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1.
Nat Commun ; 11(1): 4899, 2020 09 29.
Artigo em Inglês | MEDLINE | ID: mdl-32994420

RESUMO

Chemical synthesis of amino acids from renewable sources is an alternative route to the current processes based on fermentation. Here, we report visible-light-driven amination of biomass-derived α-hydroxyl acids and glucose into amino acids using NH3 at 50 °C. Ultrathin CdS nanosheets are identified as an efficient and stable catalyst, exhibiting an order of magnitude higher activity towards alanine production from lactic acid compared to commercial CdS as well as CdS nanoobjects bearing other morphologies. Its unique catalytic property is attributed mainly to the preferential formation of oxygen-centered radicals to promote α-hydroxyl acids conversion to α-keto acids, and partially to the poor H2 evolution which is an undesired side reaction. Encouragingly, a number of amino acids are prepared using the current protocol, and one-pot photocatalytic conversion of glucose to alanine is also achieved. This work offers an effective catalytic system for amino acid synthesis from biomass feedstocks under mild conditions.


Assuntos
Alanina/síntese química , Compostos de Cádmio/química , Sulfetos/química , Alanina/química , Biomassa , Catálise/efeitos da radiação , Hidrogênio/química , Ácido Láctico/química , Luz , Modelos Químicos , Oxigênio/química
2.
Ecotoxicol Environ Saf ; 205: 111330, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32977288

RESUMO

Constructed wetland has attracted more and more attention for wastewater purification due to its low construction cost and convenient operation recently. However, the unique waterflooding structure of constructed wetland makes the low dissolved oxygen level, which limits the effect of nitrogen removal in the system. Therefore, it is necessary to develop the oxygen-increasing technology to overcome the drawback in constructed wetlands. In this review, the mechanism of nitrogen removal in constructed wetland is discussed and oxygen is main influence factor is concluded. In addition, oxygen-increasing technologies in recent advances which improve the nitrogen removal efficiency greatly, are emphatically introduced. Finally, some future perspectives about oxygen-increasing techniques are also put forward in order to provide reference for further research and engineering application.


Assuntos
Nitrogênio/análise , Oxigênio/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Áreas Alagadas , Análise da Demanda Biológica de Oxigênio , Desnitrificação , Águas Residuárias/química
3.
Ecotoxicol Environ Saf ; 204: 110977, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32739673

RESUMO

Indirect oxidation induced by reactive free radicals, such as hydroxyl radical (HO), sulfate radical (SO4-) and carbonate radical (CO3-), plays an important or even crucial role in the degradation of micropollutants. Thus, the coadjutant degradation of phenacetin (PNT) by HO, SO4- and CO3-, as well as the synergistic effect of O2 on HO and HO2 were studied through mechanism, kinetics and toxicity evaluation. The results showed that the degradation of PNT was mainly caused by radical adduct formation (RAF) reaction (69% for Г, the same as below) and H atom transfer (HAT) reaction (31%) of HO. For the two inorganic anionic radicals, SO4- initiated PNT degradation by sequential radical addition-elimination (SRAE; 55%), HAT (28%) and single electron transfer (SET; 17%) reactions, while only by HAT reaction for CO3-. The total initial reaction rate constants of PNT by three radicals were in the order: SO4- > HO > CO3-. The kinetics of PNT degradation simulated by Kintecus program showed that UV/persulfate could degrade target compound more effectively than UV/H2O2 in ultrapure water. In the subsequent reaction of PNT with O2, HO and HO2, the formation of mono/di/tri-hydroxyl substitutions and unsaturated aldehydes/ketones/alcohols were confirmed. The results of toxicity assessment showed that the acute and chronic toxicity of most products to fish increased and to daphnia decreased, and acute toxicity to green algae decreased while chronic toxicity increased.


Assuntos
Carbonatos/toxicidade , Peróxido de Hidrogênio/toxicidade , Fenacetina/toxicidade , Sulfatos/toxicidade , Testes de Toxicidade Aguda , Testes de Toxicidade Crônica , Animais , Carbonatos/química , Clorófitas/efeitos dos fármacos , Daphnia/efeitos dos fármacos , Peixes , Peróxido de Hidrogênio/química , Íons/química , Íons/toxicidade , Cinética , Modelos Químicos , Oxigênio/química , Fenacetina/química , Sulfatos/química , Água/química
5.
Chem Biol Interact ; 329: 109209, 2020 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-32750325

RESUMO

Kinetic modeling of the behavior of complex chemical and biochemical systems is an effective approach to study of the mechanisms of the process. A kinetic model of coronaviral infection development with a description of the dynamic behavior of the main variables, including the concentration of viral particles, affected cells, and pathogenic microflora, is proposed. Changes in the concentration of hydrogen ions in the lungs and the pH -dependence of carbonic anhydrase activity (a key breathing enzyme) are critical. A significant result is the demonstration of an acute bifurcation transition that determines life or system collapse. This transition is connected with exponential growth of concentrations of the process participants and with functioning of the key enzyme carbonic anhydrase in development of toxic effects. Physical and chemical interpretations of the therapeutic effects of the body temperature rise and the potential therapeutic effect of "thermoheliox" (respiration with a thermolized mixture of helium and oxygen) are given. The phenomenon of "thermovaccination" is predicted, which involves stimulation of the immune response by "thermoheliox".


Assuntos
Infecções por Coronaviridae/metabolismo , Hélio/química , Oxigênio/química , Imunidade Adaptativa , Temperatura Corporal , Anidrases Carbônicas/metabolismo , Infecções por Coronaviridae/patologia , Infecções por Coronaviridae/terapia , Hélio/uso terapêutico , Humanos , Concentração de Íons de Hidrogênio , Cinética , Pulmão/metabolismo , Modelos Teóricos , Oxigênio/uso terapêutico
6.
Arch Biochem Biophys ; 690: 108474, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32687799

RESUMO

Kynurenine 3-monoxygenase (KMO) catalyzes the conversion of l-kynurenine (L-Kyn) to 3-hydroxykynurenine (3-OHKyn) in the pathway for tryptophan catabolism. We have investigated the effects of pH and deuterium substitution on the oxidative half-reaction of KMO from P. fluorescens (PfKMO). The three phases observed during the oxidative half reaction are formation of the hydroperoxyflavin, hydroxylation and product release. The measured rate constants for these phases proved largely unchanging with pH, suggesting that the KMO active site is insulated from exchange with solvent during catalysis. A solvent inventory study indicated that a solvent isotope effect of 2-3 is observed for the hydroxylation phase and that two or more protons are in flight during this step. An inverse isotope effect of 0.84 ± 0.01 on the rate constant for the hydroxylation step with ring perdeutero-L-Kyn as a substrate indicates a shift from sp2 to sp3 hybridization in the transition state leading to the formation of a non-aromatic intermediate. The pH dependence of transient state data collected for the substrate analog meta-nitrobenzoylalanine indicate that groups proximal to the hydroperoxyflavin are titrated in the range pH 5-8.5 and can be described by a pKa of 8.8. That higher pH values do not slow the rate of hydroxylation precludes that the pKa measured pertains to the proton of the hydroperoxflavin. Together, these observations indicate that the C4a-hydroperoxyflavin has a pKa ≫ 8.5, that a non-aromatic species is the immediate product of hydroxylation and that at least two solvent derived protons are in-flight during oxygen insertion to the substrate aromatic ring. A unifying mechanistic proposal for these observations is proposed.


Assuntos
Hidrogênio/química , Quinurenina 3-Mono-Oxigenase/química , Quinurenina 3-Mono-Oxigenase/metabolismo , Cinurenina/química , Pseudomonas fluorescens/química , Catálise , Domínio Catalítico , Deutério/química , Dinitrocresóis/metabolismo , Flavinas/química , Concentração de Íons de Hidrogênio , Hidroxilação , Cinética , Oxigenases de Função Mista/metabolismo , Oxirredução , Estresse Oxidativo , Oxigênio/química , Prótons , Solventes/química
7.
PLoS One ; 15(7): e0235667, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32730271

RESUMO

Botswana's Okavango Delta is a World Heritage Site and biodiverse wilderness. In 2016-2018, following arrival of the annual flood of rainwater from Angola's highlands, and using continuous oxygen logging, we documented profound aquatic hypoxia that persisted for 3.5 to 5 months in the river channel. Within these periods, dissolved oxygen rarely exceeded 3 mg/L and dropped below 0.5 mg/L for up to two weeks at a time. Although these dissolved oxygen levels are low enough to qualify parts of the Delta as a dead zone, the region is a biodiversity hotspot, raising the question of how fish survive. In association with the hypoxia, histological samples, collected from native Oreochromis andersonii (threespot tilapia), Coptodon rendalli (redbreast tilapia), and Oreochromis macrochir (greenhead tilapia), exhibited widespread hepatic and splenic inflammation with marked granulocyte infiltration, melanomacrophage aggregates, and ceroid and hemosiderin accumulations. It is likely that direct tissue hypoxia and polycythemia-related iron deposition caused this pathology. We propose that Okavango cichlids respond to extended natural hypoxia by increasing erythrocyte production, but with significant health costs. Our findings highlight seasonal hypoxia as an important recurring stressor, which may limit fishery resilience in the Okavango as concurrent human impacts rise. Moreover, they illustrate how fish might respond to hypoxia elsewhere in the world, where dead zones are becoming more common.


Assuntos
Oxigênio/química , Tilápia/metabolismo , Animais , Ceroide/metabolismo , Eritrócitos/citologia , Eritrócitos/metabolismo , Feminino , Hemossiderina/metabolismo , Hipóxia , Ferro/metabolismo , Fígado/metabolismo , Fígado/patologia , Masculino , Oxigênio/metabolismo , Rios , Baço/metabolismo , Baço/patologia
8.
Nat Commun ; 11(1): 3538, 2020 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-32669587

RESUMO

Ever since Hirata's report of yuzurimine in 1966, nearly fifty yuzurimine-type alkaloids have been isolated, which formed the largest subfamily of the Daphniphyllum alkaloids. Despite extensive synthetic studies towards this synthetically challenging and biologically intriguing family, no total synthesis of any yuzurimine-type alkaloids has been achieved to date. Here, the first enantioselective total synthesis of (+)-caldaphnidine J, a highly complex yuzurimine-type Daphniphyllum alkaloid, is described. Key transformations of this approach include a highly regioselective Pd-catalyzed hydroformylation, a samarium(II)-mediated pinacol coupling, and a one-pot Swern oxidation/ketene dithioacetal Prins reaction. Our approach paves the way for the synthesis of other yuzurimine-type alkaloids and related natural products.


Assuntos
Alcaloides/síntese química , Daphniphyllum/química , Produtos Biológicos , Catálise , Desenho de Fármacos , Etilenos/química , Cetonas/química , Espectroscopia de Ressonância Magnética , Modelos Químicos , Estrutura Molecular , Oxirredução , Oxigênio/química , Samário/química , Estereoisomerismo
9.
Chemosphere ; 259: 127331, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32650175

RESUMO

The atmospheric degradation of polycyclic aromatic hydrocarbons (PAHs) can generate organic pollutants that contribute to the formation of secondary organic aerosols (SOAs) and exacerbate their carcinogenicity. Indene is an example of styrene-like bicyclic hydrocarbons that are not fully aromatic. The OH-initiated atmospheric oxidation of indene in the presence of O2 and NO was investigated using quantum chemical methods at M06-2X/6-311++G(3df,2p)//M06-2X/6-311+G(d,p) level. The oxidation products are oxygenated polycyclic aromatic hydrocarbons (OPAHs) containing hydroxyindene, indenone, dialdehydes and 2-(formylmethyl)benzaldehyde. Calculation results showed that 7-indene radical, which is the precursor of various PAHs, has a high production ratio that is 35.29% in the initial reaction, indicating that the OH-initiated oxidation increase the environmental risks of indene in the atmosphere. The rate constants for the crucial elementary reactions were calculated based on Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The overall rate constant of the initial reaction is calculated to be 1.04 × 10-10 cm3 molecule-1 s-1 and the atmospheric lifetime of indene is determined as 2.74 h. This work provides a comprehensive understanding on the oxidation mechanisms of indene and the findings could help to clarify the fate of indene in the atmosphere.


Assuntos
Poluentes Atmosféricos/química , Atmosfera/química , Radical Hidroxila/química , Indenos/química , Aerossóis , Cinética , Óxidos de Nitrogênio/química , Oxirredução , Oxigênio/química , Hidrocarbonetos Policíclicos Aromáticos
10.
PLoS Comput Biol ; 16(7): e1007996, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32667909

RESUMO

Cortical spreading depression (CSD) is the propagation of a relatively slow wave in cortical brain tissue that is linked to a number of pathological conditions such as stroke and migraine. Most of the existing literature investigates the dynamics of short term phenomena such as the depolarization and repolarization of membrane potentials or large ion shifts. Here, we focus on the clinically-relevant hour-long state of neurovascular malfunction in the wake of CSDs. This dysfunctional state involves widespread vasoconstriction and a general disruption of neurovascular coupling. We demonstrate, using a mathematical model, that dissolution of calcium that has aggregated within the mitochondria of vascular smooth muscle cells can drive an hour-long disruption. We model the rate of calcium clearance as well as the dynamical implications on overall blood flow. Based on reaction stoichiometry, we quantify a possible impact of calcium phosphate dissolution on the maintenance of F0F1-ATP synthase activity.


Assuntos
Depressão Alastrante da Atividade Elétrica Cortical , Potenciais da Membrana , Mitocôndrias/metabolismo , Vasoconstrição , Trifosfato de Adenosina/química , Cálcio/química , Fosfatos de Cálcio/química , Córtex Cerebral/fisiopatologia , Circulação Cerebrovascular , Citosol/química , Retículo Endoplasmático/química , Substância Cinzenta/fisiopatologia , Humanos , Modelos Teóricos , Acoplamento Neurovascular , Oscilometria , Oxigênio/química , Fosforilação , ATPases Translocadoras de Prótons/química , Acidente Vascular Cerebral/fisiopatologia
11.
Proc Natl Acad Sci U S A ; 117(32): 19178-19189, 2020 08 11.
Artigo em Inglês | MEDLINE | ID: mdl-32723819

RESUMO

Lytic polysaccharide monooxygenases (LPMOs) have a unique ability to activate molecular oxygen for subsequent oxidative cleavage of glycosidic bonds. To provide insight into the mode of action of these industrially important enzymes, we have performed an integrated NMR/electron paramagnetic resonance (EPR) study into the detailed aspects of an AA10 LPMO-substrate interaction. Using NMR spectroscopy, we have elucidated the solution-phase structure of apo-BlLPMO10A from Bacillus licheniformis, along with solution-phase structural characterization of the Cu(I)-LPMO, showing that the presence of the metal has minimal effects on the overall protein structure. We have, moreover, used paramagnetic relaxation enhancement (PRE) to characterize Cu(II)-LPMO by NMR spectroscopy. In addition, a multifrequency continuous-wave (CW)-EPR and 15N-HYSCORE spectroscopy study on the uniformly isotope-labeled 63Cu(II)-bound 15N-BlLPMO10A along with its natural abundance isotopologue determined copper spin-Hamiltonian parameters for LPMOs to markedly improved accuracy. The data demonstrate that large changes in the Cu(II) spin-Hamiltonian parameters are induced upon binding of the substrate. These changes arise from a rearrangement of the copper coordination sphere from a five-coordinate distorted square pyramid to one which is four-coordinate near-square planar. There is also a small reduction in metal-ligand covalency and an attendant increase in the d(x2-y2) character/energy of the singly occupied molecular orbital (SOMO), which we propose from density functional theory (DFT) calculations predisposes the copper active site for the formation of a stable Cu-O2 intermediate. This switch in orbital character upon addition of chitin provides a basis for understanding the coupling of substrate binding with O2 activation in chitin-active AA10 LPMOs.


Assuntos
Bacillus licheniformis/enzimologia , Proteínas de Bactérias/química , Quitina/metabolismo , Oxigenases de Função Mista/química , Oxigênio/metabolismo , Bacillus licheniformis/química , Proteínas de Bactérias/metabolismo , Domínio Catalítico , Quitina/química , Cobre/química , Cobre/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Imagem por Ressonância Magnética , Oxigenases de Função Mista/metabolismo , Oxigênio/química , Especificidade por Substrato
12.
Food Chem ; 333: 127450, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32663749

RESUMO

The aged wine spirit is a beverage with great aromatic complexity. Their volatile compounds with odorant power coming from the distillate and from the wood used in its ageing, and the interactions that take place in the process, enhanced by oxygen, all contribute to this complexity. Due to time and cost inherent of ageing wine spirits in wooden barrels, research has sought to develop more sustainable alternatives to do it. In this context, the present study compares, the effect of traditional (wooden barrel) and alternative system (stainless steel tank with dipped staves and micro-oxygenation), on the odorant and sensory profile of a wine spirit, using Limousin oak and chestnut wood, after 12 months of ageing. The results suggest that the ageing process is accelerated by the alternative ageing technology and the chestnut wood, and the corresponding wine spirits presented characteristics of greater sensory evolution and strong wood compounds extraction.


Assuntos
Indústria de Processamento de Alimentos/métodos , Odorantes , Vinho , Madeira , Adulto , Aesculus , Idoso , Feminino , Indústria de Processamento de Alimentos/instrumentação , Humanos , Masculino , Pessoa de Meia-Idade , Odorantes/análise , Oxigênio/química , Quercus , Aço Inoxidável , Fatores de Tempo , Compostos Orgânicos Voláteis/análise , Vinho/análise
13.
Chemosphere ; 260: 127496, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32659541

RESUMO

Activated carbons have been reported to be useful for adsorptive removal of the volatile anaesthetic sevoflurane from a vapour stream. The surface functionalities on activated carbons could be modified through aqueous oxidation using oxidising solutions to enhance the sevoflurane adsorption. In this study, an attempt to oxidise the surface of a commercial activated carbon to improve its adsorption capacity for sevoflurane was conducted using 6 mol/L nitric acid, 2 mol/L ammonium persulfate, and 30 wt per cent (wt%) of hydrogen peroxide (H2O2). The adsorption tests at fixed conditions (bed depth: 10 cm, inlet concentration: 528 mg/L, and flow rate: 3 L/min) revealed that H2O2 oxidation gave desirable sevoflurane adsorption (0.510 ± 0.005 mg/m2). A parametric study was conducted with H2O2 to investigate the effect of oxidation conditions to the changes in surface oxygen functionalities by varying the concentration, oxidation duration, and temperature, and the Conductor-like Screening Model for Real Solvents (COSMO-RS) was applied to predict the interactions between oxygen functionalities and sevoflurane. The H2O2 oxidation incorporated varying degrees of both surface oxygen functionalities with hydrogen bond (HB) acceptor and HB donor characters under the studied conditions. Oxidised samples with enriched oxygen functionalities with HB acceptor character and fewer HB donor character exhibited better adsorption capacity for sevoflurane. The presence of a high amount of oxygen functional groups with HB donor character adversely affected the sevoflurane adsorption despite the enrichment of oxygen functional groups with HB acceptor character that have a higher tendency to adsorb sevoflurane.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/prevenção & controle , Anestésicos Inalatórios/análise , Carvão Vegetal/química , Oxigênio/química , Sevoflurano/análise , Adsorção , Ligação de Hidrogênio , Peróxido de Hidrogênio/química , Modelos Teóricos , Ácido Nítrico/química , Oxirredução , Porosidade , Propriedades de Superfície , Temperatura
14.
Chemosphere ; 258: 127363, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32554017

RESUMO

Grey water (GW) containing high levels of linear alkylbenzene sulfonates (LAS) can be a threat to the human health and organisms in the environment if not treated properly. Although aerobic treatment may achieve high GW treatment efficacy, conventional aeration can lead to serious foaming. Here, we firstly and systematically evaluated an oxygen-based membrane biofilm reactor (O2-MBfR) for its capacity to simultaneous remove organics and nitrogen from greywater with high LAS levels and carbon/nitrogen (C/N) ratios. After a five-day startup period, multifarious microorganisms formed multifunctional biofilms and the MBfR achieved high removal rates of chemical oxygen demand (COD), LAS, and total nitrogen (TN) of 88.4%, 95.6%, and 80%, respectively, with a hydraulic retention time of 7.86 h. Higher organics loading (5.53 g TCOD/m2-day) caused cell lysis and damaged the O2-MBfR system, leading to a discernible and continuous decline of the reactor performance. The O2-MBfR design completely eliminated foaming formation. LAS -biodegrading-rich genus containing Clostridium, Parvibaculum, Dechloromonas, Desulfovibrio, Mycobacterium, Pseudomonas, and Zoogloea enable the nearly complete removal of LAS even under high C/N conditions. Results demonstrated that the O2-MBfR technology is feasible for treating GW containing high LAS and C/N ratio, while remaining free of foaming formation, and at a low cost due to high O2 utilization rates.


Assuntos
Ácidos Alcanossulfônicos/análise , Biofilmes/crescimento & desenvolvimento , Reatores Biológicos/microbiologia , Carbono/análise , Nitrogênio/análise , Oxigênio/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Biodegradação Ambiental , Biofilmes/efeitos dos fármacos , Análise da Demanda Biológica de Oxigênio , Membranas Artificiais
15.
Chemosphere ; 259: 127427, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32599385

RESUMO

Spinel oxides, e.g., NiCo2O4, is a promising catalyst for the catalytic oxidation of toluene. Understanding and designing versatile NiCo2O4 spinel is important for low-temperature toluene oxidation. Here, we investigated the surface-characteristic-dependent degradation activity of NiCo2O4 crystals through experiment and characterization. NiCo2O4 nanosheet using ethanol as solvent (named E--NiCo2O4) exposing {110} crystal planes exhibited the lowest temperature toluene oxidation. The T99 of toluene conversion was 256 °C, which is much lower than that of NiCo2O4 nanosheet using ethylene glycol as solvent (named EG--NiCo2O4), NiCo2O4 octahedron (named O--NiCo2O4) and NiCo2O4 truncated octahedron (named TO--NiCo2O4). Characterization using various techniques such as XRD, TEM, BET, XPS, H2-TPR and CO2-TPD showed that Co3+ and surface adsorbed oxygen (Osur) enriched surface, excellent redox properties and effective diffusion of the reaction product reasonably explain the enhancement in catalytic activity over the E--NiCo2O4. The research reveals that the effect of specific crystal planes and solvent was the key factor to govern the activity of low-temperature toluene oxidation.


Assuntos
Óxido de Alumínio/química , Óxido de Magnésio/química , Tolueno/química , Adsorção , Catálise , Temperatura Baixa , Oxirredução , Óxidos/química , Oxigênio/química , Solventes
16.
Nat Commun ; 11(1): 2903, 2020 06 09.
Artigo em Inglês | MEDLINE | ID: mdl-32518257

RESUMO

Direct transfer of protons and electrons between two tandem reactions is still a great challenge, because overall reaction kinetics is seriously affected by diffusion rate of the proton and electron carriers. We herein report a host-guest supramolecular strategy based on the incorporation of NADH mimics onto the surface of a metal-organic capsule to encapsulate flavin analogues for catalytic biomimetic monooxygenations in conjunction with enzymes. Coupling an artificial catalysis and a natural enzymatic catalysis in the pocket of an enzyme, this host-guest catalyst-enzyme system allows direct proton and electron transport between two catalytic processes via NADH mimics for the monooxygenation of both cyclobutanones and thioethers. This host-guest approach, which involves the direct coupling of abiotic and biotic catalysts via a NADH-containing host, is quite promising compared to normal catalyst-enzyme systems, as it offers the key advantages of supramolecular catalysis in integrated chemical and biological synthetic sequences.


Assuntos
Biomimética , Oxigênio/química , Catálise , Domínio Catalítico , Cristalografia por Raios X , Transporte de Elétrons , Enzimas/química , Ligação de Hidrogênio , Íons , Cinética , Ligantes , NAD/química , Solventes/química , Zinco/química
17.
Int J Nanomedicine ; 15: 3511-3522, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32547010

RESUMO

Introduction: Diabetic wounds are challenging to treat due to a wide range of pathophysiological changes. Hypoxia is one of the predominant contributing factors of poor vascularization and chronicity in diabetic wounds. This study was designed to develop polycaprolactone (PCL)-based oxygen-releasing electrospun wound dressings and evaluate their efficacy for improved full thickness wound healing in diabetic rats. Methods: PCL-based oxygen releasing wound dressings were made using electrospinning technology. The developed dressings were characterized in terms of physical as well as biological properties both in vitro and in vivo. E-spun nanofibrous dressings were physically characterized with scanning electron microscopy, Fourier-transform infrared spectroscopy, and Energy-dispersive X-ray spectroscopy. To study the likely impact of the fabricated wound dressings in hypoxic conditions, HIF-1α expression analysis was carried out both at gene and protein levels. Wound dressings were further evaluated for their healing potential for extensive wounds in diabetic rat models. Results: The experimental results showed that the developed dressings were capable of continuously generating oxygen for up to 10 days. Cell studies further confirmed pronounced expression of HIF-1α at gene and protein levels in cells seeded on PCL-sodium percarbonate (SPC) and PCL scaffolds compared with the cells cultured on a tissue culture plate. Chorioallantoic membrane assay revealed the supportive role of oxygen releasing dressings on angiogenesis compared to the control group. Histological assessment of the regenerated skin tissues proved that full thickness wounds covered with SPC loaded PCL dressings had a comparatively better vascularized and compact extracellular matrix with completely covered thick epithelium. Discussion: The developed oxygen generating polymeric nanofibrous wound dressings could potentially be used as an envisioned approach for the efficient recovery of chronic diabetic wounds.


Assuntos
Diabetes Mellitus/patologia , Nanofibras/química , Neovascularização Fisiológica/efeitos dos fármacos , Oxigênio/química , Poliésteres/farmacologia , Cicatrização/efeitos dos fármacos , Animais , Bandagens , Bioensaio , Membrana Corioalantoide/efeitos dos fármacos , Membrana Corioalantoide/metabolismo , Diabetes Mellitus Experimental/patologia , Modelos Animais de Doenças , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Masculino , Nanofibras/ultraestrutura , Ratos Sprague-Dawley , Reprodutibilidade dos Testes , Pele/patologia , Espectroscopia de Infravermelho com Transformada de Fourier
18.
Food Chem ; 328: 127040, 2020 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-32512467

RESUMO

Wine ageing in barrels is conditioned, among other factors, by the amount of oxygen received during this process, which thus impacts its final properties. The aim of this study was to evaluate the effect of oxygen on wine colour during ageing in barrels and bottles during different times. The use of barrels with different and known rates of oxygenation allows the effect of different oxygenation conditions throughout the process in barrels and its later evolution in bottles. A simulation process of ageing in bottles was used to study the impact of bottling in wines after differing ageing periods in barrels. The study of winés oxygen consumption capacity has been tied to colour modifications during ageing in barrels and bottles. Wines aged in barrels with a high oxygenation rate showed greater avidity to consume oxygen taking less time to consume that available, which is reflected in a greater increase in colour intensity.


Assuntos
Armazenamento de Alimentos/métodos , Oxigênio/química , Vinho/análise , Cor , Cinética , Fatores de Tempo
19.
Food Chem ; 329: 127181, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32502743

RESUMO

The compounds that the wood releases to the wine and the oxygen transmission rate (OTR) of the barrel define the final wine. The new possibility of choosing the OTR of the barrel allows the winemaker to globally control the ageing process. The aim of this work was to study the volatile composition of woods classified according to their OTR, which are used to build barrels for wine ageing. The results showed that volatile composition differs depending on wood OTR and the temperature reached during toasting. On the toasted side of the stave in contact with the wine, low OTR wood had a statistically higher content in furan compounds (5-hydroxymethylfurfural, furfural and 5-methylfurfural), acetovanillone and phenolic aldehydes (vanillin and syringaldehyde), while 4-ethylguaiacol and trans-ß-methyl-γ-octalactone were significantly higher in staves with a high OTR. The same red wine aged first for three months in high and low oxygenation barrels presents different characteristics.


Assuntos
Manipulação de Alimentos/métodos , Oxigênio/química , Quercus/química , Compostos Orgânicos Voláteis/química , Vinho/análise , Benzaldeídos/química , Cromatografia Gasosa , Análise Discriminante , Furanos/química , Guaiacol/química , Temperatura , Madeira/química
20.
Proc Natl Acad Sci U S A ; 117(26): 15018-15027, 2020 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-32527859

RESUMO

The pathology of sickle cell disease is caused by polymerization of the abnormal hemoglobin S upon deoxygenation in the tissues to form fibers in red cells, causing them to deform and occlude the circulation. Drugs that allosterically shift the quaternary equilibrium from the polymerizing T quaternary structure to the nonpolymerizing R quaternary structure are now being developed. Here we update our understanding on the allosteric control of fiber formation at equilibrium by showing how the simplest extension of the classic quaternary two-state allosteric model of Monod, Wyman, and Changeux to include tertiary conformational changes provides a better quantitative description. We also show that if fiber formation is at equilibrium in vivo, the vast majority of cells in most tissues would contain fibers, indicating that it is unlikely that the disease would be survivable once the nonpolymerizing fetal hemoglobin has been replaced by adult hemoglobin S at about 1 y after birth. Calculations of sickling times, based on a recently discovered universal relation between the delay time prior to fiber formation and supersaturation, show that in vivo fiber formation is very far from equilibrium. Our analysis indicates that patients survive because the delay period allows the majority of cells to escape the small vessels of the tissues before fibers form. The enormous sensitivity of the duration of the delay period to intracellular hemoglobin composition also explains why sickle trait, the heterozygous condition, and the compound heterozygous condition of hemoglobin S with pancellular hereditary persistence of fetal hemoglobin are both relatively benign conditions.


Assuntos
Anemia Falciforme/metabolismo , Hemoglobina Falciforme/química , Oxigênio/metabolismo , Regulação Alostérica , Eritrócitos/química , Eritrócitos/metabolismo , Hemoglobina Fetal/química , Hemoglobina Fetal/metabolismo , Hemoglobina Falciforme/metabolismo , Humanos , Cinética , Oxigênio/química
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