Adsorption characteristics of a nanodiamond for oxoacid anions and their application to the selective preconcentration of tungstate in water samples.

A nanodiamond with a mean particle size of 4 nm, which was prepared by the detonation of a nanodiamond, has been characterized and used as a collector for tungstate in water samples. An aqueous solution of nanodiamond was found to be stable over the pH range from 3 to 10. Coagulation of the nanodiamond could be brought about by adding an electrolyte solution. The adsorption characteristics of nanodiamond have been elucidated to be attributable to amino groups on its surface by the elemental-analysis data and the zeta potential measured in weak acid media. The unique adsorption properties of the nanodiamond for oxoacid anions were applied to a selective preconcentration method for tungstate in water samples. An appropriate amount of nanodiamond was added to a sample solution at pH 5 and a calcium chloride solution was added to aggregate nanodiamond. The sample solution was then allowed to stand for 2 h and centrifuged. The nanodiamond was transferred onto a membrane filter, washed with a diluted calcium chloride solution and treated in advance of an ICP-AES measurement by either of the following procedures: (a) redispersion of the nanodiamond into dilute nitric acid with an ultrasonic washer and (b) ashing of the membrane filter and the coagulated nanodiamond at 700 degrees C, followed by a treatment of the ash with hydrochloric and tartaric acids. The average recovery of tungstate from 100-ml artificial river-water was found to be 99% at the 0.25 ppm level with an RSD of 2.2% (n = 3). The concentration factor at present is 10.     

Genotoxicity of dimethylarsinous acid: high induction of tetraploids

Arsenic is a carcinogen in humans. However, neither the mechanism of action nor the ultimate chemical form of arsenic which causes cancer has been clearly defined. Dimethylarsinous acid is detected in the urine of individuals who ingest arsenic‐polluted drinking water. The cytogenetic study in V79 cells using iododimethylarsine, which is easily hydrolyzed to dimethylarsinous acid in water, revealed that dimethylarsinous acid was very cytotoxic (50% growth inhibition concentration; 1.1 ± 0.14 µM ), and either induced aneuploids or a high rate of tetraploids (73% at 2.5 µM ). Dimethylarsinous acid caused mitotic arrest, since the mitotic index at toxic dose (5 µM ) was 13.9%, significantly higher than the control (2.7%). Dimethylarsinous acid significantly increased sister chromatid exchange (SCE) and chromosomal aberrations, most of which were chromatid gaps and chromatid breaks. The cytotoxicity and the activity of dimethylarsinous acid in inducing chromosomal aberration or SCE was as effective as arsenite, but the activity was much lower than that of mitomycin C, which was used as a positive control. The most potent effects of dimethylarsinous acid on the cells were induction of aneuploids, tetraploids and c‐mitosis. Our results suggest that toxicity of dimethylarsinous acid is strongly related to the disturbance of the normal cell cycle. Copyright © 2005 John Wiley & Sons, Ltd.     

Effect of Water Vapor on Benzene Decomposition Using a Nonthermal-Discharge Plasma Reactor

The effect of water vapor on benzene decomposition in air was investigatedusing a nonthermal-discharge plasma reactor packed with ferroelectricmaterials. The conversion of benzene was found to decrease with an increaseof water concentration. On the other hand, the selectivity to CO₂ in thedecomposition products increased with an increase of water concentration. Acomparison between the benzene conversion to CO and CO₂ suggested that COformation was suppressed by water to a greater extent than was CO₂formation. N₂O formation also decreased with an increase of waterconcentration. These results suggest that the activity of oxygen speciesresponsible for the formation of CO and N₂O is reduced by water.     

Fragmentation Characteristics of Deprotonated N-linked Glycopeptides: Influences of Amino Acid Composition and Sequence

Glycopeptide structural analysis using tandem mass spectrometry is becoming a common approach for elucidating site-specific N-glycosylation. The analysis is generally performed in positive-ion mode. Therefore, fragmentation of protonated glycopeptides has been extensively investigated; however, few studies are available on deprotonated glycopeptides, despite the usefulness of negative-ion mode analysis in detecting glycopeptide signals. Here, large sets of glycopeptides derived from well-characterized glycoproteins were investigated to understand the fragmentation behavior of deprotonated N-linked glycopeptides under low-energy collision-induced dissociation (CID) conditions. The fragment ion species were found to be significantly variable depending on their amino acid sequence and could be classified into three types: (i) glycan fragment ions, (ii) glycan-lost fragment ions and their secondary cleavage products, and (iii) fragment ions with intact glycan moiety. The CID spectra of glycopeptides having a short peptide sequence were dominated by type (i) glycan fragments (e.g., ^2,4A_R, ^2,4A_R-1, D, and E ions). These fragments define detailed structural features of the glycan moiety such as branching. For glycopeptides with medium or long peptide sequences, the major fragments were type (ii) ions (e.g., [peptide + ^0,2X₀–H]^– and [peptide–NH₃–H]^–). The appearance of type (iii) ions strongly depended on the peptide sequence, and especially on the presence of Asp, Asn, and Glu. When a glycosylated Asn is located on the C-terminus, an interesting fragment having an Asn residue with intact glycan moiety, [glycan + Asn–36]^–, was abundantly formed. Observed fragments are reasonably explained by a combination of existing fragmentation rules suggested for N-glycans and peptides.

High Performance Photoinitiating Systems for Holography Recording: Need for a Full Control of Primary Processes

Optimization of holography recording in photopolymers was studied from the point of view of a quite general process, that is, the photogeneration of radicals. On the basis of a dye/coinitiator photoinitiating system, the effect of primary events and their relative efficiency was investigated with respect to the final overall properties, such as the diffraction efficiency. Quenching of the dye excited states by the borate salts coinitiators exhibits important differences depending on the dye used (Rose Bengal or Safranine O). Keeping in mind that both singlet and triplet states of the dyes can react, and taking into account the viscosity of the matrix, a method to evaluate the overall quantum yield of radicals released is proposed. It is found that this quantum yield well correlates with the maximum rate of photopolymerization. More interestingly, the dose required to obtain a given diffraction efficiency was found to be also governed by the radical quantum yield, showing that the final property is directly governed by primary events. This shed some light on the efficiency of photochemical pathway to generate radicals for use in organic or polymer areas.     

Linezolid and Vancomycin Decrease the Therapeutic Effect of Methylene Blue‐Photodynamic therapy in a Mouse Model of MRSA Bacterial Arthritis

We previously reported that photodynamic therapy (PDT) using intra‐articular methylene blue (MB) could be used to treat arthritis in mice caused by bioluminescent methicillin‐resistant Staphylococcus aureus (MRSA) either in a therapeutic or in a preventative mode. PDT accumulated neutrophils into the mouse knee via activation of chemoattractants such as inflammatory cytokines or chemokines. In this study, we asked whether PDT combined with antibiotics used for MRSA could provide added benefit in controlling the infection. We compared MB‐PDT alone, systemic administration of either linezolid (LZD) alone or vancomycin (VCM) alone or the combination of PDT with either LZD or VCM. Real‐time noninvasive imaging was used to serially follow the progress of the infection. PDT alone was the most effective, whereas LZD alone was ineffective and VCM alone showed some benefit. Surprisingly the addition of LZD or VCM reduced the therapeutic effect of PDT alone (P < 0.05). Considering that PDT in this mouse model stimulates neutrophils to be antibacterial rather than actively killing the bacteria, we propose that LZD and VCM might inhibit the activation of inflammatory cytokines without eradicating the bacteria, and thereby reduce the therapeutic effect of PDT.     

Asymmetric Synthesis of (S)-4,5-Difluoro-2-Methylindoline

(S)-4,5-Difluoro-2-methylindoline (S)-11 was synthesized effectively by asymmetric reduction of N-[(R)-N-p-toIylsulfonyl]prolinyl-2-(2-oxo)propyl-3,4-difluoroanilide 4b followed by successive methylsulfonylation and intramolecular cyclization.     

Anionic Polymerizations and Copolymerizations of Methacrylates-Reactivity of Monomer and Tacticity of Polymer

The anionic polymerizations and copolymerizations of methacrylates were investigated. The studies were focused on the stereoregularity of the polymers and the relative reactivity of the monomers in relation to the stereospecificity of polymerization.     

Near‐Infrared‐Emitting CdxHg1−xSe Nanorods Fabricated by Ion Exchange in an Aqueous Medium

Whereas CdSe nanorods that are grown in organic solution have a hexagonal wurtzite structure, which is the limiting case for exchange, HgSe is more commonly encountered as a cubic zinc blende system. An exchange process was performed at room temperature and at atmospheric pressure in an aqueous environment after phase transfer of the original CdSe nanorods, which reinforced the tendency for the endpoint of HgSe to be cubic. Consequently, we observed that under ambient conditions, the exchange process terminated with an average composition of only Cd_0.9Hg_0.1Se. Following the changes during the process by optical spectroscopy and high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM), we observed that the Hg²⁺ ions diffused into the rods to a point limited by the formation of stacking faults due to the different lattice structures of the two limiting cases of zinc blende and wurtzite. HAADF‐STEM and energy dispersive spectroscopy analyses also confirmed that the Hg substitution did not occur uniformly throughout the individual nanorods, as Hg‐poor and Hg‐rich regions coexist around the stacking faults. The formation of near‐infrared‐emitting alloyed Cd_xHg_1?xSe nanorods in an aqueous medium highlights the subtle dependence of the ion‐exchange process on the differences in the crystal structures of the two endpoint lattices.     

Microscopic Imaging of Chiral Amino Acids in Agar Gel through Circularly Polarized Luminescence of EuIII Complex

We recently found that [Eu(pda)₂]^? (pda: 1,10‐phenanthroline‐2,9‐dicarboxylic acid), which has an achiral structure in crystals, exhibits circularly polarized luminescence (CPL) in aqueous solutions containing chiral amino acids such as arginine and histidine. CPL measurements were performed for agar gel, which includes an aqueous solution of [Eu(pda)₂]^? and chiral arginine or histidine. The spectral shape, concentration, and pH dependences on CPL intensity in the agar gels were very close to those in aqueous solutions, indicating that the CPL of the Eu^III complex in the agar gels was induced by mechanism similar to that in aqueous solutions. We performed spatially resolved CPL measurements using a laboratory‐built microscopic CPL spectroscopic system for agar‐gel samples, where d ‐ and l ‐ amino acids were separately dispersed. We successfully recorded CPL imaging maps showing spatial dispersions of d ‐ and l ‐amino acid in the agar gels.