Preparation of (2E)-3-(4′-halophenyl)prop-2-enoyl sulfachlorpyridazine sodium salts and their interaction with bovine serum albumin by fluorescence spectroscopy

Three (2E)-3-(4′-halophenyl)prop-2-enoyl sulfachlorpyridazine sodium salts(XPSCA) were synthesized. Their chemical structures were confirmed by 1H NMR and 13C NMR, electrospray ionization mass spectrometry (ESI-MS), and infrared(IR) spectroscopy. The interactions between XPSCA and bovine serum albumin(BSA) were investigated under imitated physiological condition by fluorescence quenching technique and UV-Vis absorption spectroscopy according to the Stern-Volmer equation. The results from the emission quenching at different temperatures indicate that the quenching mechanism of serum albumin by XPSCA was static quenching mechanism at low XPSCA concentrations or a combined quenching(static and dynamic) mechanism at higher XPSCA concentrations. At different temperatures, the binding constant and the binding sites of XPSCA with BSA were investigated, and the distances were evaluated according to Forster non-radiative resonance energy transfer theory. The thermodynamic parameters were calculated according to van’t Hoff equation, which implies that both van der Waals interaction and hydrogen bond played major roles in stabilizing the XPSCA-BSA complexes, whereas hydrophobic interactions were secondary. Moreover, the conformational changes in BSA were analyzed by synchronous fluorescence spectra.