Isothermal Titration Calorimetry Report

Calorimetric Method

Isothermal titration calorimetry (ITC) is very unique technique that can give various thermodynamic parameters such as change in enthalpy(ΔH), change in free energy (ΔG) ),change in entropy (ΔS), in a single experiment, that are also related to equilibrium binding constant (Ka). The enthalpy of binding provides us information about favorable hydrophobic, H-bonding, and electrostatic interactions whereas the entropy of binding arises due to changes in freedom of the backbone and the side chain atoms and rearrangement or escape of solvent water molecules and ions. This technique is mainly used for studying the binding of proteins with other proteins, peptide and DNA.

Instrumentation

In a usuall ITC instrument, the

Current flow is the result of a dependence of the ratio of the activities of hexacyanoferrate(III) and the hexacyanoferrate(II) ions on the electrode potential that at each potential of the working electrode there should be a specific value of the ratio a[Fe(CN)6]3−/a[Fe(CN)6]4− E = E° + RT/nF ln a[Fe(CN)6]3−/a[Fe(CN)6]4− Eq.(3)

This above equation is known as Nernst equation. This equation needs that at each potential of the working electrode there should be a specific value of the ratio a[Fe(CN)6]3−/a[Fe(CN)6]4−.The standard potential E° is related to the standard Gibbs free energy of the reaction and to equilibrium constant K according to following equation.

− nFE ° = ∆G°T,p= −RT lnk. Eq.(4)

The standard potential gives us access to the standard Gibbs free energy of a electrochemical reaction. As the Gibbs free energy is related to enthalpy and to entropy through the following