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Enzyme and Microbial Technology Jan 2013A Structure Activity Relationship (SAR) study for laccase mediator systems was performed in order to correctly classify different natural phenolic mediators. Decision... (Comparative Study)
Comparative Study
A Structure Activity Relationship (SAR) study for laccase mediator systems was performed in order to correctly classify different natural phenolic mediators. Decision tree (DT) classification models with a set of five quantum-chemical calculated molecular descriptors were used. These descriptors included redox potential (ɛ°), ionization energy (E(i)), pK(a), enthalpy of formation of radical (Δ(f)H), and OH bond dissociation energy (D(O-H)). The rationale for selecting these descriptors is derived from the laccase-mediator mechanism. To validate the DT predictions, the kinetic constants of different compounds as laccase substrates, their ability for pesticide transformation as laccase-mediators, and radical stability were experimentally determined using Coriolopsis gallica laccase and the pesticide dichlorophen. The prediction capability of the DT model based on three proposed descriptors showed a complete agreement with the obtained experimental results.
Topics: Acetophenones; Benzaldehydes; Biocatalysis; Catechols; Coumaric Acids; Decision Trees; Dichlorophen; Fungal Proteins; Hydrazones; Laccase; Models, Chemical; Models, Molecular; Molecular Structure; Nitrophenols; Oxidation-Reduction; Phenols; Polyporales; Protein Conformation; Quantitative Structure-Activity Relationship; Vanillic Acid
PubMed: 23199741
DOI: 10.1016/j.enzmictec.2012.10.009 -
Environmental Science and Pollution... Sep 2012Endocrine disrupting chemicals (EDCs) are present in the environment and can have serious effects on humans and wildlife. For the establishment of environmental quality...
INTRODUCTION
Endocrine disrupting chemicals (EDCs) are present in the environment and can have serious effects on humans and wildlife. For the establishment of environmental quality guidelines and regulation of EDCs, a better understanding and knowledge of the occurrence and the behavior of environmental EDCs is necessary. The aim of the present study was to comprehensively identify substances that are responsible for the estrogenic effect of an environmental sediment sample taken from the river Elbe/Germany.
DISCUSSION
The estrogenic effect of the organic sediment extract was determined using the yeast-estrogen-screen (YES). The sample was fractionated by liquid chromatography (LC) for effect directed analysis. The composition of estrogen-active fractions was further investigated by gas chromatography-mass spectrometry and high-resolution LC-MS analysis. The composition of the environmental sample was rebuilt with pure compounds in order to assess the partition of estrogenic activity caused by the identified compounds. The organic sediment extract showed an estrogenic potential of 1.9 ± 0.4 ng/g ethinylestradiol equivalents in the sediment. The most prominent contaminants with an estrogenic potential were 17β-estradiol, estrone, and 4-iso-nonylphenols, but other xenoestrogens like bisphenol A and stigmasterol could be found as well. A rebuild of the sample was measured in the YES in order to investigate mixture effects. About 67 % of the observed estrogenic effect in the sediment extract could be explained by a mixture which contained all identified compounds. Chlorophene (o-benzyl-p-chlorophenol)-a widely used antiseptic that was also identified in the sediment extract-has xenoestrogenic properties in the YES that are in the range of other xenoestrogens like 4-n-nonylphenol. This is the first report on chlorophene acting as a xenoestrogen.
Topics: Biological Assay; Dichlorophen; Endocrine Disruptors; Environmental Monitoring; Estrogens; Gas Chromatography-Mass Spectrometry; Geologic Sediments; Germany; Phenols; Rivers; Water Pollutants, Chemical; Yeasts
PubMed: 22421800
DOI: 10.1007/s11356-012-0852-x -
Environmental Science & Technology Mar 2012Manganese oxides typically exist as mixtures with other metal oxides in soil-water environments; however, information is only available on their redox activity as single...
Manganese oxides typically exist as mixtures with other metal oxides in soil-water environments; however, information is only available on their redox activity as single oxides. To bridge this gap, we examined three binary oxide mixtures containing MnO(2) and a secondary metal oxide (Al(2)O(3), SiO(2) or TiO(2)). The goal was to understand how these secondary oxides affect the oxidative reactivity of MnO(2). SEM images suggest significant heteroaggregation between Al(2)O(3) and MnO(2) and to a lesser extent between SiO(2)/TiO(2) and MnO(2). Using triclosan and chlorophene as probe compounds, pseudofirst-order kinetic results showed that Al(2)O(3) had the strongest inhibitory effect on MnO(2) reactivity, followed by SiO(2) and then TiO(2). Al(3+) ion or soluble SiO(2) had comparable inhibitory effects as Al(2)O(3) or SiO(2), indicating the dominant inhibitory mechanism was surface complexation/precipitation of Al/Si species on MnO(2) surfaces. TiO(2) inhibited MnO(2) reactivity only when a limited amount of triclosan was present. Due to strong adsorption and slow desorption of triclosan by TiO(2), precursor-complex formation between triclosan and MnO(2) was much slower and likely became the new rate-limiting step (as opposed to electron transfer in all other cases). These mechanisms can also explain the observed adsorption behavior of triclosan by the binary oxide mixtures and single oxides.
Topics: Adsorption; Aluminum; Dichlorophen; Environment; Hydrogen-Ion Concentration; Ions; Kinetics; Manganese Compounds; Metals; Microscopy, Electron, Scanning; Oxidation-Reduction; Oxides; Solubility; Suspensions; Triclosan
PubMed: 22309023
DOI: 10.1021/es204294c -
The association between urinary concentrations of dichlorophenol pesticides and obesity in children.Reviews on Environmental Health 2011Increasing prevalence of childhood obesity has been seen in the United States and other parts of the world. Environmental chemical exposures might play a role in the...
BACKGROUND
Increasing prevalence of childhood obesity has been seen in the United States and other parts of the world. Environmental chemical exposures might play a role in the worldwide obesity epidemic.
OBJECTIVE
This study was conducted to assess the association of exposure to environmental pesticides with childhood obesity.
METHODS
A total of 6770 subjects aged 6-19 years were selected from the 2003-2004 and 2005-2006 National Health and Nutrition Examination Survey (NHANES). Exposure to environmental pesticides was determined based on the concentrations of pesticide residues in urine. Multivariate logistic regression was performed using SAS 9.1.3 to assess the association between pesticide levels in urine and childhood obesity with the adjustment of potential confounders, including age, gender, race, income, and total fat intake.
RESULTS
A dose-dependent increase in prevalence of obesity was observed in the groups with inter-quartile urinary concentrations of 2,5-dichlorophenol (2,5-DCP). Logistic regression revealed a significant association between adjusted third (Q3) (AOR: 1.47; 95% CI: 1.09, 1.97) and fourth (Q4) (AOR: 1.44; 95% CI: 1.06, 1.95) inter-quartile urinary 2,5-DCP levels and childhood obesity. However, urinary concentrations of 2,4-dichlorophenol were not shown to be significantly associated with childhood obesity.
CONCLUSION
This study suggests a possible relationship between exposure to 2,5-DCP and obesity in children.
Topics: Adolescent; Anthelmintics; Child; Chlorophenols; Dichlorophen; Environmental Exposure; Female; Humans; Logistic Models; Male; Nutrition Surveys; Obesity; Pesticide Residues; Pesticides; United States; Young Adult
PubMed: 22206198
DOI: 10.1515/reveh.2011.029 -
BMC Oral Health May 2011The aim of this study was to compare the reaction of rat connective tissue to two root-end filling materials: white Mineral Trioxide Aggregate (WMTA) and Diaket. (Comparative Study)
Comparative Study
BACKGROUND
The aim of this study was to compare the reaction of rat connective tissue to two root-end filling materials: white Mineral Trioxide Aggregate (WMTA) and Diaket.
METHODS
Each of the materials was placed in dentine tubes and implanted subcutaneously in the dorsal connective tissue of 21 Wistar albino rats. Tissue biopsies were collected 7, 30, and 60 days after the implantation procedure. The specimens were processed and stained with hematoxylin and eosin and examined microscopically. After determining inflammatory cell numbers in sections from each specimen, inflammatory reaction scores were defined as follows: 0; no or few inflammatory cells (no reaction), 1; less than 25 cells (mild reaction), 2; 25 to 125 cells, (moderate reaction), and 3; 125 or more cells (severe reaction). Statistical analysis was performed using the Kruskal-Wallis and Mann-Whitney tests.
RESULTS
There were statistically significant differences in the median inflammatory cell numbers throughout the three test periods, with the most severe degree of inflammation observed at the one-week period. Few cases of necrosis were observed with WMTA. Diaket exhibited the most severe degree of inflammation and necrosis. After 30 days, both materials provoked moderate inflammatory reaction. The eight-week period showed the least severe degree of inflammation in all groups.
CONCLUSIONS
It was concluded that WMTA exhibits a more favourable tissue response compared with Diaket which induced more severe inflammatory reaction than WMTA and the control.
Topics: Aluminum Compounds; Animals; Bismuth; Calcium Compounds; Connective Tissue; Dentin; Drug Combinations; Humans; Inflammation; Male; Oxides; Polyvinyls; Rats; Rats, Wistar; Root Canal Filling Materials; Silicates; Statistics, Nonparametric; Time Factors; Zinc Oxide
PubMed: 21569463
DOI: 10.1186/1472-6831-11-17 -
Journal of Hazardous Materials Feb 2011Within the context of environmentally friendly methods for the elimination of surface-water pollutants, the photodegradation of the phenolic pesticides bromoxynil (BXN)...
Photosensitized degradation in water of the phenolic pesticides bromoxynil and dichlorophen in the presence of riboflavin, as a model of their natural photodecomposition in the environment.
Within the context of environmentally friendly methods for the elimination of surface-water pollutants, the photodegradation of the phenolic pesticides bromoxynil (BXN) and dichlorophen (DCP) under simulated natural conditions has been studied. The work was done in the presence of the visible-light absorber photosensitizer riboflavin (Rf), usually present in trace quantities in natural waters. Under aerobic conditions, an efficient photooxidation of both pesticides was observed. The relatively intricate photochemical mechanism involves pesticide and oxygen consumption and, to a lesser extent, Rf degradation. The kinetic and mechanistic study supports that both H(2)O(2) and singlet molecular oxygen, O(2)((1)Δ(g)), are involved in the process. Kinetic data for the O(2)((1)Δ(g))-mediated oxidation indicate that BXN and DCP are photodegraded with this species faster than the parent compound phenol, very frequently employed as a model for aquatic contaminants, likely due to their lower pK(a) values. This observation allows the design of phenolic pesticides with different photodegradation rates under environmental conditions.
Topics: Dichlorophen; Kinetics; Nitriles; Oxygen; Pesticides; Phenols; Photochemistry; Spectrum Analysis
PubMed: 21130569
DOI: 10.1016/j.jhazmat.2010.11.026 -
Journal of Environmental Science and... 2011Ozonation combined with UV irradiation (UV/O(3)) is an advanced oxidation technique that is very promising for the destruction of organic compounds in aqueous solution....
Ozonation combined with UV irradiation (UV/O(3)) is an advanced oxidation technique that is very promising for the destruction of organic compounds in aqueous solution. In this study, chlorophene was chosen as a model substrate to investigate the effects of pH, initial substrate concentration, ozone dose, and UV light intensity in degradation experiments. The pseudo-first-order rate constant for total organic carbon (TOC) removal was 2.4 × 10(-2), 9.8 × 10(-4), and 6.4 × 10(-2) min(-1) for O(3), UV, and UV/O(3) treatment, respectively. Clearly, UV-enhanced ozonation leads to a synergetic increase in the overall degradation efficiency. Comparative experiments were performed to investigate the effect of the matrix (distilled water or sewage) on chlorophene removal. The organic compounds in sewage retarded the rate of chlorophene removal by 38%, probably by competitively reacting with the oxidizing agent and screening light. The compound 2-benzoylbenzo-1,4-quinone, benzo-1,4-quinone, hydroquinone and maleic acid were identified as primary intermediates by gas chromatography-mass spectrometry. The concentrations of acetic, formic and oxalic anions were detected by ion chromatography. A possible degradation pathway is proposed on the basis of the reaction products identified.
Topics: Dichlorophen; Ozone; Ultraviolet Rays
PubMed: 21104490
DOI: 10.1080/10934529.2011.526065 -
Journal of Chromatography. A Dec 2010Targeted multidimensional liquid chromatography (MDLC), commonly referred to as 'coupled-column' or 'heartcutting', has been used extensively since the 1970s for... (Comparative Study)
Comparative Study
Targeted multidimensional liquid chromatography (MDLC), commonly referred to as 'coupled-column' or 'heartcutting', has been used extensively since the 1970s for analysis of low concentration constituents in complex biological and environmental samples. A primary benefit of adding additional dimensions of separation to conventional HPLC separations is that the additional resolving power provided by the added dimensions can greatly simplify method development for complex samples. Despite the long history of targeted MDLC, nearly all published reports involve two-dimensional methods, and very few have explored the benefits of adding a third dimension of separation. In this work we capitalize on recent advances in reversed-phase HPLC to construct a three-dimensional HPLC system for targeted analysis built on three very different reversed-phase columns. Using statistical peak overlap theory and one of the most recent models of reversed-phase selectivity we use simulations to show the potential benefit of adding a third dimension to a MDLC system. We then demonstrate this advantage experimentally by developing targeted methods for the analysis of a variety of broadly relevant molecules in different sample matrices including urban wastewater treatment effluent, human urine, and river water. We find in each case that excellent separations of the target compounds from the sample matrix are obtained using one set of very similar separation conditions for all of the target compound/sample matrix combinations, thereby significantly reducing the normally tedious method development process. A rigorous quantitative comparison of this approach to conventional 1DLC-MS/MS also shows that targeted 3DLC with UV detection is quantitatively accurate for the target compounds studied, with method detection limits in the low parts-per-trillion range of concentrations. We believe this work represents a first step toward the development of a targeted 3D analysis system that will be more effective than previous 2D separations as a tool for the rapid development of robust methods for quantitation of low concentration constituents in complex mixtures.
Topics: Chemical Fractionation; Chromatography, High Pressure Liquid; Dichlorophen; Humans; Hydrocortisone; Male; Models, Chemical; Phenytoin; Pyridines; Sewage; Sulfonylurea Compounds; Tandem Mass Spectrometry; Water; Water Pollutants, Chemical
PubMed: 21047638
DOI: 10.1016/j.chroma.2010.09.023 -
Journal of AOAC International 2010A single-laboratory validation study was conducted for an LC method using UV detection for the simultaneous determination of the active ingredients o-phenylphenol (OPP),...
A single-laboratory validation study was conducted for an LC method using UV detection for the simultaneous determination of the active ingredients o-phenylphenol (OPP), p-tert-amylphenol (PTAP), and o-benzyl-p-chlorophenol (OBPCP) in disinfectant formulations. Samples were extracted, the extracts diluted with acidified methanol, and the active ingredients separated by LC with a gradient mobile phase and quantified by using UV detection at 285 nm. For each active ingredient, the RSD was < or = 3.7%, and the intermediate reproducibility was < or = 3.4%. The active ingredient content of the spiked samples analyzed in this study ranged from 0.075 to 10.1% for the individual phenol active ingredients. The average recovery ranges were 86.7-104.9, 82.8-115.6, and 91.6-114.7% for the active ingredients OPP, PTAP, and OBPCP, respectively, for the concentration range of 0.075-10.1%. This method, with a relatively short chromatographic run time (about 15 min), proved to be reliable and convenient for analyses of products or samples containing all or a combination of these phenol active ingredients.
Topics: Biphenyl Compounds; Chromatography, Liquid; Dichlorophen; Disinfectants; Phenols; Spectrophotometry, Ultraviolet
PubMed: 20629411
DOI: No ID Found -
Journal of Applied Oral Science :... 2010This paper reports the nonsurgical endodontic therapy using calcium hydroxide intracanal dressing and prosthetic treatment of 9 teeth with periapical lesions in a...
This paper reports the nonsurgical endodontic therapy using calcium hydroxide intracanal dressing and prosthetic treatment of 9 teeth with periapical lesions in a 16-year-old female patient. The periodontal treatment plan included oral hygiene instructions, mechanical debridement and gingivectomy in the maxillary incisors to improve gingival contouring. Root canal treatment was indicated for teeth 11-13, 21, 22, 42-45. After successive changes of a calcium hydroxide intracanal dressing during 6 weeks, the size of the periapical radiolucencies decreased and lesion remission occurred after root canal obturation. The endodontically treated teeth received a bondable polyethylene reinforcement fiber (Ribbond) in the prepared canal space and crown buildup was done with composite resin. Prosthetic rehabilitation was planned with single-unit metal-ceramic crowns and fixed partial dentures. Clinical and radiographic evaluation after 6 months showed successful results. The outcomes of this case showed that chronic periapical lesions can respond favorably to nonsurgical endodontic treatment in adolescent patients and that, with proper indication, polyethylene fibers can provide an effective conservative and esthetic option for reinforcing endodontically treated teeth undergoing prosthetic rehabilitation.
Topics: Adolescent; Bismuth; Crowns; Dental Pulp Necrosis; Denture, Partial, Fixed; Drug Combinations; Female; Gingivectomy; Gutta-Percha; Humans; Periapical Periodontitis; Polyethylenes; Polyvinyls; Post and Core Technique; Root Canal Filling Materials; Root Canal Irrigants; Root Canal Obturation; Root Canal Therapy; Sodium Hypochlorite; Tooth Extraction; Zinc Oxide
PubMed: 20485933
DOI: 10.1590/s1678-77572010000200016