The AFM measurements were performed on an Asylum MFP-3D-BIO AFM instrument (Oxford Instruments) in the AC mode. Amylin 20-29 polymorph 1 (Figure ) was imaged using an ultra-sharp commercial probe with a 26 N m -1 force constant and 300 kHz resonance frequency. Amylin 20-29 polymorph 2 (Figure ) and Aβ 25-35 fibrils (Figure ) were imaged using a standard AFM probe with a 42 N m -1 force constant and 330 kHz resonance frequency.