From small fluctuations to large-scale phase separation: lateral organization in model membranes containing cholesterol.

Macroscopic coexisting liquid phases are readily observed in certain model membranes containing cholesterol and at least two other lipid components. Recent fluorescence microscopy and deuterium NMR work indicates that submicron fluctuations are also found, in vesicles with near-critical lipid compositions. In principle, the magnitude of critical fluctuations can be controlled by changing temperature, or through other means of shifting the phase boundary such as including impurities or cross-linking components. Critical fluctuations are dynamic submicron domains in model membranes, and provide a plausible physical mechanism to produce putative 'raft' domains in cholesterol-rich biomembranes.