Interfaces Determine the Fate of Seeded α‐Synuclein Aggregation

Abstract Amyloid fibrils formed by the α‐Synuclein (α‐Syn) protein are the pathological hallmark of multiple human disorders, generally termed α‐synucleinopathies. The aggregation process of α‐Syn into amyloids appears to be highly dependent on the presence of: i) hydrophobic–hydrophilic interfaces, and ii) pre‐formed seed fibrils. By combining Thioflavin T binding measurements with different microscopy techniques (direct stochastic optical reconstruction microscopy, atomic force microscopy, correlative super‐resolution light microscopy, and scanning electron microscopy), the effect of the air–water interface (AWI) is tested on seeded α‐Syn aggregation. The correlation of the results provided by each method reveals striking differences in the mechanism of formation, yield, length, thickness, and morphology of fibrils obtained from samples having equal initial amounts of seeds and monomers, but incubated in the presence or absence of an AWI. Overall, the results indicate that the AWI determines how amyloids grow and proliferate, the final balance between monomer and aggregates, and the morphological properties of the aggregates themselves. These observations may set the basis for amplifying and tuning the properties of specific fibril polymorphs of interest, in structural biology and cytotoxicity studies, as well as in those materials science applications featuring amyloids.