EVIDENCE FOR FORMATION OF DNA-BOUND PROTONATED PORPHYRIN ADDUCTS EVEN AT PH-7

An absorption and a positive circular dichroism (CD) band in the Soret region at 451 nm and a fluorescent emission band at 725 nm provide compelling evidence that the binding of a tentacle tetracationic porphyrin, meso-tetrakis[4-{(3-trimethylaminopropyl)oxy)phenyl]porphine (TthetaOPP), to calf thymus (CT) DNA leads to extensive porphyrin protonation, even at pH 7, and that a protonated porphyrin can form DNA adducts with a binding mode different from that of the unprotonated species.