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Freeze‐fracturing and freeze‐etching of cardiac myosin filaments
Author(s) -
Rayns David G.
Publication year - 1975
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1975.tb03897.x
Subject(s) - myofilament , myosin , protein filament , materials science , etching (microfabrication) , diffraction , deformation (meteorology) , bridge (graph theory) , crystallography , oblique case , negative stain , biophysics , optics , composite material , chemistry , anatomy , biology , physics , electron microscope , linguistics , philosophy , layer (electronics)
SUMMARY Myofilament structure was studied in freeze‐etch replicas of unfixed, glycerinated beef cardiac muscle. The information which is revealed depends upon the direction of metal shadowing in relation to the filament axis. Shadows oblique to this axis reveal that the outer surface of a longitudinal half of a thick filament comprises three, sometimes four, rows of myosin molecules. These molecules are generally assembled in a braided manner with both left and right‐handed helical components. Occasionally a more parallel arrangement is seen; this may represent a split filament. Shadows parallel to the myofilament axis reveal cross‐bridges linking thick and thin filaments. These bridges are readily detectable by optical diffraction techniques, giving an axial bridge spacing of approximately 40 nm. In unetched preparations cross bridges appear as vertical rows of beads. In all replicas the effects of plastic deformation of proteins must be considered.