Deuterium nuclear magnetic resonance studies on the interaction of glycophorin with 1,2-dimyristoylamido-1,2-deoxyphosphatidylcholine

Abstract

Membrane dynamics of dimyristoylphosphatidylcholine (DMPC) lipid bilayer which contains glycophorin with an artificial boundary lipid, 1,2-dimyristoylamido-1,2-deoxyphosphatidylcholine (DDPC), was investigated by 2H-NMR technique. For this purpose, both DMPC and DDPC were deuterated at the position of the 8th carbon atom of their acyl chains. Comparing, with DMPC bilayers, DDPC bilayers showed larger deuterium quadrupole splitting ( Δν Q ) by approx. 2 kHz. This was explicable in terms of the stabilization of the membrane due to the formation of a strong hydrogen bonding in bilayers. Addition of glycophorin to the DMPC or DDPC single bilayers caused an increase in the Δν Q value. The Δν Q value of DMPC/DDPC mixed lipid bilayer was smaller than that of each single lipid bilayer. DDPC in the DDPC/DMPC mixed bilayer was not phase-separated but homogeneously distributed. In glycophorin-reconstituted DMPC- d 4/DDPC mixed bilayers, the Δν Q of DMPC- d 4 was almost identical to that of the simple DMPC- d 4 bilayer. On the other hand, the Δν Q of DDPC- d 4 in the DMPC/DDPC- d 4 mixed bilayer increased significantly upon the reconstitution of glycophorin. Judging from these data, we concluded that, in the DDPC/DMPC mixed bilayer which contains glycophorin, DMPC simply behaves as the matrix lipid, while DDPC surrounds glycophorin and certainly plays a role of the boundary lipid.