Journal of Radiation Research
Online ISSN : 1349-9157
Print ISSN : 0449-3060
Regular Papers
Quantitative Analysis of Isolated and Clustered DNA Damage Induced by Gamma-rays, Carbon Ion Beams, and Iron Ion Beams
Hiroaki TERATORuri TANAKAYusuke NAKAARAITomonori NOHARAYusuke DOIShigenori IWAIRyoichi HIRAYAMAYoshiya FURUSAWAHiroshi IDE
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2008 Volume 49 Issue 2 Pages 133-146


Ionizing radiation induces multiple damaged sites (clustered damage) together with isolated lesions in DNA. Clustered damage consists of closely spaced lesions within a few helical turns of DNA and is considered to be crucial for understanding the biological consequences of ionizing radiation. In the present study, two types of DNA, supercoiled plasmid DNA and linear lambda DNA, were irradiated with γ-rays, carbon ion beams, and iron ion beams, and the spectra and yield of isolated DNA damage and bistranded clustered DNA damage were fully analyzed. Despite using different methods for damage analysis, the experiments with plasmid and lambda DNA gave largely consistent results. The spectra of both isolated and clustered damage were essentially independent of the quality of the ionizing radiation used for irradiation. The yields of clustered damage as well as of isolated damage decreased with the different radiation beams in the order γ > C > Fe, thus exhibiting an inverse correlation with LET [γ (0.2 keV/μm) < C (13 keV/μm) < Fe (200 keV/μm)]. Consistent with in vitro data, the yield of chromosomal DNA DSBs decreased with increasing LET in Chinese hamster cells irradiated with carbon ion beams with different LETs, suggesting that the decrease in the yield of clustered damage with increasing LET is not peculiar to in vitro irradiation of DNA, but is common for both in vitro and in vivo irradiation. These results suggest that the adverse biological effect of the ionizing radiation is not simply accounted for by the yield of clustered DNA damage, and that the complexity of the clustered damage needs to be considered to understand the biological consequences of ionizing radiation.

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© 2008 by Journal of Radiation Research Editorial Committee
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