Cryo-electron microscopic studies of relaxed striated muscle thick filaments.

Electron micrograph images of rapidly frozen suspensions of thick filaments from four different muscle types are presented. Their optical and computer transforms are compared with images and diffraction patterns of negatively stained filaments and with X-ray data from the same muscles. We conclude that myosin head arrangement can be preserved on rapid freezing and that the images produced can be analysed by image processing techniques to give new information on thick filament structure.