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 ${\mathit{L}}_{\mathrm{\alpha }}$ to the ${\mathit{L}}_{\mathit{c}}$ lamellar phase occurs. Changes of the lipid bilayer conformation are discussed and the total energy function for the inverted cubic Ia3d and the lamellar ${\mathit{L}}_{\mathrm{\alpha }}$ mesophase is derived. An estimate of the energy necessary for packing the lipid hydrocarbon chains is given. © 1996 The American Physical Society.

• Received 13 May 1996

DOI:https://doi.org/10.1103/PhysRevE.54.5840