Comparison of the assembly behavior and structural characteristics of arachin and conarachin amyloid-like fibrils

In this study, the assembly behavior and structural characteristics of arachin (Ara) and conarachin (Con) amyloid-like fibrils formed by heating at 80 °C and 95 °C under acidic conditions were investigated. The results showed that Ara exhibited higher Thioflavin T fluorescence intensity during the fibrillation process and assembled into longer amyloid-like fibrils compared to Con, indicating that Ara had a stronger ability to form amyloid-like fibrils. Ara and Con were hydrolyzed into small peptides during the initial heating process, leading to decreased average particle sizes, as evidenced by the degraded subunits. Then the average particle size increased with the small peptides assembling into ordered amyloid-like fibrils with high content of β-sheets. Based on the results of surface hydrophobicity and the content of free –SH, the hydrophobic interactions played a more important role in the fibrillation process of Ara, while more surface free –SH involved in the formation of Con fibrils. Higher temperature (95 °C) accelerated the hydrolysis of proteins and subsequent self-assembly process. Furthermore, these amyloid-like fibrils had no in vitro cytotoxicity, showing the potential application in future food production. In summary, this work provides us a deep understanding of the formation mechanism and structural characteristics of Ara and Con amyloid-like fibrils.