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Monoclinic Crystals (monoclinic + crystal)

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Chemistry92%

Terms modified by Monoclinic Crystals

  • monoclinic crystal form
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  • monoclinic crystal system
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    Selected Abstracts

    Transformations for monoclinic crystal symmetry in texture analysis

    JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2009
    Siegfried Matthies
    Monoclinic crystals can be described in two settings: in the first setting the C2 rotation axis is parallel to the z axis and in the second setting it is parallel to the y axis. Transformations of lattice parameters, Miller and zone indices, and atomic coordinates is straightforward; the situation is far more complex for texture analysis with orientation distributions and corresponding representations. This article gives explicit transformations that need to be applied, not only for texture analysis but also for calculations of physical properties of materials with preferred orientation. In texture research the relationship between the Cartesian crystal coordinate system and the unit cell must be unambiguously defined and a uniform convention is desirable. [source]

    Imperfect pseudo-merohedral twinning in crystals of fungal fatty acid synthase

    ACTA CRYSTALLOGRAPHICA SECTION D, Issue 2 2009
    Simon Jenni
    The recent high-resolution structures of fungal fatty acid synthase (FAS) have provided new insights into the principles of fatty acid biosynthesis by large multifunctional enzymes. The crystallographic phase problem for the 2.6,MDa fungal FAS was initially solved to 5,Å resolution using two crystal forms from Thermomyces lanuginosus. Monoclinic crystals in space group P21 were obtained from orthorhombic crystals in space group P212121 by dehydration. Here, it is shown how this space-group transition induced imperfect pseudo-merohedral twinning in the monoclinic crystal, giving rise to a Moiré pattern-like interference of the two twin-related reciprocal lattices. The strategy for processing the twinned diffraction images and obtaining a quantitative analysis is presented. The twinning is also related to the packing of the molecules in the two crystal forms, which was derived from self-rotation function analysis and molecular-replacement solutions using a low-resolution electron microscopy map as a search model. [source]

    Dramatic improvement of crystal quality for low-temperature-grown rabbit muscle aldolase

    ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2010
    HaJeung Park
    Rabbit muscle aldolase (RMA) was crystallized in complex with the low-complexity domain (LC4) of sorting nexin 9. Monoclinic crystals were obtained at room temperature that displayed large mosaicity and poor X-ray diffraction. However, orthorhombic RMA,LC4 crystals grown at 277,K under similar conditions exhibited low mosaicity, allowing data collection to 2.2,Å Bragg spacing and structure determination. It was concluded that the improvement of crystal quality as indicated by the higher resolution of the new RMA,LC4 complex crystals was a consequence of the introduction of new lattice contacts at lower temperature. The lattice contacts corresponded to an increased number of interactions between high-entropy side chains that mitigate the lattice strain incurred upon cryocooling and accompanying mosaic spread increases. The thermodynamically unfavorable immobilization of high-entropy side chains used in lattice formation was compensated by an entropic increase in the bulk-solvent content owing to the greater solvent content of the crystal lattice. [source]

    Imperfect pseudo-merohedral twinning in crystals of fungal fatty acid synthase

    ACTA CRYSTALLOGRAPHICA SECTION D, Issue 2 2009
    Simon Jenni
    The recent high-resolution structures of fungal fatty acid synthase (FAS) have provided new insights into the principles of fatty acid biosynthesis by large multifunctional enzymes. The crystallographic phase problem for the 2.6,MDa fungal FAS was initially solved to 5,Å resolution using two crystal forms from Thermomyces lanuginosus. Monoclinic crystals in space group P21 were obtained from orthorhombic crystals in space group P212121 by dehydration. Here, it is shown how this space-group transition induced imperfect pseudo-merohedral twinning in the monoclinic crystal, giving rise to a Moiré pattern-like interference of the two twin-related reciprocal lattices. The strategy for processing the twinned diffraction images and obtaining a quantitative analysis is presented. The twinning is also related to the packing of the molecules in the two crystal forms, which was derived from self-rotation function analysis and molecular-replacement solutions using a low-resolution electron microscopy map as a search model. [source]

    Crystallization and preliminary X-ray diffraction analysis of the , subunit Yke2 of the Gim complex from Saccharomyces cerevisiae

    ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2008
    Rebeca Pérez de Diego
    The Gim complex (GimC) from Saccharomyces cerevisiae is a heterohexameric protein complex, also known as prefoldin (PFD), which binds and stabilizes unfolded target polypeptides and subsequently delivers them to chaperonins for completion of folding. In this study, the crystallization and preliminary X-ray analysis of one of the , subunits of the Gim complex (Yke2) from S. cerevisiae are described. The purified protein was crystallized by the vapour-diffusion method, producing two types of crystals that belonged to the orthorhombic space group C222 or the primitive monoclinic space group P21. The unit-cell parameters for the C -centred orthorhombic crystal were a = 48.2, b = 168.86, c = 131.81,Å and the unit-cell parameters for the primitive monoclinic crystal were a = 47.83, b = 134.90, c = 81.50,Å, , = 100.71°. The Yke2 crystals diffracted to 4.2 and 3.1,Å resolution, respectively, on a rotating-anode generator under cryoconditions. This is the first report concerning the crystallization of a , subunit of a eukaryotic prefoldin. [source]

    Dimer-Based Three-Dimensional Photonic Crystals

    ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
    Ian D. Hosein
    Abstract The self-assembly of polystyrene dimer- and spherocylinder-shaped colloids is achieved via controlled drying on glass and silicon substrates. 3D monoclinic colloidal crystal structures are determined from scanning electron microscopy images of sections prepared using focused ion-beam (FIB) milling. Full photonic bandgaps between the eighth and ninth bands are found for a systematic range of colloidal dimer shapes explored with respect to the degree of constituent lobe fusion and radius ratio. The pseudogap between bands 2 and 3 for spherocylinder-based monoclinic crystals is also probed using normal incidence reflection spectroscopy. [source]

    The Orthogonal (e,e,e)-Tris-Adduct of 9,10-Dimethylanthracene with C60 -Fullerene: A Hidden Cornerstone of Fullerene Chemistry.

    HELVETICA CHIMICA ACTA, Issue 8 2008
    Preliminary Communication
    Abstract Tris(9,,10,-dimethyl[9,10]ethanoanthracene[11,,12,:,1,9;11,,12,:,16,17;11,,,,12,,,:,30,31])[5,6]fullerene C60, the orthogonal (e,e,e)-tris-adduct of C60 and 9,10-dimethylanthracene, was obtained from [4+2]-cycloaddition (Diels,Alder reaction) at room temperature. The thermally unstable orange red (e,e,e)-tris-adduct was purified by chromatography and was isolated in the form of red monoclinic crystals. Its C3 -symmetric addition pattern was established spectroscopically. Its structure could be further investigated by single crystal X-ray diffraction. The (e,e,e)-tris-adduct of C60 and 9,10-dimethylanthracene has earlier been suggested as intermediate and reversibly formed critical component in ,template directed' addition reactions of C60. This previously elusive compound has now been isolated and structurally characterized. [source]

    The sodium salt of a tris­(tridentate anion)­gadolinium(III) complex: penta­sodium bis­[chelidamato(3,)][chelidamato(2,)]­gadolinate(III) hexa­deca­hydrate

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2000
    Annegret K. Hall
    The sodium salt of a complex anion formed between gadolinium(III) and three variously deprotonated chelidamic acid (4-hydroxy­pyridine-2,6-di­carboxyl­ic acid) ligand moi­eties, assigned as Na5[Gd(C7H2NO5)2(C7H3NO5)]·16H2O, i.e. pentasodium (4-hydroxy­pyridine-2,6-di­carboxyl­ate)­bis(4-oxido­pyridine-2,6-di­carboxyl­ate)­gadolinium(III) hexadecahydrate, forms as colourless monoclinic crystals upon vapour diffusion of ethanol into its aqueous solution. The ligand moieties, assigned as two trianionic and one dianionic chelidamate species, are all tridentate in the complex anion of tricapped trigonal prismatic donor-atom geometry. The geometry of the ligands and that of the primary coordination sphere is very similar to that of the analogous anionic tris­(ligand),rare earth complexes of the pyridine-2,6-di­carboxyl­ate (dipicolinate) dianion. [source]

    Pseudo-merohedral twinning in monoclinic crystals of wild-type human brain neuroglobin

    ACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2009
    Djemel Hamdane
    The purification, crystallization and successful structure determination by molecular replacement of wild-type human brain neuroglobin at 1.8,Å resolution is reported. The apparent space group was orthorhombic C2221, but the real space group was monoclinic P21, which resulted from twinning. Indeed, the unit-cell parameters, a = 31.2, b = 139.1, c = 31.2,Å, , = 102°, display a fortuitously close to c and twinning by the operator l, ,k, h occurs. Twinning was not evident from the initial analysis of intensity distribution, but pseudo-merohedral twinning was revealed by the Padilla and Yeates test based on local intensity differences. A twinning fraction of 0.5 was determined in SHELXL, indicating a perfect hemihedrally twinned crystal. To date, this type of twinning has been reported in more than ten structures, which makes it quite a common case in proteins. [source]

    Expression, crystallization and preliminary structural analysis of the ectoplasmic region of apical membrane antigen 1 from Plasmodium vivax, a malaria-vaccine candidate

    ACTA CRYSTALLOGRAPHICA SECTION D, Issue 11 2004
    Brigitte Vulliez-Le Normand
    Apical membrane antigen 1 (AMA1), a type 1 transmembrane protein present in the microneme organelles of Plasmodium, is a leading malaria-vaccine candidate. The ectoplasmic region of AMA1 from P. vivax has been expressed in Pichia pastoris and crystallized in two different forms: an orthorhombic form (space group P212121, unit-cell parameters a = 54.1, b = 76.1, c = 103.9,Å) and a monoclinic form (space group C2, unit-cell parameters a = 150.0, b = 53.8, c = 60.3,Å, , = 113.2°). Native data have been collected to 2.0,Å resolution for the orthorhombic form and 1.8,Å for the monoclinic form. A platinum derivative was prepared for the orthorhombic and monoclinic crystals using K2PtCl4 and data were collected at several wavelengths to obtain phases by the MAD technique. A partial model has been built from the electron-density maps of both forms and refinement is in progress. [source]

    Analysis of quinazoline and pyrido[2,3- d]pyrimidine N9,C10 reversed-bridge antifolates in complex with NADP+ and Pneumocystis carinii dihydrofolate reductase

    ACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2002
    Vivian Cody
    Structural studies of two ternary complexes of Pneumocystis carinii dihydrofolate reductase (pcDHFR) with the cofactor NADP+ and potent antifolates, the N9,C10 reversed-bridge inhibitor 2,4-diamino-6-[N -(2,,5,-dimethoxybenzyl)- N -methyl­amino]quinazoline (1) and its 3,,5,-dimethoxypyrido[2,3- d]pyrimidine analog (2), were carried out. Data for the monoclinic crystals were refined to 1.90,Å resolution for the complex with (1) (R = 0.178) and to 2.1,Å resolution for the complex with (2) (R = 0.193). The effect of the N9,C10 reversed-bridge geometry is to distort the bridge from coplanarity with the pyrido[2,3- d]pyrimidine or quinazoline ring system and to twist the C10 methylene conformation toward a gauche conformation. This change also influences the conformation of the methoxybenzyl ring, moving it away from a trans position. This change places the 5,-methoxy group deeper within the hydrophobic pocket made by Ile65, Pro66 and Phe69 of the pcDHFR active site. These results also revealed the first observation of an unusual conformation for the reversed-bridge geometry (C5,C6,N9,C10 torsion angle) in antifolate (2). The electron density is consistent with the presence of two models (conformers 2-1 and 2-2) that result from inversion of the geometry at N9. The four examples of N9,C10 reversed-bridge antifolates cluster in two conformations, with the structure of quinazoline (1) similar to that previously reported for its 2,,5,-dimethoxypyrido[2,3- d]pyrimidine analog (3). The two conformers of (2) differ from these and each other by a twisted-bridge geometry that results in the dimethoxybenzyl ring occupying the same conformational space. Conformer 2-2 also has the N9,C10 reversed bridge perpendicular to the pyrido[2,3- d]pyrimidine plane, in contrast to the gauche,trans conformation normally observed. As a result of these changes, the N9 methyl probes conformational space in the active site not normally occupied by antifolate structures. The N9 methyl of conformer 2-2 makes close contacts to the conserved Leu25 as well as the hydroxyl O atoms of the nicotinamide ribose and Ser64, whereas the other three reversed-bridge conformers make weak hydrophobic contacts with Ile123, Thr61 and Ile65. These antifolates are ten times more selective for pcDHFR than the C9,N10 bridge parent trimetrexate. However, pyrido[2,3- d]pyrimidines (2) and (3) are three times more selective for pcDHFR than quinazoline (1) is for rat liver DHFR. These data suggest that the loss of hydrogen-bonding interactions with N8 is more important to potency than the interactions of the methoxybenzyl substituents. [source]

    Crystallization and preliminary X-ray analysis of a thermoalkalophilic lipase from Bacillus stearothermophilus L1

    ACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2001
    Seong-Tae Jeong
    A thermoalkalophilic lipase from Bacillus stearothermophilus L1 (L1 lipase) was crystallized in two different crystal forms using a low concentration of the enzyme and a calcium-exchange process. The first, needle-like, crystal form, which diffracts to about 3.5,Å, belongs to the orthorhombic space group P212121, with unit-cell parameters a = 67.84, b = 72.96, c = 104.41,Å. The second, monoclinic, crystal form, which behaves better than the first form for crystallographic analyses, belongs to the monoclinic space group C2 and has unit-cell parameters a = 119.62, b = 85.05, c = 98.36,Å, , = 99.73°. From the monoclinic crystals, a native data set and a samarium-derivative data set were collected to 2.0 and 2.3,Å resolution, respectively. The difference Patterson map between the two data sets shows strong heavy-atom peaks, indicating that the crystals are suitable for a high-resolution structure determination. [source]

    Preliminary crystallographic studies of an extremely thermostable KDG aldolase from Sulfolobus solfataricus

    ACTA CRYSTALLOGRAPHICA SECTION D, Issue 11 2000
    Elaine J. Hendry
    Crystals have been grown of 2-keto-3-deoxygluconate aldolase (KDG aldolase) from the hyperthermophilic archaeon Sulfolobus solfataricus that diffract to 2.2,Å resolution. The enzyme catalyses the reversible aldol cleavage of 2-keto-3-dexoygluconate to pyruvate and glyceraldehyde, the third step of a modified non-phosphorylated Entner,Doudoroff pathway of glucose oxidation. S. solfataricus grows optimally at 353,K and the enzyme itself has a half-life of 2.5,h,at 373,K. Knowledge of the crystal structure of KDG aldolase will further understanding of the basis of protein hyperthermostability and create a target for site-directed mutagenesis of active-site residues, with the aim of altering substrate specificity. Three crystal forms have been obtained: orthorhombic crystals of space group P212121, which diffract to beyond 2.15,Å, monoclinic crystals of space group C2, which diffract to 2.2,Å, and cubic crystals of space group P4232, which diffract to 3.4,Å. [source]

    Crystallization and preliminary X-ray diffraction studies of phospholipase D from Streptomyces sp.

    ACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2000
    Ingar Leiros
    Crystals of purified phospholipase D (E.C. 3.1.4.4) from Streptomyces sp. strain PMF have been grown under two different crystallization conditions using vapour diffusion. Both conditions gave monoclinic crystals in space group P21. The unit-cell parameters were a = 57.28, b = 57.42, c = 68.70,Å, , = 93.17°. The crystals diffract at 110,K to a resolution beyond 1.4,Å using synchrotron radiation. [source]