Heat capacity of protein folding

We construct a Hamiltonian for a single domain protein where the contact en thalpy and the chain entropy decrease linearly with the number of native co ntacts. The hydration effect upon protein unfolding is included by modeling water as ideal dipoles that are ordered around the unfolded surfaces, wher e the influence of these surfaces, covered with an "ice-like" shell of wate r, is represented by an effective field that directs the water dipoles. An intermolecular pair interaction between water molecules is also introduced. The heat capacity of the model exhibits, the common feature of small globu lar proteins, two peaks corresponding to cold and warm unfolding, respectiv ely. By introducing ad hoc vibrational modes, we obtain quantitatively good accordance with experiments on myoglobin.