976 research outputs found
Antisense-induced suppression of taxoid 14β- hydroxylase gene expression in transgenic Taxus × media cells
The enzyme taxoid 14β-hydroxylase (14OH) directs a side-route of taxol pathway to 14β-hydroxy taxoids. Suppression of this side-route could increase the production of taxol. To suppress taxoid 14β- hydroxylase gene (14OH) expression in the Taxus × media TM3 cell line, antisense RNA inhibition approach was used in this study. Following the construction of an antisense RNA expression vector of 14OH from Taxus chinensis, the antisense 14OH cDNA (as14OH) was introduced into TM3 cells by Agrobacterium tumefaciens-mediated transformation. Southern blot analysis of hygromycin phosphotransferase gene (HYG) revealed that this selection gene was integrated successfully into the genome of Taxus × media cells. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that the 14OH mRNA level in transgenic cells dropped dramatically, suggesting that the expression of endogenous14OH gene was significantly suppressed by the exogenous as14OH gene. Correspondingly, the total yield of three major C-14 oxygenated taxoids (yunnanxane, taxuyunnanine C, sinenxan C) was markedly reduced in the silenced cell lines when compared with those of the nontransgenic controls. These results indicated that the antisense RNA strategy is a useful tool in suppressing the expression of genes in Taxus and this method could be used to silence other important genes that divert Taxol pathway to side-route metabolites.Key words: Taxus × media, taxoid 14β-hydroxylase, antisense, gene suppression
Polyaxial figures of the moon
Author name used in this publication: X. L. Ding2011-2012 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Orientation of the geometrically best fitting triaxial lunar ellipsoid with respect to the mean earth/polar axis reference frame
Author name used in this publication: X. L. Ding2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
基于小波变换的单历元算法及其在结构振动监测中的应用研究
Author name used in this publication: 丁晓利Author name used in this publication: 黄丁发, HUANG Ding-faAuthor name used in this publication: 陈惠珊Title in Traditional Chinese: 基于小波變換的單歷元算法及其在結構振動監測中的應用研究Journal title in Traditional Chinese: 測繪學報2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Facile Synthesis of High Quality Graphene Nanoribbons
Graphene nanoribbons have attracted attention for their novel electronic and
spin transport properties1-6, and because nanoribbons less than 10 nm wide have
a band gap that can be used to make field effect transistors. However,
producing nanoribbons of very high quality, or in high volumes, remains a
challenge. Here, we show that pristine few-layer nanoribbons can be produced by
unzipping mildly gas-phase oxidized multiwalled carbon nanotube using
mechanical sonication in an organic solvent. The nanoribbons exhibit very high
quality, with smooth edges (as seen by high-resolution transmission electron
microscopy), low ratios of disorder to graphitic Raman bands, and the highest
electrical conductance and mobility reported to date (up to 5e2/h and 1500
cm2/Vs for ribbons 10-20 nm in width). Further, at low temperature, the
nanoribbons exhibit phase coherent transport and Fabry-Perot interference,
suggesting minimal defects and edge roughness. The yield of nanoribbons was ~2%
of the starting raw nanotube soot material, which was significantly higher than
previous methods capable of producing high quality narrow nanoribbons1. The
relatively high yield synthesis of pristine graphene nanoribbons will make
these materials easily accessible for a wide range of fundamental and practical
applications.Comment: Nature Nanotechnology in pres
Tunable Multifunctional Topological Insulators in Ternary Heusler Compounds
Recently the Quantum Spin Hall effect (QSH) was theoretically predicted and
experimentally realized in a quantum wells based on binary semiconductor
HgTe[1-3]. QSH state and topological insulators are the new states of quantum
matter interesting both for fundamental condensed matter physics and material
science[1-11]. Many of Heusler compounds with C1b structure are ternary
semiconductors which are structurally and electronically related to the binary
semiconductors. The diversity of Heusler materials opens wide possibilities for
tuning the band gap and setting the desired band inversion by choosing
compounds with appropriate hybridization strength (by lattice parameter) and
the magnitude of spin-orbit coupling (by the atomic charge). Based on the
first-principle calculations we demonstrate that around fifty Heusler compounds
show the band inversion similar to HgTe. The topological state in these
zero-gap semiconductors can be created by applying strain or by designing an
appropriate quantum well structure, similar to the case of HgTe. Many of these
ternary zero-gap semiconductors (LnAuPb, LnPdBi, LnPtSb and LnPtBi) contain the
rare earth element Ln which can realize additional properties ranging from
superconductivity (e. g. LaPtBi[12]) to magnetism (e. g. GdPtBi[13]) and
heavy-fermion behavior (e. g. YbPtBi[14]). These properties can open new
research directions in realizing the quantized anomalous Hall effect and
topological superconductors.Comment: 20 pages, 5 figure
Search for K_S K_L in psi'' decays
K_S K_L from psi'' decays is searched for using the psi'' data collected by
BESII at BEPC, the upper limit of the branching fraction is determined to be
B(psi''--> K_S K_L) < 2.1\times 10^{-4} at 90% C. L. The measurement is
compared with the prediction of the S- and D-wave mixing model of the
charmonia, based on the measurements of the branching fractions of J/psi-->K_S
K_L and psi'-->K_S K_L.Comment: 5 pages, 1 figur
Room temperature texturing of austenite/ferrite steel by electropulsing
The work reports an experimental observation on crystal rotation in a duplex (austenite + ferrite) steel induced by the electropulsing treatment at ambient temperature, while the temperature rising due to ohmic heating in the treatment was negligible. The results demonstrate that electric current pulses are able to dissolve the initial material’s texture that has been formed in prior thermomechanical processing and to produce an alternative texture. The results were explained in terms of the instability of an interface under perturbation during pulsed electromigation
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