Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the viral pathogen causing the coronavirus disease 2019 (COVID-19) global pandemic. No effective treatment for COVID-19 has been ...established yet. The serine protease transmembrane protease serine 2 (TMPRSS2) is essential for viral spread and pathogenicity by facilitating the entry of SARS-CoV-2 into host cells. The protease inhibitor camostat, an anticoagulant used in the clinic, has potential anti-inflammatory and antiviral activities against COVID-19. However, the potential mechanisms of viral resistance and antiviral activity of camostat are unclear. Herein, we demonstrate high inhibitory potencies of camostat for a panel of serine proteases, indicating that camostat is a broad-spectrum inhibitor of serine proteases. In addition, we determined the crystal structure of camostat in complex with a serine protease (uPA urokinase-type plasminogen activator), which reveals that camostat is inserted in the S1 pocket of uPA but is hydrolyzed by uPA, and the cleaved camostat covalently binds to Ser195. We also generated a homology model of the structure of the TMPRSS2 serine protease domain. The model shows that camostat uses the same inhibitory mechanism to inhibit the activity of TMPRSS2, subsequently preventing SARS-CoV-2 spread.
Serine proteases are a large family of enzymes critical for multiple physiological processes and proven diagnostic and therapeutic targets in several clinical indications. The serine protease transmembrane protease serine 2 (TMPRSS2) was recently found to mediate SARS-CoV-2 entry into the host. Camostat mesylate (FOY 305), a serine protease inhibitor active against TMPRSS2 and used for the treatment of oral squamous cell carcinoma and chronic pancreatitis, inhibits SARS-CoV-2 infection of human lung cells. However, the direct inhibition mechanism of camostat mesylate for TMPRSS2 is unclear. Herein, we demonstrate that camostat uses the same inhibitory mechanism to inhibit the activity of TMPRSS2 as uPA, subsequently preventing SARS-CoV-2 spread.
For the advantages of low cost, excellent thermal insulation, and sound absorption properties, the rigid isocyanate-based polyimide foam (RPIF) presents great application prospects as a building ...insulation material. However, its inflammability and the accompanying toxic fumes create huge safety hazard. In this paper, reactive phosphate-containing polyol (PPCP) is synthesized and employed with expandable graphite (EG) to obtain RPIF with excellent use safety. EG can be considered as an ideal partner for PPCP to weaken the drawbacks in toxic fume release. Limiting oxygen index (LOI), cone calorimeter test (CCT), and toxic gas results show that the combination of PPCP and EG can synergistically enhance flame retardancy and the use safety of RPIF owing to the unique structure of a dense char layer possessing a flame barrier and toxic gas adsorption effects. When EG and PPCP are simultaneously applied to the RPIF system, the higher EG dosage will bring higher positive synergistic effects in the use safety of RPIF. The most preferred ratio of EG and PPCP is 2:1 (RPIF-10-5) in this study; RPIF-10-5 shows the highest LOI, low CCT results and specific optical density of smoke, and low HCN concentration. This design and the findings are of great significance to improving the application of RPIF.
The competitive balance between uranium (VI) (U(VI)) adsorption and fouling resistance is of great significance in guaranteeing the full potential of U(VI) adsorbents in seawater, and it is faced ...with insufficient research. To fill the gap in this field, a molecular dynamics (MD) simulation was employed to explore the influence and to guide the design of mass-produced natural hemp fibers (HFs). Sulfobetaine (SB)- and carboxybetaine (CB)-type zwitterions containing soft side chains were constructed beside amidoxime (AO) groups on HFs (HFAS and HFAC) to form a hydration layer based on the terminal hydrophilic groups. The soft side chains were swayed by waves to form a hydration-layer area with fouling resistance and to simultaneously expel water molecules surrounding the AO groups. HFAS exhibited greater antifouling properties than that of HFAO and HFAC. The U(VI) adsorption capacity of HFAS was almost 10 times higher than that of HFAO, and the max mass rate of U:V was 4.3 after 35 days of immersion in marine water. This paper offers a theory-guided design of a method to the competitive balance between zwitterion-induced fouling resistance and seawater U(VI) adsorption on natural materials.
Lightweight and fire-resistant isocyanate-based polyimide foams (PIFs) were rapidly formed via a simple one-pot process; polymethylene polyphenylene isocyanate (PAPI) was added into a solution ...containing refilled aromatic dianhydride. The obtained Fourier transform infrared spectra (FT-IR) showed that the refilled 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA) reacted with isocyanate and amino groups in PIFs during the forming and postcuring process. These reactions increased the percentage of polyimide in the foams. Meanwhile, the reaction between refilled BTDA which has a higher reactivity than its derivatives and amino groups, reduced the reaction between isocyanate and amino groups. Subsequently, the generation of ureido was restrained. Thermal gravimetric analysis (TGA) and differential thermogravimetry (DTG) results presented that when the refilled BTDA dosage was increased, the percentage of polyimide and ureido were increased and reduced, respectively. However, the proportion of different ingredients in the PIFs prepared by different formulations was basically the same when the refilled BTDA dosage exceeded 50%. As such, the refilled dosage of BTDA between 50% and 60% was sufficient for this system, the refilled BTDA had extreme effects on enhancing polyimide proportion and reducing the generation of ureido. Fire resistance was characterized by limiting oxygen index (LOI) and cone calorimeter (CCT). Results showed that with the gradual increasing in polyimide proportion of the PIFs resulting from the increase in refilled BTDA dosage, their fire resistance was remarkably improved, which was mainly reflected by the following: gradual increase in LOI value, decrease in heat release rate (HRR), decrease in the peak of HRR (PHRR), decrease in total smoke production (TSP), and decrease in average specific extinction area (ASEA). Compared with the foam prepared without refilled BTDA, the foam prepared with 60% BTDA refilled dosage exhibited increased LOI value from 20.8% to 30.1%, PHRR reduction from 181.91 kW/m super(2) to 41.54 kW/m super(2), and significant reduction of HRR. The reduction in TSP and ASEA reached up to 78.2% and 83.1%, respectively. Meanwhile, when the refilled dosage of BTDA exceeded 60%, the LOI value also showed a slower increase. This change was possibly due to the residual BTDA in foams, which acted as a retardant packing role. The density of foams also increased when the post-additive dosage of BTDA was increased. Possible chemical reactions involved in this preparation method of isocyanate-based PIFs were also discussed in this paper.
Activation of pro-σK processing requires a signaling protease SpoIVB that is secreted from the forespore into the space between the two cells during sporulation in Bacillus subtilis. Bypass of ...forespore protein C (BofC) is an inhibitor preventing the autoproteolysis of SpoIVB, ensuring the factor σK operates regularly at the correct time during the sporulation. However, the regulatory mechanisms of BofC on pro-σK processing are still unclear, especially in the aspect of the interaction between BofC and SpoIVB. Herein, the recombinant BofC (rBofC) was expressed in the periplasm by the E. coli expression system, and crystal growth conditions were obtained and optimized. Further, the crystal structure of rBofC was determined by X-ray crystallography, which is nearly identical to the structures determined by NMR and predicted by AlphaFold. In addition, the modeled structure of the BofC–SpoIVB complex provides insights into the molecular mechanism by which domain 1 of BofC occupies the active site of the SpoIVB serine protease domain, leading to the inhibition of the catalytical activity of SpoIVB and prevention of the substrate of SpoIVB (SpoIVFA) from binding to the active site.
The sandwich structure based on Triply periodic minimal surface (TPMS) is a lightweight and high-strength multifunctional composite material that combines the versatility of heat exchange, impact ...resistance, and energy absorption, and has been widely used in various fields such as aviation and aerospace. However, its sound absorption performance has not meant fully studied. In this paper, a Micro-perforated plate Diamond sandwich structure (MPP-DSS) was designed based on TPMS method, which was composed of aluminum alloy solid panel, aluminum alloy macroscopically ordered porous Diamond structure and aluminum alloy micro-perforated plate. The acoustic absorption performance in low and medium frequency band was studied by impedance tube method. The results show that MPP-DSS has higher absorption coefficient and bandwidth than traditional perforated plate structure with the same structural parameters. Increasing the thickness of micro-perforated plate can improve the sound absorption capacity of MPP-DSS in the low frequency range, but the width of the sound absorption band will be narrowed accordingly. Different from the resonant sound absorption mechanism of the traditional perforated plate structure, the sound absorption mechanism of MPP-DSS is the combined effect of resonant sound absorption and friction loss sound absorption. This study broadens the versatility of the TPMS structure and can serve as a reference for the design of integrated load-bearing and sound-absorbing structures.
Hydrogen peroxide (H2O2) replaced oxygen (O2) as oxidant has been widely investigated due to its faster reduction kinetics, easier storage and handling than gaseous oxygen. The main challenge of ...using H2O2 as oxidant is the chemical decomposition. In this article, by using different C2H5OH/H2O volume ratio as the solvent, Co3O4 with different morphologies (nanosheet, nanowire, ultrafine nanowire net, nanobelts, and honeycomb-like) direct growth on Ni foam are synthesized via a simple solvothermal method for the first time. Results show that the introduction of ethanol could obviously improve the catalytic performance toward H2O2 electroreduction. The sample prepared in the solution with the C2H5OH/H2O volume ratio of 1:2 shows the best catalytic performance among the five samples and a current density of 0.214 A cm−2 is observed in 3.0 mol L−1 KOH + 0.5 mol L−1 H2O2 at −0.4 V (vs. Ag/AgCl KCl), which is much larger than that on the other metal oxides reported previously, almost comparable with the precious metals. This electrode of Co3O4 directly grown on Ni foam has superior mass transport property, which combining with its low-cost and facile preparation, make it a promising electrode for fuel cell using H2O2 as the oxidant.
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•Co3O4 with different morphologies are synthesized via a simple solvothermal method.•The influences of solvent and probable growth mechanism are discussed.•The electrode exhibits high performance and good stability for H2O2 reduction.
Polyimide (PI) possesses excellent thermal stability, mechanical, chemical stability, and electrical insulation properties. Thus, PI has become the most important polymer as interlayer insulating ...materials in microelectronics industry. However, with the development of integrated circuits for the continuously decreasing component size and increasing device integration, the high dielectric constant (k) and dielectric loss (Df) of ordinary aromatic PI film has been unable to meet the demand of microelectronics industry. Therefore, many efforts have been exerted to reduce k and Df of PI film. This article reviews the relative and systematic works about low-k PI film, and mainly summarizes the recent research progresses in intrinsic and porous low-k PI film. The Df of these low-k PI films is briefly introduced, and the influencing factors of Df are analyzed. On this basis, this review also summarizes the advantages and disadvantages of different route to generate low-k PI film, and furtherly compares the dielectric properties, thermal stability, and mechanical properties of different low-k PI film. Finally, this paper aims to gain a deeper understanding about low-k PI film and provide a reference for the future development of low-k PI film. The comprehensive and in-depth insights provide a sufficient basic theories and research results reference to guide the future development and optimization of PI films possessing excellent mechanical, flexible, and electrical insulation properties.
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•Intrinsic and porous routes to decrease k and Df of PI film are mainly reviewed.•Dielectric, mechanical, and thermal properties of different PI films are involved.•Intrinsic low-k PI film has limited decrease in both k and mechanical properties.•Porous low-k PI film has more decrease in k and loss in mechanical properties.•Challenges and prospects to prepare new generation low-k PI film are also mentioned.
Uranium is an important fuel for nuclear power, with 4.5 billion tons of it stored in the oceans, 1,000 times more than on land. Polymer membrane materials are widely used in the marine resources ...fields, due to their convenient collection, good separation and can work continuously. Herein, a poly(amidoxime)-polyacrylonitrile blend membrane (PCP) with high flux, excellent antibacterial properties and uranium adsorption performance has been prepared by using the phase inversion method, and the prepared membrane was used for highly efficient uranium extraction from seawater. In static adsorption experiments, the PCP membrane reached adsorption equilibrium after 48 h, and the adsorption capacity was 303.89 mg/g (C0 =50 mg/L). In dynamic adsorption experiments, it was found that the lower flow rate and higher number of membrane layers were favorable for dynamic adsorption. In addition, the water flux of the PCP membrane was 7.4 times higher than that of the PAN membrane. The adsorption mechanism can be attributed to the chelation between amino and hydroxyl groups in CS, amidoxime group in poly(amidoxime) and uranyl ions. The simple preparation process coupled with the excellent adsorption performance indicated that the PCP membrane would be a promising material for the uranium extraction from seawater.
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•Poly(amidoxime)-polyacrylonitrile membrane has been synthesized by phase inversion method.•Poly(amidoxime) acts as a "surfactant" in the preparation of blended membrane.•The PCP membrane shows high flux, excellent antibacterial and adsorption performance.•Plausible synergistic adsorption mechanism was further discussed.
•A bi-photothermal composite nanofiber membrane was prepared by electrospinning.•The prepared membrane exhibited high optical absorption.•The prepared membrane presented excellent photothermal ...conversion efficiency.•The prepared membrane demonstrated remarkable water evaporation rate.•The prepared membrane showed superb desalination performance.
We have identified a synergistic effect between graphene oxide (GO) and silver (Ag) that significantly enhances the light absorption capacity of silver-loaded graphene oxide (GO-Ag) composite materials. Here we have developed a bi-photothermal electrospun nanofiber membrane (EFM), combining the GO-Ag and polyacrylonitrile (PAN), to improve solar-driven desalination. The characterization results demonstrate that GO-Ag uniformly dispersed within the fiber membrane as a photothermal conversion material enables the GO-Ag/PAN EFM to achieve a remarkable optical absorption of 97 %. And under 1 sun irradiation, the membranes rapidly reach a maximum temperature of 56.3 °C, showcasing exceptional photothermal conversion ability during evaporation. Additionally, the super-hydrophilic porous materials GO-Ag/PAN EFMs exhibit an impressive water evaporation rate of 1.61 kg m-2h−1, accompanied by a photothermal conversion efficiency of 93.3 % under 1 sun. Moreover, the GO-Ag/PAN EFMs demonstrate a remarkable desalination of 99.9 % and salt resistance performance for seawater.
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