Am. Brun et A. Harriman, ENERGY-TRANSFER AND ELECTRON-TRANSFER PROCESSES INVOLVING PALLADIUM PORPHYRINS BOUND TO DNA, Journal of the American Chemical Society, 116(23), 1994, pp. 10383-10393
The interaction of a series of isomeric palladium tetrakis(N-methyl-x-
pyridinium)porphyrin (x = 2, 3, and 4) with DNA and synthetic polynucl
eotides has been studied. Both intercalation between base pairs (x = 3
and 4) and electrostatic binding to the external phosphate chain (x =
2) are observed. Once bound to DNA, the excited triplet state of thes
e cationic porphyrins can be quenched by oxygen dissolved in the surro
unding aqueous reservoir and by methyl viologen bound to the phosphate
chain. Rates' of quenching can be related to the location of the boun
d porphyrin on the DNA duplex. Singlet and triplet energy transfer is
also observed from intercalated acridine orange to a porphyrin (x = 3)
that is intercalated into the same helix. The rates of singlet energy
transfer are discussed in terms of competing Forster- and Dexter-type
mechanisms, and it is concluded that the DNA duplex does not provide
a particularly attractive medium for electron exchange.