Influence Of Hydrogen Ion Concentration Research Articles

The influence of hydrogen-ion concentration on the production of intermediate compounds in degradation reaction of D-giucose

In the paper there is considered the question of the influence of hydrogen-ions concentration on the formation of intermediates (unsaturated carbonyl-containing compounds with Lambda max 225 nm and carbonyl-containing compounds with Lambda max 285 nm ) of the early stages of degradation D-glucose in aqueous solutions in pH range 1,0–7,0. By UV-spectroscopy there is demonstrated that an increase in hydrogen-ions concentration slows the formation of basic intermediates of the early stages, but it accelerates the transformation of unsaturated carbonyl-containing intermediates (Lambda max 225 nm ) to 5-hydroxymethylfurfural. It was shown that reactions of the formation of unsaturated carbonyl-containing compounds, as starting intermediates for further transformations, slowed down at pH 3, indicating a certain stability of D -glucose under these conditions.

Depletion/protection of β-carotene in estimating antioxidant activity by β-carotene bleaching assay

The β-carotene bleaching assay belongs to the oldest and commonly applied methods of estimating the antioxidant activity of different substances and mixtures. In this method, the antioxidant activity of the examined substance is evaluated by the spectrophotometric measurement of β-carotene concentration changes in β-carotene/peroxyl radicals (LOO•) systems with and without antioxidant. The presented results confirm the essential influence of hydrogen ion concentration on the estimation of antioxidant activity of phenolic compounds and prove that the formation of peroxyl radicals in measuring system is inhibited by the presence of hydrogen ions. Contrary to hydrogen ions, alkali metal ions accelerate the formation of peroxyl radicals quickening β-carotene depletion, thus indicating the seemingly weaker antioxidant properties of the antioxidant at the presence of metal ions. The LOO•/β–carotene reaction rate, and hence the estimated antioxidative potential of the examined compound, is also dependent on the type and concentration of the anion accompanying the cation. The presented results show the difficulty in the estimation of true antioxidant properties of food components, plant extracts and even antioxidant additives protecting products against oxidative changes.

Extraction separation of Cu(II) and Co(II) from sulfuric solutions by hollow fiber renewal liquid membrane

Extraction separation of Cu(II) and Co(II) from sulfuric wastewater is studied with hollow fiber renewal liquid membrane (HFRLM) technique. The organic solution of LIX 984N in kerosene is used as the liquid membrane phase to selectively separate and concentrate Cu(II) from aqueous solution; and the extractant of CYANEX 272 is used as carrier to remove and concentrate Co(II) from aqueous solution. In the selective separation process, LIX 984N has good selectivity on Cu(II); the interactions among metal ions can be negligible; the pH in the feed aqueous solution has significant influence, while the influence of hydrogen ion concentration in the stripping phase is slight. The removal efficiency of Cu(II) increases with the increasing flow rate on lumen side, while decreases with the increasing flow rate on shell side. The results of lab-scale cascade experiments show that the HFRLM technique is a promising treatment method for simulated sulfuric wastewater containing copper and cobalt with separation factor higher than 100. The Cu(II) and Co(II) concentrations in the raffinate are lower than 0.50 mg L −1 and 1.0 mg L −1, respectively, which are both below the standard of wastewater discharge in China. Based on the surface renewal theory, resistance-in-series model and mass balance law, a corresponding mass transfer mathematical model is developed; and the calculated results are in good agreement with experimental data.

Oxalic Acid Production by Aspergillus niger: Influence of Hydrogen Ion Concentration and Nitrogen Source

Oxalic Acid Production by Aspergillus niger: Influence of Hydrogen Ion Concentration and Nitrogen Source

In situ Fourier transform infrared spectroscopy as an efficient tool for determination of reaction kinetics.

The performance of new FTIR-based monitoring technology to representatively determine reaction kinetics has been demonstrated on an example of homogeneously catalyzed liquid-phase sucrose hydrolysis to fructose and glucose. The reaction kinetics were investigated by using the ReactIR 1000 reaction analysis system, which enables determination of the component concentration from its characteristic FTIR spectrum. During the sucrose inversion, the ReactIR 1000 instrument connected to a computer controlled standard glass batch reactor provided the required operating conditions and information about the component concentration in real-time. We have studied the influence of hydrogen ion concentration, temperature and initial concentration of sucrose on the sucrose disappearance rate. It was found out that the inversion of sucrose is an irreversible reaction, which is not affected by the formation of fructose and glucose in the liquid-phase. Then, the parameters of the kinetic model (i.e., reaction rate constant and activation energy) were calculated. A comparison of the model output and the measured data showed that the kinetics of the sucrose inversion could be well described by means of the pseudo first-order kinetic model. Finally, the method of determining the kinetic model by FTIR spectroscopy was verified by comparing the results obtained in the batch reactor with the results obtained in the continuously stirred tank reactor.

Organosolv Delignification of Eucalyptus globulus: Kinetic Study of Autocatalyzed Ethanol Pulping

The autocatalyzed delignification of Eucalyptus globulus in 50% ethanol (w/w) was modeled as the irreversible and consecutive dissolution of initial, bulk, and residual lignin. Their respective contributions to total lignin was estimated as 9, 75, and 16%. Isothermal pulping experiments were carried out to evaluate an empirical kinetic model among eight proposals corresponding to different reaction schemes. The calculated activation energy was found to be 96.5, 98.5, and 40.8 kJ mol-1 for initial, bulk, and residual delignification, respectively. The influence of hydrogen ion concentration was expressed by a power-law function model. The kinetic model developed here was validated using data from nonisothermal pulping runs.

Kinetics of Eucalyptus globulus Delignification in a Methanol−Water Medium

The kinetics of Eucalyptus globulus delignification in methanol−water pulping has been studied. A total of 17 isothermal runs at a liquor-to-wood ratio of 50 L kg-1 were carried out to develop the kinetic model describing the system. In a first series of experiments, eight models were considered to study the influence of temperature on the delignification rate. The most suitable model, which was discriminated according to statistical criteria, describes delignification as the consecutive dissolution of three lignin species: initial, bulk, and residual lignin, their content in wood being 10, 69, and 21%, respectively. Initial and residual delignification were considered as irreversible reactions and bulk delignification as reversible. The influence of hydrogen ion concentration was taken into account by means of a general power-law expression. The model proposed was validated by reproducing the experimental data from four runs carried out under nonisothermal conditions and a liquor-to-wood ratio of 7 L kg-1, which are closer to industrial operating conditions.

Influence of hydrogen ion concentration versus carbon dioxide tension on pulmonary vascular resistance after cardiac operation

Disturbances of respiratory acid-base status are common in patients supported with mechanical ventilation of the lungs after cardiac operations. This study was conducted with two protocols. The purpose was to determine whether respiratory acid-base status influences pulmonary vascular resistance in adults after cardiac operations and whether the influence is mediated by hydrogen ion concentration or carbon dioxide tension. Patients were studied while under general anesthesia immediately after aorta-coronary bypass. In the first protocol, with seven patients, arterial carbon dioxide tension was manipulated by the addition of 5% carbon dioxide to the breathing circuit. Pulmonary vascular resistance index was determined as arterial carbon dioxide tension rose from 30 mm Hg to 50 mm Hg and back to 30 mm Hg. In the second protocol, with 10 different patients, hydrogen ion concentration was manipulated by the addition of 0.2N hydrochloric acid, sodium bicarbonate, or both as arterial carbon dioxide tension was held constant. We used analysis of variance for statistical data. The results of the first protocol showed that pulmonary vascular resistance index rose by 44% (p < 0.05) as arterial carbon dioxide tension rose from 30 to 50 mm Hg. The results of the second protocol showed that changes in pulmonary vascular resistance index were parallel to changes in hydrogen ion concentration as arterial carbon dioxide tension was held constant (p < 0.05). These data demonstrate that respiratory acid-base status is an important determinant of pulmonary vascular resistance in the adult after cardiac operations. Furthermore, these data suggest the effect is mediated by hydrogen ion concentration, not carbon dioxide tension.

The mechanism of pH-dependent hydrogen peroxide cytotoxicity in vitro

The present paper is concerned with the influence of hydrogen ion concentration and composition of the medium on clonogenic survival of epithelial cells exposed to hydrogen peroxide in vitro. The survival of cells incubated with H2O2 in phosphate-buffered saline at pH 6.5 was 1 x 10(-2) and increased abruptly to 9 x 10(-2) at pH 7.0. The pH dependence of the cytocidal effect was particularly conspicuous when Eagle's minimum essential medium (SFMEM) was used for cell exposure to H2O2: the survival was characterized by exponential pH dependence and varied from 1 x 10(-1) to 9 x 10(-1) for pH 6.5 and 7.5, respectively, with a superimposed sharp peak value of 9 x 10(-1) at pH 7.0. The enhanced pH dependence of the H2O2 cytotoxicity in SFMEM was found to result from the additive action of glucose and histidine present in this medium. Glucose alone protected the cells with the efficiency decreasing with increasing hydrogen ion concentration. Histidine was responsible for the intermediate maximum in the pH-dependent survival spectrum. In addition, the changes in cell survival were accompanied by pH-dependent release of GSSG from the exposed cells. The GSSG efflux was inhibited by glucose in the medium. The influence of glucose on both the pattern of cell survival and the associated GSSG release indicate that the glutathione peroxidase activity supported by the pentose phosphate pathway is crucial in cell protection against extracellular H2O2 toxicity.

Comparative Toxicity of Hypochlorous Acid and Hypochlorite Ions to Mosquitofish

Abstract We examined the relative toxicity of hypochlorous acid (HOCl) and the hypochlorite ion (OCl−) by exposing mosquitofish Gambusia affinis for 1 hour to predominantly free residual chlorine (FRC) at six levels of pH following a 7-day acclimation to the test pH. Median lethal concentrations (LC50), in terms of total residual chlorine (TRC), increased with increasing pH, ranging from 0.41 mg/liter at pH 6.05 to 1.28 mg/liter at pH 8.42. Because of the influence of hydrogen ion concentration on dissociation of HOCI, the percent of FRC present as HOCl is about 97% and 13%, respectively, at the low and high pH. Cursory examination of toxicity of monochloramine (NH2Cl) and mixtures of NH2Cl and dichloramine (NHCl2) suggested that their contributions to toxicity were negligible at the concentrations existing at any test pH. Free residual chlorine concentrations at the LC50 for each pH were fitted to a theoretical model derived from an assumption that toxicities of HOCl and OCl− were additive. More than 99%...

Influence of hydrogen ion concentration on bile acid induced acute gastric mucosal ulcerogenesis.

Aggressive treatment with H(2) receptor blocking agents and/or antacids has been advocated as effective prophylaxis against and treatment for "stress ulcer," based on the logical but infrequently tested assumption that the severity of the disease is critically determined by the concentration of intraluminal acid. The present study investigated this assumption in a model which employed topical acid, topical bile acid and mucosal ischemia to induce ulcerogenesis. With vascularized, chambered ex vivo wedges of canine proximal gastric wall, groups of animals were studied during three sequential periods using topical test solutions (TS) containing either 0 mM, 100 mM or 160 mM HCI. During period 1, mucosae were exposed to TS alone; during period 2, either to TS containing 1 mM sodium taurocholate (TC) or to TS and concomitant vasopressin infusion (VP); and during period 3, to TS + TC + VP. Parameters evaluated included net H(+) flux ( big up tri, openH(+)), aminopyrine clearance (AC), a measure of mucosal blood flow, net TC flux ( big up tri, openTC) and the lesion index, graded 0-5. The data indicate that in nonischemic mucosa exposed to constant [TC], AC was significantly increased, big up tri, openH(+) ("back-diffusion") increased as a linear function of [H(+)] and no lesions were observed. Under the same circumstances in ischemic mucosa, big up tri, openH(+) increased as linear function of [H(+)]. As a consequence, lesion severity was also a linear function of [H(+)]. big up tri, openTC was enhanced at low pH but bore no relation to the degree of mucosal damage induced. Assuming applicability of the model, these studies provide support for the use of H(2) receptor blocking agents and/or antacids to prevent or ameliorate "stress ulcer" disease.

Kinetic Studies of the Reaction Between Bromine and Malic Acid (Influence of Hydrogen Ion Concentration)

Kinetic Studies of the Reaction Between Bromine and Malic Acid (Influence of Hydrogen Ion Concentration)

The Functional Groups of the Mg–Ca ATPase from Escherichia coli

The influence of hydrogen ion concentration on binding and conversion of MgATP and CaATP by membrane bound and solubilized ATPase from Escherichia coli has been investigated. The reaction of enzyme (E), hydrogen ion (H+), and substrate (S) procedes according to the following scheme, where Me is the metal ion and P is the product(s). (See article for formular). Within experimental error, the results obtained with membrane-bound and solubilized ATPase are identical. Changing the concentration of Mg2+ ions or replacement of Mg2+ by Ca2+ ions alters the dissociation constants Kb, KHMeATP, and Ka'. The kinetics and experiments with group-specific inhibitors suggest that integrity for amino, imidazole, tyrosyl, carboxyl, and arginyl residues is required for activity of membrane-bound and solubilized E. coli ATPase.

Influence of Hydrogen Ion Concentration on Extractability and Flavor of Bitter and Astringent Flavor Components from Cheddar Cheese and Cultured Milk

Extractability of bitter and astringent flavor components from Cheddar cheese and cultured milk by a chloroform-methanol solvent system was demonstrated to be dependent on acid pH conditions. Similarly, the quantity of peptides extractable from acid samples was much greater than that from neutral or alkaline samples. Bitter and astringent flavor responses to the acidic extracts were independent of pH between 3.0 and 8.7. At pH 10.5 and above bitterness was not affected but a marked loss occurred in astringency which was restored by lowering pH.

The influence of hydrogen ion concentration on calcium binding and release by skeletal muscle sarcoplasmic reticulum.

Calcium release and binding produced by alterations in pH were investigated in isolated sarcoplasmic reticulum (SR) from skeletal muscle. When the pH was abruptly increased from 6.46 to 7.82, after calcium loading for 30 sec, 80-90 nanomoles (nmole) of calcium/mg protein were released. When the pH was abruptly decreased from 7.56 to 6.46, after calcium loading for 30 sec, 25-30 nmole of calcium/mg protein were rebound. The calcium release process was shown to be a function of pH change: 57 nmole of calcium were released per 1 pH unit change per mg protein. The amount of adenosine triphosphate (ATP) bound to the SR was not altered by the pH changes. The release phenomenon was not due to alteration of ATP concentration by the increased pH. Native actomyosin was combined with SR in order to study the effectiveness of calcium release from the SR by pH change in inducing super-precipitation of actomyosin. It was found that SR, in an amount high enough to inhibit superprecipitation at pH 6.5, did not prevent the process when the pH was suddenly increased to 7.3, indicating that the affinity of SR for calcium depends specifically on pH. These data suggest the possible participation of hydrogen ion concentration in excitation-contraction coupling.

Influence of hydrogen ion concentration on oxygen consumption in bovine dental pulp.

Oxygen consumption rates in bovine dental pulp were measured by the Warburg method under varied conditions of hydrogen ion concentration. The pH of the suspending fluid ranged from 5.0 to 8.6. The rate of oxygen consumption was not impaired when the pH remained between 6.2 and 7.5. The rate was higher between pH 6.4 and 7.0 and it was greatest at pH 6.6 and 6.8. Respiration was stopped at pH 5.0 and 8.6.

Acid-base balance and the effect of oxyhemoglobin reduction on CO 2 transport

The CO 2 content and [H+] of oxygenated and reduced whole blood of the dog were measured in vitro at constant P CO 2 but at varying levels of [H+]. The magnitude of increase in CO 2 content and decrease in hydrogen ion concentration at constant P CO2, which results from oxyhemoglobin reduction (CDH effect), is a decreasing linear function of the [H+] at which reduction takes place. The relationship is expressed by the equation CDH effect = −0.0034 [H+] + 0.518 and is similar at P CO 2's of 43 and 60 mm Hg. This effect is presumably the result of the influence of hydrogen ion concentration on formation of carbamino-bound CO 2 and explains the variations in the magnitude of the C-D-H effect which have been previously reported. The decreases in hydrogen ion concentration which accompanied oxyhemoglobin reduction were small and consistent with the hypothesis that carbamino-bound CO 2 is derived from oxylabile α-NH 2 groups with pK's between 6.5 and 8. Since carbamate formation results in the release of hydrogen ion, the relationship between its formation and the existing hydrogen ion concentration represents a mechanism for hydrogen ion homeostasis.

: A method for studying the influence of hydrogen ion concentration on the aggregation of Aphelenchus avenae

: A method for studying the influence of hydrogen ion concentration on the aggregation of Aphelenchus avenae

The Specificity of pH and Ionic Strength Effects on the Kinetics of the Rh (D)-Anti-Rh (D) System

Summary Under physiologic conditions of pH and ionic strength, the I* anti-D appears to react with intact Rh(D) red cells and their Rh(D) stroma according to reversible, second-order kinetics. At equilibrium the influence of hydrogen ion concentration in the pH range 6.4 to 8.4 on the I* anti-D system is slight. Beyond this pH range the profound depression of the I* anti-D system is consistent with marked conformational changes in the I* anti-D molecule. The effect of lowered ionic strength on the kinetics of the nonspecific reaction between I* anti-D and rh(d) stroma appears electrostatically controlled if a first-order reaction is assumed. In contrast, the specific reaction between intact Rh(D) red cells or Rh(D) stroma appears to follow a reversible, second-order reaction when the ionic strength of the system is lowered. Consequently, the electrostatic effect of ionic strength on the I* anti-D system seems to be exerted predominantly at the specific Rh(D) site in the case of the intact Rh(D) red cell, but both specifically and nonspecifically in the case of Rh(D) stroma. These results are considered in view of the known effects of pH and ionic strength on other immunologic systems and their components.

A New Species of Trematode, Urotocus kenyensis from the Grey Woodpecker, Mesopicos goertae (Picidae), in Kenya

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