Strong Solute−Solute Dispersive Interactions in a Protein−Ligand Complex

The contributions of solute−solute dispersion interactions to binding thermodynamics have generally been thought to be small, due to the surmised equality between solute−solvent dispersion interactions prior to the interaction versus solute−solute dispersion interactions following the interaction. The thermodynamics of binding of primary alcohols to the major urinary protein (MUP-I) indicate that this general assumption is not justified. The enthalpy of binding becomes more favorable with increasing chain length, whereas the entropy of binding becomes less favorable, both parameters showing a linear dependence. Despite the hydrophobicity of the interacting species, these data show that binding is not dominated by the classical hydrophobic effect, but can be attributed to favorable ligand−protein dispersion interactions.