Conformation of the lecithin molecule with attached water molecules

Abstract

CNDO/2 studies on the conformation of the α chain of lecithin indicated a strong preference for a gauche-gauche arrangement about the phosphodiester group. Folding the α chain about

and α4 was energetically very favorable. Hydration of the same segment revealed three levels of water-binding energies. The ion-dipole interactions of water and the choline moiety were energetically non-substantial. In contrast, binding of water to the unesterified phosphate oxygens produced the highest enthalpies. Attachment of water to the esterified phosphate oxygens or the ester oxygens of the β chain resulted in intermediate binding strengths. By investigating complete incorporation of nine water molecules into a chosen lipid structure, a plausible lecithin-water geometry was deduced for a liquid crystalline system.