A multi-scale time-resolved study of photoactivated dynamics in 5-benzyl uracil, a model for DNA/protein interactions. Issue 48 (5th November 2019)

• Record Type: Journal Article
• Authors: Valadan, Mohammadhassan; Pomarico, Enrico; Della Ventura, Bartolomeo; Gesuele, Felice; Velotta, Raffaele; Amoresano, Angela; Pinto, Gabriella; Chergui, Majed; Improta, Roberto; Altucci, Carlo
• Is Part Of: Physical chemistry chemical physics. Volume 21:Issue 48(2019)
• Page Start: 26301
• Page End: 26310
• Publication Date: 2019-11-05
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c9cp03839f
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Ultrafast photo-induced dynamics of 5-benzyl uracil: a model system to understand DNA/protein interactions. 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.