Comprehensive Study of Guanine Excited State Relaxation and Photoreactivity in G-quadruplexes

Lara Martinez-Fernandez (1, 2) , Pascale Changenet (3) , Akos Banyasz (1, 2) , Thomas Gustavsson (1, 2) , Dimitra Markovitsi (1, 2) , Roberto Improta (4, 2)

1 DICO - Dynamique et Interactions en phase Condensée
2 LIDYL - Laboratoire Interactions, Dynamiques et Lasers (ex SPAM)
3 LOB - Laboratoire d'Optique et Biosciences
4 CNR – Istituto di Biostrutture e Bioimmagini

G-quadruplexes (G4) are four-stranded DNA/RNA structures playing a key role in many biological functions and promising for nanotechnology applications. Here, combining theoretical calculations and multiscale time-resolved fluorescence, we describe, for the first time, an ensemble of photoactivated processes involving the guanines of the G4 core. We use as showcase the G4 formed by the human telomeric sequence GGG(TTAGGG)3 in the presence of Na+ ions. According to quantum mechanical/molecular mechanics calculations, the hyperchromism at the red part of the absorption spectrum, typical of G4 structures, arises mainly from the inner Na+ ions. Various relaxation pathways, leading to excited states localized on individual bases, neutral excimers, and excited charge transfer states between two guanines or a guanine and a thymine in the loop, are mapped. Their fingerprints are detected in the fluorescence anisotropies and the fluorescence decays, spanning five decades of time. Finally, a reaction funnel leading to guanine dimerization is identified.

Domaines: Chimie théorique et/ou physique

Lara Martinez-Fernandez, Pascale Changenet, Akos Banyasz, Thomas Gustavsson, Dimitra Markovitsi, et al.. Comprehensive Study of Guanine Excited State Relaxation and Photoreactivity in G-quadruplexes. Journal of Physical Chemistry Letters, 2019, 10 (21), pp.6873-6877. ⟨10.1021/acs.jpclett.9b02740⟩. ⟨hal-02362223⟩