Analytical Sciences

Spectroscopic Studies on the Binding of a New Quinolone Antibacterial Agent: Sinafloxacin to DNA

Yan FEI,*1,*2,*3 Guocai LU,*4 Guorong FAN,*1,*2 and Yutian WU*1,*2

*1 Department of Pharmaceutical Analysis, School of Pharmacy, Second Military Medical University, No. 325 Guohe Road, Shanghai 200433, P. R. China
*2 Shanghai Key Laboratory for Pharmaceutical Metabolite Research, No. 325 Guohe Road, Shanghai 200433, P. R. China
*3 Department of Pharmacy, 175th Hospital of PLA, Zhangzhou 363000, P. R. China
*4 Center for New Drug Evaluation, Institute of Basic Medical Science, Second Military Medical University, No. 800 Xiang Yin Road, Shanghai 200433, P. R. China

The binding of sinafloxacin to DNA has been studied by fluorescence spectroscopy and UV-vis absorption spectroscopy. The variations in the spectroscopic characteristics of sinafloxacin upon addition of DNA were observed. Salt concentration effect, KI quenching, fluorescence polarization, DNA denaturation experiments, melting temperature (T_m) curves and viscosity measurements were studied to investigate the binding mechanism. It was proved that the fluorescence quenching of sinafloxacin is a result of the formation of sinafloxacin-DNA complex. Quenching constants were determined using the Stern-Volmer equation. From the experiment evidence, the major binding mode of sinafloxacin with DNA was evaluated to be the groove binding.

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