Open AccessUse of europium ions for SAD phasing of lysozyme at the Cu K α wavelength
Author(s) -
Vijayakumar Balakrishnan,
Velmurugan Devadasan
Publication year - 2013
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s1744309112047562
Subject(s) - europium , lysozyme , phaser , ion , wavelength , tetragonal crystal system , molecule , chemistry , crystallography , materials science , optics , physics , crystal structure , organic chemistry , biochemistry
Europium is shown to be a good anomalous scatterer in SAD phasing for solving the structure of biological macromolecules. The large value of the anomalous contribution of europium, f ′′ = 11.17 e − , at the Cu K α wavelength is an advantage in de novo phasing and automated model building. Tetragonal crystals of hen egg‐white lysozyme (HEWL) incorporating europium(III) chloride (50 m M ) were obtained which diffracted to a resolution of 2.3 Å at a wavelength of 1.54 Å (Cu K α). The master data set (360° frames) was split and analyzed for anomalous signal‐to‐noise ratio, multiplicity, completeness, SAD phasing and automated building. The structure solution and model building of the split data sets were carried out using phenix.autosol and phenix.autobuild . The contributions of the Eu ions to SAD phasing using in‐house data collection are discussed. This study revealed successful lysozyme phasing by SAD using laboratory‐source data involving Eu ions, which are mainly coordinated by the side chains of Asn46, Asp52 and Asp101 together with some water molecules.