Acidity enhances the formation of a persistent ozonide at aqueous ascorbate/ozone gas interfaces
Acidity enhances the formation of a persistent ozonide at aqueous ascorbate/ozone gas interfaces
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DOI：
10.1073/pnas.0710791105
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发表时间：
2008-05-27
影响因子：
11.1
通讯作者：
Colussi, A. J.
中科院分区：
文献类型：
--
作者：
Enami, Shinichi;Hoffmann, M. R.;Colussi, A. J.
与大多数空气生物表面一样，肺上皮细胞通过含有抗坏血酸（AH（2））和相关清除剂的流体膜天然保护免受大气臭氧（O-3）的影响。然而，如果特定的共污染物改变AH（2）和O-3（g）的方向，产生能够阻止氧化损伤底层组织的物质，这种保护机制就会失效。在这里，通过暴露于O-3（g）的AH（2）水液滴的电喷雾质谱法研究了流行病学研究揭示的大气O-3（g）和酸性颗粒物的协同不利健康影响可能是由迄今未识别的物种介导的可能性。AH（2）臭氧分解在相关的空气-水界面的产品从无害的脱氢抗坏血酸在生物pH值的C-4-羟基酸加上以前未报道的抗坏血酸臭氧化物（m/z = 223）低于pH值接近5。这种臭氧化物的结构被确认，通过串联质谱和动力学研究描绘其形成机制。目前的研究结果表明，在预先存在的病理或吸入的颗粒物酸化的气道衬里流体中，持久性臭氧化物的产量增加。已知臭氧类化合物在体内产生细胞毒性自由基，因此可以抑制氧化损伤。
The pulmonary epithelium, like most aerial biosurfaces, is naturally protected against atmospheric ozone (O-3) by fluid films that contain ascorbic acid (AH(2)) and related scavengers. This mechanism of protection will fail, however, if specific copollutants redirect AH(2) and O-3(g) to produce species that can transduce oxidative damage to underlying tissues. Here, the possibility that the synergistic adverse health effects of atmospheric O-3(g) and acidic particulate matter revealed by epidemiological studies could be mediated by hitherto unidentified species is investigated by electrospray mass spectrometry of aqueous AH(2) droplets exposed to O-3(g). The products of AH(2) ozonolysis at the relevant air-water interface shift from the innocuous dehydroascorbic acid at biological pH to a C-4-hydroxy acid plus a previously unreported ascorbate ozonide (m/z = 223) below pH approximate to 5. The structure of this ozonide is confirmed,by tandem mass spectrometry and its mechanism of formation delineated by kinetic studies. Present results imply enhanced production of a persistent ozonide in airway-lining fluids acidified by preexisting pathologies or inhaled particulate matter. Ozonides are known to generate cytotoxic free radicals in vivo and can, therefore, transduce oxidative damage.