title: Fluorescence emission properties of 8-aza analogues of caffeine, theophylline, and related N-alkyl xanthines.
abstract: Fluorescence emission properties of 8-azacaffeine, 8-azatheophylline and other N-alkylated 8-azaxanthines (8-azaXan) have been examined. It is shown that N-methylated 8-azaxanthines, as well as 8-azatheophylline, are highly fluorescent in aqueous medium as the neutral, and, in some instances, also as the monoanionic, forms. 8-Azacaffeine exhibits moderate emission, but its isomer, 1,3,8-trimethyl-8-azaXan, is highly fluorescent. All three 8-azaxanthines monomethylated on the triazole ring, as well as 8-azaxanthosine, exhibit increased acidity in the excited state. Some fluorescent pyrazolo[4,3-d]pyrimidine-5,7-diones, xanthine congeners of pyrazolo[4,3-d]pyrimidines, are also reported. Many of these are good fluorescent probes in enzymatic, receptor binding, and nucleic acid systems, some examples of which are presented. In particular, 8-azaXan is an excellent fluorescent probe for purine nucleoside phosphorylases, as a fluorogenic substrate in the reverse, synthetic pathway.
authors.affiliation: Department of Biophysics, University of Warmia and Mazury, 4 Oczapowskiego Street, PL-10-719 Olsztyn, Poland.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Medza
authors.forename: Jacek
authors.initials: J
authors.lastname: Wierzchowski
authors.forename: Borys
authors.initials: B
authors.lastname: Kierdaszuk
authors.forename: David
authors.initials: D
authors.lastname: Shugar
mesh_terms: D001372:Aza Compounds / Q000737:chemistry*; D002110:Caffeine / Q000031:analogs & derivatives* / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet; D013806:Theophylline / Q000031:analogs & derivatives* / Q000737:chemistry; D014970:Xanthines / Q000737:chemistry*
chemical_list: D001372:Aza Compounds; D014970:Xanthines; D002110:Caffeine; D013806:Theophylline