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1 October 2000 A Laser Flash Photolysis and Pulse Radiolysis Study of Primary Photochemical Processes of Flumequine
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The 355 nm laser flash photolysis of argon-saturated pH 8 phosphate buffer solutions of the fluoroquinolone antibiotic flumequine produces a transient triplet state with a maximum absorbance at 575 nm where the molar absorptivity is 14 000 M−1 cm−1. The quantum yield of triplet formation is 0.9. The transient triplet state is quenched by various Type-1 photodynamic substrates such as tryptophan (TrpH), tyrosine, N-acetylcysteine and 2-deoxyguanosine leading to the formation of the semireduced flumequine species. This semireduced form has been readily identified by pulse radiolysis of argon-saturated pH 8 buffered aqueous solutions by reaction of the hydrated electrons and the CO2·− radicals with flumequine. The absorption maximum of the transient semireduced species is found at 570 nm with a molar absorptivity of 2500 M−1 cm−1. In argon-saturated buffered solutions, the semireduced flumequine species formed by the reaction of the flumequine triplet with TrpH stoichiometrically reduces ferricytochrome C (Cyt Fe3 ) under steady state irradiation with ultraviolet-A light. In the presence of oxygen, O2·− is formed but the photoreduction of Cyt Fe3 by O2·− competes with an oxidizing pathway which involves photo-oxidation products of TrpH.

M. Bazin, F. Bosca, M. L. Marin, M. A. Miranda, L. K. Patterson, and R. Santus "A Laser Flash Photolysis and Pulse Radiolysis Study of Primary Photochemical Processes of Flumequine," Photochemistry and Photobiology 72(4), 451-457, (1 October 2000).<0451:ALFPAP>2.0.CO;2
Received: 1 March 2000; Accepted: 1 July 2000; Published: 1 October 2000

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