Comparison of the structures of dimyristoylphosphatidylcholine in the presence and absence of cholesterol by molecular dynamics simulations

Molecular dynamics simulations were carried out on bilayers consisting of dimyristoylphosphatidylcholine dihydrate (DMPC) and DMPC-cholesterol at a 1:1 mole ratio. The calculations were carried out under NPT conditions (constant number of molecules, pressure and temperature, with volume and bilayer area per molecule free to change). Raising the simulation temperature from 200 to 325 K caused the surface area per DMPC molecule to increase from 39 to 50 Angstrom(2) in the pure bilayer: the area per heterodimer of DMPC and cholesterol increased from 79 to 91 Angstrom(2) for the same temperature range. The properties of the high-temperature state approximates that of a liquid crystalline array, although the area per molecule in the pure DMPC bilayer remains smaller than the experimentally determined value of 65-69 Angstrom(2) The number of gauche bonds, the P-N vector angle distribution, and the internal dipole potential are also reported for the simulated liquid crystalline state in the presence and absence of cholesterol.