2,2′‐Anhydro‐1‐(3′,5′‐di‐O‐acetyl‐β‐D‐arabinofuranosyl)uracil,a cyclouridine nucleoside with a C4′‐endo furanosyl conformation

2,2′‐Anhydro‐1‐(3′,5′‐di‐O‐acetyl‐β‐D‐arabinofuranosyl)uracil, C₁₃H₁₄N₂O₇, was obtained by refluxing 2′,3′‐O‐(methoxymethylene)uridine in acetic anhydride. The structure exhibits a nearly perfect C4′‐endo (⁴E) conformation. The best four‐atom plane of the five‐membered furanose ring is O—C—C—C, involving the C atoms of the fused five‐membered oxazolidine ring, and the torsion angle is only −0.4 (2)°. The oxazolidine ring is essentially coplanar with the six‐membered uracil ring [r.m.s. deviation = 0.012 (5) Å and dihedral angle = −3.2 (3)°]. The conformation at the exocyclic C—C bond is gauche–trans which is stabilized by various C—H...π and C—O...π interactions.     

Polyhedral oligomeric silsesquioxanes as functional monomer to prepare hybrid monolithic columns for capillary electrochromatography and capillary liquid chromatography

A simple approach to fabricate hybrid monolithic column within the confines of fused-silica capillaries (75 μm i.d.) was introduced. A polyhedral oligomeric silsesquioxanes (POSS) reagent containing a methacrylate group was selected as functional monomer, and copolymerized with bisphenol A dimethacrylate (BPADMA) or ethylene dimethacrylate (EDMA) in the presence of porogenic solvents via thermally initiated free radical polymerization. After optimization of the preparation conditions, two POSS-containing hybrid monoliths were successfully prepared and exhibited good permeability and stability. By comparison of the separation efficiencies of the resulting poly(POSS-co-BPADMA) and poly(POSS-co-EDMA) monoliths in capillary electrochromatography (CEC) and capillary liquid chromatography (cLC), it was indicated the former has better column efficiencies for alkylbenzenes, phenols, anilines and PAHs in CEC and cLC than the latter. Particularly, the hybrid poly(POSS-co-BPADMA) monolith is more suitable for separation of PAHs due to π–π interaction between the analytes and aromatic rings in the surface of monolithic stationary phase.     

Molecule-binding dependent assembly of split aptamer and γ-cyclodextrin: A sensitive excimer signaling approach for aptamer biosensors

A highly sensitive and selective fluorescence aptamer biosensors for the determination of adenosine triphosphate (ATP) was developed. Binding of a target with splitting aptamers labeled with pyrene molecules form stable pyrene dimer in the γ-cyclodextrin (γ-CD) cavity, yielding a strong excimer emission. We have found that inclusion of pyrene dimer in γ-cyclodextrin cavity not only exhibits additive increases in quantum yield and emission lifetime of the excimer, but also facilitates target-induced fusion of the splitting aptamers to form the aptamer/target complex. As proof-of-principle, the approach was applied to fluorescence detection of adenosine triphosphate. With an anti-ATP aptamer, the approach exhibits excimer fluorescence response toward ATP with a maximum signal-to-background ratio of 32.1 and remarkably low detection limit of 80 nM ATP in buffer solution. Moreover, due to the additive fluorescence lifetime of excimer induced by γ-cyclodextrin, time-resolved measurements could be conveniently used to detect as low as 0.5 μM ATP in blood serum quantitatively.     

Hyphenation of optimized microfluidic sample preparation with nano liquid chromatography for faster and greener alkaloid analysis

A glass liquid–liquid extraction (LLE) microchip with three parallel 3.5 cm long and 100 μm wide interconnecting channels was optimized in terms of more environmentally friendly (greener) solvents and extraction efficiency. In addition, the optimized chip was successfully hyphenated with nano-liquid chromatography with ultraviolet and mass spectrometric detection (nanoLC–UV–MS) for on-line analysis. In this system, sample pretreatment, separation and detection are integrated, which significantly shortens the analysis time, saves labor and drastically reduces solvent consumption. Strychnine was used as model analyte to determine the extraction efficiency of the optimized 3-phase chip. Influence of organic solvent, pH of feed phase, type of alkaloid, and flow rates were investigated. The results demonstrated that the 3-phase chip nanoLC–UV/MS hyphenation combines rapid (∼25 s) and efficient (extraction efficiency >90%) sample prep, with automated alkaloid analyses. The method was applied to real samples including Strychnos nux-vomica seeds, Cephaelis ipecacuanha roots, Atropa belladonna leaves, and Vinca minor leaves.     

Development of a Sensitive Method for the Determination of 4‐(Methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanol in Human Urine Using Solid‐phase Extraction Combined with Ultrasound‐assisted Dispersive Liquid–liquid Microextraction and LC‐MS/MS Detection

An efficient and sensitive analytical method based on molecularly imprinted solid‐phase extraction (MISPE) and reverse‐phase ultrasound‐assisted dispersive liquid–liquid microextraction (USA‐DLLME) coupled with LC–MS/MS detection was developed and validated for the analysis of urinary 4‐(methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanol (NNAL), a tobacco‐specific nitrosamine metabolite. The extraction performances of NNAL on three different solid‐phase extraction (SPE) sorbents including the hydrophilic‐lipophilic balanced sorbent HLB, the mixed mode cationic MCX sorbent and the molecularly imprinted polymers (MIP) sorbent were evaluated. Experimental results showed that the analyte was well retained with the highest extraction recovery and the optimum purification effect on MIP. Under the optimized conditions of MIP and USA‐DLLME, an enrichment factor of 23 was obtained. Good linearity relationship was obtained in the range of 5‐1200 pg/mL with a correlation coefficient of 0.9953. The limit of detection (LOD) was 0.35 pg/mL. The recoveries at three spiked levels ranged between 88.5% and 93.7%. Intra‐ and inter‐day relative standard deviations varied from 3.6% to 7.4% and from 5.4% to 9.7%, respectively. The developed method combing the advantages of MISPE and DLLME significantly improves the purification and enrichment of the analyte and can be used as an effective approach for the determination of ultra‐trace NNAL in complex biological matrices.     

(Δ)[Fe(II)(phen)3]2+ Filled in the Chiral Cavitiy Constituted by {(Δ)[Fe(III)(C2O4)3](NH42+)(DMF)(H2O)32−}n

A chiral coordination compound {(Δ)[Fe(II)(phen)₃][(Δ)Fe(III)(C₂O₄)₃](NH₄)(H₂O)₃(DMF)}_n (phen = 1,10‐phenanthroline), (DMF = N,N'‐Dimethylformamide), has been synthesized, and the structure has been revealed by infrared spectroscopy and X‐ray single‐crystal diffraction. The framework consists of two chiral subunits. One subunit (Δ)[(Fe(III)(C₂O₄)₃]^3? which as host anion forms a chiral porous three‐dimensional supermolecular network with lattice water, lattice DMF and lattice ammonium cation through hydrogen bonds. And then the other is Δ[Fe(II)(phen)₃]²⁺ which as guest cation fills in the chiral cavity located in the previously mentioned host porous network.     

PPy modified titanium foam electrode with high performance for supercapacitor

Pyrrole was polymerized on the surface of titanium foam using FeCl₃ as oxidant and the as-synthesized product could be directly used as electrode for supercapacitor. The globular polypyrrole (PPy) particles were firmly loaded on the substrate with high density. The morphology study of PPy film is observed in SEM images, the XRD, FTIR and UV–vis spectra reveal the structure and crystalline of PPy nanoparticles. The electrochemical properties of PPy modified electrode are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and cycle life techniques. The electrochemical measurements showed such a PPy–Ti electrode had a wide working potential window, a high specific capacitance of 855 F g⁻¹ and excellent cycle stability at a discharge current density of 1 A g⁻¹.     

Bismuth Trichloride–Catalyzed C‐Alkylation of Pyrroles with Electron‐Deficient Olefins

The BiCl₃‐catalyzed reaction of pyrroles with electron‐deficient olefins generated the corresponding Michael adducts in high yields.