Aminomethylanthracene Dyes as High‐Ionic‐Strength DNA‐Photocleaving Agents: Two Rings are Better than One

This paper compares the DNA interactions of a bis 9‐aminomethylanthracene dye ( 2 ) vs. a mono‐anthracene ( 4 ) under high ionic strength conditions similar to those in the cell nucleus (∼150 mM NaCl and 260 mM KCl). The chloride salts triggered an enhancement in anthracene‐sensitized DNA photocleavage, where bis‐anthracene 2 exhibited superior DNA binding affinity, faster reaction kinetics, and higher levels of DNA damage at low‐ to sub‐micro molar dye concentrations (350 nm hν , pH 7.0). While spectroscopic and viscometric data suggested that the chloride salts reduced DNA intercalation in favor of a non‐intercalative binding mode in which 2 and 4 were better able to generate hydroxyl radicals, there was evidence of persistent intercalation of the second anthracene ring of 2 . We propose that such an interaction anchored the bis‐anthracene to DNA under the high ionic strength conditions, increasing its binding affinity and photocleaving capabilities relative to the mono analog ( 4 ).