Isothermal titration calorimetry: feeling the heat

Isothermal titration calorimetry (ITC) has become one of the mainstays of determining the affinity of small molecules with macromolecules. As such there has been a resurgence in interest in the underlying processes that contribute to a ‘good’ ITC experiment. In this article we discuss the thermodynamic origins of the data seen in an ITC experiment, some of the background theory and exemplars of what good data look like. We also discuss the origins of more complex phenomena seen with ITC, and how these may be interpreted.