EDM–DEDM and protein crystal structure solution

✍ Scribed by Caliandro, Rocco ;Carrozzini, Benedetta ;Cascarano, Giovanni Luca ;Giacovazzo, Carmelo ;Mazzone, Anna Maria ;Siliqi, Dritan

• Book ID: 104478463
• Publisher: International Union of Crystallography
• Year: 2009
• Tongue: English
• Weight: 804 KB
• Volume: 65
• Category: Article
• ISSN: 0907-4449
• DOI: 10.1107/s0907444909008609

✦ Synopsis

Electron-density modification (EDM) procedures are the classical tool for driving model phases closer to those of the target structure. They are often combined with automated model-building programs to provide a correct protein model. The task is not always performed, mostly because of the large initial phase error. A recently proposed procedure combined EDM with DEDM (difference electron-density modification); the method was applied to the refinement of phases obtained by molecular replacement, ab initio or SAD phasing [Caliandro, Carrozzini, Cascarano, Giacovazzo, Mazzone & Siliqi (2009), Acta Cryst. D65, 249-256] and was more effective in improving phases than EDM alone. In this paper, a novel fully automated protocol for protein structure refinement based on the iterative application of automated model-building programs combined with the additional power derived from the EDM-DEDM algorithm is presented. The cyclic procedure was successfully tested on challenging cases for which all other approaches had failed.