Relation of Surfactant Monomer Structure to Flip-Flop Dynamics in Surface-Differentiated Synthetic Bilayer Membranes

摘要

The transverse or flip-flop migration of a lipid molecule from one leaflet of ahydrated bilayer membrane to the other is an activated process that requires disruption of the membrane packing, as well as energetically costly transient interactions of the polar lipid head group with the bilayer's hydrocarbon interior, and of the lipid's hydrocarbon chains with water. There is intense current interest in the dynamics of lipid flip-flop in biological membranes or liposomes created from naturally occurring lipids. Recently, we showed that bilayer vesicles created from simple tetraalkylammonium ion surfactants could be chemically differentiated at their exovesicular and endovesicular surfaces, enabling us to visualize the dynamics of subsequent endovesicular/exovesicular exchanges. Here we demonstrate that bilayer vesicles constructed of structurally diverse synthetic surfactants can be similarly studied, and that monomer structure can be readily related to flip-flop dynamics within the membrane. Reprints.(JS)