Lacy carbon coated copper grid

Vitreous cryo-TEM samples of Aβ_12–28 were prepared for imaging as follows. A 5 μL droplet of the amyloid peptide solution (10.0 μM, incubated for 3 days) was placed on a lacy carbon-coated copper grid (Ted Pella, Inc.) in a humidity- and temperature-controlled environment vitrification system (Vitrobot, FEI, Inc.). The humidity was controlled at 100%, and the temperature of the chamber was 22.0 °C. Then, the sample was blotted to remove excess solvent and create a thin film of the peptide on the grid surface using a −2 mm blotting force, a 1.0 s blot time, and a 10 s drain time to equilibrate any stresses in the sample caused by blotting. The resulting sample grid was vitrified by plunge freezing into liquid ethane (−183 °C). A Tecnai T-12 TEM operating at 120 kV was used to obtain the cryo-TEM images in Supporting Information Figure S1.