UV-Induced Adenine Radicals Induced in DNA A-Tracts: Spectral and Dynamical Characterization

Bányász, Ákos; Ketola, Tiia-Maaria; Muñoz-Losa, Aurora; Rishi, Sunny; Adhikary, Amitava; Sevilla, Michael D.; Martínez‐Fernández, Lara; Improta, Roberto; Markovitsi, Dimitra

doi:10.1021/acs.jpclett.6b01831

Cited by 37 publications

(122 citation statements)

References 39 publications

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“…4–18 This conclusion is well-supported by electron spin resonance (ESR) spectral studies at low temperature, 4–18 and by pulse radiolysis, flash photolysis along with product analyses studies in aqueous solutions at ambient temperature. 19–29 In addition, our ESR studies showed that RNH• plays an important role in the prototropic equilibria of DNA-base delocalized π-cation radicals 5–15 (such as, guanine cation radical, 5–9 cytosine cation radical, 10–12 adenine cation radical 13–15 ). Pulse radiolysis and product analyses studies established that hydroxyl radical (•OH) can produce the same delocalized π-type RNH• in purines, via either •OH addition to the C4=C5 double bond along with subsequent water elimination or by direct abstraction.…”

Section: Introductionmentioning

confidence: 72%

Prehydrated One-Electron Attachment to Azido-Modified Pentofuranoses: Aminyl Radical Formation, Rapid H-Atom Transfer, and Subsequent Ring Opening

et al. 2017

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Methyl 2-azido-2-deoxy-α-D-lyxofuranoside (1a) and methyl 2-azido-2-deoxy-β-D-ribofuranoside (2) were prepared from D-xylose or D-arabinose, respectively. Employing ESR and DFT/B3LYP/6-31G* calculations, we investigated (i) aminyl radical (RNH•) formation and (ii) reaction pathways of RNH•. Prehydrated electron attachment to 1a and 2 at 77 K produced transient azide anion radical (RN3•−) which reacts via rapid N2 loss at 77 K, forming nitrene anion radical (RN•−). Rapid protonation of RN•− at 77 K formed RNH• and −OH. 15N-labeled-1a confirmed this mechanism. Investigations employing in-house synthesized site-specifically deuterated derivatives of 1a (e.g., CH3 (1b), C4 (1c), and C5 (1d)) established that: (a) a facile intramolecular H-atom transfer from C5 to RNH• generated C5• and RNH2. C5• formation had a small deuterium kinetic isotope effect suggesting that this reaction does not occur via direct H-atom abstraction. (b) Subsequently, C5• underwent a facile unimolecular conversion to ring-opened C4• under a reductive environment. Identification of ring-opened C4• intermediate confirms the mechanism of C5′• mediated unaltered base release associated with DNA-strand break. However, for 2, ESR studies established thermally-activated intermolecular H-atom abstraction by RNH• from methyl group at C1. Thus, sugar ring configuration strongly influence site and pathways of RNH• mediated reactions in pentafuranoses.

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Section: Introductionmentioning

confidence: 72%

Prehydrated One-Electron Attachment to Azido-Modified Pentofuranoses: Aminyl Radical Formation, Rapid H-Atom Transfer, and Subsequent Ring Opening

et al. 2017

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“…Following our works, 22–29, 31, 36–38 a Varian Century Series X-band (9.3 GHz) ESR spectrometer with an E-4531 dual cavity, 9-inch magnet, and a 200 mW Klystron was used for the ESR studies. For the field calibration, Fremy’s salt ( g center = 2.0056, A (N) = 13.09 G) was employed.…”

Section: Methodsmentioning

confidence: 99%

Modulating the Catalytic Activity of Cerium Oxide Nanoparticles with the Anion of the Precursor Salt

et al. 2017

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In this work, we tested our hypothesis that surface chemistry and antioxidant properties of cerium nanoparticles (CNPs) are affected by presence of counterions. We first employed various precursor cerium (III) (Ce(III)) salts with different counterions (acetate, nitrate, chloride, sulfate) to synthesize CNPs following the same wet chemical methodology. Electron spin resonance (ESR) studies provided evidence for the formation of radicals from counterions (e.g., NO3•2− from reduction of NO3− in CNPs synthesized from Ce(III) nitrate). Physicochemical properties of these CNPs, e.g., dispersion stability, hydrodynamic size, signature surface chemistry, SOD-mimetic activity, and oxidation potentials were found to be significantly affected by the anions of the precursor salts. CNPs synthesized from Ce(III) nitrate and Ce(III) chloride exhibited higher extent of SOD-mimetic activities. Therefore, these CNPs were studied extensively employing in-situ UV-Visible spectroelectrochemistry and changing the counterion concentrations affected the oxidation potentials of these CNPs. Thus, the physicochemical and antioxidant properties of CNPs can be modulated by anions of the precursor. Furthermore, our ESR studies present evidence of the formation of guanine cation radical (G•+) in 5′-dGMP via UV-photoionization at 77 K in the presence of CNPs synthesized from Ce(III) nitrate and chloride and CNPs act as the scavenger of radiation-produced electrons.

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“…In addition, either 5-FoUra or 5-HmUra, the two methyl oxidation products of thymine were formed with a yield of 60-fold higher than dG*-dT*. Interestingly, the ability of 4 to form dG*-dT* and to a lesser extent dG*pdT*in which both modified bases are vicinal was previously observed in model studies involving single-stranded oligonucleotides [68] and DNA duplexes [318]. It was recently shown that DNA repair glycosylases were able to cleave the N- glycosidic bond of dG*-dT* and dG*dC-dT* [319] which were site-specifically inserted into oligodeoxynucleotides with a defined sequence [63] (Crean et al 2008).…”

Section: Complex Modificationsmentioning

confidence: 67%

“…One- and two-photon photolysis of DNA-A tracts with energies inferior to the ionization potential were recently shown to generate N 6-centered radicals nearly quantitatively in low temperate glasses [68]. The reaction of hypochlorite with adenine and cytosine in DNA, RNA and polynucleotides also lead to N -centered radicals through the decomposition of intermediate chloramines [69].…”

Section: Main Reactive Endogenous and Exogenous Cellular Oxidizing Spmentioning

confidence: 99%

Formation and repair of oxidatively generated damage in cellular DNA

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Davies

Medeiros

et al. 2017

Free Radical Biology and Medicine

272

228

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In this review article, emphasis is placed on the critical survey of available data concerning modified nucleobase and 2-deoxyribose products that have been identified in cellular DNA following exposure to a wide variety of oxidizing species and agents including, hydroxyl radical, one-electron oxidants, singlet oxygen, hypochlorous acid and ten-eleven translocation enzymes. In addition, information is provided about the generation of secondary oxidation products of 8-oxo-7,8-dihydroguanine and nucleobase addition products with reactive aldehydes arising from the decomposition of lipid peroxides. It is worth noting that the different classes of oxidatively generated DNA damage that consist of single lesions, intra- and interstrand cross-links were unambiguously assigned and quantitatively detected on the basis of accurate measurements involving in most cases high performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry. The reported data clearly show that the frequency of DNA lesions generated upon severe oxidizing conditions, including exposure to ionizing radiation is low, at best a few modifications per 106 normal bases. Application of accurate analytical measurement methods has also allowed the determination of repair kinetics of several well-defined lesions in cellular DNA that however concerns so far only a restricted number of cases.

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UV-Induced Adenine Radicals Induced in DNA A-Tracts: Spectral and Dynamical Characterization

Cited by 37 publications

References 39 publications

Prehydrated One-Electron Attachment to Azido-Modified Pentofuranoses: Aminyl Radical Formation, Rapid H-Atom Transfer, and Subsequent Ring Opening

Prehydrated One-Electron Attachment to Azido-Modified Pentofuranoses: Aminyl Radical Formation, Rapid H-Atom Transfer, and Subsequent Ring Opening

Modulating the Catalytic Activity of Cerium Oxide Nanoparticles with the Anion of the Precursor Salt

Formation and repair of oxidatively generated damage in cellular DNA

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