Simultaneous chiral analysis of methamphetamine and related compounds by capillary electrophoresis/mass spectrometry using anionic cyclodextrin.

A capillary electrophoresis/mass spectrometry method for the simultaneous chiral analysis of enantiomers of methamphetamine (MA), amphetamine (AP), dimethylamphetamine (DMA), ephedrine (EP), norephedrine (NE) and methylephedrine (ME) in urine has been developed. The background electrolyte was 1 M formic acid (pH 1.7). Using 0.85 mM heptakis(2,6-diacethyl-6-sulfato)-beta-cyclodextrin as the chiral selector, the 12 enantiomers were completely separated within 25 min. The detection limits were 0.01 microg mL(-1) for the enantiomers of MA, AP, DMA, EP and ME, and 0.02 microg mL(-1) for the enantiomers of NE using selected ion monitoring. The reproducibilities of within-run (n = 4) for the migration times and peak areas of the standard mixture were under 0.58% and 7.83%, respectively. The calibration curves of the peak areas of the 12 enantiomers were linear in the range of 0.05 - 10 microg mL(-1). This method was applicable to the analysis of urine samples.     

Synthesis and photo DNA-damaging activities of fluoroquinolone analogues

Fluoroquinolone (FLQ) analogues were synthesized and their DNA photocleaving abilities were assayed. The photo-bioactivities of the fluoroquinolones were dependent on the carbonyl moieties attached to quinolone ring.     

Analysis of gardenia blue in foods by thin-layer chromatography

In the present study, a thin-layer chromatography (TLC) method for the analysis of gardenia blue was described. Gardenia blue is obtained from the fruits of Gardenia augusta Merrill or Gardenia jasminoides Ellis. Recently, gardenia blue has frequently been used in Japan as a natural coloring in various foods. However, the structural characterization of gardenia blue components has not been yet clarified and even chromatographic separation of the components has not been reported. Synthetic colors in foods are generally analyzed by TLC; so, we therefore investigated the analysis of gardenia blue in foods with TLC. We established two TLC conditions; reversed phase C-18 TLC using a solvent system of aqueous 0.2% TFA–acetonitrile–ethanol (1:2:3) and TLC on cellulose plate using a solvent system consisting of acetone–3-methyl-1-butanol–water (6:5:5). Both conditions yielded three well-delineated spots with good separation. We applied these separations to the analyses of gardenia blue in coloring matter preparations from different manufacturers and in foods on the market. After the gardenia blue was extracted from the samples with water, the extract was evaporated and the residue was dissolved in water–methanol (1:1). Aliquots of the dissolved solutions were then applied to TLC and their chromatographic behaviors were observed. Each preparation showed characteristic spot patterns depending on the manufacturers. The R_f values of the separated spots when extracted from foods are slightly different from the R_f values of the spots observed for standards, and we were thus able to identify the manufacturers using the spot pattern of gardenia blue. The present study is considered to be useful for the establishment of a method of analysis for gardenia blue in coloring preparations and foods.     

Co6H8(PiPr3)6: A Cobalt Octahedron with Face‐Capping Hydrides

A square‐planar Co₄ amide cluster, Co₄{N(SiMe₃)₂}₄ ( 2 ), and an octahedral Co₆ hydride cluster, Co₆H₈(PⁱPr₃)₆ ( 4 ), were obtained from metathesis‐type amide to hydride exchange reactions of a Co^II amide complex with pinacolborane (HBpin) in the absence/presence of PⁱPr₃. The crystal structure of 4 revealed face‐capping hydrides on each triangular [Co₃] face, while the formal Co^II₂Co^I₄ oxidation state of 4 indicated a reduction of the cobalt centers during the assembly process. Cluster 4 catalyzes the hydrosilylation of 2‐cyclohexen‐1‐one favoring the conjugate reduction. Generation of the catalytically reactive Co cluster species was indicated by a trapping experiment with a chiral chelating agent.     

Spiroborate-Based Host Materials with High Triplet Energies and Ambipolar Charge-Transport Properties

Organic light-emitting diodes (OLEDs) receive considerable attention because of their commercial use in flat panel displays. Herein, highly efficient spiroborate-based host materials are reported for use in blue OLEDs. Our designed spiroborates ( SBOX ) were simple to synthesize and exhibited high triplet excitation energies, narrow S-T gaps, and balanced charge carrier mobilities. A blue OLED containing one of the designed spiroborates, SBON , as a host exhibited a high external quantum efficiency (27.6 %) and low turn-on voltage (3.7 V) compared to those observed using 3,3′-di(9H-carbazol-9-yl)-1,1′-biphenyl (17.6 % and 4.5 V, respectively), indicating their potential as host materials in OLEDs.     

Temperature-controlled photooxygenation with polymer nanocapsules encapsulating an organic photosensitizer

A cross-linked poly- N-isopropylacrylamide (polyNIPAM) nanocapsule, TH@PC, containing thionine (TH), an organic photosensitizer, has been synthesized. This capsulated polymeric photosensitizer promotes a singlet oxygen oxygenation ( (1)O 2) accurately controlled by temperature: it shows high oxygenation activity at low temperature, but shows activity decrease with a rise in temperature, resulting in almost zero activity at >40 degrees C. The clear on-off activity control is driven by a heat-induced structure change of the capsule from the swollen single capsule to contracted state, and then to aggregate, behaving as an intelligent (1)O 2 filter. At low temperature, the capsule exists as the swollen single capsule, which allows (1)O 2 diffusion to bulk water, resulting in high oxygenation activity. A rise in temperature leads to contraction of the capsule, reducing the mesh size of the capsule wall. This suppresses (1)O 2 diffusion to bulk water and shows decreased activity. Intercapsule aggregation at >30 degrees C further suppresses (1)O 2 diffusion and shows almost no activity. The capsule promotes reversible activity control regardless of the heating/cooling process and can be reused with a simple recovery process.     

Revisiting silicate substituted hydroxyapatite by solid-state NMR

Silicon-substituted hydroxyapatite (Si-HAp) has shown promising properties such as high-bone remodeling around implants. So far, the techniques used for the structural characterization of the Si-HAp have given indirect evidence of the presence of silicon inside the structure (by X-ray and neutron diffraction). In this paper, we focus on Si-HAp derivatives obtained by a precipitation method (widely described in the literature). We demonstrate here by solid-state NMR spectroscopy that only a fraction of the silicon atoms are incorporated into the HAp lattice in the form of Q(0) (SiO(4) (4-)) species, for 4.6 wt% Si-HAp. A large amount of silicate units are located outside the HAp structure and correspond to silica-gel units. All results were established through (29)Si MAS, (1)H -->(29)Si CP MAS and T(1)rho((1)H) edited (1)H -->(29)Si CP MAS experiments. This last pulse scheme acted as a powerful editing sequence, leading to unambiguous spectroscopic conclusions, concerning the location of the SiO(4) (4-) moieties.     

Biological selection of peptides for poly(l-lactide) substrates

Short peptides that recognize the alpha form of poly( l-lactide) (PLLA) crystalline films were identified from a phage-displayed peptide library. An enzyme-linked immunosorbent assay (ELISA) revealed that the apparent binding constants of the phage clones for the alpha form of PLLA were greater than those of the unselected phage library. The specificity index for the alpha form of PLLA referred to a structurally similar atactic poly(methyl methacrylate) (at-PMMA), supporting the alpha form of PLLA specific binding of the selected phage. Amino acid residues with proton-donor lateral groups and hydrophobic alkyl groups were relatively enriched in a sequence of heptapeptides on the specific phage clones, thereby suggesting the presence of hydrogen bonding as well as hydrophobic interactions between the alpha form of PLLA and the peptides. Surface plasmon resonance (SPR) analysis revealed that the binding constant of the freed c22 heptapeptide (Gln-Leu-Met-His-Asp-Tyr-Arg) for the alpha form of PLLA was greater than those for reference at-PMMA, amorphous PLLA, and the beta form of PLLA. It was found that c22 peptide can recognize slight differences in PLLA polymorphs such as a crystalline state and an arrangement of PLLA functional groups.     

Photocatalytic conversion of methane

Various efforts have been carried out to convert methane to more useful chemicals and hydrogen. However, due to its high stability, high energy is usually consumed for its conversion, which still remains as a problem to be solved. Recently, photocatalysis has been proposed to be one of the answers to break the thermodynamic barrier. This tutorial review provides a brief history about developments in the methane conversion and specially highlights the developments in the photocatalytic conversion of methane, such as methane coupling and methane conversion with other molecules.     

Chiral bis(2-oxazolinyl)xanthene (xabox)/transition-metal complexes catalyzed 1,3-dipolar cycloaddition reactions and Diels-Alder reactions

A series of chiral 4,5-bis(2-oxazolinyl)-(2,7-di-tert-butyl-9,9-dimethyl)-9H-xanthenes (xabox) and their transition-metal complexes were synthesized. The X-ray analysis of xabox-RhCl₃ complex shows a unique facial type structure. Xabox-Bn-Mn(II) and xabox-Bn-Mg(II) complexes were found to be efficient catalysts in nitrone 1,3-dipolar cycloaddition (1,3-D.C.) reaction resulting in good to excellent enantioselectivities ranging from 96:4 to >99:1of endo/exo ratio and 91-96% ee for the endo adduct. The correlation between enantiomeric excess of the ligand and the product in the nitrone 1,3-D.C. reaction shows a clear linear relationship, which suggests xabox-metal catalyst worked as a single molecular catalyst. In addition, xabox-i-Pr-Mn(II) complex was also found to be an active catalyst for Diels-Alder (D-A) reaction of acryloyloxazolidinone and cyclopentadiene affording the corresponding cycloadduct in quantitative yield along with 82% ee and 98:2 endo/exo ratio.