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Construction of a mutant of Actinoplanes sp. N902-109 that produces a new rapamycin analog

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Chinese Journal of Natural Medicines 2018年第3期16卷 210-218页

作者： huANG He GAO Ping ZHAO Qi hu Hai-Feng Shanghai Institute of Pharmaceutical Industry Shanghai 201203 China Institute of Plant Physiology and Ecology Shanghai Institutes for Biological Sciences Chinese Academy of Sciences Shanghai 200032 China

In the present study, we introduced point mutations into Ac_rap A which encodes a polyketide synthase responsible for rapamycin biosynthesis in Actinoplanes sp. N902-109, in order to construct a mutant with an inactivated enoylreductase(ER) domain, which was able to synthesize a new rapamycin analog. Based on the homologous recombination induced by double-strand breaks in chromosome mediated by endonuclease I-SceI, the site-directed mutation in the first ER domain of Ac_rapA was introduced using non-replicating plasmid pL YERIA combined with an I-SceI expression plasmid. Three amino acid residues of the active center, Ala-Gly-Gly, were converted to Ala-Ser-Pro. The broth of the mutant strain SIPI-027 was analyzed by HPLC and a new peak with the similar UV spectrum to that of rapamycin was found. The sample of the new peak was prepared by solvent extraction, column chromatography, and crystallization methods. The structure of new compound, named as SIPI-rapxin, was elucidated by determining and analyzing its MS and NMR spectra and its biological activity was assessed using mixed lymphocyte reaction(MLR). An ER domain–deficient mutant of Actinoplanes sp. N902-109, named as SIPI-027, was constructed, which produced a novel rapamycin analog SIPI-rapxin and its structure was elucidated to be 35, 36-didehydro-27-O-demethylrapamycin. The biological activity of SIPI-rapxin was better than that of rapamycin. In conclusion, inactivation of the first ER domain of rap A, one of the modular polyketide synthase responsible for macro-lactone synthesis of rapamycin, gave rise to a mutant capable of producing a novel rapamycin analog, 35, 36-didehydro-27-O-demethylrapamycin, demonstrating that the enoylreductase domain was responsible for the reduction of the double bond between C-35 and C-36 during rapamycin synthesis.

关键词： Actinoplanes sp. N902-109 Rapamycin Structural analog Polyketide synthase Enoylreductase

Thermoelectric properties of I-doped n-type Bi2Te3-based material prepared by hydrothermal and subsequent hot pressing

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Progress in Natural Science:Materials International 2017年第2期27卷 203-207页

作者： Fang Wu Wei Wang Xing hu Mingsheng Tang College of Physical Engineering and Laboratory of Material Physics Zhengzhou University College of Physical and Electronic Engineering Henan Institute of Finance and Banking College of Chemistry and Molecular Engineering Zhengzhou University College of Information Engineering Zhengzhou Institute of Technology

I-doped Bi2Te3-xIx（x=0, 0.05, 0.1, 0.2） flower-like nanoparticles were synthesized by a hydrothermal method through a careful adjustment of the amount of ethylenediamine tetraacetic acid surfactant. The nanopowders of flower-like nanoparticles were hot-pressed into bulk pellets and the thermoelectric properties of the pellets were investigated. The results showed that I-doping decreased the electrical resistivity effectively, and the thermal conductivitives of the Bi2Te3-xIxbulk samples was lower because of the closer atomic mass of I compared to *** a result, a ZT value of 1.1 was attained at 448 K for the Bi2Te2.9I0.1sample.

关键词： n-type Bi2Te3 Element doping Nanostructure Hot pressing Thermoelectric properties

Kinetics of Precipitation Behavior of Second Phase Particles in Ferritic Ti-Mo Microalloyed Steel

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Journal of Iron and Steel Research International 2013年第7期20卷 69-77页

作者： hu Bin-hao CAI Qing-wu WU hui-bin Engineering Research Institute University of Science and Technology Beijing

Two types of stress relaxation tests were carried out to investigate the incubation time for incipient precipi-tation of Ti（C,N） in deformed austenite and （Ti,Mo）C in ferrite of ferritic Ti-Mo microalloyed steel The size dis-tribution, amount and chemical composition of precipitates were obtained by using physicochemical phase analysis, and calculated according to thermodynamics and kinetics. The experimental results demonstrated that the incubation time was reduced with increasing Ti content, and prolonged with the addition of Mo. After 30 % deformation at 850 ℃, the nucleation of strain-induced Ti（C,N） was a relatively slow process. On the other hand, the temperature where the nucleation rate of （Ti, Mo）C in ferrite was the highest descended first and then ascended with increasing Ti content, and so did the temperature where the incubation time was the shortest. The key point is that the tempera-ture of steel containing about 0.09 % Ti is the lowest. The mass fraction of MC-type particles with size smaller than 10 nm in steel containing 0.09% Ti and 0.2% Mo reached 73.7%. The size distributions of precipitates in steel containing 0.09% Ti were relatively concentrated compared with that in steel containing 0.07% Ti.

关键词： ferritic Ti-Mo microalloyed steel precipitation behavior second phase particle stress relaxation parti-cle size distribution

Conversion of N-Acyl-4-phenyl/benzyl-oxazolidine-2-thiones into Thiol Esters in the Presence of EtSH-K2CO3

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Chinese Journal of Chemistry 2005年第11期23卷 1561-1563页

作者： hu, Qi SUN, Ya-Ping WU, Yi-Kang State Key Laboratory of Bioorganic and Natural Products Chemistry Shanghai Institute of Organic Chemistry Chinese Academy of Sciences Shanghai 200032 China

N-Acyl-β-hydroxy-4-phenyl-oxazolidinethiones could be rapidly converted into their ethyl thiol esters in high yields by treatment with EtSH at 0 ℃ in CH3CN or 9 ： 1 （V ： V） THF-H2O in the presence of a catalytic... 详细信息

关键词： chiral auxiliary cleavage thiol ester aldol

Fractal Characteristics of Oil-Gas-Water Multiphase Flow

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Journal of Thermal Science 2002年第1期11卷 49-52页

作者： huanqun Qian Zhihua hu Hedong Sun Fangde Zhou Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Experiments were conducted with oil-gas-water multiphase flow in a horizontal pipe under different flow patterns. The fractal method was applied to analyze the pressure drop signals measured in the experiments. The fractal dimensions of the signals were calculated. Preliminary results indicated that the fractal dimensions were small and different under different flow patterns. The fractal dimensions could be used to identify the flow patterns of the oil-gas-water multiphase flows.

关键词： oil-gas/air-water correlation dimension fractals flow regime.

A New p-Terphenyl Derivative from Basidiomycetes Boletopsis grisea

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Chinese Chemical Letters 2001年第4期12卷 335-336页

作者： Lin hu Ze Jun DON Ji Kai LIU Kunming Institute of Botany Chinese Academy of SciencesKunming 650204

A new p-terphenyl derivative 1 was isolated from the fruiting bodies of Boletopsis grisea. Its structure was established as 2. 3-diacetoxy-4 ', 4 ', 5, 6-tetrahydroxy-p-terphenyl by spectroscopic and chemical means.

关键词： Boletopsis grisea p-terphenyl derivative Basidiomycetes.

Andreev Tunneling Through a Ferromagnet/Quantum-Dot/Superconductor System

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Communications in Theoretical Physics 2002年第5期38卷 629-633页

作者： RAO Hong-hu Zhu Yu LIN Tsung-Han State Key Laboratory for Mesoscopic Physics and Department of Physics Peking University Beijing 100871 China State Key Laboratory for Mesoscopic Physics and Department of Physics Peking University Beijing 100871 China State Key Laboratory for Mesoscopic Physics and Department of Physics Peking University Beijing 100871 China

We study Andreev tunneling through a ferromagnet/quantum-dot (QD)/superconductor system. By usingnonequilibrum Green function method, the averaged occupation of electrons in QD and the Andreev tunneling currentare studied. Comparing to the norma-metal/quantum-dot/superconductor, the system shows significant changes: (i)The averaged occupations of spin-up and spin-down electrons are not equal. (ii) With the increase of the polarizationof ferromagnetic lead, the Andreev reflection current decreases. (iii) However, even the ferromagnetic lead reaches fullpolarization, the averaged occupation of spin-down electrons is not zero. The physics of these changes is discussed.

关键词： Andreev tunneling, ferromagnet/quantum-dot/superconductor system

A novel caged-prenylxanthone from Garcinia bracteata

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Chinese Chemical Letters 2010年第4期21卷 443-445页

作者： Na, Zhi hu, hua Bin Fan, Qing Fei Chinese Acad Sci Xishuangbanna Trop Bot Garden Mengla 666303 Peoples R China

A novel caged-prenylxanthone xanthone,neobractatin(1),was isolated from the twig of Garcinia *** structure was elucidated by spectroscopic methods,especially 2D NMR techniques.

关键词： Garcinia bracteata Caged-prenylxanthone Neobractatin

NONLINEAR J-E CHARACTERISTICS IN THE ELECTRIC-THERMAL EQUILIBRIUM STATE FOR HIGH DENSITY POLYETHYLENE CONDUCTIVE COMPOSITES

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Chinese Journal of Polymer Science 2001年第1期19卷 19-23页

作者： Qiang Zheng Yi-hu Song Xiao-su Yi Department of Polymer Science and Engineering Zhejiang University Hangzhou 310027 China Department of Polymer Science and Engineering Zhejiang University Hangzhou 310027 China National Key Laboratory of Advanced Composites P.O. Box 81-3 Beijing 100095 China

The nonlinear J-E characteristics under self-heating equilibrium for conductive composites based on high density polyethylene were studied. The results show that there are identical conduction mechanisms under self-heating equilibrium for the composites with various initial resistivities determined by filler content or ambient temperature. The nonlinear conduction behavior was involved in the limited microstructure transformations of the conducting network induced by electrical field applied and the corresponding self-heating effect. A reversible thermal fuse (RTF) model was suggested to interpret the physical origin of the nonlinear J-E characteristics.

关键词： J-E characteristics nonlinear conduction self-heating equilibrium reversible thermal fuse model