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1.
J Colloid Interface Sci ; 605: 513-527, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34340036

RESUMO

Hyper-crosslinked polymers (HCPs) have been produced by the Friedel-Crafts reaction using anthracene, benzene, carbazole or dibenzothiophene as precursors and dimethoxymethane as crosslinker, and the effect of graphene oxide (GO) addition has been studied. The resulting HCPs were highly microporous with BET areas (ABET) between 590 and 1120 m2g-1. The benzene-derived HCP (B1FeM2) and the corresponding composite with GO (B1FM2-GO) exhibited the highest ABET and were selected to study their hydrogen adsorption capacities in the pressure range of 0.1 - 14 MPa at 77 K. The maximum H2 excess uptake was 2.1 and 2.0 wt% for B1FeM2 and B1FeM2-GO, respectively, at 4 MPa and 77 K. The addition of GO reduced the specific surface area but increased the density of the resultant HCP-GO composites, which is beneficial for practical applications and proves that materials giving higher gravimetric storage capacities are not necessarily those that offer higher volumetric capacities. H2 adsorption-desorption cycles up to 14 MPa showed irreversible deformation of both HCP and HCP-GO materials, which calls into question their application for hydrogen adsorption at pressures above 4 MPa.


Assuntos
Hidrogênio , Polímeros , Adsorção , Benzeno
2.
Sci Total Environ ; 804: 149971, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34509831

RESUMO

BACKGROUND: Conducting a risk assessment can be challenging, especially when dealing with several reference indices, which could lead to conflicting conclusions between studies. The common approach is to use a reference index from a single source based on the risk assessor's preference. OBJECTIVES: To propose an approach for constructing a multi-reference index-based aggregated risk estimate using mathematical objectivity to reflect all of the available information. METHODS: The aggregated risk estimate based on multiple reference indices (AREMRI) results from the weighted linear combination of risk distributions that were obtained with each reference index available. The weights were calculated using the degree of agreement among the reference index-based risk distributions. The approach is illustrated through three practical cases of benzene inhalation cancer risk assessment using inhalation unit risks (IURs) from six different regulatory agencies. RESULTS: The degrees of agreement between the reference index-based risk distribution, obtained with the six IURs, ranged from 0.7 to 92%. The highest weights were attributed to reference index-based risk distributions that had the highest degree of agreement with the maximum number of other reference index-based risk distributions. Regardless of the practical case considered, the AREMRI risk distribution resulted in the third highest risk compared to the six single risk distributions. CONCLUSION: Our approach can be useful in the presence of several reference indices by providing useful insights, consistency and direct comparisons between studies to support better-informed risk assessment and management decisions. This approach can shed some light on some of the uncertainties associated with the toxicological reference values in a risk assessment associated with the toxicological reference values. If the uncertainty is large, more detailed evaluation of the toxicological reference values would be needed.


Assuntos
Benzeno , Probabilidade , Medição de Risco , Incerteza
3.
Chemosphere ; 286(Pt 1): 131590, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34293566

RESUMO

OBJECTIVE: We aimed to evaluate the relationship between blood volatile organic aromatic compounds (VOACs) across adulthood and mortality. METHODS: A total of 16,968 participants from the National health and Nutrition Examination Surveys (NHANES 1988-1994 and 1999-2014) were included in the present study. Cox proportional hazards models were used to explore the associations between VOACs and total or cause-specific mortality. RESULTS: A total of 1,282 deaths occurred among 16,968 participants with a median follow-up of 8.06 years. We observed significant positive dose-response relationship between VOACs including benzene, ethylbenzene, o-xylene, m-/p-xylene and BEX (the sum of benzene, ethylbenzene, m-/p-and o-xylene concentrations) and total mortality, the multiple adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were 1.24 (1.13, 1.36), 1.15 (1.04, 1.27), 1.10 (1.00, 1.23), 1.09 (1.01, 1.19) and 1.21 (1.08, 1.35), respectively. In addition, all VOACs significantly elevated risk of the mortality from cancer, and benzene was associated with risk of the mortality from heart disease and the HRs and 95% CIs was 1.39 (1.09-1.77). For non-smokers, benzene, ethylbenzene and BEX were associated with elevated risk of total mortality and the mortality from cancer, and benzene was associated with risk of the mortality from heart disease. CONCLUSIONS: Blood VOACs are associated with increased risks of total and specific-cause mortality, which are also observed among non-smokers.


Assuntos
Compostos Orgânicos Voláteis , Adulto , Benzeno/toxicidade , Causas de Morte , Humanos , Inquéritos Nutricionais , Estudos Prospectivos
4.
Artigo em Inglês | MEDLINE | ID: mdl-34770026

RESUMO

Indoor air quality (IAQ) can greatly affect health in people spending much time indoors. However, the influence of IAQ on personal exposure to chemical compounds in Japan remains poorly investigated. Hence, this study aimed to clarify this influence thoroughly within one apartment. We surveyed the concentrations of 61 chemical compounds in the air in nine different spaces within an apartment unit, as well as the personal exposure of two residents in Japan. Using three kinds of diffusive samplers, this study was conducted continuously for 7 days in summer and winter. Health risks were evaluated by calculating the margin of exposure (MOE) using the measured concentrations. Some chemical concentrations showed large spatial variations and the personal exposure concentrations of these compounds also differed among residents. According to the calculated MOE, the chemicals with the highest health risk were acrolein, p-dichlorobenzene, and acetaldehyde in summer and acrolein, nitrogen dioxide, formic acid, p-dichlorobenzene, and benzene in winter. The IAQ of the house could be divided in two, and the IAQ in the space where residents spent much time (i.e., bedroom) highly affected each of the residents' exposure. Investigating chemical concentrations in multiple spaces (including bedroom and living room) is necessary to understand the effect of IAQ on personal exposure.


Assuntos
Poluentes Atmosféricos , Poluição do Ar em Ambientes Fechados , Poluentes Atmosféricos/análise , Poluição do Ar em Ambientes Fechados/análise , Benzeno , Monitoramento Ambiental , Humanos , Dióxido de Nitrogênio/análise , Estações do Ano
5.
Huan Jing Ke Xue ; 42(11): 5210-5219, 2021 Nov 08.
Artigo em Chinês | MEDLINE | ID: mdl-34708960

RESUMO

Real-time BTEX(including benzene, toluene, ethylbenzene, m-, p-, and o-xylenes) were measured continuously in Tianjin urban site in July 2019 and January 2020 using a Syntech Spectras GC955 analyzer. The BTEX concentration levels, composition, and evolutionary mechanisms during typical pollution episodes were investigated. The potential sources of BTEX were analyzed qualitatively using the diagnostic ratios method. Finally, the BTEX health risk was evaluated by using the human exposure analysis and evaluation method according to US EPA. The averaged total mixing ratio of BTEX were 1.32×10-9 and 4.83×10-9 during ozone pollution and haze episodes, respectively. Benzene was the most abundant species, followed by toluene. The mixing ratio of BTEX was largely affected by short southwestern distance transportation in January, while local emissions in July. In addition, the BTEX mixing ratio depended on the influence of temperature and relative humidity(RH) in July, while the concentration was more sensitive to changes in RH when the temperature was low in January. Diagnostic ratios and source implications suggested that the BTEX was affected mainly by biomass/biofuel/coal burning during haze episodes. The traffic related emissions also had an impact except for the influence of biomass/biofuel/coal burning in July. The averaged hazard quotient(HQ) values were 0.072 and 0.29 during ozone pollution and haze episodes, respectively, which were in the upper safety range limit recommended by the US EPA. The carcinogenic risk posed by benzene in both cleaning and pollution processes was higher than the safety threshold set by the US EPA, which should be monitored carefully.


Assuntos
Poluentes Atmosféricos , Poluentes Atmosféricos/análise , Poluentes Atmosféricos/toxicidade , Benzeno/análise , Benzeno/toxicidade , Derivados de Benzeno/análise , Derivados de Benzeno/toxicidade , Monitoramento Ambiental , Humanos , Medição de Risco , Tolueno/análise , Tolueno/toxicidade , Xilenos
6.
Artigo em Inglês | MEDLINE | ID: mdl-34639318

RESUMO

This cross-sectional study examined the risk factors affecting adverse health effects from benzene exposure among gasoline station workers in Khon Kean province, Thailand. An interview questionnaire of adverse symptoms relating to benzene toxicity was administered to 151 workers. Area samplings for benzene concentration and spot urine for tt-muconic acid (tt-MA), a biomarker of benzene exposure, were collected. The factors associated with adverse symptoms were analysed by using multiple logistic regression. It was found that these symptoms mostly affected fuelling workers (77.5%), and the detected air benzene reached an action level or higher than 50% of NIOSH REL (>50 ppb). The top five adverse symptoms, i.e., fatigue, headache, dizziness, nasal congestion, and runny nose, were reported among workers exposed to benzene. More specific symptoms of benzene toxicity were chest pain, bleeding/epistaxis, and anaemia. The detected tt-MA of workers was 506.7 ug/g Cr (IQR), which was a value above the BEI and higher than that of asymptomatic workers. Risk factors significantly associated with adverse symptoms, included having no safety training experience (ORadj = 5.22; 95% CI: 2.16-12.58) and eating during work hours (ORadj = 16.08; 95% CI: 1.96-131.74). This study urges the tightening of health and safety standards at gasoline stations to include training and eating restrictions while working in hazardous areas.


Assuntos
Poluentes Ocupacionais do Ar , Exposição Ocupacional , Poluentes Ocupacionais do Ar/análise , Benzeno/análise , Benzeno/toxicidade , Estudos Transversais , Gasolina , Humanos , National Institute for Occupational Safety and Health, U.S. , Exposição Ocupacional/efeitos adversos , Exposição Ocupacional/análise , Estados Unidos
7.
J Environ Sci (China) ; 109: 26-35, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34607671

RESUMO

Microcosmic experiments were performed under a simulated marine environment to investigate the natural attenuation of C9 aromatics using nine components (propylbenzene, isopropylbenzene, 2-ethyltoluene, 3-ethyltoluene, 4-ethyltoluene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, and indene). This research aims to assess the contribution of biodegradation and abiotic activity to total attenuation of C9 aromatics and ascertain the changes in the comprehensive toxicity of seawater in the natural environment. The process of natural attenuation indicates the agreement with pseudo-first-order kinetics for all nine components in microcosmic experiments. The half-lives of the nine main compounds in C9 aromatics ranged between 0.34 day and 0.44 day under optimal conditions. The experiments showed that the natural attenuation of nine aromatic hydrocarbons mainly occurred via abiotic processes. Seawater samples significantly inhibited the luminescence of P. phosphoreum (the luminescence inhibition ratio reached 100%) at the beginning of the experiment. In addition, the toxicity declined slowly and continued for 25 days. The attenuation kinetics and changes in toxicity could be applied to explore the natural attenuation of C9 aromatics in the marine environment.


Assuntos
Benzeno , Água do Mar , Biodegradação Ambiental , Cinética
8.
Analyst ; 146(20): 6239-6244, 2021 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-34528640

RESUMO

Hazardous volatile organic compounds (VOCs) can significantly impact human health and the environment. Hence, the detection of VOCs is of foremost importance. A quinoxaline-based fluorimetric probe (1) unveils a notable "turn-on" fluorescence response towards mesitylene in the presence of other VOCs and common interfering ions in aqueous media. The sensing phenomenon involves specific 1 : 1 stoichiometric binding of the probe with mesitylene with a ∼2.66 ppm detection limit. Furthermore, the probe experiences morphological transformations from a fibril-network to a stone-shaped hetero-structure upon treatment with mesitylene, indicating mesitylene induced self-assembly. The detection induced self-assembly of the probe was further corroborated by dynamic-light-scattering (DLS) and fluorescence microscopy study. Importantly, this proposed approach is applicable to detect mesitylene in natural water sources and in the vapor phase using portable, low-cost filter paper strips.


Assuntos
Compostos Orgânicos Voláteis , Benzeno , Humanos , Íons , Quinoxalinas , Espectrometria de Fluorescência
9.
Ecotoxicol Environ Saf ; 226: 112803, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34571417

RESUMO

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme deficiency. Our previous study revealed the level of G6PD changed in wild type (WT) mice after benzene exposure. In this study, the pentose phosphate pathway (PPP) in regulation of benzene-induced hematotoxicity was investigated and other potential pathways were discovered in a G6PD deficiency mouse model. WT and G6PD mutation (G6PDmut) mice were exposed to benzene (diluted in corn oil) at doses of 0 and 160 mg/kg by subcutaneous injection for 5 days/week, 4 weeks. Peripheral blood samples and bone marrow cells (BMCs) were obtained and measured. The levels of nicotinamide adenine dinucleotide phosphate (NADPH),reduced glutathione (GSH) and malondialdehyde (MDA) were detected and comet assay was analyzed for DNA damage in BMCs. Finally, RNA sequencing (RNA-seq) of BMCs was performed. The results showed that white blood cells decreased significantly in G6PDmut mice compared with WT mice after benzene treatment. The ratio of hematopoietic stem/progenitor cells significantly decreased in G6PDmut mice exposed to benzene. The reduction of NADPH and GSH revealed the effect on PPP with G6PD deficiency, which then caused the increase of MDA and DNA damage. Finally, RNA-seq results suggested potential genes including SHROOM4, CAMK2B and REN1 played potential roles of G6PD deficiency on benzene-induced hematotoxicity. Renin-angiotensin system and cAMP signaling pathway were potentially involved in the process. Our study provides a better understanding for the effects of G6PD deficiency on benzene-induced hematotoxicity.


Assuntos
Deficiência de Glucosefosfato Desidrogenase , Animais , Benzeno/toxicidade , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina , Glucosefosfato Desidrogenase/genética , Glucosefosfato Desidrogenase/metabolismo , Glutationa , Camundongos , Transdução de Sinais
10.
Talanta ; 235: 122722, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34517590

RESUMO

In-vehicle air pollution has become a major concern to public health in recent years. The traditional analytical methods for detection of volatile organic compounds (VOCs) pollutants in air are based on gas chromatography - mass spectrometry (GC-MS) or high-performance liquid chromatography (HPLC), including complicated pretreatment and separation procedures, which are not only time-consuming and labor-intensive, but also incapable of simultaneously measuring both aldehydes and benzenes. In this work, a new photoionization-induced NO+ chemical ionization time-of-flight mass spectrometry (PNCI-TOFMS) was developed for real-time and continuous measurement of aldehydes and benzenes in vehicles. High-intensity NO+ reactant ions could be generated by photoionization of NO reagent gas, and efficient chemical ionization between NO+ reactant ions and analyte molecules occurred to produce adduct ions M·NO+ at an elevated ion source pressure of 800 Pa. Consequently, the achieved LODs for aldehydes and benzenes were down to sub-ppbv within 60 s. The analytical capacity of this system was demonstrated by continuous and online monitoring of in-vehicle VOCs in a used car, exhibiting broad potential applications of the PNCI-TOFMS in air pollutants monitoring and in-vehicle air quality analysis.


Assuntos
Poluentes Atmosféricos , Compostos Orgânicos Voláteis , Poluentes Atmosféricos/análise , Aldeídos , Benzeno , Cromatografia Gasosa-Espectrometria de Massas , Compostos Orgânicos Voláteis/análise
11.
Anal Chim Acta ; 1179: 338835, 2021 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-34535252

RESUMO

Although electron impact ionization (EI) remains the standard ionization source for GC-MS, it presents extensive fragmentation as its main limitation. The potential of a novel plasma-based soft ionization source named controlled-atmosphere flexible microtube plasma (CA-FµTP) has been evaluated in this work for the determination of monoaromatic volatile BTEX group (namely benzene, toluene, ethylbenzene, and o-, m- and p-xylenes) in olive oil, based on headspace technique. The obtained results show an attractive advantage over EI due to no fragmentation was observed. A nitrosated ion [M + NO]+ is obtained as the most abundant species. Thus, the BTEX mass spectrum identification can be carried out without major effort. In general, the sensitivity for CA-FµTP was comparable to those obtained by EI, achieving LODs ranged from 0.6 to 1.0 µg kg-1. The potential usefulness of GC-CA-FµTP-MS for the detection of BTEX was demonstrated by analyzing olive oil samples and identifying traces of these compounds in one sample. Therefore, the proposed plasma-based soft ionization is suitable for BTEX analysis in fatty complex matrixes as olive oil.


Assuntos
Derivados de Benzeno , Xilenos , Atmosfera , Benzeno/análise , Derivados de Benzeno/análise , Cromatografia Gasosa-Espectrometria de Massas , Espectrometria de Massas , Azeite de Oliva , Tolueno/análise , Xilenos/análise
12.
J Hazard Mater ; 416: 126208, 2021 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-34492969

RESUMO

Aromatic hydrocarbon is a representative type of VOCs, which causes adverse effects to human health. The degradation stability of aromatic hydrocarbon is of vital importance to commercializing a photocatalyst for its practical application. The most commonly used titanium dioxide photocatalyst (P25) was deactivated rapidly in the photocatalytic VOCs degradation process. In this work, the indium hydroxide (In(OH)3) photocatalyst was developed, which exhibited not only higher efficient activity but also ultra-stable stability for degradation of benzene, toluene and their mixtures. The origin of the activity difference between two catalysts was investigated by combined experimental and theoretical ways. Based on in situ DRIFTS and GC-MS, it was revealed that benzoic acid and carbonaceous byproducts were specifically formed and accumulated on P25, which were responsible for deactivation of photocatalyst. In contrast, as revealed by both DFT calculations and experimental results, the reaction pathway with byproducts blocking the active sites can be thermodynamically avoided on In(OH)3. This rendered high durability to In(OH)3 photocatalyst in degradations of aromatic pollutants. The elucidation of deactivation-resistant effect and reaction mechanism as an ideal photocatalyst for practical usage were provided.


Assuntos
Benzeno , Tolueno , Catálise , Humanos , Hidróxidos , Fotólise , Titânio
13.
J Org Chem ; 86(17): 11545-11556, 2021 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-34479410

RESUMO

α,ß-Unsaturated carbonyl compounds are significant moieties in many biological molecules and have attracted considerable attention in organic synthetic chemistry. A Pd-catalyzed cascade cyclization for the synthesis of (E)-α,ß-unsaturated carbonyl compounds with the sequential formation of C-C bonds was developed. This method offers high efficiency, good functional group tolerance, and moderate to excellent yields and generally displays high stereoselectivity.


Assuntos
Benzeno , Paládio , Catálise , Ciclização , Estereoisomerismo
14.
Chemosphere ; 282: 131110, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34470162

RESUMO

Fibrous activated carbon has attracted emerging research interests due to its remarkable adsorption performance for volatile organic compounds (VOCs). Though this adsorption behavior for VOCs is closely related to the pore structure on the surface of activated carbon fiber (ACF), few researchers paid attentions to the influence of textural properties of this adsorption process. Especially, cotton-based activated carbon fiber (CACF) for adsorbing benzene pollutant is rarely reported. Herein, in order to develop a high-performance adsorbent for the removal of VOCs pollutants, this work studied the influence of textural properties of CACF on the adsorption of benzene. The results showed that the increase of carbonization temperature would lead to the reduction of mesopores but the increase of micropores for CACF; the embedment of phosphoric acid and its derivatives into the carbon layers contributed to the formation of pore structure for CACF; furthermore, specific surface area of CACF can also be enlarged by increasing the concentration of phosphoric acid. More importantly, it was found that the adsorption capacity of CACF for benzene was strongly dependent on the specific surface area and volume of micropores within CACF because micropores can provide more favorable binding sites. This adsorption process preferred to occur on the wall of micropores, then the accumulated benzene would slowly fill the pores. Interestingly, the decrease of pore size of micropores can unexpectedly improve the affinity of CACF to benzene on the contrary. This work provides a new strategy to develop porous structured ACF materials for the high-performance adsorption of VOCs.


Assuntos
Benzeno , Carvão Vegetal , Adsorção , Fibra de Carbono , Porosidade
15.
Nature ; 597(7874): 33-34, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34471278
16.
J Hazard Mater ; 418: 126405, 2021 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-34351297

RESUMO

Hydrogels are often claimed as optimal adsorbents for water treatment; however, their efficiency towards the removal of hydrophobic pollutants is still limited. As an alternative, hydrogels prepared from polymers functionalized with siliceous materials can overcome this issue. Here, a composite hydrogel (denoted as GEL-SBA15) was prepared using alginate grafted with mesoporous silica (SBA15) and poly(vinyl alcohol) for benzene and toluene adsorption from aqueous solutions. Adsorption studies demonstrated that a low dosage of GEL-SBA15 (10 mg) has a high adsorption capacity for benzene (1482.8 mg/g) and toluene (596.6 mg/g) under mild experimental conditions (pH 7.0, at 25 °C). Besides, the adsorption capacities of GEL-SBA15 for both pollutants were enhanced compared to the conventional hydrogel. Kinetic analysis showed that the adsorption of benzene and toluene follows a pseudo-second order model, while the experimental adsorption data were well-fitted by the Freundlich isotherm. According to this isotherm, the adsorption occurs via a collaborative process, and weak physical forces (π-π interactions, van der Waals and hydrophobic) are involved. Hence, the post-utilized GEL-SBA15 can be recycled and reused up to 6 times without losing adsorption performance. Although hydrogels are not common adsorbents for aromatic hydrocarbons, the results reported here rank GEL-SBA15 as a promising adsorbent for the removal of these pollutants from water.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Adsorção , Alginatos , Benzeno , Hidrogéis , Cinética , Dióxido de Silício , Tolueno , Poluentes Químicos da Água/análise
17.
Sci Total Environ ; 800: 149484, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34392216

RESUMO

Organic pollutants are common in the environment, very difficult to remove, and pose a serious threat to human health. Probabilistic risk assessment advances conservative single-point estimation and brings a new perspective to risk assessment. From 2009 to 2019, we monitored the distribution of major pollutants in an industrial park in Northeastern China. The result showed the maximum concentration of benzene reached 73,680 µg/L in 2009, benzo[a]pyrene reached 36.80 ng/L in 2016. These concentrations are significantly above the levels set by Chinese regulatory agencies. The single-factor index increases year by year, and pollutants gradually spread from the pollution leakage source to surrounding areas. A new method was used to quantify the human health risk from groundwater organic pollution accurately, based on the triangular fuzzy numbers coupled with the Monte Carlo simulation. The Monte Carlo simulation was used to simulate the triangular fuzzy numbers. This simplified the operation between the triangular fuzzy numbers and their function successfully and obtained the risk as a set of values. The results indicated that non-carcinogenic risk was negligible in all age groups (children, adolescents, and adults). Conversely, when it comes to carcinogenic risks, adults were about 50-270 times the tolerable level of risk due to long exposure years and wide skin contact areas. Oral ingestion played an essential role in total exposure (>90%) compared to dermal contact. Control of exposure duration and intake should be prioritized when making decisions to reduce risk uncertainty. Monte Carlo simulation-triangular fuzzy numbers can effectively reduce the risk of uncertainty and reflect the complex conditions of the groundwater environment for small amounts of data or inaccurate data.


Assuntos
Água Subterrânea , Poluentes Químicos da Água , Adolescente , Adulto , Benzeno , Criança , China , Monitoramento Ambiental , Humanos , Medição de Risco , Poluentes Químicos da Água/análise
18.
Chemistry ; 27(59): 14765-14777, 2021 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-34350662

RESUMO

The serine 244 to aspartate (S244D) variant of the cytochrome P450 enzyme CYP199A4 was used to expand its substrate range beyond benzoic acids. Substrates, in which the carboxylate group of the benzoic acid moiety is replaced were oxidised with high activity by the S244D mutant (product formation rates >60 nmol.(nmol-CYP)-1 .min-1 ) and with total turnover numbers of up to 20,000. Ethyl α-hydroxylation was more rapid than methyl oxidation, styrene epoxidation and S-oxidation. The S244D mutant catalysed the ethyl hydroxylation, epoxidation and sulfoxidation reactions with an excess of one stereoisomer (in some instances up to >98 %). The crystal structure of 4-methoxybenzoic acid-bound CYP199A4 S244D showed that the active site architecture and the substrate orientation were similar to that of the WT enzyme. Overall, this work demonstrates that CYP199A4 can catalyse the stereoselective hydroxylation, epoxidation or sulfoxidation of substituted benzene substrates under mild conditions resulting in more sustainable transformations using this heme monooxygenase enzyme.


Assuntos
Benzeno , Sistema Enzimático do Citocromo P-450 , Sistema Enzimático do Citocromo P-450/genética , Sistema Enzimático do Citocromo P-450/metabolismo , Hidroxilação , Oxirredução , Especificidade por Substrato
19.
J Phys Chem B ; 125(31): 8855-8861, 2021 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-34339214

RESUMO

The pressure dependence of the solubility of hydrophobic solutes in aqueous solutions is equivalent to volume changes upon hydrophobic hydration. This phenomenon has been attributed to the packing effects induced by the van der Waals volume difference between the solute and water. However, the volume changes may also be related to the chemical properties of the solute. In this study, we investigated hydrophobic hydration using a series of halogenated benzenes. Solution density measurements revealed negative volume changes for benzene, fluorobenzene, and chlorobenzene, whereas those for bromobenzene and iodobenzene were positive. Subsequent volumetric analyses demonstrated that the relationship between the excess particle number for hydration water and the van der Waals volume for bromobenzene and iodobenzene significantly deviated from the universal line for hydrophobic solutes. This behavior suggests that the volume changes are due to factors other than the packing effect with bromo and iodine functional groups acting as modulators of the hydration structure, resulting in enhanced water depletion.


Assuntos
Benzeno , Água , Halogenação , Solubilidade , Soluções
20.
Environ Pollut ; 289: 117893, 2021 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-34385133

RESUMO

Health risks of typical benzene series and halocarbons (BSHs) in a densely populated area near a large-scale chemical industrial park were investigated. Ambient and indoor air and tap water samples were collected in summer and winter; and the concentration characteristics, sources, and exposure risks of typical BSH species, including five benzene series (benzene, toluene, ethylbenzene, o-xylene, m,p-xylene) and five halocarbons (dichloromethane, trichloromethane, trichloroethylene, tetrachloromethane, and tetrachloroethylene), were analysed. The total mean concentrations of BSHs were 53.32 µg m-3, 36.29 µg m-3, and 26.88 µg L-1 in indoor air, ambient air, and tap water, respectively. Halocarbons dominated the total BSHs with concentrations relatively higher than those in many other industrial areas. Industrial solvent use, industrial processes, and vehicle exhaust emissions were the principal sources of BSHs in ambient air. The use of household products (e.g., detergents and pesticides) was the principal source of indoor BSHs. Inhalation is the primary human exposure route. Ingestion of drinking water was also an important exposure route but had less impact than inhalation. Lifetime non-cancer risks of individual and cumulative BSHs were below the threshold (HQ = 1), indicating no significant lifetime non-cancer risks in the study area. However, tetrachloromethane, benzene, trichloromethane, ethylbenzene, and trichloroethylene showed potential lifetime cancer risk. The cumulative lifetime cancer risks exceeded the tolerable benchmark (1 × 10-4), indicating a lifetime cancer risk of BSHs to residents near the chemical industry park. This study provides valuable information for the management of public health in chemical industrial parks.


Assuntos
Poluentes Atmosféricos , Benzeno , Poluentes Atmosféricos/análise , Benzeno/análise , Derivados de Benzeno/análise , Monitoramento Ambiental , Humanos , Tolueno/análise , Emissões de Veículos/análise
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