Hofmeister and electrostatic modulation of the structure and polymorphism of rice protein fibrils

Hofmeister anions are critical regulators of protein structure and solubility. While their effects on fibrillization in certain plant proteins have been explored, their role in modulating the structural transformation, mesoscopic polymorphism, and functional properties of rice protein fibrils remains poorly understood. This study demonstrates that Hofmeister anions promoted fibrillization following the reverse Hofmeister series, enhancing the formation of β-sheet structure. Particularly, I^- enhanced antiparallel β-sheet formation and increased fibril-binding site accessibility. Notably, these anions induced distinct mesoscopic polymorphisms and facilitated compact cross-β stacking, producing elongated, rigid fibrils with reduced periodicity. Improved colloidal properties, including enhanced zeta potential, solubility, and particle size, were observed alongside superior emulsifying, foaming, and viscoelastic capacities. Furthermore, I^- significantly enhanced antioxidant activity, while other anions exhibit minor inhibitory effects. These findings offer an original perspective on the structural control of functional protein fibrils through anion-mediated tailoring, advancing their potential in protein-based applications.