Protonation State of Norfloxacin and Their Interaction with DNA
Protonation State of Norfloxacin and Their Interaction with DNA
Journal of the Korean Chemical Society. 2000. Feb, 44(1): 4-9
  • Published : February 20, 2000
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Yeo, Jeong-Ah
Son, Gwan-Su
Kim, Jong-Moon
Moon, Hyung-Rang
Jun, Eun-Duk
Cho, Tae-Sub

We investigated the self-association and protonation state of norfloxacin, a member of quinokme antibiotics, using electric absorption and potentiom,etric titration. Both nitrogen at the piperazine ring and carboxylic acid were protonated at a low pH (cationic norfloxacin), and deprotonated at a high pH (anionic norfloxacin). In the intermediate pH range, a neutral species was dominant with the possibility of forming a zwitter ion. We also observed that nortloxacin molecules can be sracked to form a dimer at an intermediate pH, The equilibrium constant of the norfloxacin-DNA complex formation, which was measured by Stem-Volmermethod, increases as the pH of the system is lowered. This observation indicates that it is the cationic nortloxacin that forms a complex with DNA among various norfloxacin species in aqueous solution.