ORIGIN OF ENTROPY CONVERGENCE IN HYDROPHOBIC HYDRATION AND PROTEIN-FOLDING

An information theory model is used to construct a molecular explanati on why hydrophobic solvation entropies measured in calorimetry of prot ein unfolding converge at a common temperature. The entropy convergenc e follows from the weak temperature dependence of occupancy fluctuatio ns for molecular-scale volumes in water. The macroscopic expression of the contrasting entropic behavior between water and common organic so lvents is the relative temperature insensitivity of the water isotherm al compressibility. The information theory model provides a quantitati ve description of small molecule hydration and predicts a negative ent ropy at convergence. Interpretations of entropic contributions to prot ein folding should account for this result.