title: On the interpretation of electron microscopic maps of biological macromolecules.
abstract: The images of flash-frozen biological macromolecules produced by cryo-electron microscopy (EM) can be used to generate accurate, three-dimensional, electric potential maps for these molecules that resemble X-ray-derived electron density maps. However, unlike electron density maps, electric potential maps can include negative features that might for example represent the negatively charged, backbone phosphate groups of nucleic acids or protein carboxylate side chains, which can complicate their interpretation. This study examines the images of groups that include charged atoms that appear in recently-published, high-resolution EM potential maps of the ribosome and β-galactosidase. Comparisons of simulated maps of these same groups with their experimental counterparts highlight the impact that charge has on the appearance of electric potential maps.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, 06520.
authors.forename: Jimin
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, 06520.|Department of Chemistry, Yale University, New Haven, Connecticut, 06520.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Moore
mesh_terms: D020285:Cryoelectron Microscopy / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D012313:RNA / Q000648:ultrastructure*; D012270:Ribosomes / Q000648:ultrastructure*; D001616:beta-Galactosidase / Q000648:ultrastructure*
chemical_list: D012313:RNA; D001616:beta-Galactosidase
keywords: X-ray scattering; electric potential; electron atomic scattering factor; electron density; electron microscopy; electron scattering