估算手性二氯酚-甲基的潜在毒性:对对映体选择性行为的机制见解。
Estimating the potential toxicity of chiral diclofop-methyl: Mechanistic insight into the enantioselective behavior.
机构信息
Department of Environmental Engineering, Chang'an University, Xi'an, 710054, China; Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Chang'an University, No. 126 Yanta Road, Yanta District, Xi'an 710054, China.
State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
出版信息
Toxicology. 2020 May 30;438:152446. doi: 10.1016/j.tox.2020.152446. Epub 2020 Apr 8.
Chiral pollutants are widely distributed in the environment; however, the enantioselective toxic effects of these chemicals have still not fully been clarified. Using wet experiments and computational toxicology, this story was to explore the static and dynamic toxic reactions between chiral diclofop-methyl and target protein at the enantiomeric level, and further unveil the microscopic mechanism of enantioselective toxicity of chiral pesticide. Steady-state and time-resolved results indicated that both (R)-/(S)-enantiomers can form the stable toxic conjugates with target protein and the bioaffinities were 1.156 × 10 M/1.734 × 10 M, respectively, and significant enantioselectivity was occurred in the reaction. Results of the modes of toxic action revealed that diclofop-methyl enantiomers located in the subdomain IIA, and the strength of important noncovalent interactions between (S)-diclofop-methyl and the residues was greater than that of (R)-diclofop-methyl. The Gibbs free energies of the chiral reactions were -26.89/-29.40 kJ mol and -25.79/-30.08 kJ mol, respectively, which was consistent with the outcomes of photochemistry and site-specific competitive assay. Dynamic enantioselective processes explained that the impact of intrinsic protein conformational flexibility on the toxic reaction of (R)-diclofop-methyl was lower than that of (S)-diclofop-methyl, which originates from the conformational changes and spatial displacement of the four loop regions (i.e. h6↔h7, h1↔h2, h5↔h6, and h8↔h9). The quantitative data of circular dichroism spectra confirmed such results. Energy decomposition displayed that the electrostatic energy of the target protein-(S)-diclofop-methyl system (-25.86 kJ mol) was higher than that of the target protein-(R)-diclofop-methyl complex (-18.21 kJ mol). Some crucial residues such as Lys-195, Lys-199, Ser-202, and Trp-214 have been shown to be of different importance for the enantioselective toxicity of chiral diclofop-methyl. Obviously this scenario will contribute mechanistic clues to assessing the potential hazards of chiral environmental pollutants to the body.
手性污染物广泛分布于环境中,但这些化学物质的对映选择性毒性作用仍未完全阐明。本研究采用湿实验和计算毒理学方法,从对映体水平上探讨了手性二氯酚-甲基与靶蛋白之间的静态和动态毒性反应,进一步揭示了手性农药对映选择性毒性的微观机制。稳态和时间分辨结果表明,(R)-/(S)-对映体均可与靶蛋白形成稳定的毒性加合物,生物亲和力分别为 1.156×10^M 和 1.734×10^M,且反应中存在显著的对映选择性。毒性作用模式的结果表明,二氯酚-甲基对映体位于亚结构域 IIA 中,(S)-二氯酚-甲基与残基之间的重要非共价相互作用的强度大于(R)-二氯酚-甲基。手性反应的吉布斯自由能分别为-26.89/-29.40 kJ mol 和-25.79/-30.08 kJ mol,与光化学和位点特异性竞争测定的结果一致。动态对映选择性过程表明,内在蛋白质构象灵活性对(R)-二氯酚-甲基毒性反应的影响低于(S)-二氯酚-甲基,这源于四个环区(即 h6↔h7、h1↔h2、h5↔h6 和 h8↔h9)的构象变化和空间位移。圆二色光谱的定量数据证实了这一结果。能量分解显示,靶蛋白-(S)-二氯酚-甲基体系的静电能(-25.86 kJ mol)高于靶蛋白-(R)-二氯酚-甲基配合物的静电能(-18.21 kJ mol)。一些关键残基,如 Lys-195、Lys-199、Ser-202 和 Trp-214,对于手性二氯酚-甲基的对映选择性毒性具有不同的重要性。显然,这种情况将为评估手性环境污染物对人体的潜在危害提供机制线索。