Lipid Domains, Chemistry of

Abstract

Abstract Biological membranes are composed largely of proteins and lipids. A wide range of molecular structures exists among these molecules. It is therefore not surprising that biological membranes are not uniform but rather cluster certain molecules in specific regions or domains. This behavior can be mimicked in model systems comprising a limited number of components to study in more detail the molecular nature of this domain formation. Two types of domains exist that have been more extensively studied. One is a membrane domain enriched in polyanionic lipids, such as phosphatidylinositol diphosphate. Such domains are formed by the presence of proteins with segments containing several cationic amino acid residues. Such proteins have been termed “pipmodulins.” Another kind of domain is formed as a consequence of the nonuniform distribution of cholesterol in the membrane. Caveolae represent one type of cholesterol‐rich domain that is well characterized. Other cholesterol‐rich domains are termed “rafts.” Characterization of rafts in model membranes is well documented, but the nature of cholesterol‐rich domains in biological membranes remains a subject of controversy. Several imaging and fluorescence methods are being employed to further characterize the size and lifetime of small raft domains in biological membranes.