Acid-base properties and DNA-binding of water soluble N-confused porphyrins with cationic side-arms

Water soluble N-confused porphyrins, 5,10,15,20-tetrakis(alpha-pyridinio-p-tolyl)-2-aza-21-carbaporphyrin (pPyNCP) and its N-methyl derivative, 2-N-methyl-5,10,15,20-tetrakis(alpha-pyridinio-p-tolyl)-2-aza-21-carbaporphyrin (NMe-pPyNCP), have been synthesized by introducing cationic side-arms at the meso-positions of N-confused porphyrin. Their acid-base properties (pK(1-4)) and DNA-binding ability in aqueous solutions were elucidated in comparison with the corresponding porphyrin derivative. Photophysical behaviors of pPyNCP were largely influenced by buffer compositions and DNA structures, whereas NMe-pPyNCP is considerably robust against these factors. In addition, significant enhancement of the fluorescence was observed with NMe-pPyNCP by the addition of DNA. The unique properties of pPyNCP and NMe-pPyNCP stem from the confused pyrrole rings in the macrocycle.