Piezoelectric ammonium tartrate, (NH4)2C4H406, crystallizes in the monoclinic space group P21 with a=7.083 (1), b=6.128 (3), c=8.808 (1) ,~; fl=92.42 (1) ° and Z=2. The crystal structure has been determined from three-dimensional X-ray diffraction data by the symbolic addition method and refined by full-matrix least squares to an R index of 0-086. The tartrate ion consists of two planar halves, each having a carboxyl group, a tetrahedral carbon atom and a hydroxyl oxygen atom. The two parts are found to be identical within experimental error, with an interplanar angle of 62 °. The structure is stabilized by a three-dimensional network of hydrogen bonds.
A single-crystal neutron-diffraction investigation of sodium thiosulphate pentahydrate, Na2S203.5H20, has been made with three sets of zonal data. The structure was refined by least-squares techniques, with individual temperature factors, to an R value of 8.2%. The geometry of the $203 group and sodium-oxygen framework agree with those of X-ray studies. The positional parameters of some of the atoms differ from those p3stulated from the X-ray and nuclear magnetic resonance studies. The O-H and H-H bond distances and the H-O-H valence angle of all the five water molecules were found to be normal. The hydrogen-bond scheme falls into four classes: two strong water-thiosulphate oxygen, two weak water-thiosulphate oxygen, two water-water, and three water-sulphur hydrogen bonds. From the geometry of its surroundings one of the hydrogen atoms H(9) may be regarded as not participating in hydrogen bonding.
The crystal structure of glycyl-L-threonine dihydrate, C6N206H16, has been determined from threedimensional X-ray diffraction data. The peptide glycyl-L-threonine crystallizes in the orthorhombic space group P2~2121 with two molecules of water per asymmetric unit. Cell dimensions are a = 9.72 (2), b= 10.03 (2), c= 10.73 (2) A. The structure was solved using the symbolic addition method and refined by full-matrix least-squares calculations to an R index of 0.094 for 830 observed reflexions. Both the carboxyl and the peptide groups are planar; the dihedral angle between the planes is 56.2 °. The dimensions of the peptide group are in agreement with the respective weighted mean values proposed by Marsh & Donohue [Advanc. Protein Chem. (1968). 22, 235-256]. The peptide chain is in the extended conformation. The conformation of the threonine side group in the dipeptide is different from that in free threonine.
The phoN gene of Salmonella enterica sv. Typhimurium strain MD6001 was cloned in the multicopy plasmid pBluescript SK(-). The nucleotide sequence of the cloned gene differs from the corresponding S. typhimurium LT2 sequence at 23 residues, leading to 15 amino-acid differences, but was very close to the S. typhi phoN sequence (only three nucleotide and two amino-acid differences). The recombinant PhoN protein was purified to homogeneity. Two forms of crystals were harvested from a single crystallization condition. Diffraction intensity data were collected using a laboratory X-ray source to resolution limits of 2.5 and 2.8 A for crystals belonging to space group C2 and C222(1), respectively. Based on non-crystallographic symmetry, four monomers of PhoN are expected to be present in the asymmetric unit of the C2 unit cell. Two monomers of a biologically active dimer in the asymmetric unit of the C222(1) unit cell are expected from the Matthews coefficient.
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