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African swine fever virus (ASFV) causes a highly contagious and often lethal swine viral disease, and leads to tremendous economic losses to the swine industry. Unfortunately, there are no vaccines and effective antiviral agents available to prevent and control ASFV outbreaks. Therefore, it is necessary to develop simple and rapid strategies to monitor ASFV-infected pigs to restrain its spread. In the current study, ASFV capsid protein p72 was expressed along with its chaperone pB602L to form trimers in human embryonic kidney 293 (HEK293) cells. The p72 trimers were subsequently labeled with colloidal gold to develop a immunochromatographic strip. The strip showed high specificity to ASFV-positive serum and no cross-reactivity to other swine virus positive sera. Importantly, the strip showed a higher sensitivity of detecting ASFV antibodies in both positive standard serum and clinical serum samples than a commercial enzyme-linked immunosorbent assay (ELISA) kit. Taken together, these results demonstrate the strip as a reliable diagnostic tool against ASFV infection, which will be appropriate for application in prevention and control of ASFV. Key points • ASFV p72 trimers were successfully generated . • A colloidal gold strip was developed based on ASFV p72 trimers . • The strip is appropriate for detecting ASFV antibodies in the field .

PIEZO channels respond to piconewton-scale forces to mediate critical physiological and pathophysiological processes 1 – 5 . Detergent-solubilized PIEZO channels form bowl-shaped trimers comprising a central ion-conducting pore with an extracellular cap and three curved and non-planar blades with intracellular beams 6 – 10 , which may undergo force-induced deformation within lipid membranes 11 . However, the structures and mechanisms underlying the gating dynamics of PIEZO channels in lipid membranes remain unresolved. Here we determine the curved and flattened structures of PIEZO1 reconstituted in liposome vesicles, directly visualizing the substantial deformability of the PIEZO1–lipid bilayer system and an in-plane areal expansion of approximately 300 nm 2 in the flattened structure. The curved structure of PIEZO1 resembles the structure determined from detergent micelles, but has numerous bound phospholipids. By contrast, the flattened structure exhibits membrane tension-induced flattening of the blade, bending of the beam and detaching and rotating of the cap, which could collectively lead to gating of the ion-conducting pathway. On the basis of the measured in-plane membrane area expansion and stiffness constant of PIEZO1 (ref. 11 ), we calculate a half maximal activation tension of about 1.9 pN nm −1 , matching experimentally measured values. Thus, our studies provide a fundamental understanding of how the notable deformability and structural rearrangement of PIEZO1 achieve exquisite mechanosensitivity and unique curvature-based gating in lipid membranes. Cryo-electron microscopy structures of PIEZO1 in liposome vesicles in curved and flattened conformations demonstrate the high deformability underlying the high mechanosensitivity and ion selectivity of PIEZO channel gating.

Lead halide perovskite light-emitting diodes (PeLEDs) have demonstrated remarkable optoelectronic performance 1 – 3 . However, there are potential toxicity issues with lead 4 , 5 and removing lead from the best-performing PeLEDs—without compromising their high external quantum efficiencies—remains a challenge. Here we report a tautomeric-mixture-coordination-induced electron localization strategy to stabilize the lead-free tin perovskite TEA 2 SnI 4 (TEAI is 2-thiopheneethylammonium iodide) by incorporating cyanuric acid. We demonstrate that a crucial function of the coordination is to amplify the electronic effects, even for those Sn atoms that aren’t strongly bonded with cyanuric acid owing to the formation of hydrogen-bonded tautomeric dimer and trimer superstructures on the perovskite surface. This electron localization weakens adverse effects from Anderson localization and improves ordering in the crystal structure of TEA 2 SnI 4 . These factors result in a two-orders-of-magnitude reduction in the non-radiative recombination capture coefficient and an approximately twofold enhancement in the exciton binding energy. Our lead-free PeLED has an external quantum efficiency of up to 20.29%, representing a performance comparable to that of state-of-the-art lead-containing PeLEDs 6 – 12 . We anticipate that these findings will provide insights into the stabilization of Sn(II) perovskites and further the development of lead-free perovskite applications. Lead-free perovskite light-emitting diodes (LEDs) prepared using tautomeric mixture coordination provide improved ordering in the crystal structure, reduced recombination and enhanced exciton binding energy compared with lead-containing perovskite-based LEDs.

We synthesized the liquid crystal dimer and trimer members of a series of flexible linear oligomers and characterized their microscopic and nanoscopic properties using resonant soft X-ray scattering and a number of other experimental techniques. On the microscopic scale, the twist–bend phases of the dimer and trimer appear essentially identical. However, while the liquid crystal dimer exhibits a temperature-dependent variation of its twist–bend helical pitch varying from 100 to 170 Å on heating, the trimer exhibits an essentially temperature-independent pitch of 66 Å, significantly shorter than those reported for other twist–bend forming materials in the literature. We attribute this to a specific combination of intrinsic conformational bend of the trimer molecules and a sterically favorable intercalation of the trimers over a commensurate fraction (two-thirds) of the molecular length. We develop a geometric model of the twist–bend phase for these materials with the molecules arranging into helical chain structures, and we fully determine their respective geometric parameters.

We consider a Bose-Hubbard (BH) trimer, i.e. an ultracold Bose gas populating three quantum states. The latter can be either different sites of a triple-well potential or three internal states of the atoms. The bosons can tunnel between different states with variable tunnelling strength between two of them. This will allow us to study; (i) different geometrical configurations, i.e. from a closed triangle to three aligned wells and (ii) a triangular configuration with a -phase, i.e. by setting one of the tunnellings negative. By solving the corresponding three-site BH Hamiltonian we obtain the ground state of the system as a function of the trap topology. We characterize the different ground states by means of the coherence and entanglement properties. For small repulsive interactions, fragmented condensates are found for the -phase case. These are found to be robust against small variations of the tunnelling in the small interaction regime. A low-energy effective many-body Hamiltonian restricted to the degenerate manifold provides a compelling description of the -phase degeneration and explains the low-energy spectrum as excitations of discrete semifluxon states.

Certainly, the success of polythiophenes is due in the first place to their outstanding electronic properties and superior processability. Nevertheless, there are additional reasons that contribute to arouse the scientific interest around these materials. Among these, the large variety of chemical modifications that is possible to perform on the thiophene ring is a precious aspect. In particular, a turning point was marked by the diffusion of synthetic strategies for the preparation of terthiophenes: the vast richness of approaches today available for the easy customization of these structures allows the finetuning of their chemical, physical, and optical properties. Therefore, terthiophene derivatives have become an extremely versatile class of compounds both for direct application or for the preparation of electronic functional polymers. Moreover, their biocompatibility and ease of functionalization make them appealing for biology and medical research, as it testifies to the blossoming of studies in these fields in which they are involved. It is thus with the willingness to guide the reader through all the possibilities offered by these structures that this review elucidates the synthetic methods and describes the full chemical variety of terthiophenes and their derivatives. In the final part, an in-depth presentation of their numerous bioapplications intends to provide a complete picture of the state of the art.

HIV-1 mutates rapidly, making it difficult to design a vaccine that will protect people against all of the virus' iterations. A potential successful vaccine design might protect by eliciting broadly neutralizing antibodies (bNAbs), which target specific regions on HIV-1's trimeric envelope glycoprotein (Env) (see the Perspective by Mascola). Jardine et al. used mice engineered to express germline-reverted heavy chains of a particular bNAb and immunized them with an Env-based immunogen designed to bind to precursors of that bNAb. Sanders et al. compared rabbits and monkeys immunized with Env trimers that adopt a nativelike conformation. In both cases, immunized animals produced antibodies that shared similarities with bNAbs. Boosting these animals with other immunogens may drive these antibodies to further mutate into the longsought bNAbs. Chen et al. report that retaining the cytoplasmic domain of Env proteins may be important to attract bNAbs. Removing the cytoplasmic domain may distract the immune response and instead generate antibodies that target epitopes on Env that would not lead to protection. Science , this issue p. 139 , 10.1126/science.aac4223 , p. 156 ; see also p. 191 Recombinant, native-like, HIV-1 envelope trimers induce neutralizing antibody responses in animal models. [Also see Perspective by Mascola ] A challenge for HIV-1 immunogen design is the difficulty of inducing neutralizing antibodies (NAbs) against neutralization-resistant (tier 2) viruses that dominate human transmissions. We show that a soluble recombinant HIV-1 envelope glycoprotein trimer that adopts a native conformation, BG505 SOSIP.664, induced NAbs potently against the sequence-matched tier 2 virus in rabbits and similar but weaker responses in macaques. The trimer also consistently induced cross-reactive NAbs against more sensitive (tier 1) viruses. Tier 2 NAbs recognized conformational epitopes that differed between animals and in some cases overlapped with those recognized by broadly neutralizing antibodies (bNAbs), whereas tier 1 responses targeted linear V3 epitopes. A second trimer, B41 SOSIP.664, also induced a strong autologous tier 2 NAb response in rabbits. Thus, native-like trimers represent a promising starting point for the development of HIV-1 vaccines aimed at inducing bNAbs.

Understanding the photophysics and photochemistry of molecular π -stacked chromophores is important for utilizing them as functional photonic materials. However, these investigations have been mostly limited to covalent molecular dimers, which can only approximate the electronic and vibronic interactions present in the higher oligomers typical of functional organic materials. Here we show that a comparison of the excited-state dynamics of a covalent slip-stacked perylenediimide dimer (2) and trimer (3) provides fundamental insights into electronic state mixing and symmetry-breaking charge separation (SB-CS) beyond the dimer limit. We find that coherent vibronic coupling to high-frequency modes facilitates ultrafast state mixing between the Frenkel exciton (FE) and charge-transfer (CT) states. Subsequently, solvent fluctuations and interchromophore low-frequency vibrations promote CT character in the coherent FE/CT mixed state. The coherent FE/CT mixed state persists in 2, but, in 3, low-frequency vibronic coupling collapses the coherence, resulting in ultrafast SB-CS between the distal perylenediimide units. Molecular π -stacked chromophores are promising photonic materials, but much of our understanding is limited to covalent dimers. Now it has been shown that, in a slip-stacked perylenediimide trimer, coherent vibronic coupling to high-frequency modes facilitates ultrafast state mixing between the Frenkel exciton and charge-transfer states, which then collapses by solvent fluctuations and low-frequency vibronic coupling, resulting in ultrafast symmetry-breaking charge separation.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virions are surrounded by a lipid bilayer from which spike (S) protein trimers protrude 1 . Heavily glycosylated S trimers bind to the angiotensin-converting enzyme 2 receptor and mediate entry of virions into target cells 2 – 6 . S exhibits extensive conformational flexibility: it modulates exposure of its receptor-binding site and subsequently undergoes complete structural rearrangement to drive fusion of viral and cellular membranes 2 , 7 , 8 . The structures and conformations of soluble, overexpressed, purified S proteins have been studied in detail using cryo-electron microscopy 2 , 7 , 9 – 12 , but the structure and distribution of S on the virion surface remain unknown. Here we applied cryo-electron microscopy and tomography to image intact SARS-CoV-2 virions and determine the high-resolution structure, conformational flexibility and distribution of S trimers in situ on the virion surface. These results reveal the conformations of S on the virion, and provide a basis from which to understand interactions between S and neutralizing antibodies during infection or vaccination. Cryo-electron microscopy and tomography studies reveal the structures, conformations and distributions of spike protein trimers on intact severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virions and provide a basis for understanding the interactions of the spike protein with neutralizing antibodies.

The π-bond Seiwatz chain (SC) is one of the well-known reconstruction induced by alkaline or rare earth metals on Si(111) surface. Here we identify by ab initio calculations a new reconstruction of La induced quasi-two-dimensional Si3 trimer monolayer on Si(111)-\\((3 3)R30^\\) surface. Its surface unit cell has one La atom and one Si3 trimer with the same La coverage (1/3 monolayer) as SC structure and the Si3 trimer satisfies the electron counting rule with a transfer of valence electrons from La atom, formally as \\(La^3+[Si^-]_3\\), in correspondence to the milkstool model for Bi trimers on Si(111) surface. Band structure calculations show a semiconducting character with an indirect surface band gap of 0.76 eV. Moreover, a two-stage conversion process between the Si3 trimer and SC structure is verified by the climbing-image nudged elastic band method. These findings pave the way for further exploration of the new surface structure and its outstanding properties.