Excited State Proton Transfer Is Not Involved in the Ultrafast Deactivation of Guanine-Cytosine Pair in Solution
Excited State Proton Transfer Is Not Involved in the Ultrafast Deactivation of Guanine-Cytosine Pair in Solution
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DOI：
10.1021/ja2089734
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发表时间：
2011-12-14
影响因子：
15
通讯作者：
Improta, Roberto
中科院分区：
文献类型：
--
作者：
Biemann, Lars;Kovalenko, Sergey A.;Improta, Roberto
用宽带暂态吸收光谱方法研究了鸟嘌呤(G)和胞嘧啶(C)的不同衍生物在CHCl3中对Watson-Crick(WC)构象的立体强化作用。我们的实验排除了激发态质子转移(ESPT)的参与，它主导了GC在气相中的激发态衰减。相反，通过内部转换的超快动力学发生在极性环境中，主要是通过单体部分的弛豫。含时密度泛函理论(TD-DFT)在溶液中的计算确实表明，在CHCl3中，布居从亮激发态向电荷转移是无效的，并且ESPT反应中存在明显的能垒。因此，预计ESPT不会成为DNA内GC对的主要失活途径。
Different derivatives of Guanine (G) and Cytosine (C), which sterically enforce the Watson-Crick (WC) conformer, have been studied in CHCl3 by means of broad-band transient absorption spectroscopy. Our experiments rule out the involvement of an Excited State Proton Transfer (ESPT), which dominates the excited state decay of GC in the gas phase. Instead, the ultrafast dynamics via internal conversion occurs in a polar environment mainly by relaxation in the monomer moieties. Time-dependent density functional theory (TD-DFT) calculations in solution indeed indicate that population transfer from the bright excited states toward the charge transfer state is not effective in CHCl3 and a noticeable energy barrier is associated with the ESPT reaction. ESPT is therefore not expected to be a main deactivation route for GC pairs within DNA.