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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 27, Number 12
BKCSDE 27(12)
December 20, 2006

Title	Quenching of Ofloxacin and Flumequine Fluorescence by Divalent Transition Metal Cations
Author	Hyoung-Ryun Park, Chu-Ha Oh, Hyeong-Chul Lee, Jae Gyu Choi, Beung-In Jung, Ki-Min Bark*
Keywords	Fluorescence quenching, Fluoroquinolone antibiotics, Transition metal cation, Stern-Volmer plot, Intramolecular charge transfer
Abstract	This study examined the quenching of ofloxacin (OFL) and flumequine (FLU) fluorescence by Cu²⁺, Ni²⁺, Co²⁺ and Mn²⁺ in an aqueous solution. The change in the fluorescence intensity and lifetime was measured at various temperatures as a function of the quencher concentration. According to the Stern-Volmer plots, the fluorescence emission was quenched by both collisions (dynamic quenching) and complex formation (static quenching) with the same quencher but the effect of static quenching was larger than that of dynamic quenching. Large static and dynamic quenching constants for both OFL and FLU support significant ion-dipole and orbital-orbital interactions between fluorophore and quencher. For both molecules, the static and dynamic quenching constants by Cu²⁺ were the largest among all the metal quenchers examined in this study. In addition, both the static and dynamic quenching mechanisms by Cu²⁺ were somewhat different from the quenching caused by other metals. Between Ni²⁺ and FLU, a different form of chemical interaction was observed compared with the interaction by other metals. The change in the absorption spectra as a result of the addition of a quencher provided information on static quenching. With all these metals, the static quenching constant of FLU was larger than those of OFL. The fluorescence of OFL was quite insensitive to both the dynamic and static quenching compared with FLU. This property of OFL can be explained by the twisted intramolecular charge transfer in the excited state.
Page	2002 - 2010
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