Double-strand hydrolysis of plasmid DNA by dicerium complexes at 37 degrees C

Significant effort has been made to develop synthetic metal complexes that hydrolyze DNA. Here we report a new dicerium complex, Ce-2(HXTA) (HXTA = 5- methyl-2-hydroxy-1,3-xylene-alpha,alpha -diamine-N,N,N',N'-tetraacetic acid ), which can hydrolyze DNA at pH 8 and 37 degreesC. This complex hydrolyzes DNA restriction fragments to give products with high regioselectivity, aff ording >90% 5'-OPO3 and 3'-OH ends, like the products of DNA hydrolyzing en zymes. Ce-2(HXTA) also hydrolyzes Litmus 29 plasmid DNA to afford both nick ed and linear DNA. Analysis of the relative amounts of supercoiled, nicked, and linear DNA present show that there is one double-strand cleavage per t en single-strand cleavages, indicating that the linear DNA formed cannot be the result of two random single-strand cleavage events. The kinetics of ni cked and linear DNA formation are comparable, both being associated with ap parent first-order rate constants of approximately 1 x 10(-4) s(-1) for com plex concentrations of 10(-5)-10(-4) M. These observations suggest that sim ilar factors affect the hydrolysis of the first and second DNA strands and that cleaving the phosphodiester bond is likely the rate determining step i n both cases. This is the first detailed study of a metal complex shown to mimic DNA hydrolases in their capability to effect double-strand DNA hydrol ysis regioselectively at the 3'-O-P bond.