Formation of tiger nut protein fibrils through self-assembly and different nuclei-induced pathways: Focus on structure and core peptide region

Tiger nut protein fibrils (TNPFs) were prepared through three pathways: self-assembly (TNPF), Homogeneous nuclei (HN)-induced (HN-TNPF), and Secondary nuclei (SN)-induced (SN-TNPF). Differences in morphology, structure, and formation mechanisms among the three TNPFs were examined. HN and SN, serving as fibrillation seeds, enhanced both fibril production and fibrillation rate. Compared to TNPF, the addition of HN and SN shortening the lag time from 3 (TNPF) to 2.2 (HN-TNPF) and 1.89 h (SN-TNPF), respectively. All three TNPFs exhibited fibril structures, notably, SN-TNPF displayed bifurcations on the trunk. Regarding secondary structure, a transition from α-helix to β-sheet was observed in all samples. The dynamic evolution of tertiary structure demonstrated that fibrillation was driven by non-covalent interactions and disulfide bond. After hydrolysis, the identification of specific peptides by LC-MS/MS and core region prediction using AMYLPRED2 showed 89.29 %, 82.22 %, and 89.74 % of peptide sequences in TNPF, HN-TNPF, and SN-TNPF, respectively, possessed fibril forming potential.