Abstract:

The interaction between chromium(Ⅵ) and bovine serum albumin(BSA) was investigated via fluorescence, UV/Vis and CD spectroscopies. It is shown that Cr(Ⅵ) decreased the intensity of UV absorption peak of BSA, accompanied by red-shift. The fluorescence experimental results show that the fluorescence quenching of BSA by chromium(Ⅵ) is a result of the formation of Cr(Ⅵ) BSA complex; static quenching was confirmed to result in the fluorescence quenching. The thermodynamic parameters were calculated(ΔGθ＜0，  ΔHθ=-12.60 kJ/mol, ΔSθ=56.60 J/(mol·k)), the process of binding Cr(Ⅵ) molecule on BSA was a spontaneous molecular interaction procedure, during which the entropy increased and the Gibbs free energy decreased. The electrostatic force interaction plays a major role in stabilizing the complex. The distance between the tryptophane residue of BSA and Cr2O2-7  anion(2.85 nm) was determined by the mechanism of the energy transfer of dipole dipole interaction. The results of synchronous fluorescence spectroscopy and CD spectroscopy indicate that Cr(Ⅵ) had a strong impact on BSA conformation, resulting in the change of the tryptophane residues environments and the decrease of the α-helical content of the protein.

Key words: chromium(Ⅵ),bovine serum albumin,fluorescence spectroscopy,CD spectroscopy