Yield of Single-Strand Breaks Due to Attack on DNA by Scavenger-Derived Radicals

We have measured the yield of single-strand breaks (SSBs) in plasmid DNA after 137 Cs γ irradiation, in the presence of dimethyl sulfoxide (DMSO). In the presence of oxygen, the formation of SSBs is due to hydroxyl radical attack. As the DMSO concentration is increased from $10^{-4}\ {\rm mol}\ {\rm...

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Bibliographic Details
Published in:Radiation research 1994-03, Vol.137 (3), p.295-299
Main Authors: Milligan, Jamie R., Ward, John F.
Format: Article
Language:English
Subjects:
Alcohols
Biological and medical sciences
Biological effects of radiation
Dimethyl Sulfoxide - chemistry
Dimethyl Sulfoxide - toxicity
DNA
DNA Damage
DNA, Recombinant - drug effects
DNA, Recombinant - radiation effects
DNA, Single-Stranded
Free Radical Scavengers
Free Radicals
Fundamental and applied biological sciences. Psychology
Gamma Rays
Hydroxyl radicals
Ionizing radiations
Irradiation
Kinetics
Oxygen
Oxygen - pharmacology
Plasmids
Plasmids - drug effects
Plasmids - radiation effects
Protons
Radiation dosage
Tissues, organs and organisms biophysics
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Summary:We have measured the yield of single-strand breaks (SSBs) in plasmid DNA after 137 Cs γ irradiation, in the presence of dimethyl sulfoxide (DMSO). In the presence of oxygen, the formation of SSBs is due to hydroxyl radical attack. As the DMSO concentration is increased from $10^{-4}\ {\rm mol}\ {\rm dm}^{-3}$ to $1\ {\rm mol}\ {\rm dm}^{-3}$, the SSB yield in the presence and absence of oxygen decreases by over 100-fold and less than 10-fold, respectively. From the DMSO and DNA concentration dependencies of the SSB yield in the absence of oxygen, the second-order rate constant for the reaction of the methyl radical (derived from DMSO) and DNA can be estimated as $k_{2}=8.8\times 10^{4}\ {\rm dm}^{3}\ {\rm mol}^{-1}\ {\rm s}^{-1}$. Several other scavengers were compared with DMSO under anoxia. Radicals derived from isopropyl alcohol and glycerol also caused SSB formation in DNA, while those from 2-deoxyribose, thymine, 1,3-dimethylthymine and 1,3-dimethyluracil did not. In the case of the scavenger tert-butyl alcohol, it is unclear whether the hydrogen atom (${\rm H}^{\bullet}$) or an organic radical is responsible for the higher SSB yield under anoxic conditions.
ISSN:0033-7587
1938-5404
DOI:10.2307/3578702