Isothermal Titration Calorimetry for Studying Protein–Ligand Interactions

Abstract

Isothermal titration calorimetry (ITC) is a biophysical technique that allows a thermodynamic characterization of an interactive system. It is a free in solution technique that requires no labeling, using heat as signal. ITC allows simultaneous determination of affinity K a, stoichiometry n, enthalpy change ΔH and calculation of free energy change ΔG and entropy change ΔS in one single experiment. It is the only technique that allows direct enthalpy change measurement. By accessing the enthalpy change, we get a step closer in estimating the driving forces that characterize the interaction of a protein with a ligand, information much needed in the drug discovery process.

The binding interaction between cadmium‐based, aqueous‐phase quantum dots with Candida rugosa lipase

“…This technique is widely used in biochemistry in the exploring of the ligand‐protein interactions to provide a detailed thermodynamic description and a better understanding of the mechanism . The interaction of MPA‐capped CdTe QDs continuously titrating into CRL is endothermic as shown in Figure 7.…”

“…This technique is widely used in biochemistry in the exploring of the ligand-protein interactions to provide a detailed thermodynamic description and a better understanding of the mechanism. 20,60,61 The interaction of MPA-capped CdTe QDs continuously titrating into CRL is endothermic as shown in Figure 7. Each injection was observed as a spike on the thermogram that corresponded to the heat absorbed upon binding of the QDs to the lipase.…”

Anti-cooperative ligand binding and dimerisation in the glycopeptide antibiotic dalbavancin

“…S3a–S3d, see ESI†), which corresponded to a 1 : 1 binding complex for the monomer and 2 : 2 for the dimer. 46 Our data is in agreement with a previous study. 40 For teicoplanin and dalbavancin, the calorimeter cell was pre-rinsed with the experimental concentration of glycopeptides to prevent non-specific binding of these lipophilic antibiotics to the metal surface of the calorimeter cell.…”

“…The binding stoichiometry of the teicoplanin monomer was 0.8, which fitted to a 1 : 1 binding. 46 Interestingly, the ligand-binding of the dalbavancin monomer fitted to a 2 : 1 dalbavancin : ligand complex ( N closer to 0.5), while its dimer bound to ligand in a 1 : 1 ratio ( N closer to 1, Fig. S3e–S3f, see ESI†).…”

“…The Gibbs free energy (Δ G ) was calculated using the Gibbs–Helmholtz thermodynamic and van't Hoff equations as previously described. 46 …”