Synthesis and Antitumor Evaluation in Vitro of NO‐Donating Ursolic Acid‐Benzylidene Derivatives

Antitumor activity of triterpenoid and its derivatives has attracted great attention recently. Our previous efforts led to the discovery of a series of NO‐donor betulin derivatives with potent antitumor activity. Herein, we prepared eight compounds derived from ursolic acid (UA). All the compounds were evaluated for their in vitro cytotoxicity against four human cancer cell lines (HepG‐2, MCF‐7, HT‐29 and A549). Among the compounds tested, compound 4a was found to be most active against HT‐29 (IC₅₀=4.28 μm ). Further biological assays demonstrated that compound 4a could induce cell cycle arrest at G1 phase and apoptosis in a dose‐dependent manner. In addition, compound 4a was found to upregulate pro‐apoptotic Bax, p53 and downregulate anti‐apoptotic Bcl‐2. All these results suggested that compound 4a is a potential candidate drug for the therapy of colon cancer.     

High Thermoelectric Performance in p‐type Polycrystalline Cd‐doped SnSe Achieved by a Combination of Cation Vacancies and Localized Lattice Engineering

Herein, a high figure of merit (ZT) of ≈1.7 at 823 K is reported in p‐type polycrystalline Cd‐doped SnSe by combining cation vacancies and localized‐lattice engineering. It is observed that the introduction of Cd atoms in SnSe lattice induce Sn vacancies, which act as p‐type dopants. A combination of facile solvothermal synthesis and fast spark plasma sintering technique boosts the Sn vacancy to a high level of ≈2.9%, which results in an optimum hole concentration of ≈2.6 × 10¹⁹ cm^?3 and an improved power factor of ≈6.9 µW cm^?1 K^?2. Simultaneously, a low thermal conductivity of ≈0.33 W m^?1 K^?1 is achieved by effective phonon scattering at localized crystal imperfections, as observed by detailed structural characterizations. Density functional theory calculations reveal that the role of Cd atoms in the SnSe lattice is to reduce the formation energy of Sn vacancies, which in turn lower the Fermi level down into the valence bands, generating holes. This work explores the fundamental Cd‐doping mechanisms at the nanoscale in a SnSe matrix and demonstrates vacancy and localized‐lattice engineering as an effective approach to boosting thermoelectric performance. The work provides an avenue in achieving high‐performance thermoelectric properties of materials.     

Oriented Transformation of Co‐LDH into 2D/3D ZIF‐67 to Achieve Co–N–C Hybrids for Efficient Overall Water Splitting

Construction of well‐defined metal–organic framework precursor is vital to derive highly efficient transition metal–carbon‐based electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water splitting. Herein, a novel strategy involving an in situ transformation of ultrathin cobalt layered double hydroxide into 2D cobalt zeolitic imidazolate framework (ZIF‐67) nanosheets grafted with 3D ZIF‐67 polyhedra supported on the surface of carbon cloth (2D/3D ZIF‐67@CC) precursor is proposed. After a low‐temperature pyrolysis, this precursor can be further converted into hybrid composites composed of ultrafine cobalt nanoparticles embedded within 2D N‐doped carbon nanosheets and 3D N‐doped hollow carbon polyhedra (Co@N‐CS/N‐HCP@CC). Experimental and density functional theory calculations results indicate that such composites have the advantages of a large number of accessible active sites, accelerated charge/mass transfer ability, the synergistic effect of components as well as an optimal water adsorption energy change. As a result, the obtained Co@N‐CS/N‐HCP@CC catalyst requires overpotentials of only 66 and 248 mV to reach a current density of 10 mA cm^?2 for HER and OER in 1.0 m KOH, respectively. Remarkably, it enables an alkali‐electrolyzer with a current density of 10 mA cm^?2 at a low cell voltage of 1.545 V, superior to that of the IrO₂@CC||Pt/C@CC couple (1.592 V).     

Atomic Sn4+ Decorated into Vanadium Carbide MXene Interlayers for Superior Lithium Storage

Ion intercalation is an important way to improve the energy storage performance of 2D materials. The dynamic energy storage process in such layered intercalations is important but still a challenge mainly due to the lack of effective operando methods. Herein, a unique atomic Sn⁴⁺–decorated vanadium carbide (V₂C) MXene not only exhibiting highly enhanced lithium‐ion battery (LIB) performance, but also possessing outstanding rate and cyclic stability because of the expanded interlayer space and the formation of V? O? Sn bonding is demonstrated. In combination with ex situ tests, an operando X‐ray absorption fine structure measurement is developed to explore the dynamic mechanism of V₂C@Sn MXene electrodes in LIBs. The results clearly reveal the valence changes of vanadium (V), tin (Sn), and positive contribution of oxygen (O) atoms during the charging/discharging process, confirming their contribution for lithium storage capacity. The stability of intercalated MXene electrode is further in situ studied to prove the key role of V? O? Sn bonding.     

Magnetic Field–Suppressed Lithium Dendrite Growth for Stable Lithium‐Metal Batteries

Lithium metal is the most attractive anode material due to its extremely high specific capacity, minimum potential, and low density. However, uncontrollable growth of lithium dendrite results in severe safety and cycling stability concerns, which hinders the application in next generation secondary batteries. In this paper, a new and facile method imposing a magnetic field to lithium metal anodes is proposed. That is, the lithium ions suffering Lorentz force due to the electromagnetic fields are put into spiral motion causing magnetohydrodynamics (MHD) effect. This MHD effect can effectively promote mass transfer and uniform distribution of lithium ions to suppress the dendrite growth as well as obtain uniform and compact lithium deposition. The results show that the lithium metal electrodes within the magnetic field exhibit excellent cycling and rate performance in a symmetrical battery. Additionally, full batteries using limited lithium metal as anodes and commercial LiFePO₄ as cathodes show improved performance within the magnetic field. In summary, a new and facile strategy of suppressing lithium dendrites using the MHD effect by imposing a magnetic field is proposed, which may be generalized to other advanced alkali metal batteries.     

Progress and Challenges for Live-cell Imaging of Genomic Loci Using CRISPR-based Platforms

Chromatin conformation,localization,and dynamics are crucial regulators of cellular behaviors. Although fluorescence in situ hybridization-based techniques have been widely utilized for investigating chromatin architectures in healthy and diseased states,the requirement for cell fix-ation precludes the comprehensive dynamic analysis necessary to fully understand chromatin activ-ities. This has spurred the development and application of a variety of imaging methodologies for visualizing single chromosomal loci in the native cellular context. In this review,we describe currently-available approaches for imaging single genomic loci in cells,with special focus on clus-tered regularly interspaced short palindromic repeats (CRISPR)-based imaging approaches. In addition,we discuss some of the challenges that limit the application of CRISPR-based genomic imaging approaches,and potential solutions to address these challenges. We anticipate that,with continued refinement of CRISPR-based imaging techniques,significant understanding can be gained to help decipher chromatin activities and their relevance to cellular physiology and pathogenesis.     

Aminopeptidase N Knockout Pigs Are Not Resistant to Porcine Epidemic Diarrhea Virus Infection

<正>Dear Editor,Porcine epidemic diarrhea virus(PEDV) is the etiologic agent of porcine epidemic diarrhea(PED), which is an acute, highly contagious, and devastating enteric viral disease in pigs(Lee 2015). PEDV is a coronavirus that mainly infects and replicates in villous enterocytes of the small intestine in pigs(Li et al. 2016). PEDV can infect     

Autographa Californica Multiple Nucleopolyhedrovirus P48 (Ac103) Is Required for the Efficient Formation of Virus-Induced Intranuclear Microvesicles

Our previous study has shown that the Autographa californica multiple nucleopolyhedrovirus(AcMNPV) p48(ac103)gene is essential for the nuclear egress of nucleocapsids and the formation of occlusion-derived virions(ODVs). However,the exact role of p48 in the morphogenesis of ODVs remains unknown. In this study, we demonstrated that p48 was required for the efficient formation of intranuclear microvesicles. To further understand its functional role in intranuclear microvesicle formation, we characterized the distribution of the P48 protein, which was found to be associated with the nucleocapsid and envelope fractions of both budded virions and ODVs. In Ac MNPV-infected cells, P48 was predominantly localized to nucleocapsids in the virogenic stroma and the nucleocapsids enveloped in ODVs, with a limited but discernible distribution in the plasma membrane, nuclear envelope, intranuclear microvesicles, and ODV envelope. Furthermore,coimmunoprecipitation assays showed that among the viral proteins required for intranuclear microvesicle formation, P48 associated with Ac93 in the absence of viral infection.     

High efficiency Agrobacterium‐mediated site‐specific gene integration in maize utilizing the FLP‐FRT recombination system

An efficient Agrobacterium‐mediated site‐specific integration (SSI) technology using the flipase/flipase recognition target (FLP/FRT) system in elite maize inbred lines is described. The system allows precise integration of a single copy of a donor DNA flanked by heterologous FRT sites into a predefined recombinant target line (RTL) containing the corresponding heterologous FRT sites. A promoter‐trap system consisting of a pre‐integrated promoter followed by an FRT site enables efficient selection of events. The efficiency of this system is dependent on several factors including Agrobacterium tumefaciens strain, expression of morphogenic genes Babyboom (Bbm) and Wuschel2 (Wus2) and choice of heterologous FRT pairs. Of the Agrobacterium strains tested, strain AGL1 resulted in higher transformation frequency than strain LBA4404 THY‐ (0.27% vs. 0.05%; per cent of infected embryos producing events). The addition of morphogenic genes increased transformation frequency (2.65% in AGL1; 0.65% in LBA4404 THY‐). Following further optimization, including the choice of FRT pairs, a method was developed that achieved 19%–22.5% transformation frequency. Importantly, >50% of T0 transformants contain the desired full‐length site‐specific insertion. The frequencies reported here establish a new benchmark for generating targeted quality events compatible with commercial product development.