Spectroscopic investigation on the toxic interactions of Ni2+ with bovine hemoglobin

The toxic interaction between Ni2+ and bovine hemoglobin (BHb) was investigated using fluorescence spectroscopy, synchronous fluorescence spectroscopy, ultraviolet–visible (UV–vis) absorption spectroscopy and circular dichroism spectroscopy (CD) under simulated physiological conditions. The experimental results showed that both dynamic and static quenching occurred simultaneously when Ni2+ quenched the fluorescence of BHb. The binding site number n, apparent binding constant Ka and corresponding thermodynamic parameters were measured at different temperatures. There was formation of Ni–BHb complex, but the binding between Ni2+ and BHb was not strong. The process of the formation of Ni–BHb complex was a spontaneous interaction procedure in which electrostatic interaction played a major role. In addition, UV–vis and CD results showed that the addition of Ni2+ changed the conformation of BHb.