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171.
《Journal of Natural History》2012,46(39-40):2605-2607
ABSTRACTThe purpose of this paper is to describe the circumstances of publication of an unavailable name of chalcid wasps, and to make the name Balcha opaca Fusu sp. n. (Hymenoptera: Eupelmidae) available.www.zoobank.org/urn:lsid:zoobank.org:pub:38F49D79-F5AA-4516-8E48-55CFFA61A71C 相似文献
172.
173.
174.
针对倾斜转弯导弹,提出了最优/经典综合设计方法设计自动驾驶仪.该方法应用最优控制设计出俯仰/偏航混合通道三回路自动驾驶仪,设计中同时对开环系统的奇异值频域曲线进行约束,以保证系统具有一定的鲁棒性,获得的三回路自动驾驶仪结构简单,易于工程实现.仿真结果证实了其具有良好的跟踪性能和鲁棒性,也表明该自动驾驶仪能满足倾斜转弯导弹协调倾斜转弯的要求. 相似文献
175.
176.
MurNAc etherases cleave the uniqued-lactyl ether bond of the bacterial cell wall sugar N-acetylmuramic acid (MurNAc). Members of this newly discovered family of enzymes are widely distributed among bacteria and
are required to utilize peptidoglycan fragments obtained either from the environment or from the endogenous cell wall (i.e.,
recycling). MurNAc etherases are strictly dependent on the substrate MurNAc possessing a free reducing end and a phosphoryl
group at C6. They carry a single conserved sugar phosphate isomerase/sugar phosphate- binding (SIS) domain to which MurNAc
6-phosphate is bound. Two subunits form an enzymatically active homodimer that structurally resembles the isomerase module
of the double-SIS domain protein GlmS, the glucosamine 6-phosphate synthase. Structural comparison provides insights into
the two-step lyase-type reaction mechanism of MurNAc etherases: β-elimination of the D-lactic acid substituent proceeds through
a 2,3-unsaturated sugar intermediate to which water is subsequently added.
Received 31 August 2007; received after revision 12 October 2007; accepted 1 November 2007 相似文献
177.
Starch-binding domains in the post-genome era 总被引:1,自引:1,他引:0
Starch belongs to the most abundant biopolymers on Earth. As a source of energy, starch is degraded by a large number of various
amylolytic enzymes. However, only about 10% of them are capable of binding and degrading raw starch. These enzymes usually
possess a distinct sequence-structural module, the so-called starchbinding domain (SBD). In general, all carbohydrate-binding
modules (CBMs) have been classified into the CBM families. In this sequence-based classification the individual types of SBDs
have been placed into seven CBM families: CBM20, CBM21, CBM25, CBM26, CBM34, CBM41 and CBM45. The family CBM20, known also
as a classical C-terminal SBD of microbial amylases, is the most thoroughly studied. The three-dimensional structures have
already been determined by X-ray crystallography or nuclear magnetic resonance for SBDs from five CBM families (20, 25, 26,
34 and 41), and the structure of the CBM21 has been modelled. Despite differences among the amino acid sequences, the fold
of a distorted β-barrel seems to be conserved together with a similar way of substrate binding (mainly stacking interactions
between aromatic residues and glucose rings). SBDs have recently been discovered in many non-amylolytic proteins. These may,
for example, have regulatory functions in starch metabolism in plants or glycogen metabolism in mammals. SBDs have also found
practical uses.
Received 25 May 2006; received after revision 26 June 2006; accepted 3 August 2006 相似文献
178.
Site- and state-specific lysine methylation of histones is catalyzed by a family of proteins that contain the evolutionarily
conserved SET domain and plays a fundamental role in epigenetic regulation of gene activation and silencing in all eukaryotes.
The recently determined three-dimensional structures of the SET domains from chromosomal proteins reveal that the core SET
domain structure contains a two-domain architecture, consisting of a conserved anti-parallel β-barrel and a structurally variable
insert that surround a unusual knot-like structure that comprises the enzyme active site. These structures of the SET domains,
either in the free state or when bound to cofactor S-adenosyl-L-homocysteine and/or histone peptide, mimicking an enzyme/cofactor/substrate complex, further yield the structural insights
into the molecular basis of the substrate specificity, methylation multiplicity and the catalytic mechanism of histone lysine
methylation.
Received 10 June 2006; accepted 22 August 2006 相似文献
179.
Kertész A Váradi G Tóth GK Fajka-Boja R Monostori E Sármay G 《Cellular and molecular life sciences : CMLS》2006,63(22):2682-2693
Phosphopeptides interacting with src homology 2 (SH2) domains can activate essential signaling enzymes in vitro. When delivered to cells, they may disrupt protein-protein interactions, thereby influencing intracellular signaling. We
showed earlier that phosphopeptides corresponding to the inhibitory motif of Fcγ receptor IIb and a motif of the Grb2-associated
binder 1 adaptor protein activate SH2-containing tyrosine phosphatase 2 in vitro. To study the ex vivo effects of these peptides, we have now compared different methods for peptide delivery: (i) permeabilization of the target
cells and (ii) the use of cell-permeable vectors, which are potentially able to transport biologically active compounds into
B cells. We found octanoyl-Arg8 to be an optimal carrier for the delivery of phosphopeptides to the cells. With this strategy, the function of cell-permeable
SHP-2-binding phosphopeptides was analyzed. These peptides modulated the protein phosphorylation in B cells in a dose- and
time-dependent manner.
Received 27 July 2006; received after revision 4 September 2006; accepted 18 September 2006 相似文献
180.
构造领域本体所需的信息源选取方法的研究对解决本体的构造质量、构造效率等问题,以及推广与发展领域本体有着重要意义.传统的信息源文档选取方法只考虑概念因素,不能很好地解决该问题.因此,首先利用抽象方法分析了领域本体所需信息源具有的概念性、关系性和预测性等特点.然后,针对这些特点分别采用改进的VSM方法、基于本体关系距离的方法以及神经网络方法计算文档权值.最后,通过编写的软件OnMaker产生模拟数据得到概念、关系和预测3个权值,从而计算出每个文档权值,并使用与"湿地保护"相关的真实文档验证该模型,达到了较好排序选取的效果. 相似文献