Academic literature on the topic 'Initiator tRNAs'
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Journal articles on the topic "Initiator tRNAs"
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Drabkin, Harold J., and Uttam L. RajBhandary. "Initiation of Protein Synthesis in Mammalian Cells with Codons Other Than AUG and Amino Acids Other Than Methionine." Molecular and Cellular Biology 18, no. 9 (September 1, 1998): 5140–47. http://dx.doi.org/10.1128/mcb.18.9.5140.
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ABSTRACT Protein synthesis is initiated universally with the amino acid methionine. In Escherichia coli, studies with anticodon sequence mutants of the initiator methionine tRNA have shown that protein synthesis can be initiated with several other amino acids. In eukaryotic systems, however, a yeast initiator tRNA aminoacylated with isoleucine was found to be inactive in initiation in mammalian cell extracts. This finding raised the question of whether methionine is the only amino acid capable of initiation of protein synthesis in eukaryotes. In this work, we studied the activities, in initiation, of four different anticodon sequence mutants of human initiator tRNA in mammalian COS1 cells, using reporter genes carrying mutations in the initiation codon that are complementary to the tRNA anticodons. The mutant tRNAs used are aminoacylated with glutamine, methionine, and valine. Our results show that in the presence of the corresponding mutant initiator tRNAs, AGG and GUC can initiate protein synthesis in COS1 cells with methionine and valine, respectively. CAG initiates protein synthesis with glutamine but extremely poorly, whereas UAG could not be used to initiate protein synthesis with glutamine. We discuss the potential applications of the mutant initiator tRNA-dependent initiation of protein synthesis with codons other than AUG for studying the many interesting aspects of protein synthesis initiation in mammalian cells.
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Mangroo, Dev, Xin-Qi Wu, and Uttam L. Rajbhandary. "Escherichia coliinitiator tRNA: structure–function relationships and interactions with the translational machinery." Biochemistry and Cell Biology 73, no. 11-12 (December 1, 1995): 1023–31. http://dx.doi.org/10.1139/o95-109.
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We showed previously that the sequence and (or) structural elements important for specifying the many distinctive properties of Escherichia coli initiator tRNA are clustered in the acceptor stem and in the anticodon stem and loop. This paper briefly describes this and reviews the results of some recently published studies on the mutant initiator tRNAs generated during this work. First, we have studied the effect of overproduction of methionyl-tRNA transformylase (MTF) and initiation factors IF2 and IF3 on activity of mutant initiator tRNAs mat are defective at specific steps in the initiation pathway. Overproduction of MTF rescued specifically the activity of mutant tRNAs defective in formylation but not mutants defective in binding to the P site. Overproduction of IF2 increased me activity of all mutant tRNAs having the CUA anticodon but not of mutant tRNA having me GAC anticodon. Overproduction of IF3 had no effect on the activity of any of me mutant tRNAs tested. Second, for functional studies of mutant initiator tRNA in vivo, we used a CAU→CUA anticodon sequence mutant mat can initiate protein synthesis from UAG instead of AUG. In contrast with me wild-type initiator tRNA, the mutant initiator tRNA has a 2-methylthio-N6-isopentenyl adenosine (ms2i6A) base modification next to the anticodon. Interestingly, this base modification is now important for activity of the mutant tRNA in initiation. In a miaA strain of E. coli deficient in biosynthesis of ms2i6A, the mutant initiator tRNA is much less active in initiation. The defect is specifically in binding to the ribosomal P site.Key words: initiator tRNA, initiation Factors, formylation, P site binding, base modification.
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Farruggio, D., J. Chaudhuri, U. Maitra, and U. L. RajBhandary. "The A1 x U72 base pair conserved in eukaryotic initiator tRNAs is important specifically for binding to the eukaryotic translation initiation factor eIF2." Molecular and Cellular Biology 16, no. 8 (August 1996): 4248–56. http://dx.doi.org/10.1128/mcb.16.8.4248.
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The formation of a specific ternary complex between eukaryotic initiation factor 2 (eIF2), the initiator methionyl-tRNA (Met-tRNA), and GTP is a critical step in translation initiation in the cytoplasmic protein-synthesizing system of eukaryotes. We show that the A1 x U72 base pair conserved at the end of the acceptor stem in eukaryotic and archaebacterial initiator methionine tRNAs plays an important role in this interaction. We changed the A1 x U72 base pair of the human initiator tRNA to G1 x C72 and expressed the wild-type and mutant tRNA genes in the yeast Saccharomyces cerevisiae by using constructs previously developed in our laboratory for expression of the human initiator tRNA gene in yeasts. We show that both the wild-type and mutant human initiator tRNAs are aminoacylated well in vivo. We have isolated the wild-type and mutant human initiator tRNAs in substantially pure form, free of the yeast initiator tRNA, and have analyzed their properties in vitro. The G1 x C72 mutation affects specifically the binding affinity of eIF2 for the initiator tRNA. It has no effect on the subsequent formation of 40S or 80S ribosome initiator Met-tRNA-AUG initiation complexes in vitro or on the puromycin reactivity of the Met-tRNA in the 80S initiation complex.
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Drabkin, Harold J., Melanie Estrella, and Uttam L. Rajbhandary. "Initiator-Elongator Discrimination in Vertebrate tRNAs for Protein Synthesis." Molecular and Cellular Biology 18, no. 3 (March 1, 1998): 1459–66. http://dx.doi.org/10.1128/mcb.18.3.1459.
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ABSTRACT Initiator tRNAs are used exclusively for initiation of protein synthesis and not for the elongation step. We show, in vivo and in vitro, that the primary sequence feature that prevents the human initiator tRNA from acting in the elongation step is the nature of base pairs 50:64 and 51:63 in the TΨC stem of the initiator tRNA. Various considerations suggest that this is due to sequence-dependent perturbation of the sugar phosphate backbone in the TΨC stem of initiator tRNA, which most likely blocks binding of the elongation factor to the tRNA. Because the sequences of all vertebrate initiator tRNAs are identical, our findings with the human initiator tRNA are likely to be valid for all vertebrate systems. We have developed reporter systems that can be used to monitor, in mammalian cells, the activity in elongation of mutant human initiator tRNAs carrying anticodon sequence mutations from CAU to CCU (the C35 mutant) or to CUA (the U35A36 mutant). Combination of the anticodon sequence mutation with mutations in base pairs 50:64 and 51:63 yielded tRNAs that act as elongators in mammalian cells. Further mutation of the A1:U72 base pair, which is conserved in virtually all eukaryotic initiator tRNAs, to G1:C72 in the C35 mutant background yielded tRNAs that were even more active in elongation. In addition, in a rabbit reticulocyte in vitro protein-synthesizing system, a tRNA carrying the TΨC stem and the A1:U72-to-G1:C72 mutations was almost as active in elongation as the elongator methionine tRNA. The combination of mutant initiator tRNA with the CCU anticodon and the reporter system developed here provides the first example of missense suppression in mammalian cells.
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Das, Gautam, T. K. Dineshkumar, Swapna Thanedar, and Umesh Varshney. "Acquisition of a stable mutation in metY allows efficient initiation from an amber codon in Escherichia coli." Microbiology 151, no. 6 (June 1, 2005): 1741–50. http://dx.doi.org/10.1099/mic.0.27915-0.
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Escherichia coli strains harbouring elongator tRNAs that insert amino acids in response to a termination codon during elongation have been generated for various applications. Additionally, it was shown that expression of an initiator tRNA containing a CUA anticodon from a multicopy plasmid in E. coli resulted in initiation from an amber codon. Even though the initiation-based system remedies toxicity-related drawbacks, its usefulness has remained limited for want of a strain with a chromosomally encoded initiator tRNA ‘suppressor’. E. coli K strains possess four initiator tRNA genes: the metZ, metW and metV genes, located at a single locus, encode tRNA1 fMet, and a distantly located metY gene encodes a variant, tRNA2 fMet. In this study, a stable strain of E. coli K-12 that affords efficient initiation from an amber initiation codon was isolated. Genetic analysis revealed that the metY gene in this strain acquired mutations to encode tRNA2 fMet with a CUA anticodon (a U35A36 mutation). The acquisition of the mutations depended on the presence of a plasmid-borne copy of the mutant metY and recA + host background. The mutations were observed when the plasmid-borne gene encoded tRNA2 fMet (U35A36) with additional changes in the acceptor stem (G72; G72G73) but not in the anticodon stem (U29C30A31/U35A36/ψ39G40A41). The usefulness of this strain, and a possible role for multiple tRNA1 fMet genes in E. coli in safeguarding their intactness, are discussed.
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Starck, Shelley, Vivian Jiang, Mariana Pavon-Eternod, Sharanya Prasad, Tao Pan, and Nilabh Shastri. "Cryptic tRNAi shapes the pMHC I repertoire (100.5)." Journal of Immunology 186, no. 1_Supplement (April 1, 2011): 100.5. http://dx.doi.org/10.4049/jimmunol.186.supp.100.5.
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Abstract MHC class I molecules present peptides on the cell surface for immune surveillance of viruses and cancer. Interestingly, the peptides are encoded not only in conventional AUG-initiated translational reading frames but also in non-AUG initiated cryptic reading frames. Whether the same or distinct translational machinery is used to produce cryptic peptides at non-AUG start codons, such as CUG, is not known. Here, we show that translational initiation of antigenic precursors at cryptic CUG codons is differentially regulated by ribosomal initiation complexes that contain novel initiator tRNAs. This tRNA is distinct from Met-initiator tRNA and enhances initiation at CUG start codons. Thus, a novel tRNA -based mechanism can supply peptides for presentation by MHC I.
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Samhita, L., S. Shetty, and U. Varshney. "Unconventional initiator tRNAs sustain Escherichia coli." Proceedings of the National Academy of Sciences 109, no. 32 (July 24, 2012): 13058–63. http://dx.doi.org/10.1073/pnas.1207868109.
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Arhin, George K., Shuiyuan Shen, Henriette Irmer, Elisabetta Ullu, and Christian Tschudi. "Role of a 300-Kilodalton Nuclear Complex in the Maturation of Trypanosoma brucei Initiator Methionyl-tRNA." Eukaryotic Cell 3, no. 4 (August 2004): 893–99. http://dx.doi.org/10.1128/ec.3.4.893-899.2004.
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ABSTRACT tRNAs are transcribed as precursors containing 5′ leader and 3′ extensions that are removed by a series of posttranscriptional processing reactions to yield functional mature tRNAs. Here, we examined the maturation pathway of tRNAMet in Trypanosoma brucei, an early divergent unicellular eukaryote. We identified an approximately 300-kDa complex located in the nucleus of T. brucei that is required for trimming the 5′ leader of initiator tRNAMet precursors. One of the subunits of the complex (T. brucei MT40 [TbMT40]) is a putative methyltransferase and a homolog of Saccharomyces cerevisiae Gcd14, which is essential for 1-methyladenosine modification in tRNAs. Down-regulation of TbMT40 by RNA interference resulted in the accumulation of precursor initiator tRNAMet containing 5′ extensions but processed 3′ ends. In addition, immunoprecipitations with anti-La antibodies revealed initiator tRNAMet molecules with 5′ and 3′ extensions in TbMT40-silenced cells, albeit at a much lower level. Interestingly, silencing of TbMT40, as well as of TbMT53, a second subunit of the complex, led to an increase in the levels of mature elongator tRNAMet. Taken together, our data provide a glance at the maturation of tRNAs in parasitic protozoa and suggest that at least for initiator tRNAMet, 3′ trimming precedes 5′ processing.
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Crausaz Esseiva, Anne, Laurence Maréchal-Drouard, Anne Cosset, and André Schneider. "The T-Stem Determines the Cytosolic or Mitochondrial Localization of Trypanosomal tRNAsMet." Molecular Biology of the Cell 15, no. 6 (June 2004): 2750–57. http://dx.doi.org/10.1091/mbc.e03-11-0821.
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The mitochondrion of Trypanosoma brucei lacks tRNA genes. Organellar translation therefore depends on import of cytosolic, nucleus-encoded tRNAs. Except for the cytosol-specific initiator tRNAMet, all trypanosomal tRNAs function in both the cytosol and the mitochondrion. The initiator tRNAMet is closely related to the imported elongator tRNAMet. Thus, the distinct localization of the two tRNAsMet must be specified by the 26 nucleotides, which differ between the two molecules. Using transgenic T. brucei cell lines and subsequent cell fractionation, we show that the T-stem is both required and sufficient to specify the localization of the tRNAsMet. Furthermore, it was shown that the tRNAMet T-stem localization determinants are also functional in the context of two other tRNAs. In vivo analysis of the modified nucleotides found in the initiator tRNAMet indicates that the T-stem localization determinants do not require modified nucleotides. In contrast, import of native tRNAsMet into isolated mitochondria suggests that nucleotide modifications might be involved in regulating the extent of import of elongator tRNAMet.
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Wu, X. Q., P. Iyengar, and U. L. RajBhandary. "Ribosome-initiator tRNA complex as an intermediate in translation initiation in Escherichia coli revealed by use of mutant initiator tRNAs and specialized ribosomes." EMBO Journal 15, no. 17 (September 1996): 4734–39. http://dx.doi.org/10.1002/j.1460-2075.1996.tb00850.x.
Full textDissertations / Theses on the topic "Initiator tRNAs"
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CAROTTI, MARCELLO. "Mechanism of ribosomal recruitment of initiator tRNA in bacteria." Doctoral thesis, Università degli Studi di Camerino, 2008. http://hdl.handle.net/11581/401875.
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Initiation of mRNA translation in prokaryotes requires the small ribosomal subunit (30S), three initiation factors, IF1, IF2 and IF3, initiator tRNA (fMet-tRNAfMet) and the large ribosomal subunit (50S). During initiation, the 30S ribosomal subunit interacts with the three factors and binds in a presumably random manner fMet-tRNAfMet and mRNA. This initially formed 30S pre-initiation complex is a kinetic intermediate of the stable 30S initiation complex which is formed upon base pairing of the anticodon of fMet-tRNAfMet and the intiation codon of the mRNA in the P-site. In a subsequent step the 50S subunit binds to the 30S initiation complex giving rise to a 70S initiation complex. During this step, a molecule of GTP bound to IF2 is hydrolyzed, the initiation factors are released from the ribosome and fMet-tRNAfMet is stabilized in the P site ready to enter in the elongation phase of translation. In turn, each of these major steps involves numerous elemental steps, whose sequence and timing are largely unknown. How the fMettRNAfMet is bound to the ribosome during the assembly of the initiation complex is one of the many questions still remaining open. According to the classical model, IF2 acts as a carrier of fMet-tRNAfMet to the ribosome. An alternative model predicts that the IF2, prebound to the 30S subunit awaits the arrival of fMet-tRNAfMet with which it interacts only at the ribosomal surface. This work presents results of a kinetic analysis of binding to the 30S subunit of various ribosomal ligands (Initiation Factors, fMet-tRNAfMet, mRNA), performed with fast kinetic techniques (rapid filter binding, fluorescence stopped flow). The data obtained strongly support the model in which IF2 is not a fMettRNAfMet carrier. The elemental rate constants determined here give us a more detailed description of the process of 30S initiation complex assembly, of the interplay of the various ribosomal ligands and of the functional significance of different structural modules of IF2.
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Faruggio, Dawn C. (Dawn Catherine) 1965. "Stucture-function relationships of human initiator tRNA mutants and attempted regulated expresion of tRNA genes in yeast." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/32665.
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Zorzet, Anna. "Mechanisms of Adaptation to Deformylase Inhibitors." Doctoral thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-123242.
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Antibiotic resistance is a growing problem on a global scale. Increasing numbers of bacteria resistant toward one or multiple antibiotics could return us to the high mortality rates for infectious diseases of the pre-antibiotic era. The need for development of new classes of antibiotics is great as is increased understanding of the mechanisms underlying the development of antibiotic resistance. We have investigated the emergence of resistance to peptide deformylase inhibitors, a new class of antibiotics that target bacterial protein synthesis. The fitness of resistant mutants as well as their propensity to acquire secondary compensatory mutations was assessed in order to gain some insight into the potential clinical risk of resistance development. Most of this work was done in the bacterium Salmonella typhimurium, due to the availability of excellent genetic tools to study these phenomena. In addition, we have studied the bacterium Staphylococcus aureus as peptide deformylase inhibitors have been shown to have the greatest effect on Gram-positive organisms. In the course of this work we also examined the mechanistic aspects of translation initiation. Using a cell-free in vitro translation system we studied the effects of various components on translation initiation. These results have been combined with results obtained from resistant and compensated bacterial strains in vivo to gain new insights into the mechanisms of translation initiation.
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Ibrahim, Isak Georgina. "Studies on Translation Initiation and Termination in Escherichia coli." Doctoral thesis, Stockholms universitet, Institutionen för genetik, mikrobiologi och toxikologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-69954.
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Translation initiation factor 1 (IF1) has been shown to be an RNA chaperone. In order to find functional interactions that IF1 may have with rRNA, we have isolated second-site suppressors of a cold-sensitive IF1 mutant. Joining of the ribosomal subunit seems to be affected in the IF1 mutant strain and the suppressive effect is a consequence of decreasing the available pool of mature 50S subunits. The results serve as additional evidence that IF1 is an RNA chaperone and that final maturation of the ribosome takes place during translation initiation. In this study we have also investigated the effect of a cold-sensitive mutant IF1 or kasugamycin addition on gene expression using a 2D gel electrophoresis technique. The effect is much more dramatic when cells are treated with kasugamycin compared to mutant IF1. The ybgF gene is uniquely sensitive to the IF1 mutation as well as the addition of kasugamycin. This effect on the native gene could be connected with some property of the TIR sequence of ybgF and supports the notion that kasugamycin addition and the IF1 cold-sensitive mutation have a similar TIR-specific effect on mRNA translation. Finally we have isolated a suppressor of a temperature-sensitive mutation in ribosomal release factor 1 (RF1) to shed more light on the translation termination process. The suppressor mutation is linked to an IS10 insertion into the cysB gene and results in a Cys- phenotype. Our results suggest that suppression of the thermosensitive growth is a consequence of the mnm5s2U hypomodification of certain tRNA species. The ability of mnm5s2U hypomodified tRNA to induce frameshifting may be responsible for the suppression mechanism and it supports the hypothesis that modified nucleosides in the anticodon of tRNA act in part to prevent frameshifting by the ribosome.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Manuscript.
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Garside, Paul. "Analysis of the canonical initiation and trans-acting factor requirements of 5'TOP containing mRNAs." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/14089/.
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All eukaryotic mRNAs process a cap structure (m7G(5')ppp(5')N) at the S' end of their message and most have an A as the first nucleotide after the cap. However, 30% of messages within eukaryotic cells have a C (m7G(t')ppp(5')C) as the first nucleotide followed by a short polypyrimidine tract. These mRNAs are termed TOP (Tenninal Oligopyrimidine tract) messages and are co-ordinately regulated by mitogenic, growth and nutritional stimuli. This work describes the construction of a reporter vector that encodes mRNA containing the TOP motif, and its use in a series of systematic experiments to further investigate the translational regulation of TOP messages. Given that TOP containing mRNAs are known to encode proteins involved in the translational machinery, these findings have important implications with regard to translational control and translation related disease. In this study, reporter vectors have been used to investigate the role of the mTOR and PI3K signalling pathways, which have previously been implicated in the translational regulation of TOP containing mRNAs. The data obtained suggests that the mTOR signalling pathway may be involved in the regulation of TOP containing mRNAs. The canonical initiation and frans-acting factor requirements of TOP mRNAs were also investigated using a combination of protein over-expression and affinity purification of TOP-containing-mRNA:protein complexes. The data obtained raises the possibility that eIF4E may not be required in the initiation of TOP containing mRNA translation. The candidate trans-acting factors that were identified include La, ILF2 and EBPl, the latter of which has previously been shown to associate with mature ribosomes in the cytoplasm. Finally, affinity purification of TOP-containing-mRNA:microRNA complexes was carried out. Candidate microRNAs which may be involved in the regulation of TOP containing mRNAs were identified. The data obtained was consistent with a previous study, which suggested that microRNA-IOa may bind to the S'UTR of TOP containing mRNAs.
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Kinzy, Terri Goss. "Characterization of GTP and aminoacyl-tRNA binding to eukaryotic initiation factor 2 and elongation factor 1." Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055276346.
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Kemp, Michael George. "Regulation of DNA Replication Initiation by Histone Acetylation and the DNA Unwinding Element Binding Protein DUE-B." Wright State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=wright1156358849.
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Huang, Yue. "Primer tRNA-Lys3 incorporation, genomic placement and initiation of reverse transcription in human immunodeficiency virus type 1." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0005/NQ44459.pdf.
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Prabhakaran, Ramanandan. "Factors Affecting Translational Efficiency of Bacteriophages." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32106.
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Mass production of translationally optimized bacteriophages (hereafter referred to as phages) is the need of the hour in the application of phages to therapy. Understanding translational efficiency of phages is the major preliminary step for mass producing efficient phages. The objective of this thesis is to understand factors affecting translational efficiency of phages.
In chapter two, we hypothesized that weak translation initiation efficiency is responsible for weak codon concordance of Escherichia coli lambdoid phages with that of their hosts. We measured the strength of translation initiation using two indices namely minimum folding energy (MFE) and proportion of Shine-Dalgarno sequence (PSD). Empirical results substantiate our hypothesis suggesting lack of strong selection for improving codon adaptation in these phages is due to their weak translation initiation.
In chapter three, we measured codon usage concordance between GC-rich and GC-poor Aeromonas phages with their GC-rich host Aeromonas salmonicida. We found low codon usage concordance in the GC-poor Aeromonas phages. We were interested in testing for the role of tRNAs in the GC-poor phages. We observed that the GC-poor phages carry tRNAs for codons that are overused by the phages and underused by the host. These findings suggest that the GC-poor Aeromonas phages carry their own tRNAs for compensating for the compositional difference between their genomes and that of their host.
Previously several studies have reported observed avoidance of stable secondary structures in start site of mRNA in a wide range of species. We probed the genomes of 422 phage species and measured their secondary structure stability using MFE. We observed strong patterns of secondary structure avoidance (less negative MFE values) in the translation initiation region (TIR) and translation termination region (TTR) of all analyzed phages. These findings imply selection is operating at these translationally important sites to control stable secondary structures in order to maintain efficient translation.
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Conand, Clément. "Etude tectonique, pétrographique et géochimique de la zone de transition subduction-collision à Taïwan : rôle de l'héritage et de l'obliquité de la convergence." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30262.
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La chaîne de Taïwan est un exemple unique où il est possible d’étudier une transition subduction/collision active. L’obliquité de la convergence permet en effet d’observer du Sud vers le Nord les stades initiaux de l’accrétion continentale en mer jusqu’au stade mature de la collision. Je montre que la Chaîne Centrale au Sud de Taiwan, située la zone de transition, exhume des assemblages pétrographiques de grades croissants vers le Nord, dans un couloir décrochant senestre qui résulte du partitionnement de la convergence. Dans ce couloir l’extension sub-parallèle à la chaîne accommode une partie de l’exhumation. A proximité de la zone de suture principale, des assemblages de haute pression (12-15 kbars et 380-420 °C) associés à des blocs exotiques de serpentinites se sont mis en place dans un encaissant d’âge Miocène HT-BP associé à une intense déformation cisaillante senestre. Les analyses pétrologiques et géochimiques des mélanges ophiolitiques de Kenting et Lichi montrent que ces mélanges proviennent de deux sources situées à l’origine au pied de la marge continentale et dans la croûte océanique. Enfin, je propose, un nouveau modèle tectonique 3D du sud de Taïwan qui tient compte de l’architecture de la marge continentale, et qui met en avant la formation de la chaîne de Taiwan en contexte décrochantThe Taiwan collision is the unique example where to examine ongoing tectonic processes at the subduction/collision transition. The oblique convergence setting allows observations of first continental accretion offshore to the mature stage of collision onshore. I show that the southern Central Range, located at the transition, exhumed petrographic assemblages with peak metamorphism increasing northwards, in a corridor characterized by left-lateral transcurrent deformation. Extension sub-parallel to the belt is also understood as a major ingredient of rock exhumation. Near the suture zone, HP rocks (12-15 kbars and 380-420 °C) associated with isolated serpentinite bodies were emplaced in association with intense ductile strain localization in the strike-slip corridor. Petrographc and geochemical analyses of the Kenting and Lichi ophiolitic mélanges reveal that these mélanges originated from the distal rifted margin and the oceanic crust of the South China Sea. I propose a 3D geodynamic model of the evolution of the Taiwan orogen in which the rifted margin architecture is taken into account and the strike-slip kinematic component of the convergence is the main driver of mountain building
Books on the topic "Initiator tRNAs"
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Yakov, Gluzman, and Cold Spring Harbor Laboratory, eds. Eukaryotic transcription: The role of cis- and trans-acting elements in initiation. Cold Spring Harbor, N.Y: Cold Spring Harbor Laboratory, 1985.
Find full textBook chapters on the topic "Initiator tRNAs"
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RajBhandary, Uttam L., and C. Ming Chow. "Initiator tRNAs and Initiation of Protein Synthesis." In tRNA, 511–28. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555818333.ch25.
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Dyson, Michael R., Chan Ping Lee, Nripendranath Mandal, Baik L. Seong, Umesh Varshney, and Uttam L. RajBhandary. "Identity of a Prokaryotic Initiator tRNA." In The Translational Apparatus, 23–33. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4615-2407-6_3.
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Jennings, Martin D., and Graham D. Pavitt. "Quantifying the Binding of Fluorescently Labeled Guanine Nucleotides and Initiator tRNA to Eukaryotic Translation Initiation Factor 2." In Methods in Molecular Biology, 89–99. New York, NY: Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-1975-9_6.
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Byström, Anders S., Ulrich von Pawel-Rammingen, and Stefan U. Åström. "Genetic Systems in Yeast for Analysis of Initiator/ Elongator tRNA Specificity." In The Translational Apparatus, 35–45. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4615-2407-6_4.
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Fechter, Pierre, Clément Chevalier, Gulnara Yusupova, Marat Yusupov, Pascale Romby, and Stefano Marzi. "Ribosomal Initiation Complexes Probed by Toeprinting and Effect of trans-Acting Translational Regulators in Bacteria." In Methods in Molecular Biology, 247–63. Totowa, NJ: Humana Press, 2009. http://dx.doi.org/10.1007/978-1-59745-558-9_18.
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"Initiator tRNA." In Encyclopedia of Genetics, Genomics, Proteomics and Informatics, 999. Dordrecht: Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-6754-9_8506.
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Lucchesi, John C. "The basic mechanism of gene transcription." In Epigenetics, Nuclear Organization & Gene Function, 17–32. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198831204.003.0003.
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Transcription is initiated by factors that interact with RNA polymerases and recruit them to specific sites, unwind the DNA molecules and allow the synthesis of RNA transcripts complementary to one of the single DNA strands. RNA polymerase II (RNAPII) transcribes genes that encode proteins and some non-coding RNAs; RNAPI transcribes ribosomal RNA genes; RNAPIII transcribes genes that encode tRNAs and other non-coding RNAs. The transcription process starts with a pre-initiation complex (PIC), its activation and promoter clearance. Activation involves chromatin looping, usually promoted by the large multiprotein Mediator complex. RNAPII often makes a promoter-proximal pause, then resumes productive elongation of the transcript. Transition through the different phases of transcription is orchestrated by the phosphorylation of the main subunit of RNAPII. The 5´ end of many transcripts is protected by a methylated guanosine “cap,” and the 3´ end by the addition of a chain of adenosine monophosphates (polyadenylation). Many transcripts undergo splicing to remove regions that interrupt the coding sequence.
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Shekau, Abubakar. "A Message to the African Leaders, Specifically, Idriss Déby." In The Boko Haram Reader, 377–82. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190908300.003.0059.
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(9 FEBRUARY 2015) [Trans.: Abdulbasit Kassim] Available at: http://jihadology.net/2015/02/09/new-video-messagefrom-jamaat-ahl-al-sunnah-li-l-dawah-wa-l-jihad-boko-%e1%b8%a5aram-abu-bakr-shekau-a-message-to-african-leadersespecially-idris-david/ Of all the opponents that the activities of Boko Haram had brought upon themselves by the beginning of 2015, the doughtiest were the Chadians. Boko Haram had initiated several operations threatening Chad, including the 28–29 December 2014 full-scale attack on Cameroon, close to the Chadian capital of N’Djamena. Thus, it was not a surprise when President Idriss Déby began to initiate military operations against Boko Haram first in Cameroon on 9 January 2015, and then into northeastern Nigeria on 16 January 2015. Obviously, these operations angered Boko Haram...
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Shalloe, Harper. "Trans/sexual Negativity and the Ethics of (S)exploitation in Let Me Die a Woman." In ReFocus: The Films of Doris Wishman, 47–64. Edinburgh University Press, 2021. http://dx.doi.org/10.3366/edinburgh/9781474482349.003.0004.
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This chapter underscores important links between trans studies and psychoanalysis through the case study of Let Me Die a Woman (1978) and presents the film as a site of struggle pertaining to genre classifications (documentary and pornography), the psychoanalytic concept of sublimation, and recent theorizations of trans negativity in trans studies. The chapter arguing that trans studies’ ontological turn has underacknowledged relations to psychoanalytic understandings of the process of sublimation. The author discusses editing as the key formal element in the film that initiates a sublimation-like process, coining a novel conceptual parallel that the author calls “editing as edging.”
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Chakma, Bhumitra. "Beyond SAARC: Sub-Regional and Trans-Regional Cooperation." In South Asian Regionalism, 121–36. Policy Press, 2020. http://dx.doi.org/10.1332/policypress/9781529205152.003.0007.
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This chapter analyses sub-regional and trans-regional cooperation that has developed within the framework of SAARC and beyond and their implications for South Asian regionalism. Within the framework of SAARC, the South Asian Growth Quadrangle (SAGQ) which came to be known as ‘Bangladesh, Bhutan, India and Nepal’ (BBIN) initiative was approved in the 1997 Male summit. To support the sub-regional initiative, the Asian Development Bank initiated the ‘South Asian Sub-regional Cooperation’ (SASEC). Beyond SAARC, the ‘Bangladesh, China, India and Myanmar Economic Corridor’ (BCIM-EC) and the ‘Bay of Bengal Initiative for Multi-Sectoral Technical and Economic Cooperation’ (BIMSTEC) have emerged which are trans-national in character. These initiatives have got implications for SAARC-led regionalism which are analysed in this chapter.
Conference papers on the topic "Initiator tRNAs"
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Hill, R. A., A. Knoesen, D. R. Yankelevich, and R. Twieg. "Optically initiated orientation of nonlinear photoisomers." In Organic Thin Films for Photonic Applications. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/otfa.1995.the.1.
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Second order nonlinearities can be imposed in a disordered polymer film by poling. Electric field poling is the most common technique but poling can also be achieved optically. In optical poling, a sample is irradiated with linearly polarized light and the nonlinear molecules undergo successive isomerizations, contractions and relaxations and eventually become aligned perpendicular to the incident polarization.1 This photoisomerization can also increase the mobility of the nonlinear molecules within the polymer and permit improved alignment to an electric field.2 The previous reports of optically induced reorientation have used continuous-wave illumination and required long exposure times.3-11However, the trans-cis photoisomerization has been shown to be extremely fast.12 We are investigating the dynamics of the trans-cis isomerization and orientation of nonlinear stilbene molecules in the presence of an electric field by monitoring the changes in the second order nonlinearity. In our research we have used short optical pulses to initiate molecular reorientation by photoisomerization. The unstable cis-isomer of azobenzene is used to enable a transition between two states which both involve the stable trans-isomer. Because of the extreme speed with which the photoisomerization can be initiated, it could find an application in digital optical storage.
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Pullen, Stuart, Larry A. Walker, Neil Anderson, and Roseanne J. Sension. "Femtosecond Studies of Isomerization and Energy Relaxation in Small Polyenes." In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/up.1996.tue.28.
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Recent advances in laser technology have permitted the extension of femtosecond transient absorption studies into the deep ultraviolet. In the present investigation we have used tunable pump and probe pulses to study the photochemically initiated ring-opening reaction of 1,3-cyclohexadiene (CHD). A proper interpretation of the transient absorption signals obtained in the investigation of this ring-opening reaction requires an understanding of the vibrational and conformational relaxation processes which occur following formation of the hot cis-1,3,5-hexatriene photoproduct. To this end, we have also investigated the conformational and vibrational relaxation of hot cis-1,3,5-hexatriene and trans-1,3,5-hexatriene (HT) produced via ultrafast internal conversion following direct excitation of these two isomers.
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Andreev, D. E., M. Terenin, S. E. Dmitriev, M. Niepmann, and I. N. Shatsky. "MOONLIGHTING FUNCTIONS OF GLYCYL-TRNA SYNTHETASE IN MAMMALIAN CELLS: THE ROLE IN THE TRANSLATION INITIATION ON THE IRES ELEMENTS OF ENTEROVIRUS RNAS." In Viruses: Discovering Big in Small. TORUS PRESS, 2019. http://dx.doi.org/10.30826/viruses-2019-13.
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Kim, Hak Kyun, Jianpeng Xu, Kirk Chu, Hyesuk Park, Hagoon jang, Pan Li, Paul Valdmanis, Qiangpeng Zhang, and Mark Kay. "Abstract LB-343: A Leu(CAG)-tRNA derived small RNA regulates ribosomal protein S28 after translation initiation in both human and mouse liver cancers." In Proceedings: AACR Annual Meeting 2020; April 27-28, 2020 and June 22-24, 2020; Philadelphia, PA. American Association for Cancer Research, 2020. http://dx.doi.org/10.1158/1538-7445.am2020-lb-343.
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Lee, Taerim. "Mobile e-book for BITEC MOOC." In Teaching Statistics in a Data Rich World. International Association for Statistical Education, 2017. http://dx.doi.org/10.52041/srap.17405.
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This paper describes an implementation of mobile e-Book initiative in the Bioinformatics Training & Education Center (BITEC) MOOC project supported by the South Korean Ministry of Welfare and Public Health. This project was initiated by Dept. of Bioinformatics & Statistics KNOU and Dept. of Medical Informatics of SNU Medical College for training medical doctors. High penetration rates of mobile phone subscriptions and rapid growth of handheld users show that mobile devices are a viable alternative learning mode. The mobile e-Book initiative is aimed to encourage learning and interactions in distance learning communities, aiming to bridge trans- actional distances faced by learners and adopt mobility as the key tool in Bioinformatics courses delivery. The BITEC m-Learning initiative focuses on introducing Bioinformatics using easily accessible handheld and mobile devices, since the learners are very busy medical doctors in an ubiquitous learning environment. The m-Learning approach is considered as a learning alternative to support distance learners, mainly working doctors and medical researchers in Korea. This research paper discusses the implementation of the mobile e-Book approach which has better affordable, accessible and flexible educational media.
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Regalla, Srinivasa Prakash, P. V. Shyam, Sampath Mylavarapu, Sai Harshini Irigineni, and Prakash Narayan Shrivastava. "Study of Flexural Strength and Fracture of Additive Manufactured Parts With Stiffeners." In ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-71519.
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Abstract The authors have developed trans-tibial prosthetic sockets using additive manufacturing. These sockets made with mono-material thermoplastics such as Acrylonitrile Butadiene Styrene (ABS) and Polylactic Acid (PLA) at lower thicknesses were found to fracture within a few days of use by the amputees. The fracture was repeatedly found to occur at specific locations such as the lobe corners and the socket’s lower one-third zone. The most probable causes of crack initiation are lack of fusion (LOF) sites and voids. The causes of crack propagation are the lower interlayer bond strength compared to intra-layer bond strength. However, no scientific work exists that clearly explains these phenomena and methods to prevent such potential crack initiation sites and arrest the propagation of such fracture in additively manufactured polymeric structures. Therefore, in the present work, the investigation was carried out into possible enhancement in the resistance to fracture by different strength-enhancing post-processing techniques. In the first technique, the placement of stiffener features at selected locations on the socket was investigated. Three-point bending tests were carried out on D790 standard ABS specimens with different stiffeners introduced on the bottom face. The study focused on fracture characteristics in the stiffener-based topologically optimized geometric design of plate structures made by Fused Deposition Modeling (FDM) under flexural loading. The D790 three-point bending specimens were provided with differently shaped stiffeners, namely, triangular, prismatic, cuboidal, and pyramidal, extending all along the specimen’s length and spread with differential gaps in the width direction. In the second method, thermosetting epoxy resin coatings were applied on the three-point bending specimens of ABS, and the effect of the coating on the flexural strength was investigated. Bending tests were done on three specimens, the first specimen without any coating, the second specimen with only the epoxy resin coating, and the third specimen with two different coating layers. The first of the two coating layers on the third specimen was with primer and the second layer was with epoxy resin. Scanning electron microscope (SEM) and energy dispersion spectroscopy (EDS) scanning analyses were conducted on the fractured specimens. The scanning images indicated that both the primer and resin materials showed a tendency to diffuse into the substrate of ABS, thereby weakening the extreme fibers of material on the specimen’s tension side, resulting in premature crack initiation and propagation. Significant gain in the flexural strength was observed in both the strength enhancement techniques compared to plain specimens.
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Tropea, Cameron, Bernhard Weigand, and Kathri Schulte. "Selected Results of the Collaborative Research Center "Droplet Dynamics under Extreme Ambient Conditions" SFB/TRR 75." In ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4597.
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The Collaborative Research Center (CRC) SFB-TRR 75 was established in January 2010 to focus on the dynamicsof basic drop processes, and in particular on processes involving extreme boundary conditions, for example, near thermodynamic critical conditions, very low temperatures, under strong electric fields or in situations involving extremely large gradients. The CRC is a joint initiative of the University of Stuttgart, the TU Darmstadt and the German Aerospace Center (DLR) in Lampoldshausen, operating with 17 projects structured into three main research areas and involving researchers from numerous faculties: Mathematics, Chemistry, Electrical Engineering, Aerospace Engineering, Mechanical Engineering, Informatics and Computer Sciences. Some of the topics pursued at the CRC include•The behaviour of supercooled and potentially electrified droplets in clouds•The impact of Supercooled Large Droplets (SLD) on aircraft icing•The behaviour of strongly electrified drops on insulator surfaces, which can be found on high voltagepower lines, affecting the partial discharge behaviour and performance and durability of the insulator.•Trans-critical injection conditions of fuel with flash boiling in rocket combustion chambers•Atomization and vaporization of droplets at high pressures and temperature, as occurring in futurecombustion systemsThis article provides an overview of the projects being carried out at the SFB-TRR 75 and highlights scientific results from selected subprojects. The main purpose of the paper is to familiarize colleagues with this extensive and dedicated research effort in the area of drop dynamics and to motivate and initiate future collaboration with others in this field.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4597
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Pascualinotto Junior, Vagner, and Diego Felipe Sarzosa Burgos. "Fatigue Life Estimation Using Frequency Domain Technique and Probabilistic Linear Cumulative Damage Model." In ASME 2020 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/pvp2020-21536.
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Abstract Engineering critical structures, such as pressure vessels and pipelines, are designed to withstand a variety of in-service loading specific to their intended application. Random vibration excitation is observed in most of the structural component applications in the offshore, aerospace, and nuclear industry. Likewise, fatigue life estimation for such components is fundamental to verify the design robustness assuring structural integrity throughout service. The linear damage accumulation model (Palmgren-Miner rule) is still largely used for damage assessment on fatigue estimations, even though, its limitations are well-known. The fact that fatigue behavior of materials exposed to cyclic loading is a random phenomenon at any scale of description, at a specimen scale, for example, fatigue initiation sites, inclusions, defects, and trans-granular crack propagation are hardly predicted, indicates that a probabilistic characterization of the material behavior is needed. In this work, the methodology was applied to a Titanium alloy structural component. Low alloyed titanium alloys have no tendency to corrosion cracking in high-temperature high-pressure water containing impurities of chloride and oxygen found in a steam generator of nuclear power plants. The inherent uncertainties of the fatigue life and fatigue strength of the material are characterized using the random fatigue limit (RFL) statistic method. Furthermore, a frequency domain technique is used to determine the response power spectrum density (PSD) function of a structural component subjected to a random vibration profile excitation. The fatigue life of the component is then estimated through a probabilistic linear damage cumulative model.
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Westwood, Stephen, and Arti Bhatia. "Inline Inspection Decisions and Results Using an Integrated Technology for a Baseline Inspection Program on a Large Diameter High Pressure Gas Transmission and Interconnect System." In 2004 International Pipeline Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ipc2004-0100.
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The Alliance Pipeline System consists of 2664 Km of NPS 36 high pressure transmission pipeline and 339 Km of NPS 42 high pressure transmission pipeline. The mainline systems are connected by lateral and interconnect pipeline sections ranging in diameter from NPS 4 to NPS 24. The pipeline system extends from northeast British Columbia to Illinois. The Trans border nature of the pipeline means that it needs to satisfy both the Canadian and US regulatory requirements related to pipeline integrity management. Part of the approval process for the pipeline system was that it had to be inspected on a regular basis with a baseline inspection program to be initiated upon start-up of the pipeline system in 2000. This paper outlines some of the unique challenges the high pressure transmission pipeline presented to both the operator and the inline inspection (ILI) vendor in developing a successful in line inspection program. It discusses the vendor selection criteria used by the pipeline operator and the design process undertaken by the ILI Vendor to meet the requirements of this unique pipeline system. By the end of 2004, the mainline sections in Canada and the US will have been inspected as well as most of the smaller diameter interconnect and lateral system. Results are presented from the ILI inspection of both the high pressure system and the smaller diameter system. While the inspections have used Magnetic Flux leakage (MFL) Technology to detect metal loss features, the use of integrated technology in particular the inertial navigation system aboard the vendor’s inspections tools has allowed geometric features to be detected as well. Lessons learned from both the operator and the ILI Vendor will be presented on the execution of the inline inspection program as well as discussion on ways of ensuring that the ILI process goes smoothly and if not how to address these concerns.
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Zhuang, Chuanjing. "Safety Requirements for the Second High-Pressure and Large-Diameter West-East Gas Pipeline." In ASME 2007 Pressure Vessels and Piping Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/pvp2007-26823.
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The Second West-East Gas Pipeline (WEGP) is planed be constructed trans-China within recent years. The Pipeline is about 7,000 kilometers with outside diameter 1219mm, operation pressure 12MPa, and steel grade API-X80 [1], all of which is the first time in China. Both safety and reliability of the Pipeline are the most important issues which should be thought over by the gas company. In this paper, the method of limit state analysis is used to study the effect of strength, toughness and allowable flaw size on the safety and reliability of the Pipeline. The calculation results suggest that the overmatched weld has the advantages of improving limit load and maximum allowable defect sizes of the pipelines. When Ms (Ms is the ratio of yield strength of weld σSW over that of base metal σSB, i.e. MS = σSW / σSB) is lower than 0.9, there is much possibility for the happening of fracture initiation in the weld zone. When Ms is higher than 1.2, the limit load will not increase with the increase of weld strength. Although the Second WEGP will transmit sweet gas, there is still possibility that sour gas releases to the Pipeline in case of operation accident. As to the high-grade pipeline, in order to reduce the sensitivity of cold crack, hydrogen induced crack (HIC) and stress induced corrosion crack (SCC), etc., However, chemical composition and hardness of both base and weld metal can influence the resistance to HIC and SCC. It can be concluded that the best range of strength mismatched ratios Ms is 0.9 ∼ 1.2 for the Second WEGP. The critical defect sizes proposal is 10.0mm of maximum allowable defect length and 0.95mm of maximum allowable defect depth at the weld mismatch.
Reports on the topic "Initiator tRNAs"
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Elroy-Stein, Orna, and Dmitry Belostotsky. Mechanism of Internal Initiation of Translation in Plants. United States Department of Agriculture, December 2010. http://dx.doi.org/10.32747/2010.7696518.bard.
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Original objectives Elucidation of PABP's role in crTMV148 IRES function in-vitro using wheat germ extract and krebs-2 cells extract. Fully achieved. Elucidation of PABP's role in crTMV148 IRES function in-vivo in Arabidopsis. Characterization of the physical interactions of PABP and other potential ITAFs with crTMV148 IRES. Partly achieved. To conduct search for additional ITAFs using different approaches and evaluate the candidates. Partly achieved. Background of the topic The power of internal translation via the activity of internal ribosomal entry site (IRES) elements allow coordinated synthesis of multiple gene products from a single transcription unit, and thereby enables to bypass the need for sequential transformation with multiple independent transgenes. The key goal of this project was to identify and analyze the IRES-trans-acting factors (ITAFs) that mediate the activity of a crucifer-infecting tobamovirus (crTMV148) IRES. The remarkable conservation of the IRES activity across the phylogenetic spectrum (yeast, plants and animals) strongly suggests that key ITAFs that mediate its activity are themselves highly conserved. Thus, crTMV148 IRES offers opportunity for elucidation of the fundamental mechanisms underlying internal translation in higher plants in order to enable its rational manipulation for the purpose of agricultural biotechnology. Major conclusions and achievements. - CrTMV IRES requires PABP for maximal activity. This conclusion was achieved by PABP depletion and reconstitution of wheat germ- and Krebs2-derived in-vitro translation assays using Arabidopsis-derived PABP2, 3, 5, 8 and yeast Pab1p. - Mutations in the internal polypurine tract of the IRES decrease the high-affinity binding of all phylogenetically divergent PABPs derived from Arabidopsis and yeast in electro mobility gel shift assays. - Mutations in the internal polypurine tract decrease IRES activity in-vivo. - The 3'-poly(A) tail enhances crTMV148 IRES activity more efficiently in the absence of 5'-methylated cap. - In-vivo assembled RNPs containing proteins specifically associated with the IRES were purified from HEK293 cells using the RNA Affinity in Tandem (RAT) approach followed by their identification by mass spectroscopy. - This study yielded a list of potential protein candidates that may serve as ITAFs of crTMV148 IRES activity, among them are a/b tubulin, a/g actin, GAPDH, enolase 1, ribonuclease/angiogenin inhibitor 1, 26S proteasome subunit p45, rpSA, eEF1Bδ, and proteasome b5 subunit. Implications, both scientific and agriculture. The fact that the 3'-poly(A) tail enhances crTMV148 IRES activity more efficiently in the absence of 5'-methylated cap suggests a potential joint interaction between PABP, the IRES sequence and the 3'-poly(A). This has an important scientific implication related to IRES function in general.
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Honegger and Nyman. L51927 Guidelines for the Seismic Design and Assessment of Natural Gas and Liquid Hydrocarbon Pipelines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), October 2004. http://dx.doi.org/10.55274/r0010350.
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Much of the current seismic practice can be traced to research conducted in the 1970s to develop design criteria and procedures for the Trans-Alaska oil pipeline. The major natural gas pipeline operators in California have implemented many of the procedures in these guidelines, in one form or another. The recognition of credible seismic hazards in other parts of the United States has been the primary driver for extending current practices in California to the rest of the United States. The experience in designing pipelines in seismically active regions of the United States has also provided a basis for specifying pipeline seismic design practices in other parts of the world. This project was initiated to provide current seismic guidelines for the design and assessment of natural gas transmission pipelines. These guidelines were refined using two rounds of review by outside technical experts in 1999 and 2000. The PRCI ad hoc steering group for the project also provided regular input regarding the scope and technical content for these guidelines. A decision was made in late 2000 to expand the scope to liquid hydrocarbon pipelines (crude oil and refined products) based upon the identical analytical treatment of seismic design and assessment of these types of pipelines.
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Parkins. L51743 Stress Corrosion Cracking of Pipelines in Contact with Near-Neutral pH Solutions. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), July 1995. http://dx.doi.org/10.55274/r0010322.
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While much has been learned about low pH stress corrosion cracking in the decade since it was recognized, a review of the published papers and reports since the last overview of the subject in 1992 indicates that there is still much to be understood about this matter. Most of the laboratory studies have involved dilute solutions based upon those found in the vicinity of cracks in operating lines, but the possible role of bacteria, for which there is supporting field evidence, has not received systematic study. The trans-granular service cracking has been reproduced in the laboratory, most readily when relatively high stresses and/or strains are applied to specimens, but there is still difficulty in reproducing cracking in the laboratory with stressing conditions similar to those on an operating pipeline. If meaningful modeling of low pH cracking is to be achieved, there is need for more data on crack initiation and the early stages of growth with stressing conditions no overly excessive by comparison with service conditions. There is also a need, related to modeling, of an understanding of the mechanistic aspects of cracking, since while it is known, not least from visible evidence of corrosion on the sides of cracks, that dissolution occurs within the crack enclave, there is indirect evidence that the ingress of hydrogen into the steel may be involved also in the overall crack growth process. If hydrogen is involved then existing models based upon high pH cracking, and involving a quantifiable dissolution mechanism, will not be directly applicable to the low pH problem.
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O'Neill, Sharman, Abraham Halevy, and Amihud Borochov. Molecular Genetic Analysis of Pollination-Induced Senescence in Phalaenopsis Orchids. United States Department of Agriculture, 1991. http://dx.doi.org/10.32747/1991.7612837.bard.
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The project investigated the molecular genetic and biochemical basis of pollination-induced senescence of Phalaenopsis flowers. This experimental system offered unique advantages in that senescence is strictly regulated by pollination, providing the basis to experimentally initiate and synchronize senescence in populations of flowers. The postpollination syndrome in the Phalaenopsis orchid system was dissected by investigating the temporal and spatial regulation of ACC synthase gene expression. In the stigma, pollen-borne auxin induces the expression of the auxin-regulated ACC synthase (PS-ACS2) gene, resulting in ACC synthesis within 1 h following pollination. Newly formed ACC is oxidized by basal constitutive ACC oxidase to ethylene, which then induces the expression of the ethylene-regulated ACC synthase(PS-ACS1) and oxidase (ACO1) genes for further autocatalytic production of ethylene. It is speculated that during the 6-h period following pollination, emasculation leads to the production or release of a sensitivity factor that sensitizes the cells of the stigma to ethylene. ACC and ethylene molecules are translocated from the stigma to the labellum and perianth where ethylene induces the expression of PS-ACS1 and ACO1 resulting in an increased production of ACC and ethylene. Organ-localized ethylene is responsible for inrolling and senescence of the labellum and perianth. The regulation of ethylene sensitivity and signal transduction events in pollinated flowers was also investigated. The increase in ethylene sensitivity appeared in both the flower column and the perianth, and was detected as early as 4 h after pollination. The increase in ethylene sensitivity following pollination was not dependent on endogenous ethylene production. Application of linoleic and linoleic acids to Phalaenopsis and Dendrobium flowers enhanced their senescence and promoted ethylene production. Several major lipoxygenase pathway products including JA-ME, traumatic acid, trans-2-hexenal and cis-3-hexenol, also enhanced flower senescence. However, lipoxygenase appears to not be directly involved in the endogenous regulation of pollination-induced Phalaenopsis and Dendrobium flower senescence. The data suggest that short-chain saturated fatty acids may be the ethylene "sensitivity factors" produced following pollination, and that their mode of action involves a decrease in the order of specific regions i the membrane lipid bilayer, consequently altering ethylene action. Examination of potential signal transduction intermediates indicate a direct involvement of GTP-binding proteins, calcium ions and protein phosphorylation in the cellular signal transduction response to ethylene following pollination. Modulations of cytosolic calcium levels allowed us to modify the flowers responsiveness to ethylene.
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Mawassi, Munir, Adib Rowhani, Deborah A. Golino, Avichai Perl, and Edna Tanne. Rugose Wood Disease of Grapevine, Etiology and Virus Resistance in Transgenic Vines. United States Department of Agriculture, November 2003. http://dx.doi.org/10.32747/2003.7586477.bard.
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Rugose wood is a complex disease of grapevines, which occurs in all growing areas. The disease is spread in the field by vector transmission (mealybugs). At least five elongated-phloem- limited viruses are implicated in the various rugose wood disorders. The most fully characterized of these are Grapevine virus A (GV A) and GVB, members of a newly established genus, the vitivirus. GVC, a putative vitivirus, is much less well characterized than GV A or GVB. The information regarding the role of GVC in the etiology and epidemiology of rugose wood is fragmentary and no sequence data for GVC are available. The proposed research is aimed to study the etiology and epidemiology of rugose wood disease, and to construct genetically engineered virus-resistant grapevines. The objectives of our proposed research were to construct transgenic plants with coat protein gene sequences designed to induce post-transcriptional gene silencing (pTGS); to study the epidemiology and etiology of rugose wood disease by cloning and sequencing of GVC; and surveying of rugose wood- associated viruses in Californian and Israeli vineyards. In an attempt to experimentally define the role of the various genes of GV A, we utilized the infectious clone, inserted mutations in every ORF, and studied the effect on viral replication, gene expression, symptoms and viral movement. We explored the production of viral RNAs in a GV A-infected Nicotiana benthamiana herbaceous host, and characterized one nested set of three 5'-terminal sgRNAs of 5.1, 5.5 and 6.0 kb, and another, of three 3'-terminal sgRNAs of 2.2, 1.8 and 1.0 kb that could serve for expression of ORFs 2-3, respectively. Several GV A constructs have been assembled into pCAMBIA 230 I, a binary vector which is used for Angrobacterium mediated transformation: GV A CP gene; two copies of the GV A CP gene arranged in the same antisense orientation; two copies of the GV A CP gene in which the downstream copy is in an antigens orientation; GV A replicase gene; GV A replicase gene plus the 3' UTR sequence; and the full genome of GV A. Experiments for transformation of N. benthamiana and grapevine cell suspension with these constructs have been initiated. Transgenic N. benthamiana plants that contained the CP gene, the replicase gene and the entire genome of GV A were obtained. For grapevine transformation, we have developed efficient protocols for transformation and successfully grapevine plantlets that contained the CP gene and the replicase genes of GV A were obtained. These plants are still under examination for expression of the trans genes. The construction of transgenic plants with GV A sequences will provide, in the long run, a means to control one of the most prevalent viruses associated with grapevines. Our many attempts to produce a cDNA library from the genome of GVC failed. For surveying of rugose wood associated viruses in California vineyards, samples were collected from different grape growing areas and tested by RT-PCR for GV A, GVB and GVD. The results indicated that some of the samples were infected with multiple viruses, but overall, we found higher incidence of GVB and GV A infection in California vineyards and new introduction varieties, respectively. In this research we also conducted studies to increase our understanding of virus - induced rootstock decline and its importance in vineyard productivity. Our results provided supporting evidence that the rootstock response to virus infection depends on the rootstock genotype and the virus type. In general, rootstocks are differ widely in virus susceptibility. Our data indicated that a virus type or its combination with other viruses was responsible in virus-induced rootstock decline. As the results showed, the growth of the rootstocks were severely affected when the combination of more than one virus was present.