1,721,084 research outputs found
Production of p-amino-l-phenylalanine (l-PAPA) from glycerol by metabolic grafting of Escherichia coli
No full textAbstract Background The non-proteinogenic aromatic amino acid, p-amino-l-phenylalanine (l-PAPA) is a high-value product with a broad field of applications. In nature, l-PAPA occurs as an intermediate of the chloramphenicol biosynthesis pathway in Streptomyces venezuelae. Here we demonstrate that the model organism Escherichia coli can be transformed with metabolic grafting approaches to result in an improved l-PAPA producing strain. Results Escherichia coli K-12 cells were genetically engineered for the production of l-PAPA from glycerol as main carbon source. To do so, genes for a 4-amino-4-deoxychorismate synthase (pabAB from Corynebacterium glutamicum), and genes encoding a 4-amino-4-deoxychorismate mutase and a 4-amino-4-deoxyprephenate dehydrogenase (papB and papC, both from Streptomyces venezuelae) were cloned and expressed in E. coli W3110 (lab strain LJ110). In shake flask cultures with minimal medium this led to the formation of ca. 43 ± 2 mg l−1 of l-PAPA from 5 g l−1 glycerol. By expression of additional chromosomal copies of the tktA and glpX genes, and of plasmid-borne aroFBL genes in a tyrR deletion strain, an improved l-PAPA producer was obtained which gave a titer of 5.47 ± 0.4 g l−1 l-PAPA from 33.3 g l−1 glycerol (0.16 g l-PAPA/g of glycerol) in fed-batch cultivation (shake flasks). Finally, in a fed-batch fermenter cultivation, a titer of 16.7 g l−1 l-PAPA was obtained which is the highest so far reported value for this non-proteinogenic amino acid. Conclusion Here we show that E. coli is a suitable chassis strain for l-PAPA production. Modifying the flux to the product and improved supply of precursor, by additional gene copies of glpX, tkt and aroFBL together with the deletion of the tyrR gene, increased the yield and titer
MOESM2 of Production of p-amino-l-phenylalanine (l-PAPA) from glycerol by metabolic grafting of Escherichia coli
No full textAdditional file 2. Comparison of mass spectra of commercially available L-PAPA (A) with fermentatively produced L-PAPA from E. coli FUS4.7R/pC53BC/pJNTaroFBL (B). The mass spectra were recorded with an Agilent 6130 mass spectrometer system with electron spray ionization in positive mode (Agilent Technologies; Germany). In both measurements the L-PAPA+H+ mass of 181 was detected
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
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
Conoscenza/Disegno/Progetto della città sostenibile
No full textMarco bovati, "Conoscenza/Disegno/Progetto della città sostenibile" in Atti del Convegno: Il disegno delle trasformazioni, Università degli Studi di Napoli Federico II - Polo delle Scienze e delle Tecnologie - DPUU: Dipartimento di Progettazione Urbana e di Urbanistica, 1 e 2 dicembre 2011
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