Spectroscopic studies on binding of 1-phenyl-3-(coumarin-6-yl)sulfonylurea to bovine serum albumin

The interaction of 1-phenyl-3-(coumarin-6-yl)sulfonylurea (SU22) with bovine serum albumin (BSA) has been investigated by fluorescence quenching spectroscopy combined with UV-absorption, circular dichroism (CD), Fourier transform infrared (FT-IR) spectroscopy techniques under simulative physiological conditions for the first time. Fluorescence data and UV-absorption spectra revealed that the quenching mechanism of fluorescence of BSA by SU22 was a static quenching process and the number of binding sites was about 0.8858; the thermodynamic parameters (ΔG = −29.23 kJ mol−1, ΔH = −47.48 kJ mol−1, and ΔS = −61.24 J mol−1 K−1) explained that hydrogen bond and Van der Waals interaction were the main binding force stabilizing the complex. The binding average distance between SU22 and BSA was obtained (3.20 nm) on the basis of the Förster’s theory. In addition, The CD spectra and FT-IR spectra have proved that BSA secondary structure changed in the presence of SU22 in aqueous solution.