Membrane lipid phase behaviour and lipid-protein interactions

Abstract

One of the most distinguishing features of nearly all biological membranes is that they contain a highly complex assortment of polar lipids. Only a few major lipid classes can be recognized but there is a whole spectrum of molecular species within each of these major lipid classes which differ in the type, length, and number of unsaturated residues of their hydrophobic component. There is a general consensus, based on observations that have been obtained by a variety of biophysical methods, that the lipid constituents of all biological membranes are arranged in a bilayer configuration in which the polar groups are located on the outside, in contact with the aqueous medium, and the hydrocarbon substituents are oriented toward the interior to form a hydrophobic domain that excludes water. It has been argued on the basis of the hydrophilic to hydrophobic balance within the molecules that membrane lipids have a relatively low critical micellar concentration and a discrete distribution of domains within the molecule and this is responsible for creating a stable bilayer structure.