1,720,985 research outputs found
A chemical investigation of the Antarctic sponge Lyssodendoryx flabellata
No full textFrom the Antarctic sponge Lyssodendoryx flabellata, a new polycyclic
compound, which we named flabellone, related to the oestrogenic hormone
oestrone, has been elucidated by spectrometric and spectroscopic means.
Along with flabellone, a glycosphingolipid (GSL) mixture featuring an
unusual -fucofuranosyl-3--glucopyranoside unit structurally identical to
the previously reported terpioside has been isolated and identified. The
mixture of GSL homologues exhibited inhibitory effects in mixed lymphocyte
reactions on human cells
Acido fusarico e suo metilestere, potenziali bioerbicidi di Striga hermonthica: determinazione e degradazione nel terreno mediante analisi per gas-cromatografia accoppiata alla spettrometria di massa (GC-MS)
No full textUPLC-MS/MS method for analysis of sphingosine 1-phosphate in biological samples
No full textA simple and sensitive liquid chromatography–tandem mass spectrometry (negative ion-electrospray
ionization) methodology to determine sphingosine 1-phosphate (S1P) and sphinganine 1-phosphate
(DH-S1P) in biological samples is described. The method has been validated over the linearity range
of 2–100 ng/ml (r > 0.999) using synthetic C17-sphingosine 1-phosphate (C17-S1P) as an internal standard.
In multiple reaction monitoring analysis (378.2 > 79.2), the lower limit of quantification for S1P
was 5.0 ng/ml but the detection limit for the bioactive lipid was below 5 pg (12 fmol). Chromatographic
separation was achieved on a UPLC BEH Hilic column with a binary mobile phase consisting of 30mM
ammonium acetate (pH 4.0) and acetonitrile/MeOH/30mM ammonium acetate buffer (pH 4.0). The
methodology detected 176.7±54.0 ng/ml of S1P and 81.2±23.3 ng/ml of DH-S1P in human plasma, as
well as 201.0±72.0 ng/ml of S1P and 96.5±20.1 ng/ml of DH-S1P in mice plasma
One Metabolite, Two Pathways: Convergence of Polypropionate Biosynthesis in Fungi and Marine Molluscs
No full textStructural similarity or even the identity of polyketide compounds does not necessarily imply unique biosynthesis. Feeding experiments with a 13C
labeled precursor establish that the C3 units in 7-methyl-cyercene-1 (1) are derived from intact propionate in the marine mollusc Ercolania funerea.
The same compound in the terrestrial fungus Leptosphaeria maculans/Phoma lingam is synthesized by an acetate/SAM pathway thus proving for
the first time metabolic convergence of polyketide biosynthesis in eukaryotes. Traditional 1H13C NMR correlation spectroscopy has been
successfully applied to estimate 13C incorporation in biosynthetic experiments
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
Fusaripyrones, novel polypropionates from the Mediterranean mollusc Haminoea fusari
No full textA novel regular polypropionate skeleton has been characterized in two new pyrones, named fusaripyrone A (1) and fusaripyrone B
(2), from the lipid extracts of the mollusc Haminoea fusari. Here we report elucidation of the polyketide structures of 1 and 2, isolated as either
natural products or isomeric pairs of a-/g-pyrone methyl derivative
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
Polypropionates from Bulla occidentalis: chemical markers and trophic relationships in cephalaspidean molluscs
No full textA chemical investigation on the cephalaspidean Bulla occidentalis from the Gulf of Mexico led to known
niuhinones A (1) and B (2) along with a new acyclic polypropionate, named niuhinone C (3). A complete
NMR assignment of niuhinone A has been achieved by spectroscopic experiments, thus revising the D14
configuration. The occurrence of structurally related polypropionates in Bullidae species from different
geographical areas is in agreement with a de novo origin in this family of molluscs and adds a further
piece of evidence on prey–predator relationships among cephalaspidean
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