Bulk aggregation kinetics of α-synuclein amyloid fibrils were performed in a FLUOstar Omega fluorescence microplate reader (BMG Labtech, Germany). All aggregation experiments were performed in 20 mM sodium phosphate buffer with 150 mM NaCl at pH 7.4. Amyloid aggregation was monitored under quiescent conditions at 25 • C by exciting the sample at 440 nm and recording the emission at 480 nm every 10 minutes. α-synuclein amyloid fibrils were grown at 50µM monomer concentration with 5% sonicated amyloid seeds. Aggregation was monitored for two of the six wells by addition of 100 µM Thioflavin T (ThT) and fibrils were grown until a plateau was reached. Half the wells were incubated with 200 nM proteinase K (PK) for 30 minutes. 100 µM PMSF is added to all wells as a PK inhibitor and incubated overnight. 50 µM monomer is added to each well and 100 µM ThT to all ThT-free wells and the monitoring of the aggregation reaction is resumed until a plateau in ThT fluorescence is reached.