6I5A

Tobacco Mosaic Virus

ELECTRON MICROSCOPY

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Sample
Tobacco mosaic virus

Specimen Preparation
Sample Aggregation State	HELICAL ARRAY
Vitrification Instrument	FEI VITROBOT MARK IV
Cryogen Name	ETHANE
Sample Vitrification Details	Quantifoil 400 mesh copper grids R 1.2/1.3 were used (Quantifoil Micro Tools GmbH, Jena, Germany). Grids were glow discharged in air at a pressure of 2.2x10-2 Torr for 2 min at medium power with a Harrick Plasma cleaner (PDC-002). Subsequently, 3-4 ul of the sample was pipetted onto the glow discharged grids and plunge frozen in liquid Ethane with a Vitrobot IV (FEI). The sample chamber of the Vitrobot was maintained at 4C and 100% humidity. Wait time between sample application and blotting was 45 s, the drain time 0 s, the blot time 3 s and the blot force 0.

3D Reconstruction
Reconstruction Method	HELICAL
Number of Particles	91927
Reported Resolution (Å)	2.3
Resolution Method	FSC 0.143 CUT-OFF
Other Details
Refinement Type
Symmetry Type	HELICAL
Axial Symmetry	C1
Axial Rise	1.39615
Angular Rotation	22.037

Map-Model Fitting and Refinement
Id	1
Refinement Space	RECIPROCAL
Refinement Protocol	AB INITIO MODEL
Refinement Target
Overall B Value	105
Fitting Procedure
Details

Data Acquisition
Detector Type	FEI FALCON III (4k x 4k)
Electron Dose (electrons/Å**2)	55

Imaging Experiment	1
Date of Experiment
Temperature (Kelvin)
Microscope Model	FEI TITAN KRIOS
Minimum Defocus (nm)	1000
Maximum Defocus (nm)	1800
Minimum Tilt Angle (degrees)
Maximum Tilt Angle (degrees)
Nominal CS	2.7
Imaging Mode	BRIGHT FIELD
Specimen Holder Model	FEI TITAN KRIOS AUTOGRID HOLDER
Nominal Magnification	75000
Calibrated Magnification
Source	FIELD EMISSION GUN
Acceleration Voltage (kV)	300
Imaging Details

EM Software
Task	Software Package	Version
PARTICLE SELECTION	RELION	3.0
IMAGE ACQUISITION	EPU
CTF CORRECTION	RELION
MODEL FITTING	Warp	8.0
MODEL REFINEMENT	Warp	8.0
INITIAL EULER ASSIGNMENT	RELION
FINAL EULER ASSIGNMENT	RELION	3.0
CLASSIFICATION	RELION	3.0
RECONSTRUCTION	RELION	3.0

Image Processing
CTF Correction Type	CTF Correction Details	Number of Particles Selected	Particle Selection Details
PHASE FLIPPING AND AMPLITUDE CORRECTION		393692	For TMV, some helices were picked manually with the helix picker implemented in relion 2.1. An initial 3D model of these segments was determined using the relion helix option with a cylinder as the starting reference. The aligned helical segments after 3D refinement were subjected to 2D classification without alignment. Three of the 2D class averages were selected as templates for automatic picking of the TMV segments in relion.