STUDY ON ELECTROANALYTICAL CHEMISTRY OF S MALL BIOLOGICAL MOLECULES .2. MOLECULAR-ORIENTATION AND SURFACE INTERACTION OF GUANINE, ADENINE AND HYPOXANTHINE ON ROUGH PYROLYTIC-GRAPHITE ELECTRODE

In this paper, the reactivity of guanine, adenine and hypoxanthine hav e been discussed on different materials electrode- The Tough pyrolytic graphite Electrode (RPGE) was selected for the eletrochemical study o f properties. The experiment data indicate that the electrode process is controlled by adsorption and the probes, guanine, adenine and hypox anthine as mono-molecular layer are adsorbed toward the electrode, sur face of RPGE in a perpendicular orientation with the H group at C(2)-N H2 position for guanine, C(6)-NH2 position for adenine and N(1)-H posi tion for hypoxanthine. Adsorbed molecules have a repulsive interaction at either surface. The equilibrium constants of adsorption for guanin e, adenine and hypoxanthine are about 3.34 x 10(5), 4.38 x 10(5) and 4 .18 x 10(5) respectively, and the energies of adsorption at RPGE are a bout 31.5, s2.i, and 82.0 kJ/mol respectively, which indicate that gua nine, adenine and hypoxanthine all have a moderate to strong physical adsorption on RPGE.