Biophysical Journal 7: 555-565 (1967)
© 1967 the Biophysical Society

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DNA Degradation in Escherichia coli 15 T^-L^- Induced by Fast Proton Bombardment

ABSTRACT

DNA degradation and its temperature dependence as a function of linear energy transfer were studied in Excherichia coli using fast proton irradiation as the initiating agent. The data indicate that radiation-induced DNA degradation can proceed by two processes. The first, or fast component, begins immediately after irradiation with ⁶⁰Co -rays or with fast protons at doses less than 10¹⁰ protons/cm². The rate is high and involves a maximum of about 50% degradation. It is elicited more efficiently by protons of high linear energy transfer. The second, or slow component, results from higher doses of fast proton bombardment. There is a delay between irradiation and the initiation of this slower component, but 100% of the DNA complement is degraded. The data indicate that both processes are enzyme-mediated, the first probably by normal DNA-related activity and the second by DNAase activity.