title: Temperature dependence of ofloxacin fluorescence quenching and complexation by Cu(II).
abstract: The coexistence of heavy metals and antibiotics is common in the environment, and their interactions may mutually alter their environmental behaviors and risks. This study investigated ofloxacin (OFL)-Cu(II) interaction using fluorescence quenching experiments. The possible artifacts were excluded and OFL quenching was attributed to static quenching as suggested by the linear Stern-Volmer plot and decreased quenching with increased temperature. The OFL-Cu(II) interaction was quantitatively described using a stoichiometry equation. The calculation suggested that OFL-Cu(II) association was the mixture of 1:1 and 1:2 complexes. The negative ΔG values and the negative ΔH values suggested that the complexation is a spontaneous and exothermic process. Cation-π binding and electrostatic interaction were excluded and the complexation of Cu(II) with OFL ketonic and carboxyl groups was proposed through UV-visible spectrum characterization, pH dependent complexation, and thermodynamic analysis.
authors.affiliation: Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming 650500, China. panbocai@gmail.com
authors.forename: Bo
authors.initials: B
authors.lastname: Pan
authors.forename: Xuejiao
authors.initials: X
authors.lastname: Han
authors.forename: Min
authors.initials: M
authors.lastname: Wu
authors.forename: Hongbo
authors.initials: H
authors.lastname: Peng
authors.forename: Di
authors.initials: D
authors.lastname: Zhang
authors.forename: Hao
authors.initials: H
authors.lastname: Li
authors.forename: Baoshan
authors.initials: B
authors.lastname: Xing
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D004785:Environmental Pollutants / Q000737:chemistry; D005453:Fluorescence; D007700:Kinetics; D008956:Models, Chemical; D015242:Ofloxacin / Q000737:chemistry*; D013696:Temperature
chemical_list: D000900:Anti-Bacterial Agents; D004785:Environmental Pollutants; D003300:Copper; D015242:Ofloxacin