Cr（VI）与牛血清白蛋白的相互作用

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–12.60 kJ/mol 和 56.60 J/(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＝2.85 nm；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。

Studies on the interaction between chromium (VI) and bovine serum albumin

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.