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1.
Micron ; 143: 103012, 2021 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-33524916

RESUMO

The electronic structure of GaN and GaN:Zn was investigated by electron energy loss spectroscopy and first-principles calculations. In the low-loss spectrum, the interband transitions are assigned to the observed energy loss peaks. After Zn doping, impurity levels are introduced to the density of states and hybrid orbitals of N 2p and Zn 3d are formed around the Fermi level. In the nitrogen K-edge, an additional peak was observed due to the formation of donor defect states. A core-hole effect is believed to be significant for simulation of the N K-edge for both GaN and GaN:Zn.

2.
Biosci Biotechnol Biochem ; 85(2): 272-279, 2021 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-33604619

RESUMO

AGO2 is the only member of mammalian Ago protein family that possesses the catalytic activity and plays a central role in gene silencing. Recently researches reported that multiple gene silencing factors, including AGO2, function in the nuclei. The molecular mechanisms of the gene silencing factors functioning in nuclei are conducive to comprehend the roles of gene silencing in pretranslational regulation of gene expression. Here, we report that AGO2 interacts with DDX21 indirectly in an RNA-dependent manner by Co-IP and GST-Pulldown assays and the 2 proteins present nuclei foci in the immunofluorescence experiments. We found that DDX21 up-regulated the protein level of AGO2 and participated in target gene, SNM2, alternative splicing involved in AGO2 by the indirect interaction with AGO2, which produced different transcripts of SMN2 in discrepant expression level. This study laid important experiment foundation for the further analysis of the nuclear functions of gene silencing components.

4.
Cell Prolif ; : e12991, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33522656

RESUMO

OBJECTIVE: Premature senescence is related to progerin and involves in endothelial dysfunction and liver diseases. Activating sirtuin 1 (SIRT1) ameliorates liver fibrosis. However, the mechanisms of premature senescence in defenestration of hepatic sinusoidal endothelial cells (HSECs) and how SIRT1 affects HSECs fenestrae remain elusive. METHODS: We employed the CCl4 -induced liver fibrogenesis rat models and cultured primary HSECs in vitro, administered with the SIRT1-adenovirus vector, the activator of SIRT1 and knockdown NOX2. We measured the activity of senescence-associated ß-galactosidase (SA-ß-gal) in HSECs. Meanwhile, the protein expression of SIRT1, NOX2, progerin, Lamin A/C, Ac p53 K381 and total p53 was detected by Western blot, co-immunoprecipitation and immunofluorescence. RESULTS: In vivo, premature senescence was triggered by oxidative stress during CCl4 -induced HSECs defenestration and liver fibrogenesis, whereas overexpressing SIRT1 with adenovirus vector lessened premature senescence to relieve CCl4 -induced HSECs defenestration and liver fibrosis. In vitro, HSECs fenestrae disappeared, with emerging progerin-associated premature senescence; these effects were aggravated by H2 O2 . Nevertheless, knockdown of NOX2, activation of SIRT1 with resveratrol and SIRT1-adenovirus vector inhibited progerin-associated premature senescence to maintain fenestrae through deacetylating p53. Furthermore, more Ac p53 K381 and progerin co-localized with the abnormal accumulation of actin filament (F-actin) in the nuclear envelope of H2 O2 -treated HSECs; in contrast, these effects were rescued by overexpressing SIRT1. CONCLUSION: SIRT1-mediated deacetylation maintains HSECs fenestrae and attenuates liver fibrogenesis through inhibiting oxidative stress-induced premature senescence.

5.
Ecotoxicol Environ Saf ; 210: 111864, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33412282

RESUMO

Volatile organic compounds (VOCs) are important and ubiquitous air pollutants, which may lead to a significant increase in the prevalence of respiratory diseases. To investigate the relationships between VOCs exposure and childhood asthma, 252 asthmatic children and 69 healthy children were recruited. Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG, a biomarker of oxidative DNA damage), trans-3'-hydroxycotinine (OH-Cot, a biomarker of passive smoking) and 27 VOC metabolites were simultaneously determined by an ultra-high-performance liquid chromatography-tandem mass spectrometer. Results showed that levels of 8-OHdG and most VOC metabolites in asthmatic children were significantly higher than those in healthy children. More than half of the VOC metabolites were significantly and positively associated with OH-Cot with maximal ß coefficient of 0.169, suggesting that second-hand smoking is one important source of VOCs exposure for children in Guangzhou. Significant dose-response relationships between most VOC metabolites and 8-OHdG were observed. Each unit increase in ln-transformed VOC metabolite levels was significantly associated with 5.5-32% increase in ln-transformed 8-OHdG level. Moreover, each unit increase in ln-transformed 8-OHdG level was associated with an 896% increased odd ratios (OR) of asthma in children (OR = 9.96, 95% confidence intervals (CI): 4.75, 20.9), indicating that oxidative stress induced by VOCs exposure may have a significant impact on childhood asthma. Urinary 3-&4-Methylhippuric acid (3-&4-MHA, OR: 5.78, 95% CI: 3.50, 9.54), rac 2-Aminothiazoline-4-carboxylic acid (ATCA, OR: 2.90, 95% CI: 1.69, 4.99) and N-Acetyl-S-(3,4-dihydroxybutyl)-L-cysteine (DHBMA, OR: 2.76, 95% CI: 1.73, 4.43) which may derive from m/p-xylene, cyanide and 1,3-butadiene exposure, respectively, could significantly and maximally increase the odds of asthma. Interestingly, they also had the strongest associations with 8-OHdG among all investigated VOC metabolites. Moreover, DHBMA strongly correlated with most VOC metabolites. Hence, DHBMA is a suitable biomarker to indicate not only VOCs exposure profile, but also the DNA damage-mediated asthma induced by VOCs.


Assuntos
Asma/urina , Poluentes Ambientais/urina , Estresse Oxidativo , Poluição por Fumaça de Tabaco/efeitos adversos , Compostos Orgânicos Voláteis/urina , 8-Hidroxi-2'-Desoxiguanosina/urina , Asma/epidemiologia , Monitoramento Biológico , Biomarcadores/urina , Criança , China/epidemiologia , Cotinina/análogos & derivados , Cotinina/urina , Poluentes Ambientais/metabolismo , Feminino , Humanos , Masculino , Compostos Orgânicos Voláteis/metabolismo
6.
Food Chem ; 346: 128956, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33418414

RESUMO

In this study, the rice glutelin (RG)/sugar beet pectin (SBP) composite gels were prepared by laccase induced cross-linking and subsequent heat treatment, and the effects of different calcium ion concentrations (0-400 mM) on the gelation, structural properties and microstructure of the RG/SBP composite gels were investigated. The results showed that the addition of 200 mM calcium ion could improve the rheological, textural properties and water holding capacity of the RG/SBP composite gels. The addition of SBP and calcium ions enhanced the hydrophobic interaction between RG molecules, thereby increased the gel properties of RG. The changes in Raman spectroscopy reflected the positive effect of the addition of SBP and calcium ions on the formation of a denser and more homogeneous protein gel, as evidenced by the results of scanning electron microscopy. Overall, SBP and calcium ions could be applied to the plant protein gel systems as gel-strengthening agents.


Assuntos
Beta vulgaris/química , Géis/química , Glutens/química , Oryza/química , Pectinas/química , Beta vulgaris/metabolismo , Lacase/metabolismo , Microscopia Eletrônica de Varredura , Oryza/metabolismo , Concentração Osmolar , Reologia , Solubilidade , Espectrometria de Fluorescência , Análise Espectral Raman , Água/química
7.
Dev Comp Immunol ; 117: 103981, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33340592

RESUMO

Peritrophic membrane (PM) refers to a vital physical barrier enabling shrimp to resist pathogen invasion. It primarily consists of chitin and proteins, mostly chitin-binding protein (CBP). CBPs have been identified from microorganisms to higher organisms. In the present study, a CBP, designated MjCBP, was reported from Marsupenaeus japonicus. The open reading frame of MjCBP was 1854 bp, encoding a protein with 618 amino acids (MH544098). To be specific, the theoretical pI and molecular mass of mature MjCBP reached 5.43 and 66064.00 Da, respectively. MjCBP consisted of seven type Ⅱ chitin-binding domains (ChtB D2), which was up-regulated after being challenged with Vibrio anguillarum and then agglutinating several bacteria. In addition, MjCBP and the first chitin-binding domain (CBD1) could bind to several Gram-positive and Gram-negative bacteria via the binding process to lipopolysaccharides and peptidoglycans, whereas CBD1 was not capable of agglutinating bacteria. Moreover, the anterior and posterior segments of CBD1 were synthesized in vitro, and the posterior segment could bind to lipopolysaccharides. However, both segments fail to agglutinate bacteria. Furthermore, MjCBP and CBD1 facilitated the clearance of V. anguillarum in vivo, and the silencing of MjCBP via RNA interference reduced the ability of bacterial clearance. As revealed from the mentioned results, MjCBP acts as an opsonin or pattern recognition receptor to achieve antibacterial immune response in shrimp.

8.
Chem Commun (Camb) ; 2020 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-33290466

RESUMO

Highly branched PdP nanosheets (NSs) rich in defects and with a thickness of ∼3.2 nm were synthesized, for the first time, via a nanoconfined attachment growth mechanism inside assembled lamellar micelles. Owing to the synergistic structural (being a highly branched, ultrathin, and defect-rich material) and compositional (P-alloyed) advantages, the PdP NSs exhibited remarkable electrocatalytic activity (3.2 A mgPd-1), a low reaction activation energy (16.0 kJ mol-1), good CO anti-poisoning ability, and electrocatalytic stability during the ethanol oxidation reaction (EOR) in alkaline conditions.

9.
Appl Opt ; 59(33): 10523-10531, 2020 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-33361987

RESUMO

The initial value estimation for seed point is the first step in digital image correlation calculation. Among the existing algorithms, the Fourier-Mellin transform-based cross correlation (FMT-CC) algorithm is one of the most efficient and robust owing to its rotation- and scale-invariance. However, when the displacement is large (more than a hundred pixels), the FMT-CC algorithm fails. In this paper, an automated and efficient initial value estimation method based on an FMT-CC algorithm is presented to deal with large displacement, large rotation, and large isotropic scaling. The relationship between subset size and the maximal displacement in the FMT-CC algorithm is studied, and a strategy of setting the subset size according to the estimated displacement is proposed to improve the robustness of the FMT-CC algorithm. In addition, in cases of large displacement, a multi-scale search method is proposed to improve efficiency. The experimental results show that the proposed methods can realize rapid and automated initial value estimation even under conditions of large displacement, large rotation, and large isotropic scaling. The computational efficiency of the multi-scale search method is about one order of magnitude higher than the traditional FMT-CC method.

10.
Cell Microbiol ; : e13294, 2020 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-33222390

RESUMO

Gametogenesis, the formation of gametes from gametocytes, an essential step for malaria parasite transmission, is targeted by transmission-blocking drugs and vaccines. We identified a conserved protein (PBANKA_0305900) in Plasmodium berghei, which encodes a protein of 22 kDa (thus named Pb22) and is expressed in both asexual stages and gametocytes. Its homologues are present in all Plasmodium species and its closely related, Hepatocystis, but not in other apicomplexans. Pb22 protein was localised in the cytosols of schizonts, as well as male and female gametocytes. During gamete-to-ookinete development, Pb22 became localised on the plasma membranes of gametes and ookinetes. Compared to the wild-type (WT) parasites, P. berghei with pb22 knockout (KO) showed a significant reduction in exflagellation (~89%) of male gametocytes and ookinete number (~97%) during in vitro ookinete culture. Mosquito feeding assays showed that ookinete and oocyst formation of the pb22-KO line in mosquito midguts was almost completely abolished. These defects were rescued in parasites where pb22 was restored. Cross-fertilisation experiments with parasite lines defective in either male or female gametes confirmed that the defects in the pb22-KO line were restricted to the male gametes, whereas female gametes in the pb22-KO line were fertile at the WT level. Detailed analysis of male gametogenesis showed that 30% of the male gametocytes in the pb22-KO line failed to assemble the axonemes, whereas ~48.9% of the male gametocytes formed flagella but failed to egress from the host erythrocyte. To explore its transmission-blocking potential, recombinant Pb22 (rPb22) was expressed and used to immunise mice. in vitro assays showed that the rPb22-antisera significantly inhibited exflagellation by ~64.8% and ookinete formation by ~93.4%. Mosquitoes after feeding on rPb22-immunised mice also showed significant decreases in infection prevalence (83.3-93.3%) and oocyst density (93.5-99.6%). Further studies of the Pb22 orthologues in human malaria parasites are warranted.

11.
Food Chem ; : 128270, 2020 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-33069526

RESUMO

Glucose oxidase (Gox) is a biocatalyst that is widely applied in the food industry, as well as other biotechnological industries. However, the industrial application of Gox is hampered by its low thermostability and activity. Here, we aimed to improve the thermostability of GoxM4 from Aspergillus niger without reducing its activity due to the activity-stability trade-off. A simple and effective approach combining enzyme activity and structure stability was adopted to evaluate the thermostability of GoxM4 and its mutants. After four rounds of computer-aided rational design, the best mutant, GoxM8, was obtained. The melting temperature (Tm) of GoxM8 was increased by 9 °C compared with GoxM4. The catalytic efficiency of GoxM8 was similar to GoxM4, suggesting that the enzyme activity-stability trade-off was counteracted. To explore its mechanism, we performed molecular dynamics simulations of GoxM4 and its mutants. Our findings provided a typical example for researching the enzyme activity-stability trade-off.

12.
Front Immunol ; 11: 1865, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32983103

RESUMO

Neurally mediated syncope (NMS) is the most common underlying disease of pediatric syncope, which generally includes vasovagal syncope (VVS), postural tachycardia syndrome (POTS), and situational syncope. Allergic diseases involving the respiratory system, digestive system, skin, and other systems are prevalent in children. In recent years, increasing attention has been paid to children with the comorbidity of NMS and allergic diseases. This article reviews the featured clinical manifestations and pathogenesis of the comorbidity according to the progress of related studies. Clinical studies have shown that the comorbidity rate of pediatric VVS and/or POTS with allergic diseases amounts to ~30-40%, referring to the whole population of children with VVS and/or POTS. Additionally, children with the comorbidity present some relatively special clinical characteristics. A series of mechanisms or regulatory factors relating to allergies, such as the imbalance of vasoactive elements, dysfunction of the autonomic nervous system (ANS), and autoimmunity may play a role in the development of the comorbidity. Moreover, 90% of children with cough syncope, a type of situational syncope, have a history of asthma, indicating a potential relationship between asthma and NMS. Further studies exploring the clinical characteristics and pathogenesis of the comorbidity are still needed to aid in the diagnosis and treatment of children with NMS.

13.
PLoS Pathog ; 16(9): e1008933, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32976518

RESUMO

Nucleotide-binding domain and leucine-rich repeat-containing (NLR) proteins function as sensors that perceive pathogen molecules and activate immunity. In plants, the accumulation and activation of NLRs is regulated by SUPPRESSOR OF G2 ALLELE OF skp1 (SGT1). In this work, we found that an effector protein named RipAC, secreted by the plant pathogen Ralstonia solanacearum, associates with SGT1 to suppress NLR-mediated SGT1-dependent immune responses, including those triggered by another R. solanacearum effector, RipE1. RipAC does not affect the accumulation of SGT1 or NLRs, or their interaction. However, RipAC inhibits the interaction between SGT1 and MAP kinases, and the phosphorylation of a MAPK target motif in the C-terminal domain of SGT1. Such phosphorylation is enhanced upon activation of immune signaling and contributes to the activation of immune responses mediated by the NLR RPS2. Additionally, SGT1 phosphorylation contributes to resistance against R. solanacearum. Our results shed light onto the mechanism of activation of NLR-mediated immunity, and suggest a positive feedback loop between MAPK activation and SGT1-dependent NLR activation.


Assuntos
Proteínas de Bactérias/metabolismo , Doenças das Plantas/imunologia , Imunidade Vegetal/imunologia , Proteínas de Plantas/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Fosforilação , Proteínas de Plantas/imunologia , Ralstonia solanacearum/imunologia , Ralstonia solanacearum/metabolismo , Tabaco/metabolismo
14.
ACS Appl Mater Interfaces ; 12(41): 46719-46732, 2020 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-32945656

RESUMO

Although progress has been made in the construction of stimulus-responsive actuators, the performance of these smart materials is still unsatisfactory, owing to their slow response, small deformation amplitude, uncontrollable bending direction, and unidirectional (2D to 3D) transformation. Herein, we employ a structural bionic strategy to design and fabricate a novel water/moisture responsive nanofibrous actuator with an alignment degree gradient. Owing to its different contraction gradient amplitudes along the thickness direction and the unique physical property of the nanofibrous material, the prepared actuator exhibits excellent shape deformation performance, including superfast response (less than 150 ms), controllable deformation directions, multiple actuation models, multiple dimensional deformation (0D-3D, 1D-3D, 2D-3D, and 3D-3D), large bending curvature (25.3 cm-1), and a repeatability rate of at least 1000. The actuation performance of the nanofibrous actuator is superior to the currently reported actuators. The nanofibers are integrated into layer-by-layer and side-by-side structures to achieve competitive and independent actuation, respectively. The outstanding shape-changing properties of the nanofibrous actuator result in the construction of practical intelligent devices for applications such as amphibious movement, intelligent protection, and cargo transportation. The nanofibrous actuator designed herein exhibits tremendous potential in soft robotics, sensors, and biomedicine.

15.
Sci China Life Sci ; 2020 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-32915406

RESUMO

Neuroblastoma (NB) is one of the most common malignant tumors in children, with variable clinical behaviors and a 15% death rate of all malignancies in childhood. However, genetic susceptibility to sporadic NB in Han Chinese patients is largely unknown. To identify genetic risk factors for NB, we performed an association study on 357 NB patients and 738 control subjects among Han Chinese children. We focused on DEAD box 1 (DDX1), a putative RNA helicase, which is involved in NB carcinogenesis. The potential association of DDX1 polymorphisms with NB has not been discovered. Our results demonstrate that rs72780850 (NM_004939.2:c.-1555T>C) located in the DDX1 promoter region is significantly associated with higher expression of DDX1 transcript and increased NB risk (odds ratio=1.64, 95% confidence interval=1.03%-2.60%, P=0.004), especially in aggressive NB compared with ganglioneuroma and ganglioneuroblastoma in a dominant model (TC+CC vs. TT). Furthermore, the MYC-associated protein X (MAX) transcription factor showed stronger binding affinity to the DDX1 rs 72780850 CC allele compared with the TT allele, explaining the molecular mechanism of the increased NB risk caused by the rs72780850 polymorphism. Our results highlight the involvement of regulatory genetic variants of DDX1 in NB.

16.
Artigo em Inglês | MEDLINE | ID: mdl-32876999

RESUMO

Lead halide perovskites are considered to be most promising photovoltaic materials. Highest efficiency and improved stability of perovskite solar cells have been achieved by using cation and anion mixtures. Experimental information on electronic and ionic charge carriers is key to evaluate device performance, as well as processes of photo-decomposition and photo-demixing which are observed in these materials. Here, we measure ionic and electronic transport properties and investigate various cation and anion substitutions with a special eye on their photo-ionic effect, following our previous study on CH3 NH3 PbI3 , where we found that light enhances not only electronic but also ionic conductivities. We find that this phenomenon is very sensitive to the nature of the halide, while the cationic substitutions are less relevant. Based on the observation that the ionic conductivity enhancement found for iodide perovskites is significantly weakened by bromide substitution, we provide a chemical rationale for the photo-demixing in mixed halide compositions.

17.
Sheng Wu Gong Cheng Xue Bao ; 36(7): 1431-1439, 2020 Jul 25.
Artigo em Chinês | MEDLINE | ID: mdl-32748601

RESUMO

The purpose of this study is to provide a culture for mouse bone marrow-derived macrophages (BMDM) and peritoneal macrophages (PM) and to characterize their molecular and cellular biology. The cell number and purity from the primary culture were assessed by cell counter and flow cytometry, respectively. Morphological features were evaluated by inverted microscope. Phagocytosis by macrophages was detected by the neutral red dye uptake assay. Phenotypic markers were analyzed by real-time fluorescent quantitative PCR. Our results show that the cell number was much higher from culture of BMDM than PM, while there was no significant difference regarding the percentage of F4/80+CD11b+ cells (98.30%±0.53% vs. 94.83%±1.42%; P>0.05). The proliferation rate of BMDM was significantly higher than PM in the presence of L929 cell conditioned medium, by using CCK-8 assay. However, PM appeared to adhere to the flask wall and extend earlier than BMDM. The phagocytosis capability of un-stimulated BMDM was significantly higher than PM, as well as lipopolysaccharide (LPS)-stimulated BMDM, except the BMDM stimulated by low dose LPS (0.1 µg/mL). Furthermore, Tnfα expression was significantly higher in un-stimulated BMDM than PM, while Arg1 and Ym1 mRNA expression were significantly lower than PM. The expression difference was persistent if stimulated by LPS+IFN-γ or IL-4. Our data indicate that bone marrow can get larger amounts of macrophages than peritoneal cavity. However, it should be aware that the molecular and cellular characteristics were different between these two culture systems.


Assuntos
Células da Medula Óssea , Macrófagos , Fagocitose , Animais , Células da Medula Óssea/fisiologia , Células Cultivadas , Meios de Cultivo Condicionados , Lipopolissacarídeos/metabolismo , Macrófagos/classificação , Macrófagos/fisiologia , Camundongos
18.
Proc Natl Acad Sci U S A ; 117(35): 21391-21402, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32817423

RESUMO

Syntaxin17, a key autophagosomal N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein, can associate with ATG8 family proteins SNAP29 and VAMP8 to facilitate the membrane fusion process between the double-membraned autophagosome and single-membraned lysosome in mammalian macroautophagy. However, the inherent properties of Syntaxin17 and the mechanistic basis underlying the interactions of Syntaxin17 with its binding proteins remain largely unknown. Here, using biochemical, NMR, and structural approaches, we systemically characterized Syntaxin17 as well as its interactions with ATG8 family proteins, SNAP29 and VAMP8. We discovered that Syntaxin17 alone adopts an autoinhibited conformation mediated by a direct interaction between its Habc domain and the Qa-SNARE motif. In addition, we revealed that the Qa-SNARE region of Syntaxin17 contains one LC3-interacting region (LIR) motif, which preferentially binds to GABARAP subfamily members. Importantly, the GABARAP binding of Syntaxin17 can release its autoinhibited state. The determined crystal structure of the Syntaxin17 LIR-GABARAP complex not only provides mechanistic insights into the interaction between Syntaxin17 and GABARAP but also reveals an unconventional LIR motif with a C-terminally extended 310 helix for selectively binding to ATG8 family proteins. Finally, we also elucidated structural arrangements of the autophagic Syntaxin17-SNAP29-VAMP8 SNARE core complex, and uncovered its conserved biochemical and structural characteristics common to all other SNAREs. In all, our findings reveal three distinct states of Syntaxin17, and provide mechanistic insights into the Syntaxin17-mediated autophagosome-lysosome fusion process.


Assuntos
Autofagossomos/fisiologia , Lisossomos/fisiologia , Proteínas Qa-SNARE/metabolismo , Proteínas Qb-SNARE/metabolismo , Proteínas Qc-SNARE/metabolismo , Proteínas R-SNARE/metabolismo , Motivos de Aminoácidos , Proteínas Reguladoras de Apoptose/metabolismo , Família da Proteína 8 Relacionada à Autofagia/metabolismo , Escherichia coli , Humanos , Proteínas Associadas aos Microtúbulos/metabolismo
19.
J Phys Chem Lett ; 11(16): 6632-6639, 2020 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-32787228

RESUMO

Alloying is one of the most promising routes for tuning the physicochemical properties of noble metal-based nanocatalysts and thus improving their (electro)catalytic performance. Despites numerous achievements, bimetallic and trimetallic nanoalloys have still been thoroughly studied for the past two decades. In this study, metalloid boron (B) was alloyed within palladium (Pd)-based nanocatalysts to promote the electrochemical ethanol oxidation reaction (EOR) in alkaline media. The optimum PdCuB nanocatalyst exhibited remarkable electrochemical EOR activity (5.83 A mgPd-1) and good operation stability (both cycling and chronoamperometric studies). Mechanistic studies in both pure KOH and a KOH/ethanol mixture attributed superior EOR performance to positive synergistic effects of B in Pd-based nanocatalysts that kinetically accelerated the removal of poisoning ethoxy intermediates (the rate-determining step of EOR). They included (i) an electronic effect that changed the electronic structure of Pd and thus weakened the adsorption of poisoning ethoxy intermediates, (ii) a bifunctional effect that facilitated the adsorption of OHads and thus kinetically accelerated the further oxidation of poisoning intermediates, and (iii) a structural effect in which smaller B interstitially inserted into Pd-based nanocrystals and thus suppressed the physical Ostwald ripening processes.

20.
Sci Total Environ ; 748: 141099, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32814283

RESUMO

Measuring the change of the livelihood capitals of rural households in park-adjacent communities under the background of tourism development is an important predictor to identify the sustainable development status of national parks. This paper constructs measurement indicators of the livelihood capitals of rural household in communities surrounding national parks and takes Huangshan National Park, located in eastern China, as an example to calculate characteristics of spatiotemporal changes in the livelihood capitals of rural households, analyze the effect of tourism development on livelihood capitals in adjacent communities in 2006 and 2015. The findings indicate that the annual growth of the total livelihood capital has comparatively strong rigidity. However, there are some differences in temporal changes between different types of livelihood capitals. The distribution of zones of medium and high livelihood capital is mainly distributed in the communities adjacent to the national park research, education and recreation area (RERA). In addition, the total livelihood capital takes the RERA as the centre and decays over distance, which demonstrates that tourism development is an effective way to enhance the livelihood capitals. On the other hand, there is a spatial attenuation effect of tourism development on the enhancement of the livelihood capitals.

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