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 52 94 water molecules. The structure, shape, hydrocarbon chain fluidity, the h ydration of the head group and the hydrocarbon chain, and the dynamics of t he micelle were analyzed from the 1.2 ns constant pressure MD simulation. T he 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 m icelle is limited. The interaction of water with the micelle mainly comes f rom the head group, and the modes of interaction with the positively charge d choline group and the negatively charged phosphate group can be deciphere d 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 va rious carbons with respect to the center of the mass of the micelle, the co nformational properties of the hydrocarbon chains have been analyzed. The d ynamics of the micelle was probed by the trans-gauche conformational transi tion rates and from the time correlation function of the C-H bonds. From th e latter, the order parameters and the correlation times for the internal m otions have been obtained. These parameters were found to be, for the most part, in excellent agreement with those obtained from NMR relaxation. (C) 1 999 Elsevier Science B.V. All rights reserved.