Electron injection from the side of an M-DNA duplex.

M-DNA is a complex formed between duplex DNA and divalent metal ions (Zn2+, Cu2+ or Ni2+) at pHs above 8. Previous results showed that the fluorescence of an electron donor fluorophore was quenched when an acceptor flourophore was placed in the opposite end of an M-DNA duplex suggesting electron transfer through the duplex and indicating M-DNA may operate as a better conductor than B-DNA. To further investigate the properties of M-DNA, oligodeoxynucleotides were prepared with fluorescein (Fl) as an electron donor placed at different positions along the helix. An internal position of the chromophore was made possible by attaching it to the extra hydroxyl arm in the branched monomer 4'-C-hydroxymethylthymidine. Upon excitation of the donor fluorophore, it was demonstrated that electrons could be injected into the side of an M-DNA helix thereby extending the range of nanoelectronic structures that can be prepared from DNA.