Continuum model calculations of solvation free energies: Accurate evaluation of electrostatic contributions

The electrostatic contributions to free energies of solvation of several small molecules have been calculated, treating the solvent as a statistical continuum. The computational method is based on solving the linearized Poisson-Boltzmann equation for the electrostatic potentials using the finite-difference scheme. A careful study of convergence indicates the importance of a fine grid spacing, as well as the short comings of rotational averaging. The computed free energies of solvation are in excellent agreement with the experimental results as well as the free energy perturbation calculations. The free energies of hydration of the natural nucleic acid bases are calculated and shown to be somewhat sensitive to charge model.