Use of Urea Solutions to Study Backbone Hydration in Protein Folding

The focus of this research was to understand the role of bulk water in protein-folding equilibria. Several thermodynamic properties of bulk water were measured as a function of urea concentration, and the results were used to relate changes in the free energy of water in protein-folding equilibria and other hydration phenomena in general. An isothermal titration calorimeter (ITC) was used to obtain ΔHH2O values from simple dilution experiments. Pressure perturbation experiments employing a differential scanning calorimeter (DSC) was used to determine ΔΔSH2O values, and density measurements were made to calculate the apparent molar water volume, jV1, as a function of urea concentration. Solubility measurements were conducted using triglycine as a mimic of the protein backbone. Future work will aim to link the bulk solution properties reported here to the observed solubility values of triglycine and other model compounds, revealing the total desolvation energy, ΔGH2O, as required for understanding the contribution of water in biothermodynamics