A multi-scale time-resolved study of photoactivated dynamics in 5-benzyl uracil, a model for DNA/protein interactions

We combine fluorescence up-conversion and time correlated single photon counting experiments to investigate the 5-benzyl uracil excited state dynamics in methanol from 100 fs up to several ns. This molecule has been proposed as a model for DNA/protein interactions. Our results show emission bands at about 310 and 350 nm that exhibit bi-exponential sub-ps decays. Calculations, including solvent effects by a mixed discrete-continuum model, indicate that the Franck Condon region is characterized by significant coupling between the excited states of the benzyl and the uracil moieties, mirrored by the short-lived emission at 310 nm. Two main ground state recovery pathways are identified, both contributing to the 350 nm emission. The first 'photophysical' decay path involves a pp* excited state localized on the uracil and is connected to the ground electronic state by an easily accessible crossing with S-0, accounting for the short lifetime component. Simulations indicate that a possible second pathway is characterized by exciplex formation, with partial benzene - uracil charge transfer character, that may lead instead to photocyclization. The relevance of our results is discussed in view of the photoactivated dynamics of DNA/protein complexes, with implications on their interaction mechanisms.


Published in:
Physical Chemistry Chemical Physics, 21, 48, 26301-26310
Year:
Dec 28 2019
Publisher:
Cambridge, ROYAL SOC CHEMISTRY
ISSN:
1463-9076
1463-9084
Keywords:
Laboratories:




 Record created 2020-01-02, last modified 2020-01-07


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