Fiche publication
Date publication
mars 2019
Journal
Chemistry (Weinheim an der Bergstrasse, Germany)
Auteurs
Membres identifiés du Cancéropôle Est :
Pr MELY Yves
,
Dr RICHERT Ludovic
Tous les auteurs :
Martinez-Fernandez L, Gavvala K, Sharma R, Pascal D, Richert L, Segarra Martì J, Mori M, Mely Y, Improta R
Lien Pubmed
Résumé
Thienoguanosine (thG) is an isomorphic analogue of guanosine with promising potentialities as fluorescent DNA label. As a free probe in protic solvents, thG exists in two tautomeric forms, identified as H1, the only one observed in non protic solvents, and H3 keto-amino tautomers. We here investigate the photophysics of thG in solvents of different polarity, from water to dioxane by combining time-resolved fluorescence with PCM/TD-DFT and CASSCF calculations. Fluorescence lifetimes of 14.5-20.5 ns and 7-13 ns were observed for the H1 and H3 tautomers, respectively in the tested solvents. In methanol and ethanol, an additional fluorescent decay lifetime ( ~ 3 ns) at the blue emission side (~430 nm) as well as a 0.5 ns component with negative amplitude at the red edge of the spectrum, typical of an excited-state reaction, were observed. Our computational analysis explains the solvent effects observed on the tautomeric equilibrium. The main radiative and non-radiative deactivation routes have been mapped by PCM/TD-DFT in solution and CASSCF in the gas phase. The most easily accessible conical intersection, involving an out-of plane motion of the sulphur atom in the five membered ring of thG, is separated by a sizeable energy barrier (≥ 0.4 eV) from the minimum of the spectroscopic state, which explains the large experimental fluorescence quantum yield.
Référence
Chemistry. 2019 Mar 18;:
