ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 52, Number 6
JKCSEZ 52(6)
December 20, 2008 

A thermodynamic study on the interaction between magnesium and cobalt ions (M²⁺), and human growth hormone, hGH, was studied at 27 °C in NaCl solution (50 mM) using the isothermal titration calorimetry. Isothermal titration calorimetry was applied to obtain the binding isotherm for hGH+M²⁺. The results obtained indicate that there is a set of three identical and noninteracting binding sites for Cobalt ions and a set of two for magnesium. The extended solvation model was used to reproduce the enthalpies of M²⁺+hGH interactions over the whole metal ions concentrations. The solvation parameters recovered from the solvation model were attributed to the structural change of hGH due to the metal ion interaction. The extended solvation model was applied to elucidate the effect of Mg²⁺ and Co²⁺ binding on the protein stability.