Intersystem Crossing Dynamics in Thio-Substituted Pyrimidine Nucleobases Studied by Time-resolved Photoionization Techniques

通过时间分辨光电离技术研究硫取代嘧啶核碱基的系统间交叉动力学

• 批准号: 1800050
• 负责人: Susanne Ullrich
• 金额: $ 40.2万
• 依托单位: University of Georgia Research Foundation Inc
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-01 至 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1800050&HistoricalAwards=false
• 关键词: Intersystem; Crossing; Dynamics; Thio; Substituted

In this project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Prof. Ullrich of the University of Georgia is using laser spectroscopy to study the response of modified nucleobases to ultraviolet (UV) irradiation. Nucleobases are molecular components of DNA, and thus form the building blocks of our genetic coding material. Naturally occurring nucleobases are known to protect themselves against UV radiation through processes within the nucleobase molecule that dissipate potentially harmful UV energy into heat. However, the details of these processes are not well understood. Prof. Ullrich is uncovering these details by making slight changes to the nucleobase structure, and observing changes in how UV light is dissipated. In some cases, for example when an oxygen atom is replaced by a sulfur atom, the nucleobase has difficulty dissipating the energy from the UV light. This is to say it remains "excited", and therefore vulnerable to damage. While such a condition may not be desirable for normal strand of DNA, it may be beneficial in cancer treatments, where UV or other light energy may be used to specifically attack cancer cells.In this project time-resolved photoelectron spectroscopy is applied to the study of pyrimidine thiobases to unravel the mechanistic details governing their unique ultrafast intersystem crossing dynamics. Supplemented by ab-initio calculations and dynamics simulations intricate specifics of the excited state potential energy surfaces such as couplings between the lowest excited states, potential energy barriers, and accessibility of conical intersections are revealed. Particular focus is on the role of low-lying singlet states of n-pi character, given their widespread emergence as the key doorway for accessing the triplet manifold. The project trains undergraduate and graduate students as well as summer interns who participate in the research activities and outcomes of the research are broadly disseminated to the public through science show performances.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.

乔治亚大学的Ullrich教授在化学学部化学结构动力学和机理（CSDM-A）项目资助下，利用激光光谱学研究了修饰核碱基对紫外线（UV）照射的反应。核碱基是DNA的分子组成部分，因此构成了我们遗传编码物质的基石。已知天然存在的核碱基通过核碱基分子内部的过程将潜在有害的紫外线能量消散为热量来保护自己免受紫外线辐射。然而，这些过程的细节还没有被很好地理解。乌尔里希教授通过对核碱基结构进行微小的改变，并观察紫外线如何消散的变化，来揭示这些细节。在某些情况下，例如当氧原子被硫原子取代时，核碱基难以消散紫外线的能量。也就是说，它仍然“兴奋”，因此容易受到损害。虽然这种情况可能不适合正常的DNA链，但在癌症治疗中可能是有益的，因为紫外线或其他光能可以用来专门攻击癌细胞。在这个项目中，时间分辨光电子能谱应用于嘧啶硫基的研究，以揭示其独特的超快系统间交叉动力学的机理细节。辅以从头算和动力学模拟，揭示了激发态势能面复杂的特性，如最低激发态之间的耦合、势能势垒和锥形交叉点的可及性。特别关注的是n-pi特征的低洼单线态的作用，考虑到它们作为访问三重流形的关键门户的广泛出现。项目培养参与研究活动的本科生、研究生和暑期实习生，研究成果通过科普演出向公众广泛传播。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Intersystem crossing dynamics in singly substituted thiouracil studied by time-resolved photoelectron spectroscopy: Micro-environmental effects due to sulfur position

• DOI: 10.1016/j.chemphys.2018.08.011
• 发表时间: 2018-11
• 期刊: Chemical Physics
• 影响因子: 2.3
• 作者: Abed Mohamadzade;Shuming Bai;M. Barbatti;S. Ullrich

Femtosecond photodecarbonylation of photo-ODIBO studied by stimulated Raman spectroscopy and density functional theory

受激拉曼光谱和密度泛函理论研究photo-ODIBO的飞秒光脱羰作用

• DOI: 10.1039/d1cp03512f
• 发表时间: 2021
• 期刊: Physical Chemistry Chemical Physics
• 影响因子: 3.3
• 作者: Shenje, Learnmore;Qu, Yingqi;Popik, Vladimir;Ullrich, Susanne
• 通讯作者: Ullrich, Susanne

The effect of methylation on the intersystem crossing dynamics of 2-thiouracil: Time-resolved photoelectron spectroscopy of 2-thiothymine

甲基化对 2-硫尿嘧啶系间交叉动力学的影响：2-硫胸腺嘧啶的时间分辨光电子能谱

• DOI: 10.1364/up.2022.w4a.7
• 发表时间: 2022
• 期刊: International Conference on Ultrafast Phenomena
• 作者: Ullrich, Susanne;Mohamadzade, Abed;Shrestha, Sarita;Qu, Yingqi
• 通讯作者: Qu, Yingqi

Ultrafast transient absorption spectroscopy of the photodecarbonylation of photo-oxadibenzocyclooctyne (photo-ODIBO)

光-氧杂二苯并环辛炔 (photo-ODIBO) 光脱羰的超快瞬态吸收光谱

• DOI: 10.1063/5.0041161
• 发表时间: 2021
• 期刊: The Journal of Chemical Physics
• 作者: Shenje, Learnmore;Thompson, William;Ren, Zichun;Lin, Nannan;Popik, Vladimir;Ullrich, Susanne
• 通讯作者: Ullrich, Susanne

The Effect of Methylation on the Triplet-State Dynamics of 2-Thiouracil: Time-Resolved Photoelectron Spectroscopy of 2-Thiothymine

甲基化对 2-硫尿嘧啶三重态动力学的影响：2-硫胸腺嘧啶的时间分辨光电子能谱

• DOI: 10.1021/acs.jpca.2c06051
• 发表时间: 2022
• 期刊: The Journal of Physical Chemistry A
• 作者: Ullrich, Susanne;Qu, Yingqi;Mohamadzade, Abed;Shrestha, Sarita
• 通讯作者: Shrestha, Sarita