A joint effect of cationic and anionic amphiphilic compounds on the desorption of calcium ions from lecithin liposome membranes

cationic amphiphilic compounds: N-benzyl-N,N-dimethyl-N-tetradecylammonium chloride (BDTA), N-benzyl-N,N-dimethyl-N-dodecylammonium chloride (BDDA), N -methyl-N-tetradecyl-morpholinium bromide (MTM), N,N,N-trimethyl-N-tetradec ylammonium bromide (TMTA) and those of tripropyltin chloride in a mixture w ith amphiphilic anionic compounds (a homologous series of sodium alkylsulfo nates with n = 2, 4, 6, 8, 10, 12 and 14 alkyl carbon atoms) in the process of calcium ion desorption from liposome lecithin membranes. Radioactive la bels and spin labels were used in the investigations. All compounds studied caused an increase in the kinetic rate constant of ca lcium ion desorption from liposome membranes with increasing concentration. In case of mixtures containing cationic and anionic compounds both synergi sm and antagonism were observed. It was shown that the regulatory effect de pended on the properties of both cationic and anionic compounds. A mixture of the most effective cationic compound (BDTA) with each of the anionic com pounds decreased the effect. Mixtures of the remaining ammonium compounds w ith sodium alkylsulfonates produced both synergism and antagonism. Anionic compounds with short chains increased, and with longer chains decreased eff iciency, while compounds with comparable chains caused totally blocked deso rption. A mixture of an organometallic compound having three short chains w ith anionic compounds gave a reversed effect: short-chain compounds caused a decreased and those with long-chains - increased efficiency of tripropylt in chloride. Studies with spin labels supported the conclusion that the most important f actor responsible for the regulatory effect is the molecular shape of the c omplexes formed in a mixture of both groups of compounds - a factor that de termines membrane packing density.