Improving Generalized Born Models by Exploiting Connections to Polarizable Continuum Models. II. Corrections for Salt Effects

A previous analytical investigation of the generalized Born (GB) implicit solvation model is extended to solvents of nonzero ionic strength. The GB model with salt effects (GB-SE) is shown to resemble the Debye-Huckel-like screening Model (DESMO), a polarizable continuum model (PCM) that we have recently developed for salty solutions. DESMO may be regarded either as a generalization of the conductor-like PCM (C-PCM) that extends C-PCM to electrolyte solutions or alternatively as a generalization Of Debye-Huckel theory to arbitrary cavity shapes. The connection between GB-SE and DESMO Suggests how the former can be modified to account for the exclusion of mobile ions from the cavity interior, an effect that is typically absent in GB-SE models. We propose two simple GB-SE Models that are exact for a point charge in a spherical cavity and that introduce the ability to account, albeit approximately; for the finite size of the mobile ions. The accuracy of these new models is demonstrated by applications to both model systems and teal proteins: These tests also demonstrate the accuracy of the DESMO approach, as compared to more sophisticated PCMs developed for electrolyte solutions.