EFFECT OF CATIONIC DRUGS ON SUPRAHELICAL ORGANIZATION OF DNA

Interaction of a minor groove-binding drug Hoechst-33258, and an inter calating drug, proflavin, with the PSI(+) form of DNA, was studied usi ng CD spectroscopy. Both drugs are shown to relax the suprahelical org anization of DNA, leading to the formation of a B-like structure, abov e a certain drug to phosphate ratio. However, unlike proflavin, Hoechs t-33258 brings about further structural changes after formation of the B-like structure whereas proflavin does not. A reversal of the CD sig nal in the 300-450-nm spectral region is also observed with Hoechst-33 258, indicating a change in the handedness of the suprahelical organiz ation of DNA. To the best of our knowledge, drug-mediated changes as p resented in this paper have not been reported so far. (C) 1993 John Wi ley & Sons, Inc.