Abstract
Biomembranes have been modeled as a complex of lipid bilayer sheet embedding various membrane proteins. The lipid bilayer is assumed to be in liquid disordered state and hence, the lipid composition is uniform everywhere within the membrane. However, recent studies have revealed the existence of lipid raft, a lipid microdomain consisting of sphingolipids and cholesterol, in the outer leaflet of the cell membrane. Within the raft lipids are in liquid-ordered state and their mobility is strongly suppressed. The raft seems to serve as a platform where glycosil phosphatidylinositol (GPI) -or acyl chain-anchored proteins interact with each other thereby participating in intracellular signaling events and other cellular activities. Easily coalescing nature of rafts, when raft-residing proteins are cross-linked, may be important in raft function. The lipid bilayers may be better described as a mosaic of small domains.
