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Crystallographic System (crystallographic + system)
Selected AbstractsStructure, crystal growth and physical anisotropy of KYb(WO4)2, a new laser matrixJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2002M. C. Pujol The crystal structure of monoclinic KYb(WO4)2 (KYbW) crystals has been refined (in space group C2/c) at room temperature by using single-crystal X-ray diffraction data. KYbW undoped crystals were grown by the TSSG (top-seeded-solution growth) slow-cooling method. The crystals show {110}, {11}, {010} and {310} faces, which basically define their habit. The linear thermal expansion tensor has been determined and the principal axis with maximum thermal expansion ( = 16.68 × 10,6,K,1), , was located 12° from the c axis. Its principal , and axes are [302], [010] and [106] directions, respectively, in the crystallographic system. The optical tensor has been studied at , = 632.8,nm at room temperature; two principal axes, Ng and Nm, are located in the ac plane, while the other, Np, is parallel to [010]. The principal axis with maximum refractive index (ng = 2.45), Ng, was located 19° from the c axis. [source] Cross-linking of protein crystals as an aid in the generation of binary protein,ligand crystal complexes, exemplified by the human PDE10a,papaverine structureACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2009Ole Andreas Andersen Protein crystallography has proven to be an effective method of obtaining high-resolution structures of protein,ligand complexes. However, in certain cases only apoprotein structures are readily available and the generation of crystal complexes is more problematic. Some crystallographic systems are not amenable to soaking of ligands owing to crystal-packing effects and many protein,ligand complexes do not crystallize under the same conditions as used for the apoprotein. Using crystals of human phosphodiesterase 10a (hPDE10a) as an example of such a challenging crystallographic system, the structure of the complex with papaverine was obtained to 2.8,Å resolution using protein crystals cross-linked by glutaraldehyde prior to soaking of the ligand. Inspection of the electron-density maps suggested that the correct mode of binding was obtained in one of the two monomers in the asymmetric unit and inspection of crystal-packing contacts explained why cocrystallization experiments and soaking of crystals that were not cross-linked were unsuccessful. [source] Pair distribution functions calculated from interatomic potential models using the General Utility Lattice ProgramJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2007Elizabeth R. Cope A new module has been developed for the widely used General Utility Lattice Program (GULP). The phonon-based theory developed by Chung & Thorpe [Phys. Rev. B (1999), 59, 4807,4812] to calculate pair distribution function (PDF) peak widths has been utilized to give a selection of commonly used correlation functions. A numerical library of neutron scattering information is now available within GULP, and is used to produce results that can be compared with neutron scattering experimental data. The influence of different phonon modes on the PDF can be assessed by excluding modes above or below a cut-off frequency. Results are presented for sample crystallographic systems, MgO, SrTiO3 and ,-cristobalite, as well as CaxSr1,xTiO3 at x = 0.5, which makes use of the capability to handle partial occupancies to compare different Ca/Sr ordering arrangements with a disordered model in which every Ca/Sr site has 50% occupancy of both species. [source] Cross-linking of protein crystals as an aid in the generation of binary protein,ligand crystal complexes, exemplified by the human PDE10a,papaverine structureACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2009Ole Andreas Andersen Protein crystallography has proven to be an effective method of obtaining high-resolution structures of protein,ligand complexes. However, in certain cases only apoprotein structures are readily available and the generation of crystal complexes is more problematic. Some crystallographic systems are not amenable to soaking of ligands owing to crystal-packing effects and many protein,ligand complexes do not crystallize under the same conditions as used for the apoprotein. Using crystals of human phosphodiesterase 10a (hPDE10a) as an example of such a challenging crystallographic system, the structure of the complex with papaverine was obtained to 2.8,Å resolution using protein crystals cross-linked by glutaraldehyde prior to soaking of the ligand. Inspection of the electron-density maps suggested that the correct mode of binding was obtained in one of the two monomers in the asymmetric unit and inspection of crystal-packing contacts explained why cocrystallization experiments and soaking of crystals that were not cross-linked were unsuccessful. [source] | ||||||||||