E scanner

AFM is an appropriate method for the characterization of pre-fibrillar protein assemblies. Here, 5 μl of a 40 μM Aβ peptide solution were applied on a 0.5 mm² freshly cleaved sheet of mica for 10–30 seconds and then removed by fast spinning off. AFM images were recorded using a MultiMode scanning probe microscope (either NanoScope IIIa, Digital Instruments Inc., or NanoScope IV, Veeco Instruments Inc., Santa Barbara, California, USA), equipped with a 10 μm scanner (E-scanner). Height and phase images were recorded in tapping mode with scan rates of 2–4 lines per second and a resolution of 512 × 512 pixels. Olympus etched silicon cantilevers were used with a typical resonance frequency in the range of 60–80 kHz and a spring constant of 2 N/m. All samples were investigated on dry substrates of mica (PLANO W. Plannet GmbH, Wetzlar, Germany) at room temperature open to air.

AFM measurements were performed at room temperature using scan rates between 1.0 and 1.5 Hz in the tapping mode on a MultiMode scanning probe microscope equipped with a Nano-Scope IIIa controller (Digital Instruments) using an E-scanner (scan size 15 mm-615 mm) and a MMMC cantilever holder (Veeco Instruments, Mannheim, Germany) equipped with a silicon SPM sensor (PPPNCHR, NanoAndMore, Wetzlar, Germany) as previously described^{62 (link)}. hIAPP (50 µM) without and with anle145c (10 µM) was incubated for various time intervals in 10 mM Tris-HCl, 150 mM NaCl buffer solution and then deposited on freshly cleaved mica. The samples were dried with a gentle stream of nitrogen, rinsed with water, dried again with a stream of nitrogen and finally freeze-dried overnight, as described previously^{61 (link)}. The dried samples were scanned in air with drive frequencies around 240 kHz and drive amplitudes between 15 and 379 mV. All height and amplitude images of sample regions were acquired with resolution of 5.1 Mpixels. For image analysis and processing, the software NanoScope version 5 (Veeco Instruments, Mannheim, Germany) was used.