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


ABSTRACT: 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.

SUBMITTER: Balanikas E 

PROVIDER: S-EPMC7248781 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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

Balanikas Evangelos E   Banyasz Akos A   Baldacchino Gérard G   Markovitsi Dimitra D  

Molecules (Basel, Switzerland) 20200430 9


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)<sub>3</sub> single strands in the presence of K<sup>+</sup> ions, <b>TEL21/K<sup>+</sup></b>. The quantum yield for o  ...[more]

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