Latest ArticlesLiquid biopsy is a highly promising method for non-invasive detection of tumor-associated nucleic acid fragments in body fluids but is challenged by the low abundance of nucleic acids of clinical interest and their sequence homology with the vast background of nucleic acids from healthy cells. Recently, programmable endonucleases such as clustered regularly interspaced short palindromic repeats (CRISPR) associated protein (Cas) and prokaryotic Argonautes have been successfully used to remove background nucleic acids and enrich mutant allele fractions, enabling their detection with deep next generation sequencing (NGS). However, the enrichment level achievable with these assays is limited by futile binding events and off-target cleavage. To overcome these shortcomings, we conceived a new assay (Programmable Enzyme-Assisted Selective Exponential Amplification, PASEA) that combines the cleavage of wild type alleles with concurrent polymerase amplification. While PASEA increases the numbers of both wild type and mutant alleles, the numbers of mutant alleles increase at much greater rates, allowing PASEA to achieve an unprecedented level of selective enrichment of targeted alleles. By combining CRISPR-Cas9 based cleavage with recombinase polymerase amplification, we converted samples with 0.01% somatic mutant allele fractions (MAFs) to products with 70% MAFs in a single step within 20 min, enabling inexpensive, rapid genotyping with such as Sanger sequencers. Furthermore, PASEA's extraordinary efficiency facilitates sensitive real-time detection of somatic mutant alleles at the point of care with custom designed Exo-RPA probes. Real-time PASEA' performance was proved equivalent to clinical amplification refractory mutation system (ARMS)-PCR and NGS when testing over hundred cancer patients' samples. This strategy has the potential to reduce the cost and time of cancer screening and genotyping, and to enable targeted therapies in resource-limited settings.
Surfactants with polyoxometalates (POMs) as polar head groups have shown fascinating self-assembly behaviors and various functional applications. However, self-assembly them into reverse micelles is still challenging owing to the large molecular size and intermolecular strong electrostatic repulsions of POM heads. In this work, a zwitterionic POM-based surfactant was synthesized by covalently grafting two cationic long alkyl tails onto the lacunary site of [PW11O39]7−. With decreased electrostatic repulsions and increased hydrophobic effect, the POM-based reverse micelles with an average diameter of 5 nm were obtained. Interestingly, when these reverse micelles were applied for catalyzing the oxidation of styrene, an unprecedented β-hydroxyl peroxide compound of 2-hydroxyl-2-phenylethan-1-tert-butylperoxide was produced in high selectivity of 95.2%. In comparison, the cetyltrimethylammonium electrostatically encapsulated POMs mainly generated the epoxides or 1, 2-diols. A free radical mechanism was proposed for the oxidation reaction catalyzed by the zwitterionic POM surfactants.
Rechargeable aqueous zinc-ion batteries are recently gaining incremental attention because of low cost and material abundance, but their development is plagued by limited choices of cathode materials with satisfactory cycling performance. The polyoxometalates perform formidable redox stability and able to participate in multi-electron transfer, which was well-suited for energy storage. Herein, a bi-component polyoxometalate-derivative KNiVO (K2[Ni(H2O)6]2[V10O28]·4H2O polyoxometalates after annealing) is firstly demonstrated as a cathode material for aqueous ZIBs. The layered KV3O8 (KVO) In the bi-component material constitutes Zn2+ migration and storage channels (K+ were substantially replaced by Zn2+ in the activation phase), and the three-dimensional NiV3O8 (NiVO) part acts as skeleton to stabilize the ion channels, which assist the cell to demonstrate a high-rate capacity and specific energy of 229.4 mAh/g and satisfactory cyclability (capacity retention of 99.1% after 4500 cycles at a current density of 4 A/g). These results prove the feasibility of POM as cathode materials precursor and put forward a novel pattern of the Zn2+ storage mechanism in the activated-KNiVO clusters, which also provide a new route for selecting or designing high-performance cathode for aqueous ZIBs and other advanced battery systems.
The paper describes a kind of truly full-color photoluminescence (PL) CDs. The CDs were prepared by using one-pot hydrothermally heating citric acid and formamide at 200 ℃ for 2 h. The CDs have three fluorescent centers at blue, green, and red light region. Their color was regulated through two means, including changing excitation wavelengths or CDs concentrations. The emission maxima changed from blue to red with the increase of excitation wavelengths or CDs concentrations. The full-color PL behavior of the CDs was inherited and conserved in the solid polymer matrix, giving multicolor CDs/polymer films and light emitting diodes (LEDs). White-light LED (WLED) with the CIE coordinate approaching to (0.31, 0.32) were also achieved.
Two novel seco-polycyclic polyprenylated acylphloroglucinols (PPAPs), hyperbenzones A (1) and B (2), were isolated from the roots of Hypericum beanii, together with one known biosynthetic congener 3. Compound 1 incorporates a 6/5/5 ring system with an unprecedented spiro[bicyclo[3.3.0]octane-3,1ʹ-cyclohexane]-2,2ʹ-dione motif. The structures of 1 and 2 were determined by a combination of high resolution electrospray ionization mass spectroscopy (HRESIMS), nuclear magnetic resonance (NMR) spectroscopic analyses, gage-independent atomic orbital (GIAO) NMR chemical shift calculation with DP4+ analyses, electronic circular dichroism (ECD) calculation, and X-ray diffraction analysis. A 1,2-seco retro-Claisen rearrangement from a bicyclo[3.3.1]nonane PPAP precursor and following chemodivergent radical cascade cyclizations are proposed as the key steps in the biosynthetic pathway to yield compounds 1 and 2. Biological investigations indicated that compounds 1 and 3 could decrease intracellular lipid accumulation in a palmitic acid-induced nonalcoholic steatohepatitis (NASH) cell model.
The development of efficient and cost-effective oxygen evolution reaction (OER) electrocatalysts is crucial for clean energy conversion and storage devices, such as water-splitting, CO2 reduction, and metal-air batteries. Herein, we report an efficient 2-dimensional OER catalyst of ultrathin nickel-iron sulfide nanosheets (NiFeS-NS). Dodecanethiol is employed in the synthesis, which prohibits the growth along the Z-axis, thus a nanosheet is obtained. The NiFeS-NS shows high OER catalytic activity, which only requires a small overpotential of 273 mV to achieve the OER current density of 10 mA/cm2 in alkaline electrolyte, and almost no decay after 150 h of chronopotentiometry test. The high performance is attributed to the 2-dimensional structure, the synergistic effect from the Ni and Fe components which promotes the formation of the high valence Ni species, and the tuning effect from the in-situ generated sulfate doping. This work demonstrates the advantages of the 2-dimensional sulfides in electrocatalysis.
Red emissive carbon dots (CDs) are highly desired for biological applications. However, serious luminescence quenching of red emissive CDs in aqueous solution greatly hinders their application in high performance biological imaging. Herein, we reported a facile strategy to realize enhanced red emission of CDs in aqueous solution by surface modification with polyetherimide (PEI) via microwave heating method. High photoluminescence quantum yield (PLQY) of 25% was realized from the PEI functionalized CDs (CDs@PEI) in aqueous solution. The proposed PEI functionalization strategy not only protects the red emission against water molecules quenching, but also reverses the surface charges from negativity to positivity to promote cellular uptake of CDs, leading to clear cell imaging in red fluorescence region. More important, CDs@PEI exhibits much better photostability than commercial red emissive dye (MitoTracker red) in cell fluorescent imaging. Potential application of CDs@PEI on fast staining of cells for clonogenic assay has also been demonstrated.
Hierarchical porous carbon (HPC) from bituminous coal was designed and synthesized through pyrolysis foaming and KOH activation. The obtained HPC (NCF-KOH) were characterized by a high specific surface area (SBET) of 3472.41 m2/g, appropriate mesopores with Vmes/Vtotal of 57%, and a proper amount of surface oxygen content (10.03%). This NCF-KOH exhibited a high specific capacitance of 487 F/g at 1.0 A/g and a rate capability of 400 F/g at 50 A/g based on the three-electrode configuration. As an electrode for a symmetric capacitor, a specific capacitance of 299 F/g at 0.5 A/g was exhibited, and the specific capacitance retained 96% of the initial capacity at 5 A/g after 10,000 cycles. Furthermore, under the power density of 249.6 W/kg in 6 mol/L KOH, a high energy density of 10.34 Wh/kg was obtained. The excellent charge storage capability benefited from its interconnected hierarchical pore structure with high accessible surface area and the suitable amount of oxygen-containing functional groups. Thus, an effective strategy to synthesize HPC for high-performance supercapacitors serves as a promising way of converting coal into advanced carbon materials.
Lithium-ion capacitor (LIC), which combines the advantages of lithium-ion battery (LIB) and electrical double layer capacitor (EDLC), has a rapid development during last decade, however, the poor low temperature performance still limits its application. In this paper, three electrolyte additives including vinylene carbonate (VC), fluoroethylene carbonate (FEC) and 1,3,2-dioxathiolane 2,2-dioxide (DTD) have been utilized and their effects on the rate performance of hard carbon (HC) anode of LIC at various temperatures ranging from 25 ℃ to −40 ℃ have been well evaluated. The cell containing FEC shows the best rate performance at various temperatures and has the charge and discharge capability even at −40 ℃. For HC anode, the charge transfer impedance (RCT) increases exponentially at low temperature, while the equivalent series resistance (Rs) and the impedance of solid electrolyte interface (SEI) increase relatively few. At low temperatures, the effect of FEC may be mainly reflected in its effect on the charge transfer process.
Elemental doping confined in atomically-thin 2D semiconductors offers a compelling strategy for constructing high performance photocatalysts. Although impressive progress has been achieved based on co-thermolysis method, the choices of dopants as well as semiconductor hosts are still quite limited to yield the elaborate photocatalyst with atomic-layer-confined doping defects, owing to the difficulty in balancing the reaction kinetics of different precursors. This study shows that the cation exchange reaction, which is dictated by the Pearson's hard and soft acids and bases (HSAB) theory and allowed to proceed at mild temperatures, can be developed into a conceptually new protocol for engineering elemental doping confined in semiconductor atomic layers. To this aim, the two atomic layers of a new type of 2D photocatalyst PdSeO3 (PdSeO3 2ALs, 1.1 nm) are created by liquid exfoliation and exploited as a proof-of-concept prototype. It is demonstrated that the Mn(II) dopants with controlled concentrations can be incorporated into PdSeO3 2ALs via topological Mn2+-for-Pd2+ cation exchange performed in water/isopropanol solution at 30 ℃. The resulting Mn-doped PdSeO3 2ALs present enhanced capacity for driving photocatalytic oxidation reactions in comparison with their undoped counterparts. The findings here suggest that the new route mediated by post synthetic cation exchange promises to give access to manifold 2D confined-doping photocatalysts, with little perturbations on the thickness, morphology, and crystal structure of the atomically-thin semiconductor hosts.
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