Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cations”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed1985

Influence of the intracellular and extracellular cation concentration on monovalent cation efflux of resealed human erythrocyte ghosts.

Tracer efflux measurements (86Rb+ and 22Na+) were performed on resealed human erythrocyte ghosts at different intra- and extracellular NaCl concentrations. Using a modified Goldman equation the observed alterations of the rate constants could be explained by taking into account the transmembrane and surface potentials, at constant permeability coefficient. These results emphasize the importance of membrane surface potentials in triggering ion transport across biological membranes.

Biological Transport, Active↗
PubMed1983

Stabilization of glucocorticoid receptors in vitro using divalent cations plus cation chelators.

The specific glucocorticoid receptor binding of rat liver cytosol was very unstable in vitro at 25 and 4 degrees C. However, 5 mM CaCl2 added with 5 mM EDTA to cytosol prior to incubation markedly stabilized unbound glucocorticoid receptors at both temperatures. Optimal effectiveness was achieved using equimolar (5 mM) amounts of CaCl2 and EDTA. On the other hand, 5 mM CaCl2 (added alone) further destabilized the unbound glucocorticoid receptor, while 5 mM EDTA (added alone) had no effect at 25 degrees C. EGTA (in lieu of EDTA) added with CaCl2 stabilized hepatic receptor binding at 25 degrees C. On the other hand, citrate added with calcium was ineffective in stabilizing the hepatic glucocorticoid receptor. MgCl2 effectively replaced CaCl2 as a stabilizing agent at 25 degrees C if added with 5 mM EDTA. When added alone, MgCl2 slightly destabilized the unbound receptor. Sucrose density gradient analysis (in low salt) revealed that CaCl2 plus EDTA enhanced the steroid-receptor complex sedimentation coefficient from 7 S to about 10 S. Unlike molybdate, CaCl2 plus EDTA had no apparent effect on steroid-receptor complex thermal transformation into a nuclear binding form, while MgCl2 plus EDTA partially reduced transformation. These results suggest a novel means to chemically stabilize unbound hepatic glucocorticoid receptors in vitro which may be of particular importance for receptor purification studies.

Animals↗
PubMed2003

Determination of the DS and substituent distribution of cationic alkyl polyglycosides and cationic starch ethers by GLC after dealkylation with morpholine.

The total DS and substituent distribution of starch and alkyl polyglycosides functionalised as O-(2-hydroxy-3-trimethylammonium)propyl ethers were determined by GLC. To achieve volatile analytes, the samples were submitted to methanolysis, N-demethylation and O-trimethylsilylation. Alternatively hydrolysis, reduction with NaBH(4) and subsequent O-acetylation were performed, but suffered from intramolecular acetal formation of 2-O-substituted residues, preventing reduction. Morpholine as nucleophile was superior to thiophenolate with regard to quantitative dealkylation and side product formation. The ratio of un-, mono-, di-, tri-, and tetrasubstituted compounds was determined. The total DS values calculated from these mole fractions were in good agreement with those obtained from elemental analysis or NMR from standards. Regioselectivity of the cationisation reaction was determined after methanolysis, permethylation and Hofmann elimination by GLC.

Cations↗
PubMed2002

Gas-phase fragmentation of the Ag+-phenylalanine complex: cation-pi interactions and radical cation formation.

Collision-induced dissociation experiments on the Ag+-phenylalanine complex using several collision energies were shown to yield ten different fragment ions. Unambiguous assignment of these fragment ions were made by careful analysis of deuterium labeling experiments. The losses of H2O, CO, CO2, and AgH were commonly observed; also encountered were the losses of H2, Ag, and H. Deuterium labeling experiments and density functional calculations have been employed to probe fragmentation mechanisms that account for all experimental results.

Cations↗
PubMed2006

Tuning substrate selectivity of a cationic enzyme using cationic polymers.

Noncovalent interactions between an artificial molecular scaffold and a protein are interesting due to the possibility of reversible modulation of the activity of the protein. alpha-Chymotrypsin is a positively charged protein that has been shown to interact with negatively charged polymers. Here we show that positively charged polymers are also capable of electrostatically binding to this protein. The resulting experiments show that the ability of a polymer to bind a protein does not depend only on the pI of the protein. We also realized that the variations in charge density in the polymer backbone afford different selectivities of the enzyme toward charged substrates.

Cations↗
PubMed1994

Electronic absorption spectroscopy of matrix-isolated polycyclic aromatic hydrocarbon cations. II. The phenanthrene cation (C14H10+) and its 1-methyl derivative.

The ultraviolet, visible, and near infrared absorption spectra of phenanthrene (C14H10), 1-methylphenanthrene [(CH3)C14H9], and their radical ions [C14H10+; (CH3)C14H9+], formed by vacuum-ultraviolet irradiation, were measured in neon matrices at 4.2 K. The associated vibronic band systems and their spectroscopic assignments are discussed. The oscillator strengths were calculated for the phenanthrene ion and found lower than the theoretical predictions. This study presents the first spectroscopic data for phenanthrene and its methyl derivative trapped in a neon matrix where the perturbation of the isolated species by its environment is minimum; a condition crucial to astrophysical applications.

Argon↗
PubMed1986

Intracellular cations and transmembrane cation transport in essential hypertension: the importance of controlled clinical observations.

We measured Na+, K+ and total Ca2+ concentrations as well as first order efflux rate constants for Na+ and Ca2+ in red cells from 22 patients with untreated essential hypertension and 22 normotensive control subjects. Both groups were individually and prospectively matched for age, sex and weight. Intracellular Na+ and K+ were also measured in a separate population consisting of 31 hypertensive patients and 41 normotensive subjects who were not matched. In order to test for possible plasma inhibitors of Na+ or Ca2+ transport in hypertension, Na+ and Ca2+ efflux rate constants in 15 paired patients were measured in red cells which were incubated in either homologous or paired plasma. Intracellular Na+ and K+ concentrations and Na+ and Ca2+ efflux rate constants were similar in the matched subjects. Significant positive correlations were found between intracellular Na+ and body weight (r = 0.27, P = 0.041) and between intracellular K+ and age (r = 0.29, P = 0.028). In the unmatched population intracellular Na+ correlated significantly with age (r = 0.25, P = 0.029) and was significantly increased in hypertensive patients. This difference was due wholly to increased intracellular Na+ in hypertensive females. After correction for age and weight, intracellular Na+ was similar in both hypertensive and normotensive subjects. Intracellular K+ did not differ between these groups but was significantly lower in males. Intracellular Ca2+ was similar in the matched groups after correction for age and weight, but the regression equations containing age and weight as independent variables were significantly different in hypertensive and normotensive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Transport↗