The interest in DNA as a building block for nano-electric sensors and devices stemmed from the ability to construct various nanometer-sized two and three-dimensional structures and its amazing positive charge conducting properties. However, since a positive charge migrates along DNA through the HOMO of G-C base-pairs, the conductivity of DNA strongly decreases with the increasing A-T base-pair content hampering the construction of nano-electric circuits in which the use of various sequence patterns is indispensable. In this chapter, we demonstrated that the charge transfer efficiency can be drastically increased in a G-C content independent manner by adjusting the HOMO-level of the A-T base-pair closer to that of the G-C base-pair. This was achieved either by substituting the N7 nitrogen of A with a C-H group (deazaadenine: Z) or substituting C2 hydrogen with an amino group (diaminopurine: D). Since Z and D selectively pair with T without significantly perturbing the thermo-stability of the duplex, Z and D can be used to increase the charge transfer efficiency through DNA while properly maintaining the sequence information carried by DNA.
Graphical Abstract