Dynamic Molecular Organization in Vesicles and Membranes

Abstract

AbstractThe physico chemical properties of lipid layers and membranes which are of special interest in connection with processes in organized molecular assemblies are summarized. In particular the basic physical principles governing structure formation in lipid/protein/water systems are discussed. As a first step towards structure formation the self association of lipids in water is discussed. It is then shown that 2‐dimensional lipid mixtures possess an intrinsic tendency towards lateral structure (domain) formation which originates in differences in symmetry of the possible polymorphic states of lipid layers. Evidence is provided that the lateral structure formation is greately enforced by incorporation of macromolecules into lipid layers, while in membranes containing charged lipids, domain formation may also be triggered by electrostatic binding of water soluble proteins. ‐The origins of the spontaneous structure formation in lipid/protein systems are (1) cooperative lipid protein interaction which is caused by lipid‐mediated elastic long range forces, (2) the capacity of proteins to select specific lipids in lipid alloys either by electrostatic forces or by a steric‐elastic effect. Finally, it is shown that (domain) structure formation is a very fast process, which, in the presence of charged lipids, may be accompanied by pronounced hysteresis effects. The close analogies between the physical properties of lipid mixtures and metal alloy are discussed.