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21.
Elucidation of Pseurotin Biosynthetic Pathway Points to Trans‐Acting C‐Methyltransferase: Generation of Chemical Diversity 下载免费PDF全文
Dr. Yuta Tsunematsu Manami Fukutomi Dr. Takayoshi Saruwatari Prof. Dr. Hiroshi Noguchi Prof. Dr. Kinya Hotta Prof. Dr. Yi Tang Prof. Dr. Kenji Watanabe 《Angewandte Chemie (International ed. in English)》2014,53(32):8475-8479
Pseurotins comprise a family of structurally related Aspergillal natural products having interesting bioactivity. However, little is known about the biosynthetic steps involved in the formation of their complex chemical features. Systematic deletion of the pseurotin biosynthetic genes in A. fumigatus and in vivo and in vitro characterization of the tailoring enzymes to determine the biosynthetic intermediates, and the gene products responsible for the formation of each intermediate, are described. Thus, the main biosynthetic steps leading to the formation of pseurotin A from the predominant precursor, azaspirene, were elucidated. The study revealed the combinatorial nature of the biosynthesis of the pseurotin family of compounds and the intermediates. Most interestingly, we report the first identification of an epoxidase C‐methyltransferase bifunctional fusion protein PsoF which appears to methylate the nascent polyketide backbone carbon atom in trans. 相似文献
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Koji Ishizu Shojiro Kuwabara Hui Chen Hirohide Mizuno Takashi Fukutomi 《Journal of polymer science. Part A, Polymer chemistry》1986,24(8):1735-1746
Soluble microgels with several pendant vinyl groups were synthesized by radical copolymerization of methyl methacrylate (MMA) with p-divinyl benzene (p-DVB). The polymerization conditions used for intramolecular crosslinking of microgels were chosen from gel permeation chromatograph (GPC) measurements of the reaction products. The rate constant of intramolecular crosslinking (kpi) was estimated from the changes in the concentration of pendant vinyl groups of microgel by using photometrical measurements at 30°C assuming a unimolecular termination mechanism of polymer radicals. As a result, kpi showed larger values than kp of styrene and depended strongly on the internal structure of the microgels. 相似文献
24.
Aoki S Sakurama K Ohshima R Matsuo N Yamada Y Takasawa R Tanuma S Takeda K Kimura E 《Inorganic chemistry》2008,47(7):2747-2754
8-Benzenesulfonyloxy-5- N,N-dimethylaminosulfonylquinolin-2-ylmethyl-pendant cyclen (BS-caged-L(4), BS = benzenesulfonyl) was designed and synthesized as a "caged" derivative of a previously described Zn(2+) fluorophore, 8-hydroxy-5- N,N-dimethylaminosulfonylquinolin-2-ylmethyl-pendant cyclen (L(4)) (cyclen = 1,4,7,10-tetraazacyclododecane). In the absence of metal ions and in the dark, BS-caged-L(4) (10 microM) showed negligible fluorescence emission at pH 7.4 (10 mM HEPES with I = 0.1 (NaNO3)) and 25 degrees C (excitation at 328 nm). Addition of Zn(2+) induced an increase in the UV/vis absorption of BS-caged-L(4) (10 microM) at 258 nm and a significant increase in fluorescence emission at 512 nm. These responses are results from the formation of Zn(H-1L(4)) by the hydrolysis of the sulfonyl ester at the 8-position of the quinoline unit promoted by the Zn(2+)-bound HO(-). Improvement of cell membrane permeation in comparison with L(4) is also described. 相似文献
25.
Koji Ishizu Atsushi Ohtaka Takashi Fukutomi Toshio Kakurai 《Journal of polymer science. Part A, Polymer chemistry》1982,20(11):3199-3205
Lithium-metallated (styrene-p-benzylstyrene)copolymer was reacted with chlorine-terminated polystyrene as a crosslinker polymer in a mixture of tetrahydrofuran (THF)–n-hexane at 25°C in the presence of lithium chloride(LiCl). The rate constants were estimated from the changes in the concentration of metallated polymer by photometrical measurements. As a result, the rate constant of grafting (k1) showed a constant value in spite of a change in molecular weight of the crosslinker polymers and the addition of n-hexane. The rate constant of intramolecular crosslinkings (k2intra) obtained in a mixed solvent (21 ~ 36 vol % of n-hexane) increased when the molecular weight of the crosslinker polymers and the extent of n-hexane were increased. 相似文献
26.
Motomasa Yonezumi Nanako Takano Shokyoku Kanaoka Sadahito Aoshima 《Journal of polymer science. Part A, Polymer chemistry》2008,46(20):6746-6753
A quite small dose of a poisonous species was found to induce living cationic polymerization of isobutyl vinyl ether (IBVE) in toluene at 0 °C. In the presence of a small amount of N,N‐dimethylacetamide, living cationic polymerization of IBVE was achieved using SnCl4, producing a low polydispersity polymer (weight–average molecular weight/number–average molecular weight (Mw/Mn) ≤ 1.1), whereas the polymerization was terminated at its higher concentration. In addition, amine derivatives (common terminators) as stronger bases allow living polymerization when a catalytic quantity was used. On the other hand, EtAlCl2 produced polymers with comparatively broad MWDs (Mw/Mn ~ 2), although the polymerization was slightly retarded. The systems with a strong base required much less quantity of bases than weak base systems such as ethers or esters for living polymerization. The strong base system exhibited Lewis acid preference: living polymerization proceeded only with SnCl4, TiCl4, or ZnCl2, whereas a range of Lewis acids are effective for achieving living polymerization in the conventional weak base system such as an ester and an ether. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6746–6753, 2008 相似文献
27.
Yoko Kawata Yuko Adachi Saori Haga Junko Fukutomi Hirohiko Imai Atsuomi Kimura Hideaki Fujiwara 《Analytical sciences》2007,23(12):1397-1402
Temperature and pressure dependences of the 129Xe NMR chemical shift and the signal intensity have been investigated using ZSM-5 as an adsorbent under routine conditions without using any high-pressure or especially high-temperature facilities. The use of a rigorously shielded system and a calibration sample for the signal intensity was found to be valuable to obtain reliable data about the chemical shift and the signal intensity. The 129Xe NMR data obtained between 0.05 and 1.5 atm and from 24 to 80 degrees C were analyzed based on the Dubinin-Radushkevich equation as well as the Langmuir type equation. In both analyses, chemical shift data succeeded only partially in providing the profile of adsorption, such as energetic aspects, surface area, saturated amount of Xe adsorption and specific parameters of 129Xe chemical shift. It was shown that the reliable total analysis was achieved when the chemical shift data were used together with the intensity data. Such an analysis of the chemical shift data, aided by the intensity data, will be useful in performing nano-material analysis on 129Xe NMR without invoking the traditional methodology of gravimetric or volumetric adsorption experiments. 相似文献
28.
Minoru Takizawa Yoshifumi Sugito Naomi Oguma Michiei Nakamura Shojiro Horiguchi Takashi Fukutomi 《Journal of polymer science. Part A, Polymer chemistry》2003,41(9):1251-1261
A new type of charge‐mosaic membrane was prepared from poly(4‐vinyl pyridine) microspheres 250–350 nm in diameter as an anion‐exchange element and from linear poly(sodium styrene sulfonic acid) as a cation‐exchange element. The mosaic structure on the surface of the membrane and the continuous connection of the microspheres in the membrane were confirmed by scanning electron microscopy observations and the electrical conductivity of the membrane. The microspheres were continuously connected from one side to the other side of the membrane surface when the weight fraction of the microspheres increased more than 20–25 wt % in the membrane. The flux of KCl, the permeability coefficient of KCl, the volume flux, and the selectivity dialysis separation of the electrolyte (KCl) and nonelectrolyte (glucose and saccharose) of the membrane indicated that it had the characteristic properties of a charge‐mosaic membrane. Ion‐exchange membranes composed of each raw material of the charge‐mosaic membrane did not show these properties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1251–1261, 2003 相似文献
29.
Dr. Gesa Schäfer Dr. Jelena Milić Dr. Adeeb Eldahshan Dr. Frank Götz Dr. Kerstin Zühlke Christian Schillinger Annika Kreuchwig Dr. Jonathan M. Elkins Kamal R. Abdul Azeez Andreas Oder Dr. Marie C. Moutty Nanako Masada Monika Beerbaum Brigitte Schlegel Sylvia Niquet Dr. Peter Schmieder Dr. Gerd Krause Dr. Jens Peter von Kries Prof. Dermot M. F. Cooper Prof. Dr. Stefan Knapp Prof. Jörg Rademann Prof. Dr. Walter Rosenthal Priv.‐Doz. Dr. Enno Klussmann 《Angewandte Chemie (International ed. in English)》2013,52(46):12187-12191
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