The influence of electron donating and accepting functional groups OCH3, CH3/CN and CHO on electron transport properties of a single Adenine-based molecular junction has been numerically studied using the density functional based tight-binding method. It has been found that the above mentioned electron acceptor groups have a strong effect on transmission of the molecular junction resulting in a strong drop of conductance. On the other hand, in both electron donating and accepting categories, the partial density of states indicates that the delocalized nature of the porbitals of the adenine is responsible for the impressive effect of the functional group with -symmetric valence orbitals. Furthermore, the CN functional group has an effect on the current-voltage characteristics of the junction, which is distinct from the effects of all the other functional groups studied here.
