COMPUTATIONAL CONFORMATIONAL-ANALYSIS OF NEURAL MEMBRANE-LIPIDS - DEVELOPMENT OF FORCE-FIELD PARAMETERS FOR PHOSPHOLIPIDS USING SEMIEMPIRICAL MOLECULAR-ORBITAL CALCULATIONS

MM2 force field parameters for phospholipids were developed. These par ameters - MM2(Lipid) - were employed in energy-minimization calculatio ns (using crystal structures as starting conformations) on four phosph olipids: dimyristoylphosphatidylglycerol, dilauroylphosphatidyl-N,N-di methylamine, 1,2-dilauroyl-dl-phosphatidylethanolamin and deoxylysopho sphatidylcholine. After minimization, slight conformational changes we re seen in the hydrocarbon chains, while greater change was seen at th e head group. The diacylglycerol backbone of the energy-minimized stru ctures exhibited conformations corresponding to experimentally observe d conformations. The energy minimization of a randomly and significant ly altered geometry of 1,2-dilauroyl-dl-phosphatidylethanolamine resul ted in a head group conformation that closely agreed with ab initio th eoretical calculations. The utility of AM1 in molecular mechanics para meterization was demonstrated.