Cobalt-based catalysts are widely used to produce liquid fuels through the Fischer–Tropsch (FT) reaction. However, the cobalt nanocatalysts can exhibit intriguing size-dependent activity whose origin ...remains heavily debated. To shed light on this issue, the electronic structures of cobalt nanoparticles with size ranging from 4 to 10 nm are studied using soft X-ray absorption (XAS) and resonant inelastic X-ray scattering (RIXS) spectroscopies. The RIXS measurements reveal the significant size-dependent d–d excitations, from which we determine that the crystal-field splitting energy 10Dq changes from 0.6 to 0.9 eV when the particle size is reduced from 10 to 4 nm. The finding that larger Co nanoparticles have smaller 10Dq value is further confirmed by the Co L-edge RIXS simulations with atomic multiplet code. Our RIXS results demonstrate a stronger Co–O bond in smaller Co nanoparticles, which brings in further insight into their size-dependent catalytic performance.
The isolation of human monoclonal antibodies with broadly neutralizing breadth can provide a promising countermeasure for influenza A viruses infection. Most broadly neutralizing antibodies against ...influenza A viruses bind to the conserved stem region or the receptor-binding cavity of hemagglutinin and the interaction is dominated by the heavy chain. The light chain, however, contributes few or no direct contacts to the antigen. Here we report an H3-clade neutralizing human monoclonal antibody, AF4H1K1, which recognizes the hemagglutinin glycoproteins of all group 2 influenza A viruses. This human monoclonal antibody has been obtained through the screening by pairing different heavy and light chains from an H7N9-infected patient based on the next-generation sequencing technology. Further structural studies revealed that light chains modulate the neutralizing spectrum by affecting the local conformation of heavy chains, instead of direct interaction with the antigen. These findings provide important clues to understand the molecular basis of light chains in antigen recognition and to explore the strategies in particular of the use of light chain modification to develop broadly protective monoclonal antibodies against influenza A viruses and other emerging viruses.
Astragaloside IV (AS-IV) is one of the main active ingredients of Astragalus membranaceus. This study is aimed to investigate AS-IV׳s effects on Ca2+ channel activity of single cardiomyocytes and ...single Ca2+ channels. Whole-cell Ca2+ currents in freshly dissociated cardiomyocytes were measured using the whole-cell patch-clamp technique. Single Ca2+ channel currents were examined in cell-attached patches and inside-out patches. In the whole-cell recording, AS-IV reduced the amplitude of l-type Ca2+ currents (ICaL) in a concentration-dependent manner. Although AS-IV did not alter the steady-state activation curves, the voltage dependence of the current inactivation curves was negatively shifted by AS-IV in a concentration dependent manner. Consistent with the results of the whole-cell recording, in the inside-out configuration the ensemble average of single Ba2+ current via l-type Ca2+ channel was dose-dependently reduced by AS-IV. The reduction of unitary Ba2+ current at 0.1 or 1µM AS-IV was accounted for a decrease in the channel activity (NPo). In addition to the decrease in NPo, there was a reduction of Po without a change in channel number or an apparent change in single channel current. Furthermore, we found that the open-closed kinetics of the channel were affected by AS-IV. AS-IV induced the shift of l-type Ca2+ channels from either brief openings (mode 1) or long-lasting openings (mode 2) to no active opening (mode 0). Our results suggest that AS-IV blocks the currents through Ca2+ channels in guinea-pig ventricular myocytes by affecting the open-closed kinetics of l-type Ca2+ channels to inhibit the channel activities. This study could provide theoretical basis for the drug exploiting of the monomer of Astragalus membranaceus.
Stress and strain distributions in and around a single or two-coupled pyramidal InAs quantum dots (QDs) embedded in GaAs are calculated by finite element methods according to the continuum elasticity ...theory. By changing the quantum dot spacing and thickness of cap layer, the results about strain and stress distributions show compressive strain and stress distribution in the QDs and relaxation undergoes two stages with different speeds for different quantum dot height, quantum width and thickness of cap layer. The stress and strain distributions of pyramidal QDs would not vary monotonously with geometric dimensions. The height of quantum dot and cap layer thickness can effectively adjust the vertical correlation of self-assembly QDs according to the calculation. The shape of stress distribution at surface of cap layer can be tuned from a quadrangle into a circle by increasing the thickness of cap layer or decreasing the height of quantum dot. Also, a new approach to grow quantum ring is found in this paper. The calculations of two-coupled QDs show that the self-assembly technology might fail if the horizontal distance between two QDs is not large enough. The stress induced by upper QDs will be relaxed to zero with a longer distance downwards is found in this paper.
Graphical abstract
•In0.25Ga0.75P is found to be much different with In0.5Ga0.5P and In0.75Ga0.25P.•A new way to obtain closely physical properties of surface InxGa1−xP is found.•Interface strain can effectively affect ...the properties of surface InxGa1−xP.
Electronic and optical properties such as the density of states, dielectric function, absorption, reflectivity, loss function and refractive index of surface InxGa1−xP(0 0 1) are investigated first time with first principle methods based on plane-wave pseudo-potentials method within the LDA approximation in this paper, and the results show that the physical properties are much different from bulk materials. The physical properties of surface In0.25Ga0.75P is observed to be very different from In0.5Ga0.5P and In0.75Ga0.25P and the causes are analyzed in this paper. An indium-gradient surface InxGa1−xP structure has been calculated first time as well, and small differences in electronic and optical properties are found from In0.5Ga0.5P and indium-gradient structures except for x = (0.75, 0.25, 0.5), by which a new way is found to improve the physical properties with a given indium composition.
To investigate the correlation between the clinical classification of coronavirus disease 2019 (COVID-19) and the imaging characteristics of multislice spiral computed tomography (MSCT) volume ...scanning of the lungs.
The clinical data and thoracic MSCT volume scanning data were analyzed retrospectively for 102 patients with COVID-19 diagnosed and hospitalized in the First Affiliated Hospital of Bengbu Medical College between January 18 and February 26, 2020. According to the Fifth Edition of the Diagnosis and Treatment Guidelines by the National Health Commission, the patients were divided into common type, severe type and critical type. The imaging characteristics including the lung sides of the lesions, lung segment involved, lesion distribution, and lesion number and density were compared among the patients with different clinical types of COVID-19.
Seventy-seven of the patients had common type, 18 had severe type and 7 had critical type of COVID-19. The main clinical manifestations included fever, cough an
Abstract
Bimolecular fluorescence complementation (BiFC) is a popular method used to detect protein–protein interactions. For a BiFC assay, a fluorescent protein is usually split into two parts, and ...the fluorescence is recovered upon the interaction between the fused proteins of interest. As an elegant extension of BiFC, a tripartite superfold green fluorescent protein (sfGFP) system that has the advantages of low background fluorescence and small fusion tag size has been developed. However, the tripartite system exhibits a low fluorescence signal in some cases. To address this problem, we proposed to increase the affinity between the two parts, G1–9 and G11, of the tripartite system by adding affinity pairs. Among the three affinity pairs tested, LgBiT-HiBiT improved both the signal and signal-to-noise (S/N) ratio to the greatest extent. More strikingly, the direct covalent fusion of G11 to G1–9, which converted the tripartite system into a new bipartite system, enhanced the S/N ratio from 20 to 146, which is superior to the bipartite sfGFP system split at 157/158 or 173/174. Our results implied that the 10th β-strand of sfGFP has a low affinity and a good recovery efficiency to construct a robust BiFC system, and this concept might be applied to other fluorescent proteins with similar structure to construct new BiFC systems.
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