Computer Simulation of a DPPC Phospholipid Bilayer:  Structural Changes as a Function of Molecular Surface Area

Abstract

A series of molecular dynamics computer simulations have been carried out on fully hydrated liquid crystalline dipalmitoyl phosphatidylcholine (DPPC) bilayers at constant surface areas corresponding to 59.3, 62.9, 65.5, or 68.1 Å 2 /lipid, the range of values suggested by different experiments in different laboratories. Simulated quantities are compared with those from NMR (deuterium order parameters and contribution of molecular tilt to the order parameter), X-ray scattering ( D -spacings and detailed density profiles), and partial molar volumes. The results strongly support the value of 62.9 Å 2 /DPPC recently proposed by Nagle et al. ( Biophys. J. 1996, 70, 1419) and demonstrate the feasibility of a combined experimental, and simulation-based approach for determining membrane structure.