INFLUENCE OF SOME LYSOSOMOTROPIC COMPOUNDS ON CALCIUM-ION DESORPTION PROCESS FROM LIPOSOME MEMBRANE

The effect of a group of model lysosomotropic compounds on the process of Ca2+ ion desorption from lecithin liposome membranes was studied. The compounds studied were: hydrochlorides of fatty acids 2-dimethylam inoethyl esters (DM-n) for n = 9, 11, 13 and 15 carbon atoms in the fa tty acid alkyl chain and methochloride of 2-dimethylaminoethyl laurate . It was found that all the compounds studied caused increased desorpt ion with increasing concentration of the compound. Most effective was the quaternary ammonium salt, DMs-11. Moreover, it was found that the process of Ca2+ desorption from the membrane depended on pH of the med ium. Compound DM-11 was more active at pH 8 than at pH 5. The action o f DM-n compounds depended on the alkyl chain length, DM-11 and DM-13 b eing the most active. Apparently free amines penetrate the phospholipi d membranes and incorporate into its hydrophobic core causing structur al deformations. Hydrochlorides of fatty acids and the quaternary ammo nium salt induce desorption of calcium ions mostly as a result of comp etitive electrostatic interactions. By quantum chemistry, PM3 method, and methods of molecular modelling we established the higher hydrophil icity of the polar head of DM-n series with respect to the polar head of the DMs-n compounds. DM-n compounds possess both acceptor and donor properties for hydrogen bonding while DMs-n are instrumental as accep ters only. It should be noted, that the results obtained in this paper for model membranes are in accordance with those for biological ones.