National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
P41GM103832
United States
National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)
AI057156
United States
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
R01GM080139
United States
Cancer Prevention and Research Institute of Texas (CPRIT)
RP140113
United States
Robert Welch
Q1242
United States
Citation
Journal: J Struct Biol / Year: 2016 Title: Alignment algorithms and per-particle CTF correction for single particle cryo-electron tomography. Authors: Jesús G Galaz-Montoya / Corey W Hecksel / Philip R Baldwin / Eryu Wang / Scott C Weaver / Michael F Schmid / Steven J Ludtke / Wah Chiu / Abstract: Single particle cryo-electron tomography (cryoSPT) extracts features from cryo-electron tomograms, followed by 3D classification, alignment and averaging to generate improved 3D density maps of such ...Single particle cryo-electron tomography (cryoSPT) extracts features from cryo-electron tomograms, followed by 3D classification, alignment and averaging to generate improved 3D density maps of such features. Robust methods to correct for the contrast transfer function (CTF) of the electron microscope are necessary for cryoSPT to reach its resolution potential. Many factors can make CTF correction for cryoSPT challenging, such as lack of eucentricity of the specimen stage, inherent low dose per image, specimen charging, beam-induced specimen motions, and defocus gradients resulting both from specimen tilting and from unpredictable ice thickness variations. Current CTF correction methods for cryoET make at least one of the following assumptions: that the defocus at the center of the image is the same across the images of a tiltseries, that the particles all lie at the same Z-height in the embedding ice, and/or that the specimen, the cryo-electron microscopy (cryoEM) grid and/or the carbon support are flat. These experimental conditions are not always met. We have developed a CTF correction algorithm for cryoSPT without making any of the aforementioned assumptions. We also introduce speed and accuracy improvements and a higher degree of automation to the subtomogram averaging algorithms available in EMAN2. Using motion-corrected images of isolated virus particles as a benchmark specimen, recorded with a DE20 direct detection camera, we show that our CTF correction and subtomogram alignment routines can yield subtomogram averages close to 4/5 Nyquist frequency of the detector under our experimental conditions.
History
Deposition
Feb 7, 2016
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Header (metadata) release
Apr 13, 2016
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Map release
Apr 13, 2016
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Update
Jan 29, 2020
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Current status
Jan 29, 2020
Processing site: RCSB / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Shell ID: 1 / Name: Capsid / Diameter: 700.0 Å / T number (triangulation number): 4
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Experimental details
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Structure determination
Method
cryo EM
Processing
subtomogram averaging
Aggregation state
particle
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Sample preparation
Buffer
pH: 7.4
Grid
Model: Quantifoil R1.2/1.3 / Material: COPPER / Mesh: 200 / Support film - #0 - Film type ID: 1 / Support film - #0 - Material: CARBON / Support film - #0 - topology: HOLEY / Support film - #1 - Film type ID: 2 / Support film - #1 - Material: CARBON / Support film - #1 - topology: CONTINUOUS / Pretreatment - Type: GLOW DISCHARGE
Energy filter - Name: JEOL Omega / Energy filter - Upper energy threshold: 25 eV
Image recording
Film or detector model: DIRECT ELECTRON DE-20 (5k x 3k) / Detector mode: INTEGRATING / Average exposure time: 0.5 sec. / Average electron dose: 3.0 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
Electron optics
Illumination mode: FLOOD BEAM / Imaging mode: BRIGHT FIELD
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