1,720,960 research outputs found
Ru(II) complexes with bioactive molecules: from 5-(N-heterocycles) to Ruthenacycles
No full textNovel metal Ru(II) complexes were selectively obtained, upon the reaction of [Ru(H)2(CO)(PPh3)3] with bioactive molecules as pyrrole carboxylate ligand, with the purpose to investigate the potential positive alterations added by metal coordination to promote enhanced bioactivity as prodrugs or a diagnostic metallo-tracers . Pyrrole 2−carboxilic acid (A), 2−pyrrolyl imino-phenol (B), 5−hydroxy−L−triptophan (5−HTP) (C) and Lasparagine (D) have been selected to form stable chelate organometallic systems, based on homoleptic O,O− or heteroleptic N,O−bonding fashion mode. Experiments were run by varying the reaction conditions (stoichiometry, temperature, solvent, time duration, and energy source) to selectively drive the reactions towards a single desired isomer. Stereo−electronic features and rotameric behaviour have been studied by spectroscopic techniques (ESI−MS, IR, heteronuclear NMR and VT NMR) and DFT (Density Functional Theory) calculations. The complexes obtained by double coordination through adding two equivalents of pyrrolyl carboxylate form bismonohapto (k1 -O) species, which have been further investigated in MeCN or EtOH/H2O mixture. Longer reaction times are required to afford the mixed species exhibiting simultaneous monohapto−, dihapto [k1 (O), k2 (O,O)−] coordination. Much drastic conditions are required for obtaining conjugated trans−bis-chelate species, which has been calculated to possess a relative higher energy. The B, C and D molecules, exhibiting a preferential N,Ocoordination mode, are reported in the following scheme, likely resulting in stabilized five−membered metallacycle species
Synthesis, characterization and biological studies of heterobimetallic Ru(II)-Au(I) complexes involving N-heterocyclic bidentate ligands.
No full textHeterobimetallic complexes are designed to exploit the chemistry and the beneficial effects shown by different metal species.Based on the combined anticancer properties of numerous ruthenium and gold compounds, the heterobimetallic ruthenium(II)-gold(I) complexes were obtained with the aim of investigating whether multifunctional heterometallic compounds could be promising candidates for cancer treatment.
The new complexes were synthesized starting from ruthenium(II) precursors bearing bidentate nitrogen donor heterocyclic ligands, specifically [Ru(bpy)2Cl2] (1) and [Ru(phen)2Cl2] (2) (bpy = 2,2’bipyridine or phen = 1,10-phenanthroline). Both ruthenium(II) and gold(I) organometallic fragments were incorporated through linkers trifunctional diphosphane methanide ligands.
The resulting complexes have been studied by analytical and spectroscopic techniques (ESI-ms, IR and heteronuclear bidimensional NMR). The cytotoxic activity of these complexes in cancer cells have been studied and in addition, as they have luminescent properties, biodistribution studies in order to know the possible biological target have been performed
Novel metallacyclic systems of Ru(II) as potential anticancer derivatives: Chemistry and Bioactivity.
No full textMany Ru(II) complexes are considered valid candidates as anticancer drugs since they show reduced cytotoxicity and genotoxicity in non-tumor cells. In addition, these compounds present lower chances of cancer cells developing intrinsic or acquired resistance due to their peculiar paths of action. Many cytotoxic metal complexes of Ru(II) with NSAIDs (as ibuprofen, naproxen or acetylsalicylic acid) have been reported as effective antitumor agents.Furthermore, we are convinced that the incorporation of a gold atom into the Ru(II) metal skeleton may induce cooperative features, potentially enhancing anticancer properties.
Complexation studies of [Ru(H)2(CO)(PPh3)3] (1) with several ligands such as amino acid derivates as 5-hydroxy-L-triptophane or NSAIDs as ibuprofen or thiosalicylic acid (TSA), and its corresponding gold(I) complex [Au(TSA)(PPh3)], have been carried out with the aim to investigate the antitumor properties in addition to the potential increased bioactivity added by gold coordination. The ligands bearing oxygen or nitrogen donor heteroatoms are coordinated to the Ru(II) center through O,O- or N,O- bidentate fashion modes.
The resulting complexes have been studied by analytical and spectroscopic techniques (ESI-MS, IR and heteronuclear bidimensional NMR) and their cytotoxic activities have been evaluated towards cancer cells
“Synthesis and Antiproliferative study of Ru(II) – Hydroxy Stearic Acids ”
No full textProspectives on Ruthenium anticancer agents are encouraging since Ru(II) can directly interact on tumor cells via multiple mechanisms provoking their death. The selection of ligands plays a key role in anticancer activity, the addition of hydrophobic species such as PPh3 to a metal center increases drug uptake in cancer cells and could allow the intercalation in DNA nucleobases pairs. Metallodrugs often show an enhanced anticancer activity compared to free ligands.
In this context, ligands with well-established antitumor activity as 7- and (R)-9-Hydroxy stearic acid (HSA) were selected and reacted with mer-[Ru(H)2(CO)(PPh3)3] to give Ru(II) anticancer species.2 The anticancer in vitro properties of this class of metallo-prodrugs could be ascribed to synergistic effects between the metal center and bioactive ligands. The results have been compared with the analogously coordinated innocuous 12-HSA. The three novel Ru(II)-HSA complexes were fully characterized spectroscopically by using ESI-MS, IR, UV-Vis, and NMR techniques. The nature of Ru-12-HSA was also determined by single crystal X-ray diffraction, Cytotoxicity, cell proliferation, and DNA damage tests were performed demonstrating the biological activity of Ru-7-HSA and Ru-9-HSA
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
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