Aqueous synthesis of single-crystalline ZnO prisms on graphite substrates

Morphological change from ZnO films to ZnO prisms is achieved by an electrochemical deposition method on a graphite substrate at the low temperature of 70 °C. The ZnO prisms, which are prism-shaped ZnO rods with a wide diameter, have hexagonal well-defined crystallographic facets. The ZnO prism is 1.4 μm in diameter and 1.3 μm in length. Transmission electron microscopy and electron diffraction patterns indicate that the ZnO prisms have a single-crystalline wurtzite structure with c-axis orientation. Additionally, cathodoluminescence shows that the annealed ZnO prisms in nitrogen gas emit a significant level of near-band-edge ultraviolet light.     

High-pressure synthesis, crystal structures, and characterization of CdVO3−δ and solid solutions CdVO3-NaVO3

CdVO_3−δ and solid solutions of Cd_1−xNa_xVO₃ with the GdFeO₃-type perovskite structure were prepared using a high-pressure (6 GPa) and high-temperature technique. No significant oxygen and cation deficiency was found in CdVO₃. Cd_1−xNa_xVO₃ are formed in the compositional range of 0?x?0.2. CdVO₃ and Cd_1−xNa_xVO₃ demonstrate metallic conductivity and Pauli paramagnetism between 2 and 300 K. A large electronic contribution to the specific heat (γ=13.4 and ) for CdVO₃ and Cd_0.8Na_0.2VO₃, respectively) was observed at low temperatures due to the strongly correlated electrons. Crystal structures of CdVO₃ and Cd_0.8Na_0.2VO₃ were refined by X-ray powder diffraction: space group Pnma; Z=4; , , and for CdVO₃ and , , and for Cd_0.8Na_0.2VO₃.     

Synthesis of 2-azaindolizines by using an iodine-mediated oxidative desulfurization promoted cyclization of N-2-pyridylmethyl thioamides and an investigation of their photophysical properties

Iodine-mediated, oxidative desulfurization promoted cyclization of N-2-pyridylmethyl thioamides serves as an efficient and versatile method for the preparation of 2-azaindolizines (imidazo[1,5-a]pyridines) and rare 2-azaindolizine sulfur-bridged dimers. The 2-azaindolizines prepared in this manner are readily converted to a variety of fluorescent compounds by using transition-metal-catalyzed cross-coupling reactions. [reaction: see text].     

Determination of spinosad in vegetables and fruits by high-performance liquid chromatography with UV and mass spectrometric detection after gel permeation chromatography and solid-phase extraction cleanup on a 2-layered column

A simple and reliable method was developed for the determination of spinosyns A and D, the active ingredients of spinosad, in vegetables and fruits, by high-performance liquid chromatography with UV detection (HPLC-UV) and confirmation by mass spectrometry (MS); the method uses selected gel permeation chromatography (GPC) and a 2-layered column for solid-phase extraction system. An aliquot of the crude sample extract obtained by acetonitrile extraction is loaded into the GPC system. The fraction containing spinosyns A and D is selectively collected and loaded directly onto a 2-layered column consisting of graphitized carbon (upper layer) and cyclohexyl-bonded silica gel (lower layer). After the column is washed with the GPC mobile phase acetone-cyclohexane (3 + 7), the column is eluted with acetonitrile containing 2% triethylamine. The eluate is used for HPLC-UV/MS analysis. Average recoveries from fortified cabbage, green perilla, fig, and strawberry at analyte concentrations of 0.05 and 0.25 microg/g were >85%, and the relative standard deviations were <9%. The detection limits for spinosyns A and D in green perilla were 0.005 microg/g by UV detection and 0.001 microg/g by MS detection.     

Effective detection of peptides containing cysteine sulfonic acid using matrix-assisted laser desorption/ionization and laser desorption/ionization on porous silicon mass spectrometry

Cysteine sulfonic acid-containing peptides, being typical acidic peptides, exhibit low response in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. In this study, matrix conditions and the effect of diammonium hydrogencitrate (DAHC) as additive were investigated for ionization of cysteine sulfonic acid-containing peptides in MALDI. A matrix-free ionization method, desorption/ionization on porous silicon (DIOS), was also utilized to evaluate the effect of DAHC. When equimolar three-component mixtures of peptides carrying free cysteine, cysteine sulfonic acid, and carbamidomethyl cysteine were measured by MALDI using a common matrix, alpha-cyano-4-hydroxycinnamic acid (CHCA), no signal corresponding to cysteine sulfonic acid-containing peptide could be observed in the mass spectrum. However, by addition of DAHC to CHCA, the peaks of cysteine sulfonic acid-containing peptides were successfully observed, as well as when using 2,4,6-trihydroxyacetophenone (THAP) and 2,6-dihydroxyacetophenone with DAHC. In the DIOS mass spectra of these analytes, the use of DAHC also enhanced the peak intensity of the cysteine sulfonic acid-containing peptides. On the basis of studies with these model peptides, tryptic digests of oxidized peroxiredoxin 6 were examined as a complex peptide mixture by MALDI and DIOS. In MALDI, the peaks of cysteine sulfonic acid-containing peptides were observed when using THAP/DAHC as the matrix, but this was not so with CHCA. In DIOS, the signal from cysteine sulfonic acid-containing peptides was suppressed; however, the use of DAHC significantly enhanced the signal intensity with an increase in the number of observed peptides and increased signal-to-noise ratio in the DIOS spectra. The results show that DAHC in the matrix or on the DIOS chip decreases discrimination and suppression effects in addition to suppressing alkali-adduct ions, which leads to a beneficial effect on protonation of peptides containing cysteine sulfonic acid.     

Oligoresorcinols fold into double helices in water

We report the first double helices with a controlled helicity in water based on oligoresorcinols as a new, simplest water-soluble structural motif. The molecular strands of the oligoresorcinols self-assemble into double helices with the aid of aromatic interactions in water as characterized by 1H NMR and absorption spectroscopies together with the X-ray crystallographic study of the pentamer. The double helix formation is sensitive to the chain length, solvent composition, and temperature. Moreover, a bias in the screw sense of the double helices was achieved by covalently attaching chiral substituents to both ends of the molecular strands.     

Control of the optical properties of quantum dots by surface coating with calix[n]arene carboxylic acids

A new method for the control of the optical properties of quantum dots (QDs) has been developed using calix[n]arene carboxylic acids (1-3) as surface coating agents for QDs. The calixarene coating of CdSe/ZnS QDs was easily performed in tetrahydrofuran at room temperature. Deprotonation of the carboxyl groups of the calixarene derivatives surrounding the QDs resulted in highly fluorescent water-soluble QDs. The emission peak of the calixarene-coated QDs shifted to longer wavelengths depending on the oligomer size of the calix[n]arene derivative used for the surface coating. Although the red shift of the emission peak decreases with the increase in the particle size of QDs, this surface coating method is useful for the preparation of multi-colored water-soluble QDs from a single-colored hydrophobic QD.     

Studies on the constituents of Scutellaria species (XXII). Constituents of the roots of Scutellaria amabilis HARA

From the roots of Scutellaria amabilis HARA, eleven new flavonoids, 5,7,2'-trihydroxy-8-methoxyflavone 7-O-beta-D-glucopyranoside, 5,7,2'-trihydroxy-8-methoxyflavone 2'-O-beta-D-glucopyranoside, 5,7-dihydroxy-8,2'-dimethoxyflavone 7-O-beta-D-glucopyranoside, 5,7,2'-trihydroxyflavone 2'-O-beta-D-glucopyranoside, 5,7,2',5'-tetrahydroxyflavone 7-O-beta-D-glucuronopyranoside, (2S)-5,7,2',5'-tetrahydroxyflavanone, (2S)-5,7,2',5'-tetrahydroxyflavanone 7-O-beta-D-glucopyranoside, (2S)-5,7,2',5'-tetrahydroxyflavanone 7-O-beta-D-glucuronopyranoside, (2S)-7,2'-dihydroxy-5-methoxyflavanone 7-O-beta-D-glucuronopyranoside, (I-2S)-I-5,II-5,I-7,II-7,I-2',II-2',II-5'-heptahydroxy-[I-6,II-6']-flavanonylflavone and (I-2S)-I-5,II-5,I-7,II-7,I-2',II-2',I-5',II-5'-octahydroxy-[I-6,II-6']-flavanonylflavone, were isolated, together with ten known flavonoids, wogonin (5,7-dihydroxy-8-methoxyflavone), 5,7-dihydroxy-8,2'-dimethoxyflavone, (2S)-5,7,2'-trihydroxyflavanone, scutevulin (5,7,2'-trihydroxy-8-methoxyflavone), 5,7,4'-trihydroxy-8-methoxyflavone, alpinetin ((2S)-7-hydroxy-5-methoxyflavanone), 5,7,2'-trihydroxyflavone, 5,7,2',5'-tetrahydroxyflavone, (2S)-7,2'-dihydroxy-5-methoxyflavanone and 5,7-dihydroxy-8,2'-dimethoxyflavone 7-O-beta-D-glucuronopyranoside. The structures were determined on the basis of chemical and spectral data.     

Ratiometric fluorescence detection of a tag fused protein using the dual-emission artificial molecular probe

We have successfully developed a ratiometric detection system for protein of interest using the complementary recognition pair of the tetra-aspartate peptide tag and the SNARF-appended Zn(ii)-DpaTyr probe.