The crystal structure of kalsilite, KAlSiO4

1965 ◽  
Vol 35 (272) ◽  
pp. 588-595 ◽  
Author(s):  
A. J. Perrotta ◽  
J. V. Smith
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Crystal Structures ◽  
Bond Angle ◽  
Three Dimensional ◽  
Full Matrix ◽  
Ideal Position ◽  
Wide Range ◽  
The Ideal

SummaryA full-matrix, three-dimensional refinement of kalsilite, KAlSi04 (hexagonal, a 5·16, c 8.69 Å, P6a), shows that the silicon and aluminium atoms are ordered. The respective tetrahedral distances of 1·61 and 1·74 Å agree with values of 1·61 and 1·75 Å taken to be typical of framework structures. As in nepheline, an oxygen atom is statistically distributed over three sites displaced 0·25 Å from the ideal position on a triad axis. This decreases the bond angle from 180° to 163° in conformity with observations on some other crystal structures. The potassiumoxygen distances of 2·77, 2·93, and 2·99 Å are consistent with the wide range normally found for this weakly bonded atom.

Geometric Three-Dimensional End-to-Side Microvascular Anastomosis: A Simple and Reproducible Technique

2017 ◽  
Vol 34 (04) ◽  
pp. 258-263 ◽  
Author(s):  
Adrian Ooi ◽  
Daniel Butz ◽  
Sean Fisher ◽  
Zachary Collier ◽  
Lawrence Gottlieb
Keyword(s):  
Three Dimensional ◽  
Free Tissue Transfer ◽  
Free Flaps ◽  
Suture Line ◽  
Success Rates ◽  
Recipient Vessel ◽  
Wide Range ◽  
Extremity Reconstruction ◽  
Geometric Technique ◽  
The Ideal

Background End-to-side (ETS) anastomoses are useful when preservation of distal vascularity is critical. The ideal ETS microanastomosis should maintain a wide aperture and have a smooth take-off point to minimize turbulence, vessel spasm, and thrombogenicity of the suture line. We have developed a unique, dependable, and reproducible geometric technique for ETS anastomoses, and analyze its efficacy in our series of patients. Methods The geometric ETS technique involves creating a three-dimensional (3D) diamond-shaped defect on the recipient vessel wall, followed by a slit incision of the donor vessel to create a “spatula” fitting this defect. This technique removes sutures from the point of most turbulent blood flow while holding the recipient vessel open with a patch vesselplasty effect. We perform a retrospective review of a single surgeon's experience using this technique. Results The geometric 3D ETS technique was used in 87 free flaps with a total of 102 ETS anastomoses in a wide range of cases including head and neck, trunk and genitourinary, and extremity reconstruction. Overall, free flap success rates were 98%. Conclusions The geometric 3D ETS technique creates a wide anastomosis, minimizes turbulence-inducing thrombogenicity, and mechanically holds the recipient vessel open. It is reliable and reproducible, and when performed properly has been shown to have high rates of success in a large group of free tissue transfer patients.

scholarly journals Binding of cardiotonic steroids to Na+,K+-ATPase in the E2P state

2020 ◽  
Vol 118 (1) ◽  
pp. e2020438118
Author(s):  
Ryuta Kanai ◽  
Flemming Cornelius ◽  
Haruo Ogawa ◽  
Kanna Motoyama ◽  
Bente Vilsen ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Conformational Changes ◽  
Ground State ◽  
Sodium Pump ◽  
Structural Features ◽  
Animal Cells ◽  
Inhibitory Potency ◽  
New Members ◽  
Wide Range

The sodium pump (Na+, K+-ATPase, NKA) is vital for animal cells, as it actively maintains Na+ and K+ electrochemical gradients across the cell membrane. It is a target of cardiotonic steroids (CTSs) such as ouabain and digoxin. As CTSs are almost unique strong inhibitors specific to NKA, a wide range of derivatives has been developed for potential therapeutic use. Several crystal structures have been published for NKA-CTS complexes, but they fail to explain the largely different inhibitory properties of the various CTSs. For instance, although CTSs are thought to inhibit ATPase activity by binding to NKA in the E2P state, we do not know if large conformational changes accompany binding, as no crystal structure is available for the E2P state free of CTS. Here, we describe crystal structures of the BeF3− complex of NKA representing the E2P ground state and then eight crystal structures of seven CTSs, including rostafuroxin and istaroxime, two new members under clinical trials, in complex with NKA in the E2P state. The conformations of NKA are virtually identical in all complexes with and without CTSs, showing that CTSs bind to a preformed cavity in NKA. By comparing the inhibitory potency of the CTSs measured under four different conditions, we elucidate how different structural features of the CTSs result in different inhibitory properties. The crystal structures also explain K+-antagonism and suggest a route to isoform specific CTSs.

The crystal structure of gersdorffite (III), a distorted and disordered pyrite structure

1968 ◽  
Vol 36 (283) ◽  
pp. 940-947 ◽  
Author(s):  
P. Bayliss ◽  
N. C. Stephenson
Keyword(s):  
Crystal Structure ◽  
Metal Atom ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Partially Ordered ◽  
The Ideal

SummaryThe crystal structure of gersdorffite (III) has been examined with three-dimensional Weissenberg X-ray diffraction data. The unit cell is isometric with a 5·6849 ± 0·0003 Å, space group PI, and four formula units per cell. This structure has the sulphur and arsenic atoms equally distributed over the non-metal atom sites of pyrite. All atoms show significant random displacements from the ideal pyrite positions to produce triclinic symmetry, which serves to distinguish this mineral from a disordered cubic gersdorffite (II) and a partially ordered cubic gersdorffite (I). Factors responsible for the atomic distortions are discussed.

A REFINEMENT OF THE CRYSTAL STRUCTURES OF (NH4)2TeBr6 AND Cs2TeBr6

1966 ◽  
Vol 44 (8) ◽  
pp. 939-943 ◽  
Author(s):  
A. K. Das ◽  
I. D. Brown
Keyword(s):  
Least Squares ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Bromine Atom ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray ◽  
Anisotropic Temperature ◽  
Temperature Factors

(NH4)2TeBr6 and Cs2TeBr6 crystals have the cubic K2PtCl6 structure with space group: [Formula: see text] with a0 = 10.728 ± 0.003 Å and 10.918 ± 0.002 Å respectively. The positional coordinate of the bromine atom, and the anisotropic temperature factors of all atoms in the unit cell, have been refined for both crystals by a full matrix least-squares analysis of the three dimensional X-ray diffraction data (R = 0.08). The Te—Br distance, corrected for probable thermal motions of atoms forming the bond, is 2.70 ± 0.01 Å in both crystals.

Nobiletin: a citrus flavonoid displaying potent physiological activity

2016 ◽  
Vol 72 (2) ◽  
pp. 124-127 ◽  
Author(s):  
Shuji Noguchi ◽  
Haruka Atsumi ◽  
Yasunori Iwao ◽  
Toshiyuki Kan ◽  
Shigeru Itai
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Physiological Activity ◽  
Covalent Bond ◽  
Physiological Properties ◽  
Wide Range ◽  
Methoxy Groups ◽  
Citrus Peels ◽  
Anti Inflammatory ◽  
Chromene Ring

Nobiletin [systematic name: 2-(3,4-dimethoxyphenyl)-5,6,7,8-tetramethoxy-4H-chromen-4-one; C21H22O8] is a flavonoid found in citrus peels, and has been reported to show a wide range of physiological properties, including anti-inflammatory, anticancer and antidementia activities. We have solved the crystal structure of nobiletin, which revealed that the chromene and arene rings of its flavone moiety, as well as the two methoxy groups bound to its arene ring, were coplanar. In contrast, the C atoms of the four methoxy groups bound to the chromene ring are out of the plane, making the molecule conformationally chiral. A comparison of the crystal structures of nobiletin revealed that it could adopt a variety of different conformations through rotation of the covalent bond between the chromene and arene rings, and the orientations of methoxy groups bound to the chromene ring.

Crystal chemistry of zirconosilicates and their analogs: topological classification of MT frameworks and suprapolyhedral invariants

2002 ◽  
Vol 58 (2) ◽  
pp. 198-218 ◽  
Author(s):  
G. D. Ilyushin ◽  
V. A. Blatov
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Crystal Chemistry ◽  
Three Dimensional ◽  
Geometrical Interpretation ◽  
Topological Classification ◽  
Hierarchical Analysis ◽  
Framework Structure ◽  
Coordination Spheres

The first attempt is undertaken to consider systematically topological structures of zirconosilicates and their analogs (60 minerals and 34 synthetic phases), where the simplest structure units are MO6 octahedra and TO4 tetrahedra united by vertices ([TO4]:[MO6] = 1:1–6:1). A method of analysis and classification of mixed three-dimensional MT frameworks by topological types with coordination sequences {N k } is developed, which is based on the representation of crystal structure as a finite `reduced' graph. The method is optimized for the frameworks of any composition and complexity and implemented within the TOPOS3.2 program package. A procedure of hierarchical analysis of MT-framework structure organization is proposed, which is based on the concept of polyhedral microensemble (PME) being a geometrical interpretation of coordination sequences of M and T nodes. All 12 theoretically possible PMEs of MT 6 polyhedral composition are considered where T is a separate and/or connected tetrahedron. Using this methodology the MT frameworks in crystal structures of zirconosilicates and their analogs were analyzed within the first 12 coordination spheres of M and T nodes and related to 41 topological types. The structural correlations were revealed between rosenbuschite, lavenite, hiortdahlite, woehlerite, siedozerite and the minerals of the eudialyte family.

Refinement of the structure of Mg2As2O7

1970 ◽  
Vol 48 (6) ◽  
pp. 890-894 ◽  
Author(s):  
C. Calvo ◽  
K. Neelakantan
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Least Squares ◽  
Unit Cell ◽  
Full Matrix ◽  
Space Group ◽  
Cell Dimensions ◽  
Central Oxygen ◽  
R Value ◽  
Unit Cell Dimensions

The crystal structure of Mg2As2O7 has been refined by full matrix least squares procedures using 587 observed reflections. The structure of Mg2As2O7 is of the thortveitite type, as reported by Łukaszewicz, with space group C2/m and unit cell dimensions a = 6.567(2) Å, b = 8.524(4) Å, c = 4.739(1) Å, β = 103.8(1)°, and Z = 2. The As—O—As group in the anion appears to be linear but the central oxygen atom undergoes considerable disorder in the plane perpendicular to this group. The AsO bond distances uncorrected for thermal motion are 1.67 Å for the As—O(—As) bond and 1.66 and 1.65 Å for the terminal As—O bonds. The final R value obtained is 0.088.

Crystal Structure of α-Zn2V2O7

1973 ◽  
Vol 51 (7) ◽  
pp. 1004-1009 ◽  
Author(s):  
Ramanathan Gopal ◽  
Crispin Calvo
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Bond Length ◽  
Fold Axis ◽  
Full Matrix ◽  
X Ray ◽  
R Value ◽  
The Individual ◽  
Zn Ions ◽  
Oxygen Atoms

α-Zn2V2O7 is monoclinic with lattice parameters a = 7.429(5), b = 8.340(3), c = 10.098(3) Å, β = 111.37(5)°, Z = 4 and space group C2/c. The structure was refined using a full matrix least-squares with 1034 reflections measured with a quarter-circle General Electric automatic X-ray diffractometer to a final R value of 0.066. The anion consists of a pair of VO4 tetrahedra sharing an oxygen atom which lies on a two-fold axis. The bridging V—O bond length is 1.775(4) Å while the three independent terminal ones are 1.728(4), 1.704(7), and 1.658(8) Å long. These bond lengths are consistent with the charge character around the individual oxygen atoms. The Zn ions are coordinated to five oxygen atoms with Zn—O bonds ranging from 1.973 to 2.088°Å. The structure is similar to that of α-CU2P2O7 and transforms to the thortvietite structure at about 615 °C.

Crystal Structure of α-VPO5

1973 ◽  
Vol 51 (16) ◽  
pp. 2621-2625 ◽  
Author(s):  
Byron Jordan ◽  
Crispin Calvo
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Least Squares ◽  
Least Squares Method ◽  
Fold Axis ◽  
Full Matrix ◽  
Bond Lengths ◽  
R Value ◽  
A Site ◽  
Vanadium Ion

α-VPO5 crystallizes in the tetragonal space group P4/n with a = 6.014(7) and c = 4.434(2) Å. The structure, isotypic with that of α-VSO5, was refined by full-matrix least-squares method to an R value of 0.089 using 239 independent reflections. The vanadium ion lies on a crystallographic four-fold axis, as does one of the oxygen atoms, and the P on a site of [Formula: see text] symmetry. A second oxygen atom, as a result of disorder, occurs in two positions which are mirror reflected with respect to the ac plane. The structure consists of highly distorted VO6 groups with bond lengths along the c axis of 1.580(11) and 2.853(11) Å while the remaining four V—O bond lengths are all 1.858(8) Å. The P—O bond lengths in the PO4. tetrahedron are 1.541(8) Å with the PO4 groups bridging across four chains of VO6 groups.

THE CRYSTAL STRUCTURE AND PHASE TRANSITIONS OF β-Zn2P2O7

1965 ◽  
Vol 43 (5) ◽  
pp. 1147-1153 ◽  
Author(s):  
Crispin Calvo
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Oxygen Atom ◽  
Bond Angle ◽  
Thermal Motion ◽  
Mirror Plane ◽  
Red Emission ◽  
Space Group ◽  
Central Oxygen ◽  
Cation Coordination

β-Zn2P2O7 crystallizes in the C2/m space group with lattice parameters a = 6.61 ± 0.01 Å, b = 8.29 ± 0.01 Å, c = 4.51 ± 0.01 Å, β = 105.4° ± 0.2° and z = 2. The anion, P2O7−4, is centered with its mirror plane coinciding with the mirror plane of the space group. The central oxygen atom, however, shows high anisotropic thermal motion and thus it appears that the P—O—P bond angle is linear only as a result of thermal averaging. The cations are found on twofold axes in irregular sixfold coordination and these ZnO6 groups share three edges with neighboring cations. This cation coordination is, therefore, consistent with that predicted from the red emission of β-Zn2P2O7:Mn++.

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