The Effect of Incorporation of Gramicidin on the Translational Lipid Diffusion in Bicontinuous Cubic Monoolein/Water Mesophases

The influence of incorporating the polypeptide gramicidin on the lateral mobility of the monoacylglyceride monoolcin (MO) in its bicontinuous cubic lipid mesophases is studied applying static field gradient NMR. The effects of gramicidin on the topology, structure and phase behaviour of the system are characterized by small-angle x-ray scattering (SAXS) experiments. On the structural level the experiments show significant shifts in the boundaries of the various mesophases. Measurements of the translational dynamics are restricted to cubic mesophases, where the diffusion coefficients of lipid and additive are determined both by geometrical obstruction and by lipid-protein interaction effects.