Controlling effect of TiO2 carrier on formed vanadium species for effective catalytic oxidization of chlorobenzene

Catalytic oxidization of the dioxins is critical to the atmosphere since medical-waste incineration is globally increased due to COVID-19. Vanadium supported TiO2 is the most-widely investigated catalyst. However, previous reports usually investigated V-Ti relationships after vanadate was loaded on TiO2 and an activation was completed. In comparison, this work emphasizes on the influence of TiO2 surface chemistries on properties of formed vanadium species during a thermal activation. The vanadate loaded TiO2 are detailedly analyzed by both experimental characterizations and theoretical calculations. As a result, TiO2 with more Ti4+ is inclined to be reductive, and promotes the formation of more low-valence vanadium and surface vacancies. On the contrary, TiO2 with more Ti3+ is inclined to be oxidative, and promotes the formation of more lattice oxygens and high-valence vanadium. When they were compared in catalytic oxidization of chlorobenzene, the Ti4+-induced catalyst attains a conversion of 98.0 % at 250 °C, far bigger than that (11.3 %) of the Ti3+-induced catalyst. The main result of this work helps readers to understand the process of the catalyst preparation, which is in favor of producing a more effective catalyst by regulating the catalyst carrier.

A novel cell culture system modeling the SARS-CoV-2 life cycle (preprint)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the global pandemic of COVID-19, and no effective antiviral agents and vaccines are available. SARS-CoV-2 is classified as a biosafety level-3 (BLS-3) agent, impeding the basic research into its biology and the development of effective antivirals. Here, we developed a biosafety level-2 (BSL-2) cell culture system for production of transcription and replication-competent SARS-CoV-2 virus-like-particles (trVLP). This trVLP expresses a reporter gene (GFP) replacing viral nucleocapsid gene (N), which is required for viral genome packaging and virion assembly (SARS-CoV-2-GFP/{Delta}N trVLP). The complete viral life cycle can be achieved and exclusively confined in the cells ectopically expressing SARS-CoV or SARS-CoV-2 N proteins, but not MERS-CoV N. Genetic recombination of N supplied in trans into viral genome was not detected, as evidenced by sequence analysis after one-month serial passages in the N-expressing cells. Moreover, intein-mediated protein trans-splicing approach was utilized to split the viral N gene into two independent vectors, and the ligated viral N protein could function in trans to recapitulate entire viral life cycle, further securing the biosafety of this cell culture model. Based on this BSL-2 SARS-CoV-2 cell culture model, we developed a 96-well format high throughput screening for antivirals discovery. We identified salinomycin, tubeimoside I, monensin sodium, lycorine chloride and nigericin sodium as potent antivirals against SARS-CoV-2 infection. Collectively, we developed a convenient and efficient SARS-CoV-2 reverse genetics tool to dissect the virus life cycle under a BSL-2 condition. This powerful tool should accelerate our understanding of SARS-CoV-2 biology and its antiviral development.

Could the Ambient Higher Temperature Decrease the Transmissibility of COVID-19 in China? (preprint)

Background: Existing literatures demonstrated that meteorological factors could be of importance in affecting the spread patterns of the respiratory infectious diseases. However, how ambient temperature may influence the transmissibility of COVID-19 remains unclear. Objectives: We explore the association between ambient temperature and transmissibility of COVID-19 in different regions across China. Methods: : The surveillance data on COVID-19 and meteorological factors were collected from 28 provincial level regions in China, and estimated the instantaneous reproductive number ( R t ). The generalized additive model was used to assess the relationship between mean temperature and R t . Results: : There were 12745 COVID-19 cases collected in the study areas. We report the effect of temperature on R t is not of statistical significance, which holds for most of included regions except for those in North China. Conclusions: We found little statistical evidence for that the higher temperature may reduce the transmissibility of COVID-19.

Molecular architecture of the SARS-CoV-2 virus (preprint)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an enveloped virus responsible for the COVID-19 pandemic. Despite recent advances in the structural elucidation of SARS-CoV-2 proteins and the complexes of the spike (S) proteins with the cellular receptor ACE2 or neutralizing antibodies, detailed architecture of the intact virus remains to be unveiled. Here we report the molecular assembly of the authentic SARS-CoV-2 virus using cryo-electron tomography (cryo-ET) and subtomogram averaging (STA). Native structures of the S proteins in both pre- and postfusion conformations were determined to average resolutions of 9-11 Å. Compositions of the N-linked glycans from the native spikes were analyzed by mass spectrometry, which revealed highly similar overall processing states of the native glycans to that of the recombinant glycoprotein glycans. The in situ architecture of the ribonucleoproteins (RNP) and its higher-order assemblies were revealed. These characterizations have revealed the architecture of the SARS-CoV-2 virus to an unprecedented resolution, and shed lights on how the virus packs its ~30 Kb long single-segmented RNA in the ~80 nm diameter lumen. Overall, the results unveiled the molecular architecture and assembly of the SARS-CoV-2 in native context.Competing Interest StatementThe authors have declared no competing interest.View Full Text