REACTION OF ALPHA-HYDROXYALKYL RADICALS AND THEIR ANIONS WITH OXIDIZED DITHIOTHREITOL - A PULSE-RADIOLYSIS AND PRODUCT ANALYSIS STUDY
REACTION OF ALPHA-HYDROXYALKYL RADICALS AND THEIR ANIONS WITH OXIDIZED DITHIOTHREITOL - A PULSE-RADIOLYSIS AND PRODUCT ANALYSIS STUDY
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DOI：
10.1021/j100347a083
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发表时间：
1989-05-18
影响因子：
--
通讯作者：
VONSONNTAG, C
中科院分区：
文献类型：
--
作者：
AKHLAQ, MS;MURTHY, CP;VONSONNTAG, C
The reductionof the disulfide zrazii-4, 5-dihydroxy-l, 2-dithiane (oxidizeddithiothreitol, ox-DTT) by the radicals derived from methanol, ethanol, 2-propanol, and formate has been investigated by pulse radiolysis and steady-state “Co-radiolysis. By following pulse radiolytically the rate of formation of the disulfide radical anion, ox-DTT", in N20-saturated aqueous solutions of ox-DTT (5 X 10" 1 234 mol dm" 3) in the presence of an excess of the radical-forming substrate (eg, 0.5 mol dm'3 methanol) at different pH values, it was found that essentially only the anions of the-hydroxyalkyl radical reduce ox-DTT to ox-DTT"(eg,¿(* CH20")= 2.3 X 108 dm3 mol'1 s'1 at 25 C) while the neutral forms react with ox-DTT with rate constants< 106 dm3 mol'1 s'1. The temperature dependence of the rate of ox-DTT" formation by the radical anions has been measured. With all systems studied, Arrhenius plots are strongly curved which indicates that the redox process cannot be adequately described by a simple one-step mechanism. It is suggested that the alcohol radical anions react by reversible addition to form an adduct radical with ox-DTT followed by decomposition into ox-DTT" and carbonyl compounds (k 1.3 X 106 s'1 in the case of the 2-propanol radical anion, at 20 C). With “Co-radiolysis at pH 4 where the alcohol radical anions no longer play a role (eg, p. 8Ta (* CH2OH)= 10.7) reduction of ox-DTT also occurs. The estimated overall rate constant of the reaction of the-hydroxyalkyl radicals with ox-DTT is on the order of 105 dm3 mol'1 s'1.
