Change in Aggregation of Lecithin Due to Valinomycin-Lipid Interaction in Vesicle Membranes

Abstract

Vesicles obtained by sonication of chlorophyll-lecithin mixtures dispersed in an aqueous medium are bounded by a single bilayer membrane with incorporated chlorophyll a or b in monomeric form. Valinomycin added to a suspension of such vesicles induces slight changes in the absorption spectrum of the chlorophylls. This effect is neither associated with the ionophoric properties of valinomycin nor due to a direct interaction of this agent with chlorophyll, but indicates an interaction between lecithin and valinomycin. This interaction alters the aggregational state of about 35 lipids around each valinomycin molecule, and the chlorophylls act as sensors for this phenomenon. The sensor ability stems predominantly from different electrostatic interactions to which the chromophores are subjected in different lipid aggregations.