Latest ArticlesThe interaction among type Ⅱ collagen (CII), human DR4 major histocompatibility complex type Ⅱ molecule (MHC Ⅱ) and T-cell receptor (TCR) is associated with the development of rheumatoid arthritis (RA). The activation of T cells can be reduced through exposure to modified CII(263–272) glycopeptide fragment via competitive inhibition with self-antigen. In this work, 30 peptides based on the sequence of CII(263–272) were prepared and evaluated for their binding to DR4 protein by surface plasmon resonance (SPR) assay. The effect on the secretion of pro-inflammatory factors by the spleen cells in collagen induced rheumatoid arthritis (CIA) mouse was also investigated. Two N-glycosylated CII peptides were identified to have strong binding to the human recombinant DR4 protein and weak proinflammatory effect. These glycopeptides could be developed as therapeutic saccharide vaccines for the treatment of rheumatoid arthritis (RA).
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.
Grain boundary (GB), as a kind of lattice defect, widely exists in two-dimensional transition metal dichalcogenides (2D TMDs), which has complex and diverse influences on the physical/chemical properties of 2D TMDs. GBs are universally considered to be a double-edged sword, although some electrical and mechanical properties of 2D TMDs would be adversely affected leading to the reduced overall quality, certain structure-oriented applications could be realized based on its unique properties. In this review, we first detailed the atomic structure characteristics of GBs and the corresponding techniques, then we systematically summarized the methods of introducing GBs into 2D TMDs. Next, we expounded unique electrical, mechanical, and chemical properties of the GBs in 2D TMDs and clarified its internal relationship with the atomic structure. Moreover, the application of GB structure in hydrogen evolution reaction (HER) is also discussed. In the end, we make a conclusion and put forward outlooks, hoping to further promote the basic research of GB and boost the wide application of 2D TMDs.
The fascinating chemical structure and broad application prospect of Keggin-type polyoxometalates (POMs) have attracted many chemists to explore and discover continuously. Unlike the traditional Keggin, larger metal atomic radius, higher metal coordinated numbers, lower metal valence states and other features allow the group IVB metal-based Keggin (IVB-Keggin) more space and unknown in terms of structure and performance. Herein, density functional theory (DFT) calculations were performed to explore the influences including cores, shells, caps, and terminal ligands, et al. on IVB-Keggin, and analyze the possibility of novel structure synthesis. From the perspective of multi-layer onion-like clusters, molecular energy level, host-guest interaction energy, surface charge and covalent bond polarity can be further adjusted to achieve the oriented design of functional IVB-Keggin. These insights are expected to provide theoretical support for experimental synthesis, opening a new perspective to understand the growth of Keggin.
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.
Single crystallization is an important strategy to resolve intergranular cracks and unnecessary side reactions with electrolytes in layered transition metal oxide cathodes LiNi0.8Mn0.1Co0.1O2 (NMC811). Due to the limitations of high-temperature sintering and multi-step calcination, single crystal NMC811 generally shows irregular particles with a size of 2–3 µm. However, the prolonged Li-ion diffusion pathway and the stress generated by the uneven de-/intercalation sluggish Li-ion diffusion kinetics, what is more, cause structural damage such as intragranular cracks. A slow Li extraction rate or particle size reduction will ameliorate the structural damage and improve the cycling stability. As the most promising cathodes for next-generation power batteries, NMC811 required fast charge performance and cycle stability. Particle size reduction appears to be the displacement option. Nanonization is an effective strategy to mitigate intragranular cracks of single crystal NMC811. However, the serious aggregation and increased specific surface area become new challenges. In this article, we synthesized monodisperse nanoscale single crystal NMC811 by molten salt method and modified the surface by LiNbO3 coating. The electrochemical performance shows that nanoscale single crystal NMC811 has faster kinetic and higher capacity retention, so the strategy of combining nanonization and surface coating is an alternative way to prepare high specific capacity and cycle stable single crystal NMC811.
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.
Increasing use of silver in various fields has caused Ag+ pollution in water environment, taking great threats to people's health. As a consequence, establishing rapid and reliable methods for sensitive determination of Ag+ is of great significance. Fluorescent (FL) sensors based on carbon dots (CDs), an excellent carbonaceous nanomaterial with strong and stable fluorescence, have absorbed extensive attentions in analysis of pollutants due to its advantages of carbon sources being readily available, low cost, easy operation and fast response. Moreover, ion-imprinting is a better way to increase the selectivity of the proposed method. Present work described an effective method for the sensitive measurement of silver ion in water samples in combination with magnetic ion-imprinted solid phase extraction and CDs based fluorescent sensor, which took full advantages of easy separation and high enrichment of magnetic solid phase extraction, high selectivity of ion-imprinting technology, and sensitivity and rapid response of fluorescent sensor from CDs. Sulfur-doped CDs derived from dithizone and magnetic ion-imprinted nanomaterial were prepared, and characterized with Fourier transform infrared spectroscopy and transmission electron microscope, etc. Magnetic Ag+ imprinted nanomaterial based solid phase extraction was employed for separating and enriching Ag+ from water samples. The significant parameters were optimized in detail. Under the optimal conditions, the proposed method provided good linearity in the range of 0.01–0.4 µmol/L and low detection limit of 3 nmol/L. The reliability of the proposed method was validated with real water samples, and the results demonstrated that the proposed method was simple, robust, selective and sensitive detection tool for Ag+ in real water samples.
The detrimental "shuttle effect" of lithium polysulfides (LiPSs) together with sluggish multi-order reaction kinetics are the main drawbacks hindering lithium-sulfur (Li-S) batteries from commercial success. Here, we first propose the implementability of layered rare-earth hydroxides (LREHs) in Li-S batteries to optimize electrochemical performance. In this work, a two-dimensional (2D) rare-earth-based composite constructed by the layered gadolinium hydroxy chloride [Gd2(OH)5(H2O)]Cl nanoplates (LGdH NPs) and graphene oxide (GO) was designed as a sulfur immobilizer for Li-S batteries. Combining the experimental results and density functional theory (DFT) calculations, it is revealed that the LGdH@GO composite not only provides a strong anchoring of the intermediates during cycling, but also acts as an effective catalyst to accelerate the liquid-solid conversion of polysulfides. The Li-S batteries assembled by LGdH@GO modified separators delivered a superior rate performance with a specific capacity of 605.34 mAh/g at 5 C, as well as excellent cycle stability with a decay rate of 0.087% over 500 cycles at 2 C. This study provided a deep understanding of the mechanism to suppress the "shuttle effect" by the LREHs, and a guide to design effective functional interlayers for high-performance Li-S batteries with excellent electrocatalytic activity.
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.
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