Chemical shift anisotropies obtained from aligned egg yolk phosphatidylcholine by solid-state 13C nuclear magnetic resonance

Abstract

Natural abundance solid-state 13C NMR spectra were obtained from orientated egg yolk phosphatidylcholine multilayers in which peaks from the different types of carbon in the lipid were resolved. The residual chemical shift anisotropy of the choline, glycerol, and olefinic carbons, as well as the carbonyl and acyl chain methylene carbons, were estimated. This information provided the basis for a qualitative description of the order and conformation of egg yolk phosphatidylcholine in the L alpha phase. The results suggested the gauche conformation for the C alpha-C beta bond in the choline moiety, a constrained glycerol region, a magic angle orientation for the sn-2 carbonyl, and a preferred orientation close to the bilayer normal for the plane of the sn-1 carbonyl bond and acyl chain C = C bond. The orientations of the carbon nuclei are in accord with the molecular conformation derived from previous 2H, 31P, and 13C NMR studies.