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REFINED STRUCTURE OF THE NICOTINIC ACETYLCHOLINE RECEPTOR AT 4A RESOLUTION.
ELECTRON MICROSCOPY
Sample
NICOTINIC ACETYLCHOLINE RECEPTOR in postsynaptic membrane
Specimen Preparation
Sample Aggregation State
HELICAL ARRAY
Vitrification Instrument
Cryogen Name
Sample Vitrification Details
LIQUID ETHANE
3D Reconstruction
Reconstruction Method
HELICAL
Number of Particles
Reported Resolution (Å)
4
Resolution Method
OTHER
Other Details
Refinement Type
Symmetry Type
HELICAL
Data Acquisition
Detector Type
KODAK SO-163 FILM
Electron Dose (electrons/Å**2)
Imaging Experiment
1
Date of Experiment
2000-10-01
Temperature (Kelvin)
4.2
Microscope Model
JEOL 3000SFF
Minimum Defocus (nm)
800
Maximum Defocus (nm)
1800
Minimum Tilt Angle (degrees)
Maximum Tilt Angle (degrees)
Nominal CS
1.3
Imaging Mode
BRIGHT FIELD
Specimen Holder Model
Nominal Magnification
40000
Calibrated Magnification
36800
Source
FIELD EMISSION GUN
Acceleration Voltage (kV)
300
Imaging Details
THE SPECIMENS WERE TUBULAR CRYSTALS GROWN IN LOW SALT BUFFER FROM ISOLATED TORPEDO POSTSYNAPTIC MEMBRANES. THEY WERE APPLIED TO THE MICROSCOPE GRIDS AND FROZEN IN THE SAME SOLUTION. THESE CRYSTALS WERE TOO SMALL AND DISTORTED TO YIELD MEANINGFUL ELECTRON DIFFRACTION PATTERNS, SO BOTH THE AMPLITUDE AND THE PHASE TERMS HAD TO BE MEASURED FROM FOURIER TRANSFORMS OF THE IMAGES. THE IMAGES WERE RECORDED USING A DOSE OF 2000 ELECTRONS/NM2 DURING THE PERIOD: JAN-1996 TO OCT-2002. THE DATASETS INVOLVED 4 HELICAL FAMILIES OF TUBES. STRUCTURES WERE SYNTHESISED FROM THE AMPLITUDE AND PHASE TERMS DERIVED FROM EACH FAMILY. THE FINAL DATASET WAS OBTAINED BY AVERAGING THESE 4 STRUCTURES IN REAL SPACE.