# Potassium Ions Enhance Guanine Radical Generation upon Absorption of Low-Energy Photons by G-Quadruplexes and Modify Their Reactivity

1 DICO - Biomolécules Excitées
IRAMIS - Institut Rayonnement Matière de Saclay, LIDyl - Laboratoire Interactions, Dynamiques et Lasers (ex SPAM)
Abstract : G-Quadruplexes are formed by guanine rich DNA/RNA sequences in the presence of metal ions, which occupy the central cavity of these four-stranded structures. We show that these metal ions have a significant effect on the photogeneration and the reactivity of guanine radicals. Transient absorption experiments on G-quadruplexes formed by association of four TGGGGT strands in the presence of K$^+$ reveal that the quantum yield of one-photon ionization at 266 nm (8.1 × 10$^{–3}$) is twice as high as that determined in the presence of Na$^+$. Replacement of Na$^+$ with K$^+$ also suppresses one reaction path involving deprotonated radicals, (G-H2)$^•$ → (G-H1)$^•$ tautomerization. Such behavior shows that the underlying mechanisms are governed by dynamical processes, controlled by the mobility of metal ions, which is higher for Na$^+$ than for K$^+$. These findings may contribute to our understanding of the ultraviolet-induced DNA damage and optimize optoelectronic devices based on four-stranded structures, beyond DNA.
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Journal articles
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https://hal-cea.archives-ouvertes.fr/cea-03053797
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Submitted on : Friday, December 11, 2020 - 11:08:49 AM
Last modification on : Wednesday, October 20, 2021 - 3:17:38 AM
Long-term archiving on: : Friday, March 12, 2021 - 7:12:40 PM

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### Citation

Behnaz Behmand, Evangelos Balanikas, Lara Martinez-Fernandez, Roberto Improta, A. Banyasz, et al.. Potassium Ions Enhance Guanine Radical Generation upon Absorption of Low-Energy Photons by G-Quadruplexes and Modify Their Reactivity. Journal of Physical Chemistry Letters, American Chemical Society, 2020, 11 (4), pp.1305-1309. ⟨10.1021/acs.jpclett.0c00815⟩. ⟨cea-03053797⟩

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