The (6–4) Dimeric Lesion as a DNA Photosensitizer. Issue 13 (31st March 2016)

• Record Type: Journal Article
• Authors: Vendrell‐Criado, Victoria; Rodríguez‐Muñiz, Gemma M.; Lhiaubet‐Vallet, Virginie; Cuquerella, M. Consuelo; Miranda, Miguel A.
• Is Part Of: Chemphyschem. Volume 17:Issue 13(2016)
• Page Start: 1979
• Page End: 1982
• Publication Date: 2016-03-31
• Subjects: cyclobutane pyrimidine dimers -- DNA damage -- photochemistry -- pyrimidone -- triplet excited states; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201600154
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: Based on our previous investigations into the photophysical properties of the 5‐methyl‐2‐pyrimidone (Pyo) chromophore, we now extend our studies to the photobehavior of the dimeric (6–4) thymine photoproducts (6–4 PP) to evaluate their capability to act as instrinsic DNA photosensitizers. The lesion presents significant absorption in the UVB/UVA region, weak fluorescence emission, a singlet‐excited‐state energy of approximately 351 kJ mol −1, and a triplet‐excited‐state energy of 297 kJ mol −1 . Its triplet transient absorption has a maximum at 420–440 nm, a lifetime of around 7 μs, and a high formation quantum yield, ΦISC =0.86. This species is efficiently quenched by thymidine. Its DNA photosensitizing properties are demonstrated by a series of experiments run on a pBR322 plasmid. The lesion photoinduces both single‐strand breaks and the formation of cyclobutane thymine dimers. Altogether, these results show that, the substitution of the pyrimidone ring at C4 by a 5‐hydroxy‐5, 6‐dihydrothymine does not cancel out the photosensitization properties of the chromophore. Abstract : So excited ! The primary (6–4) dimeric DNA lesion acts as a photosensitizer, leading to the formation of secondary cyclobutane dimers in its vicinity.