[Physical state of crystalline proteins. III. Structure of thermal heating curves]

By microcalorimetry the processes proceeding in crystals of aspartate-transaminase and catalase during their termal heating have been studied. Decrease of temperature range within which heat is absorbed during a reduction of heating rate shows that the process of the destruction of crystal order is determined by the denaturation of protein molecules. A thin structure of heat absorption curve is found at some heating rates. It is found that during heating no perfection of defect crystallite structures takes place. The protein state in crystal is either equilibrium or quasiequilibrium.