title: Review: resolution issues in single-particle reconstruction.
abstract: Specific factors that affect the resolution of single-particle reconstructions are discussed. We present reconstructions of six particles (DNA-dependent protein kinase catalytic subunit, alphaB-crystallin, the ribonucleoprotein vault, hepatitis A virus, adenovirus type 2, and the adenovirus type 12/alpha(v)beta5 integrin complex), which have a variety of symmetries (asymmetric to 60-fold) and a wide range of molecular masses (470 kDa to 150 MDa). In the case of icosahedral viruses, we have found that applying a "soft" mask to remove regions of disordered density improves the resolution given by the Fourier shell correlation 0.5 criterion. This masking procedure is also useful during refinement to improve the quality of the reference model and thus aid in precise alignment of the particle images. For asymmetric particles, we note that image classification, although often a necessary step to generate a first reconstruction, can limit the achievable resolution. The diameter of the particle and the available computational power can also affect the resolution, as can structural variability within the particle.
authors.affiliation: Crump Institute for Biological Imaging, UCLA School of Medicine, Los Angeles, California 90095, USA. pstewart@mednet.ucla.edu
authors.forename: P L
authors.initials: PL
authors.lastname: Stewart
authors.forename: C Y
authors.initials: CY
authors.lastname: Chiu
authors.forename: D A
authors.initials: DA
authors.lastname: Haley
authors.forename: L B
authors.initials: LB
authors.lastname: Kong
authors.forename: J L
authors.initials: JL
authors.lastname: Schlessman
mesh_terms: D000256:Adenoviridae / Q000648:ultrastructure; D020285:Cryoelectron Microscopy / Q000379:methods*; D003459:Crystallins / Q000648:ultrastructure; D005583:Fourier Analysis; D006507:Hepatovirus / Q000648:ultrastructure; D007091:Image Processing, Computer-Assisted; D016023:Integrins / Q000648:ultrastructure; D019030:Receptors, Vitronectin; D019892:eIF-2 Kinase / Q000648:ultrastructure
chemical_list: D003459:Crystallins; D016023:Integrins; D019030:Receptors, Vitronectin; C064660:integrin alphaVbeta5; D019892:eIF-2 Kinase