Stereoselective Isomerization of Unsymmetrical Diallyl Ethers to Allyl (E)-Vinyl Ethers by a Cationic Iridium Catalyst

The stereoselective isomerization of unsymmetrical diallyl ethers to allyl (E)-vinyl ethers was carried out in the presence of a cationic iridium(I) catalyst. The catalyst prepared in situ by treating [Ir(cod)(PPh₂Me)₂]PF₆ with hydrogen was found to be an excellent catalyst to selectively isomerize the less substituted allyl group to an (E)-vinyl ether.     

Structural transition of pentacene monolayer on Ga bilayer: From brick-wall structure to herringbone pattern of molecular dimers

Utilizing the substrate of Ga bilayer grown on Si(1 1 1)-√3 × √3-Ga, we have investigated the structural transition of pentacene monolayer induced by moderate annealing. Short-range ordering has been observed in the monolayer pentacene deposited at room temperature. Annealing the sample at ∼350 K produced ordered pentacene monolayer with the “brick-wall” adsorption pattern. The STM images with sub-molecular resolution revealed that the orbital symmetry of the HOMO is reduced from D_2h to C_2v, due to the substrate-molecule interaction, while the deeper HOMO-1 orbital remains intact. Further annealing at ∼400 K led to the formation of molecular dimers as well as the structural transition from “brick-wall” packing to “herringbone” pattern.     

Dynamical stability of the BRS supersymmetry and the Gribov problem

The stability of the Becchi-Rouet-Stora supersymmetry is studied on the basis of a simple non-gauge model invariant under BRS supersymmetry. The Nambu-Goldstone theorem is stated and the spontaneous breakdown of the BRS supersymmetry is illustrated by the above non-gauge model. This indicates that the dynamical stability of BRS supersymmetry in non-abelian gauge theories should also be carefully examined, if one takes the Faddeev-Popov lagrangian as a basis of the formal canonical treatment. We show that a better understanding of the Gribov problem is required to establish the stability of the BRS supersymmetry in non-abelian gauge theories to non-perturbative accuracy.     

Stereoregulation in the radical polymerization of vinyl esters

To determine favorable conditions for preparation of syndiotactic polymers, various factors which influence the stereoregulation of vinyl esters were studied. In bulk polymerizations, vinyl esters having bulky substituents or polar substituents were found most suitable for the syndiotactic polymerization. Tri-n-butylborane and azobisisobutylonitrile showed some difference in stereoregulation, the magnitude of the difference being dependent on the type of vinyl ester used. Solvents were found to have a significant effect on stereoregulation. Some gave higher syndiotacticity than bulk and some gave lower syndiotacticity.     

Design and synthesis of highly sensitive fluorogenic substrates for glutathione S-transferase and application for activity imaging in living cells

Here we report the development of fluorogenic substrates for glutathione S-transferase (GST), a multigene-family enzyme mainly involved in detoxification of endogenous and exogenous compounds, including drug metabolism. GST is often overexpressed in a variety of malignancies and is involved in the development of resistance to various anticancer drugs. Despite the medical significance of this enzyme, no practical fluorogenic substrates for fluorescence imaging of GST activity or for high-throughput screening of GST inhibitors are yet available. So, we set out to develop new fluorogenic substrates for GST. In preliminary studies, we found that 3,4-dinitrobenzanilide (NNBA) is a specific substrate for GST and established the mechanisms of its glutathionylation and denitration. Using these results as a basis for off/on control of fluorescence, we designed and synthesized new fluorogenic substrates, DNAFs, and a cell membrane-permeable variant, DNAT-Me. These fluorogenic substrates provide a dramatic fluorescence increase upon GST-catalyzed glutathionylation and have excellent kinetic parameters for the present purpose. We were able to detect nuclear localization of GSH/GST activity in HuCCT1 cell lines with the use of DNAT-Me. These results indicate that the newly developed fluorogenic substrates should be useful not only for high-throughput GST-inhibitor screening but also for studies on the mechanisms of drug resistance in cancer cells.     

Facile fabrication of silver nanofin array via electroless plating

The fabrication of metallic nanostructures is one of the main issues in nanotechnology. This article describes the fabrication of a silver nanofin array by combining microlithography, electroless plating, and an etching technique. Fabricated Ag nanofins have a high aspect ratio (height/width = 10, width = 60 nm, height = 600 nm), and their widths and heights can be controlled by the period of electroless plating and the height of the original line pattern. An isolated Ag nanofin was proven to show metallic electrical conductivity. The current process provides a rapid and shape-designable fabrication method of metallic nanostructures.     

Increased levels of 8-hydroxy-2'-deoxyguanosine in Drosophila larval DNA after irradiation with 364-nm laser light but not with X-rays

Exposure to UVA light causes damage to cellular components such as DNA and membrane lipids. We showed previously that UVA irradiation can induce mutations in Drosophila larvae and that the major lesions responsible for mutations were not thymidine dimers when wavelengths tested became longer. The use of a longer wavelength with UVA laser apparatus (364 nm) has made it possible to test the effects of this powerful light in biological organisms. In the present study, we irradiated third instar larvae of the urate-null Drosophila mutant strain y v ma-l, which is sensitive to oxidative stress, and compared the effects of 364 nm light irradiation with the effects of X-rays. To assay viability, some of the larvae were kept at 25 degrees C until they eclosed in order to obtain a measure of viability. The remaining larvae were used to measure the amount of 8-hydroxydeoxyguanosine (8-OHdG), an indicator of oxidative DNA damage. The amount of 8-OHdG increased and viability decreased in response to increased UV dose in both the y v ma-l and wild-type strains. With irradiation of 600 kJ m(-2), 8-OHdG/10(6)dG was 7.2 +/- 3.2 and 6.2 +/- 2.0 in y v ma-l and wild-type strains, respectively, whereas the respective levels were 2.2 +/- 0.6 and 2.3 +/- 0.8 without irradiation. Our results indicated that irradiation with a 364-nm laser light caused significant oxidative damage in Drosophila larval DNA; however, induction of the damage was not prohibited by urate. To the best of our knowledge, this is the first report of a study in whole animals that shows increased levels of 8-OHdG in response to 364-nm UVA. X-ray ionizing radiation is also thought to generate reactive oxygen species in irradiated cells. We found that the amount of 8-OHdG in DNA following X-ray radiation remained unchanged in both strains, though survival rates were affected. X-ray-generated oxidative damage in Drosophila cells was followed by cell death but not DNA base oxidation, and the damage was suppressed by urate. The overall results suggest significant differences in the major in vivo oxidative damage caused by 364-nm light and X-rays.     

Self-organization of surfactant-metal-ion complex nanofibers on graphite surfaces and their application to fibrously concentrated platinum nanoparticle formation

We report the fabrication of self-organized surfactant nanofibers containing platinum ions on a highly oriented pyrolytic graphite (HOPG) surface from mixed solutions of hexadecyltrimethylammonium hydroxide (C16TAOH) and hydrogen hexachloroplatinate (IV) (H2PtCl6). The fibrous surfactant self-assembly was stable in air, even after being soaked in water, in contrast to surfactant hemicylindrical micelles, which are stable only at graphite/solution interfaces. The results show that the graphite surface served as an essential template for the specific formation of fibrous surfactant self-assemblies. In addition, when surfactant nanofibers containing metal ions were treated with hydrazine, platinum nanoparticles concentrated in the nanofibers formed on the HOPG surface. We also prepared surfactant nanofibers containing gold ions on HOPG surfaces and formed gold nanoparticles in the nanofibers.     

Larch (Larix kaempferi) xylem parenchyma cells respond to subfreezing temperature by deep supercooling

In previous studies, xylem parenchyma cells (XPCs) in the boreal softwood species larch, which has thick and rigid walls similar to those of XPCs in boreal hardwood species, were shown to respond to subfreezing temperature by deep supercooling during summer but change their freezing behavior to extracellular freezing during winter. In this study, we re-examined freezing behavior of XPCs in larch by observation of deep etching of frozen samples as well as observation of re-warmed samples after freezing using a cryo-scanning electron microscope. The results showed that XPCs in larch adapts to subfreezing temperature by deep supercooling throughout all seasons. Such freezing behavior is the same as that of XPCs in boreal hardwood species.