Kinetics of the Oxidation of Thymine and Thymidine by Triplet 2,2鈥?Dipyridyl in Aqueous Solutions at Different pH Values

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• 作者：Truong X. Nguyen ; G眉nter Grampp ; Alexandra V. Yurkovskaya ; Nikita Lukzen
• 刊名：The Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：August 22, 2013
• 年：2013
• 卷：117
• 期：33
• 页码：7655-7660
• 全文大小：275K
• 年卷期：v.117,no.33(August 22, 2013)
• ISSN：1520-5215

文摘

The photo-oxidation of the nucleobase, thymine (Thy), and nucleoside, thymidine (dThy), by dipyridyl (DP) has been investigated in aqueous solution using time-resolved laser flash photolysis. The pH dependence of the oxidation rate constants is measured within a large pH scale. As a consequence, the chemical reactivity of the reactants existing in solution at a certain range of pH is predicted. Bimolecular rate constants of the quenching reactions between triplet dipyridyl and thymine and thymidine are, respectively, k_q = 2.4 脳 10⁷ M^鈥? s^鈥? (pH < 5.8) and k_q = 1.0 脳 10⁷ M^鈥? s^鈥? (5.8 < pH < 9.8). Cyclic voltammetry was used to measure the potentials of thymine oxidation and dipyridyl reduction in water at pH < 7. Both results give hints for a proton coupled electron-transfer (PCET) reaction from thymine to triplet dipyridyl.