The stereochemistry of the stable conformational diastereomers in substituted dihydrodibenzo[ef,kl]heptalenes, the doubly bridged biphenyls. Synthesis, structural elucidation and barrier to conformational diastereomerismElectronic supplementary information (ESI) available: Tables I–III comparing X-ray structural data for 2Aendo–exo, 1Aendo–exo and 1Aexo–exo with AM1 calculations. See http://www.rsc.org/suppdata/p2/b1/b109336n/

2002 ◽  
pp. 545-551 ◽  
Author(s):  
Parviz Rashidi-Ranjbar ◽  
Ebrahim Kianmehr ◽  
Sue-Lein Wang ◽  
Fen-Ling Liao
Keyword(s):  
Structural Data ◽  
Structural Elucidation ◽  
Supplementary Information ◽  
Am1 Calculations ◽  
X Ray

Tubulin structure at intermediate resolution

1995 ◽  
Vol 53 ◽  
pp. 852-853
Author(s):  
K. H. Downing ◽  
S. G. Wolf ◽  
E. Nogales
Keyword(s):  
High Resolution ◽  
Structural Data ◽  
Therapeutic Drug ◽  
Zinc Ions ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Negative Stain ◽  
Functional Mechanisms ◽  
Tubulin Structure

Microtubules are involved in a host of critical cell activities, many of which involve transport of organelles through the cell. Different sets of microtubules appear to form during the cell cycle for different functions. Knowledge of the structure of tubulin will be necessary in order to understand the various functional mechanisms of microtubule assemble, disassembly, and interaction with other molecules, but tubulin has so far resisted crystallization for x-ray diffraction studies. Fortuitously, in the presence of zinc ions, tubulin also forms two-dimensional, crystalline sheets that are ideally suited for study by electron microscopy. We have refined procedures for forming the sheets and preparing them for EM, and have been able to obtain high-resolution structural data that sheds light on the formation and stabilization of microtubules, and even the interaction with a therapeutic drug.Tubulin sheets had been extensively studied in negative stain, demonstrating that the same protofilament structure was formed in the sheets and microtubules. For high resolution studies, we have found that the sheets embedded in either glucose or tannin diffract to around 3 Å.

Compressibility of β-As4S4: an in situ high-pressure single-crystal X-ray study

2012 ◽  
Vol 76 (4) ◽  
pp. 963-973 ◽  
Author(s):  
G. O. Lepore ◽  
T. Boffa Ballaran ◽  
F. Nestola ◽  
L. Bindi ◽  
D. Pasqual ◽  
...  
Keyword(s):  
Pressure Range ◽  
Substantial Reduction ◽  
Structural Data ◽  
Unit Cell ◽  
Van Der Waals Interactions ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Intermolecular Distances

AbstractAmbient temperature X-ray diffraction data were collected at different pressures from two crystals of β-As4S4, which were made by heating realgar under vacuum at 295ºC for 24 h. These data were used to calculate the unit-cell parameters at pressures up to 6.86 GPa. Above 2.86 GPa, it was only possible to make an approximate measurement of the unit-cell parameters. As expected for a crystal structure that contains molecular units held together by weak van der Waals interactions, β-As4S4 has an exceptionally high compressibility. The compressibility data were fitted to a third-order Birch–Murnaghan equation of state with a resulting volume V0 = 808.2(2) Å3, bulk modulus K0 = 10.9(2) GPa and K' = 8.9(3). These values are extremely close to those reported for the low-temperature polymorph of As4S4, realgar, which contains the same As4S4 cage-molecule. Structural analysis showed that the unit-cell contraction is due mainly to the reduction in intermolecular distances, which causes a substantial reduction in the unit-cell volume (∼21% at 6.86 GPa). The cage-like As4S4 molecules are only slightly affected. No phase transitions occur in the pressure range investigated.Micro-Raman spectra, collected across the entire pressure range, show that the peaks associated with As–As stretching have the greatest pressure dependence; the S–As–S bending frequency and the As–S stretching have a much weaker dependence or no variation at all as the pressure increases; this is in excellent agreement with the structural data.

Steric Parameters of Conformationally Flexible Ligands from X-ray Structural Data. 1. P(OR)3Ligands in Equivalent Ligand Environments

2000 ◽  
Vol 19 (25) ◽  
pp. 5273-5280 ◽  
Author(s):  
Jeremy M. Smith ◽  
Neil J. Coville ◽  
Leanne M. Cook ◽  
Jan C. A. Boeyens
Keyword(s):  
Structural Data ◽  
X Ray ◽  
Equivalent Ligand ◽  
Flexible Ligands

scholarly journals Purification, crystallization and preliminary X-ray diffraction analysis of a hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyltransferase (HCT) fromCoffea canephorainvolved in chlorogenic acid biosynthesis

2012 ◽  
Vol 68 (7) ◽  
pp. 824-828 ◽  
Author(s):  
Laura A. Lallemand ◽  
James G. McCarthy ◽  
Sean McSweeney ◽  
Andrew A. McCarthy
Keyword(s):  
Structural Data ◽  
Coffea Canephora ◽  
Molecular Replacement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Key Enzyme ◽  
Substrate Specifities ◽  
Drop Technique ◽  
Better Than

Chlorogenic acids (CGAs) are a group of soluble phenolic compounds that are produced by a variety of plants, includingCoffea canephora(robusta coffee). The last step in CGA biosynthesis is generally catalysed by a specific hydroxycinnamoyl-CoA quinate hydroxycinnamoyltransferase (HQT), but it can also be catalysed by the more widely distributed hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyltransferase (HCT). Here, the cloning and overexpression of HCT fromC. canephorainEscherichia colias well as its purification and crystallization are presented. Crystals were obtained by the sitting-drop technique at 293 K and X-ray diffraction data were collected on the microfocus beamline ID23-2 at the ESRF. The HCT crystals diffracted to better than 3.0 Å resolution, belonged to space groupP42212 with unit-cell parametersa=b= 116.1,c= 158.9 Å and contained two molecules in the asymmetric unit. The structure was solved by molecular replacement and is currently under refinement. Such structural data are needed to decipher the molecular basis of the substrate specifities of this key enzyme, which belongs to the large plant acyl-CoA-dependent BAHD acyltransferase superfamily.

A EuIIITetrakis(β-diketonate) Dimeric Complex: Photophysical Properties, Structural Elucidation by Sparkle/AM1 Calculations, and Doping into PMMA Films and Nanowires

2014 ◽  
Vol 53 (16) ◽  
pp. 8407-8417 ◽  
Author(s):  
Silvanose Biju ◽  
Ricardo O. Freire ◽  
Yu Kyung Eom ◽  
Rosario Scopelliti ◽  
Jean-Claude G. Bünzli ◽  
...  
Keyword(s):  
Photophysical Properties ◽  
Structural Elucidation ◽  
Am1 Calculations ◽  
Dimeric Complex

Isolation and structure of combretastatin

1982 ◽  
Vol 60 (11) ◽  
pp. 1374-1376 ◽  
Author(s):  
George R. Pettit ◽  
Gordon M. Cragg ◽  
Delbert L. Herald ◽  
Jean M. Schmidt ◽  
Prasert Lohavanijaya
Keyword(s):  
Total Synthesis ◽  
South African ◽  
Spectral Methods ◽  
Biological Evaluation ◽  
Crystallographic Analysis ◽  
Structural Elucidation ◽  
The South ◽  
X Ray

The South African tree Combretumcaffrum has been shown to contain a constituent capable of significantly reversing astrocyte formation employing the National Cancer Institute's 9ASK system. The constituent responsible for astrocyte reversal was isolated and designated combretastatin (1). Structural elucidation was initiated employing spectral methods and completed by X-ray crystallographic analysis. By this means combretastatin was assigned structure 1. Further biological evaluation and a total synthesis are now in progress.

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