title: Cryo-EM and the elucidation of new macromolecular structures: Random Conical Tilt revisited.
abstract: Cryo-Electron Microscopy (cryo-EM) of macromolecular complexes is a fundamental structural biology technique which is expanding at a very fast pace. Key to its success in elucidating the three-dimensional structure of a macromolecular complex, especially of small and non-symmetric ones, is the ability to start from a low resolution map, which is subsequently refined with the actual images collected at the microscope. There are several methods to produce this first structure. Among them, Random Conical Tilt (RCT) plays a prominent role due to its unbiased nature (it can create an initial model based on experimental measurements). In this article, we revise the fundamental mathematical expressions supporting RCT, providing new expressions handling all key geometrical parameters without the need of intermediate operations, leading to improved automation and overall reliability, essential for the success of cryo-EM when analyzing new complexes. We show that the here proposed RCT workflow based on the new formulation performs very well in practical cases, requiring very few image pairs (as low as 13 image pairs in one of our examples) to obtain relevant 3D maps.
authors.affiliation: National Center for Biotechnology (CSIC), c/Darwin, 3, Campus Universidad Autónoma, 28049 Cantoblanco, Madrid, Spain.|Universidad CEU San Pablo, Campus Urb. Montepríncipe s/n, 28668 Boadilla del Monte, Madrid, Spain.
authors.forename: C O S
authors.initials: CO
authors.lastname: Sorzano
authors.affiliation: Center for Biological Research (CSIC), c/Ramiro de Maeztu, 9, 28040, Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Alcorlo
authors.affiliation: National Center for Biotechnology (CSIC), c/Darwin, 3, Campus Universidad Autónoma, 28049 Cantoblanco, Madrid, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: de la Rosa-Trevín
authors.affiliation: Center for Biological Research (CSIC), c/Ramiro de Maeztu, 9, 28040, Madrid, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Melero
authors.affiliation: National Center for Biotechnology (CSIC), c/Darwin, 3, Campus Universidad Autónoma, 28049 Cantoblanco, Madrid, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Foche
authors.affiliation: National Center for Biotechnology (CSIC), c/Darwin, 3, Campus Universidad Autónoma, 28049 Cantoblanco, Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Zaldívar-Peraza
authors.affiliation: National Center for Biotechnology (CSIC), c/Darwin, 3, Campus Universidad Autónoma, 28049 Cantoblanco, Madrid, Spain.
authors.forename: L
authors.initials: L
authors.lastname: del Cano
authors.affiliation: National Center for Biotechnology (CSIC), c/Darwin, 3, Campus Universidad Autónoma, 28049 Cantoblanco, Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Vargas
authors.affiliation: National Center for Biotechnology (CSIC), c/Darwin, 3, Campus Universidad Autónoma, 28049 Cantoblanco, Madrid, Spain.
authors.forename: V
authors.initials: V
authors.lastname: Abrishami
authors.affiliation: National Center for Biotechnology (CSIC), c/Darwin, 3, Campus Universidad Autónoma, 28049 Cantoblanco, Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Otón
authors.affiliation: Escuela Politécnica Superior, Universidad Autónoma de Madrid, Campus Universidad Autónoma, 28049 Cantoblanco, Madrid, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Marabini
authors.affiliation: National Center for Biotechnology (CSIC), c/Darwin, 3, Campus Universidad Autónoma, 28049 Cantoblanco, Madrid, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Carazo
mesh_terms: D003179:Complement C3b / Q000648:ultrastructure; D020285:Cryoelectron Microscopy / Q000379:methods*; D007091:Image Processing, Computer-Assisted; D046911:Macromolecular Substances / Q000648:ultrastructure*; D008962:Models, Theoretical
chemical_list: D046911:Macromolecular Substances; D003179:Complement C3b