title: Monolayer-crystal streptavidin support films provide an internal standard of cryo-EM image quality.
abstract: Analysis of images of biotinylated Escherichia coli 70S ribosome particles, bound to streptavidin affinity grids, demonstrates that the image-quality of particles can be predicted by the image-quality of the monolayer crystalline support film. The quality of the Thon rings is also a good predictor of the image-quality of particles, but only when images of the streptavidin crystals extend to relatively high resolution. When the estimated resolution of streptavidin was 5Å or worse, for example, the ribosomal density map obtained from 22,697 particles went to only 9.5Å, while the resolution of the map reached 4.0Å for the same number of particles, when the estimated resolution of streptavidin crystal was 4Å or better. It thus is easy to tell which images in a data set ought to be retained for further work, based on the highest resolution seen for Bragg peaks in the computed Fourier transforms of the streptavidin component. The refined density map obtained from 57,826 particles obtained in this way extended to 3.6Å, a marked improvement over the value of 3.9Å obtained previously from a subset of 52,433 particles obtained from the same initial data set of 101,213 particles after 3-D classification. These results are consistent with the hypothesis that interaction with the air-water interface can damage particles when the sample becomes too thin. Streptavidin monolayer crystals appear to provide a good indication of when that is the case.
authors.affiliation: Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720, USA.
authors.forename: Bong-Gyoon
authors.initials: BG
authors.lastname: Han
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720, USA.
authors.forename: Zoe
authors.initials: Z
authors.lastname: Watson
authors.affiliation: Department of Molecular and Cell Biology and California Institute of Quantitative Biosciences, University of California, Berkeley, CA 94720, USA; Department of Chemistry, University of California, Berkeley, CA 94720, USA; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720, USA.
authors.forename: Jamie H D
authors.initials: JHD
authors.lastname: Cate
authors.affiliation: Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720, USA. Electronic address: rmglaeser@lbl.gov.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Glaeser
mesh_terms: D020285:Cryoelectron Microscopy / Q000295:instrumentation / Q000379:methods*; D004926:Escherichia coli; D007091:Image Processing, Computer-Assisted; D012270:Ribosomes / Q000737:chemistry*; D019809:Streptavidin / Q000737:chemistry*
chemical_list: D019809:Streptavidin
keywords: Cryo-EM