Interfacial surface charge and free accessibility to the PLA(2)-active site-like region are essential requirements for the activity of Lys49 PLA(2) homologues

Lys49 phospholipase A(2) homologues are highly myotoxic and cause extensive tissue damage but do not display hydrolytic activity towards natural phospholipids. The binding of heparin, heparin derivatives and polyanionic compounds such as suramin result in partial inhibition (up to 60%) of the myotoxic effects due to a change in the overall charge of the interfacial surface. In vivo experiments demonstrate that polyethylene glycol inhibits more than 90% of the myotoxic effects without exhibiting secondary toxic effects. The crystal structure of bothropstoxin-I complexed with polyethylene glycol reveals that this inhibition is due to steric hindrance of the access to the PLA(2)-active site-like region. These two inhibitory pathways indicate the roles of the overall surface charge and free accessibility to the PLA2-active site-like region in the functioning of Lys49 phospholipases A(2) homologues. Molecular dynamics simulations, small angle X-ray scattering and structural analysis indicate that the oligomeric states both in solution and in the crystalline states of Lys49 phospholipases A2 are principally mediated by hydrophobic contacts formed between the interfacial surfaces. These results provide the framework for the potential application of both clinically approved drugs for the treatment of Viperidae snakebites. (c) 2006 Elsevier Ltd. All rights reserved.

Revisiting the addition reaction of TeCl4 to alkynes: the crystal structure and docking studies of 1-chloro-2-trichlorotelluro-3-phenyl-propen-2-ol

Tellurium tetrachloride adds to alkynes via two pathways: a concerted syn addition, that yields Z-tri- and tetra-substituted alkenes or by an anti addition that yields E-alkenes. The mechanistic aspects of these divergent pathways have been reevaluated at the light of crystallographic data. The molecules, of the title compound, in the crystal, are associated in a helical fashion with a Te...Te pitch of 6.3492(6) angstrom. As it exhibits inhibitory activity for cathepsin B and in order to gain more insight of the inhibition mechanism, a docking study was undertaken providing insight on why organic telluranes are more efficient inhibitors than inorganic ones as AS-101. (c) 2006 Elsevier B.V. All rights reserved.

Crystal structure and infrared analysis of a new trinuclear platinum(II) complex with L-cysteine

A new trinuclear platinum(II) complex with cysteine of composition [Pt(C3H6NO2S)Cl](3)center dot(C2H6SO)(3) was obtained and structurally characterized by X-ray diffraction and infrared analysis. The compound crystallizes in the trigonal system, space group R3, and is described in a hexagonal cell with a=17.739(1), c=9.531(1) and Z=3. Cysteine is coordinated to Pt(II) through the nitrogen and sulphur atoms. Each cysteine sulphur bridges between two metal atoms. A square planar coordination sphere of platinum is completed by a chlorine atom. The complex is soluble in dimethyl sulfoxide.

Synthesis, crystal structure and theoretical studies of aryltellurenyl tetramethylthiourea(tmtu) iodine complexes: Ph-Te(tmtu)I (1) and beta-naphtyl-Te(tmtu)I (2)

(1) C11H17IN2STe, Mr = 463.83, P2(1)/n, a 7.6582(8), b = 13.8008(9), c = 15.026(3) angstrom, beta = 96.233(12)degrees, Z = 4, R-1 = 0.0318. (2) C15H19IN2STe, Mr = 513.88, P2(1)/n, a = 8.434(5), b = 11.697(5), c = 18.472(5) angstrom, beta = 98.556(5)degrees, Z = 4, R-1 = 0.0236. The synthesis of the aryltellurenyl N,N',-tetramethylthiourea (tmtu) iodide has been performed by ligand exchange with potassium iodide and the corresponding aryltellurenyl(tmtu) bromide. In both structures the tellurium atom is primarily three-coordinated, being bonded to a carbon atom of the organic ring and, in directions nearly perpendicular to the Te-C bond, to one tmtu sulfur atom and one iodine. In addition there are Te...secondary bonds, joining the molecules in centrosymmetric dimers, which in turn are joined through C-H...1 and C-H... S interactions, in (1) and (2), respectively.

Effect of niobia on the crystal structure and dielectric characteristics of Pb(Zr0.45Ti0.55)O-3 prepared from polymeric precursor

The influence of niobia addition on the phase formation and dielectric properties of Pb(Zr0.45Ti0.55)O-3 powder prepared from polymeric precursor was analyzed. The weight fraction and unit-cell volume of the tetragonal phase decreased, and the mass fraction of the rhombohedral phase increased, with increasing niobia concentration. The rhombohedral unit-cell volume increased up to 5 mol% of added Nb and then decreased. Small amounts of pyrochlore and tetragonal zirconia phases were observed in PZT powder with more than 10 mol% Nb. These results were interpreted as an indication that the Nb ion was substituted for the zirconium ion in the tetragonal phase. For sintered PZT samples at 1100 degrees C, no free-zirconia phase was observed. The dielectric constant increased with the niobia addition up to 5 mol% and decreased for higher concentrations. The Curie temperature decreased with niobia addition up to 10 mol% before the formation of pyrochlore phase. (C) 2000 Elsevier B.V. Ltd. All rights reserved.

Pt(II) and Ag(I) complexes with acesulfame: Crystal structure and a study of their antitumoral, antimicrobial and antiviral activities

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, characterization, crystal structure, and biological studies of vanadium complexes with glycolic acid

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The production structure and the dynamics of development

Includes bibliography

Synthesis, crystal structure and photoluminescence of a binuclear complex of europium(III) containing 3,5-dicarboxypyrazolate and succinate

The new europium binuclear complex [Eu2(dcpz) 2(suc)(H2O)8]·(H2O) 1.5 (dcpz = 3,5-dicarboxypyrazolate and suc = succinate) has been synthesized and structurally characterized by single crystal X-ray diffraction methods. The binuclear complex crystallizes in the triclinic space group P1̄ and consists of two lanthanide ions linked by two different bridging organic ligands. 3D supramolecular framework is constructed by hydrogen bonds. The compound shows strong red emission under UV excitation at room temperature associated to IL transitions indicating a ligand to metal energy transfer mechanism since the triplet energy level lies higher than that of europium 5D0 level. Magnetic susceptibility studies showed weak temperature dependence characteristic of the Van Vleck paramagnetism. © 2013 Elsevier Ltd. All rights reserved.

Isolation, X-ray crystal structure and theoretical calculations of the new compound 8-Eepicordatin and identification of others terpenes and steroids from the bark and leaves of Croton palanostigma Klotzsch

Estudos fitoquímicos com as cascas do caule e com as folhas de Croton palanostigma Klotzsch (Euphorbiaceae) levaram ao isolamento do novo diterpeno clerodânico 8-epicordatina (2), além de éster metílico do ácido 12-oxohardwickiico (3), aparisthmano, cordatina (1), ácido ent-trachiloban-18-óico, óxido de ent-13-epimanoila, óxido de ent-3-oxo-13-epimanoila, óxido de ent-3β-hidroxi-13-epimanoila, sitosterol, estigmasterol, estigmastan-3-ona, 6β-hidroxiestigmast-4-en-3-ona, 6β-hidroxiestigmasta-4,22-dien-3-ona, estigmast-4-en-3-ona, estigmasta-4,22-dien-3-ona, ácido 3-O-acetilaleuritolico, 11α-hidroxiurs-12-en-3-ona, α-amirenona, 24-metilenocicloartenona e lupenona. Estas substâncias foram isoladas através de procedimentos fitoquímicos usuais e suas estruturas foram deduzidas por estudos espectroscópicos, incluindo experimentos em 2D. Adicionalmente, a estrutura cristalina de 8-epicordatina (2) foi determinada por difração de raios-X. Cálculos teóricos de RMN ao nível B3PW91/DGDZVP foram usados para confirmação dos assinalamentos dos deslocamentos químicos dos hidrogênios H-7α e H-7β de 8-epicordatina.

Community Structure and Seasonal Dynamics of Dactylogyrus spp. (Monogenea) on the Fathead Minnow (Pimephales promelas) from the Salt Valley Watershed, Lancaster County, Nebraska

The gill monogene communities of Pimephales promelas (fathead minnow) in three distinct sites on converging streams were investigated from 2004 to 2006 in three different seasons. Thirty collections of P. promelas were made in southeastern Nebraska along three converging tributaries: Elk Creek (40.88534°N, 96.83366°W), West Oak Creek (40.9082°N, 96.81432°W), and Oak Creek (40.91402°N, 96.770583°W), Lancaster County, Nebraska. In all, 103 P. promelas were collected from Elk Creek, 115 from West Oak Creek, and 78 from Oak Creek and examined for gill monogenes. Among the P. promelas collected, 93.5% were infected with up to three species of Dactylogyrus, including Dactylogyrus simplex Mizelle, 1937, Dactylogyrus bychowskyi Mizelle, 1937, and Dactylogyrus pectenatus Mayes, 1977. Mean intensities at Elk Creek, West Oak Creek, and Oak Creek were 17.6, 22.8, and 25.1, and prevalences 88, 95, and 97%, respectively. At these three sites: (1) P. promelas does not share Dactylogyrus species with Semotilus atromaculatus (creek chub) or Notropis stramineus (sand shiner); (2) fish size and sex are not predictive of Dactylogyrus infection; (3) Dactylogyrus spp. vary (not always predictably) in their seasonal occurrence; (4) populations of Dactylogyrus spp. respond to environmental differences among sites; and (5) the community structure of Dactylogyrus spp. (order of abundance) is independent of environment.

Synthesis, crystal structure and magnetic properties of the helical oxalate-bridged copper(II) chain {[(CH3)(4)N](2)[Cu(C2O4)(2)] center dot H2O}(n)

The preparation, crystal structure and magnetic properties of a new oxalate-containing copper(II) chain of formula {[(CH3)(4)N](2)]Cu(C2O4)(2)] center dot H2O}(n) (1) [(CH3)(4)N+ = tetramethylammonium cation] are reported. The structure of 1 consists of anionic oxalate-bridged copper(II) chains, tetramethylammoniun cations and crystallization water molecules. Each copper(II) ion in 1 is surrounded by three oxalate ligands, one being bidentate and the other two exhibiting bis-bidenate coordination modes. Although all the tris-chelated copper(H) units from a given chain exhibit the same helicity, adjacent chains have opposite helicities and then an achiral structure results. Variable-temperature magnetic susceptibility measurements of 1 show the occurrence of a weak ferromagnetic interaction through the oxalate bridge [J = +1.14(1)cm(-1), the Hamiltonian being defined as H = -J Sigma nm S-i . S-j]. This value is analyzed and discussed in the light of available magnetostructural data for oxalate-bridged copper(H) complexes with the same out-of-plane exchange pathway. (C) 2012 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Crystal structure and spectroscopic properties of polymeric adducts of the tetra-mu-haloaspirinate-dicopper(II)

Eight new copper(II) complexes with halo-aspirinate anions have been synthesized: [Cu-2(Fasp)(4)(MeCN)(2)] center dot 2MeCN (1), [Cu-2(Clasp)(4)(MeCN)(2)]center dot 2MeCN (2), [Cu-2(Brasp)(4) (MeCn)(2)] center dot 2MeCn (3), {[Cu-2(Fasp)(4)(Pyrz)] center dot 2MeCN}(n) (4) {[Cu-2(Clasp)(4)(Pyrz)] center dot 2MeCN}(n) (5), [Cu-2(Brasp)(4)(Pyrz)](n) (6), [Cu-2(Clasp)(4)(4,4'-Bipy)](n) (7), and [Cu-2(Brasp)(4)(4,4'-Bipy)](n) (8) (Fasp: fluor-aspirinate; Clasp: chloro-aspirinate; Brasp: bromo-aspirinate; MeCN: acetonitrile; Pyrz: pyrazine; 4,4'-Bipy: 4,4'-bipyridine). The crystal structure of two 2 and 4 have been determined by X-ray diffraction methods. All compounds have been studied employing elemental analysis, IR, and UV-Visible spectroscopic techniques. The results have been compared with previous data reported for complexes with similar structures.

Characterization of suramin binding sites on the human group IIA secreted phospholipase A(2) by site-directed mutagenesis and molecular dynamics simulation

Suramin is a polysulphonated naphthylurea with inhibitory activity against the human secreted group IIA phospholipase A(2) (hsPLA2GIIA), and we have investigated suramin binding to recombinant hsPLA2GIIA using site-directed mutagenesis and molecular dynamics (MD) simulations. The changes in suramin binding affinity of 13 cationic residue mutants of the hsPLA2GIIA was strongly correlated with alterations in the inhibition of membrane damaging activity of the protein. Suramin binding to hsPLA2GIIA was also studied by MD simulations, which demonstrated that altered intermolecular potential energy of the suramin/mutant complexes was a reliable indicator of affinity change. Although residues in the C-terminal region play a major role in the stabilization of the hsPLA2GIIA/suramin complex, attractive and repulsive hydrophobic and electrostatic interactions with residues throughout the protein together with the adoption of a bent suramin conformation, all contribute to the stability of the complex. Analysis of the h5PLA2GIIA/suramin interactions allows the prediction of the properties of suramin analogues with improved binding and higher affinities which may be candidates for novel phospholipase A(2) inhibitors. (C) 2012 Elsevier Inc. All rights reserved.