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PubMed2003

Competitive quenching fluorescence immunoassay for chlorophenols based on laser-induced fluorescence detection in microdroplets.

An improved biomonitoring system for the analysis of 2,4,6-trichlorophenol (TCP) in urine samples has been developed. The principle of the biosensor device is the detection of laser-induced fluorescence (LIF) in single microdroplets by a homogeneous quenching fluorescence immunoassay (QFIA). The competitive immunoassay occurs in microdroplets (d = 58,4 microm) produced by a piezoelectric generator system with 10-microm-diameter orifice. A continuous Ar ion laser (488 nm) excites the fluorescent tracer; its fluorescence is detected by a spectrometer attached to a 512 x 512 cooled, charge-coupled device camera. Fluorescence is quenched by specific binding of TCP polyclonal antibodies to the fluorescent tracer (hapten A-fluorescein); the quenching effect is diminished by the presence of the analyte. Thus, an increase in the signal is produced in a positive dose-dependent manner when TCP is present in the sample. In 10 mM PBS buffer, the IC50 of the LIF-microdroplet QFIA is 0.45 microg L(-1) reaching a LOD of 0.04 microg L(-1). The QFIA with the same reagents performed in microtiter plate format achieved a LOD of 0.36 microg L(-1) in buffer solution. Performance in human urine was similar to that observed in the buffer. A LOD of 1.6 ,g L(-1), with a dynamic range between 4 and 149.5 microg L(-1) in urine, was obtained without any sample treatment other than dilution with the assay buffer. The detectability achieved is sufficient for occupational exposure risk assessment.

Binding, Competitive↗
PubMedDate not supplied

Oxidation of chlorophenols catalyzed by Coprinus cinereus peroxidase with in situ production of hydrogen peroxide.

Degradation of 2,6-dichlorophenol (2,6-DCP) was accomplished by oxidation catalyzed by Coprinus cinereus peroxidase. Immobilization of the enzyme in a polyacrylamide matrix enhanced DCP oxidation. Hydrogen peroxide, peroxidase's natural substrate, was produced enzymatically in situ to avoid peroxidase inactivation by its too high concentration. In the case of larger scale utilization, the method would also avoid direct handling of this hazardous reagent.

Catalysis↗
PubMed2006

Biomonitoring human exposure to organohalogenated substances by measuring urinary chlorophenols using a high-throughput screening (HTS) immunochemical method.

The widespread contamination of the environment by persistent organochlorinated substances is well-known. High-throughput immunochemical methods may improve routine assessment of the exposure of the population to these chemicals by analyzing urinary biomarkers. Trichlorophenols (TCP) have often been considered as biomarkers of many organochlorinated compounds. With the aim to assess exposure of the population to these substances a high-throughput immunosorbent solid-phase extraction (HTS-IS-SPE) procedure coupled to ELISA for simultaneous analyses of 2,4,6-TCP immunoreactivity equivalents (2,4,6-TCP-IR equiv) in multiple hydrolyzed urine samples has been developed. Around 100 urine samples can be processed simultaneously with an inter- and intraassay precision lower than 23% CV and a limit of detection of 0.3 microg L(-1). The analyses by HTS-IS-SPE-ELISA and HTS-IS-SPE-GC/MS of urine samples (N = 117) collected from three different population groups point to a broad exposure of the Catalonian population to organohalogenated substances including the recently emerging organobrominated pollutants. Environment and edible products seem to be the most likely sources of exposure, since excretion of 2,4,6-TCP-IR equiv has been found to be independent from the occupational sector. An excellent correlation was observed between the 2,4,6-TCP-IR equiv determined by HTS-IS-SPE-ELISA and the concentrations measured by HTS-IS-SPE-GC/MS (R2 = 0.912). The results show that immunochemical screening methods, based on the quantification of urinary biomarkers, can be excellent tools for exposure assessment. The HTS-IS-SPE-ELISA presented here has proved to be efficient, precise, accurate, rapid, and specific, which opens up the possibility for a broad variety of applications where routine testing of large number of samples is required.

Chlorophenols↗
PubMed1999

Detection of chlorophenolics in effluents from bleaching processes of rice-straw pulp.

A number of chlorinated derivatives of phenols, catechols, guaiacols, syringaldehydes, have been detected and their concentrations estimated, using gas chromatography in the chlorination (C) and extraction (E) stage of spent bleach liquor generated in the laboratory by bleaching rice-straw soda pulp. The concentration of various compounds detected have also been compared with their reported 96LC50 values.

Animals↗
PubMed2004

Crystal structure of 4-chlorocatechol 1,2-dioxygenase from the chlorophenol-utilizing gram-positive Rhodococcus opacus 1CP.

The crystal structure of the 4-chlorocatechol 1,2-dioxygenase from the Gram-positive bacterium Rhodococcus opacus (erythropolis) 1CP, a Fe(III) ion-containing enzyme involved in the aerobic biodegradation of chloroaromatic compounds, has been solved by multiple wavelength anomalous dispersion using the weak anomalous signal of the two catalytic irons (1 Fe/257 amino acids) and refined at a 2.5 A resolution (R(free) 28.7%; R factor 21.4%). The analysis of the structure and its comparison with the structure of catechol 1,2-dioxygenase from Acinetobacter calcoaceticus ADP1 (Ac 1,2-CTD) highlight significant differences between these enzymes. The general topology of the present enzyme comprises two catalytic domains (one for each subunit) related by a noncrystallographic 2-fold axis and separated by a common alpha-helical zipper motif consisting of five N-terminal helices from each subunit; furthermore the C-terminal tail is shortened significantly with respect to the known Ac 1,2-CTD. The presence of two phospholipids binding in a hydrophobic tunnel along the dimer axis is shown here to be a common feature for this class of enzyme. The active site cavity presents several dissimilarities with respect to the known catechol-cleaving enzyme. The catalytic nonheme iron(III) ion is bound to the side chains of Tyr-134, Tyr-169, His-194, and His-196, and a cocrystallized benzoate ion, bound to the metal center, reveals details on a novel mode of binding of bidentate inhibitors and a distinctive hydrogen bond network with the surrounding ligands. Among the amino acid residues expected to interact with substrates, several are different from the corresponding analogs of Ac 1,2-CTD: Asp-52, Ala-53, Gly-76, Phe-78, and Cys-224; in addition, regions of largely conserved amino acid residues in the catalytic cleft show different shapes resulting from several substantial backbone and side chain shifts. The present structure is the first of intradiol dioxygenases that specifically catalyze the cleavage of chlorocatechols, key intermediates in the aerobic catabolism of toxic chloroaromatics.

Amino Acid Sequence↗
PubMed2005

Effect of sulfidogenic and methanogenic inhibitors on reductive dehalogenation of 2-chlorophenol.

The potential for reductive dehalogenation of 2-CP in anaerobic batch cultures of fresh-water digested sludge under sulfidogenic and methanogenic conditions was investigated in the presence or absence of respective inhibitors: molybdate and BESA at various concentrations (0 to 10 mM). Triplicate cultures (50% vol/vol) were set-up under an atmosphere of 20% CO2 and 80% N2 in 160 ml serum bottles using anaerobic digester sludge and a mineral medium containing 0.1% yeast extract. The dehalogenation of 2-CP, as well as methanogenesis, occurred at the same rate in the presence or absence of sulphate. Sulphate reduction did not inhibit 2-CP degrading populations. The presence of BESA--a known inhibitor of methane producers partially inhibited methanogenesis and slowed 2-CP dehalogenation at even 1 mM concentration with phenol and acetate accumulation in the cultures. The accumulation was proportional to the increase in concentration of BESA in the system. Molybdate on the other hand completely inhibited both sulphate reduction and 2-CP dehalogenation at a concentration of 10 mM. The dehalogenation of 2-CP continued in the presence of 1 mM molybdate even after the cessation of sulphate reduction indicating that sulphate-reducing bacteria were not directly involved in the dehalogenation of 2-CP in this study. Inhibition of 2-CP dehalogenation and sulphate reduction along with accumulation of propionate at 10 mM molybdate in the cultures strongly suggests that the dehalogenation of 2-CP was more directly linked to syntrophic activity of the mixed culture compared to sulphate reduction.

Anaerobiosis↗
PubMed2004

Emission characteristics of PCDD/Fs, PCBs, chlorobenzenes, chlorophenols, and PAHs from polyvinylchloride combustion at various temperatures.

The effect of temperature on polyvinylchloride (PVC) combustion using a downstream tubular furnace was investigated for the formation of polycylcic aromatic hydrocarbons (PAHs) and chlorinated compounds. As the temperature increased, higher levels of PAHs were generated. Chlorinated compounds reached a peak at 600 degrees C, with low emissions recorded at 300 and 900 degrees C. There was a close correlation (R2 = 0.97) among polychlorinated biphenyls (PCBs), hexachlorobenzene, pentachlorobenzene, and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). PAHs at all temperatures were analyzed in the gas phase. PCDD/Fs and PCBs were emitted as a solid phase at 300 and 600 degrees C and as a gas phase at 900 degrees C. For some PAHs, chlorobenzenes, and PCDD/Fs, a mathematical equation between the gas and solid phase and the reciprocal temperature in semilog proportion was derived. The proposed equation, which is log (amount in gas phase/amount in solid phase) = -A/T + B, where T is the temperature of the furnace and A and B are constants, for these species relating their gas/solid distributions showed a good relationship.

Air Pollutants↗
PubMed2003

Influence of surface modification on catalytic activity of activated carbon toward decomposition of hydrogen peroxide and 2-chlorophenol.

The objective of this research was to investigate the influence of the activated carbons modified by chemical treatment on the surface catalyzed loss of H2O2 and 2-CP. The characteristics of the modified activated carbons were examined by several techniques including nitrogen adsorption, SEM, and EDS. The H2O2 decomposition rate would be suppressed significantly either by the change of surface properties modified with chemical treatment or the reduction of active sites occupied with the adsorption of 2-CP. In addition, the H2O2 decomposition rate with activated carbons within a specific time can be described by a second-order kinetic expression with respect to the concentration of GAC and H2O2 in the absence or presence of 2-CP. The catalytic activities of the three activated carbons toward 2-CP reduction followed the inverse sequence of those toward H2O2 loss, implying that acidic surface functional group could retard the H2O2 loss and reduce the effect of surface scavenging resulting in increasing the reduction efficiency of 2-CP. By the detection of chloride ions in reaction mixture, it can be demonstrated that the reduction of 2-CP was not only attributed to the advanced adsorption but also the oxidation of the 2-CP with effective radicals. The real oxidation efficiency of 2-CP for the activated carbon modified with hot nitric acid was observed between 0.04 and 0.01 (mol/mol), offering a comparable efficiency to that of the other oxidation system using metal oxide as catalyst.

Adsorption↗
PubMed1994

Isolation and characterization of Desulfitobacterium dehalogenans gen. nov., sp. nov., an anaerobic bacterium which reductively dechlorinates chlorophenolic compounds.

An organism that is able to reductively ortho-dechlorinate 2,4-dichlorophenol and 3-chloro-4-hydroxyphenylacetate (3-Cl-4-OHPA) was isolated from a methanogenic lake sediment. This organism, an anaerobic, motile, Gram-type-positive, rod-shaped bacterium, grew in the presence of 0.1% yeast extract when pyruvate, lactate, formate, or hydrogen was used as the electron donor for reductive dehalogenation of 3-Cl-4-OHPA. Sulfite, thiosulfate, and sulfur were reduced to sulfide, nitrate was reduced to nitrite, and fumarate was reduced to succinate. Dissimilatory reduction of sulfate could not be demonstrated, and no adenylylsulfate reductase was detected with an immunoassay. The organism fermented two pyruvate molecules to one lactate molecule, one acetate molecule, and one carbon dioxide molecule. The pH and temperature optima for both growth and dechlorination of 3-Cl-4-OHPA were 7.5 and 38 degrees C, respectively. The doubling time under these conditions was approximately 3.5 h. On the basis of the results of a 16S rRNA analysis and the inability of the organism to use sulfate as an electron acceptor, strain JW/IU-DC1 is described as the type strain of the new taxon Desulfitobacterium dehalogenans gen. nov., sp. nov.

Bacteria, Anaerobic↗
PubMed1996

Description of chlorophenol-degrading Pseudomonas sp. strains KF1T, KF3, and NKF1 as a new species of the genus Sphingomonas, Sphingomonas subarctica sp. nov.

Gram-negative polychlorophenol-degrading bacterial strains KF1T (T = type strain), KF3, and NKF1, which were described previously as Pseudomonas saccharophila strains, were studied by chemotaxonomic, genetic, and physiological methods and by electron microscopy and compared with selected xenobiotic compound-degrading bacteria. These strains contained sphingolipids with d-18:0, d-20:1, and d-21:1 as the main dihydrosphingosines, ubiquinone 10 as the main respiratory quinone, and spermidine as the major polyamine, and the DNA G + C content was 66 mol%. The cellular fatty acids included about 60% octadecenoic acid, 9% 2-hydroxymyristic acid, 14% cis-9-hexadecenoic acid, and 10% hexadecanoic acid. These strains exhibited less than 97% 16S ribosomal DNA sequence similarity to all of the other taxa studied. In the DNA-DNA reassociation studies the highest levels of reassociation between these strains and previously described species were less than 40%. Thin sections of cells of strains KF1T, KF3, and NKF1 were examined by electron microscopy, and the results showed that the cells had peculiar concentrically arranged layered membranous blebs that extruded from the outer membrane, especially at the cell division points. On the basis of the results of this study, polychlorophenol-degrading strains KF1T, KF3, and NKF1 are considered members of a new species of the genus Sphingomonas, Sphingomonas subarctica. The polycyclic aromatic hydrocarbon-degrading organism Sphingomonas paucimobilis EPA 505 was closely related to Sphingomonas chlorophenolica as determined by chemotaxonomic, phylogenetic, and physiological criteria. The xenobiotic compound degraders Alcaligenes sp. strain A175 and Pseudomonas sp. strain BN6 were identified as members of species of the genus Sphingomonas.

Base Sequence↗
PubMed2002

4-Chlorocatechol 1,2-dioxygenase from the chlorophenol-utilizing Gram-positive Rhodococcus opacus 1CP: crystallization and preliminary crystallographic analysis.

4-Chlorocatechol 1,2-dioxygenase (4-ClC1,2DO) from the Gram-positive bacterium Rhodococcus opacus (erythropolis) 1CP, an enzyme involved in the aerobic biodegradation of chloroaromatic compounds, has been crystallized. 4-ClC1,2DO, which specifically catalyzes the intradiol cleavage of 4-substituted catechols, which are intermediates in the degradation of a variety of aromatic pollutants, to the corresponding maleylacetates, has recently been purified to homogeneity. The enzyme is an homodimer composed of two identical subunits in an alpha(2)-type quaternary structure; it has a molecular weight of about 29 kDa per monomer and contains one Fe(III) and one Mn(II) ion per homodimer. Hexagonal crystals grown in 1.6 M ammonium sulfate, 0.1 M sodium chloride, 100 mM Tris-HCl pH 9.0, 5-15% glycerol were successfully frozen under liquid nitrogen, adding 30% glycerol to the mother-liquor solution as a cryoprotectant. A complete data set was collected at 2.8 A resolution using the EMBL beamline BW7A at the DORIS storage ring, DESY, Hamburg, Germany with a MAR CCD detector and a wavelength of 1.01 A. The crystals belong to the primitive hexagonal space group P6(3)22, with unit-cell parameters a = 90.4, c = 307.5 A. This is the first intradiol dioxygenase which specifically catalyzes the cleavage of chlorocatechols in Gram-positive bacteria to give diffraction-quality crystals.

Chlorophenols↗
PubMed1958

The biological action of chlorophenols.

The biological action of a series of chlorinated phenols has been investigated. With increasing chlorination there is an increase in toxicity in which the convulsant action of phenol is replaced by the signs characteristic of poisoning by dinitrophenol; the higher chlorinated phenols produce a contracture of the isolated rat phrenic nerve diaphragm and a stimulation of in vitro oxygen uptake of rat brain homogenate. These actions of the chlorinated phenols have been correlated with their dissociation constants; it is suggested that the higher chlorinated phenols interfere with oxidative phosphorylation, and that this property may be attributed to the chlorophenate ion. The convulsant action of the lower chlorinated phenols is probably associated with the undissociated molecule.

Animals↗
PubMed1999

Lux-biosensor assessment of pH effects on microbial sorption and toxicity of chlorophenols.

Lux-marked bacterial biosensors and a commercial toxicity testing bacterial strain (Microtox) were exposed to 2,4-dichlorophenol (DCP) and the light output response measured. Increasing DCP concentrations caused a decrease in light output in all three biosensors with an order of sensitivity (in terms of luminescence decrease over the DCP concentration range) of Pseudomonas fluorescens < Escherichia coli < Microtox. Adsorption of DCP to E. coli was measured using uniformly ring labelled [14C]DCP and found to be very rapid. The effect of pH on toxicity and adsorption was also investigated. Low pH values increased the amount of DCP adsorbed to the cell and increased the toxicity of DCP.

Adsorption↗
PubMed2002

Rapid total destruction of chlorophenols by activated hydrogen peroxide.

A practical, inexpensive, green chemical process for degrading environmental pollutants is greatly needed, especially for persistent chlorinated pollutants. Here we describe the activation of hydrogen peroxide by tetraamidomacrocylic ligand (TAML) iron catalysts, to destroy the priority pollutants pentachlorophenol (PCP) and 2,4,6-trichlorophenol (TCP). In water, in minutes, under ambient conditions of temperature and pressure, PCP and TCP are completely destroyed at catalyst:substrate ratios of 1:715 and 1:2000, respectively. The fate of about 90% of the carbon and about 99% of the chlorine has been determined in each case. Neither dioxins nor any other toxic compounds are detectable products, and the catalysts themselves show low toxicity.

Catalysis↗
PubMed1983

Regulation of 2,4,5-trichlorophenoxyacetic acid and chlorophenol metabolism in Pseudomonas cepacia AC1100.

The expression of the degradative genes encoding 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 2,4,5-trichlorophenol (2,4,5-TCP), and pentachlorophenol (PCP) dechlorination in a 2,4,5-T-degrading strain of Pseudomonas cepacia was examined during growth on alternate carbon sources. The dechlorination mechanisms for all three compounds were expressed in 2,4,5-T- and 2,4,5-TCP-grown cells but were not expressed in cells grown on succinate, glucose, or lactate. The addition of 2,4,5-TCP or PCP to cells grown on succinate or lactate resulted in the expression of the 2,4,5-TCP dechlorination mechanism in resting cells after 1-h lag. This expression was prevented by the presence of chloramphenicol in the resting cell suspension. Succinate-plus-PCP-grown resting cells preincubated with 2,4,5-TCP fully induced the trichlorophenol dechlorination system and partially induced the PCP dechlorination system. Preincubation of succinate-plus-PCP-grown resting cells with PCP induced neither the 2,4,5-TCP nor the PCP dechlorinating system. Succinate-grown resting cells converted 2,4,5-T to 2,4,5-TCP even in the presence of chloramphenicol. Thus, the data indicate that the enzyme(s) which converts 2,4,5-T to 2,4,5-TCP is constitutively expressed, whereas those that convert 2,4,5-TCP to central intermediates are induced by 2,4,5-TCP but not by 2,4,5-T or PCP and are repressed in the presence of an alternate carbon source.

2,4,5-Trichlorophenoxyacetic Acid↗