Chemical Reactions of the Radical Cations of Nucleobases in Isolated and Cellular DNA. Formation of Single‐Base Lesions

Cadet, Jean; Douki, Thierry; Gasparutto, Didier; Ravanat, Jean‐Luc; Wagner, J. Richard

doi:10.1002/9780470526279.ch3

Cited by 14 publications

(15 citation statements)

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“…These include Type I and Type II photosensitization mechanisms that involve predominantly one-electron transfer (or hydrogen atom abstraction) mediated by triplet excited photosensitizers and the formation of singlet oxygen by energy transfer, respectively (7,103,134). In that respect guanine (135) is the major target of one-electron oxidation reactions of most Type I photosensitizers (136). A few photosensitizers including anthraquinone (137), benzophenone (138), 1,4-dimethyl-2-naphthoquinone (139) and riboflavin (140) are able to abstract one electron from adenine and pyrimidine bases in addition to guanine.…”

Section: Sensitized Reactions To Uva Radiation By Exogenous Compoundsmentioning

confidence: 99%

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Photoinduced Damage to Cellular DNA: Direct and Photosensitized Reactions^†

Cadet¹,

Mouret²,

Ravanat³

et al. 2012

Photochem & Photobiology

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271

251

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The survey focuses on recent aspects of photochemical reactions to cellular DNA that are implicated through the predominant formation of mostly bipyrimidine photoproducts in deleterious effects of human exposure to sunlight. Recent developments in analytical methods have allowed accurate and quantitative measurements of the main DNA photoproducts in cells and human skin. Highly mutagenic CC and CT bipyrimidine photoproducts, including cyclobutane pyrimidine dimers and pyrimidine (6-4) pyrimidone photoproducts (6-4PPs) are generated in low yields with respect to TT and TC photoproducts. Another striking finding deals with the formation of Dewar valence isomers, the third class of bipyrimidine photoproducts that is accounted for by UVA-mediated isomerization of initially UVB generated 6-4PPs. Cyclobutadithymine (T< >T) has been unambiguously shown to be involved in the genotoxicity of UVA radiation. Thus, T< >T is formed in UVA-irradiated cellular DNA according to a direct excitation mechanism with a higher efficiency than oxidatively generated DNA damage that arises mostly through the Type II photosensitization mechanism. C<>C and C< >T are repaired at rates intermediate between those of T< >T and 6-4TT. Evidence has been also provided for the occurrence of photosensitized reactions mediated by exogenous agents that act either in an independent way or through photodynamic effects.

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Section: Sensitized Reactions To Uva Radiation By Exogenous Compoundsmentioning

confidence: 99%

“…•+ , the predominant oneelectron DNA oxidation transient radical formed, with relevant biological nucleophiles (111,134,136,217). In addition to water that was found initially to efficiently react with Gua…”

Section: Oxidation Reactions Mediated By Photosensitizersmentioning

confidence: 99%

Photoinduced Damage to Cellular DNA: Direct and Photosensitized Reactions^†

Cadet¹,

Mouret²,

Ravanat³

et al. 2012

Photochem & Photobiology

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271

251

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“…Although these values are 2 to 3 orders of magnitude lower than those generally accepted until the end of the 1990s (Mori and Dizdaroglu 1994, Olinski et al 1996), they fit better with predictions concerning the levels of base damage (Goodhead 1994). Another important message was that aqueous solution systems used for mechanistic studies are able to reproduce the cellular conditions in terms of reactivity and chemical reactions (Cadet et al 2009, 2010). This is not the case when DNA and its components are exposed to ionizing radiation either as partially hydrated solids or in frozen aqueous solutions.…”

Section: Introductionmentioning

confidence: 99%

One-electron oxidation reactions of purine and pyrimidine bases in cellular DNA

Cadet

Wagner

Shafirovich

et al. 2014

International Journal of Radiation Biology

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136

143

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Purpose The aim of this survey is to critically review the available information on one-electron oxidation reactions of nucleobases in cellular DNA with emphasis on damage induced through the transient generation of purine and pyrimidine radical cations. Since the indirect effect of ionizing radiation mediated by hydroxyl radical is predominant in cells, efforts have been made to selectively ionize bases using suitable one-electron oxidants that consist among others of high intensity UVC laser pulses. Thus, the main oxidation product in cellular DNA was found to be 8-oxo-7,8-dihydroguanine as a result of direct bi-photonic ionization of guanine bases and indirect formation of guanine radical cations through hole transfer reactions from other base radical cations. The formation of 8-oxo-7,8-dihydroguanine and other purine and pyrimidine degradation products was rationalized in terms of the initial generation of related radical cations followed by either hydration or deprotonation reactions in agreement with mechanistic pathways inferred from detailed mechanistic studies. The guanine radical cation has been shown to be implicated in three other nucleophilic additions that give rise to DNA-protein and DNA-DNA cross-links in model systems. Evidence was recently provided for the occurrence of these three reactions in cellular DNA. Conclusion There is growing evidence that one-electron oxidation reactions of nucleobases whose mechanisms have been characterized in model studies involving aqueous solutions take place in a similar way in cells. It may also be pointed out that the above cross-linked lesions are only produced from the guanine radical cation and may be considered as diagnostic products of the direct effect of ionizing radiation.

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“…The pathway of decomposition of thymidine by gamma radiation involves the generation hydroxyl radicals with addition of • OH to the 5,6-double bond of thymine or H-atom abstraction from the 2-deoxyribose moiety. The resulting carbon-centered radicals of thymidine lead to a large number of stable modifications 26 . In view of the profiles of products observed by HPLC-UV of samples exposed to gamma and laser radiation, the mechanism of formation of products by laser radiation also likely involves • OH radicals.…”

Section: Resultsmentioning

confidence: 99%

Filamentation of femtosecond laser pulses as a source for radiotherapy

et al. 2011

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Here, we report that intense ultra-short laser pulses produce a plasma of low energy electrons (LEEs) by the inverse Bremsstrahlung effect and multiphoton ionization process. The phenomena show five striking characteristics. First, the self-focusing of ultra-short laser pulses creates a plasma of LEEs (6.5 eV), which is concentrated in filaments through an avalanche process. Second, kinetically hot 6.5 eV electrons interact with surrounding molecules resulting in reactive radical species. Third, the dose rate reaches an enormous level of ∼2.8 × 10 11 Gy/s as determined by a cericcerous sulfate dosimetry and this leads to an ultra-high deposition of energy of between 4.6 × 10 7 to 8.16 × 10 7 keV/μm. Fourth, filaments of variable length are produced by femtosecond pulses depending on the pulse duration as determined by a tissue-equivalent radiation polymer gel dosimeter and imaged by magnetic resonance imaging (MRI). These results reveal that one of the very interesting novelty of filamentation is the very low entrance dose, similar to proton irradiation. Lastly, filamentary irradiation results in the decomposition of thymidine in the absence and the presence of oxygen similar to the radiolysis of water.

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Chemical Reactions of the Radical Cations of Nucleobases in Isolated and Cellular DNA. Formation of Single‐Base Lesions

Cited by 14 publications

References 100 publications

Photoinduced Damage to Cellular DNA: Direct and Photosensitized Reactions^†

Photoinduced Damage to Cellular DNA: Direct and Photosensitized Reactions^†

One-electron oxidation reactions of purine and pyrimidine bases in cellular DNA

Filamentation of femtosecond laser pulses as a source for radiotherapy

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Chemical Reactions of the Radical Cations of Nucleobases in Isolated and Cellular DNA. Formation of Single‐Base Lesions

Cited by 14 publications

References 100 publications

Photoinduced Damage to Cellular DNA: Direct and Photosensitized Reactions†

Photoinduced Damage to Cellular DNA: Direct and Photosensitized Reactions†

One-electron oxidation reactions of purine and pyrimidine bases in cellular DNA

Filamentation of femtosecond laser pulses as a source for radiotherapy

Contact Info

Product

Resources

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Photoinduced Damage to Cellular DNA: Direct and Photosensitized Reactions^†

Photoinduced Damage to Cellular DNA: Direct and Photosensitized Reactions^†