Iron(II) Supramolecular Helicates Condense Plasmid DNA and Inhibit Vital DNA‐Related Enzymatic Activities

The dinuclear iron(II) supramolecular helicates Fe₂L₃]Cl₄ (L=C₂₅H₂₀N₄) bind to DNA through noncovalent (i.e., hydrogen‐bonding, electrostatic) interactions and exhibit antimicrobial and anticancer effects. In this study, we show that the helicates condense plasmid DNA with a much higher potency than conventional DNA‐condensing agents. Notably, molecules of DNA in the presence of the M enantiomer of Fe₂L₃]Cl₄ do not form intermolecular aggregates typically formed by other condensing agents, such as spermidine or spermine. The helicates inhibit the activity of several DNA‐processing enzymes, such as RNA polymerase, DNA topoisomerase I, deoxyribonuclease I, and site‐specific restriction endonucleases. However, the results also indicate that the DNA condensation induced by the helicates does not play a crucial role in these inhibition reactions. The mechanisms for the inhibitory effects of Fe₂L₃]Cl₄ helicates on DNA‐related enzymatic activities have been proposed.