Structure of C15-, C17- and C19-mono-acid β-triacylglycerols

2001 ◽  
Vol 58 (1) ◽  
pp. 134-139 ◽  
Author(s):  
Robert B. Helmholdt ◽  
René Peschar ◽  
Henk Schenk
Keyword(s):  
High Resolution ◽  
Powder Diffraction ◽  
Layered Structure ◽  
Diffraction Data ◽  
Tuning Fork ◽  
Acyl Chain ◽  
Grid Search ◽  
Powder Diffraction Data ◽  
Chain Packing ◽  
X Ray

The crystal structures of β-1,2,3-tris(pentadecanoyl)glycerol (β-C15C15C15), β-1,2,3-tris(heptadecanoyl)glycerol (β-C17C17C17) and β-1,2,3-tris(nonadecanoyl)glycerol (β-C19C19C19) have been determined from high-resolution X-ray powder diffraction data. Grid search and Rietveld refinement have been used to determine and refine the structures, respectively. As in β-1,2,3-tris(tridecanoyl)glycerol (β-C13C13C13) and the even-numbered mono-acid triacylglycerols, all three odd-numbered monoacid triacylglycerols crystallize in space group P\bar 1 with Z = 2 in an asymmetric tuning-fork conformation and have a lateral acyl chain packing resulting in a layered structure.

Structure of β-trimyristin and β-tristearin from high-resolution X-ray powder diffraction data

2001 ◽  
Vol 57 (3) ◽  
pp. 372-377 ◽  
Author(s):  
Arjen van Langevelde ◽  
René Peschar ◽  
Henk Schenk
Keyword(s):  
High Resolution ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
Grid Search ◽  
Powder Diffraction Data ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Distance Restraints

The crystal structures of β-1,2,3-tritetradecanoylglycerol (β-trimyristin or β-MMM) and β-1,2,3-trioctadecanoylglycerol (β-tristearin or β-SSS) have been determined from high-resolution synchrotron X-ray powder diffraction data. Grid search and Rietveld refinement have been used to determine and refine the structure, respectively. Both substances crystallize in space group P\bar 1 with Z = 2. The unit-cell parameters for β-MMM are a = 12.0626 (6), b = 41.714 (1), c = 5.4588 (3) Å, α = 73.388 (4), β = 100.408 (5) and γ = 118.274 (4)°. For β-SSS the unit-cell parameters are a = 12.0053 (7), b = 51.902 (2), c = 5.4450 (3) Å, α = 73.752 (5), β = 100.256 (6) and γ = 117.691 (5)°. Soft-distance restraints have been applied to the molecules during refinement. For β-MMM the final Rp value obtained is 0.053 and for β-SSS the final Rp value is 0.041.

The crystal structures of solvent-free alkali-metal squarates from powder diffraction data

2005 ◽  
Vol 220 (11) ◽  
Author(s):  
Robert E. Dinnebier ◽  
Hanne Nuss ◽  
Martin Jansen
Keyword(s):  
High Resolution ◽  
Alkali Metal ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Room Temperature ◽  
Solvent Free ◽  
Crystallographic Data ◽  
Powder Diffraction Data ◽  
X Ray

AbstractThe crystal structures of solvent-free lithium, sodium, rubidium, and cesium squarates have been determined from high resolution synchrotron and X-ray laboratory powder patterns. Crystallographic data at room temperature of Li

Combined Rietveld and stereochemical restraint refinement of a protein crystal structure

1999 ◽  
Vol 32 (6) ◽  
pp. 1084-1089 ◽  
Author(s):  
R. B. Von Dreele
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Tertiary Structure ◽  
Protein Crystal ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Protein Crystal Structure

By combining high-resolution X-ray powder diffraction data and stereochemical restraints, Rietveld refinement of protein crystal structures has been shown to be feasible. A refinement of the 1261-atom protein metmyoglobin was achieved by combining 5338 stereochemical restraints with a 4648-step (dmin= 3.3 Å) powder diffraction pattern to give the residualsRwp= 2.32%,Rp= 1.66%,R(F2) = 3.10%. The resulting tertiary structure of the protein is essentially identical to that obtained from previous single-crystal studies.

Crystal structure determination of mebendazole form A using high‐resolution synchrotron x‐ray powder diffraction data

2010 ◽  
Vol 99 (4) ◽  
pp. 1734-1744 ◽  
Author(s):  
Fabio Furlan Ferreira ◽  
Selma Gutierrez Antonio ◽  
Paulo César Pires Rosa ◽  
Carlos de Oliveira Paiva‐Santos
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Crystal Structure Determination ◽  
Powder Diffraction Data ◽  
X Ray

Crystal and molecular structures of 2-[1-(2-aminoethyl)-2-imidazolidinylidene]-2-nitroacetonitrile (C7H11N5O2) and 2,6-diamino-5-hydroxy-3-nitro-4H-pyrazolo[1,5-a]pyrimidin-7-one monohydrate (C6H6N6O4·H2O) from X-ray, synchrotron and neutron powder diffraction data

1999 ◽  
Vol 55 (4) ◽  
pp. 554-562 ◽  
Author(s):  
V. V. Chernyshev ◽  
A. N. Fitch ◽  
E. J. Sonneveld ◽  
A. I. Kurbakov ◽  
V. A. Makarov ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Neutron Powder Diffraction ◽  
Molecular Structures ◽  
Search Procedure ◽  
Grid Search ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Crystal And Molecular Structures ◽  
Neutron Powder Diffraction Data

The crystal and molecular structures of 2-[1-(2-aminoethyl)-2-imidazolidinylidene]-2-nitroacetonitrile [C7H11N5O2; space group P21/n; Z = 4; a = 7.4889 (8), b = 17.273 (2), c = 7.4073 (8) Å, β = 111.937 (6)°], (I), and 2,6-diamino-5-hydroxy-3-nitro-4H-pyrazolo[1,5-a]pyrimidin-7-one monohydrate [C6H6N6O4·H2O; space group P21/n; Z = 4; a = 17.576 (3), b = 10.900 (2), c = 4.6738 (6) Å, β = 92.867 (8)°], (II), have been determined from X-ray, synchrotron and neutron powder diffraction data using various methods. The structures were originally solved from Guinier photographs with a grid search procedure and the program MRIA using a priori information from NMR and mass spectra on the possible geometry of the molecules. Because the conformation of molecule (I) changed during the bond-restrained Rietveld refinement, solvent water was found in (II) and, moreover, as both Guinier patterns were corrupted by texture, high-resolution texture-free synchrotron data were collected at the BM16 beamline, ESRF, to confirm the original results. Using the set of |F| 2 values derived from the synchrotron patterns after full-pattern decomposition procedures, the structures of (I) and (II) were solved by direct methods via SHELXS96, SIRPOW.92 and POWSIM without any preliminary models of the molecules, and by Patterson search methods via DIRDIF96 and PATSEE with the use of rigid fragments from each of the molecules. The neutron patterns allowed (I) and (II) to be solved using the grid search procedure and correct initial models of the molecules including H atoms. The results obtained from powder patterns measured on different devices demonstrate the high level of reproducibility and reliability of various powder software and equipment, with a certain preference for synchrotron facilities.

A grid search procedure of positioning a known molecule in an unknown crystal structure with the use of powder diffraction data

1998 ◽  
Vol 213 (1) ◽  
pp. 1-3 ◽  
Author(s):  
V. V. Chernyshev ◽  
H. Schenk
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Neutron Powder Diffraction ◽  
Molecular Structures ◽  
Search Procedure ◽  
Grid Search ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data

AbstractAn efficient grid search procedure successfully applied to the solution of three unknown molecular structures from X-ray and neutron powder diffraction data is presented.

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