title: EDM-DEDM and protein crystal structure solution.
abstract: 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.
authors.affiliation: Institute of Crystallography, Consiglio Nazionale della Ricerche, Via G. Amendola 122/0, Bari, Italy.
authors.forename: Rocco
authors.initials: R
authors.lastname: Caliandro
authors.forename: Benedetta
authors.initials: B
authors.lastname: Carrozzini
authors.forename: Giovanni Luca
authors.initials: GL
authors.lastname: Cascarano
authors.forename: Carmelo
authors.initials: C
authors.lastname: Giacovazzo
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Mazzone
authors.forename: Dritan
authors.initials: D
authors.lastname: Siliqi
mesh_terms: D000465:Algorithms; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods* / Q000706:statistics & numerical data; D004583:Electrons; D008956:Models, Chemical; D008958:Models, Molecular; D011336:Probability; D011487:Protein Conformation; D012984:Software