Response functions of proteins.

The thermodynamics of protein folding can be studied by a variety of different techniques such as differential scanning calorimetry, differential scanning densimetry and sound velocity measurements. These three methods monitor the different response functions heat capacity, expansion coefficient and compressibility that characterise various aspects of protein dynamics such as equilibrium energy and volume fluctuations and energy-volume correlations. For the development of a comprehensive thermodynamic description of protein behaviour information on these response functions should be combined. As a starting point we provide in the present paper analytical solutions for the determination of the response functions and demonstrate on several examples how to extract a maximum of thermodynamic information on proteins from the measurements of Cp, alpha p and kappa T.