Synthesis of pennogenin utilizing the intact skeleton of diosgenin

Pennogenin (1) is an aglycone of bioactive com-ponents of Chinese traditional medicine named Chonglou(Paris),[1] which belongs to C-17-hy- droxyl-steroidal sapogenin. It is well known that Chonglou as well as the related herbs containing pennogenin and its glycosides have been used as haemostatic agents in clinic. They also exhibit antibi-otic and antitumor activity[1,2]. With the demand amount of Chonglou as well as the related drugs increasing while the plant resource decreasing day by day…     

基于蛋白和多肽为模板的贵金属纳米簇合成研究

贵金属(Au, Ag, Pt等)纳米簇通常指的是由几个到约一百个原子组成的分子聚集体, 具有生物相容性好、超小尺寸(<2 nm)以及优异的物理化学性质, 尤其是能发出较强荧光等特点引起了人们的广泛关注. 目前多种贵金属纳米簇的合成方法已相继被报道, 且已应用于生物荧光成像、电化学发光、生物传感器以及细胞标记等多个领域. 本文共分为五部分, 首先重点介绍近几年兴起的以蛋白和多肽为模板来合成纳米簇的方法及优点, 并随后总结列举了文献中所采用的蛋白以及自主设计的多肽组分序列的类别, 随后探索了蛋白和多肽中的特定氨基酸与合成的贵金属纳米簇的荧光波长、量子产率、粒径之间的联系. 本文最后总结阐述了蛋白和多肽为模板成功合成贵金属纳米簇的先决条件并对其生物医学应用前景进行了展望.     

Adsorption separation of CO2 and N2 on MIL-101 metal-organic framework and activated carbon

In this work, the CO₂ and N₂ adsorption properties of MIL-101 metal-organic framework (MOF) and activated carbon (AC) were investigated using a standard gravimetric method within the pressure range of 0–30 bar and at four different temperatures (298, 308, 318 and 328 K). The dual-site Langmuir–Freundlich (DSLF) model was used to describe the CO₂ adsorption behaviors on these two adsorbents. The diffusion coefficients and activation energy E _a for diffusion of CO₂ in the MIL-101 and AC samples were estimated separately. Results showed that the isosteric heat of CO₂ adsorption on the MIL-101 at zero loading was much higher than that on the AC due to a much stronger interaction between CO₂ molecule and the unsaturated metal sites Cr³⁺ on MIL-101. Meanwhile, the dramatically decreased isosteric heats of CO₂ adsorption on MIL-101 indicated a more heterogeneous surface of MIL-101. Furthermore, the adsorption kinetic behaviors of CO₂ on the two samples can be well described by the micropore diffusion model. With the increase of temperature, the diffusion coefficients of CO₂ in the two samples both increased. The activation energy E _a for diffusion of CO₂ in MIL-101 was slightly lower than that in AC, suggesting that MIL-101 was much favorable for the CO₂ adsorption. The CO₂/N₂ selectivities on MIL-101 and AC were separately estimated to be 13.7 and 9.2 using Henry law constant, which were much higher than those on other MOFs.     

Characteristics of an oxa-diamide–HNO3 extractant in the supercritical fluid extraction of uranium

An extractant is required in the recovery process to drive the uranium to a stage that enables it to be extracted using the extraction solvent. This paper proposes the composition of a composite extractant, N,N,N′,N′-tetrabutyl-3-oxapentane-diamide–HNO₃ (TBODA–HNO₃) as an extractant, to successfully achieve the objective using supercritical carbon dioxide (sc-CO₂). The composite TBODA–HNO₃ extractant has a chemical composition of TBODA(HNO₃)_1.0(H₂O)_1.5. The U(IV) in the UO₂ containing solid phase is directly oxidized to U(VI) in the form of $ {\rm UO}_{2}^{2 + } $ in sc-CO₂, which contains a CO₂-soluble TBODA–HNO₃ extractant at 200 atm and 50 °C. The resulting $ {\rm UO}_{2}^{2 + } $ /TBODA complex can be consequently extracted using acetone-modified sc-CO₂. The chemical composition of the $ {\rm UO}_{2}^{2 + } $ /TBODA complex, which can be extracted by nonpolar sc-CO₂, is proposed in the form of an ion pair: [UO₂(TBODA)₂]²⁺–2( $ {\rm NO}_{3}^{ - } $ ).     

Enhanced Separation of Potassium Ions by Spontaneous K+‐Induced Self‐Assembly of a Novel Metal–Organic Framework and Excess Specific Cation–π Interactions

A novel metal–organic framework (MOF) was fabricated by spontaneous K⁺‐induced supramolecular self‐assembly with the embedded tripodal ligand units. When the 3D ligand was loaded onto Fe₃O₄@mSiO₂ core‐shell nanoparticles, it could effectively separate K⁺ ions from a mixture of Na⁺, K⁺, Mg²⁺, and Ca²⁺ ions through nanoparticle‐assisted MOF crystallization into a Fe₃O₄@mSiO₂@MOF hybrid material. Excess potassium ions could be extracted because of the specific cation–π interaction between K⁺ and the aromatic cavity of the MOF, leading to enhanced separation efficiency and suggesting a new application for MOFs.     

Function-Oriented: The Construction of Lanthanide MOF Luminescent Sensors Containing Dual-Function Urea Hydrogen-Bond Sites for Efficient Detection of Picric Acid

Two novel lanthanide metal–organic framework (Ln-MOF) luminescent sensors for the detection of picric acid have been successfully assembled. Following a function-oriented strategy, urea hydrogen-bonding functional sites were introduced into two MOF frameworks. A structural analysis indicated that the two MOFs have the exact same structure, namely 2D layers with diamond-shaped holes that are accumulated into a 3D framework through the hydrogen-bonding interactions between urea and carboxylate groups. Interestingly, only half of the urea units are involved in supporting the MOF framework through N−H⋅⋅⋅O hydrogen-bonding interactions, whereas the other half are located in the pore channel and act as empty recognition sites. Abundant N−H urea bonds are present in the inner walls of three types of interpenetrating 1D channels. Luminescence studies revealed that the two Ln-MOFs exhibit high sensitivity, good selectivity, and a fast luminescence quenching response towards picric acid. In particular, the two Ln-MOFs can be simply and quickly regenerated, and exhibit excellent recyclability. In summary, we have successfully used a function-oriented strategy to achieve multiple functions in a ligand to construct lanthanide MOF luminescent sensors for the detection of picric acid, thereby providing a potential strategy for the future development of MOF luminescent sensors with a specific target.     

碱性配体对氯铝酞菁催化CO2与环氧烷烃合成烷撑碳酸酯的促进作用

解决由二氧化碳引起的"温室效应"已经成为世界性难题,回收利用CO2是最理想的解决办法.随着煤、石油和天然气等资源消耗殆尽又将引发世界范围内的碳源危机,因此如何有效地利用CO2作为碳资源变得越来越重要.由于CO2的化学性质极不活泼,必须经催化活化后才能被利用.在CO2的催化活化及合成化学领域中人们已开展了一些工作,如以CO2为原料合成了甲酸、水杨酸、甲醇、尿素和聚碳酸酯等[1].     

Cytotoxic Polyhydroxylated Oleanane Triterpenoids from Cissampelos pareira var. hirsuta

Three new polyhydroxylated oleanane triterpenoids, cissatriterpenoid A−C (1−3), along with one known analogue (4), were isolated from the whole plant of Cissampelos pareira var. hirsuta. Their chemical structures were elucidated by extensive spectroscopic data (IR, HR-ESI-MS, ¹H-NMR, ¹³C-NMR, DEPT, ¹H-¹H COSY, HSQC, HMBC, NOESY) and the microhydrolysis method. The isolation of compounds 1–4 represents the first report of polyhydroxylated oleanane triterpenoids from the family Menispermaceae. All isolated compounds were evaluated for their cytotoxicity against five human cancer cell lines, and the inhibitory activity against NO release in LPS-induced RAW 264.7 cells. Compound 3 showed the most potent cytotoxic activities against the A549, SMMC-7721, MCF-7, and SW480 cell lines, with IC₅₀ values of 17.55, 34.74, 19.77, and 30.39 μM, respectively, whereas three remaining ones were found to be inactive. The preliminary structure–activity relationship analysis indicated that the γ-lactone ring at C-22 and C-29, and the olefinic bond at C-12 and C-13 were structurally required for the cytotoxicity of polyhydroxylated oleanane triterpenoids against these four cell lines. Based on lipid-water partition coefficients, compound 3 is less lipophilic than 1 and 4, which agrees with their cytotoxic activities. This confirms the potential of C. pareira var. hirsuta in the tumor treatment.     

Sensitive fluorescent light-up probe for enzymatic determination of glucose using carbon dots modified with MnO<Subscript>2</Subscript> nanosheets

We describe a highly sensitive glucose probe based on carbon dots modified with MnO₂. A strong reduction of the green fluorescence of the carbon dots (CDs) happened due to the surface energy transfer (SET) from CDs to the deposited MnO₂. In the presence of H₂O₂ (formed via enzymatic oxidation of glucose), fluorescence is restored because the MnO₂ nanosheets are reduced to form colorless Mn(II) ions. These findings were used to design a fluorometric glucose assay that has a detection limit as low as 44 nM (at an S/N ratio of 3).

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Graphical Abstract A strong reduction of the green fluorescence of the carbon dots (CDs) occurs due to surface energy transfer (SET) from CDs to the deposited MnO₂. In the presence of H₂O₂ (formed by enzymatic action of glucose oxidase) the MnO₂ nanosheets are reduced to form colorless Mn(II) ions, and glucose can be quantified by the fluorescence restored.