Simplification of Force fields

When simulating a biomolecule in aqueous solution, the bulk of the computing effort is spent on simulating water. Omitting the solvent degrees of freedom saves a factor of 10-50 in computer time. However, the mean force exerted by the solvent must be retained for a proper treatment of the solute. Various representations of the mean solvation force for biomolecules are investigated and tested. Another way to simplify a force field is to consider only a few degrees of freedom per group of atoms, e.g. an amino acid residue. Such a simplified coarse-grained force field is under development for water, co-solvents and lipids.