1,721,001 research outputs found
Complete Characterization of Extracts of Onopordum illyricum L.(Asteraceae) by HPLC/PDA/ESIMS and NMR
No full textThe aerial parts of Onopordum illyricum L. (Asteraceae) are eaten raw in salad in the Mediterranean area, representing a food of good nutritional value. Extracts of different parts of this plant have been analyzed by HPLC/DAD/ESIMS and the major compounds identified by NMR spectroscopy. Fatty acids, sesquiterpene lactones, triterpenes and polyphenols (flavones and caffeoyl quinic acids) fully describe the plant metabolism during the vegetation year. All the metabolites are non toxic nutrients, and are reported in the literature to possess biological activities positive for health, confirming the beneficial use in the diet of this thistl
A conformational study of N-tosyl oxazolidines using molecular mechanics and crystallography
No full textDesign, Synthesis, Conformational Analysis and Application of Azabicyclo-alkane Amino Acids as Constrained Dipeptide Mimics
No full textIn the field of peptidomimetics, major efforts have been focused on the design and synthesis of conformationally constrained compounds that mimic or induce reverse-turn motifs of peptides and proteins which are thought to play important roles in recognition and biological activity. In this regard, a particularly attractive class of compounds are the azabicyclo[X.Y.O]alkane dipeptide mimics. We present our efforts on the design, synthesis, and conformational analysis of a series of rigid surrogates of dipeptide units for applications within constrained peptide analogues, for employment as inputs for combinatorial science and biological applications. Several general and versatile synthetic approaches have been conceived to deliver a variety of enantiornerically pure azabi-cycloalkanes. All of these methodologies rely on the construction of a 5-, 6-, or 7-membered lactam, on a preformed proline based nucleus. Different strategies were adopted to perform the key cyclization step: a) radical addition to an olefinic double bond, b) alkylation of a malonate enolate, c) ring-closing metathesis (RCM), and d) lactam bond formation
Assessing the influence of electrostatic schemes on molecular dynamics simulations of secondary structure forming peptides
No full textElectrostatic interactions play a fundamental role in determining the
structure and dynamics of biomolecules in solution. However the accurate
representation of electrostatics in classical mechanics based simulation
approaches such as molecular dynamics (MD) is a challenging task. Given
the growing importance that MD simulation methods are taking on in the
study of protein folding, protein stability and dynamics, and in
structure prediction and design projects, it is important to evaluate
the influence that different electrostatic schemes have on the results
of MD simulations. In this paper we performed long timescale simulations
(500 ns) of two peptides, beta3 and RN24 forming different secondary
structures, using for each peptide four different electrostatic schemes
(namely PME, reaction field correction, and cut-off schemes with and
without neutralizing counterions) for a total of eight 500 ns long MD
runs. The structural and conformational features of each peptide under
the different conditions were evaluated in terms of the time dependence
of the flexibility, secondary structure evolution, hydrogen-bonding
patterns, and several other structural parameters. The degree of
sampling for each simulation as a function of the electrostatic scheme
was also critically evaluated. Our results suggest that, while in the
case of the short peptide RN24 the performances of the four methods are
comparable, PME and RF schemes perform better in maintaining the
structure close to the native one for the beta-sheet peptide beta3, in
which long range contacts are mostly responsible for the definition of
the native structure
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
- …
