Nevertheless, at higher concentrations, the protein becomes preferentially hydrated and, additionally, there is an inversion in the solvation strength of [EMIM] + and [BMIM] + . Here, these concentration-dependent phenomena are explained with the analysis of cation coordination numbers and water concentrations in each system. The coordination numbers are zero in the protein immediate vicinity due to the exclusion volume. Beyond this region, the coordination numbers increase. At lower concentrations (Figures ) the coordination number of [BMIM] + is greater than that of [EMIM] + , which complies with the greater affinity of the more hydrophobic cation to the protein surface. Nevertheless, as the concentration increases (Figures ), the two curves become similar, indicating saturation of interaction sites that display any specificity for the cations. Since the number of cations in the protein domain is similar, it is not the determining factor leading to the greater [EMIM] + preferential solvation at the higher concentrations.