Showing papers on "Buffer solution published in 1990"
TL;DR: The results support the concept that the apatite phase on the surface of glass-ceramic A-W is formed by a chemical reaction of the glass- Aceramic with the Ca2+, HPO4(2-), and OH- ions in the body fluid.
Abstract: High-strength bioactive glass-ceramic A-W was soaked in various acellular aqueous solutions different in ion concentrations and pH. After soaking for 7 and 30 days, surface structural changes of the glass-ceramic were investigated by means of Fourier transform infrared reflection spectroscopy, thin-film x-ray diffraction, and scanning electronmicroscopic observations, in comparison with in vivo surface structural changes. So-called Tris buffer solution, pure water buffered with trishydroxymethyl-aminomethane, which had been used by various workers as a "simulated body fluid," did not reproduce the in vivo surface structural changes, i.e., apatite formation on the surface. A solution, ion concentrations and pH of which are almost equal to those of the human blood plasma--i.e., Na+ 142.0, K+ 5.0, Mg2+ 1.5, Ca2+ 2.5, Cl- 148.8, HCO3- 4.2 and PO4(2-) 1.0 mM and buffered at pH 7.25 with the trishydroxymethyl-aminomethane--most precisely reproduced in vivo surface structure change. This shows that careful selection of simulated body fluid is required for in vitro experiments. The results also support the concept that the apatite phase on the surface of glass-ceramic A-W is formed by a chemical reaction of the glass-ceramic with the Ca2+, HPO4(2-), and OH- ions in the body fluid.
3,597 citations
TL;DR: The quality of a buffer is dependent on its buffering capacity and its ability to maintain a stable pH upon dilution or addition of neutral salts as discussed by the authors, and there are many factors that must be considered when choosing a buffer.
Abstract: Publisher Summary Biochemical processes can be severely affected by minute changes in hydrogen ion concentrations. At the same time, many protons may be consumed or released during an enzymatic reaction. It has become increasingly important to find buffers to stabilize hydrogen ion concentrations while not interfering with the function of the enzyme being examined. The quality of a buffer is dependent on its buffering capacity and its ability to maintain a stable pH upon dilution or addition of neutral salts. There are many factors that must be considered when choosing a buffer. When studying an enzyme, the pH optimum of the enzyme, nonspecific buffer effects on the enzyme, and interactions with substrates or metals must be considered. When purifying a protein, cost becomes an important consideration, as does the compatibility of the buffer with different purification techniques. The good buffers have been shown to be relatively free of side effects. However, inorganic buffers do have a high potential for specific buffer effects. Many enzymes are inhibited by phosphate buffer, including carboxypeptidase, urease, as well as many kinases and dehydrogenases.
220 citations
TL;DR: In this article, the open circuit potential of an electrochemically grown iridium oxide film is measured and shows a pH sensitivity between −60 and −80 mV/pH.
Abstract: The open-circuit potential of an electrochemically grown iridium oxide film is measured and shows a pH sensitivity between −60 and −80 mV/pH. This sensitivity is found to depend on the state of oxidation of the iridium oxide film; for a higher state of oxidation (or more of the oxide in the high valence state), the sensitivity is also higher. This high sensitivity can be explained on the basis of the extra proton release as a result of the acidic character of the porous hydrous oxyhydroxide, in combination with the redox behaviour.
The response time to a pH step is measured and is found to depend mainly on the thickness of the oxide; it varies from 40 ms to 0.35 s due to the porous nature of the film.
Drift measurements show that an iridium oxide film in reduced state is slowly oxidized by dissolved oxygen, whereas a pre-oxidized film in a pH = 4.01 buffer solution in contact with air shows a long-term drift of <0.3 mV/h.
148 citations
TL;DR: In this article, a point defect model for the passive film was proposed to reproduce the experimental impedance at frequencies from 10 kHz to 1 mHz, at pH values from 9 to 11, and at applied voltages of 0.l and 0.5 V/sce.
102 citations
TL;DR: The hydrogen ion concentration in the vicinity of DNA was mapped out within the Poisson-Boltzmann approximation and three regions of high H+ concentration are predicted: one throughout the minor groove of DNA and two localized in the major groove near N7 of guanine and C5 of cytosine for a G.C base pair.
Abstract: The hydrogen ion concentration in the vicinity of DNA was mapped out within the Poisson-Boltzmann approximation. Experimental conditions were modeled by assuming Na-DNA to be solvated in a buffer solution containing 45 mM Tris and 3 mM Mg cations at pH 7.5. Three regions of high H+ concentration (greater than 10 microM) are predicted: one throughout the minor groove of DNA and two localized in the major groove near N7 of guanine and C5 of cytosine for a G.C base pair. These acidic domains correlate well with the observed covalent binding sites of benzo[a]pyrene epoxide (N2 of guanine) and of aflatoxin B1 epoxide (N7 of guanine), chemical carcinogens that presumably undergo acid catalysis to form highly reactive carbocations that ultimately bind to DNA. It is suggested that these regions of high H+ concentration may also be of concern in understanding interactions involving proteins and noncarcinogenic molecules with or near nucleic acids.
75 citations
TL;DR: In this article, a self-assembled monolayer of organic material is used to impart pH-dependent electrostatic-based recognition capability to an Au electrode, and the results show that 4-aminothiophenol and related mercaptans change the surface characteristics of naked Au toward the adsorption of positively and negatively charged ions as a function of pH.
Abstract: A single, self-assembled monolayer of organic material is used to impart pH-dependent electrostatic-based recognition capability to an Au electrode. The results show that 4-aminothiophenol and related mercaptans change the surface characteristics of naked Au toward the adsorption of positively and negatively charged ions as a function of pH. For example, anthraquinone-2,6-disulfonate irreversibly adsorbs to naked Au surfaces over a broad range of pH. However, a preadsorbed monolayer of 4-aminothiophenol prevents adsorption of anthraquinone-2,6-disulfonate at high pH but electrostatically binds it at low pH. The principle of pH-dependent binding is general for a number of amine-, carboxylic acid-, and pyridine-terminated mercaptan derivatives adsorbed to Au surfaces.
72 citations
TL;DR: In this article, the effect of buffer cation on mobility, resolution and selectivity in capillary zone electrophoresis was investigated and the results showed that mobility times of analyte increased with increasing cation size Cs+Rb+K+Na+Li+.
Abstract: The effect of the buffer cation on mobility, resolution and selectivity in capillary zone electrophoresis was investigated. The results show that mobility times of analyte increased with increasing cation size Cs+Rb+K+Na+Li+. The increase in mobility times was verified by measuring the electroosmotic flows of benzene, mesityl oxide and guanosine in the five alkali buffers. The results show that electroosmotic flows of the three above markers decreased as the cation size increased. The separation of a test mixture of nine dansylated amino acids was better when 0.1 H cesium acetate solution was used rather than lithium acetate. Also, there was no change in the order of elution of the solutes in the test mixture in the five acetate solutions having the same pH and concentration. It was observed that at the same applied voltage (20 kV) the resulting current increased as the atomic weight of the cation increased, which is expected based on charge/size distribution.
62 citations
TL;DR: In this article, reaction rate constants for the hydrolysis of organic esters and amides were determined at temperatures of 100-240°C in aqueous solutions buffered at pH values between 5.5 and 7.3.
Abstract: Reaction rate constants for the hydrolysis of organic esters and amides were determined at temperatures of 100–240°C in aqueous solutions buffered at pH values between 5.5 and 7.3. Experiments are modeled assuming alkaline hydrolysis with a thermodynamic solution model included to account for the temperature dependence of hydroxide ion concentration. In most cases, the ester hydrolysis second order rate constants agree well with published values from experiments in strongly basic solutions at pH values from 11 to 14 and temperatures from 25–80°C, despite the large extrapolations required to compare the data sets. The amide hydrolysis rate constants are about one order of magnitude higher than the extrapolated results from other investigators, but the reaction rate increased proportionally with hydroxide ion concentration, suggesting that an alkaline hydrolysis mechanism is also appropriate. These data establish the validity of the alkaline hydrolysis mechanism and can be used to predict hydrolysis reaction rates in neutrally-buffered solutions such as many groundwater and geothermal fluids.
53 citations
TL;DR: Affinity chromatography is one of the most powerful procedures that can be applied to protein purification and the solvent system chosen for the entire affinity chromatography separation is also a critical factor to a good separation.
Abstract: Publisher Summary Affinity chromatography is one of the most powerful procedures that can be applied to protein purification. The solvent system chosen for the entire affinity chromatography separation is also a critical factor to a good separation. The solvent should not degrade the sample. After choosing the affinity gel type, the resin (gel) is prepared for use. The manufacturer usually supplies the instructions needed to prepare the gel correctly. If the gel is supplied in a preswollen state, reconstituting the gel is unnecessary to obtain the full swollen volume. A wash is all that is usually required. The swollen gel is typically supplied in glycerin or similar material, which is used to help in the gel preparation and to stabilize the ligand or activated coupling complex. If the gel needs to be swollen to regain full working volume, then a swelling buffer is used prior to washing. This buffer is often a low concentration phosphate buffer (0.1 M) at or near neutral pH. Swelling times vary between 15 min and 1 hr. After swelling, the gel is washed in the buffer solution used for swelling, distilled water, or starting buffer.
51 citations
TL;DR: The in vitro degradation of glycine-DL-lactic acid copolymers was studied and it was concluded that the degradation was best described by hydrolysis of ester bonds via a bulk erosion process, autocatalyzed by the generated carboxylic acid end groups.
Abstract: The in vitro degradation of glycine-DL-lactic acid copolymers was studied as a function of the composition. These polydepsipeptides were prepared by ring-opening copolymerization of 6-methyl-2,5-morpholinedione and DL-lactide. The degradation of discs of the copolymers was performed in a phosphate buffer at pH 7.4 and 37°C. The decrease in molecular weight and weight was determined until complete weight loss had occurred. Poly(DL-lactide) was used as a reference material. All (co)-polymers show an immediate decrease in molecular weight, whereas the weight remains almost unchanged during a longer period of time. Decrease in weight started earlier as the glycine content of the copolymer increased. The lactic acid content of the residual material increased during the weight loss showing a higher solubility of polymer fragments with a relatively high content of glycine residues. From the hydrolysis constants it was concluded that the degradation was best described by hydrolysis of ester bonds via a bulk erosion process, autocatalyzed by the generated carboxylic acid end groups. The rate constants varied from 4-7 × 10-2 (day-1) for all (co)polymers. All (co)polymers show an increase in the molecular weight distribution upon weight loss.
47 citations
TL;DR: The simultaneous determination of salicylic acid in binary and/or ternary mixtures and its two main urinary metabolites is proposed.
Abstract: The simultaneous determination of salicylic acid in binary and/or ternary mixtures and its two main urinary metabolites is proposed. Mixtures of salicylic, salicyluric and gentisic acids are resolved by synchronous spectrofluorimetry, in combination with first-derivative measurements. The urine is extracted with diethyl ether in acid medium. Salicylic and salicyluric acids are re-extracted into glycine-sodium hydroxide buffer solution of pH 11.6 and determined at that pH, and salicylic and gentisic acids are re-extracted into boric acid-sodium hydroxide buffer solution of pH 8.5 and determined at pH 6.
TL;DR: A mathematical model describing the passive transmembrane distribution of permeant species and the expected equilibrium values of these electrochemical parameters were calculated by solving (numerically) the three model equations.
Abstract: 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.
TL;DR: The results indicate that the presence of a low-pH compartment indeed facilitates the dissociation of mixed micelles made of taurocholate and oleic acid in an asymptotic fashion.
Abstract: The presence of a mucin layer on the surface of the intestinal epithelium has been suggested as an important factor in maintaining an acidic microclimate The presence of such a low-pH compartment has been shown to facilitate fatty acid uptake The mechanisms leading to the enhancement of fatty acid uptake were investigated in a purified acidic mucin layer Our results indicate that the presence of a low-pH compartment indeed facilitates the dissociation of mixed micelles made of taurocholate and oleic acid The released fatty acid formed an emulsion at the mucin layer, and this event could be visualized by the naked eye When the size of the particles in the micelle solution was examined by photon correlation spectroscopy, it was found that acidification alone can lead to the formation of particles with size substantially greater than that of micelles With the use of labeled fatty acid, the change in optical density can be correlated to the amount of fatty acid appearing in the mucin layer in an asymptotic fashion, suggesting that using the turbidity as an indicator might underestimate fatty acid diffusion Despite this limitation, the rate of fatty acid diffusion in the mucin layer was estimated to be 400% of that in the buffer solution
TL;DR: In this paper, the effect of buffer type on mobility, selectivity and resolution in capillary zone electrophoresis (CZE) was studied, and the results showed that the sodium phosphate buffer gave shorter mobility times (tM) for a test dansyl amino acid mixture than the potassium phosphate buffer having the same concentration and pH.
Abstract: The effect of buffer type on mobility, selectivity and resolution in capillary zone electrophoresis (CZE) was studied. The results show that the sodium phosphate buffer gave shorter mobility times (tM) for a test dansyl amino acid mixture than the potassium phosphate buffer having the same concentration and pH. The resolution and selectivity were also better using the sodium phosphate buffer. A comparison of resolution, tM and selectivity using a monohydrogen and a dihydrogen sodium phosphate buffer (0. 1 M, pH 7. 0) showed no appreciable differences in selectivity and resolution, but the dihydrogen phosphate buffer gave tM which are almost 45% shorter than those obtained with the monohydrogen phosphate buffer. When monohydrogen and dihydrogen potassium phosphate (0. 1 M, pH 7) were used, differences in tM, selectivity and resolution were observed. Resolution improved with an increase in the buffer concentration (0. 2 M vs. 0. 1 M) but worsened and tM got considerably shorter when the concentrati...
TL;DR: Guanine was determined at the 5.0×10−10 −2 level by differential-pulse adsorptive stripping voltammetry at a hanging mercury drop electrode using the reduction peak of its copper (II) complex at −0.21 V vs. Ag-AgCl electrode as discussed by the authors.
Abstract: Guanine is determined at the 5.0×10−10 −2.0×10−7 mol/l level by differential-pulse adsorptive stripping voltammetry at a hanging mercury drop electrode using the reduction peak of its copper (II) complex at −0.21 V vs. Ag-AgCl electrode. The optimum analytical conditions were found to be Britton-Robinson buffer solution (pH 4.8), an accumulation potential of 0.0 V and an accumulation time of 3 min. Under these conditions, the detection limit is 5.0×10−10 mol/l and the relative standard deviation 2.6% for 1.0×10−7 mol/l guanine. The method is compared with the previous voltammetric methods. The presence of some purine derivatives does not interfere.
Journal Article•
TL;DR: Cyclodextrin sandwiched porphyrin catalysed epoxidation of hydrophobic alkenes in an aqueous buffer solution.
Abstract: Cyclodextrin sandwiched porphyrin catalysed epoxidation of hydrophobic alkenes in an aqueous buffer solution
TL;DR: Secreted levels of lysozyme were maximal in the 50–100 mm range of added phosphate buffer although mycelial yields were reduced by one third of mycelia yields in medium unsupplemented with phosphate buffer.
Abstract: Aspergillus niger was grown in batch culture containing various initial concentrations of sodium phosphate buffer (pH 6.5). A wild-type strain of A. niger and a transformed strain producing hen egg-white lysozyme were studied. The maximum cell yield was attained in medium not supplemented with phosphate. In those cultures acidification of the medium resulted in a minimum of pH 2.0 before reverting to near neutrality. Increasing the initial levels of phosphate buffer reduced the fall in pH but lowered cell yields. Secreted levels of lysozyme were maximal in the 50–100 mm range of added phosphate buffer although mycelial yields were reduced by one third of mycelial yields in medium unsupplemented with phosphate buffer.
TL;DR: In this paper, the authors performed extensive measurements of the heat-capacity changes accompanying the unfolding transition of bovine pancreatic ribonuclease A in buffered aqueous solutions in a differential scanning calorimeter over a range of experimental conditions.
TL;DR: By determining the degradation rate of I at various pH values, it was found that I was most stable at around pH 4.0, while the solubility of I in aqueous solution was more than 10 mg/ml, and I in the solid state was found to be amorphous.
Abstract: The stability and some physicochemical properties of a novel hexapeptide, (Me)Arg-Lys-Pro-Trp-tert-Leu-Leu-OEt (I), with neurotensin activity, were investigated. The degradation of I in aqueous solution was observed as a pseudo-first order reaction. By determining the degradation rate of I at various pH values, it was found that I was most stable at around pH 4. The activation energies of the degradation in aqueous solutions at pH 2.2, 6.1, 7.0 and 8.0 were 16.3, 22.2, 23.9 and 24.2 kcal/mol, respectively. The enzymatic hydrolysis of I was studied in vitro with a porcine liver esterase at 37 degrees C. The degradation of I in this system was observed as a pseudo-first order reaction. The degradation rate of I in the presence of the esterase was about 10000 times larger than the rate in a buffer solution. I in the solid state was stable under 65 degrees C and labilized by strong light and/or high humidity. The pKa1, pKa2 and pKa3 of I were 7.1, 10.0 and 11.3, respectively. The partition coefficients between n-octanol and the buffer solution at pH values ranging from 2 to 11 were measured. The partition coefficient increased with the increase of the pH value. But the value at pH 7.0 was 2.10 x 10(-2), which was very low. The solubility of I in aqueous solution was more than 10 mg/ml. From the results of the powder X-ray diffraction pattern, I in the solid state was found to be amorphous. The dissolution rates in the 1st and 2nd fluid of JPXI at 37 degrees C and 100 rpm were 19.4 and 9.0 mg/cm2.min, respectively.
TL;DR: It was found that the interfacial pressures of these polymer surfaces were drastically lowered by immobilizing the peptides, RGDS and GGGRGDS.
Abstract: Tetrapeptide Arg-Gly-Asp-Ser (RGDS) exhibiting cell-attachment activity was immobilized to poly(vinyl alcohol) (PVA), and to ethylene-acrylic acid copolymer (PEA) conaining 2.84 mol% acrylic acid. RGDS was also immobilized to PEA via Gly-Gly-Gly (GGG) as a spacer. Adsorption behaviors of plasma proteins, albumin and γ-globulin, on these peptide-immobilized PVA and PEA surfaces were examined in phosphate buffer solution by means of interfacial pressure. It was found that the interfacial pressures of these polymer surfaces were drastically lowered by immobilizing the peptides, RGDS and GGGRGDS.
Patent•
08 Jan 1990
TL;DR: In this paper, a method for preparing a highly purified lysozyme dimer product which comprises dimerizing the Lysozyme monomer with a suberimidate coupling reagent in a buffer solution adjusted to pH 10, stopping the dimerization at a given point by lowering the pH to 7 via addition of HCl or other suitable acid solution.
Abstract: A method is provided for preparing a highly purified lysozyme dimer product which comprises dimerizing the lysozyme monomer with a suberimidate coupling reagent in a buffer solution adjusted to pH 10, stopping the dimerization at a given point by lowering the pH to 7 via addition of HCl or other suitable acid solution, and purifying the dimeric lysozyme by a series of elution steps carried out using ion exchange resin column chromatography Monomeric lysozyme remaining undimerized by the initial dimerization step is recycled into the process in order to increase yield The present system is advantageous in that large amounts of purified lysozyme dimer can be prepared efficiently and relatively inexpensively, and the lysozyme dimer so produced is useful in treating viral and/or bacterial diseases without causing the cytotoxic effects associated with the lysozyme monomer
TL;DR: In this paper, the application of a hanging mercury drop electrode, modified by adsorption of poly-L-histidine, to the determination of CuII in aqueous solutions has been studied.
Abstract: The application of a hanging mercury drop electrode, modified by adsorption of poly-L-histidine, to the determination of CuII in aqueous solutions has been studied. Selective and rapid pre-concentration of CuII on the poly-L-histidine film was observed, even from dilute and quiescent solutions. Copper(II) was determined by differential-pulse adsorptive stripping voltammetry between 5 × 10–9 and 4 × 10–7M after a 2-min accumulation time, using the reduction peak of its complex, at –0.4 V versus an Ag-AgCl reference electrode, obtained in acetate buffer solution of pH 4.5. No significant interference was observed from 1 × 10–6M levels of ethylenediaminetetraacetic acid, chromium(III), lead(II), nickel(II), cadmium(II) and manganese(II).
TL;DR: In this paper, the electrocatalytic behavior of H2O2 oxidation at a cobalt protoporphyrin modified pyrolytic graphite electrode (CoPP/PG) in various pH buffer solutions has been investigated.
TL;DR: The effects of mobile phase composition on the reversed-phase separation of several dipeptide and tripeptides with a gamma-cyclodextrin-bonded-phase column have been studied and the presence of Cu(II) salt in the mobile phase allows further modifications of separation selectivity.
TL;DR: Une microbalance electrochimique a cristal de quartz is utilisee for etudier le depot de Pb(II) sur des electrodes d'or et d'argent dans des solutions de borate for des pH de 8 a 10,5 as discussed by the authors.
Abstract: Une microbalance electrochimique a cristal de quartz est utilisee pour etudier le depot de Pb(II) sur des electrodes d'or et d'argent dans des solutions de borate pour des pH de 8 a 10,5
TL;DR: In this paper, the reduction at the mercury electrode of midazolam, (7-chloro-5-(O-fluorophenyl)-3H-(2'-methylimidazo) [1,5-a][1,4]-benzodiazepine has been examined by means of pulse voltammetry with a graphical method of analysis of the data.
Patent•
19 Apr 1990TL;DR: A gel electrophoresis/electro-blot transfer apparatus comprising a buffer tank having a upper and lower section adapted to maintain a buffer solution, a support frame for supporting a gel slab, a first member for securing the gel slab in a substantially vertical direction in the support frame, a second member for supporting the filter paper, gel slab and a blotter membrane in intimate contact with support frame as mentioned in this paper.
Abstract: A gel electrophoresis/electro-blot transfer apparatus comprising a buffer tank having a upper and lower section adapted to maintain a buffer solution, a support frame for supporting a gel slab, a first member for securing the gel slab in a substantially vertical direction in the support frame, a support frame for supporting a filter paper, gel slab, and a blotter membrane, a second member for securing the filter paper, gel slab, and membrane in intimate contact with the support frame. Assembly of the buffer tank, support frame, and securing means or the buffer tank and electro-blot support frame forms an upper buffer solution reservoir and a lower buffer solution reservoir substantially isolated from each other. The upper buffer solution reservoir and the lower buffer solution reservoir are electrically connected so that electrophoresis or electro-blot transfer can be performed.
TL;DR: In this paper, the authors investigated the survival and death of Chara internodal cells in one of the alkali metal salts KCl, some alkali earth metal salts CaCl2, Ca(NO3)2, MgCl2 and BaCl2 solutions of higher concentrations, calcium buffer solutions of pCa 6.0 and pCa 5.0, and deionized water.
Abstract: . Survival and death of Chara internodal cells were investigated in one of the alkali metal salts KCl, some of the alkali earth metal salts CaCl2, Ca(NO3)2, MgCl2, Mg(NO3)2, SrCl2, Sr(NO3)2, BaCl2 and Ba(NO3)2, potassium phosphate pH buffer solution (pH 7.0), Tris-maleate pH buffer solution (pH 7.0), HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulphonic acid)-KOH (pH 7.0) pH buffer solution, calcium buffer solutions, and deionized water. Most of the internodal cells died within a day or a few days in KCl, MgCl2, Mg(NO3)2, BaCl2 and Ba(NO3)2 solutions of higher concentrations, calcium buffer solutions of pCa 6.0, 10.0 mol m-3 potassium phosphate pH buffer solution and 10.0 mol m-3 Trismaleate pH buffer solution. However, all of the internodal cells survived more than 10 d in deionized water, 80.0 mol m-3 CaCl2, 80.0 mol m-3 Ca(NO3)2, 80.0 mol m-3 SrCl2, 80.0 mol m-3 Sr(NO3)2 calcium buffer solutions of pCa 4.0 and pCa 5.0, and 10.0 mol m-3 HEPES-KOH (pH 7.0) pH buffer solution. Addition of Ca2+ or Sr2+ to K+, Mg2+ and Ba2+ salt solutions increased the survival rates of the internodal cells. Calcium release from the internodal cell wall was measured in deionized water, KCl, NaCl, MgCl2, CaCl2, SrCl2 and BaCl2 solutions. Except in deionized water and CaCl2 solution, most of the calcium binding to the cell wall was released within one or a few hours in respective electrolyte solutions. Thus, survival and death of the internodal cells in the electrolyte solutions tested were interpreted in terms of the calcium release from the cell wall and the cell membrane, and intrinsic ability of Sr2+ to maintain the cell membrane normal.
TL;DR: When exposed to temperatures in excess of 60 °C, the immobilized glucose oxidase was less sensitive to thermal inactivation than the native enzyme, and the membranes still have 92% glucose oxid enzyme activity even after eight weeks of storage.
Abstract: A polyethylene-g-acrylic acid (PE-g-AA) graft copolymer was prepared via gamma-ray-irradiation-induced postirradiation procedures, and was used as support material for the immobilization of glucose oxidase. Soluble carbodiimides were used as the coupling agent. Reasonable yields were obtained with CMC but not with EDAC, EEDQ, or WRK. A number of factors were studied. (1) The use of water-soluble carbodiimides as condensing agent was attempted and the optimum condition for coupling glucose oxidase to PE-g-AA was established; (2) the effect of pH and temperature on the reactivity of native and immobilized glucose oxidase was studied. When exposed to temperatures in excess of 60 degrees C, the immobilized glucose oxidase was less sensitive to thermal inactivation than the native enzyme. The optimum pH value for the performance of the enzyme-immobilized membrane was 5. 6. For 200 tests, the response error of glucose sensor was less than 4% and its linear detected range was 0-1000 ppm. The obtained glucose oxidase-immobilized PE-g-AA membranes were kept in pH 5. 6 acetate buffer solution at 4 degrees C. The glucose oxidase activity of the membrane was determined at sevenday intervals. The membranes still have 92% glucose oxidase activity even after eight weeks of storage.
TL;DR: In this article, a buffer system consisting of formic acid and ammonium formate was investigated as a strongly acidic mobile phase for thermospray liquid chromatography/mass spectrometry (TSP LC/MS).
Abstract: A buffer system consisting of formic acid and ammonium formate was investigated as a strongly acidic mobile phase for thermospray liquid chromatography/mass spectrometry (TSP LC/MS). The behavior of the buffer was examined with regard to the relation between vaporizer control temperature and vaporizer tip temperature. Total intensity of solvent ions and sensitivity for target compounds as a function of vaporizer control temperature were also presented. The behavior of the formic acid-ammonium formate buffer was similar to that of an ammonium acetate aqueous solution, the usual mobile phase for TSP LC/MS. The applicability of the new buffer system to the compounds which required an acidic mobile phase was investigated. The new buffer system was found to reduce the peak tailing of amines and retain acids better than an ammonium acetate solution or an acetic acid-ammonium acetate buffer system.