Measurement of the lateral diffusion of dipalmitoylphosphatidylcholine adsorbed on silica beads in the absence and presence of melittin:: A 31P two-dimensional exchange solid-state NMR study

P-31 two-dimensional exchange solid-state NMR spectroscopy was used to measure the lateral diffusion, D-L, in the fluid phase of dipalmitoylphosphatidylcholine (DPPC) in the presence and absence of melittin. The use of a spherical solid support with a radius of 320 +/- 20 nm, on which lipids and peptides are adsorbed together, and a novel way of analyzing the two-dimensional exchange patterns afforded a narrow distribution of D-L centered at a value of (8.8 +/- 0.5) x 10(-8) cm(2)/s for the pure lipid system and a large distribution of D-L spanning 1 x 10(-8) to 10 x 10(-8) cm(2)/s for the lipids in the presence of melittin. In addition, the determination of D-L for nonsupported DPPC multilamellar vesicles (MLVs) suggests that the support does not slow down the lipid diffusion and that the radii of the bilayers vary from 300 to 800 nm. Finally, the DPPC-melittin complex is stabilized at the surface of the silica beads in the gel phase, opening the way to further study of the interaction between melittin and DPPC.