Aphamines A–C (1–3), three pairs of acyclic diterpene dimer enantiomers with an unprecedent ploymerization pattern, were discovered from Aphanamixis polystachya by NMR-guided isolation and chiral resolution. The elucidation of their novel carbon skeletons was achieved based on spectroscopic analysis, exciton chirality, and calculated electronic circular dichroism (ECD). Plausible Claisen rearrangement, 5-exo-trig cyclization, and reduction reactions may play important roles in the polymeric biosynthesis pathway. Compounds 1 and 3 showed inhibitory effects on nitric oxide (NO) production (IC50: 6.71–15.36 μmol/L) and reduced the expression of iNOS in LPS-induced RAW 264.7 macrophages. 相似文献
Oxidative stress (OS) damage can cause significant injury to cells, which is related to the occurrence and development of many diseases. This pathological process is considered to be the first step to trigger the death of outer retinal neurons, which is related to the pathology of retinal degenerative diseases. Hydrogen sulfide (H2S) has recently received widespread attention as a physiological signal molecule and gas neuromodulator and plays an important role in regulating OS in eyes. In this article, we reviewed the OS responses and regulatory mechanisms of H2S and its donors as endogenous and exogenous regulators in retinal degenerative diseases. Understanding the relevant mechanisms will help to identify the therapeutic potential of H2S in retinal degenerative diseases. 相似文献
An effective method was developed for the synthesis of three cluster‐based frameworks with multifarious secondary building units (SBUs) and various structures, which were formulated as [Me2NH2]2[Zn10(BTC)6(μ3‐O)(μ4‐O)(H2O)5] · 3DMA · 9H2O ( FJI ‐ 3 ), [Me2NH2]2[Zn9(μ3‐OH)2(BTC)6(H2O)3] · 5DMA · 6H2O ( FJI ‐ 4 ) and [Me2NH2][Zn3(μ3‐OH)(BTC)2DMF] · H2O ( FJI ‐ 5 ) (H3BTC = 1,3,5‐benzenetricarboxylic acid, DMA = N,N′‐dimethyl acetamide and DMF = N,N′‐dimethyl formamide), respectively. X‐ray structural analysis reveals that FJI ‐ 3 displays 3D highly porous metal‐organic framework with four kinds of microporous cages constructed by two paddle‐wheel Zn2(CO2)4, trimeric Zn3O(CO2)6, and tetrameric Zn4O(CO2)6 SBUs. FJI ‐ 4 exhibits 3D microporous MOFs with a dodecahedral cavities built by paddle‐wheel Zn2(CO2)4 and trimeric Zn3O(CO2)6. FJI ‐ 5 shows 3D microporous MOFs with an 1D channel assembled by the Zn3O(CO2)6 SBUs. In addition, the fluorescence and sorption properties in these cluster‐based frameworks were also investigated. Furthermore, the method employed in this work may provide an useful approach to the design and synthesis of novel cluster‐based frameworks. 相似文献
The morphology and structure of zinc oxide(ZnO), one of the important semiconductors, are relevant to its properties and applications. The preparation of ZnO with tunable morphology and desired structure is an attractive topic in the field of material synthesis. This work reports a facile method for the synthesis of Zn O with controllable morphology and crystal orientation using Zn-based coordination polymer particles(Zn-CPP) as precursors. Using hydrothermal method, Zn-CPP with morphologies of microrod, nanoplate, flower-like, arrow-tipped microsheet, and square cylinder were successfully synthesized via the coordination between metal ions Zn2+ and organic ligand 1,4,5,8-naphthalenetetracarboxylic dianhydride in aqueous solution. Subsequent thermal treatment of the Zn-CPP successfully resulted in the formation of porous Zn O with similar morphology to Zn-CPP. It is also found that the Zn O with enhanced(002) orientation could be obtained from Zn-CPP with preferred(002) orientation. This strategy could be extended for the preparation of other metal oxides with desired shape and structure. 相似文献
Polymer microcavities with adjustable openings and surface roughness are fabricated on a large scale via single‐hole poly(glycidyl methacrylate) (PGMA) swelling seed particles. The size of openings of these microcavities can be adjusted by changing the amount of hydrophilic monomer, and the degree of surface roughness is easily regulated relying on the adjustment of the polarity of monomer. Furthermore, the morphology of PGMA/poly(styrene‐methacrylic acid) (PGMA/P(S‐MAA)) microparticles from microcavity to erythrocyte shape is controlled by the polarity of seed surface. From transmission electron microscopy images of PGMA/P(S‐MAA) microparticles, a fresh polymer particle appears in the cavity. To confirm this phenomenon, thermal annealing process in dioxane/water solution is carried out. Considering the flexibility of polymers, the openings and closing of the prepared microparticles are regulated following the increase in volume ratio of dioxane/water. Ball‐in‐bowl‐shaped PGMA/P(S‐MAA) microparticles are further presented, which proves secondary nucleation of monomer in the polymerization stage.
Organic electrochromic materials change color rapidly under applied potential. A butterfly‐shaped compound, 5,5′,‐5″,‐5′″‐(thieno[3,2‐b]thiophene‐2,3,5,6‐tetrayl) tetrakis‐(2,3‐dihydrothieno[3,4‐b][1,4]dioxine) (t‐EDOT‐TT) is synthesized for the first time and polymerized at different potentials via electropolymerization technique. By applying different polymerization potentials, the optical and electrochromic properties of this newly synthesized polymer can be tuned. Owing to the dependence of functional group position in the polymer structure on the redox potential, this polymer can be utilized in very interesting organic optoelectronic applications.
In this article, an acid-responsive luminescent material, 1,4-di(quinoline-6-yl)buta-1,3-diyne (DQBD) is designed and synthesized. Upon different pH values, gradual changes of fluorescence colors for DQBD in both solution and solid phases are demonstrated due to the protonation effect. Moreover, such responsive characteristics can also be reversible, suggesting DQBD as a promising fluorescent material with great potential for reusable- and accurate-pH sensors in the future. 相似文献
The electrochemical nitrogen reduction reaction (NRR) is a promising energy-efficient and low-emission alternative to the traditional Haber–Bosch process. Usually, the competing hydrogen evolution reaction (HER) and the reaction barrier of ambient electrochemical NRR are significant challenges, making a simultaneous high NH3 formation rate and high Faradic efficiency (FE) difficult. To give effective NRR electrocatalysis and suppressed HER, the surface atomic structure of W18O49, which has exposed active W sites and weak binding for H2, is doped with Fe. A high NH3 formation rate of 24.7 μg h−1 mgcat−1 and a high FE of 20.0 % are achieved at an overpotential of only −0.15 V versus the reversible hydrogen electrode. Ab initio calculations reveal an intercalation-type doping of Fe atoms in the tunnels of the W18O49 crystal structure, which increases the oxygen vacancies and exposes more W active sites, optimizes the nitrogen adsorption energy, and facilitates the electrocatalytic NRR. 相似文献