A novel three-dimensional strategy to elucidate the interactions of two fluoroquinolones with DNA using two-dimensional fluorescence maps

A novel three-dimensional strategy was introduced to elucidate the interactions of two fluoroquinolones, ciprofloxacin (CIP) and norfloxacin (NOR), with DNA using two-dimensional fluorescence maps (fluorescence excitation and emission measurements). This chemometric strategy is based on decomposing fluorescence excitation-emission matrices to extract detailed excitation, emission, and concentration profiles. By recording the fluorescence spectra after the reactions of CIP and NOR with calf thymus DNA and applying parallel factor analysis (PARAFAC) to the resulting data array, the quantitative estimations of the excitation and emission curves and the relative concentrations of the drugs and their DNA complexes were achieved. This investigation revealed the intricate interactions between CIP and DNA and NOR and DNA, characterized by Stern-Volmer constants (K_sv) and quenching rate constants (K_q). These constants related to the drug-DNA reaction equilibrium were derived from the correlation between actual DNA concentrations and the estimated relative amounts of CIP and NOR. The binding constants obtained through our innovative three-dimensional strategy were rigorously compared with those determined by classic spectrophotometric and spectrofluorometric methods, highlighting the efficacy and accuracy of our proposed approach.