Synthesis, characterization and molecular structures of the pyridinium trans-bis(pyridine)tetrachlororuthenate(III) and pyridinium trans-(carbonyl)(pyridine)tetrachlororuthenate(III)

The pyH[trans-RuCl4(py)2](1) and pyH[trans-RuCl4(CO)(py)](2) complexes were synthesized and found to crystallize in space group P21/n, Z = 4 with a = 8.080(7), b = 22.503(7), c = 10.125(6) Å, β = 93.19(6)° for (1) and a = 7.821(1), b = 10.337(3), c = 19.763(3) Å, β = 93.07(1)° for (2). The structures were solved by Patterson and difference Fourier techniques and refined to R = 0.062 for (1) and R = 0.038 for (2). In both cases the Ru(III) ion is octahedrally coordinated to four co-planar chlorine atoms, the nitrogen of the pyridine rings or carbon from the carbon monoxide. Another protonated pyridine group, which forms the counter-cation completes the crystal structures. The UV-Vis absorption spectra show three bands: (1) 360 (ε = 1180 M-1 cm-1), 441 (ε = 3200 M-1 cm-1) and 532 nm (ε = 400 M-1 cm-1); (2) 315(ε = 1150 M-1 cm-1), 442 (ε = 3170 M-1 cm-1) and 530 nm (ε = 390 M-1 cm-1). The two higher energy bands were associated with ligand-to-metal charge transfer transitions and a third band at lower energy was assigned to a d-d transition. Low temperature EPR data confirmed the presence of the paramagnetically active Ru(III) and it is consistent with axial symmetry of the complexes. The position of the stretching CO band in complex (2) is discussed in terms of metal-CO backbonding.

Synthesis of PbTiO3 by use of polymeric precursors

Lead titanate powders were synthesized through the use of polymeric precursors according to the Pechini Process. The polymeric precursor was calcined at temperatures ranging from 300 to 600°C for 1 or 2 h. X-ray diffraction (XRD) showed that lead titanate crystallizes from the precursor at temperatures as low as 400°C. No intermediate carbonate phase was detected by Fourier transform infrared spectroscopy (FTIR) or by XRD. A powder with mean particle size of 150 nm was obtained after calcination of the precursor at 600°C for 1 h. © 1998 Elsevier Science B.V. All rights reserved.

Plant Cell Wall Research Related to Evolution and Chemical Defenses

The plant cell wall is composed mainly of polysaccharides some constituted of repeating units of a single sugar, as cellulose or by two or more sugars grouped in repeating oligosaccharide blocks as the galactomannans and xyloglucans. Variations in composition and fine structure of these cell wall polysaccharides have been used as taxonomic markers and in the comprehension of the evolutive process, particularly in the Leguminosae. Partial hydrolysis of these compounds give rise to oligomers, some of which are capable of eliciting the synthesis of defensive substances in plants named phytoalexins. Species which differ in respect to phytoalexin liberation also differ in cell wall composition, particularly in the pectic fraction of the wall. Pectinases (mainly endopolygalacturonases) present in fungi, have been shown to hydrolyze plant cell walls yielding phytoalexin-eliciting oligosaccharides which differ in composition and in eliciting capacity in different species. These differences can be associated with the capacity of a given species to produce phytoalexins. On the other hand, the phytoalexin induction in plants is being used as a method of producing novel bioactive secondary metabolites.

Synthesis and thermal study of 8-hydroxy-quinoline derivatives of the alkaline Earth metals: I. Strontium complexes

Strontium complexes of 5,7-dibromo-, 5,7-dichloro-, 7-iodo- and 5-chloro-7-iodo-8-hydroxyquinoline were precipitated from an aqueous ammonia and acetone medium. The complexes obtained were Sr[(C9H4ONBr2)2]·2.5H 2O; Sr[(C9H4ONCl2)(OH)]·1.5H2O; Sr[(C9H5ONI)2]·5H2O and Sr[(C9H4ONICl)(OH)]·1.25H2O. The residues of their thermal decomposition were SrBr2; a mixture of SrCl2, SrCO3 and SrO3 SrCO3, and SrCO3, respectively. All were characterized by means of thermogravimetry, differential thermal analysis, complexometry with EDTA, atomic absorption spectroscopy, IR spectroscopy and X-ray diffraction. © 1999 Akadémiai Kiadó.

Synthesis and spectroscopic characterization of a novel coordination polymer of palladium(II) with pyrazole and azido ligands

The one-dimensional coordination polymer of palladium(II) with pyrazolato (Pz -) and azide (N 3 -) as bridging ligands, of formula [Pd 3(μ-N 3)(μ-Pz) 5] n, has been prepared. From IR and Raman studies it was evidenced the exobidentate nature of pyrazole ligands as well the μ-1,1-bridging coordination of azido groups. NMR experiments showed two sets of broadened signals with different intensities indicating the presence of pyrazolato groups in distinct chemical environments. The proposed structure of [Pd 3(μ-N 3)(μ-Pz) 5] n consists of a zigzag ribbon in which each (Pz) 2Pd(Pz) 2 entity is bound to two stacked planar units [Pd(μ-Pz)(μ-N 3)Pd core] with very weak Pd-Pd interaction, based on UV-Vis spectroscopy.

Synthesis and spectroscopic characterization of new metal(II) complexes with methionine sulfoxide

Methionine sulfoxide complexes of iron(II) and copper(II) were synthesized and characterized by chemical and spectroscopic techniques. Elemental and atomic absorption analyses fit the compositions K2[Fe(metSO) 2]SO4 · H2O and [Cu(metSO)2] · H2O. Electronic absorption spectra of the complexes are typical of octahedral geometries. Infrared spectroscopy suggests coordination of the ligand to the metal through the carboxylate and sulfoxide groups. An EPR spectrum of the Cu(II) complex indicates tetragonal distortion of its octahedral symmetry. 57Fe Mössbauer parameters are also consistent with octahedral stereochemistry for the iron(II) complex. The complexes are very soluble in water.

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.

Synthesis, characterization, and biological activity of a new palladium(II) complex with deoxyalliin

Synthesis, characterization, and biological activity of a new water-soluble Pd(II)-deoxyalliin (S-allyl-L-cysteine) complex are described in this article. Elemental and thermal analysis for the complex are consistent with the formula [Pd(C6H10NO2S)2]. 13C NMR, 1H NMR, and IR spectroscopy show coordination of the ligand to Pd(II) through S and N atoms in a square planar geometry. Final residue of the thermal treatment was identified as a mixture of PdO and metallic Pd. Antiproliferative assays using aqueous solutions of the complex against HeLa and TM5 tumor cells showed a pronounced activity of the complex even at low concentrations. After incubation for 24 h, the complex induced cytotoxic effect over HeLa cells when used at concentrations higher than 0.40 mmol/L. At lower concentrations, the complex was nontoxic, indicating its action is probably due to cell cycle arrest, rather than cell death. In agreement with these results, the flow cytometric analysis indicated that after incubation for 24 h at low concentrations of the complex cells are arrested in G0/G1. © 2005 NRC Canada.

Synthesis, characterization and thermal behaviour of solid-state compounds of 4-methoxybenzoate with some bivalent transition metal ions

Solid-state M-4-MeO-Bz compounds, where M stands for bivalent Mn, Co, Ni, Cu and Zn and 4-MeO-Bz is 4-methoxybenzoate, have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results led to have information about the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds. © 2005 Akadémiai Kiadó, Budapest.

Mechanochemical synthesis of Bi4Ti3O12

Our efforts were directed to the preparation of bismuth titanate - Bi 4e;Ti3O12 (BIT) by mechanically assisted synthesis. The mechanical activation was applied to prepare bismuth titanate, Bi4e;Ti3O12, from bismuth oxide, Bi 2O3, and titanium oxide, TiO2 (in an anatase crystal form). Mechanochemical synthesis was performed in a planetary ball mill in air atmosphere. Bismuth titanate ceramics was obtained by sintering at 1000° C The formation of Bi4e;Ti3O12 in the sintered samples was confirmed by X-ray diffraction analysis. Scanning electron microscopy, SEM, was used to study the particle size and powder morphology. The obtained results indicate that Bi4e;Ti3O12 from the powder synthesized by high-energy ball milling exhibits good sinterability, showing advantage of the mechanochemical process over conventional solid-state reaction.

Structural control of photoluminescence of four poly(urethane-urea-co-1,3,5-triazine)s: Synthesis and characterization

A series of segmented poly(urethane-urea)s containing 1,3,5 triazine in the hard block and hexamethylene spacers in the soft block was prepared. The hard to soft segment ratio was varied systematically, to afford a series of polymers in which the chromophore concentration varied from 4.2% to 18.1%. Although triazine emission is located in the UV region, the films with higher content of the chromophore emitted a visible blue light (425 nm) when excited at the very red-edge of the absorption band. The photophysical properties of the materials were strongly dependent on the relative amount of triazine moieties along the main chain. Isolated moieties emit in copolymers with small amount of triazine groups, indicating that even though in solid state, these moieties tend to be apart. Two photophysical consequences were observed when the amount of triazine increases: there is some energy transfer process involving isolated moieties with consequent decrease of the lifetime and an additional red-edge emission attributed to aggregated lumophores. The mono-exponential decay observed for the isolated form is substituted by a bi-exponential decay of the aggregated species. The materials were not strong emitters, but since the N-containing triazine moieties are good electron transport groups, the polymers have potential application as electron transport enhancers in various applications. © 2006 Elsevier B.V. All rights reserved.

Chalcopyrite and bornite differentially affect protein synthesis in planktonic cells of Acidithiobacillus ferrooxidans

Acidithiobacillus ferrooxidans is used in bioleaching industrial operations to recover metal ions from mineral sulfides. Chalcopyrite and bornite are copper sulfides that have the same elemental composition, but differ in their susceptibility to the bioleaching process. Our objective was to identify differentially expressed proteins in A. ferrooxidans LR cells exposed to chalcopyrite or bornite, as a sole energy source, for 24 hours. Compared to the control (without minerals), proteins were induced or repressed in planktonic cells after contact with chalcopyrite or bornite by 24 hours. These results demonstrated that the time of exposure to the copper minerals was enough to trigger distinct responses in the A. ferrooxidans metabolism. © 2007 Trans Tech Publications.

Chemical and biological characterization of four new linear cationic α-helical peptides from the venoms of two solitary eumenine wasps

Four novel peptides were isolated from the venoms of the solitary eumenine wasps Eumenes rubrofemoratus and Eumenes fraterculus. Their sequences were determined by MALDI-TOF/TOF (matrix assisted laser desorption/ionization time-of-flight mass spectrometry) analysis, Edman degradation and solid-phase synthesis. Two of them, eumenitin-R (LNLKGLIKKVASLLN) and eumenitin-F (LNLKGLFKKVASLLT), are highly homologous to eumenitin, an antimicrobial peptide from a solitary eumenine wasp, whereas the other two, EMP-ER (FDIMGLIKKVAGAL-NH 2) and EMP-EF (FDVMGIIKKIAGAL-NH 2), are similar to eumenine mastoparan-AF (EMP-AF), a mast cell degranulating peptide from a solitary eumenine wasp. These sequences have the characteristic features of linear cationic cytolytic peptides; rich in hydrophobic and basic amino acids with no disulfide bond, and accordingly, they can be predicted to adopt an amphipathic α-helix secondary structure. In fact, the CD (circular dichroism) spectra of these peptides showed significant α-helical conformation content in the presence of TFE (trifluoroethanol), SDS (sodium dodecylsulfate) and asolectin vesicles. In the biological evaluation, all the peptides exhibited a significant broad-spectrum antimicrobial activity, and moderate mast cell degranulation and leishmanicidal activities, but showed virtually no hemolytic activity. © 2011 Elsevier Ltd.

Characterization of a tannase from Emericela nidulans immobilized on ionic and covalent supports for propyl gallate synthesis

The extracellular tannase from Emericela nidulans was immobilized on different ionic and covalent supports. The derivatives obtained using DEAE-Sepharose and Q-Sepharose were thermally stable from 60 to 75 °C, with a half life (t50) >24 h at 80 °C at pH 5. 0. The glyoxyl-agarose and amino-glyoxyl derivatives showed a thermal stability which was lower than that observed for ionic supports. However, when the stability to pH was considered, the derivatives obtained from covalent supports were more stable than those obtained from ionic supports. DEAE-Sepharose and Q-Sepharose derivatives as well as the free enzyme were stable in 30 and 50 % (v/v) 1-propanol. The CNBr-agarose derivative catalyzed complete tannic acid hydrolysis, whereas the Q-Sepharose derivative catalyzed the transesterification reaction to produce propyl gallate (88 % recovery), which is an important antioxidant. © 2012 Springer Science+Business Media Dordrecht.

Synthesis, characterization and antifungal activity of quaternary derivatives of chitosan on Aspergillus flavus

Two series of new chitosan derivatives were synthesized by reaction of deacetylated chitosan (CH) with propyl (CH-Propyl) and pentyl (CH-Pentyl) trimethylammonium bromides to obtain derivatives with increasing degrees of substitution (DS). The derivatives were characterized by 1H NMR and potentiometric titration techniques and their antifungal activities on the mycelial growth of Aspergillus flavus were investigated in vitro. The antifungal activities increase with DS and the more substituted derivatives of both series, CH-Propyl and CH-Pentyl, exhibited antifungal activities respectively three and six times higher than those obtained with commercial and deacetylated chitosan. The minimum inhibitory concentrations (MIC) were evaluated at 24, 48 and 72h by varying the polymer concentration from 0.5 to 16g/L and the results showed that the quaternary derivatives inhibited the fungus growth at polymer concentrations four times lower than that obtained with deacetylated chitosan (CH). The chitosans modified with pentyltrimethylammonium bromide exhibited higher activity and results are discussed taking into account the degree of substitution (DS). © 2012 Elsevier GmbH.