DNA, a target of mixed chelate copper(II) compounds (Casiopeinas®) studied by electrophoresis, UV-vis and circular dichroism techniques.

Casiopeinas are a family of mixed chelate copper(II) complexes with antiproliferative and antineoplastic activities, results that have positioned them as an alternative for cancer treatment. Because DNA is one of their principal targets, it is of our interest to find out the effect of substituents on the diiamine ligands over mode of interaction. Therefore, we studied 21 Casiopeinas upon DNA by gel electrophoresis, UV-vis and circular dichroism (CD) spectroscopic techniques, previously studied by DFT calculations and Quantitative Structure-Activity Relationship (QSAR). According to electrophoresis results, the interaction modes between Casiopeinas with DNA may be through the intercalation or in the minor groove. UV-vis spectroscopy showed a hypochromic or hyperchromic effect as a consequence of each interaction. The analysis suggests the binding along the minor groove and intercalation are both influenced by the substituents in the diimine ligands and depend on the nature of the secondary moiety (acetylacetonate or glycinate). Additionally, a new band in electrophoresis and CD spectra suggests adducts formation. In general, we prove that molecules with the highest molecular weight, electron donating substituents and glycinate as secondary ligand are intercalating agents; unlike molecules with electron withdrawing substituents as chloride or nitro and acetylacetonate as secondary ligand which interact in the minor groove.