Recent applications of the Poisson-Boltzmann theory include computations of electrostatic forces on solvated
We evaluate two different ways of calculating the contribution of the electrostatic stress to the free energy integral based on Sharp molecules [8], solvation energies for charged rods in the and Ho ¨nig's method within the finite difference nonlinear Poissonpresence of salt [9], solvation of vesicles of ionic amphi-Boltzmann equation method with the University of Houston philes [10], interaction energies and forces for colloidal Brownian Dynamics program. We show that only one of these apparticles [11,12], membrane-electrolyte systems [13] and proaches gives consistent results in the limit of zero ionic concentranumerous others. It has been considered a reference for tion for interactions of the order of magnitude of the hydrogen bond. The results are compared with results from both the linear other approximate methods [14,15] and has been parame-Poisson-Boltzmann equation and the Debye-Hu ¨ckel theory, for ion terized to give results in qualitative agreement with expericoncentrations within the limits of validity of these approximental quantities for a range of compounds while the freemate methods. We demonstrate this by application to DNA energy perturbation technique has proven to be both more molecules. ᮊ 1997 Academic Press costly and problematic [16], although potentially exact. Comparisons with grand canonical Monte Carlo methods and the hyper-netted chain formalism have shown that 263