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KMID : 0364920080330020053
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Journal of Radiation Protection and Research
2008 Volume.33 No. 2 p.53 ~ p.59
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DNA Damage by X-ray and Low Energy Electron Beam Irradiation
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Park Yeun-Soo
Noh Hyung-Ah
Cho Hyuck
Dumont Ariane
Ptasinska Sylwia
Bass Andrew D.
Sanche Leon
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Abstract
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We observed DNA damages as a function of mean absorbed dose to identify the indirect effect of high-energy radiation such as x-ray. Monolayer films of lyophilized pGEM-3Zf(-) plasmid DNA deposited on tantalum foils were exposed to Al Kα X-ray (1.5 keV) for 0, 3, 7 and 10 min, respectively, in a condition of ultrahigh vacuum state. We compared DNA damages by X-ray irradiation with those by 3 eV electron irradiation. X-ray photons produced low-energy electrons (mainly below 20 eV) from the tantalum foils and DNA damage was induced chiefly by these electrons. For electron beam irradiation, DNA damage was directly caused by 3 eV electrons. Irradiated DNA was analyzed by agarose gel electrophoresis and quantified by ImagaQuant program. The quantities of remained supercoiled DNA after irradiation were linearly decreased as a function of mean absorbed dose. On the other hand, the yields of nicked circular (single strand break, SSB) and interduplex crosslinked form 1 DNA were linearly increased as a function of mean absorbed dose. From this study, it was confirmed that DNA damage was also induced by low energy electrons (0~10 eV) even below threshold energies for the ionization of DNA.
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KEYWORD
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DNA damage, Indirect action, X-ray, Low-energy electron beam, Dissociative electron attachment
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