Summary
Infectious DNA from coliphage T1 suspended in 4 % Difco nutrient broth was inactivated by60Co-gamma rays in the absence and in the presence of 0.1 M cysteamine. HCI (CSH). The influence of CSH on the occurrence of radiation-induced double- (dsb) and single-strand breaks (ssb) as well as on the inactivation of infectivity (lethal event) was studied. The ratio of dsb to lethal event rises by about 60 % from 0.18 in the absence to 0.29 when irradiated in the presence of CSH. However, an equal number of dsb is produced by treatment with CSH after irradiation. These additional dsb do not increase radiation damage to the biological activity of infectious DNA. It is suggested that CSH breaks labile bonds in native DNA at sites of radiation lesions unknown so far. These CSH-labile bonds in double-stranded DNA are alkali-labile in denatured DNA. The biological relevance of DNA breaks measured by ultra-centrifugation is discussed in the light of these findings.
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Hotz, G. Infectious DNA from coliphage Tl. Radiat Environ Biophys 11, 157–164 (1974). https://doi.org/10.1007/BF01559766
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DOI: https://doi.org/10.1007/BF01559766