Electron microscopical localization of nucleic acids by means of nuclease--gold complexes

Nucleic acids can be specifically localized at the electron microscope level by means of enzyme--gold complexes. Two enzymes RNAase A and DNAase I were labelled with colloidal gold, and the enzyme--gold complexes obtained applied on thin sections of glutaraldehyde-fixed and Epon-embedded tissues. Using RNAase--gold, the rough endoplasmic reticulum and the nucleolus of different cells appeared densely labelled. With the DNAase--gold the labelling was present over the euchromatin and the mitochondria. The quantitative evaluation, performed on different cellular compartments of the pancreatic acinar cells, confirmed the qualitative observations and ascertained the specificity of the labelling. The application of this technique, for the demonstration of nucleic acids in different tissues, is illustrated.