Flow-based and sieving matrix-free DNA differentiation by a miniaturized field flow fractionation device

DNA separation is typically done by gel electrophoresis based on its charge property. In our previous work, we reported that dielectrophoresis could be used to manipulate polystyrene nanoparticles' motion by using a miniaturized electrical field flow fractionation device (micro-EFFF) with a segmented electrode operated under a pulsed voltage (PV). In this work, we report the manipulation and separation of DNA molecules using the micro-EFFF. DNA motion was in situ visualized inside the device. Results revealed that dielectrophoresis governed DNA motion, which was strongly correlated with the pulse frequency but not the duty cycle of a PV. A longer retention time of DNA molecules was measured under a PV. The retention time increased with the length of DNA molecules. As the micro-EFFF is flow-based and sieving-matrix-free, it has a potential to be applied to sample preparation in a micrototal analysis system or when fractionated molecules are needed for downstream analysis.     

Nitrogen-doped carbon encapsulated in mesoporous TiO_2 nanotubes for fast capacitive sodium storage

Controllable synthesis of insertion-type anode materials with beneficial micro-and nanostructures is a promising approach for the synthesis of sodium-ion storage devices with high-reactivity and excellent electrochemical performance.In this study,we developed a sacrificial-templating route to synthesize TiO₂@N-doped carbon nanotubes(TiO₂@NC-NTs)with excellent electrochemical performance.The asprepared mesoporous TiO₂@NC-NTs with tiny nanocrystals of anatase TiO₂ wrapped in N-doped carbon layers showed a well-defined tube structure with a large specific surface area of 198 m² g^-1 and a large pore size of~5 nm.The TiO₂@NC-NTs delivered high reversible capacities of 158 m A h g^-1 at 2 C(1 C=335 m A g^-1)for 2200 cycles and 146 m A h g^-1 at 5 C for 4000 cycles,as well as an ultrahigh rate capability of up to 40 C with a capacity of 98 m A h g^-1.Even at a high current density of 10 C,a capacity of 138 m A h g^-1 could be delivered over 10,000 cycles.Thus,the synthesis of mesoporous TiO₂@NC-NTs was demonstrated to be an efficient approach for developing electrode materials with high sodium storage and long cycle life.     

Symmetrical electrochemical cell for determination of coextraction constants of metal salts for ion-selective polymeric membranes

A symmetrical electrochemical cell has been developed to perform cyclic voltammetric study of a plasticised poly(vinyl chloride) (PVC) membrane. The plasticised PVC membrane of ca. 100 μm thickness was mounted in a specially laboratory-made electrochemical cell for voltammetric analysis on exposure to various sodium salt and metal chloride solutions. Symmetrical cyclic voltammograms were obtained when the sample and internal solutions contained same kind of metal salts. The coextraction constant of a metal salt for the plasticised PVC could be determined from either the positive or negative potential scans of a cyclic voltammetry. In addition, two coextraction constants could also be simultaneously obtained when the membrane was exposed to two different metal salts in the sample and internal solutions, respectively. It was observed that the more lipophilic of the cations or anions, the larger the coextraction constants of these ions for the plasticised PVC membrane. The results followed the Hofmeister sequence of ClO₄⁻>NO₃⁻>Br⁻>Cl⁻>OAc⁻ for anions and the ease of extraction of cations was in the order of Cs⁺>K⁺>Na⁺>Li⁺. The proposed method provides a simpler, faster and more convenient method to obtain the coextraction constants of metal salts for plasticised polymeric membranes.     

Polyhydroxylated steroids and other constituents of the soft coral Nephthea chabroli

Polyhydroxylated steroids and other metabolites were isolated from the soft coral Nephthea chabroli collected in South China Sea. The structures of two new compounds were determined to be 24-methylcholesta-9(11), 24(28)-diene-3beta,12alpha,19-triol and 4alpha-methyl-3beta,14beta-dihydroxy-5alpha-ergost-24(28)-en-23-one on the basis of spectroscopic analysis. Cytotoxic activities of the polyhydroxylated sterols were evaluated on prostate carcinoma LNCaP cell line.     

Synthesis,optical and photoconducting properties of platinum poly‐yne polymers functionalized with electron‐donating and electron‐withdrawing bithiazole units

By virtue of the electron‐donating and electron‐withdrawing properties of the thiazole ring, a new soluble rigid‐rod organometallic polymer containing electron‐donating and electron‐withdrawing trans‐[‐Pt‐(PBu₃)₂‐C≡C—R—C≡C—]_n (R = bithiazolediyl) groups is prepared by CuI‐catalyzed dehydrohalogenation. The thermal properties and the optical absorption and photoluminescence spectra of the polymer are reported. The polymer is luminescent with a singlet emission peak at 539 nm and photoconducting in a single‐layer sandwich structure photocell. The optical gap of the polymer is reduced compared to that for the oligothienyl analogue.     

pH and concentration dependence of luminescent characteristics in glass-encapsulated Eu-complex

In order to improve the stability of red phosphor with efficient and high color-purity characteristics under ultraviolet excitation, we encapsulated Eu(TTA)₃phen(tris(2-thenoyltrifluoroacetonato)(1,10-phenanthroline)europium(III)) by sol–gel derived silica glasses and studied their photoluminescence (PL) characteristics. The dependence of pH values in the starting solution revealed that the process condition should be within the modest region with the optimum pH value around 6–7. The PL intensity increased with increasing the concentration of Eu(TTA)₃phen initially, then it showed saturating tendency above 0.6 mol%. An improvement of reliability by the glass encapsulation was exemplified by monitoring the long-term PL intensity under constant UV irradiation. We consider that the glass network carefully prepared by sol–gel process is effective for preventing free oxygen and water from attacking Eu(TTA)₃phen molecule without loss of PL output.     

Synthesis of Bis(Trifluoromethyl)-2,2′- Bipyridines by Nickel Catalysed Homocoupling Reactions

Bis(trifluoromethyl)-2,2′-bipyridines have been synthesized in moderate yields by nickel or palladium catalysed homocoupling of 2-chloro(trifluoromethyl) pyridines.     

Poly(ethylene glycol) enhances the surface activity of a pulmonary surfactant

The primary role of lung surfactant is to reduce surface tension at the air–liquid interface of alveoli during respiration. Axisymmetric drop shape analysis (ADSA) was used to study the effect of poly(ethylene glycol) (PEG) on the rate of surface film formation of a bovine lipid extract surfactant (BLES), a therapeutic lung surfactant preparation. PEG of molecular weights 3350; 8000; 10,000; 35,000; and 300,000 in combination with a BLES mixture of 0.5 mg/mL was studied. The adsorption rate of BLES alone at 0.5 mg/mL was much slower than that of a natural lung surfactant at the same concentration; more than 200 s are required to reach the equilibrium surface tension of 25 mJ/m². PEG, while not surface active itself, enhances the adsorption of BLES to an extent depending on its concentration and molecular weight. These findings suggest that depletion attraction induced by higher molecular weight PEG (in the range of 8000 to 35,000) may be responsible for increasing the adsorption rate of BLES at low concentration. The results provide a basis for using PEG as an additive to BLES to reduce its required concentration in clinical treatment, thus reducing the cost for surfactant replacement therapy.     

HypoGel负载Pd纳米催化剂制备与表征及温和条件下催化Suzuki反应(英文)

A new heterogeneous catalyst composed of Pd nanoparticles immobilized within a HypoG el resin has been prepared in the absence of any ligands using an extensive cross-linking method.This newly developed nanocatalyst was characterized by N_2 adsorption-desorption,X-ray diffraction(XRD),transmission electron microscopy(TEM),scanning electron microscopy(SEM),energy dispersive X-ray(EDX),Fourier transform infrared spectroscopy and inductively coupled plasma-mass spectrometer(ICP-MS)techniques.TEM and XRD results revealed that the Pd nanoparticles were well dispersed with diameters in the range of 4–12 nm,and an average size of about 8 nm.The cross-linked Pd catalyst demonstrated excellent catalytic activity towards the synthesis of a series of biaryl compounds by the reaction of various aryl halides(e.g.,bromides andiodides)with phenylboronic acid in the presence of tetrabutylammonium bromide.ICP-MS analysis indicated that there was only 0.25%weight loss of Pd(0.55±0.02 ppm)from the supported catalyst after the first cycle reaction.Furthermore,the catalyst showed excellent reusability(up to five uses)with consistently high levels of catalytic activity following its recovery by filtration.