[Heat denaturation of paramyosin]

Heat denaturation of paramyosin and its two proteolytic fragments has been studied by scanning microcalorimetry. It has been shown that paramyosin denaturation proceeds in several stages, each stage corresponding to the melting of a cooperative block in the macromolecule. The junctions between the blocks are the most strongly affected by proteolytic fragments. Enthalpies of paramyosin and its fragment denaturation and their temperature dependencies have been measured. It has been shown that the mean value of the specific enthalpy extrapolated to 110 degrees is noticeably lower than for globular proteins and is close to the values obtained earlier for L-meromyosin and tropomyosin. A conclusion has been drawn that the lower, in comparison with globular proteins, value of the denaturation enthalpy of alpha-superhelical structure is of a general character.