Protein Denaturation During Heat Shock

Publisher Summary This chapter describes measurements of protein denaturation in cells and correlates denaturation with cell death because of hyperthermia. Differential scanning calorimetry (DSC) is the most direct method of monitoring protein denaturation or unfolding. Because of the fundamental parameter measured, heat flow, DSC can be used to detect and quantitate endothermic transitions in complex structures, such as isolated organelles and intact cells. DSC profiles demonstrating endothermic transitions in the hyperthermic region are given for human erythrocytes, a number of tissue culture lines, rat hepatocytes, and several species of Bacillus. The profiles for the mammalian cells (isolated rat hepatocytes, liver homogenate, and the tissue culture lines) have several common features. There are five main transitions, several of which are resolvable into subcomponents, observed with transition temperatures (Tm) of 45–98°C. The onset temperature is approximately 40 °C, but some transitions may extend as low as 37–38°C. In addition to acting as the primary signal for heat shock proteins (hsp) synthesis, the inactivation of critical proteins may lead to cell death.