Observation of unstained biological macromolecules with the STEM.

We discuss the observation of an unstained single biological macromoilecule of human serum low density lipoprotein in a scanning transmission electron microscope (STEM). Using a carbon substrate with 16 A average thickness and an electron dose of 19 electrons/A2 the image obtained from the unstained molecule shows a similar surface substructure as that seen in a negatively stained conventional transmission electron microscope (CTEM) micrograph.