DISTANCE-DEPENDENT ELECTRON-TRANSFER IN DNA HAIRPINS

The distance dependence of photoinduced electron transfer in duplex DN A was determined for a family of synthetic DNA hairpins in which a sti lbene dicarboxamide forms a bridge connecting two oligonucleotide arms . Investigation of the fluorescence and transient absorption spectra o f these hairpins established that no photoinduced electron transfer oc curs for a hairpin that has six deoxyadenosine-deoxythymidine base pai rs. However, the introduction of a single deoxyguanosine-deoxycytidine base pair resulted in distance-dependent fluorescence quenching and t he formation of the stilbene anion radical. Kinetic analysis suggests that duplex DNA is somewhat more effective than proteins as a medium f or electron transfer but that it does not function as a molecular wire .