Support for the shape concept of lipid structure based on a headgroup volume approach

Headgroup volumes of seven dioleoyl lipid species, calculated from covalent radii, are shown to correlate linearly (r = 0.95) with the ability of those lipids to alter the midpoint temperature of the lamellar to inverted hexagonal phase transition (L alpha-->HII) of a 95 mole fraction percent phosphatidylethanolamine matrix. The results illustrate the utility of the shape concept and basic considerations of headgroup volume as a predictive tool for the determination of lipid structure.