Apolar and polar solvation thermodynamics related to the protein unfolding process

ABSTRACT Thermodynamics related to hydrated water upon protein unfolding is studied over a broad temperature range (5-125 deg C). The hydration effect arising from the apolar interior is modeled as an increased number of hydrogen bonds between water molecules compared with bulk water. The corresponding contribution from the polar interior is modeled as a two-step process. First, the polar interior breaks hydrogen bonds in bulk water upon unfolding. Second, due to strong bonds between the polar surface and the nearest water molecules, we assume quantization using a simplified two-state picture. The heat capacity change upon hydration is compared with model compound data evaluated …