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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Interplay between vibrational energy transfer and excited state deactivation in DNA components
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Interplay between vibrational energy transfer and excited state deactivation in DNA components

机译：DNA组件中振动能量转移与激发态失活之间的相互作用

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Femtosecond laser spectroscopies are used to examine a thymine family of systems chosen to expose the interplay between excited state deactivation and two distinct vibrational energy transfer (VET) pathways: (i) VET from the base to the deoxyribose ring; (ii) VET between neighboring units in a dinucleotide. We find that relaxation in the ground electronic state accelerates markedly as the molecular sizes increase from the nucleobase to the dinucleotide. This behavior directly reflects growth in the density of vibrational quantum states on the substituent of the base. Excited state lifetimes are studied at temperatures ranging from 100 to 300 K to characterize the thermal fluctuations that connect the Franck-Condon geometries and the conical intersections leading back to the ground state. An Arrhenius analysis yields an approximate excited state energy barrier of 13 meV in the thymine dinucleotide. In addition, we find that the transfer of vibrational energy from the base to the substituent suppresses thermal fluctuations across this energy barrier. The possibility that the solvent viscosity imposes friction on the reaction coordinate is examined by comparing thymine and adenine systems. Experiments suggest that the solvent viscosity has little effect on barrier crossing dynamics in thymine because the conical intersection is accessed through relatively small out-of-plane atomic displacements. Overall, we conclude that the transfer of vibrational quanta from thymine to the deoxyribose ring couples significantly to the internal conversion rate, whereas the neighboring unit in the dinucleotide serves as a secondary heat bath. In natural DNA, it follows that (local) thermal fluctuations in the geometries of subunits involving the base and deoxyribose ring are most important to this subpicosecond relaxation process.
机译：飞秒激光光谱法用于检查选择的胸腺嘧啶家族系统，以揭示激发态失活与两种不同的振动能量转移（VET）途径之间的相互作用：（i）从基部到脱氧核糖环的VET; （ii）二核苷酸中相邻单元之间的VET。我们发现，随着分子大小从核碱基到二核苷酸的增加，基态电子态的弛豫明显加快。此行为直接反映了碱基取代基上振动量子态密度的增长。在100至300 K的温度范围内研究了激发态的寿命，以表征将Franck-Condon几何形状和圆锥相交点连接回到基态的热涨落。 Arrhenius分析在胸腺嘧啶二核苷酸中产生约13 meV的激发态能垒。此外，我们发现，振动能从基体转移到取代基上，抑制了跨越该能垒的热波动。通过比较胸腺嘧啶和腺嘌呤体系，检查了溶剂粘度对反应坐标施加摩擦的可能性。实验表明，溶剂粘度对胸腺嘧啶中的势垒穿越动力学影响很小，因为圆锥形的相交点通过相对较小的平面外原子位移即可到达。总的来说，我们得出的结论是，振动量子从胸腺嘧啶到脱氧核糖环的转移与内部转化率显着耦合，而二核苷酸中的相邻单元则作为辅助热浴。在天然DNA中，随之而来的是，涉及碱基和脱氧核糖环的亚基的几何结构中的（局部）热波动对于此亚皮秒松弛过程最为重要。

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