NMR investigation of pefioxacin/cation/DNA interactions. Mg 2+ and Ca 2+ binding

Abstract

Pefloxacin at low concentration (10 −4 mol l −1 and high [cation] 0/[quinolone] 0 ratios forms 1:1 and 1:2 (drug:cation) complexes with magnesium or calcium cation, at pH 7.4. The binding sites are, first, the carbonyl and carboxyl groups, then, the N-4′ piperazinyl atom, as shown by the investigation of the pefloxacin ethyl ester/magnesium interaction. As expected, the apparent affinity constants are larger for magnesium than for calcium. When the pefloxacin concentration increases to 10 −3 mol −1, the affinity of this drug for magnesium becomes much larger. That is due to the formation of a 2:2 complex, what enhances the stacking of this fluoroquinolone.