| In this study imidazole was observed to have no effect on the oxidation of dopamine, indicating that dopamine is not oxidized by concerted proton and electron transfer. The oxidation of two dopamine analogs, catechol and 4methylcatechol, were studied to investigate the properties of dopamine. The rate of water addition to catechol quinone was determined as 0.03171+/-0.00155 per second in phosphate buffer at pH 8.0. Therefore, if dopamine quinone adds water at comparable rate, then up to 6 percent of the quinone is converted to 6-hydroxydopamine, a chemical highly toxic to neurons.; The extinction coefficient of methylcatechol quinone/aniline adduct was determined as 3419 M-1cm-1. With this coefficient, the rate of 4-methylcatechol oxidation was measured with a spectrophotometer. The rate increased with the concentration of substrate in a nonlinear pattern, and this process was accelerated in the presence of catalase, indicating that superoxide is not necessary in the oxidation of 4-methylcatechol. Based on these findings, the mechanisms of 4-methylcatechol oxidation with or without aniline were proposed.; In the last part of the study, the aniline adduct MAQ was synthesized and purified. Its property of mediating the redox reaction between ascorbate and oxygen was observed, which is useful in studying the redox reactions associated with the respiration chain in the mitochondria. |
