细菌DNA磷硫酰化的生化、结构、分子和细胞生物学实验数据日见丰富；为了更好地开发其生物医学应用潜力，该生理修饰的三个关键生物过程微观机理亟待突破：1)Dnd功能蛋白如何靶向DNA磷酸单元中非桥键氧原子并将其转化为硫原子？2)硫修饰位点如何被限制性专一核酸酶识别？3)以及稀疏硫修饰(平均100到10000个碱基长度上有1个硫修饰)如何能够有效抵抗活性氧的进攻？本项目拟利用量子力学、分子力场、动力学模拟等现代多层次计算化学方法，结合生化分析、分子光谱和化学计量学体内和体外实验验证，“干-湿”交叉、系统深入地研究DNA硫修饰生理过程的热力学和动力学问题，特别是在电子、原子和分子等微观水平上重现该化学修饰与ScoMrcA核酸酶和DndE蛋白等功能蛋白的分子识别以及抵抗活性氧的动态过程。在此基础上构建细菌DNA硫修饰、转化和再生的代谢模型，并挖掘其抗氧化抗辐射的潜在生物医学应用。

Up to date, tremendous amount of experimental data for DNA phosphorothioation have accumulated in biochemistry, structural biology, molecular biology, and cell biology. In order to further develop its biomedical applications, three key biological processes for the physiological modification need to be fully understood at the microscopic level: how do the Dnd functional proteins target the specific non-bridging oxygen atom of DNA molecule and transform it to sulfur atom? how is phosphorothioated DNA recognized by the specific nuclease in the restrict-modification system? how can sparse phosphorothioate sites in 0.1-10 kb commit ROS resistance? In this project, we plan to employ state-of-the-art multi-scale computational chemistry, including high-level quantum calculation, force field improvement, and molecular dynamics simulation, to investigate thermodynamics and kinetics of DNA phosphorothioation at electronic, atomic, and molecular levels. We will combine these theoretical studies with both in vivo and in vitro experiments, such as biochemical assay, molecular spectroscopy, chemometrics, metabolomics, etc. to validate these plausible mechanisms of molecular recognition toward ScoMrcA and DndE, and resistant tolerance toward ROS species. Accordingly, we will establish a metabolic model for the PO-PS modification and PS-PO transformation, and unearth its potential biomedical applications of anti-oxidativity and anti-radiation.