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1.
Inorg Chem ; 58(21): 14617-14625, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31626549

RESUMO

Titanium-oxo clusters (TOCs) are attractive as a rapidly growing class of molecular materials due to their use as molecular models and precursors of nano-titanium-oxide. However, most TOCs can only be dissolved in nonaqueous solvents, which largely limits their potential applications in biological or environmental situations. Very few water-soluble TOCs were reported, which can be used directly in aqueous biomedical systems. However, until now, no research studies of such TOCs involved in biomedical fields have been documented. We report here a series of lanthanide-titanium-oxo clusters (LnTOCs) formulated as {H2@[Ln2Ti8(µ3-O)8(µ2-O)4(Ac)16]}3·24CH3CN·23H2O (Ln = Eu(III) 1, Tb(III) 2, and Yb(III) 3). The compounds are easily soluble in water and form a stable solution of the cluster aggregates (LnTOC-a). Therefore, nano-biocompatible TiO materals can be prepared from these LnTOCs just by dissolving them in water. The nanoscale aggregates in water solutions were characterized by SEI-MS, 1H NMR, XPS, IR, and EDS mapping. Using the EuTOC-a solution, excellent fluorescence sensor properties for biomolecule ascorbic acid were found. Furthermore, biocompatibility and fluorescent labeling properties of the EuTOC-a for HeLa cells were evaluated. The results indicated that water-soluble LnTOCs can be used to prepare biocompatible fluorescent Ln-Ti-O nanomaterials.


Assuntos
Materiais Biocompatíveis/química , Elementos da Série dos Lantanídeos/química , Nanoestruturas/química , Oxigênio/química , Titânio/química , Água/química , Células HeLa , Humanos , Tamanho da Partícula , Solubilidade
2.
Inorg Chem ; 58(20): 13933-13944, 2019 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-31566371

RESUMO

Density functional vibrational frequency calculations have been performed on eight geometry optimized cytochrome c oxidase (CcO) dinuclear center (DNC) reaction cycle intermediates and on the oxymyoglobin (oxyMb) active site. The calculated Fe-O and O-O stretching modes and their frequency shifts along the reaction cycle have been compared with the available resonance Raman (rR) measurements. The calculations support the proposal that in state A[Fea33+-O2-•···CuB+] of CcO, O2 binds with Fea32+ in a similar bent end-on geometry to that in oxyMb. The calculations show that the observed 20 cm-1 shift of the Fea3-O stretching mode from the PR to F state is caused by the protonation of the OH- ligand on CuB2+ (PR[Fea34+═O2-···HO--CuB2+] → F[Fea34+═O2-···H2O-CuB2+]), and that the H2O ligand is still on the CuB2+ site in the rR identified F[Fea34+═O2-···H2O-CuB2+] state. Further, the observed rR band at 356 cm-1 between states PR and F is likely an O-Fea3-porphyrin bending mode. The observed 450 cm-1 low Fea3-O frequency mode for the OH active oxidized state has been reproduced by our calculations on a nearly symmetrically bridged Fea33+-OH-CuB2+ structure with a relatively long Fea3-O distance near 2 Å. Based on Badger's rule, the calculated Fea3-O distances correlate well with the calculated νFe-O-2/3 (νFe-O is the Fea3-O stretching frequency) with correlation coefficient R = 0.973.


Assuntos
Teoria da Densidade Funcional , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Ferro/química , Oxigênio/química , Biocatálise , Domínio Catalítico , Cristalografia por Raios X , Complexo IV da Cadeia de Transporte de Elétrons/química , Ferro/metabolismo , Ligantes , Modelos Moleculares , Oxigênio/metabolismo , Vibração
3.
Chem Rec ; 19(9): 2044-2057, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31483089

RESUMO

This review covers the characteristics of pyrolysis and catalytic pyrolysis bio-oils by focusing on the fundamental factors that determine bio-oil upgradability. The abundant works on the subject of bio-oil production from lignocellulosic biomass were studied to establish the essential attributes of the bio-oils for assessment of the oil stability and upgradability. Bio-oils from catalytic pyrolysis processes relating to catalysts of different compositions and structures are discussed. A general relationship between the higher heating value and the oxygen content in the catalytic pyrolysis oils exists, but this relationship does not apply to the thermal pyrolysis oil. Reporting bio-oil yield is meaningful only when the oxygen content of the oil is measured because the pyrolytic oil stability is mainly determined by the oxygen content. Isoenergy plot that associates bio-oil yield with oxygen content is presented and discussed.


Assuntos
Biomassa , Lignina/química , Óleos Vegetais/química , Catálise , Oxigênio/química , Plantas/química , Pirólise
4.
Chemosphere ; 235: 1146-1153, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561305

RESUMO

Waste is a misplaced resource. Herein, anionic (orange II sodium salt and Ponceau 2R) and cationic (Rhodamine B and Methylene blue) dye wastewater assisted photo-treatment (referred as DAPT) method was developed to modify sol-gel synthesized CeO2-TiO2 (CeTi) mixed oxide catalyst. Catalytic activity test results showed that both anionic and cationic dye wastewater could be used as "fuel" of photo-treatment to enhance the activity of CeTi catalyst in NO reduction and dichloromethane oxidation. Characterization and DFT calculation results revealed that DAPT process increased the amount of Ce3+ ions on CeTi samples, which could induce the formation of Ce-VO-Ti (oxygen vacancy (VO) in Ce-O-Ti short range structure). These Ce-VO-Ti defects not only could be adsorption sites for NH3, dichloromethane and oxygen, but also promoted the redox shift of Ce3++ Ti4+ ⇋ Ce4++ Ti3+ by enhancing the oxidizability of Ce4+ and Ti4+ species. Furthermore, defects changed the polarity of Ce-O and Ti-O, which was conducive to the activation of lattice oxygen. All these improvements contributed to the excellent catalytic activity of CeTi catalysts. We expected this work to be instructive on constructing structure-activity over CeO2-TiO2 based catalysts and utilizing dye wastewater.


Assuntos
Cério/química , Cloreto de Metileno/química , Óxido Nítrico/química , Titânio/química , Águas Residuárias/química , Adsorção , Catálise , Corantes , Oxirredução , Oxigênio/química
5.
J Agric Food Chem ; 67(39): 10823-10831, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31487159

RESUMO

The development of technology to improve the mineralization of organic fertilizer and to enhance crop production is essential to achieve the transition from traditional farming to eco-friendly organic farming. Nanobubble oxygation (NB) was employed for comparison with traditional pump-aerated oxygation (AW) and a control group through both soil incubation and soil column experiments. Plant-available N and P contents in the NB treatment group were higher than those in the AW and control groups. Enzymatic activities including ß-1,4-N-acetyl-glucosaminidase, phosphatase, α-1,4-glucosidase, ß-1,4-xylosidase, peroxidase, and phenol oxidase were significantly higher in both oxygation groups compared with the control. The soil microbial biomass, activity, and diversity were also significantly improved due to the oxygation treatment. Additionally, the microbial metabolic functions were shifted in both oxygation treatments compared with the control group. The final tomato yield increase from the NB treatment group was 23%, and that from the AW treatment was 17%, compared with the control.


Assuntos
Lycopersicon esculentum/crescimento & desenvolvimento , Lycopersicon esculentum/metabolismo , Nanotecnologia/métodos , Oxigênio/metabolismo , Produção Agrícola , Lycopersicon esculentum/enzimologia , Oxigênio/química , Proteínas de Plantas/metabolismo , Solo/química , Microbiologia do Solo
6.
Phys Chem Chem Phys ; 21(37): 20840-20848, 2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31517382

RESUMO

The room temperature pump-probe X-ray free electron laser (XFEL) measurements used for serial femtosecond crystallography provide remarkable information about the structures of the catalytic (S-state) intermediates of the oxygen-evolution reaction of photosystem II. However, mixed populations of these intermediates and moderate resolution limit the interpretation of the data from current experiments. The S3 XFEL structures show extra density near the OEC that may correspond to a water/hydroxide molecule. However, in the latest structure, this additional oxygen is 2.08 Šfrom the Oε2 of D1-E189, which is closer than the sum of the van der Waals radii of the two oxygens. Here, we use Boltzmann statistics and Monte Carlo sampling to provide a model for the S2-to-S3 state transition, allowing structural changes and the insertion of an additional water/hydroxide. Based on our model, water/hydroxide addition to the oxygen-evolving complex (OEC) is not thermodynamically favorable in the S2g = 2 state, but it is in the S2g = 4.1 redox isomer. Thus, formation of the S3 state starts by a transition from the S2g = 2 to the S2g = 4.1 structure. Then, electrostatic interactions support protonation of D1-H190 and deprotonation of the Ca2+-ligated water (W3) with proton loss to the lumen. The W3 hydroxide moves toward Mn4, completing the coordination shell of Mn4 and favoring its oxidation to Mn(iv) in the S3 state. In addition, binding an additional hydroxide to Mn1 leads to a conformational change of D1-E189 in the S2g = 4.1 and S3 structures. In the S3 state a fraction of D1-E189 release from Mn1 and bind a proton.


Assuntos
Modelos Químicos , Oxigênio/química , Complexo de Proteína do Fotossistema II/química , Termodinâmica
7.
Phys Chem Chem Phys ; 21(35): 19226-19233, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31441492

RESUMO

As one of the main air pollutants, nitrogen oxides (NOx) have serious effects on human health and the environment. In our previous study, we found that Mn-MOF-74 shows excellent catalytic performance for the selective catalytic reduction (SCR) reaction with NH3 being the reductant (NH3-SCR) at low temperature. To obtain a further understanding of the NH3-SCR mechanism in Mn-MOF-74, in this paper, we investigated two important parts of the NH3-SCR process in Mn-MOF-74 using the density functional theory (DFT) method. On the one hand, the structural characteristics of two types of oxygen vacancies of Mn-MOF-74, namely carboxyl oxygen vacancies and hydroxyl oxygen vacancies, and their adsorption properties to reaction species were calculated. It was found that the oxygen vacancies not only activate the reaction species, but also promote the desorption of NO2 molecules from metal sites for the subsequent rapid SCR reactions. On the other hand, we studied the effect of H2O on the structural stability and catalytic performance of Mn-MOF-74. It was found that the interaction of Mn-O bonds was weakened by H2O. Therefore, the influence of H2O should be considered for the future design of MOF-based catalysts for the SCR process.


Assuntos
Teoria da Densidade Funcional , Estruturas Metalorgânicas/química , Oxigênio/química , Água/química , Poluentes Atmosféricos/química , Poluentes Atmosféricos/isolamento & purificação , Catálise , Óxidos de Nitrogênio/química , Óxidos de Nitrogênio/isolamento & purificação , Substâncias Redutoras/química
8.
Phys Chem Chem Phys ; 21(35): 19480-19487, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31461090

RESUMO

The deoxygenation reaction of m-benzenediol (resorcinol), an important lignin model compound, was studied in a hot microreactor. We revealed three decomposition channels by detecting elusive and reactive intermediates and product isomers selectively and found that resorcinol, similarly to catechol (o-benzenediol) and hydroquinone (p-benzenediol), (i) gets decarbonylated to yield hydroxycyclopentadiene. Additionally, (ii) decarboxylation (CO2 loss) yields C5H6 species in a retro-Diels-Alder reaction from a lactone species. Only acyclic products are detected at lower reactor temperatures and the most stable C5H6 isomer, cyclopentadiene (c-C5H6), is only observed at higher temperatures. Finally, (iii) two reactive ketene species, ethenone and buta-1,3-dienal, were observed in a third reaction channel. Both decarboxylation and ketene formation channels are unique among benzenediols for the meta-isomer, resorcinol. We have explored the resorcinol potential energy surface to rationalize the observed reactions. These findings may help to understand the source of ketenes in catalytic lignin depolymerization and give new insight into isomer-specific deoxygenation processes.


Assuntos
Dióxido de Carbono/síntese química , Etilenos/síntese química , Cetonas/síntese química , Resorcinóis/química , Reação de Cicloadição , Isomerismo , Oxigênio/química , Temperatura Ambiente
9.
Chemistry ; 25(58): 13285-13289, 2019 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-31441974

RESUMO

A calix[4]arene ligand, in which two of the phenol functions are replaced by pyrazole units has been employed to mimic the His2 -Tyr2 (His: histidine, Tyr: tyrosine) ligand sphere within the active site of the galactose oxidase (GO). The calixarene backbone forces the corresponding copper(II) complex into a see-saw-type structure, which is hitherto unprecedented in GO modelling chemistry. It undergoes a one-electron oxidation that is centered at the phenolate donor leading to a copper-coordinated phenoxyl radical like in the GO. Accordingly, the complex was tested as a functional model and indeed proved capable of oxidizing benzyl alcohol to the respective aldehyde using two phenoxyl-radical equivalents as oxidants. Finally, the results show that the calixarene platform can be utilized to arrange donor functions to biomimetic binding pockets that allow for the creation of novel types of model compounds.


Assuntos
Calixarenos/química , Galactose Oxidase/química , Oxigênio/química , Aldeídos/química , Sequência de Aminoácidos , Catálise , Domínio Catalítico , Complexos de Coordenação/química , Cobre/química , Técnicas Eletroquímicas/métodos , Ligantes , Modelos Moleculares , Estrutura Molecular , Níquel/química , Oxirredução , Fenóis/química , Ligação Proteica , Zinco/química
10.
J Food Sci ; 84(9): 2507-2519, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31432530

RESUMO

Metal oxide coated multilayered polymeric pouches provide a suitable alternative to foil-based packaging for shelf-stable products with extended shelf-life. The barrier performance of these films depends upon the integrity of the metal oxide coating which can develop defects as a result of thermal processing and improper handling. In this work, we developed a methodology to visually identify these defects using an oxygen-sensitive model gel system. Four pouches with different metal oxide coatings: MOA (Coated PET), MOB (SiOx -coated PET), MOC (Overlayer-AlOx -Organic-coated PET), MOD (Overlayer-SiOx -coated PET) were filled with water and retort-processed for 30 and 40 min at 121 °C. After processing, the pouches were cut open, dried and subsequently filled with a gel containing methylene blue that changes color in the presence of oxygen. The pouches were then stored at 23 and 40 °C for 180 and 90 days, respectively. Defects were identified by observing the localized color change from yellow to blue in the packaged gel. These observations were confirmed through measurement of oxygen and water vapor transmission rates, as well as SEM and CLSM analyses. The MOC pouches showed the least change in barrier properties after thermal processing. This was due to crosslinking in the organic coating and protection provided by the overlayer. The melting enthalpy of all films increased significantly (P < 0.05) after sterilization. This may increase the brittleness of the substrates after processing. Findings may be used to improve the barrier performance of metal oxide coated polymeric films intended for food packaging applications. PRACTICAL APPLICATION: In this study, we developed a methylene blue-based, oxygen-sensitive model gel system to identify defects in metal oxide coated polymeric structures induced by thermal processing and mechanical stresses. We also performed a comprehensive analysis of these defects through CLSM and SEM. The gel system and methodology developed may be useful in the design and development of high barrier metal oxide coated films.


Assuntos
Técnicas de Química Analítica/métodos , Embalagem de Alimentos/instrumentação , Géis/química , Metais/química , Oxigênio/química , Polímeros/química , Cor , Óxidos/química , Vapor/análise
11.
Bioelectrochemistry ; 130: 107335, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31400569

RESUMO

High carbon catalyst loadings are commonly used for the catalyst layer (CL) in air-cathodes to obtain a performance comparable with that using platinum. This results in a much thicker CL, which severely limits mass transfer. In this study, we developed a porosity-gradient CL to passively enhance mass transfer in the air-cathode of microbial fuel cells (MFCs) for the first time. Computational results demonstrated that a cathode CL with increasing porosity (CL-IP) and decreasing porosity (CL-DP) from the water to the air-facing side exhibited improved transport of oxygen and OH-, respectively, alleviating concentration overpotentials in the CL. Experimental results also showed that an MFC that included a cathode with CL-IP achieved a maximum power density of 1781 ±â€¯92 mW m-2, which was higher than that achieved with CL-DP and a homogeneous CL (1614 ±â€¯72 and 1183 ±â€¯205 mW m-2).


Assuntos
Fontes de Energia Bioelétrica , Ar/análise , Fontes de Energia Bioelétrica/economia , Carbono/química , Catálise , Simulação por Computador , Eletrodos , Desenho de Equipamento , Oxigênio/química , Porosidade , Água/química
12.
Food Chem ; 301: 125287, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31387048

RESUMO

The surface browning usually occurs on fresh-cut potato during storage. The effect of short-time high oxygen pretreatment on anti-browning of fresh-cut potato slices was investigated. The whole potato tubers were firstly immersed in the oxygen concentration of 21%, 60% and 80% for 20 min. Then, the potatoes were peeled, cut and stored at 4 °C for 8 days. The results showed that the short-time 80% oxygen pretreatment possessed significantly anti-browning effect by retarding the increase of polyphenol oxidase (PPO) activity and the accumulation of malondialdehyde (MDA) content, maintaining the cell integrity. Meanwhile, the 80% oxygen treatment could increase the activities of phenylalanine ammonia lyase (PAL) and peroxidase (POD), and the total phenolic content. Importantly, the 80% oxygen treatment could effectively improve the antioxidant capacity. Overall, all results suggest that the short-time high oxygen pretreatment holds great promise on anti-browning of fresh-cut potato.


Assuntos
Catecol Oxidase/metabolismo , Manipulação de Alimentos , Oxigênio/química , Peroxidase/metabolismo , Fenilalanina Amônia-Liase/metabolismo , Solanum tuberosum/enzimologia , Antioxidantes/análise , Malondialdeído/análise , Oxirredução , Oxigênio/farmacologia , Fenóis/metabolismo , Tubérculos/efeitos dos fármacos , Tubérculos/enzimologia , Solanum tuberosum/efeitos dos fármacos
13.
Chemphyschem ; 20(19): 2451-2460, 2019 10 02.
Artigo em Inglês | MEDLINE | ID: mdl-31365183

RESUMO

Computer simulation studies of the molecular basis for ligand migration in proteins allow the description of key events such as the transition between docking sites, displacement of existing ligands and solvent molecules, and open/closure of specific "gates", among others. In heme proteins, ligand migration from the solvent to the active site preludes the binding to the heme iron and triggers different functions. In this work, molecular dynamics simulations, a Markov State Model of migration and empirical kinetic equations are combined to study the migration of O2 and NO in two truncated hemoglobins of Mycobacterium tuberculosis (Mt-TrHbN and Mt-TrHbO). For Mt-TrHbN, we show that the difference in the association constant in the oxy and deoxy states relies mainly in the displacement of water molecules anchored in the distal cavity in the deoxy form. The results here provide a valuable approach to study ligand migration in globins.


Assuntos
Hemoglobinas/química , Cadeias de Markov , Simulação de Dinâmica Molecular , Sítios de Ligação , Cinética , Ligantes , Mycobacterium tuberculosis/química , Óxido Nítrico/química , Oxigênio/química
14.
Phytochemistry ; 166: 112056, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31302342

RESUMO

The chemical investigation of the wheat plant pathogen Parastagonospora nodorum SN15 led to the purification of seven highly oxygenated acetylenic cyclohexanoids named stagonosporynes A-G. Their structures were determined on the basis of extensive NMR and the relative and absolute configurations by an array of computational methods including simulation of NOESY spectrum and electronic circular dichroism (ECD). All compounds were evaluated for their herbicidal activity and stagonosporyne G displayed the most significant herbicidal activity.


Assuntos
Ascomicetos/química , Cicloexanóis/química , Oxigênio/química , Prenilação , Modelos Moleculares , Conformação Molecular
15.
Bioresour Technol ; 291: 121859, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31362200

RESUMO

The adsorption mechanisms of Pb(II) and Cd(II) in aqueous solution using camellia seed husk biochars pyrolyzed at different temperatures were studied. The adsorption of Pb(II) and Cd(II) on biochars are mainly controlled by ion exchange, oxygen functional groups (OFGs) complexation, Pb(II)/Cd(II)-π interactions, and precipitation with minerals. Compared to the raw biochars, both carboxyl and phenolic hydroxyl groups increased in the biochars washed with HCl. However, the previous research ignored the effect of the increased OFGs. Thus, a revised method was proposed from this study to more accurately calculate the contribution of four different mechanisms. Precipitation with minerals was the dominant mechanism for Pb(II) and Cd(II) removal, accounting for 80.61-89.03% and 53.57-75.84%, respectively, of the total adsorption as the pyrolysis temperature increased from 300 °C to 700 °C. As for oxygen functional groups complexation, the percentage of Pb(II) and Cd(II) removal were 4.76-8.55% and 11.34-29.59%, respectively.


Assuntos
Cádmio/química , Carvão Vegetal/química , Ácido Clorídrico/química , Chumbo/química , Oxigênio/química , Adsorção , Temperatura Alta , Oxirredução , Pirólise
16.
Chem Commun (Camb) ; 55(62): 9108-9111, 2019 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-31298230

RESUMO

Inhibition of myostatin is an attractive treatment for muscular dystrophy and other amyotrophic diseases. A myostatin-binding peptide was functionalized by equipped with an on/off switchable photo-oxygenation catalyst. This peptide induces a selective oxygenation of myostatin under near-infrared light, resulting in inactivation of myostatin. This peptide shows several orders of magnitude greater inhibitory effect than the original peptide.


Assuntos
Miostatina/efeitos dos fármacos , Miostatina/efeitos da radiação , Oxigênio/química , Oxigênio/efeitos da radiação , Peptídeos/farmacologia , Processos Fotoquímicos/efeitos da radiação , Catálise/efeitos dos fármacos , Catálise/efeitos da radiação , Humanos , Raios Infravermelhos , Modelos Moleculares , Estrutura Molecular , Miostatina/metabolismo , Peptídeos/química
17.
Inorg Chem ; 58(15): 9557-9561, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31313577

RESUMO

An iron(III) methoxide complex reacts with para-substituted triarylmethyl radicals to give iron(II) and methoxyether products. Second-order rate constants for the radical derivatives were obtained. Hammett and Marcus plots suggest the radical transfer reactions proceed via a concerted process. Calculations support the concerted nature of these reactions involving a single transition state with no initial charge transfer. These findings have implications for the radical "rebound" step invoked in nonheme iron oxygenases, halogenases, and related synthetic catalysts.


Assuntos
Compostos Férricos/metabolismo , Compostos Ferrosos/metabolismo , Oxirredutases/metabolismo , Oxigênio/metabolismo , Oxigenases/metabolismo , Biocatálise , Compostos Férricos/química , Compostos Ferrosos/química , Estrutura Molecular , Oxirredutases/química , Oxigênio/química , Oxigenases/química
18.
Environ Sci Pollut Res Int ; 26(25): 26134-26145, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31280443

RESUMO

Nitrous acid (HONO) is an important atmospheric pollutant that can strongly absorb ultraviolet irradiation in the region of 300-400 nm, as previously reported. Since the solar irradiance that reaches the surface of the earth has wavelengths greater than 290 nm, the photodissociation of HONO is considered the major method of hydroxyl radical formation in the troposphere. Thus, the photoinduced chemical reactivity of HONO is important. The present work investigated the reaction mechanism and kinetic parameters of HONO and sulfamethazine by using a laser flash photolysis technique and liquid chromatography-mass spectrometry. The results indicated that the sulfamethazine degradation rate was influenced by the HONO concentration and the initial concentration of sulfamethazine. Hydroxyl radicals derived from the photolysis of HONO attacked the aromatic ring of sulfamethazine to form sulfamethazine-OH adducts with a second-order rate constant of (3.8 ± 0.3) × 109 L mol-1 s-1. This intermediate would then react with HO· and oxygen molecules. The reaction rate constants of sulfamethazine-OH adducts with oxygen are (1.3 ± 0.1) × 107 L mol-1 s-1. The generation of sulfanilic acid and pyrimidine implies that the breaking down of S-N bonds of sulfamethazine and its HO adducts probably occur at the same time.


Assuntos
Radical Hidroxila/química , Ácido Nitroso/química , Oxigênio/química , Sulfametazina/química , Cinética , Fotólise , Raios Ultravioleta , Água/química
19.
Phys Chem Chem Phys ; 21(28): 15478-15486, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31259327

RESUMO

Complex chemical and biochemical systems are susceptible to damage from ionising radiation. However, questions remain over the extent to which such damage is influenced by the nature of the surrounding chemical environment, which can consist of both hydrophobic and hydrophilic domains. To gain fundamental insight into the first crucial mechanistic steps of radiation damage in such systems, we need to understand the initial radiation response, i.e. dynamics occurring on the same timescale as electronic relaxation, which occur in these different environments. Amphiphilic molecules contain both hydrophobic and hydrophilic domains, but the propensity for charge delocalisation and proton dynamics to occur in these different domains has been largely unexplored so far. Here, we present carbon and oxygen 1s Auger spectra for liquid methanol, one of the simplest amphiphilic molecules, as well as its fully deuterated equivalent d4-methanol, in order to explore X-ray induced charge delocalisation and proton dynamics occurring on the few femtosecond timescale. Unexpectedly, we find a similar propensity for proton dynamics to occur at both the carbon and oxygen site within the lifetime of the core hole. Our results could serve as a model for decay processes that are likely to occur in other more complex amphiphilic systems.


Assuntos
Metanol/química , Metanol/efeitos da radiação , Raios X , Carbono/química , Oxigênio/química , Prótons
20.
Food Chem ; 299: 125172, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31325716

RESUMO

The composition of inorganic elements is a key factor in determining the quality of fruit wines. However, the use of direct sample injection is challenging for multi-elemental analysis of fruit wine samples. In this paper, an analytical method using inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) was established for determining multiple elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Hg, and Pb) in fruit wine. The fruit wine was diluted using ultrapure water and acidified with nitric acid before injecting into the ICP-MS/MS. Spectral interferences in the complex matrix composition of different fruit wine samples, in the MS/MS mode, were eliminated using mixed reaction gases of O2/H2 and NH3/He/H2 through the mass shift and on-mass methods. The limits of detection ranged from 0.41 to 58.1 ng L-1. This study demonstrates a new approach for multi-elemental analysis in fruit wine with great convenience and high accuracy.


Assuntos
Análise de Alimentos/métodos , Espectrometria de Massas em Tandem/métodos , Oligoelementos/análise , Vinho/análise , Amônia/química , Frutas , Gases/química , Hidrogênio/química , Ácido Nítrico/química , Oxigênio/química
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