Ponceau 2R staining of proteins and periodic acid bleaching of osmicated subcellular structures on semi‐thin sections of tissues processed for electron microscopy: a simplified procedure

SUMMARY An aqueous solution (pH 1·5) of 0·5% Ponceau 2R (C.I. 16150) and 2% periodic acid was used at 318 K to stain proteins (brilliant red) and simultaneously to bleach the osmicated non‐proteinaceous cell structures on 1–2 μm thick sections of tissues fixed in glutaraldehyde‐osmium tetroxide and embedded in epoxy resins. This H5IO6 bleaching‐Ponceau 2R staining procedure only stains the proteins so that black‐and‐white films can be used.