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1
Sivia, Sebenova, Katarina Krajcova und Velisek Karol. „Sensors in the Subsystems of Intelligent Assembly Cell“. Applied Mechanics and Materials 220-223 (November 2012): 1825–28. http://dx.doi.org/10.4028/www.scientific.net/amm.220-223.1825.
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Intelligent assembly cell conception includes new solution kind of how to create structures of automated and flexible assembly system. Intelligent behavior of the system as the control system will repose on monitoring of important parameters of the system in the real time. The designed automation sensory equipment provides for automatic monitoring of all automated equipment motions in the first case and in the second important level is important to obtain the information about the status, presence and character of the assembled objects or assembly process. The application of the sensory equipment in the intelligent assembly process is designed on the ground of the sensory object properties of the pneumatic actuator model.
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Mao, Yong, und Jean E. Schwarzbauer. „Fibronectin fibrillogenesis, a cell-mediated matrix assembly process“. Matrix Biology 24, Nr. 6 (September 2005): 389–99. http://dx.doi.org/10.1016/j.matbio.2005.06.008.
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3
Palm, R. „Interaction Process Models in a Robotized Assembly Cell“. IFAC Proceedings Volumes 22, Nr. 10 (August 1989): 385–90. http://dx.doi.org/10.1016/s1474-6670(17)53204-8.
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4
Rónai, László, und Tamás Szabó. „Stability Analysis of an Assembly Process Using Simulation“. Acta Technica Jaurinensis 13, Nr. 1 (14.02.2020): 14–24. http://dx.doi.org/10.14513/actatechjaur.v13.n1.531.
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This paper deals with an assembly process of batteries with cell holder. The operation involves snap-fitting phenomenon, which is a mechanical stability problem. The structure of the cell holder is modelled with 2D flexible beam elements assuming large displacements. The stability of the equilibrium is investigated taking into consideration non-frictional and Coulomb frictional contacts. The goal of the analysis to determine the boundary point of the feed-motion from which the battery snaps-in to the final assembled position autonomously. The effect of the velocity of the battery feed-motion is also considered with energy approach.
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Ružarovský, Roman, Nina Danišová und Karol Velíšek. „Sensory System Design as an Implement for the Development of the Intelligent Assembly Cell“. Advanced Materials Research 628 (Dezember 2012): 287–91. http://dx.doi.org/10.4028/www.scientific.net/amr.628.287.
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Intelligent assembly cell conception includes new solution kind of how to create structures of automated and flexible assembly system. Intelligent behavior of the system as the control system will repose on monitoring of important parameters of the system in the real time. The designed automation sensory equipment provides for automatic monitoring of all automated equipment motions in the first case and in the second important level is important to obtain the information about the status, presence and character of the assembled objects or assembly process. The application of the sensory equipment in the intelligent assembly process is designed on the ground of the sensory object properties of the pneumatic actuator model. In the paper is described the sensor equipment application for the assembly part sorting situated before the input of the object into the assembly process and for the check function of assembly product is designed the combination of sensory equipment.
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Parker, Scott D., und Eric Hunter. „A Cell-Line-Specific Defect in the Intracellular Transport and Release of Assembled Retroviral Capsids“. Journal of Virology 74, Nr. 2 (15.01.2000): 784–95. http://dx.doi.org/10.1128/jvi.74.2.784-795.2000.
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ABSTRACT Retrovirus assembly involves a complex series of events in which a large number of proteins must be targeted to a point on the plasma membrane where immature viruses bud from the cell. Gag polyproteins of most retroviruses assemble an immature capsid on the cytoplasmic side of the plasma membrane during the budding process (C-type assembly), but a few assemble immature capsids deep in the cytoplasm and are then transported to the plasma membrane (B- or D-type assembly), where they are enveloped. With both assembly phenotypes, Gag polyproteins must be transported to the site of viral budding in either a relatively unassembled form (C type) or a completely assembled form (B and D types). The molecular nature of this transport process and the host cell factors that are involved have remained obscure. During the development of a recombinant baculovirus/insect cell system for the expression of both C-type and D-type Gag polyproteins, we discovered an insect cell line (High Five) with two distinct defects that resulted in the reduced release of virus-like particles. The first of these was a pronounced defect in the transport of D-type but not C-type Gag polyproteins to the plasma membrane. High Five cells expressing wild-type Mason-Pfizer monkey virus (M-PMV) Gag precursors accumulate assembled immature capsids in large cytoplasmic aggregates similar to a transport-defective mutant (MA-A18V). In contrast, a larger fraction of the Gag molecules encoded by the M-PMV C-type morphogenesis mutant (MA-R55W) and those of human immunodeficiency virus were transported to the plasma membrane for assembly and budding of virions. When pulse-labeled Gag precursors from High Five cells were fractionated on velocity gradients, they sedimented more rapidly, indicating that they are sequestered in a higher-molecular-mass complex. Compared to Sf9 insect cells, the High Five cells also demonstrate a defect in the release of C-type virus particles. These findings support the hypothesis that host cell factors are important in the process of Gag transport and in the release of enveloped viral particles.
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Vetríková, Nina, und Michala Šimúnová. „Algorithms and Evolution Diagrams Application for Determining the New Assembly Process Sequences“. Applied Mechanics and Materials 693 (Dezember 2014): 16–21. http://dx.doi.org/10.4028/www.scientific.net/amm.693.16.
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In this contribution is presented application of evolution diagrams at the assembly process of at the intelligent manufacturing and assembly cell. At this assembly cell was designed new assembly configuration for next research to our department and institute. Intelligent manufacturing and assembly cell is situated at the Institute of Production Systems and Applied Mechanics. The complex design of assembly sequences at the intelligent manufacturing and assembly cell is realized on the basis of evolution diagrams and outgoing from knowledge about intelligent manufacturing and assembly systems. For intelligence increase of assembly process was this cell completed by additional sensors. This assembly process is possible to name intelligent assembly process.
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Koch, G. L., C. Booth und F. B. Wooding. „Dissociation and re-assembly of the endoplasmic reticulum in live cells“. Journal of Cell Science 91, Nr. 4 (01.12.1988): 511–22. http://dx.doi.org/10.1242/jcs.91.4.511.
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The endoplasmic reticulum (ER) of a typical interphase 3T3 fibroblast consists of a compact perinuclear arrangement of cisternae and lamellae which can be observed by immunofluorescence with anti-endoplasmin. During mitosis the reticulum dissociates into small fragments from which it appears to re-assemble in the daughter cells. When interphase 3T3 cells are exposed to calcium ionophores, but not other ionophores, there is a similar dissociation of the ER into small uniform fragments, which are dispersed throughout the cytoplasm. Electron microscopy shows that the fragments consist of small vesicular structures and that essentially all of the rough ER except the nuclear envelope is dissociated. The dissociation of the ER by calcium ionophore is a relatively specific process since other organelles and supramolecular assemblies remain unaffected. When cells with dissociated ER are returned to normal medium, there is a rapid reassembly of the fragments into the continuous reticulum. In a proportion of the cells it is possible to observe linear arrays of the fragments, which probably represent intermediates in the re-assembly process. These observations demonstrate that the ER in interphase 3T3 cells can be dissociated into, and re-assembled from, small fragments. Re-assembly of the ER from the fragments is dependent on the presence of millimolar levels of calcium in the external medium. In the presence of calcium, re-assembly is inhibited by the calcium channel blocker, verapamil. Thus calcium ions appear to play an important role in ER structure and assembly.
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Agnetis, A., R. Macchiaroli und F. Nicolò. „Optimization of the Assembly Process in a Flexible Cell“. IFAC Proceedings Volumes 29, Nr. 1 (Juni 1996): 613–18. http://dx.doi.org/10.1016/s1474-6670(17)57730-7.
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Liu, Hai Xia, Sheng Jie Li, Feng Lin und Yong Nian Yan. „Modified Gelatin-Based Cell Assembling Process Using Glycerin“. Advanced Materials Research 476-478 (Februar 2012): 443–47. http://dx.doi.org/10.4028/www.scientific.net/amr.476-478.443.
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Cell assembly technology adopting the gelatin-based composite materials has found broad application in the field of disease mechanism research, drug development and organ reconstruction etc. But there are still several troublesome problems, such as the necessaries of high forming concentration of gelatin-based materials and the cell damage produced during extrusion. In view of existing situation, a modified gelatin-based cell assembling process using glycerin was brought forward. The results showed that adding 10% (v/v) glycerin to the existing gelatin-based composite materials, the cells inactivation effect under 4 °C or lower temperature environment can be reduced obviously, meanwhile, the glycerin has a compensatory effect of gelatin. It can significantly improve the forming temperature and the cell survival rate, get high cell survival rate even when the scanning speed is on 40 mm/s. In addition, the glycerin is easier to dissolve in culture medium in the tissue analog training process; it is more conducive to the rapid materials degradation, as well as cell proliferation and tissue regeneration. Therefore, modified gelatin-based cell assembly process with glycerin will be more widely used in tissue or organ in vitro assembly process.
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Khmelinskii, Anton, Clare Lawrence, Johanna Roostalu und Elmar Schiebel. „Cdc14-regulated midzone assembly controls anaphase B“. Journal of Cell Biology 177, Nr. 6 (11.06.2007): 981–93. http://dx.doi.org/10.1083/jcb.200702145.
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Spindle elongation in anaphase of mitosis is a cell cycle–regulated process that requires coordination between polymerization, cross-linking, and sliding of microtubules (MTs). Proteins that assemble at the spindle midzone may be important for this process. In this study, we show that Ase1 and the separase–Slk19 complex drive midzone assembly in yeast. Whereas the conserved MT-bundling protein Ase1 establishes a midzone, separase–Slk19 is required to focus and center midzone components. An important step leading to spindle midzone assembly is the dephosphorylation of Ase1 by the protein phosphatase Cdc14 at the beginning of anaphase. Failure to dephosphorylate Ase1 delocalizes midzone proteins and delays the second, slower phase of anaphase B. In contrast, in cells expressing nonphosphorylated Ase1, anaphase spindle extension is faster, and spindles frequently break. Cdc14 also controls the separase–Slk19 complex indirectly via the Aurora B kinase. Thus, Cdc14 regulates spindle midzone assembly and function directly through Ase1 and indirectly via the separase–Slk19 complex.
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Connolly, Amy A., Kenji Sugioka, Chien-Hui Chuang, Joshua B. Lowry und Bruce Bowerman. „KLP-7 acts through the Ndc80 complex to limit pole number in C. elegans oocyte meiotic spindle assembly“. Journal of Cell Biology 210, Nr. 6 (14.09.2015): 917–32. http://dx.doi.org/10.1083/jcb.201412010.
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During oocyte meiotic cell division in many animals, bipolar spindles assemble in the absence of centrosomes, but the mechanisms that restrict pole assembly to a bipolar state are unknown. We show that KLP-7, the single mitotic centromere–associated kinesin (MCAK)/kinesin-13 in Caenorhabditis elegans, is required for bipolar oocyte meiotic spindle assembly. In klp-7(−) mutants, extra microtubules accumulated, extra functional spindle poles assembled, and chromosomes frequently segregated as three distinct masses during meiosis I anaphase. Moreover, reducing KLP-7 function in monopolar klp-18(−) mutants often restored spindle bipolarity and chromosome segregation. MCAKs act at kinetochores to correct improper kinetochore–microtubule (k–MT) attachments, and depletion of the Ndc-80 kinetochore complex, which binds microtubules to mediate kinetochore attachment, restored bipolarity in klp-7(−) mutant oocytes. We propose a model in which KLP-7/MCAK regulates k–MT attachment and spindle tension to promote the coalescence of early spindle pole foci that produces a bipolar structure during the acentrosomal process of oocyte meiotic spindle assembly.
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Jánoš, Rudolf, und Baňasová Antónia. „CELL DESIGN FOR GEARBOX ASSEMBLY“. TECHNICAL SCIENCES AND TECHNOLOG IES, Nr. 3(13) (2018): 49–54. http://dx.doi.org/10.25140/2411-5363-2018-3(13)-49-54.
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Urgency of the research. Automation is the next step in increasing productivity and performance. It represents the autonomous management of the entire system as well as the assembly or production process. This completely eliminates a human factor from the work process. Target setting. Today's robots and manipulators are now autonomous. Automated systems can be found in almost all industries. They are an indispensable part of non-productive environments, but we can also find them in non-industrial areas as well. Their dynamic development extends to service robotics. For their productivity, they have reached a high level, but their development is constantly advancing by refining their subsystems, introducing new functional principles, or upgrading compo-nents and elements involved in the construction of these mechanisms. Actual scientific researches and issues analysis. To meet the requirements of automatition cells, it was slowly being applied to flexible production systems. These are systems that consist of computers and are connected by means of control units. They are characterized by complexity, flexibility and, above all, the multiplicity of elements. Such flexible systems based on the modularity, that systems are composed of individual modules and subsystems that can be adapted as needed. Uninvestigated parts of general issues defining. Design of automated robotic workplaces, based on the intensive development of functional and especially kinematic structures of the workplace as a whole. The research objective. To what extent is it possible for the work process to be mechanized or automated depends also on the level of development of the used equipment. In today's development stage, design of automated device is also automated. The statement of basic materials. This article focuses on the design of the manipulator, whose main task is to perform the assembly. Analysis of the task illustrates the principle design of the solution, which is also the starting point for the design of the universal manipulator. Current requirements of application practice for robotic technology have caused increased requirements for its functions, characteristics and parameters which cannot be always covered by the traditional approach to its design and construction. Conclusions. In this article describes in more detail the knowledge and division of the proposed devices and mechanisms, which provides an initial understanding of design. By analyzing the problem and defining the necessary parameters, the design of the manipulator was developed. Festo's design software also helped to make the right choice.
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Peng, Lin Fa, Dian Kai Qiu, Pei Yun Yi und Xin Min Lai. „Investigation of Thermal Influence on the Assembly of Polymer Electrolyte Membrane Fuel Cell Stacks“. Advanced Materials Research 512-515 (Mai 2012): 1509–14. http://dx.doi.org/10.4028/www.scientific.net/amr.512-515.1509.
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The assembly force in a proton exchange membrane fuel cell (PEMFC) stack affects the characteristics of the porosity and electrical conductivity. Generally, the stack is assembled at room temperature while it’s operated at about 80 °Cor even higher. As a result, the assembly pressure can’t keep constant due to thermal expansion. This paper focuses on the contact pressure between membrane electrode assembly (MEA) and bipolar plates in real operations. A three-dimensional finite element (FE) model for the assembly process is established with coupled thermal-mechanical effects. The discipline of contact pressure under thermal-mechanical effect is investigated. A single cell stack is fabricated in house for the analysis of contact pressures on gas diffusion layer at different temperatures. The results show that as the temperature increases, contact pressure increases due to thermal expansion. It indicates that the influence of thermal expansion due to temperature variation should be taken into consideration for the design of the stack assembly process.
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Kleffe, Jürgen, Robert Weißmann und Florian F. Schmitzberger. „Single Nucleotide Polymorphisms Caused by Assembly Errors“. Genomics Insights 3 (Januar 2010): GEI.S3653. http://dx.doi.org/10.4137/gei.s3653.
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We compare the results of three different assembler programs, Celera, Phrap and Mira2, for the same set of about a hundred thousand Sanger reads derived from an unknown bacterial genome. In difference to previous assembly comparisons we do not focus on speed of computation and numbers of assembled contigs but on how the different sequence assemblies agree by content. Threefold consistently assembled genome regions are identified in order to estimate a lower bound of erroneously identified single nucleotide polymorphisms (SNP) caused by nothing but the process of mathematical sequence assembly. We identified 509 sequence triplets common to all three de-novo assemblies spanning only 34% (3.3 Mb) of the bacterial genome with 175 of these regions (~1.5 Mb) including erroneous SNPs and insertion/deletions. Within these triplets this on average leads to one error per 7,155 base pairs. Replacing the assembler Mira2 by the most recent version Mira3, the letter number even drops to 5,923. Our results therefore suggest that a considerably high number of erroneous SNPs may be present in current sequence data and mathematicians should urgently take up research on numerical stability of sequence assembly algorithms. Furthermore, even the latest versions of currently used assemblers produce erroneous SNPs that depend on the order reads are used as input. Such errors will severely hamper molecular diagnostics as well as relating genome variation and disease. This issue needs to be addressed urgently as the field is moving fast into clinical applications.
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Bareth, Bettina, Miroslav Nikolov, Isotta Lorenzi, Markus Hildenbeutel, David U. Mick, Christin Helbig, Henning Urlaub, Martin Ott, Peter Rehling und Sven Dennerlein. „Oms1 associates with cytochrome c oxidase assembly intermediates to stabilize newly synthesized Cox1“. Molecular Biology of the Cell 27, Nr. 10 (15.05.2016): 1570–80. http://dx.doi.org/10.1091/mbc.e15-12-0811.
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The mitochondrial cytochrome c oxidase assembles in the inner membrane from subunits of dual genetic origin. The assembly process of the enzyme is initiated by membrane insertion of the mitochondria-encoded Cox1 subunit. During complex maturation, transient assembly intermediates, consisting of structural subunits and specialized chaperone-like assembly factors, are formed. In addition, cofactors such as heme and copper have to be inserted into the nascent complex. To regulate the assembly process, the availability of Cox1 is under control of a regulatory feedback cycle in which translation of COX1 mRNA is stalled when assembly intermediates of Cox1 accumulate through inactivation of the translational activator Mss51. Here we isolate a cytochrome c oxidase assembly intermediate in preparatory scale from coa1Δ mutant cells, using Mss51 as bait. We demonstrate that at this stage of assembly, the complex has not yet incorporated the heme a cofactors. Using quantitative mass spectrometry, we define the protein composition of the assembly intermediate and unexpectedly identify the putative methyltransferase Oms1 as a constituent. Our analyses show that Oms1 participates in cytochrome c oxidase assembly by stabilizing newly synthesized Cox1.
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Mozdy, A. D., J. M. McCaffery und J. M. Shaw. „Dnm1p Gtpase-Mediated Mitochondrial Fission Is a Multi-Step Process Requiring the Novel Integral Membrane Component Fis1p“. Journal of Cell Biology 151, Nr. 2 (16.10.2000): 367–80. http://dx.doi.org/10.1083/jcb.151.2.367.
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Yeast Dnm1p is a soluble, dynamin-related GTPase that assembles on the outer mitochondrial membrane at sites where organelle division occurs. Although these Dnm1p-containing complexes are thought to trigger constriction and fission, little is known about their composition and assembly, and molecules required for their membrane recruitment have not been isolated. Using a genetic approach, we identified two new genes in the fission pathway, FIS1 and FIS2. FIS1 encodes a novel, outer mitochondrial membrane protein with its amino terminus exposed to the cytoplasm. Fis1p is the first integral membrane protein shown to participate in a eukaryotic membrane fission event. In a related study (Tieu, Q., and J. Nunnari. 2000. J. Cell Biol. 151:353–365), it was shown that the FIS2 gene product (called Mdv1p) colocalizes with Dnm1p on mitochondria. Genetic and morphological evidence indicate that Fis1p, but not Mdv1p, function is required for the proper assembly and distribution of Dnm1p-containing fission complexes on mitochondrial tubules. We propose that mitochondrial fission in yeast is a multi-step process, and that membrane-bound Fis1p is required for the proper assembly, membrane distribution, and function of Dnm1p-containing complexes during fission.
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He, Hongjian, und Bing Xu. „Instructed-Assembly (iA): A Molecular Process for Controlling Cell Fate“. Bulletin of the Chemical Society of Japan 91, Nr. 6 (15.06.2018): 900–906. http://dx.doi.org/10.1246/bcsj.20180038.
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Javorova, Angela, Erika Hrušková und Karol Velíšek. „Designing of Assembly Cell by CA System Support“. Key Engineering Materials 467-469 (Februar 2011): 2060–65. http://dx.doi.org/10.4028/www.scientific.net/kem.467-469.2060.
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This paper deals with a designing process of assembly cell using CA systems. Methodology solved in the paper is applying CA tools. The methodology is divided in to five main project phases: assembly product analysis, hardware specification, selection of proper control system, control system simulation and whole process simulation.
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Redick, S. D., und J. E. Schwarzbauer. „Rapid intracellular assembly of tenascin hexabrachions suggests a novel cotranslational process“. Journal of Cell Science 108, Nr. 4 (01.04.1995): 1761–69. http://dx.doi.org/10.1242/jcs.108.4.1761.
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Tenascin, an extracellular matrix protein that modulates cell adhesion, exists as a unique six-armed structure called a hexabrachion. The human hexabrachion is composed of six identical 320 kDa subunits and the structure is stabilized by inter-subunit disulfide bonds between amino-terminal segments. We have examined the biosynthesis of tenascin and its assembly into hexabrachions using pulsechase labeling of U-138 MG human glioma cells. Newly synthesized tenascin hexamers are secreted within 60 minutes of translation initiation. Intracellularly, as early as full length tenascin can be detected in pulse-labeled cell lysates, it is already in hexameric form. No precursors, such as monomers, dimers, or trimers, were identified that could be chased into hexamers. This lack of assembly intermediates suggests that nascent tenascin polypeptides associate prior to completion of translation. In contrast, fibronectin monomers in the same lysates are gradually formed into disulfide-bonded dimers. Although hexamer assembly is rapid, the rate-limiting step in secretion appears to be transport to the medial Golgi as endoglycosidase H-resistance was not detected until after a 30 minute chase. These results provide evidence for a novel co-translational mechanism of tenascin assembly which would be facilitated by its length and by the amino-terminal location of the assembly domain.
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Steen, Rikke L., und Philippe Collas. „Mistargeting of B-Type Lamins at the End of Mitosis“. Journal of Cell Biology 153, Nr. 3 (30.04.2001): 621–26. http://dx.doi.org/10.1083/jcb.153.3.621.
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We previously showed that targeting of protein phosphatase 1 (PP1) to the nuclear envelope (NE) by the A-kinase anchoring protein, AKAP149, correlates with nuclear assembly of B-type lamins in vitro. We demonstrate here that failure of AKAP149-mediated assembly of B-type lamins into the nuclear lamina at the end of mitosis is followed by apoptosis, and induces expression of the gene encoding A-type lamins in cells that normally do not express lamins A/C. In HeLa cells, inhibition of PP1 association with the NE mediated by a peptide containing the PP1-binding domain of AKAP149 results in failure of B-type lamins to assemble, and in their rapid caspase-dependent proteolysis. However, assembly of lamins A/C is not affected. Nonetheless, apoptosis follows within hours of nuclear reformation after mitosis. In lymphoid KE37 cells, which do not express lamins A/C, inhibition of B-type lamin assembly triggers rapid synthesis and nuclear assembly of both lamins A and C before apoptosis takes place. The results indicate that nuclear assembly of B-type lamins is essential for cell survival. They also suggest that mistargeting of B-type lamins at the end of mitosis elicits a tentative rescue process to assemble a nuclear lamina in lymphoid cells that normally do not express lamins A/C.
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McGill, Melanie A., R. F. Andrew McKinley und Tony J. C. Harris. „Independent cadherin–catenin and Bazooka clusters interact to assemble adherens junctions“. Journal of Cell Biology 185, Nr. 5 (25.05.2009): 787–96. http://dx.doi.org/10.1083/jcb.200812146.
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Proper epithelial structure requires adherens junction (AJ) assembly. In the early Drosophila embryo, AJ assembly depends on Bazooka (Baz; PAR-3), but it is unclear how Baz affects AJ assembly and what precursors are involved. To understand this process at the molecular level, we counted the number of core AJ proteins and Baz proteins at an average spot AJ (SAJ) and determined their dynamics with fluorescence recovery after photobleaching experiments. These data reveal that SAJs are subdivided into Baz clusters and cadherin–catenin clusters with independent protein numbers and dynamics. This independence suggests that precursory cadherin–catenin clusters might form before SAJ assembly. We identify cadherin–catenin clusters forming between apical microvilli. Further analyses show that they form independently of Baz and that Baz functions in repositioning them to apicolateral sites for full SAJ assembly. Our data implicate cell protrusions in initial cadherin–catenin clustering in the Drosophila melanogaster embryo. Then, independent Baz clusters appear to engage the cadherin–catenin clusters to assemble SAJs.
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Davies, Alexander E., und Kenneth B. Kaplan. „Hsp90–Sgt1 and Skp1 target human Mis12 complexes to ensure efficient formation of kinetochore–microtubule binding sites“. Journal of Cell Biology 189, Nr. 2 (19.04.2010): 261–74. http://dx.doi.org/10.1083/jcb.200910036.
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The formation of functional kinetochores requires the accurate assembly of a large number of protein complexes. The Hsp90–Sgt1 chaperone complex is important for this process; however, its targets are not conserved and its exact contribution to kinetochore assembly is unclear. Here, we show that human Hsp90–Sgt1 interacts with the Mis12 complex, a so-called keystone complex required to assemble a large fraction of the kinetochore. Inhibition of Hsp90 or Sgt1 destabilizes the Mis12 complex and delays proper chromosome alignment due to inefficient formation of microtubule-binding sites. Interestingly, coinhibition of Sgt1 and the SCF subunit, Skp1, increases Mis12 complexes at kinetochores and restores timely chromosome alignment but forms less-robust microtubule-binding sites. We propose that a balance of Mis12 complex assembly and turnover is required for the efficient and accurate assembly of kinetochore–microtubule binding sites. These findings support a novel role for Hsp90–Sgt1 chaperones in ensuring the fidelity of multiprotein complex assembly.
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Fowler, Devin, Vladimir Gurau und Daniel Cox. „Bridging the Gap between Automated Manufacturing of Fuel Cell Components and Robotic Assembly of Fuel Cell Stacks“. Energies 12, Nr. 19 (20.09.2019): 3604. http://dx.doi.org/10.3390/en12193604.
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Recently demonstrated robotic assembling technologies for fuel cell stacks used fuel cell components manually pre-arranged in stacks (presenters). Identifying the original orientation of fuel cell components and loading them in presenters for a subsequent automated assembly process is a difficult, repetitive work cycle which if done manually, deceives the advantages offered by either the automated fabrication technologies for fuel cell components or by the robotic assembly processes. We present for the first time a robotic technology which enables the integration of automated fabrication processes for fuel cell components with a robotic assembly process of fuel cell stacks into a fully automated fuel cell manufacturing line. This task uses a Yaskawa Motoman SDA5F dual arm robot with integrated machine vision system. The process is used to identify and grasp randomly placed, slightly asymmetric fuel cell components, to reorient them all in the same position and stack them in presenters in preparation for a subsequent robotic assembly process. The process was demonstrated as part of a larger endeavor of bringing to readiness advanced manufacturing technologies for alternative energy systems, and responds the high priority needs identified by the U.S. Department of Energy for fuel cells manufacturing research and development.
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Sakalian, Michael, und Eric Hunter. „Separate Assembly and Transport Domains within the Gag Precursor of Mason-Pfizer Monkey Virus“. Journal of Virology 73, Nr. 10 (01.10.1999): 8073–82. http://dx.doi.org/10.1128/jvi.73.10.8073-8082.1999.
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ABSTRACT Mason-Pfizer monkey virus (M-PMV), the prototypical type D retrovirus, assembles immature capsids within the cytoplasm of the cell prior to plasma membrane interaction. Several mutants of M-PMV Gag have been described which display altered transport, assembly, or both. In this report, we describe the use of an in vitro synthesis and assembly system to distinguish between defects in intracellular transport and the process of assembly itself for two previously describedgag gene mutants. Matrix domain mutant R55W converts the type D morphogenesis of M-PMV particles into type C and has been hypothesized to alter the transport of Gag, redirecting it to the plasma membrane where assembly subsequently occurs. We show here that R55W can assemble in both the in vitro translation-assembly system and within inclusion bodies in bacteria and thus has retained the capacity to assemble in the cytoplasm. This supports the concept that R55 is located within a domain responsible for the transport of Gag to an intracellular site for assembly. In contrast, deletions within the p12 domain of M-PMV Gag had previously been shown to affect the efficiency of particle formation such that under low-level expression conditions, Gag would fail to assemble. We demonstrate here that the efficiency of assembly in the in vitro system mirrors that seen in cells under expression conditions similar to that of an infection. These results argue that the p12 domain of this D-type retrovirus plays a critical role in the membrane-independent assembly of immature capsids.
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Grobelny, Paweł, Lukasz Furmanski, Jolanta B. Krolczyk und Stanisław Legutko. „Comparison of the Assembly Line and Cell Assembly - A Case Study in Mechanical Engineering Company“. Applied Mechanics and Materials 809-810 (November 2015): 1331–36. http://dx.doi.org/10.4028/www.scientific.net/amm.809-810.1331.
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The paper compares the assembly process of milling machine using two systems: cell system and production line which was introduced after the changes in the machine assembly system of the company. Assembly in both systems takes place in the SKD (semi-knocked-down) system, which consists of assembly finished, large parts of the machine (higher completeness units) imported into the country of installation. The illustrated example presents advantages and disadvantages of assembly of milling machines in two systems: cell assembly and on the assembly line. In this example, the employees in each cells conducted assembly of machines divided into stages, which was dependent on the supply of items in the designated field by warehouse workers. Warehouse department receives a signal at what stage the assembly process is and whether the delivery of certain items is necessary. The assembly system was reorganized and replaced by the assembly line. This assembly, as previously cell assembly, is carried out in SKD system, which is a partially exploded into components. Previously assembly method took place in three stages. After the change to the assembly line this process takes 14 steps.
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Ott, David E., Lori V. Coren, Raymond C. Sowder, Julian Adams und Ulrich Schubert. „Retroviruses Have Differing Requirements for Proteasome Function in the Budding Process“. Journal of Virology 77, Nr. 6 (15.03.2003): 3384–93. http://dx.doi.org/10.1128/jvi.77.6.3384-3393.2003.
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ABSTRACT Proteasome inhibitors reduce the budding of human immunodeficiency virus types 1 (HIV-1) and 2, simian immunodeficiency virus, and Rous sarcoma virus. To investigate this effect further, we examined the budding of other retroviruses from proteasome inhibitor-treated cells. The viruses tested differed in their Gag organization, late (L) domain usage, or assembly site from those previously examined. We found that proteasome inhibition decreased the budding of murine leukemia virus (plasma membrane assembly, PPPY L domain) and Mason-Pfizer monkey virus (cytoplasmic assembly, PPPY L domain), similar to the reduction observed for HIV-1. Thus, proteasome inhibitors can affect the budding of a virus that assembles within the cytoplasm. However, the budding of mouse mammary tumor virus (MMTV; cytoplasmic assembly, unknown L domain) was unaffected by proteasome inhibitors, similar to the proteasome-independent budding previously observed for equine infectious anemia virus (plasma membrane assembly, YPDL L domain). Examination of MMTV particles detected Gag-ubiquitin conjugates, demonstrating that an interaction with the ubiquitination system occurs during assembly, as previously found for other retroviruses. For all of the cell lines tested, the inhibitor treatment effectively inactivated proteasomes, as measured by the accumulation of polyubiquitinated proteins. The ubiquitination system was also inhibited, as evidenced by the loss of monoubiquitinated histones from treated cells. These results and those from other viruses show that proteasome inhibitors reduce the budding of viruses that utilize either a PPPY- or PTAP-based L domain and that this effect does not depend on the assembly site or the presence of monoubiquitinated Gag in the virion.
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Rollenhagen, Christiane, und Nelly Panté. „Nuclear import of spliceosomal snRNPsThis paper is one of a selection of papers published in this Special Issue, entitled The Nucleus: A Cell Within A Cell.“ Canadian Journal of Physiology and Pharmacology 84, Nr. 3-4 (März 2006): 367–76. http://dx.doi.org/10.1139/y05-101.
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Uridine-rich small nuclear ribonucleoproteins (U snRNPs) are the building units of the spliceosome. These RNA and protein complexes assemble in the cytoplasm. After proper assembly and RNA maturation, mature U snRNPs are imported into the cell nucleus, where they take part in the splicing process. In this paper we review the current knowledge of how U snRNPs enter the nucleus.
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Rabito, C. A., J. A. Jarrell und J. A. Scott. „Gap junctions and synchronization of polarization process during epithelial reorganization“. American Journal of Physiology-Cell Physiology 253, Nr. 2 (01.08.1987): C329—C336. http://dx.doi.org/10.1152/ajpcell.1987.253.2.c329.
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The formation of intercellular communication during epithelial reorganization of LLC-PK1 cells was studied with a new, nondisruptive flow cytometric technique. The assembly of these junctions, as demonstrated by cell-to-cell transfer of the fluorescent dye carboxy dimethyl fluorescein, occurs very early during epithelial reorganization. Close cell-to-cell interaction is required for the assembly to occur. Low temperature, treatment with 10(-3) M ouabain, or treatment with the Ca2+ ionophore A23187 inhibits assembly of these junctions. Removal of Ca2+ from the incubation medium, on the other hand, has no effect. Cycloheximide (10(-6) M) is also without effect, suggesting that protein synthesis is not required during the assembly of the junctions and that either the trypsin used to disperse the cells does not affect the junctional components or the cells have a rather extensive reserve pool of junctional precursors. The concomitant delay in the development of intercellular communication and the reorganization of the epithelial membrane, as previously observed with cells in asynchronous growth [Am. J. Physiol. 251 (Renal Fluid Electrolyte Physiol. 20): F978-F987, 1986], is consistent with the theory that junctional intercellular communication coordinates cellular activity during epithelial reorganization.
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Féral, Chloé C., Andries Zijlstra, Eugene Tkachenko, Gerald Prager, Margaret L. Gardel, Marina Slepak und Mark H. Ginsberg. „CD98hc (SLC3A2) participates in fibronectin matrix assembly by mediating integrin signaling“. Journal of Cell Biology 178, Nr. 4 (06.08.2007): 701–11. http://dx.doi.org/10.1083/jcb.200705090.
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Integrin-dependent assembly of the fibronectin (Fn) matrix plays a central role in vertebrate development. We identify CD98hc, a membrane protein, as an important component of the matrix assembly machinery both in vitro and in vivo. CD98hc was not required for biosynthesis of cellular Fn or the maintenance of the repertoire or affinity of cellular Fn binding integrins, which are important contributors to Fn assembly. Instead, CD98hc was involved in the cell's ability to exert force on the matrix and did so by dint of its capacity to interact with integrins to support downstream signals that lead to activation of RhoA small GTPase. Thus, we identify CD98hc as a membrane protein that enables matrix assembly and establish that it functions by interacting with integrins to support RhoA-driven contractility. CD98hc expression can vary widely; our data show that these variations in CD98hc expression can control the capacity of cells to assemble an Fn matrix, a process important in development, wound healing, and tumorigenesis.
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Lalitha, Krishnamoorthy, und Subbiah Nagarajan. „Strongly fluorescent organogels and self-assembled nanostructures from pyrene coupled coumarin derivatives: application in cell imaging“. Journal of Materials Chemistry B 3, Nr. 28 (2015): 5690–701. http://dx.doi.org/10.1039/c5tb00694e.
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The present work reports facile synthesis of pyrene coupled coumarin derivatives which could form self-assembled molecular gel and nano-flakes. The nanomaterials obtained via a self-assembly process could be potentially used in fluorescence imaging applications.
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Rahman, Sheikh Abdul, Peter Koch, Julian Weichsel, William J. Godinez, Ulrich Schwarz, Karl Rohr, Don C. Lamb, Hans-Georg Kräusslich und Barbara Müller. „Investigating the Role of F-Actin in Human Immunodeficiency Virus Assembly by Live-Cell Microscopy“. Journal of Virology 88, Nr. 14 (30.04.2014): 7904–14. http://dx.doi.org/10.1128/jvi.00431-14.
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ABSTRACTHuman immunodeficiency virus type 1 (HIV-1) particles assemble at the plasma membrane, which is lined by a dense network of filamentous actin (F-actin). Large amounts of actin have been detected in HIV-1 virions, proposed to be incorporated by interactions with the nucleocapsid domain of the viral polyprotein Gag. Previous studies addressing the role of F-actin in HIV-1 particle formation using F-actin-interfering drugs did not yield consistent results. Filamentous structures pointing toward nascent HIV-1 budding sites, detected by cryo-electron tomography and atomic force microscopy, prompted us to revisit the role of F-actin in HIV-1 assembly by live-cell microscopy. HeLa cells coexpressing HIV-1 carrying fluorescently labeled Gag and a labeled F-actin-binding peptide were imaged by live-cell total internal reflection fluorescence microscopy (TIR-FM). Computational analysis of image series did not reveal characteristic patterns of F-actin in the vicinity of viral budding sites. Furthermore, no transient recruitment of F-actin during bud formation was detected by monitoring fluorescence intensity changes at nascent HIV-1 assembly sites. The chosen approach allowed us to measure the effect of F-actin-interfering drugs on the assembly of individual virions in parallel with monitoring changes in the F-actin network of the respective cell. Treatment of cells with latrunculin did not affect the efficiency and dynamics of Gag assembly under conditions resulting in the disruption of F-actin filaments. Normal assembly rates were also observed upon transient stabilization of F-actin by short-term treatment with jasplakinolide. Taken together, these findings indicate that actin filament dynamics are dispensable for HIV-1 Gag assembly at the plasma membrane of HeLa cells.IMPORTANCEHIV-1 particles assemble at the plasma membrane of virus-producing cells. This membrane is lined by a dense network of actin filaments that might either present a physical obstacle to the formation of virus particles or generate force promoting the assembly process. Drug-mediated interference with the actin cytoskeleton showed different results for the formation of retroviral particles in different studies, likely due to general effects on the cell upon prolonged drug treatment. Here, we characterized the effect of actin-interfering compounds on the HIV-1 assembly process by direct observation of virus formation in live cells, which allowed us to measure assembly rate constants directly upon drug addition. Virus assembly proceeded with normal rates when actin filaments were either disrupted or stabilized. Taken together with the absence of characteristic actin filament patterns at viral budding sites in our analyses, this indicates that the actin network is dispensable for HIV-1 assembly.
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Czirok, Andras, Julia Zach, Beth A. Kozel, Robert P. Mecham, Elaine C. Davis und Brenda J. Rongish. „Elastic fiber macro-assembly is a hierarchical, cell motion-mediated process“. Journal of Cellular Physiology 207, Nr. 1 (April 2006): 97–106. http://dx.doi.org/10.1002/jcp.20573.
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Wu, Jiang, Quan Wei Zhang, Dong Lai, Jia Fa Liao und Chun Lan Jia. „Research on Cell Production Layout of TV Assembly Line“. Advanced Materials Research 926-930 (Mai 2014): 818–21. http://dx.doi.org/10.4028/www.scientific.net/amr.926-930.818.
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Traditional TV assembly line production mode faced with the problem of low productivity in response to the varieties of small batch orders. The paper studies Cell production mode, combined with television assembly process characteristics, to explore the Cell production layout mode that is suitable for TV assembly line.
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Kmiec, Eric B., JoAnn M. Sekiguchi und Allyson D. Cole. „Studies on the ATP requirements of in vitro chromatin assembly“. Biochemistry and Cell Biology 67, Nr. 8 (01.08.1989): 443–54. http://dx.doi.org/10.1139/o89-070.
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To gain a more complete understanding of the process of in vitro chromatin assembly, an examination of the energy requirements of nucleosome formation must be undertaken. The experiments outlined in this manuscript address this issue by making use of the Xenopus laevis S-150 cell-free extract. The S-150 catalyzes chromatin assembly on circular DNA templates dependent either on the exogenous addition of ATP or regeneration of endogenous ATP. We define two distinct, but temporally ordered, phases of the overall process. The first, nucleosome formation, occurs in the presence of endogenous levels of ATP, while the second phase, chromatin assembly, which we define as the development of properly spaced nucleosomes, requires a higher level of ATP. Both phases lead to a distribution of molecules with similar superhelical densities. Taken together, these data suggest that chromatin assembly may consist of two distinct steps differing in their strategy cofactor requirement. The experiments presented in this manuscript support the concept that nucleosomes first assemble, perhaps randomly, on the DNA and are gradually matured into a canonical chromatin structure with periodic spacing.Key words: DNA topoisomerase, chromatin assembly, energy requirements.
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Zaidel-Bar, R., M. Cohen, L. Addadi und B. Geiger. „Hierarchical assembly of cell–matrix adhesion complexes“. Biochemical Society Transactions 32, Nr. 3 (01.06.2004): 416–20. http://dx.doi.org/10.1042/bst0320416.
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The adhesion of cells to the extracellular matrix is a dynamic process, mediated by a series of cell-surface and matrix-associated molecules that interact with each other in a spatially and temporally regulated manner. These interactions play a major role in tissue formation, cellular migration and the induction of adhesion-mediated transmembrane signals. In this paper, we show that the formation of matrix adhesions is a hierarchical process, consisting of several sequential molecular events. One of the earliest steps in surface recognition is mediated, in some cells, by a 1 μm-thick cell-surface hyaluronan coat, which precedes the establishment of stable, cytoskeleton-associated adhesions. The earliest forms of these integrin-mediated contacts are dot-shaped FXs (focal complexes), which are formed under the protrusive lamellipodium of migrating cells. These adhesions recruit, sequentially, different anchor proteins that are involved in binding the actin cytoskeleton to the membrane. Conspicuous in its absence from FXs is zyxin, which is recruited to these sites only on retraction of the leading edge and the transformation of the FXs into a focal adhesion. Continuing application of force to focal adhesions results in the formation of fibrillar adhesions and reorganization of the extracellular matrix. The formation of these adhesions depends on actomyosin contractility and matrix pliability.
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Javorova, Angela, Martina Kusa und Miriam Matúšová. „Flexible Assembly Cell Optimization by Operational Analysis“. Applied Mechanics and Materials 309 (Februar 2013): 55–61. http://dx.doi.org/10.4028/www.scientific.net/amm.309.55.
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Operation analysis one of the system scientific disciplines closely related to system engineering. This discipline is part of praxeology. Praxeology deals with the research effectiveness of the procedure methods for all areas of human activity. The aim of this analysis is creating solved situation model and their optimization. Optimization is model extremes finding. There are model parameters values that output achieved minimum or maximum. Competitive environment is the reason for finding optimal solutions in the production process.
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Kim, Jane H., Amitava Mukherjee, Sethu M. Madhavan, Martha Konieczkowski und John R. Sedor. „WT1-interacting protein (Wtip) regulates podocyte phenotype by cell-cell and cell-matrix contact reorganization“. American Journal of Physiology-Renal Physiology 302, Nr. 1 (01.01.2012): F103—F115. http://dx.doi.org/10.1152/ajprenal.00419.2011.
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Podocytes respond to environmental cues by remodeling their slit diaphragms and cell-matrix adhesive junctions. Wt1-interacting protein (Wtip), an Ajuba family LIM domain scaffold protein expressed in the podocyte, coordinates cell adhesion changes and transcriptional responses to regulate podocyte phenotypic plasticity. We evaluated effects of Wtip on podocyte cell-cell and cell-matrix contact organization using gain-of- and loss-of-function methods. Endogenous Wtip targeted to focal adhesions in adherent but isolated podocytes and then shifted to adherens junctions after cells made stable, homotypic contacts. Podocytes with Wtip knockdown (shWtip) adhered but failed to spread normally. Noncontacted shWtip podocytes did not assemble actin stress fibers, and their focal adhesions failed to mature. As shWtip podocytes established cell-cell contacts, stable adherens junctions failed to form and F-actin structures were disordered. In shWtip cells, cadherin and β-catenin clustered in irregularly distributed spots that failed to laterally expand. Cell surface biotinylation showed diminished plasma membrane cadherin, β-catenin, and α-catenin in shWtip podocytes, although protein expression was similar in shWtip and control cells. Since normal actin dynamics are required for organization of adherens junctions and focal adhesions, we determined whether Wtip regulates F-actin assembly. Undifferentiated podocytes did not elaborate F-actin stress fibers, but when induced to overexpress WTIP, formed abundant stress fibers, a process blocked by the RhoA inhibitor C3 toxin and a RhoA kinase inhibitor. WTIP directly interacted with Rho guanine nucleotide exchange factor (GEF) 12 (Arhgef12), a RhoA-specific GEF enriched in the glomerulus. In conclusion, stable assembly of podocyte adherens junctions and cell-matrix contacts requires Wtip, a process that may be mediated by spatiotemporal regulation of RhoA activity through appropriate targeting of Arhgef12.
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Hill, Sam R., Reidun Twarock und Eric C. Dykeman. „The impact of local assembly rules on RNA packaging in a T = 1 satellite plant virus“. PLOS Computational Biology 17, Nr. 8 (24.08.2021): e1009306. http://dx.doi.org/10.1371/journal.pcbi.1009306.
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The vast majority of viruses consist of a nucleic acid surrounded by a protective icosahedral protein shell called the capsid. During viral infection of a host cell, the timing and efficiency of the assembly process is important for ensuring the production of infectious new progeny virus particles. In the class of single-stranded RNA (ssRNA) viruses, the assembly of the capsid takes place in tandem with packaging of the ssRNA genome in a highly cooperative co-assembly process. In simple ssRNA viruses such as the bacteriophage MS2 and small RNA plant viruses such as STNV, this cooperative process results from multiple interactions between the protein shell and sites in the RNA genome which have been termed packaging signals. Using a stochastic assembly algorithm which includes cooperative interactions between the protein shell and packaging signals in the RNA genome, we demonstrate that highly efficient assembly of STNV capsids arises from a set of simple local rules. Altering the local assembly rules results in different nucleation scenarios with varying assembly efficiencies, which in some cases depend strongly on interactions with RNA packaging signals. Our results provide a potential simple explanation based on local assembly rules for the ability of some ssRNA viruses to spontaneously assemble around charged polymers and other non-viral RNAs in vitro.
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Barrientos, Antoni, Karine Gouget, Darryl Horn, Ileana C. Soto und Flavia Fontanesi. „Suppression mechanisms of COX assembly defects in yeast and human: Insights into the COX assembly process“. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 1793, Nr. 1 (Januar 2009): 97–107. http://dx.doi.org/10.1016/j.bbamcr.2008.05.003.
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Lévy, F., R. Larsson und S. Kvist. „Translocation of peptides through microsomal membranes is a rapid process and promotes assembly of HLA-B27 heavy chain and beta 2-microglobulin translated in vitro.“ Journal of Cell Biology 115, Nr. 4 (15.11.1991): 959–70. http://dx.doi.org/10.1083/jcb.115.4.959.
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We have translated major histocompatibility complex (MHC) class I heavy chains and human beta 2-microglobulin in vitro in the presence of microsomal membranes and a peptide from the nucleoprotein of influenza A. This peptide stimulates assembly of HLA-B27 heavy chain and beta 2-microglobulin about fivefold. By modifying this peptide to contain biotin at its amino terminus, we could precipitate HLA-B27 heavy chains with immobilized streptavidin, thereby directly demonstrating class I heavy chain-peptide association under close to physiological conditions. The biotin-modified peptide stimulates assembly to the same extent as the unmodified peptide. Both peptides bind to the same site on the HLA-B27 molecule. Immediately after synthesis of the HLA-B27 heavy chain has been completed, it assembles with beta 2-microglobulin and peptide. These interactions occur in the lumen of the microsomes (endoplasmic reticulum), demonstrating that the peptide must cross the microsomal membrane in order to promote assembly. The transfer of peptide across the microsomal membrane is a rapid process, as peptide binding to heavy chain-beta 2-microglobulin complexes is observed in less than 1 min after addition of peptide. By using microsomes deficient of beta 2-microglobulin (from Daudi cells), we find a strict requirement of beta 2-microglobulin for detection of peptide interaction with the MHC class I heavy chain. Furthermore, we show that heavy chain interaction with beta 2-microglobulin is likely to precede peptide binding. Biotin-modified peptides are likely to become a valuable tool in studying MHC antigen interaction and assembly.
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WANG, XIAOFEI, ALESSANDRO IANNACCONE und MONICA M. JABLONSKI. „Contribution of Müller cells toward the regulation of photoreceptor outer segment assembly“. Neuron Glia Biology 1, Nr. 3 (August 2004): 291–96. http://dx.doi.org/10.1017/s1740925x05000049.
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The assembly of photoreceptor outer segments into stacked discs is a complicated process, the precise regulation of which remains a mystery. It is known that the integrity of the outer segment is heavily dependent upon surrounding cell types including the retinal pigment epithelium and Müller cells; however the role played by Müller cells within this photoreceptor-specific process has not been fully explored. Using an RPE-deprived but otherwise intact Xenopus laevis eye rudiment preparation, we reveal that Müller cell involvement in outer segment assembly is dependent upon the stimulus provided to the retina. Pigment epithelium-derived factor is able to support proper membrane folding after inhibition of Müller cell metabolism by alpha-aminoadipic acid, while isopropyl beta-D-thiogalactoside, a permissive glycan, requires intact Müller cell function. These results demonstrate that both intrinsic and extrinsic redundant mechanisms exist to support the ability of photoreceptors to properly assemble their outer segments. Our study further suggests that the receptor for pigment epithelium-derived factor resides in photoreceptors themselves while that for permissive glycans is likely localized to Müller cells, which in turn communicate with photoreceptors to promote proper membrane assembly.
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Coulombe, P. A., Y. M. Chan, K. Albers und E. Fuchs. „Deletions in epidermal keratins leading to alterations in filament organization in vivo and in intermediate filament assembly in vitro.“ Journal of Cell Biology 111, Nr. 6 (01.12.1990): 3049–64. http://dx.doi.org/10.1083/jcb.111.6.3049.
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To investigate the sequences important for assembly of keratins into 10-nm filaments, we used a combined approach of (a) transfection of mutant keratin cDNAs into epithelial cells in vivo, and (b) in vitro assembly of mutant and wild-type keratins. Keratin K14 mutants missing the nonhelical carboxy- and amino-terminal domains not only integrated without perturbation into endogenous keratin filament networks in vivo, but they also formed 10-nm filaments with K5 in vitro. Surprisingly, keratin mutants missing the highly conserved L L E G E sequence, common to all intermediate filament proteins and found at the carboxy end of the alpha-helical rod domain, also assembled into filaments with only a somewhat reduced efficiency. Even a carboxy K14 mutant missing approximately 10% of the rod assembled into filaments, although in this case filaments aggregated significantly. Despite the ability of these mutants to form filaments in vitro, they often perturbed keratin filament organization in vivo. In contrast, small truncations in the amino-terminal end of the rod domain more severely disrupted the filament assembly process in vitro as well as in vivo, and in particular restricted elongation. For both carboxy and amino rod deletions, the more extensive the deletion, the more severe the phenotype. Surprisingly, while elongation could be almost quantitatively blocked with large mutations, tetramer formation and higher ordered lateral interactions still occurred. Collectively, our in vitro data (a) provide a molecular basis for the dominance of our mutants in vivo, (b) offer new insights as to why different mutants may generate different phenotypes in vivo, and (c) delineate the limit sequences necessary for K14 to both incorporate properly into a preexisting keratin filament network in vivo and assemble efficiently into 10-nm keratin filaments in vitro.
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Lu, Z. H., D. B. Sittman, D. T. Brown, R. Munshi und G. H. Leno. „Histone H1 modulates DNA replication through multiple pathways in Xenopus egg extract“. Journal of Cell Science 110, Nr. 21 (01.11.1997): 2745–58. http://dx.doi.org/10.1242/jcs.110.21.2745.
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We investigated the effects of histone H1s on DNA replication using Xenopus egg extract. Mouse variants H1c and H10 were assembled onto Xenopus sperm chromatin by the extract during the remodeling that accompanies nuclear decondensation. The association of H1 with chromatin was rapid and concentration dependent. H1-associated chromatin displayed a typical nucleosomal repeat pattern indicating that linker histones are properly positioned along the DNA. The presence of H1 on sperm chromatin reduced both the rate and extent of DNA replication in egg extract. This reduction in rate is due, in part, to a delay in initiation of replication within individual nuclei. Initiation in extract is dependent upon nuclear assembly. Analysis of the assembly process revealed that H1 does not inhibit nuclear membrane formation or the import of nuclear protein, however, it does slow the rate of nuclear lamina formation. This H1-induced delay in lamina assembly is responsible for the delay in initiation as pre-assembled H1-containing nuclei initiate replication at the same time as control nuclei. However, H1 inhibits replication even when lamina assembly is complete suggesting that H1 also affects replication directly. These data indicate that H1 modulates DNA replication through multiple pathways in egg extract.
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FLANDERS, BRET N. „DIRECTED ELECTROCHEMICAL NANOWIRE ASSEMBLY: PRECISE NANOSTRUCTURE ASSEMBLY VIA DENDRITIC SOLIDIFICATION“. Modern Physics Letters B 26, Nr. 01 (10.01.2012): 1130001. http://dx.doi.org/10.1142/s0217984911300018.
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The electrode-nanowire-target architecture, where the target is a second electrode or, say, a biological cell, is critical to fundamental experiments and high performance devices in low dimensional charge transport and nanomaterials based bio-instrumentation. The relatively new technique of directed electrochemical nanowire assembly, which is based on the diffusion limited process of dendritic solidification, permits the single step fabrication of electrode-nanowire-target assemblies. Hence, this technique is reviewed here in order to assess its current state and to elucidate aspects where further study of the underlying solidification process would be likely to expand its capabilities and applications.
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Sechler, Jan L., Hongwei Rao, Anne Marie Cumiskey, Irbert Vega-Colón, Michael S. Smith, Takatoshi Murata und Jean E. Schwarzbauer. „A novel fibronectin binding site required for fibronectin fibril growth during matrix assembly“. Journal of Cell Biology 154, Nr. 5 (03.09.2001): 1081–88. http://dx.doi.org/10.1083/jcb.200102034.
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Fibronectin (FN) assembly into a fibrillar extracellular matrix is a stepwise process requiring participation from multiple FN domains. Fibril formation is regulated in part by segments within the first seven type III repeats (III1–7). To define the specific function(s) of this region, recombinant FNs (recFNs) containing an overlapping set of deletions were tested for the ability to assemble into fibrils. Surprisingly, recFN lacking type III repeat III1 (FNΔIII1), which contains a cryptic FN binding site and has been suggested to be essential for fibril assembly, formed a matrix identical in all respects to a native FN matrix. Similarly, displacement of the cell binding domain in repeats III9–10 to a position close to the NH2-terminal assembly domain, as well as a large deletion spanning repeats III4–7, had no effect on assembly. In contrast, two deletions that included repeat III2, ΔIII1–2 and ΔIII2–5, caused significant reductions in fibril elongation, although binding of FN to the cell surface and initiation of assembly still proceeded. Using individual repeats in binding assays, we show that III2 but not III1 contains an FN binding site. Thus, these results pinpoint repeat III2 as an important module for FN–FN interactions during fibril growth.
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Jurczyk, Agata, Adam Gromley, Sambra Redick, Jovenal San Agustin, George Witman, Gregory J. Pazour, Dorien J. M. Peters und Stephen Doxsey. „Pericentrin forms a complex with intraflagellar transport proteins and polycystin-2 and is required for primary cilia assembly“. Journal of Cell Biology 166, Nr. 5 (30.08.2004): 637–43. http://dx.doi.org/10.1083/jcb.200405023.
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Primary cilia are nonmotile microtubule structures that assemble from basal bodies by a process called intraflagellar transport (IFT) and are associated with several human diseases. Here, we show that the centrosome protein pericentrin (Pcnt) colocalizes with IFT proteins to the base of primary and motile cilia. Immunogold electron microscopy demonstrates that Pcnt is on or near basal bodies at the base of cilia. Pcnt depletion by RNA interference disrupts basal body localization of IFT proteins and the cation channel polycystin-2 (PC2), and inhibits primary cilia assembly in human epithelial cells. Conversely, silencing of IFT20 mislocalizes Pcnt from basal bodies and inhibits primary cilia assembly. Pcnt is found in spermatocyte IFT fractions, and IFT proteins are found in isolated centrosome fractions. Pcnt antibodies coimmunoprecipitate IFT proteins and PC2 from several cell lines and tissues. We conclude that Pcnt, IFTs, and PC2 form a complex in vertebrate cells that is required for assembly of primary cilia and possibly motile cilia and flagella.
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Sechler, J. L., Y. Takada und J. E. Schwarzbauer. „Altered rate of fibronectin matrix assembly by deletion of the first type III repeats.“ Journal of Cell Biology 134, Nr. 2 (15.07.1996): 573–83. http://dx.doi.org/10.1083/jcb.134.2.573.
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The assembly of fibronectin (FN) into a fibrillar matrix is a complex stepwise process that involves binding to integrin receptors as well as interactions between FN molecules. To follow the progression of matrix formation and determine the stages during which specific domains function, we have developed cell lines that lack an endogenous FN matrix but will form fibrils when provided with exogenous FN. Recombinant FNs (recFN) containing deletions of either the RGD cell-binding sequence (RGD-) or the first type III repeats (FN delta III1-7) including the III1 FN binding site were generated with the baculovirus insect cell expression system. After addition to cells, recFN matrix assembly was monitored by indirect immunofluorescence and by insolubility in the detergent deoxycholate (DOC). In the absence of any native FN, FN delta III1-7 was assembled into fibrils and was converted into DOC-insoluble matrix. This process could be inhibited by the amino-terminal 70 kD fragment of FN, showing that FN delta III1-7 follows an assembly pathway similar to FN. The progression of FN delta III1-7 assembly differed from native FN in that the recFN became DOC-insoluble more quickly. In contrast, RGD- recFNs were not formed into fibrils except when added in combination with native FN. These results show that the RGD sequence is essential for the initiation step but fibrils can form independently of the III1-7 modules. The altered rate of FN delta III1-7 assembly suggests that one function of the missing repeats might be to modulate an early stage of matrix formation.
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Li, Shaohua, David Harrison, Salvatore Carbonetto, Reinhard Fässler, Neil Smyth, David Edgar und Peter D. Yurchenco. „Matrix assembly, regulation, and survival functions of laminin and its receptors in embryonic stem cell differentiation“. Journal of Cell Biology 157, Nr. 7 (24.06.2002): 1279–90. http://dx.doi.org/10.1083/jcb.200203073.
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Laminin-1 is essential for early embryonic basement membrane assembly and differentiation. Several steps can be distinguished, i.e., the expression of laminin and companion matrix components, their accumulation on the cell surface and assembly into basement membrane between endoderm and inner cell mass, and the ensuing differentiation of epiblast. In this study, we used differentiating embryoid bodies derived from mouse embryonic stem cells null for γ1-laminin, β1-integrin and α/β-dystroglycan to dissect the contributions of laminin domains and interacting receptors to this process. We found that (a) laminin enables β1-integrin–null embryoid bodies to assemble basement membrane and achieve epiblast with β1-integrin enabling expression of the laminin α1 subunit; (b) basement membrane assembly and differentiation require laminin polymerization in conjunction with cell anchorage, the latter critically dependent upon a heparin-binding locus within LG module-4; (c) dystroglycan is not uniquely required for basement membrane assembly or initial differentiation; (d) dystroglycan and integrin cooperate to sustain survival of the epiblast and regulate laminin expression; and (e) laminin, acting via β1-integrin through LG1–3 and requiring polymerization, can regulate dystroglycan expression.
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Liu, Hai Xia, Sheng Jie Li und Yong Nian Yan. „Cell Direct Assembly Technology Adopting Hybrid of Gelatin-Based Hydrogels“. Advanced Materials Research 189-193 (Februar 2011): 2986–92. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.2986.
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Through analyzing cell direct assembly process requirements and existing hydrogel materials properties, employing the discrete/deposit rapid prototyping technique, developed a cell direct assembly technology adopting the hybrid of gelatin-based hydrogels. The cell assembly technology skillfully combined with the sol/gel transition mechanism about chemical and physical crosslink of gelatin-based hydrogels, in consideration of the main forming factors, through controlling the extruded materials rheological properties and optimizing the forming process, thereby achieved a promising assembling process with high cell survival rate and its corresponding biological viability. The technology can form a predefined three-dimensional structure with certain shape and size, suitable for variety of natural polymer materials (the most similar with extracellular matrix, such as fibrin, sodium alginate, chitosan, hyaluronic acid) with gelatin coupling forming; therefore, it satisfied majority cells needs of choosing the gelatin-based composite hydrogels reasonably. With the limitative extrusion pressure, more than 90% of the cells survived through this process and performed metabolic functions during a long term culture. This technology is a front research of biotechnology manufacturing science, is an important expansion of manufacturing technology.