Different binding to DNA of enantiomeric platinum complexes assessed by inhibition of restriction enzyme activity

The ability of enantiomeric platinum complexes to block the action of selected restriction enzymes has been investigated. The complexes [PtCl2(DAC)], [PtCl2(DAB)] and [PtCl2(DAP)] (DAC = 1,2-diamminocyclohexane; DAB = 2,3-diamminobutane; DAP = 1,2-diamminopropane) exhibit a guanine-cytosine preference in accord with previous results on cis-[PtCl2(NH3)2] (cis-DDP). The extent of inhibition, however, is significantly different for the different isomers; the R,R form is more active than the others at short incubation time, as the time becomes longer, the differences among isomers level off. It also appears that cis-DDP is more active than [PtCl2(DAC)] in blocking the Cfo I enzyme, though it shows a preference for the G-X-G sequences.