Lipid bilayer standing wave conformations in aqueous cubic phases

Abstract

Certain lipid bilayers in water adapt cubic conformations of hyperbolic geometry, like periodic minimal- or nodal surfaces, and these can be dispersed into particles called cubosomes. The hyperbolic geometry requires a wide span of molecular conformations in this packing environment, and a high degree of mobility in the bilayers is therefore likely in order to provide the packing equilibrium between molecules at the flat points and those at the necks. It is here proposed that the lipid bilayers form standing waves, with the middle of the bilayers represented by the corresponding nodal surface. Transversal vibrations result in a vibration mode and longitudinal in a breathing mode, both of them being more emphasised at the flat points. The standing wave description is extended to cubosome particles, and as examples cubosomes with D-surface internal structure and tetrahedral external boundaries are presented.