ELECTRON MICROSCOPY

Sample

Anti-CRISPRs AcrF1 and AcrF2 bound P. aeruginosa crRNA-guided CRISPR surveillance(Csy)complex.

Specimen Preperation
Sample Aggregation State PARTICLE
Vitrification Instrument HOMEMADE PLUNGER
Cryogen Name ETHANE
Sample Vitrification Details Sample was applied to poly-L-lysine hydrobromide pre-treated amorphous carbon film coated over a holey grid. Excess sample was blotted with Whatman-1 filter paper and plunge frozen. Manual plunge freezing was performed in a cold room.
3D Reconstruction
Reconstruction Method SINGLE PARTICLE
Number of Particles 51212
Reported Resolution (Å) 3.4
Resolution Method FSC 0.143 CUT-OFF
Other Details Per-frame dose weighting was performed using the RELION particle polishing method. A B-factor of -71 square angstrom was applied to sharpen the final map. Signal subtracted focused classification and refinement was performed for the "tail" region of the complex. This lead to a 4 angstrom (Gold standard FSC 0.143) map.
Refinement Type
Symmetry Type POINT
Map-Model Fitting and Refinement
ID 1
Refinement Space REAL
Refinement Protocol AB INITIO MODEL
Refinement Target ?
Overall B Value ?
Fitting Procedure ?
Details Top scoring five models out of two hundred models generated using Rosetta were refined using Phenix and deposited as an ensemble atomic model for the final EM map.
Data Acquisition
Detector Type GATAN K2 SUMMIT (4k x 4k)
Electron Dose (electrons/Å2) 46
Imaging Experiment
Date of Experiment ?
Temprature (Kelvin)
Microscope Model FEI TITAN KRIOS
Minimum Defocus (nm) 1200
Maximum Defocus (nm) 2500
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 29000
Calibrated Magnification ?
Source FIELD EMISSION GUN
Acceleration Voltage (kV) 300
Imaging Details Objective astigmatism was corrected at nominal magnification of 29000X, using Thon rings visualized with a K2 camera.
Imaging Experiment
Task Software Package Version
PARTICLE SELECTION FindEM ?
IMAGE ACQUISITION Leginon ?
CTF CORRECTION CTFFIND3 3
MODEL FITTING Coot 0.8.7
INITIAL EULER ASSIGNMENT RELION 1.4
FINAL EULER ASSIGNMENT RELION 1.4
CLASSIFICATION RELION 1.4
RECONSTRUCTION RELION 1.4
MODEL REFINEMENT PHENIX 1.11.1
MODEL FITTING UCSF Chimera 1.12
MODEL REFINEMENT PHENIX 1.11.1
MODEL FITTING UCSF Chimera 1.12
MODEL REFINEMENT PHENIX 1.11.1
Image Processing
CTF Correction Type CTF Correction Details Number of Particles Selected Particle Selection Details
NONE Particles were ctf-corrected during 2D and 3D processing.
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