Electrostatic engineering of charge clouds around DNA inhibits strand breakages

Femtosecond laser-induced damage to plasmid DNA in aqueous medium manifests itself as strand breaks arising from interactions with slow OH-radicals (and electrons) in the laser-induced plasma generated in water. Such strand breakages are found to be significantly inhibited upon addition of salts (in physiologically significant concentrations) to the aqueous medium. A simple model rationalizes our observations and suggests the feasibility of electrostatically “engineering” DNA's ion atmosphere so as to prevent damage-inducing free radicals accessing DNA strands. These findings may aid development of new strategies for cancer treatment.