Structure Transformation of Methylammonium Polyoxomolybdates via In-Solution Acidification and Solid-State Heating from Methylammonium Monomolybdate and Application as Negative Staining Reagents for Coronavirus Observation.

We prepared polyoxomolybdates with methylammonium countercations from methylammonium monomolybdate, (CH3NH3)2[MoO4], through two dehydrative condensation methods, acidifying in the aqueous solution and solid-state heating. Discrete (CH3NH3)10[Mo36O112(OH)2(H2O)14], polymeric ((CH3NH3)8[Mo36O112(H2O)14])n, and polymeric ((CH3NH3)4[γ-Mo8O26])n were selectively isolated via pH control of the aqueous (CH3NH3)2[MoO4] solution. The H2SO4-acidified solution of pH < 1 produced "sulfonated α-MoO3", polymeric ((CH3NH3)2[(MoO3)3(SO4)])n. The solid-state heating of (CH3NH3)2[MoO4] in air released methylamine and water to produce several methylammonium polyoxomolybdates in the sequence of discrete (CH3NH3)8[Mo7O24-MoO4], discrete (CH3NH3)6[Mo7O24], discrete (CH3NH3)8[Mo10O34], and polymeric ((CH3NH3)4[γ-Mo8O26])n, before their transformation into molybdenum oxides such as hexagonal-MoO3 and α-MoO3. Notably, some of their polyoxomolybdate structures were different from polyoxomolybdates produced from ammonium molybdates, such as (NH4)2[MoO4] or (NH4)6[Mo7O24], indicating that countercation affected the polyoxomolybdate structure. Moreover, among the tested polyoxomolybdates, (CH3NH3)6[Mo7O24] was the best negative staining reagent for the observation of the SARS-CoV-2 virus using transmission electron microscopy.

Capture and neutralization of SARS-CoV-2 and influenza virus by algae-derived lectins with high-mannose and core fucose specificities.

We first investigated the interactions between several algae-derived lectins and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). We created lectin columns using high-mannose (HM)-type glycan-specific lectins OAA and KAA-1 or core fucose-specific lectin hypninA-2 and conducted binding experiments with SARS-CoV-2. The results showed that these lectins were capable of binding to the virus. Furthermore, when examining the neutralization ability of nine different lectins, it was found that KAA-1, ESA-2, and hypninA-2 were effective in neutralizing SARS-CoV-2. In competitive inhibition experiments with glycoproteins, neutralization was confirmed to occur through HM-type or core fucose-type glycans. However, neutralization was not observed with other lectins, such as OAA. This trend of KAA-1 and ESA-2 having the neutralizing ability and OAA not having it was also similar to influenza viruses. Electron microscopy observations revealed that KAA-1 and hypninA-2 strongly aggregated SARS-CoV-2 particles, while OAA showed a low degree of aggregation. It is believed that the neutralization of SARS-CoV-2 involves multiple factors, such as glycan attachment sites on the S protein, the size of lectins, and their propensity to aggregate, which cause inhibition of receptor binding or aggregation of virus particles. This study demonstrated that several algae-derived lectins could neutralize SARS-CoV-2 and that lectin columns can effectively recover and concentrate the virus.

Thermal Structure Transformation of Methylammonium Vanadate and it's Application as a Negative Staining Reagent for Observing SARS-CoV-2.

The solid-state thermal structure transformation of methylammonium vanadate, (CH3NH3)VO3, from -150 °C to 350 °C is reported. Variable-temperature X-ray single-crystal structure analysis at 23, 0, -50, -100, and -150 °C reveal (CH3NH3)VO3 comprises of methylammonium cations and "snake-like" ([VO3]-)n anion chains propagating along the c-direction in the Pna21 space group. In between -150 and -100 °C, we observe a reversible structural transformation due to the re-orientation of the methylammonium cations in the crystal packing, which is also confirmed by the reversible profiles observed in differential scanning calorimetry. The methylammonium vanadate is stable until at ca. 100 °C and further heating releases methylamine and water and V2O5 is formed at ca. 275 °C . Furthermore, we show that the methylammonium vanadate can be used as a negative staining reagent for visualizing SARS-CoV-2, allowing us to discern the spike proteins from the body of the virus using transmission electron microscopy.

In vitro anti-severe acute respiratory syndrome coronavirus 2 effect of Ephedra przewalskii Stapf extract.

ETHNOPHARMACOLOGICAL RELEVANCE: The terrestrial stems of Ephedra (Ephedra spp.; including Ephedra sinica Stapf and Ephedra przewalskii Stapf) extracts are used in traditional medicines in East Asia. In Japan, the Kampo formula containing E. sinica extract is prescribed for the treatment of the common cold, influenza virus infections, and mild symptoms of coronavirus disease 2019 (COVID-19). Although ephedrine alkaloids in E. sinica exert antitussive effects, they may have side effects associated with the sympathetic nervous system. E. przewalskii extract, a drug used in traditional Uyghur and Mongolian medicine, is considered to be free of ephedrine alkaloids and is a promising candidate for the treatment of infectious diseases. However, its use is currently limited because evidence of its antiviral efficacy remains inconclusive. AIM OF THE STUDY: We compared the anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) effects of E. przewalskii and E. sinica extracts in vitro. Additionally, we examined the differences in their antiviral effects against different SARS-CoV-2 strains. MATERIALS AND METHODS: VeroE6/TMPRSS2 cells were infected with SARS-CoV-2 (Conventional, Delta, and Omicron strains-BA.1, BA.2, BA.4, and BA.5), and lysates prepared from each herbal extract were added. The infectious titer was determined using the 50% tissue culture infectious dose (TCID50) method; in turn, the half-maximal inhibitory concentration (IC50) was calculated for each extract to compare the antiviral efficacy of E. sinica and E. przewalskii extracts. Further, the extracts were compared with remdesivir for their antiviral efficacy against the conventional viral strain. To verify the effect of the inactivation of virus particles, these extracts were added to each SARS-CoV-2 strain, and the infectious titers were determined using the TCID50 method. RESULTS: The antiviral efficacy (i.e., IC50) of the E. przewalskii extract against each SARS-CoV-2 strain was 2.7-10.8-fold greater than that of the E. sinica extract. The antiviral efficacy of the E. przewalskii extract against conventional viral strains was compared with that of remdesivir, which was 1/27.6 of remdesivir's efficacy. The E. sinica extract showed minimal inactivation of virus particles of each strain, whereas the E. przewalskii extract resulted in substantial viral inactivation. CONCLUSIONS: The E. przewalskii extract showed higher antiviral activity against SARS-CoV-2 than the E. sinica extract. Overall, our study suggests that E. przewalskii extract can be used for the treatment of viral infections, including COVID-19.

Virus purification highlights the high susceptibility of SARS-CoV-2 to a chlorine-based disinfectant, chlorous acid.

Chlorous acid water (HClO2) is known for its antimicrobial activity. In this study, we attempted to accurately assess the ability of chlorous acid water to inactivate SARS-CoV-2. When using cell culture supernatants of infected cells as the test virus, the 99% inactivation concentration (IC99) for the SARS-CoV-2 D614G variant, as well as the Delta and Omicron variants, was approximately 10ppm of free chlorine concentration with a reaction time of 10 minutes. On the other hand, in experiments using a more purified virus, the IC99 of chlorous acid water was 0.41-0.74ppm with a reaction time of 1 minute, showing a strong inactivation capacity over 200 times. With sodium hypochlorite water, the IC99 was 0.54ppm, confirming that these chlorine compounds have a potent inactivation effect against SARS-CoV-2. However, it became clear that when using cell culture supernatants of infected cells as the test virus, the effect is masked by impurities such as amino acids contained therein. Also, when proteins (0.5% polypeptone, or 0.3% BSA + 0.3% sheep red blood cells, or 5% FBS) were added to the purified virus, the IC99 values became high, ranging from 5.3 to 76ppm with a reaction time of 10 minutes, significantly reducing the effect. However, considering that the usual usage concentration is 200ppm, it was shown that chlorous acid water can still exert sufficient disinfection effects even in the presence of proteins. Further research is needed to confirm the practical applications and effects of chlorous acid water, but it has the potential to be an important tool for preventing the spread of SARS-CoV-2.

Structural basis of spike RBM-specific human antibodies counteracting broad SARS-CoV-2 variants.

The decrease of antibody efficacy to mutated SARS-CoV-2 spike RBD explains the breakthrough infections and reinfections by Omicron variants. Here, we analyzed broadly neutralizing antibodies isolated from long-term hospitalized convalescent patients of early SARS-CoV-2 strains. One of the antibodies named NCV2SG48 is highly potent to broad SARS-CoV-2 variants including Omicron BA.1, BA.2, and BA.4/5. To reveal the mode of action, we determined the sequence and crystal structure of the Fab fragment of NCV2SG48 in a complex with spike RBD from the original, Delta, and Omicron BA.1. NCV2SG48 is from a minor VH but the multiple somatic hypermutations contribute to a markedly extended binding interface and hydrogen bonds to interact with conserved residues at the core receptor-binding motif of RBD, which efficiently neutralizes a broad spectrum of variants. Thus, eliciting the RBD-specific B cells to the longitudinal germinal center reaction confers potent immunity to broad SARS-CoV-2 variants emerging one after another.