A study of mobility and order in model membranes using 2H NMR relaxation rates and quadrupole splittings of specifically deuterated lipids

2H NMR spectra have been observed for several selectively deuterated phospholipid and fatty acid probes intercalated in the liquid crystalline phase of egg phosphatidylcholine in aqueous dispersion. For unsonicated lamellar dispersions and planar multibilayers, quadrupole splittings may be observed which lead directly to a value for the order parameter for the carbon-deuterium bond. Sonicated dispersions yield high-resolution spectra, from which spin-lattice relaxation rates and correlation times for rotational diffusion can be obtained. The presence of cholesterol in the dispersion has no effect on the quadrupole splittings and relaxation rates for 2H in the choline methyl groups, in contrast to its profound effect on the spectra for 2H in the hydrocarbon chains.