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Journal Article

The Severity of Alpha-Particle-Induced DNA Damage Is Revealed by Exposure to Cell-Free Extracts

Paul S. Hodgkins, Peter O'Neill, David Stevens and Micaela P. Fairman
Radiation Research
Vol. 146, No. 6 (Dec., 1996), pp. 660-667
DOI: 10.2307/3579382
https://www.jstor.org/stable/3579382
Page Count: 8
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The Severity of Alpha-Particle-Induced DNA Damage Is Revealed by Exposure to Cell-Free Extracts
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Abstract

The rejoining of single-strand breaks induced by α-particle and γ irradiation in plasmid DNA under two scavenging conditions has been compared. At the two scavenger capacities used of 1.5× 107 and $3\times 10^{8}\ {\rm s}^{-1}$ using Tris-HCl as the scavenger, the ratio of single- to double-strand breaks for α particles is fivefold less than the corresponding ratios for γ irradiation. The repair of such radiation-induced single-strand breaks has been examined using a cell-free system derived from human whole-cell extracts. We show that the rejoining of single-strand breaks for both α-particle- and γ-irradiated plasmid is dependent upon the scavenging capacity and that the efficiency of rejoining of α-particle-induced single-strand breaks is significantly less than that observed for γ-ray-induced breaks. In addition, for DNA that had been irradiated under conditions that mimic the cellular environment with respect to the radical scavenging capacity, 50% of α-particle-induced single-strand breaks are converted to double-strand breaks, in contrast with only ∼12% conversion of γ-ray-induced single-strand breaks, indicating that the initial damage caused by α particles is more severe. These studies provide experimental evidence for increased clustering of damage which may have important implications for the induction of cancer by low-level α-particle sources such as domestic radon.