SIR2004: an improved tool for crystal structure determination and refinement

2005 ◽  
Vol 38 (2) ◽  
pp. 381-388 ◽  
Author(s):  
Maria C. Burla ◽  
Rocco Caliandro ◽  
Mercedes Camalli ◽  
Benedetta Carrozzini ◽  
Giovanni L. Cascarano ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ab Initio ◽  
Structure Determination ◽  
Protein Structures ◽  
Medium Size ◽  
Graphical Interface ◽  
Asymmetric Unit ◽  
Density Maps ◽  
Data Resolution ◽  
User Friendly

SIR2004is the evolution of theSIR2002program [Burla, Camalli, Carrozzini, Cascarano, Giacovazzo, Polidori & Spagna (2003).J. Appl. Cryst.36, 1103]. It is devoted to the solution of crystal structures by direct and Patterson methods. Several new features implemented inSIR2004make this program efficient: it is able to solveab initioboth small/medium-size structures as well as macromolecules (up to 2000 atoms in the asymmetric unit). In favourable circumstances, the program is also able to solve protein structures with data resolution up to 1.4–1.5 Å, and to provide interpretable electron density maps. A powerful user-friendly graphical interface is provided.

Structure of [(tmpp)2Ag]+2[Ag5I7]2-; an Unusual Ionic Adduct of Tris(2,4,6-trimethoxyphenyl)phosphine (tmpp) With Silver(I) Iodide

1992 ◽  
Vol 45 (11) ◽  
pp. 1909 ◽  
Author(s):  
LJ Baker ◽  
GA Bowmaker ◽  
y Effend ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Structure Determination ◽  
Crystal Structure Determination ◽  
Asymmetric Unit ◽  
Tertiary Phosphine ◽  
Polymeric Structure ◽  
Coordination Numbers ◽  
Ladder Polymer ◽  
Silver Atoms

A single-crystal structure determination is reported for [( tmpp )2Ag]+2 [Ag5I7]2-, a product isolated from the reaction of the highly basic, sterically hindered tertiary phosphine ligand tris (2,4,6-trimethoxypheny1) phosphine ( tmpp ) with silver(I) iodide. This complex is triclinic, P1, a 22.01(2), b 19.98(1), c 16.48(1) � , α 94.49(6), β 92.46(7), γ 116.76(5)',Z 2; R was 0.11 for 3436 'observed' reflections. The asymmetric unit contains two crystallographically inequivalent [( tmpp )2Ag]+ cations in which the silver atoms are quasi-linearly coordinated to two phosphorus atoms with P-Ag-P angles of 175.9(9) and 179(1)°, and a mean Ag-P distance of 2.38 � . The anion has a novel one-dimensionally polymeric structure which is based on a double-stranded 'ladder' polymer of AgI units to which are bonded one I- and one AgI2-unit for every four AgI units. In the resulting polymer, all silver atoms are four-coordinate, while iodide coordination numbers of two, three and four are observed, with associated Ag-I distances of 2.75-2.86(1), 2.72-2.91(1) and 2.90-3-08(1) � respectively.

The revenge of the Patterson methods. II. Substructure applications

2007 ◽  
Vol 40 (2) ◽  
pp. 211-217 ◽  
Author(s):  
Maria Cristina Burla ◽  
Rocco Caliandro ◽  
Benedetta Carrozzini ◽  
Giovanni Luca Cascarano ◽  
Liberato De Caro ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ab Initio ◽  
Electron Density ◽  
Direct Methods ◽  
Large Set ◽  
Common Belief ◽  
Anomalous Diffraction ◽  
Density Maps ◽  
Structure Solution ◽  
The Common

The Patterson techniques, recently developed by the same authors for theab initiocrystal structure solution of proteins, have been applied to single and multiple anomalous diffraction (SAD and MAD) data to find the substructure of the anomalous scatterers. An automatic procedure has been applied to a large set of test structures, some of which were originally solved with remarkable difficulty. In all cases, the procedure automatically leads to interpretable electron density maps. Patterson techniques have been compared with direct methods; the former seem to be more efficient than the latter, so confirming the results obtained forab initiophasing, and disproving the common belief that they could only be applied to determine large equal-atom substructures with difficulty.

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