α-synuclein fibrils at 100 µM equivalent monomer mass are treated with 2-iminothiolane at 0.15 mg/mL for 5 minutes prior to being incubated with an UV-ozone activated QCM gold-sensor for 1 hr. The sensors are rinsed in buffer and then incubated with 1 vol. % mPEG-thiol in buffer for 30 min. Sensors are rinsed with miliQ water and dried prior to being inserted into the instrument. All treatment of fibrils in the QCM instrument is performed at 20 mM sodium phosphate buffer with 150 mM NaCl. We measure the elongation rate of amyoid fibrils by injecting 3 cell volumes (60 µl) of monomeric protein solutions at 50µM in 20 mM sodium phosphate buffer with 150 mM NaCl and 1 mM PMSF into different sensor chambers and monitor the third overtone frequency. PMSF is added to ensure that residual active Proteinase K is inhibited. PMSF is added to the α-synuclein solutions from a 0.2 M stock dissolved in ethanol, leaving a residual volume fraction of 0.5 % ethanol. Fibril "shaving" is achieved by injecting 3 cell volumes of 20 nM Proteinase K and subsequent incubation. Proteinase is washed out by flushing the cell with at least 20 cell volumes of buffer. To inhibit remaining proteinase, 3 cell volumes of 5 mM PMSF are injected then and incubated for at least 10 minutes. The cell is then flushed with at least 20 cell volumes of buffer.