a calorimetric study on the interaction of zinc ion with human growth hormone

a thermodynamic study on the interaction between zinc ion (zn2+) and human growth hormone(hgh) was studied at two temperatures of 27c and 37c in aqueous solution using an isothermal titrationcalorimetry. it was found that there is a set of three identical and non-interacting binding sites for zn2+ ions. the intrinsic dissociation equilibrium constant and the molar enthalpy of binding are 1.54 mm and 17.6 kj mol-1 at 27c and 1.93 mm and 7.1 kj mol-1 at 37c, respectively. to reproduce the binding parameters of metal ionhormone interaction over the whole range of zn2+ concentrations a solvation theory was applied. the binding parameters deduced from the solvation model were attributed to the structural change of hgh and its biological activity due to the metal ion interaction