论文标题
通过结合时间分辨光谱和量子机械计算研究的诱变胞苷乙烯加合物的激发态动力学
The Excited State Dynamics of a Mutagenic Cytidine Etheno Adduct Investigated by Combining Time-Resolved Spectroscopy and Quantum Mechanical Calculations
论文作者
论文摘要
联合飞秒荧光上转换实验和理论计算提供了迄今为止对诱变乙烯加合物3，N4-乙诺基 - 二氧基胞丁丁氨酸（$ε$ $ dc）激发状态放松的迄今为止无关紧要的表征和理解。这种内源性形成的病变引起了人们的极大兴趣，因为它在人体组织及其高度诱变的特性中存在着极大的兴趣。 $ε$ DC荧光相对于规范基础DC的荧光进行了修改，中性pH时的寿命增加了3倍和量子产率。这种行为在乙诺环（$ε$ dCH+）的质子化时会放大。量子机械计算表明，最低的能量状态$π$$π$*1是造成荧光的原因，而通往基态的主要非放射性衰减途径经过乙烯样圆锥形交叉点，涉及C5和C6替代物的平面运动外运动。该圆锥形交叉路口的能量低于$π$π$*状态（$π$π$* 1）的最低限度，但是相当大的能量屏障解释了相对于DC的$ε$ DC和$ε$ DC+ $ε$ DCH+荧光寿命的增加。
Joint femtosecond fluorescence upconversion experiments and theoretical calculations provide a hitherto unattained degree of characterization and understanding of the mutagenic etheno adduct 3,N4-etheno-2'-deoxycytidine ($ε$dC) excited state relaxation. This endogenously formed lesion is attracting great interest because of its ubiquity in human tissues and its highly mutagenic properties. The $ε$dC fluorescence is modified with respect to that of the canonical base dC, with a 3-fold increased lifetime and quantum yield at neutral pH. This behavior is amplified upon protonation of the etheno ring ($ε$dCH+). Quantum mechanical calculations show that the lowest energy state $π$$π$*1 is responsible for the fluorescence and that the main nonradiative decay pathway to the ground state goes through an ethene-like conical intersection, involving the out-of-plane motion of the C5 and C6 substituents. This conical intersection is lower in energy than the $π$$π$* state ($π$$π$*1) minimum, but a sizable energy barrier explains the increase of $ε$dC and $ε$dCH+ fluorescence lifetimes with respect to that of dC.
