Deprotonation Kinetics of 1-Methylguanine After One-Electron Oxidation

吴丽丹,; 节家龙,; 刘坤辉,; Su, Hongmei

doi:10.6023/a14090666

Cited by 7 publications

(11 citation statements)

References 14 publications

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“…The transient absorption of sulfate radical SO 4 −• is featured with the resolved band at 450 nm and a shoulder at 330 nm (FIG. 2(a)), which agrees with previous spectra [4,10,12,13]. The rapid photodissociation of S 2 O 8 2− results in the generation of SO 4 −• within the ∼14 ns laser pulse duration.…”

Section: A Transient Absorption Spectra Of a +• And Its Deprotonatiosupporting

confidence: 90%

“…As shown in FIG. 1, G +• has two deprotonation sites, the imino proton (N 1 -H, pK a =3.9) and the amino proton (N 2 -H, pK a =4.7) [1,2,8,9,12 [10,16]. Kobayashi et al measured deprotonation rate constants of (3.3−3.6)×10 6 s −1 in different duplex DNA, and suggested that the whole deprotonation process can be interpreted by the following steps: proton transfer from the base-pair cation radical G +• :C first gives deprotonated G radical and the cytosine base pair (G(-H) • :C(+H + )) and then the proton of C(+H + ) is expected to be finally picked up by a water molecule [10].…”

Section: Fig 1 the Molecular Structures Of Guanine (G) And Adenine (A)mentioning

confidence: 99%

“…Kobayashi et al measured deprotonation rate constants of (3.3−3.6)×10 6 s −1 in different duplex DNA, and suggested that the whole deprotonation process can be interpreted by the following steps: proton transfer from the base-pair cation radical G +• :C first gives deprotonated G radical and the cytosine base pair (G(-H) • :C(+H + )) and then the proton of C(+H + ) is expected to be finally picked up by a water molecule [10]. Recently, our group used nanosecond laser flash photolysis to investigate the deprotonation of 1-methylguanine (mG), of which N 1 -H is substituted by methyl group, and thus obtained the rate constant and activation energy of deprotonation from N 2 -H [12]. Further, our group also examined the unique deprotonation behaviors of G-quadruplexes, revealing the unusual deprotonation site of amino proton N 2 -H and much slower rate constants of (1.8−2.1)×10 5 s −1 in G-quadruplexes that are different from duplex DNA [13].…”

Section: Fig 1 the Molecular Structures Of Guanine (G) And Adenine (A)mentioning

confidence: 99%

“…As a result, the formation dynamics of SO 4 −• does not interfere with the detection for the subsequent oxidation reaction of SO 4 −• +A (Eq.(2)). The concentration of SO 4 −• can be estimated by the absorbance at 450 nm using an extinction coefficient of 1600 (mol/L) −1 cm −1 [4,10,12,13], which is ∼25 µmol/L and much smaller than the concentration of A (6 mmol/L). The large excess concentration of A ensures the oxidation reaction of A by SO 4…”

Section: A Transient Absorption Spectra Of a +• And Its Deprotonatiomentioning

confidence: 99%

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Experimental and Theoretical Study of Deprotonation of DNA Adenine Cation Radical

Jie

Wang

Zhao

et al. 2017

Chinese Journal of Chemical Physics

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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(N 6-H) • is observed and the deprotonation rate constant, (2.0±0.1)×10 7 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 N 6-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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Section: A Transient Absorption Spectra Of a +• And Its Deprotonatiosupporting

confidence: 90%

Section: Fig 1 the Molecular Structures Of Guanine (G) And Adenine (A)mentioning

confidence: 99%

Section: Fig 1 the Molecular Structures Of Guanine (G) And Adenine (A)mentioning

confidence: 99%

Section: A Transient Absorption Spectra Of a +• And Its Deprotonatiomentioning

confidence: 99%

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Experimental and Theoretical Study of Deprotonation of DNA Adenine Cation Radical

Jie

Wang

Zhao

et al. 2017

Chinese Journal of Chemical Physics

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“…G +• 上亚氨基质子N 1 -H的酸性图 4 SP反应的T 1 和S 0 态势能剖面. 所给出的能量为相对于基态反应物的能量差, 单位为kcal/mol [29] (网络版彩图) (pK a =3.9 [46] )比氨基质子N 2 -H的酸性(pK a =4.7 [46] )更强, [40] , 而脱氨基质子N 2 -H速率常数为3.5×10 5 s −1 (pH 7.1) [45,47] . 在双链…”

Section: G-四链体中鸟嘌呤单电子氧化及脱质子反应unclassified

Photochemical reaction dynamics studies of nucleic acids

et al. 2017

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Nucleic acids are the most important biomolecules, which function to express, store and transmit genetic information. The major radiation damages to the living things are essentially relative to the physical and chemical reactions of nucleic acids. Therefore, interests in photochemical reaction dynamics of nucleic acids have been intensified in recent years with the development of powerful experimental and computational techniques, boosting a challenging and promising subfield of chemical reaction dynamics interdisciplinary with molecular biology. In this context, we have made great efforts in developing the transient spectroscopic methods, particularly time-resolved infrared, to investigate the excited state and free radical reaction dynamics involved in the photochemical reactions of nucleic acid bases and DNA secondary structures (duplex, quadruplex etc.). By capturing the fast chemical events of these key short-lived transient species and combining quantum chemical calculations, we revealed the reaction mechanisms of [2+2] photocycloaddition, spore photoproduct (SP) photolesion, electron transfer, proton transfer, photosensitization, ROS oxidation, and photocleavage that are closely associated with the crosslink or oxidative DNA damages. The key roles of non-adiabatic surface intersections, excited state electronic structure property, conformation of secondary structure, base-pairing, π-stacking, and hydrogen-bonding in affecting the photochemical reaction pathways are elucidated. Our results provided important chemical insights to understand the DNA damage at the molecular and quantum state specific levels. This review mainly summarizes the recent progress made by our groups and the related work in literatures.

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Independent Generation and Time‐Resolved Detection of 2′‐Deoxyguanosin‐N2‐yl Radicals

Zheng

Dai

et al. 2020

Angewandte Chemie

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Guanine radicals are important reactive intermediates in DNA damage. Hydroxyl radical (HO.) has long been believed to react with 2′‐deoxyguanosine (dG) generating 2′‐deoxyguanosin‐N1‐yl radical (dG(N1‐H).) via addition to the nucleobase π‐system and subsequent dehydration. This basic tenet was challenged by an alternative mechanism, in which the major reaction of HO. with dG was proposed to involve hydrogen atom abstraction from the N2‐amine. The 2′‐deoxyguanosin‐N2‐yl radical (dG(N2‐H).) formed was proposed to rapidly tautomerize to dG(N1‐H).. We report the first independent generation of dG(N2‐H). in high yield via photolysis of 1. dG(N2‐H). is directly observed upon nanosecond laser flash photolysis (LFP) of 1. The absorption spectrum of dG(N2‐H). is corroborated by DFT studies, and anti‐ and syn‐dG(N2‐H). are resolved for the first time. The LFP experiments showed no evidence for tautomerization of dG(N2‐H). to dG(N1‐H). within hundreds of microseconds. This observation suggests that the generation of dG(N1‐H). via dG(N2‐H). following hydrogen atom abstraction from dG is unlikely to be a major pathway when HO. reacts with dG.

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Deprotonation Kinetics of 1-Methylguanine After One-Electron Oxidation

Cited by 7 publications

References 14 publications

Experimental and Theoretical Study of Deprotonation of DNA Adenine Cation Radical

Experimental and Theoretical Study of Deprotonation of DNA Adenine Cation Radical

Photochemical reaction dynamics studies of nucleic acids

Independent Generation and Time‐Resolved Detection of 2′‐Deoxyguanosin‐N2‐yl Radicals

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