Recent studies on thermal properties of globular proteins are reviewed with emphasis on conformational transitions.
In many cases, thermal denaturation of globular proteins can be interpreted well by the two-state approximation whose validity has been tested calorimetrically. Significant deviations from the two-state approximation were observed in some cases, which shows the existence of stable intermediate states.
Existence of a prodenaturational stage has been suggested by gradual increase of heat capacity prior to the denaturational stage.
Thermal denaturation of the protein was also observed in a crystalline state. The melting temperature of crystalline lysozyme changes reversively from aobut 70 to 200°C depending upon the water content of the crystal. Merit of studies in a crystalline state is discussed.