Actinomycin D binds to single stranded DNA oligomers which contain double GTC triplets

The present work carried out a study on the interactions between Actinomycin D (ActD) and some single-stranded DNA oligomers, which contain double GTC triplets separated by TTT sequence. The interactions of drugs with DNA oligomers were investigated by UV, circular dichroism (CD) spectroscopy and isothermal titration calorimetry (ITC). The results indicate that ActD binds to the single stranded DNA oligomers in the fold back binding model as supported by added A/T base at DNA strand terminal which facilitates the formation of hairpin. The apparent binding constant Kb, the apparent binding molar enthalpy ΔH0 and other thermodynamic data were obtained. The binding affinities are sequence dependent and related to the length of DNA strand. And the higher molar binding enthalpy indicates that the binding process is enthalpy driven.