title: Use of the avidin-biotin complex for specific staining of biological membranes in electron microscopy.
abstract: To expand the electron microscopist's options in localization and visualization, a new and general staining technique has been tested. The avidin-biotin complex serves as a coupling between the electron-dense marker, ferritin, and points of interest in biological samples. When specific cellular components are tagged with biotin, those components may be visualized with ferritin-linked avidin. Because of the remarkably strong affinity of avidin and biotin (characterized by an association constant of 10(15) M(-1)), the staining is rapid and stable. The preparation of ferritin-avidin conjugate is described, and examples are presented of the application of this complex to biotin-tagged membranes. The ghosts of Acholeplasma laidlawii have been treated with biotinyl-N-hydroxysuccinimide ester to label protein amino groups. Erythrocyte membrane oligosaccharides have been oxidized by periodate or by galactose oxidase, and the resulting aldehydes labeled with biotin hydrazide. The avidin-biotin complex in electron microscopy seems especially appropriate for seqential staining procedures, as well as for visualization of reaction sites of biotin-labeled, low-molecular-weight reagents.
mesh_terms: D000128:Acholeplasma laidlawii / Q000737:chemistry; D001360:Avidin; D001426:Bacterial Proteins / Q000032:analysis; D001710:Biotin; D002241:Carbohydrates / Q000032:analysis; D002250:Carbon Radioisotopes; D004912:Erythrocytes / Q000737:chemistry; D005293:Ferritins; D005779:Immunodiffusion; D008024:Ligands; D008566:Membranes / Q000737:chemistry; D008854:Microscopy, Electron / Q000379:methods*; D010047:Ovalbumin; D011506:Proteins / Q000032:analysis; D013194:Staining and Labeling
chemical_list: D001426:Bacterial Proteins; D002241:Carbohydrates; D002250:Carbon Radioisotopes; D008024:Ligands; D011506:Proteins; D001360:Avidin; D001710:Biotin; D010047:Ovalbumin; D005293:Ferritins