Structural and thermodynamic determinants of chain-melting transition temperatures for phospholipid and glycolipids membranes.

For optimum function, biological membranes need a fluid environment, which is afforded by the liquid-disordered phase of lipids with low chain-melting temperatures or the liquid-ordered phase that is formed by combining high chain-melting lipids with cholesterol. The dependence of chain-melting transition temperature on lipid chain structure is therefore of central importance. The currently available database, including sphingolipids and glycolipids, is summarised here by parameterising systematic dependences on molecular structure in terms of suitable thermodynamic models. Chain-length dependence, chain asymmetry of lipids forming partially interdigitated and mixed interdigitated gel phases, chain unsaturation, positional dependence of methyl branching, headgroup-attached and alpha-branched chains, and length of zwitterionic headgroups are all covered. This type of information is essential for biophysical approaches to functional lipidomics.