[Temperature and time stability of proteins in concentrated solutions]

A comparative calorimetric study of temperature stability of proteins in reversible and nonreversible denaturation has been carried out by means of continuous heating of its concentrated solutions. A wide range of heating rates (vh) was used. The dependence of denaturation temperature Td on the total heating time is quite different in cases of reversible (RNase, Ph 4) and nonreversible (catalase, PH 7) denaturation. At moderate heating rates (vh less than 5 deg/min) the temperature Td does not depend on vh for reversible denaturation in contrast to nonreversible denaturation where Td decreases with the decrease of vh. At high heating rates (vh greater than 10 deg/min) Td increases along with heating rate for both types of denaturation. It is assumed that the dependence of Td on the heating time for catalase at low and moderate heating rates is caused by the nonreversible nature of denaturation process. The increase of Td with vh at high heating rates is connected with superheating of native structure for td greater than 1 degree/vh.