In vitro conversion and AFM characterization of three different recombinant α-syn assemblies. Kinetics for the formation of β-sheet-rich assemblies: human α-syn oligomer (dotted black line), human α-syn short fibrils (red triangle line) and human α-syn long fibrils (gray dotted line), and control (gray solid line). (A) Red arrows indicate the collection time of the aggregates. (B) The lag phase, in hours, of all β-sheet structure preparations was measured using Thioflavin T assay. The lag phase distribution of α-syn and FLAG-α-syn amyloid preparations showed no difference (P > 0.5), indicating that the presence of FLAG-tag did not affect fibril formation. (C) AFM imaging analysis was performed at the end of the fibrillization reactions. AFM scan topographical images of α-syn deposited on mica surface. (D) The size of particles was measured: the typical height of α-syn oligomers was 0.65 ± 0.11 nm, the height of short and log fibrils was 2.79 ± 1.20 nm, and 6.08 ± 1.38 nm, respectively. The values are the average calculated on 20 fibrils. The error is the standard deviation.