Soon after the emergence and global spread of the SARS-CoV-2 Omicron lineage BA.1, another Omicron lineage, BA.2, began outcompeting BA.1. The results of statistical analysis showed that the ...effective reproduction number of BA.2 is 1.4-fold higher than that of BA.1. Neutralization experiments revealed that immunity induced by COVID vaccines widely administered to human populations is not effective against BA.2, similar to BA.1, and that the antigenicity of BA.2 is notably different from that of BA.1. Cell culture experiments showed that the BA.2 spike confers higher replication efficacy in human nasal epithelial cells and is more efficient in mediating syncytia formation than the BA.1 spike. Furthermore, infection experiments using hamsters indicated that the BA.2 spike-bearing virus is more pathogenic than the BA.1 spike-bearing virus. Altogether, the results of our multiscale investigations suggest that the risk of BA.2 to global health is potentially higher than that of BA.1.
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•The effective reproduction number of BA.2 is 1.4-fold higher than that of BA.1•BA.2 is resistant to BA.1-induced humoral immunity•The BA.2 spike is more fusogenic than BA.1 spike•BA.2 spike-bearing virus is more pathogenic than BA.1 spike-bearing virus
Yamasoba and G2P-Japan Consortium et al. elucidate the characteristics of SARS-CoV-2 Omicron variant BA.2—transmissibility, immune resistance, virological property, and pathogenicity. The effective population number of BA.2 is higher than that of BA.1, and the antigenicity of BA.2 is different from that of BA.1. The BA.2 spike is more fusogenic than the BA.1 spike, and notably, the BA.2 spike-bearing virus is more pathogenic than the BA.1 spike-bearing virus. This multiscale investigation suggests the potential risk of BA.2 to global health.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
After the global spread of the SARS-CoV-2 Omicron BA.2, some BA.2 subvariants, including BA.2.9.1, BA.2.11, BA.2.12.1, BA.4, and BA.5, emerged in multiple countries. Our statistical analysis showed ...that the effective reproduction numbers of these BA.2 subvariants are greater than that of the original BA.2. Neutralization experiments revealed that the immunity induced by BA.1/2 infections is less effective against BA.4/5. Cell culture experiments showed that BA.2.12.1 and BA.4/5 replicate more efficiently in human alveolar epithelial cells than BA.2, and particularly, BA.4/5 is more fusogenic than BA.2. We further provided the structure of the BA.4/5 spike receptor-binding domain that binds to human ACE2 and considered how the substitutions in the BA.4/5 spike play roles in ACE2 binding and immune evasion. Moreover, experiments using hamsters suggested that BA.4/5 is more pathogenic than BA.2. Our multiscale investigations suggest that the risk of BA.2 subvariants, particularly BA.4/5, to global health is greater than that of original BA.2.
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•BA.4/5 is resistant to immunity induced by BA.1 and BA.2 infections•Substitutions in the BA.4/5 spike contribute to immune escape and ACE2 binding strength•BA.4/5 is more fusogenic and more efficiently spread in human lung cells than BA.2•BA.4/5 spike-bearing virus is more pathogenic than BA.2 spike-bearing virus
The SARS-CoV-2 Omicron variants BA.4 and BA.5 are currently causing infections and COVID-19 morbidities worldwide. Compared with the earlier variant BA.2, BA.4/5 shows more efficient replication and is more fusogenic. Structural views as well as in vivo studies in hamsters explain the antibody evasion and increased pathogenicity of BA.4/5 over BA.2.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Chromium-based cocatalysts influence H2 evolution during the overall water splitting reaction in the photocatalytic conversion of CO2 in the presence of H2O as an electron donor. To clarify the ...mechanism by which chromium species promote or suppress H2 evolution, the reaction was carried out in the presence of α- and β-Ga2O3, NaTaO3, ZnTa2O6, and SrTa2O6 photocatalysts with the in situ addition of chromate ions. We found that chromate ions suppress H2 evolution during the photocatalytic conversion of CO2 by H2O when the surface of the photocatalyst is highly protonated.
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•Na2CrO4 suppressed the evolution of H2 over highly protonated photocatalysts.•Na2CrO4 enhanced the evolution of H2 over lowly protonated photocatalysts.•The formation of Cr(OH)3 was critical to the enhancement effect in H2 evolution.•Dissolved chromate affected the evolution of H2 to a large degree.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Amino acids are the building blocks for protein biosynthesis and find use in myriad industrial applications including in food for humans, in animal feed, and as precursors for bio-based plastics, ...among others. However, the development of efficient chemical methods to convert abundant and renewable feedstocks into amino acids has been largely unsuccessful to date. To that end, here we report a heterogeneous catalyst that directly transforms lignocellulosic biomass-derived α-hydroxyl acids into α-amino acids, including alanine, leucine, valine, aspartic acid, and phenylalanine in high yields. The reaction follows a dehydrogenation-reductive amination pathway, with dehydrogenation as the rate-determining step. Ruthenium nanoparticles supported on carbon nanotubes (Ru/CNT) exhibit exceptional efficiency compared with catalysts based on other metals, due to the unique, reversible enhancement effect of NH₃ on Ru in dehydrogenation. Based on the catalytic system, a two-step chemical process was designed to convert glucose into alanine in 43% yield, comparable with the well-established microbial cultivation process, and therefore, the present strategy enables a route for the production of amino acids from renewable feedstocks. Moreover, a conceptual process design employing membrane distillation to facilitate product purification is proposed and validated. Overall, this study offers a rapid and potentially more efficient chemical method to produce amino acids from woody biomass components.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Rhodium-doped gallium oxide (Ga2O3:Rh) that was prepared by a simple coprecipitation method exhibited activity for the photocatalytic conversion of CO2 by H2O under photoirradiation with light of ...>300 nm wavelength. Although Ga2O3 is a wide-band-gap photocatalyst that is active only under photoirradiation with <300 nm light, the absorption edge shifted to >300 nm as a result of Rh doping. Ag–Cr-loaded Ga2O3:Rh (0.7 mol %) showed activity for the production of CO (3.9 μmol h–1) as a reduction product of CO2. The formation of a stoichiometric amount of O2 indicated that H2O acts as an electron donor for the photocatalytic conversion of CO2. Characterization using several techniques such as X-ray absorption spectroscopy (XAS) revealed that after doping in Ga2O3 the trivalent Rh species substituted not for the tetrahedral Ga site but for the octahedral Ga site of β-Ga2O3. From the result of DFT calculations, the new energy level owing to Rh3+ was within the Ga2O3 band gap. It was concluded that the new absorption due to the Rh d t2g orbital to the conduction band contributed to the activity of photocatalytic conversion of CO2 by H2O under photoirradiation with light of >300 nm wavelength.
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Current environmental issues, such as global warming and the exhaustion of fossil fuels, call for innovative technologies. In this context, efficient photocatalysts that enable the selective ...reduction of CO2 to CO in aqueous media are highly sought after. Although the beneficial use of Ag cocatalysts in ZnTa2O6-based photocatalytic systems has been previously studied, the CO evolution selectivity has remained moderate owing to the competing formation of H2. Herein, we report that the modification of 3.0 wt % Ag-loaded ZnTa2O6 with 10 mol % Zn leads to a significant increase in the CO evolution selectivity to 90.0% while maintaining the rate of CO formation at 25.7 μmol h–1. Thus, the modified Zn species play an important role in the suppression of the H2 evolution. Although an Ag-less, Zn-modified photocatalyst performed relatively well, the combination of a Ag cocatalyst and Zn modifier is required to ensure CO evolution at a high selectivity and rate. Furthermore, full characterization of the Zn-modified photocatalysts allowed the proposal of two putative structures. In addition to serving as ZnTa2O6 surface modifiers, the Zn species may be incorporated in the Zn/ZnTa2O6 bulk. Finally, we propose that three types of active sites exist for (1) the reduction of CO2 to CO, (2) the reduction of H+ to H2, and (3) the oxidation of H2O to O2.
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La L1 and L3-edge X-ray absorption near-edge structure (XANES) of various La oxides were classified according to the local configuration of La. We found a correlation between both of the areas of the ...pre-edge peaks of the La L1-edge XANES spectra and the full width at half-maximum of white line of La L3-edge XANES spectra and the local configuration of La. Theoretical calculation of the XANES spectra and local density of states reveals the difference of La L1 and L3-edge XANES spectra of various La compounds is related to the p–d hybridization of the unoccupied band and broadening of the d band of La induced by the difference of local configuration. In addition, simplified bond angle analysis parameters defined by the angles of the La atom and the two adjacent oxygen atoms are correlated to the pre-edge peak intensity of the La L1-edge XANES spectra. These results indicate that quantitative analysis of La L1 and L3-edge XANES spectra could be an indicator of the local structure of La materials.
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K2RETa5O15 (RE=rare-earth element) fabricated using a flux method showed good activity on photoreduction of CO2 to CO with excellent selectivity toward CO evolution by using H2O as an electron donor.
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•Flux method was applied to fabricate K2RETa5O15 for the first time.•Photoreduction of CO2 by H2O was achieved over Ag-modified K2RETa5O15.•The activity was found to be affected by the amount of KCl flux used.
A facile one-pot flux method was applied to fabricate K2RETa5O15 (RE=rare-earth element) with tetragonal tungsten bronze (TTB) structures. Pure TTB structures of K2RETa5O15 (RE=La, Ce, Pr, Nd, and Sm) with rod-like morphologies were obtained using KCl as the potassium source and flux. For other potassium rare-earth tantalates, the TTB structure was dominant, with an additional RETaO4 phase present. Among all these K2RETa5O15, K2YTa5O15 gave the highest activity for photoreduction of CO2 with good selectivity toward CO evolution using H2O as an electron donor, even in the presence of additional YTaO4 phase. YTaO4 fabricated using the flux method under same condition was inactive for photoreduction of CO2 using H2O. It was found that the activity for the photoreduction of CO2 to be significantly affected by the weight ratio of potassium chloride to yttrium oxide and tantalum oxide (K/YT) in the fabrication process. The highest photoreduction activity achieved in CO evolution was 91.9μmolh−1 (for 1.0-g catalyst), with CO selectivity of 84.9%, at K/YT=1.0. Surface analysis of these tantalates fabricated with different K/YT ratios showed that a high ratio of surface yttrium to tantalum (Y/Ta) was important to achieve a high CO evolution rate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This study shows that a vacuum heat treatment of Nb2O5 permits the ligand-to-metal charge transfer (LMCT) transition between its surface and adsorbed aromatic hydrocarbons, which corresponds to ...visible light (>390 nm) absorption. Selective photooxidation of aromatic hydrocarbons to form the corresponding carbonyl compounds could effectively proceed under visible light irradiation by using this LMCT transition, and the catalytic activity is much superior to that of TiO2. Specifically, the LMCT bands of toluene-adsorbed Nb2O5 correlated well with the action spectrum for toluene photooxidation, suggesting that the reaction proceeded via the LMCT photoexcitation. We successfully detected toluene radical cation and its further oxidation product of benzylperoxy radical as intermediate species on toluene-adsorbed Nb2O5 through the LMCT transition. These findings suggest a novel reaction mechanism for the selective photooxidation of aromatic hydrocarbons via LMCT transition on Nb2O5.
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