1,721,126 research outputs found
Estimating the kinetic parameters of DNA sequence-selective drugs by footprinting
No full textSIGLEAvailable from British Library Document Supply Centre-DSC:DX190420 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Dissociation kinetics of actinomycin D from individual GpC sites in DNA
No full textWe have examined the kinetics of dissociation of actinomycin from GpC sites in several DNA fragments containing synthetic DNA inserts, by a variation of the footprinting technique. Complexes of the ligand with radiolabelled DNA fragments were dissociated by adding a large excess of unlabelled calf thymus DNA. Samples were removed from this mixture at subsequent time intervals and subjected to DNase I footprinting. The rate of disappearance of the footprints varied considerably between the GpC sites located in different sequence environments. Actinomycin dissociates more slowly from GpC sites flanked by (AT)n than An · Tn. Within regions of alternating AT, TGCA represents a better binding site than AGCT, and CGCA is a better binding site than GGCA. GpC sites flanked by (AC)n · (GT)n present good binding sites; in this context, dissociation from CGCG is faster than from TGCA.</p
Visualising the kinetics of dissociation of actinomycin from individual sites in mixed sequence DNA by DNase I footprinting
No full textWe have Investigated the kinetics of dissociation of actlnomycin D from DNA by a variation of the foot-printing technique. Complexes of actlnomycin with a radiolabelied DNA fragment (tyrT) were dissociated by addition of a large excess of uniabelled calf thymus DNA and the mixture subjected to DNase I footprinting at subsequent intervals. The rates at which the footprints disappeared varied between the different binding sites. The dissociation was temperature dependent with average time constants of 30 s, 10 mins and 2 hours at temperatures of 37°C, 20°C and 4°C respectively. The dissociation from a DNA fragment containing the synthetic insert T9GCA9 was significantly faster, with a half-life of about 1 min at 20°C. In contrast, the dissociation of distamycln was too fast to measure (<5 s) even at 4°C.</p
Dissociation kinetics of echinomycin from CpG binding sites in different sequence environments
No full textWe have examined the kinetics of dissociation of echinomycin from CpG sites in several DNA fragments containing synthetic DNA inserts by a variation of the footprinting technique. Complexes of the ligand with radiolabeled DNA fragments were dissociated by adding an excess of unlabeled calf thymus DNA. Samples were removed from this mixture at subsequent time intervals and subjected to DNase I footprinting. The rate of disappearance of the footprints varied considerably between the various CpG sites. At 20 °C, echinomycin dissociates more slowly from CpG sites flanked by (AT)(n) (t( 1/2 ) ~ .40 min) and (CA)n) · (TG)(n) (t( 1/2 ) ~ 11 min) than by A(n) · T(n) (t( 1/2 ) < 3 min). In each sequence context the dissociation from ACGT is slower than that from TCGA. (TAA)4CG(TTA)4 also represents a very good binding site (t 1/2 ) ~ 35 min), which is less sensitive to changes in temperature than most other sites. Within sequences (AT)10(G/C)4(AT)10, the dissociation from CGGC is slower than that from CCCG or CCGC.</p
Scientific Drilling at Darwin Crater and Lake Selina: Long Continental Sedimentary Archives from Tasmania
Full text linkPresented at the 2019 Santa Fe Conference on Rock MagnetismLise-Pronovost, Agathe; Fletcher, Michael-Shawn; Mariani, Michela; Simon, Quentin. (2019). Scientific Drilling at Darwin Crater and Lake Selina: Long Continental Sedimentary Archives from Tasmania. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/204557
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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