Protonation of nucleobase anions in gamma-irradiated DNA and model systems. Which DNA base is the ultimate sink for the electron

Journal Article · Thu Mar 31 23:00:00 EST 1994 · Radiation Research; (United States)

DOI:https://doi.org/10.2307/3578841· OSTI ID:6480145

Wang, Wending; Sevilla, M D ^[1]

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1. Oakland Univ., Rochester, MI (United States)

Electron spin resonance (ESR) spectroscopy has been used to investigate irreversible protonations of the nucleobase anions in [gamma]-irradiated frozen aqueous solutions of dGMP[center dot]dCMP, polyG[center dot]polyC, poly[dGdC][center dot]poly[dGdC], dAMP[center dot]dTMP, poly[dAdT][center dot]poly-[dAdT] and DNA itself. Analysis of the ESR spectra at a dose of 22 kGy shows that fractional conversion of total radicals to carbon-protonated species on annealing is in the order: dAMP[center dot]dTMP (43%) > pdAdT = DNA (23%) > dGMP[center dot]dCMP (15%) > poly-dGdC[center dot]polydGdC (6%) > polyG[center dot]polyC (3%). Two hydrogen addition radicals make contributions to the polyG[center dot]polyC, poly[dGdC][center dot]poly[dGdC] and dGMP[center dot]dCMP spectra in H[sub 2]O on annealing. They are those formed by protonations at C6 of the cytosine anion radical, C(C6)H[sup *], and at C8 of the guanine anion radical, G(c8)H[sup *]. Computer analysis reveals that anion protonation reaction in dGMP[center dot]dCMP results in mainly C(C6)H[sup *], whereas protonation reaction in polyG[center dot]polyC and poly[dGdC][center dot]poly-[dGdC] yields mainly G(C8)H[sup *]. In dAMP[center dot]dTMP and poly[dAdT][center dot]poly[dAdT] as in DNA itself, the only DNA itself, the only DNA base found to undergo an irreversible protonation at a carbon site is thymine, resulting in T(C6)H[sup *]. The conversion of DNA anion to T(C6)H[sup *] is found to be dependent on dose. At low doses (5 kGy), about 30% conversion to T(C6)H[sup *] is found, whereas at high doses (94 kGy), only 13% conversion is found. The dose dependence is ascribed in part to ion radical recombinations whose probabilities are increased at high doses. 33 refs., 8 figs., 1 tab.

• OSTI ID: 6480145
• Journal Information: Radiation Research; (United States), Journal Name: Radiation Research; (United States) Vol. 138:1; ISSN 0033-7587; ISSN RAREAE
• Country of Publication: United States
• Language: English

Related Subjects

550200 -- Biochemistry
560151* -- Radiation Effects on Animals-- Man
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMINES
AROMATICS
AZAARENES
AZINES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
CYTOSINE
DNA
DNA BASE TRANSITIONS
DOSE-RESPONSE RELATIONSHIPS
DOSES
ELECTROMAGNETIC RADIATION
ELECTRON SPIN RESONANCE
EPR SPECTROMETERS
GAMMA RADIATION
GUANINE
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
IONIZING RADIATIONS
KINETICS
MAGNETIC RESONANCE
MEASURING INSTRUMENTS
NUCLEIC ACIDS
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PURINES
PYRIMIDINES
RADIATION DOSES
RADIATION EFFECTS
RADIATIONS
REACTION KINETICS
RESONANCE
SPECTROMETERS
THYMINE
URACILS