In this paper complexation reaction between Yb3+ and Human serum albumin is examined using isothermal titration calorimetry (ITC). The extended solvation model was used to reproduce the enthalpies of HAS+Yb3+ interactions over the whole range of Yb3+ concentrations. The binding parameters recovered from this model were attributed to the structural change of HSA. The results show that Yb3+ ions bind to HSA with three equivalent affinity sites. It was found that in the high concentrations of the ytterbium ions, the HSA structure was destabilized.

The interaction of Jack Bean Urease with cobalt (II) ion was studied by Isothermal Titration Calorimetry (ITC) at 300 K and 310 K in 30 mM Tris buffer, pH=7. The stability of the enzyme increases due to its binding with cobalt ions. The extended solvation model was used to reproduce the heats of Co2++JBU interaction. It was found that there is a set of 12 equivalent and noninteracting binding sites for Co2+ ions. The association equilibrium constant and the molar enthalpy of binding are 4260.76M-1, -16.5 kJmol-1 at 300 K and 3438M-1, -16 kJmol-1 at 310 K, respectively.