Amyloid Oligomers: Capturing the threat between disorder and order

Amyloid proteins are species whose aggregation has been associated with various neurodegenerative diseases. While intrinsically disordered in their monomeric form, they tend to aggregate into highly ordered β-sheet rich fibrils. Nevertheless, many studies indicate that intermediate species known as amyloid oligomers, which are linked to neurotoxicity, may be the connection between amyloid proteins and their pathology. However, oligomers are very transient, non-covalently bound, heterogeneous, and at a very low concentration relative to monomers and fibrils. Due to this, oligomers are challenging to study with conventional methods. and developing and optimizing methods for analyzing oligomers is crucial for the advancement of the amyloid field. In this thesis, we aim to optimize two oligomer analysis methods and use them to improve our understanding of the amyloid system. On one hand, we optimize the Photo-induced cross-linking of unmodified proteins (PICUP) for the study of αSyn, and we use it to identify transient interactions within and between α-synuclein monomers in solution, bound to lipid membranes, and in fibrils. On the other hand, we use microfluid free flow electrophoresis (μFFE) for the study of Aβ42 oligomer populations. Doing so, we learn how oligomer population is affected by the protein production source as well as sheer forces, and we show that amyloid fibrils do not only catalyze oligomer formation but also play a key role in oligomer dissociation.