title: Fluorescence quenching of fluoroquinolone antibiotics by 4-hydroxy-TEMPO in aqueous solution.
abstract: The fluorescence quenching of norfloxacin, danofloxacin, enrofloxacin and levofloxacin, belonging to a group of fluoroquinolone antibiotics, by 4-hydroxy-TEMPO was studied in aqueous solutions with the use of steady-state, time-resolved fluorescence spectroscopy as well as UV-VIS absorption spectroscopy methods. In order to understand the mechanism of quenching the absorption and fluorescence emission spectra of all fluoroquinolone antibiotics studied as well as decreases of their fluorescence were registered as a function of the 4-hydroxy-TEMPO concentration. No deviations from a linearity in the Stern-Volmer plots (determined from both, steady-state and time-resolved measurements) were observed. The fluorescence quenching mechanism was proved to be totally dynamic, what was additionally confirmed by the registration of Stern-Volmer plots at 5 temperatures ranging from 15 to 55°C. On the basis of theoretical calculations of fluoroquinolones' molecular radii and ionization potentials the mechanism of electron transfer was rejected. It seems that the fluorescence quenching is diffusion-limited and is caused by the increase of nonradiative processes, such as internal conversion or intersystem crossing. The Stern-Volmer quenching constants and bimolecular quenching constants were determined at the room temperature for all fluoroquinolone antibiotics studied.
authors.affiliation: University of Gdansk, Faculty of Chemistry, Wita Stwosza 63, 80-308 Gdansk, Poland. Electronic address: krzysztof.zamojc@ug.edu.pl.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Żamojć
authors.affiliation: University of Gdansk, Faculty of Chemistry, Wita Stwosza 63, 80-308 Gdansk, Poland.
authors.forename: Wiesław
authors.initials: W
authors.lastname: Wiczk
authors.affiliation: University of Gdansk, Faculty of Chemistry, Wita Stwosza 63, 80-308 Gdansk, Poland.
authors.forename: Bartłomiej
authors.initials: B
authors.lastname: Zaborowski
authors.affiliation: University of Gdansk, Faculty of Chemistry, Wita Stwosza 63, 80-308 Gdansk, Poland.
authors.forename: Mariusz
authors.initials: M
authors.lastname: Makowski
authors.affiliation: University of Gdansk, Faculty of Chemistry, Wita Stwosza 63, 80-308 Gdansk, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Pranczk
authors.affiliation: University of Gdansk, Faculty of Chemistry, Wita Stwosza 63, 80-308 Gdansk, Poland.
authors.forename: Dagmara
authors.initials: D
authors.lastname: Jacewicz
authors.affiliation: University of Gdansk, Faculty of Chemistry, Wita Stwosza 63, 80-308 Gdansk, Poland.
authors.forename: Lech
authors.initials: L
authors.lastname: Chmurzyński
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D003497:Cyclic N-Oxides / Q000737:chemistry*; D005453:Fluorescence; D024841:Fluoroquinolones / Q000737:chemistry*; D019811:Hydroxylamine / Q000737:chemistry*; D008958:Models, Molecular; D013050:Spectrometry, Fluorescence
chemical_list: D000900:Anti-Bacterial Agents; D003497:Cyclic N-Oxides; D024841:Fluoroquinolones; D019811:Hydroxylamine; C505333:TEMPOL-H
keywords: 4-Hydroxy-TEMPO; Dynamic quenching; Fluorescence quenching; Fluoroquinolone antibiotics