5 μl of dArc1 or dArc2 capsids at a concentration of ~1
mg/ml were applied to glow-discharged continuous carbon lacey grids (Lacey
Carbon Films on 300 Mesh Copper Grids, Agar scientific), blotted and
plunge-frozen in liquid ethane using a FEI Vitrobot Mark IV. Cryo-EM images were
acquired on a 300 keV FEI Titan Krios microscope equipped with a Gatan K2-Summit
4Kx4K detector operated in counting mode. A GIF-quantum energy filter (Gatan)
was used with a slit width of 20 eV to remove inelastically scattered electrons.
Both the dArc1 and dArc2 datasets were collected using SerialEM19 at a nominal magnification of
105,000 with calibrated pixel sizes of 1.211 Å for dArc1 and 1.388
Å for dArc2. Micrographs were recorded as movies divided into 75 frames.
For dArc1 we used a total exposure time of 6.6 s. and an accumulated dose of
35.4 electrons per Å2. For dArc2, the total exposure time used
was 16.8 s and the accumulated dose 34.9 electrons per Å2.
Defocus values ranged from −1.0 to −4.0 μm. Data collection
parameters are summarized inSupplementary Table 1 .
mg/ml were applied to glow-discharged continuous carbon lacey grids (Lacey
Carbon Films on 300 Mesh Copper Grids, Agar scientific), blotted and
plunge-frozen in liquid ethane using a FEI Vitrobot Mark IV. Cryo-EM images were
acquired on a 300 keV FEI Titan Krios microscope equipped with a Gatan K2-Summit
4Kx4K detector operated in counting mode. A GIF-quantum energy filter (Gatan)
was used with a slit width of 20 eV to remove inelastically scattered electrons.
Both the dArc1 and dArc2 datasets were collected using SerialEM19 at a nominal magnification of
105,000 with calibrated pixel sizes of 1.211 Å for dArc1 and 1.388
Å for dArc2. Micrographs were recorded as movies divided into 75 frames.
For dArc1 we used a total exposure time of 6.6 s. and an accumulated dose of
35.4 electrons per Å2. For dArc2, the total exposure time used
was 16.8 s and the accumulated dose 34.9 electrons per Å2.
Defocus values ranged from −1.0 to −4.0 μm. Data collection
parameters are summarized in