Structural analysis of hydrated egg lecithin and cholesterol bilayers I. X-ray diffraction

Abstract

Lamellar X-ray diffraction from hydrated multilayers of a 3:2 molar mixture of egg lecithin and cholesterol has been analysed. Electron density profiles of the bilayer have been derived and interpreted in terms of the molecular configurations of the component lipids. Molecular models of the bilayer are presented. The model calculations show the cholesterol molecule to be largely immersed in the hydrocarbon core of the bilayer, with its hydroxyl group near the water interface. The models show the phosphorylcholine headgroup of the lecithin molecule lying approximately in the bilayer plane, consistent with the neutron scattering experiments described in the accompanying paper ( Worcester & Franks, 1976) .