Domains in membranes and vesicles

Biomimetic membranes such as lipid bilayers with several molecular components exhibit intramembrane domains. These domains are formed after the membranes are quenched into a two-phase coexistence region. Solid domains tend to form facets or cylindrical segments whereas liquid domains tend to form spherical buds. In the latter case, one can distinguish three tension regimes; budding always occurs in the low tension regime for which we present preliminary experimental results for vesicle membranes composed of phospholipid, sphingomyelin and cholesterol. A multicomponent vesicle which adheres to a substrate surface consists of a bound and an unbound membrane segment which differ in their compositions. This shift in composition can induce domains within the bound segment. Such domains are also formed when membranes adhere via sticker molecules and can be driven (i) by the interplay of sticker adhesion and shape fluctuations and (ii) by the competition between sticker and repeller molecules.