Metal ions binding study on human growth hormone by isothermal titration calorimetric method

The interaction of hGH with some metal ions ( ) at 27°C in NaC1 solution, 50 mM was studied using Isothermal titration calorimetry. There is a set of three identical and non-interacting binding sites for binding of all these metal ions, expect . The intrinsic association equilibrium constants () are not very different for  and , and also their molar enthalpies of binding (KJ/mol for  and  KJ/mol for ) are similar showing same thermodynamical properties for hGH upon interaction  with both  and . Thermodynamical properties for hGH upon interaction  with both  is completely different from those of  and . The affinity of binding is the highest (), but the molar enthalpy of binding is the lowest () for  . There is a set of four identical and independent binding sites for . The binding process for iron ions is more exothermic (KJ/mol) than other three metal ions and with a higher affinity () respect to and