The broad objective of this project is to characterize the structural, thermodynamic, and kinetic aspects of the interaction if intercalating drugs with DNA, nucleosome subunits of chromatin, and higher order chromosomal units. Specific emphasis is being placed on the anthracycline drugs with the goal of providing information for the design of analogs in this series which have improved antitumor activity and lower toxicity. We have numerous mono- and bisanthracycline derivaties available for testing specific ideas about the anthracycline-DNA complex. Additional compounds have been synthesized by us or obtained from others which will be used to test specific points concerning the effects of intercalating drugs on DNA and chromatin and how these effects relate to the antitumor activity of the anthracycline drugs. For example, a series of neutral, monocationic, and dicationic compounds are available for analyzing cooperativity and electrostatic effects in terncalation. Derivatives have been prepared with substituents which vary in electronic character to determine how this affects the binding free energy of intercalating drugs and how the effect depends on base pair composition. Structural effects of intercalation will be evaulated using viscometric studies with linear and closed circular DNA, and using 31P NMR spectroscopy. 31P NMR will be an excellent method to bridge the gap between the effects of intercalating drugs on purified DNA and on chromatin. The 31P NMR technique will be used specifically to investigate the effects of intercalating drugs on nucleosomes. The binding strength of intercalating drugs to nucleosomes and higher order chromsomal units will also be investigated fof correlation with medicinal activity. We have also synthesized a series of intercalating drugs with bulky substituents placed on the intercalating ring in such a way that one of the bulky groups must slide between base pairs during intercalation of the drugs. By varying the substituent size we can vary the kinetics of intercalation to enhance our understanding of the relationship of binding rates and binding strength to the anticancer activity of intercalating drugs.