Pressure induced superconductivity bordering a charge-density-wave state in NbTe4 with strong spinorbit coupling

Transition-metal chalcogenides host various phases of matter, such as charge-density wave (CDW), superconductors, and topological insulators or semimetals. Superconductivity and its competition with CDW in low-dimensional compounds have attracted much interest and stimulated considerable research. Here we report pressure induced superconductivity in a strong spin-orbit (SO) coupled quasi-one-dimensional (1D) transition-metal chalcogenide NbTe$_4$, which is a CDW material under ambient pressure. With increasing pressure, the CDW transition temperature is gradually suppressed, and superconducting transition, which is fingerprinted by a steep resistivity drop, emerges at pressures above 12.4 GPa. Under pressure $p$ = 69 GPa, zero resistance is detected with a transition temperature $T_c$ = 2.2 K and an upper critical field $H_{c2}$= 2 T. We also find large magnetoresistance (MR) up to 102\% at low temperatures, which is a distinct feature differentiating NbTe$_4$ from other conventional CDW materials.Comment: https://rdcu.be/LX8

Characterization of the salivary microbiome in people with obesity

Background The interactions between the gut microbiome and obesity have been extensively studied. Although the oral cavity is the gateway to the gut, and is extensively colonized with microbes, little is known about the oral microbiome in people with obesity. In the present study, we investigated the salivary microbiome in obese and normal weight healthy participants using metagenomic analysis. The subjects were categorized into two groups, obesity and normal weight, based on their BMIs. Methods We characterized the salivary microbiome of 33 adults with obesity and 29 normal weight controls using high-throughput sequencing of the V3–V4 region of the 16S rRNA gene (Illumina MiSeq). None of the selected participants had systemic, oral mucosal, or periodontal diseases. Results The salivary microbiome of the obesity group was distinct from that of the normal weight group. The salivary microbiome of periodontally healthy people with obesity had both significantly lower bacterial diversity and richness compared with the controls. The genus Prevotella, Granulicatella, Peptostreptococcus, Solobacterium, Catonella, and Mogibacterium were significantly more abundant in the obesity group; meanwhile the genus Haemophilus, Corynebacterium, Capnocytophaga, and Staphylococcus were less abundant in the obesity group. We also performed a functional analysis of the inferred metagenomes, and showed that the salivary community associated with obesity had a stronger signature of immune disease and a decreased functional signature related to environmental adaptation and Xenobiotics biodegradation compared with the normal weight controls. Discussion Our study demonstrates that the microbial diversity and structure of the salivary microbiome in people with obesity are significantly different from those of normal weight controls. These results suggested that changes in the structure and function of salivary microbiome in people with obesity might reflect their susceptibility to oral diseases

Mechanics of biosurfactant aided liquid phase exfoliation of 2D materials

Biosurfactant-aided liquid-phase exfoliation (LPE) is emerging as a biocompatible, green, economical, safe, and efficient approach to prepare two-dimensional (2D) materials for biomedical applications. However, relatively little is known about the molecular mechanisms of this process. Herein, we present the first study of how flavin mononucleotide (FMN) interacts with hexagonal boron nitride (hBN) nanosheets in the context of LPE. We demonstrate that FMN molecules can self-assemble on hBN via π-π interactions, as well as intermolecular hydrogen bonds (H-bonds) between the isoalloxazine moieties. Binding free energy analysis has shown FMN to be an efficient surfactant for LPE of hBN in water. According to the theoretical simulations, stable water suspension of hBN were experimentally obtained by LPE using FMN. With this work, we aim to exemplify how molecular dynamics (MD) simulation can predict and guide empirical LPE experiments, direct the surfactant screening and improve scalable production of 2D materials for biomedical applications

Hydrogen-bonds mediate liquid-liquid phase separation of mussel derived adhesive peptides

Marine mussels achieve strong underwater adhesion by depositing mussel foot proteins (Mfps) that form coacervates during the protein secretion. However, the molecular mechanisms that govern the phase separation behaviors of the Mfps are still not fully understood. Here, we report that GK-16*, a peptide derived from the primary adhesive protein Mfp-5, forms coacervate in seawater conditions. Molecular dynamics simulations combined with point mutation experiments demonstrate that Dopa- and Gly- mediated hydrogen-bonding interactions are essential in the coacervation process. The properties of GK-16* coacervates could be controlled by tuning the strength of the electrostatic and Dopa-mediated hydrogen bond interactions via controlling the pH and salt concentration of the solution. The GK-16* coacervate undergoes a pH induced liquid-to-gel transition, which can be utilized for the underwater delivery and curing of the adhesives. Our study provides useful molecular design principles for the development of mussel-inspired peptidyl coacervate adhesives with tunable properties.Agency for Science, Technology and Research (A*STAR)Ministry of Education (MOE)National Research Foundation (NRF)Published versionQ.G., S.C., and J.Y. thank the Singapore National Research Fellowship (NRF-NRFF11-2019-0004) and the Singapore Ministry of Education (MOE) Tier 2 Grant (MOE-T2EP30220-0006). X.Q. and H.G. acknowledge support from the Singapore Ministry of Education (MOE) AcRF Tier 1 (Grants RG138/20). G.Z. and H.G. also acknowledge a start-up grant from Nanyang Technological University and A*STAR, Singapore

Complete mitochondrial genome of the Yangtze grenadier anchovy, Coilia Brachygnathus (Clupeiformes: Engraulidae) from the upper Yangtze River

The Yangtze grenadier anchovy, Coilia brachygnathus, is a commercial fishery species in the middle and lower Yangtze River of China. Here, we describe a complete mitochondrial genome from the newly found population of C. brachygnahus in the upper Yangtze River. It was 16,857 bp in size and encodes for 2 rRNAs, 22 tRNAs, 13 protein-coding genes as well as a D-loop control region. Phylogenetic analysis confirmed the evolutionary relationship of the C. brachygnathus in the upper Yangtze to other five species of the genus Coillia. The mitochondrial genome would help to elucidate the origin of the new population of C. brachygnathus

Boron Nitride Nanosheets Can Induce Water Channels Across Lipid Bilayers Leading to Lysosomal Permeabilization

While the interaction between 2D materials and cells is of key importance to the development of nanomedicines and safe applications of nanotechnology, still little is known about the biological interactions of many emerging 2D materials. Here, an investigation of how hexagonal boron nitride (hBN) interacts with the cell membrane is carried out by combining molecular dynamics (MD), liquid-phase exfoliation, and in vitro imaging methods. MD simulations reveal that a sharp hBN wedge can penetrate a lipid bilayer and form a cross-membrane water channel along its exposed polar edges, while a round hBN sheet does not exhibit this behavior. It is hypothesized that such water channels can facilitate cross-membrane transport, with important consequences including lysosomal membrane permeabilization, an emerging mechanism of cellular toxicity that involves the release of cathepsin B and generation of radical oxygen species leading to cell apoptosis. To test this hypothesis, two types of hBN nanosheets, one with a rhomboidal, cornered morphology and one with a round morphology, are prepared, and human lung epithelial cells are exposed to both materials. The cornered hBN with lateral polar edges results in a dose-dependent cytotoxic effect, whereas round hBN does not cause significant toxicity, thus confirming our premise

Unveiling liquid-phase exfoliation of graphite and boron nitride using fluorescent dyes through combined experiments and simulations

Liquid-phase exfoliation (LPE) in aqueous solutions provides a simple, scalable and green approach to produce two-dimensional (2D) materials. By combining atomistic simulations with exfoliation experiments, the interaction between a surfactant and a 2D layer at the molecular scale can be better understood. In this work, two different dyes, corresponding to rhodamine B base (Rbb) and to a phenylboronic acid BODIPY (PBA-BODIPY) derivative, are employed as dispersants to exfoliate graphene and hexagonal boron nitride (hBN) through sonication-assisted LPE. The exfoliated 2D sheets, mostly as few-layers, exhibit good quality and high loading of dyes. Using molecular dynamics (MD) simulations, the binding free energies are calculated and the arrangement of both dyes on the layers are predicted. We find that the dyes show a higher affinity towards hBN than graphene, which is consistent with the higher yields of exfoliated hBN. Furthermore, we demonstrate that the adsorption behavior of Rbb molecules on graphene and hBN is quite different compared to PBA-BODIPY

Guanidinium-Assisted Surface Matrix Engineering for Highly Efficient Perovskite Quantum Dot Photovoltaics

Metal halide perovskite quantum dots (Pe-QDs) are of great interest in new-generation photovoltaics (PVs). However, it remains challenging in the construction of conductive and intact Pe-QD films to maximize their functionality. Herein, a ligand-assisted surface matrix strategy to engineer the surface and packing states of Pe-QD solids is demonstrated by a mild thermal annealing treatment after ligand exchange processing (referred to as "LE-TA") triggered by guanidinium thiocyanate. The "LE-TA" method induces the formation of surface matrix on CsPbI3 QDs, which is dominated by the cationic guanidinium (GA(+)) rather than the SCN-, maintaining the intact cubic structure and facilitating interparticle electrical interaction of QD solids. Consequently, the GA-matrix-confined CsPbI3 QDs exhibit remarkably enhanced charge mobility and carrier diffusion length compared to control ones, leading to a champion power conversion efficiency of 15.21% when assembled in PVs, which is one of the highest among all Pe-QD solar cells. Additionally, the "LE-TA" method shows similar effects when applied to other Pe-QD PV systems like CsPbBr3 and FAPbI(3) (FA = formamidinium), indicating its versatility in regulating the surfaces of various Pe-QDs. This work may afford new guidelines to construct electrically conductive and structurally intact Pe-QD solids for efficient optoelectronic devices