Nitrosation and Nitration Reactions of the Radical Cations of Guanine, 8-Oxoguanine and their Derivatives by NOx: Radical-radical Interactions at Multiple Electron Configurations

在化学系化学结构、动力学和机理A(CSDM-A)项目的支持下，皇后学院的刘建波教授正在用电喷雾电离和质谱仪研究鸟嘌呤及其氧化衍生物8-氧鸟嘌呤与一氧化氮(NO)和二氧化氮(NO2)的自由基阳离子的反应。在DNA碱基中，鸟嘌呤的氧化电离势最低，导致鸟嘌呤和8-氧鸟嘌呤在DNA氧化电离过程中优先形成自由基阳离子。这些自由基阳离子的反应很难在溶液中研究，因为它们快速去质子化，并且无法分离、检测和表征产物。刘教授和他的学生将在稀薄的气相环境中研究这些自由基阳离子与NO和NO2的反应，在那里可以测量单个产品。这些研究有望更好地了解DNA在氧化、亚硝化和亚硝化应激下的损伤。从事这个项目的学生将获得反应动力学、仪器开发和计算建模方面的经验。皇后学院是一所为少数族裔服务的机构，40%的学生来自传统上服务不足的群体。该项目对多样性和扩大参与度有直接影响，包括与拉瓜迪亚社区学院合作，将合格的学生从副学士学位转移到化学学士学位课程。许多为研究而开发的仪器也将用于本科实验室课程。该项目将利用电喷雾电离和导离子束串联质谱来进行离子-分子反应，其中鸟嘌呤和8-氧鸟嘌呤的自由基阳离子是通过电子转移诱导铜(II)-核碱络合物解离而产生的。选择质量自由基阳离子与NO和NO2的反应将在导离子束散射实验中提供的气相单碰撞条件下进行，其中将测量单个产物离子的结构和截面作为碰撞能量的函数。实验将得到电子结构计算、动力学模拟和动力学分析的补充。内部的协同实验和计算应该允许解释反应机理和非绝热动力学的各个方面。这项研究的一个主要目的是对处理双重-双重电子态反应中的多参照特征和非绝热转变的实验和理论进行基准测试。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program in the Division of Chemistry, Professor Jianbo Liu of Queens College is investigating the reactions of the radical cations of guanine and its oxidized derivative 8-oxoguanine with nitric oxide (NO) and nitrogen dioxide (NO2) using electrospray ionization and mass spectrometry. Guanine has the lowest oxidation and ionization potential among DNA nucleobases, leading to the preferential formation of the radical cations of guanine and 8-oxoguanine upon the oxidation and ionization of DNA. Reactions of these radical cations are difficult to study in solution due to their rapid deprotonation and the inability to separate, detect, and characterize products. Professor Liu and his students will study the reactions of these radical cations with NO and NO2 in a rarefied gas-phase environment where individual products can be measured. These studies are expected to provide a better understanding of DNA damage upon oxidative, nitrosative, and nitrative stress. The students working on this project will gain experience in reaction dynamics, instrumentation development, and computational modeling. Queens College is a Minority Serving Institution, with 40% of students from traditionally underserved groups. This project have direct implications for diversity and broadening participation, including collaboration with LaGuardia Community College to transfer qualified students from an associate degree to the Chemistry B.S. program. Many of the instruments developed for research will also used in undergraduate laboratory courses.The project will utilize electrospray ionization and guided-ion beam tandem mass spectrometry to conduct ion-molecule reactions wherein the radical cations of guanine and 8-oxoguanine are produced by electron-transfer induced-dissociation of Cu(II)-nucleobase complexes. Reactions of mass-selected radical cations with NO and NO2 will be carried out under gas-phase single-collision conditions provided in the guided-ion beam scattering experiment where structures and cross sections of individual product ions will be measured as a function of collision energy. Experiments will be complemented by electronic structure calculations, dynamics simulations, and kinetic analysis. The in-house, synergetic experiments and computations should allow for interpretation of various aspects of reaction mechanism and non-adiabatic kinetics. A major thrust of this research is to benchmark experiment and theory for tackling multireferential characters and non-adiabatic transitions in doublet-doublet electronic-state reactions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.