The relationship of plastic deformation in freeze-etching to the orientation of a protein particle.

Freeze-fracturing of face-centered, cubically packed, intracellular crystals of fraction 1 protein result in two distinct fracture responses of the constituent particles, according to their orientation relative to the plane of fracture. If a square-packed plane is revealed, fracture occurs either between particles or the particles plastically deform. Conversely, if a hexagonally-packed plane is revealed, fracture occurs either betwen particles or cleanly at internal planes of the particles, without any plastic deformation. It is proposed that this information may be of value in determining the arrangement of the axes of the covalently bound polypeptide protomer chains which constitute the oligomer.