MOLECULAR MODELS OF AVERAGED RIGOR CROSSBRIDGES FROM TOMOGRAMS OF INSECT FLIGHT MUSCLE
ELECTRON MICROSCOPY
Sample
INSECT FLIGHT MUSCLE OF THE LARGE WATER BUG LETHOCERUS MAXIMUS
Specimen Preparation
Sample Aggregation State
TISSUE
Vitrification Instrument
Cryogen Name
Sample Vitrification Details
NO VITRIFICATION. SAMPLES WERE VIEWED AT ROOM TEMPERATURE.
Staining Type
NEGATIVE
Staining Material
Osmium tetroxide, Uranyl Acetate
Staining Details
3D Reconstruction
Reconstruction Method
TOMOGRAPHY
Number of Particles
Reported Resolution (Å)
70
Resolution Method
Other Details
3-D MOTIFS WERE IDENTIFIED IN THE TOMOGRAM BY FIRST PRODUCING A CROSS CORRELATION MAP FROM WHICH PEAK COORDINATES WERE DETERMINED FROM THEIR CENTER OF ...
3-D MOTIFS WERE IDENTIFIED IN THE TOMOGRAM BY FIRST PRODUCING A CROSS CORRELATION MAP FROM WHICH PEAK COORDINATES WERE DETERMINED FROM THEIR CENTER OF GRAVITY. WE DEFINE A 3-D MOTIF AS ONE, ENTIRE 38.7 NM CROSSBRIDGE REPEAT ALONG ACTIN. THESE MOTIFS USUALLY CONTAIN AT LEAST FOUR MYOSIN HEADS IN TWO PAIRED CROSSBRIDGES (SINGLE CHEVRONS) AND SOMETIMES CONTAIN AS MANY AS SIX MYOSIN HEADS IN FOUR PAIRED CROSSBRIDGES (DOUBLE CHEVRONS). THE REFERENCE FOR THE ANALYSIS WAS SELECTED TO BE CENTERED BETWEEN SUCCESSIVE TROPONIN DENSITIES WHICH COULD BE IDENTIFIED FROM THE IN-PLANE PROJECTION. THE INDIVIDUAL CROSSBRIDGE MOTIFS WERE THEN SUBJECTED TO MULTIVARIATE STATISTICAL ANALYSIS TO IDENTIFY CLUSTERS OF MOTIFS SHOWING SIMILAR CROSSBRIDGE STRUCTURE. THESE CLUSTERS FORMED THE CLASS AVERAGES. THE CHOICE OF STRUCTURE TO BE CLASSIFIED WAS DECIDED BY THE RESOLUTION AND THE LATER PROCESS OF MODEL BUILDING. AVERAGING WAS DONE ACCORDING TO THE HEIRARCHICAL ASCENDENT METHOD. THE RESOLUTION IN EACH OF THE CLASS AVERAGES WAS 7 NM BY THE SPECTRAL SIGNAL TO NOISE RATIO.
Refinement Type
Symmetry Type
POINT
Point Symmetry
C1
Map-Model Fitting and Refinement
Id
1 (2MYS, 1ATN)
Refinement Space
REAL
Refinement Protocol
RIGID BODY FIT
Refinement Target
BEST CORRELATION COEFFICIENT AND FEWEST POOR CONTACTS
Overall B Value
Fitting Procedure
Details
METHOD--INITIAL MODELS WERE FIT BY HAND USING O. THE FIT WAS THEN REFINED USING
REAL SPACE REFINEMENT. REFINEMENT PROTOCOL--RIGID BODY
