  We present a first-principle study of the electronic and conduction
properties of a few classes of nanowires constituted of guanine (G) molecules,
self-assembled in different geometries. We first analyze the effect of the
vertical $\pi$-$\pi$ interaction in model G-stack columns. Then, we exploit the
results obtained from those models to interpret the features of realistic
stacked and hydrogen-bonded structures, namely the guanine quadruple helices
and the planar ribbons. With respect to natural DNA, the different structures
as well as the inclusion of metal cations, drastically affect the bonding
pattern among the bases, introducing novel features in the electronic
properties of the systems. These supramolecular G-aggregates, alternative to
DNA, are expected to show intersting properties for molecular elec tronics
applications.
