Membrane Structure

Abstract

Membrane lipids self-assemble into dynamic polymorphic macrostructures in water such that the hydrophobic portion of the amphiphilic lipids move away from water, and the hydrophilic head groups interact with water. The lipids’ ability to form various polymorphic structures or lipid phases is a function of its composition, lipid shape, concentration, ionic strength, pH, degree of hydration, temperature, and pressure. The shape of the lipid defined by its critical packing parameter determines which lipid phase would be the most stable polymorphic aggregate structure. For example, membrane phospholipids with cylindrical shape form stable bilayers (lamellar phase). Polymorphic lipid phases play a very important role in regulating various membrane functions like endocytosis, exocytosis, membrane fusion. A wide variety of simpler membrane model systems have been developed with specific configuration to study membrane structure and function. These include, from the simplest, the monolayers to liposomes and nanodisks.