提高Bt毒素与受体的互作，是治理害虫抗性的关键，也是Bt毒素定向改造的方向。申请者团队在前期啶虫脒巯基丙酸的结构改造及其与Bt Cry2Ab毒素偶联修饰研究的基础上，探索不同碳链长度的啶虫脒巯基酸的偶联修饰对Cry2Ab活性的影响。合成不同碳链长度的系列啶虫脒巯基酸（啶虫脒巯基乙酸、丙酸和丁酸等）作为Cry2Ab的偶联配基对Cry2Ab定向改造，合成偶联型毒素Cry2Ab-Ac，以期提高Cry2Ab与小菜蛾中肠受体氨肽酶的互作，并探索Cry2Ab-Ac对小菜蛾抗性治理的效果。利用偶联药物鉴定分析技术鉴定偶联型毒素Cry2Ab-Ac，测定偶联比，鉴定偶联位点，对Cry2Ab-Ac的结构进行表征。此工作将为Bt毒素的定向改造及新型生物农药的研发奠定理论基础。

Improving the affinity between Bt toxin and its receptor proteins is key to overcome Bt toxin resistance, which is also the main approach for directed engineering of Bt toxin. In our previous studies, acetamiprid (Ac) was screened as a lead compound for the bioconjugate ligand of Cry2Ab by bioinformatics from chemical pesticides. Acetamiprid mercaptopropionic acid was then synthesized by nucleophilic substitution and coupled with Cry2Ab. This engineering of Cry2Ab improved the affinity between Cry2Ab and its receptor proteins on the BBMV of Plutella xylostella. To further investigate the effect of the length of mercaptan acid to the affinity between Cry2Ab and its receptor protein (PxAPN5) on the BBMV of Plutella xylostella, a series of acetamiprid mercaptan acids were synthesized and coupled with Cry2Ab to form novel toxins Cry2Ab-Ac. The affinity between Cry2Ab-Ac and PxAPN5 was measured by protein-protein interaction system (Octet red). The activity of Cry2Ab-Ac to the Bt-resistant of Plutella xylostella was then analyzed. The advanced characterization of Cry2Ab-Ac was performed by LC-MS, LC-MS/MS, HIC-UV and so on. This directed engineering of Bt insecticidal protein may provide a new platform for the development of biological insecticide.