Study On The Microenvironment Effect Of Catecholamine Electrode And The Substituent Effect

Dopamine and norepinephrine belong to catecholamine, and they play important role in mammals. Therefore, to research their biochemical redox ability under physical environment is of significant importance. Due to the phenolic hydroxyl group and amino group of catecholamine, materials, such as protein, amino acid, and nucleic acid, can influence the redox ability through hydrogen bond interaction. As is known to all, redox potentials can predict the ability of a molecule to lose and gain electron, therefore, we study the transference of electrons of catecholamine and the effection of amino acid by comparing the experimental and theoretical potentials.Cyclic voltammetry(CV) is adopted to detect the redox potentials of dopamine and norepinephrine, while theoretical potentials are calculated with DFT method. From the results,there is an excellent agreement between experimental and theoretical values. And the computing method we have adopted here is accurate enough to calculate the potentials of catecholamine.Based on this, experiments combined with DFT method is adopted to predict the influence of glycine on the electron donating ability of catecholamine. The result shows that hydrogen bond interaction can increase the redox potential through weakening the electron-donating ability.Besides, p-hydroquinone and pyrocatechol, chosen to be on behalf of the hydroquinone including catecholamine, their redox potentials are calculated at the B3LYP/6-311+G(d,p) level,and values are verified by cyclic voltammetry experiments. Then we discuss the substituent effect on the redox potentials of hydroquinone in detailed. The study of the seven substituent groups(-F,-Cl,-OH,-COOH,-CN,-NH2, and-NO2 groups) shows that-NH2 and-OH groups can decrease the redox potentials, while-F,-Cl,-COOH,-CN, and-NO2 groups enlarge potential values of p-hydroquinone and pyrocatechol. In additionally, the correlations between the calculated energies of HOMO, LUMO, and potential values are investigated to facilitate the further prediction on the potential values of unknown electroactive materials.At last, we stimulate the reaction of norepinephrine on Au surface, and explore the micro-environment effection of electrode surface. All of these deepen the recognization of the the oxidation scheme of hydroquinone, and realize the combination of experiment and theory.