Fiche publication
Date publication
septembre 2025
Journal
Physical chemistry chemical physics : PCCP
Auteurs
Membres identifiés du Cancéropôle Est :
Pr MELY Yves
,
Dr BOURDERIOUX Aurélie
,
Dr RICHERT Ludovic
,
Mr HUMBERT Nicolas
,
Pr DIDIER Pascal
,
Dr BOMBARDA Elisa
,
Dr DZIUBA Dmytro
Tous les auteurs :
Tkach O, Martinez-Fernandez L, Ruiz-Lera AE, Humbert N, Richert L, Dziuba D, Bombarda E, Bourderioux A, Hanser F, Didier P, Tor Y, Improta R, Léonard J, Mély Y
Lien Pubmed
Résumé
To fully exploit the potential of isothiazologuanosine (G), an isomorphic and isofunctional fluorescent analogue of guanosine, as a probe for DNA and RNA, we characterized its photophysics and in particular its excited-state reactions over a wide pH range (-0.6 to 12) and time scale (100 fs-100 ns) by combining transient absorption and time-correlated single photon counting measurements with quantum mechanical calculations. At acidic pH, the dominant ground-state species G-H1-H3, where the N atoms in positions 1 and 3 are protonated, rapidly converts to the more stable tautomer G-H1-H7 in its excited state. The latter then deprotonates to form the G-H1 neutral species with an excited-state p* value that differs by three pH units from the ground-state p value. The rate constants governing the excited-state reactions and the fluorescence lifetime of each species were all determined. With the exception of intramolecular and solvent relaxations, no excited-state reactions in the femtosecond to nanosecond time scale were, however, observed between the dominant G-H1 and G-H3 tautomers in equilibrium at neutral pH or for G-H1 deprotonation at high pH. Because of the distinct spectra, fluorescence quantum yields and lifetimes of its different protonated and deprotonated forms, G is highly responsive over a wide range of acidic (0-5) and basic pH values (8-10). The mechanisms revealed herein will be instrumental for G-labelled oligonucleotides in order to interpret proton transfer reactions as well as interactions with specific protein domains, which, due to local electrostatic changes and water exclusion effects, may shift the p values of G to a more physiologically relevant range.
Référence
Phys Chem Chem Phys. 2025 09 3;:
