EM Sample
Sample Vitrification Details No vitrification. Samples were viewed at room temperature.
Sample Aggregation State TISSUE
Sample Reconstruction Method TOMOGRAPHY
Name of Sample Insect flight muscle of the large water bug Lethocerus maximus
EM Data Acquisition
Date of Experiment --
Temperature (Kelvin) --
Microscope Model FEI/PHILIPS EM400
Detector Type KODAK SO-163 FILM
Minimum Defocus (nm) --
Maximum Defocus (nm) --
Minimum Tilt Angle (degrees) --
Maximum Tilt Angle (degrees) --
Nominal CS --
Electron Dose (electrons per Å**-2) --
Illumination Mode FLOOD BEAM
Nominal Magnification 17000
Calibrated Magnification --
Acceleration Voltage (kV) 100
Imaging Details --
3D Reconstruction
Software Package(s) Custom
Reconstruction Method(s) --
EM Image Reconstruction Statistics
Number of Particles --
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 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.
Effective Resolution 70.0
EM Map-Model Fitting and Refinement
Refinement Space Refinement Protocol Refinement Target Overall B Value Fitting Procedure Fitting Software
REAL RIGID BODY FIT Best correlation coefficient and fewest poor contacts -- -- --