Insight into the Kinetics of Isomerization and ß-Scission Reactions Following H-Abstraction in 2-Pentanone Combustion.

2-Pentanone is a significant carbon-neutral fuel. To better understand 2-pentanone combustion, the CCSD(T)/CBS method was used to calculate the potential energy surfaces (PES) for H-abstraction, isomerization, and ß-scission reactions of 2-pentanone. Rate constants for the above reactions were calculated by the MESS employing conventional transition state theory (CTST) at 300-2000 K. The findings reveal adherence to the Evans-Polanyi principle in the H-abstraction reactions of 2-pentanone by H atoms. Specifically, the 2-site shows more competitive kinetics due to having the lowest energy barrier of 7.8 kcal/mol. The 4-position has the highest energy barrier, making the reaction difficult to occur. In the subsequent reactions, the breaking of C-H bonds is most competitive at low temperatures. In particular, the H transfer from INT1 to INT3 has a potential well height of 24.8 kcal/mol. The ß-scission reactions become the main pathway for the depletion of pentanone radicals with increasing temperature. This study significantly extends the kinetic parameters of 2-pentanone combustion over a wide range of temperatures and pressures, which is expected to contribute to the development of 2-pentanone combustion models.

Interfacial engineering of cobalt sulfide/graphene hybrids for highly efficient ammonia electrosynthesis.

Electrocatalytic N2 reduction reaction (NRR) into ammonia (NH3), especially if driven by renewable energy, represents a potentially clean and sustainable strategy for replacing traditional Haber-Bosch process and dealing with climate change effect. However, electrocatalytic NRR process under ambient conditions often suffers from low Faradaic efficiency and high overpotential. Developing newly regulative methods for highly efficient NRR electrocatalysts is of great significance for NH3 synthesis. Here, we propose an interfacial engineering strategy for designing a class of strongly coupled hybrid materials as highly active electrocatalysts for catalytic N2 fixation. X-ray absorption near-edge spectroscopy (XANES) spectra confirm the successful construction of strong bridging bonds (Co-N/S-C) at the interface between CoS x nanoparticles and NS-G (nitrogen- and sulfur-doped reduced graphene). These bridging bonds can accelerate the reaction kinetics by acting as an electron transport channel, enabling electrocatalytic NRR at a low overpotential. As expected, CoS2/NS-G hybrids show superior NRR activity with a high NH3 Faradaic efficiency of 25.9% at -0.05 V versus reversible hydrogen electrode (RHE). Moreover, this strategy is general and can be extended to a series of other strongly coupled metal sulfide hybrids. This work provides an approach to design advanced materials for ammonia production.

Dynamic Surface Reconstruction of Single-Atom Bimetallic Alloy under Operando Electrochemical Conditions.

The atomic-level understanding of the dynamic evolution of the surface structure of bimetallic nanoparticles under industrially relevant operando conditions provides a key guide for improving their catalytic performance. Here, we exploit operando X-ray absorption fine structure spectroscopy to determine the dynamic surface reconstruction of Cu/Au bimetallic alloy where single-atom Cu was embedded on the Au nanoparticle, under electrocatalytic conditions. We identify the migration of isolated Cu atoms from the vertex position of the Au nanoparticle to the stable (100) plane of the Au first atom layer, when the reduction potential is applied. Density functional theory calculations reveal that the surface atom migration would significantly modulate the Au electronic structure, thus serving as the real active site for the catalytic performance. These findings demonstrate the real structural change under electrochemical conditions and provide guidance for the rational design of high-activity bimetallic nanocatalysts.

The NEDD8-activating enzyme E1 UBA3 orchestrates the immunosuppressive microenvironment in lung adenocarcinoma via the NF-кB pathway.

Immunosuppressive cells play important roles in generating an immunosuppressive tumor microenvironment and facilitating tumor immune escape. However, the molecular mechanisms underlying their immunosuppressive effects remain unclear. UBA3, the sole catalytic subunit of the neural precursor cell expressed developmentally down-regulated protein 8 (NEDD8)-activating enzyme E1, is highly expressed in various human malignancies, along with an activated neddylation pathway. In this study, we investigated the relationships between the UBA3-dependent neddylation pathway and the infiltration of several immunosuppressive cell populations in lung adenocarcinoma (LUAD). We explored the regulatory mechanisms of UBA3 in LUAD cells by using mRNA sequencing and functional enrichment analyses. Correlations between neddylation and immune infiltrates were assessed by Western blotting, real-time PCR, and analyses of public databases. We found elevated levels of UBA3 expression in LUAD tissues compared to adjacent normal tissues. Blocking UBA3 and the neddylation pathway promoted the accumulation of the phosphorylated nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor (p-IκBα), inhibiting the gene expression of tumor cell-derived cytokines such as C-C motif chemokine ligand (CCL) 2, C-X-C motif ligand (CXCL)1, CXCL2, colony-stimulating factor (CSF) 1, CSF2 interleukin (IL)-6, and IL-1B. Moreover, the overexpression of UBA3 in LUAD cells was associated with the secretion of these cytokines, and the recruitment and infiltration of immunosuppressive cells including tumor-associated macrophages (TAMs), plasmacytoid dendritic cells (pDCs), Th2 cells and T-regulatory cells (Tregs). This could facilitate the tumor immune escape and malignant progression of LUAD. Our findings provide new insights into the role of UBA3 in establishing an immunosuppressive tumor microenvironment by modulating nuclear factor kappa B (NF-кB) signaling and the neddylation pathway.

Evolution hydrothermal aging mechanism for Ag/CeO2 catalysts in regeneration of catalytic diesel particulate filter with DFT calculation.

In order to avoid the high cost of existing precious metal catalyst like Pt, Ag/CeO2 was the most promising catalysts for mobile source soot emission control technologies, but there was a clear trade-off between hydrothermal aging resistance and catalytic oxidation performance hindered the application of this catalyst. In order to reveal the hydrothermal aging mechanism of Ag/CeO2 catalysts, the TGA (thermogravimetric analysis) experiments were investigated to reveal the mechanism of Ag modification on catalytic activity of CeO2 catalyst between fresh and hydrothermal aging and were also characterized with the related characterization experiments to in-depth research the lattice morphology and valence changes. The degradation mechanism of Ag/CeO2 catalysts in vapor with high-temperature was also explained and demonstrated based on density functional and molecular thermodynamics theories. The experimental and simulation data showed that the catalytic activity of soot combustion within Ag/CeO2 decreased more significantly after hydrothermal aging than CeO2 due to the less agglomerated, which caused by the decreased in OII/OI and Ce3+/Ce4+ compared with CeO2. As shown in density function theory (DFT) calculation, the decreased surface energy and the increased oxygen vacancy formation energy of the low Mille index surface after Ag modification led to the instability structure and the high catalytic activity. Ag modification also increased the adsorption energy and Gibbs free energy of H2O on the low Miller index surface compared to CeO2, indicating that the desorption temperature of H2O molecules in (1 1 0) and (1 0 0) was higher than (1 1 1) in CeO2 and Ag/CeO2, which led to the migration of (1 1 1) crystal surfaces to (1 1 0) and (1 0 0) in the vapor environment. These conclusions can provide a valuable addition to the regenerative application of Ce-based catalysts in diesel exhaust aftertreatment system the aerial pollution.

Catalytic combustion of methyl butanoate over HZSM-5 zeolites.

Catalytic combustion technology is an exciting prospect for the removal of pollutants, especially in the field of transportation. Applying zeolites in fuel combustion has gained increasing importance in heterogeneous catalysis arising from their properties such as economical practicability and high activity. However, compared with the extensively investigated homogeneous combustion, few studies have been reported to explore the catalytic combustion of large-molecule fuels, especially for the catalytic combustion of biodiesel surrogate fuels. The purpose of this feature article is to describe the catalytic combustion of methyl butanoate (one of the biodiesel surrogate fuels) over unmodified HZSM-5 zeolites with a particular focus on the catalytic reaction mechanism. Experiments and theoretical calculations were considered here to help explain the proposed catalytic mechanism. This paper can provide new insights into the catalytic mechanism of biodiesel fuels that will guide the improvement of combustion efficiency in internal combustion engines and in the control of pollutant emissions.

Au@Pt Nanotubes within CoZn-Based Metal-Organic Framework for Highly Efficient Semi-hydrogenation of Acetylene.

Designing nanocatalysts with synergetic functional component is a desirable strategy to achieve both high activity and selectivity for industrially important hydrogenation reaction. Herein, we fabricated a core-shell hollow Au@Pt NTs@ZIFs (ZIF, zeolitic imidazolate framework; NT, nanotube) nanocomposite as highly efficient catalysts for semi-hydrogenation of acetylene. Hollow Au@Pt NTs were synthesized by epitaxial growth of Pt shell on Au nanorods followed with oxidative etching of Au@Pt nanorod. The obtained hollow Au@Pt NTs were then homogeneously encapsulated within ZIFs through in situ crystallization. By combining the high activity of bimetallic nanotube and gas enrichment property of porous metal-organic frameworks, hollow Au@Pt NT@ZIF catalyst was demonstrated to show superior catalytic performance for the semi-hydrogenation of acetylene, in terms of both selectivity and activity, over those of monometallic Au and solid bimetal nanorod@ZIF counterparts. This catalysts design idea is believed to be inspirable for the development of highly efficient nanocomposite catalysts.

A simulation investigation on interaction mechanism between Ebola nucleoprotein and VP35 peptide.

Ebola viruses (EBOV) will induce acute hemorrhagic fever, which is fatal to humans and nonhuman primates. The combination of EBOV VP35 peptide with nucleoprotein N-terminal (NPNTD) is proposed based on static crystal structures in recent studies, but VP35 binding mechanism and conformational dynamics are still unclear. This investigation, using Molecular Dynamic (MD) simulation and Molecular Mechanics Generalized Born Surface Area (MM-GB/SA) energy calculation, more convincingly proves the greater roles of the protein binding mechanisms than do hints from the static crystal structure observations. Conformational analysis of the systems demonstrate that combination with VP35 may lead to the conformational transition of NPNTD from "open" to "closed" state. According to the analyses of binding free energies and their decomposition, VP35 residue R37 plays a crucial role in wild type as well as mutant systems. Mutations of I29 and L33 to aspartate as well as M34 to proline affect binding affinity mainly through influencing electrostatic interaction, which is closely related to H-bonds formation. In addition, mutations mainly affect ß-hairpin and loop regions, among which, M34P may have the greatest influence to the binding. This study may provide specific binding mechanisms between VP35 peptide and NPNTD, especially some important residues concerning binding.

An all-atom molecular dynamics study of the anti-interferon signaling of Ebola virus: interaction mechanisms of EBOV VP24 binding to Karyopherin alpha5.

Ebola virus (EBOV) is highly lethal due to virally encoded immune antagonists, and the combination of EBOV VP24 with karyopherin alpha (KPNA) will trigger anti-interferon (IFN) signaling. The crystal structure of VP24-KPNA5 has been proposed in recent studies, but the precise binding mechanisms are still unclear. In order to explore the VP24-KPNA5 protein binding micro-mechanisms, Molecular Dynamic (MD) simulations and Molecular Mechanics Generalized Born Surface Area (MM-GB/SA) energy calculation are performed. The obtained results show that EBOV VP24 binding to KPNA5 will rigidify their binding-face, and both proteins will be compacted during binding. According to the analyses of binding free energies of WT and the eight mutant systems, MUT3 makes the most effective contributions to the interaction; additionally MUT4, R398A and the double mutant have the second most effective influence. Hydrogen bond analysis demonstrates that inhibitors which can interfere with the formation of hydrogen bonds D480-T138, E483-R137 and D205-R396 will prevent the anti-IFN effect. Meanwhile, by combining the decomposition of binding free energies (DC) with computational alanine scanning (CAS) results, it is shown that VP24 residues R137 and T138 will be potential targets for EBOV VP24 inhibitors, and KPNA5 residues R396, R398, R480, Y477 and F484 will be potential targets to prevent KPNA5 binding to VP24, which will ultimately block anti-IFN signaling. Our investigations provide theoretical data to understand the binding modes of VP24-KPNA5. The precise binding mechanisms of the complex may shed light on the development of potential novel inhibitors against EBOV infection.