The question whether DNA can sustain an electronic current has suscitated, in the last few years, considerable interest both theoretically [1] and experimentally [2] and is still a matter under debate. The biological relevance of this issue is mainly related to the role of electron transfer as a repair mechanism after radiation damage to the DNA helix. A similar concernment, even though in a different contest, has recently emerged regarding the possibility to use DNA as a constituent of molecular scale electronic devices. After a period of high hopes but few tangible results, it was shown that single molecules can conduct, switch electric current and store information [3]. To this porpuse, DNA possesses additional alluring features like the appropriate molecular recognition, self assembly, and mechanical properties which are necessary conditions to lead to the realization and eventual integration into useful nano circuits; a deeper understanding of conduction mechanisms is -as a consequence- urgently required. In this talk, I will first describe the status-of-the-art of research on the conduction properties of the DNA strand, giving emphasis to their possible integration in electronic circuits. Thus, I will address the problem of electron transport across a system consisting of a molecular wire (an archetype for a biomolecular chain) attached to two semi-infinite carbon nanotubes acting as contacting leads. The latter are rolled graphene sheets in a seamless cylindrical structure, with typical diameter of few nanometer and millimeter size lengths, and with extremely well taylorable electronic features [4]. The electrical conductance of the hybrid system can be obtained by means standard theoretical physics techniques as a function of system parameters such as the wire-nanotube coupling strength, and the contact geometry. Electron transport exhibits markedly different behaviors depending on the contacting between the wire and the nanotube interfacial atoms. Possible implications for experiments are finally discussed.

[1] M. A. Ratner, Electronic Motion in DNA, Nature 397, 480 (1999); D. N. Beratan et al., DNA: Insulator or wire?, Chemistry and Biology 4, 3 (1997).
[2] F. D. Lewis et al., Direct measurement of hole transport dynamics in DNA, Nature 406, 51 (2000); D. Porath et al., Direct measurement of electrical transport through DNA molecules, Nature 403, 635 (2000); H. Fink and C. Schönenberger, Electronic conduction through DNA molecules, Nature 398, 407 (1999); E. Braun et al., DNA-templated assembly and electrode attachment of a conducting silver wire, Nature 391, 775 (1999).
[3] M. A. Reed et al., Conductance of a Molecular Junction, Science 278, 252 (1997).
[4] R. Saito, G. Dresselhaus, and M. S. Dresselhaus, Physical Properties of Carbon Nanotubes (World Scientific Pub., 1998).