COMPUTER-SIMULATION OF A DPPC PHOSPHOLIPID-BILAYER - STRUCTURAL-CHANGES AS A FUNCTION OF MOLECULAR-SURFACE AREA

A series of molecular dynamics computer simulations have been carried out on fully hydrated Liquid crystalline dipalmitoyl phosphatidylcholi ne (DPPC) bilayers at constant surface areas corresponding to 59.3, 62 .9, 65.5, or 68.1 A(2)/lipid, the range of values suggested by differe nt experiments in different laboratories. Simulated quantities are com pared with those from NMR (deuterium order parameters and contribution of molecular tilt to the order parameter), X-ray scattering (D-spacin gs and detailed density profiles), and partial molar volumes. The resu lts strongly support the value of 62.9 Angstrom(2)/DPPC recently propo sed by Nagle et al. (Biophys. J. 1996, 70, 1419) and demonstrate the f easibility of a combined experimental, and simulation-based approach f or determining membrane structure.