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1.
PLoS One ; 15(9): e0238470, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32911526

RESUMO

We report a powerful method for capturing the time-resolved concentration profiles, liquid swelling and surface phenomena during the absorption of methane (CH4) in still liquid ethanol (C2D6O) and n-decane (n-C10D22) and at high spatial resolution (pixel size 21.07 µm) using neutron imaging. Absorption of supercritical methane was followed at two temperatures and two pressures of methane, namely 7.0, 37.8 °C and 80, 120 bar. Fick's second law, which was used in the liquid-fixed coordinates, enabled for an adequate parameterization of the observed concentration profiles and liquid levels using simple analytical expressions. For both studied liquids, anomalously slow diffusion was observed in the initial stage of the absorption experiment. This was ascribed to the slow formation of the surface excess on the interface, time constant ranged 130-275 s. The axial symmetry of the cell allowed for the tomographic reconstructions of the profiles of the menisci. Based on these profiles, contact angle and surface tension were evaluated using the Young-Laplace equation. Overall, neutron imaging made it possible to capture time- and space-resolved information from which the methane concentration, liquid level and meniscus shape under high-pressure conditions inside a cylindrical titanium vessel were quantitatively derived. Multiple characteristics of ethanol, a methane hydrate inhibitor, and n-decane, a model constituent of crude oil, were thus measured for the first time under industrially relevant conditions in a one-pot experiment.


Assuntos
Metano/química , Imagem Individual de Molécula/métodos , Alcanos/química , Difusão , Etanol/química , Modelos Estatísticos , Nêutrons , Petróleo , Fenômenos Físicos , Imagem Individual de Molécula/instrumentação , Temperatura , Água
2.
Int J Nanomedicine ; 15: 5345-5360, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32801693

RESUMO

Background: Soft corals have been endorsed as a plentiful source of bioactive compounds with promising anti-inflammatory activities; therefore, exploring their potential as source of anti-inflammatory metabolites has stimulated a growing research interest. Purpose: To investigate the anti-inflammatory potential of the soft coral, Nephthea sp., in its bulk and silver nanostructure. Metabolomics analysis of Nephthea sp., followed by molecular docking studies, was also conducted in order to explore and predict the secondary metabolites that might provide its inhibitory actions on inflammation. Materials and Methods: The petroleum ether and ethyl acetate fractions were used to synthesize silver nanoparticles. The prepared silver nanoparticles were characterized through UV-vis spectrophotometric, transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR) analyses. Testing for the anti-inflammatory activity was performed against COX-1 and COX-2. Furthermore, liquid chromatography-mass spectrometry (LC-MS) based metabolomics analysis and molecular docking were also applied. Results: A variety of secondary metabolites were identified, among them, sesquiterpenes were found to prevail. The petroleum ether and acetone fractions of Nephthea sp. showed the highest COX-2 inhibitory activities, possibly attributable to their substantial contents of terpenoids. Additionally, the green synthesized silver nanoparticles of both the petroleum ether and ethyl acetate fractions of Nephthea sp. demonstrated higher anti-COX-2 properties. Conclusion: The obtained results showed the effectiveness of non-targeted metabolomics technique in metabolic profiling of Nephthea sp., helping the search for new bioactive metabolites in future chemical studies on this soft coral. The interesting anti-inflammatory potential of the tested extracts and their nanoparticles could also be relevant to the development of new, effective anti-inflammatory agents.


Assuntos
Antozoários/metabolismo , Anti-Inflamatórios/química , Anti-Inflamatórios/farmacologia , Nanopartículas Metálicas/química , Prata/química , Alcanos/química , Animais , Antozoários/química , Anti-Inflamatórios/síntese química , Ciclo-Oxigenase 1/química , Ciclo-Oxigenase 1/metabolismo , Inibidores de Ciclo-Oxigenase 2/química , Inibidores de Ciclo-Oxigenase 2/farmacologia , Inibidores de Ciclo-Oxigenase/química , Inibidores de Ciclo-Oxigenase/farmacologia , Química Verde , Humanos , Metabolômica , Simulação de Acoplamento Molecular , Metabolismo Secundário , Sesquiterpenos/análise , Espectrometria de Massas por Ionização por Electrospray , Espectroscopia de Infravermelho com Transformada de Fourier
3.
Mol Pharmacol ; 98(2): 156-167, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32591477

RESUMO

The natural product (+)-discodermolide (DDM) is a microtubule stabilizing agent and potent inducer of senescence. We refined the structure of DDM and evaluated the activity of novel congeners in triple negative breast and ovarian cancers, malignancies that typically succumb to taxane resistance. Previous structure-activity analyses identified the lactone and diene as moieties conferring anticancer activity, thus identifying priorities for the structural refinement studies described herein. Congeners possessing the monodiene with a simplified lactone had superior anticancer efficacy relative to taxol, particularly in resistant models. Specifically, one of these congeners, B2, demonstrated 1) improved pharmacologic properties, specifically increased maximum response achievable and area under the curve, and decreased EC50; 2) a uniform dose-response profile across genetically heterogeneous cancer cell lines relative to taxol or DDM; 3) reduced propensity for senescence induction relative to DDM; 4) superior long-term activity in cancer cells versus taxol or DDM; and 5) attenuation of metastatic characteristics in treated cancer cells. To contrast the binding of B2 versus DDM in tubulin, X-ray crystallography studies revealed a shift in the position of the lactone ring associated with removal of the C2-methyl and C3-hydroxyl. Thus, B2 may be more adaptable to changes in the taxane site relative to DDM that could account for its favorable properties. In conclusion, we have identified a DDM congener with broad range anticancer efficacy that also has decreased risk of inducing chemotherapy-mediated senescence. SIGNIFICANCE STATEMENT: Here, we describe the anticancer activity of novel congeners of the tubulin-polymerizing molecule (+)-discodermolide. A lead molecule is identified that exhibits an improved dose-response profile in taxane-sensitive and taxane-resistant cancer cell models, diminished risk of chemotherapy-mediated senescence, and suppression of tumor cell invasion endpoints. X-ray crystallography studies identify subtle changes in the pose of binding to ß-tubulin that could account for the improved anticancer activity. These findings support continued preclinical development of discodermolide, particularly in the chemorefractory setting.


Assuntos
Alcanos/química , Carbamatos/química , Lactonas/síntese química , Neoplasias Ovarianas/metabolismo , Pironas/química , Neoplasias de Mama Triplo Negativas/metabolismo , Moduladores de Tubulina/síntese química , Células A549 , Área Sob a Curva , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Cristalografia por Raios X , Relação Dose-Resposta a Droga , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Feminino , Humanos , Lactonas/química , Lactonas/farmacologia , Estrutura Molecular , Neoplasias Ovarianas/tratamento farmacológico , Taxoides/farmacologia , Neoplasias de Mama Triplo Negativas/tratamento farmacológico , Moduladores de Tubulina/química , Moduladores de Tubulina/farmacologia
4.
Int J Nanomedicine ; 15: 3377-3389, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32494136

RESUMO

Background: Hepatitis C virus (HCV) infection is a major cause of hepatic diseases all over the world. This necessitates the need to discover novel anti-HCV drugs to overcome emerging drug resistance and liver complications. Purpose: Total extract and petroleum ether fraction of the marine sponge (Amphimedon spp.) were used for silver nanoparticle (SNP) synthesis to explore their HCV NS3 helicase- and protease-inhibitory potential. Methods: Characterization of the prepared SNPs was carried out with ultraviolet-visible spectroscopy, transmission electron microscopy, and Fourier-transform infrared spectroscopy. The metabolomic profile of different Amphimedon fractions was assessed using liquid chromatography coupled with high-resolution mass spectrometry. Fourteen known compounds were isolated and their HCV helicase and protease activities assessed using in silico modeling of their interaction with both HCV protease and helicase enzymes to reveal their anti-HCV mechanism of action. In vitro anti-HCV activity against HCV NS3 helicase and protease was then conducted to validate the computation results and compared to that of the SNPs. Results: Transmission electron-microscopy analysis of NPs prepared from Amphimedon total extract and petroleum ether revealed particle sizes of 8.22-14.30 nm and 8.22-9.97 nm, and absorption bands at λmax of 450 and 415 nm, respectively. Metabolomic profiling revealed the richness of Amphimedon spp. with different phytochemical classes. Bioassay-guided isolation resulted in the isolation of 14 known compounds with anti-HCV activity, initially revealed by docking studies. In vitro anti-HCV NS3 helicase and protease assays of both isolated compounds and NPs further confirmed the computational results. Conclusion: Our findings indicate that Amphimedon, total extract, petroleum ether fraction, and derived NPs are promising biosources for providing anti-HCV drug candidates, with nakinadine B and 3,4-dihydro-6-hydroxymanzamine A the most potent anti-HCV agents, possessing good oral bioavailability and penetration power.


Assuntos
Simulação por Computador , DNA Helicases/antagonistas & inibidores , Química Verde , Metabolômica , Nanopartículas Metálicas/química , Poríferos/química , Prata/farmacologia , Proteínas não Estruturais Virais/antagonistas & inibidores , Alcanos/química , Animais , Antivirais/farmacologia , Hepacivirus/efeitos dos fármacos , Oceano Índico , Nanopartículas Metálicas/ultraestrutura , Simulação de Acoplamento Molecular , Peptídeo Hidrolases/metabolismo , Inibidores de Proteases/farmacologia , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier
5.
Pharm Res ; 37(6): 99, 2020 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-32435855

RESUMO

PURPOSE: To evaluate the performance of artificial membranes in in vitro lipolysis-permeation assays useful for absorption studies of drugs loaded in lipid-based formulations (LBFs). METHODS: Polycarbonate as well as PVDF filters were treated with hexadecane, or lecithin in n-dodecane solution (LiDo) to form artificial membranes. They were thereafter used as absorption membranes separating two compartments mimicking the luminal and serosal side of the intestine in vitro. Membranes were subjected to dispersions of an LBF that had been digested by porcine pancreatin and spiked with the membrane integrity marker Lucifer Yellow (LY). Three fenofibrate-loaded LBFs were used to explore the in vivo relevance of the assay. RESULTS: Of the explored artificial membranes, only LiDo applied to PVDF was compatible with lipolysis by porcine pancreatin. Formulation ranking based on mass transfer in the LiDo model exposed was the same as drug release in single-compartment lipolysis. Ranking based on observed apparent permeability coefficients of fenofibrate with different LBFs were the same as those obtained in a cell-based model. CONCLUSIONS: The LiDo membrane was able to withstand lipolysis for a sufficient assay period. However, the assay with porcine pancreatin as digestive agent did not predict the in vivo ranking of the assayed formulations better than existing methods. Comparison with a Caco-2 based assay method nonetheless indicates that the in vitro in vivo relationship of this cell-free model could be improved with alternative digestive agents.


Assuntos
Portadores de Fármacos/química , Fenofibrato/química , Lipídeos/química , Lipólise , Membranas Artificiais , Administração Oral , Adsorção , Alcanos/química , Animais , Bioensaio/métodos , Células CACO-2 , Digestão , Composição de Medicamentos/métodos , Liberação Controlada de Fármacos , Excipientes/química , Fenofibrato/administração & dosagem , Humanos , Lecitinas/química , Modelos Biológicos , Pancreatina/metabolismo , Permeabilidade , Solubilidade , Suínos
6.
Eur J Med Chem ; 200: 112409, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32460114

RESUMO

A series of new benzothiazinone derivatives containing a symmetric 2-benzyl-2,7-diazaspiro[3.5]nonane moiety, based on the structure of LK02 discovered in our lab, were designed and synthesized. With one exception 3, all of them show excellent in vitro activity against both drug-sensitive and clinically isolated multidrug-resistant Mycobacterium tuberculosis (MTB) strains (MIC: < 0.016 µg/mL). Compound 2d with a methyl group at the benzylic carbon, was identified to have good safety and significant efficacy in an acute mouse model of TB, as well as better PK profiles than PBTZ169.


Assuntos
Alcanos/química , Antituberculosos/química , Desenho de Fármacos , Tiazinas/química , Animais , Antituberculosos/síntese química , Resistência a Medicamentos , Camundongos , Mycobacterium tuberculosis/efeitos dos fármacos , Relação Estrutura-Atividade , Tuberculose Resistente a Múltiplos Medicamentos/tratamento farmacológico
7.
J Chromatogr A ; 1622: 461111, 2020 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-32450988

RESUMO

A method to thermodynamically model the alkane isovolatility curves of a comprehensive two dimensional gas chromatography (GC × GC) separation is presented. This method omits all instrument modifications, additional chromatogram collection, or method alterations which typical isovolatility curve generation requires. Provided that the thermodynamic indices of reference alkanes are available, chromatographers only need to specify the GC × GC method parameters of their separation to output the isovolatility curves. The curves can then be used alongside reference retention indices to generate two dimensional retention times for each analyte. Agreement between the modeled and experimental retention times provides a secondary mechanism for compound identification, supporting the results of a mass spectral search. The technique was used to model the retention times of a GC × GC separation of aromatic hydrocarbons, achieving an average first dimension retention time modeling error of 11 s and an average second dimension retention time modeling error of 0.09 s. Retention indices modeled retention times provide a simpler analyte identification procedure compared to conventional two dimensional retention indices matching.


Assuntos
Cromatografia Gasosa/métodos , Alcanos/análise , Alcanos/química , Modelos Químicos , Termodinâmica
8.
J Chromatogr A ; 1621: 461084, 2020 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-32303345

RESUMO

This work presents a new triptycene-based dicationic guanidinium ionic liquid (TPG) as the stationary phase for gas chromatography (GC). To our knowledge, this is the first example of employing a dicationic guanidinium ionic liquid (GIL) for chromatographic analyses. As a result, the TPG column exhibited moderate polarity and column efficiency of 3840 plates/m and 3120 plates/m measured by naphthalene and 1-octanol at 120 °C, respectively. Particularly, the TPG column exhibited distinctly advantageous performance for the challenging Grob test mixture and the isomer mixture of phenols and anilines over the monocationic GIL and its counterpart with dicationic immidazolium units (TP-2IL). Also, it showed higher selectivity towards the isomers of alkanes, alcohols, diethylbenzenes, bromotoluenes, bromonitrobenzenes than the commercial DB-35MS column. Moreover, the TPG column achieved improved thermal stability over the GIL column and excellent repeatability with the RSD values of 0.01-0.05% for run-to-run, 0.11-0.24% for day-to-day and 2.4-4.1% for column-to-column. Its application to GC-MS analysis of the essential oil of Mentha haplocalyx proved its good potential for analysis of complex samples.


Assuntos
Antracenos/química , Guanidina/química , Líquidos Iônicos/química , Alcanos/química , Compostos de Anilina/química , Cromatografia Gasosa-Espectrometria de Massas , Líquidos Iônicos/análise , Isomerismo , Mentha/química , Óleos Voláteis/análise , Fenóis/química , Reprodutibilidade dos Testes , Solventes , Temperatura
9.
Nat Commun ; 11(1): 1956, 2020 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-32327665

RESUMO

The dehydrogenative alkenylation of C-H bonds with alkenes represents an atom- and step-economical approach for olefin synthesis and molecular editing. Site-selective alkenylation of alkanes and aldehydes with the C-H substrate as the limiting reagent holds significant synthetic value. We herein report a photocatalytic method for the direct alkenylation of alkanes and aldehydes with aryl alkenes in the absence of any external oxidant. A diverse range of commodity feedstocks and pharmaceutical compounds are smoothly alkenylated in useful yields with the C-H partner as the limiting reagent. The late-stage alkenylation of complex molecules occurs with high levels of site selectivity for sterically accessible and electron-rich C-H bonds. This strategy relies on the synergistic combination of direct hydrogen atom transfer photocatalysis with cobaloxime-mediated hydrogen-evolution cross-coupling, which promises to inspire additional perspectives for selective C-H functionalizations in a green manner.


Assuntos
Aldeídos/química , Alcanos/química , Alcenos/química , Alcenos/síntese química , Catálise , Técnicas de Química Sintética , Química Verde , Estrutura Molecular , Compostos Organometálicos/química , Processos Fotoquímicos , Estereoisomerismo
10.
J Chromatogr A ; 1622: 461120, 2020 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-32345440

RESUMO

The characterisation of the energetic properties of liquid crystals, i.e., esters with elongated molecules has been performed. The changes of the free energies of adsorption and absorption (dissolutions), ΔG, for liquid crystals have been estimated, based on the retention times of the centre of gravity of the elution peaks determined for the substances with defined physicochemical properties. The temperature-dependent van der Waals component of the free energy, [Formula: see text] , for a crystalline form of liquid crystal has been estimated by employing the Dorris-Gray approach. These approaches have been widened to mesophases, namely, the absorption(dissolution) of n-alkanes in the smectic B and nematic phases.


Assuntos
Benzoatos/química , Absorção Fisico-Química , Adsorção , Alcanos/química , Cromatografia Gasosa , Entropia , Temperatura
11.
J Chromatogr A ; 1620: 461002, 2020 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-32143874

RESUMO

Micro gas chromatography (µGC) is a technique developed for rapid, in situ analysis of volatile organic compounds (VOCs) for environmental protection, industrial monitoring, and toxicology. While reduced µGC size and power requirements allow for increased portability, the low moisture and oxygen resilience of current microcolumn technology result in increased peak broadening and tailing for humid samples, which necessitates the use of bulky helium or nitrogen carrier gas cartridges. Developing a microcolumn to address these deficiencies is desirable to improve µGC field performance and further reduce µGC system size. This paper reports the development and characterization of a microfabricated phosphonium ionic liquid (µIL) column and demonstrates separation of both polar and nonpolar compounds using this column via analyses of alcohols, chloroalkanes, aromatics, aldehydes, fatty acid methyl esters, and alkanes. The µIL column achieved operation at temperatures up to 345 °C for fatty acid methyl ester and alkane separation. Notably, all separations in this study used dry air as the carrier gas, showing that analysis of a diverse range of compounds was possible in the presence of oxygen. After exposure to dry air for 48 h at temperatures up to 220 °C, the µIL column's peak capacity was only degraded by 8.92%, which validated its long-term robustness against oxygen. The column's separation performance was not degraded by high moisture concentrations or long-term moisture exposure, also manifesting its robustness to moisture. The high temperature, moisture, and oxygen resilience of the µIL column enable more rapid separations in varying field environments without requiring additional µGC accessories (e.g., humidity filters and carrier gas cartridges). The µIL column is therefore expected to be useful for integration into future µGC devices.


Assuntos
Cromatografia Gasosa/métodos , Líquidos Iônicos/química , Ar , Alcanos/química , Ácidos Graxos/química , Temperatura Alta , Hidrocarbonetos Aromáticos/química , Microtecnologia
12.
Chemosphere ; 250: 126202, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32092569

RESUMO

As the primary source of a wide range of industrial products, the study of petroleum-derived compounds is of pivotal importance. However, the process of oil extraction and refinement is among the most environmentally hazardous practices, impacting almost all levels of the ecological chain. So far, the most appropriate strategy to overcome such an issue is through bioremediation, which revolves around the employment of different microorganisms to degrade hazardous compounds, generating less environmental impact and lower monetary costs. In this sense, a myriad of organisms and enzymes are considered possible candidates for the bioremediation process. Amidst the potential candidates is α-amylase, an evolutionary conserved starch-degrading enzyme. Notably, α-amylase was not only seen to degrade n-alkanes, a subclass of alkanes considered the most abundant petroleum-derived compounds but also low-density polyethylene, a dangerous pollutant produced from petroleum. Thus, due to its high conservation in both eukaryotic and prokaryotic lineages, in addition to the capability to degrade different types of hazardous compounds, the study of α-amylase becomes a rising interest. Nevertheless, there are no studies that review all biotechnological applications of α-amylase for bioremediation. In this work, we critically review the potential biotechnological applications of α-amylase, focusing on the biodegradation of petroleum-derived compounds. Evolutionary aspects are discussed, as well for all structural information and all features that could impact on the employment of this protein in the biotechnological industry, such as pH, temperature, and medium conditions. New perspectives and critical assessments are conducted regarding the application of α-amylase in the bioremediation of n-alkanes.


Assuntos
Biodegradação Ambiental , Alcanos/química , Biotecnologia , Petróleo/metabolismo , alfa-Amilases
13.
J Chromatogr A ; 1620: 460982, 2020 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-32098681

RESUMO

Dynamic pressure gradient modulation (DPGM) is investigated for comprehensive two-dimensional gas chromatography (GC × GC) with time-of-flight mass spectrometry (TOFMS) detection. With DPGM, a commercial pneumatic "pulse" valve is opened to introduce a suitably high auxiliary gas pressure at a T-junction connecting the first dimension (1D) and second dimension (2D) columns during the modulation period (PM), temporarily stopping the 1D flow. The valve is then closed for the duration of a pulse width (pw) to "re-inject" temporally focused 1D eluate onto the 2D column for separation. This flow modulation technique is observed to be compatible with TOFMS detection using a 2D flow rate of 4 ml/min for the separation of a 90-component test mixture. A 25 min separation window using a PM = 1 s and pw = 200 ms for full modulation (and 100% duty cycle) provided an average 1Wb = 4.5 s and 2Wb = 130 ms for a 2D peak capacity of nc,2D = 2700 (100 peaks per min). The detector response enhancement factor (DREF) serves as a metric for the enhanced sensitivity of the modulated relative to the unmodulated 1D peaks, with DREFs ranging between 10 and 20 and about a 5-fold improvement in signal-to-noise ratio (S/N). The bilinear "quality" of the GC × GC data is studied using the chemometric method parallel factor analysis (PARAFAC). Since PARAFAC requires sufficiently trilinear data, the reproducibility of the 2D peak shape for a given analyte is confirmed using lack-of-fit (LOF) and percent variation (R2) metrics. The limit-of-detection (LOD) for the representative analyte hexadecane is determined using PARAFAC, providing an LOD of 0.7 ppb (±0.03 ppb) for three replicates. Seven heavily overlapped analytes are also fully resolved by PARAFAC down to the part-per-million (ppm) concentration level, producing reproducible spectra with a majority of spectral match values (MV) over 800 (RSD ≤ 7.1%). This study provides promising results for DPGM as a flow modulation technique compatible with GC × GC-TOFMS, providing high sensitivity data suitable for chemometric analysis.


Assuntos
Cromatografia Gasosa-Espectrometria de Massas/métodos , Espectrometria de Massas/métodos , Pressão , Alcanos/química , Análise Fatorial , Limite de Detecção , Reprodutibilidade dos Testes
14.
J Chromatogr A ; 1618: 460928, 2020 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-32008822

RESUMO

This work presents a new triptycene-based stationary phase (TP-PEG) combining the three-dimensional (3D) triptycene (TP) framework with polyethylene glycol (PEG) moieties for gas chromatographic (GC) separations. Its statically coated capillary column showed high column efficiency of 5263 plates/m determined by naphthalene at 120 °C. Its Rohrschneider-McReynolds constants and Abraham solvation system constants were measured to characterize its polarity and molecular interactions with analytes of different types. As evidenced, the TP-PEG column showed high-resolution performance for the isomers of anilines, phenols, halobenzenes and alkanes with distinct advantages over the PEG columns, particularly those critical isomers such as 3,5-/2,3-xylidine (R = 2.94), m-/p-chlorotoluene (R = 1.92), p-/m-cresol (R = 1.89), 2,2-dimethylbutane/2-methylpentane (R = 1.51), 2,2,3-trimethylbutane /2,3-dimethyl pentane (R = 1.74) and 2,3-dimethylpentane/n-heptane (R = 1.92). In addition, it exhibited good column repeatability and reproducibility with the relative standard deviation (RSD) values of 0.02%-0.09% for run-to-run, 0.13%-0.22% for day-to-day and 2.7%-4.1% for column-to-column, respectively, and a wide operational temperature range (30 °C-280 °C) . Its application to GC-MS analysis of the essential oil of Osmanthus fragrans has proven its good potential for practical analysis of complex samples.


Assuntos
Antracenos/química , Cromatografia Gasosa-Espectrometria de Massas/métodos , Óleos Voláteis/química , Oleaceae/química , Polietilenoglicóis/química , Alcanos/análise , Alcanos/química , Compostos de Anilina/análise , Compostos de Anilina/química , Derivados de Benzeno/química , Isomerismo , Fenóis/análise , Fenóis/química , Reprodutibilidade dos Testes
15.
Environ Toxicol Chem ; 39(4): 775-786, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32022323

RESUMO

To accurately predict the environmental fate of per- and polyfluoroalkyl substances (PFAS), high-quality physicochemical property data are required. Because such data are often not available from experiments, assessment of the accuracy of existing property estimation models is essential. The quality of predicted physicochemical property data for a set of 25 PFAS was examined using COSMOtherm, EPI Suite, the estimation models accessible through the US Environmental Protection Agency's CompTox Chemicals Dashboard, and Linear Solvation Energy Relationships (LSERs) available through the UFZ-LSER Database. The results showed that COSMOtherm made the most accurate acid dissociation constant and air-water partition ratio estimates compared with literature data. The OPEn structure-activity/property Relationship App (OPERA; developed through the CompTox Chemicals Dashboard) estimates of vapor pressure and dry octanol-air partition ratios were the most accurate compared with other models of interest. Wet octanol-water partition ratios were comparably predicted by OPERA and EPI Suite, and the organic carbon soil coefficient and solubility were well predicted by OPERA and COSMOtherm. Acid dissociation of the perfluoroalkyl acids has a significant impact on their physicochemical properties, and corrections for ionization were included where applicable. Environ Toxicol Chem 2020;39:775-786. © 2020 SETAC.


Assuntos
Alcanos/química , Monitoramento Ambiental/métodos , Poluentes Ambientais/química , Hidrocarbonetos Fluorados/química , Modelos Químicos , Alcanos/análise , Alcanos/toxicidade , Poluentes Ambientais/análise , Poluentes Ambientais/toxicidade , Hidrocarbonetos Fluorados/análise , Hidrocarbonetos Fluorados/toxicidade , Estrutura Molecular , Relação Quantitativa Estrutura-Atividade , Solubilidade , Termodinâmica , Estados Unidos , United States Environmental Protection Agency
16.
Molecules ; 25(2)2020 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-31936557

RESUMO

Synthesis of new chromium(II) complexes with chelating bis(alkoxide) ligand [OO]Ph (H2[OO]Ph = [1,1':4',1''-terphenyl]-2,2''-diylbis(diphenylmethanol)) and their subsequent reactivity in the context of catalytic production of carbodiimides from azides and isocyanides are described. Two different Cr(II) complexes are obtained, as a function of the crystallization solvent: mononuclear Cr[OO]Ph(THF)2 (in toluene/THF, THF = tetrahydrofuran) and dinuclear Cr2([OO]Ph)2 (in CH2Cl2/THF). The electronic structure and bonding in Cr[OO]Ph(THF)2 were probed by density functional theory calculations. Isolated Cr2([OO]Ph)2 undergoes facile reaction with 4-MeC6H4N3, 4-MeOC6H4N3, or 3,5-Me2C6H3N3 to yield diamagnetic Cr(VI) bis(imido) complexes; a structure of Cr[OO]Ph(N(4-MeC6H4))2 was confirmed by X-ray crystallography. The reaction of Cr2([OO]Ph)2 with bulkier azides N3R (MesN3, AdN3) forms paramagnetic products, formulated as Cr[OO]Ph(NR). The attempted formation of a Cr-alkylidene complex (using N2CPh2) instead forms chromium(VI) bis(diphenylmethylenehydrazido) complex Cr[OO]Ph(NNCPh2)2. Catalytic formation of carbodiimides was investigated for the azide/isocyanide mixtures containing various aryl azides and isocyanides. The formation of carbodiimides was found to depend on the nature of organoazide: whereas bulky mesitylazide led to the formation of carbodiimides with all isocyanides, no carbodiimide formation was observed for 3,5-dimethylphenylazide or 4-methylphenylazide. Treatment of Cr2([OO]Ph)2 or H2[OO]Ph with NO+ leads to the formation of [1,2-b]-dihydroindenofluorene, likely obtained via carbocation-mediated cyclization of the ligand.


Assuntos
Quelantes/química , Cromo/química , Compostos Organometálicos/química , Alcanos/química , Azidas/química , Catálise , Quelantes/síntese química , Cristalografia por Raios X , Ligantes , Estrutura Molecular , Compostos Organometálicos/síntese química
17.
J Colloid Interface Sci ; 564: 264-275, 2020 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-31923825

RESUMO

HYPOTHESIS: Saponins are natural surfactants which can provide highly viscoelastic interfaces. This property can be used to quantify precisely the effect of interfacial dilatational elasticity on the various rheological properties of bulk emulsions. EXPERIMENTS: We measured the interfacial dilatational elasticity of adsorption layers from four saponins (Quillaja, Escin, Berry, Tea) adsorbed on hexadecane-water and sunflower oil-water interfaces. In parallel, the rheological properties under steady and oscillatory shear deformations were measured for bulk emulsions, stabilized by the same saponins (oil volume fraction between 75 and 85%). FINDINGS: Quillaja saponin and Berry saponin formed solid adsorption layers (shells) on the SFO-water interface. As a consequence, the respective emulsions contained non-spherical drops. For the other systems, the interfacial elasticities varied between 2 mN/m and 500 mN/m. We found that this interfacial elasticity has very significant impact on the emulsion shear elasticity, moderate effect on the dynamic yield stress, and no effect on the viscous stress of the respective steadily sheared emulsions. The last conclusion is not trivial, because the dilatational surface viscoelasticity is known to have strong impact on the viscous stress of steadily sheared foams. Mechanistic explanations of all observed effects are described.


Assuntos
Alcanos/química , Saponinas/química , Água/química , Elasticidade , Emulsões , Reologia
18.
Int J Mol Sci ; 21(2)2020 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-31963543

RESUMO

Sexually deceptive orchids typically depend on specific insect species for pollination, which are lured by sex pheromone mimicry. European Ophrys orchids often exploit specific species of wasps or bees with carboxylic acid derivatives. Here, we identify the specific semiochemicals present in O. insectifera, and in females of one of its pollinator species, Argogorytes fargeii. Headspace volatile samples and solvent extracts were analysed by GC-MS and semiochemicals were structurally elucidated by microderivatisation experiments and synthesis. (Z)-8-Heptadecene and n-pentadecane were confirmed as present in both O. insectifera and A. fargeii female extracts, with both compounds being found to be electrophysiologically active to pollinators. The identified semiochemicals were compared with previously identified Ophrys pollinator attractants, such as (Z)-9 and (Z)-12-C27-C29 alkenes in O. sphegodes and (Z)-9-octadecenal, octadecanal, ethyl linoleate and ethyl oleate in O. speculum, to provide further insights into the biosynthesis of semiochemicals in this genus. We propose that all these currently identified Ophrys semiochemicals can be formed biosynthetically from the same activated carboxylic acid precursors, after a sequence of elongation and decarbonylation reactions in O. sphegodes and O. speculum, while in O. insectifera, possibly by decarbonylation without preceding elongation.


Assuntos
Alcanos/farmacologia , Alcenos/farmacologia , Flores/fisiologia , Orchidaceae/fisiologia , Feromônios/farmacologia , Atrativos Sexuais/farmacologia , Alcanos/análise , Alcanos/química , Alcenos/análise , Alcenos/química , Animais , Abelhas , Flores/efeitos dos fármacos , Orchidaceae/efeitos dos fármacos , Feromônios/análise , Feromônios/química , Polinização , Atrativos Sexuais/análise , Atrativos Sexuais/química , Especificidade da Espécie , Vespas
19.
Biochim Biophys Acta Biomembr ; 1862(5): 183201, 2020 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-31972164

RESUMO

Alkanes are known to promote the fluid lamellar (Lα)-to-inverted hexagonal (HII) phase transition of different phospholipids. In this work, we studied the interaction of decane and tetradecane with self-assemblies formed of 1-palmitoyl-2-oleoyl-sn-glycero-phosphoethanolamine (POPE), using sequential 2H and 31P solid-state NMR spectroscopy. This technique allowed calculating the partitioning constant of the alkanes between the Lα and HII phases of POPE. Our results show that both alkanes are preferentially distributed in the HII phase compared to the Lα phase. In the HII phase, both alkanes display a very high conformational disorder, consistent with their location in the intercylinder voids. This preferential partitioning in the HII phase is more pronounced for tetradecane than for decane. This finding is proposed to be associated with a less energetically favored insertion (limited solubility) of tetradecane in the lamellar phase. This proposition is supported by the observation that tetradecane experiences more conformational freedom than its shorter analog in POPE bilayers, suggesting that it is located, on average, closer to the middle of the bilayers. It is also established that the increase in size of the intercylinder voids, by the addition of 1-palmitoyl-2-oleoyl-sn-glycero-phosphocholine (POPC) in the HII cylinders, enhances the partitioning of decane in the HII phase compared to the Lα phase. These findings propose handles to modulate the balance of the relative Lα/HII phase stability.


Assuntos
Alcanos/química , Bicamadas Lipídicas/química , Fosfatidiletanolaminas/química , Varredura Diferencial de Calorimetria/métodos , Espectroscopia de Ressonância Magnética/métodos , Conformação Molecular , Transição de Fase , Temperatura
20.
Chemosphere ; 247: 125855, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31935577

RESUMO

To preliminarily investigate the occurrence, spatial distributions, homolog compositions, and ecological risks of chlorinated paraffins (CPs) in Yunnan, China, 110 soil samples were collected from an area part of Yunnan, representative of the whole Yunnan area, where had similar characteristics to most parts of Yunnan and 22 pooled soil samples were analyzed for 50 CP congener groups (C9-17Cl5-10). The chlorinated nonane paraffin (C9-CP), short chain (SCCP), and medium chain chlorinated paraffin (MCCP) concentrations in soil samples were 8-109 ng/g (average 39 ng/g), 79-948 ng/g (average 348 ng/g), and 20-1206 ng/g (average 229 ng/g), respectively. The C9-CP homologs contributed 5%-16% of the C9-13-CP concentrations in soils. No significant correlation was found between CP concentrations and the total organic carbon content (P > 0.05). The CP levels in soils from Yunnan were at a medium level compared with those in other areas worldwide. Human activity and atmosphere deposition would influence the levels and spatial distributions of CPs in this area. The concentrations of CPs in east area were higher than those in west area. C10Cl6-7 were the major SCCP congeners and C14Cl6-7 were the major MCCP congeners. Principal component analysis indicated that SCCPs and MCCPs came from different sources. A preliminary risk assessment indicated that these concentrations of CPs in soil from Yunnan do not pose a significant ecological risk for soil organisms.


Assuntos
Hidrocarbonetos Clorados/análise , Parafina/análise , Solo/química , Alcanos/química , China , Monitoramento Ambiental/métodos , Humanos , Parafina/química , Medição de Risco
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