Angewandte Chemie International Edition
Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
For full article and contact information, see Angew. Chem. Int. Ed. 1999, 38 (7), 941-949 and 996-998
Research controversy: Can the genetic molecule conduct
electrical current? / Contradictory results
The DNA molecule was developed by nature to store the genetic information of its creations. However, in recent years it has been shown that this giant molecule could also have other qualities - it may also conduct electric current. Three research groups that are looking into this subject have now published their results in Angewandte Chemie.
The idea that DNA could transport electric charges came to chemists quite early. The building blocks of DNA, the base pairs, which are stacked within the spiral staircase-like molecule, are packed so densely together that their electron clouds come very close to each other - almost like in a metal. Nevertheless, experiments that should verify the conductivity of DNA give contradictory results.
Two current examples: The groups working with Michael G. Hill of Occidental College in Los Angeles and Jacqueline K. Barton of Caltech examined short pieces of DNA, which were attached vertically on a gold surface. In this way, they could measure conductivity along the length of the molecule - independent of the length of the DNA section. In contrast, other measurements carried out by Anthony Harriman at Louis-Pasteur University in Strasbourg make it "very clear" that DNA "is a relatively poor conductor of electrons."
Why these contradictory results? This is because the conductivity of DNA also depends on its composition, and above all on the order of its building blocks, suspects Bernd Giese, who teaches chemistry at the University of Basel. The electrons do not flow through DNA exactly like in a cable; rather they must hop from base to base. However, not all bases make equally good destinations: for example, positive charges can only jump from guanine to guanine (the other three bases thymine, adenine, and cytosine are out of the question for this). The conductivity of the DNA "wire" thus depends on the distribution of these guanine bases - the closer together they are, the easier it is for the charge to jump from base to base.
If special DNA did indeed conduct electricity, it may be possible to use this robust molecule to wire tiny machines. Moreover, defective DNA could be recognized by its conductivity. This debate will certainly continue to keep us in suspense for quite some time.