Structure-dynamics relations in bicontinuous cubic lipid mesophases

Abstract

We investigated the structural and dynamic properties of water in aqueous dispersions of the monoacylglycerides monoolein and monoelaidin, which exhibit a rich lyotropic mesophase behaviour [1-3]. We present data on the long-range diffusion coefficient of the lipid and the water in their bicontinuous cubic phases at several hydration levels. Using the proton/deuteron selectivity, field-gradient NMR makes the determination of the diffusion coefficients of both, water and lipid molecules, possible. Owing to the mesoscopic structure, effective diffusion coefficients are measured. The water diffusion is drastically slowed down compared to bulk water. In addition, we present a wide-angle neutron scattering study of the water structure in confined cubic geometries. By applying the H/D-substitution technique [4], the structural information could be obtained on the partial structure factor level. Dependent on level of hydration and mean water channel thickness, small, but significant changes of the structure of confined water compared to bulk water are observed.