Efficient enhancement of DNA cleavage activity by introducing guanidinium groups into diiron(III) complex

Inspired by the structures of natural nucleases, guanidinium groups were introduced into binuclear iron(III) systems. Compared with the corresponding analogue without guanidinium groups, the new diiron(III) system led to considerable rate enhancement on DNA cleavage. The cooperativity between metal ions and guanidine groups was evidenced by the fact that no significant cleavage was observed after incubating pBR322 plasmid DNA with non-metalated ligands or free Fe³⁺ ion. DNA binding experiments indicated that introduction of positively charged guanidinium groups can obtain more than one order of magnitude enhancement in the affinity of complex with DNA.