SOLVATION THERMODYNAMICS OF AMINO-ACIDS - ASSESSMENT OF THE ELECTROSTATIC CONTRIBUTION AND FORCE-FIELD DEPENDENCE

The free energies of hydration of the 20 amino acids in their zwitteri onic form, their pK(a) shifts and the side-chain free energies of tran sfer have been calculated using the finite difference Poisson-Boltzman n methodology. A comparison of the results obtained with charge and si ze parameters from some popular force fields used in modelling biomole cules is presented. The force fields considered include recent version s of AMBER, CHARMM, CVFF, GROMOS and OPLS, PARSE and an ab initio-deri ved charge set. A general agreement between the theoretical prediction s, emerging from each of the parameter sets, and experiment is discern ible A critique on the current status of theoretical studies on amino acids in solution is also advanced.