Global S&T Development Trend Analysis Platform of Resources and Environment
Alzheimer'
Room-temperature electrical switching of a topological antiferromagnetic state in polycrystalline Mn3Sn thin films is demonstrated using the same protocol as that used for conventional ferromagnetic metals.
Electrical manipulation of phenomena generated by nontrivial band topology is essential for the development of next-generation technology using topological protection. A Weyl semimetal is a three-dimensional gapless system that hosts Weyl fermions as low-energy quasiparticles(1-4). It has various exotic properties, such as a large anomalous Hall effect (AHE) and chiral anomaly, which are robust owing to the topologically protected Weyl nodes(1-16). To manipulate such phenomena, a magnetic version of Weyl semimetals would be useful for controlling the locations of Weyl nodes in the Brillouin zone. Moreover, electrical manipulation of antiferromagnetic Weyl metals would facilitate the use of antiferromagnetic spintronics to realize high-density devices with ultrafast operation(17,18). However, electrical control of a Weyl metal has not yet been reported. Here we demonstrate the electrical switching of a topological antiferromagnetic state and its detection by the AHE at room temperature in a polycrystalline thin film(19) of the antiferromagnetic Weyl metal Mn3Sn9,10,12,20, which exhibits zero-field AHE. Using bilayer devices composed of Mn3Sn and nonmagnetic metals, we find that an electrical current density of about 10(10) to 10(11) amperes per square metre induces magnetic switching in the nonmagnetic metals, with a large change in Hall voltage. In addition, the current polarity along the bias field and the sign of the spin Hall angle of the nonmagnetic metals-positive for Pt (ref. (21)), close to 0 for Cu and negative for W (ref. (22))-determines the sign of the Hall voltage. Notably, the electrical switching in the antiferromagnet is achieved with the same protocol as that used for ferromagnetic metals(23,24). Our results may lead to further scientific and technological advances in topological magnetism and antiferromagnetic spintronics.
The production of pore-forming toxins that disrupt the plasma membrane of host cells is a common virulence strategy for bacterial pathogens such as methicillin-resistant Staphylococcus aureus (MRSA)(1-3). It is unclear, however, whether host species possess innate immune mechanisms that can neutralize pore-forming toxins during infection. We previously showed that the autophagy protein ATG16L1 is necessary for protection against MRSA strains encoding alpha-toxin(4)-a pore-forming toxin that binds the metalloprotease ADAM10 on the surface of a broad range of target cells and tissues(2,5,6). Autophagy typically involves the targeting of cytosolic material to the lysosome for degradation. Here we demonstrate that ATG16L1 and other ATG proteins mediate protection against alpha-toxin through the release of ADAM10 on exosomes-extracellular vesicles of endosomal origin. Bacterial DNA and CpG DNA induce the secretion of ADAM10-bearing exosomes from human cells as well as in mice. Transferred exosomes protect host cells in vitro by serving as scavengers that can bind multiple toxins, and improve the survival of mice infected with MRSA in vivo. These findings indicate that ATG proteins mediate a previously unknown form of defence in response to infection, facilitating the release of exosomes that serve as decoys for bacterially produced toxins.
Mycobacterium tuberculosis (Mtb) is an obligate human pathogen and the causative agent of tuberculosis(1-3). Although Mtb can synthesize vitamin B-12 (cobalamin) de novo, uptake of cobalamin has been linked to pathogenesis of tuberculosis2. Mtb does not encode any characterized cobalamin transporter(4-6)
After activation by an agonist, G-protein-coupled receptors (GPCRs) recruit beta-arrestin, which desensitizes heterotrimeric G-protein signalling and promotes receptor endocytosis(1). Additionally, beta-arrestin directly regulates many cell signalling pathways that can induce cellular responses distinct from that of G proteins(2). In contrast to G proteins, for which there are many high-resolution structures in complex with GPCRs, the molecular mechanisms underlying the interaction of beta-arrestin with GPCRs are much less understood. Here we present a cryo-electron microscopy structure of beta-arrestin 1 (beta arr1) in complex with M2 muscarinic receptor (M2R) reconstituted in lipid nanodiscs. The M2R-beta arr1 complex displays a multimodal network of flexible interactions, including binding of the N domain of beta arr1 to phosphorylated receptor residues and insertion of the finger loop of beta arr1 into the M2R seven-transmembrane bundle, which adopts a conformation similar to that in the M2R-heterotrimeric G(o) protein complex(3). Moreover, the cryo-electron microscopy map reveals that the C-edge of beta arr1 engages the lipid bilayer. Through atomistic simulations and biophysical, biochemical and cellular assays, we show that the C-edge is critical for stable complex formation, beta arr1 recruitment, receptor internalization, and desensitization of G-protein activation. Taken together, these data suggest that the cooperative interactions of beta-arrestin with both the receptor and the phospholipid bilayer contribute to its functional versatility.
The discovery of superconductivity at 200 kelvin in the hydrogen sulfide system at high pressures(1) demonstrated the potential of hydrogen-rich materials as high-temperature superconductors. Recent theoretical predictions of rare-earth hydrides with hydrogen cages(2,3) and the subsequent synthesis of LaH10 with a superconducting critical temperature (T-c) of 250 kelvin(4,5) have placed these materials on the verge of achieving the long-standing goal of room-temperature superconductivity. Electrical and X-ray diffraction measurements have revealed a weakly pressure-dependent T-c for LaH10 between 137 and 218 gigapascals in a structure that has a face-centred cubic arrangement of lanthanum atoms(5). Here we show that quantum atomic fluctuations stabilize a highly symmetrical Fm (3) over barm crystal structure over this pressure range. The structure is consistent with experimental findings and has a very large electron-phonon coupling constant of 3.5. Although ab initio classical calculations predict that this Fm (3) over barm structure undergoes distortion at pressures below 230 gigapascals(2,3,) yielding a complex energy landscape, the inclusion of quantum effects suggests that it is the true ground-state structure. The agreement between the calculated and experimental Tc values further indicates that this phase is responsible for the superconductivity observed at 250 kelvin. The relevance of quantum fluctuations calls into question many of the crystal structure predictions that have been made for hydrides within a classical approach and that currently guide the experimental quest for room-temperature superconductivity(6-8). Furthermore, we find that quantum effects are crucial for the stabilization of solids with high electron-phonon coupling constants that could otherwise be destabilized by the large electron-phonon interaction(9), thus reducing the pressures required for their synthesis.