Development and validation of a force-field for biologically important sterols in biomembranes

We have performed a molecular mechanics force field parametrization for the biologically important sterols cholesterol, ergosterol and lanosterol using an automated refinement method. The parameters derived have been incorporated in the CHARMM force field. Parameter sets are designed to fit results of quantum chemical calculations. The force field is validated on 2ns MD simulations of hydrated sterol:lipid systems (cholesterol, ergosterol and lanosterol, respectively). The results show different ordering effects of the hydrocarbon chains upon addition of the different sterols and with respect to their orientation in the pure bilayer. Different sterol hydration levels in the membrane are also presented.