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1.
Artigo em Chinês | MEDLINE | ID: mdl-35915947

RESUMO

This article reports a poisoning case after occupational exposure to toluene, xylene, and ethylbenzene for 3 days. The main clinical manifestation of the patient was consciousness disorder. After dehydration, cerebral awakening, anti-epileptic and anti-myoclonic treatment, the patient had secondary epilepsy and cerebellar ataxia for a long time. According to diagnostic criteria, the patient was diagnosed with occupational acute chemical poisoning (severe) , occupational acute chemical poisoning sequelae. It is suggested that the clinical awareness of benzene compound poisoning should be strengthened, early diagnosis and early treatment should be carried out to improve the prognosis of patients.


Assuntos
Tolueno , Xilenos , Benzeno , Derivados de Benzeno , Humanos
2.
J Am Chem Soc ; 144(27): 12212-12218, 2022 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-35786875

RESUMO

Industrial-scale thermal separation processes have contributed greatly to the rise in carbon dioxide emissions. Porous materials, such as metal-organic frameworks (MOFs), can potentially reduce these emissions by achieving nonthermal chemical separations through the physical adsorption of targeted species with high selectivity. Here, we report the synthesis of the channel-based MOFs NU-2000 and NU-2001, which are constructed from three-dimensional (3D) linkers, to separate the industrially relevant xylene isomers under ambient conditions by leveraging sub-Ångstrom differences in the sizes of each isomer. While the rotation of two-dimensional (2D) linkers in MOFs often affords changes in pore apertures and pore sizes that are substantial enough to hinder separation efficiency, increasing the linker dimensionality from 2D to three-dimensional (3D) enables precise control of the MOF pore size and aperture regardless of the linker orientation, establishing this design principle as a broadly applicable strategy.


Assuntos
Estruturas Metalorgânicas , Adsorção , Isomerismo , Porosidade , Xilenos
3.
Arh Hig Rada Toksikol ; 73(2): 107-118, 2022 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-35792774

RESUMO

The aim of introducing occupational exposure limits (OELs) is to use them as a risk management tool in order to protect workers' health and well-being against harmful agents at the workplace. In this review we identify OELs for benzene, toluene, ethylbenzene, xylene (BTEX), and styrene concentrations in air and assess occupational exposure to these compounds through a systematic literature search of publications published in West Asian countries from 1980 to 2021. OELs for BTEX and styrene have been set in Iran and Turkey to levels similar to those in European countries and the US. The search yielded 49 full-text articles that cover studies of exposure assessment in six countries, but most (n=40) regard Iran. Average occupational exposure to benzene of workers in oil-related industries is higher than recommended OEL, while average occupational exposure to other compounds is lower than local OELs (where they exist). Currently, information about levels of occupational exposure to BTEX and styrene is insufficient in West Asian countries, which should be remedied through OEL regulation and application. Furthermore, coherent research is also needed to determine actual levels of occupational exposure, dose-responses, and the economic and technical capacity of local industries to address current issues.


Assuntos
Exposição Ocupacional , Xilenos , Benzeno/análise , Benzeno/toxicidade , Derivados de Benzeno , Humanos , Exposição Ocupacional/análise , Estireno , Tolueno/análise , Xilenos/análise
4.
Analyst ; 147(16): 3783-3794, 2022 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-35876175

RESUMO

In this study, parylene-C films from plasma deposition as well as thermal deposition were pyrolyzed to prepare a carbon electrode for application in electrochemical immunoassays. Plasma deposition could prepare parylene-C in a faster deposition rate and more precise control over the thickness in comparison with the conventional thermal deposition. To analyze the influence of the deposition method, the crystal and electronic structures of the pyrolyzed parylene-C films obtained via both deposition methods were compared using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. For application as a carbon electrode in immunoassays, the electrochemical properties of the pyrolyzed carbon films from two both deposition methods were analyzed, including the double layer capacitance (2.10 µF cm-2 for plasma deposition and 2.20 µF cm-2 for thermal deposition), the apparent electron transfer rate (approximately 1.1 × 10-3 cm s-1 for both methods), and the electrochemical window (approximately -1.0 ∼ 2.1 V for both methods). Finally, the applicability of the pyrolyzed carbon electrode from parylene-C was demonstrated for the diagnosis of human hepatitis-C using various amperometric methods, such as cyclic voltammetry, chronoamperometry, square-wave voltammetry and differential pulse voltammetry.


Assuntos
Carbono , Pirólise , Carbono/química , Eletrodos , Humanos , Imunoensaio , Polímeros , Xilenos
5.
Artigo em Inglês | MEDLINE | ID: mdl-35886652

RESUMO

By using compound-specific isotope analysis (CSIA) in combination with high-throughput sequencing analysis (HTS), we successfully evaluated the benzene and toluene biodegradation in a bio-permeable reactive barrier (bio-PRB) and the stress response of the microbial community. Under stress conditions, a greater decline in the biodegradation rate of BTEX was observed compared with the apparent removal rate. Both an increase in the influent concentration and the addition of trichloroethylene (TCE) inhibited benzene biodegradation, while toluene biodegradation was inhibited by TCE. Regarding the stress response, the relative abundance of the dominant bacterial community responsible for the biodegradation of BTEX increased with the influent concentration. However, the dominant bacterial community did not change, and its relative abundance was restored after the influent concentration decreased. On the contrary, the addition of TCE significantly changed the bacterial community, with Aminicenantes becoming the dominant phyla for co-metabolizing TCE and BTEX. Thus, TCE had a more significant influence on the bio-PRB than an increasing influent concentration, although these two stress conditions showed a similar degree of influence on the apparent removal rate of benzene and toluene. The present work not only provides a new method for accurately evaluating the biodegradation performance and microbial community in a bio-PRB, but also expands the application of compound-specific isotope analysis in the biological treatment of wastewater.


Assuntos
Tricloroetileno , Poluentes Químicos da Água , Benzeno/análise , Derivados de Benzeno/análise , Biodegradação Ambiental , Isótopos/análise , Tolueno/análise , Tricloroetileno/análise , Tricloroetileno/metabolismo , Poluentes Químicos da Água/análise , Xilenos/análise
6.
Pak J Pharm Sci ; 35(3): 835-840, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35791484

RESUMO

The present paper presents results of analgesic, antipyretic activity and anti-inflammatory potential of extract obtained from Acacia cyanophylla when tested at different doses. Analgesic potential of the crude methanolic extract tested by acetic acid assay was dose dependent and maximum activity of 61.60% was measured at 400 mg/kg. Analgesic activity by hot plate method revealed that maximum activity of 36.98% was noted when the mice were exposed to 90 minutes at higher dose of 400 mg/kg. Similar pattern for antipyretic activity was observed as noted for analgesic activity. Anti-inflammatory activity was dose and time dependent when evaluated by Carrageenan-induced paw edema and Xylene-induced ear edema model. Maximum anti-inflammatory activity (43.32%) was shown by crude methanolic extract of Acacia cyanophylla at 400mg/kg-1 after 5 hours on Carrageenan-induced paw edema model. Similarly, maximum (68.80%) anti-inflammatory activity was noted when accessed by Xylene-induced ear edema model at the dose of 200mg/kg after 60 minutes. No in vivo toxicity of the extracts up to the dose of 2000mg/kg was observed using albino mice.


Assuntos
Acacia , Analgésicos , Anti-Inflamatórios , Antipiréticos , Acacia/química , Analgésicos/farmacologia , Animais , Anti-Inflamatórios/farmacologia , Antipiréticos/farmacologia , Carragenina , Edema/induzido quimicamente , Edema/tratamento farmacológico , Febre/tratamento farmacológico , Camundongos , Extratos Vegetais/farmacologia , Xilenos
7.
Opt Lett ; 47(13): 3247-3250, 2022 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-35776597

RESUMO

A mid-infrared absorption-based laser sensor is developed for selective and simultaneous benzene, toluene, ethylbenzene, and xylenes (BTEX) measurements under ambient conditions. The sensor is based on a distributed feedback inter-band cascade laser emitting near 3.3 µm. Wavelength tuning and deep neural networks were employed to differentiate the broadband absorbance of BTEX species. The sensor was validated with gas mixtures and real-time measurements were demonstrated at a temporal resolution of 1 s. Minimum detection limits for BTEX in air are 8, 20, 5, and 46 ppm, respectively. This sensor can be utilized to monitor BTEX emissions in the petrochemical, rubber, and paint industries to avoid hazardous health effects.


Assuntos
Tolueno , Xilenos , Benzeno , Derivados de Benzeno , Lasers , Redes Neurais de Computação
8.
Sci Rep ; 12(1): 9506, 2022 06 09.
Artigo em Inglês | MEDLINE | ID: mdl-35681067

RESUMO

We propose two novel methods to effectively utilize parylene C films. First, we demonstrate a vertical deposition method capable of depositing a parylene C film of the same thickness on both sides of a sample. Through this method, we have formed parylene C films with a thickness of 4 µm on both sides of the sample with a thickness deviation of less than 2.5%. Further optical verification indicates that parylene C films formed by this method have a very uniform thickness distribution on each side of the surfaces. Second, we propose a debris-tolerant laser patterning method as a mask-less means to fabricate self-supporting ultrathin parylene C films. This method does not involve any photolithography and entails a simple and rapid process that can be performed using only a few materials with excellent biocompatibility. It is demonstrated that patterned parylene C films exhibit a high degree of surface uniformity and have various geometrical shapes so that they can be used for substrates of highly flexible and/or stretchable devices. Finally, we use both of the proposed methods to fabricate flexible, stretchable, and waterproof-packaged bifacial blue LED modules to illustrate their potential in emerging applications that would benefit from such versatile form factors.


Assuntos
Polímeros , Xilenos , Lasers
9.
Phytochem Anal ; 33(6): 886-894, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35644373

RESUMO

INTRODUCTION: Urtica dioica (nettle) is a plant species of the Urticaceae family that grows in various parts of the world and exerts antioxidant, antibacterial, antiulcer, antiviral, and anti-inflammatory effects. Their leaves, roots, and seeds are used in various fields such as food, medicine, and cosmetics. OBJECTIVES: Inverse gas chromatography (IGC) was used to evaluate the surface characteristics and separation ability of U. dioica leaves, roots, and seeds. Characterization of these biomasses was performed by Fourier transform infrared spectroscopy (FTIR) analyses. METHODOLOGY: The surface properties of the biomasses including dispersive surface energy, adsorption enthalpy, Gibbs free energy, and acidity-basicity constants were determined at infinite dilution using various organic solvents. These properties were compared with each other. Dispersive surface energies were calculated using the Dorris-Gray, Donnet-Park, and Schultz methods. The accuracy of these methods and their applicability were evaluated. In the last stage of this study, the separation of xylene isomers was investigated by using U. dioica biomasses as stationary phases. RESULTS: The surface functional groups were determined by FTIR analysis. As a result of the IGC studies, it was found that the adsorption of polar solvents on biomasses occurred exothermically and spontaneously. Besides, it was found that the surfaces of biomasses were basic. From the retention diagrams and selectivity coefficients, it was determined that xylene isomers were effectively separated. CONCLUSION: IGC is a promising, low-cost, easy-to-apply, and high-accuracy technique for the investigation of the surface properties of biomasses and their ability to separate isomers.


Assuntos
Urtica dioica , Urticaceae , Sementes , Solventes , Propriedades de Superfície , Xilenos
10.
Ying Yong Sheng Tai Xue Bao ; 33(6): 1679-1685, 2022 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-35729147

RESUMO

In order to examine the toxic effects of p-xylene on the hepatopancreas of Haliotis discus hannai, a subchronic toxicity test was carried out for 21 days by setting 4 concentrations (0.5, 1.0, 1.5, and 2.0 mg·L-1) and the control group. DNA damage in hepatopancreas cells of H. discus hannai was analyzed by comet assay. The CASP analysis software was used to analyze the damage indices, including tail rate, tail length, percentage of tail DNA, and olive moment. The results showed that DNA damage in hepatopancreas cells occured in all exposed groups, with different degrees of damage. The DNA damage of hepatopancreas cells was aggravated with the increase of exposure concentration. High concentration of p-xylene could induce apoptosis, showing a certain dose-damage effect. Short-term exposure to medium concentration of p-xylene could cause DNA damage in hepatopancreas cells of H. discus hannai, and the damage degree increased with the extension of exposure time, showing a certain time-damage effect. However, the damage indices of DNA decreased after prolonged exposure, which might be related to the DNA repair mechanism of the cell and the metabolic mechanisms of the detoxification system. In conclusion, p-xylene could induce oxidative damage in hepatopancreas cells of H. discus hannai, resulting in DNA fragmentation. Prolonged exposure to high concentration of p-xylene could lead to apoptosis.


Assuntos
Gastrópodes , Hepatopâncreas , Animais , DNA/metabolismo , Dano ao DNA , Gastrópodes/genética , Gastrópodes/metabolismo , Xilenos
11.
Sci Total Environ ; 838(Pt 3): 156344, 2022 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-35654203

RESUMO

Atmospheric volatile organic compounds (VOCs) in Seoul, the capital of South Korea, have attracted increased attention owing to their emission, secondary formation, and human health risk. In this study, we collected 24 hourly samples once a month at an urban site in Seoul for a year (a total of 288 samples) using a sequential tube sampler. Analysis results revealed that toluene (9.08 ± 8.99 µg/m3) exhibited the highest annual mean concentration, followed by ethyl acetate (5.55 ± 9.09 µg/m3), m,p-xylenes (2.79 ± 4.57 µg/m3), benzene (2.37 ± 1.55 µg/m3), ethylbenzene (1.81 ± 2.27 µg/m3), and o-xylene (0.91 ± 1.47 µg/m3), indicating that these compounds accounted for 77.8-85.6% of the seasonal mean concentrations of the total (Σ59) VOCs. The concentrations of the Σ59 VOCs were statistically higher in spring and winter than in summer and fall because of meteorological conditions, and the concentrations of individual VOCs were higher during the daytime than nighttime owing to higher human activities during the daytime. The conditional bivariate probability function and concentration weighted trajectory analysis results suggested that domestic effects (e.g., vehicular exhaust and solvents) exhibited a dominant effect on the presence of VOCs in Seoul, as well as long-range atmospheric transport of VOCs. Further, the most important secondary organic aerosol formation potential (SOAFP) compounds included benzene, toluene, ethylbenzene, and m,p,o-xylenes, and the total SOAFP of nine VOCs accounted for 5-29% of the seasonal mean PM2.5 concentrations. The cancer and non-cancer risks of the selected VOCs were below the tolerable (1 × 10-4) and acceptable (Hazard quotient: HQ < 1) levels, respectively. Overall, this study highlighted the feasibility of the sequential sampling of VOCs and hybrid receptor modeling to further understand the source-receptor relationship of VOCs.


Assuntos
Poluentes Atmosféricos , Compostos Orgânicos Voláteis , Aerossóis/análise , Poluentes Atmosféricos/análise , Benzeno/análise , China , Monitoramento Ambiental , Humanos , Seul , Tolueno/análise , Compostos Orgânicos Voláteis/análise , Xilenos/análise
12.
Sci Total Environ ; 838(Pt 4): 156390, 2022 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-35654176

RESUMO

Epidemiological studies have shown that long-term exposure to toxic volatile organic compounds, such as benzene, toluene, ethylbenzene, and xylene (BTEX), is associated with preterm births (PTB). However, global PTB attributable to long-term BTEX exposure has not been reported in the literature yet. In this study, we employed a global chemical transport model, GEOS-Chem (Goddard Earth Observing System coupled with chemistry), in conjunction with an epidemiological model, to quantify the global country-specific PTB associated with long-term BTEX exposure at the horizontal resolution of 1 km × 1 km for the year 2015. Model simulated surface annual mean BTEX concentrations in GEOS-Chem have been thoroughly evaluated against global in-situ observations, which demonstrated that model simulated BTEX concentrations fairly agreed with observations but tended to be underestimated in India. Our study found that the global annual total PTB attributable to BTEX was 2.01 million [95% confidence interval (95CI): 1.16-2.70 million] in 2015, with largest contributions from India (28.3%), followed by China (27.5%), Pakistan (6.2%), Indonesia (4.2%), Bangladesh (3.7%) and United States (2.3%). The global annual total PTB due to BTEX exposure accounted for 19.6% (95CI: 11.3-26.4%) relative to the global annual total all-cause PTB (10.24 million) in 2015. Our study has significant implications on air pollution mitigation policy associated with country-specific anthropogenic BTEX emission reductions to achieve the benefit of human health.


Assuntos
Poluentes Atmosféricos , Nascimento Prematuro , Poluentes Atmosféricos/análise , Benzeno/análise , Derivados de Benzeno/análise , Monitoramento Ambiental , Feminino , Humanos , Recém-Nascido , Nascimento Prematuro/induzido quimicamente , Nascimento Prematuro/epidemiologia , Tolueno/análise , Xilenos/análise
13.
Chemosphere ; 303(Pt 2): 135184, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35654237

RESUMO

The LaMnO3 catalysts doped with transition metal (Zr, Co, Fe) were prepared. The influencing factors (the catalyst type, the initial concentration, the gas flow, and oxygen content) on the degradation efficiency by the non-thermal plasma synergistic the LaMnO3 catalysts doped with Zr, Co and Fe were investigated systematically. The degradation mechanism of the meta-xylene degradation by the non-thermal plasma synergistic Mn-Zr-La/Al2O3 was researched. The results showed that the Mn-Zr-La/Al2O3 catalyst in the four catalysts had the best degradation efficiency for meta-xylene, which was 99.6% at the applied voltage of 44 kV. The by-product ozone concentration was low, and the NOx was not detected. Meanwhile, the XPS characterization analysis study revealed that the proportion of Mn4+ element and the proportion of Osur in the Zr-doped Mn-Zr-La/Al2O3 catalyst were both the highest. The degradation efficiency decreased with the increasing of the initial concentration and gas flow, but first increased and then decreased with the increasing of oxygen content. The fresh and used Mn-Zr-La/Al2O3 were characterized by SEM, XRD, BET, FT-IR, O2-TPD, and the tail gas was treated by GC-MS. Then synergistic degradation mechanism for the meta-xylene by the non-thermal plasma over the Mn-Zr-La/Al2O3 catalyst are proposed.


Assuntos
Ozônio , Catálise , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Xilenos
14.
ACS Sens ; 7(6): 1666-1675, 2022 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-35674347

RESUMO

Detection and recognition of volatile organic compounds (VOCs) are crucial in many applications. While pure VOCs can be detected by various sensors, the discrimination of VOCs in mixtures, especially of similar molecules, is hindered by cross-sensitivities. Isomer identification in mixtures is even harder. Metal-organic frameworks (MOFs) with their well-defined, nanoporous, and versatile structures have the potential to improve the VOC sensing performance by tailoring the adsorption affinities. Here, we detect and identify ternary xylene isomer mixtures by using an array of six gravimetric, quartz crystal microbalance (QCM)-based sensors coated with selected MOF films with different isomer affinities. We use classical molecular simulations to provide insights into the sensing mechanism. In addition to the attractive interaction between the analytes and the MOF film, the isomer discrimination is caused by the rigid crystalline framework sterically controlling the access of the isomers to different adsorption sites in the MOFs. The sensor array has a very low limit of detection of 1 ppm for each pure isomer and allows the isomer discrimination in mixtures. At 100 ppm, 16 different ternary o-p-m-xylene mixtures were identified with high classification accuracy (96.5%). This work shows the unprecedented performance of MOF-sensor arrays, also referred to as MOF-electronic nose (MOF-e-nose), for sensing VOC mixtures. Based on the study, guidelines for detecting and discriminating complex mixtures of volatile molecules are also provided.


Assuntos
Estruturas Metalorgânicas , Compostos Orgânicos Voláteis , Nariz Eletrônico , Estruturas Metalorgânicas/química , Técnicas de Microbalança de Cristal de Quartzo , Compostos Orgânicos Voláteis/química , Xilenos
15.
Chemosphere ; 304: 135328, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-35700810

RESUMO

The gas-liquid mass transfer rate of hydrophobic volatile organic compounds (VOCs) is the limiting step in a biological treatment system. The present study aimed to utilize self-producing biosurfactants to enhance the bioavailability of hydrophobic gaseous VOCs. Two novel gram-negative rod-shaped bacteria, Enterobacter cloacae strain HN01 and Klebsiella pneumoniae strain HN02 were successfully isolated from sewage sludge by using blood agar and methylene blue agar plates. The two strains can use para-xylene (PX), a hydrophobic VOC model, as the only carbon source for biosurfactant production. Both strains can produce glycolipid biosurfactants, as confirmed by the emulsification index, Nuclear magnetic resonance, and Fourier transform infrared spectroscopy. Results indicated that PX can be completely decomposed at an initial concentration of 15.50 mg L-1, pH value of 7.0, and temperature of 30 °C within 36 h. The Yano model is suitable for the prediction of the growth kinetics of strains over the entire PX concentration range. Gas chromatography/mass spectrometry analysis indicated that PX was converted into four and four intermediates in the presence of the strains HN01 and HN02, respectively, and the possible mechanisms were proposed. The results can be used in purifying industrial hydrophobic gaseous VOCs and improving the bioavailability of VOCs with self-produced biosurfactants.


Assuntos
Enterobacter cloacae , Compostos Orgânicos Voláteis , Ágar , Biodegradação Ambiental , Disponibilidade Biológica , Enterobacter cloacae/metabolismo , Gases , Klebsiella pneumoniae/metabolismo , Esgotos , Solubilidade , Tensoativos/química , Xilenos
16.
J Hazard Mater ; 437: 129343, 2022 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-35716574

RESUMO

Benzene, toluene, ethylbenzene, and xylene (BTEX) can be released during extensive activities associated with the disposal of electronic waste (e-waste), which might pose deleterious health effects on workers. In this study, pollution profiles of BTEX in air and their urinary excretive profiles in occupational workers were investigated in a typical e-waste recycling industrial park. The results showed that the workers in the park were generally exposed to high levels of BTEX. The median levels of urinary metabolites were approximately 6-orders of magnitude higher than those of unmetabolized BTEX, indicating that pollutants efficiently metabolize at those occupational levels. The analytes presented differential profiles in external and internal exposure. Among the metabolites, significant correlation (p < 0.05) was observed between N-acetyl-S-benzyl-L-cysteine (S-BMA) concentration and atmospheric individual BTEX derived from the e-waste recycling area, suggesting that S-BMA is a potential marker for BTEX exposure to e-waste occupational workers. Notably, 95.2 % of all the workers showed a cumulative carcinogenic risk induced by BTEX exposure via inhalation, with 99.9 % of the carcinogenic risk distribution based on concentration of benzene metabolite (N-acetyl-S-(phenyl)-L-cysteine) exceeding 1.0E-6. This study holds potential in providing valuable inferences for the development of remediation strategies focusing on BTEX exposure reduction to protect workers' health at e-waste recycling industries.


Assuntos
Poluentes Atmosféricos , Resíduo Eletrônico , Exposição Ocupacional , Poluentes Atmosféricos/análise , Benzeno/metabolismo , Derivados de Benzeno/análise , Derivados de Benzeno/toxicidade , Monitoramento Ambiental/métodos , Humanos , Exposição Ocupacional/análise , Tolueno/análise , Tolueno/toxicidade , Xilenos/análise
17.
Appl Environ Microbiol ; 88(13): e0035822, 2022 07 12.
Artigo em Inglês | MEDLINE | ID: mdl-35736230

RESUMO

Toluene o-xylene monooxygenase (ToMO) was found to oxidize chlorobenzene to form 2-chlorophenol (2-CP, 4%), 3-CP (12%), and 4-CP (84%) with a total product formation rate of 1.2 ± 0.17 nmol/min/mg protein. It was also discovered that ToMO forms 4-chlorocatechol (4-CC) from 3-CP and 4-CP with initial rates of 0.54 ± 0.10 and 0.40 ± 0.04 nmol/min/mg protein, respectively, and chlorohydroquinone (CHQ, 13%), 4-chlororesorcinol (4-CR, 3%), and 3-CC (84%) from 2-CP with an initial product formation rate of 1.1 ± 0.32 nmol/min/mg protein. To increase the oxidation rate and alter the oxidation regiospecificity of chloroaromatics, as well as to study the roles of active site residues L192 and A107 of the alpha hydroxylase fragment of ToMO (TouA), we used the saturation mutagenesis approach of protein engineering. Thirteen TouA variants were isolated, among which some of the best substitutions uncovered here have never been studied before. Specifically, TouA variant L192V was identified which had 1.8-, 1.4-, 2.4-, and 4.8-fold faster hydroxylation activity toward chlorobenzene, 2-CP, 3-CP, and 4-CP, respectively, compared to the native ToMO. The L192V variant also had the regiospecificity of chlorobenzene changed from 4% to 13% 2-CP and produced the novel product 3-CC (4%) from 3-CP. Most of the isolated variants were identified to change the regiospecificity of oxidation. For example, compared to the native ToMO, variants A107T, A107N, and A107M produced 6.3-, 7.0-, and 7.3-fold more 4-CR from 2-CP, respectively, and variants A107G and A107G/L192V produced 3-CC (33 and 39%, respectively) from 3-CP whereas native ToMO did not. IMPORTANCE Chlorobenzene is a commonly used toxic solvent and listed as a priority environmental pollutant by the US Environmental Protection Agency. Here, we report that Escherichia coli TG1 cells expressing toluene o-xylene monooxygenase (ToMO) can successfully oxidize chlorobenzene to form dihydroxy chloroaromatics, which are valuable industrial compounds. ToMO performs this at room temperature in water using only molecular oxygen and a cofactor supplied by the cells. Using protein engineering techniques, we also isolated ToMO variants with enhanced oxidation activity as well as fine-tuned regiospecificities which make direct microbial oxygenations even more attractive. The significance of this work lies in the ability to degrade environmental pollutants while at the same time producing valuable chemicals using environmentally benign biological methods rather than expensive, complex chemical processes.


Assuntos
Oxigenases de Função Mista , Oxigenases , Catecóis , Clorobenzenos , Escherichia coli/genética , Escherichia coli/metabolismo , Oxigenases de Função Mista/metabolismo , Oxigenases/metabolismo , Tolueno/metabolismo , Xilenos
18.
Ecotoxicol Environ Saf ; 241: 113717, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35679732

RESUMO

The aim of this study was to compare the concentrations of the benzene, toluene, ethylbenzene, and xylene (BTEX) compounds in the urine of smokers and the control group considering the role of age, weight, job, history of waterpipe and cigarette smoking, and driving time. The chemicals in the urine of 99 smokers and 31 nonsmokers were extracted by liquid-liquid extraction method and their concentrations were measured by liquid injection GC/MS. The mean concentration of benzene, toluene, ethylbenzene, m-xylene, o-xylene, p-xylene, and total BTEX in waterpipe smokers were found to be 471.40, 670.90, 127.91, 167.64, 90.62, 46.04, and 1574.50 ng/g. creatinine, respectively. For the waterpipe&cigarette smokers, the concentration of the compounds were 708.00, 959.00, 146.40, 192.50, 93.30, 53.07, and 2152.00 ng/g.creatinine, respectively. For nonsmokers the concentrations of these compounds were 88.12, 140.40, 36.68, 57.29, 31.53, 26.21, and 380.30 ng/g.creatinine, respectively. Driving time, waterpipe smoking and cigarette smoking were positively associated with BTEX concentration (p < 0.05). Fruity tobacco showed higher concentrations of BTEX compared to the regular tobacco, and athlete persons had les urinary BTEX than the non-athletes. There was not significant correlation between the BTEX and age, height, weight, and BMI. High concentrations of BTEX compounds in the urine of waterpipe and cigarette smokers compared to nonsmokers indicate that waterpipe and cigarette can be an important source of exposure to these compounds and the known adverse effects of these compounds, especially carcinogenicity, threaten the health of smokers.


Assuntos
Benzeno , Fumar Cachimbo de Água , Derivados de Benzeno/urina , Creatinina , Humanos , não Fumantes , Fumantes , Tolueno/urina , Xilenos/urina
19.
J Chromatogr A ; 1673: 463083, 2022 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-35508097

RESUMO

The analysis of toxic volatile organic compounds (VOCs) in environmental air is important because toxic VOCs induce adverse effects on human health. Although gas chromatography- mass spectrometry (GC-MS) is the standard instrument for analysis of trace VOCs in air, this mode of analysis requires preconcentration and cryogenic processes. The preconcentration and subsequent thermal desorption of VOCs require special instruments and a long time of processing sample that significantly limit applications of GC-MS for monitoring indoor and outdoor VOC levels. Using a microfabricated preconcentrator for VOC analysis also has the challenge of a large sample volume for concentration. Using solid-phase microextraction (SPME) for VOC analysis by GC-MS often approaches the limit of detection of the GC-MS instrument for trace VOCs in air. This work reports a simple method to integrate microfabricated preconcentrators with commercial SPME fibers in a two-stage concentration processes to achieve rapid and reliable measurement of trace VOCs in air by GC-MS. We designed and fabricated a preconcentrator with micropillars in a microfluidic chamber to support sorbents and to increase the heat transfer rate to the sorbents for rapid thermal desorption. The effects of air flow rates through the preconcentrator on VOCs adsorption and thermal desorption were optimized for increasing analytical accuracy of VOCs measurements. The integration of a micropreconcentrator with SPME enabled measurements of sub-ppb levels of benzene, toluene, ethylbenzene, and xylene (BTEX), and trichloroethylene (TCE) in environmental air by GC-MS.


Assuntos
Microextração em Fase Sólida , Compostos Orgânicos Voláteis , Cromatografia Gasosa-Espectrometria de Massas/métodos , Humanos , Microextração em Fase Sólida/métodos , Tolueno/análise , Compostos Orgânicos Voláteis/análise , Xilenos/análise
20.
J Chromatogr A ; 1673: 463091, 2022 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-35525192

RESUMO

The separation of p-xylene (PX) and m-xylene (MX) isomers with near boiling points is a worldwide problem. The metal-organic framework material is an ideal stationary phase for chromatographic separation because of its high porosity, homogeneous pore diameter and good chemical stability. In this paper, a simulated moving bed (SMB) chromatography system with MIL-53(Fe) as the stationary phase and petroleum ether-dichloromethane as the mobile phase was designed to separate PX and MX at ambient temperature. Firstly, according to the elution curves of a single column, nonlinear competitive Langmuir adsorption isotherm equation was confirmed by equilibrium dispersive chromatography model. Then, the SMB separation zone was determined based on triangle theory, and the SMB operating conditions were optimized. Finally, the purity, recovery and productivity of PX reached 100.0%, 99.1% and 93.1 g/L/h, respectively; the purity, recovery and productivity of MX reached 96.4%, 100.0% and 23.5 g/L/h, respectively; the solvent consumption was 0.42 L/g.


Assuntos
Cromatografia , Xilenos , Adsorção , Cromatografia/métodos , Dietilamida do Ácido Lisérgico/análogos & derivados , Solventes/química
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