Thermodynamic Study on the Interaction of Copper Ion with Human Growth Hormone

A thermodynamic study on the interaction between the Cu2+ ion and human growth hormone (hGH) was studied at the temperatures 300.15 and 310.15 K in NaCl solution using isothermal titration calorimetry. The new solvation model was used to reproduce the enthalpies of Cu2+ + hGH interaction over the whole range of Cu2+ concentrations. It was found that there is a set of three identical and non-interacting binding sites for Cu2+ ions. The intrinsic dissociation equilibrium constant and the molar enthalpy of binding are 1313.4 mu mol.L-1 and -16.80 kJ.mol(-1) at 300.15 K, and 1648.2 mu mol.L-1 and -16.40 kJ.mol(-1) and 310.15 K, respectively. The binding parameters recovered from the new equation are attributed to a structural change of hGH and its biological activity due to metal ion interaction.