Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.500
Filtrar
1.
Waste Manag ; 126: 274-282, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33784571

RESUMO

Levoglucosan (LGA) is a promising chemical platform derived from the pyrolysis of biomass that offers access to a variety of value-added products. We report an efficient route to produce LGA via the pretreatment of biomass with niobium compounds (oxalate, chloride and oxide) followed by fast pyrolysis coupled with gas chromatography-mass spectrometry (Py-GC-MS) at temperatures of 350-600 °C. Catalytic pretreatment reduces the quantity of lignin in the biomass, concentrates the cellulose and enhance LGA formation during fast pyrolysis. The pretreatment also removes alkaline metals, preventing competitive side reactions. The effect of several parameters such as catalyst weight, time, temperature, and solvent, with the optimal pretreatment conditions determined to be 3 (wt.%) niobium oxalate for 1 h at 23 °C in water. Pretreatment increased the LGA yields by 6.40-fold for sugarcane bagasse, 4.15-fold for elephant grass, 4.13-fold for rice husk, 2.86-fold for coffee husk, and 1.86-fold for coconut husk as compared to the raw biomasses. These results indicate that biomass pretreatment using niobium derivates prior fast pyrolysis can be a promising technique for biomass thermochemical conversion in LGA and others important pyrolytic products.


Assuntos
Nióbio , Pirólise , Biomassa , Glucose/análogos & derivados , Temperatura Alta , Lignina
2.
Environ Sci Technol ; 55(8): 5525-5536, 2021 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-33754698

RESUMO

Levoglucosan has been widely used to quantitatively assess biomass burning's contribution to ambient aerosols, but previous such assessments have not accounted for levoglucosan's degradation in the atmosphere. We develop the first global simulation of atmospheric levoglucosan, explicitly accounting for its chemical degradation, to evaluate the impacts on levoglucosan's use in quantitative aerosol source apportionment. Levoglucosan is emitted into the atmosphere from the burning of plant matter in open fires (1.7 Tg yr-1) and as biofuels (2.1 Tg yr-1). Sinks of atmospheric levoglucosan include aqueous-phase oxidation (2.9 Tg yr-1), heterogeneous oxidation (0.16 Tg yr-1), gas-phase oxidation (1.4 × 10-4 Tg yr-1), and dry and wet deposition (0.27 and 0.43 Tg yr -1). The global atmospheric burden of levoglucosan is 19 Gg with a lifetime of 1.8 days. Observations show a sharp decline in levoglucosan's concentrations and its relative abundance to organic carbon aerosol (OC) and particulate K+ from near-source to remote sites. We show that such features can only be reproduced when levoglucosan's chemical degradation is included in the model. Using model results, we develop statistical parametrizations to account for the atmospheric degradation in levoglucosan measurements, improving their use for quantitative aerosol source apportionment.


Assuntos
Poluentes Atmosféricos , Monitoramento Ambiental , Aerossóis/análise , Poluentes Atmosféricos/análise , Atmosfera , Biomassa , Glucose/análogos & derivados , Glucose/análise , Material Particulado/análise , Estações do Ano
3.
Nucleic Acids Res ; 49(4): 1828-1839, 2021 02 26.
Artigo em Inglês | MEDLINE | ID: mdl-33544849

RESUMO

We recently showed that site-specific incorporation of 2'-modifications or neutral linkages in the oligo-deoxynucleotide gap region of toxic phosphorothioate (PS) gapmer ASOs can enhance therapeutic index and safety. In this manuscript, we determined if introducing substitution at the 5'-position of deoxynucleotide monomers in the gap can also enhance therapeutic index. Introducing R- or S-configured 5'-Me DNA at positions 3 and 4 in the oligodeoxynucleotide gap enhanced the therapeutic profile of the modified ASOs suggesting a different positional preference as compared to the 2'-OMe gap modification strategy. The generality of these observations was demonstrated by evaluating R-5'-Me and R-5'-Ethyl DNA modifications in multiple ASOs targeting HDAC2, FXI and Dynamin2 mRNA in the liver. The current work adds to a growing body of evidence that small structural changes can modulate the therapeutic properties of PS ASOs and ushers a new era of chemical optimization with a focus on enhancing the therapeutic profile as opposed to nuclease stability, RNA-affinity and pharmacokinetic properties. The 5'-methyl DNA modified ASOs exhibited excellent safety and antisense activity in mice highlighting the therapeutic potential of this class of nucleic acid analogs for next generation ASO designs.


Assuntos
DNA/química , Oligonucleotídeos Antissenso/química , Animais , Glucose/análogos & derivados , Glucose/química , Células HeLa , Humanos , Fígado/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Células NIH 3T3 , Oligonucleotídeos Antissenso/uso terapêutico , Oligonucleotídeos Antissenso/toxicidade , Compostos Organofosforados/síntese química , Ribonuclease H
4.
Environ Sci Technol ; 55(3): 1497-1507, 2021 02 02.
Artigo em Inglês | MEDLINE | ID: mdl-33423493

RESUMO

Levoglucosan (LG) emitted from non-biomass burning (non-BB) sources has given rise to biased or even unreasonable source identification results when adopting LG as a distinct marker of biomass burning (BB). The estimation of LG emission and its spatiotemporal variation for various sources are the keys to reducing uncertainty. This study first developed a LG emission inventory for China from 25 sub-type sources belonging to eight categories, with a 3 km × 3 km spatial resolution and monthly distribution. The total LG emission in 2014 was 145.7 Gg. Domestic BB and open BB contributed 39.2 and 34.3% of the total emission. Non-BB sources, including municipal solid waste burning (9.7%), firework burning (9.6%), meat cooking (5.4%), domestic coal burning (1.5%), ritual item burning (0.2%), and industrial coal burning (0.1%), contributed to 26.5% of the total emission. LG emission varied spatially and temporally. Non-BB sources have a significant spatiotemporal impact on BB source contributions, even in high BB emission regions or in sowing, harvesting, and winter heating seasons. The local BB contributions have been substantially overestimated by 4.28-369% in previous studies, wherein LG was solely referred to as the BB source. By 2018, LG emission from BB might decrease to 63.9% of its total emission. This high-resolution LG emission inventory can be greatly useful for source identification studies in China. It also supports future research on the modeling of smoke aging and pollution control.


Assuntos
Poluentes Atmosféricos , Material Particulado , Aerossóis/análise , Poluentes Atmosféricos/análise , Biomassa , China , Monitoramento Ambiental , Glucose/análogos & derivados , Material Particulado/análise , Estações do Ano
5.
Chemosphere ; 263: 127982, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32854009

RESUMO

Scarce information is available concerning the presence of carbohydrates in rainwater. The existence of carbohydrates in bulk deposition at the town of Estarreja (Portugal), at industrial (I) and background (BG) locals, in winter and spring seasons 2016, was assessed. Seventeen carbohydrates and related compounds were identified: monosaccharides (ribose, arabinose, xylose, glucose, galactose, fructose), disaccharides (sucrose, trehalose, maltose, cellobiose), polyols (arabinitol, xylitol, myo-inositol, mannitol, glucitol, maltitol), and the anhydromonosaccharide levoglucosan. Higher content of carbohydrates was observed in spring (BG: 670 nM; I: 249 nM) than in winter (BG: 168 nM; I: 195 nM), and fructose was the carbohydrate with the highest contribution in both seasons (spring: 32%/44% (I/BG); winter: 24% (at both sites)). Fructose, myo-inositol, glucose and sucrose showed higher volume-weighted averages (VWA) concentrations in spring than in winter, possibly due to biogenic emissions typical of spring, such as pollen, and fungal spores for myo-inositol. Fructose may have derived from isomerization of glucose in biomass burning, namely in winter. Levoglucosan and galactose presented higher VWA concentration in winter than in spring, suggesting a seasonal effect related with the biomass combustion. The carbohydrates VWA concentrations were similar for samples associated with maritime and terrestrial air masses, indicating that local sources were their main contributors. Source assessment of carbohydrates by factor analysis suggested: biogenic sources for the arabinitol, myo-inositol, glucose, fructose and sucrose; soil dust for the trehalose; and anthropogenic sources from biomass burning for the galactose, arabinose and levoglucosan. The bulk deposition showed to be fundamental on removing carbohydrates from the atmosphere.


Assuntos
Carboidratos/análise , Monitoramento Ambiental , Poluentes Químicos da Água/análise , Atmosfera , Biomassa , Dissacarídeos , Poeira/análise , Frutose , Galactose , Glucose/análogos & derivados , Maltose/análogos & derivados , Estações do Ano , Sacarose , Álcoois Açúcares
6.
Proc Natl Acad Sci U S A ; 117(52): 33549-33560, 2020 12 29.
Artigo em Inglês | MEDLINE | ID: mdl-33318216

RESUMO

Thymineless death in Escherichia coli thyA mutants growing in the absence of thymidine (dT) is preceded by a substantial resistance phase, during which the culture titer remains static, as if the chromosome has to accumulate damage before ultimately failing. Significant chromosomal replication and fragmentation during the resistance phase could provide appropriate sources of this damage. Alternatively, the initial chromosomal replication in thymine (T)-starved cells could reflect a considerable endogenous dT source, making the resistance phase a delay of acute starvation, rather than an integral part of thymineless death. Here we identify such a low-molecular-weight (LMW)-dT source as mostly dTDP-glucose and its derivatives, used to synthesize enterobacterial common antigen (ECA). The thyA mutant, in which dTDP-glucose production is blocked by the rfbA rffH mutations, lacks a LMW-dT pool, the initial DNA synthesis during T-starvation and the resistance phase. Remarkably, the thyA mutant that makes dTDP-glucose and initiates ECA synthesis normally yet cannot complete it due to the rffC defect, maintains a regular LMW-dT pool, but cannot recover dTTP from it, and thus suffers T-hyperstarvation, dying precipitously, completely losing chromosomal DNA and eventually lysing, even without chromosomal replication. At the same time, its ECA+ thyA parent does not lyse during T-starvation, while both the dramatic killing and chromosomal DNA loss in the ECA-deficient thyA mutants precede cell lysis. We conclude that: 1) the significant pool of dTDP-hexoses delays acute T-starvation; 2) T-starvation destabilizes even nonreplicating chromosomes, while T-hyperstarvation destroys them; and 3) beyond the chromosome, T-hyperstarvation also destabilizes the cell envelope.


Assuntos
Cromossomos Bacterianos/metabolismo , DNA Bacteriano/metabolismo , Escherichia coli/metabolismo , Viabilidade Microbiana , Polissacarídeos Bacterianos/farmacologia , Timina/metabolismo , Antígenos de Bactérias/metabolismo , Replicação do DNA/efeitos dos fármacos , Proteínas de Escherichia coli/metabolismo , Glucose/análogos & derivados , Glucose/metabolismo , Viabilidade Microbiana/efeitos dos fármacos , Peso Molecular , Mutação/genética , Estresse Fisiológico/efeitos dos fármacos , Timidina/metabolismo , Nucleotídeos de Timina/metabolismo
7.
Waste Manag ; 114: 43-52, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32673980

RESUMO

The liquid product from biomass direct pyrolysis is usually complex and difficult to effectively utilize. By combining hydrothermal conversion and low-temperature pyrolysis, the hemicellulose and cellulose of biomass can be transformed into value-added furfural and levoglucosan (LG), respectively. The effects of temperature during hydrothermal treatment (160-240 °C) and subsequent pyrolysis (340-400 °C) on the production of furfural and LG were investigated by using three typical agricultural wastes, namely corn stalk, peanut shells, and rice stalk. The maximum furfural yield of 4.2% was achieved upon hydrolysis of peanut shells at 200 °C. The hydrochar produced from peanut shells presented the highest LG yield of 7.3% (based on original biomass weight) for a pyrolysis temperature of 360 °C. Under this optimal condition, the total revenue from various products of the hybrid thermochemical process was estimated at $0.362 per kilogram of peanut shells, whereas furfural and LG account for 90% of the revenue.


Assuntos
Furaldeído , Pirólise , Biomassa , Glucose/análogos & derivados , Temperatura Alta , Temperatura
8.
Chemosphere ; 257: 127154, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32512328

RESUMO

Carcinogenic polycyclic aromatic hydrocarbons (cPAHs) in ambient PM2.5 and a specific molecular marker of biomass burning, levoglucosan, are used to investigate the influence on public health of biomass burning. In this work, we present an effective method for one-time analysis of cPAHs and levoglucosan by GC-MS without derivatization. The method was applied for the analysis of PM2.5 samples (64.3 ±â€¯17.6 µg m-3, n = 57) collected during a smoke haze period in Chiang Mai, Thailand. Levoglucosan was analyzed by using both the developed method (GC-MS) and a reference method (HPAEC-PAD) for comparison. Its average concentration obtained from GC-MS (0.31 ±â€¯0.21 µg m-3) was about 4 times less than the concentration obtained from the reference method (1.22 ±â€¯0.76 µg m-3). Therefore, a correcting factor (CF = 4) was used as a multiplying factor, to obtain a comparative value (1.23 ±â€¯0.86 µg m-3). The average concentration of cPAHs found in PM2.5 samples was 5.88 ±â€¯1.97 ng m-3 with the highest value of 10.86 ng m-3 indicating medium to high cancer risk due to PAHs exposure when referring to values of toxicity equivalence and inhalation cancer risk. Diagnostic ratios of BaA/(BaA + CHR) (0.48 ± 0.04) and IND/(IND + BPER) (0.58 ± 0.04) and strong correlations between PM2.5, levoglucosan and cPAHs concentrations implied that the major source of air pollution in the study period was biomass burning. PM2.5 concentration as a pollution indicator was labelled as BB-low, BB-medium, BB-high or BB-extreme; <50, 50-75, 75-100 and > 100 µg m-3, respectively. The levoglucosan and cPAHs concentration during BB-extreme pollution was 4.3 times and 2.34 times, respectively, that during BB-low pollution, and the correlation coefficient (r) between the concentrations of levoglucosan and cPAHs was as high as 0.987, indicating that the more intense the burning of biomass, the higher the carcinogenic risk in the urban air.


Assuntos
Poluentes Atmosféricos/toxicidade , Monitoramento Ambiental/métodos , Material Particulado/toxicidade , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Poluição do Ar/estatística & dados numéricos , Biomassa , Carcinógenos/análise , Poluição Ambiental/análise , Cromatografia Gasosa-Espectrometria de Massas , Glucose/análogos & derivados , Humanos , Material Particulado/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Estações do Ano , Fumaça/análise , Tailândia
9.
Sci Total Environ ; 733: 138991, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32470716

RESUMO

Levoglucosan, an anhydrosaccharide, is commonly used as an organic tracer for biomass burning, but has also been identified from coal smoke particulate matter (PM) including lignites. Here we showed that stable carbon isotope analysis specifically of levoglucosan may be one possible way to determine the relative contributions from coal combustion versus biomass burning sources. PM samples were collected from low-temperature burning/smoldering of Miocene lignites from Poland and basket willow (Salix viminalis L.) representative of biomass. The calculated levoglucosan δ13C values of xylites varied from -23.6 to -21.6‰, while for detritic coal samples they ranged from -24.2 to -23.1‰, with means of -22.7 and -23.7‰, respectively. The calculated levoglucosan δ13C value of basket willow wood was -27.1‰. Values of willow wood mixtures with xylite varied from -25.8 to -23.4‰ (with an increasing proportion of xylite), while values of mixtures of willow and detritic coal ranged from -26.9 to -24.6‰ (with an increasing proportion of detritic coal). The δ13C values for the mixtures changed proportionally to the contents of individual components with R2 = 0.88 and 0.89 for willow with xylite and detritic coal, respectively. The hopanoid distributions characteristic for low-temperature lignite/peat burning, with a predominance of 22R-α,ß-homohopane, ßß-hopanes and hopenes, as well as low or very low values of the homohopane index, were observed in smoke PM from most lignite samples and absent in the basket willow sample. Thus, the relatively high content of hopanes (with the occurrence of 22R-α,ß-homohopane, ßß-hopanes and hopenes) in atmospheric PM samples can be treated as additional tracers of lignite combustion.


Assuntos
Poluentes Atmosféricos/análise , Carvão Mineral/análise , Biomassa , Monitoramento Ambiental , Glucose/análogos & derivados , Material Particulado/análise , Polônia , Temperatura
10.
Waste Manag ; 108: 70-77, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32335489

RESUMO

Levoglucosan is served as a significant versatile product to generate high value-added chemicals and pharmaceutical additives. Levoglucosan was predominately produced from pyrolysate of cellulose. However, the direct fast pyrolysis of waste biomass produces a small quantity of levoglucosan in comparison with the theoretical value of cellulose. This study explored Fenton pretreatment as a possible route to enhance levoglucosan yield during the fast pyrolysis of the waste corncob. The experimental results showed that different Fenton pretreated conditions and pyrolytic temperatures played vital roles in the formation of levoglucosan. The levoglucosan yield from fast pyrolysis at 500 °C of corncob pretreated by Fenton reaction of 14 mL/g H2O2 and 16 mM FeSO4 was about 95% higher than that of the untreated corncob. Additionally, Fenton pretreated corncob was capable of obtaining the levoglucosan at a low pyrolytic temperature (300 °C). It was mainly attributed to the effective disrupting of biomass structures and the selective degradation of lignin and hemicellulose during pretreatment. Furthermore, the powerful removal of alkali and alkaline earth metals during Fenton pretreatment was beneficial to increasing the levoglucosan yield. These findings demonstrate that Fenton pretreatment can provide a novel effective method to enhance levoglucosan yield during biomass fast pyrolysis.


Assuntos
Peróxido de Hidrogênio , Pirólise , Biomassa , Glucose/análogos & derivados , Lignina
11.
Nature ; 580(7804): 511-516, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32322067

RESUMO

The taste of sugar is one of the most basic sensory percepts for humans and other animals. Animals can develop a strong preference for sugar even if they lack sweet taste receptors, indicating a mechanism independent of taste1-3. Here we examined the neural basis for sugar preference and demonstrate that a population of neurons in the vagal ganglia and brainstem are activated via the gut-brain axis to create preference for sugar. These neurons are stimulated in response to sugar but not artificial sweeteners, and are activated by direct delivery of sugar to the gut. Using functional imaging we monitored activity of the gut-brain axis, and identified the vagal neurons activated by intestinal delivery of glucose. Next, we engineered mice in which synaptic activity in this gut-to-brain circuit was genetically silenced, and prevented the development of behavioural preference for sugar. Moreover, we show that co-opting this circuit by chemogenetic activation can create preferences to otherwise less-preferred stimuli. Together, these findings reveal a gut-to-brain post-ingestive sugar-sensing pathway critical for the development of sugar preference. In addition, they explain the neural basis for differences in the behavioural effects of sweeteners versus sugar, and uncover an essential circuit underlying the highly appetitive effects of sugar.


Assuntos
Encéfalo/fisiologia , Comportamento de Escolha/fisiologia , Açúcares da Dieta/metabolismo , Preferências Alimentares/fisiologia , Glucose/metabolismo , Intestinos/fisiologia , Animais , Encéfalo/citologia , Açúcares da Dieta/química , Glucose/análogos & derivados , Glucose/química , Masculino , Metilglucosídeos/química , Metilglucosídeos/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Neurônios/fisiologia , Paladar/fisiologia , Tiazinas/metabolismo , Água/metabolismo
12.
Bioresour Technol ; 307: 123179, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32222688

RESUMO

This study aimed to evaluate the environmental impacts (i.e. global warming potential (GWP) and resource depletion (RD)) of the bio-based levoglucosan production process through fast pyrolysis of cotton straw via life cycle assessment (LCA). An LCA model consisting of feedstock transportation, biomass pretreatment, fast pyrolysis, bio-oil transportation, bio-oil recovery and levoglucosan extraction was developed. Results indicated that GWP and RD of bio-based levoglucosan production were approximately 2 and 32.5 times less than that of the petroleum-based counterpart. Sensitivity analysis showed that the GWP and RD of levoglucosan production were highly sensitive to plant size, hydrochloric acid usage, cooling energy, levoglucosan yield and bio-oil yield. The results of this research could provide a framework for robust decision making at an industrial level, which is useful for the commercial-scale production of levoglucosan.


Assuntos
Biocombustíveis , Pirólise , Biomassa , Glucose/análogos & derivados
13.
Soft Matter ; 16(10): 2540-2551, 2020 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-32095796

RESUMO

Lipid lamellar hydrogels are a class of soft materials composed of a defectuous lipid lamellar phase, where defects are classically stabilized by polymer or surfactant inclusions in lipid membranes. We have recently shown that bolaform microbial glucolipids, composed of a single glucose headgroup and a C18:0 fatty acid, with the carboxylic acid group located opposite to glucose, spontaneously form lamellar hydrogels at room temperature below pH 8. In this work, we combine rheology with small angle X-ray scattering (SAXS), rheo-SAXS, to correlate, in situ, the structural and mechanical properties of microbial glycolipid lamellar hydrogels upon application of three different stimuli: pH, temperature and a shear rate. In all cases we find unusual structural features of the lamellar phase if compared to classical phospholipid lamellar structures: reducing pH from alkaline to acidic induces a sol-to-gel transition during which an increasing elastic modulus is associated with an oscillatory evolution of lamellar d(100) spacing; temperature above Tm and increasing shear induce the formation of spherulitic crumpled domains, instead of a classically-expected lamellar-to-vesicle or lamellar-to-onion phase transitions.


Assuntos
Glucose/análogos & derivados , Glicolipídeos/química , Hidrogéis/química , Leveduras/química , Módulo de Elasticidade , Concentração de Íons de Hidrogênio , Transição de Fase , Reologia , Espalhamento a Baixo Ângulo , Temperatura , Difração de Raios X
14.
Soft Matter ; 16(10): 2528-2539, 2020 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-32076696

RESUMO

Lipid lamellar hydrogels are rare soft fluids composed of a phospholipid lamellar phase instead of fibrillar networks. The mechanical properties of these materials are controlled by defects, induced by local accumulation of a polymer or surfactant in a classical lipid bilayer. Herein we report a new class of lipid lamellar hydrogels composed of one single bolaform glycosylated lipid obtained by fermentation. The lipid is self-organized into flat interdigitated membranes, stabilized by electrostatic repulsive forces and stacked in micrometer-sized lamellar domains. The defects in the membranes and the interconnection of the lamellar domains are responsible, from the nano- to the micrometer scales, for the elastic properties of the hydrogels. The lamellar structure is probed by combining small angle X-ray and neutron scattering (SAXS, SANS), the defect-rich lamellar domains are visualized by polarized light microscopy while the elastic properties are studied by oscillatory rheology. The latter show that both storage G' and loss G'' moduli scale as a weak power-law of the frequency, that can be fitted with fractional rheology models. The hydrogels possess rheo-thinning properties with second-scale recovery. We also show that ionic strength is not only necessary, as one could expect, to control the interactions in the lamellar phase but, most importantly, it directly controls the elastic properties of the lamellar gels.


Assuntos
Glucose/análogos & derivados , Glicolipídeos/química , Hidrogéis/química , Leveduras/química , Elasticidade , Concentração Osmolar , Reologia , Eletricidade Estática , Viscosidade
15.
Environ Pollut ; 260: 114029, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32018200

RESUMO

Extreme droughts associated with changes in the climate have occurred every 5 years in the Amazon during the 21st century, with the most severe being in 2015. The increase in biomass burning (BB) events that occurred during the 2015 drought had several negative socioeconomic and environmental impacts, one of which was a decrease in the air quality. This study is an investigation into the air quality in the Manaus Metropolitan Region (MMR) (central Amazon, Brazil) during the dry (September to October) and wet (April to May) seasons of 2015 and 2016. A strong El Niño event began during the wet season of 2015 and ended during the wet season of 2016. Particulate matter samples were collected in the MMR during 2015 and 2016, and analyses of the satellite-estimated total carbon monoxide (CO) column and observed levoglucosan concentrations were carried out. Levoglucosan has been shown to be significantly correlated with regional fires and is a well-established chemical tracer for the atmospheric particulates emitted by BB, and CO can be treated as a gaseous-phase tracer for BB. The number of BB events increased significantly during the El Niño period when compared to the average number during 2003-2016. Consequently, the total CO column and levoglucosan concentration values in the MMR increased by 15% and 500%, respectively, when compared to the normal conditions. These results indicate that during the period that was analyzed, the impacts of BB were exacerbated during the strong El Niño event as compared to the non-El Niño period. In this study, we provided evidence that the air quality in the MMR will degrade in the future if droughts and BB occurrences continue to increase.


Assuntos
El Niño Oscilação Sul , Monitoramento Ambiental , Incêndios , Glucose/análogos & derivados , Biomassa , Brasil , Monóxido de Carbono , Secas , Glucose/análise , Estações do Ano
16.
Nature ; 579(7799): 443-447, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32103179

RESUMO

In eukaryotic protein N-glycosylation, a series of glycosyltransferases catalyse the biosynthesis of a dolichylpyrophosphate-linked oligosaccharide before its transfer onto acceptor proteins1. The final seven steps occur in the lumen of the endoplasmic reticulum (ER) and require dolichylphosphate-activated mannose and glucose as donor substrates2. The responsible enzymes-ALG3, ALG9, ALG12, ALG6, ALG8 and ALG10-are glycosyltransferases of the C-superfamily (GT-Cs), which are loosely defined as containing membrane-spanning helices and processing an isoprenoid-linked carbohydrate donor substrate3,4. Here we present the cryo-electron microscopy structure of yeast ALG6 at 3.0 Å resolution, which reveals a previously undescribed transmembrane protein fold. Comparison with reported GT-C structures suggests that GT-C enzymes contain a modular architecture with a conserved module and a variable module, each with distinct functional roles. We used synthetic analogues of dolichylphosphate-linked and dolichylpyrophosphate-linked sugars and enzymatic glycan extension to generate donor and acceptor substrates using purified enzymes of the ALG pathway to recapitulate the activity of ALG6 in vitro. A second cryo-electron microscopy structure of ALG6 bound to an analogue of dolichylphosphate-glucose at 3.9 Å resolution revealed the active site of the enzyme. Functional analysis of ALG6 variants identified a catalytic aspartate residue that probably acts as a general base. This residue is conserved in the GT-C superfamily. Our results define the architecture of ER-luminal GT-C enzymes and provide a structural basis for understanding their catalytic mechanisms.


Assuntos
Microscopia Crioeletrônica , Retículo Endoplasmático/enzimologia , Glicosiltransferases/genética , Glicosiltransferases/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/enzimologia , Biocatálise , Domínio Catalítico , Sequência Conservada , Dolicol Monofosfato Manose/metabolismo , Fosfatos de Dolicol/metabolismo , Glucose/análogos & derivados , Glucose/metabolismo , Glicosiltransferases/deficiência , Técnicas In Vitro , Lipídeos , Proteínas de Membrana/deficiência , Modelos Moleculares , Mutação , Monossacarídeos de Poli-Isoprenil Fosfato/química , Monossacarídeos de Poli-Isoprenil Fosfato/metabolismo , Ligação Proteica , Saccharomyces cerevisiae/genética , Especificidade por Substrato
17.
Nefrología (Madrid) ; 40(1): 99-103, ene.-feb. 2020. tab, graf
Artigo em Espanhol | IBECS | ID: ibc-198959

RESUMO

ANTECEDENTES Y OBJETIVOS: La cistinosis es un error innato del metabolismo cuyas características clínicas incluyen compromiso renal severo y formación de cristales de cistina en la córnea, especialmente en la presentación adulta de la enfermedad. Es una enfermedad tratable, por lo cual establecer el diagnóstico de forma oportuna es fundamental para iniciar la terapia. Para la confirmación bioquímica de la enfermedad se requiere determinar las concentraciones intracelulares de cistina, para lo cual se han reportado diferentes métodos tanto para el aislamiento de las células como para la cuantificación del aminoácido. Con el objetivo de mejorar el diagnóstico bioquímico confirmatorio en nuestro medio establecimos un protocolo de cuantificación intraleucocitaria de cistina. MÉTODOS: Se implementó un método de cuantificación de cistina en polimorfonucleares por cromatografía líquida de alta resolución, evaluando el mejor anticoagulante a utilizar, la estabilidad de la muestra a 4̊ C y estableciendo valores de referencia para nuestra población. RESULTADOS: Se determinó que la muestra para cuantificación intraleucocitaria de cistina debe ser anticoagulada mediante la adición de ácido cítrico-dextrosa como anticoagulante. La muestra debe ser procesada inmediatamente, dada su baja estabilidad incluso en refrigeración. Con 50 individuos sanos se estableció como punto de corte para nuestra población 0,34 nmol 1/2 cistina/mg. CONCLUSIÓN: La adaptación realizada del método de cuantificación de cistina utiliza el número más alto de muestras control hasta ahora reportado en la literatura. Nuestros resultados dan cuenta de la necesidad de implementar el método a nivel local y reafirman la conveniencia de que cada laboratorio establezca sus propios valores de referencia para proporcionar una mayor confiabilidad a la hora de interpretar los resultados


Background and aims: Cystinosis is an inborn error of metabolism, clinically characterised by severe renal involvement and development of corneal cystine deposits, especially in the adult form of the disease. Cystinosis is a treatable condition. Therefore, an early diagnosis is necessary to start therapy. For biochemical confirmation of the condition it is necessary to quantify intracellular cystine concentrations. For this, different methods have been described with variations in cell isolation strategies and the amino acid quantification techniques used. In order to improve confirmatory biochemical diagnosis in our setting, a protocol for intraleukocitary cystine quantification was established. METHODS: A high performance liquid chromatography based method for cystine quantification in polymorphonuclear cells was implemented. Evaluation of the best anticoagulant to use and temperature stability of the sample at 4̊C were performed. In addition, we established reference values for our population. RESULTS: It was determined that intraleukocitary cystine quantification must be performed in blood samples containing acid-citrate-dextrose as anticoagulant. Samples must be processed immediately due to their poor stability even when refrigerated. Based on the results from 50 healthy individuals, the cut-off point established for our population was 0.34 nmol 1/2 cystine/mg. CONCLUSION: The adaptation performed to the cystine quantification method here presented the highest control population that has been reported in the literature so far. Our results highlight the need for making available a cystine quantification method locally and confirm the convenience for each laboratory to establish its own reference values to provide greater reliability for interpreting results


Assuntos
Humanos , Cistina/sangue , Cistinose/diagnóstico , Neutrófilos/química , Anticoagulantes , Cromatografia Líquida de Alta Pressão , Ácido Cítrico , Temperatura Baixa , Colômbia , Síndrome de Fanconi/etiologia , Glucose/análogos & derivados , Valores de Referência
18.
Food Funct ; 11(1): 211-220, 2020 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-31915766

RESUMO

Evolution of important glucosinolates (GLSs), namely, sinigrin, glucoraphanin, glucoerucin and glucobrassicin, in three commonly consumed Brassica vegetables viz. white cabbage, Chinese cabbage and bok choy during their processing into vegetable powder was investigated. Drying was noted to be a major processing step causing significant losses of GLSs. Interestingly, different GLSs and even the same GLSs in different vegetables showed different thermal stabilities during drying. The stability of GLSs in vegetable powder during in vitro gastric digestion was also studied. Glucoraphanin exhibited the highest stability while glucobrassicin was the most vulnerable GLS under in vitro gastric conditions. White cabbage is found to be a promising material for the production of vegetable powder as it contains high contents of GLSs, especially glucoraphanin and glucoerucin, which are important precursors of anticarcinogenic compounds, namely sulforaphane and erucin. These two GLSs were also noted to be stable during in vitro gastric digestion.


Assuntos
Brassica/química , Digestão , Manipulação de Alimentos , Glucosinolatos/análise , Fibras na Dieta/metabolismo , Glucose/análogos & derivados , Imidoésteres , Indóis , Valor Nutritivo , Pós/análise , Verduras
19.
J Med Chem ; 63(2): 747-755, 2020 01 23.
Artigo em Inglês | MEDLINE | ID: mdl-31846326

RESUMO

Glycomimetic drugs have attracted increasing interest as unique targeting vectors or surrogates for endogenous biomolecules. However, it is generally difficult to determine the in vivo pharmacokinetic profile of these compounds. In this work, two galectin-3 inhibitors were radiolabeled with fluorine-18 and used as surrogate PET tracers of TD139 and GB1107. Both compounds are promising drugs for clinical applications. In vivo evaluation revealed that both surrogates strongly differed with respect to their biodistribution profile. The disaccharide (TD139 surrogate) was rapidly eliminated from blood while the monosaccharide (GB1107 surrogate) showed no sign of excretion. The data obtained allowed us to infer the different in vivo fate of TD139 and GB1107 and rationalize how different administration routes could boost efficacy. Whereas the fast excretion profile of the TD139 surrogate indicated that systemic application of disaccharides is unfavorable, the extended biological half-life of the GB1107 surrogate indicated that systemic administration is possible for monosaccharides.


Assuntos
Radioisótopos de Flúor/química , Galectina 3/antagonistas & inibidores , Glucose/farmacologia , Compostos Radiofarmacêuticos/síntese química , Compostos Radiofarmacêuticos/farmacocinética , Animais , Feminino , Glucose/análogos & derivados , Glucose/síntese química , Meia-Vida , Marcação por Isótopo , Tomografia por Emissão de Pósitrons , Ratos , Ratos Long-Evans , Distribuição Tecidual
20.
J Chromatogr A ; 1610: 460557, 2020 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-31570193

RESUMO

Biomass burning (BB) emissions are a significant source of particles to the atmosphere, especially in the Southern Hemisphere, where the occurrence of anthropogenic and natural wild fires is common. These emissions can threaten human health through increased exposure, whilst simultaneously representing a significant source of trace metals and nutrients to the ocean. One well known method to track BB emissions is through monitoring the atmospheric concentration of specific monosaccharide anhydrides (MAs), specifically levoglucosan and its isomers, mannosan and galactosan. Herein, a new method for the determination of levoglucosan and its isomers in marine and terrestrial aerosol samples is presented, which delivers both high selectivity and sensitivity, through the coupling of ion chromatography and triple quadrupole tandem mass spectrometry. Optimal chromatographic conditions, providing baseline separation for target anhydrosugars in under 8 min, were obtained using a Dionex CarboPacⓇ PA-1 column with an electrolytically generated KOH gradient. To improve the ionisation efficiency for MS detection, an organic make-up solvent was fed into the IC column effluent before the ESI source, and to further increase both sensitivity and selectivity, cationisation of levoglucosan was investigated by adding salts into the make-up solvent, namely, sodium, ammonium and lithium salts. Using positive lithium cationisation with 0.5 mM lithium chloride in methanol as the make-up solvent, delivered at a flow rate of 0.02 mL min-1, the levoglucosan response was improved by factors of 100 and 10, comparing to negative ionisation and positive sodium cationisation, respectively. Detection was carried out in SRM mode for quantitation and identification, achieving an instrumental LOD of 0.10, 0.12 and 0.5 µg L-1 for levoglucosan, mannosan and galactosan, respectively. Finally, the method was applied to the analysis of 41 marine and terrestrial aerosol samples from Australia, its surrounding coastal waters and areas within the remote Southern Ocean, covering a large range of BB marker concentrations.


Assuntos
Atmosfera/química , Cromatografia/métodos , Glucose/análogos & derivados , Lítio/química , Espectrometria de Massas em Tandem/métodos , Anidridos/análise , Atmosfera/análise , Austrália , Cátions , Monitoramento Ambiental/métodos , Galactose/análogos & derivados , Galactose/análise , Glucose/análise , Isomerismo , Limite de Detecção , Manose/análogos & derivados , Manose/análise , Monossacarídeos/análise , Padrões de Referência
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...