1,720,965 research outputs found
Coordination Compounds with Triazolopyrimidines: Versatile Building Blocks Towards Nanomedicine and Nanomaterials
No full textOrganotin(IV) coordination compounds with triazolopyrimidines as cytotoxic agents in human cancer cells and their action mechanism on apoptosis in HCT-116 colon cancer cells.
No full textCytotoxic Activity of Organotin(IV) Derivatives with Triazolopyrimidine Containing Exocyclic Oxygen Atoms
Full text link: In this study cytotoxicity of organotin(IV) compounds with 1,2,4-triazolo[1,5-a]pyrimidines,
Me3Sn(5tpO) (1), n-Bu3Sn(5tpO) (2), Me3Sn(mtpO) (3), n-Bu3Sn(mtpO) (4), n-Bu3Sn(HtpO2) (5),
Ph3Sn(HtpO2) (6) where 5HtpO = 4,5-dihydro-5-oxo-[1,2,4]triazolo-[1,5-a]pyrimidine, HmtpO =
4,7-dihydro-5-methyl-7-oxo-[1,2,4]triazolo-[1,5-a]pyrimidine, and H2tpO2 = 4,5,6,7-tetrahydro-5,7-
dioxo-[1,2,4]triazolo-[1,5-a]-pyrimidine, was assessed on three different human tumor cell lines:
HCT-116 (colorectal carcinoma), HepG2 (hepatocarcinoma) and MCF-7 (breast cancer). While 1 and
3 were inactive, compounds 2, 4, 5 and 6 inhibited the growth of the three tumor cell lines with
IC50 values in the submicromolar range and showed high selectivity indexes towards the tumor
cells (SI > 90). The mechanism of cell death triggered by the organotin(IV) derivatives, investigated
on HCT-116 cells, was apoptotic, as evident from the externalization of phosphatidylserine to the
cell surface, and occurred via the intrinsic pathway with fall of mitochondrial inner membrane
potential and production of reactive oxygen species. While compound 6 arrested the cell progression
in the G2/M cell cycle phase and increased p53 and p21 levels, compounds 2, 4 and 5 blocked cell
duplication in the G1 phase without affecting the expression of either of the two tumor suppressor
proteins. Compounds 1 and 2 were also investigated using single crystal X-ray diffraction and
found to be, in both cases, coordination polymers forming 1 D chains based on metal-ligand
interactions. Interestingly, for n-Bu3Sn(5tpO)(2) H-bonding interactions between 5tpO− ligands
belonging to adjacent chains were also detected that resemble the “base-pairing” assembly and could
be responsible for the higher biological activity compared to compound 1. In addition, they are the
first example of bidentate N(3), O coordination for the 5HtpO ligand on two adjacent metal atoms
ATTIVITA’ CITOTOSSICA DI COMPLESSI ORGANOSTAGNO(IV) CON TRIAZOLOPIRIMIDINE CONTENENTI ATOMI DI OSSIGENO ESOCICLICO
No full textLe triazolopirimidine sono leganti eterociclici di crescente interesse. I composti di organostagno(IV) sono caratterizzati dalla presenza di un atomo di stagno (Sn) legato covalentemente ad uno o più sostituenti organici. In questo studio1 sono stati sintetizzati: Me3Sn(5tpO)(1); n-Bu3Sn(5tpO)(2); Me3Sn(mtpO)(3); n-Bu3Sn(mtpO)(4); n-Bu3Sn(HtpO2)(5); Ph3Sn(HtpO2)(6) e la loro citotossicità valutata su tre differenti linee cellulari tumorali umane: HCT-116 (carcinoma del colon retto), HepG2 (epatocarcinoma) e MCF-7 (carcinoma mammario).
I complessi 2, 4, 5 e 6 hanno mostrato attività citotossica di 1-2 ordini di grandezza superiore al cis-platino, sulle 3 linee cellulari tumorali. Il meccanismo di morte cellulare è stato quindi indagato sulle cellule HCT-116, le più sensibili all’azione dei composti. Tutti hanno mostrato: a) attività proapoptotica, come evidente dall’esternalizzazione della fosfatidilserina; b) meccanismo di esecuzione intrinseco come evidente dalla caduta di potenziale mitocondriale e dall’incremento di specie reattive dell’ossigeno (ROS); c) i complessi 2 e 4 pur avendo leganti differenti causano un blocco del ciclo in fase G0/G1 mentre il complesso 6 blocca le cellulle in fase G2/M. Infine l’indice di selettività calcolato su cellule intestinali normal-like indica che il complesso 6 è il più specifico contro le cellule tumorali. I complessi 1 e 2 sono stati sottoposti ad uno studio strutturale mediante raggi X per correlarne la struttura all'attività biologica
Nanowire iron(III) coordination polymer based on 1,2,4-triazolo[1,5-a]pyrimidine and chloride ligands
Full text linkThe neutral ligand 1,2,4-triazolo[1,5-a]pyrimidine (tp) has been employed to prepare a new coordination compound of Fe(III), [FeCl 3 (tp) 2 ] n (1). Compound 1 was investigated by single crystal X-ray diffraction and found to be a coordination polymer forming a ladder structure based on metal–ligand interactions, while H-bonding and aromatic interactions contribute to the supramolecular self-assembly into a 3D nanostructured material. The polymeric assembly is retained also in solution, where a metallo-supramolecular polymer based on coordinative metal–ligand binding is present, as shown by dynamic light scattering (DLS) measurements. The redox properties of the Fe(III) coordination polymer have also been investigated in different solvents and its nanowire structure has been assessed by Atomic Force Microscopy (AFM) imaging of the species deposited onto a freshly cleaved mica surface
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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