Molecular motion and order in single-bilayer vesicles with multilamellar dispersions of egg lecithin and lecithin-cholesterol mixtures. A deuterium nuclear magnetic resonance study of specifically labeled lipids

作者：Gerald W. Stockton, Carl F. Polnaszek, ALEXANDER P. TULLOCH, Fariza B. Hasan, Ian C. P. Smith · 发表于：Biochemistry · 年份：1976 · DOI：10.1021/bi00650a003 · 被引用次数：287 · 研究领域：Lipid Membrane Structure and Behavior、Sphingolipid Metabolism and Signaling、Surfactants and Colloidal Systems

Deuterium (2H) nuclear magnetic resonance (NMR) quadrupole splittings and relaxation times have been measured for a variety of specifically deuterated lipids intercalated in lamellar-multibilayer dispersions and single-bilayer vesicles of egg lecithin and lecithin-cholesterol mixtures. The deduced order parameters and relaxation times vary with position of deuteration, acyl chain length, unsaturation, and temperature. The order parameters and spinlattice relaxation times T1 indicate rapid intramolecular motions of restricted amplitude in both the choline head group and hydrocarbon chains. The ordering profile for the acyl chains is similar to that predicted by statistical-mechanical theory. The order parameters yield estimates of the bilayer thickness and linear coefficient of expansion in close agreement with the x-ray determinations. A comparison of the deuterium and electron spin resonance spinprobe order parameters demonstrates the perturbation of the bilayer by the bulky nitroxide probe. The transverse relaxation time T2 for single-bilayer vesicles is quantitatively accounted for by a simple modification of classical relaxation theory which takes into account the modulation of the static quadrupole interaction by rapid local molecular motions and the modulation of the residual quadrupole interaction by the slower overall tumbling of the vesicle. It is unambiguously demonstrated that molecular motion and order in single-bilayer vesicles are very similar to those in lamell...