Isothermal Titration Calorimetry Characterization of Drug-Binding Energetics to Blood Proteins

Techniques such as calorimetry, spectroscopy, and hydrodynamic methods can be used to investigate the binding energetics of drugs bound to macromolecules. In this chapter, the authors describe the use of isothermal titration calorimetry (ITC) to measure the binding energetics of drugs bound to blood proteins (i.e., human serum albumin [HSA] and α-acid glycoprotein [AGP]). The stoichiometry (n ), the association-binding constant (K _a ), and the enthalpy (ΔH ⁰ ) of binding can be rapidly, directly, and precisely measured using ITC. Because the free energy (ΔG ⁰ ) and the entropy (ΔS ⁰ ) are readily calculated from K _a and ΔH ⁰ , a complete thermodynamic characterization of binding can be acquired in a single experiment.