Bubblegrams reveal the inner body of bacteriophage φKZ.

Dense packing of macromolecules in cellular compartments and higher-order assemblies makes it difficult to pick out even quite large components in electron micrographs, despite nominally high resolution. Immunogold labeling and histochemical procedures offer ways to map certain components but are limited in their applicability. Here, we present a differential mapping procedure, based on the physical principle of protein's greater sensitivity to radiation damage compared with that of nucleic acid.