The formation of highly concentrated hydrogen peroxide (H₂O₂) clusters (localized circumstance) in an aqueous solution during X-ray irradiation was demonstrated. The relationship between H₂O₂ concentration and hydrogen donor-independent reduction of nitroxyl radicals was examined. The method to measure the distance between the clusters (localized circumstance) was assessed by comparing the simulation and the experimental results. Reaction mixtures containing a nitroxyl redox probe, 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL) and 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl (CmP) at 0.1 mM were prepared containing several different concentrations (1.0 mM‒9.8 M) of H₂O₂. The reaction mixture was irradiated by 12000 μW/cm² UVB for 2 min, and reduction of the electron paramagnetic resonance (EPR) signal of the nitroxyl radicals was measured. An aliquot (2 µL) of 200 mM K₃[Fe(CN)₆] or FeCl₃ solution was added to 200 µL of the reaction mixture, and the time course of the EPR signal of the nitroxyl radicals was measured. To estimate the distance between the H₂O₂ clusters, a series of nitroxyl radical solutions with several different concentrations (0.06 μM‒2.28 mM) was irradiated with X-rays, and the degree of reduction of nitroxyl radicals in each sample was measured. UVB, K₃[Fe(CN)₆], or FeCl₃-induced EPR signal loss of the nitroxyl radicals was observed with H₂O₂ concentrations greater than 10 mM or 100 mM, respectively. The EPR signal loss of nitroxyl radicals, TEMPOL or CmP, may occur in highly concentrated H₂O₂ circumstances after oxidative stimulation. Plotting the X-ray-induced reduction of nitroxyl radicals versus their density revealed the high-concentration H₂O₂ clusters to be separated by 40‒47 nm. Ionizing irradiation of an aqueous solution creates a localized highly concentrated H₂O₂ environment.

证实了在X射线照射期间在水溶液中形成高浓度过氧化氢（H ₂ O ₂）团簇（局部环境）。研究了H ₂ O ₂浓度与不依赖氢供体的硝基氧基自由基还原之间的关系。通过比较仿真结果和实验结果，评估了测量簇之间距离的方法（局部情况）。包含硝氧基氧化还原探针，4-羟基-2,2,6,6-四甲基哌啶-N-氧基（TEMPOL）和3-氨基甲酰基-2,2,5,5-四甲基吡咯烷-N-氧基（CmP）的反应混合物制备了0.1 mM的氢气，其中包含几种不同浓度（1.0 mM‒9.8 M）的H₂ O ₂。用12000μW/ cm ^2的UVB照射反应混合物2分钟，并测量了硝酰基自由基的电子顺磁共振（EPR）信号的降低。将200 mM K ₃ [Fe（CN）₆ ]或FeCl ₃溶液的等分试样（2 µL）添加到200 µL反应混合物中，并测量硝酰基自由基的EPR信号的时间过程。为了估计H ₂ O ₂簇之间的距离，用X射线照射一系列具有几种不同浓度（0.06 μM‒2.28 mM）的硝酰自由基溶液，并测量每个样品中硝酰自由基的还原程度。UVB，K ₃ [Fe（CN）参见图₆ ]，或在H ₂ O ₂浓度分别大于10 mM或100 mM时观察到FeCl ₃诱导的硝基氧基自由基的EPR信号损失。氧化刺激后，在高浓度H ₂ O _2的情况下，可能会发生硝基氧基TEMPOL或CmP的EPR信号丢失。绘制X射线诱导的硝基氧基自由基还原与其密度的关系图，结果表明高浓度的H ₂ O ₂簇被隔开40‒47 nm。水溶液的电离辐射产生局部高浓度的H ₂ O ₂环境。