RESUMEN
Kinetic studies of the reaction of ethyl glycolate HOCH2C(O)OCH2CH3 with OH radicals (kOH) and Cl atoms (kCl) have been conducted by the relative method using a glass atmospheric reactor by "in situ" Fourier Transform Infrared (FTIR) and Gas Chromatography equipped with flame ionization detection by Solid Phase Micro Extraction (GC-FID/SPME) at room temperature and atmospheric pressure. The following relative rate coefficients were determined using several reference compounds and two different techniques: kEG + OH-FTIR = (4.36 ± 1.21) × 10-12; kEG + OH-GC-FID= (3.90 ± 0.74) × 10-12; and kEG + Cl-GC-FID= (6.40 ± 0.72) × 10-11 all values in units of cm3.molecule-1.s-1. Complementary product studies were performed under comparable conditions to the kinetic tests, in order to identify the reaction products and to postulate their tropospheric oxidation mechanisms. The reaction of OH radicals and Cl atoms with ethyl glycolate initiates via H-atom abstraction from alkyl groups of the molecule. Formic acid was positively identified as a reaction product by FTIR. On the other hand, formaldehyde, acetaldehyde, glycolic acid; and formic acid were identified by the GC-MS technique. The Structure-Activity Relationship, (SAR) calculations were also implemented to estimate the more favorable reaction pathways and compare them with the products identified. Tropospheric lifetimes of τOH = 34 h and τCl = 5.5 days were estimated to determine how these investigated reactions might affect the air quality. In this sense, average ozone production of [O3] = 0.75 and a Photochemical Ozone Creation Potential, POCP, of 38 were calculated for the hydroxyl ester studied.
Asunto(s)
Ésteres , Ozono , Ésteres/química , Cloro/química , Cinética , Ozono/análisis , Glicolatos , Radical Hidroxilo/químicaRESUMEN
A product study was performed for the reaction of γ-caprolactone (GCL) and γ-heptalactone (GHL) initiated by OH radicals at (298 ± 2) K and atmospheric pressure, in presence of NOx. The identification and quantification of the products were performed in a glass reactor coupled with in situ FT-IR spectroscopy. The following products were identified and quantified with the corresponding formation yields (in %) for the OH + GCL reaction: peroxy propionyl nitrate (PPN) (52 ± 3), peroxy acetyl nitrate (PAN) (25 ± 1), and succinic anhydride (48 ± 2). For the GHL + OH reaction, the products detected with their corresponding formation yields (in %) were the following: peroxy n-butyryl nitrate (PnBN) (56 ± 2), peroxy propionyl nitrate (PPN) (30 ± 1) and succinic anhydride and (35 ± 1). Upon these results, an oxidation mechanism is postulated for the title reactions. The positions with the highest H-abstraction probabilities for both lactones are analyzed. Specifically, the increased reactivity of the C5 site, as indicated by structure reactivity estimations (SAR), is suggested by the identified products. For both GCL and GHL degradation appears to follow degradation paths including ring preservation and opening. The atmospheric implications of the APN formation as a photochemical pollutant and as NOx reservoirs of species is assessed.
Asunto(s)
Radical Hidroxilo , Anhídridos Succínicos , Espectroscopía Infrarroja por Transformada de Fourier , Radical Hidroxilo/química , Nitratos , Presión Atmosférica , Lactonas , Compuestos OrgánicosRESUMEN
The main causes of food spoilage come from the process of oxidation and the contamination by microorganisms. For the purpose of increasing food shelf-life the industries employ different techniques, being the addition of preservatives, one of the most used. The aim of this contribution was to investigate the potential antioxidant properties of tyrosol (4-hydroxyphenethyl alcohol, 4-OH) and tyrosol derived isomers (2-hydroxyphenethyl alcohol, 2-OH and 3-hydroxyphenethyl alcohol, 3-OH) against reactive oxygen species (ROS) and the antimicrobial effect on Staphylococcus aureus and Escherichia coli. Furthermore, the type of antioxidant effect of substrates and commercial antioxidants mixtures was studied. Upon visible-light, the substrates interacted with the vitamin B2 and different ROS were generated. All the compounds deactivated O2(1Δg) and O2â-, whereas only 2-OH and 3-OH inhibited H2O2 and HOâ. The substrates exhibited a synergistic antioxidant effect when combined with commercial antioxidants. 2-OH showed antimicrobial activity against strains tested.
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Aditivos Alimentarios/farmacología , Alcohol Feniletílico/análogos & derivados , Riboflavina/farmacología , Antiinfecciosos/química , Antiinfecciosos/farmacología , Antioxidantes/química , Antioxidantes/farmacología , Sinergismo Farmacológico , Peróxido de Hidrógeno/química , Radical Hidroxilo/química , Alcohol Feniletílico/química , Alcohol Feniletílico/farmacologíaRESUMEN
Isoprene is the dominant non-methane organic compound emitted to the atmosphere1-3. It drives ozone and aerosol production, modulates atmospheric oxidation and interacts with the global nitrogen cycle4-8. Isoprene emissions are highly uncertain1,9, as is the nonlinear chemistry coupling isoprene and the hydroxyl radical, OH-its primary sink10-13. Here we present global isoprene measurements taken from space using the Cross-track Infrared Sounder. Together with observations of formaldehyde, an isoprene oxidation product, these measurements provide constraints on isoprene emissions and atmospheric oxidation. We find that the isoprene-formaldehyde relationships measured from space are broadly consistent with the current understanding of isoprene-OH chemistry, with no indication of missing OH recycling at low nitrogen oxide concentrations. We analyse these datasets over four global isoprene hotspots in relation to model predictions, and present a quantification of isoprene emissions based directly on satellite measurements of isoprene itself. A major discrepancy emerges over Amazonia, where current underestimates of natural nitrogen oxide emissions bias modelled OH and hence isoprene. Over southern Africa, we find that a prominent isoprene hotspot is missing from bottom-up predictions. A multi-year analysis sheds light on interannual isoprene variability, and suggests the influence of the El Niño/Southern Oscillation.
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Atmósfera/química , Butadienos/análisis , Butadienos/química , Mapeo Geográfico , Hemiterpenos/análisis , Hemiterpenos/química , Imágenes Satelitales , África , Australia , Brasil , Conjuntos de Datos como Asunto , El Niño Oscilación del Sur , Formaldehído/química , Radical Hidroxilo/análisis , Radical Hidroxilo/química , Ciclo del Nitrógeno , Óxidos de Nitrógeno/análisis , Óxidos de Nitrógeno/química , Oxidación-Reducción , Estaciones del Año , Sudeste de Estados UnidosRESUMEN
Fish by-products are excellent sources of collagen. Acid-soluble collagen (ASC) derived from a mixed by-product of different fish species was hydrolyzed to obtain peptide fractions and evaluate their biological and functional activities. All fractions obtained (F1: ≥30, F2: 10-30, F3: 5-10, F4: 1-5, and F5: ≤1kDa) exhibited antioxidant activity at concentrations of 5, 10, and 15 mg/mL. However, F5 registered the highest reducing power (absorbance 0.366) and hydroxyl-radical-scavenging activity (91%) at 15 mg/mL; whereas the highest DPPH scavenging activity (81%) was also detected in F5 at 5 mg/mL. The solubility of F1, F2, and F3 was ≥ 95% at pH 7. The highest foaming capacity (78%), foaming stability (60%), and emulsion stability index (42 min) were registered for F1. However, the highest emulsifying activity index (130 m2/g) was for F3. These results place collagen obtained from a mixed by-product of different fish species as a potential biotechnological alternative for the industry.
Asunto(s)
Antioxidantes/farmacología , Colágeno/química , Productos Pesqueros , Proteínas de Peces/química , Péptidos/química , Péptidos/farmacología , Aminoácidos/análisis , Animales , Antibacterianos/química , Antibacterianos/farmacología , Antioxidantes/química , Emulsionantes/química , Proteínas de Peces/farmacología , Depuradores de Radicales Libres/química , Concentración de Iones de Hidrógeno , Hidrólisis , Radical Hidroxilo/química , Hidrolisados de Proteína/química , SolubilidadRESUMEN
It has previously been established during the elimination of organic matter that the addition of sodium dodecyl sulfate in solution is an important condition in the electrochemical oxidation approach that allows to increase the production of persulfate, enhancing the efficacy of the treatment. This outcome was observed when using the anodic oxidation with boron doped diamond (BDD), the extra production of persulfate was achieved after the SDS-sulfate released in solution and it reacts with hydroxyl radicals electrogenerated at BDD surface. However, this effect was not already tested by using active anodes. For this reason, the effect of sodium dodecyl sulfate (SDS) during the electrochemical treatment of caffeine was investigated by comparing non-active and active anodes performances. A significant decrease on the oxidation efficiency of caffeine was observed by using Ti/IrO2-Ta2O5 anode at high current density when SDS was added to the solution. Conversely, at BDD anode, the presence of SDS enhanced the degradation efficiency, depending on the applied current density. This behavior is mainly due to the degradation of SDS molecules, which allows to increase the amount of sulfate in solution, promoting the production of persulfate via the mechanism involving hydroxyl radicals when BDD is used. Meanwhile, no oxidation improvements were observed when Ti/IrO2-Ta2O5 anode was employed, limiting the caffeine oxidation. Results clearly showed that the surfactant concentration had little influence on the degradation efficiency, but this result is satisfactory for the BDD system, since it demonstrates that effluents with complex matrices containing surfactants could be effectively degraded using the electrooxidation technique. Degradation mechanisms were explained by electrochemical measurements (polarization curves) as well as the kinetic analysis. Costs and energy consumption were also evaluated.
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Cafeína/química , Electrodos , Dodecil Sulfato de Sodio/química , Contaminantes Químicos del Agua/química , Boro/química , Diamante/química , Radical Hidroxilo/química , Cinética , Oxidación-Reducción , Sulfatos/química , TitanioRESUMEN
In this work, experimental conditions were established to fabricate self-ordered rutile-TiO2 nanotube arrays, coated with a conformal anatase-TiO2 thin layer using atomic layer deposition. E. coli inactivation tests showed a considerable increase in photocatalytic activity using rutile-TiO2 nanotubes coated with anatase-TiO2 compared to that using single rutile or anatase TiO2 nanotubes only. Photocatalytic hydroxyl radical generation rates (determined by pNDA bleaching) were also meaningfully enhanced for the combined anatase/rutile TiO2 nanostructures. Therefore, we show that it is possible to take advantage of the morphological properties of the materials and the synergic effect from the combination of both TiO2 polymorphs during the design of novel materials, which could be used as antibacterial agents to improve the quality of drinking water.
Asunto(s)
Antibacterianos/farmacología , Escherichia coli/efectos de los fármacos , Nanotubos/química , Titanio/farmacología , Antibacterianos/química , Catálisis , Radical Hidroxilo/síntesis química , Radical Hidroxilo/química , Pruebas de Sensibilidad Microbiana , Procesos Fotoquímicos , Titanio/químicaRESUMEN
Heterogeneous electro-Fenton (HEF) is as an alternative to the conventional electro-Fenton (EF) process. HEF uses a solid phase catalyst, whereas EF employs a solubilized one. This implies that in HEF, material can be recovered through a simple separation process such as filtration or magnetic separation in HEF. HEF also has the advantage of not requires a previous pH adjustment, which facilitates working in a higher pH range. In this work, Fe, Cu and Fe/Cu bimetallic nanoparticles (Fe/Cu NPs) were synthesized, characterized and used for the degradation of Nafcillin (NAF). The effect of the adsorption and the anodic oxidation (AO-H2O2) process was tested to assess their influence on HEF. NAF adsorption did not exceed 24% of antibiotic removal and the AO-H2O2 process eliminated the total NAF after 240 min of electrolysis. Through the HEF process, the antibiotic was completely removed using Fe/Cu NPs after 7.0 min of electrolysis, while these NPs, mineralization reached 41% after 240 min. In this case, NAF degradation occurs mainly due to the generation of hydroxyl radicals in the BDD electrode, and the Fenton reaction with Fe and Cu NPs. The main organic intermediates produced during the degradation of NAF by HEF were identified allowing the proposal of degradation pathway. Finally, the antibiotic was also completely eliminated from a wastewater from slaughterhouse after 15 min of treatment by HEF and using Fe/Cu bimetallic NPs.
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Cobre/química , Peróxido de Hidrógeno/química , Hierro/química , Nanopartículas del Metal/química , Nafcilina/química , Antibacterianos/química , Catálisis , Técnicas Electroquímicas , Electrólisis/instrumentación , Electrólisis/métodos , Radical Hidroxilo/química , Oxidación-Reducción , Aguas Residuales/química , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/químicaRESUMEN
In this work, we studied the anthracene oxidation by hydroxyl radicals. Hydroxyl radical was generated by reaction of 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin Fe (III) (TPPFe) with hydrogen peroxide under visible radiation at a nitrogen atmosphere. The TPPFe was synthesized by Adler Method followed by metal complexation with Fe (III) chloride hexahydrate. Hydroxyl radical was detected by fluorescence emission spectroscopy and we studied kinetic of anthracene selective oxidation by hydroxyl radicals through the differential method. The TPPFe was characterized by UV-Vis spectrophotometry, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM) measurements. The results indicated that TPPFE was compound by micro-particles with a size distribution of around 2500 nm. Kinetic results showed that the apparent rate constant for the oxidation of anthracene increased exponentially on as temperature increases, furthermore, the activation energy for the Anthracene oxidation by hydroxyl radicals under visible irradiation was 51.3 kJ/mol. Finally, anthraquinone was the main byproduct generated after oxidation of anthracene by TPP-Fe under visible irradiation.
Asunto(s)
Antracenos/química , Radical Hidroxilo/química , Antracenos/efectos de la radiación , Dispersión Dinámica de Luz , Compuestos Férricos/síntesis química , Compuestos Férricos/química , Peróxido de Hidrógeno/química , Cinética , Luz , Microscopía Electrónica de Rastreo , Nitrógeno , Oxidación-Reducción , Porfirinas/síntesis química , Porfirinas/química , Porfirinas/efectos de la radiación , Espectrometría de FluorescenciaRESUMEN
The free radical nitric oxide (NOâ¢) exerts biological effects through the direct and reversible interaction with specific targets (e.g. soluble guanylate cyclase) or through the generation of secondary species, many of which can oxidize, nitrosate or nitrate biomolecules. The NOâ¢-derived reactive species are typically short-lived, and their preferential fates depend on kinetic and compartmentalization aspects. Their detection and quantification are technically challenging. In general, the strategies employed are based either on the detection of relatively stable end products or on the use of synthetic probes, and they are not always selective for a particular species. In this study, we describe the biologically relevant characteristics of the reactive species formed downstream from NOâ¢, and we discuss the approaches currently available for the analysis of NOâ¢, nitrogen dioxide (NO2â¢), dinitrogen trioxide (N2O3), nitroxyl (HNO), and peroxynitrite (ONOO-/ONOOH), as well as peroxynitrite-derived hydroxyl (HOâ¢) and carbonate anion (CO3â¢-) radicals. We also discuss the biological origins of and analytical tools for detecting nitrite (NO2-), nitrate (NO3-), nitrosyl-metal complexes, S-nitrosothiols, and 3-nitrotyrosine. Moreover, we highlight state-of-the-art methods, alert readers to caveats of widely used techniques, and encourage retirement of approaches that have been supplanted by more reliable and selective tools for detecting and measuring NOâ¢-derived oxidants. We emphasize that the use of appropriate analytical methods needs to be strongly grounded in a chemical and biochemical understanding of the species and mechanistic pathways involved.
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Radicales Libres/química , Óxido Nítrico/química , Oxidantes/química , Biología de Sistemas , Radicales Libres/metabolismo , Humanos , Radical Hidroxilo/química , Nitratos/química , Óxido Nítrico/genética , Oxidación-Reducción , Ácido Peroxinitroso/química , Especies de Nitrógeno Reactivo/química , Especies de Nitrógeno Reactivo/genéticaRESUMEN
The effect of a hydroxyl radical generating system (HRGS), which contained FeCl3, sodium ascorbate, and different concentrations of H2O2, on the physiochemical properties of myofibrillar protein (MP) from squid mantles, has been investigated. The effect of different exposure times to HRGS was also considered. Compared to non-oxidized MP, a significant (pâ¯<â¯0.05) increase in carbonyl content (more than 50% of its original content) and protein solubility, as well as in surface hydrophobicity, was observed in the oxidative MP. With different treatment times, a sharp decrease (pâ¯<â¯0.05) in sulfhydryl content was detected. In addition, hydroxyl radical treatment significantly reduced the MP gel's texture properties, whiteness and water holding capacity, especially at higher concentrations of H2O2. This observation could be attributed to extensive disorderly and less compact structure of MP gels. The results demonstrate the negative effect of HRGS on the structural and functional properties of MP from squid mantles.
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Decapodiformes/metabolismo , Proteínas de Mariscos/química , Animales , Ácido Ascórbico/química , Geles/química , Interacciones Hidrofóbicas e Hidrofílicas , Radical Hidroxilo/química , Oxidación-Reducción , Reología , Proteínas de Mariscos/metabolismo , Solubilidad , Compuestos de Sulfhidrilo/análisis , Agua/químicaRESUMEN
Coumestrol is a polyphenol with promising therapeutic applications as phytoestrogen, antioxidant and potential cancer chemoprevention agent. The presence of two hydroxyl groups on its chemical structure, with orientation analogous to estradiol, is responsible of both, its antioxidant capacity and its estrogenic activity. However, several studies show that the interaction of polyphenols with food and plasma proteins reduces their antioxidant efficacy. We studied the interaction of coumestrol with bovine serum albumin protein (BSA) by fluorescence spectroscopy and circular dichroism techniques, and the effect of this interaction on its antioxidant activity as a hydroxyl radical scavenger. In addition, coumestrol antioxidant capacity profile using different assays (DPPH, ORAC-FL and ORAC-EPR) was studied. To explain its reactivity we used several methodologies, including DFT calculations, to define its antioxidant mechanism. Coumestrol antioxidant activity unveiled interesting antioxidant properties. BSA interaction with coumestrol reduces significantly photolytic degradation in several media thus preserving its antioxidant properties. Results suggest no significant changes in BSA structure and activity when interacting with coumestrol. Furthermore, this interaction is stronger than for other phytoestrogens such as daidzein and genistein. Considering our promising results, we reported for the first time the fabrication and characterization of coumestrol-loaded albumin nanoparticles. The resulting spherical and homogeneous nanoparticles showed a diameter close to 96â¯nm. The coumestrol incorporation efficiency in BSA NPs was 22.4%, which is equivalent to 3 molecules of coumestrol for every 10 molecules of BSA.
Asunto(s)
Antioxidantes/química , Cumestrol/química , Portadores de Fármacos/química , Nanopartículas/química , Fitoestrógenos/química , Albúmina Sérica Bovina/química , Radical Hidroxilo/químicaRESUMEN
Iron-supported catalyst on granular activated carbon was prepared for its use in heterogeneous Fenton reaction coupled to an in situ H2O2 electro-generation. For this process, an electrolysis cell was employed, using carbon felt as cathode and graphite as anode. A solution of H2O2 (electrogenerated at a rate of 30â¯mgâ¯L-1 h-1) was obtained using a current intensity of 12â¯mA. In order to promote the decomposition of H2O2 to OH, a Carbon-Fe catalyst was used. This catalyst was prepared by incipient wet impregnation using FeSO4 as precursor salt to obtain samples with 9% wt of iron. Samples were characterized by EDX, FTIR and XPS spectroscopy before and after wastewater treatment using phenol as model molecule. Two iron oxidation states on the samples were found, Fe2+ and Fe3+. The ratio between Fe2+/Fe3+ was 1.29 which was later reduced to 0.92 after Fenton process; this might be associated with the metal oxidation (Fe2+ to Fe+3) occurring during Fenton-reaction, thus indicating that H2O2 decomposition was carried out by Fe2+ on carbon surface. Detection and quantification of hydroxyl radical were carried out by fluorescence spectroscopy, obtaining a radical concentration of 3.5⯵M in solution. Iron in solution were determined, showing a concentration of 0.1â¯mgâ¯L-1, making evident that the supported metal is stable and the reaction is carried out in a heterogeneous phase. Results showed an environmentally friendly process that can generate reagents in situ, with high efficiencies in the degradation of pollutants and minimizing the formation of toxic byproducts, which are common in conventional treatments.
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Carbón Orgánico/química , Restauración y Remediación Ambiental/métodos , Peróxido de Hidrógeno/química , Hierro/química , Aguas Residuales/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Catálisis , Electrodos , Electrólisis , Compuestos Férricos/química , Compuestos Ferrosos/química , Grafito/química , Radical Hidroxilo/química , Oxidación-Reducción , FenolRESUMEN
Ampicillin (AMP) is an antibiotic widely used in hospitals and veterinary clinics around the world for treating infections caused by bacteria. Therefore, it is common to find traces of this antibiotic in wastewater from these entities. In this work, we studied the mineralization of this antibiotic in solution as well as the elimination of its antimicrobial activity by comparing different electrochemical advanced oxidation processes (EAOPs), namely electro-oxidation with hydrogen peroxide (EO-H2O2), electro-Fenton (EF), and photo electro-Fenton (PEF). With PEF process, a high degradation, mineralization, and complete elimination of antimicrobial activity were achieved in 120-min electrolysis with high efficiency. In the PEF process, fast mineralization rate is caused by hydroxyl radicals (·OH) that are generated in the bulk, on the anode surface, by UV radiation, and most importantly, by the direct photolysis of complexes formed between Fe3+ and some organic intermediates. Moreover, some products and intermediates formed during the degradation of the antibiotic Ampicillin, such as inorganic ions, carboxylic acids, and aromatic compounds, were determined by photometric and chromatographic methods. An oxidation pathway is proposed for the complete conversion to CO2.
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Ampicilina/análisis , Antibacterianos/análisis , Técnicas Electroquímicas/métodos , Fotólisis , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos , Ampicilina/efectos de la radiación , Antibacterianos/efectos de la radiación , Electrodos , Peróxido de Hidrógeno/química , Radical Hidroxilo/química , Hierro/química , Oxidación-Reducción , Rayos Ultravioleta , Aguas Residuales/química , Contaminantes Químicos del Agua/efectos de la radiaciónRESUMEN
The synthetic hormone sodium levothyroxine (LTX) is one of the most prescribed drugs in the world and the most effective in hypothyroidism treatment. The presence of LTX in the environment has become a matter of major concern due to the widespread use of this hormone and by the fact that it is only partially removed in conventional water and sewage treatment plants. However, information regarding the photochemical fate of this hormone in environmental or engineered systems is scarce in the literature. In this work, the sunlight-driven direct and indirect LTX degradation was investigated by determining the photolysis quantum yield, ΦLTX = 3.80 (± 0.02) × 10-5, as well as the second-order kinetic constants of the reactions with hydroxyl radicals, kLTX,â¢OH = 1.50 (± 0.01) × 1010 L mol-1 s-1 and singlet oxygen, kLTX,1O2 = 1.47 (± 0.66) × 108 L mol-1 s-1. Mathematical simulations indicate that LTX photodegradation is favored in shallow, nitrite-rich, and dissolved organic matter (DOM)-poor environments, with LTX half-life times varying from less than 10 days to about 80 days. LTX removals of 85 and 95% were achieved by UVC photolysis and UVC/H2O2 after 120 min, respectively. Three transformation products, triiodothyronine, diiodothyronine, and diiodotyrosine, were identified during LTX degradation by the UVC-based processes studied. The results herein regarding photo-induced kinetics coupled with environmental fate simulations may help evaluate LTX persistence and also the design of water and wastewater treatment processes.
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Procesos Fotoquímicos , Tiroxina/química , Contaminantes Químicos del Agua/química , Biodegradación Ambiental , Diyodotironinas/química , Diyodotirosina/química , Peróxido de Hidrógeno/química , Radical Hidroxilo/química , Cinética , Modelos Teóricos , Fotólisis , Oxígeno Singlete/química , Luz Solar , Triyodotironina/química , Aguas Residuales/químicaRESUMEN
Feather hydrolysates were obtained through submerged cultivation of 50 g/L feathers with Chryseobacterium sp. kr6. Culture supernatants, displaying antioxidant properties, as evaluated by the 2,2'-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) radical scavenging method, were partially purified by gel-filtration chromatography. Fractions showing scavenging activity were pooled, lyophilized and tested at different concentrations (0.1-1.0 mg/mL) by the total reactive antioxidant potential (TRAP) method, showing promising antioxidant capacities. Antioxidant activities of the partially purified feather hydrolysate (PPFH; 24.5 µg) were demonstrated by its ability to scavenge hydroxyl radicals and to inhibit lipid peroxidation. In addition, PPFH (0.24-24.5 µg) was found to reduce ferric ion (Fe3+), but did not display Fe2+-chelating activity. Thus, the main antioxidant activities could be related to the donation of hydrogen atoms, electron transfer and scavenging of hydroxyl radicals. PPFH was analyzed by mass spectrometry and five peptides were identified and chemically synthesized. The antioxidant activity of one peptide LPGPILSSFPQ was confirmed by ABTS and TRAP. The structure of this keratin-derived bioactive peptide has not been previously described.
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Antioxidantes/química , Plumas/química , Queratinas/química , Péptidos/química , Hidrolisados de Proteína/química , Secuencia de Aminoácidos , Animales , Pollos , Depuradores de Radicales Libres/química , Radical Hidroxilo/química , Peroxidación de LípidoRESUMEN
In this work photo-electro-Fenton (PEF) processes using a dimensionally stable anode-gas diffusion electrode (DSA-GDE) system under light emission diodes (LED)-type radiation were used in the degradation of the angiotensin-II-receptor antagonists (ARA II), valsartan (VAL), and losartan (LOS), which are used in the treatment of hypertension diseases, and are considered among the emerging contaminants (ECs). Organic acids as citric, tartaric, and oxalic acids were used as complexing agents of iron ions in order to maintain the performance of the Fenton reaction at near-neutral pH value. The results show that at 3.42 mA/cm2 after 90 min of electro-Fenton (EF) treatment, degradation of 70% of VAL and 100% of LOS were observed. Total degradation of VAL and LOS was reached with a PEF process at the same time with mineralization of 30%. When citric and tartaric acids were used instead of oxalic acid, similar results were obtained, i.e., total degradation of both compounds, LOS and VAL, after 90 min of treatment. The degradation performance can be attributed to the increase of the initial dissolved iron in the system, facilitating the Fe3+/Fe2+ turnover in the catalytic photo-Fenton reaction and consequently, hydroxyl radical (â¢OH) production. In addition, the increased photo-activity of the complexes can be associated with their high capability to complex Fe3+ and to promote ligand-to-metal charge transfer, which is of key importance to feed Fe2+ to the Fenton process. The results show that the system evaluated was more efficient to eliminate sartan family compounds using LED lighting in comparison with traditional UV-A lamps used in this kind of work. Moreover, three transformation products of VAL degradation and two transformation products of LOS degradation were identified by high-resolution mass spectrometry (HRMS) using hybrid quadrupole-time-of-flight (QTOF) MS and, at the end of the PEF system, the several organic compounds accumulated and no mineralized were effectively treated in a subsequent aerobic biological system.
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Electrodos , Losartán/química , Valsartán/química , Contaminantes Químicos del Agua/química , Antihipertensivos/química , Antihipertensivos/metabolismo , Biodegradación Ambiental , Ácido Cítrico/química , Difusión , Peróxido de Hidrógeno/química , Concentración de Iones de Hidrógeno , Radical Hidroxilo/química , Hierro/química , Iluminación/instrumentación , Iluminación/métodos , Losartán/metabolismo , Oxidación-Reducción , Tartratos/química , Valsartán/metabolismo , Contaminantes Químicos del Agua/metabolismoRESUMEN
The purpose of this study was to investigate the aqueous phase photochemical behavior of enoxacin (ENO), an antibiotic selected as a model pollutant of emerging concern. The second-order reaction rate constants of ENO with hydroxyl radicals (HOâ) and singlet oxygen (1O2) were determined at pH 3, 7, and 9. Also, the rate constants of the electron transfer reaction between ENO and triplet states of chromophoric dissolved organic matter (3CDOM*) are reported for the first time, based on anthraquinone-2-sulfonate (AQ2S) as CDOM proxy. The sunlight-driven direct and indirect ENO degradation in the presence of dissolved organic matter (DOM) is also discussed. The results show that direct photolysis, which occurs more rapidly at higher pH, along with the reactions with HOâ and 3AQ2S*, is the key pathway involved in ENO degradation. The ENO zwitterions, prevailing at pH 7, show kENO, HOâ, kENO,1O2, and kENO,3AQ2S* of (14.0 ± 0.8) × 1010, (3.9 ± 0.2) × 106, and (61.5 ± 0.7) × 108 L mol-1 s-1, respectively, whose differences at pH 3, 7, and 9 are due to ENO pH-dependent speciation and reactivity. These k values, along with the experimental ENO photolysis quantum yield, were used in mathematical simulations for predicting ENO persistence in sunlit natural waters. According to the simulations, dissolved organic matter and water depth are expected to have the highest impacts on ENO half-life, varying from a few hours to days in summertime, depending on the concentrations of relevant waterborne species (organic matter, NO3-, NO2-, HCO3-).
Asunto(s)
Antibacterianos/análisis , Enoxacino/análisis , Radical Hidroxilo/química , Fotólisis , Contaminantes Químicos del Agua/análisis , Antibacterianos/efectos de la radiación , Enoxacino/efectos de la radiación , Semivida , Cinética , Modelos Teóricos , Oxidación-Reducción , Oxígeno Singlete/química , Luz Solar , Contaminantes Químicos del Agua/efectos de la radiaciónRESUMEN
A computational kinetics study of the antioxidant activity of tryptamine toward HO⢠and HOO⢠radicals in water at 298 K has been carried out. Density functional methods have been employed for the quantum chemical calculations, and the conventional transition state theory was used for rate constant evaluation. Different mechanisms have been considered: radical adduct formation (RAF), single electron transfer (SET), and hydrogen atom transfer (HAT). For the reaction of tryptamine with the hydroxyl radical, nearly all channels are diffusion-controlled, and the overall rate constant is very high, 6.29 × 1010 M-1 s-1. The RAF mechanism has a branching ratio of 55%, followed by the HAT mechanism (31%), whereas the SET mechanism accounts just for 13% of the products. The less hindered carbon atom neighboring to the nitrogen of the indole ring seems to be the preferred site for the RAF mechanism, with a branching ratio of 16%. The overall rate constant for the reaction of tryptamine with the HOO⢠radical is 3.71 × 104 M-1 s-1, suggesting that it could be a competitive process with other reactions of hydroperoxyl radicals in biological environments. For this reaction only the HAT mechanism seems viable. Furthermore, only two centers may contribute to the HAT mechanism, the nitrogen atom of the indole ring and a carbon atom of the aminoethyl chain, the former accounting for more than 91% of the total products. Our results suggest that tryptamine could have a noticeable scavenging activity toward radicals, and that this activity is mainly related to the nitrogen atom of the indole ring, thus showing the relevance of their behavior in the study of aminoindoles.
Asunto(s)
Antioxidantes/química , Triptaminas/química , Transporte de Electrón , Hidrógeno/química , Radical Hidroxilo/química , Cinética , Termodinámica , Agua/químicaRESUMEN
Oxidative stress signaling is essential for plant adaptation to hostile environments. Previous studies revealed the essentiality of hydroxyl radicals (HOâ¢)-induced activation of massive K⺠efflux and a smaller Ca2+ influx as an important component of plant adaptation to a broad range of abiotic stresses. Such activation would modify membrane potential making it more negative. Contrary to these expectations, here, we provide experimental evidence that HO⢠induces a strong depolarization, from -130 to -70 mV, which could only be explained by a substantial HOâ¢-induced efflux of intracellular anions. Application of Gd3+ and NPPB, non-specific blockers of cation and anion conductance, respectively, reduced HOâ¢-induced ion fluxes instantaneously, implying a direct block of the dual conductance. The selectivity of an early instantaneous HOâ¢-induced whole cell current fluctuated from more anionic to more cationic and vice versa, developing a higher cation selectivity at later times. The parallel electroneutral efflux of K⺠and anions should underlie a substantial leak of the cellular electrolyte, which may affect the cell's turgor and metabolic status. The physiological implications of these findings are discussed in the context of cell fate determination, and ROS and cytosolic K⺠signaling.