Open AccessRapid model building of α‐helices in electron‐density maps
Author(s) -
Terwilliger Thomas C.
Publication year - 2010
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s0907444910000314
Subject(s) - resolution (logic) , electron density , crystallography , low resolution , alpha (finance) , atom (system on chip) , chain (unit) , protein structure , chemistry , high resolution , electron , physics , mathematics , nuclear magnetic resonance , computer science , artificial intelligence , statistics , psychometrics , construct validity , remote sensing , quantum mechanics , astronomy , embedded system , geology
A method for the identification of α‐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 α‐helices appear as tubes of density. The positioning and direction of the α‐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 Å. An average of 63% of the α‐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 α‐helices and the nearest atom with the same name in the refined models of the proteins was 1.3 Å.