Fig. 3. Immunoelectron microscopic visualisation of PcG proteins in (A) an osmium-ammine-stained section of a paraformaldehyde-fixed SW480 cell (anti-HPC2 labelling) and (B) in high pressure frozen and cryosubstituted rat liver tissue (anti-BMI labelling); uranyl-lead stained. The primary antibodies were revealed by goat anti-rabbit secondary antibody conjugated with 12 nm colloidal gold particles. PcG proteins mainly occur at the periphery of condensed chromatin (c). Some perichromatin fibrils are indicated by arrowheads. Bars, 0.2 µm.