All-atom molecular dynamics simulations are used to study the condensation behavior of monovalent (Na(+)) and multivalent (Ca(2+)) salt counterions associated with the co-ions (Cl(-)) surrounding the charged poly(methacrylic acid) (PMAA) chain in water. The study is extended to the influences on chain conformation, local arrangement, and dynamics of water in the highly diluted aqueous solutions...

The relative permeability of endplate channels to monovalent and divalent metal ions was determined from reversal potentials. Thallium is the most permeant ion with a permeability ratio relative to Na+ of 2.5. The selectivity among alkali metals is weak with a sequence, Cs+ greater than Rb+ greater than K+ greater than Na+ greater than Li+, and permeability ratios of 1.4, 1.3, 1.1, 1.0, and 0.9...

Here we demonstrate that monovalent cations can localize around B-DNA in geometrically regular, sequence-specific sites in oligonucleotide crystals. Positions of monovalent ions were determined from high-resolution X-ray diffraction of DNA crystals grown in the presence of thallium(I) cations (Tl(+)). Tl(+) has previously been shown to be a useful K(+) mimic. Tl(+) positions determined by refin...

We address theoretically aggregation of DNA segments by multivalent polyamines such as spermine and spermidine. In experiments, the aggregation occurs above a certain threshold concentration of multivalent ions. We demonstrate that the dependence of this threshold on the concentration of DNA has a simple form. When the DNA concentration c(DNA) is smaller than the monovalent salt concentration, ...

The regulation of cellular ion levels has been an important issue of cell physiology since the beginning of the century. A special interest was focused on the monovalent ions which are involved in several cellular functions; in fact, the maintenance of high K+ level inside the cells is one of the most basic life-phenomena. Regarding the regulation of monovalent ions in general, two opposing ide...

Forces between charged particles in aqueous solutions containing multivalent coions and monovalent counterions are studied by the colloidal probe technique. Here, the multivalent ions have the same charge as the particles, which must be contrasted to the frequently studied case where multivalent ions have the opposite sign as the substrate. In the present case, the forces remain repulsive and a...

Enzymes activated by monovalent cations are abundantly represented in plants and the animal world. They have evolved to exploit Na+ and K+, readily available in biological environments, as major driving forces for substrate binding and catalysis. Recent progress in the structural biology of such enzymes has answered long standing questions about the molecular mechanism of activation and the ori...

We used a force-measuring laser tweezers apparatus to determine the elastic properties of lambda-bacteriophage DNA as a function of ionic strength and in the presence of multivalent cations. The electrostatic contribution to the persistence length P varied as the inverse of the ionic strength in monovalent salt, as predicted by the standard worm-like polyelectrolyte model. However, ionic streng...

In rat basophilic leukemia (RBL) cells and Jurkat T cells, Ca(2+) release-activated Ca(2+) (CRAC) channels open in response to passive Ca(2+) store depletion. Inwardly rectifying CRAC channels admit monovalent cations when external divalent ions are removed. Removal of internal Mg(2+) exposes an outwardly rectifying current (Mg(2+)-inhibited cation [MIC]) that also admits monovalent cations whe...

From our theoretical treatment which is an extension of the classical Donnan theory, we have estimated the rational selectivity coefficients of the carboxylic groups of the walls during exchanges of divalent ions against monovalent ones (i.e. calcium and potassium or calcium and sodium ions). These coefficients express the interactions between the different ions, those between the counter-ions ...