【摘要】 本文采用纳秒时间分辨吸收光谱研究了A^+·的脱质子过程.通过瞬态吸收光谱观察到A^+·脱质子产物A（N₆-H）^·,结合动力学分析得到了室温下A^+·脱质子的速率常数为（2.0±0.1）×10⁷ s^-1.进一步通过不同温度下的脱质子速率常数,借助阿伦尼乌斯公式拟合得到A^+·脱N6-H的活化能为17.1kJ/mol.此外,我们还采用DFT方法计算了单体及DNA双链中的A^+·脱质子路径,结合实验结果,揭示了单体及DNA双链中的A^+·脱质子路径.更多还原

【Abstract】 Among all the DNA components, extremely redox-active guanine（G） and adenine（A） bases are subject to facile loss of an electron and form cation radicals(G^+· and A^+·) when exposed to irradiation or radical oxidants. The subsequent deprotonation of G^+·and A^+· can invoke DNA damage or interrupt hole transfer in DNA. However, compared with intensive reports for G^+·, studies on the deprotonation of A^+· are still limited at present. Herein,we investigate the deprotonation behavior of A^+· by time-resolved laser flash photolysis.The deprotonation product of A（N₆-H）^· is observed and the deprotonation rate constant,（2.0±0.1）×10⁷ s^-1, is obtained at room temperature. Further, the deprotonation rate constants of A^+· are measured at temperatures varying from 280 K to 300 K, from which the activation energy for the N₆-H deprotonation is determined to be（17.1 ± 1.0） kJ/mol by Arrhenius equation. In addition, by incorporating the aqueous solvent effect, we perform density functional theory calculations for A^+· deprotonation in free base and in duplex DNA.Together with experimental results, the deprotonation mechanisms of A^+· in free base and in duplex DNA are revealed, which are of fundamental importance for understanding the oxidative DNA damage and designing DNA-based electrochemical devices.更多还原