Nearly all single-particle cryo-EM structures resolved to better than 4-Å
resolution have been determined using 300-keV transmission electron microscopes
(TEMs). We demonstrate that it is possible to obtain reconstructions of
macromolecular complexes of different sizes to better than 3-Å resolution using
a 200-keV TEM. These structures are of sufficient quality to unambiguously
assign amino acid rotameric conformations and identify ordered water molecules.
