Electronic structure of DNA derivatives and mimics by Density Functional Theory

Experiments for the measurement of quantum transport through single native and modified DNA molecules probe the electronic structure of the conducting material. In this chapter, most recent results for two selected periodic polymers constructed as DNA modifications are probed, which may constitute valid alternatives to native DNA for the development of molecular electronics. From the analysis of the experimental literature, authors concluded that charges may be transported with poor conductivity in short single DNA molecules or in longer molecules organized in bundles and networks and that charge flow is blocked for long molecules deposited onto "hard" inorganic substrates. Given the situation, two solutions remain to continue pursuing the route toward DNA-based electronics: either to reduce/avoid substrate-induced deformations or to explore stiffer molecules. Given the fact that currents are detected only for very short DNA fragments and have low intensities even when the problem of substrate contact is avoided, metal incorporation and base alteration are pursued to enhance the intrinsic conductivity: the CuHy-wire encloses both aspects. In the latter possibility, G4-DNA emerges as a valuable candidate, and also bears the promise of a better conductivity. The two candidates are presented from the point of view of density functional theory (DFT) calculations, and conclusions are drawn in detail. DFT along the years is proving itself as a valuable tool to describe the electronic structure of nucleotide aggregates and explore the possible applications for transporting currents.