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

基本信息

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

项目摘要

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.

在化学部的化学结构动力学和机制（CSDM-A）计划资助的项目中，佐治亚大学的Ullrich教授使用激光光谱研究研究了改良的核仁酶对紫外线（UV）辐射的反应。核苷酸酶是DNA的分子成分，因此形成了我们基因编码材料的构件。已知天然存在的核碱基通过核碱基分子中的过程保护自己免受紫外线辐射的影响，从而将潜在有害的紫外线耗散成热量。但是，这些过程的细节尚不清楚。 Ullrich教授通过对核碱酶结构进行略有更改，并观察紫外光散发方式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，核碱酶很难从紫外线散发能量。这就是说它仍然“兴奋”，因此容易受到损害。尽管对于正常的DNA链，这种情况可能是不可取的，但在癌症治疗中可能是有益的，在癌症治疗中可能会使用紫外线或其他光能来专门攻击癌细胞。补充了Ab-Initio计算和动力学模拟，揭示了激发状态势能表面的精细细节，例如最低激发态之间的耦合，势能屏障和圆锥交叉点的可及性。鉴于它们广泛出现是访问三胞胎歧管的钥匙门，因此特别关注N-PI角色的低洼单元状态的作用。该项目培训本科生和研究生以及参加研究活动和研究成果的暑期实习生通过科学表演的表演将广泛传播给公众。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的评估审查标准来通过评估来通过评估来支持的。