Orthogonal arrays or assemblies of intramembranous particles (OAPs) are structures in the
membrane of diverse cells which were initially discovered by means of the freeze-fracturing
technique. This technique, developed in the 1960s, was important for the acceptance of the
fluid mosaic model of the biological membrane. OAPs were first described in liver cells, and
then in parietal cells of the stomach, and most importantly, in the astrocytes of the brain.
Since the discovery of the structure of OAPs and the identification of OAPs as the …