INTERACTIONS BETWEEN EXPANDED PORPHYRINS AND NUCLEIC-ACIDS

Two types of interaction of expanded porphyrins and nucleic acids are discussed. The first involves the specific chelation of the anionic ph osphate diester backbone of DNA by the monoprotonated form of the wate r soluble sapphyrin 2. Support for the proposed binding mode derives f rom a variety of spectroscopic and biochemical studies, including visi ble absorption spectroscopy, circular dichroism spectroscopy, and supe rcoiled DNA unwinding experiments. The second interaction described is that of the water soluble europium texaphyrin complex Eu(T2B2 txph)(N O3)2 and RNA. This complex acts as a hydrolytic cleaving agent for uri dyl uridine monophosphate, UpU, with a pseudo-first order rate constan t of 0.057 +/- 2 h-1 at 37-degrees-C and pH = 7.0 with 0.49 mM UpU and 0.3 mM Eu(T2B2 txph)(NO3)2. Under identical conditions a 0.26 mM solu tion of Eu(NO3)3 hydrolyses UpU with a rate constant of 0.007 +/- 3 h- 1.