Organization of phospholipids in biological membranes

Abstract

Preferred conformations of phospholipids have been predicted through quantum-chemical techniques and classical potential functions. An essential condition for a conformation to exist in a biomembrane is that it should be possible for it to organize in the form of a bilayer. Taking into consideration the conformational flexibility of the polar head group, organization at the lipid-water interface has been considered. The biological implications of such an organization in terms of formation of "hydrophobic channels" is discussed. Quantum-mechanical investigations on the transport phenomenon have shown that the "selectivity" of biological membranes is connected with the "organization." Calculations of the quantum-mechanical transmission coefficients for different model potential profiles indicate that minor differences in the height of potential barriers in certain regions can lead to significant changes in transmission coefficients. The "directional selectivity" of substrates (differences in transmission coefficients for flow in and out of the cell) can be explained on the basis of differences in membrane organization. These results have some important consequences in the evolutionary process in biological membranes.