nitrophenols and hydroquinone

Methyl parathion is an organophosphorus pesticide widely employed worldwide to control pests in agricultural and domestic environments. However, due to its intensive use, high toxicity, and environmental persistence, methyl parathion is recognized as an important ecosystem and human health threat, causing severe environmental pollution events and numerous human poisoning and deaths each year. Therefore, identifying and characterizing microorganisms capable of fully degrading methyl parathion and its degradation metabolites is a crucial environmental task for the bioremediation of pesticide-polluted sites. Burkholderia zhejiangensis CEIB S4-3 is a bacterial strain isolated from agricultural soils capable of immediately hydrolyzing methyl parathion at a concentration of 50 mg/L and degrading the 100% of the released p-nitrophenol in a 12-hour lapse when cultured in minimal salt medium. In this study, a comparative proteomic analysis was conducted in the presence and absence of methyl parathion to evaluate the biological mechanisms implicated in the methyl parathion biodegradation and resistance by the strain B. zhejiangensis CEIB S4-3. In each treatment, the changes in the protein expression patterns were evaluated at three sampling times, zero, three, and nine hours through the use of two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), and the differentially expressed proteins were identified by mass spectrometry (MALDI-TOF). The proteomic analysis allowed the identification of 72 proteins with differential expression, 35 proteins in the absence of the pesticide, and 37 proteins in the experimental condition in the presence of methyl parathion. The identified proteins are involved in different metabolic processes such as the carbohydrate and amino acids metabolism, carbon metabolism and energy production, fatty acids β-oxidation, and the aromatic compounds catabolism, including enzymes of the both p-nitrophenol degradation pathways (Hydroquinone dioxygenase and Hydroxyquinol 1,2 dioxygenase), as well as the overexpression of proteins implicated in cellular damage defense mechanisms such as the response and protection of the oxidative stress, reactive oxygen species defense, detoxification of xenobiotics, and DNA repair processes. According to these data, B. zhejiangensis CEIB S4-3 overexpress different proteins related to aromatic compounds catabolism and with the p-nitrophenol  degradation pathways, the higher expression levels observed in the t

Topics: Amino Acids; Burkholderiaceae; Carbohydrates; Carbon; Dioxygenases; Ecosystem; Fatty Acids; Hydroquinones; Methyl Parathion; Nitrophenols; Organophosphorus Compounds; Pesticides; Proteomics; Reactive Oxygen Species; Soil

Topics: Bacteria; Bacterial Physiological Phenomena; Biodegradation, Environmental; Biofilms; Bioreactors; Hydroquinones; Membranes, Artificial; Nitrophenols; Phenol; RNA, Ribosomal, 16S; Salinity; Wastewater; Water Pollutants, Chemical

The crystal structure of hydroquinone 1,2-dioxygenase, a Fe(II) ring cleaving dioxygenase from Sphingomonas sp. strain TTNP3, which oxidizes a wide range of hydroquinones to the corresponding 4-hydroxymuconic semialdehydes, has been solved by Molecular Replacement, using the coordinates of PnpCD from Pseudomonas sp. strain WBC-3. The enzyme is a heterotetramer, constituted of two subunits α and two β of 19 and 38kDa, respectively. Both the two subunits fold as a cupin, but that of the small α subunit lacks a competent metal binding pocket. Two tetramers are present in the asymmetric unit. Each of the four β subunits in the asymmetric unit binds one Fe(II) ion. The iron ion in each β subunit is coordinated to three protein residues, His258, Glu264, and His305 and a water molecule. The crystal structures of the complexes with the substrate methylhydroquinone, obtained under anaerobic conditions, and with the inhibitors 4-hydroxybenzoate and 4-nitrophenol were also solved. The structures of the native enzyme and of the complexes present significant differences in the active site region compared to PnpCD, the other hydroquinone 1,2-dioxygenase of known structure, and in particular they show a different coordination at the metal center.

Topics: Amino Acid Sequence; Binding Sites; Catalytic Domain; Crystallography, X-Ray; Dioxygenases; Hydroquinones; Iron; Nitrophenols; Parabens; Protein Conformation; Sequence Homology, Amino Acid; Sphingomonas

Rhodococcus imtechensis RKJ300 (DSM 45091) grows on 2-chloro-4-nitrophenol (2C4NP) and para-nitrophenol (PNP) as the sole carbon and nitrogen sources. In this study, by genetic and biochemical analyses, a novel 2C4NP catabolic pathway different from those of all other 2C4NP utilizers was identified with hydroxyquinol (hydroxy-1,4-hydroquinone or 1,2,4-benzenetriol [BT]) as the ring cleavage substrate. Real-time quantitative PCR analysis indicated that the pnp cluster located in three operons is likely involved in the catabolism of both 2C4NP and PNP. The oxygenase component (PnpA1) and reductase component (PnpA2) of the two-component PNP monooxygenase were expressed and purified to homogeneity, respectively. The identification of chlorohydroquinone (CHQ) and BT during 2C4NP degradation catalyzed by PnpA1A2 indicated that PnpA1A2 catalyzes the sequential denitration and dechlorination of 2C4NP to BT and catalyzes the conversion of PNP to BT. Genetic analyses revealed that pnpA1 plays an essential role in both 2C4NP and PNP degradations by gene knockout and complementation. In addition to catalyzing the oxidation of CHQ to BT, PnpA1A2 was also found to be able to catalyze the hydroxylation of hydroquinone (HQ) to BT, revealing the probable fate of HQ that remains unclear in PNP catabolism by Gram-positive bacteria. This study fills a gap in our knowledge of the 2C4NP degradation mechanism in Gram-positive bacteria and also enhances our understanding of the genetic and biochemical diversity of 2C4NP catabolism.

Topics: Bacterial Proteins; Biocatalysis; Hydroquinones; Mixed Function Oxygenases; Nitrophenols; Rhodococcus; Substrate Specificity

Aerobic microorganisms have evolved a variety of pathways to degrade aromatic and heterocyclic compounds. However, only several classes of oxygenolytic fission reaction have been identified for the critical ring cleavage dioxygenases. Among them, the most well studied dioxygenases proceed via catecholic intermediates, followed by noncatecholic hydroxy-substituted aromatic carboxylic acids. Therefore, the recently reported hydroquinone 1,2-dioxygenases add to the diversity of ring cleavage reactions. Two-subunit hydroquinone 1,2-dioxygenase PnpCD, the key enzyme in the hydroquinone pathway of para-nitrophenol degradation, catalyzes the ring cleavage of hydroquinone to γ-hydroxymuconic semialdehyde. Here, we report three PnpCD structures, named apo-PnpCD, PnpCD-Fe(3+), and PnpCD-Cd(2+)-HBN (substrate analog hydroxyenzonitrile), respectively. Structural analysis showed that both the PnpC and the C-terminal domains of PnpD comprise a conserved cupin fold, whereas PnpC cannot form a competent metal binding pocket as can PnpD cupin. Four residues of PnpD (His-256, Asn-258, Glu-262, and His-303) were observed to coordinate the iron ion. The Asn-258 coordination is particularly interesting because this coordinating residue has never been observed in the homologous cupin structures of PnpCD. Asn-258 is proposed to play a pivotal role in binding the iron prior to the enzymatic reaction, but it might lose coordination to the iron when the reaction begins. PnpD also consists of an intriguing N-terminal domain that might have functions other than nucleic acid binding in its structural homologs. In summary, PnpCD has no apparent evolutionary relationship with other iron-dependent dioxygenases and therefore defines a new structural class. The study of PnpCD might add to the understanding of the ring cleavage of dioxygenases.

Topics: Amino Acid Sequence; Bacterial Proteins; Catalysis; Catalytic Domain; Circular Dichroism; Crystallography, X-Ray; Dioxygenases; Hydroquinones; Ions; Iron; Metabolism; Metals; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Nitriles; Nitrophenols; Oxygen; Protein Binding; Protein Folding; Protein Structure, Secondary; Pseudomonas aeruginosa; Sequence Homology, Amino Acid

The electrochemical oxidation of pesticide, o-nitrophenol (ONP) as one kind of pesticide that is potentially dangerous and biorefractory, was studied by galvanostatic electrolysis using boron-doped diamond (BDD) as anode. The influence of several operating parameters, such as applied current density, supporting electrolyte, and initial pH value, was investigated. The best degradation occurred in the presence of Na2SO4 (0.05 M) as conductive electrolyte. After 8h, nearly complete degradation of o-nitrophenol was achieved (92%) using BDD electrodes at pH 3 and at current density equals 60 mA cm(-2). The decay kinetics of o-nitrophenol follows a pseudo-first-order reaction. Aromatic intermediates such as catechol, resorcinol, 1,2,4-trihydroxybenzene, hydroquinone and benzoquinone and carboxylic acids such as maleic glycolic, malonic, glyoxilic and oxalic, have been identified and followed during the ONP treatment by chromatographic techniques. From these anodic oxidation by-products, a plausible reaction sequence for ONP mineralization on BDD anodes is proposed.

Topics: Benzoquinones; Boron; Carboxylic Acids; Catechols; Diamond; Electrodes; Electrolysis; Hydrogen-Ion Concentration; Hydroquinones; Kinetics; Models, Chemical; Nitrophenols; Oxygen; Pesticides; Resorcinols; Water Pollutants, Chemical; Water Purification

A sequencing batch reactor (SBR) was inoculated with p-nitrophenol-degrading activated sludge to biodegrade a mixture of monosubstituted phenols: p-nitrophenol (PNP), PNP and o-cresol; and PNP, o-cresol and o-chlorophenol. Settling times were progressively decreased to promote biomass granulation. PNP was completely biodegraded. The PNP and o-cresol mixture was also biodegraded although some transitory accumulation of intermediates occurred (mainly hydroquinone and catechol). o-Chlorophenol was not biodegraded and resulted in inhibition of o-cresol and PNP biodegradation and complete failure of the SBR within a few days. The biomass had very good settling properties when a settling time of 1 min was applied: sludge volume index (SVI₅) below 50 mL g(-1), SVI₅/SVI₃₀ ratio of 1 and average particle size of 200 μm.

Topics: Acinetobacter; Aerobiosis; Arthrobacter; Batch Cell Culture Techniques; Biodegradation, Environmental; Biomass; Bioreactors; Catechols; Chlorophenols; Cresols; Hydroquinones; In Situ Hybridization, Fluorescence; Nitrophenols; Pseudomonas; Sewage; Temperature; Time Factors

The predictions of mixture toxicity for chemicals are commonly based on two models: concentration addition (CA) and independent action (IA). Whether the CA and IA can predict mixture toxicity of phenolic compounds with similar and dissimilar action mechanisms was studied. The mixture toxicity was predicted on the basis of the concentration-response data of individual compounds. Test mixtures at different concentration ratios and concentration levels were designed using two methods. The results showed that the Weibull function fit well with the concentration-response data of all the components and their mixtures, with all relative coefficients (Rs) greater than 0.99 and root mean squared errors (RMSEs) less than 0.04. The predicted values from CA and IA models conformed to observed values of the mixtures. Therefore, it can be concluded that both CA and IA can predict reliable results for the mixture toxicity of the phenolic compounds with similar and dissimilar action mechanisms.

Topics: Benzyl Alcohols; Chlorophenols; Dose-Response Relationship, Drug; Drug Interactions; Environmental Pollutants; Hydroquinones; Nitrophenols; Phenols; Phloroglucinol; Resorcinols; Vibrio

Cupriavidus necator JMP134 utilizes meta-nitrophenol (MNP) as the sole source of carbon, nitrogen, and energy. The metabolic reconstruction of MNP degradation performed in silico suggested that MnpC might have played an important role in MNP degradation. In order to experimentally confirm the prediction, we have now characterized the mnpC-encoded (amino)hydroquinone dioxygenase involved in the ring-cleavage reaction of MNP degradation. Real-time PCR analysis indicated that mnpC played an essential role in MNP degradation. MnpC was purified to homogeneity as an N-terminal six-His-tagged fusion protein, and it was proved to be a dimer as demonstrated by gel filtration. MnpC was a Fe(2+)- and Mn(2+)-dependent dioxygenase, catalyzing the ring-cleavage of hydroquinone to 4-hydroxymuconic semialdehyde in vitro and proposed as an aminohydroquinone dioxygenase involved in MNP degradation in vivo. Phylogenetic analysis suggested that MnpC diverged from the other (chloro)hydroquinone dioxygenases at an earlier point, which might result in the preference for its physiological substrate.

Topics: Amino Acid Sequence; Carbon; Cloning, Molecular; Cupriavidus necator; Dioxygenases; Gene Expression; Genes, Bacterial; Hydroquinones; Nitrogen; Nitrophenols; Nitroreductases; Phylogeny; Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; Substrate Specificity

A new and straightforward method for screening highly catalytically active silver nanoparticle-polymer composites derived from branched polyethyleneimine (PEI) is reported. The one-step systematic derivatization of the PEI scaffold with alkyl (butyl or octyl) and ethanolic groups led to a structural diversity correlated to the stabilization of silver nanoparticles and catalysis. Analysis of PEI derivative libraries identified a silver nanoparticle-polymer composite that was able to efficiently catalyze the p-nitrophenol reduction by NaBH(4) in water with a rate constant normalized to the surface area of the nanoparticles per unit volume (k(1)) of 0.57 s(-1) m(-2) L. Carried out in the presence of excess NaBH(4), the catalytic reaction was observed to follow pseudo-first-order kinetics and the apparent rate constant was linearly dependent on the total surface area of the silver nanoparticles (Ag-NPs), indicating that catalysis takes place on the surface of the nanoparticles. All reaction kinetics presented induction periods, which were dependent on the concentration of substrates, the total surface of the nanoparticles, and the polymer composition. All data indicated that this induction time is related to the resistance to substrate diffusion through the polymer support. Hydrophobic effects are also assumed to play an important role in the catalysis, through an increase in the local substrate concentration.

Topics: Borohydrides; Catalysis; Hydrophobic and Hydrophilic Interactions; Hydroquinones; Kinetics; Metal Nanoparticles; Nitrophenols; Oxidation-Reduction; Particle Size; Polyethyleneimine; Reducing Agents; Silver; Silver Nitrate; Water

Pseudomonas sp. strain WBC-3 utilizes para-nitrophenol (PNP) as a sole source of carbon, nitrogen, and energy. In order to identify the genes involved in this utilization, we cloned and sequenced a 12.7-kb fragment containing a conserved region of NAD(P)H:quinone oxidoreductase genes. Of the products of the 13 open reading frames deduced from this fragment, PnpA shares 24% identity to the large component of a 3-hydroxyphenylacetate hydroxylase from Pseudomonas putida U and PnpB is 58% identical to an NAD(P)H:quinone oxidoreductase from Escherichia coli. Both PnpA and PnpB were purified to homogeneity as His-tagged proteins, and they were considered to be a monomer and a dimer, respectively, as determined by gel filtration. PnpA is a flavin adenine dinucleotide-dependent single-component PNP 4-monooxygenase that converts PNP to para-benzoquinone in the presence of NADPH. PnpB is a flavin mononucleotide-and NADPH-dependent p-benzoquinone reductase that catalyzes the reduction of p-benzoquinone to hydroquinone. PnpB could enhance PnpA activity, and genetic analyses indicated that both pnpA and pnpB play essential roles in PNP mineralization in strain WBC-3. Furthermore, the pnpCDEF gene cluster next to pnpAB shares significant similarities with and has the same organization as a gene cluster responsible for hydroquinone degradation (hapCDEF) in Pseudomonas fluorescens ACB (M. J. Moonen, N. M. Kamerbeek, A. H. Westphal, S. A. Boeren, D. B. Janssen, M. W. Fraaije, and W. J. van Berkel, J. Bacteriol. 190:5190-5198, 2008), suggesting that the genes involved in PNP degradation are physically linked.

Topics: Benzoquinones; Chromatography, Affinity; Chromatography, Gel; Cloning, Molecular; Coenzymes; Dimerization; DNA, Bacterial; Gene Order; Genes, Bacterial; Hydroquinones; Molecular Sequence Data; Multigene Family; NADP; Nitrophenols; Oxygenases; Pseudomonas; Quinone Reductases; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Synteny

Experiments have been performed with a semicontinuous batch reactor to compare the degradation efficiency of nitrobenzene in aqueous solution by the ultrasonic processes of single field, opposite dual fields, and orthogonal dual fields. Ultrasound with dual fields can improve the degradation efficiency of nitrobenzene compared to that of single field, and the improvement phenomenon is even more pronounced in the orthogonal dual-field system. The degradation reactions of nitrobenzene in the three processes all follow the pseudofirst-order kinetic model. The mechanism investigation indicates the degradation proceeds via hydroxyl radical (*OH) oxidation. The enhancement efficiency of orthogonal dual fields is attributed to an obvious synergetic effect, which accelerates the *OH initiation from 0.28 micromol L(-1) min(-1) for a single field to 0.98 micromol L(-1) min(-1) compared with 0.42 micromol L(-1) min(-1) for opposite dual fields, resulting in rapid formation of an increased diversity of byproducts and an advanced degree of mineralization of total organic carbon (TOC). The introduction of an ultrasonic field placed in the different spatial position causes a variable kinetic order during the removal of TOC. The degradation byproducts are identified by gas chromatography mass spectrometry and ion chromatography, including p-, m-nitrophenol, malonic acid, nitrate ion, 4-nitrocatechol, phenol, maleic acid, oxalic acid, hydroquinone, 1,2,3-trihydroxy-5-nitrobenzene, and acetic acid.

Topics: Acetic Acid; Carbon; Catechols; Chromatography, Gas; Hydroquinones; Hydroxyl Radical; Ions; Kinetics; Maleates; Malonates; Nitrates; Nitrobenzenes; Nitrophenols; Oxalic Acid; Ultrasonics; Water

This study deals with the degradation of various nitrophenols by cathode reduction and electro-Fenton methods. Phenols (Poh), 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), 4-nitrophenol (4-NP), and 2,4-dinitrophenol (2,4-DNP) are treated and different degradation sequences are obtained. The relationship between the structure and activities of nitrophenols is discussed. Using 4-NP as a model nitrophenol, the electrochemical behaviors on graphite cathode and Pt anode are analyzed by cyclic voltammetry. The contribution of different reactions to the degradation of 4-NP is investigated in divided cells. The degradation of 4-NP is much faster in the cathode cell than in the anodic cell. In the cathode cell, the degradation of 4-NP is significantly enhanced by the introduction of aeration and Fe(2+). Ultraviolet-visible (UV-vis) spectra reveal different reaction pathways for the degradation in the anodic cell and cathode cell. Treatment of high concentration of 4-NP in the undivided cell shows that more than 98% removal of 4-NP and about 13% removal of total organic carbon (TOC) are obtained for both processes, while the subsequent biodegradability test shows that electro-Fenton can eliminate the toxicity and improve the biodegradability of 4-NP. Negligible quantity of nitrate and nitrite ions detected in both processes indicates that there is no direct release of -NO(2) and -NO groups from 4-NP and its degradation intermediates. Intermediates such as hydroquinone and bezoquinone are detected by gas chromatography/mass spectrum (GC/MS). The degradation pathway of 4-NP in electro-Fenton process is proposed as the cathode reduction followed by hydroxyl oxidation.

Topics: Benzoquinones; Biodegradation, Environmental; Carbon; Electrochemistry; Electrodes; Hydroquinones; Nitrates; Nitrites; Nitrophenols; Spectrophotometry; Time Factors; Ultraviolet Rays; Waste Disposal, Fluid; Water Purification

Adsorption of phenol, hydroquinone, m-cresol, p-cresol and p-nitrophenol from aqueous solutions onto high specific area activated carbon cloth has been studied. The effect of ionization on adsorption of these ionizable phenolic compounds was examined by studying the adsorption from acidic, basic and natural pH solutions. Kinetics of adsorption was followed by in situ UV spectroscopy over a period of 90 min. First-order rate law was found to be valid for the kinetics of adsorption processes and the rate constants were determined. The highest rate constants were obtained for the adsorption from solutions at the natural pH. The lowest rate constants were observed in basic solutions. The rate constants decreased in the order p-nitrophenol approximately m-cresol>p-cresol>hydroquinone approximately phenol. Adsorption isotherms were derived at 30 degrees C and the isotherm data were treated according to Langmuir, Freundlich and Tempkin isotherm equations. The goodness of fit of experimental data to these isotherm equations was tested and the parameters of equations were determined. The possible interactions of compounds with the carbon surface were discussed considering the charge of the surface and the possible ionization of compounds at acidic, basic and natural pH conditions.

Topics: Adsorption; Charcoal; Cresols; Hydrogen-Ion Concentration; Hydroquinones; Nitrophenols; Osmolar Concentration; Phenols; Temperature; Water; Water Pollutants, Chemical; Water Pollution, Chemical

The effect of cellular p-nitrophenol (PNP) metabolism on the electro-optical (EO) characteristics of Pseudomonas putida C-11, P. putida BA-11, and Acinetobacter calcoaceticum A-122 was studied. When P. putida C-11 was incubated with hydroquinone, the orientational spectra of the cell suspensions changed considerably. When P. putida BA-11 and A. calcoaceticum A-122 were incubated with hydroquinone, no orientational spectrum changes were noted, possibly attesting to the operation of different PNP-metabolic pathways. In C-11, the initial metabolism of PNP may occur via the production of hydroquinone, an intermediate for PNP metabolism; in BA-11 and A. calcoaceticum A-122, via the production of 4-nitropyrocatechin, followed by a rupture of the aromatic ring. The respiratory activity of the strains toward hydroquinone was investigated concurrently. The results suggest that EO analysis is a good candidate for the study of cellular metabolism.

Topics: Acinetobacter calcoaceticus; Biomass; Electrophysiology; Hydroquinones; Nitrophenols; Optics and Photonics; Oxygen Consumption; Pseudomonas putida

Specific step-by-step instructions are given for coupling nucleosides to LCAA-CPG supports (supports consisting of a long-chain alkylamine linked to controlled-pore glass). Protocols are given for a succinic acid linker and a hydroquinone-O,O'-diacetic acid linker. The former is the most widely used linker arm, and the starting materials are widely available. The latter offers greater compatibility with base-sensitive sequence modifications and great synthetic throughput because it can be cleaved under milder and faster conditions. Additional guidelines are given for selecting a linker arm and coupling protocol. Almost any application requiring synthetic oligonucletodies can be satisfied using one of these linker arms.

Topics: Biochemistry; Carboxylic Acids; Esters; Glass; Hydroquinones; Hydroxylation; Nitrophenols; Nucleosides; Polymers; Porosity; Solubility; Succinic Acid; Trityl Compounds

A Pseudomonas cepacia strain RKJ 200 capable of utilising p-nitrophenol (PNP+) as the sole source of carbon, nitrogen, and energy was isolated by selective enrichment. The degradation of PNP by this strain proceeds through an oxidative route as indicated by the accumulation of nitrite molecules in the culture medium. Initial studies indicate that the degradation of PNP occurs via hydroquinone as shown by thin layer chromatography and gas chromatography studies; hydroquinone is further degraded via the beta-ketoadipate pathway. A plasmid of approximately 50 kilobase pairs was found to be responsible for carrying genes for PNP degradation in this strain. This was based on the facts that the PNP- mutants lacked the plasmid and that the PNP+ phenotype could conjugally be transferred. In addition, the same plasmid also encoded resistance to inorganic zinc ions.

Topics: Biotransformation; Burkholderia cepacia; Conjugation, Genetic; Genes, Bacterial; Hydroquinones; Mitomycin; Mutagenesis; Nitrophenols; Parathion; Plasmids

Topics: Animals; Dinitrophenols; Hydroquinones; Metabolism; Nitrophenols; Oxygen Consumption; Phenols; Rats; Thiourea