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861.
Marcia M. de O. Buanafina Tim Langdon Barbara Hauck Sue J D Alton Phil Morris 《Applied biochemistry and biotechnology》2006,130(1-3):416-426
In grass cell walls, ferulic acid esters linked to arabinosyl residues in arabinoxylans play a key role in crosslinking hemicellulose.
Although such crosslinks have a number of important roles in the cell wall, they also hinder the rate and extent of cell wall
degradation by ruminant microbes and by fungal glycohydrolyase enzymes. Ferulic acid esterase (FAE) can release both monomeric
and dimeric ferulic acids from arabinoxylans making the cell wall more susceptible to further enzymatic attack. Transgenic
plants of Lolium multiflorum expressing a ferulic acid esterase gene from Aspergillus niger, targeted to the vacuole under a constitutive rice actin promoter, have been produced following microprojectile bombardment
of embryogenic cell cultures. The level of FAE activity was found to vary with leaf age and was highest in young leaves. FAE
expression resulted in the release of monomeric and dimeric ferulic acids from cell walls on cell death and this was enhanced
severalfold by the addition of exogenous β-1,4-endoxylanase. We also show that a number of plants expressing FAE had reduced
levels of cell wall esterified monomeric and dimeric ferulates and increased in vitro dry-matter digestibility compared with
nontransformed plants. 相似文献
862.
Human β-defensin (HBD)-2 is a small cationic peptide with a broad range of antimicrobial activity. In this study, multiple
copies of the hBD2 gene were linked in tandem, and a number of different Escherichia coli expression vectors were evaluated, including pQE-30, pBV220, pET-28a(+), and pGEX-4T-2. No expression of multiple joined
genes was detectable in the pQE-30 expression system, whereas in pBV220 with one or two joined hBD2 genes and in pET-28a(+)
with one, two, or four copies, target proteins were expressed at a low level. Only when pGEX-4T-2 was applied as expression
plasmid with one or two joined hBD2 genes were target proteins expressed in high level, and the expressed fusion proteins
account for 26 and 16% of the total insoluble proteins, respectively. In the pGEX-4T-2 and pET-28a(+) expression systems,
the effects of multiple joined genes on the growth of host strains and plasmid stability were examined. Host cells containing
plasmid carrying fewer copies of hBD2 genes were faster in cell growth. Plasmid stability decreased with an increase in multiple
joined genes, which was especially noticeable in the pET-28a(+) system. Furthermore, the presence of glucose in culture medium
brought about a positive effect on plasmid stability when using pET28-nhBD2 as expression vectors. 相似文献
863.
N. P. Mertvetsov 《Russian Chemical Bulletin》1996,45(12):2688-2697
Chemo-enzymatic synthesis of the gene of human angiogenin, a stimulator of blood vessel growth, was performed for the first time. Cloning of the human angiogenin gene in several expressing vector systems was carried out, and several bacterial strains, producers of human angiogenin were constructed. In particular, strains, producers of angiogenin--galactosidase and angiogenin-domains of staphylococcal protein A hybrid proteins were obtained, as well as a bacterial strain efficiently expressing free angiogenin. Large-scale preparation of purified recombinant human angiogenin was accomplished using theE.coli JM103 pRITA16 producer strain constructed, and the biological activity of the resulting preparation was studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12. pp. 2837–2846, December, 1996. 相似文献
864.
Xijun Li Kebin Li Jiaju Du Xiaojun Xu Jun Fang Zhihe Wang Xiaowen Cao Jingsheng Zhu Yuheng Zhang 《中国科学A辑(英文版)》1998,41(3):308-312
The electrical resistance in zero magnetic field and magnetoresistance in different external magnetic fields have been measured
in a temperature range of 77—300 K. It is found that the temperature dependence of magnetoresistance can be well described
by a phenomenofogical formula of
where the fitting parameters α, β vary as the external magnetic fieldH changes,E
0 is the activation energy,E
0/k
B = 1160 K,M
s is the saturation magnetization, the temperature and magnetic field dependence ofM/M
s is obtained by the mean-field expression.
Project supported by the National Natural Science Foundation of China and partly by the Chinese Academy of Sciences. 相似文献
865.
Luo Chuanyi Tang Yinghui Liu Renbin 《高校应用数学学报(英文版)》2007,22(1):95-100
In this paper, the Geometry/G/1 queueing model with inter-arrival times generated by a geometric(parameter p) distribution according to a late arrival system with delayed access and service times independently distributed with distribution {gj }, j≥ 1 is studied. By a simple method (techniques of probability decomposition, renewal process theory) that is different from the techniques used by Hunter(1983), the transient property of the queue with initial state i(i ≥ 0) is discussed. The recursion expression for u -transform of transient queue-length distribution at any time point n^+ is obtained, and the recursion expression of the limiting queue length distribution is also obtained. 相似文献
866.
In this paper we investigate the approximation behaviour of the so‐called Hermite–Fejér interpolation operator based on the zeros of Jacobi polynomials. As a result we obtain the asymptotic formula of approximation rate for these operators. Moreover, such a formula is valid for any individual continuous function. We will also study the K ‐functional deduced by this operator. Consequently the asymptotic term of this K ‐functional is established. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
867.
868.
869.
870.
本文利用油藏渗流力学原理,结合留数方法和特殊函数理论,求出了考虑井储和二次压力梯度影响的无穷均质油藏试并模型的解析解,并给出了渐近表逸式。该方法可用于求无穷双孔介质油藏、多层油藏、复合油藏等试井模型的解析解,对试井分析有理论应用价值。 相似文献