PMC

(A) Scanning Electron Micrograph of a HeLa cell labeled in vivo with RNA polymerase II-specific Fab fragments conjugated to ultrasmall gold particles. The nuclear (nuc) and cytoplasmic (cyt) compartments are indicated. The bar represents 0.5 μm. (B) Enlargement of the area delineated in (A) to show the amplified gold particles highlighted arrowheads circles. (C) Gallery of 4 amplified gold particles (columns) imaged by SEM on successive 5 nm thick FIB sections (D) Three-dimensional reconstruction of a series of FIB/SEM images representing the whole nucleus. The electron dense nuclear envelope and the nucleolus are represented by blue isodensity surfaces. The amplified gold particles are represented in yellow. Dense heterochromatin domains are represented in red.

(A) Antibodies coupled to 6 nm colloidal gold particles are found aggregated in large cytoplasmic vesicles. (B) Antibodies coupled to 0.8 nm gold particles are detected as individual spots after silver enhancement in the cytoplasm and are enriched in the nucleus. (C) Distribution of the amplified gold particles coupled to IgG molecules directed against RNA polymerase II. (D) Distribution of the amplified gold particles coupled to Fab fragments directed against RNA polymerase II. The bar represents 1 μm in (A), 0.2 μm in (B) and 0.6 μm in (C) and (D).