1,720,959 research outputs found
Investtiigattiion on riibosome structure and dynamiics:: Mycobactteriium riibosome iin focus
No full textThis doctoral study deals primarily with the application of cryo-EM and single particle reconstruction technique to investigate three major aspects of translation machinery in prokaryotes. Kinetic studies indicate that in vivo, protein synthesis and ribosome biogenesis involves interaction of additional factors, capable of enhancing efficient assembly and protein synthesis. The first part of the study deals with the characterization of hitherto unknown association of cellular protein factors with the bacterial ribosome and functional importance of such interactions with the ribosome. Biochemical studies and a 3D cryo-EM map of a ribosome sample purified directly from cell extract revealed strong association of two cellular proteins namely Aldehyde alcohol dehydrogenase (AdhE) and Outer membrane protein C (OmpC) with E. coli 70S ribosome. Additional ribosome associated functions of these two proteins reflect multi-tasking activity of proteins within cell. The second part of the study deals with structural characterization of ribosome from bacteria that are of clinical importance to human health like Mycobacterium. The 12Å resolution 3D cryo-EM map of Mycobacterium smegmatis revealed unique additional structural components in the mycobacterial ribosome. Identification of several rRNA helices particularly a rRNA helix lying close to mRNA exit and extensions of ribosomal proteins around the peptide exit tunnel in M. smegmatis 70S ribosome structure reflects diversity of ribosome structure across bacterial kingdom and involvement of species specific structural elements in fine tuning the process of protein biosynthesis. The third part of the study addresses structure of the largest ribosomal protein S1 and its interaction with ribosomes from E. coli and M. smegmatis. Dynamic ribosome binding nature of S1 protein in a species specific manner has been explored. The study also presents a model of full length S1 protein from E. coli and interprets the organization of the domains and interaction of S1 with mRNA as well as ribosomal components
34 Cyo-EM visualization of Mycobacterium 70S ribosome reveals unique structural components at the function sites
No full textThe 3D structures of prokaryotic and eukaryotic ribosomes by crystallography and electron microscopy have revealed that they share an evolutionarily conserved core (Schmeing & Ramakrishnan, 2009), but each of the ribosomes contains its own set of specific proteins (or extensions of conserved proteins) and expansion segments of rRNAs (Melnikov et al., 2012). How these differences correlate to function still remains largely unknown. A 3D cryo-EM map of the 70S ribosome from Mycobacterium smegmatis (Msm70S) unveiled striking new structural features (Shasmal & Sengupta, 2012). The core of the Msm70S shows overall similarity with the core of the Escherichia coli 70S ribosome while containing additional mass in the periphery and solvent exposed sides. Some of the Mycobacterium ribosomal proteins are significantly bigger as compared to the E. coli counter parts. The rRNAs also contain extra helices, also revealed by their secondary structures. Most of the additional density of the Msm70S can be largely attributed to the extra helices present in the rRNAs, and extra domains of homologous proteins. One of the most notable features appears in the large subunit near L1 stalk as a structure forming a long helix with its upper end located in the vicinity of the mRNA exit channel (which we term the ‘steeple’). We propose that the prominent helical structure in mycobacterium 23S rRNA participates in modulating different steps of translation, especially the E site tRNA exit mechanism and propagation of mRNA 5′ en
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Structural diversity in bacterial ribosomes: mycobacterial 70S ribosome structure reveals novel features.
No full textHere we present analysis of a 3D cryo-EM map of the 70S ribosome from Mycobacterium smegmatis, a saprophytic cousin of the etiological agent of tuberculosis in humans, Mycobacterium tuberculosis. In comparison with the 3D structures of other prokaryotic ribosomes, the density map of the M. smegmatis 70S ribosome reveals unique structural features and their relative orientations in the ribosome. Dramatic changes in the periphery due to additional rRNA segments and extra domains of some of the peripheral ribosomal proteins like S3, S5, S16, L17, L25, are evident. One of the most notable features appears in the large subunit near L1 stalk as a long helical structure next to helix 54 of the 23S rRNA. The sharp upper end of this structure is located in the vicinity of the mRNA exit channel. Although the M. smegmatis 70S ribosome possesses conserved core structure of bacterial ribosome, the new structural features, unveiled in this study, demonstrates diversity in the 3D architecture of bacterial ribosomes. We postulate that the prominent helical structure related to the 23S rRNA actively participates in the mechanisms of translation in mycobacteria
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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