Coupling nonpolar and polar solvation free energies in implicit solvent models

Abstract

Recent studies on the solvation of atomistic and nanoscale solutes indicate that a strong coupling exists between the hydrophobic, dispersion, and electrostatic contributions to the solvation free energy, a facet not considered in current implicit solvent models. We suggest a theoretical formalism which accounts for coupling by minimizing the Gibbs free energy of the solvent with respect to a solvent volume exclusion function. The resulting differential equation is similar to the Laplace-Young equation for the geometrical description of capillary interfaces but is extended to microscopic scales by explicitly considering curvature corrections as well as dispersion and electrostatic contributions. Unlike existing implicit solvent approaches, the solvent accessible surface is an output of our model. The presented formalism is illustrated on spherically or cylindrically symmetrical systems of neutral or charged solutes on different length scales. The results are in agreement with computer simulations and, most importantly, demonstrate that our method captures the strong sensitivity of solvent expulsion and dewetting to the particular form of the solvent-solute interactions.

Poisson–Boltzmann model analysis of binding mRNA cap analogues to the translation initiation factor eIF4E

“…This overestimation would be greater with the vdW model for the dielectric boundary, what supports conclusions of the present work. However we should add that some consistent coupling of non polar and polar solvation free energies in the context of computation of the binding free energies is desired and such work is in progress [50]. It is also useful to point to recent important improvements in modelling non polar contributions to free energy of binding, particularly a recognition of non polar attractive and repulsive contributions to free energy of binding which must be modelled separately [51,52,53].…”

Electrostatic Free Energy and Its Variations in Implicit Solvent Models

“…We now consider the solvation of molecules in the framework of variational implicit solvent approach [19,20]. We denote by Ω the entire region of an underlying solvation system.…”

“…In order to couple the polar and non-polar parts of the free energy and to include the curvature effect in a unified treatment, Dzubiella, Swanson, and McCammon [19,20] have recently developed a class of variational implicit solvent models. The basic idea of this approach is to introduce a free energy functional that depends solely on a possible solutesolvent interface.…”

Interface dynamics of microscopic cavities in water

“…alkanes and noble gases, and quantitatively account for dewetting effects in nanometer-sized hydrophobic confinement. 19 While we conclude that the equilibrium location of the solute-solvent interface seems to be well described by those techniques, nothing is known about the interface dynamics of evolution and relaxation. In this study we address two fundamental questions: First, what are the equations which govern the interface motion on atomistic (∼1nm) scales?…”