1,721,129 research outputs found
The coordination core of Ag(i) N-heterocyclic carbene (NHC) complexes with anticancer properties as revealed by synchrotron radiation X-ray absorption spectroscopy
No full textAn X-ray absorption structural study has been carried out on three N-heterocyclic carbene (NHC) complexes of group 11 metals (Ag, Au), which were previously shown to possess promising anticancer properties. Extended X-ray Absorption Fine Structure (EXAFS) data concerning the Au complex, besides confirming the structure already available by crystallography, allowed the comparison between the crystalline and the amorphous state of the same compound. The EXAFS study conducted on the most biologically active complex, {[ImB]2AgCl}, revealed the occurrence of an unusual coordination geometry, where two ligand molecules and one chlorine atom interact with the Ag core to form a three coordinate complex. The present analysis firmly underlines the reliability of the EXAFS approach when X-ray diffraction data are not available. The suitable strategy, also including the statistical evaluation of the results, which has permitted us to build up the structural model for fitting the Ag complex starting from the Au one, is highlighted here
Complessi carbenici N-eterociclici simmetrici e asimmetrici dei metalli da conio: sintesi, citotossicità e studi in soluzione
No full textRecentemente la chimica farmaceutica organometallica ha sperimentato una rinascita1. Il nostro gruppo di ricerca, negli ultimi 8 anni, ha sviluppato diverse classi dei comlessi NHC (carbeni N-eterociclici) con metalli da conio. Recentemente abbiamo concentrato il lavoro di ricerca sullo sviluppo di nuovi complessi NHC di argento(I), oro(I) e rame(I) ottenuti dai leganti idrosolubili HIm1R,3RCl (R = COOCH3, COOCH2CH3 o CON(CH2CH3)2)2 o dal legante precarbenico zwitterionico simmetrico NaHIm1R,3R,4R’’ (R = (CH2)3SO3-, R’’ = H, CH3)3,4 (Figura 1), NaHBzim1R,3R (R = (CH2)3SO3-) e leganti precarbenici non simmetrici NaHIm1R,3R’ (R = (CH2)3SO3-, R’ = CH2C6H5), {[HBzim1R,3R’]Br} (R = (CH2)3SO3Na, R’ = CH2C6H5) e i relativi complessi di rame(I) e argento(I)4. Abbiamo anche studiato la coordinazione del nuovo legante precarbenico {[HTz(pNO2Bz)2]Br} con accettori di Ag(I), Au(I) e Cu(I)5. Sono stati condotti studi di citotosicità su tutti i complessi ottenuti
Phosphino copper(I) complexes as antitumor agents
No full textAmong non-Pt compounds, copper complexes are considered good alternatives to platinum drugs as antitumor agents [1]. Elevated levels of copper have been detected in various types of human cancer cells, and the altered copper metabolism of cancer cells as well as the differential response between normal and tumor cells to copper are the basis for the development of copper complexes endowed with antineoplastic characteristics.
Recent studies have demonstrated that specific copper compounds are able to overcome classical drawbacks associated with Pt(II) drugs by virtue of a selective action toward tumor cells and the possibility to act against Pt-resistant tumor cells [2-5]. These features are consistent with the fact that copper complexes possess mechanism(s) of action different from platinum drugs.
Among the variety of copper-based compounds synthesized so far for application in pharmaceutical studies endowing such properties, phosphine copper complexes represent an intriguing class. SARs revealed that structural modifications of phosphine copper(I) complexes through the modulation of ligand physicochemical characteristics as well as the stability/lability of the coordinative bonds lead to major changes in the biological activity, pharmacodynamic properties and cellular bioavailability.
Recently, the monocationic copper(I) complex [Cu(thp)4][PF6] (CP) has been highlighted as a very promising agent [4]. The in vitro antitumor activity studies revealed a broad-spectrum and potent cytotoxicity against cancer cells derived from solid tumors, with IC50 values up to 15 and 35-fold lower than oxaliplatin and cisplatin, respectively. Interestingly, the selectivity index (SI) values were about 20- and 3-fold higher than those obtained with cisplatin and oxaliplatin, respectively. The characterization of CP-induced effects in cancer cells revealed the triggering of a non-apoptotic programmed cell death defined as paraptosis likely due to the inhibition of proteolytic activities of the 26S proteasome. By in vivo animal tests, the toxicity profile of CP has been explored after acute and repeated dose administrations. Studies on the antitumor efficacy of CP in models of solid tumor showed that CP was safe at a therapeutically effective dose, had a favorable pharmacokinetic profile and was effective against solid tumor models. The examination of CP biodistribution characteristics in tumor-bearing mice demonstrated that a significant and selective accumulation in the solid tumor mass was achieved [5]
Novel NHC complexes of coinage metals: synthesis, cytotoxicity and solution behavior
No full textN-Heterocyclic carbenes (NHCs) complexes represent new anticancer agents, normally with low toxicity profiles, and they provide a range of versatile structures for targeted biological applications [1]. In this field novel 1,3-symmetrically and 1,3-unsymmetrically substituted NHCs precursors have been synthesized (Figure 1) and used in the synthesis of multicharged metal-NHC complexes. In addition the novel NHC ligand precursor 1,4-bis(4-nitrobenzyl)-1H-1,2,4-triazol-4-ium bromide, [HTz(pNO2Bz)2]Br (Figure 1), has been synthesized and used in the synthesis of the corresponding metal complexes M[Tz(pNO2Bz)2]Br (M = Cu(I), Ag(I) or Au(I)). The cytotoxic properties of the NHCs complexes and of the corresponding uncoordinated ligands have been assessed in various human cancer cell lines, including cisplatin sensitive and resistant cells. Moreover, a detailed analysis of their molecular and cellular pharmacology has been performed in order to elucidate the role of the metallic core in determining the biological properties of this class of NHCs complexes. In particular, the ability of triazolium NHC compounds to hamper mammalian TrxR activity and proteasome functionality in human A431 cervical was investigated
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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