Molecular interaction of Sunset Yellow with whey protein: Multi-spectroscopic techniques and computational study

Abstract

Sunset Yellow (SY) dye is an essential component in the food, pharmaceutical, and cosmetic, industries. Therefore, we studied its interaction with whey protein (β-lactoglobulin (β-LG)) using spectroscopic and molecular modeling techniques at pH 7.4. Intrinsic fluorescence data at three different temperatures suggested that the fluorescence intensity decreased upon the addition of SY dye. The fluorescence quenching constant (Ksv) values decreases in response to increase in temperature which signified the a static quenching mechanism was taking place between SY and β-LG. The thermodynamic data revealed that hydrophobic interaction was dominantly involved in the SY–β-LG interaction. The negative sign of standard Gibbs free energy (ΔG°) denoted that the SY-β-LG complex formed via spontaneous molecular interaction. The UV–Vis spectroscopy results showed that the absorbance of β-LG increased with increasing SY concentration because of complex formation. The far-UV CD data suggested that the secondary structure of β-LG increased in the presence of SY dye and the overall β-LG conformation changed. Molecular docking results showed the high-affinity binding (-11.27 kcal/mol) of SY with β-LG through hydrogen bonds and hydrophobic interactions. This study provides detailed information about food additive dye interactions with dairy products and shows conformational changes of dairy proteins due to interaction with dye.