Abstract: The interactions between cyanidin-3-O-glucoside (C3G) and wheat gluten (gliadin and glutenin) under neutral conditions were studied by fluorescence spectroscopy and Fourier transform infrared spectroscopy. The results showed that C3G had strong quenching effects on both proteins, and the fluorescence quenching mechanism of glutenin was static quenching, while the fluorescence of gliadin was quenched through the combination of dynamic quenching and static quenching mechanism. The binding constant (KA) and the number of binding sites (n) for the interaction between C3G and gliadin were larger, indicating stronger interaction with gliadin. Thermodynamic data indicated that the interaction between C3G and gliadin was mainly hydrophobic, while the interaction between C3G and glutein was mainly driven by van der Waals force and hydrogen bond. Synchronous fluorescence spectroscopy indicated that the binding site of C3G to gliadin was closer to the tryptophan residue, while the binding site of C3G to glutein was closer to the tyrosine residue. Fourier transform infrared spectroscopic data showed that C3G interacted with gliadin and glutein, altering the protein conformation.

Key words: cyanidin-3-O-glucoside, gliadin, glutenin, fluorescence quenching, Fourier transform infrared spectroscopy