An in-lens Schottky field emission scanning electron microscope (SEM) combined with a transmission
electron microscope (TEM)-type cold-stage and a chromium (Cr) sputter-coating system was developed
to rapidly prepare and cryo-image biological specimens to attain accurate nanometer-level structural information.
High-resolution topographic images at high primary magnification ([eg ]200,000 times) were digitally recorded
with very short dwell times and without beam damage. Plunge freezing in ethane, followed by fracturing, Cr
coating, and in-lens cryo-high-resolution scanning electron microscope (HRSEM) imaging directly revealed
macromolecular features of yeast cells, platelets, and cell-free elastin analogues. The 'vitreous' nature of bulk
water in its solid state appeared featureless in cryo-HRSEM images, suggesting that if ice crystals were present
they would be [el ]2–3 nm (the approximate instrument resolution on cryo-specimens). Compared to technically
difficult and indirect freeze-fracture TEM replicas, cryo-HRSEM samples are fully hydrated, unfixed, noncryoprotected
specimens immersed in featureless ice. The time necessary to cryo-immobilize the specimen and
record the image is <3 hr. The hexagonal arrays of intramembrane particles on the protoplasmic face of yeast
cells and differences in surface morphology between thrombin-stimulated and quiescent platelets were assessed.
A clear interface line between collapsed elastin fibril lacework and vitreous lakes was commonly observed. These
experiments demonstrate the feasibility of this technique to rapidly evaluate macromolecular features in
cryofixed cells and cell-free systems.