scholarly journals X-ray diffraction studies of enkephalins. Crystal structure of [(4′-bromo) Phe4,Leu5]enkephalin

1984 ◽  
Vol 218 (3) ◽  
pp. 677-689 ◽  
Author(s):  
T Ishida ◽  
M Kenmotsu ◽  
Y Mino ◽  
M Inoue ◽  
T Fujiwara ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Least Squares Method ◽  
Heavy Atom ◽  
Three Dimensional ◽  
Diffraction Method ◽  
Biologically Active ◽  
Type I ◽  
X Ray Diffraction ◽  
X Ray ◽  
Relationship Of

In order to investigate the structure-activity relationship of [Leu5]- and [Met5]enkephalins, [(4′-bromo)Phe4, Leu5]-, [(4′-bromo)Phe4, Met5]- and [Met5] enkephalins were synthesized and crystallized. The crystal structure of [(4′-bromo) Phe4, Leu5]- enkephalin was determined by X-ray diffraction method using the heavy atom method and refined to R = 0.092 by the least-squares method. The molecule in this crystal took essentially the same type I' beta-turn conformation found in [Leu5]enkephalin [Smith & Griffin (1978) Science 199, 1214-1216). On the other hand, the preliminary three-dimensional Patterson analyses showed that the most probable conformations of [(4′-bromo)Phe4,Met5]- and [Met5]enkephalins are both the dimeric extended forms. Based on these insights, the biologically active conformation of enkephalin was discussed in relation to the mu- and delta-receptors.

Crystal and molecular structure of carbonylcyanide-4-chlorophenylhydrazone(4-chlorophenylhydrazonopropanedinitrile)

1984 ◽  
Vol 49 (10) ◽  
pp. 2363-2370
Author(s):  
Viktor Vrábel ◽  
Ernest Šturdík ◽  
Michal Dunaj-Jurčo ◽  
Jan Lokaj ◽  
Ján Garaj
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Structural Analysis ◽  
Least Squares Method ◽  
Crystal And Molecular Structure ◽  
Heavy Atom ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Heavy Atom Method

The crystal structure of carbonylcyanide-4-chlorophenylhydrazone was solved by the single crystal X-ray diffraction method and interpreted by the heavy atom method. The compound crystallizes in the P21/c monoclinic group with 4 molecules per unit cell and with lattice parameters: a = 1.1843(3), b = 0.5944(1), c = 1.4922(3) nm and β = 117.92(2)°. The structure was refined by the least squares method for 1 078 observed reflections to a final value of R = 4.9%. The crystal structure consists of monomeric units, where hydrogen bonds were observed between atoms N3...H5 0.2193 nm and N3...H3 0.2404 nm between two molecules transformable through centre of symmetry -x, -y, -z. The name 4-chlorophenylhydrazonopropanedinitrile is recommended for the studied compound on the basis of this X-ray structural analysis.

Crystal Structure of ζ2' Martensite in Au-49.5at%Cd Alloy

1991 ◽  
Vol 246 ◽  
Author(s):  
Yutaka Emura ◽  
Takuya Ohba ◽  
Kazuhiro Otsuka
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Crystal Lattice ◽  
Least Squares ◽  
Least Squares Method ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray ◽  
Lattice Constants

AbstractCrystal structure of the ζ2' martensite in a Au-49.5at%Cd ally has been analyzed by the single crystal x-ray diffraction method. The crystal lattice was trigonal and the lattice constants were a:0.8095(3) and c=o.57940(6) nm. There were 18 atoms in a unit cell. The space group was P3, which was different from that previously determined by Vatanayon and Hehemann. The structure was refined by the full matrix least squares method to a final R factor of 7.8% and a weighted R factor of 4.1%.

The crystal structure of tetraethylammonium Tris(O-ethylxanthato)tellurate(II): An example of five-coordinate pentagonal-planar geometry

1976 ◽  
Vol 29 (11) ◽  
pp. 2337 ◽  
Author(s):  
BF Hoskins ◽  
CD Pannan
Keyword(s):  
Crystal Structure ◽  
Least Squares Method ◽  
Three Dimensional ◽  
Planar Geometry ◽  
Maximum Deviation ◽  
Valence Shell ◽  
X Ray Diffraction ◽  
Electron Pairs ◽  
Fourier Methods ◽  
X Ray

The crystal structure of tetraethylammonium tris(O-ethylxanthato) tellurate(11), [Et4N] [Te(S2COEt)3], has been determined by single-crystal three-dimensional X-ray diffraction methods. Crystals are monoclinic of space group P21/c with four cation-anion pairs per unit cell which has the dimensions a 8.121(1), b 18.858(2), c 19.260(2) � and β 105.22(2)�. The structure was solved by the normal Fourier methods and was refined with anisotropic thermal parameters by a full-matrix least-squares method converging with R and Rw values of 0.061 and 0.082 for the 2404 independent statistically significant reflections collected by counter methods. The tris(ethylxanthato)tellurate(11) anion has a novel five-coordinate pentagonal-planar structure with only two of the xanthato ligands bidentate and with the Te-S bond distances having values in the range 2.503(4)-3.059(3)�. The TeS5 atoms are coplanar, the maximum deviation from the plane being 0.122 �. This, together with the intra-planar S...S distances of 3.340-3.661 �, indicates that the ligand atoms of the pentagonal plane are not over-crowded. The geometry of the anion configuration can be explained in terms of the VSEPR theory using a pentagonal-bipyramidal arrangement of the seven electron pairs in the valence shell of the tellurium.

The crystal structure of potassium ΛΔ-rac-2,3-butanediamine-N,N,N',N'-tetraacetatecobaltate hemihydrate

1985 ◽  
Vol 50 (1) ◽  
pp. 171-187 ◽  
Author(s):  
Marián Kalina ◽  
Viktor Kettmann ◽  
František Pavelčík ◽  
Jaroslav Majer
Keyword(s):  
Crystal Structure ◽  
Equatorial Plane ◽  
Least Squares Method ◽  
Chelate Ring ◽  
Diffraction Method ◽  
Methyl Groups ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Energy Preference

The crystal structure of ΛΔ-K [Co(rac-bdta)] . 1/2 H2O was solved by the X-ray diffraction method and refined by the least squares method to R = 0.047 on the basis of 3 847 diffraction values. The substance crystallizes in a space group with symmetry P 1 with the following lattice parameters: a = 0.9412(5), b = 1.2166(6), c = l.5370(9)nm, α = 70.68(4), β = 73.45(4), γ = 83.24(4)°. The crystal structure consists of two symmetrically independent enantiomer pairs Δ-[Co(R,R)-bdta] and Λ-[Co(S,S)-bdta]- K+ ions and molecules of water of crystallization. The Co(III) atom is octahedrally coordinated by rac(bdta)4- forming four glycine and one ethylenediamine chelate ring. The stereospecific coordination of rac(bdta)4- is based on an energy preference for equatorially located methyl groups on the central ethylenediamine ring. Two types of strain in the [Co(rac-bdta)]- complex are derived from the three five-membered rings in the equatorial plane of the complex and repulsion between the methyl and methylene hydrogen atoms.

scholarly journals A NOVEL OCTAHEDRAL NIOBIUM OXYCHLORIDE CLUSTER BUILT FROM INTERCONNECTED Nb6Cl12O4 UNITS: Cs2Sc3Nb1227O8

2011 ◽  
Vol 11 (2) ◽  
pp. 109-116
Author(s):  
Fakhili Gulo
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Three Dimensional ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
Stoichiometric Mixture ◽  
Orthorhombic System ◽  
X Ray ◽  
Solid State Route ◽  
Valence Electrons

A novel octahedral niobium cluster oxychloride compound, Cs2Sc3Nb12Cl27O8 was synthesized by solid-state route techniques from stoichiometric mixture of CsCl, Sc2O3, Nb, NbCl5, and Nb2O5, heated at 700 °C for two days. The crystal structure was determined by single crystal X-ray diffraction method. It crystallizes in orthorhombic system with space group of Pnma, a = 17.5206(1) Å, b = 29.6899(3) Å, c = 9.2114(1) Å, and V = 4791.63(8) Å3. The structure is based on  unit in which four oxygen ligands selectively occupy inner positions arranged in sets of three and one on opposite side of the Nb6 octahedron. Each cluster shares three apical-chlorine ligands with three adjacent clusters to form layers with topology similar to that of graphite. The cluster units are also connected to each other by both cesium and scandium atoms to form a three-dimensional framework. This compound exhibits 14 valence electrons per cluster.

scholarly journals Synthesis, crystal structure, spectroscopic and thermal investigations of neodymium(III) biphenyl-4,4′-dicarboxylate framework

2012 ◽  
Vol 10 (4) ◽  
pp. 1165-1174 ◽  
Author(s):  
Renata Łyszczek ◽  
Liliana Mazur
Keyword(s):  
Crystal Structure ◽  
Thermal Analysis ◽  
Oxygen Atom ◽  
Solvothermal Method ◽  
3D Structure ◽  
Three Dimensional ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Investigations

AbstractThe three-dimensional complex {[Nd(bpdc)1.5(DMF)]·1.4DMF}n (DMF=N,N′-dimethylformamide, bpdc=biphenyl-4,4′-dicarboxylate) was synthesized using the solvothermal method. The crystal structure of the neodymium(III) complex has been determined by single-crystal X-ray diffraction method at 100(2) K. The polymeric structure consists of neodymium polyhedra bridged by bpdc ligands. Eight-coordinated Nd(III) atoms are surrounded by seven oxygen atoms from six bpdc moieties and one oxygen atom from the DMF molecule. The 3D structure of the complex contains two types of channels occupied by DMF molecules. Thermal analysis revealed that DMF molecules are lost in a stepwise manner. The infrared spectrum confirmed full deprotonation of acid and presence of DMF molecules in the structure.

scholarly journals An investigation of polyhedral deformation in two mixed-metal diarsenates: SrZnAs2O7and BaCuAs2O7

2015 ◽  
Vol 71 (4) ◽  
pp. 330-337 ◽  
Author(s):  
Sabina Kovač ◽  
Ljiljana Karanović ◽  
Tamara Đorđević
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
General Formula ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Open Framework ◽  
Geometrical Characteristics ◽  
Barium Copper

Two isostructural diarsenates, SrZnAs2O7(strontium zinc diarsenate), (I), and BaCuAs2O7[barium copper(II) diarsenate], (II), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. The three-dimensional open-framework crystal structure consists of corner-sharingM2O5(M2 = Zn or Cu) square pyramids and diarsenate (As2O7) groups. Each As2O7group shares its five corners with five differentM2O5square pyramids. The resulting framework delimits two types of tunnels aligned parallel to the [010] and [100] directions where the large divalent nine-coordinatedM1 (M1 = Sr or Ba) cations are located. The geometrical characteristics of theM1O9,M2O5and As2O7groups of known isostructural diarsenates, adopting the general formulaM1IIM2IIAs2O7(M1II= Sr, Ba, Pb;M2II= Mg, Co, Cu, Zn) and crystallizing in the space groupP21/n, are presented and discussed.

A new model for packing of type-I collagen molecules in the native fibril

1981 ◽  
Vol 1 (10) ◽  
pp. 801-810 ◽  
Author(s):  
Karl A. Piez ◽  
Benes L. Trus
Keyword(s):  
Type I Collagen ◽  
Hexagonal Lattice ◽  
Three Dimensional ◽  
Equatorial Region ◽  
Type I ◽  
X Ray Diffraction ◽  
X Ray ◽  
Left Handed ◽  
Crystal Model ◽  
Collagen Molecules

A specific fibril model is presented consisting of bundles of five-stranded microfibrils, which are usually disordered (except axially) but under lateral compression become ordered. The features are as follows (where D = 234 residues or 67 nm): (1) D-staggered collagen molecules 4.5 D long in the helical microfibril have a left-handed supercoil with a pitch of 400–700 residues, but microfibrils need not have helical symmetry. (2) Straight-tilted 0.5-D overlap regions on a near-hexagonal lattice contribute the discrete x-ray diffraction reflections arising from lateral order, while the gap regions remain disordered. (3) The overlap regions are equivalent, but are crystallographically distinguished by systematic displacements from the near-hexagonal lattice. (4) The unit cell is the same as in a recently proposed three-dimensional crystal model, and calculated intensities in the equatorial region of the x-ray diffraction pattern agree with observed values.

A New X‐Ray Diffraction Method for Studying Imperfections of Crystal Structure in Polycrystalline Specimens

1951 ◽  
Vol 22 (5) ◽  
pp. 665-672 ◽  
Author(s):  
Alfred J. Reis ◽  
Jerome J. Slade ◽  
Sigmund Weissmann
Keyword(s):  
Crystal Structure ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
X Ray

The crystal structure of gatehouseite

2011 ◽  
Vol 75 (6) ◽  
pp. 2823-2832
Author(s):  
P. Elliott ◽  
A. Pring
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Three Dimensional ◽  
Direct Methods ◽  
Chemical Analyses ◽  
X Ray Diffraction ◽  
X Ray ◽  
Manganese Phosphate ◽  
Phosphate Mineral ◽  
Unit Formula

AbstractThe crystal structure of the manganese phosphate mineral gatehouseite, ideally Mn52+(PO4)2(OH)4, space group P212121, a = 17.9733(18), b = 5.6916(11), c = 9.130(4) Å, V= 933.9(4) Å3, Z = 4, has been solved by direct methods and refined from single-crystal X-ray diffraction data (T = 293 K) to an R index of 3.76%. Gatehouseite is isostructural with arsenoclasite and with synthetic Mn52+(PO4)2(OH)4. The structure contains five octahedrally coordinated Mn sites, occupied by Mn plus very minor Mg with observed <Mn—O> distances from 2.163 to 2.239 Å. Two tetrahedrally coordinated P sites, occupied by P, Si and As, have <P—O> distances of 1.559 and 1.558 Å. The structure comprises two types of building unit. A strip of edge-sharing Mn(O,OH)6 octahedra, alternately one and two octahedra wide, extends along [010]. Chains of edge- and corner-shared Mn(O,OH)6 octahedra coupled by PO4 tetrahedra extend along [010]. By sharing octahedron and tetrahedron corners, these two units form a dense three-dimensional framework, which is further strengthened by weak hydrogen bonding. Chemical analyses by electron microprobe gave a unit formula of (Mn4.99Mg0.02)Σ5.01(P1.76Si0.07(As0.07)Σ2.03O8(OH)3.97.

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