Study of the disassembly–assembly process of α-synuclein fibrils by in situ atomic force microscopy

In this report, we applied in situ atomic force microscopy (AFM) to study the dynamic process of disassembly–assembly of α-synuclein (α-Syn) fibrils in different solutions. Most of the mica-adsorbed α-Syn fibrils disassemble into small particles step-by-step on the mica surface in diluted solutions, yet a few short fibrils still extend to form longer fibrils. This process usually started randomly at the center of the long fibrils, which progressively disassemble into short fragments and small protein particles of varying size. Compared to disassembly, assembly happened infrequently when the protein concentration was low. It was observed directly by AFM that the chaotropic agent guanidinium chloride rapidly breaks the long α-Syn fibrils.