The noncovalent binding interactions of biological molecules involve the stripping away of solvent water from regions of contact between the binding partners. Accordingly, the net strength of their interactions with other molecules can be considered to include the cost of removing the interacting molecules (at least those parts that make contact with each other) from the solvent to which they were previously exposed. Free energies of solvation of biological molecules also play a major role in determining the positions of their chemical equilibria. For example, the products of hydrolysis of ATP are so much more strongly solvated than the reactants that changing solvation fully accounts for the favorable equilibrium of hydrolysis of ATP to ADP and inorganic phosphate (Williams and Wolfenden, 1985).
It has long been suspected that solvent water plays a major role in the equilibrium structure of globular proteins in solution,...
