Latest ArticlesSuperlattices in crystals, particularly in perovskite oxides with strong correlation effects, can create new states of matter and produce peculiar physicochemical phenomena. However, the newfangled perovskite superlattices depend on physical deposition with unit-cell precision. It has been challenging to explore a new suitable chemical method to tailor perovskite superlattices. Herein, we present a new bottom-up strategy to precisely prepare atomic-scale oxide superlattices of (LaMnO3)1-(La1-x-yCaxKyMnO3)2 in a monodispersed perovskite La0.66Ca0.29K0.05MnO3 (LCKMO). The special atomic-scale perovskite superlattices are demonstrated using SAED, HAADF-STEM, XRD, and atomic-resolution elemental mapping. Our experiments reveal that the perovskite superlattices can be fabricated under extreme hydrothermal conditions utilizing ultra-high concentrations of KOH. An approximate molten salt system in the hydrothermal process can induce the disproportionation reaction of MnO2 solids, which is vital to the growth of ordered perovskite superlattices. This work not only clarifies the hydrothermal growth process of perovskite oxides in extreme conditions, but also proposes a novel engineering route toward perovskite superlattices.
Highly enantioselective sulfa-Michael additions (SMA) between 2-alkenyl quinoxalines and aromatic thiols are accomplished using a low loading of chiral phosphoric acid catalyst (1 mol%). It was confirmed by an investigation of a lot of azaarenes that the two C=N units of quinoxalines are indispensable for controlling the reaction enantioselectivities. A series of non-terminal 2-alkenes substituted with aryls or alkyls, even other electro-withdrawing groups such as ketones, esters, or amides, selectively reacted and afforded the desired SMA products (48 examples) in good regioselectivities with high yields (up to 99%) and good ee values (up to 97%).
Photodynamic therapy (PDT) has emerged as an efficient cancer treatment method with minimal invasiveness. However, the majority of current photosensitizers (PSs) display severe dark toxicity and low tumor specificity due to their "always-on" photoactivity in blood circulation. To address this concern, we herein report a series of acid-activatable PSs for ultrasensitive PDT of triple-negative breast tumors. These set of novel PSs are synthesized by covalently modifying tetrakis(4-carboxyphenyl)porphyrin (TCPP) with a variety of tertiary amines for acidity-activatable fluorescence imaging and reactive oxygen species (ROS) generation. The resultant TCPP derivatives are grafted with a poly(ethylene glycol) (PEG) chain via a matrix metalloproteinase-2 (MMP-2)-liable peptide spacer and chelated with Mn2+ for magnetic resonance imaging (MRI) capability. The PEGylated TCPP derivatives are amphiphilic and self-assemble into micellar nanoparticles to elongate blood circulation and for tumor-specific PDT. We further demonstrate that the PEGylated TCPP nanoparticles could serve as a nanoplatform to deliver the anticancer drug doxorubicin (DOX) and perform fluorescence image-guided combinatorial PDT and chemotherapy, which efficiently suppress the growth of 4T1 breast tumors and lung metastases in a mouse model. These acid-activatable PS-incorporated nanoparticles might provide a versatile platform for precise PDT and combinatorial breast cancer therapy.
To improve operation efficiency, an interlayered thin-film composite forward osmosis (iTFC-FO) membrane was designed by introducing an ultrathin and porous interlayer based on aluminum tetra-(4-carboxyphenyl)porphyrin (a stable metal−organic framework nanosheet, Al-MOF). Surface characterization results revealed that Al-MOF spread evenly in the macro-porous substrate, and provided a flat and smooth reaction interface with moderate hydrophilicity and uniform small aperture. The resultant polyamide (PA) layer had a thin base (without intrusion into substrate) and crumpled surface (with abundant leaves). The leaves size and cross-linking degree of PA layer firstly increased and then decreased with the Al-MOF loading. Compared to the original membrane, the iTFC-FO showed an enhanced water permeability and a reduced reverse sodium flux in both modes of active layer facing feed solution (AL-FS) and active layer facing draw solution (AL-DS). To be specific, the specific reverse sodium flux (reverse sodium flux/pure water flux) decreased from 0.27 g/L to 0.04 g/L in the AL-FS mode, while from 1.36 g/L to 0.23 g/L in the AL-DS mode with 2 mol/L NaCl as DS. Moreover, the iTFC-FO maintained high stability and high permeability under high-salinity and contaminated environment. This study offers a new possibility for the rational fabrication of high-performance TFC-FO membranes.
Manganese oxides show a strong catalytic activity in the peroxymonosulfate (PMS) advanced oxidation process but have poor chemical stability and a propensity to cause the aggregation of nanoparticles. Here, a novel composite material (abbreviated as MnOx@ACF) was synthesized, characterized, and applied. Activated carbon fiber (ACF) was selected as a carrier, which modulated the composition of manganese oxides. The results showed that MnOx@ACF had a strong adsorption ability and successfully activated PMS to degrade tetracycline hydrochloride (TCH), with a removal efficiency of 89.0% in 30 min. Influencing factors such as pH and coexisting ion species were investigated, and a five-cycle test was conducted. Singlet oxygen (1O2) was predominated in the MnOx@ACF/PMS system. A possible explanatory pathway of TCH was proposed based on the results of the high performance liquid chromatography-mass spectrometry. It was concluded that this study provides a novel insight into the activation of PMS for the degradation of organic matter by carbon-loaded multivalent manganese oxides.
Rho-associated coiled-coil-containing protein kinase (ROCK) belongs to the serine-threonine family, and ROCK is involved in a variety of biological processes including cell migration, adhesion, proliferation and differentiation through phosphorylation of different downstream substrates. The aberrant activation of ROCK is associated with the pathological conditions in different systems including various diseases, including cancer, neurological diseases, inflammation, cardiovascular diseases and glaucoma. Therefore, the ROCK inhibitors have potential applicability for treating the aforementioned diseases. Four small molecule ROCK inhibitors have been approved for clinical use: fasudil, ripasudil, netarsudil and belumosudil. In recent years, more small molecule ROCK inhibitors have been identified. This paper reviews the ROCK inhibitors reported in past seven years. We mainly focused on the summarization of the structure–activity relationships, inhibitory efficacy, pharmacological mechanisms and the relevant clinical studies of the reported ROCK inhibitors. Besides the small molecular inhibitors, the peptides and biological extracts which exhibit ROCK inhibitory effects are also included. We also provide suggestions for the future development of the potent ROCK inhibitors.
We here present a Förster resonance energy transfer (FRET)-based and environment-sensitive fluorescent probe VG-1 for vicinal-dithiol-containing proteins (VDPs). VG-1 uniquely contains two sites sensitive to the protein environment (SPE), thus it shows weak fluorescence in both blue and green channels (a low FRET efficiency) in solution. After specifically binding with VDPs, its fluorescence in the green channel increases, while that in the blue channel disappears, achieving the specific detection of VDPs. The obvious signal changes in fluorescence may be attributed to that the increased rigidity of the molecular skeletons causes the enhanced FRET efficiency. The probe also achieved the cell super-resolution imaging of VDPs and the confocal imaging of VDPs in zebrafish.
A flexible organic artificial synapse (OAS) for tunable time-frequency signal processing was fabricated using a tri-blend film that had been fabricated using a one-step solution method. When combined with a chitosan film, this OAS can achieve an ultrashort-term retention time of only 49 ms for instant electrical-computing applications; this is the shortest retention time yet achieved by a two-terminal artificial synapse. An array of these flexible OASs can withstand a high bending strain of 5% for 104 cycles; this deformation endurance is a new record. The OAS was also sensitive to the number and frequency of electrical inputs; a tunable cut-off frequency enables dynamic filtering for use in image detail enhancement. This work provides a new resource for development of future neuromorphic computing devices
Replicating extraordinarily high membrane transport selectivity of protein channels in artificial channel is a challenging task. In this work, we demonstrate that a strategic application of steric code-based social self-sorting offers a novel means to enhance ion transport selectivities of artificial ion channels, alongside with boosted ion transport activities. More specifically, two types of mutually compatible sterically bulky groups (benzo-crown ether and tert-butyl group) were appended onto a monopeptide-based scaffold, which can order the bulky groups onto the same side of a one-dimensionally aligned H-bonded structure. Strong steric repulsions among the same type of bulky groups (either benzo-crown ethers or tert-butyl groups), which are forced into proximity by H-bonds, favor the formation of hetero-oligomeric ensembles that carry an alternative arrangement of sterically compatible benzo-crown ethers and tert-butyl groups, rather than homo-oligomeric ensembles containing a single type of either benzo-crown ethers or tert-butyl groups. Coupled with side chain tuning, this social self-sorting strategy delivers highly active hetero-oligomeric K+-selective ion channel (5F12·BF12)n, displaying the highest K+/Na+ selectivity of 20.1 among artificial potassium channels and an excellent EC50 value of 0.50 µmol/L (0.62 mol% relative to lipids) in terms of single channel concentration
Because of the widespread applications of optically active alkyl fluorides in medicinal and agro chemicals, enantioselective and even stereodivergent construction of alkyl fluorides remains highly desirable but underdeveloped. Transition-metal-catalyzed asymmetric hydrofluoroalkylation of readily available dienes represents a novel route to achieve this goal, yet receives scarce study. Here we report an intriguing palladium-catalyzed enantioselective hydromonofluoroalkylation reaction of conjugated dienes. Both monosubstituted and internal dienes proceed well with the transformation and furnish alkyl fluorides in generally > 80% yield and > 90% ee. A stereodivergent hydromonofluoroalkylation protocol via Pd/Cu co-catalysis is also established for the access to all four stereoisomers of corresponding moieties bearing a fully-substituted F-stereogenic center and vicinal tertiary carbon center. In addition, asymmetric migratory hydromonofluoroalkylation of skipped dienes is developed to realize the direct allylic CH fluoroalkylation. A compound library of enantioenriched cyclic fluorides is thus built to highlight the transformation potential of present methodology.
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