V1 grade mica discs

AFM images were acquired in tapping mode with Bruker Fastscan-D silicon nitride probes on a Dimension Fastscan System (Bruker Nano Surfaces, Santa Barbara, CA). Scans were taken of 2 µm regions at 3.92 Hz and 1024×1024 resolution in a single scan direction with feature tracking enabled (except 4F-RT for which 4 µm region were scanned at 2048×2048 resolution with feature tracking disabled). Regions of interest were then cropped from the original images and analysed using Nanoscope Analysis 1.8 and 1.9 software (Bruker Nano Surfaces). Samples were prepared by incubating 25 µl of 400 µM (2F-RT and 3F-RT) or 800 µM (RT, 1F-RT and 4F-RT) peptide solution on freshly cleaved V1 grade mica discs (Ted Pella, Redding, CA) for 30 min followed by 2× gentle washes with UltraPure Distilled Water (Life Technologies, Carlsbad, CA). All samples were imaged under a column of water with a new probe and, to achieve higher resolution, samples were thermally equilibrated for 30 min prior to imaging. Each supplementary time lapse video was assembled in Nanoscope analysis 1.8 using 11 sequential images of a continuously scanned region of interest that were acquired with the aforementioned parameters and played back at 1 frame per second.