Crystallographic studies of SarV, a global regulator fromStaphylococcus aureus

SarV, a member of the SarA protein family, is a global transcriptional regulator which has been reported to be involved in the regulation of autolysis inStaphylococcus aureus. In this study, SarV fromS. aureuswas successfully cloned, expressed, purified and crystallized. X-ray diffraction data were collected to 2.10 Å resolution. The crystals of SarV belonged to the monoclinic space groupP21, with unit-cell parametersa= 36.40,b= 119.64,c= 66.80 Å, α = γ = 90, β = 98.75°. The Matthews coefficient and the solvent content were estimated to be 2.57 Å3 Da−1and 52%, respectively, suggesting the presence of four molecules in the asymmetric unit. The results of size-exclusion chromatography (SEC) indicated thatS. aureusSarV exists as a homodimer in solution. Unfortunately, the structure cannot be solved by molecular replacement because of the low sequence identity ofS. aureusSarV to known structures. Further phase determination by selenomethionine single-wavelength anomalous dispersion (SAD) and the heavy-atom method is in progress.

Redetermination of tetramethyl tetrathiafulvalene-2,3,6,7-tetracarboxylate

An improved crystal structure of the title compound, C14H12O8S4, is reported. The structure, previously solved using the heavy-atom method (R= 7.1%), has now been solved using direct methods. Due to the improved quality of the data set anRvalue of 2.06% could be achieved. In the crystal, C—H...S and C—H...O contacts link the molecules.

Ab initio determination and Rietveld refinement of the crystal structure of Ni0.50TiO(PO4)

The structure of the oxyphosphate Ni0.50TiO(PO4) has been determined ab initio from conventional X-ray powder diffraction data by the “heavy atom” method. The cell is monoclinic (space group P21/c, Z=4) with a=7.3830(5) Å, b=7.3226(5) Å, c=7.3444(5) Å, and β=120.233(6)°. Refinement of 46 parameters by the Rietveld method, using 645 reflexions, leads to cRwp=0.152, cRp=0.120, and RB=0.043. The structure of Ni0.50TiO(PO4) can be described as a TiOPO4 framework constituted by chains of tilted corner-sharing TiO6 octahedra running parallel to the c axis, crosslinked by phosphate tetrahedra and in which one-half of octahedral cavities created are occupied by Ni atoms. Ti atoms are displaced from the center of octahedra units in alternating long (2.231) and short (1.703 Å) Ti–O bonds along chains.

Structures of Fluoroarsenates KAsF6n (OH) n , n = 0, 1, 2: Application of the Heavy-Atom Method for Modulated Structures

Structures of KAsF6−n (OH) n , n = 0, 1, 2, have been determined from single-crystal X-ray diffraction data. Potassium hexafluoroarsenate, KAsF6, has a standard structure, potassium hydroxopentafluoroarsenate, KAsF5(OH), has a superstructure, and potassium dihydroxotetrafluoroarsenate, KAsF4(OH)2, has an incommensurate modulated structure. The superstructure has been solved both in the supercell by standard methods and in the basic cell as a commensurate modulated structure, giving the same results in both cases. The heavy-atom method for modulated structures has been developed and applied to identify a good starting point for the refinement of strongly modulated KAsF4(OH)2. Moreover, the influence of hydrogen bonding on a regular disturbance of simple translation symmetry of the structure is discussed.

Ab initio determination and Rietveld refinement of the crystal structure of Ba7Cl2F12

The structure of Ba7Cl2F12 has been determined ab initio from conventional X-ray powder diffraction data by the “heavy atom” method. The cell is hexagonal (space group P6¯, Z=1), with a=10.6373(2) Å and c=4.1724(2) Å. Refinement of 38 parameters by the Rietveld method, using 278 reflections, leads to cRwp=0.173, cRp=0.135, and RB=0.054. The structure has common characteristics with that of the other BaF2-rich fluorochloride, Ba12Cl5F19. In both phases Ba2+ ions lie in tricapped trigonal prisms formed by nine halide ions, and Cl− ions occupy the center of trigonal prisms of Ba2+ ions. F− ions are located in cationic tetrahedra or square pyramids.

A two-dimensional copper(I) polymer containing both molecular rod and anionic bridges: synthesis and crystal structure of (µ-chloro)-(µ-pyrazine)copper(I)

The crystal structure of bright-red crystals of the bidimensional polynuclear diamagnetic (µ-chloro)(µ-pyrazine)copper(I) complex has been analyzed from X-ray diffraction data. The structure was solved by the heavy-atom method. Full-matrix least-squares refinement based on 673 reflections with F > 4σ(F) converged to a final R = 0.043 and Rw = 0.048. Crystals of this complex are monoclinic, space group P2/c, a = 3.814(1), b = 6.356(1) and c = 11.497(5) Å; β = 96.04(2)°, Z = 2. The structure consists of planes of copper(I) atoms linked by pyrazine and Cl− bridges, each Cu(I) being in a distorted tetrahedral environment formed by two chloride ions and two nitrogen atoms belonging to two pyrazine molecules, with bond distances of Cu—Cl = 2.349(1) and Cu—N = 2.038(4) Å. Vibrational and electronic spectroscopy of the title compound is also reported. Keywords: two-dimensional copper(I)–pyrazine complexes.

The Crystal and Molecular Structure of sym-fac-(1,4,7-Triazaheptane)-(S)-aspartatocobalt(III) Diperchlorate Dihydrate

The crystal and molecular structure of s-fac-[Co((S)-Asp)(dien)]ClO4 . HClO4 .2 H2O (dien = 1,4,7-triazaheptane) was solved by the heavy atom method. The position parameters of the non-hydrogen atoms and their anisotropic temperature parameters were refined based on 1 726 observed reflections with a final value of R = 0.073. The substance crystallizes in the orthorhombic system in the space group P212121, Z = 4, a = 8.506(1), b = 17.171(2), c = 13.277(1) Å. The structure involves hydrogen bonds between the O2, O4 and HN2 atoms of aspartic acid and the two molecules of water. The five-membered dien chelate rings take the asymmetric envelope conformations. The five-membered ring of (S)-aspartic acid possesses the symmetric envelope conformation whereas the six-membered ring exhibits the skew boat conformation.

The Structure of Bis(isopropylxanthato)nickel(II)

The structure of [Ni(i-PrXa)2] (i-Pr = i-C3H7, Xa = S2CO-) was solved by the heavy-atom method and refined anisotropically to R = 0.044 for 985 unique observed reflections. The compound crystallizes in the P21/c space group with a = 8.879(2), b = 6.086(1), c = 13.203(3) Å, β = 94.74(3)°, V = 711.0(3) Å3, T = 296 K, Z = 2. The molecule contains the NiS4 chromophore with an approximately planar configuration of the four sulfur atoms around the Ni(II). The Ni atom is located in the centre of symmetry.

Crystal and Molecular Structure of the s-fac-[Co((S)-Asp)(medien)]ClO4 . H2O . HClO4 Isomer

The crystal and molecular structure of s-fac-[Co((S)-Asp)(medien)]ClO4 . H2O . HClO4 was elucidated by the heavy atom method. The positional parameters of the nonhydrogen atoms and their anisotropic temperature parameters were refined based on 2 474 observed reflection with final values of R = 0.0603 and wR = 0.0616. The substance crystallized in the orthorhombic system in the space group P212121, Z = 4, a = 8.536(1), b = 13.378(1), c = 16.899(2) Å. The structure comprises layers of the complex cation which alternate with layers containing two perchlorate anions and one hydroxonium cation. The five-membered chelate ring of 4-methyl-1,4,7-triazaheptane exist in the asymmetric λ, δ envelope conformations and the N-CH3 group of the triamine has the exo orientation. The five-membered ring of (S)-aspartic acid assumes the symmetric envelope conformation, the six-membered chelate ring, the skew boat conformation.

Structure of Sodium Hydrogen Selenite-Selenious Acid Adduct (1:3), NaHSeO3.3H2SeO3

Structure of sodium hydrogen selenite-selenious acid (1:3) was solved by heavy-atom method and refined anisotropically to R = 0.098 for 1223 unique observed reflections. The title compound crystallizes in the Pc space group with a = 5.756(2), b = 4.911(2), c = 20.010(5) Å, β = 100.48(3)°, V = 556(1) Å3, T = 293 K, (a = 5.763(2), b = 4.878(1), c = 20.03(1) Å, β = 100.48(3)°, V = 554(1) Å3, T = 173 K), Z = 2. The structure consist of HSeO3- anions, molecules of selenious acid and Na+ cations which are octahedrally coordinated with oxygen atoms. The structure is stabilized by a system of hydrogen bonds.