title: Rapid model building of alpha-helices in electron-density maps.
abstract: A method for the identification of alpha-helices in electron-density maps at low resolution followed by interpretation at moderate to high resolution is presented. Rapid identification is achieved at low resolution, where alpha-helices appear as tubes of density. The positioning and direction of the alpha-helices is obtained at moderate to high resolution, where the positions of side chains can be seen. The method was tested on a set of 42 experimental electron-density maps at resolutions ranging from 1.5 to 3.8 A. An average of 63% of the alpha-helical residues in these proteins were built and an average of 76% of the residues built matched helical residues in the refined models of the proteins. The overall average r.m.s.d. between main-chain atoms in the modeled alpha-helices and the nearest atom with the same name in the refined models of the proteins was 1.3 A.
authors.affiliation: Los Alamos National Laboratory, Los Alamos, NM 87545, USA. terwilliger@lanl.gov
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Terwilliger
mesh_terms: D018360:Crystallography, X-Ray / Q000379:methods*; D004583:Electrons; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000032:analysis* / Q000737:chemistry; D013997:Time Factors
chemical_list: D011506:Proteins