Comparative study of the binding of Trypsin with bifendate and analogs by spectrofluorimetry

The interactions between Trypsin and bifendate (DDB) or analogs (I, II and III) were investigated by fluorescence, UV–visible absorption, resonance light scattering, synchronous fluorescence and 3D spectroscopy under mimic physiological conditions. The results revealed that DDB and analogs caused the fluorescence quenching of Trypsin by the formation of DDB/I/II/III–Trypsin complex. The quenching and energy transfer mechanisms were discussed. The binding constants and thermodynamic parameters at three different temperatures were obtained. The hydrophobic interaction was the predominant intermolecular forces to stabilize the complex. Results showed that DDB was the stronger quencher and bound to Trypsin with higher affinity than other three analogs.