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1.
Materials (Basel) ; 16(24)2023 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-38138675

RESUMO

Advanced high-strength steels (AHSS) have a wide range of applications in equipment safety and lightweight design, and enhancing the strength of AHSS to the ultra-high level of 2 GPa is currently a key focus. In this study, a new process of thermo-mechanical control process followed by direct quenching and partitioning (TMCP-DQP) was developed based on Fe-0.4C-1Mn-0.6Si (wt.%) low-alloy steel, and the effects of microstructure evolution on mechanical properties under TMCP-DQP process and conventional hot rolled quenched and tempered process (HR-QT) were comparatively studied. The results show that the TMCP-DQP process not only shortened the processing steps but also achieved outstanding comprehensive mechanical properties. The TMCP-DQP steel exhibited a tensile strength of 2.23 GPa, accompanied by 11.9% elongation and a Brinell hardness of 624 HBW, with an impact toughness of 28.5 J at -20 °C. In contrast, the HR-QT steel exhibited tensile strengths ranging from 2.16 GPa to 1.7 GPa and elongations between 5.2% and 12.2%. The microstructure of TMCP-DQP steel primarily consisted of lath martensite, containing thin-film retained austenite (RA), nanoscale rod-shaped carbides, and a minor number of nanoscale twins. The volume fraction of RA reached 7.7%, with an average carbon content of 7.1 at.% measured by three-dimensional atom probe tomography (3DAP). Compared with the HR-QT process, the TMCP-DQP process resulted in a finer microstructure, with a prior austenite grain (PAG) size of 11.91 µm, forming packets and blocks with widths of 5.12 µm and 1.63 µm. The TMCP-DQP process achieved the ultra-high strength of low-alloy steel through the synergistic effects of grain refinement, dislocation strengthening, and precipitation strengthening. The dynamic partitioning stage stabilized the RA through carbon enrichment, while the relaxation stage reduced a small portion of the dislocations generated by thermal deformation, and the self-tempering stage eliminated internal stresses, all guaranteeing considerable ductility and toughness. The TMCP-DQP process may offer a means for industries to streamline their manufacturing processes and provide a technological reference for producing 2.2 GPa grade AHSS.

2.
Molecules ; 28(20)2023 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-37894692

RESUMO

We have prepared and characterized two Ru(III) compounds based on the 2,2'-biimidazole (H2biim) ligand, namely, a single complex of formula cis-[RuCl2(H2biim)2]Cl·4H2O (1) and a racemic mixture of formula {cis-[RuCl2(H2biim)2]Cl}2·4H2O (2), which contains 50% of Ru(III) complex 1. Both compounds crystallize in the monoclinic system with space groups C2 and P21 for 1 and 2, respectively. These complexes exhibit the metal ion bonded to four nitrogen atoms from two H2biim molecules and two chloride ions, which balance part of the positive charges in a distorted octahedral geometry. Significant differences are observed in their crystal packing, which leads to the observation of differences in their respective magnetic behaviors. Despite having imidazole rings in both compounds, π-π stacking interactions occur only in the crystal structure of 2, and the shortest intermolecular Ru···Ru separation in 2 is consequently shorter than that in 1. Variable-temperature dc magnetic susceptibility measurements performed on polycrystalline samples of 1 and 2 reveal different magnetic behaviors at low temperatures: while 1 behaves pretty much as a magnetically isolated mononuclear Ru(III) complex with S = 1/2, 2 exhibits the behavior of an antiferromagnetically coupled system with S = 0 and a maximum in the magnetic susceptibility curve at approximately 3.0 K.

3.
J Appl Crystallogr ; 56(Pt 3): 611-623, 2023 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-37284254

RESUMO

In recent years, transition metal dichalcogenides have received great attention since they can be prepared as two-dimensional semiconductors, presenting heterodesmic structures incorporating strong in-plane covalent bonds and weak out-of-plane interactions, with an easy cleavage/exfoliation in single or multiple layers. In this context, molybdenite, the mineralogical name of molybdenum disulfide, MoS2, has drawn much attention because of its very promising physical properties for optoelectronic applications, in particular a band gap that can be tailored with the material's thickness, optical absorption in the visible region and strong light-matter interactions due to the planar exciton confinement effect. Despite this wide interest and the numerous experimental and theoretical articles in the literature, these report on just one or two specific features of bulk and layered MoS2 and sometimes provide conflicting results. For these reasons, presented here is a thorough theoretical analysis of the different aspects of bulk, monolayer and bilayer MoS2 within the density functional theory (DFT) framework and with the DFT-D3 correction to account for long-range interactions. The crystal chemistry, stiffness, and electronic, dielectric/optical and phonon properties of single-layered, bilayered and bulk molybdenite have been investigated, to obtain a consistent and detailed set of data and to assess the variations and cross correlation from the bulk to single- and double-layer units. The simulations show the indirect-direct transition of the band gap (K-K' in the first Brillouin zone) from the bulk to the single-layer structure, which however reverts to an indirect transition when a bilayer is considered. In general, the optical properties are in good agreement with previous experimental measurements using spectroscopic ellipsometry and reflectivity, and with preliminary theoretical simulations.

4.
ACS Appl Mater Interfaces ; 15(23): 27789-27800, 2023 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-37261999

RESUMO

Alzheimer's disease is associated with the aggregation of the misfolded neuronal peptide, amyloid-ß42 (Aß42). Evidence has suggested that several reasons are responsible for the toxicity caused by the aggregation of Aß42, including the conformational restriction of Aß42. In this study, one of the toxic conformers of Aß42, which contains a Glu-to-Pro substitution (E22P-Aß42), was explored using atomic force microscopy and molecular docking to study the aggregation dynamics. We proposed a systematic model of fibril formation to better understand the molecular basis of conformational transitions in the Aß42 species. Our results demonstrated the formation of amorphous aggregates in E22P-Aß42 that are stem-based, network-like structures, while the formation of mature fibrils occurred in the less toxic conformer of Aß42, E22-Aß42, that are sphere-like flexible structures. A comparison was made between the biophysical properties of E22P-Aß42 and E22-Aß42 that revealed that E22P-Aß42 had greater stiffness, dihedral angle, number of ß sheets involved, and elasticity, compared with E22-Aß42. These findings will have considerable implications toward our understanding of the structural basis of the toxicity caused by conformational diversity in Aß42 species.


Assuntos
Doença de Alzheimer , Peptídeos beta-Amiloides , Humanos , Peptídeos beta-Amiloides/toxicidade , Peptídeos beta-Amiloides/química , Simulação de Acoplamento Molecular , Microscopia de Força Atômica , Amiloide , Proteínas Amiloidogênicas , Fragmentos de Peptídeos/química
5.
Food Chem X ; 18: 100644, 2023 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-37032744

RESUMO

The aim of this study was to establish a human digestion model in vitro to explore the degradation characteristics of a novel high-purity polysaccharide from Clitocybe squamulosa (CSFP2). The results showed that the content of reducing sugars (CR ) of CSFP2 increased from 0.13 to 0.23 mg/mL, the molecular weight (Mw) of CSFP2 decreased significantly during the saliva-gastrointestinal digestion. The constituent monosaccharides of CSFP2, including galactose, glucose, and mannose, were stable during in vitro digestion, but their molar ratios were changed from 0.023: 0.737: 0.234 to 0.496: 0.478: 0.027. The surface of CSFP2 changes from a rough flaky structure to a scattered flocculent or rod-shaped structure after the gastrointestinal digestion. However, the apparent viscosity of CSFP2 was overall stable during in vitro digestion. Moreover, CSFP2 still maintains its strong antioxidant capacity after saliva-gastrointestinal digestion. The results showed that CSFP2 can be partially decomposed during digestion. Meanwhile, some physico-chemical properties of the fermentation broth containing CSFP2 changed significantly after gut microbiota fermentation. For example, the pH value (from 8.46 to 4.72) decreased significantly (p < 0.05) after 48 h of fermentation. the OD 600 value increased first and then decreased (from 2.00 to 2.68 to 1.32) during 48-h fermentation. In addition, CSFP2 could also increase the amounts of short-chain fatty acids (SCFAs) (from 5.5 to 37.15 mmol/L) during fermentation (in particular, acetic acid, propionic acid, and butyric acid). Furthermore, the relative abundances of Bacteriodes, Bifidobacterium, Catenibacterium, Lachnospiraceae_NK4A136_group, Megasphaera, Prevotella, Megamonas, and Lactobacillus at genus level were markedly increased with the intervention of CSFP2. These results provided a theoretical basis for the further development of functional foods related to CSFP2.

6.
Molecules ; 28(5)2023 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-36903384

RESUMO

Five new metal-organic frameworks based on Mn(II) and 2,2'-bithiophen-5,5'-dicarboxylate (btdc2-) with various chelating N-donor ligands (2,2'-bipyridyl = bpy; 5,5'-dimethyl-2,2'-bipyridyl = 5,5'-dmbpy; 4,4'-dimethyl-2,2'-bipyridyl = 4,4'-dmbpy) [Mn3(btdc)3(bpy)2]·4DMF, 1; [Mn3(btdc)3(5,5'-dmbpy)2]·5DMF, 2; [Mn(btdc)(4,4;-dmbpy)], 3; [Mn2(btdc)2(bpy)(dmf)]·0.5DMF, 4; [Mn2(btdc)2(5,5'-dmbpy)(dmf)]·DMF, 5 (dmf, DMF = N,N-dimethylformamide) have been synthesized, and their crystal structure has been established using single-crystal X-ray diffraction analysis (XRD). The chemical and phase purities of Compounds 1-3 have been confirmed via powder X-ray diffraction, thermogravimetric, and chemical analyses as well as IR spectroscopy. The influence of the bulkiness of the chelating N-donor ligand on the dimensionality and structure of the coordination polymer has been analyzed, and the decrease in the framework dimensionality, as well as the secondary building unit's nuclearity and connectivity, has been observed for bulkier ligands. For three-dimensional (3D) coordination polymer 1, the textural and gas adsorption properties have been studied, revealing noticeable ideal adsorbed solution theory (IAST) CO2/N2 and CO2/CO selectivity factors (31.0 at 273 K and 19.1 at 298 K and 25.7 at 273 K and 17.0 at 298 K, respectively, for the equimolar composition and the total pressure of 1 bar). Moreover, significant adsorption selectivity for binary C2-C1 hydrocarbons mixtures (33.4 and 24.9 for C2H6/CH4, 24.8 and 17.7 for C2H4/CH4, 29.3 and 19.1 for C2H2/CH4 at 273 K and 298 K, respectively, for the equimolar composition and the total pressure of 1 bar) has been observed, making it possible to separate on 1 natural, shale, and associated petroleum gas into valuable individual components. The ability of Compound 1 to separate benzene and cyclohexane in a vapor phase has also been analyzed based on the adsorption isotherms of individual components measured at 298 K. The preferable adsorption of C6H6 over C6H12 by 1 at high vapor pressures (VB/VCH = 1.36) can be explained by the existence of multiple van der Waals interactions between guest benzene molecules and the metal-organic host revealed by the XRD analysis of 1 immersed in pure benzene for several days (1≅2C6H6). Interestingly, at low vapor pressures, an inversed behavior of 1 with preferable adsorption of C6H12 over C6H6 (KCH/KB = 6.33) was observed; this is a very rare phenomenon. Moreover, magnetic properties (the temperature-dependent molar magnetic susceptibility, χp(T) and effective magnetic moments, µeff(T), as well as the field-dependent magnetization, M(H)) have been studied for Compounds 1-3, revealing paramagnetic behavior consistent with their crystal structure.

7.
Food Chem X ; 17: 100577, 2023 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-36845496

RESUMO

Studies are being carried out on achieving the maximum quality of garlic through various approaches. In Bangladesh, new garlic varieties (BARI 1-4, BAU-1, BAU-2, BAU-5) have been recently developed by artificial selection to enhance their quality. The present study aimed to evaluate their potency in terms of bioactive properties and organosulfur compounds content using different bioassay and GC-MS techniques while comparing them with other accessible varieties (Chinese, Indian, Local). The new variety, BARI-3 showed the highest antioxidant activity and total phenolic content. It was also found with the highest level of a potent blood pressure-lowering agent, 2-vinyl-4H-1,3-dithiine (78.15 %), which is never reported in any garlic at this percentage. However, the local variety exhibited greater inhibitory properties against the tested organisms including multidrug-resistant pathogens compared to other varieties. This study primarily shows the potential of these two kinds of garlic for their further utilization and development.

8.
Molecules ; 28(2)2023 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-36677784

RESUMO

New Tb(III) and Eu(III) complexes based on aryl-2,2'-bipyridine ligands with a cyclic DO3A chelating unit appended in the alpha position of the bipyridine core were synthesized. The photophysical properties of these complexes were compared with those of complexes of ligands with identical aryl-2,2'-bipyridine chromophores, but with an acyclic DTTA residue as an additional chelating site in the alpha position of the bipyridine core. The nature of the polyaminocarboxylic acid fragments was found to have a significant influence on the luminescence. For some of the Eu(III) complexes, upon the transition from acyclic DTTA- to the cyclic DO3A-appended ligands, a noticeable increase in the intensity of Eu(III) luminescence was observed, with an increase in the quantum yield of up to 2.55 times. In contrast, for most of the Tb(III) complexes, a similar transition resulted in a noticeable decrease in the luminescence intensity of the Tb(III) cation.

9.
Molecules ; 27(20)2022 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-36296472

RESUMO

A series of new α-(N-biphenyl)-substituted 2,2'-bipyridines were obtained through the combination of the ipso-nucleophilic aromatic substitution of the C5-cyano group, aza-Diels-Alder and Suzuki cross-coupling reactions, starting from 5-cyano-1,2,4-triazines. For the obtained compounds, photophysical and fluorosolvatochromic properties were studied. Fluorophores 3l and 3b demonstrated unexpected AIEE activity, while 3a and 3h showed promising nitroexplosive detection abilities.


Assuntos
2,2'-Dipiridil , Corantes Fluorescentes , Compostos de Bifenilo , Ionóforos , Triazinas
10.
J Mol Graph Model ; 116: 108235, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-35716640

RESUMO

To study the properties of 2,3,5,6-tetra(1H-tetrazol-5-yl)pyrazine (H4TTP) and 1,1'-diamino-2,2'-dinitroethylene (FOX-7) blending system, the structures of H4TTP, FOX-7, and H4TTP/FOX-7 dimers were optimized using density functional theory (DFT), and the mechanical properties and cohesive energy densities (CED) of H4TTP/FOX-7 blends with different mass ratios were calculated by molecular dynamics (MD) simulation. The results show that the HOMO of H4TTP is distributed on the pyrazine and tetrazole rings, while the LUMO is mainly distributed on the pyrazine ring, with a small contribution from the tetrazole ring. The HOMO of FOX-7 molecules is mainly located on the CC bonds, while the LUMO is mainly located on the nitro groups. The most stable dimer, (I), was formed when the interaction between frontier MOs is possible and hydrogen bond is formed between two monomers, which was confirmed by the Reduced Density Gradient (RDG) isosurface graph. MD studies were carried out to examine the mechanical properties and cohesive energy density of the blending systems. In monomer systems, FOX-7 has the strongest rigidity and best ductility, while H4TTP has the largest elasticity and best toughness. In the blending systems, we found that various mechanical properties and CED values were different from those of monomers, which improves the sensitivity of H4TTP and the safety of explosives.


Assuntos
Nitrocompostos , Pirazinas , Etilenos , Modelos Moleculares , Nitrocompostos/química , Pirazinas/química , Tetrazóis/química
11.
Luminescence ; 37(8): 1328-1334, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35641133

RESUMO

The synthesis and characterization of a series of octa-coordinated Sm(III) complexes with 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (TFNB) and 2,2'-bipyridine (Bpy) derivatives as ancillary ligand are described here. The complexes were analyzed by elemental, spectroscopic such as infrared spectroscopy, 1 H NMR, and thermogravimetric analyses. The fluorinated TFNB ligand absorbs in the range from 200 to 400 nm. The complexes show the sharp and structured Sm-based emissions in visible region upon irradiation in UV range. Excitation spectra of complexes show similarity to the absorption spectra of ligands suggesting that excitation energy is transferred from ligands to Sm(III) centre by the antenna effect. Photoluminescence emission spectra and colour parameters affirmed that the complexes show luminescence in orange-red region. These luminous Sm(III) complexes might be applied as emissive layer in organic electroluminescent devices.

12.
Materials (Basel) ; 14(21)2021 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-34772132

RESUMO

This article deals with the dissimilar joining of two different grade Cr-Mo steel (2.25Cr-1Mo: P22 and modified 9Cr-1Mo: P91) for power plant application. The dissimilar butt-welded joint was produced for conventional V groove design by using the gas tungsten arc welding (GTAW) process with the application of an ERNiCrMo-3 Ni-based super alloy filler. A microstructure characterization was performed to measure the inhomogeneity in the microstructure and element diffusion across the interface in a welded joint. The experiments were also performed to evaluate the mechanical properties of the dissimilar welded joint in as-welded (AW) and post-weld heat treatment (PWHT) conditions. An acceptable level of the mechanical properties was obtained for the AW joint. After PWHT, a significant level of the element diffusion across the interface of the weld metal and P22 steel was observed, resulting in heterogeneity in microstructure near the interface, which was also supported by the hardness variation. Inhomogeneity in mechanical properties (impact strength and hardness) was measured across the weldments for the AW joint and was reduced after the PWHT. The tensile test results indicate an acceptable level of tensile properties for the welded joint in both AW and PWHT conditions and failure was noticed in the weak region of the P22 steel instead of the weld metal.

13.
Materials (Basel) ; 14(9)2021 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-33925398

RESUMO

The high tensile strength and irradiation resistance of oxide dispersion strengthened (ODS) ferritic steels is attributed to the ultrafine and dispersed oxides within the matrix. The high content of oxygen and yttrium is critical for the formation of dense Y-rich oxides. However, only few studies have reported the effect of oxygen content on the microstructure and mechanical properties of ODS steels. Herein, we employed gas atomization reactive synthesis to prepare pre-alloy powders and then hot isostatic pressing (HIP) to consolidate two 22Cr-5Al ODS steels with different oxygen content. Our results showed Y-rich precipitates at and near grain boundaries of the as-HIPed alloys. Moreover, with the oxygen content increasing from 0.04 to 0.16 wt%, more precipitates precipitated in the as-HIPed alloy, and the ultimate tensile strength of the alloy was improved. However, increasing the oxygen content to 0.16 wt% led to formation of stripe and chain precipitates at and near grain boundaries, which caused a partial intergranular fracture of the as-HIPed alloy.

14.
Food Chem ; 347: 129084, 2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-33486366

RESUMO

Milk proteins and polyphenols are increasingly being studied as functional ingredients due to the epidemiologically-proved health benefits. In this study, composite ß-lactoglobulin (ß-lg) or ß-lactoglobulin nanoparticles (ß-lgNPs)-3,5-di-O-caffeoylquinic acid (3,5diCQA) with superior physicochemical and antioxidant activity (AA) were produced using ß-lg and 3,5-di-O-caffeoylquinic acid. The main interactions between ß-lg or ß-lgNPs with 3,5diCQA were hydrogen bonding and hydrophobic effects. The 3,5diCQA caused a decrease in α-helix and ß-sheet structure with a corresponding increase in unordered structure. Compared to ß-lg alone, composite ß-lg or ß-lgNPs-3,5diCQA slightly decreased the particle size but increased their negative surface potentials especially for ß-lg or ß-lgNPs at a molar ratio of 5:1. The addition of 3,5diCQA appreciably improved the AA in a dose-dependent manner. These results shed light on the structural, physicochemical, and AA of composite ß-lg or ß-lgNPs-3,5diCQA non-covalent complexes, important for application as functional ingredients in food solutions as well as in the pharmaceutical industry.


Assuntos
Antioxidantes/química , Ácido Clorogênico/análogos & derivados , Lactoglobulinas/química , Nanopartículas/química , Animais , Ácido Clorogênico/química , Ácido Clorogênico/metabolismo , Ligação de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Lactoglobulinas/metabolismo , Tamanho da Partícula , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta
15.
Food Chem ; 336: 127669, 2021 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32758804

RESUMO

Curcumin was recently attracted great interest owing to its multiple bioactivities; however, the use of curcumin was hindered by its poor solubility and stability. In this study, curcumin-nisin-soy soluble polysaccharide nanoparticles (Cur-Nisin-SSPS-NPs, size = 118.76 nm) have been successfully elaborated to improve the application of curcumin. The formation of Cur-Nisin-SSPS-NPs was mediated by amphiphilic and positively charged nisin: SSPS encapsulated nisin, which was mainly driven by electrostatic attraction. And nisin-SSPS complex encapsulated curcumin mainly through hydrophobic interactions between nisin and curcumin. The encapsulation efficiency of curcumin (91.66%) in this novel nanocarriers was significantly higher than that in nanoparticles prepared by a single SSPS (31.82%) or nisin (41.69%), most likely because more hydrophobic regions of nisin were exposed after interacting with SSPS through electrostatic interaction. Consequently, this facile and green nanocarriers improved the solubility/dispersibility and stability of curcumin and nisin, as well as endowed SSPS-based nanoparticles with antioxidant and antimicrobial activities.


Assuntos
Curcumina/administração & dosagem , Portadores de Fármacos/química , Nanopartículas/química , Nisina/química , Polissacarídeos/química , Antibacterianos/administração & dosagem , Antibacterianos/química , Antibacterianos/farmacologia , Antioxidantes/química , Antioxidantes/farmacologia , Curcumina/química , Curcumina/farmacocinética , Liberação Controlada de Fármacos , Interações Hidrofóbicas e Hidrofílicas , Imidazóis , Testes de Sensibilidade Microbiana , Microscopia Eletrônica de Transmissão , Morfolinas , Solubilidade , Espectrofotometria Ultravioleta
16.
IUCrJ ; 7(Pt 1): 83-89, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31949907

RESUMO

Although a plethora of metal complexes have been characterized, those having multifunctional properties are very rare. This article reports three isotypical complexes, namely [Cu(benzoate)L 2], where L = 4-styryl-pyridine (4spy) (1), 2'-fluoro-4-styryl-pyridine (2F-4spy) (2) and 3'-fluoro-4-styryl-pyridine (3F-4spy) (3), which show photosalient behavior (photoinduced crystal mobility) while they undergo [2+2] cyclo-addition. These crystals also exhibit anisotropic thermal expansion when heated from room temperature to 200°C. The overall thermal expansion of the crystals is impressive, with the largest volumetric thermal expansion coefficients for 1, 2 and 3 of 241.8, 233.1 and 285.7 × 10-6 K-1, respectively, values that are comparable to only a handful of other reported materials known to undergo colossal thermal expansion. As a result of the expansion, their single crystals occasionally move by rolling. Altogether, these materials exhibit unusual and hitherto untapped solid-state properties.

17.
Nanomaterials (Basel) ; 10(1)2020 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-31947956

RESUMO

2,2'-(Ethylenedioxy)bis(ethylamine)-functionalized graphene quantum dots (GQDs) were prepared under mild conditions from graphene oxide (GO) via oxidative fragmentation. The as-prepared GQDs have an average diameter of ca. 4 nm, possess good colloidal stability, and emit strong green-yellow light with a photoluminescence (PL) quantum yield of 22% upon excitation at 375 nm. We also demonstrated that the GQDs exhibit high photostability and the PL intensity is poorly affected while tuning the pH from 1 to 8. Finally, GQDs can be used to chelate Fe(II) and Cu(II) cations, scavenge radicals, and reduce Fe(III) into Fe(II). These chelating and reducing properties that associate to the low cytotoxicity of GQDs show that these nanoparticles are of high interest as antioxidants for health applications.

18.
Carbohydr Polym ; 231: 115729, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31888843

RESUMO

This paper reports the preparation, characterization and properties of synthetic melanin-like nanoparticle (MNP) reinforced chitosan nanocomposite films. The MNP was prepared using dopamine hydrochloride and sodium hydroxide which followed by spontaneous oxidation. The prepared MNP was spherical in shape and in the size range of ∼100 nm. The MNP was used as a functional nanofiller to produce the chitosan/MNP nanocomposite films using simple solution mixing and casting method. The MNP are evenly dispersed and biocompatible with chitosan to form the nanocomposite films. The incorporation of MNP enhances the ultraviolet blocking, mechanical properties, swelling ratio, and hydrophobicity of the nanocomposite films. The reinforcement of MNP in chitosan does not deteriorate the thermal stability and water vapor barrier property of the nanocomposite films. Furthermore, the prepared nanocomposite films show strong antioxidant activity. The developed chitosan/MNP nanocomposite films can applied to active food packaging and biomedical packaging.

19.
Food Chem ; 309: 125738, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-31706679

RESUMO

In the present study, the impact of ultraviolet (UV)-C treatment and ultrafine grinding on the conversion of ergosterol to vitamin D2, physiochemical properties, and antioxidant properties of shiitake and Jew's ear was assessed. After exposure to UV-C, vitamin D2 contents of both the mushroom samples has increased significantly (p < 0.05). Whereas, ultrafine grinding along with UV-C treatment has a synergistic effect on bioconversion of ergosterol to vitamin D2 and this effect is more prominent in low dose UV-C irradiation groups (2 kJ/m2). Ultrafine grinding significantly (p < 0.05) improved the water holding capacity (WHC), water solubility index (WSI) and polysaccharide dissolution rate (PDR). However, UV-C treatment led to insignificant changes in the physiochemical properties of mushroom samples. A significant improvement was also observed in the antioxidant profiles especially tannin contents of mushrooms followed by the ultrafine grinding and UV-C treatment.


Assuntos
Agaricales/metabolismo , Agaricales/efeitos da radiação , Antioxidantes/metabolismo , Ergocalciferóis/metabolismo , Ergosterol/metabolismo , Cogumelos Shiitake/metabolismo , Cogumelos Shiitake/efeitos da radiação , Agaricales/química , Antioxidantes/química , Biotransformação , Ergocalciferóis/química , Ergosterol/química , Cogumelos Shiitake/química , Raios Ultravioleta
20.
Antioxidants (Basel) ; 8(6)2019 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-31174351

RESUMO

Grape foods with probiotics are sources of beneficial bacteria for the gastrointestinal (GI) tract and also have a high antioxidant capacity. The addition of probiotics to dairy food is a traditional process; therefore, probiotic non-dairy products might contribute to a daily antioxidant diet to improve consumer life quality and health. This research was undertaken to develop a grape marmalade with a probiotic base to investigate the potential antioxidant activity in the probiotic non-dairy product. Thus, changes in active culture numbers, pH level, glucose concentration, and antioxidant properties were evaluated. Most of the isolates demonstrated higher growth in the grape marmalade than the synthetic grape marmalade, which was greater than 7 log colony-forming units (CFU)/g within 90 days of storage at 4 °C. In addition, most of the wild isolates grew beyond the critical count of 106 CFU/g in sampling between 60 and 90 days of storage. Moreover, probiotic grape marmalade with probiotics showed a strong antioxidant capacity that failed to differ significantly with the synthetic medium. The study confirmed Lactobacillus paraplantarum AB362736.1, Lactobacillus plantarum MF369875.1, Weissella paramesenteroides CP023501.1, and Enterococcus faecalis HQ802261.1 were ideal bacteria for the probiotic process of grape marmalade.

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