Kinetic and thermodynamic aspects on the interaction of serum albumin with sodium hydrosulfite: Spectroscopic and molecular docking methods

Abstract

Sodium hydrosulfite is a sulfur-containing food additive that is used as a decolorizing agent in the sugar industry to purify syrup and remove natural color compounds obtained from sugar beet, sugar cane, and color compounds created during production. Recent studies show gastrointestinal, aspiration, skin and eye complications from excessive use of sulfur-containing compounds. According to recent studies and the importance of investigating the interaction of food additives with biological molecules, we also investigated the binding properties of sodium hydrosulfite to blood serum albumin through UV–Vis spectroscopy, fluorescence spectroscopy, competitive binding experiments, Fourier transform infrared spectrometry (FT-IR), surface plasmon resonance (SPR), and molecular simulation analysis. According to the results, Sodium hydrosulfite decreased the fluorescence intensity of BSA through both static and dynamic quenching mechanisms after forming a complex with BSA. The results of synchronous fluorescence and FT-IR demonstrated that the microenvironment and the secondary structure of BSA were changed in the presence of sodium hydrosulfite. The negative values of ΔH° and ΔS° indicated that van der Waals force or hydrogen bonding is the main factor of binding between sodium hydrosulfite and BSA. The result of UV–Vis spectroscopy confirmed the binding of sodium hydrosulfite to BSA. Binding constant decreases from 13.06 to 0.24 (103 M−1) with increasing temperature, which indicates a decrease in complex formation owing to the interaction of sodium hydrosulfite with BSA. Molecular docking experiments confirm the binding tendency of sodium hydrosulfite to a cavity between domains II and III (Site I and Site II) through residues Cys460, Cys476, Asn457, Arg483, Lys204, and Ala200 with a binding energy of −12.86 kJ mol−1.