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排序方式: 共有126条查询结果,搜索用时 15 毫秒
1.
Reconstitution of Biosynthetic Machinery for the Synthesis of the Highly Elaborated Indole Diterpene Penitrem 下载免费PDF全文
Dr. Chengwei Liu Koichi Tagami Dr. Atsushi Minami Tomoyuki Matsumoto Jens Christian Frisvad Hideyuki Suzuki Jun Ishikawa Katsuya Gomi Prof. Dr. Hideaki Oikawa 《Angewandte Chemie (International ed. in English)》2015,54(19):5748-5752
Penitrem A is one of the most elaborated members of the fungal indole diterpenes. Two separate penitrem gene clusters were identified using genomic and RNA sequencing data, and 13 out of 17 transformations in the penitrem biosynthesis were elucidated by heterologous reconstitution of the relevant genes. These reactions involve 1) a prenylation‐initiated cationic cyclization to install the bicyclo[3.2.0]heptane skeleton (PtmE), 2) a two‐step P450‐catalyzed oxidative processes forming the unique tricyclic penitrem skeleton (PtmK and PtmU), and 3) five sequential oxidative transformations (PtmKULNJ). Importantly, without conventional gene disruption, reconstitution of the biosynthetic machinery provided sufficient data to determine the pathway. It was thus demonstrated that the Aspergillus oryzae reconstitution system is a powerful method for studying the biosynthesis of complex natural products. 相似文献
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Cover Picture: Reconstitution of Biosynthetic Machinery for the Synthesis of the Highly Elaborated Indole Diterpene Penitrem (Angew. Chem. Int. Ed. 19/2015) 下载免费PDF全文
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Machiko Shigemi Takahiro Takekiyo Hiroshi Abe Nozomu Hamaya Yukihiro Yoshimura 《Journal of solution chemistry》2014,43(9-10):1614-1624
We have used Raman spectroscopy to investigate the high-pressure phase behavior of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), a representative ionic liquid, at pressures up to ~7.5 GPa. We have also studied how increasing pressure leads to conformational changes in the [bmim]+ cation. We have found that liquid [bmim][BF4] undergoes pressure-induced solidification (freezing) into a superpressed (metastable) state at 2.5 GPa; another structural change probably occurs at ~6 GPa. Remarkably, conformational changes in the [bmim]+ cation between trans and gauche conformers are concordant with the metastable structural changes of [bmim][BF4]. As the pressure is increased from ambient, the fraction of gauche conformers increases, but the gauche fraction decreases above the solidification pressure (2.5 GPa), and slope of the gauche/trans ratio changes again above 6 GPa. We interpret these results in terms of the fragility of the ionic liquid. 相似文献
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Miyazaki H. Kato J. Kawai S. Hatayama H. Uchida K. Otsuki M. Tagami J. Yokoo S. 《Laser Physics》2011,21(12):2128-2131
This study evaluated the surgical performance of a 405-nm diode laser in vivo, using living rat liver tissue. Tissue was incised
by irradiation with the laser at low output power ranging from 1 W (722 W/cm2) to 3 W (2165 W/cm2) on a manual control at a rate of 1 mm/s. As a control, incisions using a stainless scalpel were compared. Immediately after
operation, the surface of the incisions was macroscopically observed and histopathologically evaluated by microscopy. Laser-ablated
liver tissue was smooth with observable signs of remnant carbonization and easily acquired hemostasis. The thickness of the
denatured layer increased in proportion to the output power; the coagulation layer did not thicken accordingly. Bleeding could
not be stopped for tissues incised with the stainless scalpel. The 405-nm diode laser thus proved to be effective for ablating
soft tissue with high hemostatic ability at low power. 相似文献
7.
D'Arceuil HE de Crespigny AJ Pelc L Howard D Alley M Seri S Hashiguchi Y Nakatani A Moseley ME 《Magnetic resonance imaging》2004,22(9):1243-1248
PURPOSE: This study used an experimental arterial stenosis model in pigs to evaluate the utility of a new medium-weight MRI contrast agent, NMS60 (a synthetic oligomeric Gd complex containing three Gd(3+) atoms, molecular weight of 2158 Da) compared to Gd-DTPA for contrast-enhanced MRA. MATERIALS AND METHODS: We used six male white hybrid pigs. Under anesthesia, one femoral artery was exposed and an inflatable cuff placed around it. The cuff was tightened around the vessel until 80-90% stenosis was achieved using digital subtraction angiography as a guide. Animals were then immediately transferred to the MRI scanner and images acquired pre- and postcontrast injection (0.1 or 0.2 mmol Gd/kg Gd-DTPA or NMS60, as a rapid bolus) using high-resolution and dynamic MRA. RESULTS: The dynamic MRA scans acquired during contrast bolus injection clearly showed the stenosed femoral artery as a segment of close to zero enhancement during the arterial phase of the bolus transit, while on the high-resolution scans the stenosis was difficult to detect due to venous signal contamination. The signal-to-noise at peak enhancement on the dynamic scans was significantly greater with 0.1 mmol Gd/kg NMS60 compared to 0.1 mmol Gd/kg Gd-DTPA (14.6 vs. 9.9, P < .05) and not significantly greater than 0.2 mmol Gd/kg (14.6 vs. 12.8). DISCUSSION AND CONCLUSION: This new medium-weight contrast agent demonstrated significantly greater enhancement than Gd-DTPA and may be valuable to aid detection of vascular stenosis in humans. 相似文献
8.
Uchida S Kawamoto R Tagami H Nakagawa Y Mizuno N 《Journal of the American Chemical Society》2008,130(37):12370-12376
Ag2[Cr3O(OOCC2H5)6(H2O)3]2[alpha-SiW12O40] [1] is a nonporous flexible ionic crystal composed of 2D-layers of polyoxometalates ([alpha-SiW12O40](4-)) and macrocations ([Cr3O(OOCC2H5)6(H2O)3](+)) stacking along the b-axis. The silver ions are located in the vicinity of the oxygen atoms of the polyoxometalates. The sorption amounts of small unsaturated hydrocarbons such as ethylene, propylene, n-butene, acetylene, and methyl acetylene into 1 are comparable to or larger than 1.0 mol mol(-1) and large hystereses are observed, while those of paraffins and larger unsaturated hydrocarbons are smaller than the adsorption on the external surface (<0.2 mol mol(-1)). Fine crystals of 1 exhibit ethylene/ethane and propylene/propane sorption ratios over 100 at 298 K and 100 kPa, and the values are larger by 1 order of magnitude among those reported. The results of sorption kinetics, in situ IR spectroscopy, single crystal X-ray crystallography, and in situ powder XRD studies show that small unsaturated hydrocarbons penetrate into the solid bulk of 1 through the pi-complexation with Ag(+). The sorption property of 1 is successfully applied to the collection of ethylene from the gas mixture of ethane and ethylene. 相似文献
9.
Y. Muramatsu K. Tagami S. Uchida 《Journal of Radioanalytical and Nuclear Chemistry》1994,188(4):305-311
Measurements of some selected radionuclides were carried out in rain waters collected from Ibaraki Prefecture, Japan, following the nuclear accident at Tomsk-7, Russian Federation, in April 1993. The concentrations obtained for artificial radionuclides were90Sr1.8 mBq l–1,137Cs0.1 Bq l–1,131I0.1 Bq l–1 and129I4 Bq l–1. Uranium (238U) concentrations in rainfalls in April 1993 were 6.3–39 ng l–1. These data were compared to control values obtained previously and there was no appreciable influence on the radioactivity levels in Japan after the Tomsk-7 accident. Since only limited data on the concentrations of129I and uranium in rain water are available, these new analytical results contribute to understanding the background levels for these nuclides. 相似文献
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