation of 2,2’-azino-di-(3-ethylbenzthiazoline-6-sulphonate) assays. Results: The mean difference of the two groups; caries-free and caries active were proved to be statistically significant (P < 0.05) for salivary calcium, total protein and total antioxidant level for both the sexes in the age group 7–10 years and for the age 11–15 years the mean difference of the two groups were proved to be statistically significant (P < 0.05) for salivary calcium level for both the sexes. Salivary total protein and total antioxidant level were proved to be statistically significant for male children only. Conclusions: In general, total protein and total antioxidants in saliva were increased with caries activity. Calcium content of saliva was found to be more in caries-free group and increased with age. PMID:25821379

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. A buffer value index to evaluate effects of buffers on ruminal milieu in cows fed high or low concentrate, silage, or hay diets.

    PubMed

    Tucker, W B; Hogue, J F; Aslam, M; Lema, M; Martin, M; Owens, F N; Shin, I S; Le Ruyet, P; Adams, G D

    1992-03-01

    Our objective was to develop a buffer value index that would incorporate alterations in both ruminal fluid pH and buffering capacity as indicators of the influence of dietary buffering and alkalinizing agents on ruminal acid-base status. This index was evaluated using ruminal fluid from four lactating Holstein cows fed either sorghum silage or alfalfa hay in high or low concentrate diets. Ruminal fluid was incubated in vitro for 1, 2, 3, 4, or 5 h with no buffer or with 7.1 g of either NaHCO3, sodium sesquicarbonate, or a multielement buffer added per liter of ruminal fluid. Ruminal fluid pH was lower for diets based on high concentrate or alfalfa; buffering capacity between pH 5 and 7 was greater for high concentrate diets but was not affected by forage type. Ruminal fluid pH was higher for sesquicarbonate than for NaHCO3, the multielement buffer, or the control; however, ruminal fluid H+ concentration was similar between sesquicarbonate and NaHCO3, and both were lower than for the multielement buffer. Hydrogen ion concentration for the multielement buffer was lower than for the control. Buffering capacity was highest for NaHCO3, followed by sesquicarbonate, the multielement buffer, and the control. The buffer value index, which accounted for alterations in both H+ concentration and buffering capacity, was highest for NaCHO3, followed by sesquicarbonate, the multielement buffer, and the control. The poor response to the multielement buffer may be attributable to our relatively short incubation interval (less than 5 h). Dietary buffers increase both ruminal fluid pH and buffering capacity; both of these responses are beneficial.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1314858

  4. Mitochondrial, acidic, and cytosolic pHs determination by ³¹P NMR spectroscopy: design of new sensitive targeted pH probes.

    PubMed

    Culcasi, Marcel; Thétiot-Laurent, Sophie; Atteia, Ariane; Pietri, Sylvia

    2015-01-01

    (31)P nuclear magnetic resonance (NMR) is a unique technique to monitor noninvasively the energetics of living systems at real time through the detection of a variety of phosphorylated metabolites. Using adequately designed α-aminophosphonates as external probes, we have shown earlier that (31)P NMR can also give access simultaneously to the accurate pH of cytosolic and acidic compartments in normal and stressed cultured cells or isolated perfused organs, a feature that was not possible using endogenous inorganic phosphate as the probe. More recently, we obtained a series of derivatives of these new pH probes that incorporate a triphenylphosphonium cation as a specific vector to the mitochondrion. Here, we describe the synthesis, (31)P NMR pH titrating properties in buffers, and application in cultures of the green alga Chlamydomonas reinhardtii of two of these mitochondria-targeted pH probes in comparison with one nonvectorized, yet still informative α-aminophosphonate.

  5. Mitochondrial, acidic, and cytosolic pHs determination by ³¹P NMR spectroscopy: design of new sensitive targeted pH probes.

    PubMed

    Culcasi, Marcel; Thétiot-Laurent, Sophie; Atteia, Ariane; Pietri, Sylvia

    2015-01-01

    (31)P nuclear magnetic resonance (NMR) is a unique technique to monitor noninvasively the energetics of living systems at real time through the detection of a variety of phosphorylated metabolites. Using adequately designed α-aminophosphonates as external probes, we have shown earlier that (31)P NMR can also give access simultaneously to the accurate pH of cytosolic and acidic compartments in normal and stressed cultured cells or isolated perfused organs, a feature that was not possible using endogenous inorganic phosphate as the probe. More recently, we obtained a series of derivatives of these new pH probes that incorporate a triphenylphosphonium cation as a specific vector to the mitochondrion. Here, we describe the synthesis, (31)P NMR pH titrating properties in buffers, and application in cultures of the green alga Chlamydomonas reinhardtii of two of these mitochondria-targeted pH probes in comparison with one nonvectorized, yet still informative α-aminophosphonate. PMID:25634273

  6. 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.

  7. 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.

  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. Influence of buffered and unbuffered acetylsalicylic acid on dental enamel and dentine in human teeth: an in vitro pilot study.

    PubMed

    Rogalla, K; Finger, W; Hannig, M

    1992-06-01

    An in vitro study was conducted to investigate the erosive effect of buffered and unbuffered acetylsalicylic acid (ASA) on dental enamel and dentine in human teeth by scanning electron microscopy. In order to standardize the specimens and to improve comparability the dental enamel and dentine were superficially abraded. The enamel and dentine specimens were therefore particularly sensitive to the influences of acid agents. Concentrated solution of buffered chewable ASA tablets (500 mg ASA and 300 mg calcium carbonate in 5 ml water) showed no changes in the enamel surface structure after exposure times of 1 min, 5 min and 60 min. In contrast, minimal corrosive effects were already seen after exposure of the enamel surface to the unbuffered ASA solutions for 1 min. After exposure times of 5 min and 60 min erosion of the enamel was more pronounced. Immersion in the unbuffered ASA solution led to clearly visible micromorphological changes on the dentine surfaces even after exposure for 1 min. Exposure of the dentine specimens to the buffered ASA solutions led to only very slight changes in the surface morphology. Therefore, the scanning electron micrograph after exposure to buffered ASA is comparable to the picture of untreated dentine. PMID:1513188

  11. 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.

  12. 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.

  13. Airborne soil dust and its importance in buffering of atmospheric acidity and critical load assessment, over the semi arid tract of northern India.

    NASA Astrophysics Data System (ADS)

    Sharma, Disha; Kulshrestha, Umesh

    Airborne soil dust and its importance in buffering of atmospheric acidity and critical load assessment, over the semi arid tract of northern India. The Critical Load approach alongwith integrated assessment models has been used in the European nations for policy formations to reduce acidic emissions. This unique approach was applied to assess the of vulnerability of natural systems to the present day atmospheric pollution scenario. The calculated values of critical loads of sulphur ( 225 - 275 eq/ha/yr) and nitrogen (298 - 303 eq/ha/yr), for the soil system in Delhi, were calculated with respect to Anjan grass, Hibiscus and Black siris. The present loads of sulphur (PL(S) = 26.40 eq/ha/yr) and nitrogen (PL(N) = 36.51 eq/ha/yr) were found to be much lower than their critical loads without posing any danger of atmospheric acidic deposition on the soil systems. The study indicated that the system is still protective due to high pH of soil. The nature of buffering capability of calcium derived from soil dust can be considered as a natural tool to combat acidification in the Indian region. The results showed that the pollution status in Delhi is still within the safe limits. However, at the pace at which the city is growing, it is likely that in coming decades, it may exceed these critical values. In order to set deposition limits and avoid adverse effects of acidic deposition this approach can be applied in India too. Such approach is very useful, not only in abating pollution but also in devising means of cost optimal emission abatement strategies.

  14. The buffer capacity of airway epithelial secretions

    PubMed Central

    Kim, Dusik; Liao, Jie; Hanrahan, John W.

    2014-01-01

    The pH of airway epithelial secretions influences bacterial killing and mucus properties and is reduced by acidic pollutants, gastric reflux, and respiratory diseases such as cystic fibrosis (CF). The effect of acute acid loads depends on buffer capacity, however the buffering of airway secretions has not been well characterized. In this work we develop a method for titrating micro-scale (30 μl) volumes and use it to study fluid secreted by the human airway epithelial cell line Calu-3, a widely used model for submucosal gland serous cells. Microtitration curves revealed that HCO−3 is the major buffer. Peak buffer capacity (β) increased from 17 to 28 mM/pH during forskolin stimulation, and was reduced by >50% in fluid secreted by cystic fibrosis transmembrane conductance regulator (CFTR)-deficient Calu-3 monolayers, confirming an important role of CFTR in HCO−3 secretion. Back-titration with NaOH revealed non-volatile buffer capacity due to proteins synthesized and released by the epithelial cells. Lysozyme and mucin concentrations were too low to buffer Calu-3 fluid significantly, however model titrations of porcine gastric mucins at concentrations near the sol-gel transition suggest that mucins may contribute to the buffer capacity of ASL in vivo. We conclude that CFTR-dependent HCO−3 secretion and epithelially-derived proteins are the predominant buffers in Calu-3 secretions. PMID:24917822

  15. 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.

  16. 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

  17. Buffer Standards for the Physiological pH of N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine (TRICINE) from T = (278.15 to 328.15) K

    PubMed Central

    Roy, Rabindra N.; Roy, Lakshmi N.; Henson, Isaac B.; Stegner, Jessica M.; Dinga, John J.; Summers, Clark E.; Suhrheinrich, Gregory L.; Veliz, Jaime A.; Dieterman, Lauren A.

    2012-01-01

    The pH values of two buffer solutions without NaCl and seven buffer solutions with added NaCl, having ionic strengths (I = 0.16 mol·kg−1) similar to those of physiological fluids, have been evaluated at 12 temperatures from T = (278.15 to 328.15) K by way of the extended form of the Debye-Hückel equation of the Bates-Guggenheim convention. The residual liquid junction potentials (δEj) between the buffer solutions of TRICINE and saturated KCl solution of the calomel electrode at T = (298.15 and 310.15) K have been estimated by measurement with a flowing junction cell. For the buffer solutions with the molality of TRICINE (m1) = 0.06 mol·kg−1, NaTRICINE (m2) = 0.02 mol·kg−1, and NaCl (m3) = 0.14 mol·kg−1, the pH values at 310.15 K obtained from the extended Debye-Hückel equation and the inclusion of the liquid junction correction are 7.342 and 7.342, respectively. These are in excellent agreement. The zwitterionic buffer TRICINE is recommended as a secondary pH standard in the region for clinical application. PMID:22745513

  18. Buffer Standards for the Physiological pH of N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine (TRICINE) from T = (278.15 to 328.15) K.

    PubMed

    Roy, Rabindra N; Roy, Lakshmi N; Henson, Isaac B; Stegner, Jessica M; Dinga, John J; Summers, Clark E; Suhrheinrich, Gregory L; Veliz, Jaime A; Dieterman, Lauren A

    2012-09-01

    The pH values of two buffer solutions without NaCl and seven buffer solutions with added NaCl, having ionic strengths (I = 0.16 mol·kg(-1)) similar to those of physiological fluids, have been evaluated at 12 temperatures from T = (278.15 to 328.15) K by way of the extended form of the Debye-Hückel equation of the Bates-Guggenheim convention. The residual liquid junction potentials (δE(j)) between the buffer solutions of TRICINE and saturated KCl solution of the calomel electrode at T = (298.15 and 310.15) K have been estimated by measurement with a flowing junction cell. For the buffer solutions with the molality of TRICINE (m(1)) = 0.06 mol·kg(-1), NaTRICINE (m(2)) = 0.02 mol·kg(-1), and NaCl (m(3)) = 0.14 mol·kg(-1), the pH values at 310.15 K obtained from the extended Debye-Hückel equation and the inclusion of the liquid junction correction are 7.342 and 7.342, respectively. These are in excellent agreement. The zwitterionic buffer TRICINE is recommended as a secondary pH standard in the region for clinical application.

  19. 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.

  20. 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.

  1. Redox buffered hydrofluoric acid etchant for the reduction of galvanic attack during release etching of MEMS devices having noble material films

    DOEpatents

    Hankins, Matthew G.

    2009-10-06

    Etchant solutions comprising a redox buffer can be used during the release etch step to reduce damage to the structural layers of a MEMS device that has noble material films. A preferred redox buffer comprises a soluble thiophosphoric acid, ester, or salt that maintains the electrochemical potential of the etchant solution at a level that prevents oxidation of the structural material. Therefore, the redox buffer preferentially oxidizes in place of the structural material. The sacrificial redox buffer thereby protects the exposed structural layers while permitting the dissolution of sacrificial oxide layers during the release etch.

  2. 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

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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

  12. Acidic Digestion in a Teleost: Postprandial and Circadian Pattern of Gastric pH, Pepsin Activity, and Pepsinogen and Proton Pump mRNAs Expression

    PubMed Central

    Yúfera, Manuel; Moyano, Francisco J.; Astola, Antonio; Pousão-Ferreira, Pedro; Martínez-Rodríguez, Gonzalo

    2012-01-01

    Two different modes for regulation of stomach acid secretion have been described in vertebrates. Some species exhibit a continuous acid secretion maintaining a low gastric pH during fasting. Others, as some teleosts, maintain a neutral gastric pH during fasting while the hydrochloric acid is released only after the ingestion of a meal. Those different patterns seem to be closely related to specific feeding habits. However, our recent observations suggest that this acidification pattern could be modified by changes in daily feeding frequency and time schedule. The aim of this study was to advance in understanding the regulation mechanisms of stomach digestion and pattern of acid secretion in teleost fish. We have examined the postprandial pattern of gastric pH, pepsin activity, and mRNA expression for pepsinogen and proton pump in white seabream juveniles maintained under a light/dark 12/12 hours cycle and receiving only one morning meal. The pepsin activity was analyzed according to the standard protocol buffering at pH 2 and using the actual pH measured in the stomach. The results show how the enzyme precursor is permanently available while the hydrochloric acid, which activates the zymogen fraction, is secreted just after the ingestion of food. Results also reveal that analytical protocol at pH 2 notably overestimates true pepsin activity in fish stomach. The expression of the mRNA encoding pepsinogen and proton pump exhibited almost parallel patterns, with notable increases during the darkness period and sharp decreases just before the morning meal. These results indicate that white seabream uses the resting hours for recovering the mRNA stock that will be quickly used during the feeding process. Our data clearly shows that both daily illumination pattern and feeding time are involved at different level in the regulation of the secretion of digestive juices. PMID:22448266

  13. 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

  14. 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

  15. Effect of pH buffering capacity and sources of dietary sulfur on rumen fermentation, sulfide production, methane production, sulfate reducing bacteria, and total Archaea in in vitro rumen cultures.

    PubMed

    Wu, Hao; Meng, Qingxiang; Yu, Zhongtang

    2015-06-01

    The effects of three types of dietary sulfur on in vitro fermentation characteristics, sulfide production, methane production, and microbial populations at two different buffer capacities were examined using in vitro rumen cultures. Addition of dry distilled grain with soluble (DDGS) generally decreased total gas production, degradation of dry matter and neutral detergent fiber, and concentration of total volatile fatty acids, while increasing ammonia concentration. High buffering capacity alleviated these adverse effects on fermentation. Increased sulfur content resulted in decreased methane emission, but total Archaea population was not changed significantly. The population of sulfate reducing bacteria was increased in a sulfur type-dependent manner. These results suggest that types of dietary sulfur and buffering capacity can affect rumen fermentation and sulfide production. Diet buffering capacity, and probably alkalinity, may be increased to alleviate some of the adverse effects associated with feeding DDGS at high levels. PMID:25797103

  16. Effect of pH buffering capacity and sources of dietary sulfur on rumen fermentation, sulfide production, methane production, sulfate reducing bacteria, and total Archaea in in vitro rumen cultures.

    PubMed

    Wu, Hao; Meng, Qingxiang; Yu, Zhongtang

    2015-06-01

    The effects of three types of dietary sulfur on in vitro fermentation characteristics, sulfide production, methane production, and microbial populations at two different buffer capacities were examined using in vitro rumen cultures. Addition of dry distilled grain with soluble (DDGS) generally decreased total gas production, degradation of dry matter and neutral detergent fiber, and concentration of total volatile fatty acids, while increasing ammonia concentration. High buffering capacity alleviated these adverse effects on fermentation. Increased sulfur content resulted in decreased methane emission, but total Archaea population was not changed significantly. The population of sulfate reducing bacteria was increased in a sulfur type-dependent manner. These results suggest that types of dietary sulfur and buffering capacity can affect rumen fermentation and sulfide production. Diet buffering capacity, and probably alkalinity, may be increased to alleviate some of the adverse effects associated with feeding DDGS at high levels.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. 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).

  5. 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.

  6. 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

  7. 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.

  8. 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

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

    NASA Astrophysics Data System (ADS)

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

    2004-10-01

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

  10. 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

  11. 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.

  12. 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.

  13. Antigen retrieval using pH 3.5 glycine-HCl buffer or urea solution for immunohistochemical localization of Ki-67.

    PubMed

    Shi, S R; Chaiwun, B; Young, L; Imam, A; Cote, R J; Taylor, C R

    1994-07-01

    A new antibody (MIB-1) has been described, permitting the demonstration of Ki-67 proliferation antigen in paraffin sections. However, satisfactory results were obtained only after subjecting tissue sections to microwave based antigen retrieval in citrate buffer solution. Other buffer solutions produce equivalent or better results and also permit use of the original Ki-67 antibody, which hitherto has been considered ineffective for paraffin sections.

  14. 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

  15. 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

  16. 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

  17. 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.

  18. Evaluation of Flow Rate, pH, Buffering Capacity, Calcium, Total Proteins and Total Antioxidant Capacity Levels of Saliva in Caries Free and Caries Active Children: An In Vivo Study.

    PubMed

    Preethi, B P; Reshma, Dodawad; Anand, Pyati

    2010-10-01

    The purpose of this study was to evaluate the relationship between the physicochemical properties of saliva such as flow rate, pH, buffering capacity, calcium level, total protein and total antioxidant levels in caries free and caries active children. The present study included one hundred and twenty healthy children who were divided into two groups; group I and group II comprising of age groups 7-10 and 11-14 years, respectively. Both the groups were then sub-divided equally according to gender. They were further divided into caries free and caries active with 15 children in each group. Unstimulated saliva was collected by suction method and flow rates were determined. The samples were then analyzed for pH, buffering capacity, total protein, calcium and total antioxidant capacity. The data was statistically analyzed using student t test (unpaired). The results revealed that when all these parameters were compared among the caries free and caries active children, flow rate, pH, buffering capacity were slightly reduced in caries active children, but total protein and total antioxidant capacity of saliva increased significantly in caries active children and the total calcium decreased significantly in caries active children. Within the limitation of this study, we conclude that, the physicochemical properties of saliva play a major role in the development of caries. PMID:21966118

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. The effects of a simulated acid precipitation on leaf litter quality and the growth of a detritivore in a buffered lotic system.

    PubMed

    Garden, A; Davies, R W

    1988-01-01

    The effects of a simulated acid rain on leaf litter quality and the growth of a detritivore in a buffered lotic system were investigated. Exposure of Populus balsamifera L. saplings to a simulated acid precipitation prior to leaf abscission resulted in significant decreases in foliar nitrogen content and increases in carbon: nitrogen ratios. During decomposition of the leaf litter in a buffered lotic system, microbial activity was significantly reduced. Growth of Tipula commiscibilis Diane (Diptera: Tipulidae) larvae decreased significantly when fed conditioned leaves exposed to a simulated acid precipitation prior to abscission. Reductions in detritivore growth were correlated with lower potential quality of the leaf litter resulting from increased carbon: nitrogen ratios and reduced levels of microbial activity. Thus, even in well buffered freshwater ecosystems, acid precipitation can have significant indirect effects on microbial activity and macroinvertebrate growth.

  4. The effects of a simulated acid precipitation on leaf litter quality and the growth of a detritivore in a buffered lotic system.

    PubMed

    Garden, A; Davies, R W

    1988-01-01

    The effects of a simulated acid rain on leaf litter quality and the growth of a detritivore in a buffered lotic system were investigated. Exposure of Populus balsamifera L. saplings to a simulated acid precipitation prior to leaf abscission resulted in significant decreases in foliar nitrogen content and increases in carbon: nitrogen ratios. During decomposition of the leaf litter in a buffered lotic system, microbial activity was significantly reduced. Growth of Tipula commiscibilis Diane (Diptera: Tipulidae) larvae decreased significantly when fed conditioned leaves exposed to a simulated acid precipitation prior to abscission. Reductions in detritivore growth were correlated with lower potential quality of the leaf litter resulting from increased carbon: nitrogen ratios and reduced levels of microbial activity. Thus, even in well buffered freshwater ecosystems, acid precipitation can have significant indirect effects on microbial activity and macroinvertebrate growth. PMID:15092603

  5. Geographical variation of the acid buffering of vegetated catchments: Factors determining the bicarbonate leaching

    NASA Astrophysics Data System (ADS)

    Ohte, Nobuhito; Tokuchi, Naoko

    1999-12-01

    In order to understand the determining factors of the geographical variation of buffering in the world's vegetated catchments, this study examined the HCO3- leaching of 107 experimental watersheds selected from regions ranging from tropical rain forests to humid continental or subpolar forests including several temperate grassland. With consideration of the soil development and the factors controlling it, the influences of geological, climatological, and topographical conditions on discharge HCO3- concentrations and fluxes are examined. The HCO3- discharge fluxes from catchments were correlated with climatological indexes. The increase of annual mean temperature reflected the increase in fluxes, although this tendency was not that significant in the precipitation-flux relationships. Notable differences in these correlations were not found among three major groups of bedrock types; igneous, metamorphic, and sedimentary groups, with exceptions being noted at the sites having materially HCO3--rich calcite, dolomite and volcanic ash. There were, however, exceptionally high flux sites whose fluxes could not be predicted by the empirical model when considering only temperature and precipitation controls. These sites belong to the mountainous part of the Japanese archipelago that is orogenically active and have in common steep hillslopes. Positive correlations were found between relief ratio, which was calculated by dividing elevation difference between highest and lowest points in the catchment by the distance between those two points, and fluxes in igneous and sedimentary groups including these high- HCO3- flux sites. These facts suggest that it is a fundamental requirement to consider the status of the soil forming when discussing the global variations in the buffering of watersheds. The differences in geomorphologic conditions controlling soil development are also just as important as the climatological effects.

  6. Acidification and buffering mechanisms in acid sulfate soil wetlands of the Murray-Darling Basin, Australia.

    PubMed

    Glover, Fiona; Whitworth, Kerry L; Kappen, Peter; Baldwin, Darren S; Rees, Gavin N; Webb, John A; Silvester, Ewen

    2011-04-01

    The acid generation mechanisms and neutralizing capacities of sulfidic sediments from two inland wetlands have been studied in order to understand the response of these types of systems to drying events. The two systems show vastly different responses to oxidation, with one (Bottle Bend (BB) lagoon) having virtually no acid neutralizing capacity (ANC) and the other (Psyche Bend (PB) lagoon) an ANC that is an order of magnitude greater than the acid generation potential. While BB strongly acidifies during oxidation the free acid generation is less than that expected from the measured proton production and consumption processes, with additional proton consumption attributed to the formation of an acid-anion (chloride) FeIII (oxyhydr)oxide product, similar to akaganéite (Fe(OH)2.7Cl0.3). While such products can partially attenuate the acidification of these systems, resilience to acidification is primarily imparted by sediment ANC. PMID:21375259

  7. 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...

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. Nonclinical safety evaluation of boric acid and a novel borate-buffered contact lens multi-purpose solution, Biotrue™ multi-purpose solution.

    PubMed

    Lehmann, David M; Cavet, Megan E; Richardson, Mary E

    2010-12-01

    Multipurpose solutions (MPS) often contain low concentrations of boric acid as a buffering agent. Limited published literature has suggested that boric acid and borate-buffered MPS may alter the corneal epithelium; an effect attributed to cytotoxicity induced by boric acid. However, this claim has not been substantiated. We investigated the effect of treating cells with relevant concentrations of boric acid using two cytotoxicity assays, and also assessed the impact of boric acid on corneal epithelial barrier function by measuring TEER and immunostaining for tight junction protein ZO-1 in human corneal epithelial cells. Boric acid was also assessed in an in vivo ocular model when administered for 28 days. Additionally, we evaluated Biotrue multi-purpose solution, a novel borate-buffered MPS, alone and with contact lenses for ocular compatibility in vitro and in vivo. Boric acid passed both cytotoxicity assays and did not alter ZO-1 distribution or corneal TEER. Furthermore, boric acid was well-tolerated on-eye following repeated administration in a rabbit model. Finally, Biotrue multi-purpose solution demonstrated good ocular biocompatibility both in vitro and in vivo. This MPS was not cytotoxic and was compatible with the eye when administered alone and when evaluated with contact lenses. We demonstrate that boric acid and a borate-buffered MPS is compatible with the ocular environment. Our findings provide evidence that ocular effects reported for some borate-buffered MPS may be incorrectly attributed to boric acid and are more likely a function of the unique combination of ingredients in the MPS formulation tested.

  16. Buffers more than buffering agent: introducing a new class of stabilizers for the protein BSA.

    PubMed

    Gupta, Bhupender S; Taha, Mohamed; Lee, Ming-Jer

    2015-01-14

    In this study, we have analyzed the influence of four biological buffers on the thermal stability of bovine serum albumin (BSA) using dynamic light scattering (DLS). The investigated buffers include 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), 4-(2-hydroxyethyl)-1-piperazine-propanesulfonic acid (EPPS), 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid sodium salt (HEPES-Na), and 4-morpholinepropanesulfonic acid sodium salt (MOPS-Na). These buffers behave as a potential stabilizer for the native structure of BSA against thermal denaturation. The stabilization tendency follows the order of MOPS-Na > HEPES-Na > HEPES ≫ EPPS. To obtain an insight into the role of hydration layers and peptide backbone in the stabilization of BSA by these buffers, we have also explored the phase transition of a thermoresponsive polymer, poly(N-isopropylacrylamide (PNIPAM)), a model compound for protein, in aqueous solutions of HEPES, EPPS, HEPES-Na, and MOPS-Na buffers at different concentrations. It was found that the lower critical solution temperatures (LCST) of PNIPAM in the aqueous buffer solutions substantially decrease with increase in buffer concentration. The mechanism of interactions between these buffers and protein BSA was probed by various techniques, including UV-visible, fluorescence, and FTIR. The results of this series of studies reveal that the interactions are mainly governed by the influence of the buffers on the hydration layers surrounding the protein. We have also explored the possible binding sites of BSA with these buffers using a molecular docking technique. Moreover, the activities of an industrially important enzyme α-chymotrypsin (α-CT) in 0.05 M, 0.5 M, and 1.0 M of HEPES, EPPS, HEPES-Na, and MOPS-Na buffer solutions were analyzed at pH = 8.0 and T = 25 °C. Interestingly, the activities of α-CT were found to be enhanced in the aqueous solutions of these investigated buffers. Based upon the Jones-Dole viscosity parameters, the

  17. Complexation of buffer constituents with neutral complexation agents: part I. Impact on common buffer properties.

    PubMed

    Riesová, Martina; Svobodová, Jana; Tošner, Zdeněk; Beneš, Martin; Tesařová, Eva; Gaš, Bohuslav

    2013-09-17

    The complexation of buffer constituents with the complexation agent present in the solution can very significantly influence the buffer properties, such as pH, ionic strength, or conductivity. These parameters are often crucial for selection of the separation conditions in capillary electrophoresis or high-pressure liquid chromatography (HPLC) and can significantly affect results of separation, particularly for capillary electrophoresis as shown in Part II of this paper series (Beneš, M.; Riesová, M.; Svobodová, J.; Tesařová, E.; Dubský, P.; Gaš, B. Anal. Chem. 2013, DOI: 10.1021/ac401381d). In this paper, the impact of complexation of buffer constituents with a neutral complexation agent is demonstrated theoretically as well as experimentally for the model buffer system composed of benzoic acid/LiOH or common buffers (e.g., CHES/LiOH, TAPS/LiOH, Tricine/LiOH, MOPS/LiOH, MES/LiOH, and acetic acid/LiOH). Cyclodextrins as common chiral selectors were used as model complexation agents. We were not only able to demonstrate substantial changes of pH but also to predict the general complexation characteristics of selected compounds. Because of the zwitterion character of the common buffer constituents, their charged forms complex stronger with cyclodextrins than the neutral ones do. This was fully proven by NMR measurements. Additionally complexation constants of both forms of selected compounds were determined by NMR and affinity capillary electrophoresis with a very good agreement of obtained values. These data were advantageously used for the theoretical descriptions of variations in pH, depending on the composition and concentration of the buffer. Theoretical predictions were shown to be a useful tool for deriving some general rules and laws for complexing systems.

  18. Complexation of buffer constituents with neutral complexation agents: part I. Impact on common buffer properties.

    PubMed

    Riesová, Martina; Svobodová, Jana; Tošner, Zdeněk; Beneš, Martin; Tesařová, Eva; Gaš, Bohuslav

    2013-09-17

    The complexation of buffer constituents with the complexation agent present in the solution can very significantly influence the buffer properties, such as pH, ionic strength, or conductivity. These parameters are often crucial for selection of the separation conditions in capillary electrophoresis or high-pressure liquid chromatography (HPLC) and can significantly affect results of separation, particularly for capillary electrophoresis as shown in Part II of this paper series (Beneš, M.; Riesová, M.; Svobodová, J.; Tesařová, E.; Dubský, P.; Gaš, B. Anal. Chem. 2013, DOI: 10.1021/ac401381d). In this paper, the impact of complexation of buffer constituents with a neutral complexation agent is demonstrated theoretically as well as experimentally for the model buffer system composed of benzoic acid/LiOH or common buffers (e.g., CHES/LiOH, TAPS/LiOH, Tricine/LiOH, MOPS/LiOH, MES/LiOH, and acetic acid/LiOH). Cyclodextrins as common chiral selectors were used as model complexation agents. We were not only able to demonstrate substantial changes of pH but also to predict the general complexation characteristics of selected compounds. Because of the zwitterion character of the common buffer constituents, their charged forms complex stronger with cyclodextrins than the neutral ones do. This was fully proven by NMR measurements. Additionally complexation constants of both forms of selected compounds were determined by NMR and affinity capillary electrophoresis with a very good agreement of obtained values. These data were advantageously used for the theoretical descriptions of variations in pH, depending on the composition and concentration of the buffer. Theoretical predictions were shown to be a useful tool for deriving some general rules and laws for complexing systems. PMID:23889602

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. Dissolution reaction and surface iron speciation of UICC crocidolite in buffered solution at pH 7.4: A combined ICP-OES, XPS and TEM investigation

    NASA Astrophysics Data System (ADS)

    Pacella, Alessandro; Fantauzzi, Marzia; Turci, Francesco; Cremisini, Carlo; Montereali, Maria Rita; Nardi, Elisa; Atzei, Davide; Rossi, Antonella; Andreozzi, Giovanni B.

    2014-02-01

    The dissolution reaction and the surface modifications of crocidolite asbestos fibres incubated for 0.5, 1, 24, 48, 168 and 1440 h in a phosphate buffered solution at pH 7.4 with and without hydrogen peroxide were investigated. Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) was used to monitor the ion release into solution, X-ray Photoelectron Spectroscopy (XPS) was performed to unveil the chemistry of the leached surface, and High Resolution Transmission Electron Microscopy (HR-TEM) was carried out to monitor the structural modifications of the fibres. No significant differences were observed between dissolution experiments carried out with and without H2O2 with the exception of results after the first hour, from which it may be inferred that the dissolution proceeds faster in the presence of H2O2 but only in its very early steps. Congruent mobilization of Si and Mg from crocidolite was observed, increasing with time especially in the range between 1 and 48 h, while Ca decreased after 48 h and Fe was not detected at any incubation time. In the undersaturated conditions (0-48 h), dissolution rate of UICC crocidolite fibres has been estimated to be d(Si)/dt = 0.079 μmol h-1. The fibre surface modification is continuous with time: XPS results showed a regular depletion of Si and Mg and enrichment of Fe along dissolution. The Fe2p3/2 signal on the surface was fitted with four components at 709.0, 710.5, 711.6 and 712.8 eV binding energy values corresponding to: (i) Fe(II)-O and (ii) Fe(III)-O surrounded by oxygen atoms in the silicate structure, (iii) Fe(III)-OOH as a product of the dissolution process, and (iv) Fe in a phosphate precipitate (Fe-P), respectively. The evolution of Fe speciation on the crocidolite surface was followed by integrating the four photoemission peaks, and results showed that the oxidative environment promotes the formation of Fe(III)-O (up to 37% Fetot) and of Fe-P species (up to 16% Fetot), which are found on the fibre

  4. Trona and sodium bicarbonate in beef cattle diets: effects on pH and volatile fatty acid concentrations.

    PubMed

    Boerner, B J; Byers, F M; Schelling, G T; Coppock, C E; Greene, L W

    1987-07-01

    A study was conducted to evaluate the effectiveness of NaHCO3 and trona in beef cattle diets. Trace element (n = 28) analysis revealed no toxicological or safety concerns with the use of trona. Trona was more (P less than .05) soluble in ruminal fluid than Na2CO3, and NaHCO3 and had greater (P less than .05) buffering capacity (9.6 meq/g) than NaHCO3 (6.1 meq/g) but less (P less than .05) than Na2CO3 (11.1 meq/g). Calcium carbonate was insoluble and did not buffer ruminal fluid. Six yearling (avg 272 kg) Hereford X Angus steers, each with ruminal, duodenal and ileal cannulas, were fed 50:50 (cracked corn-based concentrate:cottonseed hulls) or 90:10 concentrate diets with no buffer, 1% NaHCO3 or with 1% trona. Intake, across all treatments, averaged 2.4% of body weight. Propionate (mmol/liter) increased (17.6 vs 13.5; P less than .05) and butyrate decreased (3.5 vs 5.2; P less than .05) with trona in the 90:10 diet as compared with no buffer. Propionate (16.8) increased (P less than .05) with NaHCO3 in the 90:10 diet. Average ruminal pH was greater (P less than .05) in 90:10 diets with trona or NaHCO3 than with no buffer (5.61, 5.61 vs 5.55); duodenal pH was greater (P less than .01) with trona than with no buffer (2.66 vs 2.55). Trona reduced ruminal pH-hours (P less than .05) and pH-area (P less than .12; time and area below mean pH of control) below control for both concentrate levels.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3038823

  5. [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.

  6. 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

  7. 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

  8. 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

  9. 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.

  10. Effect of temperature and solvent composition on acid dissociation equilibria, I: Sequenced (s)(s)pKa determination of compounds commonly used as buffers in high performance liquid chromatography coupled to mass spectroscopy detection.

    PubMed

    Padró, Juan M; Acquaviva, Agustín; Tascon, Marcos; Gagliardi, Leonardo G; Castells, Cecilia B

    2012-05-01

    A new automated and rapid potentiometric method for determining the effect of organic-solvent composition on pK(a) has been developed. It is based on the measurements of pH values of buffer solutions of variable solvent compositions using a combined glass electrode. Additions of small volumes of one precisely thermostated solution into another, both containing exactly the same analytical concentrations of the buffer components, can produce continuous changes in the solvent composition. Two sequences of potential measurements, one of increasing and the other of decreasing solvent content, are sufficient to obtain the pK(a) values of the acidic compound within the complete solvent-composition range in about 2h. The experimental design, procedures, and calculations needed to convert the measured pH into the thermodynamic pK(a) values are thoroughly discussed. This rapid and automated method allows the systematic study of the effect of solvent compositions and temperatures on the pK(a). It has been applied to study the dissociation constants of two monoprotic acids: formic acid and triethylamine:HCl in acetonitrile/water mixtures within the range from 0 to 90% (v/v) at temperatures between 20°C and 60°C. These volatile compounds are frequently used to control the pH of the mobile phase in HPLC, especially in methods coupled to mass-spectrometry detection. The obtained pK(a) values are in excellent agreement with those previously reported. The results were fitted to empirical functions between pK(a) and temperature and composition. These equations, which can be used to estimate the pK(a) of these substances at any composition and temperature, would be highly useful in practical work during chromatographic method development.

  11. 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.

  12. Retention of ionizable compounds on HPLC. 12. The properties of liquid chromatography buffers in acetonitrile-water mobile phases that influence HPLC retention.

    PubMed

    Espinosa, Sonia; Bosch, Elisabeth; Rosés, Marti

    2002-08-01

    The addition of acetonitrile to aqueous buffers to prepare RP HPLC mobile phases changes the buffer properties (pH and buffer capacity). This variation is studied for ace tate, phosphate, phthalate, citrate, and ammonia buffers in acetonitrile-water mixtures up to 60% in acetonitrile (v/v). Equations are proposed to relate pH and buffer capacity change of these buffers to the initial aqueous pH value and to the volume fraction of acetonitrile added. It is demonstrated that the pH change of the buffer depends not only on the initial aqueous pH of the buffer and on the percentage of acetonitrile added but also on the particular buffer used. The proposed equations allow an accurate prediction of this ionization for the studied buffers. Since the retention of acid/base compounds shows a strong dependence of their degree of ionization, the equations are used to predict the change in this ionization with addition of acetonitrile when the RP HPLC mobile phase is prepared. This prediction allows estimation of the retention of an acid/base compound in a particular acetonitrile-water buffered mobile phase.

  13. Free flow cell electrophoresis using zwitterionic buffer

    NASA Technical Reports Server (NTRS)

    Rodkey, R. Scott

    1990-01-01

    Studies of a zwitterionic buffer formulated for cell electrophoresis were done using the McDonnell-Douglas Continuous Flow Electrophoresis System. Standard buffers were analyzed for their stability in the electrical field and the results showed that both buffers tested were inherently unstable. Further, titration studies showed that the standards buffers buffered poorly at the pH employed for electrophoresis. The zwitterionic buffer buffered well at its nominal pH and was shown to be stable in the electrical field. Comparative studies of the buffer with standard cell separation buffers using formalin fixed rabbit and goose red blood cells showed that the zwitterionic buffer gave better resolution of the fixed cells. Studies with viable hybridoma cells showed that buffer Q supported cell viability equal to Hank's Balanced Salt Solution and that hybridoma cells in different stages of the growth cycle demonstrated reproducible differences in electrophoretic mobility.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. Stability of a Ag/AgCl reference electrode equipped with an ionic liquid salt bridge composed of 1-methyl-3-octylimidazolium bis(trifluoromethanesulfonyl)-amide in potentiometry of pH standard buffers.

    PubMed

    Shibata, Manabu; Yamanuki, Mikito; Iwamoto, Yasukazu; Nomura, Satoshi; Kakiuchi, Takashi

    2010-01-01

    The stability of a Ag/AgCl reference electrode equipped with a gelled ionic liquid, 1-methyl-3-octylimidazolium bis(trifluoromethanesulfonyl)amide (C(8)mimC(1)C(1)N), as a salt bridge, was examined in the potentiometry of pH standard solutions. The variation in the liquid junction potential (LJP) of the ionic liquid (IL)-type reference electrode, measured with respect to a double junction-type KCl reference electrode, was within 1 mV when one standard solution was replaced by another, except for the phthalate standard. The time course of the potential of the IL-type reference electrode showed a standard deviation of ±0.3 mV in all buffer solutions. The reproducible deviation of the potential of the IL-type reference electrode in the phthalate pH standard amounted to 5 mV. The deviation is due to the partition of the hydrogen phthalate in the C(8)mimC(1)C(1)N, influencing the phase boundary potential (PBP) across the interface between C(8)mimC(1)C(1)N and the phthalate standard. If a citrate standard is used instead of the phthalate buffer, the IL salt bridge works satisfactorily as a salt bridge for a reference electrode suitable for potentiometoric pH measurements.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Estimating the buffer capacity of forest soils

    SciTech Connect

    Hornbeck, J.W.; Federer, C.A.

    1985-11-01

    The organic-matter content of New England soils is an index of buffer capacity, and can be measured to indicate how forest soils might respond to acid precipitation. Buffer capacity, as defined herein, is the milliequivalents of H/sup +/ or OH/sup -/ that must be added to a kilogram of soil to change its pH by one unit. As such, it is an index of how soil pH will respond to H/sup +/ in acid precipitation. At four locations in New England, the buffer capacity of organic and mineral horizons for well-drained forest soils under second-growth forests and in new and regrowing clearcuts was measured. The sites included a spruce-fir forest in central Maine, two northern hardwood forests in northern New Hampshire, and a central hardwood forest in southern Connecticut. Soil materials were titrated by adding known amounts of HCl or NaOH and measuring the pH after 24 hours. Details on methods were given in this paper. 1 table.

  6. 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.

  7. 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.

  8. DISTRIBUTION OF LANTHANIDE AND ACTINIDE ELEMENTS BETWEEN BIS-(2-ETHYLHEXYL)PHOSPHORIC ACID AND BUFFERED LACTATE SOLUTIONS CONTAINING SELECTED COMPLEXANTS

    SciTech Connect

    Rudisill, Tracy S.; Diprete, David P.; Thompson, Major C.

    2013-04-15

    With the renewed interest in the closure of the nuclear fuel cycle, the TALSPEAK process is being considered for the separation of Am and Cm from the lanthanide fission products in a next generation reprocessing plant. However, an efficient separation requires tight control of the pH which likely will be difficult to achieve on a large scale. To address this issue, we measured the distribution of lanthanide and actinide elements between aqueous and organic phases in the presence of complexants which were potentially less sensitive to pH control than the diethylenetriaminepentaacetic (DTPA) used in the process. To perform the extractions, a rapid and accurate method was developed for measuring distribution coefficients based on the preparation of lanthanide tracers in the Savannah River National Laboratory neutron activation analysis facility. The complexants tested included aceto-, benzo-, and salicylhydroxamic acids, N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), and ammonium thiocyanate (NH{sub 4}SCN). The hydroxamic acids were the least effective of the complexants tested. The separation factors for TPEN and NH{sub 4}SCN were higher, especially for the heaviest lanthanides in the series; however, no conditions were identified which resulted in separations factors which consistently approached those measured for the use of DTPA.

  9. Effect of HEPES buffer on the uptake and transport of P-glycoprotein substrates and large neutral amino acids

    PubMed Central

    Luo, Shuanghui; Pal, Dhananjay; Shah, Sujay J.; Kwatra, Deep; Paturi, Kalyani D.; Mitra, Ashim. K.

    2010-01-01

    HEPES has been widely employed as an organic buffer agent in cell culture medium as well as uptake and transport experiments in vitro. However, concentrations of HEPES used in such studies vary from one laboratory to another. In this study, we investigated the effect of HEPES on the uptake and bidirectional transport of P-gp substrates employing both Caco-2 and MDCK-MDR1 cells. ATP-dependent uptake of glutamic acid was also examined. ATP production was further quantified applying ATP Determination Kit. An addition of HEPES to the cellular washing and incubation media significantly altered the uptake and transport of P-gp substrates in both Caco-2 and MDCK-MDR1 cells. Uptake of P-gp substrates substantially diminished as the HEPES concentration was raised to 25 mM. Bidirectional (A-B and B-A) transport studies revealed that permeability ratio of PappB-A to PappA-B in the presence of 25 mM HEPES was significantly higher than control. The uptake of phenylalanine is an ATP-independent process, whereas the accumulation of glutamic acid is ATP-dependent. While phenylalanine uptake remained unchanged glutamic acid uptake was elevated with the addition of HEPES. Verapamil is an inhibitor of P-gp mediated uptake, elevation of cyclosporine uptake in the presence of 5 μM verapamil was compromised by the presence of 25 mM HEPES. The results of ATP assay indicated that HEPES stimulated the production of ATP. This study suggests that the addition of HEPES in the medium modulated the energy dependent efflux and uptake processes. The effect of HEPES on P-gp mediated drug efflux and transport may provide some mechanistic insight into possible reasons for inconsistencies in the results reported from various laboratories. PMID:20163160

  10. 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.

  11. 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.

  12. [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.

  13. A study on the spectroscopy and photophysics of 4-hydroxy-3-methoxybenzoic acid in different solvents, pH and β-cyclodextrin

    NASA Astrophysics Data System (ADS)

    Stalin, T.; Rajendiran, N.

    2006-08-01

    Effect of solvents, buffer solutions of different pH and β-cyclodextrin (β-CD) on the absorption and fluorescence spectra of 4-hydroxy-3-methoxybenzoic acid (vanillic acid, HMB) have been investigated and compared with 4-hydroxy-3,5-dimethoxybenzoic acid (HDMB). The inclusion complex of β-CD with HMB is investigated by UV-vis, fluorimetry, FT-IR, 1H NMR, scanning electron microscope (SEM) and semiempirical methods. The thermodynamic parameters (Δ G, Δ H and Δ S) of inclusion process are also determined. Solvent study shows in the S 0 state, HMB is more polar than HDMB, whereas the polarity is same in the S 1 state. pH studies suggest proton transfer reactions follow the same trend in HMB and HDMB molecules. β-CD studies indicates (i) HMB forms 1:1 inclusion complex with β-CD and (ii) unusual blue shift of hydroxyl ion (dianion) in the β-CD medium confirms OH group present in the interior part of the β-CD cavity and COOH group present in the upper part of the β-CD cavity. A mechanism is proposed to explain the inclusion process.

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

    PubMed

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

    2016-02-01

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

  15. Pyrroloquinoline quinone (PQQ) is reduced to pyrroloquinoline quinol (PQQH2) by vitamin C, and PQQH2 produced is recycled to PQQ by air oxidation in buffer solution at pH 7.4.

    PubMed

    Mukai, Kazuo; Ouchi, Aya; Nagaoka, Shin-ichi; Nakano, Masahiko; Ikemoto, Kazuto

    2015-01-01

    Measurements of the reaction of sodium salt of pyrroloquinoline quinone (PQQNa2) with vitamin C (Vit C) were performed in phosphate-buffered solution (pH 7.4) at 25 °C under nitrogen atmosphere, using UV-vis spectrophotometry. The absorption spectrum of PQQNa2 decreased in intensity due to the reaction with Vit C and was changed to that of pyrroloquinoline quinol (PQQH2, a reduced form of PQQ). One molecule of PQQ was reduced by two molecules of Vit C producing a molecule of PQQH2 in the buffer solution. PQQH2, thus produced, was recycled to PQQ due to air oxidation. PQQ and Vit C coexist in many biological systems, such as vegetables, fruits, as well as in human tissues. The results obtained suggest that PQQ is reduced by Vit C and functions as an antioxidant in biological systems, because it has been reported that PQQH2 shows very high free-radical scavenging and singlet-oxygen quenching activities in buffer solutions.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. S-nitrosothiols regulate cell-surface pH buffering by airway epithelial cells during the human immune response to rhinovirus.

    PubMed

    Carraro, Silvia; Doherty, Joseph; Zaman, Khalequz; Gainov, Iain; Turner, Ronald; Vaughan, John; Hunt, John F; Márquez, Javier; Gaston, Benjamin

    2006-05-01

    Human rhinovirus infection is a common trigger for asthma exacerbations. Asthma exacerbations and rhinovirus infections are both associated with markedly decreased pH and ammonium levels in exhaled breath condensates. This observation is thought to be related, in part, to decreased activity of airway epithelial glutaminase. We studied whether direct rhinovirus infection and/or the host immune response to the infection decreased airway epithelial cell surface pH in vitro. Interferon-gamma and tumor necrosis factor-alpha, but not direct rhinovirus infection, decreased pH, an effect partly associated with decreased ammonium concentrations. This effect was 1) prevented by nitric oxide synthase inhibition; 2) independent of cyclic GMP; 3) associated with an increase in endogenous airway epithelial cell S-nitrosothiol concentration; 4) mimicked by the exogenous S-nitrosothiol, S-nitroso-N-acetyl cysteine; and 5) independent of glutaminase expression and activity. We then confirmed that decreased epithelial pH inhibits human rhinovirus replication in airway epithelial cells. These data suggest that a nitric oxide synthase-dependent host response to viral infection mediated by S-nitrosothiols, rather than direct infection itself, plays a role in decreased airway surface pH during human rhinovirus infection. This host immune response may serve to protect the lower airways from direct infection in the normal host. In patients with asthma, however, this fall in pH could be associated with the increased mucus production, augmented inflammatory cell degranulation, bronchoconstriction, and cough characteristic of an asthma exacerbation. PMID:16603595

  3. Evidence of the chemical reaction of (18)O-labelled nitrite with CO2 in aqueous buffer of neutral pH and the formation of (18)OCO by isotope ratio mass spectrometry.

    PubMed

    Tsikas, Dimitrios; Böhmer, Anke; Gros, Gerolf; Endeward, Volker

    2016-05-01

    Inorganic nitrite (NO2(-), ON-O(-) ←→ (-)O-NO) is the autoxidation product of nitric oxide (NO). Nitrite can also be formed from inorganic nitrate (ONO2(-)), the major oxidation product of NO in erythrocytes, by the catalytic action of bacterial nitrate reductase in gut and oral microflora. Nitrite can be reduced to NO by certain cellular proteins and enzymes, as well as in the gastric juice under acidic conditions. Hemoglobin, xanthine oxidoreductase and carbonic anhydrase (CA) have been reported to convert nitrite to NO. Renal CA isoforms are involved in the reabsorption of nitrite and may, therefore, play an important role in NO homeostasis. Yet, the mechanisms underlying the action of CA on nitrite are incompletely understood. The nitrate/nitrite system is regarded as a reservoir of NO. We have recently shown that nitrite reacts chemically with carbon dioxide (CO2), the regular substrate of CA. The present communication reports a stable isotope ratio mass spectrometry (IRMS) study on the reaction of NO2(-) and CO2 performed in 50 mM HEPES buffer of pH 7.4 at 37 °C. By using (18)O-labelled nitrite ((18)ON-O(-)/(-18)O-NO) and CO2 we observed formation of (18)O-labelled CO2. This finding is an unequivocal evidence of the chemical reaction of (18)ON-O(-)/(-18)O-NO with CO2. The reaction is rapid and involves nucleophilic attack of the negatively charged nitrite via one of its oxygen atoms on the partially positively charged CO2 molecule to form the putative intermediate (18)ON-O-CO2(-)/(-)O2C-(18)O-NO. The by far largest fraction of this intermediate decomposes back to (18)ON-O(-)/(-18)O-NO and CO2. A very small fraction of the intermediate, however, rearranges and finally decomposes to form (18)OCO and nitrite. This reaction is slower in the presence of an isolated erythrocytic CA isoform II. In summary, NO2(-), CO2 and CA are ubiquitous. The chemical reaction of NO2(-) with CO2 and its modulation by CA isoforms may play important roles in the transport of

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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

  9. The buffer effect in neutral electrolyte supercapacitors

    NASA Astrophysics Data System (ADS)

    Vindt, Steffen T.; Skou, Eivind M.

    2016-02-01

    The observation that double-layer capacitors based on neutral aqueous electrolytes can have significantly wider usable potential windows than those based on acidic or alkaline electrolytes is studied. This effect is explained by a local pH change taking place at the electrode surfaces, leading to a change in the redox potential of water in opposite directions on the two electrodes, resulting in the wider stability window. The magnitude of this effect is suggested to be dependent on the buffer capacity, rather than the intrinsic pH value of the electrolyte. This is confirmed by studying the impact of addition of a buffer to such systems. It is shown that a 56 % higher dynamic storage capacity may be achieved, simply by controlling the buffer capacity of the electrolyte. The model system used, is based on a well-known commercial activated carbon (NORIT™ A SUPRA) as the electrode material, aqueous potassium nitrate as the electrolyte and potassium phosphates as the buffer system.

  10. Selective detection of uric acid in the presence of ascorbic acid at physiological pH by using a beta-cyclodextrin modified copolymer of sulfanilic acid and N-acetylaniline.

    PubMed

    Wu, Shouguo; Wang, Taoling; Gao, Zongyong; Xu, Haihong; Zhou, Baineng; Wang, Chuanqin

    2008-07-15

    A beta-cyclodextrin (CD) modified copolymer membrane of sulfanilic acid (p-ASA) and N-acetylaniline (SPNAANI) on glassy carbon electrode (GCE) was prepared and used to determine uric acid (UA) in the presence of a large excess of ascorbic acid (AA) by differential pulse voltammetry (DPV). The properties of the copolymer were characterized by X-ray photoelectron spectra (XPS) and Raman spectroscopy. The oxidation peaks of AA and UA were well separated at the composite membrane modified electrode in phosphate buffer solution (PBS, pH 7.4). A linear relationship between the peak current and the concentration of UA was obtained in the range from 1.0 x 10(-5) to 3.5 x 10(-4)mol L(-1), and the detection limit was 2.7 x 10(-6)mol L(-1) at a signal-to-noise ratio of 3. Two hundred and fifty-fold excess of AA did not interfere with the determination of UA. The application of the prepared electrode was demonstrated by measuring UA in human serum samples without any pretreatment, and the results were comparatively in agreement with the spectrometric clinical assay method.

  11. 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

  12. 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.

  13. 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

  14. 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

  15. 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

  16. 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.

  17. 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

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. Effects of pH mismatch between the two dimensions of reversed-phase×reversed-phase two-dimensional separations on second dimension separation quality for ionogenic compounds-I. Carboxylic acids.

    PubMed

    Stoll, Dwight R; O'Neill, Kelly; Harmes, David C

    2015-02-27

    Two persistent impediments to wider adoption of two-dimensional liquid chromatography (2D-LC) are the perceptions that 2D methods are generally less sensitive than 1D ones, and that coupling of certain separation modes in a 2D system is difficult because of the negative impact of the effluent of the first separation on the second separation. In this work we address these problems in the specific case where reversed-phase separations are used in both dimensions of a 2D-LC system, but the pH is varied such that the ionization state of carboxylic acid analytes is different (i.e., neutral or negatively charged, in eluents buffered at pH 2 or 7) in the two columns. We first demonstrate that the effect of first dimension ((1)D) effluent on the performance of second dimension ((2)D) separation of ionogenic solutes is much more serious than it is for neutral compounds where the pH of the eluent does not play a role in retention. We have systematically varied the properties of the sample solution injected into the (2)D column (i.e., the (1)D effluent), as well as the (2)D eluent, with the goal of establishing guidelines for conditions that yield acceptable (2)D performance. We find that the organic solvent content of the (1)D effluent and (2)D eluent is not as important as the buffer concentrations in these two solutions, and that the greater the ratio of buffer concentration in the (1)D effluent relative to the (2)D eluent, the smaller the volume one can inject into the (2)D column before dramatic peak splitting occurs. We have then used the information from these simple experiments to guide both 1D experiments that mimic the (2)D separation, and actual 2D separations, to demonstrate that online adjustment of the properties of the (1)D effluent by dilution with a buffered solvent prior to injection into the (2)D column is a very effective solution to the pH mismatch problem. We find that when the buffer capacity of the diluent is high enough to effectively titrate the (1)D

  15. 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.

  16. 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.

  17. 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.

  18. [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.

  19. [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

  20. Culture of eukaryotic cells with macro-reticulate buffers: fermentation of cellulolytic fungi.

    PubMed

    Pompei, R; Lampis, G; Chiari, M; Righetti, P G

    1991-12-01

    Fermentation of fungi for large-scale production of extracellular cellulolytic enzymes requires a strict control of pH. At the lab scale, where bioreactors are not available, a culture in the exponential growth phase requires frequent manual pH adjustments. When fungi are grown in the presence of macroreticulate buffers, the culture is stable and does not require any pH control for as long as two weeks. These insoluble buffers are polyacrylamide beads (e.g., 10%T, 8%C) containing acrylamido weak acids and bases in such ratios as to unequivocally define a single pH value along the pH sale. At such pH, the macroreticulate buffers possess a strong buffering power (up to 100 milliequivalent liter-1 pH-1). In the present example, a Trichoderma sp. strain is grown in the presence of 12% beads (v/v) with an isoelectric point of 5.6, containing 100 mM of a pK 6.2 weak acrylamido base and 89 mM of a pK 4.6 weak acrylamido acid. Enzyme production (exoglucanase, endoglucanase, xylanase, beta-glucosidase) is as good as (and often better than) the control in which the pH is adjusted manually 2-3 times/day. PMID:1809319

  1. 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

  2. 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.

  3. 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.

  4. RNA extraction from various recalcitrant plant tissues with a cethyltrimethylammonium bromide-containing buffer followed by an acid guanidium thiocyanate-phenol-chloroform treatment.

    PubMed

    Suzuki, Yuji; Mae, Tadahiko; Makino, Amane

    2008-07-01

    High-quality total RNA was extracted using a cethyltrimethylammonium bromide-containing buffer followed by an acid guanidium thiocyanate-phenol-chloroform treatment from recalcitrant plant tissues such as tree leaves (pine, Norway spruce, ginkgo, Japanese cedar, rose), flowers (rose, Lotus japonicus) and storage tissues (seeds of Lotus japonicus and rice, sweet potato tuber, banana fruit). This protocol greatly reduced the time required for RNA extraction.

  5. A nitrilo-tri-acetic-acid/acetic acid route for the deposition of epitaxial cerium oxide films as high temperature superconductor buffer layers

    SciTech Connect

    Thuy, T.T.; Lommens, P.; Narayanan, V.; Van de Velde, N.; De Buysser, K.; Herman, G.G.; Cloet, V.; Van Driessche, I.

    2010-09-15

    A water based cerium oxide precursor solution using nitrilo-tri-acetic-acid (NTA) and acetic acid as complexing agents is described in detail. This precursor solution is used for the deposition of epitaxial CeO{sub 2} layers on Ni-5at%W substrates by dip-coating. The influence of the complexation behavior on the formation of transparent, homogeneous solutions and gels has been studied. It is found that ethylenediamine plays an important role in the gelification. The growth conditions for cerium oxide films were Ar-5% gas processing atmosphere, a solution concentration level of 0.25 M, a dwell time of 60 min at 900 {sup o}C and 5-30 min at 1050 {sup o}C. X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), pole figures and spectroscopic ellipsometry were used to characterize the CeO{sub 2} films with different thicknesses. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) was used to determine the carbon residue level in the surface of the cerium oxide film, which was found to be lower than 0.01%. Textured films with a thickness of 50 nm were obtained. - Graphical abstract: Study of the complexation and hydrolysis behavior of Ce{sup 4+} ions in the presence of nitrilo-tri-acetic acid and the subsequent development of an aqueous chemical solution deposition route suited for the processing of textured CeO{sub 2} buffer layers on Ni-W tapes.

  6. Rapid treatment of mild acne with a novel skin care system containing 1% salicylic acid, 10% buffered glycolic acid, and botanical ingredients.

    PubMed

    Bhatia, Ashish C; Jimenez, Felipe

    2014-06-01

    The biggest hurdle in the treatment of acne vulgaris is patient non-compliance that is due in large part to poor tolerability to common acne medications. As such, new acne treatments must be developed that balance good anti-acne efficacy with excellent tolerability in order to ensure patient adherence and by extension ensure good clinical outcomes. The goal of the present study was to determine the tolerability and efficacy of a novel skin care system, composed of a cleanser, containing 1% salicylic acid and botanical ingredients, and a treatment gel, containing 1% salicylic acid, 10% buffered glycolic acid and botanical ingredients for the treatment of mild acne. In this single-center, open-label clinical study, 25 male and female volunteers used the test cleanser and test gel twice daily over six weeks. Tolerability assessments showed that the skin care regimen was very well tolerated by all study volunteers. Acne severity was significantly reduced by two acne grades at six weeks. Inflammatory lesion counts were significantly reduced, on average, by 59.06% (P ≤ 0.0001), 91.62% (P ≤ 0.0001), 90.85% (P ≤ 0.0001) and by 98.55% (P ≤ 0.0001) at weeks 1, 2, 4, and 6, respectively. Non-inflammatory lesion counts were reduced, on average, by 13.54% (ns), 38.95% (P ≤ 0.0001), 44.48% (P ≤ 0.0001), and by 56.10% (P ≤ 0.0001) at weeks 1, 2, 4, and 6, respectively. Standardized photography also demonstrated a progressive reduction in acne lesions over time. In conclusion, results of the present study suggest that the tested skin care regimen offers rapid acne clearance and excellent tolerability that together may help to improve patient adherence as well as treatment outcome.

  7. 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.

  8. Buffer-free therapeutic antibody preparations provide a viable alternative to conventionally buffered solutions: from protein buffer capacity prediction to bioprocess applications.

    PubMed

    Bahrenburg, Sven; Karow, Anne R; Garidel, Patrick

    2015-04-01

    Protein therapeutics, including monoclonal antibodies (mAbs), have significant buffering capacity, particularly at concentrations>50 mg/mL. This report addresses pH-related issues critical to adoption of self-buffered monoclonal antibody formulations. We evaluated solution conditions with protein concentrations ranging from 50 to 250 mg/mL. Samples were both buffer-free and conventionally buffered with citrate. Samples were non-isotonic or adjusted for isotonicity with NaCl or trehalose. Studies included accelerated temperature stability tests, shaking stability studies, and pH changes in infusion media as protein concentrate is added. We present averaged buffering slopes of capacity that can be applied to any mAb and present a general method for calculating buffering capacity of buffer-free, highly concentrated antibody liquid formulations. In temperature stability tests, neither buffer-free nor conventionally buffered solution conditions showed significant pH changes. Conventionally buffered solutions showed significantly higher opalescence than buffer-free ones. In general, buffer-free solution conditions showed less aggregation than conventionally buffered solutions. Shaking stability tests showed no differences between buffer-free and conventionally buffered solutions. "In-use" preparation experiments showed that pH in infusion bag medium can rapidly approximate that of self-buffered protein concentrate as concentrate is added. In summary, the buffer capacity of proteins can be predicted and buffer-free therapeutic antibody preparations provide a viable alternative to conventionally buffered solutions. PMID:25641961

  9. Buffer-free therapeutic antibody preparations provide a viable alternative to conventionally buffered solutions: from protein buffer capacity prediction to bioprocess applications.

    PubMed

    Bahrenburg, Sven; Karow, Anne R; Garidel, Patrick

    2015-04-01

    Protein therapeutics, including monoclonal antibodies (mAbs), have significant buffering capacity, particularly at concentrations>50 mg/mL. This report addresses pH-related issues critical to adoption of self-buffered monoclonal antibody formulations. We evaluated solution conditions with protein concentrations ranging from 50 to 250 mg/mL. Samples were both buffer-free and conventionally buffered with citrate. Samples were non-isotonic or adjusted for isotonicity with NaCl or trehalose. Studies included accelerated temperature stability tests, shaking stability studies, and pH changes in infusion media as protein concentrate is added. We present averaged buffering slopes of capacity that can be applied to any mAb and present a general method for calculating buffering capacity of buffer-free, highly concentrated antibody liquid formulations. In temperature stability tests, neither buffer-free nor conventionally buffered solution conditions showed significant pH changes. Conventionally buffered solutions showed significantly higher opalescence than buffer-free ones. In general, buffer-free solution conditions showed less aggregation than conventionally buffered solutions. Shaking stability tests showed no differences between buffer-free and conventionally buffered solutions. "In-use" preparation experiments showed that pH in infusion bag medium can rapidly approximate that of self-buffered protein concentrate as concentrate is added. In summary, the buffer capacity of proteins can be predicted and buffer-free therapeutic antibody preparations provide a viable alternative to conventionally buffered solutions.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  11. 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. 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.

  14. Explaining the Spatial Variability in Stream Acid Buffering Chemistry and Aquatic Biota in the Neversink River Watershed, Catskill Mountains, New York State

    NASA Astrophysics Data System (ADS)

    Harpold, A. A.; Walter, M. T.

    2009-12-01

    The Neversink River Watershed (NRW) originates at the highest point in the Catskill Mountains and is sensitive to changing patterns in acidic deposition, precipitation, and air temperature. Despite reductions in fossil fuel emission since the Clean Air Act, past acidic deposition has accelerated the leaching of cations from the soil and reduced the stores of base cations necessary for buffering stream acidity. The goal of this study was to investigate connections between different watershed ‘features’ and the apparently complex spatial patterns of stream buffering chemistry (specifically, acid neutralizing capacity ANC and Ca concentrations) and aquatic biota (macroinvertebrate and fish populations). The ten nested NRW watersheds (2.0 km^2 to 176.0 km^2) have relatively homogeneous bedrock geology, forested cover, and soil series; therefore, we hypothesized that differing distributions of hydrological flowpaths between the watersheds control the variability in stream buffering chemistry and aquatic biota. However because the flowpath distributions are not directly measurable, this study used step-wise linear regression to develop relationships between watershed ‘features’ and buffering chemistry. The regression results showed that the mean ratio of precipitation to stream runoff (or runoff ratio) from twenty non-winter storm events explained more than 81% of the variability in mean summer ANC and Ca concentrations. The results also suggested that steeper (higher mean slope) more channelized watersheds (larger drainage density) are more susceptible to stream acidity and negative impacts on biota. A simple linear relationship (using no discharge or water chemistry measurements) was able to explain buffering chemistry and aquatic biota populations in 17 additional NRW watersheds (0.3 km^2 to 160.0 km^2), including 60-80% of the variability in macroinvertebrate populations (EPT richness and BAP) and 50-60% of the variability in fish density and species richness

  15. Analysis of acrylamido-buffers for isoelectric focusing by capillary zone electrophoresis.

    PubMed

    Righetti, P G; Ettori, C; Chiari, M

    1991-01-01

    Immobilized pH gradients use a series of weak acrylamido acids and bases (Immobiline) to create a pH gradient along the separation axis. These buffers can be degraded in water by two mechanisms: (i) hydrolysis of the amido bond, with generation of free acrylic acid and either an amino acid or a diamine; (ii) autopolymerization to oligomers and/or n-mers. In order to check for these degradation products, different capillary zone electrophoresis systems for analysis of all Immobilines have been devised. The acidic compounds are resolved in 100 mM acetate, pH 4.0, whereas the alkaline Immobilines are separated in 50 mM phosphate buffer, pH 7.7 (or pH 7.2 for the weaker species). Polymers of alkaline Immobilines are resolved in 50 mM phosphate buffer, pH 2.5, in 1% Ficoll-400. All Immobilines are detected underivatized, by their adsorption at 214 or 254 nm. A calibration curve has been constructed for quantification of acrylic acid contamination. As little as 1 mol% of acrylic acid contamination in Immobiline solutions can be detected, with a sensitivity limit below 0.2 mM (at the injection port). PMID:2050100

  16. Retention of ionizable compounds on HPLC. 4. Mobile-phase pH measurement in methanol/water

    PubMed

    Canals; Portal; Bosch; Roses

    2000-04-15

    The different procedures used in HPLC to measure the pH of a mobile phase are evaluated in terms of the rigorous IUPAC definition of pH. The three procedures evaluated are as follows: measurement of the pH of the aqueous HPLC buffer before mixing it with the organic modifier, measurement of the pH of the HPLC buffer after mixing it with the organic modifier using a pH electrode system calibrated with aqueous buffers, and measurement of the pH of the HPLC buffer after mixing it with the organic modifier but calibrating the electrode system with reference buffers prepared in the same mixed solvent used as mobile phase. Following IUPAC definitions and recommendations, the three pH values can be related with the pH scales: w(w)pH, s(w)pH, and s(s)pH, respectively. The relationships between these three pH scales are also presented. The retention of several compounds with acid/base behavior in a C-18 and a polymeric column with buffered methanol/water as mobile phase is related to the mobile phase pH value measured in the three pH scales. It is demonstrated that the s(w)pH and s(s)pH scales give better relationships than the w(w)pH scale (pH measured in the aqueous buffer before mixing it with the organic modifier), commonly used on HPLC. The s(w)pH scale is specially recommended because of its simplicity of measurement: the pH is measured after mixing the aqueous buffer with the organic modifier, but the pH calibration is performed with the common aqueous reference buffers.

  17. Computer model of unstirred layer and intracellular pH changes. Determinants of unstirred layer pH.

    PubMed

    Marrannes, Roger

    2013-06-01

    Transmembrane acid-base fluxes affect the intracellular pH and unstirred layer pH around a superfused biological preparation. In this paper the factors influencing the unstirred layer pH and its gradient are studied. An analytical expression of the unstirred layer pH gradient in steady state is derived as a function of simultaneous transmembrane fluxes of (weak) acids and bases with the dehydration reaction of carbonic acid in equilibrium. Also a multicompartment computer model is described consisting of the extracellular bulk compartment, different unstirred layer compartments and the intracellular compartment. With this model also transient changes and the influence of carbonic anhydrase (CA) can be studied. The analytical expression and simulations with the multicompartment model demonstrate that in steady state the unstirred layer pH and its gradient are influenced by the size and type of transmembrane flux of acids and bases, their dissociation constant and diffusion coefficient, the concentration, diffusion coefficient and type of mobile buffers and the activity and location of CA. Similar principles contribute to the amplitude of the unstirred layer pH transients. According to these models an immobile buffer does not influence the steady-state pH, but reduces the amplitude of pH transients especially when these are fast. The unstirred layer pH provides useful information about transmembrane acid-base fluxes. This paper gives more insight how the unstirred layer pH and its transients can be interpreted. Methodological issues are discussed. PMID:23860924

  18. Computer model of unstirred layer and intracellular pH changes. Determinants of unstirred layer pH.

    PubMed

    Marrannes, Roger

    2013-06-01

    Transmembrane acid-base fluxes affect the intracellular pH and unstirred layer pH around a superfused biological preparation. In this paper the factors influencing the unstirred layer pH and its gradient are studied. An analytical expression of the unstirred layer pH gradient in steady state is derived as a function of simultaneous transmembrane fluxes of (weak) acids and bases with the dehydration reaction of carbonic acid in equilibrium. Also a multicompartment computer model is described consisting of the extracellular bulk compartment, different unstirred layer compartments and the intracellular compartment. With this model also transient changes and the influence of carbonic anhydrase (CA) can be studied. The analytical expression and simulations with the multicompartment model demonstrate that in steady state the unstirred layer pH and its gradient are influenced by the size and type of transmembrane flux of acids and bases, their dissociation constant and diffusion coefficient, the concentration, diffusion coefficient and type of mobile buffers and the activity and location of CA. Similar principles contribute to the amplitude of the unstirred layer pH transients. According to these models an immobile buffer does not influence the steady-state pH, but reduces the amplitude of pH transients especially when these are fast. The unstirred layer pH provides useful information about transmembrane acid-base fluxes. This paper gives more insight how the unstirred layer pH and its transients can be interpreted. Methodological issues are discussed.

  19. Buffer Biology.

    ERIC Educational Resources Information Center

    Morgan, Kelly

    2000-01-01

    Presents a science experiment in which students test the buffering capacity of household products such as shampoo, hand lotion, fizzies candy, and cola. Lists the standards addressed in this experiment and gives an example of a student lab write-up. (YDS)

  20. 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.

  1. Enhancement of volatile fatty acid production by co-fermentation of food waste and excess sludge without pH control: The mechanism and microbial community analyses.

    PubMed

    Wu, Qing-Lian; Guo, Wan-Qian; Zheng, He-Shan; Luo, Hai-Chao; Feng, Xiao-Chi; Yin, Ren-Li; Ren, Nan-Qi

    2016-09-01

    The study provided a cost-effective and high-efficiency volatile fatty acid (VFA) production strategy by co-fermentation of food waste (FW) and excess sludge (ES) without artificial pH control. VFA production of 867.42mg COD/g-VS was obtained under the optimized condition: FW/ES 5, solid retention time 7d, organic loading rate 9g VS/L-d and temperature 40°C. Mechanism exploration revealed that the holistic biodegradability of substrate was greatly enhanced, and proper pH range (5.2-6.4) was formed by the high buffering capacity of the co-fermentation system itself, which effectively enhanced hydrolysis yield (63.04%) and acidification yield (83.46%) and inhibited methanogenesis. Moreover, microbial community analysis manifested that co-fermentation raised the relative abundances of hydrolytic and acidogenic bacteria including Clostridium, Sporanaerobacter, Tissierella and Bacillus, but suppressed the methanogen Anaerolineae, which also facilitated high VFA production. These results were of great guiding significance aiming for VFA recovery from FW and ES in large-scale. PMID:27289056

  2. Influence of assembling pH on the stability of poly(L-glutamic acid) and poly(L-lysine) multilayers against urea treatment.

    PubMed

    Zhou, Jie; Wang, Bo; Tong, Weijun; Maltseva, Elena; Zhang, Gang; Krastev, Rumen; Gao, Changyou; Möhwald, Helmuth; Shen, Jiacong

    2008-04-01

    Polyelectrolyte multilayers of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) were built up using the layer-by-layer (LbL) technique in low pH (3.6, PM3.6) and in neutral pH (7.4, PM7.4) solutions. The multilayers were then treated with a concentrated urea (one kind of denaturant for proteins and polypeptides) solution (8M) and rinsed with corresponding buffer. The buildup and treatment processes were investigated by ultraviolet visible spectroscopy and ellipsometry. The surface morphology was observed by scanning force microscopy (SFM). The inner structures were determined by X-ray reflectometry and circular dichroism spectroscopy (CD). An exponential growth of the optical mass and the layer thickness was observed for both PM3.6 and PM7.4. After urea treatment, a significant mass loss for PM3.6 was found, while no mass change was recorded for PM7.4. The dominant driving force for PM7.4 is electrostatic interaction, resulting in multilayers with an abundant beta-sheet structure, which has higher stability against urea treatment. By contrast, the dominant driving force for PM3.6 is hydrogen bonding and hydrophobic interaction, which are sensitive to the urea treatment. The mechanism is substantiated by molecular mechanics calculation. This has offered a convenient pathway to mediate the multilayer properties, which is of great importance for potential applications.

  3. 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.

  4. Effects of buffered vinegar and sodium dodecyl sulfate plus levulinic acid on Salmonella Typhimurium survival, shelf-life, and sensory characteristics of ground beef patties.

    PubMed

    Stelzleni, Alexander M; Ponrajan, Amudhan; Harrison, Mark A

    2013-09-01

    The inclusion of two sources of buffered vinegar and sodium dodecyl sulfate plus levulinic acid were studied as interventions for Salmonella Typhimurium and for their effect on shelf-life and sensory characteristics of ground beef. For the Salmonella challenge, beef trimmings (80/20) were inoculated then treated with 2% (w/v) liquid buffered vinegar (LVIN), 2.5% (w/w) powdered buffered vinegar (PVIN), a solution containing 1.0% levulinic acid plus 0.1% sodium dodecyl sulfate (SDLA) at 10% (w/v), or had no intervention applied (CNT). The same trim source and production methods were followed during production of patties for shelf-life and sensory testing without inoculation. SDLA patties had the largest reduction (P<0.05; 0.70 log CFU/g) of Salmonella. However, LVIN and PVIN had the least (P<0.05) psychrotrophic growth. SDLA patties had more purge (P<0.05) and lower (P<0.05) subjective color scores. There were not large differences in sensory characteristics, except PVIN exhibited stronger off-flavor (P<0.05).

  5. In vitro dissolution of proton-pump inhibitor products intended for paediatric and geriatric use in physiological bicarbonate buffer.

    PubMed

    Liu, Fang; Shokrollahi, Honaz

    2015-05-15

    Proton-pump inhibitor (PPI) products based on enteric coated multiparticulates are design to meet the needs of patients who cannot swallow tablets such as children and older adults. Enteric coated PPI preparations exhibit delays in in vivo absorption and onset of antisecretory effects, which is not reflected by the rapid in vitro dissolution in compendial pH 6.8 phosphate buffer commonly used for assessment of these products. A more representative and physiological medium, pH 6.8 mHanks bicarbonate buffer, was used in this study to evaluate the in vitro dissolution of enteric coated multiparticulate-based PPI products. Commercially available omeprazole, lansoprazole and esomeprazole products were subject to dissolution tests using USP-II apparatus in pH 4.5 phosphate buffer saline for 45 min (acid stage) followed by pH 6.8 phosphate buffer or pH 6.8 mHanks bicarbonate buffer. In pH 6.8 phosphate buffer, all nine tested products displayed rapid and comparable dissolution profiles meeting the pharmacopeia requirements for delayed release preparations. In pH 6.8 mHanks buffer, drug release was delayed and failed the pharmacopeia requirements from most enteric coated preparations. Despite that the same enteric polymer, methacrylic acid-ethyl acrylate copolymer (1:1), was applied to all commercial multiparticulate-based products, marked differences were observed between dissolution profiles of these preparations. The use of pH 6.8 physiological bicarbonate (mHanks) buffer can serve as a useful tool to provide realistic and discriminative in vitro release assessment of enteric coated PPI preparations and to assist rational formulation development of these products. PMID:25746736

  6. In vitro dissolution of proton-pump inhibitor products intended for paediatric and geriatric use in physiological bicarbonate buffer.

    PubMed

    Liu, Fang; Shokrollahi, Honaz

    2015-05-15

    Proton-pump inhibitor (PPI) products based on enteric coated multiparticulates are design to meet the needs of patients who cannot swallow tablets such as children and older adults. Enteric coated PPI preparations exhibit delays in in vivo absorption and onset of antisecretory effects, which is not reflected by the rapid in vitro dissolution in compendial pH 6.8 phosphate buffer commonly used for assessment of these products. A more representative and physiological medium, pH 6.8 mHanks bicarbonate buffer, was used in this study to evaluate the in vitro dissolution of enteric coated multiparticulate-based PPI products. Commercially available omeprazole, lansoprazole and esomeprazole products were subject to dissolution tests using USP-II apparatus in pH 4.5 phosphate buffer saline for 45 min (acid stage) followed by pH 6.8 phosphate buffer or pH 6.8 mHanks bicarbonate buffer. In pH 6.8 phosphate buffer, all nine tested products displayed rapid and comparable dissolution profiles meeting the pharmacopeia requirements for delayed release preparations. In pH 6.8 mHanks buffer, drug release was delayed and failed the pharmacopeia requirements from most enteric coated preparations. Despite that the same enteric polymer, methacrylic acid-ethyl acrylate copolymer (1:1), was applied to all commercial multiparticulate-based products, marked differences were observed between dissolution profiles of these preparations. The use of pH 6.8 physiological bicarbonate (mHanks) buffer can serve as a useful tool to provide realistic and discriminative in vitro release assessment of enteric coated PPI preparations and to assist rational formulation development of these products.

  7. Buffering dissociation/formation reaction of biogenic calcium carbonate.

    PubMed

    Ichikawa, Kazuhiko

    2007-01-01

    The oscillating stability of coral reef seawater pH has been maintained at around physiological pH values over the past 300 years (Pelejero et al., 2005). The stability mechanism of its pH has been interpreted in terms of the buffering dissolution/formation reaction of CaCO(3) as well as the proton consumption/generation reaction in CaCO(3)-saturated water. Here the pH-dependent solubility product [HCO(3)(-)][Ca(2+)] has been derived on the basis of the actual pH-dependent reactions for the atmospheric CO(2)/CO(2 (aq.))/HCO(3)(-)/CO(3)(2-)/Ca(2+)/CaCO(3) system. Overbasic pH peaks appeared between pH approximately 8 and approximately 9.5 during sodium hydroxide titration, as a result of simultaneous CaCO(3) formation and proton generation. The spontaneous and prompt water pH recovery from the acidic to the physiological range has been confirmed by the observation of acid/base time evolution, because of simultaneous CaCO(3) dissolution and proton consumption. The dissolution/formation of CaCO(3) in water at pH 7.5-9 does not take place without a proton consumption/generation reaction, or a buffering chemical reaction of HCO(3)(-)+Ca(2+)right arrow over left arrowCaCO(3)+H(+). SEM images of the CaCO(3) fragments showed that the acid water ate away at the CaCO(3) formed at physiological pH values. Natural coral reefs can thus recover the physiological pH levels of seawater from the acidic range through partial dissolution of their own skeletons.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. [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

  17. [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

  18. Peak distortion in the column liquid chromatographic determination of omeprazole dissolved in borax buffer.

    PubMed

    Arvidsson, T; Collijn, E; Tivert, A M; Rosén, L

    1991-11-22

    Injection of a sample containing omeprazole dissolved in borax buffer (pH 9.2) into a reversed-phase liquid chromatographic system consisting of a mixture of acetonitrile and phosphate buffer (pH 7.6) as the mobile phase and a C18 surface-modified silica as the solid phase resulted under special conditions in split peaks of omeprazole. The degree of peak split and the retention time of omeprazole varied with the concentration of borax in the sample solution and the ionic strength of the mobile phase buffer as well as with the column used. Borax is eluted from the column in a broad zone starting from the void volume of the column. The retention is probably due to the presence of polyborate ions. The size of the zone varies with the concentration of borax in the sample injected. In the borax zone the pH is increased compared with the pH of the mobile phase, and when omeprazole (a weak acid) is co-eluting in the borax zone its retention is affected. In the front part and in the back part of the borax zone, pH gradients are formed, and these gradients can induce the peak splitting. When the dissolving medium is changed to a phosphate buffer or an ammonium buffer at pH 9 no peak distortion of omeprazole is observed.

  19. 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

  20. 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

  1. 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.

  2. 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

  3. Cell wall pH and auxin transport velocity

    NASA Technical Reports Server (NTRS)

    Hasenstein, K. H.; Rayle, D.

    1984-01-01

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

  4. Intrinsic hydrogen ion buffering in rat CNS neurones maintained in culture.

    PubMed

    Amos, B J; Richards, C D

    1996-03-01

    The intrinsic proton buffering power (beta 1) of individual rat hippocampal and neocortical neurones maintained in culture has been investigated using the fluorescent dye 2', 7'-bis(carboxymethyl)-5, 6-(carboxyfluorescein) (BCECF). The steady-state intracellular pH (pH1) was estimated to be 7.03 +/- 0.04 (n = 22) in Hepes-buffered media and beta 1 estimated from the addition and removal of weak bases was ca 10 mM (pH unit)-1 at pH1 values near to 7. Estimates of beta 1 made from butyric acid challenges were inconsistent with estimates made at the same pH1, using NH4Cl withdrawal. However, estimating beta 1 with butyrate in the presence of the monocarboxylate ion transport inhibitor alpha-cyano-hydroxy-cinnamate (CHC) yielded beta 1 values commensurate with those measured using NH4Cl. Application of CHC alone lead to a rapid fall in pH1, suggesting a significant contribution of the monocarboxylate transporter to pH1 regulation. beta 1 was also estimated from a step increase in extracellular P(CO2). This yielded a value of 11 mM at an average pH1 of 7.1, which is similar to that of the other estimates reported here. beta 1 was found to increase with decreasing pH1: each unit drop in pH1 increased buffering power by about 60%. Blockade of pH1 regulation did not significantly affect estimates of beta 1. The change in buffering power with pH could be closely modelled from the known concentrations of free amino acids and organic phosphates. PMID:8845140

  5. Electrodialysis operation with buffer solution

    DOEpatents

    Hryn, John N.; Daniels, Edward J.; Krumdick, Greg K.

    2009-12-15

    A new method for improving the efficiency of electrodialysis (ED) cells and stacks, in particular those used in chemical synthesis. The process entails adding a buffer solution to the stack for subsequent depletion in the stack during electrolysis. The buffer solution is regenerated continuously after depletion. This buffer process serves to control the hydrogen ion or hydroxide ion concentration so as to protect the active sites of electrodialysis membranes. The process enables electrodialysis processing options for products that are sensitive to pH changes.

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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 w