title: The random-model method enables ab initio 3D reconstruction of asymmetric particles and determination of particle symmetry.
abstract: Model-based, 3D reconstruction techniques depend on reliable starting models. We present an extension of the random-model method (RMM) that allows the ab initio generation of suitable starting models directly from un-averaged, experimental images of asymmetric or symmetric particles. Therefore, the asymmetric RMM can also be used to determine point-group symmetry. The procedure is facilitated by the use of (a) variable angular step-sizes during iterative origin and orientation searches, (b) high numbers of particle images, and (c) highly defocused images. The method is inhibited by mixed-handedness orientation assignments and by particles with inconspicuous features. For symmetric particles, symmetric RMMs can overcome these deficiencies.
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Sanz-García
authors.forename: Aaron B
authors.initials: AB
authors.lastname: Stewart
authors.forename: David M
authors.initials: DM
authors.lastname: Belnap
mesh_terms: D020285:Cryoelectron Microscopy / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008962:Models, Theoretical