Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign , 205 North Mathews Avenue, Urbana, Illinois 61801, United States.
Environ Sci Technol. 2017 Jun 6;51(11):6507-6514. doi: 10.1021/acs.est.7b01272. Epub 2017 May 18.
We measured the rate of generation of reactive oxygen species (ROS) [hydroxyl radicals (OH) and hydrogen peroxide (HO)] catalyzed by ambient particulate matter (PM) in the dithiothreitol (DTT) assay. To understand the mechanism of ROS generation, we tested several redox-active substances, such as 9,10-phenanthrenequinone (PQ), 5-hydroxy-1,4-naphthoquinone (5H-1,4NQ), 1,2-naphthoquinone (1,2-NQ), 1,4-naphthoquinone (1,4-NQ), copper(II), manganese(II), and iron (II and III). Both pure compounds and their mixtures show different patterns in DTT oxidation versus ROS generation. The quinones, known to oxidize DTT in the efficiency order of PQ > 5H-1,4NQ > 1,2-NQ > 1,4-NQ, show a different efficiency order (5H-1,4NQ > 1,2-NQ ≈ PQ > 1,4-NQ) in the ROS generation. Cu(II), a dominant metal in DTT oxidation, contributes almost negligibly to the ROS generation. Fe is mostly inactive in DTT oxidation, but shows synergistic effect in OH formation in the presence of other quinones (mixture/sum > 1.5). Ten ambient PM samples collected from an urban site were analyzed, and although DTT oxidation was significantly correlated with HO generation (Pearson's r = 0.91), no correlation was observed between DTT oxidation and OH formation. Our results show that measuring both DTT consumption and ROS generation in the DTT assay is important to incorporate the synergistic contribution from different aerosol components and to provide a more inclusive picture of the ROS activity of ambient PM.
我们测量了环境颗粒物（PM）在二硫苏糖醇（DTT）测定中催化产生的活性氧物种（ROS）[羟基自由基（OH）和过氧化氢（HO）]的生成速率。为了了解 ROS 生成的机制，我们测试了几种氧化还原活性物质，如 9,10-菲醌（PQ）、5-羟基-1,4-萘醌（5H-1,4NQ）、1,2-萘醌（1,2-NQ）、1,4-萘醌（1,4-NQ）、铜（II）、锰（II）和铁（II 和 III）。纯化合物及其混合物在 DTT 氧化与 ROS 生成的关系中表现出不同的模式。醌类物质已知以 PQ > 5H-1,4NQ > 1,2-NQ > 1,4-NQ 的效率顺序氧化 DTT，在 ROS 生成中表现出不同的效率顺序（5H-1,4NQ > 1,2-NQ ≈ PQ > 1,4-NQ）。Cu（II）是 DTT 氧化中的主要金属，对 ROS 生成的贡献几乎可以忽略不计。Fe 在 DTT 氧化中大多不活跃，但在存在其他醌类物质时（混合物/总和> 1.5），对 OH 形成具有协同作用。从城市地区采集的 10 个环境 PM 样本进行了分析，尽管 DTT 氧化与 HO 生成呈显著相关（Pearson's r = 0.91），但在 DTT 氧化与 OH 形成之间未观察到相关性。我们的结果表明，在 DTT 测定中同时测量 DTT 消耗和 ROS 生成对于纳入不同气溶胶成分的协同贡献以及提供环境 PM 的 ROS 活性的更全面的图像非常重要。
