Effect Of Hydrogen Ion Concentration Research Articles

Effect of hydrogen ion concentration on rhodopsin-lipid interactions.

Effect of hydrogen ion concentration on rhodopsin-lipid interactions.

Effect of Hydrogen Ion Concentration on the Absorption Spectrum and Fluorescence Life Time of Chloroplasts

Abstract Subjecting pea chloroplasts to hydrogen ion gradients results in small but significant changes in the absorption and circular dichroic spectra. The relative intensities of the fast and slow fluorescence decays are modified by the hydrogen ion concentration. The life time of the slow components is only slightly altered. At pH 11 the circular dichroic peak at 690 nm, assigned to Photosystem I chlorophyll-protein complex, is clearly resolved. Also, there is a splitting of the peak at 650-640 nm, attributed to Photosystem II chlorophyll-protein. At pH 3.9 splitting of the 650-640 nm peak is observed. There is also a positive component at 705 nm which may be associated with an aggregated form of chlorophyll or pheophytin. The changes in absorption spectra are determined by measuring the difference in spectra between identical chloroplasts suspensions one at pH 7.6 and the other at alkaline or acidic pH. At pH 2 and pH 3.7 there are time dependent increases in absorbance at 430, 445, 520, 538, 670 nm, and a decrease in absorbance at 606 nm. After a delay of 11 min at pH 2, there is also an increase in absorbance at 700 nm. The latter is interpreted as possible formation of aggregated pheophytin. At pH 11.0 there are time dependent increases in absorbance at 638, 454 and 440 nm, and decreases in absorbance at 675, 660, 508 and 472 nm. The changes in absorbance of the pigment around 520 nm (associated with an electrochromic effect) is interpreted as resulting from a leakage of hydrogen ion across the thylakoid membrane. The spectral changes that occur during the first 9 min are reversible. After the chloroplasts have incubated for more than 15 min most of the spectral changes are not reversible.

Effect of pH and some reagents on the sucrose-independent non-specific sorption of the oral bacterium Streptococcus mutans to glass

The effect of hydrogen-ion concentration on the sucrose-independent attachment of various strains of Streptococcus mutans to glass was studied using overlapping phosphate and acetate buffers through a pH range of 4.0 to 8.0 at a constant molarity. Some strains of the same serotype showed nearly identical patterns of adhesion with respect to pH, and all strains of serotype a, d and g behaved similarly, showing increased sorption at low pH only. Studies with serotype g cells demonstrated that increased sorption at low pH was not a result of changes in the ionic strength of the buffer. Metal chloride salts increased adhesion at some concentrations. Cyclohexyl isocyanide, EDTA, Tween 80, and saccharides had varied effects on several strains of serotype b and g cells at pH 4.6. Pre-treatment of serotype b and g cells with proteolytic enzymes or 2-mercaptoethanol usually resulted in reduced adhesion at pH 4.6; pre-treatment with dextranase had no effect or increased adhesion. The results suggest that the pH-sensitive adhesin is a protein, and that low pH increases adhesion either by increasing hydrogen bonding between the adhesin and the substrate or by altering the conformation of the adhesin. Contraction of the diffuse double layer is also important in explaining how adhesion is increased at low pH.

Effects of Hydrogen Ion Concentration on Determination of Free Guanidino Coumpounds in Plasma

Effects of Hydrogen Ion Concentration on Determination of Free Guanidino Coumpounds in Plasma

Effect of hydrogen-ion concentration on the extraction of cobalt, nickel, cadmium and lead with APDC/MIBK: Time stability of the extracts

The extraction of cobalt, nicke cadmium and lead ions by means of APDC/MIBK has been studied at various acidities of the aqueous phase (pH 0.2–6). Lead and nickel are extracted equally well over this pH-range, while cobalt and cadmium require pH > 1. The time stability of the extracted complexes in MIBK increases in the order cadmium < lead < nickel < cobalt. The decomposition of the complexing agent or the metal complexes is rapid in the two-phase system MIBK/water.

Effect of variations in blood hydrogen ion concentration on pulmonary gas exchange of artificially ventilated dogs

The effect of variation of blood hydrogen ion concentration on arterial and mixed venous PO2, ideal alveolar-arterial O2 pressure difference (PAiO2--PaO2), venous admixture (Qs/Qt), arterio-alveolar CO2 pressure difference (a--A)DCO2, physiological dead space to tidal volume ratio (VD/VT), cardiac output (Qt) and mean pulmonary arterial pressure (PAP) has been studied. Arterial and mixed venous PO2 increased and (PAiO2--PaO2) decreased with increasing blood hydrogen ion concentration. No change in Qs/Qt, (a--A)DCO2, VD/VT, Qt and PAP was observed. The effect of hydrogen ion concentration on arterial and mixed venous PO2 and on (PAiO2--PaO2) is mainly due to a shift of the blood oxyhemoglobin dissociation curve (ODC), i.e. due to the Bohr effect. The upper part of the ODC is more flat in alkalosis (shift to the left) than in acidosis (shift to the right). Therefore the same end-capillary to arterial O2 content difference results in a greater (PAiO2--PaO2) in alkalosis than in acidosis. Any factor influencing the slope of the upper part of the ODC is expected to affect the arterial PO2 and the (PAiO2--PaO2) by this mechanism. Similarly any factor shifting the steep part of the ODC is expected to affect the PO2 of the mixed venous blood.

Effect of membrane potential on dialysis of calcium in a continuous flow system

It has been found that the estimation of calcium by continuous flow analysis using a 12 inch dialyser leads to discrepant results if acidified aqueous calcium standards are used as the means of primary calibration. We have examined the effects of hydrogen ion concentration on the dialysis of 45 Ca and compared the rates of dialysis with dialyser membrane potentials. The amount of calcium dialysed increased from 5% to 12% when the concentration of acid was increased on the recipient stream of the dialyser. This corresponded to a change in potential of 0 mV to + 24 mV of the donor stream with respect to the recipient stream. Further experiments including protein on either side of the dialyser show that the Donnan effect does not explain the differences in rate of dialysis between protein and aqueous samples and that the migration of H + does explain most of these differences.

The effect of hydrogen ion concentration on enzymatic O-methylation of catechol estrogens. Clinical analysis on steroids. XI.

Incubation of 2-hydroxyestradiol (1) with rat liver homogenate in the presence of Sadenosyl-L-methionine and Mg2+ gave two isomeric monomethyl ethers, 2-methoxyestradiol (2) and 2-hydroxyestradiol-3-methyl ether (3). The ratio of the 2-O-methyl ether to the 3-O-methyl ether formed was found to be dependent on hydrogen ion concentration of the medium. At pH 6.0, the ratio was about 3-4, which decreased gradually with increasing pH, and at pH>7.0, the ratio was approaching to unity. PH dependency upon the product ratio was significant when 2, 3, 17β-trihydroxyestra-1, 3, 5 (10)-trien-6-one (5) was used as a substrate, although the ratio was completely reversed in contrast with the result obtained with 2-hydroxyestradiol. At pH 6-7, the ratio of the 3-O-methyl ether (7) to 2-O-methyl ether (6) was about 6-8. With increasing pH of the medium, 2-O-methylation increased gradually, and at over pH 8.0 the ratio became constant at about 3. These results suggest that rat liver catechol O-methyltransferase catalyzes the transfer of the methyl group from S-adenosyl-L-methionine to more basic hydroxyl group of the two phenolic hydroxyl groups of estrogen catechols.

Mammalian sperm capacitation and fertilization in vitro: A critique of methodology

Mammalian sperm capacitation and fertilization in vitro: A critique of methodology

Some properties of glucose-6-phosphate dehydrogenase from rat and chick brain: A comparative study

1. 1. Glucose-6-phosphate dehydrogenase (G6PDH) has been purified to homogeneity from rat and chick brain by affinity chromatography with Sepharose bound 2′,5′ ADP. 2. 2. Some properties of the two enzymes are studied and the effects of hydrogen ion concentration, Mg 2+ ions, temperature and urea on the initial rate of enzyme are described. 3. 3. G6PDH from chick brain differs from the rat enzyme in affinity for 2′,5′ ADP Sepharose, in pH optimum, in heat stability and it is differently affected by Mg 2+ ions. No effect is detectable after urea treatment on enzymes from both sources.

フザリウム毒素の分析(第1報)水素イオン濃度に対する影響

フザリウム毒素の分析(第1報)水素イオン濃度に対する影響

Effect of hydrogen ion concentration on energy metabolism in pig platelets

Respiration and glycolysis of pig platelets suspended in a dialyzed plasma were studied at various hydrogen ion concentrations. Respiration of platelets was high at acidic pH and decreased at physiological pH. This pH profile may not be attributed to properties of mitochondria, since the respiratory rate of mitochondria prepared from platelets was maximal at physiological pH. A low respiratory rate at physiological pH seemed to be attributable to depression of respiration by glycolysis, since the addition of glucose further depressed the rate. The Crabtree effect was more prominent at alkaline pH. Glycolysis increased with an increase in the pH of the plasma, contrary to oxygen consumption. The Pasteur effect was less prominent at alkaline pH. The effect of pH on lactate production by the cytosol fraction of platelets was similar to that of whole platelets. The glycolytic intermediate pattern showed that phosphofructokinase was the committed step. Both ATP concentration and ATP formation calculated from respiratory and glycolytic rates were constant at various pH values. These observations may indicate that the pH primarily affects platelet glycolysis at the phosphofructokinase step and the respiration is secondarily controlled by glycolysis.

Effect of hydrogen ion concentration on the determination of lead by solvent extraction and atomic absorption spectrophotometry.

Effect of hydrogen ion concentration on the determination of lead by solvent extraction and atomic absorption spectrophotometry.

Effect of hydrogen-ion concentration on in vitro fertilization of mouse, golden hamster, and rat eggs.

In vitro fertilization of mouse, golden hamster, and rat eggs in media at various pH values was investigated. A modified Krebs-Ringer bicarbonate solution, a modified Tyrode’s solution with heated hamster blood serum, and a modified Krebs-Ringer bicarbonate solution with heated rat blood serum were used, respectively, for the mouse, hamster, and rat gametes. Although sperm penetration could occur in media between pH 6 and 8.5, 6.7 and 8.7, and 6.75 and 8.3, the optimal pH ranged from 7.3 to 7.7, 6.8 to 8.2, and 7.8, respectively, for the penetration of mouse, hamster, and rat eggs. It seems that in vitro fertilization of rat eggs can be achieved in media only within a relatively narrow range of pH higher than pH 7, while hamster and mouse gametes can withstand a relatively wide range of pH.

The effect of hydrogen ion concentration on the anatomy of tobacco

The effect of hydrogen ion concentration on the anatomy of tobacco

Long-Range, pH-Dependent Effects on the Carbon-13 Nuclear Magnetic Resonance Spectra of Oxytocin

The effects of hydrogen ion concentrations on the carbon-13 nuclear magnetic resonance spectra of oxytocin were investigated. The starting pD of 3.0 was increased stepwise to 8.4. A change of the state of protonation of the N-terminal amino group of oxytocin is accompanied by changes in chemical shifts of carbon-13 nuclei of amino-acid residues located in the 20-membered ring of the hormone. The resonance positions of the acyclic peptide portion, Pro-Leu-Gly-NH(2), remain constant. The pD-induced chemical-shift changes of carbons up to five bonds removed from the site of protonation are interpreted in terms of "through-bond" and "through-space" mechanisms. Chemical-shift changes of carbons more than five bonds removed are proposed to have a conformational origin. It is suggested that a change in the charge density of the amino group perturbs the dihedral angle of the -CH(2)-S-S-CH(2)- moiety of oxytocin, which in turn significantly affects the overall conformation of the 20-membered ring of the hormone.

Monoamine oxidase—I: Specificity of some substrates and inhibitors

A number of synthetic substrates and inhibitors of monoamine oxidase have been studied, using the enzyme from porcine brain. K m and V max values have been calculated for substrates using Lineweaver-Burk plots. In many cases large variations in K m and V max were observed for relatively small changes in the structure of substrates. Similar observations were made concerning K i values for some competitive inhibitors. The effects of hydrogen-ion concentration on enzyme activity are consistent with the view that unprotonated amines are the species which bind to the enzyme. This finding, together with the observation that tertiary amines can act as substrates has led to formulation of a proposed mechanism of dehydrogenation which does not depend upon intermediate formation of Schiff base from the substrate amine.

EFFECT OF HYDROGEN-ION CONCENTRATION ON THE POLAROGRAPHIC REDUCTION OF PENTAAMMINERUTHENIUM(III) COMPLEX

Abstract Polarographic studies have been made on a series of pentaammineruthenium(III) complexes in various acidic solutions. The reduction process was found to be a reversible one with an electron-transfer at the dropping mercury electrode. The effect of hydrogen-ion concentration was markedly observed on the half-wave potential, i.e., its value shifted to the positive side with the increase in the hydrogen-ion concentration. This can be interpreted by assuming that the protonation occurs prior to the electrode process, so the electron density of ruthenium ion decreases.

Studies on factors affecting survival of nile fish in the Sudan. I. The effect of hydrogen ion concentration

Young of Tilapia nilotica L. were subjected to acidic and alkaline media of different pH over 24 h periods. Dilute hydrochloric acid was used to lower the hydrogen ion concentration of the test medium. A pH lower than 2.9 resulted in immediate mortality, whereas a pH of 3.5 and above produced no mortality. Alkaline media had no serious effect on survival.

Enzymes of coccidid: Purification and properties of l-lactate dehydrogenase from Eimeria stiedae

The initial extensive purification and characterization of lactate dehydrogenase (EC 1.1.1.27) from sporozoa was accomplished. Fractional precipitation with ammonium sulfate, followed by chromatography on DEAE-Sephadex ® yielded a 500–1000-fold purification of the enzyme from unsporulated Eimeria stiedae oocysts. One isoenzyme was demonstrated by electrophoresis in polyacrylamide gel. The subunits of this isoenzyme were dissociated and recombined to form another active isoenzyme. The rate of conversion of pyruvate to lactate by this enzyme was strongly influenced by specific anions. In Γ/2 0.1 glycine-sodium glycinate buffer at 40 C, the K m for lactate was 3.03 × 10 −2 M and the K m for NAD was 3.34 × 10 −4 M. The enzyme accepted NAD and certain of its analogs as coenzymes. The 3-acetylpyridine analog of NADP served as coenzyme, whereas NADP did not. The enzyme was peculiar because it accepted α-NAD as coenzyme. A pyruvate-NAD complex apparently did not compete with NADH for the same binding site on the enzyme molecule. The rate of conversion of pyruvate to lactate was maximal at 40 C. The effect of hydrogen ion concentration on the rate of interconversion of pyruvate and lactate varied according to the buffer system in which the reaction occurred.