Freeze-fracturing splits membranes into two helves, thus allowing an
examination of the membrane interior. The 5-10 rm particles visible on both
monolayers are widely assumed to be proteinaceous in nature.
Most membranes do not reveal impressions complementary to particles on
the opposite fracture face, if the membranes are fractured under conditions
without etching. Even if it is considered that shadowing, contamination or
fracturing itself might obscure complementary pits', there is no
satisfactory explanation why under similar physical circimstances matching
halves of other membranes can be visualized. A prominent example of
uncomplementarity is found in the erythrocyte manbrane. It is wall
established that band 3 protein and possibly glycophorin represents these
nonccmplanentary particles. On the other hand a number of membrane types
show pits opposite the particles. Scme well known examples are the ";gap
junction',"; tight junction, the luminal membrane of the bladder epithelial
cells and the outer membrane of Escherichia coli.
Gap Junction-Mediated Astrocytic Networks in the Mouse Barrel Cortex