Coadsorption of the DNA bases thymine and adenine at the Au(111) electrode

We report on the adsorption of adenine as well as on the coadsorption of adenine and thymine at Au(111). Adenine is chemisorbed in two different states. Mutual interaction between adenine and thymine could be detected only at negative potentials where both molecules are oriented with their plane parallel to the surface. This interaction depends on the concentration of thymine, the pH value, the temperature and the roughness of the surface. At positive potentials where both molecules are oriented perpendicular to the electrode surface, from our experiments no hints to their interaction could be found.