Since luminescence quenching by long range electron transfer (ET) is mediated by the DNA 'pi- stack' established by the aromatic stacked base pairs, a new methodology using luminescence in solution becomes available to probe perturbations to and structure of the DNA pi-stack. Studies on DNA-mediated ET make use of the luminescent properties of intercalated [Ru(phen')2dppz)2+, by studying the rate of luminescence decay in the presence of the intercalated [Rh(phi)2phen')3+ complex. However, the factors that modulate ET remain unclear. In an effort to gain insight into the role that DNA plays as the transfer medium, studies investigating the effect on the rate of ET upon introducing site specific mismatches, bends or lesions to the middle of a Ru-DNA/DNA-Rh duplex will be undertaken. These perturbations of the DNA pi-way will be probed through electron transfer luminescence quenching. The change in luminescent characteristics of ruthenium intercalated DNA after introduction of these perturbations provides insight into the structure and dynamics of the double helix.