1,720,968 research outputs found
Use of Synthetic Peptides for Identifying Biotinylation Sites in Human Histones
No full textPosttranslational modifications of histones play an important role in the regulation of chromatin structure and, hence, gene regulation. Recently, we have identified a novel modification of histones: binding of the vitamin biotin to lysine residues in histones H2A, H3, and H4. Here, we describe a procedure to identify those amino acids that are targets for biotinylation in histones. Briefly, the following analytical sequence is used to identify biotinylation sites: (i) short peptides (<20 amino acids in length) are synthesized chemically; amino acid sequences in the peptides are based on the sequence in a given region of a given histone; (ii) peptides are incubated with biotinidase or holocarboxylase synthetase to conduct enzymatic biotinylation; and (iii) biotin in peptides are probed using streptavidin peroxidase. Amino acid substitutions (e.g., lysine-to-alanine substitutions) in synthetic peptides can be used to corroborate identification of biotinylation sites.Fil: Camporeale, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentina. Universidad de Nebraska - Lincoln; Estados UnidosFil: Chew, Yap Ching. Universidad de Nebraska - Lincoln; Estados UnidosFil: Kueh, Alice. Universidad de Nebraska - Lincoln; Estados UnidosFil: Sarath, Gautam. Universidad de Nebraska - Lincoln; Estados UnidosFil: Zempleni, Janos. Universidad de Nebraska - Lincoln; Estados Unido
Roles of histone biotinylation in gene regulation of transposable elements
No full textChromatin modifications play crucial roles in gene regulation and DNA repair. Importantly, epigenetic marks such as histone modifications and DNA methylation have been implicated in transcriptional repression of retrotransposons. Repression of retrotransposons is critical for preventing transpositions and aberrant activities of host genes. Covalent binding of the vitamin biotin to histones, mediated by holocarboxylase synthetase, is one of the very few chromatin modifications that directly depend on nutrient supply in the diet. In this dissertation I demonstrate that chromosome stability depends on biotin. I show that binding of biotin to K9 in histone H2A and K12 in histone H4 is the mechanism that causes repression of retrotransposons. I also provide evidence that silencing of retrotransposons by histone biotinylation is mediated by increased transcription of anti-sense RNA. This observation suggests that RNAi is involved in the silencing of retrotransposons by histone biotinylation. In another project of my dissertation, I developed an avidin-based assay to quantify activities of histone debiotinylases. This assay is a useful tool to achieve one of the long-term goals of our laboratory, i.e., the identification of histone debiotinylases in human cells. Identification of histone debiotinylases is a critical step to understand the regulation of histone biotinylation. Finally, I used mass spectrometry to identify novel biotinylation sites in human histones, and to identify histone marks that co-occur with biotinylation in a single histone molecule. This dissertation provides novel insights into the effects of nutrient status on cancer risk by a diet-dependent epigenetic mechanism of gene regulation, and it offers novel tools for the study of biological functions of histone biotinylation
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
