Methyl- and phenylmercury(II) derivatives of 2-mercaptobenzothiazole. Crystal structure of (2-mercaptobenzothiazolato)methylmercury(II)

The complexes MeHgL and PhHgL (HL = 2-mercaptobenzothiazole) have been obtained from the reaction of the ligand with methylmercury hydroxide and phenylmercury acetate, respectively, in methanol. MeHgL, which has been characterized by single-crystal X-ray diffraction analysis (crystal data: triclinic, space group P1, with a = 8.009 (4) Å, b = 10.042 (4) Å, c = 13.074 (3) Å, α = 101.25 (2)°, β = 102.61(3)°, γ = 101.42 (3)°, R = 0.067), crystallizes with two independent molecules, I and I′, contained in each asymmetric unit with a coordination geometry based on the almost linear C-Hg-S group (Hg-S = 2.369 (6) Å, Hg-C = 2.06 (2) Å, and C-Hg-S = 177.7 (7)° for I; Hg-S = 2.375 (6) Å, Hg-C = 2.10 (3) Å, and C-Hg-S = 178.8 (6)° for I′). A secondary intramolecular interaction between the mercury atom and the C=N group of the ring and some weak intermolecular interactions between the metal and sulfur atoms were also found. The vibrational spectra of this compound and the phenylmercury(II) compound are discussed in light of the crystal structure. Diagnostic criteria of the bonding modes for the ligand are assessed. © 1985 American Chemical Society.

Crystal structure of the triclinic form of (2tbpo·H +)2tetrachlorocuprate(II){[(PhCH2) 3PO]2H}2CuCl4: The presence of extremely short O-H-O interactions

The structure of {[(PhCH2)3PO]2H} 2CuCl4 has been shown to contain four [(PhCH 2)3PO]2H+ cations with extremely short O-H-O distances of 2.295, 2.364, 2.394, and 2.404 Å, respectively.

Crystal morphologies on a cordierite glass surface

With suitable thermal treatments, a nearly stoichiometric cordierite glass (2 MgO.2 Al2O3. 5 SiO2) shows a variety of crystal morphologies on the external surfaces: lozenges, regular and elongated hexagons, spherical and square shaped particles. We initially identified these morphologies through optical and scanning electron microscopy techniques. Their structural features were distinguished by x-ray diffraction patterns, infrared and Roman microprobe spectra. We concluded that there are close structural similarities for: lozenges and glass matrix; regular and elongated hexagons; spherical and square particles. The ordering degree increases in the following sequence: glass matrix, lozenges, hexagons, squares and spheres. The lozenge crystals are known as X-phase. The hexagons belong to the μ-cordierite (high quartz solid solution) metastable phase and the squares and spheres to the α-cordierite stable phase.

Crystal, Molecular, and Electronic Structure of 1-Acetyl-indoline and Derivatives

The crystal and molecular structures of the following molecules have been determined: 1-acetyl-indoline, 1-acetyl-5-nitro-indoline, 1-acetyl-5-nitro-7-bromo-indoline, 1-acetyl-5-bromo-7-nitro-indoline, and 1-acetyl-5-bromo-7-nitro-indol. Molecular orbital calculations are performed for these compounds and two related species.

Crystal structures and luminescence properties of La3Zr4F25 and α-LaZr3F15

During a study of the LaF3-ZrF4 system, both La3Zr4F25 and α-LaZr3F15 compounds have been evidenced. Their crystal structures have been determined from single-crystal X-ray diffraction data. La3Zr4F25 crystallises in the cubic system with a = 12.384 Å and 143d space group (no. 220). Its crystal structure is built up of (ZrF6)2- octahedra and (LaF8)5- dodecahedra sharing corners. The low temperature form, α, of LaZr3F15 is orthorhombic (space group Pmmn, no. 59) with a = 15.721 Å, b = 16.299 Å, c = 8.438 Å. Its structure is built of corner-sharing tricaped trigonal prisms surrounding the La3+ ions and both octahedra and monocapped trigonal prisms encompassing the Zr4+ ions. This structure is characterised by dynamically disordered (ZrF6)2- complex anions. The Eu3+ luminescence properties of these phases have been investigated and are discussed in relationship with their crystal structures.

Crystal structures and magnetic properties of CuX2(pdmp)2 complexes (X = Br, Cl)

We report the synthesis and the structural and magnetic characterization of two new compounds: dibromobis-(pdmp)copper(II), CuBr2C22H24N4 (1), and dichlorobis(pdmp)copper(II), CuCl2C22H24N4 (2), where pdmp = 1-phenyl-3,5-dimethylpyrazole. The structures were refined by full-matrix least-squares techniques to R1 = 0.0620 and 0.0777, respectively. Compound 1 belongs to the space group P21/n with a = 8.165(5) Å, b = 10.432(3) Å, c = 13.385(4) Å, β = 100.12(4)̊, and Z = 2. Compound 2 belongs to the space group P21/c with a = 8.379(2) Å, b = 22.630(2) Å, c = 12.256(2) Å, β= 98.43(3)°, and Z = 4. It has the same molecular formula as a compound reported previously but a different crystal structure. Detailed single-crystal EPR measurements were performed for single-crystal samples of 1 and 2 at 9 and 35 GHz and at room temperature. The positions and line widths of the EPR lines were measured as a function of the magnetic field orientation in three orthogonal planes. The data were used to study the electronic properties of the copper ions and to evaluate the exchange interactions between them. Our results are discussed in terms of the electronic pathways for superexchange between copper ions, which are provided by the stacking of pyrazole and phenyl rings of neighboring molecules and by hydrogen-halogen bonds. © 1999 American Chemical Society.

Crystal structure of BaBi2Ta2O9

The crystal structure of the Aurivillius compound Bi2BaTa2O9 prepared via the chemical route was determined by direct methods using EXPO97, and refined using the Rietveld method with conventional X-ray diffraction data. The structure was found to be tetragonal (space group I4/mmm, number 139) and Z = 2, isomorphic of the Bi2BaNb2O9 reported by Blake and co-workers in the literature (1997). Two refinements were performed using the two asymmetry functions of DBWS-9807 (release 20/May/99). The unit cell for each case are: a = 3.932 22(6) Å, c = 25.5053(6) Å (RA) and a = 3.93250(7) Å, c = 25.5069(6) Å (RCF). The differences for atom positions, interatomic distances and angles are in the range of one standard deviation. Final agreements factors are: Rwp = 7.97%, S = 1.84, RBragg = 4.28%(RA), Rwp = 7.98%, S = 1.84, RBragg = 4.30% (RCF). The occupancies of Ba and Bi in site 2b were refined but constrained to have their summation equal to 1.00. The same constraints were applied to the Ba and Bi of the 4e site. The results show that on site 2b there are 70% of Ba and 30% of Bi and on the site 4e there are 82% of Bi and 18% of Ba. The charge equilibrium is maintained for one standard deviation of the site occupancies. © 2000 International Centre for Diffraction Data.

Surface amorphization in diamond turning of silicon crystal investigated by transmission electron microscopy

Silicon crystal exhibits a ductile regime during machining prior to the onset of fracture when appropriate cutting conditions are applied. The present study shows that the ductile regime is a result of a phase transformation which is indirectly evidenced by the amorphous phase detected in the machined surface. Transmission electron microscopy (TEM) planar view studies were successfully performed on monocrystalline silicon (1 0 0) single point diamond turned. TEM electron diffraction patterns show that the machined surface presents diffuse rings along with traces of crystalline material. This is attributed to crystalline silicon immersed in an amorphous matrix. Furthermore, only diffuse rings in the diffraction patterns of the ductile chip are detected, indicating that it is totally amorphous. © 2000 Elsevier Science B.V. All rights reserved.

Transference of a crystal protein gene from bacillus thuringiensis and its expression in bradyrhizobium sp. cells

The plasmid pHT409 that harbours the cryIA(a) gene for the production of a δ-endotoxin (crystal protein) from Bacillus thuringiensis was transferred into Bradyrhizobium sp. A conjugal transfer system aiming to introduce the plasmid into the Bradyrhizobium sp. host from colonies of an Escherichia coli donor strain (DH5α

Histoenzymological and ultrastructural changes in lateral muscle fibers of Oreochromis niloticus (Teleostei: Cichlidae) after local injection of veratrine

The effects of veratrine have been investigated in mammalian, amphibian, and crustacean muscle, but not in fish. In this work, the action of veratrine was studied in the lateral muscle of the freshwater teleost Oreochromis niloticus after intramuscular injection. Histoenzymological typing and electron microscopy of muscle fibers before and 15, 30, and 60 min after veratrine injection (10 ng/kg fish) were used to indirectly assess the morphological changes and the oxidative and m-ATPase activities. In some cases, muscles were pretreated with tetrodotoxin to determine whether the ultrastructural changes were the result of Na+ channel activation by veratrine. Veratrine altered the metabolism of fibers mainly after 30 min. Oxidative fibers showed decreased NADH-TR activity, whereas that of glycolytic and oxidative-glycolytic type fibers increased. There was no change in the m-ATPase activity of the three fiber types, except at 60 min postveratrine, when a novel fiber type, which showed no reversal after acidic and alkaline preincubations, appeared. Ultrastructural damage involved sarcomeres, myofibrils, and mitochondria, but the T-tubules remained intact. Pretreatment with tetrodotoxin (1 ng/ml) prevented the ultrastructural changes caused by veratrine. These results show that in fish skeletal muscle veratrine produces some effects that are not seen in mammalian muscle.

Crystal structure of di-μ(N,S)-thiocyanato-bis[(N-benzylideneaniline-C 2,N)palladium(II)], [Pd(C6H4CH=NC 6H5)(μ-SCN)]2

C28H20N4Pd2S2, monoclinic, P121/c1 (No. 14), a = 11.325(1) Å, b = 13.530(1) Å, c = 17.925(1) Å, β = 106.23(1)°, V = 2637.1 Å 3, Z = 4, Rgt(F) = 0.052, wRref(F2) = 0.129, T = 293 K. © by Oldenbourg Wissenschaftsverlag.

Collagen fibers in human prostatic lesions: histochemistry and anisotropies

The present study focuses on establishing patterns of collagen fibers distribution in prostatic nodular hyperplasia and adenocarcinomas, in comparison with the normal tissue. Sections of prostatic transurethral resection were subjected to Gömöri's method for collagen fibers and reticulin and analyzed under ordinary and polarized light microscopy. Controls and hyperplastic regions present collagen fibers with variable thickness that run in different directions, establishing a tridimensional network. These fibers exhibit birefringence and dichroism thus demonstrating their fibrillar integrity. On the other hand, increased variability in collagen fiber distribution and anisotropical properties occur in adenocarcinomas evaluated in accordance with the Gleason's score. In some of their areas, a well-defined collagen network delimitates the base of transformed epithelial cells whereas in other areas the collagen fibers are disorganized and do not establish a boundary between the epithelial structures and the stroma. In these areas, collagen is found in the stroma. It was also observed that adenocarcinoma tumor cells rest on a scaffold of thin and dendritic collagen fibers. Collagen fibers of the prostatic stroma of the adenocarcinomas may show a modification in arrangement and fibrillar compactness. In prostatic nodular hyperplasia, there is no change in collagen molecular integrity, since collagen affinity for silver and collagen birefringence are similar to controls. In adenocarcinoma with high dedifferentiation degree, thin and branched strongly argyrophilic and birefringent collagen fibers are detected in regions of cell proliferation. In the adjacent stroma, hyaline plaques are indicative of matrix degradation or remodellation.

Synthesis and crystal phase evaluation of hydroxylapatite using the rietveld-maximum entropy method

Bioceramic systems based on hydroxylapatite (HAP) are an important class of bioactive materials that may promote bone regeneration. The aim of this research was to evaluate how the stoichiometry of HAP influences its microstructural properties when diagnosed using the combined Rietveld method and Maximum entropy method (MEM). The Rietveld Method (RM) is recognizably a powerful tool used to obtain structural and microstructural information of polycrystalline samples analyzed by x-ray diffraction. Latterly have combined the RM with the maximum entropy method (MEM), with the goal of improve structural refinement results. The MEM provides high resolution maps of electron density and their analysis leave the accurate localization of atoms inside of unit cell. Like that, cycles Rietveld-MEM allow an excellent structural refinement In this work, a hydroxylapatite sample obtained by emulsion method had its structure refined using one cycle Rietveld-MEM with x-ray diffraction data. The indices obtained in initial refinement was Rwp = 7.50%, Re = 6.56%, S - 1.14% e RB = 1.03%. After MEM refinement and electron densities maps analysis to correction of atomics positions, the news indicators of Rietveld refinement quality was Rwp = 7.35%, Re = 6.56%, S = 1.12% and RB = 0.75%. The excellent result obtained to RB shows the efficiency of MEM as auxiliary in the refinement of structure of hydroxylapatite by RM.

Kinetics and crystal structure of human purine nucleoside phosphorylase in complex with 7-methyl-6-thio-guanosine

Purine nucleoside phosphorylase (PNP) catalyzes the reversible phosphorolysis of nucleosides and deoxynucleosides, generating ribose 1-phosphate and the purine base, which is an important step of purine catabolism pathway. The lack of such an activity in humans, owing to a genetic disorder, causes T-cell impairment, and drugs that inhibit this enzyme may have the potential of being utilized as modulators of the immunological system to treat leukemia, autoimmune diseases, and rejection in organ transplantation. Here, we describe kinetics and crystal structure of human PNP in complex with 7-methyl-6-thio-guanosine, a synthetic substrate, which is largely used in activity assays. Analysis of the structure identifies different protein conformational changes upon ligand binding, and comparison of kinetic and structural data permits an understanding of the effects of atomic substitution on key positions of the synthetic substrate and their consequences to enzyme binding and catalysis. Such knowledge may be helpful in designing new PNP inhibitors. © 2005 Elsevier Inc. All rights reserved.

Morphometry and histochemistry of the Rectus abdominis muscle fibers of tufted capuchin monkeys (Cebus apella Linnaeus, 1758)

The phylogenetic proximity of primates to humans, along with their behavioral, biochemical, and anatomical similarities, make such animals more interesting experimental models for biomedical researches, as compared to classical laboratory animals. Another aspect that has called the attention of researchers is the differentiated quadrupedalism present in some primates. The tufted capuchin monkey uses the ground and tree branches as its support for locomotion, showing various postures while performing this task. On the basis of this information, we have decided to study the rectus abdominis muscle of the tufted capuchin monkey, with the following goals: the frequency and area of fiber types; its possible compartmentalization; and identify if this muscle is better adapted to phasic or postural activities. To do this, samples were removed from 4 regions of the rectus abdominis muscle of 6 adult male tufted capuchin monkeys, and were submitted to reaction with m-ATPase, (with alkaline and acid pre-incubation), NADH, and H.E.. Results showed: a statistically significant difference (P<0.05) for both frequency and area, between fiber types FG and FOG and FG and SO, but did not show a statistically significant difference between fibers FOG and SO, in all studied regions; similarity in frequency and area of a same fiber type (FG, FOG, and SO) among the studied regions. Based on these data, it was concluded that: the rectus abdominis muscle of the tufted capuchin monkey does not show fiber compartmentalization, since the distribution and size patterns of the different fiber types are similar in the studied regions; there is a predominance of fast twitch fibers (FG + FOG) over slow twitch fibers (SO), for frequency and area, which characterizes the muscle as being more dedicated to phasic than to postural activities. © 2006 Sociedad Chilena de Anatom.