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Issue 40, 2018
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Triplet photosensitization mechanism of thymine by an oxidized nucleobase: from a dimeric model to DNA environment

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Abstract

Nucleic acids are constantly exposed to external agents that can induce chemical and photochemical damage. In spite of the great advances achieved in the last years, some molecular mechanisms of DNA damage are not completely understood yet. A recent experimental report (I. Aparici-Espert et al., ACS Chem. Biol. 2018, 13, 542) proved the ability of 5-formyluracil (ForU), a common oxidatively generated product of thymine, to act as an intrinsic sensitizer of nucleic acids, causing single strand breaks and cyclobutane pyrimidine dimers in plasmid DNA. In the present contribution, we use theoretical methodologies to study the triplet photosensitization mechanism of thymine exerted by ForU in a model dimer and in DNA environment. The photochemical pathways in the former system are described combining the CASPT2 and TD-DFT methods, whereas molecular dynamics simulations and QM/MM calculations are employed for the DNA duplex. It is unambiguously shown that the 1n,π* state localised in ForU mediates the population of the triplet manifold, most likely the 3π,π* state centred in ForU, whereas the 3π,π* state localized in thymine can be populated via triplet–triplet energy transfer given the small energy barrier of <0.23 eV determined for this pathway.

Graphical abstract: Triplet photosensitization mechanism of thymine by an oxidized nucleobase: from a dimeric model to DNA environment

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Publication details

The article was received on 31 Jul 2018, accepted on 03 Oct 2018 and first published on 03 Oct 2018


Article type: Paper
DOI: 10.1039/C8CP04866E
Citation: Phys. Chem. Chem. Phys., 2018,20, 25666-25675

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    Triplet photosensitization mechanism of thymine by an oxidized nucleobase: from a dimeric model to DNA environment

    A. Francés-Monerris, C. Hognon, M. A. Miranda, V. Lhiaubet-Vallet and A. Monari, Phys. Chem. Chem. Phys., 2018, 20, 25666
    DOI: 10.1039/C8CP04866E

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