Brafia et a1.1,2 have shown that 3-nitronaphthalene mo- noimides with cationic substituents on the imide nitrogen have significant antitumor activity and have proposed that the mode of action of these compounds involves interaction with DNA. Waring et aL3 have shown that compounds of this type bind to DNA, increase the length of sonicated DNA, and cause unwinding of closed circular superhelical DNA, characteristics typical of intercalating compounds.* Yen et al.5 ...