Structural remodeling toward conformational plasticity: How phloretin binding enhances the functional versatility of perilla seed protein isolate.

This study investigated the non-covalent interactions between phloretin (PHL) and perilla seed protein isolate (PSPI) using multispectral analyses and computational simulations. Intrinsic and time-resolved fluorescence confirmed that PHL bound spontaneously to PSPI via static quenching with strong affinity (Kₐ = 2.0 × 1010 L/mol at 298 K) and 1:1 stoichiometry. FTIR and CD spectra revealed secondary structure rearrangement, with random coil content increasing from 37.30% to 40.14%. Molecular docking and molecular dynamics simulations corroborated that the PSPI binding was primarily governed by hydrogen bonds and van der Waals forces, which elicited modest conformational rearrangements. Functionally, this remodeling increased water solubility and antioxidant capacity (54.27 mg AAE/g protein). Particle size and zeta-potential analyses further supported the modulation of emulsifying behavior, characterized by decreased emulsifying activity and enhanced emulsion stability. These findings provide mechanistic insights into plant protein-polyphenol co-assembly for functional ingredient design.