共查询到20条相似文献,搜索用时 31 毫秒
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Cross-linked homopolymers and copolymers of 2-hydroxyethyl methacrylate, HEMA, and ethylene glycol methacrylate phosphate, MOEP, have been synthesized, and the diffusion of water into these systems has been investigated. Only polymers with 0-20 mol % MOEP exhibited ideal swelling behavior as extensive fracturing occurred in the systems with greater than 20 mol % MOEP as the polymers began to swell during water sorption. Gravimetric studies were used in conjunction with magnetic resonance imaging of the diffusion front to elucidate the diffusion mechanism for these systems. In the case of the cross-linked HEMA homopolymer gels, the water transport mechanism was determined to be concentration-independent Fickian diffusion. However, as the fraction of MOEP in the network increased, the transport mechanism became increasingly exponentially concentration-dependent but remained Fickian until the polymer consisted of 30 mol % MOEP where the water transport could no longer been described by Fickian diffusion. 相似文献
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The Ndc80 complex is a core component of the kinetochore, which links chromosomes to microtubules. Recently, Ciferri et al. (2008) published an atomic-level structure of the complex with implications for kinetochore architecture and for the generation and control of chromosome movements during mitosis. 相似文献
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A new paper from Campellone et al. in a recent issue of Cell identifies WHAMM, a multifunctional protein that stimulates Arp2/3-mediated actin polymerization, binds and organizes microtubules, and influences the structure and efficiency of the Golgi complex. WHAMM's membrane localization at the entry face of the Golgi complex is novel for an actin nucleation-promoting factor, and highlights the importance of the cytoskeleton in organizing the secretory pathway. 相似文献
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We have investigated the import pathway of the nuclear-encoded chloroplast protein ferredoxin. By using purified precursor protein and washed intact chloroplasts in a defined in vitro uptake system, we show that preferredoxin is fully import-competent by itself. In addition, we show also that the in vitro, in a wheat germ lysate, synthesized preferredoxin is not stably associated with another protein. Import is dependent only on ATP and does not require the presence of cytosolic proteins. Translocation could be largely stimulated by the thiol reducing agent dithiothreitol (DTT). To determine whether DTT acts on the precursor or on the chloroplast, we modified the 5 cysteines in the precursor by a reaction with iodoacetamide, thereby preventing the formation of disulfide bridges in the precursor. The import of this modified precursor was still stimulated by the addition of DTT, indicating that DTT had a stimulating effect on the chloroplast import machinery. In the case of the modified precursor, the import must have taken place without iron-sulfur cluster attachment in the stroma. The modified precursor could be imported with a similar efficiency as the parent precursor showing that import takes place independently from cofactor assembly. 相似文献
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Innexins get into the gap 总被引:9,自引:0,他引:9
Phelan P Starich TA 《BioEssays : news and reviews in molecular, cellular and developmental biology》2001,23(5):388-396
Connexins were first identified in the 1970s as the molecular components of vertebrate gap junctions. Since then a large literature has accumulated on the cell and molecular biology of this multi-gene family culminating recently in the findings that connexin mutations are implicated in a variety of human diseases. Over two decades, the terms "connexin" and "gap junction" had become almost synonymous. In the last few years a second family of gap-junction genes, the innexins, has emerged. These have been shown to form intercellular channels in genetically tractable invertebrate organisms such as Drosophila melanogaster and Caenorhabditis elegans. The completed genomic sequences for the fly and worm allow identification of the full complement of innexin genes in these two organisms and provide valuable resources for genetic analyses of gap junction function. 相似文献
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William A. Wells 《The Journal of cell biology》2004,165(4):456-457