Comparative Studies on the Interaction Between the Medicine Small Molecule with Pepsin by Fluorescence Quenching Spectroscopy and Improved Spectroscopy

The binding mechanism between cefetamet pivoxil (CFP) and pepsin (PEP) at different temperatures (298 K, 303 K, 310 K) was investigated by the classical fluorescence spectroscopy with focus on the fluorescence change of protein, as well as the improved spectroscopy with focus on the fluorescence changes of the resonance light scattering of small molecule drugs. The results showed that the main quenching mode of PEP-CFP was static quenching. The value of n was approximately equal to 1 which indicating that there was only one binding site in the interaction between PEP and CFP and the Hill coefficient was about 1 which indicating that there was no cooperative between the receptor PEP and ligand CFP. The binding constants of the PEP-CFP system obtained by the improved spectroscopic method were two orders of magnitude larger than that of the traditional fluorescence spectroscopy, which showed that the study of the small drug molecule was more practical and reasonable. The rationality of the experimental results obtained was verified by ultraviolet absorption spectroscopy