Jem 2200fs tem

Virus particles were imaged in a JEOL JEM-2200FS TEM operating at 200 keV, using low-dose conditions controlled by SerialEM (v3.5.0_beta) [32 (link)] with the use of an in-column Omega Energy Filter, operating at a slit width of 35 eV. Micrographs were recorded using a Direct Electron DE-20 camera (Direct Electron, LP, San Diego, CA, USA), cooled to −40 °C. Movie correction was performed on whole frames using the Direct Electron software package, v2.7.1 [33 (link)]. Micrographs used for single particle analysis were recorded on the DE-20 using a capture rate of 25 frames per second for a total exposure ranging from 75 to 300 frames (~35 e^-/Ų total dose recorded at the DE-20 sensor). Cryo-EM images were acquired between 4000 and 20,000× nominal magnifications (14.7–2.61 Å/pixel, respectively). The objective lens defocus settings for single particle images ranged from 15 to 25 µm underfocus.

TEM imaging was performed at the National
Center for High Resolution Electron Microscopy (nCHREM) at Lund University.
The MoO₃/HOPG samples were a few weeks old and subjected
to exposure to an inert (Ar) atmosphere for transportation and laboratory
air (typically below 5 min) to prepare TEM-suitable specimens. The
MoO₃/HOPG flakes were peeled off and mounted on a TEM grid
(lacey formvar-carbon film on 200 copper mesh, Ted Pella, Redding,
USA). The imaging was performed in a JEOL JEM-2200FS TEM at 200 keV
in a low-dose mode (total dose < 200 e Å^–2), thus minimizing possible beam damage. The images were recorded
on an F416.0 camera (TVIPS), using Serial EM software.^{47 (link)}