[Effect of valinomycin on the structure of water-lecithin liposomes]

It has been established that water--lecithin liposomes in the heptane phase are formed in the course of equilibration of lecithin solution in heptane with water phase containing Na, K-picrate. The salts penetrate both the water nucleus of liposomes and their lecithin shell. The addition of valinomycin to this system does not change the water content in liposomes, but considerably increases the salt absorbed by the lipid shell of liposomes. A characteristic S-shape curve showing the relation between picrate extraction and the valinomycin concentration might be explained as an indication of a cooperative change of the structure of lecithin shell. This phase transition is induced by one valinomycin molecule per 10(3)--10(4) lecithin molecules.