Near Threshold Excited State Dynamics in Nucleobases and Related Compounds

在这个由化学部化学结构动力学和机制（CSDM-A）项目资助的项目中，加州大学圣巴巴拉分校的de弗里斯教授将研究孤立的DNA碱基如何对紫外线（UV）光做出反应。了解DNA碱基对紫外线辐射的响应对于实际和基本原因都至关重要。紫外吸收后的碱基光化学反应是辐射诱导DNA损伤的基本步骤。核碱基对紫外线吸收的极其有效的反应通常被描述为大自然保护生命构件免受紫外线光损伤的策略。紫外光选择可能在早期地球的生物化学中发挥了关键作用。这些相同的过程也在各种现代材料中找到应用。该项目将侧重于核碱基及其簇在皮秒时域和接近吸收阈值的气相光谱。实验将研究激发态的过程与双共振光谱在气相和亚纳秒时域提供的异构体特异性。与计算化学家的合作将提供结果与量子化学建模的比较。选择低能量激发波长将使工作对弛豫过程的细节最敏感。这种方法将使直接研究核碱基对紫外线辐射的反应的关键机制成为可能，因此这项研究将有助于对控制生命分子构建模块的基本过程的最基本理解。这些主题，与尖端的激光和计算技术相结合，非常适合将以这项工作为基础的外联活动，这项工作还为本科生和研究生提供了先进实验仪器的设计和建造，复杂的计算机模拟，该奖项反映了NSF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。

In this project, funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Prof. de Vries at the University of California Santa Barbara will study how isolated DNA bases respond to ultraviolet (UV) light. Understanding the response of DNA bases to UV radiation is critical for both practical and fundamental reasons. Nucleobase photochemistry following UV absorption constitutes a fundamental step in radiation induced DNA damage. The extremely efficient response of the nucleobases to absorption of ultraviolet light is often described as nature's strategy to protect the building blocks of life against UV photodamage. UV photo-selection may have played a key role in prebiotic chemistry on an early earth. These same processes also find applications in a variety of modern materials. This project will focus on gas phase spectroscopy of nucleobases and their clusters in the picosecond time domain and close to the threshold for absorption. Experiments will study the excited state processes with the isomer specificity afforded by double resonant spectroscopy in the gas phase and in the sub-nanosecond time domain. Collaboration with computational chemists will provide comparison of the results with quantum chemical modeling. Choosing low energy excitation wavelengths will make the work most sensitive to the details of the relaxation processes. This approach will make it possible to directly investigate the key mechanisms of the response of nucleobases to UV irradiation so this research will contribute to the most basic understanding of fundamental processes that govern the molecular building blocks of life. These topics, in combination with cutting-edge laser and computational techniques, lend themselves extraordinary well to outreach activities that will be based in this work, which also provides for the training of both undergraduate and graduate students in the design and construction of advanced experimental instrumentation, complex computer simulation, and conducting fundamental research.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.