title: A 5-4 pyrimidine-pyrimidone photoproduct produced from mixtures of thymine and 4-thiouridine irradiated with 334 nm light.
abstract: 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 1H- and 13C-NMR spectroscopy, and have been identified as two diastereomers of 6-hydroxy-5-[1-(beta-D-erythro-pentofuranosyl)-4'-pyrimidin-2'- one]dihydrothymine (O6hThy[5-4]Pdo), of molecular weight = 370.32. These two diastereomers, although stable at room temperature or below, are interconvertible by heating (90 degrees C 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.
authors.affiliation: Department of Therapeutic Radiology, Rush-Presbyterian-St. Luke's Medical Center, Chicago, IL 60612.
authors.forename: E R
authors.initials: ER
authors.lastname: Blazek
authors.forename: J L
authors.initials: JL
authors.lastname: Alderfer
authors.forename: W A
authors.initials: WA
authors.lastname: Tabaczynski
authors.forename: V C
authors.initials: VC
authors.lastname: Stamoudis
authors.forename: M E
authors.initials: ME
authors.lastname: Churchill
authors.forename: J G
authors.initials: JG
authors.lastname: Peak
authors.forename: M J
authors.initials: MJ
authors.lastname: Peak
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010777:Photochemistry; D011743:Pyrimidines / Q000032:analysis*; D013056:Spectrophotometry, Ultraviolet; D013891:Thiouridine / Q000528:radiation effects*; D013941:Thymine / Q000031:analogs & derivatives* / Q000032:analysis / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D011743:Pyrimidines; D013891:Thiouridine; C080247:6-hydroxy-5-(1-pentofuranosyl-4'-pyrmidin-2'-one)dihydrothymine; D013941:Thymine