Thermodynamics of protein unfolding-refolding transition

Abstract

A phenomenological thermodynamic model is developed to investigate, in more detail than usual, the pressure-temperature phase diagram of proteins. Indeed, in the whole of previous studies the specific heat difference deltaCP is treated as pressure and temperature independent. This assumption is wrong, as confirmed by Yamaguchi et al (1995) which reported pressure dependence of deltaCP in the case of ribonuclease A. In this work, assuming that the chemical potential has a Taylor series expansion and having an additional thermodynamic piece of information, the analysis shows that it is possible to obtain a complete description of the unfolding-refolding transition of protein, to deduce the volumes, entropies, enthalpies versus transition temperatures and transition pressures and, for the first time, to deduce the specific heat changes versus transition temperatures and transition pressures. Special attention is given to the elliptical shape of the pressure-temperature phase diagram. A quantitative description of the phase transitions in the protein of Zn-Cytochrome c is given.

Keywords

• Thermodynamic; phase transition; protein

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