title: Photoinduced fluorescent cross-linking of 5-chloro- and 5-fluoro-4-thiouridines with thymidine.
abstract: Two highly fluorescent, thermally stable diastereomeric photoadducts, 3a,b, are formed when either 5-chloro-4-thiouridine, 1, or 5-fluoro-4-thiouridine, 2, are photoexcited with 366 nm UV light in the presence of thymidine (T). 5-Fluoro-4-thiouridine, 2, exhibits photoreactivity much higher than that of the 5-chloro derivative 1. In both cases the photoreaction is very clean, leading to highly eficient conversion of the 5-halogeno-4-thiouridine (1, 2) and T to photoadducts 3a,b. The identity and structure of 3a was confirmed using mass spectrometry and 2-D NMR. The epimeric relationship of 3a,b was established by UV circular dichroism spectroscopy. The geometry of the fluorescent photoadduct is consistent with formation of an interstrand cross-link in a DNA duplex if 1 or 2 is flanked by T in an opposite strand.
authors.affiliation: Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland. bskalski@amu.edu.pl
authors.forename: Bohdan
authors.initials: B
authors.lastname: Skalski
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Taras-Goślińska
authors.forename: Anna
authors.initials: A
authors.lastname: Dembska
authors.forename: Zofia
authors.initials: Z
authors.lastname: Gdaniec
authors.forename: Stefan
authors.initials: S
authors.lastname: Franzen
mesh_terms: D003432:Cross-Linking Reagents; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010777:Photochemistry; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013891:Thiouridine / Q000031:analogs & derivatives* / Q000737:chemistry; D013936:Thymidine / Q000737:chemistry*
chemical_list: C548252:5-chloro-4-thiouridine; C548253:5-fluoro-4-thiouridine; D003432:Cross-Linking Reagents; D013891:Thiouridine; D013936:Thymidine