Academic literature on the topic 'Box C/D RNA'
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Journal articles on the topic "Box C/D RNA"
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Yang, Zuxiao, Jiayin Wang, Lin Huang, David M. J. Lilley, and Keqiong Ye. "Functional organization of box C/D RNA-guided RNA methyltransferase." Nucleic Acids Research 48, no. 9 (April 16, 2020): 5094–105. http://dx.doi.org/10.1093/nar/gkaa247.
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Abstract Box C/D RNA protein complexes (RNPs) catalyze site-specific 2′-O-methylation of RNA with specificity determined by guide RNAs. In eukaryotic C/D RNP, the paralogous Nop58 and Nop56 proteins specifically associate with terminal C/D and internal C'/D' motifs of guide RNAs, respectively. We have reconstituted active C/D RNPs with recombinant proteins of the thermophilic yeast Chaetomium thermophilum. Nop58 and Nop56 could not distinguish between the two C/D motifs in the reconstituted enzyme, suggesting that the assembly specificity is imposed by trans-acting factors in vivo. The two C/D motifs are functionally independent and halfmer C/D RNAs can also guide site-specific methylation. Extensive pairing between C/D RNA and substrate is inhibitory to modification for both yeast and archaeal C/D RNPs. N6-methylated adenine at box D/D' interferes with the function of the coupled guide. Our data show that all C/D RNPs share the same functional organization and mechanism of action and provide insight into the assembly specificity of eukaryotic C/D RNPs.
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Ye, K., R. Jia, J. Lin, M. Ju, J. Peng, A. Xu, and L. Zhang. "Structural organization of box C/D RNA-guided RNA methyltransferase." Proceedings of the National Academy of Sciences 106, no. 33 (August 5, 2009): 13808–13. http://dx.doi.org/10.1073/pnas.0905128106.
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Yu, Ge, Yu Zhao, and Hong Li. "The multistructural forms of box C/D ribonucleoprotein particles." RNA 24, no. 12 (September 25, 2018): 1625–33. http://dx.doi.org/10.1261/rna.068312.118.
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TRAN, E. "Conserved spacing between the box C/D and C'/D' RNPs of the archaeal box C/D sRNP complex is required for efficient 2'-O-methylation of target RNAs." RNA 11, no. 3 (January 20, 2005): 285–93. http://dx.doi.org/10.1261/rna.7223405.
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Moore, Terrie, Yanming Zhang, Marcia O. Fenley, and Hong Li. "Molecular Basis of Box C/D RNA-Protein Interactions." Structure 12, no. 5 (May 2004): 807–18. http://dx.doi.org/10.1016/j.str.2004.02.033.
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Deryusheva, Svetlana, and Joseph G. Gall. "Small, Smaller, Smallest: Minimal Structural Requirements for a Fully Functional Box C/D Modification Guide RNA." Biomolecules 9, no. 9 (September 7, 2019): 457. http://dx.doi.org/10.3390/biom9090457.
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Site-specific 2’-O-ribose methylation is an abundant post-transcriptional modification mediated by small non-coding nuclear RNAs known as box C/D modification guide RNAs. The minimal structural requirements for these guide RNAs to function in higher eukaryotes are still unclear. To address this question, we generated a series of mutant variants of Drosophila box C/D scaRNA:MeU2-C28 and tested their modification guide activities in the Xenopus oocyte system. Our data suggest that box C/D guide RNA function requires either a terminal or an internal consensus kink-turn structure. We identified the minimal functional box C/D guide RNA. It consists of a single-domain molecule with (i) a terminal stem with a consensus kink-turn domain, (ii) one box C and box D connected by a 14-nucleotide antisense element and (iii) a one-nucleotide spacer between the box C and the antisense element. In this single domain RNA, the sequence of the spacer is more important than its length. We suggest that the secondary structure of box C/D RNAs, essential for guide RNA function, is more complex than generally supposed. At the same time, the expression of functional extremely short single-domain box C/D RNAs is possible in higher eukaryotes.
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Bower-Phipps, K. R., D. W. Taylor, H. W. Wang, and S. J. Baserga. "The box C/D sRNP dimeric architecture is conserved across domain Archaea." RNA 18, no. 8 (June 29, 2012): 1527–40. http://dx.doi.org/10.1261/rna.033134.112.
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Speckmann, Wayne, Aarthi Narayanan, Rebecca Terns, and Michael P. Terns. "Nuclear Retention Elements of U3 Small Nucleolar RNA." Molecular and Cellular Biology 19, no. 12 (December 1, 1999): 8412–21. http://dx.doi.org/10.1128/mcb.19.12.8412.
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ABSTRACT The processing and methylation of precursor rRNA is mediated by the box C/D small nucleolar RNAs (snoRNAs). These snoRNAs differ from most cellular RNAs in that they are not exported to the cytoplasm. Instead, these RNAs are actively retained in the nucleus where they assemble with proteins into mature small nucleolar ribonucleoprotein particles and are targeted to their intranuclear site of action, the nucleolus. In this study, we have identified the cis-acting sequences responsible for the nuclear retention of U3 box C/D snoRNA by analyzing the nucleocytoplasmic distributions of an extensive panel of U3 RNA variants after injection of the RNAs into Xenopus oocyte nuclei. Our data indicate the importance of two conserved sequence motifs in retaining U3 RNA in the nucleus. The first motif is comprised of the conserved box C′ and box D sequences that characterize the box C/D family. The second motif contains conserved box sequences B and C. Either motif is sufficient for nuclear retention, but disruption of both motifs leads to mislocalization of the RNAs to the cytoplasm. Variant RNAs that are not retained also lack 5′ cap hypermethylation and fail to associate with fibrillarin. Furthermore, our results indicate that nuclear retention of U3 RNA does not simply reflect its nucleolar localization. A fragment of U3 containing the box B/C motif is not localized to nucleoli but retained in coiled bodies. Thus, nuclear retention and nucleolar localization are distinct processes with differing sequence requirements.
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Gogolevskaya, Irina K., Julia A. Makarova, Larisa N. Gause, Valentina A. Kulichkova, Irina M. Konstantinova, and Dmitri A. Kramerov. "U87 RNA, a novel C/D box small nucleolar RNA from mammalian cells." Gene 292, no. 1-2 (June 2002): 199–204. http://dx.doi.org/10.1016/s0378-1119(02)00678-9.
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Lange, Thilo Sascha, Michael Ezrokhi, Anton V. Borovjagin, Rafael Rivera-León, Melanie T. North, and Susan A. Gerbi. "Nucleolar Localization Elements of Xenopus laevis U3 Small Nucleolar RNA." Molecular Biology of the Cell 9, no. 10 (October 1998): 2973–85. http://dx.doi.org/10.1091/mbc.9.10.2973.
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The Nucleolar Localization Elements (NoLEs) of Xenopus laevis U3 small nucleolar RNA (snoRNA) have been defined. Fluorescein-labeled wild-type U3 snoRNA injected intoXenopus oocyte nuclei localized specifically to nucleoli as shown by fluorescence microscopy. Injection of mutated U3 snoRNA revealed that the 5′ region containing Boxes A and A′, known to be important for rRNA processing, is not essential for nucleolar localization. Nucleolar localization of U3 snoRNA was independent of the presence and nature of the 5′ cap and the terminal stem. In contrast, Boxes C and D, common to the Box C/D snoRNA family, are critical elements for U3 localization. Mutation of the hinge region, Box B, or Box C′ led to reduced U3 nucleolar localization. Results of competition experiments suggested that Boxes C and D act in a cooperative manner. It is proposed that Box B facilitates U3 snoRNA nucleolar localization by the primary NoLEs (Boxes C and D), with the hinge region of U3 subsequently base pairing to the external transcribed spacer of pre-rRNA, thus positioning U3 snoRNA for its roles in rRNA processing.
Dissertations / Theses on the topic "Box C/D RNA"
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Janzen, Timothy William, and University of Lethbridge Faculty of Arts and Science. "Subunit interactions within box C/D sRNPs." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Chemistry and Biochemistry, c2010, 2010. http://hdl.handle.net/10133/2547.
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Box C/D small ribonucleoproteins (box C/D sRNPs) are responsible for the 2’-O-methylation required for the complete maturation of precursor rRNA. Archaeal box C/D sRNPs, like eucarya, are composed of four components: a guide RNA (box C/D sRNA), an RNA binding protein (L7ae), a 2’-O-methyltransferase (Fibrillarin) and a structural protein (Nop5). Here we develop several approaches for studying box C/D sRNP assembly. In particular, we have used pulldown and mobility shift assays to identify box C/D sRNP assembly intermediates (Nop5-aFib and L7ae-sR1). We have also demonstrated that isothermal titration calorimetry (ITC) can be utilized to quantitatively characterize the energetics of formation for the L7ae-sRNA assembly intermediate.xi, 98 leaves : ill. (some col.) ; 29 cm
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Malliahgari, Srinivas Reddy. "Characterization of a box C/D RNA from Haloferax volcanii /." Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1240690311&sid=3&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Thesis (M.S.)--Southern Illinois University Carbondale, 2006."Department of Molecular Biology, Microbiology and Biochemisty." Includes bibliographical references (leaves 59-61). Also available online.
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Bosmeny, Michael. "Structure / Function Relationship of Archaeal Box C/D and H/ACA Proteins." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/1901.
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Ribonucleoprotein complexes are responsible for some of the post-transcriptional modifications of RNA that occur within the cell, including 2'-O-methylation and pseudouridylation. These modifications contribute, among other things, to RNA folding, inhibition of degradation, and general cellular viability. In this study, we identify residues within the proteins of these complexes that are important to the functioning of the Box C/D and Box H/ACA complexes. Candidates were selected based on previous work and mutant versions of the proteins were introduced in-vivo. Assays were done to determine the functionality of the mutant complex. This work is divided into three parts, focused on the three proteins investigated. The first part is concerned with Nop5, a protein in the Box C/D RNP complex. Nop5 is known to interact with all other proteins and RNAs in the complex, and is believed to serve a primarily structural role, aligning the other components. Mutagenesis study of suspected significant amino acids in this protein showed that it is difficult to disrupt the operation of Nop5 with single changes, but is possible with more extensive mutation. The second part concerns Fibrillarin, the catalytic protein of the Box C/D ribonucleoprotein complex. Previous mutagenesis work identified several important amino acids involved with AdoMet transfer and complex formation. The methylation ability of these mutant complexes were further examined in this work by confirming that the same modification, or lack thereof, occurred at a second rRNA position. The final part of this work is about Nop10, part of the Box H/ACA complex. This work is only preliminary, but begins the process of testing suspected essential amino acids in the structure.
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Kaushik, Saakshi. "A STUDY TO UNDERSTAND THE DYNAMICS OF ARCHAEAL BOX C/D MEDIATED RNA MODIFICATION." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1746.
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Stable cellular RNAs undergo a variety of post-transcriptional modifications, most of which are evolutionary conserved and found in functionally important regions of RNA. 2’-O-methylation of ribose sugars and conversion of uridine to pseudouridine by isomerization are the two most common modifications found in RNA in all the domains of life. 2’-O-methylation of the hydroxyl group of ribose is known to help in proper RNA folding, inhibit hydrolytic degradation and attack by nucleases on RNA. In Archaea, one of the ways this modification is known to be carried out is in an RNA-dependent manner by a Box C/D sRNP complex. This thesis sets to understand how exactly the RNA and proteins work together to bring about this modification. In the first part of this study, we aimed to investigate the role of Nop5, a protein component of the Box C/D sRNP whose function is not well understood. It was observed from previous work in our lab that aNop5p binds to single-stranded bulges and loops of some RNA. The binding seems to happen either by aNop5p alone or as a heterodimer with fibrillarin. This led us to hypothesize that Nop5 protein is responsible for binding to the target RNA to be methylated and bringing it to the assembling sRNP complex. To further investigate this idea, we identified two motifs in the C-terminal domain of the protein, the GAEK and ALFA motifs, mutated the motifs in the M. jannaschii versions of the protein and studied its significance in vitro using activity and binding assays. We have biochemically identified these motifs to be essential for the methylation activity of the sRNP complex and required to wedge open the guide strands for the target RNA to pair up. However, mutation of the motifs did not seem to change the way Nop5p binds to the bulges and loops of the RNA, inferring that these motifs are not essential for target identification and recruitment. The second part of the thesis is dedicated to the establishment and optimization of a pulldown technique using S1 RNA aptamer. This aptamer is inserted in a Box C/D guide RNA and used to purify the RNP complex formed in vivo using the strong affinity of the aptamer to streptavidin. The aptamer tag was successfully inserted into the 124mer form of sR-tMet of H. volcanii and the ability of the aptamer to bind to the streptavidin beads was tested. The roadblocks of the study, i.e. the non-specific binding and elution of the complex are currently being optimized.
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Pinzon, Restrepo Natalia. "Characterization of regulatory noncoding RNAs : the U1 small nuclear RNA and Cajal body-specific box C/D guide RNAs." Toulouse 3, 2011. http://thesesups.ups-tlse.fr/2458/.
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Les cellules contiennent de nombreux ARNs non-codants qui jouent un rôle essentiel dans toutes les étapes de l'expression génique. Nos travaux concernent la caractérisation de possibles nouvelles fonctions associés à deux classes d'ARNs non-codants : l'ARN U1 et les scaARNs. Le petit ARN nucléaire U1 forme une ribonucléoparticule (snRNP U1) qui joue un rôle clé dans l'épissage des ARN pré-messagers. De plus, l'ARN U1 semble intervenir dans d'autres étapes de la synthèse des ARNm fonctionnels. Nos travaux ont démontré qu'une fraction de l'ARN U1 interagit spécifiquement avec la protéine TAF15, dans un complexe qui diffère dans sa composition protéique de la particule d'épissage canonique Sm snRNP U1. Nous avons constaté qu'à la différence de la particule d'épissage, la snRNP U1-TAF15 est fortement attachée à la chromatine. De plus, suite à l'arrêt de la transcription par l'ARN polymérase II, la particule U1-TAF15 se relocalise dans la coiffe périnucléolaire, à l'opposé de la particule Sm snRNP U1 qui s'accumule alors dans les "speckles". Une étude protéomique de la particule U1-TAF15 nous a permis d'établir des hypothèses quant à sa fonction qui sont actuellement à l'étude dans le laboratoire. Récemment, une protéine essentielle à l'adressage des scaARNs (ARNs spécifiques des Corps de Cajal) dans les Corps de Cajal a été identifiée (Tycowski et al. , 2009; Venteicher et al. , 2009). Une analyse par séquençage à haut-débit de l'ensemble des petits ARNs associés à WDR79 a permis d'identifier de nombreux nouveaux scaARNs putatifs. Parmi eux, l'analyse de deux ARNs à boite C/D a défini des structures essentielles pour leur localisation dans les corps de Cajal. Des études plus approfondies devraient nous permettre de déterminer des éléments spécifiques nécessaires à l'adressage des scaARNs à boite C/D vers les corps de Cajal. Par ailleurs, nous avons commencé la caractérisation d'un nouveau scaARN qui ciblerait la modification d'un ARN de transfert. Alors que les ARN C/D connus chez les Eucaryotes participent à la biogenèse des ARN ribosomiques et des petits ARN nucléaires, nous avons identifié pour la première fois chez les Eucaryotes un ARN C/D qui ciblerait un ARN de transfertNoncoding regulatory RNAs (ncRNAs) are in the focus of current research, since they participate in nearly all cellular processes. To get further insights into the functional and structural complexity of ncRNAs, we studied human ncRNAs belonging to two classes of ncRNAs, the nucleoplasmic spliceosomal snRNAs and the nucleolar and Cajal body-specific box C/D 2'-O-methylation guide RNAs. The U1 snRNP is an evolutionarily conserved, abundant nucleoplasmic snRNP that plays a central role in pre-mRNA splicing. According to a recently emerging view, besides its constitutive role in splicing, the U1 snRNP has important regulatory functions in different steps of pre-mRNA production. We demonstrated that a fraction of the human U1 snRNA specifically associates with the nuclear RNA-binding protein TAF15 that is known to interact with a subpopulation of TFIID and RNA polymerase II complexes. The U1-TAF15 snRNP is structurally and functionally distinct from the well-characterized U1 spliceosomal snRNP and it tightly associates with chromatin. The function of U1-TAF15 snRNP remains unknown; it might contribute to the coupling of transcription and splicing. WDR79 (also called WRAP53) has been recently identified as an essential factor for targeting a subclass of box C/D and H/ACA modification guide RNAs, as well as telomerase H/ACA RNA, into the Cajal bodies. Accumulation of box C/D and H/ACA RNPs in Cajal bodies is essential for the biogenesis of functional spliceosomal snRNPs and telomere synthesis. Co-immunopurification of WDR79-associated human RNAs, followed by cDNA synthesis and deep sequencing identified a large number of novel Cajal body-specific RNAs. We are currently dissecting the cis-acting RNA element responsible for WDR79-binding and for targeting box C/D 2'-O-methylation guide RNPs into Cajal bodies. We have also identified a novel Cajal body-specific 2'-O-methylation guide RNA that is predicted to direct methylation of cytidine 34 at the Wobble position of tRNA-Met-CAT elongator. Interestingly, tRNA modification is a novel function for vertebrate box C/D scaRNPs
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Jana, Sujata. "STRUCTURAL AND FUNCTIONAL STUDIES OF ARCHAEAL BOX C/D GUIDE RNA AND ROLE OF A PUTATIVE HUMAN PSEUDOURIDINE SYNTHASE, PUS10 IN APOPTOSIS." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/dissertations/1362.
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RNAs undergo different posttranscriptional chemical modifications, which affect their structural stability and functional diversity. RNA methylation is a very common type of post-transcriptional modification and is present in all domains of life: Archaea, Eukaryotes and Bacteria. Some of these methylations are catalyzed either by a RNA-protein complex or by stand-alone enzymes. The RNA-protein complex (Ribonucleoprotein complex) is comprised of a small RNA known as the guide RNA (Box C/D RNA) and core proteins (L7Ae, Nop5, and Fibrillarin). Box C/D RNAs contain conserved regions, called box C and box D near their 5’ and 3’ termini, respectively, and their imperfect copies called box C’ and box D’, internally. A short stretch of sequence between these Boxes are known as the guide/spacer regions, as the guide region helps in recruiting and positioning a specific target RNA for modification. Both in Archaea and Eukarya, box C and box D, as well as box C’ and box D’ together can form a structure called a Kink-turn (K-turn) that is characterized by a canonical Watson-Crick base-paired stem on one side, and a non-canonical stem on the other, separated by a 3-nucleotide loop. In Archaea box C’ and D’ can also form a K-loop, where the canonical stem of K-turn is replaced by a loop. Archaeal L7Ae binds first to the K-turn or K-loop and allows the recruitment of other proteins to form the complex. The presence of a unique box C/D RNA of Haloferax volcanii, called sR-tMet has been reported previously to guide the 2’-O-methylation of C34 in elongator pre-tRNAMet. Here we tried to characterize the structure-function relationship of this guide RNA under in vivo conditions. This RNA lacks a conventional K-turn or K-loop at its C’/D’ motif. We have created an H. volcanii strain that has a genomic deletion of sR-tMet. The sR-tMet gene is not essential for H. volcanii but this sR-tMet deleted strain lacks the 2’-O-methylation of C34 of its elongator tRNAMet. Unlike the close sR-tMet homologs (sR8 from Methanocaldococcus jannaschii and sR49 from Pyrococcus abyssi), the Box C’/D’ motif of sR-tMet is neither a K-turn nor a K-loop. The introduction of proper K-loop in the Box C’/D’ motif (sR-tMet with K-loop) abolished its Cm34 modification function in ΔsR-tMet strain. Direct interaction between L7Ae and the K-loop is not an absolute requirement for its function. However, disruption of the G/A and A/G pairing in Box C/D motif and Box D’ suggests the importance of these non-Watson crick base pairings in respect to sR-tMet’s function. Several other mutational studies have revealed that peculiar sR-tMet guide RNA from H. volcanii, behaves more like a Eukaryotic Box C/D RNA (where the K-loop is not required and presence of longer spacer length) than regular Archaeal one. Pseudouridine synthase 10 (Pus10) is the most recently identified Ψ synthase, found only in higher eukaryotes and Archaea. Archaeal Pus10 produces either tRNA Ψ55 or both tRNA Ψ54 and Ψ55 modifications. In Human, its Ψ synthase activity is not yet confirmed and interestingly it has been implicated in apoptosis. Herein for the first time we revealed that this putative RNA Ψ synthase protein, Human Pus10 (HuP10), translocates from the nucleus to the cytoplasm in TRAIL induced apoptosis. This nucleo-cytoplasmic movement of HuP10 occurs through the CRM1 mediated nuclear export pathway and Caspase 3 influences this movement. HuP10 also mediates crosstalk between the extrinsic and intrinsic pathways during TRAIL-induced apoptosis. Other than its involvement in apoptosis, we have also uncovered that HuP10 is involved in regulation of cell proliferation. Depletion (knockdown) of this protein in different cancer cell lines, promotes cell migration and anchorage-independent cell growth in the absence of any apoptotic stimulation.
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Singh, Sanjay K. "Functional and structural studies of an archaeal intron-encoded, cis-positioned box C/D guide RNA /." Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1140183781&sid=4&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Thesis (Ph.D.)--Southern Illinois University Carbondale, 2006."Department of Molecular Biology, Microbiology and Biochemisty." Includes bibliographical references (leaves 116-136). Also available online.
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Chatterjee, Kunal. "A TALE OF TWO METHYLATION MODIFICATIONS IN ARCHAEAL RNAs." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/dissertations/806.
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In all the three domains of life, most RNAs undergo post transcriptional modifications both on the bases as well as the ribose sugars of the individual ribonucleotides. 2'-O-methylation of ribose sugars and isomerization of Uridines to Pseudouridines are two most predominant modifications in rRNAs and tRNAs across all domains of life. Besides 2'-O-methylation of ribose sugars, methylation of pseudouridine (Ø) at position 54 of tRNA, producing m1Ø, is a hallmark of many archaeal species but the specific methylase involved in the formation of this modification had yet to be characterized. A comparative genomics analysis had previously identified COG1901 (DUF358), part of the SPOUT superfamily, as a candidate for this missing methylase family. To test this prediction, the COG1901 encoding gene, HVO_1989, was deleted from the Haloferax volcanii genome. Analyses of modified base contents indicated that while m1Ø was present in tRNA extracted from the wild-type strain, it was absent from tRNA extracted from the mutant strain. Expression of the gene encoding COG1901 from Halobacterium sp. NRC-1, VNG1980C, complemented the m1Ø minus phenotype of the ÄHVO_1989 strain. This in vivo validation was extended with in vitro tests. Using the COG1901 recombinant enzyme from Methanocaldococcus jannaschii (Mj1640), purified enzyme Pus10 from M. jannaschii and full-size tRNA transcripts or TØ-arm (17-mer) fragments as substrates, the sequential pathway of m1Ø54 formation in Archaea was reconstituted. The methylation reaction is AdoMet-dependent. The efficiency of the methylase reaction depended on the identity of the residue at position 55 of the TØ-loop. The presence of Ø55 allowed the efficient conversion of Ø54 to m1Ø54, whereas in the presence of C55 the reaction was rather inefficient and no methylation reaction occurred if a purine was present at this position. These results led to renaming the Archaeal COG1901 members as TrmY proteins. Another aim of this study was to investigate the mechanism of target RNA recruitment to a box C/D sRNP. From data obtained, we have made the following hypothesis- aNop5p, either alone or as a heterodimer with Fibrillarin, binds to single stranded bulges and loops of target RNA. This aNop5p bound target is then hybridized to an assembling guide sRNP complex containing the guide RNA and L7Ae or guide RNA, L7Ae and aNop5p. If the guide:target sequences are complementary to each other, they hybridize and the target nucleotide gets modified. We also think that post modification, the guide and target strands separate, the core proteins rearrange themselves on the guide RNA and then prime the guide RNA for next round of modification. Compared to the general archaeal populations, haloarchaea contain significantly fewer number of box C/D guide RNAs. In archaea, previous studies have underscored the importance of a symmetric assembly of the core proteins on the sRNA. This meant that if the core proteins were unable to bind to either the terminal box C/D or the internal box C'/D' motifs, the sRNP was not efficient to carry out the modification of the target RNA. Essentially the only two haloarchaeal box C/D sRNPs known before had a symmetric architecture. In this study we discovered the first naturally occurring asymmetric box C/D sRNP called sR-41 in Haloferax volcannii. The architecture of Haloferax volcanii sR-41 box C/D sRNP seems to be closer in conformation to eukaryal snoRNPs (eukaryal counterparts of archaeal sRNPs) in which the core proteins assemble asymmetrically on the RNA. Till date, no information regarding the catalytic mechanism of an asymmetrically arranged eukaryal box C/D snoRNPs are available, because of unavailability of any assembly systems or crystal structures. Hence, this archaeal sR-41 guide sRNP provides a unique opportunity to study mechanism of modification in an asymmetrically arranged box C/D sRNP molecule.
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Rothé, Benjamin. "Étude des processus de biogenèse des petites particules ribonucléoprotéiques nucléolaires à boîtes C/D (snoRNP C/D) chez la levure Saccharomyces cerevisiae : caractérisation fonctionnelle et structurale d'une machinerie dédiée à l'assemblage de ces RNP." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0013/document.
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Les protéines de la famille L7Ae sont les constituants de nombreuses RNP essentielles. Chez les vertébrés, les particules snoRNP C/D et H/ACA sont impliquées dans la biogenèse des ribosomes, la UsnRNP U4 dans l'épissage des pré-ARNm, le complexe télomérase dans la réplication des télomères, et les mRNP SECIS dans la traduction des sélénoprotéines. Comme c'est le cas pour la majorité des RNP eucaryotes, leur assemblage, sous forme d'entités fonctionnelles, ne constitue pas un processus autonome et requiert l'intervention de facteurs spécialisés. En basant notre étude sur l'assemblage des snoRNP C/D, dans l'organisme modèle Saccharomyces cerevisiae, et en utilisant des approches de biologie moléculaire, de biochimie et de génétique, nous avons entrepris de caractériser ces événements. Nos travaux ont contribué à identifier un ensemble de protéines, agissant de façon coordonnée au sein d'une machinerie conservée entre la levure et l'homme. Cette dernière est composée de deux principales sous-unités : (i) Rsa1p/NUFIP, une protéine plate-forme, qui interagit avec certaines protéines de la famille L7Ae et facilite l'assemblage des RNP, (ii) le complexe R2TP (Rvb1p/TIP49, Rvb2p/TIP48, Pih1p/PIH1, Tah1p/SPAGH), qui pourrait opérer des remodelages conformationnels nécessaires à la formation des RNP matures. En plus de ces acteurs centraux, d'autres facteurs sont apparus intimement liés à ce mécanisme. La protéine Hit1p/TRIP3, interagit notamment avec Rsa1p/NUFIP et s'est avéré requise pour assurer sa stabilité chez la levure. La chaperonne HSP90, dont le rôle est prédominant chez l'homme, exerce son activité sur certains constituants des RNP. Enfin, la protéine Bcd1p/BCD1 pourrait être associée à cette machinerie dans le cadre spécifique de l'assemblage des snoRNP C/DThe L7Ae family proteins are essential components of many RNPs. In vertebrates, C/D and H/ACA snoRNPs are involved in ribosome biogenesis, the U4 snRNP in pre-mRNA splicing, the telomerase complex in telomeres replication, and mRNP SECIS in selenoproteins translation. Like most eukaryotic RNPs, assembly in functional entities is not an autonomous process and requires the intervention of specialized factors. Basing our study on the assembly of C/D snoRNP in the model organism Saccharomyces cerevisiae, and using approaches of molecular biology, biochemistry and genetics, we undertook to decipher these mechanisms. Our work has helped to identify a set of proteins, acting in a coordinated manner within a machinery conserved between yeast and human. This machinery consists of two major subunits: (i) Rsa1p/NUFIP, a platform protein that interacts with some proteins of the L7Ae family and facilitates the RNPs assembly, (ii) the R2TP complex (Rvb1p/TIP49, Rvb2p/TIP48, Pih1p/PIH1, Tah1p/SPAGH), which could induce conformational remodeling necessary for the formation of mature RNPs. In addition to these key players, other factors appeared closely linked to this mechanism. The Hit1p/TRIP3 protein interacts with Rsa1p/NUFIP and is required to ensure its stability in yeast. HSP90 chaperone, whose role is predominant in human, operates on some components of the RNPs. Finally, the Bcd1p/BCD1 protein is associated specifically with this machinery during C/D snoRNPs assembly
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Dodré, Maxime. "Étude du rôle du complexe SMN dans l’assemblage de RNP non codantes ubiquitaires : la SRP, les RNP C/D et H/ACA dont la télomérase, et étude du taux des facteurs d’assemblage de la télomérase dans les cellules cancéreuses." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0207.
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Les particules ribonucléoprotéiques (RNP) sont impliquées dans divers mécanismes cellulaires : les UsnRNP, la SRP, les RNP à boîtes C/D et H/ACA dans la modification des ARN et la maturation des ARN ribosomiques, et la télomérase dans le maintien des extrémités chromosomiques. L'assemblage de ces RNP est un processus complexe faisant intervenir de nombreux facteurs, dont le complexe SMN. Un déficit de l’une des protéines de ce complexe conduit à l’amyotrophie spinale. Il est essentiel à la survie cellulaire et est nécessaire à l’assemblage des UsnRNP et de la SRP. Il est suggèré que le complexe SMN joue un rôle dans la biogenèse des RNP à boîtes C/D et H/ACA. Nous avons montré des interactions in vitro et des associations in cellulo entre le complexe SMN et la protéine NUFIP (un facteur d’assemblage de ces RNP). Ces résultats suggèrent l’existence d’un lien fonctionnel entre le complexe SMN et NUFIP dans l'assemblage des RNP à boîtes C/D et H/ACA et de la snRNP U4. Des interactions in vitro entre le complexe SMN et la protéine NAF1 (un facteur d’assemblage des RNP à boîtes H/ACA) ont révélés, que le complexe SMN est capable de s’associer avec la RNP à boîtes H/ACA en formation. Si le complexe SMN intervient dans l’assemblage des RNP, on peut supposer que cet assemblage soit défectueux dans la SMA. Nous avons montré que certains ARN sont accumulés dans la moelle épinière et le cerveau de souris SMA. La télomérase est réactivée dans les cellules cancéreuses. En collaboration avec l’équipe de J-M Vignaud (CHU central, Nancy), nous avons montré une augmentation du taux des protéines cœur des RNP à boîtes H/ACA et de NUFIP dans les cellules tumoralesRibonucleoprotein particles (RNPs) are involved in various cellular mechanisms in eukaryotic cells: UsnRNP, SRP, C/D and H/ACA box RNPs in RNA modifications and rRNA maturation and telomerase in the synthesis of the chromosome extremities. RNP assembly is a very complex process, which involves numerous factors. One of these factors is the SMN complex. Decreased level of one of its components leads to spinal muscular atrophy. It is essential for cell survival and necessary for UsnRNP and SRP assembly. It is suggested that the SMN complex plays a role in C/D and H/ACA RNP biogenesis. We showed in vitro interactions and in cellulo associations between the SMN complex and the protein NUFIP (an assembly factor of these RNP). These results suggest the existence of a functional link between the SMN complex and NUFIP in the assembly of the C/D and H/ACA box RNPs and the U4 snRNP. In vitro interactions between the SMN complex and the protein NAF1 (an assembly factor of the H/ACA boxes RNPs) revealed, that the SMN complex is capable of joining with the H/ACA boxes RNPs in formation. If the SMN complex intervenes in the RNPs assembly, we can suppose that this assembly is defective in the SMA. We showed that any ARN is accumulated in the spinal cord and the brain of SMA mouse. The telomerase is reactivated in cancer cells. In association with the team of J-M Vignaud (CHU central, Nancy), we showed an increase of H/ACA box RNP proteins and NUFIP in these cancer cells
Book chapters on the topic "Box C/D RNA"
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Tripp, Vanessa, and Lennart Randau. "Evolution of C/D Box sRNAs." In RNA Metabolism and Gene Expression in Archaea, 201–24. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-65795-0_9.
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Huang, Chao, John Karijolich, and Yi-Tao Yu. "Post-transcriptional Modification of RNAs by Artificial Box H/ACA and Box C/D RNPs." In RNA and DNA Editing, 227–44. Totowa, NJ: Humana Press, 2011. http://dx.doi.org/10.1007/978-1-61779-018-8_14.
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Stepanov, Grigory A., Julia A. Filippova, Anna A. Nushtaeva, Elena V. Kuligina, Olga A. Koval, Vladimir A. Richter, and Dmitriy V. Semenov. "Artificial Analogues of Circulating Box C/D RNAs Induce Strong Innate Immune Response and MicroRNA Activation in Human Adenocarcinoma Cells." In Advances in Experimental Medicine and Biology, 121–25. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-42044-8_24.
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"C/D Box." In Encyclopedia of Genetics, Genomics, Proteomics and Informatics, 289. Dordrecht: Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-6754-9_2535.
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Chen, You-Yi, and Wen-Chieh Tsai. "The Function of C/D-Class MADS Box Genes in Orchid Gynostemium and Ovule Development." In Orchid Biotechnology III, 289–308. WORLD SCIENTIFIC, 2017. http://dx.doi.org/10.1142/9789813109223_0014.
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Gagnon, Keith, Xinxin Zhang, and E. Stuart Maxwell. "In Vitro Reconstitution and Affinity Purification of Catalytically Active Archaeal Box C/D sRNP Complexes." In Methods in Enzymology, 263–82. Elsevier, 2007. http://dx.doi.org/10.1016/s0076-6879(07)25012-8.
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Bellows, Ben, Aman Bhandari, Mahad Ibrahim, and Jaspal S. Sandhu. "Peering into the Black Box." In Information Communication Technologies, 1002–28. IGI Global, 2008. http://dx.doi.org/10.4018/978-1-59904-949-6.ch067.
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This chapter begins with an overview of public health in developing regions. From this population-level perspective, we discuss the information challenges in each of the four domains of public health: research, education, health-care delivery, and disease surveillance. We introduce health-related use classes—categories of specific use cases—to provide a structured presentation of health and information communication technologies in developing regions. In this regard, we define and discuss the following six use classes: (a) surveillance and information gathering, (b) research, (c) provider to provider, (d) provider to patient,(e) education, and (f) logistics. Defining ICT broadly, we argue that the design or selection of technology requires consideration of the cost, ease of use, infrastructure, culture of ICT use, penetration of different ICTs, and population health profile. All of these factors vary among resource-scarce settings, and each factor can greatly impact the appropriate choice in any given setting. We discuss the following three types of assessment, each of which plays a crucial role in project evaluation: systems issues, usability, and health outcomes. Designing ICT for health applications in developing countries requires a deep understanding of various contextual factors, such as health and ICT infrastructure, disease burden, and sociocultural issues. With this in mind, and with some understanding of future trends in health and ICT utilization, we provide forward-looking recommendations for practitioners, researchers, funders, and policy makers.
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Milhé, C. "Determination by 1H NMR of a Slow Conformational Transition and Hydration Change in the Consensus TATAAT Prsbnow Box." In Biological NMR Spectroscopy. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195094688.003.0027.
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The conformational dynamics and hydration of a DNA 14-mer containing the consensus Pribnow box sequence TATAAT have been measured using rotating frame T1 measurements and NOESY and ROESY in water. The H2 proton resonances of adenines show fast intermediate exchange behavior which can be attributed to a conformational transition that affects the distances between H2 protons of neighboring adenine residues, both sequential and cross-strand. The relaxation rate constant of the transition was measured at 4000s-1 at 25°C. Bound water close to the H2 proton of adenines was observed with residence times of >lns. At low temperature (5°C), the Pribnow box is in a closed state in which hydration water in the minor groove is tightly bound. At higher temperatures, the conformation opens up as judged by the increase in separation between sequential H2 protons of adenines and water exchanges freely from the minor groove. The conformational transition and the altered hydration pattern may be related to promoter function. The control of gene expression in procaryotes depends on the specific recognition by RNA polymerase of a six base-pair sequence (consensus: TTGACA) located at -35 from the transcription site, and a second one, named the Pribnow box (consensus: TATAAT) at about 10 base-pairs upstream the initiation site (Rosenberg and Court, 1979). It has been shown (Hawley and McClure, 1983) that strong promoters exhibit a high degree of homology with the consensus sequences, separated by an optimum consensus spacer length of 17 base pairs. The strength of a promoter depends on, among other thing, the rate of the initiation of transcription. This rate depends on the product between the thermodynamic and kinetic constants KB and k2 (McClure, 1980). The initial binding of RNA polymerase to the promoter results in the formation of a transcriptionally inactive ‘closed’ complex, characterized by the association constant KB. Isomerization to the active ‘open’ complex then occurs, and is characterized by the first order rate constant k2. Hence, the frequency of transcription initiation depends both on the strength of the polymerase-promoter interaction, and the ease with which this complex can isomerize to the productive state. Both of these events are likely to depend on the physical properties of the promoter.
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Hetherington, Paul, and Cassandra Atherton. "Women and Prose Poetry." In Prose Poetry, 199–223. Princeton University Press, 2020. http://dx.doi.org/10.23943/princeton/9780691180656.003.0009.
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This chapter highlights the tradition of English-language prose poetry by women. It explores what women's prose poetries may be — not only in terms of content and approach but in terms of technique and emphasis. The chapter begins by looking at Holly Iglesias's seminal text, Boxing Inside the Box: Women's Prose Poetry (2004), which is the most comprehensive study of women's prose poetry to date. Iglesias advocates for the liberation of women prose poets, using the prose poem box as a metaphor for their containment. Beginning with Carolyn Forché's famous and disturbing prose poem about male power and brutality, “The Colonel,” and ending with C. D. Wright's hybrid prose poem essay, Iglesias's book celebrates women prose poets by giving them space and prominence. Ultimately, the neglect of many women prose poets did not occur because women were not writing prose poems; it is just that many women were not writing the kinds of prose poems that fit the prevalent critical view of what successful prose poems might look like.
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Keefer, Robert F. "Macronutrients—Phosphorus and Potassium." In Handbook of Soils for Landscape Architects. Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780195121025.003.0014.
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Plants have a P concentration between 0.03 and 0.70%, but the usual amount is between 0.1 and 0.4%. Phosphorus is found in every living cell of a plant and is involved in genetic transfer and energy relationships. The actively growing parts, that is, stem tips, new leaves, and new roots, need much P. Seeds, especially at maturity, also have a rich supply of P acting as reserve food. Phosphorus is used in plants for (a) root development—especially the lateral and fibrous roots; (b) cell division—energy for metabolism; (c) reproduction—flowering, fruiting, seed formation all controlled by nucleic acids; (d) maturation—counteracts the ill effects of excessive N fertilization; arid (e) disease resistance— especially important in root rots of seedlings. Plant P is a major constituent of chromosomes present as DNA (deoxyribonucleic acid) used in reproduction and RNA (ribonucleic acid) used in growth processes. Plant P is also a constituent of adenosine triphosphate (ATP) that stores energy for plant use, along with many other phosphate compounds, such as phytin (inositol hexaphosphate) stored in seeds, phospholipids in the chloroplasts, and complexes of sugars, sugar amines, aldehydes, amides, and acids—all involved in plant metabolism. Deficiency of P is not striking or characteristic and is difficult to diagnose. The older leaves may be dark bluish-green, bronze, or purple. The stalks are thin, leaves small, limited lateral growth, delayed maturity, and defoliate prematurely. Probably the most obvious symptom would be the purple coloration, but this is exhibited by only a limited number of plants. The best way to determine if a plant is deficient in P would be to conduct a plant tissue test. If the P level is lower than 0.2% P, then P probably is deficient and the soil in which the plant is growing would benefit from P fertilization. . . . Phosphorus Toxicity? . . . Phosphorus toxicity has not been observed in the field and has only been evident in greenhouse culture solutions when P was present at extremely high concentrations.
Conference papers on the topic "Box C/D RNA"
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chen, Luyue, Lei Han, kailiang zhang, jianwei wei, peiyu pu, jianning zhang, and chunsheng kang. "Abstract 235: SNORD76, a box C/D snoRNA, acts as a tumor suppressor in glioblastoma." In Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA. American Association for Cancer Research, 2015. http://dx.doi.org/10.1158/1538-7445.am2015-235.
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Shima, A., N. Sugii, N. Mise, D. Hisamoto, K. Takeda, and K. Torii. "Metal Schottky S/D Technology of Ultra Thin SOTB (Silicon on Thin Box) MOSFET." In 2010 International Conference on Solid State Devices and Materials. The Japan Society of Applied Physics, 2010. http://dx.doi.org/10.7567/ssdm.2010.c-3-4.
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Al-Kubaisy, Waqar, Suzanna Daud, Mustafa Waseem Al-Kubaisy, Omar Waseem AL-Kubaisy, and NikNairan Abdullah. "MATERNAL HEPATITIS C (HCV) INFECTION AND ANTI-D IMMUNOGLOBULIN THERAPY: STUDY TESTING ANTIBODIES, RNA AND GENOTYPE OF HCV IN BAGHDAD." In THE 2ND INTERNATIONAL CONFERENCE ON PUBLIC HEALTH. Masters Program in Public Health, Graduate School, Sebelas Maret University Jl. Ir Sutami 36A, Surakarta 57126. Telp/Fax: (0271) 632 450 ext.208 First website:http//: pasca.uns.ac.id/s2ikm Second website: www.theicph.com. Email: theicph2017@gmail.com, 2017. http://dx.doi.org/10.26911/theicph.2017.020.
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Devrani, Shitanshu, Sudhanshu Pandey, Shubham Chaturvedi, Krishnakumar Sankar, Shantanu Patil, and K. Sridhar. "Design and Analysis of an Efficient Vaccine Cold Chain Box." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65858.
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Human health is one of the most important concerns for the governments around the world. Global organizations such as WHO (World Health Organization) and PATH (Program for Appropriate Technology in Health) have considerable interest in organizing vaccination programs and its cold chain delivery. The problem predominantly persists in Lower-middle income countries like India where due to inadequate infrastructure and lack of consistent Power supply, significant losses occur in the cold chain. Improvements are required to prevent the loss of costly and precious vaccines during the cold chain. India lacks a reliable power supply and the resulting power cuts interrupt the cold chain, leading to a loss of vaccine potency since they are not within the temperature range of 2–8 °C. This paper studies the current VCB (vaccine carrier box) and cold chain design through the aid of Computer modelling and simulations. Also a novel experimental setup to examine insulation R-value has been devised and studied. Based on this a new design approach is utilized to model a thermoelectric system and early designing is done through the aid of 3-D printing.
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Eguchi, Takehiko, Yohei Asai, Kazuhide Ichikawa, and Miki Takada. "Airborne and Structure-Borne Transmission of High Frequency Fan Vibration in a Storage Box." In ASME 2017 Conference on Information Storage and Processing Systems collocated with the ASME 2017 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/isps2017-5406.
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In this paper, contributions of airborne and structure-borne vibrations to head positioning error of a HDD at high frequencies up to 10 kHz were investigated. The L8 array test was conducted with four two-level factors about vibration isolation between fans and HDDs: A) Removing bracket, B) Attaching foam on backplane, C) Filling foam in the next column, and D) Filling foam in the upper and lower slots. The test results showed there were less interaction between airborne and structure-borne vibration. Then, we set a model of fan vibration transmission and the model parameters were determined so that errors between the estimated and measured values were minimized. As the results, it was confirmed that about 80% of the power of PES was caused by the airborne vibration at the normal case.
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Terres, Hilario, Sandra Chavez, Raymundo Lopez, Arturo Lizardi, and Araceli Lara. "Evaluation of Heating Process of Apple, Eggplant, Zucchini and Potato by Means of Their Thermal Properties." In ASME 2016 Heat Transfer Summer Conference collocated with the ASME 2016 Fluids Engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/ht2016-7140.
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In this work, the heating process for apple, eggplant, zucchini and potato by means of evaluation of their thermal properties and the Biot number determined in experimental form is presented. The heating process is carried out using a solar cooker box-type as heating device. The thermal experimental properties determined are conductivity (k), density (D), specific heat (C), diffusivity (Dif) and the Biot number (Bi) for each product evaluated. In the experimentation, temperatures for center and surface in each product and water were measured in controlled conditions. For those measures, a device Compact Fieldpoint and thermocouples placed in the points studied were used. By using correlations with temperature as function, k, D and C were calculated, while by using equations in transitory state for the products modeled as sphere and cylinder was possible to estimate the Biot number after calculation of the heat transfer coefficient for each case. Results indicate the higher value for k, C and Dif correspond to zucchini (0.65 W/m °C, 4084.5 J/kg °C, 1.5 × 10−7 m2), while higher value for D correspond to potato (1197.5 kg/m3). The lowest values for k and C were obtained for potato (0.59 W/m °C, 3658.3 J/kg °C) while lowest values for D and Dif, correspond to zucchini (998.2 kg/m3) and potato (1.45 × 10−7 m2/s) respectively. The maximum and minimum values for Bi corresponded to potato (21.4) and zucchini (0.41) in respective way. The results obtained are very useful in applications for solar energy devices, where estimates for properties are very important to generate new results, for example, numerical simulations. Also, results could be used to evaluate the cooking power in solar cookers when the study object is oriented in that direction.
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Costa, Sol-Carolina, Khamid Mahkamov, Murat Kenisarin, Kevin Lynn, Elvedin Halimic, and David Mullen. "Solar Salt Latent Heat Thermal Storage for a Small Solar Organic Rankine Cycle Plant." In ASME 2018 12th International Conference on Energy Sustainability collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/es2018-7326.
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The design of the Latent Heat Thermal Storage System (LHTESS) was developed with thermal capacity of about 100 kWh as a part of small solar plant, based on the Organic Rankine Cycle (ORC). The phase change material (PCM) used is Solar salt with the melting/solidification temperature of about 220°C. Thermo-physical properties of the PCM were measured, including its phase transition temperature, heat of fusion, specific heat and thermal conductivity. The design of the thermal storage was finalized by means of the 3-D CFD analysis. The thermal storage system is made of six rectangular boxes with dimensions of 1 m (width) × 0.66 m (height) × 0.47 m (depth). The thermal energy is delivered to each of the thermal storage boxes with the use of thermal oil, heated by Fresnel mirrors. The heat is transferred into and from the PCM in the box using 40 bi-directional heat pipes with the external diameter of about 12 mm. The length of the heat pipe in the PCM box is 430 mm and it is placed in the cylindrical metallic protection cartridge, installed in the thermal storage vessel. The working fluid in the heat pipe is water. A set of metallic screens are installed in the box with the pitch of 8–10 mm to enhance the heat transfer from heat pipes to the PCM and vice-versa during the charging and discharging processes, which take about 4 hours. The one unit of the described thermal storage system is undergoing the laboratory tests. Preliminary results demonstrate that the performance of the thermal storage is in a good agreement with numerical predictions. After completion of final design modifications, all units will be assembled at the plant’s demonstration site and tested with the ORC turbine.
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Itagaki, Y., A. Suzuki, and K. Higashio. "TISSUE PLASMINOGEN ACTIVATOR (T-PA) PRODUCTION BY HUMAN EMBRYONIC FIBROBLASTS, IMR-90, STIMULATED BY PROTEOSE PEPTONE." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644392.
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In order to study the mechanisms by which t-PA production by IMR-90 cells are induced, lactalbumin hydrolysates, yeast extracts, and peptones were tested for their ability to induce t-PA production by IMR-90 cells. IMR-90 cells were grown to confluency in Dulbecco's modified Eagle's medium(DMEM) supplemented with 10% fetal calf serum at 37°C in 5% CO2 in air. And the cells were maintained in serum free medium containing 1% of each additive. The plasminogen activator activity was determined by fibrin plate method, using urokinase or t-PA from WHO as a standard. It was found that proteose peptone (Difco) and neopeptone (Difco) strongly induced the t-PA production by IMR-90 cells. The t-PA production in DMEM containing 1% proteose peptone reached approx. 200IU/ml after incubation at 37°C for 6 days and was from twenty to fifty times higher than that in DMEM only (control medium). The t-PA production by IMR-90 cells stimulated by proteose peptone was strongly inhibited by RNA synthesis inhibitor(actinomycin D) or prorein synthesis inhibitor (cycloheximide). Hence, t-PA production by IMR-90 cells stimulated by proteose peptone was mediated by de novo synthesis. Chelating reagent (EGTA), Ca2+ entry blocker (verapamil), inhibitor of phospholipase A2 (quinacrine) and inhibitor of lipoxygenase (NDGA) strongly inhibited the t-PA production by IMR-90 cells stimulated by proteose peptone. Inhibitor of cyclooxygenase (indomethacin) was inert. On the contrary, activators of phospholipase A2(Ca2+,melittin) and hydroxy-unsaturated fatty acid (5-HETE) derived from arachidonic acid by lipoxygenase strongly enhanced t-PA production by IMR-90 cells stimulated by proteose peptone. These results suggest that the t-PA production by IMR-90 cells stimulated by proteose peptone is mediated by arachidonate cascade involving the following pathway; (1) proteose peptone stimulates the membrane of IMR-90, (2) this stimulus causes Ca2+ influx, (3) Ca2+ ion activates phopholipase A2, (4) activated phospholipase A2 liberates arachidonic acid from phospholipids in ceil membrane and (5) lipoxygenase converts arachidonic acid into the hydroxy-unsaturated fatty acid.
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Moormann, Rainer. "A Safety Re-Evaluation of the AVR Pebble Bed Reactor Operation and Its Consequences for Future HTR Concepts." In Fourth International Topical Meeting on High Temperature Reactor Technology. ASMEDC, 2008. http://dx.doi.org/10.1115/htr2008-58336.
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The AVR pebble bed reactor (46 MWth) was operated 1967–1988 at coolant outlet temperatures up to 990°C. Also because of a lack of other experience the AVR operation is a basis for future HTRs. This paper deals with insufficiently published unresolved safety problems of AVR and of pebble bed HTRs. The AVR primary circuit is heavily contaminated with dust bound and mobile metallic fission products (Sr-90, Cs-137) which create problems in current dismantling. The evaluation of fission product deposition experiments indicates that the end of life contamination reached several percent of a single core inventory. A re-evaluation of the AVR contamination is performed in order to quantify consequences for future HTRs: The AVR contamination was mainly caused by inadmissible high core temperatures, and not — as presumed in the past — by inadequate fuel quality only. The high AVR core temperatures were detected not earlier than one year before final AVR shut-down, because a pebble bed core cannot be equipped with instruments. The maximum core temperatures were more than 200 K higher than precalculated. Further, azimuthal temperature differences at the active core margin were observed, as unpredictable hot gas currents with temperatures > 1100°C. Despite of remarkable effort these problems are not yet understood. Having the black box character of the AVR core in mind it remains uncertain whether convincing explanations can be found without major experimental R&D. After detection of the inadmissible core temperatures, the AVR hot gas temperatures were strongly reduced for safety reasons. Metallic fission products diffuse in fuel kernel, coatings and graphite and their break through takes place in long term normal operation, if fission product specific temperature limits are exceeded. This is an unresolved weak point of HTRs in contrast to other reactors and is particularly problematic in pebble bed systems with their large dust content. Another disadvantage, responsible for the pronounced AVR contamination, lies in the fact that activity released from fuel elements is distributed in HTRs all over the coolant circuit surfaces and on graphitic dust and accumulates there. Consequences of AVR experience on future reactors are discussed. As long as pebble bed intrinsic reasons for the high AVR temperatures cannot be excluded they have to be conservatively considered in operation and design basis accidents. For an HTR of 400 MWth, 900°C hot gas temperature, modern fuel and 32 fpy the contaminations are expected to approach at least the same order as in AVR end of life. This creates major problems in design basis accidents, for maintenance and dismantling. Application of German dose criteria on advanced pebble bed reactors leads to the conclusion that a pebble bed HTR needs a gas tight containment even if inadmissible high temperatures as observed in AVR are not considered. However, a gas tight containment does not diminish the consequences of the primary circuit contamination on maintenance and dismantling. Thus complementary measures are discussed. A reduction of demands on future reactors (hot gas temperatures, fuel burn-up) is one option; another one is an elaborate R&D program for solution of unresolved problems related to operation and design basis accidents. These problems are listed in the paper.
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Haag, J. Ch, A. Hildebrandt, H. Ho¨nen, M. Assadi, and R. Kneer. "Turbomachinery Simulation in Design Point and Part-Load Operation for Advanced CO2 Capture Power Plant Cycles." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27488.
Full textAbstract:
In this paper two different power plant processes with their current optimized layouts of the AZEP project and the recently started OXYCOAL-AC project are presented. Both processes are designed for CO2-capture combined with oxygen membrane technology. As a consequence of the implementation of a membrane module there will be essential changes in the plant layout involving modifications to the turbomachinery designs due to the different working medium and interactions of different cycle components. Furthermore, there are different loops included for recirculation of the combustion gas constituents CO2 and H2O. Although, the processes presented have different boundary conditions regarding the selection of fuel and gross power output, they have in common the need for new turbomachinery designs. These two processes are thermodynamically analyzed and compared both at design point and at off-design (part-load operation) mode. Main focus are the different operation modes of AZEP and different turbomachinery layouts for OXYCOAL-AC. Special attention is paid to the modeling of the crucial components common for both power plant processes e.g. the oxygen membrane, the turbine and the compressors. The thermodynamic studies aim at analyzing a) the requirements on turbomachinery at the design point, b) how to reduce the level of requirements for the compressor and the turbine and c) the operation and potential of mismatch for the turbomachinery during part-load operation. Simplified turbomachinery maps and a simplified black box 1-D model of the membrane module and the heat exchangers are used within a commercial heat- and mass-balance program for simulation of part-load operation of both processes. The objective of this conceptual study is the investigation of parameter changes caused by the interaction of process components.