Biochemical Applications of Differential Scanning Calorimetry

Differential scanning calorimetry (DSC) and the closely related differential thermal analysis (DTA) have been widely employed during the last several decades in the thermodynamic study of processes that are initiated by either an increase or a decrease in temperature. This review focuses on biochemical applications of DSC. Macromolecular and polymolecular structures stabilized by the cooperation of numerous weak forces are important to most biochemical processes. Since such highly cooperative structures undergo conformational or phase transitions upon being heated, significant information concerning these structures can be obtained by DSC. Small molecules cannot be studied by DSC unless they form aggregates showing intermolecular cooperation, as in crystals. This is illustrated in Table 1. Since the enthalpies of chemical processes rarely are as large as 20 cal g-l, it is evident that molecules having molecular weights, or molecular aggregates having aggregate weights, in the thousands of daltons are required to give transitions sufficiently sharp for useful DSC observation. In a scanning calorimeter, one measures the specific heat of a system as a function of the temperature. For a solution, the apparent specific heat of the solute, c2, is given by the expression