Probing binding sites, conformational alterations and techno-functionalities of soybean protein isolate–lobetyolin complexes

The soybean protein isolate (SPI)–lobetyolin complexes were prepared, and the binding mechanism, structural alterations and techno-functionalities of the prepared complexes were further measured using multi-spectral technologies and molecular interaction analyses. Lobetyolin displayed strong affinity for SPI and induced static quenching of the intrinsic fluorescence. Hydrophobic contacts, hydrogen bonding, and van der Waals forces were involved in the interaction between SPI and lobetyolin. The complexes exhibited high lobetyolin binding capacity (maximum binding amount of 173 μg/mg), with decreases in free sulfhydryl and free amino group contents compared to SPI. The lobetyolin binding perturbed the microenvironment around tyrosine (Tyr) and tryptophan (Trp) residues, and thereby altered SPI secondary structure with increased β-turn content and decreased β-sheet content. The complexes (at a concentration of 400 μg/mL) exhibited DPPH•- and ABTS •+ -scavenging activities of 56.9% and 69.8%, respectively. Furthermore, the emulsifying stability index (ESI) of the complexes was improved compared to that of SPI. The use of lobetyolin enables the rational construction of food-medicinal protein-based ingredients whose techno-functional attributes can be precisely tailored. Lobetyolin (PubChem CID: 14655097) • Lobetyolin interacted and statically quenched intrinsic fluorescence of SPI. • The complexes exhibited high lobetyolin binding amount of 173 μg/mg. • Complex formation involved hydrophobic, hydrogen bond and van der Waals interactions. • Lobetyolin altered secondary structures and residue microenvironment of SPI. • The SPI–lobetyolin interaction enhanced the techno-functional properties of SPI.