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  • 1
    Publication Date: 2016-09-16
    Description: We investigated the dependency of minority carrier lifetimes on the nitrogen concentration, temperature, and the injected carrier concentration for highly nitrogen-doped 4H-SiC epilayers. The minority carrier lifetimes greatly shortened when the nitrogen concentration exceeded 10 18  cm −3 through enhancing direct band-to-band and Auger recombination and showed a slight variation in the temperature range from room temperature (RT) to 250 °C. The epilayer with a nitrogen concentration of 9.3 × 10 18 cm −3 exhibited a very short minority carrier lifetime of 38 ns at RT and 43 ns at 250 °C. The short minority carrier lifetimes of the highly nitrogen-doped epilayer were confirmed to maintain the values even after the subsequent annealing of 1700 °C. 4H-SiC PiN diodes were fabricated by depositing a highly nitrogen-doped epilayer as a “recombination enhancing layer” between an n − drift layer free from basal plane dislocations and the substrate. The PiN diodes showed no formation of stacking faults and no increase in forward voltage during current conduction of 600 A/cm 2 (DC), demonstrating that a highly nitrogen-doped buffer layer with a short minority carrier lifetime successfully suppresses the “bipolar degradation” phenomenon.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 2
    Publication Date: 2012-03-15
    Description: This paper considers a design scheme of a minimal-order observer-based guaranteed cost controller for linear uncertain time-varying delay systems. A sufficient condition for asymptotic stabilization is guaranteed via linear matrix inequality feasible solutions. Optimization is provided by minimizing an upper bound of the guaranteed cost function. To show the advantage of a minimal-order observer-based guaranteed cost control approach, a full-order observer-based case is presented as comparison. A numerical example is given to illustrate the proposed method.
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
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  • 3
    Publication Date: 2012-09-18
    Description: It is held as a paradigm that ribosomally synthesized peptides and proteins contain only l-amino acids. We demonstrate a ribosomal origin of the marine sponge-derived polytheonamides, exceptionally potent, giant natural-product toxins. Isolation of the biosynthetic genes from the sponge metagenome revealed a bacterial gene architecture. Only six candidate enzymes were identified for 48 posttranslational modifications, including 18 epimerizations and 17 methylations of nonactivated carbon centers. Three enzymes were functionally validated, which showed that a radical S-adenosylmethionine enzyme is responsible for the unidirectional epimerization of multiple and different amino acids. Collectively, these complex alterations create toxins that function as unimolecular minimalistic ion channels with near-femtomolar activity. This study broadens the biosynthetic scope of ribosomal systems and creates new opportunities for peptide and protein bioengineering.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Freeman, Michael F -- Gurgui, Cristian -- Helf, Maximilian J -- Morinaka, Brandon I -- Uria, Agustinus R -- Oldham, Neil J -- Sahl, Hans-Georg -- Matsunaga, Shigeki -- Piel, Jorn -- New York, N.Y. -- Science. 2012 Oct 19;338(6105):387-90. doi: 10.1126/science.1226121. Epub 2012 Sep 13.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Kekule Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22983711" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Ion Channels/biosynthesis/*metabolism ; Marine Toxins/biosynthesis/*metabolism ; *Metagenome ; Methylation ; Molecular Sequence Data ; Protein Biosynthesis ; *Protein Processing, Post-Translational ; Proteins/*metabolism ; Ribosomes/metabolism ; S-Adenosylmethionine/metabolism ; Theonella/*microbiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2014-01-31
    Description: Cultivated bacteria such as actinomycetes are a highly useful source of biomedically important natural products. However, such 'talented' producers represent only a minute fraction of the entire, mostly uncultivated, prokaryotic diversity. The uncultured majority is generally perceived as a large, untapped resource of new drug candidates, but so far it is unknown whether taxa containing talented bacteria indeed exist. Here we report the single-cell- and metagenomics-based discovery of such producers. Two phylotypes of the candidate genus 'Entotheonella' with genomes of greater than 9 megabases and multiple, distinct biosynthetic gene clusters co-inhabit the chemically and microbially rich marine sponge Theonella swinhoei. Almost all bioactive polyketides and peptides known from this animal were attributed to a single phylotype. 'Entotheonella' spp. are widely distributed in sponges and belong to an environmental taxon proposed here as candidate phylum 'Tectomicrobia'. The pronounced bioactivities and chemical uniqueness of 'Entotheonella' compounds provide significant opportunities for ecological studies and drug discovery.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wilson, Micheal C -- Mori, Tetsushi -- Ruckert, Christian -- Uria, Agustinus R -- Helf, Maximilian J -- Takada, Kentaro -- Gernert, Christine -- Steffens, Ursula A E -- Heycke, Nina -- Schmitt, Susanne -- Rinke, Christian -- Helfrich, Eric J N -- Brachmann, Alexander O -- Gurgui, Cristian -- Wakimoto, Toshiyuki -- Kracht, Matthias -- Crusemann, Max -- Hentschel, Ute -- Abe, Ikuro -- Matsunaga, Shigeki -- Kalinowski, Jorn -- Takeyama, Haruko -- Piel, Jorn -- England -- Nature. 2014 Feb 6;506(7486):58-62. doi: 10.1038/nature12959. Epub 2014 Jan 29.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Institute of Microbiology, Eidgenossische Technische Hochschule Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland [2] Kekule Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany [3]. ; 1] Faculty of Science and Engineering, Waseda University Center for Advanced Biomedical Sciences, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan [2]. ; Institute for Genome Research and Systems Biology, Center for Biotechnology, Universitat Bielefeld, Universitatstrasse 25, 33594 Bielefeld, Germany. ; 1] Institute of Microbiology, Eidgenossische Technische Hochschule Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland [2] Kekule Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany. ; Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. ; Department of Botany II, Julius-von-Sachs Institute for Biological Sciences, University of Wurzburg, Julius-von-Sachs-Platz 3, 97082 Wurzburg, Germany. ; Kekule Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany. ; Department of Earth and Environmental Sciences, Palaeontology and Geobiology, Ludwig Maximilians University Munich, Richard-Wagner-Strasse 10, 80333 Munich, Germany. ; Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, California 94598, USA. ; Institute of Microbiology, Eidgenossische Technische Hochschule Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland. ; Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. ; Faculty of Science and Engineering, Waseda University Center for Advanced Biomedical Sciences, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24476823" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biosynthetic Pathways/genetics ; Deltaproteobacteria/*classification/genetics/*metabolism/physiology ; *Drug Discovery ; Environmental Microbiology ; Genes, Bacterial/genetics ; Genome, Bacterial/genetics ; Metagenomics ; Molecular Sequence Data ; Multigene Family/genetics ; Peptides/metabolism ; Polyketides/metabolism ; Porifera/metabolism/microbiology ; Single-Cell Analysis ; Symbiosis
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2013-03-30
    Description: X-ray single-crystal diffraction (SCD) analysis has the intrinsic limitation that the target molecules must be obtained as single crystals. Here we report a protocol for SCD analysis that does not require the crystallization of the sample. In our method, tiny crystals of porous complexes are soaked in a solution of the target, such that the complexes can absorb the target molecules. Crystallographic analysis clearly determines the absorbed guest structures along with the host frameworks. Because the SCD analysis is carried out on only one tiny crystal of the complex, the required sample mass is of the nanogram-microgram order. We demonstrate that as little as about 80 nanograms of a sample is enough for the SCD analysis. In combination with high-performance liquid chromatography, our protocol allows the direct characterization of multiple fractions, establishing a prototypical means of liquid chromatography SCD analysis. Furthermore, we unambiguously determined the structure of a scarce marine natural product using only 5 micrograms of the compound.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Inokuma, Yasuhide -- Yoshioka, Shota -- Ariyoshi, Junko -- Arai, Tatsuhiko -- Hitora, Yuki -- Takada, Kentaro -- Matsunaga, Shigeki -- Rissanen, Kari -- Fujita, Makoto -- England -- Nature. 2013 Mar 28;495(7442):461-6. doi: 10.1038/nature11990.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23538828" target="_blank"〉PubMed〈/a〉
    Keywords: Absorption ; Alkynes/chemistry ; Analytic Sample Preparation Methods/*methods ; Animals ; Biological Products/chemistry ; Crystallization/*methods ; Crystallography, X-Ray/*methods ; Fatty Alcohols/chemistry ; Microchemistry/*methods ; Nanotechnology/*methods ; Porifera/chemistry ; Porosity
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2014-05-28
    Description: Using methodology developed herein, it is found that reactive persulfides and polysulfides are formed endogenously from both small molecule species and proteins in high amounts in mammalian cells and tissues. These reactive sulfur species were biosynthesized by two major sulfurtransferases: cystathionine β-synthase and cystathionine γ-lyase. Quantitation of these species indicates...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of natural products 54 (1991), S. 1337-1344 
    ISSN: 1520-6025
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Tetrahedron 50 (1994), S. 1105-1110 
    ISSN: 0040-4020
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Tetrahedron 50 (1994), S. 7765-7770 
    ISSN: 0040-4020
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Tetrahedron 49 (1993), S. 3749-3754 
    ISSN: 0040-4020
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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