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 K_a 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.