Study on the Interaction between Cephalosporin Drugs and Papain by Spectroscopic Method: Equivalence of Fluorescence Quenching and Enhancement Equation

The interaction between two 4th generation of new cephalosporin drugs and papain was studied through spectroscopy method at different temperatures. Their dissociation constants were calculated by using theoretical formula of fluorescence quenching and fluorescence enhancement, respectively, and their corresponding thermodynamic functions, dipole-dipole non-radiative energy-transfer-efficiency and the action distances of acceptor-substrate etc. were calculated further. Analysis reveals that, the quenching on papain by cefpirome and cefepime is basically due to the dipole-dipole non-radiation energy-transfer and certain dynamic collision between donor and acceptor, the interaction between drug and papain is mainly hydrophobic which may provide useful information for pharmacological and metabolic study on papain. In this paper fluorescence quenching is regarded as negative fluorescence enhancement, and two kinds of theoretical formula of fluorescence quenching and fluorescence enhancement were used to calculate the experimental data of fluorescence quenching of a same batch, and very close results were obtained but with certain difference. The results not only display the equivalence of the two theoretical equations when treating acceptor-substrate action, but also show that the thermodynamic data based on the theoretical formula of fluorescence enhancement (4), which is deduced by us, are more reasonable. So we suggest that even in the process of studying the fluorescence quenching between receptor-substrate, using the theoretical formula of fluorescence enhancement (4) can get more reliable results.