Chemistry of phospholipids in relation to biological membranes.

The quantitative determination of molecular species of natural phospholipids gave new information about the pairing of the fatty acid chains in a given lipid class. Cells appear to be equipped with enzymes which control the composition and pairing of hydrocarbon chains of phospholipids and display regulatory mechanism(s) which allow for adaptation of physical properties of membrane lipids to alteration in environmental conditions. Phospholipids containing various types of fatty acid combinations encountered in membranes have been prepared by chemical synthesis. Examination of these compounds in artificial membrane systems demonstrated that chain-length, degree of unsaturation, and the type of pairing of hydrocarbon chains determine the rate of diffusion of non-electrolytes and efficiency of carrier mediated transport across the hydrocarbon barrier. Comparison with natural membranes of different lipid composition revealed a close similarity with the model systems. This endorses the conclusion that the detailed chemical make-up of the lipid dictates the permeability behaviour of the region of the biological interface. The diversity of polar headgroups of phospholipids is demonstrated by the polyglycerol phospholipids of bacterial membranes, Detailed information about the structure of amino acyl and glucosamine derivatives of phosphatidyl glycerol has been obtained by combination of chemical synthesis and enzymatic methods.