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A5–4 PYRIMIDINE‐PYRIMIDONE PHOTOPRODUCT PRODUCED FROM MIXTURES OF THYMINE AND 4‐THIOURIDINE IRRADIATED WITH 334 nm LIGHT
Author(s) -
Blazek Ed Robert,
Alderfer James L.,
Tabaczynski Walter A.,
Stamoudis Vassilis C.,
Churchill Mark E.,
Peak Jennifer G.,
Peak Meyrick J.
Publication year - 1993
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.1751-1097.1993.tb02284.x
Subject(s) - thymine , chemistry , absorbance , aqueous solution , photochemistry , diastereomer , pyrimidine , oligonucleotide , mass spectrometry , dna , chromatography , stereochemistry , organic chemistry , biochemistry
The nucleoside 4‐thiouridine, present in some bacterial tRNA species, is known to be a chromophore and a target for near‐UV light‐induced growth delay and also mediates both photoprotection and near‐UV cell killing in various bacterial strains. To investigate the photoreaction of 4‐thiouridine with DNA or its precursors, we irradiated aqueous mixtures of thymine and 4‐thiouridine with 334 nm light and then separated photoproducts using two or more stages of reversed‐phase high performance liquid chromatography. The two equally abundant major photoproducts were analyzed by UV absorbance spectrophotometry, fast‐atom bombardment and electron‐impact mass spectrometry, and 1 H‐ and 13 C‐NMR spectroscopy, and have been identified as two diastereomers of 6‐hydroxy‐5‐[1‐(β‐D‐ erythro ‐pentofuranosyl)‐4′‐pyrimidin‐2′‐one]dihydrothymine (o 6 hThy[5‐4]Pdo), of molecular weight = 370.32. These two diastereomers, although stable at room temperature or below, are interconvertible by heating (90d̀C for 5 min) in aqueous solution. The possible biological significance of this photoproduct is discussed, and an application as a crosslinker for oligonucleotides to selectively block replication is suggested.