1,720,959 research outputs found
Two additional oxyprenylated phenylpropanoids in Citrus paradisi Macfad. seeds extract
No full textTwo additional oxyprenylated phenylpropanoids in Citrus paradisi Macfad. seeds extrac
Prolidase Activity Assays: a Survey of the Reported Literature Methodologies
Full text linkProlidase (EC.3.4.13.9) is a dipeptidase known nowadays to play a pivotal role in several physiological and pathological processes. More in particular, this enzyme is involved in the cleavage of proline- and hydroxyproline-containing dipeptides (imidodipeptides), thus finely regulating the homeostasis of free proline and hydroxyproline. Abnormally high or low levels of prolidase have been found in numerous acute and chronic syndromes affecting humans (chronic liver fibrosis, viral and acute hepatitis, cancer, neurological disorders, inflammation, skin diseases, intellectual disability, respiratory infection, and others) for which the content of proline is well recognized as a clinical marker. As a consequence, the accurate analytical determination of prolidase activity is of greatly significant importance in clinical diagnosis and therapy. Apart from the Chinard's assay, some other more sensitive and well validated methodologies have been published. These include colorimetric and spectrophotometric determinations of free proline produced by enzymatic reactions, capillary electrophoresis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, electrochemoluminescence, thin layer chromatography, and HPLC. The aim of this comprehensive review is to make a detailed survey of the in so far reported analytical techniques, highlighting their general features, as well as their advantages and possible drawbacks, providing in the meantime suggestions to stimulate further research in this intriguing field
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
Efficient removal of tartrazine from aqueous solutions by solid sorbents
No full textIn this study we investigated the efficiency of a wide panel of 24 solid sorbents comprising layered structures (hydrotalcites and zirconium phosphates), magnesium oxide and hydroxide, phyllosilicates, silica, and alumina, as agents for the effective and high yield removal of tartrazine from its aqueous solutions. Quantification of this azo dyes was made by HPLC analyses of the filtrate after collection of sorbents. Overnight treatment of tartrazine solutions at a concentration of 10 μg/mL with 100 mg of each solid sorbent resulted in a practically complete bleaching in 9 cases, namely Zn Al nitrate (99.9 %), Zn Al chloride (99.9 %), Mg Al nitrate (99.8 %), Mg Al azelate (99.9 %), Mg Al hydroxy chloride (99.9 %), zirconium phosphate (type B) + octadecylamine (99.9 %), MgO (99.8 %), and Mg(OH)2(99.7 %), out of 24. The most effective solids to this aim were seen to be aluminium based layered double hydroxides. The presence of this cation residues in the crystal structures of such sorbents seems to be a determinant in facilitating the adsorption of tartrazine by tight interaction with its sulfonate moieties. Recyclability and reuse of such solids have been assessed using Mg Al azelate as the reference. After its recovery and drying, five assays were accomplished under the same experimental conditions providing percentages of adsorption of tartrazine from its aqueous solution in the range 99.1 % − 99.6 %. The highest amount of tartrazine adsorbable on the most efficient sorbents have been obtained by adsorption isotherms and fall in the range 168.9–185.7 mg/g. © 2022 Elsevier B.V
Modulation of the biosynthesis of oxyprenylated coumarins in calli from Ferulago campestris elicited by ferulic acid
Full text linkPrevious and recent literature acquisitions suggested that cultured calli are an efficient and meaningful model to investigate the extent and fate of prenylation of phenylpropanoid cores in plants belonging to the Rutaceae and Apiaceae families upon administration of putative biosynthetic precursors. To this concern, in the present manuscript, we investigated the effect of supplementation of ferulic acid and umbelliferone on the biosynthesis of their oxyprenylated counterparts in Ferulago campestris (Besser) Grecescu (Fam. Apiaceae) cultured calli. Dried plant biomass material has been extracted by an ultrasound-assisted extraction with EtOH. O-prenyl secondary metabolites, namely 3,3-dimethylallyloxy, geranyloxy, and farnesyloxy derivatives of both ferulic acid and umbelliferone, were identified and quantified by HPLC/DAD analyses. Supplementation with ferulic acid was the only treatment providing appreciable results. Quite surprisingly, its addition to cultured calli did not affect the formation of its oxyprenylated phytochemicals but boosted the biosynthesis of umbelliferone and its farnesyloxy-derivative umbrelliprenin. The findings reported herein enforce and underline the role of ferulic acid as an elicitor of selected classes of secondary metabolites in apiaceous species, as recently observed. In addition to these results, a novel hitherto unknown metabolite from F. campestris, namely 7-[[(2E)-7-hydroxy-3,7-dimethyl-2-octen-1-yl]oxy]-2H-1-benzopyran-2-one, was characterized by NMR and LC–MS analyses
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
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