Isothermal titration calorimetry in drug discovery.

Publisher Summary This chapter discusses that isothermal titration calorimetry (ITC) follows the heat change when a test compound binds to a target protein. It allows precise measurement of affinity. The method is direct, making interpretation facile, because there is no requirement for competing molecules. Titration in the presence of other ligands, rapidly provides information on the mechanism of action of the test compound, identifying the intermolecular complexes that are relevant for structure-based design. Calorimetry allows measurement of stoichiometry and so evaluation of the proportion of the sample that is functional. ITC can characterize protein fragments and catalytically inactive mutant enzymes. It reviews that it is the only technique, which directly measures the enthalpy of binding (ΔH°). Interpretation of ΔH° and its temperature dependence (ΔCp) is usually qualitative, not quantitative. This is because of complicated contributions from linked equilibria and a single change in structure giving modification of several physicochemical properties. ITC can characterize protein fragments and catalytically inactive mutant enzymes. It is the only technique, which directly measures the enthalpy of binding (ΔH°). Interpretation of ΔH° and its temperature dependence (ΔCp) is usually qualitative, not quantitative. This is because of complicated contributions from linked equilibria and a single change in structure giving modification of several physicochemical properties.