Abstract

Vicinal diols and its derivatives can be exploited as model compounds for the investigation of radiation-induced free-radical transformations of hydroxyl-containing biomolecules such as carbohydrates, phospholipids, ribonucleotides, amino acids, and peptides. In this paper, for the first time, the prospects of isotope reinforcement approach in inhibiting free-radical transformations of hydroxyl-containing compounds in aqueous solutions are investigated on the example of radiolysis of 1,2-propanediol and 1,2-propanediol-2-d₁ aqueous solutions. At an absorbed dose rate of 0.110 ± 0.003 Gy·s⁻¹ a profound kinetic isotope effect (KIE) is observed for the non-branched chain formation of acetone, which is a final dehydration product of predominant carbon-centred radicals CH₃·C(OH)CH₂OH. In 0.1 and 1 M deaerated solutions at pH 7.00 ± 0.01, the values of KIE are 8.9 ± 1.7 and 15.3 ± 3.1, respectively. A rationale for the fact that a strong KIE takes place only in the case of chain processes, which may occur during free-radical transformations of vicinal diols, is also provided herein based on the results of 2-propanol and 2-propanol-2-d₁ indirect radiolysis. Lastly, the lack of KIE is shown in the case of 2-butanone formation from 2,3-butanediol or 2,3-butanediol-2,3-d₂. This indicates that the type (primary, secondary) of the β-carbonyl radicals formed as a result of CH₃·C(OH)CH(OH)R (R = H, CH₃) dehydration determines the manifestation of the effect.

摘要

邻二醇及其衍生物可用作研究含羟基生物分子（如碳水化合物、磷脂、核糖核苷酸、氨基酸和肽）的辐射诱导的自由基转化的模型化合物。本文首次以1,2-丙二醇和1,2-丙二醇-2的辐解为例，探讨了同位素增强方法抑制水溶液中含羟基化合物自由基转化的前景。 -d ₁水溶液。在 0.110 ± 0.003 Gy·s ^-1的吸收剂量率下，对于丙酮的非支链形成观察到深刻的动力学同位素效应 (KIE)，丙酮是主要以碳为中心的自由基 CH ₃的最终脱水产物·C(OH)CH ₂ OH。在 pH 7.00 ± 0.01 的 0.1 和 1 M 脱气溶液中，KIE 值分别为 8.9 ± 1.7 和 15.3 ± 3.1。本文还基于 2-丙醇和 2-丙醇-2- d ₁间接辐射分解。最后，在由 2,3-丁二醇或 2,3-丁二醇-2,3-d ₂形成 2-丁酮的情况下显示了缺乏 KIE 。这表明作为CH ₃ ·C(OH)CH(OH)R (R = H, CH ₃ ) 脱水结果形成的β-羰基自由基的类型（初级、次级）决定了效果的表现。