堆积的腺嘌呤体系新失活通道的动力学模拟

采用半经典动力学方法模拟了激光诱导下π堆积的腺嘌呤体系最低激发态的失活过程. 模拟激光脉冲仅作用于一个腺嘌呤分子. 发现随着激发态腺嘌呤分子(A)与基态腺嘌呤分子(A′)之间距离的缩短, 它们的相互作用显著增强. 分子间的相互作用导致了一条新的失活通道, 即C₂原子与C₂′原子靠拢成键, 形成“成键的激基复合体”的中间体. 中间体的寿命约为390 fs. C₂原子的畸变和H₂′原子的环面外振动导致中间体失活. 失活后C₂－C₂′断裂, 释放的键能转化为分子动能, 腺嘌呤分子恢复基态的平面结构.

Dynamics Simulation of a New Deactivation Pathway for Stacked Adenines

A semiclassical dynamics simulation study was undertaken to investigate the deactivation of the lowest excited state of π-stacked adenines, as induced by a laser pulse. Only one of the adenines was subjected to a laser pulse in this simulation. The simulation results show that the interaction between the excited adenines (A) and their unexcited neighbors (A′) increases significantly, followed by a shortening of the intermolecular distance. The interbases interaction leads to a new deactivated pathway in which atom C2 in molecule A and atom C2′ in molecule A′ are link to each other and form a "bonded excimer" intermediate. The lifetime of the "bonded excimer" intermediate is about 390 fs. The deformation of the pyrimidine ring at the C2 atom and the displacement of the H2′ atom away from the pyrimidine ring play a significant role in the deactivation process of the "bonded excimer" intermediate. After deactivation, the C2-C2′ dissociates and the released bond energy converts to molecular kinetic energy. Both adenine molecules return to the planar geometries of their ground states.