Oxidation of Purine Nucleotides by Triplet 3,3鈥?4,4鈥?Benzophenone Tetracarboxylic Acid in Aqueous Solution: pH-Dependence

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• 作者：Natalya N. Saprygina ; Olga B. Morozova ; Tatyana V. Abramova ; G眉nter Grampp ; Alexandra V. Yurkovskaya
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：July 10, 2014
• 年：2014
• 卷：118
• 期：27
• 页码：4966-4974
• 全文大小：376K
• ISSN：1520-5215

文摘

The photo-oxidation of purine nucleotides adenosine-5鈥?monophosphate (AMP) and guanosine-5鈥?monophosphate (GMP) by 3,3鈥?4,4鈥?benzophenone tetracarboxylic acid (TCBP) has been investigated in aqueous solutions using nanosecond laser flash photolysis (LFP) and time-resolved chemically induced dynamic nuclear polarization (CIDNP). The pH dependences of quenching rate constants and of geminate polarization are measured within a wide range of pH values. As a result, the chemical reactivity of reacting species in different protonation states is determined. In acidic solution (pH < 4.9), the quenching rate constant is close to the diffusion-controlled limit: kb>qb> = 1.3 脳 10⁹ M^鈥? s^鈥? (GMP), and kb>qb> = 1.2 脳 10⁹ M^鈥? s^鈥? (AMP), whereas in neutral and basic solutions it is significantly lower: kb>qb> = 2.6 脳 10⁸ M^鈥? s^鈥? (GMP, 4.9 < pH < 9.4), kb>qb> = 3.5 脳 10⁷ M^鈥? s^鈥? (GMP, pH > 9.4), kb>qb> = 1.0 脳 10⁸ M^鈥? s^鈥? (AMP, pH > 6.5). Surprisingly, the strong influence of the protonation state of the phosphoric group on the oxidation of adenosine-5鈥?monophosphate is revealed: the deprotonation of the AMP phosphoric group (6.5) decreases the quenching rate constant from 5.0 脳 10⁸ M^鈥? s^鈥? (4.9 < pH < 6.5) to 1.0 脳 10⁸ M^鈥? s^鈥? (pH > 6.5).