Synthesis and DNA-binding properties of bisdiazoliumylporphyrins

A pair of 5,15-bisdiazoliumylporphyrins with only two meso-substituents, 5, 15-bis(1,3-dimethylimidazolium-2-yl)porphyrin 1b and 5,15-bis(1,2-dimethylp yrazolium-4-yl)porphyrin 2b, has been synthesized. The crowded porphyrin 1b intercalates between base pairs of DNA to stabilize the duplex DNA to ther mal denaturation due to its high affinity for DNA. The binding of porphyrin 1b to DNA is an exothermic interaction and enthalpically driven. Porphyrin 1b interacts more strongly with poly(dA-dT)(2) than with poly(dG-dC)(2), a nd the interaction is more favorable or selective to AT-rich sites than to GC-rich sites.