1,721,127 research outputs found
Molecular analysis of the endoflagella of the pathogenic treponemes
No full text1. Motility of Treponema pallidum is mediated by endoflagella located within the periplasmic space. The endoflagella comprise a core surrounded by a sheath, with the sheath being composed of a 37-kD antigen (FlaA).
2. Treponemal endoflagella were isolated and component proteins were purified by reverse-phase high pressure liquid chromatography (HPLC). N-terminal amino acid sequence analysis was performed using the sheath protein and two core proteins from T. pallidum subsp. pallidum, T. pallidum subsp. pertenue, and T. phagedenis. For all three proteins, the N-terminal sequences found for T. pallidum and T. pertenue were identical but differed from the sequence of T. phagedenis. The sheath proteins from the three treponemes were also compared by HPLC tryptic peptide maps: maps for T. pallidum and T. pertenue were very similar but differed from T. phagedenis.
3. A λgt11 clone, λA34, that expressed a portion of FlaA was selected from a T. pallidum genomic library using a murine monoclonal antibody. The insert from λA34 provided a probe with which a chimeric plasmid, pRI4, encoding all but the nine N-terminal amino acids of FlaA was selected from a pBR322 T. pallidum genomic library.
4. The nucleotide sequence of flaA upstream of amino acid 10 could not be determined by routine cloning strategies. Instead, the remaining sequence was determined using the inverse- and asymmetric-polymerase chain reaction methods. flaA contains a consensus Escherichia coli promoter and a ribosome binding site. A single open reading frame encodes a precursor protein, pre-FlaA, of 350 amino acids with a calculated Mr 38,860. A 20 amino acid signal sequence with a typical signal peptidase I cleavage site immediately precedes the known N-terminus of FlaA. Twenty six per cent (91/350) of the DNA-derived amino acid sequence was confirmed by N-terminal sequence analysis of ten tryptic peptides derived from native FlaA.
5. Polymerase chain reaction-derived constructs lacking the native T. pallidum promoter were cloned downstream of a T7 promoter. T7 polymerase transcription was under the control of a PL λ promoter. When the λ repressor was inactivated at 42°C, FlaA was expressed at relatively low levels in E. coli. Native and recombinant FlaA were identical as assessed by antibody reactivity and electrophoretic mobility in both sodium dodecyl sulphate- and two dimensional-polyacrylamide gels.
6. Although some pre-FlaA is processed to FlaA in E. coli, pre-FlaA is accumulated indicating inefficient processing of pre-FlaA in E. coli. Soluble FlaA was not detected in either the cytoplasmic or the periplasmic fractions of E. coli transformants. Fractionation of E. coli cell envelopes unexpectedly revealed that pre-FlaA and FlaA were associated with both the inner and outer membranes.
7. Two gene fusions, cro-lacZ-flaA and lacZ’-flaA, were constructed in an attempt to increase expression of the recombinant antigen; a bovine protease Xa site was engineered into the hybrid proteins immediately upstream of the N-terminus of FlaA to allow for subsequent proteolytic cleavage of the purified hybrid proteins. The LacZ’-FlaA protein was expressed in E. coli in increased amounts as compared with FlaA, but like recombinant FlaA, associated with both the inner and outer bacterial membranes. LacZ’-FlaA can be released from the membranes by treatment with 1% [wt/vol] sarkosyl, 6 M urea, or 6 M guanidine hydrochloride
Treponema and bovine skin disease: papillomatous digital dermatitis and ulcerative mammary dermatitis
No full textLola V. Stamm and Darren J. Trotthttp://trove.nla.gov.au/work/2088512
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
Role of outer membrane architecture in immune evasion by Treponema pallidum and Borrelia burgdorferi
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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
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