Effects of hydrostatic pressure on the monoolein-water system: An estimate of the energy function of the inverted Ia3d cubic phase

Synchrotron x-ray diffraction has been used to investigate the mesomorphism of a monoolein-water dispersion under hydrostatic pressure. The results show the existence of a new phase, probably with cubic symmetry, before the transition from the L(alpha) to the L(c) lamellar phase occurs. Changes of the lipid bilayer conformation are discussed and the total energy Function or the inverted cubic Ia3d and the lamellar L(alpha) mesophase is derived. An estimate of the energy necessary for packing the lipid hydrocarbon chains is given.