Determination of metal ions in natural waters by flame-AAS after preconcentration on a 5-amino-1,3,4-thiadiazole-2-thiol modified silica gel.

5-amino-1,3,4-thiadiazole-2-thiol groups attached on a silica gel surface have been used for adsorption of Cd(II), Co(II), Cu(II), Fe(III), Ni(II), Pb(II) and Zn(II) from aqueous solutions. The adsorption capacities for each metal ion were (in mmol.g(-1)): Cd(II)= 0.35, Co(II)= 0.10, Cu(II)= 0.15, Fe(III)= 0.20, Hg(Il)= 0.46, Ni(II)= 0.16, Pb(II)= 0.13 and Zn(II)= 0.15. The modified silica gel was applied in the preconcentration and quantification of trace level metal ions present in water samples (river, and bog water).

Structural characterization of 0.5PbMg(1/3)Nb(2/3)O(3)-0.5Ba(x)Pb((1-x))TiO(3) powders

The present work reports the effects caused by barium on phase formation, morphology and sintering of lead magnesium niobate-lead titanate (PMN-50PT). Ab initio study of 0.5PbMg(1/3)Nb(2/3)O(3)-0.5Ba(x)Pb((1-x))TiO(3) ceramic powders, with x = 0, 0.20, and 0.40 was proposed, considering that the partial substitution of lead by barium can reestablish the equilibrium of monoclinic-tetragonal phases in the system. It was verified that even for 40 mol% of barium, it was possible to obtain pyrochlore-free PMN-PT powders. The increase of the lattice parameters of PMN-PT doped-powders confirmed dopant incorporation into the perovskite phase. The presence of barium improved the reactivity of the powders, with an average particle size of 120 nm for 40 mol% of barium against 167 mn for the pure sample. Although high barium content (40 mol%) was deleterious for a dense ceramic, contents up to 20 mol% allowed 95% density when sintered at 1100 degrees C for 4 h. (c) 2007 Elsevier Ltd. All rights reserved.

Evaluation of the beta-glucanolytic enzyme complex of Trichoderma harzianum Rifai for the production of gluco-oligosaccharide fragments by enzymatic hydrolysis of 1,3;1,6-beta-D-glucans

Botryosphaeran, a new exopolysaccharide from the endophytic fungus Botryosphaeria rhodina MAMB-05, and algal laminarin were hydrolyzed by partially-fractionated enzymes of the beta-glucanolytic complex from Trichoderma harzianum Rifai. beta-Glucanase fractions (F-I and F-II) separated by gel permeation chromatography presented different modes of attack on botryosphaeran and laminarin. Botryosphaeran was hydrolyzed to the extent of 66% (F-I) and 98% (F-II) within 30 min, and its main hydrolysis products were gluco-oligosaccharides of DP >= 4, with lesser amounts of glucose, di- and tri-saccharides. The action of enzyme fractions I and II on laminarin resulted in 15% conversion to glucose, while the percentage of saccharification was radically different (70% for F-I and 25% for F-II). The different product arrays within the polysaccharide hydrolysates can be explained by the difference in the enzymes' specificities within each enzyme fraction, and the molecular structures of the polysaccharides and their complexity.

Three exopolysaccharides of the beta-(1 -> 6)-D-glucan type and a beta-(1 -> 3;1 -> 6)-D-glucan produced by strains of Botryosphaeria rhodina isolated from rotting tropical fruit

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

Triple helix conformation of botryosphaeran, a (1 -> 3;1 -> 6)-beta-D-glucan produced by Botryosphaeria rhodina MAMB-05

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Binuclear cyclopalladated compounds with antitubercular activity: synthesis and characterization of [{Pd(C-2,N-dmba)(X)}(2)(mu-bpp)] (X = Cl, Br, NCO, N-3; bpp=1,3-bis(4-pyridyl)propane)

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

1,3-dipolar cycloaddition of CS2 to the coordinated azide in the cyclopalladated [Pd(bzan)(mu-N-3)](2). Crystal and molecular structure of di(mu-N,S-1,2,3,4-thiatriazole-5-thiolate)bis[(benzylideneaniline-C-2,N)palladium(II)]

The compound [Pd(bzan)(mu -N-3)](2) 1, bzan = benzylideneaniline, was prepared from [Pd(bzan) (mu -OOCCH3)](2) by an anion exchange reaction. The 1,3-dipolar cycloaddition of carbon disulfide to the bridged coordinated azide in the cyclometallated compound I was investigated. The species resulting from this reaction, di(mu -N,S-1,2,3,4-thiatriazol-5-thiolate)bis[(benzylideneaniline)palladium(II)] 2, was characterized by IR spectroscopy and X-ray diffraction. The compound 2 is a dimer containing two [Pd(benzylideneaniline)] moieties connected by two vicinal bridging N,S-1,2,3,4-thiatriazole-5-thiolate anions in a square-planar coordination geometry for the palladium atoms.

Purification and properties of acid phosphatase (EC 3.1.3.2) secreted by strain 74A of the mould Neurospora crassa

Both P-i-repressible acid phosphatases, IIb (mycelial) and IIc (extracellular), synthesized by Neurospora crassa and purified to apparent homogeneity by 7.5% PAGE, are monomers, are inhibited by 2 mM ZnCl2 and are nonspecifically stimulated by salts. However, the IIc form is activated by p-nitrophenylphosphate (in a negative cooperativity effect with a K-0.5 of 2.5 mM) whereas form IIb shows Michaelis kinetics, with a K-m of 0.5 mM. Thus, since both enzymatic forms may be expressed by the same gene (pho-3), it is possible that post-translational modifications lead to the excretion of an enzymatic form with altered Michaelis kinetics compared with the enzymatic form retained by the mycelium.

The absolute configuration of 1-(3 ',4 '-dihydroxycinnamoyl)cyclopentane-2,3-diol from the Amazonian tree Chimarrhis turbinata

An antioxidant, 1-(3',4'-dihydroxycinnamoyl) cyclopentane-2,3-diol [ or ( E)-2,3-dihydroxycyclopentyl-3-(3',4'-dihydroxyphenyl) acrylate ( 1)], and two known trans- and cis-chlorogenic acid methyl esters were isolated from the ethanolic extract of the leaves of Chimarrhis turbinata. The relative configuration of 1 was determined by NMR and by comparison of the circular dichroic spectrum ( CD) with those of the enantiomers of synthetic 3', 4'-dimethoxycinnamoyl analogues. The absolute configuration of one of the synthetic enantiomers was determined using the CD exciton chirality method. This established the structure of naturally occurring 1 as (E)- 2,3-dihydroxycyclopentyl- 3-(3', 4'-dihydroxyphenyl) acrylate.

Increased production of beta-1,3 glucanase and proteins in Bipolaris sorokiniana pathosystem treated using commercial xanthan gum

Barley plants (cultivars Embrapa 127, 128 and 129) treated with xanthan gum, and with different time intervals between the administration of the inducer and the pathogen, demonstrated induction of resistance against Bipolaris sorokiniana. Induction was shown to have local and systemic action. In order to prove the resistance effect, biochemical analyses were performed to quantify proteins and the enzymatic activity of beta-1,3 glucanase. Results demonstrated that barley plants treated with the inducer, showed an increase in the concentration of proteins, as well as in the activity of the enzyme beta-1,3 glucanase, when compared with the extract from healthy plants. In infected plants, protein concentrations decreased and enzymatic activity was lower than in healthy plants. Results suggest that barley plants treated with xanthan gum developed mechanisms responsible for induced resistance, which are still unknown. The most important macromolecule in the defense mechanism was demonstrated to be PR-protein, due to its accumulation and concentration of proteins. However, it may not be the only macromolecule responsible for the resistance effect. (C) 2004 Elsevier SAS. All rights reserved.

Crystal structure of potassium trifluoro(2-methyl-1,3-dithiano)borate, K(C5H9BF3S2)

C5H9BF3KS2, triclinic, P (1) over bar (no. 2), a = 11.9238(5) angstrom, b = 13.6060(5) angstrom, c = 14.0280(3) angstrom, alpha = 114.995(2)degrees, beta = 92.035(2)degrees, gamma = 92.390(2)degrees, V = 2057.4 angstrom(3), Z = 8, R-gt(F) = 0.049, wR(ref)(F-2) = 0.117, T = 296 K.

Crystal structure of 1,1,3-trimethyl-2-(2-(2,2,6-trimethyl-cyclohexyl)ethyl) cyclohexane, C20H34

C20H34, monoclinic, P12(1)/n1 (no. 14), a = 10.647(l) angstrom, b = 6.6844(9) angstrom, c = 11.723(1) angstrom, beta = 99.75(1)degrees, V = 822.3 angstrom(3) Z = 2, R-gt(F) = 0.043, wR(ref)(F-2) = 0.110, T = 93 K.

THE PHO-2A MUTANT OF NEUROSPORA-CRASSA WHICH IS DEFICIENT IN PI-REPRESSIBLE ALKALINE-PHOSPHATASE (EC 3.1.3.1) IS ALSO DEFECTIVE IN PI-REPRESSIBLE ACID-PHOSPHATASE (EC 3.1.3.2)

1. The mycelial Pi-repressible acid phosphatase presented p-nitrophenylphosphatase activity with negative cooperativity and Michaelian behavior when synthesized by the wild-type and pho-2A mutant strains of Neurospora crassa, respectively.2. The major acid phosphatase present in cell extracts of the pho-2A mutant of N. crassa grown in low Pi medium is more thermolabile (t1/2 = 4 min at 54-degrees-C, pH 5.4) than that of the wild strain (stable for at least 80 min at 54-degrees-C, pH 5.4).3. The pho-2A mutant of N. crassa secreted a more thermolabile acid phosphatase (t1/2 = 30 min at 50-degrees-C, pH 5.4) than the wild strain (t1/2 of at least 80 min at 50-degrees-C, pH 5.4).4. The pho-2A mutant of N. crassa synthesized a more thermolabile acid phosphatase (t1/2 = 37 min at 54-degrees-C, pH 5.4) than the wild strain in high Pi medium (t1/2 = 14 min al 54-degrees-C, pH 5.4).5. The pleiotropic nature of the pho-2 locus and its possible involvement in the mechanism of phosphatase secretion by N. crassa are proposed.

Determination of absolute configuration of 1,3-diols by the modified Mosher's method using their di-MTPA esters

1,3-Diols are frequently involved in biologically important compounds and, therefore, determination of the stereochemistry of these structural elements, in particular those in acyclic systems, has been one of the focuses of attention in natural products chemistry. The modified Mosher's method, commonly used for the determination of the absolute configuration of secondary alcohols, was applied to determine the absolute configuration of 1,3-diols with their di-MTPA esters. Several epimeric pairs of syn- and anti-1,3-diols with known absolute configurations were converted to the corresponding di-MTPA esters and the Delta delta values were then calculated. For the acyclic syn-1,3-diols, the Delta delta values were systematically arranged as predicted from the basic concept of the modified Mosher's method, demonstrating that the method is valid for these compounds. In contrast, the Delta delta values were irregularly arranged for the acyclic anti-1,3-diols and, accordingly, this method is not valid for these cases. These results are complementary to those of the previously reported CD exciton chirality method and, hence, the combined use of the modified Mosher's method and the CD exciton chirality method can determine the absolute configuration of the acyclic 1,3-diols. Also, this method is successfully applicable to cyclic 1,3-diols irrespective of their relative stereochemistry. (C) 2002 Wiley-lass, Inc.

3D hydrogen-bonded network built from copper(II) complexes of 1,3-propanediamine

The reaction of Cu(NO3)(2).3H(2)O with 1,3-propanediamine (pn), in the presence of NaN3, afforded a 1:1 co-crystal formed by [Cu(NO3)(2)(pn)(2)] and [Cu(N-3)(NO3)(pn)(2)] (1 and 2), which were characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. In both compounds, the copper(II) centers are in a distorted octahedral environment, formed by four N atoms of two bidentate pn ligands in the basal plane, whereas the axial bonds are formed by two O atoms from the nitrate ligands in 1 and one O atom from the nitrate ligand and one N atom from the azide ion in 2. The asymmetric unit of the crystal consists of two crystallographically independent 1 and 2 complexes, which are held together in a 3D network by a series of N - H center dot center dot center dot O and N - H center dot center dot center dot N hydrogen bonds, as well C - H center dot center dot center dot O interactions. New supramolecular synthons are identified by the occurrence of two geometrically distinct molecular recognition patterns involving the NO3- ion and amino groups from pn ligands.