Determination of nitroxide spin label conformations via PELDOR and X-ray crystallography

2016 ◽  
Vol 18 (15) ◽  
pp. 10428-10437 ◽  
Author(s):  
D. Abdullin ◽  
G. Hagelueken ◽  
O. Schiemann
Keyword(s):  
Spin Label ◽  
Nitroxide Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Position And Orientation ◽  
Good Agreement

PELDOR is used to unravel the position and orientation of MTSSL in six singly-labelled azurin mutants. A comparison with X-ray structures of the mutants shows good agreement with respect to the position and orientation of the nitroxide group.

scholarly journals The influence of exocyclic lone pairs on the bonding and geometry of type A mesoionic rings

2021 ◽  
Author(s):  
Christopher Antony Ramsden ◽  
Wojciech Piotr Oziminski
Keyword(s):  
Ab Initio ◽  
Type A ◽  
Nbo Analysis ◽  
Ring Systems ◽  
X Ray ◽  
X Ray Crystallography ◽  
Bond Model ◽  
Lone Pairs ◽  
Mp2 Calculations ◽  
Good Agreement

AbstractBased on structures determined by X-ray crystallography, ab initio MP2 calculations on type A mesoionic rings give geometries in good agreement with observed values. A study of four mesoionic ring systems, each with exocyclic oxygen, nitrogen or carbon groups, shows that the presence and configuration of exocyclic lone pairs significantly influences the geometry and configurational preference. Using a localised bond model and NBO analysis, these effects are rationalised in terms of an anomeric interaction of lone pairs with the antibonding orbitals of adjacent σ bonds. In agreement with experiment, similar effects are calculated for pyran-2-imines.

Synthesis of enantiopure 2-aryl-2-methoxypropionic acids and determination of their absolute configurations by X-ray crystallography

Chirality ◽  
2008 ◽  
Vol 20 (3-4) ◽  
pp. 251-264 ◽  
Author(s):  
Satoshi Sekiguchi ◽  
Junpei Naito ◽  
Hiromi Taji ◽  
Yusuke Kasai ◽  
Akinori Sugio ◽  
...  
Keyword(s):  
X Ray ◽  
X Ray Crystallography

scholarly journals Unraveling the long-pursued Au144 structure by x-ray crystallography

2018 ◽  
Vol 4 (10) ◽  
pp. eaat7259 ◽  
Author(s):  
Nan Yan ◽  
Nan Xia ◽  
Lingwen Liao ◽  
Min Zhu ◽  
Fengming Jin ◽  
...  
Keyword(s):  
Metal Nanoparticles ◽  
Weak Interactions ◽  
Gold Nanoclusters ◽  
Atomic Level ◽  
High Quality ◽  
X Ray ◽  
X Ray Crystallography ◽  
Quantum Size ◽  
First Time

The transition from nanocluster to nanocrystal is a central issue in nanoscience. The atomic structure determination of metal nanoparticles in the transition size range is challenging and particularly important in understanding the quantum size effect at the atomic level. On the basis of the rationale that the intra- and interparticle weak interactions play critical roles in growing high-quality single crystals of metal nanoparticles, we have reproducibly obtained ideal crystals of Au144(SR)60 and successfully solved its structure by x-ray crystallography (XRC); this structure was theoretically predicted a decade ago and has long been pursued experimentally but without success until now. Here, XRC reveals an interesting Au12 hollow icosahedron in thiolated gold nanoclusters for the first time. The Au–Au bond length, close to that of bulk gold, shows better thermal extensibility than the other Au–Au bond lengths in Au144(SR)60, providing an atomic-level perspective because metal generally shows better thermal extensibility than nonmetal materials. Thus, our work not only reveals the mysterious, long experimentally pursued structure of a transition-sized nanoparticle but also has important implications for the growth of high-quality, single-crystal nanoparticles, as well as for the understanding of the thermal extensibility of metals from the perspective of chemical bonding.

ChemInform Abstract: Synthesis of cis-1-((2-Hydroxymethyl)cyclopentyl)uracil and Determination of Its Conformation by X-Ray Crystallography and AM1 Theoretical Calculations.

ChemInform ◽  
2010 ◽  
Vol 27 (43) ◽  
pp. no-no
Author(s):  
L. SANTANA ◽  
M. TEIJEIRA ◽  
E. URIARTE ◽  
C. TERAN ◽  
U. CASELLATO ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
X Ray ◽  
X Ray Crystallography

scholarly journals Characterization of reactive organometallic species via MicroED

2019 ◽  
Author(s):  
Christopher Jones ◽  
Matthew Asay ◽  
Lee Joon Kim ◽  
Jack Kleinsasser ◽  
Ambarneil Saha ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Cryogenic Cooling ◽  
Structural Determination ◽  
X Ray ◽  
X Ray Crystallography ◽  
Diamagnetic Transition

Here we apply microcrystal electron diffraction (MicroED) to the structural determination of transition metal complexes. We find that the simultaneous use of 300 keV electrons, very low electron doses, and an ultra-sensitive camera allows for the collection of data without cryogenic cooling of the stage. This technique reveals the first crystal structures of the classic zirconocene hydride, colloquially known as “Schwartz’s reagent”, a novel Pd(II) complex not amenable to solution-state NMR or X-ray crystallography, and five other paramagnetic or diamagnetic transition metal complexes.

scholarly journals NMR and X-ray studies of apetalic acid isolated from Calophyllum brasiliense and of its chiral amides

2021 ◽  
Author(s):  
Marie-Rose Van Calsteren ◽  
Ricardo Reyes-Chilpa ◽  
Chistopher K Jankowski ◽  
Fleur Gagnon ◽  
Simón Hernández-Ortega ◽  
...  
Keyword(s):  
Antimycobacterial Activity ◽  
Side Chain ◽  
Carboxyl Group ◽  
X Ray Diffraction ◽  
Rain Forests ◽  
X Ray ◽  
X Ray Crystallography ◽  
Calophyllum Brasiliense ◽  
Derivatives Of

The tropical tree Calophyllum brasiliense (Clusiaceae) grows in the rain forests from Brazil to Mexico. Its leaves, as well as those of other Calophyllum species, are rich sources of chromanone acids, such as apetalic acid, isoapetalic acid, and their derivatives. Apetalic acid has shown significant antimycobacterial activity. The biological activity of apetalic acid has been related to the configuration of three asymmetric centers and the stereochemistry of the molecule; however, the C-19 configuration in the acidic side chain has not been fully resolved. For this reason, the unequivocal determination of the absolute configuration by means of X-ray crystallography in a sample of unique homogeneous apetalic acid stereoisomer was the most important point to start this study. We prepared some chiral amides using the carboxyl group. We determined the C-19 stereochemistry of apetalic acid, and its specific chiral derivatives, using NMR, X-ray diffraction methods, and molecular mechanics. Finally, we observed that steric hindrance in the side chain of apetalic acid leads to restriction of rotation around the pivotal link C-10 and C-19 establishing chiral centers at C2(R), C3(S), and C19(R). We were able to separate derivatives of these two high-rotatory-barrier conformers of apetalic acid by forming diastereoisomeric amides with phenylglycine methyl ester having a chiral center at C-2’. Our results allowed the conclusion of the existence of atropisomerism in the apetalic acid molecule.

Studies on the surface area of zeolites, as determined by physical adsorption and X-ray crystallography

1968 ◽  
Vol 46 (10) ◽  
pp. 1695-1701 ◽  
Author(s):  
D. J. C. Yates
Keyword(s):  
Surface Area ◽  
Physical Adsorption ◽  
Independent Method ◽  
Linear Portion ◽  
Adsorbed Molecules ◽  
X Ray ◽  
X Ray Crystallography ◽  
Surface Areas

The determination of the surface areas of zeolites is discussed. It is shown that it is incorrect to use the multilayer isotherm method of Brunauer, Emmett, and Teller for solids where only little more than one monolayer can be adsorbed, in cavities little larger than the adsorbed molecules. The areas of such materials can, however, be determined from the beginning of the linear portion of their isotherms (point B). In addition, X-ray spectra can provide an independent method of measuring changes in the surface areas of zeolites.

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