EXCHANGE EQUILIBRIA FOR Al–BENTONITE AND MONOVALENT CATIONS

1965 ◽  
Vol 45 (2) ◽  
pp. 177-183 ◽  
Author(s):  
David Chen
Keyword(s):  
Equilibrium Distribution ◽  
Base Saturation ◽  
Monovalent Cations ◽  
Distribution Constant ◽  
Monovalent Ions ◽  
Wyoming Bentonite ◽  
Distribution Equation

Aluminum-saturated Wyoming bentonite, suspended in a solution of NH4Cl, KCl, or LiCl, was adjusted to a range of degrees of base saturation with the respective hydroxide. The distribution of the cations between solution and pH-independent exchange sites could be represented satisfactorily by an equilibrium distribution equation when the monovalent ions were NH4 or K but not when they were Li. The ion product (Al) (OH)3 was smaller at low base saturation, and increased to about 10−33.0 with NH4 and K but to only 10−33.7 with Li. The monovalent base potential (pH–pM) was a function of the magnitude of (Al) (OH)3 and the distribution constant, as well as the degree of base saturation.

scholarly journals Regulation of Connexin Hemichannels by Monovalent Cations

2005 ◽  
Vol 127 (1) ◽  
pp. 67-75 ◽  
Author(s):  
Miduturu Srinivas ◽  
D. Paola Calderon ◽  
Jack Kronengold ◽  
Vytas K. Verselis
Keyword(s):  
Cell Death ◽  
Plasma Membrane ◽  
Divalent Cations ◽  
Signaling Molecules ◽  
Primary Effect ◽  
Monovalent Cations ◽  
Modest Increase ◽  
Monovalent Ions ◽  
The Difference ◽  
Connexin Hemichannels

Opening of connexin hemichannels in the plasma membrane is highly regulated. Generally, depolarization and reduced extracellular Ca2+ promote hemichannel opening. Here we show that hemichannels formed of Cx50, a principal lens connexin, exhibit a novel form of regulation characterized by extraordinary sensitivity to extracellular monovalent cations. Replacement of extracellular Na+ with K+, while maintaining extracellular Ca2+ constant, resulted in >10-fold potentiation of Cx50 hemichannel currents, which reversed upon returning to Na+. External Cs+, Rb+, NH4+, but not Li+, choline, or TEA, exhibited a similar effect. The magnitude of potentiation of Cx50 hemichannel currents depended on the concentration of extracellular Ca2+, progressively decreasing as external Ca2+ was reduced. The primary effect of K+ appears to be a reduction in the ability of Ca2+, as well as other divalent cations, to close Cx50 hemichannels. Cx46 hemichannels exhibited a modest increase upon substituting Na+ with K+. Analyses of reciprocal chimeric hemichannels that swap NH2- and COOH-terminal halves of Cx46 and Cx50 demonstrate that the difference in regulation by monovalent ions in these connexins resides in the NH2-terminal half. Connexin hemichannels have been implicated in physiological roles, e.g., release of ATP and NAD+ and in pathological roles, e.g., cell death through loss or entry of ions and signaling molecules. Our results demonstrate a new, robust means of regulating hemichannels through a combination of extracellular monovalent and divalent cations, principally Na+, K+, and Ca2+.

scholarly journals Zeta Potential of Pyrite Particles in Concentrated Solutions of Monovalent Seawater Electrolytes and Amyl Xanthate

Minerals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 584 ◽  
Author(s):  
Alvaro Paredes ◽  
Sergio M. Acuña ◽  
Leopoldo Gutiérrez ◽  
Pedro G. Toledo
Keyword(s):  
Zeta Potential ◽  
Streaming Potential ◽  
Monovalent Cations ◽  
Water Network ◽  
Anionic Sites ◽  
Concentrated Solutions ◽  
Salt Addition ◽  
Monovalent Ions ◽  
Low Salt ◽  
Copper Flotation

Charge screening and adsorption capacity of monovalent ions onto pyrite (Py) in aqueous suspensions and the effect of potassium amyl xanthate (PAX) has been studied by measuring the changes in zeta potential (zp) versus pH with streaming potential. PAX addition in the absence of salts leads to an increase in |zp| suggesting dissolution of the surface ferric hydroxides and recovery of bare Py, corroborating existing theories. In the presence of salt, addition of PAX at pH > 6, for which hydroxides interference in not expected, has little effect over the zp, except when Li is present. The water network around the polar head of PAX is expected to be similar to that of hydrated Li+ facilitating the linkage between them and, thus, the formation of Li-mediated Py–PAX bridges. We speculate that these bridges lead to a xanthate shield around anionic sites on Py, decreasing |zp|. An increased PAX dose amplifies the effect of Li as a Py activator but only at low salt. At high salt concentrations, >0.01 M, PAX molecules do not find room to percolate to the surface of Py. Results for monovalent cations should improve our understanding of copper flotation processes in the presence of Py in saltwater.

THE DISTRIBUTION CONSTANT FOR EXCHANGE OF CALCIUM AND MAGNESIUM IN WYOMING BENTONITE

1966 ◽  
Vol 46 (3) ◽  
pp. 271-280 ◽  
Author(s):  
J. S. Clark
Keyword(s):  
Ionic Species ◽  
Mean Value ◽  
Neutral Salt ◽  
Distribution Constant ◽  
Ph Values ◽  
Significant Difference ◽  
Calcium And Magnesium ◽  
Excess Base ◽  
Double Hydroxides ◽  
Wyoming Bentonite

The distribution constant for exchange of calcium and magnesium ions was determined in Wyoming bentonite suspensions with pH values varying from 3.5 to 9.2. Using a neutral salt to extract the exchangeable cations, the mean value of the distribution constant using ion activities in solution was found to be 1.06 and there was no significant difference in the constant at different pH values. Thus, the presence of Al ions in the acid preparations, the precipitation of hydroxy aluminum polymers on the clay surfaces at intermediate pH values, and the precipitation of excess base in the alkaline region possibly as double hydroxides of Al and Mg or Ca had no significant effect on the exchange distribution of Mg and Ca ions.Under comparable conditions, the ion product (Al) (OH)3 had the same value in the presence of Ca or Mg. Because of this and the fact that the distribution constant for exchange was approximately 1, the two ions may be considered as a single ionic species for practical purposes in suspensions of Wyoming bentonite.

scholarly journals Calcium channel selectivity for divalent and monovalent cations. Voltage and concentration dependence of single channel current in ventricular heart cells.

1986 ◽  
Vol 88 (3) ◽  
pp. 293-319 ◽  
Author(s):  
P Hess ◽  
J B Lansman ◽  
R W Tsien
Keyword(s):  
Binding Sites ◽  
Single Channel ◽  
Heart Cells ◽  
Ca Channel ◽  
Monovalent Cations ◽  
Ca Channels ◽  
Whole Cell ◽  
Double Occupancy ◽  
Monovalent Ions ◽  
Ca Ions

Single channel and whole cell recordings were used to study ion permeation through Ca channels in isolated ventricular heart cells of guinea pigs. We evaluated the permeability to various divalent and monovalent cations in two ways, by measuring either unitary current amplitude or reversal potential (Erev). According to whole cell measurements of Erev, the relative permeability sequence is Ca2+ greater than Sr2+ greater than Ba2+ for divalent ions; Mg2+ is not measurably permeant. Monovalent ions follow the sequence Li+ greater than Na+ greater than K+ greater than Cs+, and are much less permeant than the divalents. These whole cell measurements were supported by single channel recordings, which showed clear outward currents through single Ca channels at strong depolarizations, similar values of Erev, and similar inflections in the current-voltage relation near Erev. Information from Erev measurements stands in contrast to estimates of open channel flux or single channel conductance, which give the sequence Na+ (85 pS) greater than Li+ (45 pS) greater than Ba2+ (20 pS) greater than Ca2+ (9 pS) near 0 mV with 110-150 mM charge carrier. Thus, ions with a higher permeability, judged by Erev, have lower ion transfer rates. In another comparison, whole cell Na currents through Ca channels are halved by less than 2 microM [Ca]o, but greater than 10 mM [Ca]o is required to produce half-maximal unitary Ca current. All of these observations seem consistent with a recent hypothesis for the mechanism of Ca channel permeation, which proposes that: ions pass through the pore in single file, interacting with multiple binding sites along the way; selectivity is largely determined by ion affinity to the binding sites rather than by exclusion by a selectivity filter; occupancy by only one Ca ion is sufficient to block the pore's high conductance for monovalent ions like Na+; rapid permeation by Ca ions depends upon double occupancy, which only becomes significant at millimolar [Ca]o, because of electrostatic repulsion or some other interaction between ions; and once double occupancy occurs, the ion-ion interaction helps promote a quick exit of Ca ions from the pore into the cell.

scholarly journals The Influence of Monovalent Cations on Trimeric G Protein Gi1α Activity in HEK293 Cells Stably Expressing DOR-Gi1α (Cys351-Ile351) Fusion Protein

2011 ◽  
pp. 541-547 ◽  
Author(s):  
M. VOŠAHLÍKOVÁ ◽  
P. SVOBODA
Keyword(s):  
Fusion Protein ◽  
G Protein ◽  
Binding Assay ◽  
Significant Inhibition ◽  
Chloride Anion ◽  
Hek293 Cells ◽  
Monovalent Cations ◽  
High Affinity ◽  
Monovalent Ions ◽  
High Level

The effect of monovalent cations on trimeric G protein Gi1α was measured at equimolar concentration of chloride anion in pertussis-toxin (PTX)-treated HEK293 cells stably expressing PTX-insensitive DOR-Gi1α (Cys351-Ile351) fusion protein by high-affinity [35S]GTPS binding assay. The high basal level of binding was detected in absence of DOR agonist and monovalent ions and this high level was inhibited with the order of: Na+ > K+ > Li+. The first significant inhibition was detected at 1 mM NaCl. The inhibition by monovalent ions was reversed by increasing concentrations of DOR agonist DADLE. The maximum DADLE response was also highest for sodium and decreased in the order of: Na+ > K+ ≈ Li+. Our data indicate i) an inherently high activity of trimeric G protein Gi1α when expressed within DOR-Gi1α fusion protein and determined in the absence of monovalent cations, ii) preferential sensitivity of DOR-Gi1α to sodium as far as maximum of agonist response is involved.

Contribution to the thermodynamics of bromophenol blue in the two-phase water-nitrobenzene extraction system

1990 ◽  
Vol 55 (11) ◽  
pp. 2606-2609 ◽  
Author(s):  
Emanuel Makrlík
Keyword(s):  
Equilibrium Distribution ◽  
Dissociation Constants ◽  
Extraction System ◽  
Bromophenol Blue ◽  
Phase Extraction ◽  
Distribution Constant ◽  
Two Phase ◽  
Nitrobenzene Phase ◽  
Phase Water ◽  
General Relations

General relations among thermodynamic parameters characterizing dissociation equilibria with species H2A, HA- and A2- (H2A is a symbol for an electroneutral undissociated acid) in a two-phase extraction system have been derived. From the extraction measurements, the equilibrium distribution constant of electroneutral bromophenol blue between the nitrobenzene phase and the aqueous one has been determined: log KD(H2A) = 3.60 ± 0.01. By using this value and further known constants and applying the mentioned relations the following values of dissociation constants of bromophenol blue in nitrobenzene saturated with water have been calculated for a temperature of 25 °C: pKaorg(H2A) = -log Kaorg(H2A) = 10.1 and pKaorg(HA-) = -log Kaorg(HA-) = 14.5.

EXTRACTION OF EXCHANGEABLE CATIONS FROM WYOMING BENTONITE SUSPENSIONS

1965 ◽  
Vol 45 (1) ◽  
pp. 39-48 ◽  
Author(s):  
J. S. Clark
Keyword(s):  
Exchangeable Cations ◽  
Base Saturation ◽  
Theoretical Base ◽  
Salt Solutions ◽  
Single Extraction ◽  
Wyoming Bentonite

Wyoming bentonite suspensions were prepared with a range of per cent Ca saturations and the exchangeable cations were extracted with solutions of NaCl, KCl, NH4Cl, and CaCl2. The per cent base saturation values, (Ca/Ca+Al)) × 100, obtained both by serial extraction with 1 N salt solutions and by a single extraction with 2 N NaCl or KCl agreed closely with the theoretical base saturation values calculated from the corrected lime potential. Somewhat better agreement with the theoretical values was obtained, however, with a single extraction than by serial extraction. The sum of Ca + Al (effective C.E.C.) was less affected by changing extract to clay ratio when a single extraction was employed. For these reasons, it was concluded that a single extraction with 100 ml of 2 N NaCl or KCl for 0.5 to 2.5 meq of exchange sites should be employed for the determination of exchangeable cations in clays and soils.

scholarly journals Contribution to the termodynamics of 1-(2-thiazolylazo)-2-naphthol in the water-nitrobenzene extraction system

2000 ◽  
Vol 65 (8) ◽  
pp. 581-585 ◽  
Author(s):  
Emanuel Makrlik ◽  
Petr Vaňura
Keyword(s):  
Thermodynamic Parameters ◽  
Equilibrium Distribution ◽  
Dissociation Constants ◽  
Extraction System ◽  
Distribution Constant ◽  
Two Phase ◽  
Chemical Equilibria ◽  
Phase Water ◽  
General Relations

General relations among thermodynamic parameters characterizing chemical equilibria including species ?2?+, HA, H+ and A- in both phases of a two-phase water-nitrobenzene extraction system have been derived. From the extraction measurements, the equilibrium distribution constant of electroneutral 1-(2-thiazolylazo)-2-naphthol (TAN, HA) between the nitrobenzene and aqueous phases has been determined: log ATD(HA) = 3.90?0.02. By using this value and further known constants and applying the mentioned relations, the following values of dissociation constants of TAN in nitrobenzene saturated with water have been calculated for a temperature of 25?C: pKdnb(H2A+) = -log Kdnb(H2A+) = 4.9 and pKdnb(HA) = -log Kdnb(HA) = 16.5.

THE EXTRACTION OF EXCHANGEABLE CATIONS FROM SOILS

1965 ◽  
Vol 45 (3) ◽  
pp. 311-322 ◽  
Author(s):  
J. S. Clark
Keyword(s):  
Soil Ph ◽  
Experimental Error ◽  
Colorimetric Method ◽  
Soil Samples ◽  
Exchangeable Cations ◽  
Base Saturation ◽  
Ion Concentrations ◽  
Ph Values ◽  
Exchangeable Al ◽  
Wyoming Bentonite

A study was made of techniques for the measurement of soil pH and corrected lime potential and for the extraction of exchangeable cations from soils. The experiments showed that in order to obtain stable and reliable pH values and ion concentrations it was necessary to equilibrate the soil samples in CaCl2 (0.005 to 0.02 M) for 4 to 5 days. After the soil was washed twice with water, the exchangeable cations were extracted from the equilibrated samples by shaking for 16 to 24 hours with 100 ml 2 N NaCl for 0.5 to 2.5 meq of exchangeable cations. In order to obtain reliable values for exchangeable Al with the soils studied, it was necessary to use a colorimetric method instead of titration with NaOH. When these precautions were observed the relation between corrected lime potential and percent base saturation for a number of soils agreed within reasonable experimental error with the theoretical one obtained for Wyoming bentonite.

Sign in / Sign up

Export Citation Format

Share Document