Latest ArticlesCovalent organic frameworks (COFs) have been attracting growing concerns since the first report in 2005. With the well-defined and ordered structures, COFs express big potential in mass transport, storage/separation and energy conversion applications. From the perspective of both theory and application, the construction of crystalline COFs with high quality and variety is highly worth to be devoted to. To give insight into the crystalline process of COFs and deeply understand the factors of COFs crystallization, this review was concentrated on the recent progress in construction of crystalline COFs. Accordingly, the types and crystallization process of COFs were summarized firstly. And then the factors on crystallinity and the measures for improving the crystallinity of COFs were classified and discussed in detail. Finally, the perspectives for the development of COFs in further was given at the end of this review.
Inspired by the biosystems, the artificial smart membrane to control the mass transport and molecular conversion has attracted increasing attention in the fields of membrane separation, desalination, nanofiltration, healthcare and environmental remediation. However, the trade-off limitations in polymeric membranes greatly hinder the development of smart membranes with high permeability and manipulability. Recently, inspired by the unique physical/chemical properties of two-dimensional (2D) materials, 2D materials-based smart membranes (2DSMs) with the ability of intelligent regulation under different stimuli are highly suitable for membrane applications. According to the desired properties, the 2DSMs with abundant functional groups can be designed through chemical modification to change the original properties and obtain tunable interlayer spacings under different external conditions. In this review, we summarize the recent progress on artificial smart membranes based on 2D materials. The design concept and fabrication strategy of 2DSMs are first introduced. Following that, the developed 2DSMs are introduced and classified by the type of responsive stimuli, including pH, magnetic field, electric field, light and temperature. Then, the 2DSMs exhibiting unique performances as membrane separation, pressure sensors, blue energy harvesting, photoelectrochemical sensors and biomimetic devices are presented. Finally, the perspectives and challenges in the developments of 2DSMs are discussed
Valeriaquinone A (1), an unprecedented anthraquinone-coumarin hybrid, was isolated from the roots of Knoxia valerianoides. Its structure was determined by extensive spectroscopic analyses and X-ray diffraction. The plausible biosynthetic pathways for 1 were proposed. Compound 1 exhibited strong protein tyrosine phosphatase 1B (PTP1B) inhibition with high selectivity (> 30 fold) over homologous T cell protein tyrosine phosphatase (TCPTP) potentially by binding to an allosteric site predicted by kinetic analysis and molecular docking. Moreover, compound 1 showed significant cytotoxic activities against three human hepatoma cell lines (HepG2, QGY-7703, and SMMC-7721) with half maximal inhibitory concentration (IC50) values of 1.39 ± 0.2, 10.34 ± 2.09, and 5.56 ± 0.47 µmol/L, respectively.
The abnormal activation of JAK2 kinase is closely related to the occurrence and progression of myeloproliferative neoplasms (MPNs). At present, there is still an obvious unmet medical need for selective JAK2 inhibitors in clinic. In this paper, a class of 2-aminopyridine derivatives as potent and selective JAK2 inhibitors was obtained by combining drug design, synthesis and structure-activity relationship studies based on the previously identified lead Crizotinib. Among them, 21b exhibited high inhibitory activity against JAK2 with an IC50 of 9 nmol/L, moreover, it showed 276- and 184-fold selectivity over JAK1 and JAK3, respectively. Besides, 21b had a significant antiproliferative activity against HEL cells, and also inhibited the phosphorylation of JAK2 and its down-stream signaling pathway. These results indicated that 2-aminopyridine compound 21b had the potential to be developed as a selective JAK2 inhibitor for further study.
The photocatalytic reduction of CO2 to energy-rich chemicals is highly appealing for alleviation of energy crisis and environment pollution. The introduction of different active sites is a key factor to determine the reaction activity and selectivity. Here, we demonstrate the metal ion-dependent performance for photocatalytic CO2 reduction by anchoring transition metal ions (Co2+ and Ni2+) in an amine-functionalized boron imidazolate framework (BIF-43). As a result, Ni@BIF-43 realized a high selectivity of 90.2% for the CO2-to-CO, while Co@BIF-43 achieved more efficient conversion with a high CO production rate of 2036.0 µmol g−1 h−1. Significantly, precise control of isolated metal site on a well-defined structure through coordination-assisted strategies enables us to better understand the specific effects of different metal-ion species on photoreduction of CO2 as well as the catalytic mechanism.
Enzyme assisted DNA probes are powerful tools in molecular diagnostics for their simplicity, rapidity, and low detection limit. However, cost of probes, difficulty in optimization and disturbance of secondary structure hindered the wider application of enzyme assisted DNA probes. To solve the problems, we designed a new system named shared-probe system. By introducing two unlabeled single stranded DNA named Sh1 and Sh2 as the bridge between probe and the substrate, the same sequence of dually labeled probe with stable performance was shared for different mutations, thus sparing the expense and time cost on designing, synthesizing and optimizing corresponding probes. Besides, the hybridization between Sh1 and the substrate could overcome secondary structures, which guaranteed the detection of different substrates. The performance and generality of the design were tested by low abundance detection in synthetic single DNA samples and the limit of detection was 0.05% for PTENR130Q, EGFR-L858R and 0.02% for BRCA1-NM007294.3. In genomic DNA samples, the limit of detection of 0.1% can be achieved for EGFR-L858R, demonstrating the potential of clinical application in our design.
A gold nanoparticle (AuNP) aggregation-induced colorimetric aptasensing method for quantitative detection of sulfadimethoxine (SDM) with a smartphone was developed. AuNPs were complexed with aptamers which protected AuNPs from aggregating in high-concentration salt solutions. In the presence of SDM, SDM bound with the aptamer on the surface of AuNPs with higher affinity, which competitively desorbed the aptamer from the AuNP surface and resulted in AuNPs aggregation, accompanied with a color change from red to purple-blue. The R, G and B values of images taken by a smartphone camera were analyzed with an app on the smartphone, and were utilized for quantitative analysis of SDM. Under the optimized conditions, the colorimetric aptasensing method using a smartphone showed high sensitivity for SDM, with the limit of detection of 0.023 ppm, lower than the allowed maximum SDM residue limit. This study provides a simple, fast, and easy to read method for on-site quantitative biochemical and cellular analysis.
A [3 + 2]/[2 + 1] cycloaddition reaction of gem-difluorocyclopropenes is presented, offering a mild and efficient approach to accessing tri- and tetra-substituted 4-fluoropyridines in moderate to good yields with excellent regioselectivity. Multiple synthetic applications, including process-scale reactions, modification of bioactive molecules, derivatization reactions and synthesis of the analogue of the PKM2 modulator, are subsequently described.
Waste utilization is not only the protection of the environment and the practice of green chemistry, but also one of the ways to develop new materials. Herein, we report two biomass carbon dots which prepared from bee pollen waste by one-step hydrothermal method. The new two carbon dots were used in sensing, cell imaging and plant growth regulation. The differences in the structure and properties of the two carbon dots were evaluated by TEM, XPS, TG and various spectroscopic methods. Both two carbon dots contain abundant functional groups, polyatomic doping, excellent water solubility and stable photoluminescence. Due to these good properties, we have demonstrated its versatile applications in Fe3+ sensing, cell imaging and plant growth regulation. It shows sensitive and specific Fe3+ responsiveness and good biocompatibility. This research provides a green and simple method for the recycling and reuse of bee pollen waste, and also provides a reference for the application of biomass carbon dots.
The first example of stereoconvergent 1, 3-dipolar cycloaddition of nitrile oxides and nitrile imines with E/Z isomeric mixture of electron-deficient olefins is reported, delivering isoxazolines and pyrazolines bearing two vicinal stereogenic tertiary and trifluoromethylated quaternary carbon centers with perfect regio- and diastereoselectivities. The possibility of concerted cycloaddition/epimerization sequence under basic condition to form the thermodynamically stable diastereomers is excluded through some control experiments and DFT calculations, and a stepwise mechanism is proposed.
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