PHOTODYNAMICS OF NUCLEOBASES

通过这个由化学结构、动力学和机制项目资助的奖项，来自加州大学圣巴巴拉分校的Mattanjah S. de Vries教授和他的团队将测量堆叠、氢键和微溶剂化核碱基簇的光化学性质。这些研究将构成理解核碱基光动力学的还原论方法的一个新步骤。在与捷克共和国科学院的nachtigallov<e:1>博士的合作下，气相光谱将与量子计算进行比较。这种方法迄今为止应用于分离的核碱基，它表明了一个一般的过程，在吸收紫外线后，DNA碱基可以通过非常迅速地将激发能扩散到热（在一个称为内部转换的过程中）来避免化学转化，而热可以安全地转移到环境中。这一过程强烈依赖于分子结构，并且在生物环境中核碱基发生的特定形式中非常普遍。然而，分子间的相互作用也会影响这些过程。与单一碱基相比，pi-堆叠开辟了新的激发态衰减途径，包括在皮秒时域内研究的外复态，作为精确分子间结构的函数。了解这些相互作用的确切作用，这是本研究的目标，对于充分理解光与生物分子相互作用的方式至关重要。了解DNA碱基对紫外线（UV）辐射的反应对于实际和基本原因都是至关重要的。紫外吸收后的核碱基光化学是辐射诱导DNA损伤的基本步骤。DNA碱基似乎特别稳定，不受紫外线的伤害。这种独特的性质可能在40亿年前生命的组成部分的选择中发挥了作用。构成今天DNA的碱基可能是早期地球上最适合在强烈的紫外线辐射下生存的分子。这项工作将研究使我们的遗传物质对光化学损伤如此强大的分子特性的细节。这项工作采用了超快激光光谱、质谱和计算化学技术。除了用这些先进的方法培训研究生外，本科生和高中生也将作为一些拓展项目的一部分接触到这项工作，包括与杰克逊州立大学正在进行的合作。

Through this award, funded by the Chemical Structure, Dynamics, and Mechanisms - A Program of the Division of Chemistry, Prof. Mattanjah S. de Vries from the University California Santa Barbara and his team, will measure photochemical properties in clusters of stacked, hydrogen bonded, and microsolvated nucleobases. These studies will constitute a new step in the reductionist approach to understanding nucleobase photodynamics. Gas phase spectroscopy will be compared with quantum computations in collaboration with Dr. Nachtigallová at the Academy of Sciences of the Czech Republic. This approach, so far applied to isolated nucleobases, suggests a general process in which, following absorption of UV light, DNA bases can avoid chemical transformation by very rapidly diffusing the excitation energy to heat (in a process called internal conversion) which can safely be transferred to the environment. This process strongly depends on molecular structure and is remarkably prevalent in the specific forms in which nucleobases occur in biological contexts. However, intermolecular interactions also affect these processes. Compared to single bases, pi-stacking opens new possible excited state decay pathways, involving exciplex states, which will be studied in the picosecond time domain, as a function of precise intermolecular structure. Understanding the precise role of these interactions, which is the objective of this study, is crucial for fully understanding the way light interacts with biological molecules.Understanding the response of DNA bases to ultraviolet (UV) radiation is critical for both practical and fundamental reasons. Nucleobase photochemistry following UV absorption constitutes a fundamental step in radiation-induced DNA damage. It appears that DNA bases are especially stable against damage caused by UV light. This unique property may have played a role in the selection of the building blocks of life four billion year ago. The bases that make up today's DNA may be the molecules that were most suited to survive harsh UV radiation on an early earth. This work will study the details of the molecular properties that make our genetic material so robust against photochemical damage. The work employs techniques of ultrafast laser spectroscopy, mass spectrometry and computational chemistry. In addition to training graduate students in these advanced methods, undergraduate students and high school students will also be exposed to this work as part of a number of outreach programs, including an ongoing collaboration with Jackson State University.