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PubMed2001

Biofiltration of a mixture of volatile organic emissions.

Air biofiltration is now under active consideration for the removal of the volatile organic compounds (VOCs) from polluted airstreams. To optimize this emerging environmental technology and to understand compound removal mechanisms, a biofilter packed with peat was developed to treat a complex mixture of VOCs: oxygenated, aromatic, and chlorinated compounds. The removal efficiency of this process was high. The maximum elimination capacity (ECmax) obtained was approximately 120 g VOCs/m3 peat/hr. Referring to each of the mixture's components, the ECmax showed the limits in terms of biodegradability of VOCs, especially for the halogenated compounds and xylene. A stratification of biodegradation was observed in the reactor. The oxygenated compounds were metabolized before the aromatic and halogenated ones. Two assumptions are suggested. There was a competition between bacterial communities. Different communities colonized the peat-based biofilter, one specialized for the elimination of oxygenated compounds, the others more specialized for elimination of aromatic and halogenated compounds. There was also substrate competition. Bacterial communities were the same over the height of the column, but the more easily biodegradable compounds were used first for the microorganism metabolism when they were present in the gaseous effluent.

Air Pollutants↗

PubMed1997

Sulfur tuft and turkey tail: biosynthesis and biodegradation of organohalogens by Basidiomycetes.

Chlorinated aliphatic and aromatic compounds are generally considered to be undesirable xenobiotic pollutants. However, the higher fungi, Basidiomycetes, have a widespread capacity for organohalogen biosynthesis. Adsorbable organic halogens (AOX) and/or low-molecular-weight halogenated compounds are produced by Basidiomycetes of 68 genera from 20 different families. Most of the 81 halogenated metabolites identified from Basidiomycetes to date are chlorinated, although brominated and iodated metabolites have also been described. Two broad categories of Basidiomycete organohalogen metabolites are the halogenated aromatic compounds and the haloaliphatic compounds. Some of these organohalogen metabolites have demonstrable physiological roles as antibiotics and as metabolites involved in lignin degradation. Basidiomycetes produce large amounts of low-molecular-weight organohalogens or adsorbable organic halogens (AOX) when grown on lignocellulosic substrates. In our view, Basidiomycetes, as decomposers of forest litter, are a major source of natural organohalogens in terrestrial environments. Basidiomycetes are also potent degraders of a wide range of chlorinated pollutants, such as bleachery effluent from kraft mills and pentachlorophenol, polychlorinated dioxins, and polychlorinated biphenyls. The extracellular, lignin-degrading enzymes of the Basidiomycetes are involved in the oxidative degradation of chlorophenols and dioxin and can cause reductive dechlorination of halomethanes. There is no clear-cut separation between "polluters" and "clean-uppers" within the Basidiomycetes. Several genera, e.g. Bjerkandera, Hericium, Phlebia, and Trametes, produce significant amounts of chlorinated compounds but are also highly effective in metabolizing or biotransforming chlorinated pollutants.

Anti-Bacterial Agents↗

PubMed2005

Inhibitory effects of environmental chemicals on protein disulfide isomerase in vitro.

BACKGROUND: The influence of endocrine disrupting chemicals (EDCs) upon physiological functions and their mechanisms is of concern. We have previously demonstrated that protein disulfide isomerase (PDI) was a target molecule of bisphenol A (BPA), which is considered to be EDC. PDI plays a key role in protein folding as an isomerase and also possesses a 3,3',5-triiodo-L-thyronine (T3)-binding activity. Since PDI activities were inhibited by BPA in our previous study, BPA might have adverse effects on physiological functions via the inhibition of PDI activities. We conducted this study to identify the compounds which disturb PDI activities as well as BPA, and to discuss their structural characteristics. METHODS: We examined the effects of 22 suspected EDC on both the T3-binding activity and isomerase activity of rat recombinant PDI. RESULTS: Among the 22 compounds, only phenolic compounds, namely BPA, p-octylphenol, p-nonylphenol, 2,4-dichlorophenol, pentachlorophenol, tetrabromobisphenol A, and tetrachlorobisphenol A, inhibited T3 binding to PDI. Furthermore non-halogenated compounds among these phenolic compounds, such as BPA, p-octylphenol, and p-nonylphenol, showed inhibitory effects on the isomerase activity of PDI. CONCLUSIONS: Our results suggest that phenolic groups might have important inhibitory effects on the T3-binding activity of PDI, and that compounds with phenolic groups might have the same effects on PDI. Furthermore, non-halogenated phenolic compounds had inhibitory effects on the isomerase activities of PDI in addition to T3-binding activity, indicating that these compounds might also have adverse effects on protein folding, which PDI participates in by catalyzing rearrangements of disulfide bonds as an isomerase.

Animals↗

PubMed2002

Structure elucidation of four possible biogenic organohalogens using isotope exchange mass spectrometry.

The molecular structures of four unknown bioaccumulating halogenated compounds, C10H6N2Br3Cl3, C10H6N2Br4Cl2, C10H6N2Br5Cl, and C10H6N2Br6 were characterized using isotope exchange positive chemical ionization (IE-PCI) mass spectrometry (MS) and identified by comparison to synthesized standards. NH3 and ND3 were used as reagent gases for the IE-PCI-MS experiment. The shift in mass of the quasimolecular ion between the NH3 and ND3 PCI obtained spectra indicated the number of exchangeable hydrogens attached to the two nitrogen atoms in C10H6N2Br4Cl2, and thus the type of amines present (primary, secondary, or tertiary). 19 compounds (13 amines of varying degree of substitution; six containing no nitrogen) were used as reference compounds and controls in the experiment to validate the IE-PCI technique. The results of the IE-PCI-MS indicated the presence of two tertiary amine functional groups. The molecular structures of the four hexahalogenated compounds were then proposed to be 1,1'-dimethyl-3,3',4,-tribromo-4',5,5'-trichloro-2,2'-bipyrrole, 1,1'-dimethyl-3,3',4,4'-tetrabromo-5,5'-dichloro-2,2'-bipyrrole, 1,1'-dimethyl-3,3',4,4',5-pentabromo-5'-chloro-2,2'-bipyrrole, and 1,1'-dimethyl-3,3',4,4',5,5'-hexabromo-2,2'-bipyrrole and subsequently synthesized. Comparison of retention times and electron capture negative ionization (ECNI) full scans on various gas chromatography (GC) columns between the synthesized bipyrroles and the corresponding unknown compounds in biota indicated that three of the unknown compounds--possible marine natural products--were the proposed halogenated dimethyl bipyrroles. The placement of the halogen atoms on the fourth compound, C10H6N2Br3Cl3 could not be unequivocally determined since the synthesized standard could not be fully characterized.

Biological Availability↗

PubMed2001

Marine macroalgae in polar regions as natural sources for volatile organohalogens.

Marine macroalgae species from the polar regions were investigated for their importance as natural sources of volatile halogenated compounds released into the biosphere. Several different halogenated C1 to C4 hydrocarbons were identified and their release rates determined. The compounds contained mainly bromine and iodine, and form was the dominant compound released. Although an annual atmospheric input of approximately 10(8)-10(10) g bromine and 10(7)-10(8) g iodine was calculated from the release rates, marine macroalgae are apparently not the major source on a global scale, as the release is up to four orders of magnitude lower than a presumed annual flow from the oceans. Despite this, macroalgae may be more important on a local scale due to their occurrence at a high biomass in the coastal regions. The present paper gives an overview about studies done on the release of volatile halocarbons by macroalgae from polar regions. Furthermore, the function of these compounds in the macroalgal metabolism is discussed.

Cold Climate↗

PubMed1998

Halogenation of aromatic compounds: thermodynamic, mechanistic and ecological aspects.

Biological halogenation of aromatic compounds implies the generation of reducing equivalents in the form of e.g. NADH. Thermodynamic calculations show that coupling the halogenation step to a step in which the reducing equivalents are oxidized with a potent oxidant such as O2 or N2O makes the halogenation reaction thermodynamically feasible without the input of additional energy in the form of e.g. NADH. In a current model on the halogenation of tryptophan to 7-chloro-L-tryptophan NADH and O2 are proposed as co-substrates in a reaction in which the aromatic compound is oxidized via an epoxide as intermediate. The thermodynamic calculations thus indicate that such a route hinges on mechanistic insights but has no thermodynamic necessity. Furthermore the calculations suggest that halogenation of tryptophan and other aromatic compounds should be possible with N2O, and possibly even with nitrate replacing O2 as the oxidant.

Antifungal Agents↗

PubMed1983

Transformations of 1- and 2-carbon halogenated aliphatic organic compounds under methanogenic conditions.

Several 1- and 2-carbon halogenated aliphatic organic compounds present at low concentrations (less than 100 micrograms/liter) were degraded under methanogenic conditions in batch bacterial cultures and in a continuous-flow methanogenic fixed-film laboratory-scale column. Greater than 90% degradation was observed within a 2-day detention time under continuous-flow methanogenic conditions with acetate as a primary substrate. Carbon-14 measurements indicated that chloroform, carbon tetrachloride, and 1,2-dichloroethane were almost completely oxidized to carbon dioxide, confirming removal by biooxidation. The initial step in the transformations of tetrachloroethylene and 1,1,2,2-tetrachloroethane to nonchlorinated end products appeared to be reductive dechlorination to trichloroethylene and 1,1,2-trichloroethane, respectively. Transformations of the brominated aliphatic compounds appear to be the result of both biological and chemical processes. The data suggest that transformations of halogenated aliphatic compounds can occur under methanogenic conditions in the environment.

Anaerobiosis↗

PubMed2006

Maternal transfer of organohalogen contaminants and metabolites to eggs of Arctic-breeding glaucous gulls.

Eggs of seabirds have routinely been used as indicators of environmental pollution in the Arctic. However, the variability in organohalogen concentration and composition associated with the laying sequence, have not been defined. We examined a suite of PCBs, organochlorine (OC) pesticides and by-products, polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs) and methylsulfonyl- (MeSO2) PCBs in complete 3-egg clutches of glaucous gulls (Larus hyperboreus), and plasma samples of the laying females collected from the Norwegian Arctic. SigmaPCB, SigmaOC and SigmaPBDE, but not SigmaMeSO2-PCB, concentrations in eggs were positively associated, with increasing magnitude and significance from the first through the last-laid egg, with concentrations in female plasma. However, the concentrations of these organohalogen classes fluctuated irrespective of the laying order in the clutch. In general, maternal transfer favored low K(ow) and/or less persistent compounds, whereas the recalcitrant and/or higher-halogenated compounds were less readily transferred, and consequently more selectively retained in the mother.

Animals↗

PubMed1979

beta-Adrenergic blocking action of halonitrophenethanolamines.

A series of phenethanolamines with N-isopropyl and N-tertbutyl substituents and ring-substituted with nitro- and halogen groups has been prepared. Using guinea-pig isolated atrial and tracheal preparations, the influence of the nitro-group on the beta 1- and beta 2-antagonist actions of the mono-halogen compounds was determined, and the antagonist and partial agonist effects of the halo-nitro-compounds on beta-adrenoceptors in these tissues measured to help elucidate structure-activity relations in this series. The halonitro compounds did not show enhanced activity compared with the mono-halogen substituted analogues. Several of the new compounds showed slight but significant beta 2-antagonist selectivity of action, and one compound was significantly beta 1-selective.

2-Hydroxyphenethylamine↗

PubMed2003

Biological dehalogenation and halogenation reactions.

A large number of halogenated compounds is produced by chemical synthesis. Some of these compounds are very toxic and cause enormous problems to human health and to the environment. Investigations on the degradation of halocompounds by microorganisms have led to the detection of various dehalogenating enzymes catalyzing the removal of halogen atoms under aerobic and anaerobic conditions involving different mechanisms. On the other hand, more than 3500 halocompounds are known to be produced biologically, some of them in great amounts. Until 1997, only haloperoxidases were thought to be responsible for incorporation of halogen atoms into organic compounds. However, recent investigations into the biosynthesis of halogenated metabolites by bacteria have shown that a novel type of halogenating enzymes, FADH(2)-dependent halogenases, are involved in biosyntheses of halogenated metabolites. In every gene cluster coding for the biosynthesis of a halogenated metabolite, isolated so far, one or several genes for FADH(2)-dependent halogenases have been identified.

Amino Acid Sequence↗

PubMedDate not supplied

Anaerobic dechlorinating bacteria.

Anaerobic dehalogenation is attracting great interest since it opens new research horizons based on the novel biochemical mechanisms identified in this field such as halorespiration, i.e. the utilization of halogenated compounds as electron acceptors. Moreover, anaerobic bacteria seem to be more efficient than their aerobic counterparts in removing halogen atoms from polyhalogenated compounds. Thus, anaerobic dehalogenation can be considered as a promising means for bioremediation treatments of persistently polluted environments. In this line, identification of pure strains capable of dehalogenation will give important information about the diversity of organisms implicated in this process and also fundamental explanations of the diverse biochemical mechanisms involved. In light of these considerations, we chose to focus this review on the physiological descriptions, dechlorination activities, phylogenetic diversity, and potential biotechnological applications of these pure anaerobic strains capable of dehalogenation.

Bacteria, Anaerobic↗

PubMed2006

Virtual screening for environmental pollutants: structure-activity relationships applied to a database of industrial chemicals.

The current risk paradigm calls for individual consideration and evaluation of each separate environmental pollutant, but this does not reflect accurately the cumulative impact of anthropogenic chemicals. In the present study, previously validated structure-activity relationships were used to estimate simultaneously the baseline toxicity and atmospheric persistence of approximately 50,000 compounds. The results from this virtual screening indicate fairly stable statistical distributions among small anthropogenic compounds. The baseline toxicity was not changed much by halogen substitution, but a distinct increase seemed to occur in the environmental persistence with increased halogenation. The ratio of the atmospheric half-lives to the median lethal concentrations provides a continuous scale with which to rank and summarize the incremental environmental impacts in a mixture-exposure situation. Halogenated compounds as a group obtained a high ranking in this data set, with well-known pollutants at the very top: DDT metabolites and derivatives, polychlorinated biphenyls, diphenyl ethers and dibenzofurans, chlorinated paraffins, chlorinated benzenes and derivatives, hydrochlorofluorocarbons, and dichlorononylphenol. Environmentally friendly chemicals that obtained the lowest rank are nearly all hydroxylated and water-soluble. Virtual screening can assist with "green chemistry" in designing safe and degradable products and enable assessment of the efficiency in chemicals risk management.

Chemical Industry↗

PubMed2000

Application of a purge and trap TDS-GC/MS procedure for the determination of emissions from flame retarded polymers.

Emissions of volatile organic compounds (VOCs) from different thermoplastic polymers used in electrotechnical applications were investigated using a purge and trap procedure that involved adsorption on Tenax GR. Results were compared to those for an operating TV set monitored in a test chamber. The analyses were in both cases carried out using thermodesorption gas chromatography with mass spectrometric detection (TDS-GC/MS). Substances identified were monomers, volatile additives, or related compounds. Special attention was given to the detection of halogenated compounds. Their origin was studied using reference samples and synthetic standards.

Air Pollutants↗

PubMed1997

Evaluation of the rodent micronucleus assay in the screening of IARC carcinogens (groups 1, 2A and 2B) the summary report of the 6th collaborative study by CSGMT/JEMS MMS. Collaborative Study of the Micronucleus Group Test. Mammalian Mutagenicity Study Group.

To assess the correlation between micronucleus induction and human carcinogenicity, the rodent micronucleus assay was performed on known and potential human carcinogens in the 6th MMS/CSGMT collaborative study. Approximately 100 commercially available chemicals and chemical groups on which there was little or no micronucleus assay data were selected from IARC (International Agency for Research on Cancer) Groups 1 (human carcinogen), 2A (probable human carcinogen) and 2B (possible human carcinogen). As minimum requirements for the collaborative study, 5 male mice were treated by intraperitoneal injection or oral gavage once or twice with each chemical at three dose levels, and bone marrow and/or peripheral blood was analyzed. Five positives and 2 inconclusives out of 13 Group 1 chemicals, 7 positives and 5 inconclusives of 23 Group 2A chemicals, and 26 positives and 6 inconclusives of 67 Group 2B chemicals were found. Such low positive rates were not surprising because of a test chemical selection bias, and we excluded well-known micronucleus inducers. The overall evaluation of the rodent micronucleus assay was based on the present data combined with published data on the IARC carcinogens. After merging, the positive rates for Groups 1, 2A and 2B were 68.6, 54.5 and 45.6%, respectively. Structure-activity relationship analysis suggested that the micronucleus assay is more sensitive to the genetic toxicity of some classes of chemicals. Those to which it is sensitive consist of (1) aziridines and bis(2-chloroethyl) compounds; (2) alkyl sulfonate and sulfates; (3) acyl-type N-nitroso compounds; (4) hydrazines; (5) aminobiphenyl and benzidine derivatives; and (6) azo compounds. Those to which it is less sensitive consist of (1) dialkyl type N-nitroso compounds; (2) silica and metals and their compounds; (3) aromatic amines without other functional groups; (4) halogenated compounds; and (5) steroids and other hormones. After incorporation of structure-activity relationship information, the positive rates of the rodent micronucleus assay became 90.5, 65.2 and 60.0% for IARC Groups 1, 2A and 2B, respectively. Noteworthy was the tendency of the test to be more sensitive to those carcinogens with stronger evidence human carcinogenicity.

Animals↗

PubMed2001

Preparation and structural properties of 7,8-dioxa[6]helicenes and 7a,14c-dihydro-7,8-dioxa[6]helicenes.

The potentially chiral 7,8-dioxa[6]helicenes 1-1c have been prepared by oxidation of their precursors the 7a,14c-dihydro-7,8-dioxa[6]helicenes 3. The crystal structure determination of 3b cis-7a,14c-dihydro-3,12-dibromo-7,8-dioxa[6]helicene unambiguously confirms the cis configuration of the 7a,-14c hydrogens in compounds 3 as previously implied from NMR measurements and also shows that 3b crystallizes in a chiral conformation in the solid state. Selective deuteration of the sterically crowded 1,14 positions of 7,8-dioxa[6]helicene 1 influenced the crystal structure. The deuterium labeled compound D2-1 exhibits a disordered structure, whereas 1 had been found to crystallize in a complex structure which can be described as an analogous partly ordered modulated superstructure. When dehydrogenation of compound 3 to obtain compound 1 was attempted, harsh synthetic conditions gave the unexpected halogenated compounds 5-chloro-7,8-dioxa[6]helicene 1c and cis-7a,14c-dibromo-7,8-dioxa[6]helicene 3c. Compounds 1d and 3b were identified by solving their crystal structure.

Journal Article↗

PubMed1999

Ascorbic acid treatment to reduce residual halogen-based oxidants prior to the determination of halogenated disinfection byproducts in potable water.

Treatment of potable water samples with ascorbic acid has been investigated as a means for reducing residual halogen-based oxidants (disinfectants), i.e. HOCl, Cl2, Br2 and BrCl, prior to determination of EPA Method 551.1A and 551.1B analytes. These disinfection byproducts include certain haloalkanes, haloalkenes, haloethanenitriles, haloaldehydes, haloketones and trichloronitromethane. When used as a dehalogenating agent immediately before analysis, only one analyte, 2,2,2-trichloroethanediol (chloral hydrate), is significantly decomposed. Ascorbic acid is superior to thiosulfate and sulfite as it does not destroy trichloroethanenitrile (trichloroacetonitrile), trichloronitromethane (chloropicrin) or dibromoethanenitrile (dibromoacetonitrile). Unlike ammonia or amines, it is not nucleophilic and cannot form hemiaminals (carbinolamines) with carboxaldehydes and ketones. Ascorbic acid treatment can rapidly consume (reduce) large amounts of active (oxidizing) halogen compounds, producing only inorganic halides and dehydroascorbic acid and not additional halogenated organic molecules.

Ascorbic Acid↗

PubMed2005

Bacterial degradation of xenobiotic compounds: evolution and distribution of novel enzyme activities.

Bacterial dehalogenases catalyse the cleavage of carbon-halogen bonds, which is a key step in aerobic mineralization pathways of many halogenated compounds that occur as environmental pollutants. There is a broad range of dehalogenases, which can be classified in different protein superfamilies and have fundamentally different catalytic mechanisms. Identical dehalogenases have repeatedly been detected in organisms that were isolated at different geographical locations, indicating that only a restricted number of sequences are used for a certain dehalogenation reaction in organohalogen-utilizing organisms. At the same time, massive random sequencing of environmental DNA, and microbial genome sequencing projects have shown that there is a large diversity of dehalogenase sequences that is not employed by known catabolic pathways. The corresponding proteins may have novel functions and selectivities that could be valuable for biotransformations in the future. Apparently, traditional enrichment and metagenome approaches explore different segments of sequence space. This is also observed with alkane hydroxylases, a category of proteins that can be detected on basis of conserved sequence motifs and for which a large number of sequences has been found in isolated bacterial cultures and genomic databases. It is likely that ongoing genetic adaptation, with the recruitment of silent sequences into functional catabolic routes and evolution of substrate range by mutations in structural genes, will further enhance the catabolic potential of bacteria toward synthetic organohalogens and ultimately contribute to cleansing the environment of these toxic and recalcitrant chemicals.

Amino Acid Sequence↗

PubMed1984

Inactivation of microsomal NADPH-cytochrome c reductase by sulfhydryl-reactive derivatives of menadione.

Five derivatives of menadione (2-methyl-1,4-naphthoquinone) having electronegative substituents on allylic carbons were prepared for study as sulfhydryl-reactive inactivators of mouse liver microsomal NADPH-cytochrome c reductase. Each of these naphthoquinones, incubated with dilute suspensions of microsomes, produced a loss of NADPH-cytochrome c reductase activity proportional to the initial naphthoquinone concentration. Each of the compounds also reacted with cysteine, as evidenced in the case of the halogenated compounds, by loss of reactive sulfhydryl groups and, in the case of 2-p-nitrophenoxymenadione, by the displacement of the leaving group, p-nitrophenol. Menadione, incubated under identical conditions, did not inactivate NADPH-cytochrome c reductase and was unreactive with cysteine. The requirement for a halogen or a nitrophenoxy substituent on at least one of the allylic carbons suggested that the mechanism of NADPH-cytochrome c reductase inactivation involves attack on critical microsomal nucleophiles, possibly sulfhydryl groups. The possible significance of these findings is discussed in relation to the antitumor activity and bioactivation of the halomethyl naphthoquinones.

Animals↗