Differential scanning calorimetry.

Differential scanning calorimetry (DSC) has emerged as a powerful experimental technique for determining thermodynamic properties of biomacromolecules. The ability to monitor unfolding or phase transitions in proteins, polynucleotides, and lipid assemblies has not only provided data on thermodynamic stability for these important molecules, but also made it possible to examine the details of unfolding processes and to analyze the characteristics of intermediate states involved in the melting of biopolymers. The recent improvements in DSC instrumentation and software have generated new opportunities for the study of the effects of structure and changes in environment on the behavior of proteins, nucleic acids, and lipids. This review presents some of the details of application of DSC to the examination of the unfolding of biomolecules. After a brief introduction to DSC instrumentation used for the study of thermal transitions, the methods for obtaining basic thermodynamic information from the DSC curve are presented. Then, using DNA unfolding as an example, methods for the analysis of the melting transition are presented that allow deconvolution of the DSC curves to determine more subtle characteristics of the intermediate states involved in unfolding. Two types of transitions are presented for analysis, the first example being the unfolding of two large synthetic polynucleotides, which display high cooperativity in the melting process. The second example shows the application of DSC for the study of the unfolding of a simple hairpin oligonucleotide. Details of the data analysis are presented in a simple spreadsheet format.