Self-assembly of lipid domains in the extracellular leaflet of the plasma membrane and models thereof
Lipid domain formation and phase coexistence in biological membranes is a subject which has received considerable attention during the last two decades, especially the topic concerning so-called lipid rafts, a theory which has become as popular to confirm as to disproof. Regardless of the existence or precise composition and function of the classical rafts, the occurrence of lateral lipid segregation in biological membranes is indisputable. This review starts by focusing on state of the art findings concerning lipid domains and lateral heterogeneity in a biological context. Then, the physicochemical properties of lipid mixtures, phase properties and domain dynamics are considered. Canonical lipid models of the exofacial leaflet of the plasma membrane are treated in detail and the proper choices of model lipids are discussed. A special attention is given to polar lateral interactions (including carbohydrate-carbohydrate head group interactions), whose importance for spatial segregation and crystallization is commencing to be appreciated by the scientific community.