Engineering DNA to make the tiniest of wires
The use of DNA molecules to assemble nanowires for nanoelectronic devices is one of the first steps towards using biological molecules as a manufacturing tool. Instead of moulding electronic components from conventional materials, project partners experimented with ways to exploit the self-assembling properties of DNA. DNA is in itself probably not a good conductor of electricity and molecular wires are characterised by limited ability to transport electrical charges. Scientists at the Hebrew University of Jerusalem turned therefore to derivatives of DNA that can be used as templates for the formation of conducting nanowires. Composed of self-folded polydeoxyguanylate (poly(dG)) strands of thousands of guanine (dG) tetrads, G4-DNA nanowires offered the desired conductive properties. Guanine, distinctive among the DNA constituents for its low ionisation potential, had a key role to play in the electrical conductivity of G4-DNA nanowires. Guanine-rich DNA strands were synthesised from a double helical complex of polydeoxyguanylate (poly(dG)) and polydeoxycytidylate (poly(dC)). To separate poly(dG) strands, a new method was introduced that is based on the use of long and continuous poly(dG) strands attached to short poly(dC) fragments as source material. Through the controlled folding of the derived poly(dG) strands, long and uniform G4-DNA nanowires were subsequently produced. The truly innovative nature of this research work rests, firstly, in the use of the self-assembly potential of DNA strands. Secondly, it lies in combining sophisticated techniques for nanoengineering DNA strands and scanning tunnelling microscopy with computational simulations of the stability and properties of the synthesised nanostructures. As a result, designing nanowires using DNA derivatives is now a reality.
