Superconductivity in the vicinity of antiferromagnetic order in CrAs

One of the common features of unconventional, magnetically mediated superconductivity as found in the heavy-fermions, high-transition-temperature (high-Tc) cuprates, and iron pnictides superconductors is that the superconductivity emerges in the vicinity of long-range antiferromagnetically ordered state.[1] In addition to doping charge carriers, the application of external physical pressure has been taken as an effective and clean approach to induce the unconventional superconductivity near a magnetic quantum critical point (QCP).[2,3] Superconductivity has been observed in a majority of 3d transition-metal compounds,[4-9] except for the Cr- and Mn-based compounds in the sense that the low-lying states near Fermi level are dominated by their 3d electrons. Herein, we report on the discovery of superconductivity on the verge of antiferromagnetic order in CrAs via the application of external high pressure. Bulk superconductivity with Tc ~ 2 K emerges at the critical pressure Pc ~ 8 kbar, where the first-order antiferromagnetic transition at TN = 265 K under ambient pressure is completely suppressed. Abnormal normal-state properties associated with a magnetic QCP have been observed nearby Pc. The close proximity of superconductivity to an antiferromagnetic order suggests an unconventional pairing mechanism for the superconducting state of CrAs. The present finding opens a new avenue for searching novel superconductors in the Cr and other transitional-metal based systems

Crystal Structure of the Cysteine Desulfurase DndA from Streptomyces lividans Which Is Involved in DNA Phosphorothioation

DNA phosphorothioation is widespread among prokaryotes, and might function to restrict gene transfer among different kinds of bacteria. There has been little investigation into the structural mechanism of the DNA phosphorothioation process. DndA is a cysteine desulfurase which is involved in the first step of DNA phosphorothioation. In this study, we determined the crystal structure of Streptomyces lividans DndA in complex with its covalently bound cofactor PLP, to a resolution of 2.4 Å. Our structure reveals the molecular mechanism that DndA employs to recognize its cofactor PLP, and suggests the potential binding site for the substrate L-cysteine on DndA. In contrast to previously determined structures of cysteine desulfurases, the catalytic cysteine of DndA was found to reside on a β strand. This catalytic cysteine is very far away from the presumable location of the substrate, suggesting that a conformational change of DndA is required during the catalysis process to bring the catalytic cysteine close to the substrate cysteine. Moreover, our in vitro enzymatic assay results suggested that this conformational change is unlikely to be a simple result of random thermal motion, since moving the catalytic cysteine two residues forward or backward in the primary sequence completely disabled the cysteine desulfurase activity of DndA

Microplastics in three typical benthic species from the Arctic: Occurrence, characteristics, sources, and environmental implications

12 Pág. Centro de Investigación en Sanidad Animal (CISA)Microplastics (MPs) in the Arctic have raised increasing concern, but knowledge on MP contamination in benthic organisms from Arctic shelf regions, e.g., the Chukchi Sea is still limited. Therefore, the present study investigated the occurrence, characteristics, sources, and environmental implications of MPs in the three most common benthic species, namely sea anemone (Actiniidae und.), deposit-feeding starfish (Ctenodiscus crispatus), and snow crab (Chionoecetes opilio), from the Chukchi Sea. The abundances of MPs in the three benthic species were significantly greater than those from the Bering Sea, but lower than those from other regions globally. The top three compositions of MPs in the three species were polyester, nylon, and polyethylene terephthalate. The detection limit for MP size in the present study was 0.03 mm and the mean size of MP in the three species was 0.89 ± 0.06 mm. The surfaces of MPs found in the starfish and crabs were covered with many attachments, cracks, and hollows, while the surfaces of MPs found in the sea anemones were smooth, which was likely a consequence of different feeding behaviors. There was a significantly positive correlation between the abundances of MPs and other anthropogenic substances. The mean MP abundances in the sea anemones ranged from 0.2 items/individual to 1.7 items/individual, which was significantly higher than that in the deposit-feeding starfish (0.1-1.4 items/individual) and snow crabs (0.0-0.6 items/individual). Sea anemones inhabiting lower latitudes ingested relatively higher levels of MPs than those inhabiting higher latitudes. The MP abundances in the sea anemones are significantly and positively correlated with the seasonal reduced ratio of sea ice coverage from August to September. Our findings indicate that sea anemones could function as a bioindicator of MP pollution, and that the MPs in the benthos from the Chukchi Sea might originate from the melting sea ice, fishery activities and ocean currents.This work was sponsored by the Scientific Research Foundation of the Third Institute of Oceanography, Ministry of Natural Resources (No. 2018019), the Chinese Arctic and Antarctic Administration, the Ninth Chinese National Arctic Research Expedition (9th CHINARE-Arctic), the National Key Research and Development Program of China (No. 2019YFD0901101), the National Natural Science Foundation of China (Nos. 41977211 and 41722605), and the National Program on Global Change and Air-Sea Interaction (GASI-02-SCS-YDsum). CB was funded by SNF Post Doc Mobility Fellowship number P400PB_183824.Peer reviewe

Exploring events along the bacterial Twin arginine Transport pathway

Abstract Background Endothelial cell (EC) regeneration is essential for inflammation resolution and vascular integrity recovery after inflammatory vascular injury. Cdc42 is a central regulator of cell survival and vessel formation in EC development. However, it is unknown that whether Cdc42 could be a regulating role of EC repair following the inflammatory injury in the lung. The study sought to test the hypothesis that Cdc42 is required for endothelial regeneration and vascular integrity recovery after LPS-induced inflammatory injury. Methods and results The role of Cdc42 for the regulation of pulmonary vascular endothelial repair was tested in vitro and in vivo. In LPS-induced acute lung injury (ALI) mouse models, knockout of the Cdc42 gene in ECs increased inflammatory cell infiltration and pulmonary vascular leakage and inhibited vascular EC proliferation, which eventually resulted in more severe inflammatory lung injury. In addition, siRNA-mediated knockdown of Cdc42 protein on ECs disrupted cell proliferation and migration and tube formation, which are necessary processes for recovery after inflammatory vascular injury, resulting in inflammatory vascular injury recovery defects. Conclusion We found that Cdc42 deficiency impairs EC function and regeneration, which are crucial in the post-inflammatory vascular injury repair process. These findings indicate that Cdc42 is a potential target for novel treatments designed to facilitate endothelial regeneration and vascular repair in inflammatory pulmonary vascular diseases, such as ALI/ARDS

The binding site of PLP on DndA.

<p>(<b>A</b>) <b>PLP is located in a deep surface pocket on DndA.</b> The two protomers of DndA are shown in surface representation, with only one PLP shown in stick representation. The protomer of DndA harboring this PLP is colored in light grey, whereas the other protomer is colored in dark grey. Blue, red, yellow, and orange represent nitrogen, oxygen, carbon, and phosphorus atoms, respectively. (<b>B</b>) <b>The interaction interface between PLP and DndA.</b> DndA is shown in grey, with carbon atoms of its side chains and PLP shown in green. Blue, red, and orange represent nitrogen, oxygen, and phosphorus atoms, respectively. Hydrogen bonds are represented by magenta dashed lines. The orange circle indicates the presumable location of the carboxylate group of the L-cysteine substrate.</p

Structural comparison of DndA with related cysteine desulfurases/selenocysteine lyase.

<p>(<b>A</b>) Structural superimposition of DndA (red), IscS (green, PDB code 1P3W), NifS (cyan, PDB code 1ECX), CsdB (magenta, PDB code 1C0N), and SufS (blue, PDB code 1T3I). Their bound PLP's are shown as sticks. (<b>B</b>) In DndA, the active site Cys327 is located on a β strand, and its distance from PLP is ∼16 Å. In IscS (<b>C</b>) and NifS (<b>D</b>), the active site cysteines are located on relatively long loops, and are not visible in the crystal structure. Visible residues closest to the catalytic cysteines on the primary sequence are no less than 9 Å from PLP. In CsdB (<b>E</b>) and SufS (<b>F</b>), the active site cysteines are located on relatively short loops, and are ∼7 Å from PLP.</p

Specific activities of WT and point mutants of DndA measured using in vitro cysteine desulfurase activity assay.

<p>Assays were performed for five times, and the average values of specific activities along with standard deviations of the measurements were shown.</p

Crystal structure of DndA from <i>Streptomyces lividans</i>.

<p>(<b>A</b>) <b>Overall structure of the DndA dimer.</b> The structure is viewed perpendicular to the two-fold axis of the dimer. The two protomers are shown in magenta and green, respectively. Their bound PLP cofactors are presented as sticks, with carbon atoms yellow, nitrogen atoms blue, oxygen atoms red, and phosphorus atoms orange. (<b>B</b>) <b>Structure of a protomer of DndA.</b> α helices are shown in cyan, β sheets are shown in magenta, and loops are shown in pink. PLP and its covalently linked Lys200 of DndA, as well as the catalytic Cys327 (mutated to serine in our study), are shown in stick representation.</p