Jump to main content
Jump to site search


Adenine radicals generated in alternating AT duplexes by direct absorption of low-energy UV radiation

Abstract

There is increasing evidence that direct absorption of photons with energy lower than the ionization potential of the nucleobases may produce oxidative damage to DNA. The present work, associating nanosecond transient absorption spectroscopy and quantum mechanical calculations, studies this process in alternating (AT)n duplexes. We show that the one-photon ionization quantum yield of (AT)10 at 266 nm (4.66 eV) is (1.5 ± 0.3)×10-3. According to our PCM/TD-DFT calculations performed for model duplexes composed of two base pairs, (AT)1 and (TA)1, simultaneous base pairing and stacking does not induce important changes in the absorption spectra of the adenine radical cation and deprotonated radical. The adenine radicals thus identified in the time-resolved spectra, disappear with a lifetime of 2.5 ms, giving rise to a reaction product absorbing at 350 nm. In parallel, the fingerprint of reaction intermediates other than radicals, formed directly from singlet excited states and assigned to AT/TA dimers, is detected at shorter wavelengths. PCM/TD-DFT calculations map the pathways leading to such species and characterize their absorption spectra; we find that, in addition to the path leading to the well-known TA* photoproduct, an AT photo-dimerization path may be operative in duplexes.

Back to tab navigation

Publication details

The article was received on 24 Jul 2017, accepted on 12 Sep 2017 and first published on 12 Sep 2017


Article type: Paper
DOI: 10.1039/C7FD00179G
Citation: Faraday Discuss., 2017, Accepted Manuscript
  •   Request permissions

    Adenine radicals generated in alternating AT duplexes by direct absorption of low-energy UV radiation

    A. Banyasz, T. C. Ketola, L. Martinez-Fernandez, R. Improta and D. Markovitsi, Faraday Discuss., 2017, Accepted Manuscript , DOI: 10.1039/C7FD00179G

Search articles by author

Spotlight

Advertisements