Calculations of the potential of mean force from molecular dynamics simulations using different methodologies: an application to the determination of the binding thermodynamic properties of an ion pair

Abstract

We report here the calculation of the potential of mean force (PMF) of the Ca²⁺…SO ion pair in the gas phase and in water using molecular dynamics simulations. The PMF calculation is performed using different free-energy perturbation (FEP) and force constraint (FC) methods. We pay attention to the FEP method for which we propose a new development specially adapted to systems with solvent molecules. The gas-phase interionic PMFs are compared with that calculated from the primitive model. We compare the shapes of the calculated PMFs in water and the resulting thermodynamic properties (, and ) of complexation with the experimental ones. We also tend to give a molecular description of the environment of the ion pair for some regions of the PMFs.

Acknowledgement

The authors would like to acknowledge the Institut du Développement et des Ressources en Informatique Scientifique (IDRIS) for a generous allocation of CPU time.