EVIDENCE FOR FORMATION OF DNA-BOUND PROTONATED PORPHYRIN ADDUCTS EVENAT 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 co mpelling evidence that the binding of a tentacle tetracationic porphyr in, kis[4-{(3-trimethylaminopropyl)oxy)phenyl]porphine (TthetaOPP), to calf thymus (CT) DNA leads to extensive porphyrin protonation, even a t pH 7, and that a protonated porphyrin can form DNA adducts with a bi nding mode different from that of the unprotonated species.