Screening Botryosphaeria species for lipases: Production of lipase by Botryosphaeria ribis EC-01 grown on soybean oil and other carbon sources

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Purification and properties of an acid beta-xylosidase from Penicillium sclerotiorum

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Sínteses e caracterização de novos catalisadores zeolíticos e sua como suportes inorgânicos para imobilização de lipase produzida por Rhizomucor miehei e seu estudo catalítico na reação de transesterificação do óleo de soja para produção de biodiesel

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

Direct Synthesis of Ag Nanoparticles Incorporated on a Mesoporous Hybrid Material as a Sensitive Sensor for the Simultaneous Determination of Dihydroxybenzenes Isomers

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

Tailoring the structure, composition, optical properties and catalytic activity of Ag-Au nanoparticles by the galvanic replacement reaction

This Letter reports on the synthesis of Ag-Au nanoparticles (NPs) with controlled structures and compositions via a galvanic replacement reaction between Ag NPs and AuCl4(aq)- followed by the investigation of their optical and catalytic properties. Our results showed the formation of porous walls, hollow interiors and increased Au content in the Ag-Au NPs as the volume of AuCl4(aq)- employed in the reaction was increased. These variations led to a red shift and broadening of the SPR peaks and an increase of up to 10.9-folds in the catalytic activity towards the reduction of 4-nitrophenol relative to Ag NPs. (C) 2012 Elsevier B.V. All rights reserved.

4-chlorophenol biodegradation by Arthrobacter chlorophenolicus A6

A microorganism was isolated which could grow on unusually high concentrations of the toxic pollutant 4-chlorophenol. Taxonomic studies showed that the microorganism constituted a novel species within the genus Arthrobacter and it was named Arthrobacter chlorophenolicus A6. A. chlorophenolicus A6 was chromosomally tagged with either the gfp gene, encoding the green fluorescent protein (GFP), or the luc gene, encoding firefly luciferase. When the tagged cells were inoculated into 4-chlorophenol contaminated soil they could completely remove 175 µg/g 4-chlorophenol within 10 days, whereas no loss of 4-chlorophenol was observed in the uninoculated control microcosms. During these experiments the gfp and luc marker genes allowed monitoring of cell number and metabolic status. When A. chlorophenolicus A6 was grown on mixtures of phenolic compounds, the strain exhibited a preference for 4-nitrophenol over 4-chlorophenol, which in turn was preferred over phenol. Analysis of growth and degradation data indicated that the same enzyme system was used for removal of 4-chlorophenol and 4-nitrophenol. However, degradation of unbstituted phenol appeared to be mediated by another or an additional enzyme system. The luc-tagged A. chlorophenolicus A6 gave valuable information about growth, substrate depletion and toxicity of the phenolic compounds in substrate mixtures. The 4-chlorophenol degradation pathway in A. chlorophenolicus A6 was elucidated. The metabolic intermediate subject to ring cleavage was found to be hydroxyquinol and two different pathway branches led from 4-chlorophenol to hydroxyquinol. A gene cluster involved in 4-chlorophenol degradation was cloned from A. chlorophenolicus A6. The cluster contained two functional hydroxyquinol 1,2-dioxygenase genes and a number of other open reading frames presumed to encode enzymes involved in 4-chlorophenol catabolism. Analysis of the DNA sequence suggested that the gene cluster had partly been assembled by horizontal gene transfer. In summary, 4-chlorophenol degradation by A. chlorophenolicus A6 was studied from a number of angles. This organism has several interesting and useful traits such as the ability to degrade high concentrations of 4-chlorophenol and other phenols alone and in mixtures, an unusual and effective 4-chlorophenol degradation pathway and demonstrated ability to remove 4-chlorophenol from contaminated soil.

Enzyme activity and liver tissue PCB concentrations of chicks of northern fulmars (F. glacialis) and black-legged kittiwakes (R. tridactyla) from Kongsfjorden

Arctic seabirds are exposed to a wide range of halogenated organic contaminants (HOCs). Exposure occurs mainly through food intake, and many pollutants accumulate in lipid-rich tissues. Little is known about how HOCs are biotransformed in arctic seabirds. In this study, we characterized biotransformation enzymes in chicks of northern fulmars (Fulmarus glacialis) and black-legged kittiwakes (Rissa tridactyla) from Kongsfjorden (Svalbard, Norway). Phase I and II enzymes were analyzed at the transcriptional, translational and activity levels. For gene expression patterns, quantitative polymerase chain reactions (qPCR), using gene-sequence primers, were performed. Protein levels were analyzed using immunochemical assays of western blot with commercially available antibodies. Liver samples were analyzed for phase I and II enzyme activities using a variety of substrates including ethoxyresorufin (cytochrome (CYP)1A1/1A2), pentoxyresorufin (CYP2B), methoxyresorufin (CYP1A), benzyloxyresorufin (CYP3A), testosterone (CYP3A/CYP2B), 1-chloro-2,4-nitrobenzene (CDNB) (glutathione S-transferase (GST)) and 4-nitrophenol (uridine diphosphate glucuronyltransferase (UDPGT)). In addition, the hydroxylated (OH-) polychlorinated biphenyls (PCBs) were analyzed in the blood, liver and brain tissue, whereas the methylsulfone (MeSO2-) PCBs were analyzed in liver tissue. Results indicated the presence of phase I (CYP1A4/CYP1A5, CYP2B, and CYP3A) and phase II (GST and UDPGT) enzymes at the activity, protein and/or mRNA level in both species. Northern fulmar chicks had higher enzyme activity than black-legged kittiwake chicks. This in combination with the higher XOH-PCB to parent PCB ratios suggests that northern fulmar chicks have a different biotransformation capacity than black-legged kittiwake chicks.

Requirements for heme and thiols for the nonenzymatic modification of nitrotyrosine

Peroxynitrite-dependent formation of nitrotyrosine has been associated with inactivation of various enzymes and proteins possessing functionally important tyrosines. We have previously reported an enzymatic activity modifying the nitrotyrosine residues in nitrated proteins. Here we are describing a nonenzymatic reduction of nitrotyrosine to aminotyrosine, which depends on heme and thiols. Various heme-containing proteins can mediate the reaction, although the reaction also is catalyzed by heme. The reaction is most effective when vicinal thiols are used as reducing agents, although ascorbic acid also can replace thiols with lesser efficiency. The reaction could be inhibited by (z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1, but not other tested NO donors. HPLC with electrochemical detection analysis of the reaction identified aminotyrosine as the only reaction product. The reduction of nitrotyrosine was most effective at a pH close to physiological and was markedly decreased in acidic conditions. Various nitrophenol compounds also were modified in this reaction. Understanding the mechanism of this reaction could help define the enzymatic modification of nitrotyrosine-containing proteins. Furthermore, this also could assist in understanding the role of nitrotyrosine formation and reversal in the regulation of various proteins containing nitrotyrosine. It also could help define the role of nitric oxide and other reactive species in various disease states.

Characterization of Cell–Matrix Adhesion Requirements for the Formation of Fascin Microspikes

Cell adhesion to thrombospondin-1 (TSP-1) correlates with assembly of cell–substratum contact structures that contain fascin microspikes. In this analysis, cell-matrix requirements for assembly of fascin microspikes were examined in detail. In six cell lines, cell spreading on a TSP-1 substratum correlated with expression of fascin protein and formation of fascin microspikes. Microspikes were not formed by H9c2 cells adherent on fibronectin, vitronectin, collagen IV, or platelet factor 4. However, both fascin microspikes and focal contacts were assembled by cells adherent on laminin-1. Using mixed substrata containing different proportions of TSP-1, and fibronectin, fascin microspike formation by H9c2 and C2C12 cells was found to be reduced on substrata containing 25% fibronectin and abolished on substrata containing 75% fibronectin. Adhesion to intermediate mixtures of TSP-1 and fibronectin resulted in coassembly of fascin microspikes and focal contacts, colocalization of fascin with actin stress fiber bundles and altered distributions of β1 integrins, cortical α-actinin, and tropomyosin. In cells adherent on 50% TSP-1:50% fibronectin, GRGDSP peptide treatment decreased focal contact assembly and altered cytoskeletal organization but did not inhibit microspike assembly. Treatment with chondroitin sulfate A or p-nitrophenol β-d-xylopyranoside decreased microspike formation and modified cytoskeletal organization but did not inhibit focal contact formation. In polarized migratory and postmitotic C2C12 cells, fascin microspikes and ruffles were localized at leading edges and TSP matrix deposition was also concentrated in this region. Depletion of matrix TSP by heparin treatment correlated with decreased microspike formation and cell motility. Thus, the balance of adhesive receptors ligated at the cell surface during initial cell–matrix attachment serves to regulate the type of substratum adhesion contact assembled and subsequent cytoskeletal organization. A role for fascin microspikes in cell motile behavior is indicated.

A catalytic mechanism for the dual-specific phosphatases.

Dual-specific protein-tyrosine phosphatases have the common active-site sequence motif HCXXGXXRS(T). The role of the conserved hydroxyl was investigated by changing serine-131 to an alanine (S131A) in the dual-specific protein-tyrosine phosphatase VHR. The pH profile of the kcat/Km value for the S131A mutant is indistinguishable from that of the native enzyme. In contrast, the kcat value for S131A mutant is 100-fold lower than that for the native enzyme, and the shape of the pH profile was perturbed from bell-shaped in the native enzyme to a pH-independent curve over the pH range 4.5-9.0. This evidence, along with results from a previous study, suggests that the S131A mutation alters the rate-limiting step in the catalytic mechanism. Formation of a phosphoenzyme intermediate appears to be rate-limiting with the native enzyme, whereas in the S131A mutant breakdown of the intermediate is rate-limiting. This was confirmed by the appearance of a burst of p-nitrophenol formation when p-nitrophenyl phosphate rapidly reacted with the S131A enzyme in a stopped-flow spectrophotometer. Loss of this hydroxyl group at the active site dramatically diminished the ability of the enzyme to hydrolyze the thiol-phosphate intermediate without exerting any significant change in the steps leading to and including the formation of the intermediate. Consistent with rate-limiting intermediate formation in the native enzyme, the rate of burst in the S131A mutant was 1.5 s-1, which agrees well with the kcat value of 5 s-1 observed for native enzyme. The amplitude of the burst was stoichiometric with final enzyme concentration, and the slow linear rate (0.06 s-1) of p-nitrophenol formation after the burst was in agreement with the steady-state determined value of kcat (0.055 s-1).

Hybrid magnetic graphitic nanocomposites for catalytic wet peroxide oxidation applications

Hybrid magnetic graphitic nanocomposites (MGNC) prepared by inclusion of magnetite nanoparticles (obtained by coprecipitation) into an organic-organic self-assembly system, followed by calcination, revealed high activity for the catalytic wet peroxide oxidation (CWPO) of 4-nitrophenol solutions (5 g L-l), with pollutant removais up to 1245 mg g-' h-l being obtained when considering the mass ratio [pollutant]/[catalyst] =10. The stability of the MGNC catalyst against metal leaching was ascribed to the confinement effect of the carbon based material. These observations, together with the magnetically recoverable characteristics of MGNC, open new prospects for the wide use of this catalyst in highly efficient CWPO applications.

Carbon nanotubes as catalysts for wet peroxide oxidation: structure-reactivity relationships

Magnetic neat and N-doped carbon nanotubes with different properties have been synthesized by chemical vapour deposiüon and tested in the catalytic wet peroxide oxidation of 4-nitrophenol solutions (5 g L') at relatively mild operating conditions (atmospheric pressure, T = 50 °C, pH = 3)~using a catalyst load = 2.5 g L-' and [H202]o = 17.8 g L-1. The results demonstrate that the catalyst hydrophobicity/ hydrophilicity is a detenninant property in the CWPO reaction, since it affects the rate ofH202 decomposition. The controlled formation ofreactive radicais (HO* and HOO*) at hydrophobic surfaces avoids the formation of non-reactive species (02 and H20), increasing.

Metal-free catalysts derived from lignin for efficient wet peroxide oxidation

In this work, a wheat and hemp lignin (Sarkanda, Granit S.A.) has been used as raw material for the development of metal-free activated carbons. These materials were tested in the catalytic wet peroxide oxidation (CWPO) of 4-nitrophenol (4-NP; 5 g L-1) during 24 h experiments conducted at relatively mild operating conditions (p = 1 atm, t = 50 °C, pH = 3, catalyst load = 2.5 g L-1 and [H2O2]0 = 17.8 g L-1). First, the lignin was carbonized under N2 atmosphere followed by the activation of the obtained non-porous carbon (LG) under air atmosphere at different temperatures (150 to 350 ºC), leading to the generation of significant porosity.

Surface active substances in the water column during POLARSTERN cruise ANT-XXI/3 (EIFEX)

Surface active substances (SAS) in the water column were measured by voltammetry using the electrochemical probe o-nitrophenol (ONP) during EIFEX, a mesoscale open ocean iron enrichment experiment in the Southern Ocean. SAS levels were low throughout the experiment (<0.005 - 0.03 mg/L Triton X-100 equivalents). Initially SAS was extremely low in the photic zone, but as the phytoplankton bloom developed concentrations markedly increased throughout the upper 100 m (~0.02 mg/L Triton X-100 equivalents). Highest concentrations of SAS (>0.02 mg/L Triton X-100 equivalents) were found at the end of the bloom particularly at density discontinuities where organic material may accumulate. Exudates from diatoms appeared to be the major source of SAS during EIFEX, either from direct extracellular release or in the action of being grazed upon by zooplankton.

Effects of carbon surface chemistry and solution pH on the adsorption of binary aromatic solutes

Adsorption of p-cresol, nitrobenzene and p-nitrophenol on treated and untreated carbons is investigated systematically. The effects of carbon surface chemistry and solution pH are studied and discussed. All adsorption experiments were carried out in pH-controlled solutions to examine the adsorption properties of the adsorption systems where the solutes are in molecular as well as ionic forms. Using the homogeneous Langmuir equation, the single solute parameters are determined. These parameters are then used to predict the binary solute adsorption isotherms and gain further insights into the adsorption process. (C) 2002 Elsevier Science Ltd. All rights reserved.