检索结果-南通市图书馆

Molecular architecture and engineering of spider dragline silk protein

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2005年第9期15卷 769-776页

作者： ZHANG Hengmu and LIU Jinyuan(department of biological sciences and biotechnology, tsinghua university, beijing 100084. china) department of biological sciences and biotechnology Tsinghua University Beijing 100084 China

Spider dragline silk, which is produced in spider major ampullate gland, is a composite proteinacious fiber with highly repetitive Ala-Gly-rich domain. The unique combination of both high tensile strength and high elasticity makes spider dragline silk superior to almost any other natural or synthetic fibers. Cloning of the genes reveals that the silk is composed of at least two major proteins. Each protein component contains multiple repeats of modular structures that alternate between Ala-rich domains and Gly-rich domains. Molecular engineering not only opens a door to the production of spidroins but also provides a valuable experimental system to test and further establish the relationship between modular structures and mechanical properties. Here, based on our own studies, we review the latest progress of the modular structure and genetic engineering and outline the future prospects.

关键词： spider dragline silk protein modular structure molecular engineering.

Negative regulation of TGF-β signaling in development

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Cell Research 2004年第6期14卷 441-449页

作者： Ye Guang CHEN, An Ming MENG The State Key Laboratory of Biomembrane and Membrane biotechnology, department of biological sciences and biotechnology, tsinghua university, beijing 100084. china department of biological sciences and biotechnology The State Key Laboratory of Biomembrane and Membrane Biotechnology Tsinghua University Beijing 100084 China

The TGF-β superfamily members have important roles in controlling patterning and tissue formation in both invertebrates and vertebrates. Two types of signal transducers, receptors and Smads, mediate the signaling to regulate expression of their target genes. Despite of the relatively simple signal transduction pathway, many modulators have been found to contribute to a tight regulation of this pathway in a variety of mechanisms. This article reviews the negative regulation of TGF-β signaling with focus on its roles in vertebrate development.

关键词： TGF-β BMP Nodal Activin antagonist development negative regulation.

SOME PROPERTIES OF LSQR FOR LARGE SPARSE LINEAR LEAST SQUARES PROBLEMS

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2010年第4期23卷 815-821页

作者： Zhongxiao JIA department of Mathematical sciences,tsinghua university,beijing 100084.china. department of Mathematical sciences Tsinghua University

It is well-known that many Krylov solvers for linear systems,eigenvalue problems,andsingular value decomposition problems have very simple and elegant formulas for residual *** not only allow us to further understand the methods theoretically but also can be usedas cheap stopping criteria without forming approximate solutions and residuals at each step beforeconvergence takes *** for large sparse linear least squares problems is based on the Lanczosbidiagonalization process and is a Krylov ***,there has not yet been an analogouslyelegant formula for residual *** paper derives such kind of *** addition,the authorgets some other properties of LSQR and its mathematically equivalent CGLS.

关键词： CGLS krylov subspace lanczos bidiagonalization least squares lsqr normal equations.

Cloning and characterization of 37 kDa laminin receptor precursor in pearl oyster,Pinctada fucata

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2008年第2期18卷 233-238页

作者： Yaopeng Fu a,Liping Xie a,b,,Rongqing Zhang a,b,a Institute of Marine biotechnology,department of biological sciences and biotechnology,tsinghua university,beijing 100084.china b Protein Science Laboratory of the Ministry of Education,tsinghua university,beijing 100084.china Institute of Marine biotechnology Department of Biological Sciences and Biotechnology Tsinghua University Beijing 100084 China Protein Science Laboratory of the Ministry of Education Tsinghua University Beijing 100084 China

A 1063 bp cDNA clone encoding a putative 37 kDa laminin receptor precursor (37 kDa LRP) is isolated from the mantle tissue of pearl oyster,Pinctada fucata. The amino acid sequence predicted from the cDNA sequence is 301 residues long,with a calculated molec-ular mass of 33.5 kDa. RT-PCR analysis shows that 37 kDa LRP mRNA is especially highly expressed in the mantle while widely expressed in several tissues. In situ hybridization analysis reveals that 37 kDa LRP is expressed in the outer epithelial cells of the mantle edge,suggesting its involvement in cell proliferation and secretion in P. fucata. The identification and characterization of 37 kDa LRP in the pearl oyster will help us to further understand the signal transduction in the processes of mantle epithelial cell proliferation and tissue formation.

关键词： 37 kDa laminin receptor precursor Mantle epithelial cell Pearl oyster

Assembly and structure of protein phosphatase 2A

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china(Life sciences) 2009年第2期52卷 135-146页

作者： SHI Yi Gong Center for Structural Biology, department of biological sciences and biotechnology, and School of Medicine, tsinghua university, beijing 100084. china 1. Center for Structural Biology Department of Biological Sciences and Biotechnology and School of Medicine Tsinghua University Beijing 100084 China

Protein phosphatase 2A (PP2A) represents a conserved family of important protein serine/threonine phosphatases in species ranging from yeast to human. The PP2A core enzyme comprises a scaffold subunit and a catalytic subunit. The heterotrimeric PP2A holoenzyme consists of the core enzyme and a variable regulatory subunit. The catalytic subunit of PP2A is subject to reversible methylation, medi-ated by two conserved enzymes. Both the PP2A core and holoenzymes are regulated through interac-tion with a large number of cellular cofactors. Recent biochemical and structural investigation reveals critical insights into the assembly and function of the PP2A core enzyme as well as two families of holoenzyme. This review focuses on the molecular mechanisms revealed by these latest advances.

关键词： protein phosphorylation dephosphorylation PP2A structure mechanism

A measurement error model for microarray data analysis

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2005年第7期15卷 614-620页

作者： ZHOU Yiming and CHENG Jing ( department of biological sciences and biotechnology, tsinghua university, beijing 100084. china State Key Laboratory of Biomembrane and Membrane biotechnology, tsinghua university, beijing 100084. china National Engineering Research Center for beijing Biochip Technology, 18 Life Science Parkway, beijing 102206, china) department of biological sciences and biotechnology Tsinghua University Beijing 100084 China. State Key Laboratory of Biomembrane and Membrane biotechnology Tsinghua University Beijing 100084 China. National Engineering Research Center for beijing Biochip Technology 18 Life Science Parkway Beijing 102206 China

Microarray technology has been widely used to analyze the gene expression levels by detecting fluorescence intensity in a high throughput fashion. However, since the measurement error produced from various sources in microarray experiments is heterogeneous and too large to be ignored, we propose here a measurement error model for microarray data processing, by which the standard deviation of the measurement error is demonstrated to be linearly increased with fluorescence intensity. A robust algorithm, which estimates the parameters of the measurement error model from a single microarray without replicated spots, is provided. The model and algorithm for estimating of the parameters from a given data set are tested on both the real data set and the simulated data set, and the result has been proven satisfactory. And, combining the measurement error model with traditional Z-test method, a full statistical model has been developed It can significantly improve the statistical inference for identifying differentially expressed genes.

关键词： microarray measurement error model parameter estimation differentially expressed genes.

Electrophysiological research of synapse formation from beginning to maturity

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Science Bulletin 1998年第1期43卷 55-59页

作者： XIE Zuoping and ZHENG Yufang State Key Laboratory of Biomembrane and Membrane Biotechnique department of biological sciences and biotechnology, tsinghua university, beijing 100084. china State Key Laboratory of Biomembrane and Membrane Biotechnique Tsinghua University Beijing China department of biological sciences and biotechnology Tsinghua University Beijing China

The development of synapses is an important question in neurobiology. We employ patchclamp technique to record MEPCs and EPCs of myoballs in Xenopus cell culture. The rate of EPC/MEPC is related with synapses maturation. Accordingly, we define the mature synapses as those whose rate of presynaptic membrane’s EPC to MEPC is more than 8. The process of maturation needs about 2-5 h after neurites contact with myoballs. We divide the development of synapses into three stages: young, developing and mature. The neurotransmitters stack gradually and increase by hundreds of times along with young synapses growing into maturity. So the process of synapses maturation should include presynaptic membrane specialization, postsynaptic membrane specialization and neurotransmitters stack.

关键词： definition of mature synapse α latrotoxin (α LTX) neurotransmitter stack.

Structure and regulatory function of plant transcription factors

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2001年第4期46卷 271-278页

作者： LIU Qiang, ZHANG Guiyou & CHEN Shouyidepartment of biological Science and biotechnology, tsinghua Univorsity, beijing 100084. china department of biological Science and biotechnology, State Laboratory of Biomembrane and Membrane biotechnology, tsinghua university, beijing 100084. china Institute of Genetics, Chinese Academy of sciences, beijing 100101, china department of biological Science and biotechnology Tsinghua University Beijing China department of biological Science and biotechnology State Laboratory of Biomembrane and Membrane Biotechnology Tsinghua University Beijing China Institute of Genetics Chinese Academy of Sciences Beijing China

The expression of inducible genes in plants is regulated by specific transcription factors at the transcrip-tional level. A typical transcription factor usually contains a DNA-binding domain, a transcription regulation domain, a dimerization site and a nuclear localization domain. These functional domains define the characteristic, localization and regulatory role of a transcription factor. Transcription factors recognize and bind to specific cis-acting elements or interact with other proteins, and then activate or repress the transcription of target genes by their functional domains. In recent years, elucidation on the structure and function of transcription factors has become an important subject in plant molecular biology.

关键词： transcription factor DNA-binding domain cis-acting element.

Dimensions of a class of high-dimensional homogeneous Moran sets and Moran classes

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2002年第9期12卷 17-22页

作者： YAN Ping(department of Mathematical sciences, tsinghua university, beijing 100084. china) Tsing Hua Univ Dept Math Sci Beijing 100084 Peoples R China

A class of high-dimensional homogeneous Moran sets and Moran classes are introduced and some dimensional properties are studied. The Hausdorff dimension, modified lower box-counting dimension, lower and upper box-counting dimension, and packing dimension of high-dimensional homogeneous and partial homogeneous Cantor sets are determined. Moreover, a kind of fractal E is obtained, which is not regular but with the property Dimw(Ed) = dDimw(E), where w denotes any of the dimensions mentioned above.

关键词： Moran set Moran class homogeneous Cantor set partial homogeneous Cantor set dimension.