Latest ArticlesA new bismuth-based halide double perovskite Cs2KBiCl6 was isolated successfully through solid-state reactions and investigated using X-ray and neutron diffraction. Rather than an ordered structure, the crystal structure consists of shifted Cs, K, Bi, and Cl sites from the ideal positions with fractional occupancy in compensation, leading to variable local coordination of Cs+ ions, as revealed by 133Cs solid-state nuclear magnetic resonance spectroscopy. Cs2KBiCl6 displays volume hysteresis at 5–298 K range upon heating and cooling. The Cs2KBiCl6 has a direct bandgap of 3.35(2) eV and red-shift luminescence of around 600 nm upon Mn doping compared with the Na analogue. The stabilization of disordered structure in Cs2KBiCl6 is related to two factors including the large-sized K+ cation which prefers to coordinate with more than six Cl−, and the Bi3+ with 6s2 lone pair which has a preference for a local asymmetric environment. These findings could have general application and help to understand the structure and property of halide perovskites.
In persulfate-based advanced oxidation process (PS-AOPs), fixing nanosized metal oxide on processable substrates is highly desirable to avoid the aggregation and loss of nanocatalysts during the practical application. However, it is still challenging to develop a versatile strategy for the deposition of metal oxide nanocatalysts on various substrates with different physicochemical properties. Herein, polyphenols are utilized as a "molecular glue" and reductant to mediate the interfacial deposition of MnO2 nanocatalysts on different substrates. MnO2 nanocatalysts were in-situ grown on macroscope mineral substrates (e.g., airstone) via an interfacial redox strategy between tannic acid (TA) and oxidized KMnO4, and then employed as a fixed catalyst of peroxymonosulfate (PMS) activation for treating pharmaceutical and personal care products (PPCPs) in water. The fixed MnO2 exhibited superior catalytic performance toward different PPCPS via a singlet oxygen (1O2)-dominated nonradical oxidation pathway. PPCPs in the secondary effluent of wastewater treatment plants could be effectively removed by a fixed-bed column of the fixed MnO2 with long term stability. Redox cycle of Mn4+/Mn3+ and surface hydroxyl group of the fixed MnO2 was proved to be responsible for the activation of PMS. This work provides a new avenue for developing fixed metal oxides for sustainable water treatment.
Alginate is a natural polysaccharide polymer. Hydrogel filtration membranes prepared from alginate show excellent fouling resistance and controllable separation performance, but poor mechanical properties limit the use of algae hydrogels. In this study, Ba2+/Ca2+ co-crosslinked alginate (Ba/CaAlg) hydrogel membrane was prepared by cross-linking sodium alginate with a blend aqueous solution of barium ions and calcium ions, and the membrane was applied to the separation of dyes/salts from dyeing wastewater. Compared with the CaAlg membrane, the Ba/CaAlg hydrogel membrane exhibited more stable structure, and the mechanical properties and salt tolerance of the membrane were significantly improved. The flux of Ba/CaAlg membrane for methyl blue/sodium chloride mixed solution reached 43.5 L m−2 h−1, which was significantly higher than that of CaAlg membrane. Besides, the Ba/CaAlg membrane showed higher dye rejection (>99.6%) and lower salt rejection (<8.2%). The structure of Ba/CaAlg membrane was preliminarily simulated by molecular dynamics, and the pore size and distribution of the membrane were calculated. The Ba/CaAlg membrane has a broad application prospect in dyes/salts separation.
An approach for distinguishing two types of positional isomers of dimeric shikonin and its analogs was explored with 4JC, H long-range correlation by prolonging the acquisition time at 2,3JC, H values of 2.0 and 8.0 Hz. Furthermore, the 1H (proton) nuclear magnetic resonance (NMR) pattern of phenolic hydroxyl protons was developed as a "diagnosis signal" to ascertain the relative location of each side chain in DMSO–d6 at sample concentrations of 0.022–0.034 mol/L. The chemical shift differences of 0.6 ppm between OH-5′ and OH-1 and between OH-8′ and OH-4 are assigned to Type A and Type B, respectively. All reported ambiguous structures were corrected by this pattern. Additionally, the steric structures of isolated compounds were elucidated by quantum chemical calculations of electronic circular dichroism (ECD) spectra.
The clinical benefit of combination therapy is significant, but it is not easy to define the mechanism of complexity and diversity. Previous studies illustrate that phillygenin (Phi) binds in the allosteric inhibit pocket of protein kinase B (AKT), and swertiamarin (Swe) acts on the pleckstrin homology (PH) domain of AKT. However, the combined synergistic effect of relieving the inflammatory response has yet to be elucidated. Based on high sensitivity, specificity and fast-responsibility fluorescent sensors, the Förster resonance energy transfer (FRET) technique offers a route to provide clear insights into physiological and pathological processes. In the study, molecular docking, the fluorescent probes of Phi and Swe for FRET were designed and synthesized. FRET analysis shown that Swe and Phi concurrently acted on the PH domain and allosterically inhibited pocket of AKT, respectively. The combination of Swe and Phi significantly increased the heat stability of AKT and decreased protease-induced degeneration. In lipopolysaccharides (LPS)-induced mice and cells, the combination arrested AKT activation, nuclear factor kappa-B (NF-κB) phosphorylation, and the expression of tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-8. In conclusion, FRET revealed Phi and Swe concurrently targeted AKT on different domains and the combination of Phi and Swe enhanced the anti-inflammatory effect.
Ursolic acid (UA) is a naturally occurring ursane triterpenoid, which exhibits a wide range of unique biological activities. To clarify its mechanism of action (MOA), a series of fluorescent derivatives of UA (5a–c) were designed and synthesized by conjugation with 7-nitrobenzo-2-oxa-1,3-diazole (NBD) fluorophore. Among them, 5c exhibited similar anti-proliferative activity with UA against HCT116 cells (half maximal inhibitory concentration (IC50) = 9.21 ± 0.50 µmol/L). Cell imaging experiment indicated that 5c was rapidly taken up in HCT116 cells in a dose and time-dependent manner. Then, 5c was found to localize in endoplasmic reticulum (ER), lysosomes, and mitochondria, but not in nucleus of HCT116 cells by confocal microscopy studies. Preliminary MOA proved that UA induced autophagy with a unique intracellular distribution mechanism involving ER and lysosome. In all, our work provides new clues for revealing the molecular mechanism of UA as an antitumor agent.
We reported the characterization of a novel brassicicene diterpene biosynthetic gene cluster, which contains a unique α-ketoglutarate-dependent dioxygenase (αKGD) enzyme, AbnI. Our findings revealed that AbnI demonstrates remarkable substrate promiscuity and is capable of activating multiple sites on both 5–8–5 and 5–9–5 brassicicene skeletons, resulting in skeleton modifications and an unexpected ring system rearrangement. These results suggested the potential utility of AbnI as an enzymatic tool for terpene CH functionalization. In addition, the catalytic mechanism of AbnI and its potential ecological implications were discussed.
Targeted construction of new covalent organic frameworks (COFs) with specific purposes and rationalities to build colorimetric assay platform for environmental pollutant monitoring have attracted increasing interest. However, it is still challenging due to lack of available coordination sites inside COFs pores and only a slight bonding ability for anchoring metal. In this work, a two-dimensional (2D) COFs (termed as Tz-COF) with high crystallinity, excellent chemical stability, and abundant sulfur coordination in its skeletons was synthesized and used for the confined growth of Au NPs. It was found that the Au NPs showed significant dispersibility for the support of Tz-COF. The proposed Tz-COF@Au NPs possessed outstanding Hg2+-activated peroxidase-like activity benefited from physicochemical properties of gold amalgam and synergistic effect between COFs and Au NPs to oxidize chromogenic substrate. Based on highly efficient activity and distinctive color evolution, the strategy for detecting Hg2+ was developed and successfully applied to determine the content of Hg2+ in real environmental samples. This work manifests that a potential strategy to establish a colorimetric assay platform for environmental pollutant monitoring based on the targeted manufacturing of novel COFs with specific functions.
Commercial V2O5-based catalysts have been successfully applied in NH3 selective catalytic reduction (NH3-SCR) of NOx from power stations, but their poor alkali-resistance restrains the wider application in nonelectrical industries. In this study, NOx reduction against alkali poisoning over V2O5/TiO2 is greatly improved via Ce(SO4)2 modification. It has been originally demonstrated that Ce4+–SO42− pair sites play crucial roles in improving NOx reduction against alkali poisoning over V2O5/TiO2 catalysts. The strong interaction between V species and Ce sites of Ce4+–SO42− pairs triggers the reaction between NH4+species and gaseous NO via Eley-Rideal (E-R) reaction pathway. After K-poisoning, the SO42− sites of Ce4+–SO42− pairs as protective sites strongly bond with K and thus maintain the high reaction efficiency via the E-R reaction pathway. This work demonstrates an effective strategy to enhance NOx reduction against alkali poisoning over catalysts via constructing Ce4+–SO42− pair sites, contributing to developing alkali-resistant SCR catalysts for practical application in nonelectrical industries.
Hydroxylation of steroid core is critical to the synthesis of steroid drugs. Direct sp3 C–H hydroxylation is challenging through chemical catalysis, alternatively, fungal biotransformation offers a possible solution to this problem. However, mining and metabolic engineering of cytochrome P450 monooxygenases (CYPs) is usually regarded as a more eco-friendly and efficient strategy. Herein, we report the mining and identification of a new steroid CYP (CYP68BE1) from Beauveria bassiana by transcriptomics, heterologous expression, in vivo and in vitro functional characterization. The catalytic promiscuity of CYP68BE1 was explored, and CYP68BE1 showed promiscuously and catalytically versatile, which is qualified for monohydroxylation on C11α, C1α, C6β and dihydroxylation on C1β, 11α and C6β, 11α of six steroids, leading to the production of key steroid intermediates required in the industrial synthesis of some indispensable steroid drugs. Molecular dynamics simulations were performed, revealing the molecular basis of different binding orientations of CYP68BE1 with different substrates. The discovery of CYP68BE1 offers a promising biocatalyst for enriching the steroid structural and functional diversity, which also can be applied to biosynthesize valuable steroid drug intermediates.
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