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Experimental and Theoretical Study of the Deprotonation of DNA Adenine Cation Radical
苏红梅
Author NameAffiliationE-mail
苏红梅 中国科学院化学研究所 hongmei@iccas.ac.cn 
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 (DFT) 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.
Key words:  DNA adenine  deprotonation rate constant  activation energy barrier  DFT calculation
FundProject:
Experimental and Theoretical Study of the Deprotonation of DNA Adenine Cation Radical
苏红梅
摘要:
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 (DFT) 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.
关键词:  DNA adenine  deprotonation rate constant  activation energy barrier  DFT calculation
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