Lateral Organization of Lipid Membranes Induced by Amphiphilic Polymer Inclusions

Abstract

Polymers belonging to a set of amphiphilic poly(acrylic acid) derivatives of varying hydrophobicity and charge density have recently been shown to slowly break small lipid vesicles and stabilize for hours or days transient mixed states such as membrane sheets, aggregates of mixed micelles, integral membrane proteins complexes, and so forth. We used giant unilamellar vesicles labeled with fluorescent probes to observe the evolution of a whole lipid-membrane including nondisruptive events, during the polymer-induced transition. The effect on the lipid bilayer depended strongly on the chemical structure and the concentration of polymer. Polymers of high hydrophobicity needed hours to disrupt the membranes. Before breakage, we observed intermediate states such as buds and filaments. Using less hydrophobic polymers, formation of flat domains was observed over hours at high polymer concentration (0.5 g/L). A single vesicle combined, over a few tens of micrometers, both curved fluorescent zones and flat zones of...