生物小分子的电分析化学研究 Ⅱ.鸟嘌呤、腺嘌呤和次黄嘌呤在粗热解石墨电极上的分子定向和表面相互作用

本文讨论了鸟嘌呤、腺嘌呤和次黄嘌呤等嘌呤类生物小分子在几种电极上的反应活性,并选用粗热解石墨电极研究了它们的电化学性质.实验结果表明它们的电极过程是受吸附作用控制的.在粗热解石墨电极上鸟嘌呤以C(2)-NH~2、腺嘌呤以C(6)-NH~2、次黄嘌呤以N(1)-H基团按垂直方向吸附于电极表面,电极表面分子间存在着相斥的相互作用.鸟嘌呤、腺嘌呤和次黄嘌呤的吸附平衡常数分别为:(3.34±1.00)×10^5,和(4.38±1.20)×10^5和(4.13±1.21)×10^5;吸附能分别为:(31.5±0.77),(32.1±0.70)和(32.0±0.75)kJ/mol.这些数值表明它们在粗热解石墨电极上具有中等偏强的物理吸附作用.

Study on electroanalytical chemistry of small biological molecules. Ⅱ.molecular orientation and surface interaction of guanine,adenine and hypoxanthine on rough pyrolytic graphite electrode

The reactivity of guanine, adenine and hypoxanthine on electrodes made with different materials is discussed. The rough pyrolytic graphite electrode (RPGE) was selected for the electrochem. study. The experiment data indicate that the electrode process is controlled by adsorption and the probes, guanine, adenine and hypoxanthine as mono-mol. layer are adsorbed toward the electrode surface of RPGE in a perpendicular orientation with the H group at C(2)-NH2 position for guanine, C(6)-NH2 position for adenine and N(1)-H position for hypoxanthine. Adsorbed mols. have a repulsive interaction at either surface. The equilibrium constants of adsorption for guanine, adenine and hypoxanthine are about 3.34 x 105, 4.38 x 105 and 4.13 x 105 resp., and the energies of adsorption at RPGE are about 31.5, 32.1, and 32.0 kJ/mol resp., which indicate that guanine, adenine and hypoxanthine all have a moderate to strong phys. adsorption on RPGE.