Latest ArticlesPalladium-catalyzed highly meta-selective C -H iodination of phenylacetic acid, benzylphosphonate and benzylsulfonate scaffolds with molecular I2 is developed using a pyridine-type template. The practical ester linkages enable the directing template easily installed and readily removed. The substrate scope is broad, and alkyl, methoxyl, trifluomethyl, and halo substituents are compatible with this reaction. Further transformations of ibuprofen iodide intermediates by Pd-catalyzed C -C and C-heteroatom bond formation illustrate the broad utility of this method.
An efficient method was developed for the conjugate addition of water to various α, β-unsaturated ketones by using bismuth(Ⅲ) chloride as a catalyst. The reactions proceeded smoothly in the presence of a catalytic amount of BiCl3 (20 mol%) in aqueous media to furnish a variety of synthetically useful β-hydroxyl ketones in moderate to good yields. Apart from water molecule, various alcohols could also be employed as nucleophiles to react with α, β-unsaturated ketones, leading to β-alkoxyl ketones in modest to high yields. In addition, the mild reaction conditions also entailed the conjugate addition reactions to proceed with the tolerance to a range of functional groups.
An efficient gold-catalyzed anti-Markovnikov cycloisomerization-initiated tandem reaction of Bocprotected indole tethered homopropargyl amides has been achieved. This method delivers a wide range of valuable bridged aza-[n.2.1] skeletons (n=3-7) at room temperature with high diastereoselectivity and enantioselectivity by a chirality-transfer strategy. Moreover, the gold-catalyzed tandem reaction of homopropargyl alcohol is also achieved to produce the bridged oxa-[3.2.1] skeleton.
The H3 bivalent modifications of trimethylation at Lys9 and acetylation at Lys18 (H3-K9Me3-K18Ac) were identified to collectively recruit TRIM33 in the nodal signaling pathway. To understand the underlying mechanism of TRIM33 recruitment, the nucleosome core particles (NCPs) containing full-length H3-K9Me3-K18Ac were indispensable samples. Herein we developed a pseudo dipeptide strategy to efficiently prepare peptide segments, facilitating the chemical synthesis of H3-K9Me3-K18Ac at a tens of milligram scale. The synthetic H3-K9Me3-K18Ac was then examined by CD spectroscopy, which demonstrated a prominent shift compared to recombinant H3. Finally, bivalently modified NCPs were assembled and verified by gel mobility shift assay with good homogeneity.
Rapid and simultaneous in situ detection of multi-components is extremely crucial for the real-time monitoring of nutrients in fruits. Herein, a facile and user-friendly poly(carboxybetaine methacrylate)-coated paper-based microfluidic device (pCBMA-njPAD) has been exploited to synchronously identify and semi-quantify vitamin C, glucose, sucrose and fructose in fruits. The pCBMA was successfully grafted from the surface of paper sensor using a convenient and robust method, which was confirmed by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectrometry (XPS). The superior hydrophilicity and ultra-low fouling of pCBMA endowed the pCBMA-μPAD with remarkably rapid response (3 min), high sensitivity, good linear relationship and low detection limit (LOD) (vitamin C: y = 33.809 + 5.175x, R2 = 0.993, LOD = 0.179 mmol/L; glucose: y = -0.113 + 30.066lg(x), R2 = 0.988, LOD = 0.095 mmol/L; sucrose: y = -5.334 + 34.858lg(x), R2 = 0.996, LOD = 0.097 mmol/L; fructose: y = 4.996 + 23.325lg(x), R2 = 0.994, LOD = 0.140 mmol/L). Furthermore, satisfactory results were yielded in the detection of these nutrients in 9 fruits, which were much agreed well with those obtained by spectrophotometry. Such a portable and versatile pCBMA-μPAD will profoundly shape the future of food analysis, especially for the assessment of food quality and nutrition in the process of agricultural production and marketing.
Infectious diseases have always been a major cause of mobility and mortality, early and accurate diagnosis is important for their management. However, current clinical diagnosis for bacterial infection still remains troublesome. Recently, many attempts on molecular imaging have been made for prompt bacteria detection, especially for early and precise disease diagnosis. Among them, maltohexaose-based probes serve as a superb candidate due to the bacteria-specific maltodextrin transport pathway. These probes can visualize bacterial foci with unparalleled sensitivity and specificity. Such metabolism-based targeting strategy offers a powerful delivery platform for imaging and theranostic agents, providing good translational potential for developing antibacterial agents.
Developing high efficiency and low cost electrocatalysts is critical for the enhancement of oxygen reduction reaction (ORR), which is the fundamental for the development and commercialization of renewable energy conversion technology. Herein, zinc-nitrogen-carbon (Zn-N-C) was prepared by using biomass resource chitosan via a facile carbon bath method. The obtained Zn-N-C delivered a high specific surface area (794.7 cm2 /g) together with pore volume (0.49 cm3 /g). During the electrochemical evaluation of oxygen reduction reaction (ORR), Zn-N-C displayed high activity for ORR with an onset potential E0=0.96 VRHE and a half wave potential E1/2=0.86 VRHE, which were more positive than those of the commercial 20 wt% Pt/C benchmark catalyst (E0=0.96 VRHE and E1/2=0.81 VRHE). In addition, the ZnN-C catalyst also had a better stability and methanol tolerance than those of the Pt/C catalyst.
Rhenium is one of important components for heterogeneous catalysts, which has been recently used for the catalytic reactions related to the production of biomass-derived chemicals such as deoxydehydration of vicinal OH groups, C-O hydrogenolysis, and hydrogenation of carboxylic acids, and so on. Suitable oxidation state of Re as a catalytic active species is strongly dependent on the catalytic reactions. The control of the oxidation state of Re species on the catalysts is crucial on the catalyst development.
Peptide amphiphiles with well-organized secondary structure are an important family of molecules that are known to assemble into a variety of nanostructures. In this work, we present three guanidiniocarbonylpyrrole (GCP) containing peptide amphiphiles, which show versatile morphology and secondary structure changes as a result of different chain lengths and in different concentration regimes. The random coil conformation, α-helix, and β-sheet are obtained for peptide 1, peptide 2, and peptide 3, respectively under neutral aqueous conditions. Furthermore, all peptide amphiphiles can aggregate to form nanoparticles at low concentrations. However, at high concentrations, peptide 1 selfassembles into left-handed twisted helical fibers, while longer bamboo-like morphology can be observed exclusively for peptide 2. For peptide 3, freshly prepared samples show uniform spherical morphology, whereas an obvious morphological transition from original nanoparticles to disordered fibers was realized after incubating for one week. These fascinating morphology changes were determined by the combination of circular dichroism, dynamic light scattering, transmission electron microscopy, atomic force microscopy, and theoretical calculations.
Herein, we firstly developed a non-covalent glycosylated gold nanoparticles/peptides nanovaccine which is assembled by β-cyclodextrin (β-CD) based host-guest recognitions. This nanovaccine can generate significant titers of antibodies and improve the therapeutic effect against melanoma, suggesting the immunogenicity of peptide antigens can be improved by loading with this carrier. The novel vaccine carrier provides a platform for the transport of various antigens especially T cell-independent antigens.
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