Diffusion measurements in oriented phospholipid bilayers by H-1-NMR in a static fringe field gradient

For the first time, to our knowledge, self-diffusion of lipids and water in lipid bilayers is studied by proton NMR measurements in the fringe field of a superconducting magnet. Highly oriented multilayer stacks of dipalmitoyl phosphatidylcholine were used, and the lateral diffusion coefficient of the lipid D-L was measured at different temperatures and water contents of the sample. Additionally, the lateral diffusion coefficient D-W of the water between the lipid bilayers was determined. The results demonstrate that our technique is extremely well suited for a precise determination of diffusion coefficients in oriented membranes, and that it allows the simultaneous measurement of both lipid and water diffusion. The values of D-L and D-W obtained by this technique agree well with published data obtained by other NMR techniques and by fluorescence methods. A comparison of our data with those obtained in a previous study by quasielastic neutron scattering provides information about the contribution of short- and long-range diffusion to the measured diffusion coefficient due to the intrinsic length and time scale of the experiments.