ELECTRON MICROSCOPY

Sample

Cryo-EM structure of the pentameric human MRS2 magnesium channel under Mg2+ condition at an average resolution of 2.8 A, filtered to local resolution, C5

Specimen Preperation
Sample Aggregation State PARTICLE
Vitrification Instrument LEICA EM GP
Cryogen Name ETHANE
Sample Vitrification Details 400-mesh R1.2/1.3 Cu grids (Quantifoil) were made hydrophilic by glow discharging for 60 seconds with a current of 15 mA in a PELCO easiGlow system. The cryo grids were produced using a Leica EM GP2 (Leica). The chamber was kept at 4 C and set to 95% humidity. 3 microliter sample at 0.5 mg/ml was applied to a glow-discharged holey grid, blotted for 6 s, and plunge frozen into liquid ethane and stored in liquid nitrogen.
3D Reconstruction
Reconstruction Method SINGLE PARTICLE
Number of Particles 450554
Reported Resolution (Å) 2.8
Resolution Method FSC 0.143 CUT-OFF
Other Details Non-uniform refinement was performed with 450,554 selected particles, followed by local motion correction and CTF refinement to correct for beam-tilt, spherical aberrations, and per-particle defocus parameters. Non-uniform refinement with polished particles resulted in maps at 2.8 A (with C5 symmetry applied) and 3.1 A (with C1 symmetry applied), according to gold-standard FSC = 0.143 criterion.
Refinement Type
Symmetry Type POINT
Map-Model Fitting and Refinement
ID 1
Refinement Space REAL
Refinement Protocol RIGID BODY FIT
Refinement Target ?
Overall B Value 141
Fitting Procedure ?
Details ?
Data Acquisition
Detector Type GATAN K3 BIOQUANTUM (6k x 4k)
Electron Dose (electrons/Å2) 50
Imaging Experiment
Date of Experiment ?
Temprature (Kelvin)
Microscope Model FEI TITAN KRIOS
Minimum Defocus (nm) 700
Maximum Defocus (nm) 2000
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 105000
Calibrated Magnification ?
Source FIELD EMISSION GUN
Acceleration Voltage (kV) 300
Imaging Details ?
Imaging Experiment
Task Software Package Version
PARTICLE SELECTION cryoSPARC 3.3.2
IMAGE ACQUISITION SerialEM ?
CTF CORRECTION cryoSPARC 3.3.2
MODEL FITTING UCSF Chimera 1.16
INITIAL EULER ASSIGNMENT cryoSPARC 3.3.2
FINAL EULER ASSIGNMENT cryoSPARC 3.3.2
CLASSIFICATION cryoSPARC 3.3.2
RECONSTRUCTION cryoSPARC 3.3.2
MODEL FITTING Coot ?
MODEL REFINEMENT Coot ?
MODEL REFINEMENT PHENIX 1.20.1-4487
Image Processing
CTF Correction Type CTF Correction Details Number of Particles Selected Particle Selection Details
PHASE FLIPPING AND AMPLITUDE CORRECTION Patch CTF