Diffusion measurements in oriented phospholipid bilayers byNMR1in 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 ${\mathit{D}}_{\mathit{L}}$ was measured at different temperatures and water contents of the sample. Additionally, the lateral diffusion coefficient ${\mathit{D}}_{\mathit{W}}$ 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 ${\mathit{D}}_{\mathit{L}}$ and ${\mathit{D}}_{\mathit{W}}$ 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. © 1996 The American Physical Society.