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H+ Ions (h+ + ion)
Selected AbstractsStability Enhancement of All-Solid-State H+ ISEs with Cross-Linked Silicon-Urethane MatricesELECTROANALYSIS, Issue 8 2005Nak-Hyun Kwon Abstract An all-solid-state hydrogen-ion-selective electrode (ASHISE) was fabricated using the polymer hybrid membrane. Polymer membranes composed of Tecoflex polyurethane (TPU), polyvinyl chloride (PVC), silicon rubber (SR), and additives (KTpClPB, DOA, and TDDA) were cast on a carbon rod. The TPU/SR hybrid membrane exhibited a longer lifetime and a higher sensitivity in the sensing of the H+ ion compared to conventional TPU/PVC and PVC/SR hybrid membranes. Moreover, the addition of SiCl4 to TPU-based matrices enhanced the potentiometric response and ISE stability, due to the chemical bonding between Si and CO in urethane, in which the cross-linking configuration was confirmed by DSC, FT-IR, and XPS experiments. TPU/SR membranes containing SiCl4 were rendered more stable and showed a pH response over a wide range (i.e., pH,2,11.5) with the slope of 60±2,mV/pH for more than four months. The ASHISE exhibited a small interfering potential variation in the wide range of the salt concentration (from 1.0×10,6,M up to 0.1,M). The ASHISE showed a result comparable to a commercial clinical blood analyzer. [source] A mini linac based positron sourcePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2009Patrice Pérez Abstract We have installed in Saclay a demonstration setup for an intense positron source in November 2008. It is based on a compact 6 MeV electron linac to produce positrons via pair production on a tungsten target. A relatively high current of 0.15 mA compensates the low energy, which is below the neutron activation threshold. The expected production rate is 4x1011 fast positrons per second. A set of coils is arranged to select the fast positrons from the diffracted electron beam in order to study the possibility to use a rare gas cryogenic moderator away from the main flux of particles. A first part of the commissioning of the linac has been performed. First attempts at measuring the fast positron flux are underway. This setup is part of a project to demonstrate the feasibility of an experiment to produce the H+ ion for a free fall measurement of neutral antihydrogen (H). Its small size and cost could be of interest for a university laboratory or industry for materials science applications. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Functional analysis of polar amino-acid residues in membrane associated regions of the NHE1 isoform of the mammalian Na+/H+ exchangerFEBS JOURNAL, Issue 17 2001Rakhilya Murtazina The NHE1 isoform of the Na+/H+ exchanger is a ubiquitous plasma membrane protein that regulates intracellular pH in mammalian cells. Site-specific mutagenesis was used to examine the functional role of conserved, polar amino-acid residues occurring in segments of the protein associated with the membrane. Seventeen mutant proteins were assessed by characterization of intracellular pH changes in stably transfected cells that lacked an endogenous Na+/H+ exchanger. All of the mutant proteins were targeted correctly to the plasma membrane and were expressed at similar levels. Amino-acid residues Glu262 and Asp267 were critical to Na+/H+ exchanger activity while mutation of Glu391 resulted in only a partial reduction in activity. The Glu262,Gln mutant was expressed partially as a deglycosylated protein with increased sensitivity to trypsin treatment in presence of Na+. Substitution of mutated Glu262, Asp267 and Glu391 with alternative acidic residues restored Na+/H+ exchanger activity. The Glu262,Asp mutant had a decreased affinity for Li+, but its activity for Na+ and H+ ions was unaffected. The results support the hypothesis that side-chain oxygen atoms in a few, critically placed amino acids are important in Na+/H+ exchanger activity and the acidic amino-acid residues at positions 262, 267 and 391 are good candidates for being involved in Na+ coordination by the protein. [source] Cocatalysis by ruthenium(III) in hydrogen ions catalyzed oxidation of iodide ions: A kinetic studyINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2004Praveen K. Tandon RuCl3 further catalyzes the oxidation of iodide ion by K3Fe(CN)6, already catalyzed by hydrogen ions. The rate of reaction, when catalyzed only by hydrogen ions, was separated graphically from the rate when both Ru(III) and H+ ions catalyzed the reaction. Reactions studied separately in the presence as well as absence of RuCl3 under similar conditions were found to follow second-order kinetics with respect to [I,], while the rate showed direct proportionality with respect to [Fe(CN)6]3,, [RuCl3], and [H+]. External addition of [Fe(CN)6]4, ions retards the reaction velocity, while changing the ionic strength of the medium has no effect on the rate. With the help of the intercept of the catalyst graph, the extent of the reaction that takes place without adding Ru(III) was calculated and it was in accordance with the values obtained from the reaction in which only H+ ions catalyzed the reaction. It is proposed that ruthenium forms a complex, which slowly disproportionates into the rate-determining step. Arrhenius parameters at four different temperatures were also calculated. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 545,553, 2004 [source] Determination of the activity of H+ ions within and beyond the pH meter rangeAICHE JOURNAL, Issue 12 2001Eva Rodil This work confirms that the activities of individual ions measured with ion-selective electrodes are physically meaningful. The individual activities of the Cl,, Na+ and K+ ions in single-electrolyte aqueous solutions of HCl, NaOH and KOH were measured at 298.2 K in the range from 0 to 2 molal. In the pH range from 1 to 13, the pH values calculated from the measured activities of the ions are in good agreement with the values obtained with a pH probe. In agreement with previous results for potassium ions, and opposite to the behavior of other cations in 1:1 electrolyte solutions, the K+ and the H+ ions were found to have smaller activities than their conjugate anions. The experimental activity coefficients of the ions were correlated with the Khoshkbarchi-Vera equation and with the New Hydration Theory, and compared with the predictions given by the Pitzer theory. [source] Synthesis of Titanate Derivatives Using Ion-Exchange ReactionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2000Chul-Tae Lee Two types of titanate derivatives, layered hydrous titanium dioxide (H2Ti4O9·nH2O) and potassium octatitanate (K2Ti8O17) with a tunnellike structure, were synthesized using an ion-exchange reaction. Fibrous potassium tetratitanate (K2Ti4O9·nH2O) was prepared by calcination of a mixture of K2CO3 and TiO2 with a molar ratio of 2.8 at 1050°C for 3 h, followed by boiling-water treatment of the calcined products for 10 h. The material then was transformed to layered H2Ti4O9·nH2O through an exchange of K+ ions with H+ ions using HCl. K2Ti8O17 was formed by a thermal treatment of KHTi4O9·nH2O. Pure KHTi4O9·nH2O phase was effectively produced by a treatment of K2Ti4O9 with 0.005M HCl solution for 30 min. Thermal treatment at 250°,500°C for 3 h resulted in formation of only K2Ti8O17. [source] Permeant anions contribute to voltage dependence of ClC-2 chloride channel by interacting with the protopore gateTHE JOURNAL OF PHYSIOLOGY, Issue 14 2010Jorge E. Sánchez-Rodríguez It has been shown that the voltage (Vm) dependence of ClC Cl, channels is conferred by interaction of the protopore gate with H+ ions. However, in this paper we present evidence which indicates that permeant Cl, ions contribute to Vm -dependent gating of the broadly distributed ClC-2 Cl, channel. The apparent open probability (PA) of ClC-2 was enhanced either by changing the [Cl,]i from 10 to 200 mm or by keeping the [Cl,]i low (10 mm) and then raising [Cl,]o from 10 to 140 mm. Additionally, these changes in [Cl,] slowed down channel closing at positive Vm suggesting that high [Cl,] increased pore occupancy thus hindering closing of the protopore gate. The identity of the permeant anion was also important since the PA(Vm) curves were nearly identical with Cl, or Br, but shifted to negative voltages in the presence of SCN, ions. In addition, gating, closing rate and reversal potential displayed anomalous mole fraction behaviour in a SCN,/Cl, mixture in agreement with the idea that pore occupancy by different permeant anions modifies the Vm dependence ClC-2 gating. Based on the ec1-ClC anion pathway, we hypothesized that opening of the protopore gate is facilitated when Cl, ions dwell in the central binding site. In contrast, when Cl, ions dwell in the external binding site they prevent the gate from closing. Finally, this Cl, -dependent gating in ClC-2 channels is of physiological relevance since an increase in [Cl,]o enhances channel opening when the [Cl,]i is in the physiological range. [source] Effects of NHE1 Expression Level on CHO Cell Responses to Environmental StressBIOTECHNOLOGY PROGRESS, Issue 2 2005Lisa R. Abston Ammonia, lactate and CO2 inhibit animal cell growth. Accumulation of these metabolic byproducts also causes a decrease in intracellular pH (pHi). Transport systems regulate pHi in eukaryotic cells. Ion transporters have been cloned and overexpressed in cells but have not been examined for protection against the buildup of ammonia, lactate or CO2. The Na+/H+ exchangers (NHE) transport H+ ions from cells during acidification to increase pHi. We examined whether overexpression of NHE1 would provide CHO cells with greater protection from elevated ammonia, lactate or CO2. NHE1 CHO cells were compared to MT2,1-8 ("normal" levels of NHE) and AP-1 (devoid of any NHE activity) CHO cell lines. Expression of at least "normal" levels of NHE1 is necessary for CHO cell survival during exposure to 30 mM lactic acid without pH adjustment or to 20 mM NH4Cl with pH adjustment. Resistance to an acute acid-load increased when NHE1 was overexpressed in CHO cells. Surprisingly, the inhibitory effect on cell growth at 195 mmHg pCO2/435 mOsm/kg (normal levels are 40 mmHg pCO2/320 mOsm/kg) was not affected by the NHE1 level. Also, there was no further decrease in CHO cell growth in the absence of NHE1 expression during elevated osmolality alone (up to 575 mOsm/kg). [source] | |||||||||||||