Self‐Activated Vanadate Compounds Toward Realization of Rare‐Earth‐Free Full‐Color Phosphors

Rare‐earth‐free phosphors based on vanadate compounds were investigated, where the vanadates included chloride vanadates (M^II₂VO₄Cl), pyrovanadates (M^II₂V₂O₇), orthovanadates (M^II₃(VO₄)₂) with divalent cations M^II of Mg, Sr, Ba, and Zn, and oxofluorovanadates (A^IVOF₄) with an alkali metal A^I. A chloride pyrolysis method and a liquid phase precipitation method were proposed for preparing the chloride vanadates and pyro‐ and orthovanadates, respectively. These vanadate compounds showed self‐activated photoluminescence (PL) based on the VO₄ clusters against the ultraviolet (UV) light irradiation. The colors of PL covered almost the whole visible‐light region from blue to yellow as Sr₂VO₄Cl (deep blue), Ca₂VO₄Cl (sky blue), Ba₂V₂O₇ (green), Sr₂V₂O₇ (yellowish green), Zn₃(VO₄)₂ (yellow), and Mg₃(VO₄)₂ (yellow). A correlation was suggested from these compounds between the luminescent colors and the structural feature as the longer V–O distances in the VO₄ tetrahedra in the crystal structures led to the longer wavelength in PL. This seemed to be also applicable for the oxofluorovanadates A^IVOF₄ (A^I = K and Cs) which contain the VOF₄ polyhedra with one O^2? ion and four F^‐ ions as the ligands, as they exhibited the reddish PL.     

Metformin Protects against NMDA-Induced Retinal Injury through the MEK/ERK Signaling Pathway in Rats

Metformin, an anti-hyperglycemic drug of the biguanide class, exerts positive effects in several non-diabetes-related diseases. In this study, we aimed to examine the protective effects of metformin against N-methyl-D-aspartic acid (NMDA)-induced excitotoxic retinal damage in rats and determine the mechanisms of its protective effects. Male Sprague–Dawley rats (7 to 9 weeks old) were used in this study. Following intravitreal injection of NMDA (200 nmol/eye), the number of neuronal cells in the ganglion cell layer and parvalbumin-positive amacrine cells decreased, whereas the number of CD45-positive leukocytes and Iba1-positive microglia increased. Metformin attenuated these NMDA-induced responses. The neuroprotective effect of metformin was abolished by compound C, an inhibitor of AMP-activated protein kinase (AMPK). The AMPK activator, AICAR, exerted a neuroprotective effect in NMDA-induced retinal injury. The MEK1/2 inhibitor, U0126, reduced the neuroprotective effect of metformin. These results suggest that metformin protects against NMDA-induced retinal neurotoxicity through activation of the AMPK and MEK/extracellular signal-regulated kinase (ERK) signaling pathways. This neuroprotective effect could be partially attributable to the inhibitory effects on inflammatory responses.     

Fabrication of fine micro protrusions on fluoropolymer surface using ion beam irradiation

Tissue reconstruction is the aim of regeneration medicine and tissue engineering. One of the techniques is cell sheet engineering, which requires creating a contiguous cell sheet and harvesting it safely. To create a favorable substrate for cultivation, we attempted to fabricate the microstructure at polytetrafluoroethylene (PTFE) surfaces using ion beam irradiation. PTFE is a typical fluoropolymer and it possesses chemical and bioinertness. When the surface is irradiated with an ion beam, it is covered with a large number of microprotrusions, which have an aspect ratio of about 100. We previously reported that fibroblast cells grow and spread between the tops of the protrusions. In this study, we fabricated fine protrusions at both the PTFE and the poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) surfaces. The composition of FEP and PTFE is similar but FEP melts at a lower temperature than PTFE does. These samples were irradiated under controlled temperature and rubbing preparation. Their surface morphology and chemical bonding were observed. When the PTFE surface was irradiated at 350 °C, the protrusions were formed at the lower fluence, with an improved uniformity of shape. This was because the morphological change and evaporation of the thin parts were enhanced during high-temperature irradiation. In the FEP sample, very fine protrusions formed at much lower fluence by irradiation at room temperature. On the surface, the cells spread closely, like a monolayer. Further, the FEP samples were still optically transparent after the irradiation. They have an advantage in that we can observe the living cells attaching to the surface in their natural state without them being killed, fixed, and stained in an optical microscope. We found that the irradiated FEP surface is suitable for making a cell sheet.     

Twenty Years of Polymer‐Clay Nanocomposites

Summary: More than twenty years have passed since we invented PCN, in which only a few wt.‐% of silicate is randomly and homogeneously dispersed in the polymer matrix. When molded, these nanocomposites show superior properties compared to those of pristine polymers. The number of papers on PCN has increased rapidly in recent years, reaching over 500 in 2005 alone. Being pioneers of this new technology, we review its history relative to the following epochal events:

• In 1985 we invented nylon 6‐clay hybrid (NCH), the first PCN.
• In 1989, cars equipped with a NCH part were launched.
• In 1997, Gilman found revolutionary fire retardancy in NCH.
• In 1997, a PP‐clay nanocomposite was prepared using a compatibilizer.
• In 1998, a compounding method for producing PCN was completed.
• In 2002, Haraguchi invented a revolutionary nanocomposite hydrogel.

So far, only nylon‐clay nanocomposites have been used in practice, but other PCN will become increasingly useful in the future.

SEM of etched NCH film.     

Direct electrochemical detection of sodium azide in physiological saline buffers using highly boron-doped diamond electrodes

Direct detection of sodium azide was examined by using highly boron-doped diamond (BDD) electrodes in some physiological saline buffer solutions. Three important saline buffers, ADA buffer (N-(2-acetamido) iminodiacetic acid), sodium EDTA and imidazole, were investigated. Hydrogen-terminated BDD was fixed for the investigation since it showed much better sensitivity for azide oxidation in comparison with the oxygen-terminated one. Wide range of buffer concentration was examined. A well-separated peak of sodium azide was observed in its mixture with the buffers, resulting in selective sodium azide detection. The current responses were exactly total addition of sodium azide and buffer current responses. The present method was evidenced to be available for direct detection of sodium azide in two samples of commercial diluents for cell counting. A standard addition method was applied. Sodium azide concentrations of 502 and 1355 μg mL⁻¹ were detected in both samples with the R.S.D.s of 0.07 and 2.37%, respectively. Validation was achieved by the comparison with the sample concentrations given by the manufacturer. Simple, selective, good sensitivity and excellent reproducible detection make the diamond electrodes very attractive for numerous electroanalytical applications.     

Effects of hydrophobic amino acid substitution in Pleurotus ostreatus proteinase A inhibitor 1 on its structure and functions as protease inhibitor and intramolecular chaperone

We previously demonstrated that Pleurotus ostreatus proteinase A inhibitor 1 (POIA1) could function as an intramolecular chaperone of subtilisin BPN', as in the case of the propeptide of subtilisin BPN', and that its Phe44 --> Ala mutant, which lost its tertiary structure, could not assist the refolding of subtilisin BPN'. In this study, we examined the effects of hydrophobic amino acid substitutions at other sites and substitutions of Phe44 with other hydrophobic residues on the structure and functions of POIA1. These mutations were introduced into POIA1cm that had been obtained by the substitution of the C-terminal six residues of POIA1 with those of the propeptide of subtilisin BPN'. When Ile32 or Ile64 was substituted with Ala, the tertiary structure of the resultant mutant was markedly destroyed, and the activities as a protease inhibitor and an intramolecular chaperone were significantly lowered. Among the position 44 mutants, the Phe44 --> Val mutant was a much less effective intramolecular chaperone with conversion to a digestible inhibitor, possibly owing to destruction of the tertiary structure. On the other hand, the Phe44 --> Leu or Ile mutant maintained its tertiary structure, and hence could function as a more effective intramolecular chaperone than the Phe44 --> Val mutant. Furthermore, since the Phe44 --> Leu mutant was a more susceptible inhibitor than POIA1cm, the halo formed around a colony of Bacillus cells transformed with a plasmid encoding this mutant was larger than others. These results clearly show the close relationship between the tertiary structure and functions of POIA1 as a protease inhibitor and an intramolecular chaperone, and that a combination of such inhibitory properties and intramolecular chaperone activity of POIA1 might affect the diameter of the halo formed around Bacillus colonies in vivo.     

Potential of a Novel Chemical Compound Targeting Matrix Metalloprotease-13 for Early Osteoarthritis: An In Vitro Study

Osteoarthritis is a progressive disease characterized by cartilage destruction in the joints. Matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs) play key roles in osteoarthritis progression. In this study, we screened a chemical compound library to identify new drug candidates that target MMP and ADAMTS using a cytokine-stimulated OUMS-27 chondrosarcoma cells. By screening PCR-based mRNA expression, we selected 2-(8-methoxy-2-methyl-4-oxoquinolin-1(4H)-yl)-N-(3-methoxyphenyl) acetamide as a potential candidate. We found that 2-(8-methoxy-2-methyl-4-oxoquinolin-1(4H)-yl)-N-(3-methoxyphenyl) acetamide attenuated IL-1β-induced MMP13 mRNA expression in a dose-dependent manner, without causing serious cytotoxicity. Signaling pathway analysis revealed that 2-(8-methoxy-2-methyl-4-oxoquinolin-1(4H)-yl)-N-(3-methoxyphenyl) acetamide attenuated ERK- and p-38-phosphorylation as well as JNK phosphorylation. We then examined the additive effect of 2-(8-methoxy-2-methyl-4-oxoquinolin-1(4H)-yl)-N-(3-methoxyphenyl) acetamide in combination with low-dose betamethasone on IL-1β-stimulated cells. Combined treatment with 2-(8-methoxy-2-methyl-4-oxoquinolin-1(4H)-yl)-N-(3-methoxyphenyl) acetamide and betamethasone significantly attenuated MMP13 and ADAMTS9 mRNA expression. In conclusion, we identified a potential compound of interest that may help attenuate matrix-degrading enzymes in the early osteoarthritis-affected joints.     

Electroplastic behavior of doped poly(3-hexylthiophene)

Dynamic viscoelasticity of poly(3-hexylthiophene) (P3HT) doped with iodine or FeCI₃ under the influence of electric fields was studied. The doped P3HTs underwent a large decrease in elastic modulus under small electric fields on the order of 1 dc V/mm. The electric fields enhanced the loss tangent. The glass transition temperature decreased as the intensity of the applied fields was increased. This electroplastic behavior was observed also in ac excitation of less than 1 kHz. It was detected in both crystalline and amorphous P3HTs. Joule heating was a main process in the electroplastic behavior of doped P3HTs. We measured FTIR and X-ray diffraction spectra under electric fields to examine the possibility of other processes. The X-ray diffraction analysis suggested a possibility of another process caused by the formation of intraplanar packing of thiophene rings. © 1996 John Wiley & Sons, Inc.     

Energy-dispersive XAFS study on the decarbonylation process of Mo(CO)6 in NaY zeolite

The temperature-programmed decarbonylation process of Mo(CO)₆ in NaY zeolite was studied by means of a time-resolved energy-dispersive XAFS method. The XANES analysis demonstrated that the decarbonylation proceeded by two successive steps via a stable intermediate which existed between 440 and 490 K. The curve fitting analysis of the EXAFS data revealed that the intermediate was a molybdenum monomer subcarbonyl species Mo(CO)₃(O_L)₃ coordinated by three CO ligands and three oxygen atoms of zeolite framework (O_L). Molybdenum dimer subcarbonyl species were not observed. This study demonstrated that the DXAFS technique is a powerful method to study the dynamic behavior of the Mo carbonyl species during decarbonylation process.