X-ray Crystallographic Structures as a Source of Ligand Alignment in 3D-QSAR

2013 ◽  
Vol 53 (6) ◽  
pp. 1406-1414 ◽  
Author(s):  
Rafał D. Urniaż ◽  
Krzysztof Jóźwiak
Keyword(s):  
3D Qsar ◽  
X Ray ◽  
Crystallographic Structures ◽  
Ligand Alignment

Microstructure of Zr-25at. %Al Melt Spun Ribbons.

1994 ◽  
Vol 364 ◽  
Author(s):  
L. Lutterotti ◽  
S. K. Pradhan ◽  
S. Gialanella ◽  
A. R. Yavari
Keyword(s):  
Phase Diagram ◽  
Intermetallic Phases ◽  
X Ray Diffraction ◽  
Major Phase ◽  
X Ray ◽  
Metastable Structures ◽  
Melt Spun ◽  
Crystallographic Structures ◽  
Melt Spun Ribbons

AbstractFollowing a previous study in which we presented some microstructural aspects of meltspun ribbons having a composition close to Zr-25 at.% Al, we discuss now the crystallography of the phases observed in similar samples. We performed X-Ray diffraction analyses of ribbons and refined the observed crystallographic structures. We could identify a number of stable and metastable structures, according to the actual composition of the ribbons. We also estimated the percentage of each one of these phases. We did the same for some ribbons annealed at 750°C for several times. In this way we could follow the kinetics leading from the initial as-spun condition to the final one, featuring the L12 ordered Zr3Al, as the major phase, and other intermetallic phases of the Zr-Al phase diagram.

scholarly journals Mechanism of IPPase shown by high resolution Neutron and X-ray crystallography

2014 ◽  
Vol 70 (a1) ◽  
pp. C1211-C1211
Author(s):  
Joseph Ng ◽  
Ronny Hughes ◽  
Michelle Morris ◽  
Leighton Coates ◽  
Matthew Blakeley ◽  
...  
Keyword(s):  
High Resolution ◽  
Active Site ◽  
Inorganic Pyrophosphatase ◽  
Inorganic Pyrophosphate ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cellular Processes ◽  
Crystallographic Structures ◽  
Hydrolysis Of ◽  
Low Energy Conformations

Soluble inorganic pyrophosphatase (IPPase) catalyzes the hydrolysis of inorganic pyrophosphate (PPi) to form orthophosphate (Pi). The action of this enzyme shifts the overall equilibrium in favor of synthesis during a number of ATP-dependent cellular processes such as in the polymerization of nucleic acids, production of coenzymes and proteins and sulfate assimilation pathways. Two Neutron crystallographic (2.10-2.50Å) and five high-resolution X-ray (0.99Å-1.92Å) structures of the archaeal IPPase from Thermococcus thioreducens have been determined under both cryo and room temperatures. The structures determined include the recombinant IPPase bound to Mg+2, Ca+2, Br-, SO2-2 or PO4-2 involving those with non-hydrolyzed and hydrolyzed pyrophosphate complexes. All the crystallographic structures provide snapshots of the active site corresponding to different stages of the hydrolysis of inorganic pyrophosphate. As a result, a structure-based model of IPPase catalysis is devised showing the enzyme's low-energy conformations, hydration states, movements and nucleophile generation within the active site.

Crystallochemistry and structural studies of two newly CaSb0.50Fe1.50(PO4)3 and Ca0.50SbFe(PO4)3 Nasicon phases

2006 ◽  
Vol 21 (1) ◽  
pp. 45-51 ◽  
Author(s):  
Abderrahim Aatiq ◽  
My Rachid Tigha ◽  
Rabia Hassine ◽  
Ismael Saadoune
Keyword(s):  
Solid State ◽  
Room Temperature ◽  
Rietveld Analysis ◽  
Structural Studies ◽  
Hexagonal Cell ◽  
Conventional Solid State Reaction ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Crystallographic Structures

Crystallographic structures of two new orthophosphates Ca0.50SbFe(PO4)3 and CaSb0.50Fe1.50(PO4)3 obtained by conventional solid state reaction techniques at 900 °C, were determined at room temperature from X-ray powder diffraction using Rietveld analysis. The two compounds belong to the Nasicon structural family. The space group is R3 for Ca0.50SbFe(PO4)3 and R3c for CaSb0.50Fe1.50(PO4)3. Hexagonal cell parameters for Ca0.50SbFe(PO4)3 and CaSb0.50Fe1.50(PO4)3 are: a=8.257(1) Å, c=22.276(2) Å, and a=8.514(1) Å, c=21.871(2) Å, respectively. Ca2+ and vacancies in {[Ca0.50]3a[◻0.50]3b}M1SbFe(PO4)3 are ordered within the two positions, 3a and 3b, of M1 sites. Structure refinements show also a quasi-ordered distribution of Sb5+ and Fe3+ ions within the Nasicon framework. Thus, in {[Ca0.50]3a[◻0.50]3b}M1SbFe(PO4)3, each Ca(3a)O6 octahedron shares two faces with two Fe3+O6 octahedra and each vacancy (◻(3b)O6) site is located between two Sb5+O6 octahedra. In [Ca]M1Sb0.50Fe1.50(PO4)3 compound (R3c space group), all M1 sites are occupied by Ca2+ and the Sb5+ and Fe3+ ions are randomly distributed within the Nasicon framework.

scholarly journals Comparison of zwitterionic N-alkylaminomethanesulfonic acids to related compounds in the Good buffer series

2010 ◽  
Vol 6 ◽  
Author(s):  
Robert D Long ◽  
Newton P Hilliard ◽  
Suneel A Chhatre ◽  
Tatiana V Timofeeva ◽  
Andrey A Yakovenko ◽  
...  
Keyword(s):  
Sulfonic Acid ◽  
Aqueous Solubility ◽  
Carbon Chain ◽  
Secondary Amines ◽  
Ammonium Ion ◽  
X Ray ◽  
Crystallographic Structures ◽  
Related Compounds ◽  
Sulfonic Acid Groups ◽  
Biological Buffers

Several N-alkyl and N,N-dialkylaminomethanesulfonic acids were synthesized (as zwitterions and/or sodium salts) to be tested for utility as biological buffers at lower pH levels than existing Good buffer compounds (aminoalkanesulfonates with a minimum of two carbons between amine and sulfonic acid groups as originally described by Norman Good, and in common use as biological buffers). Our hypothesis was that a shorter carbon chain (one carbon) between the amino and sulfonic acid groups should lower the ammonium ion pK a values. The alkylaminomethanesulfonate compounds were synthesized in aqueous solution by reaction of primary or secondary amines with formaldehyde/sodium hydrogensulfite addition compound. The pK a values of the ammonium ions of this series of compounds (compared to existing Good buffers) was found to correlate well with the length of the carbon chain between the amino and sulfonate moeties, with a significant decrease in amine basicity in the aminomethanesulfonate compounds (pK a decrease of 2 units or more compared to existing Good buffers). An exception was found for the 2-hydroxypiperazine series which shows only a small pK a decrease, probably due to the site of protonation in this compound (as confirmed by X-ray crystal structure). X-ray crystallographic structures of two members of the series are reported. Several of these compounds have pK a values that would indicate potential utility for buffering at pH levels below the normal physiological range (pK a values in the range of 3 to 6 without aqueous solubility problems) – a range that is problematic for currently available Good buffers. Unfortunately, the alkylaminomethanesulfonates were found to degrade (with loss of their buffering ability) at pH levels below the pK a value and were unstable at elevated temperature (as when autoclaving) – thus limiting their utility.

Discovery of novel inhibitors for DHODH via virtual screening and X-ray crystallographic structures

2010 ◽  
Vol 20 (6) ◽  
pp. 1981-1984 ◽  
Author(s):  
Larry R. McLean ◽  
Ying Zhang ◽  
William Degnen ◽  
Jane Peppard ◽  
Dasha Cabel ◽  
...  
Keyword(s):  
Virtual Screening ◽  
X Ray ◽  
Crystallographic Structures
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