1,720,955 research outputs found
Bioprospecting of Antarctic fungi with potential for pigment production
No full textA demanda por pigmentos naturais vem crescendo devido a efeitos nocivos de alguns corantes sintéticos. Os pigmentos bacterianos e fúngicos fornecem uma alternativa, prontamente disponível, como fonte de corantes naturais, possuindo vantagens como o crescimento rápido do micro-organismo, processamento fácil e independência de condições do tempo. As comunidades microbianas antárticas são de grande importância para a produção de metabólitos secundários, tais como os pigmentos, pois são compostos importantes para a adaptação desses organismos ao ambiente extremo em que vivem. Recentemente, na literatura, vem sendo relatados vários estudos envolvendo a produção de pigmentos, como carotenoides, violaceína, flexirubin, entre outros, por micro-organismos provenientes da Antártica. Além disso, devido ao seu isolamento, as comunidades microbianas antárticas podem ser uma fonte rica de novos micro-organismos e/ou novos produtos naturais baseados em estruturas químicas únicas. Este trabalho visou realizar uma investigação de fungos da Antártica com potencial para produção de pigmentos e ampliar o conhecimento da diversidade fúngica e metabólica da comunidade microbiana da Antártica através da bioprospecção de 51 fungos isolados dessa região. Testou-se dois meios de cultivo, o BDA e Malte ágar 2%, e foi considerado resultados positivos aqueles que produzissem pigmentos no meio extracelular. Quatro isolados foram selecionados na produção de pigmentos: 2MA, 10.6MP, 6DC4-I e 6DC415-I, dos quais os dois últimos são do gênero Pseudogymnoascus. A extração do pigmento foi realizada com os solventes acetona e metanol e o pigmento rosa produzido pelo exemplar de 6DC415-I foi selecionado para a purificação, realizada através de CLAE-semipreparativa com coluna C18 utilizando um gradiente de 20 a 95% de metanol como eluente. O composto purificado, responsável pela coloração rosa, foi enviado para análise de RMN 1H e 13C para identificação estrutural. Os resultados mostram o potencial de micro-organismos de regiões extremas como uma nova fonte de produtos naturais que poderão ser utilizados para produção de pigmentos naturais.Não recebi financiament
Pigments production by the antarctic fungus Pseudogymnoascus sp. 6DC415-I: optimization, purification and identification
No full textA demanda por pigmentos naturais vem crescendo devido a efeitos nocivos de alguns corantes sintéticos e a busca por formas mais sustentáveis de consumo. Nesse contexto, pigmentos fúngicos fornecem uma boa alternativa aos sintéticos. As comunidades microbianas antárticas são de grande importância para a produção de metabólitos secundários, tais como os pigmentos, pois são compostos importantes para a adaptação desses organismos ao ambiente extremo em que vivem. Além disso, devido ao seu isolamento, essas comunidades podem ser uma fonte rica de novos produtos naturais com estruturas químicas únicas. Este trabalho visou analisar a produção dos pigmentos vermelhos pelo fungo Pseudogymnoascus sp. 6DC415-I, isolado de sedimentos marinhos da Antártica, bem como otimizá-la, seguida da purificação e identificação dos pigmentos produzidos. Para tal, avaliou-se a produção dos pigmentos vermelhos nas temperaturas de 15 e 25 ºC e nos pHs 3, 5, 7 e 9 em meio líquido Malte 2% por 20 dias de incubação a 150 rpm. Nas condições de 15 ºC e pH 5 se obteve a maior produção dos pigmentos, avaliada na leitura de absorbância em 500 nm, sendo que a 25 ºC não se detectou produção de pigmentos vermelhos. O fungo foi cultivado em meio Malte Ágar 1% e os pigmentos produzidos no meio de cultura foram extraídos com acetona. O extrato bruto foi submetido a cromatografia de camada reversa C18 para sua purificação, na qual obteve-se três frações vermelhas eluídas em Metanol 90 %. As frações foram submetidas às análises de RMN de 1H e FT-IR e obteve-se a confirmação da purificação de duas delas como compostos muito similares. Os espectros dessas frações indicaram tratarem-se de compostos da classe das melaninas, da categoria das feomelaninas. A atividade antibacteriana do extrato bruto e das frações obtidas foi testada contra as bactérias Xanthomonas citri, X. passiflorae, Escherichia coli, Streptococcus aureus e Bacillus subtilis, através do método de microdiluição em poços e leitura da D.O600, não sendo observada nenhuma inibição de crescimento superior a 50%. Também avaliou-se a atividade antioxidante das mesmas amostras, por meio do método de captura de DPPH, com resultado de IC50 a 1000 µg/mL para a fração 1 e 1143 µg/mL para a fração 2. Apesar do gênero Pseudogymnoascus sp. ser bastante comum ao ambiente antártico, até o momento, não há muitos estudos referentes à sua produção de pigmentos, principalmente de feomelanina. O pigmento vermelho extracelular e solúvel em água produzido pelo Pseudogymnoascus sp. 6DC415-I pode então representar um potencial para aplicações biotecnológicas.The demand for natural pigments has been growing due to the harmful effects of some synthetic dyes and the search for more sustainable forms of consumption. In this context, fungal pigments provide a good alternative to synthetics ones. Antarctic microbial communities are of great importance for the production of secondary metabolites, such as pigments, due to their role in helping these organisms adapt to the extreme environment in which they live. Furthermore, because of their isolation, these communities can be a rich source of new products with unique structures. This study aimed to analyze the production of red pigments by the fungus Pseudogymnoascus sp. 6DC415-I, isolated from antarctic marine sediments, as well as optimizing it, followed by purification and identification of the pigments produced. In order to do that, the production of red pigments was evaluated at temperatures of 15 and 25 ºC and at pHs 3, 5, 7 and 9 in 2% Malt broth for 20 days of incubation at 150 rpm. The biggest production of pigments obtained, quantified in the absorbance reading at 500 nm, was at 15 ºC and pH 5. No red pigments production was detected at 25 ºC. The fungus was cultivated in 1% Malte Agar medium and pigments produced were extracted from the culture medium with acetone. The crude extract was subjected to C18 reversed-phase chromatography for its purification, in which three red fractions were eluted in 90 % methanol. The fractions were submitted to 1H NMR and FT-IR analysis. Two of them were purified and were similar compounds. According to their spectra, the fractions are melanins, belonging to the pheomelanin category. The antibacterial activity of the crude extract and fractions was tested against the bacteria Xanthomonas citri, X. passiflorae, Escherichia coli, Streptococcus aureus e Bacillus subtilis, using the microdilution in wells method and reading of their O.D600. No growth inhibition greater than 50% was observed. The antioxidant activity of the samples was also evaluated, using the DPPH scavenging activity method, with an IC50 result of 1000 µg/mL for fraction 1 and 1143 µg/mL for fraction 2. Although the genus Pseudogymnoascus sp. is quite common in the Antarctic environment, there are not many studies regarding its production of pigments so far, specially pheomelanin. The extracellular, water-soluble red pigment produced by Pseudogymnoascus sp. 6DC415-I could then represent a potential for biotechnological applications.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)CAPES: 00
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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