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Issue 2, 2012
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Mechanism of electron transfer processes photoinduced by lumazine

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Abstract

UV-A (320–400 nm) and UV-B (280–320 nm) radiation causes damage to DNA and other biomolecules through reactions induced by different endogenous or exogenous photosensitizers. Lumazines are heterocyclic compounds present in biological systems as biosynthetic precursors and/or products of metabolic degradation. The parent and unsubstituted compound called lumazine (pteridine-2,4(1,3H)-dione; Lum) is able to act as photosensitizer through electron transfer-initiated oxidations. To get further insight into the mechanisms involved, we have studied in detail the oxidation of 2′-deoxyadenosine 5′-monophosphate (dAMP) photosensitized by Lum in aqueous solution. After UV-A or UV-B excitation of Lum and formation of its triplet excited state (3Lum*), three reaction pathways compete for the deactivation of the latter: intersystem crossing to singlet ground state, energy transfer to O2, and electron transfer between dAMP and 3Lum* yielding the corresponding pair of radical ions (Lum˙ and dAMP˙+). In the following step, the electron transfer from Lum˙ to O2 regenerates Lum and forms the superoxide anion (O2˙), which undergoes disproportionation into H2O2 and O2. Finally dAMP˙+ participates in subsequent reactions to yield products.

Graphical abstract: Mechanism of electron transfer processes photoinduced by lumazine

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Publication details

The article was received on 27 Sep 2011, accepted on 14 Nov 2011 and first published on 03 Jan 2012


Article type: Paper
DOI: 10.1039/C1PP05315A
Citation: Photochem. Photobiol. Sci., 2012,11, 409-417
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    Mechanism of electron transfer processes photoinduced by lumazine

    M. P. Denofrio, M. L. Dántola, P. Vicendo, E. Oliveros, A. H. Thomas and C. Lorente, Photochem. Photobiol. Sci., 2012, 11, 409
    DOI: 10.1039/C1PP05315A

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