Elucidating the modulatory influence of Hofmeister divalent ions on the structural dynamics and rheological properties of soy protein amyloid fibrils

The fibrillation of food proteins into amyloid fibrils, which possess unique structures, is widely acknowledged as a reliable method to enhance protein functionality. Hofmeister ions are believed to play a crucial role in the structure, solubility, and stability of proteins, as well as influencing aqueous properties. Consequently, these ions profoundly impact the folding and aggregation of amyloid fibrils. Despite this, the specific influence of Hofmeister ions on the fibrillation process of soy protein amyloid fibrils (SAFs) remains unclear. This experiment employed a comprehensive approach, utilizing atomic force microscopy, Fourier transform infrared spectroscopy, Th T fluorescence, and X-ray diffraction to investigate the microstructure and morphological changes during fibrillation. Additionally, the study aimed to explore the macro functional effects through rheological analysis. The results demonstrated that kosmotropic anions (HPO42− and SO42−) disrupted the fibril structure, resulting in shorter and looser fibrils. However, larger protein aggregation was found to enhance the viscosity of the solution, with the loose voids contributing to the formation of hydrogel networks. On the other hand, chaotropic cations (Zn2+ and Mg2+) were observed to promote fibril winding and lengthening, resulting in a denser structure and the formation of a hydrogel. This study significantly advances our understanding of the mechanism of ion effects during fibrillation and lays the groundwork for the utilization of plant protein amyloid fibrils in the food industry.