DNA binding and cleavage properties of the Ce(III) complex of a diaza-crown ether

The hydrolytic cleavage of pUC19 DNA as promoted by the trivalent cerium complex (CeL) of diaza-crown ether ligand L (1,4,10,13-tetraoxa-7,16-diazacyclooctadecane) was examined in detail. The interaction of CeL with calf thymus DNA was investigated by UV-Vis spectroscopy. Furthermore, studies on the effects of pH, reaction time, and the concentration of CeL on cleavage of pUC19 DNA were carried out by gel electrophoresis. The results indicate that CeL can bind to DNA electrostatically with a binding constant of 2.18x10(4) M-1; CeL can promote the cleavage of plasmid pUC19 DNA from supercoiled to the nicked form under the appropriate conditions, and the optimal pH value is 7.54. The lack of effect of radical scavengers indicates that the cleavage involves hydrolytic cleavage.