RESUMO
Electrochemical formic acid oxidation reaction (FAOR) is a pivotal model for understanding organic fuel oxidation and advancing sustainable energy technologies. Here, we present mechanistic insights into a novel molecular-like iridium catalyst (Ir-N4-C) for FAOR. Our studies reveal that isolated sites facilitate a preferential dehydrogenation pathway, circumventing catalyst poisoning and exhibiting high inherent activity. In-situ spectroscopic analyses elucidate that weakly adsorbed intermediates mediate the FAOR and are dynamically regulated by potential-dependent redox transitions. Theoretical and experimental investigations demonstrate a parallel mechanism involving two key intermediates with distinct pH and potential sensitivities. The rate-determining step is identified as the adsorption of formate via coupled or sequential proton-electron transfer, which aligns well with the observed kinetic properties, pH dependence, and hydrogen/deuterium isotope effects in experiments. These findings provide valuable insights into the reaction mechanism of FAOR, advancing our understanding at the molecular level and potentially guiding the design of efficient catalysts for fuel cells and electrolyzers.
RESUMO
Histone acetylation is a crucial epigenetic modification, one that holds the key to regulating gene expression by meticulously modulating the conformation of chromatin. Most histone acetylation enzymes (HATs) and deacetylation enzymes (HDACs) in fungi were originally discovered in yeast. The functions and mechanisms of HATs and HDACs in yeast that have been documented offer us an excellent entry point for gaining insights into these two types of enzymes. In the interaction between plants and pathogenic fungi, histone acetylation assumes a critical role, governing fungal pathogenicity and plant immunity. This review paper delves deep into the recent advancements in understanding how histone acetylation shapes the interaction between plants and fungi. It explores how this epigenetic modification influences the intricate balance of power between these two kingdoms of life, highlighting the intricate network of interactions and the subtle shifts in these interactions that can lead to either mutual coexistence or hostile confrontation.
RESUMO
Parasitic side reactions and dendrites formation hinder the application of aqueous zinc ion batteries due to inferior cycling life and low reversibility. Against this background, N-methyl formamide (NMF), a multi-function electrolyte additive is applied to enhance the electrochemical performance. Studied via advanced synchrotron radiation spectroscopy and DFT calculations, the NMF additive simultaneously modifies the Zn2+ solvation structure and ensures uniform zinc deposition, thus suppressing both parasitic side reactions and dendrite formation. More importantly, an ultralong cycling life of 3115 h in the Zn||Zn symmetric cell at a current density of 0.5 mA cm-2 is achieved with the NMF additive. Practically, the Zn||PANI full cell utilizing NMF electrolyte shows better rate and cycling performance compared to the pristine ZnSO4 aqueous electrolyte. This work provides useful insights for the development of high-performance aqueous metal batteries.
RESUMO
In recent years, there has been significant interest in the development of two-dimensional (2D) nanomaterials with unique physicochemical properties for various energy applications. These properties are often derived from the phase structures established through a range of physical and chemical design strategies. A concrete analysis of the phase structures and real reaction mechanisms of 2D energy nanomaterials requires advanced characterization methods that offer valuable information as much as possible. Here, we present a comprehensive review on the phase engineering of typical 2D nanomaterials with the focus of synchrotron radiation characterizations. In particular, the intrinsic defects, atomic doping, intercalation, and heterogeneous interfaces on 2D nanomaterials are introduced, together with their applications in energy-related fields. Among them, synchrotron-based multiple spectroscopic techniques are emphasized to reveal their intrinsic phases and structures. More importantly, various in situ methods are employed to provide deep insights into their structural evolutions under working conditions or reaction processes of 2D energy nanomaterials. Finally, conclusions and research perspectives on the future outlook for the further development of 2D energy nanomaterials and synchrotron radiation light sources and integrated techniques are discussed.
RESUMO
Developing highly efficient, selective and low-overpotential electrocatalysts for carbon dioxide (CO2) reduction is crucial. This study reports an efficient Ni single-atom catalyst coordinated with pyrrolic nitrogen and pyridinic nitrogen for CO2 reduction to carbon monoxide (CO). In flow cell experiments, the catalyst achieves a CO partial current density of 20.1 mA cmgeo-2 at -0.15 V vs. reversible hydrogen electrode (VRHE). It exhibits a high turnover frequency of over 274,000 site-1 h-1 at -1.0 VRHE and maintains high Faradaic efficiency of CO (FECO) exceeding 90% within -0.15 to -0.9 VRHE. Operando synchrotron-based infrared and X-ray absorption spectra, and theoretical calculations reveal that mono CO-adsorbed Ni single sites formed during electrochemical processes contribute to the balance between key intermediates formation and CO desorption, providing insights into the catalyst's origin of catalytic activity. Overall, this work presents a Ni single-atom catalyst with good selectivity and activity for CO2 reduction while shedding light on its underlying mechanism.
Assuntos
Dióxido de Carbono , Níquel , Monóxido de Carbono , Eletrodos , NitrogênioRESUMO
Deregulation of NEK2(NIMA-related serine/threonine 2) confers chemotherapeutic resistance to apoptosis and is closely correlated with poor prognosis in hepatocellular carcinoma (HCC). Here, we find that nanoparticles are prepared through hemisynthesis from natural nitidine chloride (NC) with enhanced antitumor activity. Nitidine chloride nanoparticle (TPGS-FA/NC) treatment show good therapy effect in Li-7 hepatocellular carcinoma cells. Additionally, molecular docking technologies are aimed at NEK2 protein (PDB ID: 6SGD) to analyze the detailed binding interactions with the potent target. NC participates in interactions with Asp159 residue. These studies advance the understanding of the modification of nitidine chloride substituent and provide useful drug design information for liver cancer treatment.
RESUMO
BACKGROUND: Stemness of CD133+EPCAM+ hepatocellular carcinoma cells ensures cancer resistance to apoptosis,which is a challenge to current liver cancer treatments. In this study, we evaluated the tumorcidal activity of a novel nanoparticle of nitidine chloride (TPGS-FA/NC, TPGS-FA: folic acid modified D-α-tocopheryl polyethylene glycol 1000 succinate, NC: nitidine chloride), against human hepatocellular carcinoma (HCC) cell line Huh7 growth in vitro and in vivo. METHODS: Huh7 cells were treated with TPGS-FA/NC. Cell proliferation was assessed using MTT and colony assays. The expression of cell markers and signaling proteins was detected using western blot analyses. A sphere culture technique was used to enrich cancer stem cells (CSC) in Huh7 cells. TPGS-FA/NC (7.5, 15, 30, 60, 120 µg/mL) dose-dependently inhibited the proliferation of HCC cells, which associated with a reduction in AQP3 and STAT3 expression. Importantly,TPGS-FA/NC (10, 20, and 40 µg/mL) significantly reduced the EpCAM+/CD133+cell numbers, suppressed the sphere formation. The in vivo antitumor efficacy of TPGS-FA/NC was proved in Huh7 cell xenograft model in BALB/c nude mice, which were administered TPGS-FA/NC(4 mg· kg - 1· d - 1, ig) for 2 weeks. RESULTS: TPGS-FA/NC dose-dependently suppressed the AQP3/STAT3/CD133 axis in Huh7 cells. In Huh7 xenograft bearing nude mice, TPGS-FA/NC administration markedly inhibited Huh7 xenograft tumor growth . CONCLUSIONS: TPGS-FA/NC inhibit HCC tumor growth through multiple mechanisms, and it may be a promising candidate drug for the clinical therapy of hepatocellular carcinoma.
Assuntos
Carcinoma Hepatocelular , Neoplasias Hepáticas , Nanopartículas , Células-Tronco Neoplásicas , Antígeno AC133/metabolismo , Animais , Benzofenantridinas , Carcinoma Hepatocelular/tratamento farmacológico , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/patologia , Linhagem Celular Tumoral , Molécula de Adesão da Célula Epitelial , Humanos , Neoplasias Hepáticas/tratamento farmacológico , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/patologia , Camundongos , Camundongos Nus , Nanopartículas/administração & dosagem , Células-Tronco Neoplásicas/metabolismo , Células-Tronco Neoplásicas/patologiaRESUMO
Enhancing activity and stability of iridium- (Ir-) based oxygen evolution reaction (OER) catalysts is of great significance in practice. Here, we report a vacancy-rich nickel hydroxide stabilized Ir single-atom catalyst (Ir1-Ni(OH)2), which achieves long-term OER stability over 260 h and much higher mass activity than commercial IrO2 in alkaline media. In situ X-ray absorption spectroscopy analysis certifies the obvious structure reconstruction of catalyst in OER. As a result, an active structure in which high-valence and peripheral oxygen ligands-rich Ir sites are confined onto the nickel oxyhydroxide surface is formed. In addition, the precise introduction of atomized Ir not only surmounts the large-range dissolution and agglomeration of Ir but also suppresses the dissolution of substrate in OER. Theoretical calculations further account for the activation of Ir single atoms and the promotion of oxygen generation by high-valence Ir, and they reveal that the deprotonation process of adsorbed OH is rate-determining.
RESUMO
Ruthenium (Ru)-based electrocatalysts as platinum (Pt) alternatives in catalyzing hydrogen evolution reaction (HER) are promising. However, achieving efficient reaction processes on Ru catalysts is still a challenge, especially in alkaline media. Here, the well-dispersed Ru nanoparticles with adjacent Ru single atoms on carbon substrate (Ru1,n -NC) is demonstrated to be a superb electrocatalyst for alkaline HER. The obtained Ru1,n -NC exhibits ultralow overpotential (14.8 mV) and high turnover frequency (1.25 H2 s-1 at -0.025 V vs reversible hydrogen electrode), much better than the commercial 40 wt.% Pt/C. The analyses reveal that Ru nanoparticles and single sites can promote each other to deliver electrons to the carbon substrate. Eventually, the electronic regulations bring accelerated water dissociation and reduced energy barriers of hydroxide/hydrogen desorption on adjacent Ru sites, then an optimized reaction kinetics for Ru1,n -NC is obtained to achieve superb hydrogen generation in alkaline media. This work provides a new insight into the catalyst design in simultaneous optimizations of the elementary steps to obtain ideal HER performance in alkaline media.
RESUMO
Surficial defects in semiconductor can induce high density of carriers and cause localized surface plasmon resonance which is prone to light harvesting and energy conversion, while internal defects may cause serious recombination of electrons and holes. Thus, it is significant to precisely control the distribution of defects, although there are few successful examples. Herein, an effective strategy to confine abundant defects within the surface layer of Cu1.94 S nanoflake arrays (NFAs) is reported, leaving a perfect internal structure. The Cu1.94 S NFAs are then applied in photoelectrochemical (PEC) water splitting. As expected, the surficial defects give rise to strong LSPR effect and quick charge separation near the surface; meanwhile, they provide active sites for catalyzing hydrogen evolution. As a result, the NFAs achieve the top PEC properties ever reported for Cux S-based photocathodes.
RESUMO
It is fascinating and challenging to endow conventional materials with unprecedented properties. For instance, cadmium sulfide (CdS) is an important semiconductor with excellent light response; however, its potential in gas-sensing was underestimated owing to relatively low chemical activity and poor electrical conductivity. Herein, we demonstrate that an ideal architecture, ultrathin nanoflake arrays (NFAs), can improve significantly gas-sensing properties of CdS material. The CdS NFAs are grown directly on the interdigitated electrode to expose large surface area. Their thickness is reduced below the double Debye length of CdS, permitting to achieve a full depletion of carriers. Particularly, the prepared CdS nanoflakes are enclosed with high-energy {0001} facets exposed, which provides more active sites for gas adsorption. Moreover, the NFAs exhibit the light-trapping effect, which further enhances their gas sensitivity. As a result, the as-prepared CdS NFAs demonstrate excellent gas-sensing and light-response properties, thus being capable of dual gas and light detection.
RESUMO
Freestanding ultrathin metallic nanosheets (FUMNSs) with atomic thickness attract extensive attention because they display remarkable advantages over their bulk counterparts by virtue of their large specific area, high aspect ratio, and unsaturated surface coordination. The state of the art of research on FUMNSs is reviewed here, wherein the important progress from the aspects of material category, synthetic strategy, and practical application are introduced, and it is demonstrated that FUMNSs will play an important role in the fields of optoelectrics, catalysis, and magnetism.
RESUMO
OBJECTIVE: To investigate the changes of proportion and suppression function of CD-4+ CD-25+ regulatory T cells in the peripheral blood of patients with aggressive periodontitis. METHODS: Flow cytometric analysis was used to detect the frequency of CD-4+ CD-25+ regulatory T cells in the peripheral blood of 16 patients with generalized aggressive periodontitis and 17 patients with chronic periodontitis, as well as 17 periodontal healthy controls. Furthermore, CD-4+ CD-25+ regulatory T cells and CD-4+ CD-25- T cells were separated from peripheral blood of each enrolling subject using magnetic cell sorting technology. The direct suppression effect of CD-4+ CD-25+ regulatory T cells on CD-4+ CD-25- T lymphocytes proliferation was performed by the mixed lymphocytes reaction and measured by 3H-thymidine radioactive assay. RESULTS: The patients with generalized aggressive periodontitis had a lower frequency of CD4+ CD-25+ regulatory T cells (9.71 +/- 4.01)% in the peripheral blood than periodontal healthy controls [(14.72 +/- 3.51)%] and chronic periodontitis patients [(17.01 +/- 5.16 )%], P < 0.05. A significant decrease was found in the suppression function of CD-4+ CD-25+ regulatory T cells from peripheral blood of patients with generalized aggressive periodontitis when co-cultured with CD-4+ CD-25- T lymphocytes in the proportion of 2 : 1, 1 : 1 and 1 : 2 as compared with chronic periodontitis patients and periodontal healthy controls (P < 0.05). CONCLUSIONS: Diminished numbers and decreased suppression function of CD-4+ CD-25+ regulatory T cells were found in patients with generalized aggressive periodontitis.
Assuntos
Periodontite Agressiva/sangue , Linfócitos T Reguladores/citologia , Adulto , Estudos de Casos e Controles , Feminino , Citometria de Fluxo , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
PURPOSE: To evaluate the clinical effect of repair of lateral root canal perforation with mineral trioxide aggregate (MTA). METHODS: 18 teeth with root canal perforation were selected. The root canals were shaped and cleaned, and then obturated with gutta-percha before or after MTA was used to repair the perforation. RESULTS: The postoperative X-ray films showed that the perforation of 17 teeth was repaired well, except one tooth with large and infected perforation. 10 cases showed a little over-filling of MTA. 16 patients were recalled and declared their teeth to be asymptomatic. The recall radiographs indicated that the apical radiolucent areas of teeth with pre-existing apical lesion decreased apparently or disappeared completely. No new radiolucency was found. CONCLUSIONS: MTA is effective in treatment of teeth with root canal perforation, even though the material is over-filled. Supported by 2004 Key Clinical Project of Medical Systems Affiliated to Ministry of Health and Natural Science Foundation of Guangdong Province (Grant No.5300624).
Assuntos
Compostos de Alumínio , Compostos de Cálcio , Óxidos , Materiais Restauradores do Canal Radicular , Tratamento do Canal Radicular , Silicatos , Combinação de Medicamentos , Guta-Percha , Humanos , Dente MolarRESUMO
OBJECTIVE: To investigate different angle projection technique for clinical judgment of obturation quality of molars with multiple root canals. METHODS: Eighty-seven maxillary first molars with second mesiobuccal canal (MB2) and 105 mandibular first molars were selected. The canals were instrumented by Ni-Ti rotary instruments and obturated with lateral condensation technique. To judge the obturation quality of the root canals, the radiograph was taken at a horizontal angles of 0 and 20 - 30 degrees from distal direction of the tooth after the treatment. RESULTS: For maxillary first molars, periapical radiographs showed 23.0% of MB2. Distally angulated radiographs showed 81.6% of MB2. For mandibular first molars, periapical radiographs showed 38.1% of mesiobuccal and mesiolingual canals, and distally angulated radiographs showed 90.5% of two mesial root canals. CONCLUSIONS: Most buccal-lingual distributed root canals of the first molar can be shown more clearly by distally angulated radiographs.