Spin-lattice (R1Z) and quadrupolar order (R1Q) relaxation rates were measured for bilayers of macroscopically oriented 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC-d54) containing cholesterol (1:1 molar ratio), using inversion recovery and broadband Jeener-Broekaert pulse sequences, respectively. Anisotropic deuterium (2H) NMR spin relaxation data were obtained for the first time along the entire flexible acyl chains of the phospholipid molecules in the liquid-crystalline state. Individual spectral densities J1(ω0) and J2(2ω0) were calculated from these relaxation rates, and a strong dependence on the angle θ between the macroscopic bilayer normal and the static magnetic field was observed. The spectral densities exhibited opposite angular anisotropies, which were explained in terms of a simple rotational diffusion model for the molecular dynamics of membrane lipid constituents.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry