Solvent effect on Sr2+ to Ca2+ ion mutation: Monte Carlo simulation study Original Research Article

We have investigated the solvent effects on the relative free energies of solvation and the difference in partition coefficients of Sr2+/Ca2+ mutated to each other in solvents using Monte Carlo simulations with statistical perturbation theory study. Comparing the relative free energies for interconversion of Sr2+ to Ca2+, in H2O (TIP3P), in this study with those of the published works, that of H2O (TIP3P) is −35.60±0.13 kcal/mol in this study, those of the published works in H2O are −34.7, −37.5, and −38.8 kcal/mol and that of experimental is −34.9 kcal/mol, respectively. There is a good agreement among the several studies. For the present Sr2+/Ca2+ ion pair, the relative free energies of solvation vs. Born’s function of the solvents decreased with increasing Born’s function except for CH3OH, THF and MEOME. The relative free energies of solvation Sr2+/Ca2+ pair in CH3OH, THF and MEOME could be explained by the strong ion–solvent interactions existing in CH3OH, THF and MEOME solutions. The strong ion–solvent interactions in CH3OH, THF and MEOME solutions could be due to the electron pair donor properties of the solvents to ion, i.e., donor number of CH3OH, THF and MEOME established by Gutmann. There is also a good agreement between the calculated structural properties in this study and the published results obtained by ab initio, computer simulations and experimental works.