title: Electron digital imaging toward high-resolution structure analysis of biological macromolecules.
abstract: Digital imaging has been applied to structure analysis of biological macromolecules in combination with electron energy filtering. Energy filtering can improve the image contrast of frozen-hydrated specimens, but needs a high-sensitivity imaging device instead of photographic film, because of a decrease in electrons after filtration. Here, a lens-coupled slow-scan charge-coupled device (SSCCD) camera with a post-column-type energy filter were examined to image bacterial flagellar filaments embedded in ice. We first measured the modulation transfer function of this camera and showed the remarkable improvement, compared to other fiber-coupled SSCCD cameras. The 3D structure calculated at approximately 7-angstroms resolution clearly resolves alpha-helices. Furthermore, filtered datasets recorded on the SSCCD camera with liquid-nitrogen and liquid-helium cooling were compared with the previous unfiltered one on film with liquid-helium cooling. This report describes the suitability of digital imaging with energy filtering for higher-resolution structure studies from its practical application.
authors.affiliation: The W. M. Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California, San Francisco, 1700 4th Street, San Francisco, CA 94158-2532, USA.
authors.forename: Saori
authors.initials: S
authors.lastname: Maki-Yonekura
authors.forename: Koji
authors.initials: K
authors.lastname: Yonekura
mesh_terms: D008841:Actin Cytoskeleton / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000648:ultrastructure; D005407:Flagella / Q000648:ultrastructure; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D046911:Macromolecular Substances; D008854:Microscopy, Electron / Q000379:methods*
chemical_list: D001426:Bacterial Proteins; D046911:Macromolecular Substances