A Monte Carlo simulation study of solvent effect on Ca2+ to Mg2+ ion mutation

Abstract

The solvent effects on the relative free energies of solvation for Ca2+ to Mg2+ ion mutation in several solvents have been investigated by the Monte Carlo simulations of statistical perturbation theory (SPT). We compared the relative free energies for interconversion of Ca2+ to Mg2+ in H2O (TIP3P) in this study with those of the computer simulations and experimental works: that in H2O (TIP3P) is −75.66±1.29kcal/mol in this study and those of the computer simulations in H2O are −75.3, −76.4 and −74.4kcal/mol and that of the experimental work is −74.7kcal/mol, respectively. There is good agreement among several studies if we consider both methods and the standard deviations. For the present Ca2+ and Mg2+ ions, the relative free energies of solvation vs. Born's function of solvents are decreased with increasing Born's function of solvents except for THF and MEOME. The trend of relative free energies of solvation of Ca2+ and Mg2+ ions in THF and MEOME solutions could be explained by the strong ion–solvent interactions existing in THF and MEOME solutions. There is also good agreement between the structural properties in this study and the published works by the ab initio, density function theory (DFT), computer simulation and experimental results.