Complexation of biologically active aromatic compounds with DNA in the presence of theophylline.

(1)H NMR measurements (500 MHz) have been used to determine the equilibrium hetero-association constants of theophylline (THP) with various biologically active aromatic compounds (daunomycin, novantrone, ethidium bromide, proflavine, norfloxacin) and the complexation constants of THP with both single- and double-stranded oligonucleotides in solution. The results provide a quantitative estimation of the effect of THP on the binding of aromatic ligands with DNA, and a determination of the fraction of aromatic ligand removed from DNA on addition of THP.