3J7W

Capsid Expansion Mechanism Of Bacteriophage T7 Revealed By Multi-State Atomic Models Derived From Cryo-EM Reconstructions

ELECTRON MICROSCOPY

Sample
Bacteriophage T7 MLD capsid II

Specimen Preparation
Sample Aggregation State	PARTICLE
Vitrification Instrument	FEI VITROBOT MARK I
Cryogen Name	ETHANE
Sample Vitrification Details	Blot for 2 seconds twice with 2 mm offset before plunging into liquid ethane (FEI VITROBOT MARK I).

3D Reconstruction
Reconstruction Method	SINGLE PARTICLE
Number of Particles	43417
Reported Resolution (Å)	3.5
Resolution Method	FSC 0.143 CUT-OFF
Other Details	Particles were selected from scanned micrograph images, first automatically by the ethan method and then by manual screening with the boxer program in ...	Particles were selected from scanned micrograph images, first automatically by the ethan method and then by manual screening with the boxer program in EMAN. The TEM instrument contrast transfer function parameters were determined automatically using fitctf2.py and were then visually validated using the EMAN ctfit program. The datasets were then divided into two subsets (even and odd) and processed completely independently, including both initial models and refinements. For 3D reconstructions, the whole datasets were divided into even-odd halves and the initial de novo models and subsequent iterative refinements were all independently performed for each half dataset. The images were first binned 4x to obtain initial models and particle parameters assuming icosahedral symmetry. De novo initial models were built using the random model approach. Random subsets of particles were assigned random initial orientations and iteratively refined until convergence. Consistent icosahedral capsid structures (other than occasional differences in handedness) were obtained by repeating the random model process. Particles with inconsistent/unstable view parameters in the initial refinements were excluded in further image processing. The orientation and center parameters were then transferred to the un-binned images for high-resolution refinements which included Simplex method-based orientation/center optimization and grid search-based refinement of defocus, astigmatism, and magnification of the images. All image refinement and reconstructions were performed with in-house developed programs jspr.py (for overall work-flow), jalign (for 2D alignment) and j3dr (for 3D reconstruction), which use EMAN and EMAN2 library functions.
Refinement Type
Symmetry Type	POINT
Point Symmetry	I

Map-Model Fitting and Refinement
Id	1
Refinement Space
Refinement Protocol
Refinement Target
Overall B Value
Fitting Procedure
Details

Data Acquisition
Detector Type	KODAK SO-163 FILM
Electron Dose (electrons/Å**2)	25

Imaging Experiment	1
Date of Experiment	2011-01-07
Temperature (Kelvin)	95
Microscope Model	FEI TITAN KRIOS
Minimum Defocus (nm)	500
Maximum Defocus (nm)	3300
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	59000
Calibrated Magnification	57727
Source	FIELD EMISSION GUN
Acceleration Voltage (kV)	300
Imaging Details

EM Software
Task	Software Package	Version
RECONSTRUCTION	EMAN	1
RECONSTRUCTION	EMAN	2
RECONSTRUCTION	jspr

Image Processing
CTF Correction Type	CTF Correction Details	Number of Particles Selected	Particle Selection Details
	Each particle

RCSB PDB Core Operations are funded by the U.S. National Science Foundation (DBI-2321666), the US Department of Energy (DE-SC0019749), and the National Cancer Institute, National Institute of Allergy and Infectious Diseases, and National Institute of General Medical Sciences of the National Institutes of Health under grant R01GM157729.