Analysis of the spectroscopic characteristics on the binding interaction between tosufloxacin and bovine lactoferrin

►In this paper, a new saturation spectroscopic characteristic of non-covalent binding reaction is proposed. The saturated character of interaction of tosufloxacin binding with bovine lactoferrin is firstly observed by fluorescence polarization spectroscopy. ►The unfolding procedure of bovine lactoferrin induced by drug ligand is analyzed by “fluorescence phase diagram”, and it is quantitatively characterized. ►The binding parameters and energy-transfer efficiency parameters of bovine lactoferrin-tosufloxacin/tosufloxacin-Co2+ (Ni2+) system are determined and the mechanism of interaction is discussed.