Effect Of Univalent Cations Research Articles

Na+ modulates carrier-mediated Fe2+ transport through the erythroid cell membrane

The effects of univalent cations on Fe2+ uptake by rabbit reticulocytes have been studied. The rate of Fe2+ uptake was almost identical when measured in Na(+)-free choline chloride or KCl medium. Na+ but not Li+ inhibited Fe2+ uptake even at relatively low concentrations (2.5-20 mM) in these media. In contrast to this effect of extracellular Na+, the rate of Fe2+ uptake was facilitated by an increase in the intracellular Na2+ concentration in the range 5-40 mM, suggesting that intracellular Na+ is required for the uptake process. This effect also appears to be specific for Na+. Amiloride inhibited Fe2+ uptake in KCl (or in choline chloride), but had little if any effect in NaCl. Therefore a Na(+)- and amiloride-sensitive and a Na(+)- and amiloride-insensitive component can be distinguished. The two components differ in maximum velocity and pH optimum, but not in their apparent affinity for Fe2+. The ineffectiveness of selective inhibitors excludes the involvement of the Na+/H+ or Na+/Ca2+ exchange mechanisms. To account for the results presented in this work, a Na+/Fe2+ exchange system in the erythroid cell membrane is proposed.

Effect of Univalent Cations on the Rotational Motion of Perchlorate Ion in Aqueous Solution

Abstract The rotational correlation times of ClO4− in D2O solutions of lithium, sodium, and ammonium perchlorates (0.1–2 mol/kg) were determined by measuring the 17O spin-lattice relaxation rates arid calculating the electric field gradient at the 17O nucleus by an ab initio MO method. The correlation time increased with increasing concentration of the perchlorates. The effect of cations increased in the order: Li+ < NH4+ < Na+.

Effects of Univalent Cations and Neurotransmitters on the Adenosine Triphosphate-Dependent Uptake of Calcium Ions by Brain Microsomal Fraction

The results presented here indicate that glutamine in cerebrospinal fluid is likely to be making an essential contribution in vioo as a substrate for nerve-endings, as well as to other compartments. The high activity of glutaminase in synaptosomes and their lack of formation of glutamine emphasize the possible importance of glutamine as a nitrogen and carbon source for the nerve-ending. This has already been indicated from theoretical schemes (BalBzs et a!., 1973; Van den Berg & Garfinkel, 1971) and suggests that glutamine should be included in incubation fluids as a standard component. The inhibitory effect of NH4+ on glutaminase activity indicates the likely mode of action of this ion in producing raised glutamine concentrations in brain and cerebrospinal fluid during hepatic encephalopathy and after portocaval anastomosis. Coma, which does not occur in the rat at these low blood NH4+ concentrations, could occur in other more susceptible animals such as dog, or in man, as the result of a diminution of the pools of the excitatory transmitter amino acids glutamate and aspartate if the utilization of glutamine from cerebrospinal fluid were sufficiently diminished in the nerve-terminal.

Alteration of amorphous Bi4Ge3O12 by Tl2O and Na2O

Ternary thallium and sodium bismuth germanate glasses were prepared and their densities refractive indices, and infra-red spectra obtained. The effect of univalent cations on the stability of the arrangement of decoupled GeO4 tetrahedra in amorphous Bi4Ge3O12 was compared with the effect of divalent cations. The molar volumes of glasses with the nominal mol% composition 20 M2O(MO).20 Bi2O3.60 GeO2 are directly related to the size and charge type of Mz+. However, the molar volumes of such glasses are inversely related to the ionic potential (z/r) of Mz+. The infra-red spectra of these ternary glasses exhibitvGe−O shifts that reflect the presence of both isolated and small clusters of GeO4 tetrahedra compared to amorphous Bi4Ge3O12. This slight increase in the degree of polymerization appears to be directly related to the ionic potential of Mz+.

Crystal structures of M 2SnCl 6 salts. An analysis of the “crystal field effect” in their nuclear quadrupole resonance and vibrational spectra

The effects of univalent cations, M = K +, NH 4 +, Rb +, Cs +, and (CH 3) 4N +, on divalent anions M′Cl 6 2−, where M′= So, Pt, Re, Te, and Pb, in M 2M′Cl 6 salts having space group F m3 m have been analyzed by nuclear quadrupole resonance and vibrational spectroscopy. Single crystal X-ray diffraction collected by counter methods was carried out on the SnC16 salts, and they were found to have SnCl bond lengths and unit cell dimensions respectively of 2.411(2), 9.9818(3) Å (K +); 2.421(l),10.0442(4) Å (NH 4 +); 2.423(4), 10.0961(3) Å (Rb +); 2.423(5),10.3552(2) Å (Cs +); 2.402(3), 12.835(2) Å ((CH 3) 4N +). Full matrix least-squares refinement led to R values of 0.048, 0.054, 0.092, 0.116, and 0.066, respectively. The riding and independent motion models also lead to similar bond lengths. The 35Cl NQR frequencies in the M′Cl 6 2− ion steadily increase in this series as the cation increases in size. For SnCl 6 2− the range is 15.063 to 16.674 MHz. The a 1 g vibrational motion steadily decreases and for the SnCl 6 2− ion the range is 321 to 305 cm −1. The 35Cl NQR data correlate with the Born repulsive potential, e −r ϱ , between ions and does not correlate with other reasonable potentials. This repulsive potential, probably operating through variable amounts of Sternheimer antishielding, is proposed to be the dominant factor in the crystal field effect in the NQR spectra of these salts. The decreases in the a 1 g vibrational frequencies also accompany this effect. The variable sensitivity of other M′Cl 6 2− ions to the cations is accountable in terms of differences in polarization of the anions as a function of their size.

The effect of univalent cations on the circular dichroism of pyruvate kinase

The circular dichroism spectrum of rabbit muscle pyruvate kinase in the near ultraviolet was altered by temperature changes and univalent cations. A large increase in ellipticity occurred in the 260–290-nm region when the temperature was lowered from 37 to 5°. At 25° 0.1 M K +, an activating univalent cation, and 0.1 M Li +, a non-activating univalent cation, caused significant and similar increases in ellipticity in the 250–290-nm region, both in the presence and absence of MgCl 2 and phosphoenolpyruvate. Tetramethylammonium ion (0.1 M), a non-activating univalent cation, caused relatively small changes in the circular dichroism spectrum compared to the changes produced by K + or Li +. Since pyruvate kinase is inactive in the presence of Li +, no correlation could be made between activity and enzyme conformation as determined by circular dichroism measurements.

Effects of univalent cations on the formation of nitrate reductase and nitrite reductase in rice seedlings

Effects of univalent cations on the formation of nitrate reductase and nitrite reductase in rice seedlings

Effects of Univalent Cations on the Activity of Particulate Starch Synthetase

An investigation was made to determine the univalent cation requirements of starch synthetase from a variety of plant species of economic importance. The particulate enzyme from sweet corn was shown to have an absolute requirement for potassium, with the optimum activation occurring at 0.05 M KCl. Rubidium, cesium, and ammonium were 80% as effective as potassium while sodium and lithium were respectively 21% and 8% as effective as potassium. The K(A) for potassium was determined to be 6 mM. In the case of the particulate starch synthetase from wheat, bush beans, field corn, soybeans, peas, or potatoes, considerable stimulation of enzyme activity was obtained by the addition of potassium to the reaction mixture. In these studies, low enzyme activity was observed in the absence of added potassium, but the content of endogenous univalent cations in the reactions may be sufficient to account for the activities observed. Anions of various types had no effect on starch synthetase activity. Divalent cations produced slight activation in the presence or absence of potassium. All efforts to show a potassium requirement for glycogen synthetase from rat liver have been negative.

Effect of univalent cations and role of GTP and supernatant factors during biosynthesis of polylysine chain

We studied the site of action of univalent cations, GTP and enzymes of the postribosomal supernatant during the biosynthesis of the polypeptide chain in the polyadenylic acid (poly (A))-controlled cell-free system from Escherichia coli which synthesizes polylysine. The ribosomes from E. coli bind approximately twice as much lysyl transfer RNA (lysyl-tRNA) in the presence of poly (A) and NH 4 + than in the absence of NH 4 +. Additional lysyl-tRNA which has been bound in the presence of NH 4 + can be only partly removed by washing with a buffer containing no NH 4 +. When lysyl-tRNA is incubated with washed ribosomes, poly (A) and NH 4 +, lysyl-lysyl-tRNA is formed but no peptidyl-tRNA containing higher lysine peptides. The formation of the peptide bond between two lysine residues i.e. the transpeptidation phase of the proteosynthetic cycle, is itself catalysed by ribosomal polypeptidyl transferase. This reaction does not require either GTP or enzymes of the postribosomal supernatant. On the other hand, the enzymes of the postribosomal supernatant and GTP are necessary for the synthesis of peptides higher than dilysine. These components obviously act during the translocation phase of the proteosynthetic cycle. In the translocation reaction with unpurified ribosomes and enzymes GTP can be replaced by ATP and to a lesser degree also by UTP and CTP.

Salt effects on rates of alkaline fading of sulphonphthalein dye ions

Salt effects on the rates of alkaline fading of bromophenol blue and bromophenol red have been investigated. The rate depends on the character and concentration only of the cation of the added salt and not on the ionic strength, anions being without effect. The relative effects of univalent cations in enhancing the rate lie in the order K+ > (CH3)4N+ > Na+≃ Li+. The tervalent cation Co(NH3)63+ is much more enhancing. The results are discussed in terms of the distribution of the charge on the bivalent dye ion and consequent increased charge density at or near the site of reaction.

Effect of univalent cations and colchicine on growth, respiration and carbohydrate metabolism of Cunninghamella elegans.

The results reported have a bearing on the necessity of sodium as a complementary ion for better growth ofCunninghamella. This element effected moderate sucrose absorption, polysaccharide accumulation and gain in dry weight accompanied by least galactosan building, maximum respiration rate and carbohydrate accumulation. Potassium gave the maximum gain in dry weight and least sugar absorption and polysaccharide accumulation. Although lithium exhibited a slightly higher rate of sugar absorption than potassium and showed the maximum polysaccharide formation, it about equalled potassium in having similar effects on carbon dioxide output and total carbohydrate content. Thallous ions were toxic as the fungus lost weight and showed the least carbohydrate content accompanied by very low respiration rate. Colchicine, under the above mentioned conditions, did not affect the dry weight of the fungus but increased or decreased the rate of absorption of sucrose, respiration and carbohydrate metabolism, depending on the concentration of the chemical and the type of prevalent univalent cation.

Effects of univalent cations on the properties of yeast NAD+ acetaldehyde dehydrogenase.

Summary Acetaldehyde dehydrogenase (aldehyde:NAD(P) + oxidoreductase, EC 1.2.1.5) from yeast is activated by K + and Rb + . Sodium and Li + antagonize the activation, apparently by competitive inhibition with K + . The stimulation of activity by mercaptoethanol and the activation by K + are not additive in a reaction mixture containing both. Potassium and Rb + in the order just mentioned protect acetaldehyde dehydrogenase from inactivation by heat, whereas Na + and Li + are less effective as protectants. After prolonged dialysis against Tris buffer, and consequent loss of 90–95% of activity, the enzyme can be reactivated to a considerable extent by univalent cations. The best reactivating cation is K + , followed by Rb + then by Na + and Li + and finally by Tris + . The level of K + required to half-saturate the enzyme is independent of substrate size.

Effects of univalent cations on the immunoelectrophoretic behavior of pyruvic kinase.

Effects of univalent cations on the immunoelectrophoretic behavior of pyruvic kinase.

The effect of univalent cations on the critical micelle concentration of sodium dodecyl sulphate

The effect of univalent cations on the critical micelle concentration of sodium dodecyl sulphate