7-Aminoactinomycin D is a potent inhibitor of RNA polymerase and it has been demonstrated to bind to a single stranded DNA. Wadkins and Jovin showed that there is a 20 to 40 fold enhancement in the fluorescence of 7-aminoactinomycin D upon binding to certain single stranded DNA sequences. We report studies of the thermodynamics of the binding of the parent drug, actinomycin D, to single and double stranded DNA. A five-fold range of association constants is found for the different binding sequences that we have investigated. We will correlate these thermodynamic studies with measurements of the fluorescence enhancement, lifetime, and rotational correlation time of the drug bound to the various single and double stranded oligonucleotides.
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