Scanning transmission electron microscopy of biological macromolecules

The practical usefulness of a STEM (Scanning Transmission Electron Microscope) for the study of the structure of biological macromolecules has been investigated using a STEM attachment connected to a TEM (Transmission Electron Microscope), which in one case was equipped with a tungsten hairpin cathode, and in the other case with a field emission gun. The point to point resolution has been determined. Results obtained in STEM dark field from light negatively stained specimens are compared with results obtained in TEM bright field from normal negatively stained specimens. In addition unstained molecules have been visualized. Some remarks are made about preparation methods suitable for STEM.