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Guanine Radicals Generated in Telomeric G-Quadruplexes by Direct Absorption of Low-Energy UV Photons: Effect of Potassium Ions

1
LIDYL, CEA, CNRS, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
2
Univ Lyon, ENS de Lyon, CNRS UMR 5182, Université Claude Bernard Lyon 1, Laboratoire de Chimie, F-69342 Lyon, France
*
Author to whom correspondence should be addressed.
Academic Editors: Virginie L. Lhiaubet-Vallet, Iñaki Tuñón and Daniel Roca-Sanjuán
Molecules 2020, 25(9), 2094; https://doi.org/10.3390/molecules25092094
Received: 27 March 2020 / Revised: 23 April 2020 / Accepted: 27 April 2020 / Published: 30 April 2020
(This article belongs to the Special Issue DNA Damage and Repair)
The study deals with the primary species, ejected electrons, and guanine radicals, leading to oxidative damage, that is generated in four-stranded DNA structures (guanine quadruplexes) following photo-ionization by low-energy UV radiation. Performed by nanosecond transient absorption spectroscopy with 266 nm excitation, it focusses on quadruplexes formed by folding of GGG(TTAGGG)3 single strands in the presence of K+ ions, TEL21/K+. The quantum yield for one-photon ionization (9.4 × 10−3) was found to be twice as high as that reported previously for TEL21/Na+. The overall population of guanine radicals decayed faster, their half times being, respectively, 1.4 and 6.7 ms. Deprotonation of radical cations extended over four orders of magnitude of time; the faster step, concerning 40% of their population, was completed within 500 ns. A reaction intermediate, issued from radicals, whose absorption spectrum peaked around 390 nm, was detected. View Full-Text
Keywords: guanine-quadruplexes; DNA; photo-ionization; oxidative damage; electron holes; guanine radicals; reaction dynamics; time-resolved spectroscopy guanine-quadruplexes; DNA; photo-ionization; oxidative damage; electron holes; guanine radicals; reaction dynamics; time-resolved spectroscopy
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Balanikas, E.; Banyasz, A.; Baldacchino, G.; Markovitsi, D. Guanine Radicals Generated in Telomeric G-Quadruplexes by Direct Absorption of Low-Energy UV Photons: Effect of Potassium Ions. Molecules 2020, 25, 2094.

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