Fluorescence spectra of the ofloxacin-zinc complex in the absence (dotted line) and presence of the increasing amounts of DNA in Tris-HCl buffer solution at 25 °C. ri=(DNA)/(ACC)=0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.8, 0.9, 1.0.