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1.
Environ Sci Technol ; 53(11): 6192-6202, 2019 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-31083926

RESUMO

Organosulfates (OSs) have been observed as substantial constituents of atmospheric organic aerosol (OA) in a wide range of environments; however, the chemical composition, sources, and formation mechanism of OSs are still not well understood. In this study, we first created an "OS precursor map" based on the elemental composition of previous OS chamber experiments. Then, according to this "OS precursor map", we estimated the possible sources and molecular structures of OSs in atmospheric PM2.5 (particles with aerodynamic diameter ≤ 2.5 µm) samples, which were collected in urban areas of Beijing (China) and Mainz (Germany) and analyzed by ultrahigh-performance liquid chromatography (UHPLC) coupled with an Orbitrap mass spectrometer. On the basis of the "OS precursor map", together with the polarity information provided by UHPLC, OSs in Mainz samples are suggested to be mainly derived from isoprene/glyoxal or other unknown small polar organic compounds, while OSs in Beijing samples were generated from both isoprene/glyoxal and anthropogenic sources (e.g., long-chain alkanes and aromatics). The nitrooxy-OSs in the clean aerosol samples were mainly derived from monoterpenes, while much fewer monoterpene-derived nitrooxy-OSs were obtained in the polluted aerosol samples, showing that nitrooxy-OS formation is affected by different precursors in clean and polluted air conditions.


Assuntos
Poluentes Atmosféricos , Sulfatos , Aerossóis , Pequim , China , Monitoramento Ambiental , Alemanha , Espectrometria de Massas
2.
Food Funct ; 9(11): 5950-5964, 2018 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-30379176

RESUMO

PURPOSE: Inflammatory processes are involved in many diseases. The bark of Cinnamomum verum and its extracts are well known for anti-inflammatory effects, but the underlying active compounds and chemical mechanisms are not yet fully identified. The objective of this study was to elucidate how cinnamon extract, specifically active compounds, and their combinations influence the signaling pathways of inflammation, especially through toll-like receptors TLR2 and TLR4. METHODS: Bioassay-guided fractionation was performed for standard ethanolic cinnamon extract using high performance liquid chromatography followed by compound identification in the determined active fractions by high-resolution mass spectrometry and gas chromatography-mass spectrometry. THP-1 monocytes were pre-incubated with cinnamon extract, cinnamon fractions or its compounds and stimulated with lipopolysaccharides (LPS), followed by determination of interleukin 8 (IL-8) secretion, and phosphorylation of protein kinase B (Akt), nuclear factor (NF)-κB inhibitor alpha (IκBα) and p38. Furthermore, testing was performed in stimulated HEK-TLR2 and HEK-TLR4 reporter cells for direct receptor agonistic effects. RESULTS: Among the identified compounds, trans-cinnamaldehyde and p-cymene significantly reduced the LPS-dependent IL-8 secretion in THP-1 monocytes. Synergistic anti-inflammatory effects were observed for combinations of trans-cinnamaldehyde with p-cymene, cinnamyl alcohol or cinnamic acid. Moreover, cinnamon extract as well as trans-cinnamaldehyde and p-cymene mitigated the phosphorylation of Akt and IκBα. CONCLUSIONS: Trans-cinnamaldehyde and p-cymene contribute to the strong anti-inflammatory effects of cinnamon extract. Furthermore, our experiments indicate that also synergistic effects among compounds that do not exhibit anti-inflammatory effects themselves might be present to positively influence the beneficial effects of cinnamon bark extract.


Assuntos
Anti-Inflamatórios/farmacologia , Cinnamomum zeylanicum/química , Extratos Vegetais/farmacologia , Transdução de Sinais , Receptor 2 Toll-Like/metabolismo , Receptor 4 Toll-Like/metabolismo , Acroleína/análogos & derivados , Acroleína/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Cimenos , Sinergismo Farmacológico , Humanos , Interleucina-8/genética , Interleucina-8/metabolismo , Lipopolissacarídeos/toxicidade , Monócitos/efeitos dos fármacos , Monócitos/metabolismo , Monoterpenos/farmacologia , Inibidor de NF-kappaB alfa/genética , Inibidor de NF-kappaB alfa/metabolismo , NF-kappa B/genética , NF-kappa B/metabolismo , Fosforilação , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Células THP-1 , Receptor 2 Toll-Like/genética , Receptor 4 Toll-Like/genética
3.
Chem Rev ; 118(14): 6706-6765, 2018 07 25.
Artigo em Inglês | MEDLINE | ID: mdl-29963856

RESUMO

Arylated products are found in various fields of chemistry and represent essential entities for many applications. Therefore, the formation of this structural feature represents a central issue of contemporary organic synthesis. By the action of electricity the necessity of leaving groups, metal catalysts, stoichiometric oxidizers, or reducing agents can be omitted in part or even completely. The replacement of conventional reagents by sustainable electricity not only will be environmentally benign but also allows significant short cuts in electrochemical synthesis. In addition, this methodology can be considered as inherently safe. The current survey is organized in cathodic and anodic conversions as well as by the number of leaving groups being involved. In some electroconversions the reagents used are regenerated at the electrode, whereas in other electrotransformations free radical sequences are exploited to afford a highly sustainable process. The electrochemical formation of the aryl-substrate bond is discussed for aromatic substrates, heterocycles, other multiple bond systems, and even at saturated carbon substrates. This survey covers most of the seminal work and the advances of the past two decades in this area.

4.
Sci Total Environ ; 612: 767-774, 2018 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-28866404

RESUMO

During the last decades, global cyanobacteria biomass increased due to climate change as well as industrial usage for production of biofuels and food supplements. Thus, there is a need for thorough characterization of their potential health risks, including allergenicity. We therefore aimed to identify and characterize similarities in allergenic potential of cyanobacteria originating from the major ecological environments. Different cyanobacterial taxa were tested for immunoreactivity with IgE from allergic donors and non-allergic controls using immunoblot and ELISA. Moreover, mediator release from human FcεR1-transfected rat basophilic leukemia (RBL) cells was measured, allowing in situ examination of the allergenic reaction. Phycocyanin content and IgE-binding potential were determined and inhibition assays performed to evaluate similarities in IgE-binding epitopes. Mass spectrometry analysis identified IgE-reactive bands ranging between 10 and 160kDa as phycobiliprotein compounds. Levels of cyanobacterial antigen-specific IgE in plasma of allergic donors and mediator release from sensitized RBL cells were significantly higher compared to non-allergic controls (p<0.01). Inhibition studies indicated cross-reactivity between IgE-binding proteins from fresh water cyanobacteria and phycocyanin standard. We further addressed IgE-binding characteristics of marine water and soil-originated cyanobacteria. Altogether, our data suggest that the intensive use and the strong increase in cyanobacterial abundance due to climate change call for increasing awareness and further monitoring of their potential health hazards.


Assuntos
Alérgenos/classificação , Cianobactérias/classificação , Cianobactérias/imunologia , Imunoglobulina E/imunologia , Animais , Linhagem Celular Tumoral , Mudança Climática , Água Doce , Humanos , Ratos , Água do Mar
5.
Environ Sci Technol ; 51(23): 13545-13567, 2017 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-29111690

RESUMO

Poor air quality is globally the largest environmental health risk. Epidemiological studies have uncovered clear relationships of gaseous pollutants and particulate matter (PM) with adverse health outcomes, including mortality by cardiovascular and respiratory diseases. Studies of health impacts by aerosols are highly multidisciplinary with a broad range of scales in space and time. We assess recent advances and future challenges regarding aerosol effects on health from molecular to global scales through epidemiological studies, field measurements, health-related properties of PM, and multiphase interactions of oxidants and PM upon respiratory deposition. Global modeling combined with epidemiological exposure-response functions indicates that ambient air pollution causes more than four million premature deaths per year. Epidemiological studies usually refer to PM mass concentrations, but some health effects may relate to specific constituents such as bioaerosols, polycyclic aromatic compounds, and transition metals. Various analytical techniques and cellular and molecular assays are applied to assess the redox activity of PM and the formation of reactive oxygen species. Multiphase chemical interactions of lung antioxidants with atmospheric pollutants are crucial to the mechanistic and molecular understanding of oxidative stress upon respiratory deposition. The role of distinct PM components in health impacts and mortality needs to be clarified by integrated research on various spatiotemporal scales for better evaluation and mitigation of aerosol effects on public health in the Anthropocene.


Assuntos
Aerossóis , Poluentes Atmosféricos , Estudos Epidemiológicos , Poluição do Ar , Material Particulado
8.
Faraday Discuss ; 200: 251-270, 2017 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-28574563

RESUMO

Mineral dust and secondary organic aerosols (SOA) account for a major fraction of atmospheric particulate matter, affecting climate, air quality and public health. How mineral dust interacts with SOA to influence cloud chemistry and public health, however, is not well understood. Here, we investigated the formation of reactive oxygen species (ROS), which are key species of atmospheric and physiological chemistry, in aqueous mixtures of SOA and mineral dust by applying electron paramagnetic resonance (EPR) spectrometry in combination with a spin-trapping technique, liquid chromatography-tandem mass spectrometry (LC-MS/MS), and a kinetic model. We found that substantial amounts of ROS including OH, superoxide as well as carbon- and oxygen-centred organic radicals can be formed in aqueous mixtures of isoprene, α-pinene, naphthalene SOA and various kinds of mineral dust (ripidolite, montmorillonite, kaolinite, palygorskite, and Saharan dust). The molar yields of total radicals were ∼0.02-0.5% at 295 K, which showed higher values at 310 K, upon 254 nm UV exposure, and under low pH (<3) conditions. ROS formation can be explained by the decomposition of organic hydroperoxides, which are a prominent fraction of SOA, through interactions with water and Fenton-like reactions with dissolved transition metal ions. Our findings imply that the chemical reactivity and aging of SOA particles can be enhanced upon interaction with mineral dust in deliquesced particles or cloud/fog droplets. SOA decomposition could be comparably important to the classical Fenton reaction of H2O2 with Fe2+ and that SOA can be the main source of OH radicals in aqueous droplets at low concentrations of H2O2 and Fe2+. In the human respiratory tract, the inhalation and deposition of SOA and mineral dust can also lead to the release of ROS, which may contribute to oxidative stress and play an important role in the adverse health effects of atmospheric aerosols in the Anthropocene.


Assuntos
Poluentes Atmosféricos/metabolismo , Atmosfera/química , Minerais/metabolismo , Saúde Pública , Espécies Reativas de Oxigênio/metabolismo , Aerossóis/química , Aerossóis/metabolismo , Poluentes Atmosféricos/química , Minerais/química , Material Particulado/química , Material Particulado/metabolismo , Água/química , Água/metabolismo
9.
Faraday Discuss ; 200: 413-427, 2017 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-28574569

RESUMO

The allergenic potential of airborne proteins may be enhanced via post-translational modification induced by air pollutants like ozone (O3) and nitrogen dioxide (NO2). The molecular mechanisms and kinetics of the chemical modifications that enhance the allergenicity of proteins, however, are still not fully understood. Here, protein tyrosine nitration and oligomerization upon simultaneous exposure of O3 and NO2 were studied in coated-wall flow-tube and bulk solution experiments under varying atmospherically relevant conditions (5-200 ppb O3, 5-200 ppb NO2, 45-96% RH), using bovine serum albumin as a model protein. Generally, more tyrosine residues were found to react via the nitration pathway than via the oligomerization pathway. Depending on reaction conditions, oligomer mass fractions and nitration degrees were in the ranges of 2.5-25% and 0.5-7%, respectively. The experimental results were well reproduced by the kinetic multilayer model of aerosol surface and bulk chemistry (KM-SUB). The extent of nitration and oligomerization strongly depends on relative humidity (RH) due to moisture-induced phase transition of proteins, highlighting the importance of cloud processing conditions for accelerated protein chemistry. Dimeric and nitrated species were major products in the liquid phase, while protein oligomerization was observed to a greater extent for the solid and semi-solid phase states of proteins. Our results show that the rate of both processes was sensitive towards ambient ozone concentration, but rather insensitive towards different NO2 levels. An increase of tropospheric ozone concentrations in the Anthropocene may thus promote pro-allergic protein modifications and contribute to the observed increase of allergies over the past decades.


Assuntos
Poluentes Atmosféricos/química , Atmosfera/química , Dióxido de Nitrogênio/química , Ozônio/química , Proteínas/química , Poluentes Atmosféricos/metabolismo , Dióxido de Nitrogênio/metabolismo , Ozônio/metabolismo , Proteínas/metabolismo
10.
J Chromatogr A ; 1495: 76-82, 2017 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-28342582

RESUMO

Chemical modifications such as nitration and cross-linking may enhance the allergenic potential of proteins. The kinetics and mechanisms of the underlying chemical processes, however, are not yet well understood. Here, we present a size-exclusion chromatography/spectrophotometry method (SEC-HPLC-DAD) that allows a simultaneous detection of mono-, di-, tri-, and higher protein oligomers, as well as their individual nitration degrees (NDs). The ND results of proteins from this new method agree well with the results from an alternative well-established method, for the analysis of tetranitromethane (TNM)- and nitrogen dioxide and ozone (NO2/O3)-nitrated protein samples. Importantly, the NDs for individual oligomer fractions can be obtained from the new method, and also, we provide a proof of principle for the calculation of the concentrations for individual protein oligomer fractions by their determined NDs, which will facilitate the investigation of the kinetics and mechanism for protein tyrosine nitration and cross-linking.


Assuntos
Nitratos/química , Proteínas/química , Cromatografia em Gel , Cromatografia Líquida de Alta Pressão , Dióxido de Nitrogênio/química , Ozônio/química , Proteínas/análise , Espectrofotometria Ultravioleta , Tetranitrometano/química
11.
Environ Sci Technol ; 51(8): 4119-4141, 2017 04 18.
Artigo em Inglês | MEDLINE | ID: mdl-28326768

RESUMO

Air pollution and climate change are potential drivers for the increasing burden of allergic diseases. The molecular mechanisms by which air pollutants and climate parameters may influence allergic diseases, however, are complex and elusive. This article provides an overview of physical, chemical and biological interactions between air pollution, climate change, allergens, adjuvants and the immune system, addressing how these interactions may promote the development of allergies. We reviewed and synthesized key findings from atmospheric, climate, and biomedical research. The current state of knowledge, open questions, and future research perspectives are outlined and discussed. The Anthropocene, as the present era of globally pervasive anthropogenic influence on planet Earth and, thus, on the human environment, is characterized by a strong increase of carbon dioxide, ozone, nitrogen oxides, and combustion- or traffic-related particulate matter in the atmosphere. These environmental factors can enhance the abundance and induce chemical modifications of allergens, increase oxidative stress in the human body, and skew the immune system toward allergic reactions. In particular, air pollutants can act as adjuvants and alter the immunogenicity of allergenic proteins, while climate change affects the atmospheric abundance and human exposure to bioaerosols and aeroallergens. To fully understand and effectively mitigate the adverse effects of air pollution and climate change on allergic diseases, several challenges remain to be resolved. Among these are the identification and quantification of immunochemical reaction pathways involving allergens and adjuvants under relevant environmental and physiological conditions.


Assuntos
Alérgenos/imunologia , Mudança Climática , Poluentes Atmosféricos , Poluição do Ar , Humanos , Hipersensibilidade
12.
Anal Bioanal Chem ; 409(9): 2411-2420, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28108753

RESUMO

Hydroxyl radical-induced oxidation of proteins and peptides can lead to the cleavage of the peptide, leading to a release of fragments. Here, we used high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) and pre-column online ortho-phthalaldehyde (OPA) derivatization-based amino acid analysis by HPLC with diode array detection and fluorescence detection to identify and quantify free amino acids released upon oxidation of proteins and peptides by hydroxyl radicals. Bovine serum albumin (BSA), ovalbumin (OVA) as model proteins, and synthetic tripeptides (comprised of varying compositions of the amino acids Gly, Ala, Ser, and Met) were used for reactions with hydroxyl radicals, which were generated by the Fenton reaction of iron ions and hydrogen peroxide. The molar yields of free glycine, aspartic acid, asparagine, and alanine per peptide or protein varied between 4 and 55%. For protein oxidation reactions, the molar yields of Gly (∼32-55% for BSA, ∼10-21% for OVA) were substantially higher than those for the other identified amino acids (∼5-12% for BSA, ∼4-6% for OVA). Upon oxidation of tripeptides with Gly in C-terminal, mid-chain, or N-terminal positions, Gly was preferentially released when it was located at the C-terminal site. Overall, we observe evidence for a site-selective formation of free amino acids in the OH radical-induced oxidation of peptides and proteins, which may be due to a reaction pathway involving nitrogen-centered radicals.


Assuntos
Aminoácidos/química , Radical Hidroxila/química , Peptídeos/química , Proteínas/química , Oxirredução , Espécies Reativas de Oxigênio/química
13.
Anal Bioanal Chem ; 408(23): 6337-48, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27411545

RESUMO

Metaproteomic analysis of air particulate matter provides information about the abundance and properties of bioaerosols in the atmosphere and their influence on climate and public health. We developed and applied efficient methods for the extraction and analysis of proteins from glass fiber filter samples of total, coarse, and fine particulate matter. Size exclusion chromatography was applied to remove matrix components, and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was applied for protein fractionation according to molecular size, followed by in-gel digestion and LC-MS/MS analysis of peptides using a hybrid Quadrupole-Orbitrap MS. Maxquant software and the Swiss-Prot database were used for protein identification. In samples collected at a suburban location in central Europe, we found proteins that originated mainly from plants, fungi, and bacteria, which constitute a major fraction of primary biological aerosol particles (PBAP) in the atmosphere. Allergenic proteins were found in coarse and fine particle samples, and indications for atmospheric degradation of proteins were observed. Graphical abstract Workflow for the metaproteomic analysis of atmospheric aerosol samples.


Assuntos
Aerossóis/análise , Poluentes Atmosféricos/análise , Atmosfera/análise , Material Particulado/análise , Proteínas/análise , Espectrometria de Massas em Tandem/métodos , Alérgenos/análise , Proteínas de Bactérias/análise , Cromatografia Líquida de Alta Pressão/métodos , Bases de Dados de Proteínas , Eletroforese em Gel de Poliacrilamida , Proteínas Fúngicas/análise , Proteínas de Plantas/análise , Proteômica
14.
Environ Sci Technol ; 49(18): 10859-66, 2015 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-26287571

RESUMO

Air pollution is a potential driver for the increasing prevalence of allergic disease, and post-translational modification by air pollutants can enhance the allergenic potential of proteins. Here, the kinetics and mechanism of protein oligomerization upon ozone (O3) exposure were studied in coated-wall flow tube experiments at environmentally relevant O3 concentrations, relative humidities and protein phase states (amorphous solid, semisolid, and liquid). We observed the formation of protein dimers, trimers, and higher oligomers, and attribute the cross-linking to the formation of covalent intermolecular dityrosine species. The oligomerization proceeds fast on the surface of protein films. In the bulk material, reaction rates are limited by diffusion depending on phase state and humidity. From the experimental data, we derive a chemical mechanism and rate equations for a kinetic multilayer model of surface and bulk reaction enabling the prediction of oligomer formation. Increasing levels of tropospheric O3 in the Anthropocene may promote the formation of protein oligomers with enhanced allergenicity and may thus contribute to the increasing prevalence of allergies.


Assuntos
Poluentes Atmosféricos/química , Ozônio/química , Proteínas/metabolismo , Tirosina/análogos & derivados , Poluição do Ar , Cromatografia em Gel , Difusão , Umidade , Cinética , Modelos Químicos , Multimerização Proteica , Processamento de Proteína Pós-Traducional , Proteínas/química , Soroalbumina Bovina/química , Espectrometria de Fluorescência , Tirosina/química , Tirosina/metabolismo
16.
J Phys Chem A ; 119(19): 4509-14, 2015 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-25408201

RESUMO

We have used quantum chemical methods to investigate the molecular mechanism behind the recently reported ( Kampf , C. J. ; Environ. Sci. Technol . 2013 , 47 , 4236 - 4244 ) strong dependence of the Henry's law coefficient of glyoxal (C2O2H2) on the sulfate concentration of the aqueous phase. Although the glyoxal molecule interacts only weakly with sulfate, its hydrated forms (C2O3H4 and C2O4H6) form strong complexes with sulfate, displacing water molecules from the solvation shell and increasing the uptake of glyoxal into sulfate-containing aqueous solutions, including sulfate-containing aerosol particles. This promotes the participation of glyoxal in reactions leading to secondary organic aerosol formation, especially in regions with high sulfate concentrations. We used our computed equilibrium constants for the complexation reactions to assess the magnitude of the Henry's law coefficient enhancement and found it to be in reasonable agreement with experimental results. This indicates that the complexation of glyoxal hydrates with sulfate can explain the observed uptake enhancement.


Assuntos
Simulação por Computador , Glioxal/química , Modelos Químicos , Sulfatos/química , Aerossóis/química , Atmosfera/química , Pressão , Solventes/química , Água/química
17.
Environ Sci Technol ; 48(14): 8021-7, 2014 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-24954648

RESUMO

Gaseous nitrous acid (HONO), the protonated form of nitrite, contributes up to ∼60% to the primary formation of hydroxyl radical (OH), which is a key oxidant in the degradation of most air pollutants. Field measurements and modeling studies indicate a large unknown source of HONO during daytime. Here, we developed a new tracer method based on gas-phase stripping-derivatization coupled to liquid chromatography-mass spectrometry (LC-MS) to measure the 15N relative exceedance, ψ(15N), of HONO in the gas-phase. Gaseous HONO is quantitatively collected and transferred to an azo dye, purified by solid phase extraction (SPE), and analyzed using high performance liquid chromatography coupled to mass spectrometry (HPLC-MS). In the optimal working range of ψ(15N)=0.2-0.5, the relative standard deviation of ψ(15N) is <4%. The optimum pH and solvents for extraction by SPE and potential interferences are discussed. The method was applied to measure HO15NO emissions from soil in a dynamic chamber with and without spiking 15) labeled urea. The identification of HO15NO from soil with 15N urea addition confirmed biogenic emissions of HONO from soil. The method enables a new approach of studying the formation pathways of HONO and its role for atmospheric chemistry (e.g., ozone formation) and environmental tracer studies on the formation and conversion of gaseous HONO or aqueous NO2- as part of the biogeochemical nitrogen cycle, e.g., in the investigation of fertilization effects on soil HONO emissions and microbiological conversion of NO2- in the hydrosphere.


Assuntos
Gases/química , Marcação por Isótopo/métodos , Ácido Nitroso/análise , Ácido Nitroso/química , Solo/química , Compostos Azo/química , Calibragem , Cromatografia Líquida de Alta Pressão , Espectrometria de Massas , Isótopos de Nitrogênio , Padrões de Referência , Poluentes do Solo/análise
18.
J Proteome Res ; 13(3): 1570-7, 2014 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-24517313

RESUMO

Nitration of the major birch pollen allergen Bet v 1 alters the immune responses toward this protein, but the underlying chemical mechanisms are not yet understood. Here we address the efficiency and site-selectivity of the nitration reaction of recombinant protein samples of Bet v 1.0101 with different nitrating agents relevant for laboratory investigations (tetranitromethane, TNM), for physiological processes (peroxynitrite, ONOO(-)), and for the health effects of environmental pollutants (nitrogen dioxide and ozone, O3/NO2). We determined the total tyrosine nitration degrees (ND) and the NDs of individual tyrosine residues (NDY). High-performance liquid chromatography coupled to diode array detection and HPLC coupled to high-resolution mass spectrometry analysis of intact proteins, HPLC coupled to tandem mass spectrometry analysis of tryptic peptides, and amino acid analysis of hydrolyzed samples were performed. The preferred reaction sites were tyrosine residues at the following positions in the polypeptide chain: Y83 and Y81 for TNM, Y150 for ONOO(-), and Y83 and Y158 for O3/NO2. The tyrosine residues Y83 and Y81 are located in a hydrophobic cavity, while Y150 and Y158 are located in solvent-accessible and flexible structures of the C-terminal region. The heterogeneous reaction with O3/NO2 was found to be strongly dependent on the phase state of the protein. Nitration rates were about one order of magnitude higher for aqueous protein solutions (∼20% per day) than for protein filter samples (∼2% per day). Overall, our findings show that the kinetics and site-selectivity of nitration strongly depend on the nitrating agent and reaction conditions, which may also affect the biological function and adverse health effects of the nitrated protein.


Assuntos
Antígenos de Plantas/química , Peptídeos/análise , Tirosina/química , Sequência de Aminoácidos , Antígenos de Plantas/genética , Betula/química , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Cinética , Modelos Moleculares , Dados de Sequência Molecular , Dióxido de Nitrogênio/química , Ozônio/química , Ácido Peroxinitroso/química , Pólen/química , Estrutura Secundária de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Tetranitrometano/química
19.
Anal Bioanal Chem ; 405(27): 8945-9, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24037615

RESUMO

Nitration of tyrosine residues in the major birch pollen allergen Bet v 1 may alter the allergenic potential of the protein. The kinetics and mechanism of the nitration reaction, however, have not yet been well characterized. To facilitate further investigations, an efficient method to quantify the nitration degree (ND) of small samples of Bet v 1 is required. Here, we present a suitable method of high-performance liquid chromatography coupled to a diode array detector (HPLC-DAD) that can be photometrically calibrated using the amino acids tyrosine (Tyr) and nitrotyrosine (NTyr) without the need for nitrated protein standards. The new method is efficient and in agreement with alternative methods based on hydrolysis and amino acid analysis of tetranitromethane (TNM)-nitrated Bet v 1 standards as well as samples from nitration experiments with peroxynitrite. The results confirm the applicability of the new method for the investigation of the reaction kinetics and mechanism of protein nitration.


Assuntos
Antígenos de Plantas/química , Ácido Peroxinitroso/química , Proteínas de Plantas/química , Tirosina/análogos & derivados , Tirosina/química , Antígenos de Plantas/imunologia , Betula/química , Betula/imunologia , Calibragem , Cromatografia Líquida de Alta Pressão , Proteínas de Plantas/imunologia , Pólen/química , Pólen/imunologia , Processamento de Proteína Pós-Traducional , Proteínas Recombinantes/química , Proteínas Recombinantes/imunologia , Tirosina/análise
20.
Environ Sci Technol ; 47(9): 4236-44, 2013 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-23534917

RESUMO

The reversible partitioning of glyoxal was studied in simulation chamber experiments for the first time by time-resolved measurements of gas-phase and particle-phase concentrations in sulfate-containing aerosols. Two complementary methods for the measurement of glyoxal particle-phase concentrations are compared: (1) an offline method utilizing filter sampling of chamber aerosols followed by HPLC-MS/MS analysis and (2) positive matrix factorization (PMF) analysis of aerosol mass spectrometer (AMS) data. Ammonium sulfate (AS) and internally mixed ammonium sulfate/fulvic acid (AS/FA) seed aerosols both show an exponential increase of effective Henry's law coefficients (KH,eff) with AS concentration (cAS, in mol kg(-1) aerosol liquid water, m = molality) and sulfate ionic strength, I(SO4(2-)) (m). A modified Setschenow plot confirmed that "salting-in" of glyoxal is responsible for the increased partitioning. The salting constant for glyoxal in AS is K(S)CHOCHO = (-0.24 ± 0.02) m(-1), and found to be independent of the presence of FA. The reversible glyoxal uptake can be described by two distinct reservoirs for monomers and higher molecular weight species filling up at characteristic time constants. These time constants are τ1 ≈ 10(2) s and τ2 ≈ 10(4) s at cAS < 12 m, and about 1-2 orders of magnitude slower at higher cAS, suggesting that glyoxal uptake is kinetically limited at high salt concentrations.


Assuntos
Aerossóis/química , Glioxal/química , Sais/química , Sulfatos/análise , Cromatografia Líquida de Alta Pressão , Espectrometria de Massas em Tandem
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