The spike protein of SARS-CoV-2 has been undergoing mutations and is highly glycosylated. It is critically important to investigate the biological significance of these mutations. Here, we ...investigated 80 variants and 26 glycosylation site modifications for the infectivity and reactivity to a panel of neutralizing antibodies and sera from convalescent patients. D614G, along with several variants containing both D614G and another amino acid change, were significantly more infectious. Most variants with amino acid change at receptor binding domain were less infectious, but variants including A475V, L452R, V483A, and F490L became resistant to some neutralizing antibodies. Moreover, the majority of glycosylation deletions were less infectious, whereas deletion of both N331 and N343 glycosylation drastically reduced infectivity, revealing the importance of glycosylation for viral infectivity. Interestingly, N234Q was markedly resistant to neutralizing antibodies, whereas N165Q became more sensitive. These findings could be of value in the development of vaccine and therapeutic antibodies.
Display omitted
•Over 100 mutations were selected for analyses on their infectivity and antigenicity•The dominant D614G itself and combined with other mutations are more infectious•Ablation of both N331 and N343 glycosylation at RBD drastically reduced infectivity•Ten mutations such as N234Q, L452R, A475V, and V483A was markedly resistant to some mAbs
Eighty natural variants and 26 glycosylation spike mutants of SARS-CoV-2 were analyzed in terms of infectivity and antigenicity using high throughput pseudovirus assay in conjunction with neutralizing antibodies.
Emerging and reemerging infectious diseases have a strong negative impact on public health. However, because many of these pathogens must be handled in biosafety level, 3 or 4 containment ...laboratories, research and development of antivirals or vaccines against these diseases are often impeded. Alternative approaches to address this issue have been vigorously pursued, particularly the use of pseudoviruses in place of wild-type viruses. As pseudoviruses have been deprived of certain gene sequences of the virulent virus, they can be handled in biosafety level 2 laboratories. Importantly, the envelopes of these viral particles may have similar conformational structures to those of the wild-type viruses, making it feasible to conduct mechanistic investigation on viral entry and to evaluate potential neutralizing antibodies. However, a variety of challenging issues remain, including the production of a sufficient pseudovirus yield and the inability to produce an appropriate pseudotype of certain viruses. This review discusses current progress in the development of pseudoviruses and dissects the factors that contribute to low viral yields.
The activity and stability of non-precious metal catalysts (NPMCs) for the oxygen reduction reaction (ORR) in both acid and alkaline electrolytes were studied by the rotating disk electrode ...technique. The NPMCs were prepared through the pyrolysis of cobalt–iron–nitrogen chelate followed by combination of pyrolysis, acid leaching, and re-pyrolysis. In both environments, the catalysts heat-treated at 800–900
°C exhibited relatively high activity. Particularly, an onset potential of 0.92
V and a well-defined limiting current plateau for the ORR was observed in alkaline medium. The potential cycling stability test revealed the poor stability of NPMCs in acid solution with an exponential increase in the performance degradation as a function of the number of potential cycling. In contrast, the NPMCs demonstrated exceptional stability in alkaline solution. The numbers of electron transferred during the ORR on the NPMCs in acid and alkaline electrolytes were 3.65 and 3.92, respectively, and these numbers did not change before and after the stability test. XPS analysis indicated that the N-containing sites of catalysts are stable before and after the stability test when in alkaline solution but not in acid solution.
A non-precious nitrogen-modified carbon composite (NMCC) catalyst is synthesized by the pyrolysis of cobalt, iron–ethylenediamine–chelate complexes on silica followed by chemical and pyrolysis ...treatments. Pyrolysis temperature and time have a remarkable impact on the content and the type of the nitrogen-containing functional groups in the NMCC catalysts, which affect their catalytic activity and stability. Based on the analysis of the nitrogen functional groups before and after the stability tests, the ORR active sites of the NMCC catalysts are proposed to be pyridinic-N and quaternary-N functional groups. However the pyridinic-N group is not stable in the acidic environment due to the protonation reaction.
This paper presented the measurement results of space charge distribution and high field conduction in cross-linked polyethylene (XLPE) plate sample at various electric fields for a broad temperature ...range from 30 to 90 °C. The temperature effect on charge trapping and transport mechanism is discussed based on estimation of threshold characteristic and apparent mobility. It is shown that the threshold field for space charge accumulation apparently decreased with the temperature, probably associated with acceleration of charge injection and ionic dissociation. The apparent mobility of charges showed an exponential dependence on temperature, which indicates enhancement of charge detrapping and transfer rate at higher temperature. The field dependence of the space charge decreases with the temperature, results in more space charge accumulate at room temperature than at high temperature at certain high field. This behavior indicates that the space charge formation rate increases slower than the charge detrapping rate as the temperature increases. Besides, negative charge is always dominant in the sample at the measuring field and temperature range. This is probably due to stronger electron injection at XLPE-aluminum interface or more negative ion formed by dissociation of chemical species.
SiO2 nanoparticle is one of the most popular nanomaterial which has been used in various fields, such as wastewater treatment, environmental remediation, food processing, industrial and household ...applications, biomedicine, disease labeling, and biosensor, etc. In agriculture, the use of SiO2 nanoparticles as insecticide, carriers in drug delivery, or in uptake and translocation of nutrient elements, etc., has been given attention. However, the effects of nanoparticles on plants have been seldom studied. In this work, the toxicity of SiO2 nanoparticles and their uptake, transport, distribution and bio-effects have been investigated in Bt-transgenic cotton.
The phytotoxic effects of SiO2 nanoparticles were exhibited in Bt-transgenic cotton with different SiO2 concentrations of 0, 10, 100, 500 and 2000 mg.L(-1) for 3 weeks through dry biomasses, nutrient elements, xylem sap, enzymes activities, and hormone concentrations. The uptake and distribution of nanoparticles by the plants were confirmed using transmission electron microscopy (TEM).
The SiO2 nanoparticles decreased significantly the plant height, shoot and root biomasses; the SiO2 nanoparticles also affected the contents of Cu, Mg in shoots and Na in roots of transgenic cotton; and SOD activity and IAA concentration were significantly influenced by SiO2 nanoparticles. In addition, SiO2 nanoparticles were present in the xylem sap and roots as examined by TEM showing that the SiO2 nanoparticles were transported from roots to shoots via xylem sap.
This is the first report of the transportation of SiO2 nanoparticles via xylem sap within Bt-transgenic cotton. This study provides direct evidence for the bioaccumulation of SiO2 nanoparticles in plants, which shows the potential risks of SiO2 nanoparticles impact on food crops and human health.
To improve the adsorption efficiency of layered double hydroxides (LDHs) for heavy metals, a novel sodium alginate (SA) intercalated MgAl-LDH (SA-LDH) was synthesized in this work. SA-LDH was ...characterized by XRD, FTIR, XPS and employed as adsorbent for Cd(II), Pb(II), Cu(II) elimination. Adsorbent dosage, initial pH and contact time, which are regarded as several key parameters, were optimized. The results showed that SA-LDH exhibited better adsorption performance compared with the pristine MgAl-LDH. The maximum adsorption capacities of SA-LDH for Cu(II), Pb(II) and Cd(II) reached 0.945, 1.176 and 0.850 mmol/g, respectively. The possible mechanisms were analyzed by XPS, XRD and FTIR. The results showed that Cd(II), Pb(II) and Cu(II) may be removed by SA-LDH via (i) bonding or complexation with Sur-OH or Sur-O- of SA-LDH, (ii) precipitation of metal hydroxides or carbonates, (iii) isomorphic substitution, and (iv) chelation with -COO
in the interlayers. This work provides an effective method for the development of LDH-based adsorbent and the treatment of wastewater containing heavy metals.
▶ Metal-nitrogen-based precursor is better than the single metal or nitrogen one. ▶ Heat-treatment plays a crucial role in forming active sites of catalysts. ▶ The optimized CoFeN/C catalyst exhibits ...very comparable activity with Pt/C. ▶ The maximum power density of CoFeN/C is 177
mW
cm
−2 in alkaline fuel cell.
Non-precious metal catalysts (NPMCs) synthesized from the precursors of carbon, nitrogen, and transition metals were investigated as an alternate cathode catalyst for alkaline fuel cells (AFCs). The procedures to synthesize the catalyst and the post-treatment were tailored to refine its electrocatalytic properties for oxygen reduction reaction (ORR) in alkaline electrolyte. The results indicated that the performance of NPMCs prepared with carbon-supported ethylenediamine-transition metal composite precursor and subjected to heat-treatment shows comparable activity for oxygen reduction with Pt/C catalyst. The NPMC exhibits an open circuit potential of 0.97
V and a maximum power density of 177
mW
cm
−2 at 50
°C when tested in anion exchange membrane (AEM) fuel cells.
•A two-step method was utilized to synthesize multi-element doped Ce0.3Ni1.5Co2.5Sb12 film efficiently.•Well-crystallized CoSb3 and CeSb coexisted, leading to a positive effect on electrical ...properties.•The maximum value of S and PF reach −250 μV/K and 5275 μW/(mK2) for Ce0.3Ni1.5Co2.5Sb12 film at 673 K.
The skutterudite CoSb3 has been widely concerned, as one of the most studied candidate materials for thermoelectric applications. Here, n-type bulk skutterudite Ce0.3Ni1.5Co2.5Sb12 was successfully prepared under TGZM effect and its thin film deposited by PLD on single crystal Si substrate, to further understand the effect of microstructure and the electrical transport mechanism on the thermoelectric properties from bulk to thin film. It is found that two phases of Sb and CoSb3 coexist in bulk sample, while abundant nano-granular structures with well-crystallized CoSb3 and little of CeSb generate in the film. As a result, the maximum value of S and PF reach −250 μV/K and 5275 μW/(mK2) for film sample at 673 K. The PF value of film is four times higher than that of the bulk sample. This provides a novel avenue to increase the thermoelectric properties of skutterudite.
Dental charting is a useful tool in physical examination, dental surgery, and forensic identification. However, manual dental charting faces some difficulties, such as inaccuracy and psychiatric ...burden in forensic identification. As a critical step of dental charting, tooth classification can be completed on dental cone-beam computed tomography (CBCT) automatically to solve the above difficulties. In this paper, we build a deep neuron network which accepts a 3D CBCT image patch that contains the region of interest (ROI) of a tooth as input and then outputs the type of the tooth. Although Transformer-based neural networks outperform CNN-based neural networks in many natural image processing tasks, they are difficult to apply to 3D medical images. Therefore, we combine the advantages of CNN and Transformer structure to improve the existing methods and propose the Grouped Bottleneck Transformer to overcome the drawbacks of the Transformer, namely the requirement of large training dataset and high computational complexity. We conducted an experiment on a clinical data set containing 450 training samples and 104 testing samples. Experiments show that our network can achieve a classification accuracy of 91.3% and an AUC score of 99.7%. To further evaluate the effectiveness of our method, we tested our network on the publicly available medical image classification dataset MedMNIST3D. The result shows that our network outperforms other networks on 5 out of 6 3-dimensional medical image subsets.
•Address the necessity of the tooth classification task on dental CBCT images.•Propose a novel Transformer based deep neuron network for tooth classification.•Improve the Transformer structure and integrates the CNN in the proposed network.•Grouping and bottleneck mechanism can reduce the computation cost of the network.
PDF
