A biomass phosphonamide enables biodegradable polylactide with favorable flame retardancy and rapid crystallization.

PLA is widely known as biodegradable plastics whose further application in fields such as automotive and architectural is still constrained by its flammability and unsatisfactory crystallization properties. To address the aforementioned concerns, a novel biomass phosphonamide PDPA was synthesized with chemical structure confirmed by FTIR, NMR and elemental analysis tests. Immediately thereafter, PLA/PDPA composites were prepared by melting blending, with a focus on flame retardancy, crystallization properties and flame-retardant mechanism. As expected, PDPA efficiently enhanced both the flame retardancy and crystallization properties of PLA. Specifically, the PLA/4.0PDPA obtained UL-94 V-0 grade and the LOI value increased to 28.6 % with only 4 wt% PDPA added, which comes down to the superior free radical capture and dilution effect of PDPA in the vapor phase and the melting droplet effect. More appealingly, the crystallinity of PLA/4.0PDPA was significantly enhanced to 43.4 % from 2.5 % of PLA, and the shortest t1/2 was 4 mins in the isothermal crystallization process due to the excellent heterogeneous nucleation of PDPA. Moreover, PLA/PDPA composites maintain almost the same mechanical performance as pure PLA. In brief, this work provides a green strategy for the preparation of PLA composites with excellent comprehensive performance and shows great potential in engineering materials.

Synthesis of renewable furan-based phosphate and the superior flame retardancy in biodegradable polylactide.

Currently, it has long been considered a challenge to provide sustainable additives for polylactide (PLA) in green way to endow it excellent comprehensive properties. Given the flammability and unsatisfactory crystallization performance of PLA, a furan-based phosphate furfurylamine trimethylphosphate (FATMP) was synthesized from 2-furfurylamine and amino trimethylphosphonic acid by a simple hydration reaction, and the PLA/FATMP composites were prepared by melting blending process. The tensile performance, crystallization behaviors, flame retardancy, and flame-retardant mechanism received special attention. Results showed that the incorporation of only 3 wt% FATMP could indeed increase the LOI value of PLA from 19.8 to 27.3 %, and simultaneously acquired V-0 rating in the vertical burning test owing to the favorable synergistic effect between the vapor phase and the condensed phase. Additionally, the half-crystallization time of PLA was decreased from 12.4 to 5.1 mins with the addition of FATMP, which acted as a nucleating agent. More appealingly, the tensile performance of PLA/FATMP composites was also well maintained. In general, the PLA/FATMP composites we proposed could be promising candidates in application fields where favorable flame retardancy and crystallization ability are required.

Crystal Structure of African Swine Fever Virus pS273R Protease and Implications for Inhibitor Design.

African swine fever (ASF) is a highly contagious hemorrhagic viral disease of domestic and wild pigs that is responsible for serious economic and production losses. It is caused by the African swine fever virus (ASFV), a large and complex icosahedral DNA virus of the Asfarviridae family. Currently, there is no effective treatment or approved vaccine against the ASFV. pS273R, a specific SUMO-1 cysteine protease, catalyzes the maturation of the pp220 and pp62 polyprotein precursors into core-shell proteins. Here, we present the crystal structure of the ASFV pS273R protease at a resolution of 2.3 Å. The overall structure of the pS273R protease is represented by two domains named the "core domain" and the N-terminal "arm domain." The "arm domain" contains the residues from M1 to N83, and the "core domain" contains the residues from N84 to A273. A structure analysis reveals that the "core domain" shares a high degree of structural similarity with chlamydial deubiquitinating enzyme, sentrin-specific protease, and adenovirus protease, while the "arm domain" is unique to ASFV. Further, experiments indicated that the "arm domain" plays an important role in maintaining the enzyme activity of ASFV pS273R. Moreover, based on the structural information of pS273R, we designed and synthesized several peptidomimetic aldehyde compounds at a submolar 50% inhibitory concentration, which paves the way for the design of inhibitors to target this severe pathogen.IMPORTANCE African swine fever virus, a large and complex icosahedral DNA virus, causes a deadly infection in domestic pigs. In addition to Africa and Europe, countries in Asia, including China, Vietnam, and Mongolia, were negatively affected by the hazards posed by ASFV outbreaks in 2018 and 2019, at which time more than 30 million pigs were culled. Until now, there has been no vaccine for protection against ASFV infection or effective treatments to cure ASF. Here, we solved the high-resolution crystal structure of the ASFV pS273R protease. The pS273R protease has a two-domain structure that distinguishes it from other members of the SUMO protease family, while the unique "arm domain" has been proven to be essential for its hydrolytic activity. Moreover, the peptidomimetic aldehyde compounds designed to target the substrate binding pocket exert prominent inhibitory effects and can thus be used in a potential lead for anti-ASFV drug development.

Structural Insight into African Swine Fever Virus dUTPase Reveals a Novel Folding Pattern in the dUTPase Family.

The African swine fever virus (ASFV) is the deadly pathogen of African swine fever (ASF) that induces high mortality, approaching 100% in domestic pigs, causes enormous losses to the global pig industry, and threatens food security. Currently, there is no effective treatment or preventive countermeasure. dUTPases (deoxyuridine 5'-triphosphate pyrophosphatases) are ubiquitous enzymes that are essential for the hydrolysis of dUTP and prevent the misincorporation of dUTP into newly synthesized DNA. Here, we present the crystal structures of the ASFV dUTPase in complex with the product dUMP and cofactor Mg2+ at a resolution of 2.2 Å. We observed that a unique "turning point" at G125 plays an unexpected critical role in the swapping region of the C-terminal segment, which is further stabilized by the interactions of the last C-terminal ß strand with the ß1 and ß2 strands, thereby positioning the catalytic motif 5 into the active site of its own subunit instead of into a third subunit. Therefore, the ASFV dUTPase employs a novel two-subunit active site that is different than the classic trimeric dUTPase active site, which is composed of all three subunits. Meanwhile, further results confirmed that the configuration of motifs 1 to 5 has high structural homology with and a catalytic mechanism similar to that of the known trimeric dUTPases. In general, our study expands the information not only on the structural diversity of the conserved dUTPase family but also on the details needed to utilize this dUTPase as a novel target in the treatment of ASF.IMPORTANCE African swine fever virus (AFSV), a large enveloped double-stranded DNA virus, causes a deadly infection in domestic pigs. In addition to Africa, Europe, and South America, countries in Asia, such as China, Vietnam, and Mongolia, have suffered the hazards posed by ASFV outbreaks in recent years. Until now, there has been no vaccine for protection from ASFV infection or effective treatments to cure ASF. Here, we solved the crystal structure of the ASFV dUTPase-dUMP-Mg2+ complex. The ASFV dUTPase displays a noncanonical folding pattern that differs from that of the classic homotrimeric dUTPase, in which the active site is composed of two subunits. In addition, several nonconserved residues within the 3-fold axis channel play a vital role in ASFV dUTPase homotrimer stability. Our finding on these unique structural features of the ASFV dUTPase could be explored for the design of potential specific inhibitors that target this unique enzyme.