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题名: Deprotonation Kinetics of 1-Methylguanine After One-Electron Oxidation
作者: Wu Lidan1;  Jie Jialong1;  Liu Kunhui1;  Su Hongmei1
关键词: 1-methylguanine ;  deprotonation ;  one-electron oxidation ;  rate constant ;  activation energy barrier
刊名: ACTA CHIMICA SINICA
发表日期: 2014-11-15
DOI: 10.6023/A14090666
卷: 72, 期:11, 页:1182-1186
收录类别: SCI
文章类型: Article
WOS标题词: Science & Technology ;  Physical Sciences
类目[WOS]: Chemistry, Multidisciplinary
研究领域[WOS]: Chemistry
英文摘要: Among the four natural DNA bases, guanine (G) is the most sensitive to oxidation due to its lowest oxidation potential. When G base is oxidized to guanine cation radical (G(+center dot)), it will deprotonate from both the imino proton N-1-H and the amino proton N-2-H. According to the pKa values for N-1-H and N-2-H deprotonation, the main deprotonation site in G base is N-1-H which would interfere with the N-2-H deprotonation, making the kinetics of N-2-H deprotonation difficult to be measured. Herein, the N-2-H deprotonation kinetics is investigated using 1-methylguanosine (mG), where N-1-H is substituted by methyl group to avoid the N-1-H deprotonation and N-9-H is substituted by ribose to ensure enough solubility of methylguanine in water, by nanosecond transient absorption (ns-TA) spectroscopy. By 355 nm photolysis of Na2S2O8, the highly oxidizing radical SO4-center dot is generated, which will oxidize mG to mG(+center dot) instantaneously. The time-resolved absorption spectra obtained for reaction of mG with SO4-center dot exhibits transient absorptions for mG(N-2-H)(center dot) featured by absorption band at 600 nm, indicating that the mG(+center dot) deprotonation product is mG(N-2-H)(center dot) and the deprotonation site is therefore validated to be N-2-H. The mG concentration dependence of mG(N-2-H)(center dot) formation rate constant is assessed through changing the mG concentration from 0.25 mmol.L-1 to 5 mmol.L-1. The concentration dependence experiment reveals that the rate-limiting step to form mG(N-2-H)(center dot) is the bimolecular reaction of mG with SO4-center dot when mG concentration is lower than 2 mmol.L-1 and the bimolecular reaction rate constant to form mG(+center dot) is (3.7 +/- 0.1)x10(9) L.mol(-1).s(-1); when mG concentration is above 2 mmol.L-1, the rate-limiting step to form mG(N-2-H)(center dot) is the first-order mG(+center dot) deprotonation and the N-2-H deprotonation rate constant is (7.1 +/- 0.2) x 10(6) s(-1). Furthermore, the N-2-H deprotonation rate constant is measured at different temperatures varying from 278 K to 298 K. According to Arrhenius equation, the activation energy barrier for the N-2-H deprotonation is determined to be 19.9 +/- 1.0 kJ.mol(-1). These results can provide valuable kinetic information on the oxidative damage of DNA.
关键词[WOS]: GUANINE RADICAL-CATION ;  AQUEOUS-SOLUTION ;  IRRADIATED GUANINE ;  HYDROXYL RADICALS ;  LASER PHOTOLYSIS ;  DNA-DAMAGE ;  BASE-PAIR ;  GUANOSINE ;  REPAIR ;  EQUILIBRIA
语种: 英语
WOS记录号: WOS:000346121300010
Citation statistics: 
内容类型: 期刊论文
URI标识: http://cas-ir.dicp.ac.cn/handle/321008/145699
Appears in Collections:中国科学院大连化学物理研究所_期刊论文

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作者单位: 1.Chinese Acad Sci, Inst Chem, BNLMS, State Key Lab Mol React Dynam, Beijing 100190, Peoples R China

Recommended Citation:
Wu Lidan,Jie Jialong,Liu Kunhui,et al. Deprotonation Kinetics of 1-Methylguanine After One-Electron Oxidation[J]. ACTA CHIMICA SINICA,2014,72(11):1182-1186.
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