STUDY OF THE SOLVATION OF PROTEINS BY IONIC LIQUIDS USING MINIMUM DISTANCE DISTRIBUTION FUNCTIONS

Ionic liquids are molten salts (solvents only formed by ions that have melting points lower than 100 °C) with incredible physicochemical properties (low vapor pressure, high thermal stability, variable composition, etc.). Ionic liquids have been used in industry and academy as solvents, catalysts, and cosolvents in systems with proteins. Researchers are using ionic liquids as refolding/denaturating agents of proteins in a large number of systems. Nevertheless, the number of theoretical and experimental studies that describe the interaction between proteins and ionic liquids are still small. In this thesis, the structure of ubiquitin solvation by ionic liquids was computationally studied by molecular dynamics simulation and minimum-distance distribution functions. The Kirkwood-Buff theory of solutions was applied for the calculation of thermodynamic quantities from minimum-distance distribution functions calculated from simulations. The protein was preferentially solvated by the ions from the ionic liquids, especially at the lower concentrations simulated. It was noted that the ions had a greater preferential solvation parameters when solvating denaturated and extended ubiquitin conformations. Besides that, we observed that the presence of different cations, for example, causes changes in the anion distribution functions. This fact suggests that there exists a correlation of the distribution of the ions on protein solvation by ionic liquids.