Abstract: | The effects of CaCl2, MgCl2, LaCl3 and some alkali halides on cytoplasmic membranes were studied using stearic acid spin labels. The results indicate that two mechanisms are operating when these ions interact with membranes. At low ionic concentrations (0 to 0.1 M) there is direct cation binding to the anionic membranes which in the case of Ca2+, Mg2+ and La3+, confers rigidity on the membranes and reaches saturation when the number of cations present equals the number of anionic sites on the lipids. At high concentrations there is a further effect on the membranes that parallels the known organizing/disorganizing effects that the ions studied have on water structure. |