scholarly journals The crystal structure of the N-acetylglucosamine 2-epimerase from Nostoc sp. KVJ10 reveals the true dimer

2019 ◽  
Vol 75 (1) ◽  
pp. 90-100 ◽  
Author(s):  
Marie-Josée Haglund Halsør ◽  
Ulli Rothweiler ◽  
Bjørn Altermark ◽  
Inger Lin Uttakleiv Raeder
Keyword(s):  
Crystal Structure ◽  
Sialic Acid ◽  
Age Structure ◽  
Crystal Packing ◽  
The Other ◽  
Third Age ◽  
Northern Norway ◽  
Space Group ◽  
The Third ◽  
The Face

N-Acetylglucosamine 2-epimerases (AGEs) catalyze the interconversion of N-acetylglucosamine and N-acetylmannosamine. They can be used to perform the first step in the synthesis of sialic acid from N-acetylglucosamine, which makes the need for efficient AGEs a priority. This study presents the structure of the AGE from Nostoc sp. KVJ10 collected in northern Norway, referred to as nAGE10. It is the third AGE structure to be published to date, and the first one in space group P42212. The nAGE10 monomer folds as an (α/α)6 barrel in a similar manner to that of the previously published AGEs, but the crystal did not contain the dimers that have previously been reported. The previously proposed `back-to-back' assembly involved the face of the AGE monomer where the barrel helices are connected by small loops. Instead, a `front-to-front' dimer was found in nAGE10 involving the long loops that connect the barrel helices at this end. This assembly is also present in the other AGE structures, but was attributed to crystal packing, even though the `front' interface areas are larger and are more conserved than the `back' interface areas. In addition, the front-to-front association allows a better explanation of the previously reported observations considering surface cysteines. Together, these results indicate that the `front-to-front' dimer is the most probable biological assembly for AGEs.

NOTES ON NEW MEXICO BEES

1900 ◽  
Vol 32 (12) ◽  
pp. 361-364
Author(s):  
T. D. A. Cockerell
Keyword(s):  
New Mexico ◽  
Hind Tibia ◽  
The Other ◽  
The Third ◽  
Central Depression ◽  
The Face

Bombomelecta larreœ, n. sp.♀.—Length 12½ mm.; general build and structure of B. thoracica, but the scutellum is convex with a central depression, and wholly without spines; while the claws have the inner division short and broadly truncate. The maxillary palpi are 6-jointed, and the mandibles have a strong tooth on the inner side. Black; pubescence of the face and vertex pale brown; of the occiput, labrum and clypeus, black; of the pleura, metathorax and scutellum, black; of the post-scurtellum, yellowish, especially noticeable at the sides; of the mesothorax, orange-fulvous, short, dense and conspicuous in front, thin behind. Abdomen with broad but inconspicuous ochreous bands on segments 2 to 4, more or less interrupted in the middle on 2 and 4, represented on the first segment by lateral patches, and a few ochreous hairs even in the middle; fifth segment with black hairs. Antennæ entirely black, apex truncate, the corners of the truncation rounded. Legs black, with black pubescence; spurs black, hind spur of hind tibia larger than the other, and somewhat bent. Wings dark fuliginous, with hyaline patches on the third transverso-cubital and second recurrent nervures; venation resembling that of B. thoracica, var. fulvida, except that the first recurrent nervure joins the second submarginal cell almost at its apex.

A novel one-dimensional CoIIcoordination polymer:catena-poly[[hexaaquacobalt(II)] [[diaquabis(sulfato-κO)cobalt(II)]-μ-4,4′-bipyridine-κ2N:N′] [[triaqua(sulfato-κO)cobalt(II)]-μ-4,4′-bipyridine-κ2N:N′]]

2012 ◽  
Vol 68 (9) ◽  
pp. m265-m268 ◽  
Author(s):  
Kai-Long Zhong ◽  
Ming-Yi Qian
Keyword(s):  
Crystal Structure ◽  
Three Dimensional ◽  
The Other ◽  
Water Molecules ◽  
Supramolecular Network ◽  
Sulfate Ion ◽  
Sulfate Ions ◽  
One Dimensional ◽  
The Third ◽  
Hydrogen Bonding Interactions

The title compound, {[Co(H2O)6][Co(SO4)(C10H8N2)(H2O)3][Co(SO4)2(C10H8N2)(H2O)2]}n, contains three crystallographically unique CoIIcentres, all of which are in six-coordinated environments. One CoIIcentre is coordinated by two bridging 4,4′-bipyridine (4,4′-bipy) ligands, one sulfate ion and three aqua ligands. The second CoIIcentre is surrounded by two N atoms of two 4,4′-bipy ligands and four O atoms,i.e.two O atoms from two monodentate sulfate ions and two from water molecules. The third CoIIcentre forms part of a hexaaquacobalt(II) ion. In the crystal structure, there are two different one-dimensional chains, one being anionic and the other neutral, and adjacent chains are arranged in a cross-like fashion around the mid-point of the 4,4′-bipy ligands. The structure features O—H...O hydrogen-bonding interactions between sulfate anions and water molecules, resulting in a three-dimensional supramolecular network.

Die Kristallstruktur des Lithium-Benzamidinats {Li3[C6H5 - C(NSiMe3)2]3 · NC - C6H5} / The Crystal Structure of the Lithium Phenylamidinate {Li3[C6H5 - C(NSiMe3)2]3 · NC - C6H5}

1994 ◽  
Vol 49 (10) ◽  
pp. 1444-1447 ◽  
Author(s):  
Helmut Goesmann ◽  
Dieter Fenske
Keyword(s):  
Crystal Structure ◽  
Nitrogen Atom ◽  
Single Crystals ◽  
Title Compound ◽  
The Other ◽  
Space Group ◽  
Structure Solution

AbstractSingle crystals of the title compound have been prepared by the reaction of benzonitrile with LiN-(SiMe3)2 in hexane and subsequent evaporation of the solvent. Space group P21/n, Z = 4, structure solution with 7945 observed unique reflections. R = 0.052. Lattice dimensions at -70 °C: a = 1485.2(9); b = 2486.9(11); c = 1568.9(8) pm; β = 91.06(4)°. The compound forms a trimeric ion ensemble in which two of the lithium cations are coordinated by three nitrogen atoms of two phenylamidinate an ions, the other one by four nitrogen atoms of two chelating phenylaminidate anions and in addition by the nitrogen atom of a benzonitrile molecule.

MASTERY BELIEFS AND PRODUCTIVE LEISURE ACTIVITIES IN THE THIRD AGE

2003 ◽  
Vol 31 (7) ◽  
pp. 643-656 ◽  
Author(s):  
Erika Timmer ◽  
Marja Aartsen
Keyword(s):  
Strong Predictor ◽  
Later Life ◽  
Self Esteem ◽  
Control Beliefs ◽  
Third Age ◽  
The Third ◽  
Productive Activities ◽  
Broad Concept ◽  
The Face ◽  
The Impact

In the present study we examined the associations between beliefs of mastery and 2 important kinds of productive activities in the third age: participation in education, and volunteering. Within the broad concept of mastery beliefs, differential aspects of self-regulatory cognitions were studied, that is, self-esteem, control beliefs, effort to complete behavior, persistence in the face of adversity, and willingness to initiate behavior. Effects of these aspects on carrying out activities were investigated and controlled for the impact of some situational and demographic factors. Findings suggest that a general sense of mastery, as reflected in self-esteem and control beliefs, is not a precondition for study and volunteering work in the third age. However, special components of self-efficacy turned out to play a part. Willingness to initiate behavior emerged as a strong predictor for taking on educational activities, as was persistence in the face of adversity for being active as a volunteer. In the discussion possibilities were looked at fpr how better to match productive activities in later life to personal dispositions.

Quaternäre Strontium-Kupfer(I)-Lanthanoid(III)-Selenide mit Cer und Praseodym: SrCuCeSe3 und SrCuPrSe3, ein ungleiches Geschwisterpaar / Quaternary Strontium Copper(I) Lanthanoid(III) Selenides with Cerium and Praseodymium: SrCuCeSe3 and SrCuPrSe3, Unequal Brother and Sister

2004 ◽  
Vol 59 (9) ◽  
pp. 985-991 ◽  
Author(s):  
Sabine Strobel ◽  
Thomas Schleid
Keyword(s):  
Single Crystals ◽  
Coordination Number ◽  
Unit Cell ◽  
Structural Relationship ◽  
The Other ◽  
Space Group ◽  
Lattice Constants ◽  
The Third ◽  
Other Hand ◽  
Third Dimension

Quaternary strontium copper(I) lanthanoid(III) selenides are formed by the oxidation of elemental strontium, copper and the corresponding lanthanoid with selenium. Orange to red needle-shaped single crystals of SrCuPrSe3 and SrCuCeSe3 have been synthesized by heating mixtures of Sr, Cu, Pr / Ce and Se with CsI as a flux in evacuated silica tubes to 800°C for 7 d. Both compounds crystallize orthorhombically in space group Pnma with four formula units per unit cell, but with unlike lattice constants (a = 1097.32(6), b = 416.51(2), c = 1349.64(8) pm for SrCuPrSe3 and a = 846.13(5), b = 421.69(2), c = 1663.42(9) pm for SrCuCeSe3) and therefore different structure types. The Pr3+ cations in SrCuPrSe3 are surrounded octahedrally by six Se2− anions forming chains of edge-sharing [PrSe6]9− octahedra that are joined by common vertices. Together with [CuSe4]7− tetrahedra they form [CuPrSe3]2− layers piled up parallel (001). Between those layers the Sr2+ cations are coordinated by seven Se2− anions in the shape of capped trigonal prisms linking the structure in the third dimension. On the other hand in SrCuCeSe3 the Ce3+ cations as well as the Sr2+ cations adopt a coordination number of seven. Since the bonding distances between cerium and selenium match with those of strontium and selenium the two crystallographically independent sites of these cations are occupied statistically by Ce3+ and Sr2+ with equal ratios. Nevertheless, there is a close structural relationship between SrCuPrSe3 and SrCuCeSe3. Similar to SrCuPrSe3 where Cu+ and Pr3+ cations together with Se2− anions form [CuPrSe3]2− layers parallel (001), the Cu+ cations and [(Ce1/Sr1)Se7]11.5− polyhedra in SrCuCeSe3 build strongly puckered layers which are connected by (Ce2)3+/(Sr2)2+ cations. The copper selenium part in both compounds correlates as well, with [CuSe4]7− tetrahedra linked by common vertices to form [CuSe3]5− chains running along [010].

The structure of reyerite, (Na,K)2Ca14Si22Al2O58(OH)8.6H2O

1988 ◽  
Vol 52 (365) ◽  
pp. 247-255 ◽  
Author(s):  
Stefano Merlino
Keyword(s):  
Crystal Structure ◽  
The Other ◽  
Water Molecules ◽  
Charge Balance ◽  
Alkali Cations ◽  
Structural Units ◽  
Tetrahedral Sheet ◽  
Space Group

AbstractThe crystal structure of reyerite, (Na,K)2Ca14Si22Al2O58(OH)8.6H2O, Z = 1, was refined in the space group P, a = 9.765, c = 19.067Å, to R = 0.064 for 1540 reflections. The structure is composed of the following structural units: (a) tetrahedral sheets S1, with composition (Si8O20)8−, characterized by six-membered rings of tetrahedra; (b) tetrahedral sheets S2, characterized by six-membered rings of tetrahedra, with six tetrahedra pointing in one direction and two pointing in the other direction—the apical oxygens of these two tetrahedra connect two inversion-related S2 sheets to build double sheets, with composition (Si14Al2O38)14− and ordered distribution of aluminum cations; (c) sheets O of edge-sharing calcium octahedra. The various structural units are connected through corner sharing according to the schematic sequence ……; the corresponding composition is [Ca14Si22Al2O58(OH)8]2−. The charge balance is restored by alkali cations which are placed, together with water molecules, in the cavities of the structure at the level of the double tetrahedral sheet.

scholarly journals A variable-temperature study of a phase transition in barbituric acid dihydrate

2005 ◽  
Vol 61 (4) ◽  
pp. 464-472 ◽  
Author(s):  
Gary S. Nichol ◽  
William Clegg
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Barbituric Acid ◽  
Crystal Packing ◽  
Variable Temperature ◽  
Mirror Plane ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Acta Cryst ◽  
Space Group

The crystal structure of barbituric acid dihydrate (C4H4N2O3·2H2O) has twice been reported as orthorhombic, space group Pnma, with all atoms (except for CH2 H atoms) lying on the mirror plane [Al-Karaghouli et al. (1977). Acta Cryst. B33, 1655–1660; Jeffrey et al. (1961). Acta Cryst. 14, 881–887]. The present study has found that at low temperatures, below 200 K, the crystal structure is no longer orthorhombic but is non-merohedrally twinned monoclinic, space group P21/n. This phase is stable down to 100 K. Above 220 K the crystal structure is orthorhombic, and between 200 and 220 K the structure undergoes a phase change, with the monoclinic-to-orthorhombic phase transition itself taking place at around 216–217 K. The size of the β angle in the monoclinic structure is temperature dependent; at 100 K β is around 94° and it decreases in magnitude towards 90° as the temperature increases. Although the hydrogen-bonding motifs are the same for both crystal systems, there are significant differences in the crystal packing, in particular the out-of-plane displacement of the two water molecules and the sp 3-hybridized C atom of barbituric acid.

scholarly journals Die Kristallstruktur des Cyano-Elpasoliths [N(CH3)4]2CsFe(CN)6 / The Crystal Structure of the Cyano Elpasolite [N(CH3)4]2CsFe(CN)6

1982 ◽  
Vol 37 (12) ◽  
pp. 1534-1539 ◽  
Author(s):  
D. Babel
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
The Other ◽  
Methyl Groups ◽  
Orientational Disorder ◽  
Space Group ◽  
X Ray ◽  
Ray Methods ◽  
The Ideal

The crystal structure of the cubic compound [N(CH3)4]2CsFe(CN)6 was determined by X-ray methods: a = 2527.4(6) pm, space group Fd3c, Z = 32, Rg = 0.028 (260 independent single crystal reflections). The resulting distances within the practically undistorted Fe (CN)63- - octahedron are Fe-C = 193.4(6) and C-N = 115.7(7) pm. Compared to the ideal elpasolite structure of space group Fm3m, Z = 4, the octahedra are rotated by 7.4° through their 3 axis. This is discussed as caused by steric requirements of the tetramethylammonium groups (N-C = 148.4(10) and 149.1(38) pm, resp.). Three quarters of them, of which also the hydrogen positions could be located, are well oriented. The remaining quarter shows orientational disorder to approach similar contact distances as the other N(CH3)4+ ion exhibits between the methyl groups and the nitrogen ends of the anions

scholarly journals (E)-4-[(1-Benzyl-4-benzylidene-2,5-dioxopyrrolidin-3-yl)methyl]benzaldehyde 0.25-hydrate

2012 ◽  
Vol 68 (4) ◽  
pp. o1184-o1184 ◽  
Author(s):  
Tao Yu ◽  
Yimin Hu
Keyword(s):  
Crystal Structure ◽  
Water Molecule ◽  
Title Compound ◽  
Crystal Packing ◽  
Membered Ring ◽  
Dihedral Angles ◽  
Inversion Center ◽  
Space Group ◽  
Compound C ◽  
Centrosymmetric Dimers

The crystal structure of the title compound, C26H21NO3·0.25H2O, reveals one stereogenic centre in the molecule. Nevertheless, due to the observed centrosymmetric space group, both enantiomers are present in the crystal packing. The water molecule of crystallisation is located on a crystallographic inversion center. The molecule contains one five-membered ring (A) and three six-membered rings (benzyl ringB, benzylidene ringCand formylbenzyl ringD). All four rings are not coplanar: the dihedral angles between ringsAandB,AandC, andAandDare 70.35 (9), 33.8 (1) and 60.30 (9)°, respectively. In the crystal, pairs of weak C—H...O interactions lead to the formation of centrosymmetric dimers. Additional C—H...O interactions link the dimers into chains along [011].

Crystal structure of Cd2V2O7

1967 ◽  
Vol 45 (20) ◽  
pp. 2297-2302 ◽  
Author(s):  
P. K. L. Au ◽  
C. Calvo
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Lattice Parameters ◽  
The Other ◽  
Distorted Octahedron ◽  
Thermal Activity ◽  
Space Group ◽  
Bond Angles ◽  
Central Oxygen ◽  
Oxygen Atoms

Cadmium pyrovanadate crystallizes in the C2/m space group with lattice parameters a = 7.088(5) Å, b = 9.091(5) Å, c = 4.963(5) Å, β = 103°21(5)′, and z = 2. This crystal is an isostructure of the mineral thortveitite and thus the anion consists of a pair of centrosymmetrically related corner-sharing VO4 tetrahedra while the cation resides within a distorted octahedron of oxygen atoms. The anion has a linear V—O—V group, but, as with the isostructural pyrophosphates, the central oxygen atom shows an anomalously high thermal activity. The V—O bond distances are 1.76 Å for the inner bond and 1.70 Å for the terminal bond. The bond angles about the anion and cation are similar to those found for the other analogues of thortveitite.

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