College of Chemical and Pharmaceutical Engineering, Jingchu University of Technology, Jingmen, 448000 Hubei, People's Republic of China.
Mol Biol Rep. 2012 Mar;39(3):2745-51. doi: 10.1007/s11033-011-1030-9. Epub 2011 Jun 14.
Under physiological conditions, the potential hematological toxicity of herbicide 2-methyl-4-chlorophenoxyacetic acid sodium (MCPA-Na) was discussed by fluorescence probe technology and spectroscopy methods including three-dimensional (3D) fluorescence, UV absorption and circular dichroism (CD) spectra. In vitro, MCPA-Na bound with bovine serum albumin (BSA) and formed new complex at ground state by electrostatic force and hydrogen bond. During the process, non-radiation energy transfer from BSA to MCPA-Na occurred and the distance r between donor and acceptor was obtained based on Förster theory. The binding site was investigated by fluorescence probe method and the results implied MCPA-Na was absorbed on domain II of BSA molecule. The enthalpy change (ΔH(θ)), Gibbs free energy change (ΔG(θ)) and entropy change (ΔS(θ)) were calculated at four different temperatures according to Van't Hoff isobar equation and Gibbs-Helmholtz equation. Negative value of ΔG(θ) indicated the process of binding was a spontaneous and irreversible process, which gave a broad hint that MCPA-Na was likely to be poisonous. CD spectra exhibited significant changes of secondary structures in BSA molecule and three-dimensional fluorescence spectra indicated the tryptophan residue in BSA was placed in a less hydrophobic environment, which presented additional evidence to caution the danger of MCPA-Na residue in food. Meanwhile, the mechanism and geometry of the binding was analyzed at molecular level.
在生理条件下，利用荧光探针技术和光谱方法，包括三维（3D）荧光、紫外吸收和圆二色（CD）光谱，探讨了除草剂 2-甲基-4-氯苯氧乙酸钠（MCPA-Na）的潜在血液毒性。体外，MCPA-Na 通过静电力和氢键与牛血清白蛋白（BSA）结合，在基态下形成新的复合物。在此过程中，BSA 向 MCPA-Na 发生非辐射能量转移，根据福斯特理论得到供体和受体之间的距离 r。通过荧光探针法研究了结合位点，结果表明 MCPA-Na 被吸收到 BSA 分子的 II 结构域上。根据范特霍夫等压方程和吉布斯-亥姆霍兹方程，在四个不同温度下计算了焓变（ΔH(θ)）、吉布斯自由能变（ΔG(θ)）和熵变（ΔS(θ)）。ΔG(θ)的负值表明结合过程是自发和不可逆的，这表明 MCPA-Na 可能有毒。CD 光谱显示 BSA 分子二级结构发生显著变化，三维荧光光谱表明 BSA 中的色氨酸残基处于疏水环境中，这为食品中 MCPA-Na 残留的危险提供了额外的证据。同时，在分子水平上分析了结合的机制和几何形状。
