The ab initio crystal structure solution of proteins by direct methods. IV. The use of the partial structure

1995 ◽  
Vol 51 (3) ◽  
pp. 398-404 ◽  
Author(s):  
C. Giacovazzo ◽  
J. G. Platas
Keyword(s):  
Crystal Structure ◽  
Ab Initio ◽  
Direct Methods ◽  
Partial Structure ◽  
Structure Solution

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.

Completion of Crystal Structure with Polyhedral Coordination: A New Procedure

2004 ◽  
Vol 443-444 ◽  
pp. 23-26
Author(s):  
Angela Altomare ◽  
Corrado Cuocci ◽  
Carmelo Giacovazzo ◽  
Anna Grazia ◽  
Anna Grazia Giuseppina Moliterni ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Prior Information ◽  
Direct Methods ◽  
Structure Model ◽  
Powder Diffraction Data ◽  
Partial Structure ◽  
Structure Solution ◽  
Cation Coordination

The ab-initio crystal structure solution via powder diffraction data is often uncomplete. A recent procedure POLPO [1] aims at completing a partial structure model provided by Direct Methods by exploiting the prior information on the polyhedral coordination of the located atoms (tetrahedral or octahedral) and their connectivity has been developed. The POLPO procedure requires that all the cations are correctly labelled and rightly located. This condition does not always occur, particularly when the data quality is poor. A new method is described which is able to locate missing cations and surrounding anions when the cation coordination is tetrahedral or octahedral.

Crystal structure determination and refinementviaSIR2014

2015 ◽  
Vol 48 (1) ◽  
pp. 306-309 ◽  
Author(s):  
Maria Cristina Burla ◽  
Rocco Caliandro ◽  
Benedetta Carrozzini ◽  
Giovanni Luca Cascarano ◽  
Corrado Cuocci ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ab Initio ◽  
Structure Refinement ◽  
Three Dimensional ◽  
Direct Methods ◽  
Molecular Replacement ◽  
Dimensional Electron ◽  
Large Structures ◽  
Density Maps ◽  
Structure Solution

SIR2014is the latest program of theSIRsuite for crystal structure solution of small, medium and large structures. A variety of phasing algorithms have been implemented, bothab initio(standard or modern direct methods, Patterson techniques,Vive la Différence) and non-ab initio(simulated annealing, molecular replacement). The program contains tools for crystal structure refinement and for the study of three-dimensional electron-density mapsviasuitable viewers.

THE USE OF GEOMETRICAL INFORMATION IN THE AB-INITIO POWDER STRUCTURE SOLUTION BY DIRECT METHODS

2004 ◽  
Author(s):  
A. ALTOMARE ◽  
R. CALIANDRO ◽  
I. DA SILVA ◽  
C. GIACOVAZZO ◽  
A. G. G. MOLITERNI ◽  
...  
Keyword(s):  
Ab Initio ◽  
Direct Methods ◽  
Structure Solution ◽  
Geometrical Information

A tangent formula derived from Patterson-function arguments. VII. Solution of inorganic structures from powder data with accidental overlap

2000 ◽  
Vol 33 (5) ◽  
pp. 1208-1211 ◽  
Author(s):  
J. Rius ◽  
X. Torrelles ◽  
C. Miravitlles ◽  
L. E. Ochando ◽  
M. M. Reventós ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Inorganic Compounds ◽  
Solution Process ◽  
Direct Methods ◽  
Powder Diffraction Data ◽  
Patterson Function ◽  
Structure Factors ◽  
Structure Solution ◽  
Overlapped Peaks

Accidental overlap constitutes one of the principal limitations for the solution of crystal structures from powder diffraction data, since it reduces the number of available intensities for direct-methods application. In this work, the field of application of the direct-methods sum function is extended to cope with powder patterns with relatively large amounts of accidental overlap. This is achieved by refining not only the phases of the structure factors but also the estimated intensities of the severely overlapped peaks during the structure solution process. This procedure has been specifically devised for inorganic compounds with uncertain cell contents and with probable severe atomic disorder, a situation often found when studying complex minerals with limited crystallinity. It has been successfully applied to the solution of the previously unknown crystal structure of the mineral tinticite. Finally, an estimation of the smallest ratio (number of observations to number of variables) for the procedure to be successful is given.

Ab initio crystal structure solution of the novel intermetallic compound Nd3(Fe,Ti)29

1996 ◽  
Vol 234 (1) ◽  
pp. 62-66 ◽  
Author(s):  
V. Psycharis ◽  
O. Kalogirou ◽  
D. Niarchos ◽  
M. Gjoka
Keyword(s):  
Crystal Structure ◽  
Intermetallic Compound ◽  
Ab Initio ◽  
The Novel ◽  
Structure Solution

Crystal structure determination by neutron powder diffraction using structural and packing constraints

1991 ◽  
Vol 24 (6) ◽  
pp. 1005-1008 ◽  
Author(s):  
P. G. Byrom ◽  
B. W. Lucas
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Structure Determination ◽  
Direct Methods ◽  
Neutron Powder Diffraction ◽  
Crystal Structure Determination ◽  
Diffraction Profile ◽  
Peak Separation ◽  
Structure Factors ◽  
Structure Solution

In the past, crystal structure determination of solids consisting of molecules (or atom groups) whose geometry and size are known approximately has often been attempted using neutron powder diffraction profile refinement techniques, but without inclusion of this information. A method of structure solution has therefore been developed to include it. The proposed method does not require a set of structure factors and thus avoids the problems encountered in separating peaks in a powder diffraction scan. A successful test was conducted with a previously determined (yet treated as unknown) crystal structure, where direct methods had failed to solve the structure due to incorrect peak separation. Two computer programs, MODEL and PARAM, that implement the method are described.

Sign in / Sign up

Export Citation Format

Share Document