Fig. 2: Aggregation kinetics and structural characterization of 66–140 fibrils.

a Aggregation reactions of Ac1‒140 (purple) and 66–140 (black) monitored by ThT fluorescence in pH 7.4 buffer (20 mM NaPi, 140 mM NaCl) at 37 °C with continuous linear shaking supplemented with a 2-mm glass bead. Solid lines and shaded regions represent mean and SD, respectively (n ≥ 4). For 66–140, average t_lag and t_½ values were 5 and 12 h for 40 μM and 3 and 9 h for 80 μM, respectively. For Ac1–140, average t_lag and t_½ values were 8 and 13 h for 40 μM and 5 and 14.5 h for 80 μM, respectively. b Representative TEM and AFM images of 66‒140 taken post-aggregation. Scale bars as indicated. Full-sized images are shown in Supplementary Fig. 5. c Raman spectra of Ac1‒140 (purple) and 66‒140 (black) fibrils. Solid lines and shaded regions represent the mean and SD, respectively (n ≥ 15). Amide-I, amide-II, and amide-III regions are as indicated. The frequency location of a distinguishing peak (1012.5 cm⁻¹) in 66–140 is denoted by an asterisk. Inset shows an expanded view of the boxed spectral area. Spectra have been normalized to the Phe breathing mode (1003 cm⁻¹). Difference spectrum is shown in Supplementary Fig. 6. Source data are provided as a Source Data file.