Structural Changes in Membranes of Synchronized Cells demonstrated by Freeze-cleavage

FREEZE-CLEAVAGE is a new technique for studying the ultra-structure· of biological membranes, which fractures cell membranes in half, exposing two intramembranous fracture faces^1–3: the outer fracture face (OFF) and the inner fracture face (IFF). These fracture faces are partially covered with 70 Å globular particles which are thought to be unique structural components of cell membranes, formed by the association of membrane glycoproteins and lipids⁴. The 70 Å particles are dynamic structures and rapidly increase in density in the membranes of lymphocytes following exposure to mitogenic plant proteins (Scott and Marchesi, unpublished work).