Abstract
Three cationic porphyrin-polypyridyl ruthenium(II) hybrids, differing in the planar areas of the polypyridyl moieties, were synthesized and their interactions with DNA investigated using absorption and fluorescence titration, induced circular dichroism spectra, thermal DNA denaturation measurements, as well as surface-enhanced Raman spectroscopy. Ethidium bromide competition experiments determined the binding affinity constants (Kb) of these compounds for CT DNA. DNA photocleavage experiments indicated that these hybrids have a broader cleaving wavelength range than traditional drugs and 1O2 is the reactive species responsible for the cleavage. The proper planar area was proved to be responsible for the larger Kb and higher DNA photocleavage efficiency.