Electrochemiluminescence of Ru(II) complexes immobilized on a magnetic microbead surface: distribution of magnetic microbeads on the electrode surface and effect of azide ion

The electrochemiluminescence (ECL) of magnetic microbeads modified with tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) was studied in the presence of tri-n-propylamine (TPA) to develop highly sensitive ECL detection system, where the employed microbead has a diameter of 4.5 microm. The ECL signal of the [Ru(bpy)3]2+ derivative-modified magnetic microbeads was found to be affected by the geometrical distribution of the magnetic microbeads on the electrode surface. The ECL peak intensity increased with increasing the number of the beads on the electrode surfaces up to 1.6 x 10(6) beads cm(-2), although above 1.6 x 10(6) beads cm(-2), it decreased. The ECL decrease arises from the physical prevention of the ECL from reaching the photomultiplier tube by the excessive beads. The observed peak ECL signal of the [Ru(bpy)3]2+ derivative-modified magnetic microbeads in the presence of NaN3, which serves as a preservative substance, mainly appeared at a potential of +0.90 V vs Ag/AgCl where [Ru(bpy)3]2+ is hardly oxidized, whereas the ECL signal in the absence of NaN3 appeared at a potential of +1.15 V. The presence of NaN3 on the electrode surface retards formation of an oxide layer on the electrode surfaces and promotes TPA oxidation. The ECL response at +0.90 V was mainly attributed to ECL reaction of excited-state [Ru(bpy)3]2+* formed by oxidation of [Ru(bpy)3]+ with TPA radical cation, where the [Ru(bpy)3]+ was generated by reduction of [Ru(bpy)3]2+ with TPA radical.     

Simple one-step extraction and cleanup by pressurized liquid extraction for gas chromatographic-mass spectrometric determination of pesticides in green leafy vegetables

A simple one-step extraction and cleanup using a pressurized liquid extraction method was developed for the gas chromatographic-mass spectrometric determination of pesticides in vegetables. The pressurized liquid extraction conditions were optimized and cleanup agents were evaluated. The investigated pesticides included six insecticides, chlorpyrifos methyl, pirimiphos-methyl, malathion, chlorpyrifos, O-ethyl O-4-nitrophenylphenyl phosphonothioate (EPN) and permethrins, a fungicide, isoprothiolane, and a herbicides, thiobencarb. The cleanup agent and a mixture of the vegetable and anhydrous sodium sulfate were separately packed in an extraction vessel. A transparent and colorless extract was obtained using graphitized carbon as the cleanup agent. The overall recoveries were 71-103% and the relative standard deviations ranged from 5.6 to 24%. The limit of detection values were 3-8 microg kg(-1). This method was successfully applied to green leafy vegetables.     

Phthalocyanine-based fluorescence probes for detecting ascorbic acid: phthalocyaninatosilicon covalently linked to TEMPO radicals

We have applied phthalocyaninatosilicon (SiPc) covalently linked to one or two tetramethyl-1-piperidinyloxyl (TEMPO) radicals as fluorescence probes for detecting ascorbic acid in biological systems.     

Direct synthesis of cup-stacked carbon nanofiber microspheres by the catalytic pyrolysis of poly(ethylene glycol)

Uniformly sized microspheres tangled with cup-stacked carbon nanofibers (CSCNFs) were directly synthesized by the pyrolysis of poly(ethylene glycol) (PEG) with a nickel catalyst. A PEG/Ni membrane was prepared on a silicon wafer surface by heating it to 750 °C at a heating rate of 15 °C min(-1). The wafer was heated to a temperature of 400 °C and was held at that temperature for 1 h before raising the temperature to 750 °C for 10 min to form the CSCNF microspheres. The final CSCNF microspheres and the intermediates were evaluated using scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, and Raman spectroscopy to elucidate the growth mechanism. Furthermore, the CSCNF microspheres were successfully dispersed and maintained their spherical shape in an aqueous solution containing 0.5% Nafion. The CSCNF microspheres have the potential to work as a sophisticated carrier with high adsorption and fast electron-transfer exchange properties based on the graphene edges of the nanofiber surface.     

Wave localization in randomly disordered layered three-component phononic crystals with thermal effects

In this paper, the propagation and localization of elastic waves in randomly disordered layered three-component phononic crystals with thermal effects are studied. The transfer matrix is obtained by applying the continuity conditions between three consecutive sub-cells. Based on the transfer matrix method and Bloch theory, the expressions of the localization factor and dispersion relation are presented. The relation between the localization factors and dispersion curves is discussed. Numerical simulations are performed to investigate the influences of the incident angle on band structures of ordered phononic crystals. For the randomly disordered ones, disorders of structural thickness ratios and Lamé constants are considered. The incident angles, disorder degrees, thickness ratios, Lamé constants and temperature changes have prominent effects on wave localization phenomena in three-component systems. Furthermore, it can be observed that stopbands locate in very low-frequency regions. The localization factor is an effective way to investigate randomly disordered phononic crystals in which the band structure cannot be described.     

Simultaneous determination of preservatives in beverages,vinegar, aqueous sauces,and quasi-drug drinks by stir-bar sorptive extraction (SBSE) and thermal desorption GC-MS

A method for the simultaneous determination of seven preservatives - sorbic acid, benzoic acid, and p-hydroxybenzoic acid ethyl, isopropyl, propyl, isobutyl, and butyl esters - in beverages, vinegar, aqueous sauces, and quasi-drug drinks has been developed using the stir-bar sorptive extraction technique then thermal desorption GC-MS analysis. The extraction conditions - pH, sample volume, extraction temperature, salt addition, and extraction time - were examined. d5-Benzoic acid and p-hydroxybenzoic acid sec-butyl ester were added as surrogate internal standards to compensate for the effect of sample matrix and coexisting analytes on the sorptive extraction. The linearity of the method was good over the concentration range from 1 to 1000 microg mL(-1) for sorbic acid, 10-1000 microg mL(-1) for benzoic acid, and 0.1-100 microg mL(-1) for p-hydroxybenzoic acid ethyl, isopropyl, propyl, isobutyl, and butyl esters, and the correlation coefficients were higher than 0.9984. The limit of detection ranged from 0.015 to 3.3 microg mL(-1). The recoveries (95-105%) and precision (RSD: 0.86-6.0%) of the method were examined by analyzing a sparkling soft drink, white wine, red wine, balsamic vinegar, soy sauce, and quasi-drug drink samples fortified at the 5 to 50 microg mL(-1) level.     

Control of the morphology of nanostructured particles prepared by the spray drying of a nanoparticle sol

The control of the morphology of nanostructured particles prepared by the spray drying of nanoparticle sol was investigated experimentally and the results are qualitatively explained based on available theory. A theoretical analysis indicates that the structural stability of the droplet and the hydrodynamic effects during the drying process play important roles in controlling the morphology of the resulting particles. The size of the sol in the droplet, droplet size, viscosity of droplet, drying temperature, gas flow rate, and addition of surfactant are all crucial parameters that affect the morphology of particles. Experimentally, nanostructured silica particles were prepared from a nanosize silica sol under various preparation conditions. Doughnut-shaped particles can be produced when the droplet size is large, in conjunction with high temperature, high gas flow rate and in the presence of an added surfactant. Appropriate choice of the spray drying method permits control of the particle size and shape, ranging from spheres to ellipsoids as well as doughnut-shaped particles by varying the preparation conditions. The results open a new route to controlling the formation of a wide variety of nanostructured particles.     

Selectable one-dimensional or two-dimensional gas chromatography–mass spectrometry with simultaneous olfactometry or element-specific detection

A novel selectable one-dimensional (¹D) or two-dimensional (²D) gas chromatography–mass spectrometry (selectable ¹D/²D GC–MS) system with selective detection was developed by using capillary flow technology and low thermal mass GC (LTM-GC). The main advantages of this system are the simple and fast selection of ¹D GC–MS or ²D GC–MS operation without any instrumental set-up change (e.g.²D GC–MS can be run just after ¹D GC–MS run), and simultaneous mass spectrometric and olfactometry or element-specific detection for both ¹D and ²D separation to assure selection of a heart-cut region and correct identification of compounds of interest. The feasibility and benefit of the proposed system with selective detection, e.g. olfactometry, nitrogen phosphorus detection (NPD), and pulsed flame photometric detection (PFPD), was demonstrated with an identification of trace amounts of aroma components in beverages (beer and coffee). Using stir bar sorptive extraction (SBSE) and selectable ¹D/²D GC–Olfactometry/MS on a beer sample, β-damascenone could be determined at 1.9 ng mL⁻¹ (RSD 3.1%, n = 6) as a potent aroma compound. In a coffee sample, two odor active compounds were clearly resolved from a 4.2 s heart-cut and were assigned probable identifications as 4,5-dimethyl thiazole and dimethyl trisulfide based on a NIST library search, dual linear retention indices (dual LRI) and elemental information obtained by SBSE in combination with selectable ¹D/²D GC–NPD/PFPD/MS.     

Persistence of pierisin-1 activities in the adult cabbage white butterfly,Pieris rapae,during storage after killing

Crude extracts from larvae, pupae and adults of cabbage white butterflies, Pieris rapae and Pieris brassicae, and green-veined butterfly, Pieris napi, have an ability to induce apoptosis in the human cancer cell lines. As apoptosis inducing protein, pierisin-1 and -2 have been isolated from pupae of P. rapae and P. brassicae, respectively, and shown to exhibit DNA ADP-ribosylating activity. Although the highest activity was detected in the late phase of larvae and early phase of pupae, certain activity was found in adult butterflies. In order to investigate distribution of substances having pierisin-like activities in butterflies, many species need to be analyzed. However, fresh samples of larvae and pupae are hard to obtain, especially if samples are of scarce species or from overseas. The usage of adult butterflies is practical to examine the distribution of pierisin-like activity in many species. In this study, we examined the cytotoxicity of crude extracts from adults of P. rapae against HeLa cells and DNA ADP-ribosylation ability during storage for 1, 2 and 8 weeks at room temperature after killing adult butterflies after eclosion. Body weights decreased to 18% for 8 weeks through dehydration. Cytotoxicity of samples from butterfly kept for 1, 2 and 8 weeks decreased to 47, 39 and 22%, respectively, of the control value. DNA ADP-ribosylating activity of the samples also decreased to 30, 27 and 23%. Similar reduction was observed on western blot analysis with anti-pierisin-1 antibody. Fortunately, these results suggest that cytotoxic and DNA ADP-ribosylating activity persists to some extent in the body after killing, at least for 8 weeks. Thus, butterfly adult samples kept for two months at room temperature can still be useful for examination of the presence of substance having pierisin-like activity.     

Reconstruction of glycan chains of glycoprotein : Branching mannopentaoside and mannohexaoside

Synthetic routes to the branching mannopentaoside 4 and mannohexaoside 5 are described employing properly protected mannobioside 13 as a key intermediate.