Model of interaction of polar lipids, cholesterol, and proteins in biological membranes

Abstract Membranes are proposed to consist of a hydrophobic core, two hydrogen belts, and two polar zones. The hydrogen belts consist of hydrogen bond acceptors, i.e. the carbonyl groups of phospholipids and sphingolipids, and hydrogen bond donors, i.e. the labile hydrogens of cholesterol, sphingosine, proteins, and water. The density of anhydrous hydrogen bonding and the impermeability of the membrane increase with increasing concentrations of cholesterol, sphingolipids, α‐hydroxy acyl residues, plasmalogens, and ether phospholipids. Cholesterol owes its membrane‐closing properties to its rigid longitudinal orientation in the membrane combined with the latitudinal orientation of the O−H bond. It is suggested that the intrinsic proteins of membranes are held in position by hydrogen bonding, as well as by hydrophobic and electrostatic forces, and that hydrogen bonding also mediates the penetration of membranes by proteins.