Cholesterol-induced fluid membrane domains: a compendium of lipid-raft ternary phase diagrams.
The biophysical underpinning of the lipid-raft concept in cellular membranes is the liquid-ordered phase that is induced by moderately high concentrations of cholesterol. Although the crucial feature is the coexistence of phase-separated fluid domains, direct evidence for this in mixtures of cholesterol with a single lipid is extremely sparse. More extensive evidence comes from ternary mixtures of a high chain-melting lipid and a low chain-melting lipid with cholesterol, including those containing sphingomyelin that are taken to be a raft paradigm. There is, however, not complete agreement between the various phase diagrams and their interpretation. In this review, the different ternary phase diagrams of cholesterol-containing systems are presented in a uniform way, using simple x,y-coordinates to increase accessibility for the non-specialist. It is then possible to appreciate the common features and examine critically the discrepancies and hence what direct biophysical evidence there is that supports the raft concept.
Marsh
Derek
D
Max-Planck-Institut für biophysikalische Chemie, Abteilung Spektroskopie und photochemische Kinetik, 37070 Göttingen, Germany. dmarsh@gwdg.de
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D002784:Cholesterol / Q000494:pharmacology*; D006801:Humans; D008051:Lipid Bilayers / Q000378:metabolism*; D008560:Membrane Fluidity / Q000187:drug effects*; D021962:Membrane Microdomains / Q000378:metabolism*
D008051:Lipid Bilayers; D002784:Cholesterol