The Experts below are selected from a list of 15771 Experts worldwide ranked by ideXlab platform
Karl-peter Hopfner - One of the best experts on this subject based on the ideXlab platform.
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The exosome: a macromolecular cage for controlled RNA degradation
Molecular microbiology, 2006Co-Authors: Katharina Büttner, Katja Wenig, Karl-peter HopfnerAbstract:The exosome, a large multisubunit complex with exoribonucleic activity, emerges as the central 3' RNA degradation and Processing factor in eukaryotes and archaea. But how are the many RNA substrates of the exosome degraded in a processive, yet controlled manner? Recent functional and structural progress shows that the exosome is a macromolecular cage, where the nuclease active sites are situated in a central Processing Chamber. A narrow entry pore controls access to the active sites in the Processing Chamber and prevents uncontrolled RNA decay. The emerging mechanism of exosome function suggests a strikingly parallel architectural concept to protein degradation by proteasomes.
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structural framework for the mechanism of archaeal exosomes in rna Processing
Molecular Cell, 2005Co-Authors: Katharina Büttner, Katja Wenig, Karl-peter HopfnerAbstract:Summary Exosomes emerge as central 3′→5′ RNA Processing and degradation machineries in eukaryotes and archaea. We determined crystal structures of two 230 kDa nine subunit archaeal exosome isoforms. Both exosome isoforms contain a hexameric ring of RNase phosphorolytic (PH) domain subunits with a central Chamber. Tungstate soaks identified three phosphorolytic active sites in this Processing Chamber. A trimer of Csl4 or Rrp4 subunits forms a multidomain macromolecular interaction surface on the RNase-PH domain ring with central S1 domains and peripheral KH and zinc-ribbon domains. Structural and mutational analyses suggest that the S1 domains and a subsequent neck in the RNase-PH domain ring form an RNA entry pore to the Processing Chamber that only allows access of unstructured RNA. This structural framework can mechanistically unify observed features of exosomes, including processive degradation of unstructured RNA, the requirement for regulatory factors to degrade structured RNA, and leftover tails in rRNA trimming.
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Structural Framework for the Mechanism of Archaeal Exosomes in RNA Processing
Molecular cell, 2005Co-Authors: Katharina Büttner, Katja Wenig, Karl-peter HopfnerAbstract:Summary Exosomes emerge as central 3′→5′ RNA Processing and degradation machineries in eukaryotes and archaea. We determined crystal structures of two 230 kDa nine subunit archaeal exosome isoforms. Both exosome isoforms contain a hexameric ring of RNase phosphorolytic (PH) domain subunits with a central Chamber. Tungstate soaks identified three phosphorolytic active sites in this Processing Chamber. A trimer of Csl4 or Rrp4 subunits forms a multidomain macromolecular interaction surface on the RNase-PH domain ring with central S1 domains and peripheral KH and zinc-ribbon domains. Structural and mutational analyses suggest that the S1 domains and a subsequent neck in the RNase-PH domain ring form an RNA entry pore to the Processing Chamber that only allows access of unstructured RNA. This structural framework can mechanistically unify observed features of exosomes, including processive degradation of unstructured RNA, the requirement for regulatory factors to degrade structured RNA, and leftover tails in rRNA trimming.
Katharina Büttner - One of the best experts on this subject based on the ideXlab platform.
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The exosome: a macromolecular cage for controlled RNA degradation
Molecular microbiology, 2006Co-Authors: Katharina Büttner, Katja Wenig, Karl-peter HopfnerAbstract:The exosome, a large multisubunit complex with exoribonucleic activity, emerges as the central 3' RNA degradation and Processing factor in eukaryotes and archaea. But how are the many RNA substrates of the exosome degraded in a processive, yet controlled manner? Recent functional and structural progress shows that the exosome is a macromolecular cage, where the nuclease active sites are situated in a central Processing Chamber. A narrow entry pore controls access to the active sites in the Processing Chamber and prevents uncontrolled RNA decay. The emerging mechanism of exosome function suggests a strikingly parallel architectural concept to protein degradation by proteasomes.
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structural framework for the mechanism of archaeal exosomes in rna Processing
Molecular Cell, 2005Co-Authors: Katharina Büttner, Katja Wenig, Karl-peter HopfnerAbstract:Summary Exosomes emerge as central 3′→5′ RNA Processing and degradation machineries in eukaryotes and archaea. We determined crystal structures of two 230 kDa nine subunit archaeal exosome isoforms. Both exosome isoforms contain a hexameric ring of RNase phosphorolytic (PH) domain subunits with a central Chamber. Tungstate soaks identified three phosphorolytic active sites in this Processing Chamber. A trimer of Csl4 or Rrp4 subunits forms a multidomain macromolecular interaction surface on the RNase-PH domain ring with central S1 domains and peripheral KH and zinc-ribbon domains. Structural and mutational analyses suggest that the S1 domains and a subsequent neck in the RNase-PH domain ring form an RNA entry pore to the Processing Chamber that only allows access of unstructured RNA. This structural framework can mechanistically unify observed features of exosomes, including processive degradation of unstructured RNA, the requirement for regulatory factors to degrade structured RNA, and leftover tails in rRNA trimming.
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Structural Framework for the Mechanism of Archaeal Exosomes in RNA Processing
Molecular cell, 2005Co-Authors: Katharina Büttner, Katja Wenig, Karl-peter HopfnerAbstract:Summary Exosomes emerge as central 3′→5′ RNA Processing and degradation machineries in eukaryotes and archaea. We determined crystal structures of two 230 kDa nine subunit archaeal exosome isoforms. Both exosome isoforms contain a hexameric ring of RNase phosphorolytic (PH) domain subunits with a central Chamber. Tungstate soaks identified three phosphorolytic active sites in this Processing Chamber. A trimer of Csl4 or Rrp4 subunits forms a multidomain macromolecular interaction surface on the RNase-PH domain ring with central S1 domains and peripheral KH and zinc-ribbon domains. Structural and mutational analyses suggest that the S1 domains and a subsequent neck in the RNase-PH domain ring form an RNA entry pore to the Processing Chamber that only allows access of unstructured RNA. This structural framework can mechanistically unify observed features of exosomes, including processive degradation of unstructured RNA, the requirement for regulatory factors to degrade structured RNA, and leftover tails in rRNA trimming.
Katja Wenig - One of the best experts on this subject based on the ideXlab platform.
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The exosome: a macromolecular cage for controlled RNA degradation
Molecular microbiology, 2006Co-Authors: Katharina Büttner, Katja Wenig, Karl-peter HopfnerAbstract:The exosome, a large multisubunit complex with exoribonucleic activity, emerges as the central 3' RNA degradation and Processing factor in eukaryotes and archaea. But how are the many RNA substrates of the exosome degraded in a processive, yet controlled manner? Recent functional and structural progress shows that the exosome is a macromolecular cage, where the nuclease active sites are situated in a central Processing Chamber. A narrow entry pore controls access to the active sites in the Processing Chamber and prevents uncontrolled RNA decay. The emerging mechanism of exosome function suggests a strikingly parallel architectural concept to protein degradation by proteasomes.
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structural framework for the mechanism of archaeal exosomes in rna Processing
Molecular Cell, 2005Co-Authors: Katharina Büttner, Katja Wenig, Karl-peter HopfnerAbstract:Summary Exosomes emerge as central 3′→5′ RNA Processing and degradation machineries in eukaryotes and archaea. We determined crystal structures of two 230 kDa nine subunit archaeal exosome isoforms. Both exosome isoforms contain a hexameric ring of RNase phosphorolytic (PH) domain subunits with a central Chamber. Tungstate soaks identified three phosphorolytic active sites in this Processing Chamber. A trimer of Csl4 or Rrp4 subunits forms a multidomain macromolecular interaction surface on the RNase-PH domain ring with central S1 domains and peripheral KH and zinc-ribbon domains. Structural and mutational analyses suggest that the S1 domains and a subsequent neck in the RNase-PH domain ring form an RNA entry pore to the Processing Chamber that only allows access of unstructured RNA. This structural framework can mechanistically unify observed features of exosomes, including processive degradation of unstructured RNA, the requirement for regulatory factors to degrade structured RNA, and leftover tails in rRNA trimming.
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Structural Framework for the Mechanism of Archaeal Exosomes in RNA Processing
Molecular cell, 2005Co-Authors: Katharina Büttner, Katja Wenig, Karl-peter HopfnerAbstract:Summary Exosomes emerge as central 3′→5′ RNA Processing and degradation machineries in eukaryotes and archaea. We determined crystal structures of two 230 kDa nine subunit archaeal exosome isoforms. Both exosome isoforms contain a hexameric ring of RNase phosphorolytic (PH) domain subunits with a central Chamber. Tungstate soaks identified three phosphorolytic active sites in this Processing Chamber. A trimer of Csl4 or Rrp4 subunits forms a multidomain macromolecular interaction surface on the RNase-PH domain ring with central S1 domains and peripheral KH and zinc-ribbon domains. Structural and mutational analyses suggest that the S1 domains and a subsequent neck in the RNase-PH domain ring form an RNA entry pore to the Processing Chamber that only allows access of unstructured RNA. This structural framework can mechanistically unify observed features of exosomes, including processive degradation of unstructured RNA, the requirement for regulatory factors to degrade structured RNA, and leftover tails in rRNA trimming.
John P Holland - One of the best experts on this subject based on the ideXlab platform.
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frequency dependent plasma characteristics in a capacitively coupled 300 mm wafer plasma Processing Chamber
Plasma Sources Science and Technology, 2006Co-Authors: Gregory A. Hebner, P A Miller, Edward V Barnat, A M Paterson, John P HollandAbstract:Argon plasma characteristics in a dual-frequency, capacitively coupled, 300 mm-wafer plasma Processing system were investigated for rf drive frequencies between 10 and 190 MHz. We report spatial and frequency dependent changes in plasma parameters such as line-integrated electron density, ion saturation current, optical emission and argon metastable density. For the conditions investigated, the line-integrated electron density was a nonlinear function of drive frequency at constant rf power. In addition, the spatial distribution of the positive ions changed from uniform to peaked in the centre as the frequency was increased. Spatially resolved optical emission increased with frequency and the relative optical emission at several spectral lines depended on frequency. Argon metastable density and spatial distribution were not a strong function of drive frequency. Metastable temperature was approximately 400 K.
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spatial and frequency dependence of plasma currents in a 300 mm capacitively coupled plasma reactor
Plasma Sources Science and Technology, 2006Co-Authors: P A Miller, Edward V Barnat, A M Paterson, Gregory A. Hebner, John P HollandAbstract:There is much interest in scaling rf-excited capacitively coupled plasma reactors to larger sizes and to higher frequencies. As the size approaches operating wavelength, concerns arise about non-uniformity across the work piece, particularly in light of the well-documented slow-surface-wave phenomenon. We present measurements and calculations of spatial and frequency dependence of rf magnetic fields inside argon plasma in an industrially relevant, 300 mm plasma-Processing Chamber. The results show distinct differences in the spatial distributions and harmonic content of rf fields in the plasma at the three frequencies studied (13.56, 60 and 176 MHz). Evidence of a slow-wave structure was not apparent. The results suggest that interaction between the plasma and the rf excitation circuit may strongly influence the structures of these magnetic fields and that this interaction is frequency dependent. At the higher frequencies, wave propagation becomes extremely complex; it is controlled by the strong electrical nonlinearity of the sheath and is not explained simply by previous models.
Alberto Pinto - One of the best experts on this subject based on the ideXlab platform.
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Ultrasonic Drying Processing Chamber
Physics Procedia, 2015Co-Authors: Víctor M. Acosta, José Bon, Enrique Riera, Alberto PintoAbstract:Abstract The design of a high intensity ultrasonic Chamber for drying process was investigated. The acoustic pressure distribution in the ultrasonic drying Chamber was simulated solving linear elastic models with attenuation for the acoustic-structure interaction. Together with the government equations, the selection of appropriate boundary conditions, mesh refinement, and configuration parameters of the calculation methods, which is of great importance to simulate adequately the process, were considered. Numerical solution, applying the finite element method (FEM), of acoustic-structure interactions involves to couple structural and fluid elements (with different degrees of freedom), whose solution implies several problems of hardware requirements and software configuration, which were solved. To design the drying Chamber, the influence of the directivity of the drying open camera and the staggered reflectors over the acoustic pressure distribution was analyzed. Furthermore, to optimize the influence of the acoustic energy on the drying process, the average value of the acoustic energy distribution in the drying Chamber was studied. This would determine the adequate position of the food samples to be dried. For this purpose, the acoustic power absorbed by the samples will be analyzed in later studies.
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Ultrasonic Drying Processing Chamber
Physics Procedia, 2015Co-Authors: Víctor M. Acosta, José Bon, Enrique Riera, Alberto PintoAbstract:Abstract The design of a high intensity ultrasonic Chamber for drying process was investigated. The acoustic pressure distribution in the ultrasonic drying Chamber was simulated solving linear elastic models with attenuation for the acoustic-structure interaction. Together with the government equations, the selection of appropriate boundary conditions, mesh refinement, and configuration parameters of the calculation methods, which is of great importance to simulate adequately the process, were considered. Numerical solution, applying the finite element method (FEM), of acoustic-structure interactions involves to couple structural and fluid elements (with different degrees of freedom), whose solution implies several problems of hardware requirements and software configuration, which were solved. To design the drying Chamber, the influence of the directivity of the drying open camera and the staggered reflectors over the acoustic pressure distribution was analyzed. Furthermore, to optimize the influence of the acoustic energy on the drying process, the average value of the acoustic energy distribution in the drying Chamber was studied. This would determine the adequate position of the food samples to be dried. For this purpose, the acoustic power absorbed by the samples will be analyzed in later studies.