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FORMATION OF CYCLOBUTANE THYMINE DIMERS PHOTOSENSITIZED BY PYRIDOPSORALENS: A TRIPLET‐TRIPLET ENERGY TRANSFER MECHANISM
Author(s) -
Costalat R.,
Blais J.,
Ballini J.P.,
Moysan A.,
Cadet J.,
Chalvet O.,
Vigny P.
Publication year - 1990
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1990.tb01709.x
Subject(s) - cyclobutane , photochemistry , pyrimidine dimer , thymine , energy transfer , chemistry , mechanism (biology) , triplet state , dna , molecule , physics , chemical physics , organic chemistry , biochemistry , dna damage , ring (chemistry) , quantum mechanics
— The 365 nm irradiation of thymine thin films in the presence of pyridopsoralens is shown to induce the formation of cyclobutane thymine dimers, in contrast to other compounds such as 8‐and 5‐methoxypsoralen. In order to elucidate the mechanism of such a photosensitized reaction, we have determined the energy of the lowest triplet state (T,) of these compounds, using phosphorescence spectroscopy and CNDO/S quantum chemistry calculations. The T, energy values were found to be significantly higher for pyridopsoralens–up to 0.3 eV–than for 8‐ and 5‐methoxypsoralen (approximately 2.8 eV), which are not able to photoinduce cyclobutane thymine dimers. The determination of the relative efficiency of cyclobutane thymine dimer formation was performed using chromatographic analysis. A good correlation was found between the energy of the T, state of the psoralen derivatives and the related cyclobutane thymine dimer formation. Moreover, the photosensitized cyclobutane thymine dimer formation appeared to be temperature‐dependent. Our results are consistent with a mechanism involving a triplet energy transfer from the pyridopsoralen to thymine.