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Sudan III is a coloring agent used in chemical industries and food additives. This article uses spectroscopic and molecular docking methods to investigate the interaction of Sudan III with bovine serum albumin (BSA) under a physiological condition. Spectroscopic analysis of the emission quenching revealed that the quenching mechanism of BSA by Sudan III was static. The binding sites and constants of Sudan III–BSA complex were observed to be from 0.72 and 6.41 × 102 L·mol−1 to 0.69 and 5.83 × 102 L·mol−1 at 298 and 310 K, respectively. The enthalpy change (ΔH) and entropy change (ΔS) revealed that van der Waals forces and hydrogen bonds stabilized the Sudan III–BSA complex. Energy transfer from tryptophan to Sudan III occurred by a fluorescence resonance energy transfer mechanism, and the r distance (3.32 nm) had been determined. The results of UV–Vis absorption, synchronous, three-dimensional fluorescence, and circular dichroism spectra showed that Sudan III induced conformational changes of BSA. Molecular docking studies revealed that Sudan III situated within subdomain IIA of BSA. A study on the interaction between Sudan III and BSA was of fundamental importance for providing more information about the potential toxicological effect of chemicals at the molecular level. [ABSTRACT FROM AUTHOR]

This study investigates the interaction between tebuconazole and bovine serum albumin (BSA) in a physiological buffer (pH = 7.4) using the fluorescence quenching method to obtain the apparent binding constants (K) and number of binding sites (n) in the interaction between tebuconazole and BSA. The results revealed that tebuconazole can quench the intrinsic fluorescence of BSA through a static quenching procedure. It also shows that the thermodynamic parameters of enthalpy change (ΔH) and entropy change (ΔS) are negative, indicating that the interaction of tebuconazole with BSA is mainly driven by van der Waals forces and hydrogen bonds. The process of binding was a spontaneous process in which Gibbs free energy change was negative. The distance of r between the donor (BSA) and acceptor (tebuconazole) was calculated to be 0.68 nm based on Forster's non-radiative energy transfer theory. Analysis of synchronous fluorescence, three-dimensional fluorescence and circular dichroism (CD) spectra demonstrates that tebuconazole can induce conformational changes of BSA. [ABSTRACT FROM AUTHOR]

Highlights: [•] The fluorescence quenching of bovine serum albumin (BSA) by pyrene is static. [•] The pyrene–BSA complex has been formed. [•] The energy transfer of BSA to pyrene occurs. [•] Van der Waals forces and hydrogen bonds play major roles in the binding process. [•] The conformational changes indicate that pyrene induces damage to BSA. [Copyright &y& Elsevier]