排序方式: 共有71条查询结果,搜索用时 15 毫秒
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Baslé A Rummel G Storici P Rosenbusch JP Schirmer T 《Journal of molecular biology》2006,362(5):933-942
Porins form transmembrane pores in the outer membrane of Gram-negative bacteria with matrix porin OmpF and osmoporin OmpC from Escherichia coli being differentially expressed depending on environmental conditions. The three-dimensional structure of OmpC has been determined to 2.0 A resolution by X-ray crystallography. As expected from the high sequence similarity, OmpC adopts the OmpF-like 16-stranded hollow beta-barrel fold with three beta-barrels associated to form a tight trimer. Unlike in OmpF, the extracellular loops form a continuous wall at the perimeter of the vestibule common to the three pores, due to a 14-residues insertion in loop L4. The pore constriction and the periplasmic outlet are very similar to OmpF with 74% of the pore lining residues being conserved. Overall, only few ionizable residues are exchanged at the pore lining. The OmpC structure suggests that not pore size, but electrostatic pore potential and particular atomic details of the pore linings are the critical parameters that physiologically distinguish OmpC from OmpF. 相似文献
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Michael D. Pierschbacher James W. Polarek William S. Craig Juerg F. Tschopp Nancy J. Sipes John R. Harper 《Journal of cellular biochemistry》1994,56(2):150-154
Manipulation of the Wound healing process and the manner in which tissues interact with inertbiomaterials were both made possible with the discovery of arginine-glucine (RGD) acid as a major cell recognition signal in the extracellular matrix. Whether promoting cell adhesion can be rationally designed to incorporate both stability and integrin specificity. Synthetic peptides containing this sequence have been linked to biodegradable biopolumers and introduced for the enhancement of dermal and corneal wound healing. By accelerating the healing reaction using RGD-containing peptides, the quality of regenerted tissue seems to be improved, the extent of fibrosis retricted, and the risk of microbial infection may be reduced. Controlling the degree of fibrosis that often accmmpanies the healing of wounds and the reaction of tissue to foreign materials can also be achieved by natural antagonists of fibrogenic activity of TGF-beta animal models of kidney fobrosis. There advances in the biotechnology of wound healing and tissue regeneration eventually will have an overal impact on the quality of health care. 相似文献
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Jens Leifeld Stefanie Meyer Karen Budge Maria Teresa Sebastia Michael Zimmermann Juerg Fuhrer 《PloS one》2015,10(3)
Root turnover is an important carbon flux component in grassland ecosystems because it replenishes substantial parts of carbon lost from soil via heterotrophic respiration and leaching. Among the various methods to estimate root turnover, the root’s radiocarbon signature has rarely been applied to grassland soils previously, although the value of this approach is known from studies in forest soils. In this paper, we utilize the root’s radiocarbon signatures, at 25 plots, in mountain grasslands of the montane to alpine zone of Europe. We place the results in context of a global data base on root turnover and discuss driving factors. Root turnover rates were similar to those of a subsample of the global data, comprising a similar temperature range, but measured with different approaches, indicating that the radiocarbon method gives reliable, plausible and comparable results. Root turnover rates (0.06–1.0 y-1) scaled significantly and exponentially with mean annual temperatures. Root turnover rates indicated no trend with soil depth. The temperature sensitivity was significantly higher in mountain grassland, compared to the global data set, suggesting additional factors influencing root turnover. Information on management intensity from the 25 plots reveals that root turnover may be accelerated under intensive and moderate management compared to low intensity or semi-natural conditions. Because management intensity, in the studied ecosystems, co-varied with temperature, estimates on root turnover, based on mean annual temperature alone, may be biased. A greater recognition of management as a driver for root dynamics is warranted when effects of climatic change on belowground carbon dynamics are studied in mountain grasslands. 相似文献
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Cieslak T Polepalli JS White A Müller K Borsch T Barthlott W Steiger J Marchant A Legendre L 《American journal of botany》2005,92(10):1723-1736
The genus Pinguicula is one of the three genera of the carnivorous Lentibulariaceae, comprising approximately 80 species. Phylogeny inference using nucleotide sequences of the chloroplast gene matK and the trnK group II intron, as well as a set of 32 morphological characters revealed five well-supported, major lineages within the genus. These lineages largely reflect radiations in clearly defined geographic regions, whereas most previously recognized sections of the genus are shown to be para- or polyphyletic. A species-rich Mexican-Central American-Caribbean clade has the Eurasian P. alpina and an East Asian clade as successive sisters. All three are characterized by a production of flower buds on winter-resting plants, a specific corolla hair structure and a very large corolla lower central lobe. Another diverse clade is composed of species with primarily European distribution including the widespread type species P. vulgaris. For this clade, vegetative reproduction during dormancy is synapomorphic. Species native to SE North America and the South American Andes and a group of Mediterranean and NE Atlantic coast species together appear in a fifth well-supported clade, that is characterized by a tropical-type growth habit. It is the only clade that has reached temperate zones of the southern hemisphere. 相似文献
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Cutillas PR Biber J Marks J Jacob R Stieger B Cramer R Waterfield M Burlingame AL Unwin RJ 《Proteomics》2005,5(1):101-112
Polarized epithelial cells are responsible for the vectorial transport of solutes and have a key role in maintaining body fluid and electrolyte homeostasis. Such cells contain structurally and functionally distinct plasma membrane domains. Brush border and basolateral membranes of renal and intestinal epithelial cells can be separated using a number of different separation techniques, which allow their different transport functions and receptor expressions to be studied. In this communication, we report a proteomic analysis of these two membrane segments, apical and basolateral, obtained from the rat renal cortex isolated by two different methods: differential centrifugation and free-flow electrophoresis. The study was aimed at assessing the nature of the major proteins isolated by these two separation techniques. Two analytical strategies were used: separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) at the protein level or by cation-exchange high-performance liquid chromatography (HPLC) after proteolysis (i.e., at the peptide level). Proteolytic peptides derived from the proteins present in gel pieces or from HPLC fractions after proteolysis were sequenced by on-line liquid chromatography-tandem mass spectrometry (LC-MS/MS). Several hundred proteins were identified in each membrane section. In addition to proteins known to be located at the apical and basolateral membranes, several novel proteins were also identified. In particular, a number of proteins with putative roles in signal transduction were identified in both membranes. To our knowledge, this is the first reported study to try and characterize the membrane proteome of polarized epithelial cells and to provide a data set of the most abundant proteins present in renal proximal tubule cell membranes. 相似文献
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Christine F Baes Marlies A Dolezal James E Koltes Beat Bapst Eric Fritz-Waters Sandra Jansen Christine Flury Heidi Signer-Hasler Christian Stricker Rohan Fernando Ruedi Fries Juerg Moll Dorian J Garrick James M Reecy Birgit Gredler 《BMC genomics》2014,15(1)