The ability of biological ion channels to conduct selected ions across cell membranes is critical for the survival of both animal and bacterial cells. Numerous investigations of ion selectivity have been conducted over more than 50 years, yet the mechanisms whereby the channels select certain ions and reject others are not well understood. Here we report a new application of Jarzynski's Equalit...

Silicene, germanene and stanene likely to graphene are atomic thick material with interesting properties. We employed first-principles density functional theory (DFT) calculations to investigate and compare the interaction of Na or Li ions on these films. We first identified the most stable binding sites and their corresponding binding energies for a single Na or Li adatom on the considered mem...

Introduction Cellular water content, which accounts for 70% of the cellular mass, is the main determinant of cell volume. In animal cells, which are devoid of rigid walls, it is generally accepted that the water content is dictated by the amount of osmotically active cellular particles. Inorganic ions constitute a major fraction of the cellular osmolytes. It is therefore not surprising that cha...

K(+) channels exhibit strong selectivity for K(+) ions over Na(+) ions based on electrophysiology experiments that measure ions competing for passage through the channel. During this conduction process, multiple ions interact within the region of the channel called the selectivity filter. Ion selectivity may arise from an equilibrium preference for K(+) ions within the selectivity filter or fro...

Previous studies reported from this and other Laboratories have shown that isolated mitochondria are able to maintain concentration gradients of Na+ and K+ ions. When incubated in media containing an oxidizable substrate and ATP, mitochondria from liver (Macfarlane & Spencer, 1953; Spector, 1953; Price, Fonnesu & Davies, 1956), kidney (Bartley & Davies, 1954; Ulrich, 1961), heart and skeletal m...

The neutral exchange between Na+ or K+ ions and protons across the mitochondrial membrane was studied by means of passive swelling in isotonic acetate salts. The selectivity for Na+ over K+ was approximately 50: 1. The rate of Na+-dependent swelling mediated by the natural exchange system was sensitive to pH and inhibited 70% or more by 20 rnM Mgr+. Physiological Mg 2+ levels, however, inhibite...

Renal sodium homeostasis is a major determinant of BP and is regulated by several natriuretic and antinatriuretic hormones. These hormones, acting through intracellular secondary messengers, either activate or inhibit proximal tubule Na,K-ATPase. It was shown previously that phorbol esters and angiotensin II and serotonin induce the phosphorylation of both Ser-11 and Ser-18 of the Na,K-ATPase a...

To avoid increasing costs of landfill disposal, it has become increasingly important for U.S. foundries to identify beneficial reuses for the 8 to 12 million tons of waste foundry sand (WFS) generated annually. A major drawback to the reuse of some WFSs as a soil amendment is their high soil strength, under dry conditions, where root growth may be limited. Fifteen WFSs were analyzed for strengt...

The effects of varying the sodium gradient-either by lowering [Na+]o or by increasing [Na+]i on the electromechanical properties of pregnant rat uterine smooth muscle were studied. In normal tissues, complete removal of external sodium ions (choline, Tris or sucrose as substitutes) induced a strong and maintained contraction which was dependent on the presence of extracellular calcium ions, and...

Renal function was examined in adult rainbow trout (Oncorhynchus mykiss) after chronic exposure to a sublethal level of dietary Cd (500 mg/kg diet) for 52 d and during a subsequent challenge to waterborne Cd (10 microg/L) for 72 h. Dietary Cd had no major effects on UFR (urine flow rate) and GFR (glomerular filtration rate) but caused increased renal excretion of glucose, protein, and major ion...