Shear-strain-induced two-dimensional slip avalanches in rhombohedral MoS2

Slip avalanches are ubiquitous phenomena occurring in 3D materials under shear strain and their study contributes immensely to our understanding of plastic deformation, fragmentation, and earthquakes. So far, little is known about the role of shear strain in 2D materials. Here we show some evidence of two-dimensional slip avalanches in exfoliated rhombohedral MoS2, triggered by shear strain near the threshold level. Utilizing interfacial polarization in 3R-MoS2, we directly probe the stacking order in multilayer flakes and discover a wide variety of polarization domains with sizes following a power-law distribution. These findings suggest slip avalanches can occur during the exfoliation of 2D materials, and the stacking orders can be changed via shear strain. Our observation has far-reaching implications for developing new materials and technologies, where precise control over the atomic structure of these materials is essential for optimizing their properties as well as for our understanding of fundamental physical phenomena.Comment: To be published in Nano Letter

Genetically modified adenoviral vector with the protein transduction domain of Tat improves gene transfer to CAR-deficient cells

The transduction efficiency of Ad (adenovirus) depends, to some extent, on the expression level of CAR (coxsackievirus and Ad receptor) of a target cell. The low level of CAR on the cell surface is a potential barrier to efficient gene transfer. To overcome this problem, PTD.AdeGFP (where eGFP is enhanced green fluorescent protein) was constructed by modifying the HI loop of Ad5 (Ad type 5) fibre with the Tat (trans-activating) PTD (protein transduction domain) derived from HIV. The present study showed that PTD.AdeGFP significantly improved gene transfer to multiple cell types deficient in expression of CAR. The improvement in gene transfer was not the result of charge-directed binding between the virus and the cell surface. Although PTD.AdeGFP formed aggregates, it infected target cells in a manner different from AdeGFP aggregates precipitated by calcium phosphate. In addition, PTD.AdeGFP was able to transduce target cells in a dynamin-independent pathway. The results provide some new clues as to how PTD.AdeGFP infects target cells. This new vector would be valuable in gene-function analysis and for gene therapy in cancer

Optically Probing Unconventional Superconductivity in Atomically Thin Bi2_2Sr2_2Ca0.92_{0.92}Y0.08_{0.08}Cu2_2O8+δ_{8+{\delta}}

Atomically thin cuprates exhibiting a superconducting phase transition temperature similar to bulk have recently been realized, although the device fabrication remains a challenge and limits the potential for many novel studies and applications. Here we use an optical pump-probe approach to noninvasively study the unconventional superconductivity in atomically thin Bi$_2$Sr$_2$Ca$_{0.92}$Y$_{0.08}$Cu$_2$O$_{8+{\delta}}$ (Y-Bi2212). Apart from finding an optical response due to the superconducting phase transition that is similar to bulk Y-Bi2212, we observe that the sign and amplitude of the pump-probe signal in the atomically thin flake vary significantly in different dielectric environments depending on the nature of the optical excitation. By exploiting the spatial resolution of the optical probe, we uncover the exceptional sensitivity of monolayer Y-Bi2212 to the environment. Our results provide the first optical evidence for the intralayer nature of the superconducting condensate in Bi2212, and highlight the role of double-sided encapsulation in preserving superconductivity in atomically thin cuprates.Comment: To be published in Nano Letter

Cryoelectron microscopy structure of purified gamma-secretase at 12 A resolution

Gamma-secretase, an integral membrane protein complex, catalyzes the intramembrane cleavage of the beta-amyloid precursor protein (APP) during the neuronal production of the amyloid beta-peptide. As such, the protease has emerged as a key target for developing agents to treat and prevent Alzheimer's disease. Existing biochemical studies conflict on the oligomeric assembly state of the protease complex, and its detailed structure is not known. Here, we report that purified active human gamma-secretase in digitonin has a total molecular mass of approximately 230 kDa when measured by scanning transmission electron microscopy. This result supports a complex that is monomeric for each of the four component proteins. We further report the three-dimensional structure of the gamma-secretase complex at 12 A resolution as obtained by cryoelectron microscopy and single-particle image reconstruction. The structure reveals several domains on the extracellular side, three solvent-accessible low-density cavities, and a potential substrate-binding surface groove in the transmembrane region of the complex

GJB2 mutation spectrum in 2063 Chinese patients with nonsyndromic hearing impairment

Background: Mutations in GJB2 are the most common molecular defects responsible for autosomal recessive nonsyndromic hearing impairment (NSHI). The mutation spectra of this gene vary among different ethnic groups. Methods: In order to understand the spectrum and frequency of GJB2 mutations in the Chinese population, the coding region of the GJB2 gene from 2063 unrelated patients with NSHI was PCR amplified and sequenced. Results: A total of 23 pathogenic mutations were identified. Among them, five (p.W3X, c.99delT, c.155_c.158delTCTG, c.512_c.513insAACG, and p.Y152X) are novel. Three hundred and seven patients carry two confirmed pathogenic mutations, including 178 homozygotes and 129 compound heterozygotes. One hundred twenty five patients carry only one mutant allele. Thus, GJB2 mutations account for 17.9% of the mutant alleles in 2063 NSHI patients. Overall, 92.6% (684/739) of the pathogenic mutations are frame-shift truncation or nonsense mutations. The four prevalent mutations; c.235delC, c.299_c.300delAT, c.176_c.191del16, and c.35delG, account for 88.0% of all mutantalleles identified. The frequency of GJB2 mutations (alleles) varies from 4% to 30.4% among different regions of China. It also varies among different sub-ethnic groups. Conclusion: In some regions of China, testing of the three most common mutations can identify at least one GJB2 mutant allele in all patients. In other regions such as Tibet, the three most common mutations account for only 16% the GJB2 mutant alleles. Thus, in this region, sequencing of GJB2 would be recommended. In addition, the etiology of more than 80% of the mutant alleles for NSHI in China remains to be identified. Analysis of other NSHI related genes will be necessary

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Evaluation of Toxicity, Bacteriostatic, Analgesic, Anti-Inflammatory, and Antipyretic Activities of Huangqin-Honghua-Pugongying-Jinyinhua Extract

The extensive use of antibiotics has caused the global spread of multidrug-resistant bacteria and genes, seriously reducing antibiotic efficacy and threatening animal and human health. As an alternative, traditional Chinese veterinary medicine (TCVM) was used in this study for its lack of drug resistance and low toxicity. Huangqin-honghua-pugongying-jinyinhua extract (HHPJE), a novel TCVM, consists of the extracts of Huangqin (Scutellaria baicalensis), Honghua (Carthami Flos), Pugongying (Taraxacum) and Jinyinhua (Lonicerae Japonicae Flos), and was developed to treat bovine mastitis. In this study, we evaluated the toxicity, bacteriostatic, analgesic, anti-inflammatory, and antipyretic activities of HHPJE. Our results show that HHPJE did not show any acute oral toxicity and can be considered safe for oral administration. Additionally, HHPJE possessed a dose-dependent antibacterial effect on Staphylococcus aureus, Escherichia coli, Streptococcus agalactiae and Streptococcus dysgalactiae. HHPJE (60, 30 and 15 g/kg) can reduce the abdominal pain by 44.83 ± 7.69%, 43.15 ± 9.50% and 26.14 ± 4.17%, respectively. The percentages of anti-inflammation inhibition (60, 30 and 15 g/kg) were 35.34 ± 2.17%, 22.29 ± 2.74% and 12.06 ± 3.61%, respectively. The inhibition rates (60, 30 and 15 g/kg) of antipyretic activity were 82.05%, 65.71% and 52.80%, respectively. The evaluation of pharmacodynamics and toxicity indicate that HHPJE possesses significant bacteriostatic, analgesic, anti-inflammatory and antipyretic potential, and also that it is safe for acute oral toxicity, which means it has potential value for treating bovine mastitis in future and alleviating clinical symptoms with no drug resistance or side effects

Evaluation of Toxicity, Bacteriostatic, Analgesic, Anti-Inflammatory, and Antipyretic Activities of Huangqin-Honghua-Pugongying-Jinyinhua Extract

The extensive use of antibiotics has caused the global spread of multidrug-resistant bacteria and genes, seriously reducing antibiotic efficacy and threatening animal and human health. As an alternative, traditional Chinese veterinary medicine (TCVM) was used in this study for its lack of drug resistance and low toxicity. Huangqin-honghua-pugongying-jinyinhua extract (HHPJE), a novel TCVM, consists of the extracts of Huangqin (Scutellaria baicalensis), Honghua (Carthami Flos), Pugongying (Taraxacum) and Jinyinhua (Lonicerae Japonicae Flos), and was developed to treat bovine mastitis. In this study, we evaluated the toxicity, bacteriostatic, analgesic, anti-inflammatory, and antipyretic activities of HHPJE. Our results show that HHPJE did not show any acute oral toxicity and can be considered safe for oral administration. Additionally, HHPJE possessed a dose-dependent antibacterial effect on Staphylococcus aureus, Escherichia coli, Streptococcus agalactiae and Streptococcus dysgalactiae. HHPJE (60, 30 and 15 g/kg) can reduce the abdominal pain by 44.83 ± 7.69%, 43.15 ± 9.50% and 26.14 ± 4.17%, respectively. The percentages of anti-inflammation inhibition (60, 30 and 15 g/kg) were 35.34 ± 2.17%, 22.29 ± 2.74% and 12.06 ± 3.61%, respectively. The inhibition rates (60, 30 and 15 g/kg) of antipyretic activity were 82.05%, 65.71% and 52.80%, respectively. The evaluation of pharmacodynamics and toxicity indicate that HHPJE possesses significant bacteriostatic, analgesic, anti-inflammatory and antipyretic potential, and also that it is safe for acute oral toxicity, which means it has potential value for treating bovine mastitis in future and alleviating clinical symptoms with no drug resistance or side effects