We formed PI3K-SH3 WT fibrils from protein solutions in 10 mM glycine hydrochloride pH 2 at a final concentration of 200 µM. The solutions were stirred at 42 • C overnight and the presence of fibrils was verified through atomic force microscopy (AFM). These fibrils were sonicated with a VialTweeter-sonotrode (Hielscher, Teltow, Germany) for 10 s at 100% amplitude in a total volume of 800 µl. We used the obtained seed fibrils, at 5% (equivalent monomer mass), in fresh solutions of PI3K-SH3 WT whose concentrations ranged between 200 and 400µM. We left solutions overnight at room temperature, and investigated the day after for the presence of fibrils through AFM and supernatant absorbance measurements after centrifgation. We used the fibrils thus prepared both for attachment to Quartz Crystal Microbalance (QCM) sensors and for further seeding. We prepared fibrils for equilibrium denaturation experiments starting from solutions of WT and variants at 200µM. We mixed identical volumes of these solutions with a volume of WT fibrils prepared as described above, to reach a final seed concentration of 5% in monomer equivalents. We verified the presence of fibrils by AFM.