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X-ray Study (x-ray + study)
Kinds of X-ray Study Selected AbstractsThe Network Structure [SbHg2]GaCl4: An X-Ray Study of a Temperature Driven Phase Transition.CHEMINFORM, Issue 35 2007J. Schlirf Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] XAS, ESR and Potentiometric Studies of Three Dinuclear N,N, -para -Xylylenebis(tetraazamacrocycle)copper(II) Complexes , X-ray Crystal Structure of [N,N,- p -Xylylenebis(cyclen)]copper(II)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2003Mathieu Soibinet Abstract Dicopper complexes with N,N, - p -xylylenebis(cyclam or cyclen) and with the heteroditopic N,N, - p -xylylenebis(cyclam-cyclen) were synthesized. An X-ray study of the N,N, - p -xylylenebis(cyclen)dicopper complex showed that the copper(II) ion is five-coordinate with an H2O molecule in apical position. With this ligand, a polymeric chain was also obtained in the presence of KSCN. The terminal donor atoms of the bridging NCS, anion are coordinated in apical position to the square-pyramidal copper(II) ion. Two alternating kinds of Cu2L4+ moieties are present in the chain, the first with two N4S chromophores and the second with two N5 chromophores. EXAFS and XANES results are in agreement with a five-coordinate copper ion in the cyclen unit and a six-coordinate copper ion in the cyclam unit. Thermodynamic constants were determined by potentiometry. The existence of dinuclear Cu2L4+ species (ligand/metal ratio < 1) and mononuclear CuLHn(2+n)+ species (ligand/metal ratio > 1) were confirmed by an ESR study at variable pH. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Successful treatment of extensive muscle calcification in a patient with primary idiopathic polymyositis with diltiazemINTERNATIONAL JOURNAL OF RHEUMATIC DISEASES, Issue 3 2006Yasser EMAD Abstract A 25-year-old female patient with documented diagnosis of polymyositis developed extensive muscle calcification in the left thigh muscles with overlying skin induration one year after her disease onset, despite well controlled myositis. Plain X-ray of the left femur and hip revealed extensive calcification involving the periarticular soft tissue shadows around the left hip and left upper thigh. The patient received diltiazem 90 mg/day in divided doses and follow-up plain X-ray study after 6 months of treatment revealed almost complete resolution of the muscle calcifications. [source] X-ray study of the light-induced metastable state of a spin-crossover compoundJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2000Joachim Kusz Iron(II) complexes exhibiting thermal spin crossover may be converted from the 1A1 low-spin (LS) state to the 5T2 high-spin (HS) state by irradiation with green light (light-induced excited spin-state trapping, LIESST). The lifetime of the metastable LIESST state may be sufficiently long for X-ray diffraction study. The lattice parameters of a single crystal of [Fe(ptz)6](BF4)2 (ptz = propyltetrazole) were measured between 300 and 10,K, while the crystal changed from the HS to the LS state near 135,K. Using the green light (514,nm) of an argon-ion laser, the crystal was quantitatively converted to the metastable LIESST state at 10,K; its lattice parameters were measured up to 50,K, at which point the LIESST state begins to decay on a minute timescale. The change of the lattice parameters can be interpreted by a superposition of a normal temperature dependence, for which the isostructural zinc compound served as a reference, and an almost temperature-independent part which is proportional to the fraction of molecules in the HS state. [source] Single crystal X-ray study of the modulated structure in Ga2XTe3 with the defect zinc-blende structurePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2009S. Kashida Abstract Ga2Te3 crystallizes into the zinc-blende structure, where one third of the cation sites is vacant. Single crystal X-ray diffraction studies on quenched and annealed Ga2Te3 and CuGaTe2 crystals are reported. The obtained diffraction maps show, other than the zinc-blende type main reflections, satellite reflections at q1,1/17[110]c in quenched Ga2Te3 crystals and q2,1/20[210]c in annealed Ga2Te3 crystals, where the subscript c means the cubic sub-lattice. The analysis of the satellite reflections shows that the modulation is two dimensional, and is ascribed to a coupled mode of the amplitude type modulation caused by Ga vacancies and the displacive modulation of surrounding Te atoms, which has the polarization vector along the <001>c direction. The nature of the atomic modulations is discussed and the origin of the modulation is ascribed to Jahn-Teller type distortions around Ga vacancies. The experiments done on CuGaTe2 crystals indicate that the cation disorder compound sphalerite type CuGaTe2 contain the same modulated structure as Ga2Te3 crystals, but the cation ordered compound chalcopyrite type CuGaTe2 does not show the modulation. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Experimental charge-density study of paracetamol , multipole refinement in the presence of a disordered methyl groupACTA CRYSTALLOGRAPHICA SECTION A, Issue 6 2009Joanna M. B A high-resolution single-crystal X-ray study of paracetamol has been performed at 85,K. Different approaches to modeling the experimental electron density (ED) were tested for the dynamically disordered portions of the molecule in order to check to what extent it is possible to obtain a proper ED distribution in the ordered part. Models were examined in which the methyl-group ED was built from pseudoatoms taken from the University at Buffalo Pseudoatom Databank or the Invariom database, with multipole parameters for the remaining atoms being obtained from free refinement. The ,, restricted multipolar model (KRMM) and free ,, refinements were compared; restriction of the ,, parameters was essential in order to obtain values of the electrostatic interaction energy consistent with the results of theoretical single-point periodic calculations. After simultaneous use of KRMM refinement and the databases to model the methyl group, the bond critical point properties and interaction electrostatic energy values were found to be closer to those obtained from theory. Additionally, some discrepancies in the ED distribution and dipole moment among transferred aspherical atom model refinements utilizing both theoretical databases and parameters from theoretical periodic calculations are shown. Including the influence of the crystal field in the periodic calculations increases the ED in the hydroxyl and amide groups, thus leading to higher values of the electrostatic interaction energy, changes in the electrostatic potential values mapped on the isodensity surface and changes in the shape of the anisotropic displacement parameters with respect to results found for both database models. [source] Cation movement and phase transitions in KTP isostructures; X-ray study of sodium-doped KTP at 10.5,KACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2003Stefan T. Norberg An accurate structure model of sodium-doped potassium titanyl phosphate, (Na0.114K0.886)K(TiO)2(PO4)2, has been determined at 10.5,K by single-crystal X-ray diffraction. In addition to the low-temperature data, X-ray intensities have been collected at room temperature. When the temperature was decreased from room temperature to 10.5,K, both potassium cations moved 0.033,(2),Å along the c -axis, i.e. in the polar direction within the rigid Ti,O,P network. This alkaline metal ion displacement can be related to the Abrahams,Jamieson,Kurtz TC criteria for oxygen framework ferroelectrics. Potassium titanyl phosphate (KTP) is a well known material for second harmonic generation (SHG), and the influence of sodium dopant on the TiO6 octahedral geometry and SHG is discussed. The material studied crystallizes in the space group Pna21 with Z = 4, a = 12.7919,(5), b = 6.3798,(4), c = 10.5880,(7),Å, V = 864.08,(9),Å3, T = 10.5,(3),K and R = 0.023. [source] X-ray study and structure simulation of amorphous tungsten oxideACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2002L. A. Lugovskaya In this work, X-ray studies of the amorphous oxide films obtained by thermal evaporation of WO3 powder in a vacuum and by anodic oxidation were carried out. X-ray diffraction patterns were obtained in the symmetric reflection geometry on a DRON-4 diffractometer (Mo K, radiation, LiF monochromator) in automatic mode. Molecular dynamics simulation of amorphous tungsten oxide atomic configurations has been carried out in the micro-canonical ensemble (NVE) for N,=,208 atoms and N,=,624 atoms, in a cubic cell, using pairwise Born,Mayer interaction potentials and periodic boundary conditions. One of the purposes of the present work is to analyze the influence of the parameters and the cutoff of the interaction potentials on the interatomic distances. The values obtained in the molecular dynamics simulation for the pair functions D(r) are compared with the experimental data for amorphous oxides in order to choose the most convenient aforesaid values. The values of the average interatomic distances and the coordination numbers obtained by both methods are also compared. The result shows that the tungsten subsystem can be well reproduced using the potential cutoff radius of about 4,Å, but the oxygen subsystem can be well reproduced when the cutoff of the potential for the W,O pairs is equal to 2.8,Å. The configuration built during the molecular dynamics experiment consists of distorted octahedra. These octahedra form chains, as in the WO3 phases of type ReO3, and hexagonal rings, of the same type as in the WO3(1/3)H2O phase, when we extract (1/3)O at every WO3 unit. The pair function D(r) and scattering intensity I(s) distribution curves calculated for simulation configurations show a satisfactory agreement with experiment. [source] Synchrotron X-ray study of noncentrosymmetric Tb3RuO7 with partial structural disorderACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2007Nobuo Ishizawa Single-crystal synchrotron X-ray diffraction reveals partial structural disorder of Tb atoms at 293,K in flux-grown Tb3RuO7 (triterbium ruthenium heptaoxide) crystals. The structure is noncentrosymmetric and composed of infinite single chains of corner-linked RuO6 octahedra embedded in a Tb3O matrix. Two Tb atom sites out of the six crystallographically independent Tb sites are split into two positions. The split sites are separated by approximately 0.3,0.4,Å, with slightly different coordination environments. The RuO6 octahedra in the present P21nb modification have two tilt systems about the a and c axes, in contrast with a single tilt about c in the other Cmcm modifications of Ln3RuO7 (Ln = lanthanoid elements). [source] Sgr A East and its surroundings , a view with XMM-NewtonASTRONOMISCHE NACHRICHTEN, Issue S1 2003Masaaki Sakano Abstract We present an X-ray study of the Sgr A East region based on recent XMM-Newton observations. The spectrum of Sgr A East can be represented by a two-component thin thermal plasma model with temperatures of 1 and 4 keV, both of which have reached ionization equilibrium state. The abundance of iron is found to be higher in the central region of the nebula, with Z , 3,4 solar, than in the outer area for which Z , 0.5 solar. On the other hand, the abundances of other elements appear uniformly distributed with Z , 1. We also detect a weak fluorescent K, line from neutral iron in the outer region of source. We discuss the nature of Sgr A East on the basis of these new X-ray results. [source] Crystallization and preliminary X-ray study of recombinant betaine,homocysteine S -methyltransferase from rat liverACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2002Beatriz González Betaine,homocysteine S -methyltransferase is one of the three enzymes involved in homocysteine catabolism. It uses betaine as the methyl donor to convert homocysteine into methionine, also producing dimethylglycine. Recombinant BHMT from rat liver was crystallized by the vapour-diffusion method in both native and seleniomethionyl-labelled forms. Crystals belong to space group P21, with unit-cell parameters a = 57.8, b = 149.3, c = 96.2,Å, , = 92.9°. Data from native, seleniomethionine-labelled and two heavy-atom derivatives were collected using synchrotron sources. Self-rotation function and sedimentation-velocity experiments suggest that the enzyme is tetrameric with 222 symmetry. [source] Crystallization and preliminary X-ray study of an N-terminal fragment of rat liver ribosomal P2 proteinACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2002David Mandelman Ribosomal P proteins have been shown to be involved in the binding of elongation factors and participate in factor-dependent GTP hydrolysis. The P proteins form the pentamer (P1/P2)2,P0 constituting the lateral flexible stalk of the 60S ribosomal subunit. The highly soluble domain (1,65) of rat liver P2 has been overexpressed in Escherichia coli as an N-terminal poly-His-tagged protein and crystallized. To reduce nucleation and improve crystal morphology and diffraction power, the crystals were grown in a gel matrix and an oil barrier was added between the reservoir and the drop to reduce the rate of vapour diffusion. This dramatically reduced the nucleation in the drops and yielded diffraction-quality crystals. Data were collected to 2.4,Å resolution at beamline ID 14-1, ESRF. The crystals belong to the orthorhombic space group P21212, with unit-cell parameters a = 37.7, b = 96.7, c = 135.0,Å. [source] Crystallization and preliminary X-ray study of haem-binding protein from the bloodsucking insect Rhodnius prolixusACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2001R. A. P. Nagem Rhodnius haem-binding protein (RHBP) from the bloodsucking insect Rhodnius prolixus, a 15,kDa protein, has been crystallized using polyethylene glycol as a precipitant. X-ray diffraction data have been collected at a synchrotron source. The crystals belong to the space group P41(3)212, with unit-cell parameters a = b = 64.98, c = 210.68,Å, and diffract beyond 2.6,Å resolution. [source] Crystallization and preliminary X-ray study of the d -altritol oligonucleotide GTGTACACACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 4 2010Margriet Ovaere In altritol nucleic acids (ANAs), the natural five-membered ribose ring of RNA is replaced by the six-membered d -altritol ring. ANAs are good candidates to act as siRNAs in the RNA-interference pathway. Crystals of the fully modified altritol self-complementary octamer GTGTACAC were grown by the hanging-drop vapour-diffusion technique at 289,K. Diffraction data were recorded on SLS beamline X06DA and processed to 3.0,Å resolution. The crystals belonged to the hexagonal space group P6122 or P6522, with unit-cell parameters a = 25.05, c = 117.58,Å. [source] A preliminary X-ray study of d,d -heptose-1,7-bisphosphate phosphatase from Burkholderia thailandensis E264ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2010Mi-Sun Kim d,d -Heptose-1,7-bisphosphate phosphatase (GmhB), which is involved in the third step of the NDP-heptose biosynthesis pathway, converts d,d -heptose-1,7-bisphosphate to d,d -heptose-1-phosphate. This biosynthesis pathway is a target for new antibiotics or antibiotic adjuvants for Gram-negative pathogens. Burkholderia thailandensis is a useful surrogate organism for studying the pathogenicity of melioidosis owing to its extensive genomic similarity to B. pseudomallei. Melioidosis caused by B. pseudomallei is a serious invasive disease of animals and humans in tropical and subtropical areas. In this study, GmhB has been cloned, expressed, purified and crystallized. X-ray data have also been collected to 2.50,Å resolution using synchrotron radiation. The crystal belonged to space group P6, with unit-cell parameters a = 243.2, b = 243.2, c = 41.1,Å. [source] A preliminary X-ray study of sedoheptulose-7-phosphate isomerase from Burkholderia pseudomalleiACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2009Mi-Sun Kim Sedoheptulose-7-phosphate isomerase (GmhA) converts d -sedoheptulose 7-phosphate to d,d -heptose 7-phosphate. This is the first step in the biosynthesis pathway of NDP-heptose, which is responsible for the pleiotropic phenotype. This biosynthesis pathway is the target of inhibitors to increase the membrane permeability of Gram-negative pathogens or of adjuvants working synergistically with known antibiotics. Burkholderia pseudomallei is the causative agent of melioidosis, a seriously invasive disease in animals and humans in tropical and subtropical areas. GmhA from B. pseudomallei is one of the targets of antibiotic adjuvants for melioidosis. In this study, GmhA has been cloned, expressed, purified and crystallized. Synchrotron X-ray data were also collected to 1.9,Å resolution. The crystal belonged to the primitive orthorhombic space group P212121, with unit-cell parameters a = 61.3, b = 84.2, c = 142.3,Å. A full structural determination is under way in order to provide insights into the structure,function relationships of this protein. [source] Crystallization and preliminary X-ray study of alkaline alanine racemase from Bacillus pseudofirmus OF4ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2009Jiansong Ju Alanine racemase (DadXOF4), a dimeric endogenous PLP-dependent alkaline enzyme from alkaliphilic Bacillus pseudofirmus OF4, was expressed in Escherichia coli and purified with a His6 tag in a form suitable for X-ray crystallographic analysis. Crystals were grown by the hanging-drop vapour-diffusion method at 291,K using a solution containing 1.4,M sodium/potassium phosphate pH 8.2. The protein crystallized in space group P212121, with two protein molecules in the asymmetric unit. [source] Synthesis and X-ray study of the 6-(N -pyrrolyl)purine and thymine derivatives of 1-aminocyclopropane-1-carboxylic acidCHEMICAL BIOLOGY & DRUG DESIGN, Issue 5 2004M. Cetina Abstract:, The novel purine and pyrimidine derivatives of 1-aminocyclopropane-1-carboxylic acid 1 and 2 were obtained by alkylation of 6-(N -pyrrolyl)purine and thymine with methyl 1-benzamido-2-chloromethylcyclopropanecarboxylate. X-ray crystal structure analysis shows that the cyclopropane rings in 1 and 2 posses Z -configuration. The cyclopropane ring atoms and attached atoms of the benzamido and methoxycarbonyl moiety of both molecules are disposed perpendicularly to each other. The carbonyl oxygen of the methoxycarbonyl moiety adopts in both compounds a synperiplanar conformation with respect to the midpoint of the distal bond of the cyclopropane ring. The torsion angles , and , for the 1-aminocyclopropane-1-carboxylic acid residue in 1 and 2 correspond to a folded conformation, while the torsion angles , define antiperiplanar conformation. Intermolecular hydrogen bonds connect the molecules of 1 into dimers. Each dimer is hydrogen-bonded with four ethanol molecules, thus forming discrete unit. On the contrary, intermolecular hydrogen bonds link the molecules of 2 generating three-dimensional network. [source] Molecular Recognition and Crystal Energy Landscapes: An X-ray and Computational Study of Caffeine and Other MethylxanthinesCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2005Lucia Carlucci Dr. Abstract We introduce a new approach to crystal-packing analysis, based on the study of mutual recognition modes of entire molecules or of molecular moieties, rather than a search for selected atom,atom contacts, and on the study of crystal energy landscapes over many computer-generated polymorphs, rather than a quest for the one most stable crystal structure. The computational tools for this task are a polymorph generator and the PIXEL density sums method for the calculation of intermolecular energies. From this perspective, the molecular recognition, crystal packing, and solid-state phase behavior of caffeine and several methylxanthines (purine-2,6-diones) have been analyzed. Many possible crystal structures for anhydrous caffeine have been generated by computer simulation, and the most stable among them is a thermodynamic, ordered equivalent of the disordered phase, revealed by powder X-ray crystallography. Molecular recognition energies between two caffeine molecules or between caffeine and water have been calculated, and the results reveal the largely predominant mode to be the stacking of parallel caffeine molecules, an intermediately favorable caffeine,water interaction, and many other equivalent energy minima for lateral interactions of much less stabilization power. This last indetermination helps to explain why caffeine does not crystallize easily into an ordered anhydrous structure. In contrast, the mono- and dimethylxanthines (theophylline, theobromine, and the 1,7-isomer, for which we present a single-crystal X-ray study and a lattice energy landscape) do crystallize in anhydrous form thanks to the formation of lateral hydrogen bonds. [source] Isoquinoline alkaloids: a 15N NMR and x-ray study.MAGNETIC RESONANCE IN CHEMISTRY, Issue 11 2002Part Abstract Continuing our systematic 15N NMR study of isoquinoline alkaloids, we report a contribution extending our previous paper. The 15N NMR chemical shifts and 15N,1H long-range coupling pathways of tertiary and quaternary isoquinoline alkaloids of several constitutional types are presented. The selected compounds belong to the protoberberine, proaporphine, pavinane, rhoeadine and phtalideisoquinoline classes of alkaloids and were investigated by gradient-selected inverse-detected multiple bond correlation experiments (GHMBC and GSQMBC). In addition, x-ray data and the principal geometric parameters of stylopine, mecambridine, norchelerythrine, isothebaine and mecambrine are reported and discussed. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||||||||