Electron spin resonance study of DNA irradiated with an argon-ion beam: evidence for formation of sugar phosphate backbone radicals.
In this study, the effects of high-LET radiation on DNA were investigated and compared with the effects of gamma radiation. Hydrated DNA samples at 77 K were irradiated with argon-ion beams ((36)Ar or (40)Ar beam at energies between 60 and 100 MeV/nucleon). The individual free radicals formed were identified and their yields were investigated by electron spin resonance spectroscopy. Argon-ion irradiation resulted in lower yields of base ion radicals and higher yields of neutral radicals than gamma irradiation. A hitherto unknown species was assigned to the radical formed by C-O bond rupture at the deoxyribose C3', resulting in a sugar carbon-centered radical. A previously characterized phosphorus-centered radical was also found. The formation of each of these species was accompanied by an immediate strand break. G values, k values, and analyses for the individual yields of neutral radicals and ion radical composition for argon-ion-irradiated hydrated DNA are reported and compared to those found previously for gamma-irradiated DNA. The lower G values and k values for ion radicals and the higher fraction of neutral radicals found for argon-ion-irradiated DNA are attributed to differences in track structure inherent in the two radiations.
Becker
David
D
Department of Chemistry, Oakland University, Rochester, Michigan 48309-4477, USA.
Bryant-Friedrich
Amanda
A
Trzasko
CherylAnn
C
Sevilla
Michael D
MD
D000818:Animals; D001128:Argon; D004247:DNA / Q000737:chemistry* / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005609:Free Radicals; D005720:Gamma Rays; D007477:Ions; D007554:Isotopes; D018499:Linear Energy Transfer; D008297:Male; D008956:Models, Chemical; D008958:Models, Molecular; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods; D012474:Salmon / Q000235:genetics / Q000378:metabolism; D013403:Sugar Phosphates / Q000737:chemistry* / Q000528:radiation effects*
D005609:Free Radicals; D007477:Ions; D007554:Isotopes; D013403:Sugar Phosphates; D001128:Argon; D004247:DNA