Abstract
Molten globule (MG) state, which is structurally distinct from both the native (N) and denatured (D) states, was originally proposed as an equilibrium intermediate state of denaturation of some proteins with a compact conformation, a considerable native-like secondary structure, and a largely fluctuating tertiary structure. Recently, our group has developed isothermal acid-titration calorimetry (IATC), a calorimetric method for evaluating the enthalpy change accompanying the pH-induced transition of protein using isothermal titration calorimeter. By this method, the pH-induced transition from N to MG state of cytochrome c was directly observed by calorimetry and was confirmed to be a two-state transition with small enthalpy change. Also, the MG state was detected in the thermal transition from N to D state by highly precise differential scanning calorimetry.
