ELECTRON MICROSCOPY

Sample

SEMLIKI FOREST VIRUS

Specimen Preperation
Sample Aggregation State PARTICLE
Vitrification Instrument HOMEMADE PLUNGER
Cryogen Name ETHANE
Sample Vitrification Details PLUNGE VITRIFICATION SAMPLES PREPARED AS THIN LAYERS OF VITREOUS ICE MAINTAINED AT NEAR LIQUID NITROGEN TEMPERATURE IN THE ELECTRON MICROSCOPE WITH A GATAN 626-0300 CRYOTRANSFER HOLDER.
3D Reconstruction
Reconstruction Method SINGLE PARTICLE
Number of Particles 5267
Reported Resolution (Å) 9.000
Resolution Method ?
Other Details THE ORIENTATIONS WERE REFINED BY THE CROSS COMMON LINES LINES METHOD (SIMPLEX) AND THE POLAR FOURIER TRANSFORM METHOD USING A PARALLEL IMPLEMENTATION (PYPFT). THE EFFECTIVE RESOLUTION OF THE FINAL RECONSTRUCTED DENSITY WAS DETERMINED TO BE AT LEAST 9 ANGSTROMS, AS MEASURED BY RANDOMLY SPLITTING THE PARTICLES INTO TWO SETS AND CALCULATING THE FOURIER SHELL CORRELATION OBTAINED FROM SEPARATE RECONSTRUCTIONS (HARAUZ AND VAN HEEL 1986, OPTIK 73, 146-156). THE EIGENVALUE SPECTRUM GAVE AN INDICATION OF THE RANDOMNESS OF THE DATA THAT WAS INCLUDED IN THE RECONSTRUCTION. THE COMPLETENESS OF THE DATA WAS VERIFIED IN THAT ALL EIGENVALUES EXCEEDED 100. THE COORDINATES ARE IN THE P, Q, R FRAME IN ANGSTROM UNITS AND CORRESPOND TO ICOSAHEDRAL SYMMETRY AXES. THE ORIGIN IS CHOSEN AT THE CENTER OF THE VIRUS WITH P, Q AND R ALONG MUTUALLY PERPENDICULAR TWO-FOLD AXES OF THE ICOSAHEDRON. THEY SHOULD REMAIN IN THAT FRAME FOR THE EASE OF THE USER IN CREATING THE BIOLOGICALLY SIGNIFICANT VIRAL COMPLEX PARTICLE USING THE 60 ICOSAHEDRAL SYMMETRY OPERATORS. RESIDUES NOT VISIBLE IN THE ORIGINAL CRYSTAL STRUCTURES ARE NOT INCLUDED IN THE CRYO-EM STRUCTURE MODEL. FOR EXAMPLE, C RESIDUES 1-118, ARE NOT VISIBLE IN THE CRYSTAL STRUCTURE (PDB ENTRY 1VCQ) AND THEREFORE ARE NOT INCLUDED IN THE COORDINATES BELOW.
Refinement Type
Symmetry Type POINT
Map-Model Fitting and Refinement
ID 1
Refinement Space REAL
Refinement Protocol RIGID BODY FIT
Refinement Target R-factor
Overall B Value ?
Fitting Procedure ?
Details METHOD--THE CRYSTAL STRUCTURE OF THE CAPSID PROTEIN FROM CHOI ET AL (1997) PROTEINS 3 27,345-359 (SUBUNIT A OF PDB FILE 1VCQ) WAS PLACED INTO THE CRYO-EM DENSITY MAP. THE CAPSID PROTEIN WAS FIRST MANUALLY POSITIONED INTO THE CRYO-EM DENSITY CORRESPONDING TO POSITIONS OF THE FOUR INDEPENDENT MONOMER DENSITIES BETWEEN THE INNER LEAFLET OF THE BILAYER AND THE RNA. THESE POSITIONS WERE THEN REFINED BY RIGID BODY REFINEMENT IN REAL SPACE WITH THE PROGRAM EMFIT (CHENG ET AL. 1995, CELL 80, 621-630). THE QUALITY OF THE FIT CAN BE SEEN FROM THE MAP DENSITY WITHIN THE PROTEIN. ALL 4563 ATOMS ARE IN DENSITY OF AT LEAST 4 SIGMA (96.73) ABOVE THE AVERAGE (512.04) , 1167 ATOMS ARE IN DENSITY BETWEEN 4 AND 5 SIGMA, 3174 ATOMS ARE IN DENSITY BETWEEN 5 AND 6 SIGMA, AND 222 ATOMS ARE IN DENSTY OF 6 SIGMA OR ABOVE. THE VARIATION IN DENSITY OVER THE FITTED PROTEIN CAN BE VISUALIZED WITH THE PSEUDO TEMPERATURE FACTOR. THE DENSITY VALUE AT EACH ATOM IS GIVEN IN THE 8TH COLUM (USUALLY THE OCCUPANCY) AS THE NUMBER OF STANDARD DEVIATION ABOVE BACKGROUND. COLUMN NINE (USUALLY THE TEMPERATURE FACTOR) CONTAINS THE VALUE OF THE RELATIVE DENSITY WITHIN THE FITTED PROTEIN SCALED LINEARLY SO THAT THE MINIMUM DENSITY IS 100.0 AND THE MAXIMUM DENSITY IS 1.0. THE ATOMS THAT LIE IN THE LOWER DENSITY REGIONS WILL HAVE THE HIGHEST PSEUDO TEMPERATURE FACTORS. REFINEMENT PROTOCOL--RIGID BODY REFINEMENT
Data Acquisition
Detector Type KODAK SO-163 FILM
Electron Dose (electrons/Å2) 10
Imaging Experiment
Date of Experiment 1998-06-15
Temprature (Kelvin)
Microscope Model FEI/PHILIPS CM200FEG
Minimum Defocus (nm) 975
Maximum Defocus (nm) 7600
Minimum Tilt Angle (degrees) 0
Maximum Tilt Angle (degrees) 0
Nominal CS 2
Imaging Mode BRIGHT FIELD
Specimen Holder Model .
Nominal Magnification 50000
Calibrated Magnification ?
Source FIELD EMISSION GUN
Acceleration Voltage (kV) 200
Imaging Details ?
Imaging Experiment
Task Software Package Version
MODEL FITTING EMfit ?
PARTICLE SELECTION MRC IMAGE PROCESSING PACKAGE ?
PARTICLE SELECTION SPIDER ?
Image Processing
CTF Correction Type CTF Correction Details Number of Particles Selected Particle Selection Details