Cr(Ⅵ)与牛血清白蛋白的相互作用

Interaction Between Chromium(Ⅵ) and Bovine Serum Albumin

采用荧光光谱、紫外光谱、CD光谱法研究了K2Cr2O7与牛血清白蛋白(BSA)的相互作用。实验结果表明,铬(Ⅵ)使BSA的紫外吸收降低,峰位红移,表明铬(Ⅵ)与BSA发生较强的相互作用;铬(Ⅵ)酸根离子与BSA形成基态复合物导致BSA内源荧光猝灭,猝灭机理主要为静态猝灭。测定了不同温度下该反应的热力学参数,ΔGθ<0,ΔHθ和ΔSθ分别为-12.60kJ/mol和56.60J/(mol.k),表明上述作用过程是一个熵增加、自由能降低的自发分子间作用过程,铬(Ⅵ)酸根离子与BSA之间以静电作用力为主;非辐射能量转移机理确定了铬(Ⅵ)与牛血清白蛋白中色氨酸残基之间的距离r=2.85nm;同步荧光和CD光谱研究表明,铬(Ⅵ)使BSA的二级结构发生改变,α-螺旋含量降低,色氨酸残基所处微环境的极性减小。

The interaction between chromium （VD 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（ ΔGO 〈 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 Cr2 027 - 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.