FIB Milling of Frozen Biological Specimens for 3D Electron Microscopy

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FIB Milling of Frozen Biological Specimens for 3D
Electron Microscopy
Cryo-electron microscopy and tomography of
frozen-hydrated cells and tissues is opening a
new window on the organization of the cell and
the operation of the molecular machinery inside.
A major obstacle is the preparation of specimens
from bulk-frozen biological material that are
suitably thin (a few hundred nm) for imaging in
the transmission electron microscope. Cutting
with diamond knives yields irregularly shaped
sections with compression and fracture artifacts.
Through collaboration with the CNS/NNIN, we are
exploring the use of focused ion beams to mill
frozen-hydrated specimens for electron
tomography. We have found that the ion beam does
not detectably heat these very labile specimens,
and structural detail in specimens such as
bacteria (figure) is preserved artifact-free.
Extension to frozen-hydrated mammalian cells and
tissue is underway.
250 nm
Joachim Frank, Wadsworth Center Work performed at
Center for Nanoscale Systems -Harvard