Cmos camera

A 3.5 µL aliquot of the fibril sample was applied onto C-Flat holey carbon grids (CF – 1.2/1.3 – 4Cu, Electron Microscopy Sciences) that were glow discharged for 40 s at 20 mA using a PELCO easiGLOW glow discharge cleaning system (Ted Pella). After incubation of the sample on the grid for 30 s, the grid was double side blotted for 8 s with filter paper and plunge-frozen in liquid ethane using a Vitrobot Mark 3 (Thermo Fisher Scientific). The plunged grids were screened using a JEM-2100F transmission electron microscope (JEOL) that was operated at an accelerating voltage of 200 kV and equipped with a CMOS Camera (TVIPS). The images for the reconstruction of the 3D map were recorded using a K2-Summit detector (Gatan) on a Titan Krios transmission electron microscope (Thermo Fisher Scientific) that was operated at an accelerating voltage of 300 kV. Data acquisition parameters are listed in Supplementary Table 2. Images of 100 fibrils were used to quantify fibril width and crossover distance using Fiji^{26 (link)}. Contrast enhancement was performed by using Adobe Photoshop CS6.

Four microliters of sample was adsorbed onto holey carbon-coated grid (Quantifoil, Germany) that was glow-discharged. After blotting with filter paper, the grid was vitrified into liquid ethane at −178 °C using a Vitrobot (FEI, Netherlands). The frozen grid was then transferred onto a Philips CM200-FEG electron microscope (FEI, Netherlands) using a Gatan 626 cryo-holder (GATAN Inc, USA). Electron images were acquired using a low-dose system (accelerating voltage of 200 kV; nominal magnification of 50,000; temperature of −175 °C). Defocus values ranged from −2 µm to −3 µm. Micrographs were recorded using a CMOS camera (TVIPS, Germany) at 4 K × 4 K.