Thermal Denaturation Methods in the Study of Protein Folding

This chapter focuses on the folding/unfolding equilibrium of monomeric protein systems under equilibrium conditions; however, the equations and the general treatment are applicable to other macromolecular systems or can be extended in a straightforward fashion to other systems. The absolute heat capacities can be used to obtain structure-related information and the degree of hydration or degree of solvent exposure of the polypeptide chain to the solvent. This information is extremely important and can be used to assess the degree of unfolding achieved by thermal denaturation. It has been shown that the absolute heat capacity of different protein conformations can be accurately predicted from high-resolution structural parameters. Differential scanning calorimetry measures the heat capacity of a solution directly; however, only recently have instruments with the required sensitivity and precision for absolute measurements of the heat capacity of proteins in dilute solution is developed. The heat capacity itself contains a wealth of information and can be related directly to structural parameters. The chapter discusses analysis of the heat capacity of proteins in different conformational states and its relation to structural parameters.