Nuclear magnetic resonance study on the interaction of aclacinomycin-A with a deoxyribo-hexanucleotide pentaphosphate d(CCTAGG)2 in aqueous solution.

Abstract

The interaction of aclacinomycin-A (ACM) with a deoxyribo-hexanucleotide pentaphosphate d(CCTAGG)2 in aqueous solution was studied by 1H, 31P nuclear magnetic resonance techniques and by visible absorption spectroscopy. From the visible absorption spectra, ACM was found to be bound by polynucleotides with binding constants of the order of 106, in the order poly(dA-dT)>poly(dC)+poly(dG)>poly(dA-dG)+poly(dT-dC). With gradual addition of ACM to d(CCTAGG), two 31P resonances newly appeared in the lower fied region as compared with d(CCTAGG) in the non-complex state, while the 31P resonance assignable to the TpA portion in the non-complexed state decreased in intensity. From these results, the chromophore of ACM is expected to be intercalated in the TpA portion of the oligo-deoxyribonucleic acid duplex. The line widths of the exchangeable proton resonances of complex in H2O were examined as a funciton of the temperature. The results suggested that ACM stabilizes the helix of d(CCTAGG)2 at a region around the intercalation site.