H. Aurich

Oriented incorporation of bacteriorhodopsin into the lipid shell of phospholipid-coated polymer particles

Phospholipid monolayers covalently fixed to spherical polymer carriers spontaneously form a stable bilayer‐like structure by adsorption of further added phospholipids. Bacteriorhodopsin could be incorporated into the lipid bilayer growing on these particles. From the direction of proton pumping as well as from freeze‐fracture electron micrographs and papain digestion, experimental evidence was obtained that the preferred orientation of bacteriorhodopsin within the lipid coat is ‘inside‐out’ (more than 90%). A ‘right‐side‐out’ incorporation of bacteriorhodopsin could be demonstrated, if the negative charge density of the carrier surface was lowered by chemical modification.

Immunoelectron microscopic localization of microsomal alanine aminopeptidase

The localization of microsomal alanine aminopeptidase was investigated in the rat kidney. Resin embedding failed to demonstrate the localization of the enzyme by immunogold labelling. Using a cryo-ultramicrotomy method the enzyme could be detected on the luminal side of the brush border membrane of proximal tubular cells and to a lesser degree in their mitochondria. Furthermore, vesicular structures labelled with gold were found in the cytoplasma in the apical region of these cells.