Retention of the structural properties of cholesterol on the coarse-grained level

Cholesterol is an essential component of biological systems and important to the structure of biological membranes. In order to probe the effects cholesterol has on structure and self-assembly in mixed lipid systems over time scales inaccessible by atomistic simulations, a coarse-grained model for cholesterol has been developed. Typically, in the mapping of cholesterol to the coarse-grained level important molecular features, such as the multi-ring structure and the bumpy face provided by the chiral methyls, are lost. In order to correctly reproduce and predict the structures seen in pure crystalline cholesterol and liquid-crystalline lipid mixtures we believe these features must be retained. To this end, a coarse-grained force field has been developed using the RPM method formulated by Reith, Pütz, and Müller-Plathe [1, 2]. The RPM method allows for the radial distribution function of the coarse-grained molecule to match its atomistic counterpart, and so indirectly matches the structural properties of the coarse-grained model to its atomistic equivalent. Results will be presented for pure and mixed lipid systems and comparisons made to other coarse-graining methods where appropriate.