Interaction of Aminoacridines with Nucleic Acids

Summary

Pulse radiolysis has been used to study the interaction of aminoacridines with nucleic acids. The data confirm that there are two modes of binding. These are: a weak interaction which has a maximum binding ratio of one site per dye; and a strong binding process effected by both electrostatic and Van der Waals interactions. The limit of this latter, strong binding mode is approximately six sites per dye.

The radiation-induced transient absorption spectrum of benzoflavine is characterized by a pronounced bleaching at 440 nm, which is quenched by the addition of nucleic acids. Mechanisms have been proposed for the reactions of both e_aq⁻ and ·OH with benzoflavine which account both for the observed bleaching of benzoflavine solutions and for the protective effect of nucleic acids. It is proposed that e_aq⁻ reacts with benzoflavine to form a stable benzoflavine semiquinone radical and that ·OH reacts with subsequent formation of a very stable benzoflavine hydroxycyclohexadienyl radical.