Adhesion-Induced Domain Formation in Multicomponent Membranes

Abstract

Lipid vesicles containing a relatively small number of molecular components provide simple model systems for cell membranes, which contain a large number of lipid and protein components. Such multicomponent membranes can undergo phase separation into two coexisting liquid phases and, thus, exhibit liquid domains within a liquid matrix. The associated phase diagrams depend on a number of parameters such as the overall membrane composition as well as on pH and temperature of the aqueous medium. Here, we address the influence of an adhesive substrate surface onto the phase behavior of the membranes. Specifically, we study giant unilamellar vesicles (GUVs) that can be prepared from different lipid mixtures and have sizes similar to those of cells. We control the adhesion by electrostatic membrane-surface interactions using a novel setup which allows tuning of the adhesion energy by an externally applied potential; see Fig. 1. With our single-vesicle approach, we can explore the phase behaviour of multicomponent membranes for different adhesion energies. One important objective is to identify distinct composition regimes for the phase separation in the bound and unbound part of the adhering vesicle membranes.Figure -Side views (xz scans) of a one-component GUV (about 60 µm in diameter) obtained by confocal microscopy. Fluorescence of the GUV membrane is shown in green and the adhesion surface as a red line. Left: no applied potential. Right: 1V applied potential. The change in adhesion strength can be clearly seen.