Molecular dynamics simulation of the structure and dynamics of a dodecylphosphocholine micelle in aqueous solution

A molecular dynamics (MD) simulation study of a dodecylphosphocholine (DPC) micelle in water is presented. This system contains 60 DPC molecules in 5294 water molecules. The structure, shape, hydrocarbon chain fluidity, the hydration of the head group and the hydrocarbon chain, and the dynamics of the micelle were analyzed from the 1.2 ns constant pressure MD simulation. The micelle was found to be slightly prolate, with the ratio of the moments of inertia 1:24:1.11:1. The penetration of water into the interior of the micelle is limited. The interaction of water with the micelle mainly comes from the head group, and the modes of interaction with the positively charged choline group and the negatively charged phosphate group can be deciphered from the radial distribution functions between these groups and both the hydrogen and the oxygen atoms of water. From the ratio of the trans/gauche conformers on the hydrocarbon chain, and the density distribution of the various carbons with respect to the center of the mass of the micelle, the conformational properties of the hydrocarbon chains have been analyzed. The dynamics of the micelle was probed by the trans-gauche conformational transition rates and from the time correlation function of the C-H bonds. From the latter, the order parameters and the correlation times for the internal motions have been obtained. These parameters were found to be, for the most part, in excellent agreement with those obtained from NMR relaxation. (C) 1999 Elsevier Science B.V. All rights reserved.