| Abstract
| - This paper describes the parametrization of a new coarse grained (CG) model for lipid and surfactant systems.Reduction of the number of degrees of freedom together with the use of short range potentials makes itcomputationally very efficient. Compared to atomistic models a gain of 3−4 orders of magnitude can beachieved. Micrometer length scales or millisecond time scales are therefore within reach. To encourageapplications, the model is kept very simple. Only a small number of coarse grained atom types are defined,which interact using a few discrete levels of interaction. Despite the computational speed and the simplisticnature of the model, it proves to be both versatile in its applications and accurate in its predictions. We showthat densities of liquid alkanes from decane up to eicosane can be reproduced to within 5%, and the mutualsolubilities of alkanes in water and water in alkanes can be reproduced within 0.5 kT of the experimentalvalues. The CG model for dipalmitoylphosphatidylcholine (DPPC) is shown to aggregate spontaneously intoa bilayer. Structural properties such as the area per headgroup and the phosphate−phosphate distance matchthe experimentally measured quantities closely. The same is true for elastic properties such as the bendingmodulus and the area compressibility, and dynamic properties such as the lipid lateral diffusion coefficientand the water permeation rate. The distribution of the individual lipid components along the bilayer normalis very similar to distributions obtained from atomistic simulations. Phospholipids with different headgroup(ethanolamine) or different tail lengths (lauroyl, stearoyl) or unsaturated tails (oleoyl) can also be modeledwith the CG force field. The experimental area per headgroup can be reproduced for most lipids within 0.02nm2. Finally, the CG model is applied to nonbilayer phases. Dodecylphosphocholine (DPC) aggregates intosmall micelles that are structurally very similar to ones modeled atomistically, and DOPE forms an invertedhexagonal phase with structural parameters in agreement with experimental data.
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