Enhancing Lab Source Anomalous Scattering Using Cr Kα Radiation for Its Potential Application in Determining Macromolecular Structures

Sibi Narayanan, Devadasan Velmurugan

Centre of Advanced Study in Crystallography and Biophysics, University of Madras, Maraimalai (Guindy) Campus, Chennai, India.

DOI: 10.4236/csta.2012.13016                

Abstract

Obtaining phase information for the solution of macromolecular structures is a bottleneck in X-ray crystallography. Anomalous dispersion was recognized as a powerful tool for phasing macromolecular structures. It was used mainly to supplement the isomorphous replacement or to locate the anomalous scatterer itself. The first step in solving macromolecular structures by SAD (single-wavelength anomalous diffraction) is the location of the anomalous scatterers. The SAD method for experimental phasing has evolved substantially in the recent years. A phasing tool, 5-amino-2,4,6- triiodoisophthalic acid (I3C—magic triangle), was incorporated into three proteins, lysozyme, glucose isomerase and thermolysin using quick-soaking and co-crystallization method in order to understand the binding of metal ion with proteins. The high quality of the diffraction data, the use of chromium anode X-ray radiation and the required amount of anomalous signal enabled way for successful structure determination and automated model building. An analysis and/or comparison of the sulfur and iodine anomalous signals at the Cr Kα wavelength are discussed.

Keywords

Anomalous Scattering; SAD Phasing; I3C; Lysozyme; Glucose Isomerase; Thermolysin

Conflicts of Interest

The authors declare no conflicts of interest.

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