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

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Abstract

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 ππ* excited state localized on the uracil and is connected to the ground electronic state by an easily accessible crossing with S0, 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.

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

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Publication details

The article was received on 08 Jul 2019, accepted on 14 Oct 2019 and first published on 14 Oct 2019


Article type: Paper
DOI: 10.1039/C9CP03839F
Phys. Chem. Chem. Phys., 2019, Advance Article

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

    M. Valadan, E. Pomarico, B. Della Ventura, F. Gesuele, R. Velotta, A. Amoresano, G. Pinto, M. Chergui, R. Improta and C. Altucci, Phys. Chem. Chem. Phys., 2019, Advance Article , DOI: 10.1039/C9CP03839F

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