{'fraction_non_alphanumeric': 0.041109969167523124, 'fraction_numerical': 0.024665981500513873, 'mean_word_length': 4.565714285714286, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Note: transient negative ions as initiators of oxygen fixation in <20 eV electron-irradiated DNA.

This note represents a significant addition to our previous manuscript [N. Mirsaleh-Kohan, A. D. Bass, P. Cloutier, S. Massey, and L. Sanche, J. Chem. Phys. 136, 235104 (2012)] where we demonstrated that enhancements in the electron stimulated desorption yields of O− and OH− from O2 exposed DNA samples were due to the reactions of O2 with electron-induced damage sites within the DNA. Here, we investigate the attachment of O2 to electron-irradiated DNA as a function of electron energy and find a local maximum for O2 attachment to DNA at ∼11.4 eV. This reaction is likely initiated by the production of transient negative ions that dissociate to form RCHx−1• radicals. This work is thus relevant to our understanding of how O2 modulates radiation induced damage in cellular DNA and upon the question of the radio-sensitization of cells during, for example, radiotherapy.