ChemInform Abstract: Evidence for the exo-Anomeric Stereoelectronic Effect in Cyclic Orthoester Aminals from X-Ray Structural Data. Crystal Structures of Three 2-Amino-1,3-oxazolidin-4-one Derivatives

ChemInform ◽  
2010 ◽  
Vol 22 (11) ◽  
pp. no-no
Author(s):  
V. BERTOLASI ◽  
V. FERRETTI ◽  
G. GILLI ◽  
P. MARCHETTI ◽  
F. D'ANGELI
Keyword(s):  
Crystal Structures ◽  
Structural Data ◽  
X Ray ◽  
Stereoelectronic Effect

scholarly journals Photoreduction and validation of haem–ligand intermediate states in protein crystals byin situsingle-crystal spectroscopy and diffraction

IUCrJ ◽  
2017 ◽  
Vol 4 (3) ◽  
pp. 263-270 ◽  
Author(s):  
Demet Kekilli ◽  
Tadeo Moreno-Chicano ◽  
Amanda K. Chaplin ◽  
Sam Horrell ◽  
Florian S. N. Dworkowski ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Structural Data ◽  
X Rays ◽  
Solvated Electrons ◽  
X Ray ◽  
Redox States ◽  
Density Maps ◽  
Correct Assignment ◽  
Wide Range

Powerful synergies are available from the combination of multiple methods to study proteins in the crystalline form. Spectroscopies which probe the same region of the crystal from which X-ray crystal structures are determined can give insights into redox, ligand and spin states to complement the information gained from the electron-density maps. The correct assignment of crystal structures to the correct protein redox and ligand states is essential to avoid the misinterpretation of structural data. This is a particular concern for haem proteins, which can occupy a wide range of redox states and are exquisitely sensitive to becoming reduced by solvated electrons generated from interactions of X-rays with water molecules in the crystal. Here, single-crystal spectroscopic fingerprinting has been applied to investigate the laser photoreduction of ferric haem in cytochromec′. Furthermore,in situX-ray-driven generation of haem intermediates in crystals of the dye-decolourizing-type peroxidase A (DtpA) fromStreptomyces lividansis described.

The nitration of 3,4,5-tribromo-2,6-dimethylphenol; X-ray crystal structures of C 2-epimeric 3,4,5-tribromo-6-hydroxy-2,6-dimethyl-2,5-dinitrocyclohex-3-enones ;an unusual isomerization reaction

1982 ◽  
Vol 35 (11) ◽  
pp. 2229 ◽  
Author(s):  
AM Chittenden ◽  
MP Hartshorn ◽  
KE Richards ◽  
WT Robinson ◽  
KH Sutton ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Nitric Acid ◽  
Single Crystal ◽  
Crystal Structures ◽  
Structural Data ◽  
Isomerization Reaction ◽  
X Ray ◽  
Fuming Nitric Acid

Nitration of 3,4,5-tribromo-2,6-dimethylphenol (10) with fuming nitric acid in acetic acid gives the C2-epimeric 2,5-dinitrocyclohex-3-enones (11) and (12), the structures of which were determined by single-crystal X-ray analyses. Some implications of these structural data are discussed.

Zur Stereochemie des freien Elektronenpaares in AX6E-Systemen, VIII. Statisch verzerrte Anionen in [H3N(CH2)3NH3]3(BiX6)2(H2O)2 mit X = Cl, Br/ On the Stereochemistry of the Lone-Pair Electrons in AX6E-Systems, VIII Statically Distorted Anion in [H3N(CH2)3NH3]3(BiX6)2(H2O)2 with X = Cl, Br

1988 ◽  
Vol 43 (8) ◽  
pp. 1003-1009 ◽  
Author(s):  
André du Bois ◽  
Walter Abriel
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Coordination Polyhedron ◽  
Lone Pair ◽  
Structural Data ◽  
Octahedral Coordination ◽  
Intensity Data ◽  
Space Group ◽  
X Ray ◽  
Lone Pair Electrons

Abstract Using 293 K diffractometer intensity data, the crystal structures of [H3N(CH2)3NH3]3(BiX6)2(H2O)2 with X - Cl, Br have been determined by single crystal X-ray technique and refined to a final Rw of 0.027 and 0.043, respectively. The structures are isotypic, space group P21/c, Z = 2 with a = 14.415(1). b = 9.7401(7), c = 12.4609(9)Å, β = 105.997(8)°for X - Cl and a = 14.794(2), b = 10.127(2), c = 12.853(2)Å, β = 105.68(2)° for X - Br. Statically distorted BiX63- octahedra confirm the symmetry rules for the stereochemistry of the lone pair electrons in AX6E-systems. Basic structural data for all compounds containing BiX63- and SbXh3 ions (X = Cl, Br, I) known to date are given including the ⊿-values as a measure for the distortion of the octahedral coordination polyhedron.

X-ray structures and luminescence properties of Co(II) and Co(III) complexes of cofacial diporphyrins

2003 ◽  
Vol 07 (07) ◽  
pp. 474-483 ◽  
Author(s):  
Frédéric Bolze ◽  
Marc Drouin ◽  
Pierre D. Harvey ◽  
Claude P. Gros ◽  
Enrique Espinosa ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Structural Data ◽  
Previous Literature ◽  
The Other ◽  
Luminescence Properties ◽  
X Ray ◽  
Face To Face ◽  
Other Hand

The crystal structures of two face-to-face diporphyrin compounds based upon the DPA ligand (1,8-bis(5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethyl-porphyrinyl))anthracene), i.e. H 4( DPA ) and ( DPA ) Co 2 are reported. The structural data are compared to that of other bimetallic DPA systems, and diporphyrinic Co complexes. In addition, the luminescence properties of ( OEP ) Co ( OEP = 2,3,7,8,12,13,17,18-octaethylporphyrin), H 2( DPA ) Co , H 2( DPA )( CoIm ) O 2, ( DPA ) Co 2, ( DPA )( CoIm )2 O 2 are reported, where Im is 1-t-butyl-5-phenyl imidazole. Contrary to previous literature reports, the Co (II) species are found to be weakly luminescent, where fluorescence is detected for both the mono- and diporphyrinic systems, and is assigned to emissions arising from the lowest 1 Q (ππ*) states, while phosphorescence is detected at 77 K only for the monoporphyrin species, ( OEP ) Co . On the other hand, the Co (III) complexes are not luminescent.

Transmission electron microscope studies in special ceramics

1978 ◽  
Vol 36 (1) ◽  
pp. 268-269
Author(s):  
A. Zangvil ◽  
L.J. Gauckler ◽  
G. Schneider ◽  
M. Rühle
Keyword(s):  
Phase Diagrams ◽  
Crystal Structures ◽  
Thin Foil ◽  
Limited Extent ◽  
Complex Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Lattice Resolution

The use of high temperature special ceramics which are usually complex materials based on oxides, nitrides, carbides and borides of silicon and aluminum, is critically dependent on their thermomechanical and other physical properties. The investigations of the phase diagrams, crystal structures and microstructural features are essential for better understanding of the macro-properties. Phase diagrams and crystal structures have been studied mainly by X-ray diffraction (XRD). Transmission electron microscopy (TEM) has contributed to this field to a very limited extent; it has been used more extensively in the study of microstructure, phase transformations and lattice defects. Often only TEM can give solutions to numerous problems in the above fields, since the various phases exist in extremely fine grains and subgrain structures; single crystals of appreciable size are often not available. Examples with some of our experimental results from two multicomponent systems are presented here. The standard ion thinning technique was used for the preparation of thin foil samples, which were then investigated with JEOL 200A and Siemens ELMISKOP 102 (for the lattice resolution work) electron microscopes.

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.

Crystal Structures of Fragments D and Double-D from Fibrinogen and Fibrin

1999 ◽  
Vol 82 (08) ◽  
pp. 271-276 ◽  
Author(s):  
Glen Spraggon ◽  
Stephen Everse ◽  
Russell Doolittle
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Crystal Structures ◽  
Structure And Function ◽  
X Ray ◽  
Long Period ◽  
And Function

IntroductionAfter a long period of anticipation,1 the last two years have witnessed the first high-resolution x-ray structures of fragments from fibrinogen and fibrin.2-7 The results confirmed many aspects of fibrinogen structure and function that had previously been inferred from electron microscopy and biochemistry and revealed some unexpected features. Several matters have remained stubbornly unsettled, however, and much more work remains to be done. Here, we review several of the most significant findings that have accompanied the new x-ray structures and discuss some of the problems of the fibrinogen-fibrin conversion that remain unresolved. * Abbreviations: GPR—Gly-Pro-Arg-derivatives; GPRPam—Gly-Pro-Arg-Pro-amide; GHRPam—Gly-His-Arg-Pro-amide

Synthesis of Sulfoquinovose and Sulfoquinovosyl Diacylglycerides, and a Fluorogenic Substrate for Sulfoquinovosidases

2019 ◽  
Author(s):  
Yunyang Zhang ◽  
Janice Mui ◽  
Thimali Arumaperuma ◽  
James P. Lingford ◽  
ETHAN GODDARD-BORGER ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Fluorogenic Substrate ◽  
Potassium Salts ◽  
X Ray ◽  
Sulfoquinovosyl Diacylglycerol ◽  
Sodium And Potassium

<p>The sulfolipid sulfoquinovosyl diacylglycerol (SQDG) and its headgroup, the sulfosugar sulfoquinovose (SQ), are estimated to harbour up to half of all organosulfur in the biosphere. SQ is liberated from SQDG and related glycosides by the action of sulfoquinovosidases (SQases). We report a 10-step synthesis of SQDG that we apply to the preparation of saturated and unsaturated lipoforms. We also report an expeditious synthesis of SQ and (<sup>13</sup>C<sub>6</sub>)SQ, and X-ray crystal structures of sodium and potassium salts of SQ. Finally, we report the synthesis of a fluorogenic SQase substrate, methylumbelliferyl a-D-sulfoquinovoside, and examination of its cleavage kinetics by two recombinant SQases.</p>

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