MDDFs, thus the nature of the interaction between the anions and protein surface is not affected. However, the probability of finding anions near the protein is influenced by the cation: The densities of anions in Figure , in solutions with of each specific residue to the distribution function . The cations primarily interact with neutral residues, as shown in Figures and, although interactions with polar, acidic, and basic residues are also possible. Since polar residues comprise an important fraction of ubiquitin's native conformation surface, cations are expected to be found around these regions. The cations can form ionic interactions with acidic residues, and with neutral residues because of the aliphatic chains. Interestingly, the cations also approach acidic residues, but the distributions (cyan in Figure ) are shifted towards larger distances, because of the presence of intermediating anions, as previously shown . Interactions with neutral residues contribute about 32.1% of the total peak magnitude at around 2.4 Å for [EMIM]⁺ and 36% for [BMIM]⁺, because of the greater alkyl chain of the later. the other side, must be a consequence of the greater accumulation of this cation in regions where the anion is strongly bound, associated with the greater self-association of the cations. Indeed, the cation-cation coordination number, close to the protein, is greater for [BMIM] + than for [EMIM] + (Supplementary Figure ).