Experimental and Theoretical Study of Deprotonation of DNA Adenine Cation Radical |
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| Authors: | Jia-long Jie Chen Wang Hong-mei Zhao Di Song Hong-mei Su |
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| Affiliation: | 1.Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China;University of Chinese Academy of Sciences, Beijing 100049, China2.College of Chemistry, Beijing Normal University, Beijing 100875, China3.Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China4.Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China;College of Chemistry, Beijing Normal University, Beijing 100875, China |
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| 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. |
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| Keywords: | DNA adenine Deprotonation rate constant Activation energy barrier Density functional theory calculation |
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