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1.
Environ Sci Technol ; 55(19): 13335-13344, 2021 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-34524807

RESUMO

In this paper, Gd-promoted Co3O4 catalysts were prepared via a facile coprecipitation method for low-temperature catalytic N2O decomposition. Due to the addition of Gd, the crystallite size of Co3O4 in the Gd0.06Co catalyst surprisingly decreased to 4.9 nm, which is much smaller than most additive-modified Co3O4 catalysts. This huge change in the catalyst's textural structure endows the Gd0.06Co catalyst with a large specific surface area, plentiful active sites, and a weak Co-O bond. Hence, Gd0.06Co exhibited superior activity for catalyzing 2000 ppmv N2O decomposition, and the temperature for the complete catalytic elimination of N2O was as low as 350 °C. Meanwhile, compared with pure Co3O4, Ea decreased from 77.4 to 46.8 kJ·mol-1 and TOF of the reaction increased from 1.16 × 10-3 s-1 to 5.13 × 10-3 s-1 at 300 °C. Moreover, Gd0.06Co displayed a quite stable catalytic performance in the presence of 100 ppmv NO, 5 vol % O2, and 2 vol % H2O.


Assuntos
Gases , Catálise
2.
Antioxidants (Basel) ; 10(7)2021 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-34356378

RESUMO

Two low-molecular-weight polysaccharides (GLP-1 and GLP-2) were purified from Ganoderma leucocontextum fruiting bodies, and their physicochemical properties and antioxidant activities were investigated and compared in this study. The results showed that GLP-1 and GLP-2 were mainly composed of mannose, glucose, galactose, xylose, and arabinose, with weight-average molecular weights of 6.31 and 14.07 kDa, respectively. Additionally, GLP-1 and GLP-2 had a similar chain conformation, crystal structure, and molecular surface morphology. Moreover, GLP-1 exhibited stronger antioxidant activities than GLP-2 in five different assays: 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), hydroxyl radical, superoxide anion radical, ferric reducing antioxidant power (FRAP), and oxygen radical antioxidant capacity (ORAC). The main linkage types of GLP-1 were found to be →4)-α-D-Glcp-(1→, →4)-ß-D-Glcp-(1→, →3)-ß-D-Glcp-(1→, →6)-ß-D-Galp-(1→, →6)-α-D-Glcp-(1→, →4,6)-α-D-Glcp-(1→, and Glcp-(1→ by methylation analysis and nuclear magnetic resonance (NMR) spectroscopy. In addition, GLP-1 could protect NIH3T3 cells against tert-butyl hydroperoxide (tBHP)-induced oxidative damage by increasing catalase (CAT) and glutathione peroxidase (GSH-Px) activities, elevating the glutathione/oxidized glutathione (GSH/GSSG) ratio, and decreasing the malondialdehyde (MDA) level. These findings indicated that GLP-1 could be explored as a potential antioxidant agent for application in functional foods.

3.
Carbohydr Polym ; 249: 116874, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32933694

RESUMO

Ganoderma leucocontextum is a new species of Ganoderma discovered in 2014. Up to now, the structural characteristics and immunoregulatory activity of its polysaccharides remain virtually unknown. In this study, a water-soluble polysaccharide termed, GLP-3, was purified from G. leucocontextum by ultrafiltration and column chromatography. The results revealed that GLP-3 mainly consisted of glucose (92.7 %) and its weight average molecular weight was 159.7 kDa. The structural analysis indicated that the backbone of GLP-3 was →4)-α-D-Glcp-(1→4,6)-ß-D-Glcp-(1→ with a ß-Glcp-(1→ branch. Atomic force microscopy and Congo red experiments revealed that GLP-3 might possess a globular structure with triple-helix conformation in water. Moreover, GLP-3 was recognized by toll-like receptor 2 (TLR2) and exerted immunomodulatory effects via activating mitogen-activated protein kinases (MAPKs), phosphatidylinositol-3-kinase (PI3K)/Akt and nuclear factor-κB (NF-κB) signaling pathways in RAW 264.7 macrophages. Collectively, these results suggested that GLP-3 could be developed as a potential functional food ingredient for immunomodulation.


Assuntos
Carpóforos/química , Ganoderma/química , Imunomodulação , Macrófagos/imunologia , Polissacarídeos/química , Polissacarídeos/farmacologia , Animais , Macrófagos/efeitos dos fármacos , Camundongos , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Fosfatidilinositol 3-Quinase/metabolismo , Células RAW 264.7 , Transdução de Sinais , Receptor 2 Toll-Like/metabolismo , Fator de Necrose Tumoral alfa/metabolismo
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