Early Events in Radiobiology: Isolated and Cluster DNA Damage Induced by Initial Cations and Nonionizing Secondary Electrons.

J Phys Chem Lett

Department of Nuclear Medicine and Radiobiology and Clinical Research Center, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC, Canada J1H 5N4.

Published: January 2021

Radiobiological damage is principally triggered by an initial cation and a secondary electron (SE). We address the fundamental questions: What lesions are first produced in DNA by this cation or nonionizing SE? What are their relative contributions to isolated and potentially lethal cluster lesions? Five monolayer films of dry plasmid DNA deposited on graphite or tantalum substrates are bombarded by 0.1-100 eV electrons in a vacuum. From measurements of the current transmitted through the films, 3.5 and 4.5 cations per incident 60 and 100 eV electrons, respectively, are estimated to be produced and stabilized within DNA. Damage analysis at 6, 10, 20, 30, 60, and 100 eV indicates that essentially all lesions, but preferentially cluster damages, are produced by non-ionizing or weakly ionizing electrons of energies below 12 eV. Most of these lesions are induced within femtosecond times, via transient anions and electron transfer within DNA, with little contributions from the numerous cations.

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http://dx.doi.org/10.1021/acs.jpclett.0c03341DOI Listing

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