323 research outputs found

    Ruthenium polypyridyl complexes and their modes of interaction with DNA : is there a correlation between these interactions and the antitumor activity of the compounds?

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    Various interaction modes between a group of six ruthenium polypyridyl complexes and DNA have been studied using a number of spectroscopic techniques. Five mononuclear species were selected with formula [Ru(tpy) L1L2](2-n)?, and one closely related dinuclear cation of formula [{Ru(apy)(tpy)}2{l-H2N(CH2)6NH2}]4?. The ligand tpy is 2,20:60,200-terpyridine and the ligand L1 is a bidentate ligand, namely, apy (2,20-azobispyridine), 2-phenylazopyridine, or 2-phenylpyridinylmethylene amine. The ligand L2 is a labile monodentate ligand, being Cl-, H2O, or CH3CN. All six species containing a labile L2 were found to be able to coordinate to the DNA model base 9-ethylguanine by 1H NMR and mass spectrometry. The dinuclear cationic species, which has no positions available for coordination to a DNA base, was studied for comparison purposes. The interactions between a selection of four representative complexes and calf-thymus DNA were studied by circular and linear dichroism. To explore a possible relation between DNA-binding ability and toxicity, all compounds were screened for anticancer activity in a variety of cancer cell lines, showing in some cases an activity which is comparable to that of cisplatin. Comparison of the details of the compound structures, their DNA binding, and their toxicity allows the exploration of structure–activity relationships that might be used to guide optimization of the activity of agents of this class of compounds

    Cultural Distance and Firm Internationalization:A Meta-Analytical Review and Theoretical Implications

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    This paper presents the most comprehensive review and meta-analysis of the literature on cultural distance and firm internationalization to date. We analyze the effects of cultural distance on key strategic decisions throughout the entire process of internationalization. For the preinvestment stage, we examine the decisions on where to invest (location choice), how much to invest (degree of ownership), and how to organize the foreign expansion (entry and establishment mode). For the postinvestment stage, we examine the decisions of how to integrate the foreign subsidiary into the organization (transfer of practices) as well as the performance effects of cultural distance at both the subsidiary and the firm level. We find that firms are less likely to expand to culturally distant locations but if they do, they prefer greenfield investments and integrate subsidiaries more through transfer of management practices. Cultural distance does not seem to affect how much capital firms invest and whether they enter through a joint venture or full ownership. Interestingly, cultural distance has a strong negative effect on subsidiary performance but no effect on the performance of the whole multinational company. In addition, we find that the effects of cultural distance are not sensitive to time, but they are sensitive to the cultural framework used (e.g., Hofstede vs. Global Leadership and Organizational Behavior Effectiveness) and the home country of the company (developed vs. emerging market). Based on our study, we feel confident to offer some theoretical insights, recommendations for improving the validity and reliability of cultural-distance research, and ideas for future research
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