Reparametrisation of united-atom amine solvation in the GROMOS force field

New parameters for ammonia, mono-, di- and trimethylated amine compatible with GROMOS force fields are presented. A directed search in parameter space by steepest descent minimisation led to an optimised charge set with good agreement to experimental data on absolute and relative free energies of solvation in water, chloroform and carbon tetrachloride. The final model is characterised in terms of structural and dynamic properties.