Koga Isotope Ltd.

Koga, Japan

Koga Isotope Ltd.

Koga, Japan
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Shonaka M.,Tokyo University of Agriculture and Technology | Ishii H.,Ueshima Seisakusho Co. | Hironiwa T.,Koga Isotope Ltd. | Akai N.,Tokyo University of Agriculture and Technology | Nakata M.,Tokyo University of Agriculture and Technology
Bulletin of the Chemical Society of Japan | Year: 2017

Thermoluminescence spectra of gamma-irradiated shells of oysters, scallops, mussels, littleneck clams, and freshwater clams are measured with a multichannel Fourier-transform luminescence spectrometer. Oysters, scallops, and mussels isothermally heated at 200°C show strong luminescence due to the electronic transition of Mn2+, which is included as an impurity in shells and excited to a metastable state by gammaray irradiation. Littleneck clams and freshwater clams show very weak thermoluminescence under the same experimental conditions and show strong thermoluminescence owing to phase transition when they are heated at 450°C before gammaray irradiation. The phase transition of the crystal structures from aragonite to calcite is monitored by infrared spectroscopy. © 2017 The Chemical Society of Japan.


Fukuyama S.,Kyoto University | Fukuyama S.,Koga Isotope Ltd. | Mihara H.,Kyoto University | Mihara H.,Ritsumeikan University | And 7 more authors.
Journal of Bioscience and Bioengineering | Year: 2014

2,4-Diaminopentanoate dehydrogenase (2,4-DAPDH), which is involved in the oxidative ornithine degradation pathway, catalyzes the NAD+- or NADP+-dependent oxidative deamination of (2R,4S)-2,4-diaminopentanoate (2,4-DAP) to form 2-amino-4-oxopentanoate. A Fervidobacterium nodosum Rt17-B1 gene, Fnod_1646, which codes for a protein with sequence similarity to 2,4-DAPDH discovered in metagenomic DNA, was cloned and overexpressed in Escherichia coli, and the gene product was purified and characterized. The purified protein catalyzed the reduction of NAD+ and NADP+ in the presence of 2,4-DAP, indicating that the protein is a 2,4-DAPDH. The optimal pH and temperature were 9.5 and 85°C, respectively, and the half-denaturation time at 90°C was 38min. Therefore, the 2,4-DAPDH from F.nodosum Rt17-B1 is an NAD(P)+-dependent thermophilic-alkaline amino acid dehydrogenase. This is the first thermophilic 2,4-DAPDH reported, and it is expected to be useful for structural and functional analyses of 2,4-DAPDH and for the enzymatic production of chiral amine compounds. Activity of 2,4-DAPDH from F.nodosum Rt17-B1 was suppressed by 2,4-DAP via uncompetitive substrate inhibition. In contrast, the enzyme showed typical Michaelis-Menten kinetics toward 2,5-diaminohexanoate. The enzyme was uncompetitively inhibited by d-ornithine with an apparent Ki value of 0.1mM. These results suggest a regulatory role for this enzyme in the oxidative ornithine degradation pathway. © 2013 The Society for Biotechnology, Japan.


Hironiwa T.,Tokyo University of Agriculture and Technology | Hironiwa T.,Koga Isotope Ltd. | Yamada T.,Tokyo University of Agriculture and Technology | Ishii H.,Japan Applied Technology Inc. | And 3 more authors.
Polymer Journal | Year: 2012

Chemiluminescence spectra of natural rubber, chloroprene rubber and ethylene propylene diene rubber were measured in N 2 and in air with a multichannel Fourier-transform chemiluminescence spectrometer. Samples were measured after γ-ray irradiation in air and in the absence of O 2. No strong emission was observed for natural rubber heated in N 2 after the sample was γ-irradiated in the absence of O 2, but a strong emission from the sample was observed at 631 nm in air. An emission from chloroprene rubber was observed around 659 nm even when the sample was not γ-irradiated. A similar band was observed after the sample was γ-irradiated in air and in the absence of O 2. A strong emission from ethylene propylene diene rubber was observed in air only when the sample was γ-irradiated in air. The observed spectrum was separated into two bands at 678 and 523 nm, where the former and the latter were tentatively assigned to peroxidic compounds and excited carbonyl groups, respectively. The relative intensity of the two bands changed during the measurement. It is concluded that luminescence spectroscopy using a multichannel spectrometer is a powerful technique to examine the oxidative degradation of elastomers. © 2012 The Society of Polymer Science, Japan (SPSJ) All rights reserved.


Noguchi T.,Tokyo University of Agriculture and Technology | Noguchi T.,Daikin Industries Ltd | Yamada E.,Tokyo University of Agriculture and Technology | Akai N.,Tokyo University of Agriculture and Technology | And 5 more authors.
Chemical Physics Letters | Year: 2014

Thermal chemiluminescence spectra of polytetrafluoroethylene powder irradiated by γ rays in air at room temperature were measured with a multichannel Fourier-transform chemiluminescence spectrometer. The luminescence appeared immediately after heating the irradiated samples at 160, 180 and 200 °C in dry air and in N2 and then disappeared within a few minutes, whereas virgin samples showed no luminescence. The lifetime of luminescence decreased as the heating temperature increased, but the total amount of luminescence at each temperature was nearly constant. From this observation an emission mechanism was derived with the aid of ESR and IR spectroscopy.


Yamada E.,Tokyo University of Agriculture and Technology | Noguchi T.,Tokyo University of Agriculture and Technology | Noguchi T.,Daikin Industries Ltd | Akai N.,Tokyo University of Agriculture and Technology | And 5 more authors.
Chemical Physics Letters | Year: 2014

Temperature dependence of the time evolution of chemiluminescence intensity from γ-irradiated polytetrafluoroethylene was examined by heating isothermally in the range of 150 and 200 °C. Kinetic analysis was carried out to estimate the rate constants, from which the dissociation energy of the OO bond in the fluoroperoxide group was determined to be 97 ± 4 kJ mol-1, being consistent with the corresponding value for small fluorocarbon model systems obtained by quantum chemical calculations. This strongly supports the emission mechanism [CF(OOF)CF2 → COCF2 + OF2 + hν] proposed in our previous paper to explain chemiluminescence from the γ-irradiated polytetrafluoroethylene. © 2014 Elsevier B.V. All rights reserved.


Yano A.,Tokyo University of Agriculture and Technology | Ishii H.,Japan Applied Technology Inc. | Satoh C.,Japan Applied Technology Inc. | Akai N.,Tokyo University of Agriculture and Technology | And 4 more authors.
Chemical Physics Letters | Year: 2014

Chemiluminescence emission spectra of polypropylene pellets pre-irradiated in air with γ rays were measured using a time-dependent multichannel Fourier-transform chemiluminescence spectrometer. Spectra were detected immediately after heating the irradiated polymer at 150 C, which was not the case for the virgin material, and deconvoluted into emission bands by least-squares fitting using Gaussian curves. The peak intensity of the initial emission band around 490 nm rapidly increased and then decreased with a constant peak wavelength during the thermal oxidation time between 0 and 10 min. We have elucidated the emission mechanism from the dependence of γ-irradiation dose on the peak intensity. © 2013 Elsevier B.V. All rights reserved.


Yano A.,Tokyo University of Agriculture and Technology | Akai N.,Tokyo University of Agriculture and Technology | Ishii H.,Japan Applied Technology Inc. | Satoh C.,Japan Applied Technology Inc. | And 4 more authors.
Polymer Degradation and Stability | Year: 2013

Thermal oxidative degradation of additive-free polypropylene pellets heated isothermally in dry air at 150 and 180 C (below and above the melting point of 163 C) was investigated by multichannel Fourier-transform chemiluminescence spectroscopy. The initial peak wavelength of chemiluminescence emission at 490 nm remained constant during the early stages of thermal degradation, but new emissions developed with time in the red spectral region over an extended oxidation period. The time-dependent luminescence spectra were deconvoluted into three emission bands by least-squares fitting using Gaussian curves. We concluded that at least three groups of luminescent species (luminophores), having different conjugation lengths, were generated by thermal oxidation over extended periods and show luminescence around 490, 660, and 740 nm. © 2013 Elsevier Ltd. All rights reserved.


Minatoyama M.,Tokyo University of Agriculture and Technology | Akai N.,Tokyo University of Agriculture and Technology | Yamada E.,Tokyo University of Agriculture and Technology | Noguchi T.,Tokyo University of Agriculture and Technology | And 6 more authors.
Polymer Journal | Year: 2016

In order to elucidate the mechanism of degradation of γ-irradiated polytetrafluoroethylene (PTFE), gases evolved by isothermal heating under vacuum were trapped in low-temperature argon matrices. Infrared spectra of the evolved gases were assigned to COF 2 and CF 4 by comparison with the corresponding literatures. Kinetic analyses of the IR absorbance and chemiluminescence intensity changes against heating time were carried out to determine the rate constants of the thermal reactions, showing that CF 4 was produced more rapidly than COF 2. By comparison between the rate constants obtained by infrared spectroscopy and chemiluminescence spectroscopy, we propose a new thermal reaction mechanism of γ-irradiated PTFE at the molecular level. © 2016 The Society of Polymer Science, Japan (SPSJ).

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