Studies on the interaction of DNA with some 9-aminoacridine derivatives by circular dichroism.

1. Circular dichroic spectra in the range 300-500 nm have been studied for the complexes of DNA with nitro-9-aminoacridine derivatives in which the nitro group was in position 1 or 2 and in which the dimethylaminoalkyl side chain varied from 2 to 5 carbon atoms. 2. The 1-nitro derivatives when bound to DNA gave a Cotton effect which was greatest with the derivative having a 5 carbon side chain. 3. In contrast no Cotton effect was observed with the 2-nitro derivative. 4. The maximum Cotton effect is observed with the 1-nitro derivatives when the concentration of 1-nitro derivatives to DNA nucleotides is about 1-6 to 1-7. 5. The nature of the binding of these derivatives to DNA is discussed.