Rotary-shadowed freeze-fracture replicas: a simple method for the analysis of fracture faces.

In rotary-shadowed freeze-fracture replicas, intramembrane particles on the periphery of a membrane fracture face are not uniformly shadowed from all sides. Those eccentrically positioned intramembrane particles with a net centripetally directed shadowing are on a convex fracture face. In contrast, those eccentrically positioned intramembrane particles with a net centrifugally directed shadowing are on a concave fracture face. Centrally positioned intramembrane particles on convex faces are uniformly shadowed from all sides; however, central depressions of concave faces are often unshadowed.