Definition

Isothermal Titration Calorimetry (ITC) is a technique used to directly measure the heat released or absorbed during the interaction between two molecules. By recording these heat changes, ITC can provide thermodynamic parameters of the binding reaction, such as the binding constant (Ka), enthalpy change (ΔH), free energy (ΔG), and entropy change (ΔS).
In the experiment, ITC gradually injects one reactant (such as a ligand) into a reaction vessel containing another reactant (such as a protein) and monitors the heat changes triggered by each injection. These heat changes reflect the degree of molecular binding, with the heat signal gradually decreasing as the unbound molecules in the reaction vessel are consumed, until binding saturation is reached.
The main advantage of ITC is that it does not require labeling or modification of the molecules, allowing the study of molecules in their native state. ITC is widely used in drug development, protein-ligand interaction studies, enzyme activity research, and the exploration of the formation mechanisms of biomolecular complexes. Through ITC, researchers can gain a comprehensive understanding of the interaction mechanisms and thermodynamic properties between molecules, providing key data support for biochemistry and pharmaceutical sciences.