1,721,058 research outputs found
A Biotechnological Approach for Plakortin Production: New Perspectives for Bioactive Compounds from Marine Source
No full textA variety of limiting factors currently affect the full exploitation of bioactive natural products from marine invertebrates, the most important being the supply problem. Large-scale total synthesis is usually prevented by the complex structure of most natural products, while a massive collection of the organisms producing compounds of industrial interest appears unrealistic. New perspectives were opened by the discovery that several (and probably a significant portion) of these bioactive compounds are produced by bacterial symbionts, but even so, production by fermentation is often impossible because very few symbiotic species can be cultured with the present techniques.
We are currently exploring a biotechnological approach for the inexpensive and reproducible production of marine natural compounds. Our research is focused on the study of the biosynthetic pathway of plakortin (and related compounds), a polyketide peroxide with interesting antimalarial properties which is present in the marine sponge Plakortis simplex and is biosynthesized by a uncultivable bacterial symbiont of the sponge. We intend to identify, isolate and sequence the biosynthetic gene cluster for plakortin (presumably coding for a type-I polyketide synthase), and subsequently to express the pathway heterologously to produce plakortin by fermentation.
Metagenomic DNA from Plakortis simplex was cloned to generate a 50,000 clone library which was PCR-screened in search of the PKS gene cluster involved in the biosynthesis of plakortin. One positive clone was isolated and fully shotgun sequenced. The PKS gene is located at one end of the insert, so that only a small part of the PKS gene cluster is present in the insert (9 kbp). Following these encouraging results, we are currently searching for the remaining part of the cluster.
The latest results of this project will be presented. The success of this research will demonstrate the feasibility of this strategy for the large-scale production of natural products, which could be applied to many other bioactive compounds from marine invertebrate
Biotechnological Approaches for Plakortin: New Perspectives on the Study of Bioactive Compounds from Marine Source
No full textA variety of limiting factors currently affect the full exploitation of bioactive marine natural products. Sponge symbiotic bacteria are believed to be the true producers of many of these compounds, but only a small portion of them can be cultured in the laboratory today. Moreover, large-scale total synthesis is usually prevented by the complex structure of most natural products, while a massive collection of marine organisms producing compounds of industrial interest appears unrealistic.
We are currently exploring a biotechnological approach to solve the lack of a method for inexpensive and reproducible production of marine natural compounds under controlled conditions (the so-called supply problem) and to meet the demands of pre-clinical and clinical development. Our research is focused on the study of the biosynthetic pathway of plakortin (and related compounds), a polyketide peroxide with interesting antimalarial properties which is present in the marine sponge Plakortis simplex and is biosynthesized by a uncultivable bacterial symbiont of the sponge.1 We intend to identify, isolate and sequence the biosynthetic gene cluster for plakortin (presumably coding for a type-I polyketide synthase), and subsequently to express the pathway heterologously to produce plakortin by fermentation.
Metagenomic DNA from Plakortis simplex was cloned to generate a 50000 clone library which was partially PCR-screened in search of the gene of PKS involved in the biosynthesis of plakortin. One positive clone was isolated and fully shotgun sequenced. The PKS gene is located at one end of the insert, so that only a small part of the PKS gene cluster is present in the insert (9 kbp). Following these encouraging results, we are currently searching for the remaining part of the cluster.
The presentation will report the latest results of this project. The success of this research will demonstrate the feasibility of this strategy for the large-scale production of natural products, which could be applied to all new bioactive compounds from marine organisms
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
Polyketide genes in the marine sponge Plakortis simplex: a new group of mono-modular type I polyketide synthases from sponge symbionts
No full textSponge symbionts are a largely unexplored source of new and unusual metabolic pathways. Insights into the distribution and function of metabolic genes of sponge symbionts are crucial to dissect and exploit their biotechnological potential. Screening of the metagenome of the marine sponge Plakortis simplex led to the discovery of the swf family, a new group of mono-modular type I polyketide synthase/fatty acid synthase (PKS/FAS) specifically associated with sponge symbionts. Two different examples of the swf cluster were present in the metagenome of P.simplex. A third example of the cluster is present in the previously sequenced genome of a poribacterium from the sponge Aplysina aerophoba but was formerly considered orthologous to the wcb/rkp cluster. The swf cluster was also found in six additional species of sponges. Therefore, the swf cluster represents the second group of mono-modular PKS, after the supA family, to be widespread in marine sponges. The putative swf operon consists of swfA (type I PKS/FAS), swfB (reductase and sulphotransferase domains) and swfC (radical S-adenosylmethionine, or radical SAM). Activation of the acyl carrier protein (ACP) domain of the SwfA protein to its holo-form by co-expression with Svp is the first functional proof of swf type genes in marine sponges. However, the precise biosynthetic role of the swf clusters remains unknown. © 2013 The Authors. Environmental Microbiology Reports
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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