Fluorescence quenching study of moxifloxacin interaction with calf thymus DNA

Moxifloxacin (MOX) is a fourth-generation synthetic fluoroquinolone antibacterial agent with many important therapeutic properties. Fluorescence quenching was used to study the interaction of MOX with calf thymus DNA (ct- DNA) in aqueous solution. The intercalative binding mode and a static quenching mechanism were confirmed by the Stern–Volmer quenching rate constant ( Kq ) of 3.48 × 10 ^11 M ^−1 s ^−1 at 298 K. The thermodynamic parameters ( ∆H = –118.4 KJ mol ^−1 and ∆S = –299.4 J mol ^−1 K ^−1) were calculated at different temperatures, and they indicate that the main forces between MOX and ct-DNA are hydrogen bonding and Van der Waals force. We proved at the same time the presence of one single binding site on ct-DNA, and the binding constant is 1.28 × 10 ^5 M ^−1 at physiological pH. The results may provide a basis for further studies and clinical application of antibiotics drugs.