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Comparison of binding interactions of cyanidin-3-O-glucoside to β-conglycinin and glycinin using multi-spectroscopic and thermodynamic methods

Ren, Cong, Xiong, Wenfei, Li, Jing, Li, Bin
Food hydrocolloids 2019 v.92 pp. 155-162
beta-conglycinin, binding sites, calorimetry, circular dichroism spectroscopy, electrostatic interactions, fluorescence, fluorescence emission spectroscopy, glycinin, hydrocolloids, hydrophobic bonding, hydrophobicity, pH, polyphenols, soy protein, thermal stability, titration
This work aims to explore the molecular binding mechanisms of two major soy protein fractions, β-conglycinin (7S) and glycinin (11S) with cyanidin-3-O-glucoside (C3G, a representative polyphenol in food) at pH 7.0. Circular dichroism spectroscopy manifested that C3G induced the conversion of β-sheet into α-helix and random coil. Synchronous fluorescence and three-dimensional fluorescence spectroscopy confirmed the unfolding and loosing of protein molecules. Furthermore, the results from fluorescence quenching and isothermal titration calorimetry indicated that C3G quenched fluorescence of two proteins in a static mode, and their interactions were entropically favorable processes driven by a combination of hydrophobic interaction and electrostatic force. 11S had a higher affinity for C3G than 7S, as indicated by the binding constant and binding sites. In addition, the surface hydrophobicity and thermal stability of two proteins were reduced after C3G binding. This study will help further understand the interaction mechanism between 7S/11S and polyphenols.