| Based on different glycosyls and glycosidic bond types,quercetin(Qu),quercetin(Que,monoglycoside)and rutin(Ru,diglycoside),luteolin(Lu),isoorientin(Iso,Cglycoside),luteolin(Cyn,O-glycoside)were selected,representative animal protein-β-lactoglobulin(β-LG)and plant proteins-pea protein(PP)were also selected to be the typical proteins.The influence of flavonoids glycoside on protein interaction by multispectroscopy,and molecular docking.The changes of physicochemical properties of flavonoids glycoside-protein complex were analyzed from the perspective of protein structure change.The main results are as follows:(1)The results showed that the two groups of representative flavonoids glycoside could enhance the foaming and emulsion properties of PP and β-LG.The order of effect is Qu>Ru>Que,Lu>Iso>Cyn.The addition of Qu,Que and Ru improved the foamability of PP,but was not conducive to the foam stability of PP,the result of microscopic observation showed that the foam formed by complexes became more delicate and uniform,but the foam wall thickness was reduced,and the polymerization collapsed quickly.The foamability and foam stability of β-LG were improved after adding Qu,Que and Ru.Lu,Iso and Cyn were used to improving foamability and foam stability of PP and β-LG.Besides,the two groups of representative flavonoids glycoside could reduce the interfacial tension of oil and water,and significantly improve the EAI and ESI of proteins.In addition,binding with protein can protect the antioxidation of of naturally stored flavonoids to a certain extent.The results can provide theoretical basis for the development of flavonoids glycoside-protein functional foods.(2)The interaction of flavonoids glycoside(Qu,Que,Ru)with proteins(PP,β-LG)was studied by fluorescence spectroscopy and molecular docking techniques.The results showed that the order of binding force and protein structure change was Qu > Ru >Que.The main binding force of Qu-PP,Que-PP,Ru-PP,Qu-β-LG was hydrogen bond,while the binding of Que-β-LG and Ru-β-LG were driven by hydrophobic interaction.Qu has the strongest binding ability to proteins,and Ru containing diglycoside has more hydroxyl groups than Que containing monoglycoside,showing stronger binding ability to proteins.When Qu,Que and Ru were combined with the protein,the maximum fluorescence emission wavelength of the protein was blue shifted,and the tertiary structure of the protein was changed.The results of circular dichroism showed that the secondary structure of the proteins changed from regular,tightly packed α-helix to disordered,loose and random coil.ANS fluorescence results showed that the surface hydrophobicity of the complex decreased.The interaction between flavonoids glycoside and proteins is the key reason for the improvement of functional properties such as foaming and emulsifying properties of proteins.The results can provide theoretical basis for glycoside flavonoid modified protein.(3)The results of fluorescence spectrum and molecular docking showed that the binding force of glycoside flavonoids(Lu,Iso,Cyn)with protein and the change degree of protein structure were Lu> Iso > Cyn.The main force of Iso-PP,Cyn-PP,Lu-β-LG,Iso-β-LG and Cyn-β-LG were hydrogen bonds,and there was hydrophobic interaction between Lu-PP.Among these three flavonoids,Lu had the best coplanarity and the strongest binding ability to protein.Compared with O-glycoside Cyn,Iso retained the active hydroxyl and was able to bind macromolecular proteins better.The results of fluorescence spectrum combined with circular dichroism showed that the tertiary structure and secondary structure of the protein were changed.Molecular simulation results showed that some surface hydrophobic amino acids were involved in protein-flavonoid glycoside interaction.ANS fluorescence results showed that the addition of three flavonoids glycoside reduced the surface hydrophobicity of proteins and the structure changes contributed to the improvement of protein functional properties. |
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