Electrophilic aromatic substitution of 3‐alkoxy‐6‐alkyl‐2‐cyano‐4,5,6a,11‐tetraazabenzo[a]fluorene with orthoesters

Fused tetracycles, 6‐alkyl‐3‐alkoxy‐2‐cyano‐4,5,6a,11‐tetraazabenzo[a]fluorene derivatives ( 5a , b , c , d , e , f ), are synthesized from 2‐alkoxy‐5‐(benzimidazol‐2‐ylidene)‐3‐cyano‐6‐imino‐5,6‐dihydro‐pyridines ( 4b , c ), and when refluxed in ethyl orthoacetate or ethyl orthopropionate, the elecrophilic aromatic substitution occurs at the ortho position of the cyanopyridine ring in the fused tetracycles ( 5b , c , e , f ) to afford 6‐alkyl‐3‐alkoxy‐2‐cyano‐1‐ethyl‐4,5,6a,11‐tetraazabenzo[a]fluorenes( 6b , c , e , f ).     

Kinetic studies of specific solvent effect on the thermal isomerization of palladium dithizonate in toluene‐alcohol mixtures

The kinetics of the thermal isomerization of palladium dithizonate (Pd(HD_Z)₂) in the binary mixture of toluene and alcohols has been studied. In the solvent effects on the Pd(HD_Z)₂ isomerization rates, we found that the maximum lies in the range x = 0.02 ∼ 0.2 (x represents the mole fraction of alcohols). The experimental kinetic data for the specific solvent effect with maximum can be reproduced well by taking into account hydrogen bonding and coordination of alcohols with Pd(HD_Z)₂. The rate constants for the thermal isomerization of Pd(HD_Z)₂ involving hydrogen bonding and the coordinate interaction with 1‐butanol are evaluated. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 542–547, 2000     

Acceleration of Proliferative Response of Mouse Fibroblasts by Short-Time Pretreatment with Polyphenols

Under the hypothesis that photo-irradiated proanthocyanidin could accelerate wound healing through reactive oxygen species (ROS) formation, we examined the effect of proanthocyanidin on 3T3-L1 mouse fibroblasts with or without photo-irradiation. As a result, irrespective of presence or absence of photo-irradiation, only 1 min exposure of the cells to proanthocyanidin resulted in accelerated proliferation of the cells in a concentration-dependent manner. Similarly to proanthocyanidin, 1 min pretreatment with catechin, caffeic acid, and chlorogenic acid accelerated the proliferative response, but gallic acid, epicatechin gallate, epigallocatechin, and epigallocatechin gallate failed. If incorporated active ingredient such as proanthocyanidin for such a short time as 1 min accelerates the proliferation response, a bioassay was conducted by utilizing antioxidant potential of proanthocyanidin. That is, intracellular oxidation of 2′,7′-dichlorodihydrofluorescin induced by H₂O₂ was significantly inhibited when the cells were pretreated with proanthocyanidin for 1 min, suggesting that incorporated proanthocyanidin into the cells exerted antioxidant effect. This was also supported by a liquid chromatography/mass spectrometry analysis in which incorporation of proanthocyanidin components such as catechin monomers and dimers into the cells within 1 min was confirmed. These results suggest that active polyphenolic compounds such as proanthocyanidin, catechin, caffeic acid, and chlorogenic acid incorporated into the cells in such a short time as 1 min could accelerate the proliferative response of the cells.     

Effect of UV anneal on plasma CVD low-k film

Plasma-enhanced chemical vapor deposition (PE-CVD) low-dielectric (low-k) film was irradiated with ultra violet (UV) light of wavelength 172 nm to enhance mechanical strength and reduce dielectric constant (k value). The thickness measurement method for the UV annealed low-k film is discussed. The effects of UV irradiation on dielectric constant, shrinkage, stress, density, pore size, mechanical strength, and structure are clarified and the mechanism is discussed.     

Effects of severe plastic deformation on the corrosion behavior of aluminum alloys

Effects of severe plastic deformation on the corrosion behaviors of Al alloys containing precipitates have been investigated. Al and its alloys were severely deformed by equal-channel angular pressing (ECAP) processes and the corrosion behaviors of the Al alloys were evaluated by means of potentiodynamic polarization in a neutral buffer solution containing 0.002 M chloride ion. Introduction of huge plastic deformation to both of Al-5.4 wt% Ni and Al-5 wt% Cu alloys increased pitting potential. In contrast, ECAP treatment of 4N pure Al resulted in a decrease in open circuit potential, slight increase of passive current and shift of pitting potential to the negative direction. The influence of the change in microstructures caused by severe plastic deformation was investigated. Contribution to the Fall Meeting of the European Materials Research Society, Symposium D: 9th International Symposium on Electrochemical/Chemical Reactivity of Metastable Materials, Warsaw, 17th-21st September, 2007     

Syntheses of model compounds related to an antigenic epitope in pectic polysaccharides from Bupleurum falcatum L. (II)

Stereocontrolled syntheses of model compounds related to a major antigenic epitope against antibupleurum 2IIc/PG-1-IgG from antiulcer pectic polysaccharide are described. A trisaccharide derivative (13) was prepared as a precursor and a novel and simple approach for the rational design of a glycocluster and glycodendrimer was developed, through the syntheses of the fluorescence-labeled glycocluster (2) and glycodendrimer (3).     

Light, Reactive Oxygen Species, and Magnetic Fields Activating ERK/MAPK Signaling Pathway in Cultured Zebrafish Cells

To guarantee that organism’s biological rhythms remain tied to the rhythms of its environment, the circadian clock must be able to reset itself in response to environmental cues. The main environmental stimulus for organisms is light, which is provided by day–night cycles. Cultured lines of zebrafish cells have been established as an attractive vertebrate cell-based model suitable for the examination of the light signaling pathway for entraining the circadian clock. Studies using these cell lines have revealed critical roles for the mitogen-activated protein kinase (MAPK) signaling pathways in light-dependent circadian entrainment. Here, we show in cultured zebrafish cells that artificial magnetic fields induce extracellular signal-regulated kinase (ERK)/MAPK activation with kinetics analogous to those elicited by light, suggesting that magnetic fields may influence circadian regulation in zebrafish. Our findings indicate that cultured zebrafish cells represent a valuable system for investigating the links between magnetic fields and the signaling pathways responsible for the synchronization of vertebrate circadian clocks under laboratory conditions.     

Characterization of inclusion complex of vitamin E compound with 2,6-di-O-methylated β-cyclodextrin as the solubility enhancer and its kinetic determination for radical scavenging ability

The structure of the inclusion complex of α-tocopherol (vitamin E compound) with 2,6-di-O-methylated β-cyclodextrin (DM-β-CD) was characterized by 2D ROESY NMR measurements, suggesting that DM-β-CD includes the side-chain moiety of α-tocopherol. The inclusion complexation of DM-β-CD showed the usefulness of water solubilizer for the radical scavenging assay of vitamin E compounds in aqueous solution. Using the electron paramagnetic resonance (EPR) competitive spin trapping method, we determined the oxygen radical (RO^?) scavenging abilities of seven vitamin E compounds (tocopherols and tocotrienols), which were solubilized by DM-β-CD in water. The order of the RO^? radical scavenging abilities for vitamin E compounds solubilized by DM-β-CD are α- > β- ≈ γ- > δ-, which is in agreement with the oxidation potential values of antioxidants. It is noted that the RO^? radical scavenging abilities of tocotrienols are comparable to those of tocopherols. Based on the results, the mechanism of the antioxidant reaction of vitamin E compounds with the RO^? radical is discussed.     

Mineral composition of frozen taro for determination of geographic origin

The mineral composition of frozen food of taro [Colocasia esculenta (L.) Schott] was analyzed to categorize the geographical production place of taro. The concentrations of Co and H₂PO₄ ⁻ were found to be useful to separate the producing place between Japan and China. The analysis was performed by instrumental neutron activation analysis (INAA) and ion chromatography (IC). In the case of INAA, the samples were dried and sealed in a vinyl bag and irradiated with thermal neutrons from JRR3M, installed at Japan Atomic Energy Agency (JAEA). The activated samples were cooled down for a few weeks and the elements (Co, Cr, Fe, Rb, Zn) were determined. Cobalt concentration of frozen taro from China was higher than that from Japan. The tendency was the same in the fresh sample of taro. When concentration of H₂PO₄ ⁻ of frozen sample was measured, taro from Japanese product was higher than that of Chinese one, contrary to fresh sample. This result might be caused by the leakage of H₂PO₄ ⁻ during freezing process, indicating that we should be careful to apply the discrimination indicators. In addition to Co, there was a significant difference of Rb and Fe concentrations between frozen taro from Japan and China.     

Giant colloidal crystals of fluorine-containing polymer spheres in exhaustively deionized aqueous suspensions and in the presence of sodium chloride

 Gigantic colloidal single crystals (2–6 mm) are formed for fluorine-containing polymer spheres (120–210 nm in diameter) in exhaustively deionized aqueous suspensions. The spheres used are poly(tetrafluoroethylene) (PTFEA and PTFEB), copolymer of tetrafluoroethylene and perfluorovinylether (PFA) and copolymer of tetrafluoroethylene and perfluoropropylene (PTP). The phase diagrams of these spheres are obtained in the deionized suspensions and also in the presence of sodium chloride for PFA. The critical sphere concentrations of crystal melting (φ _c) for these spheres are around 0.0006 in volume fraction, which are close to, but slightly larger than, those of monodispersed polystyrene spheres (φ _c ≈ 0.00015) and colloidal silica spheres(φ _c = 0.0002–0.0004) reported previously. The crystals are largest when the sphere concentrations are a bit higher than the φ _c value and their size decreases as the sphere concentration increases. Reflection spectra are taken in sedimentation equilibrium as a function of the height from the bottom of the suspension. The static elastic modulus is estimated to be 10.8 and 28.7 Pa for PTFEA and PTP spheres at the sphere concentrations 0.00325 and 0.00322 in volume fraction, respectively. Received: 27 October 1999 Accepted in revised form: 16 November 1999