Wolcott R G, Franks B S, Hannum D M, Hurst J K
Department of Chemistry, Biochemistry, and Molecular Biology, Oregon Graduate Institute of Science and Technology, Portland 97291-1000.
J Biol Chem. 1994 Apr 1;269(13):9721-8.
Rates of radiolytic inactivation of bacteria suspended in N2O-saturated solutions were dramatically increased over normal background levels when the media contained chloride or bicarbonate ions. The bacteria could be protected from this enhanced toxicity by the addition of free radical scavengers (ethanol, ascorbate, hydrogen peroxide, mannitol, glucose, EDTA, picolinic acid), indicating that the lethal reactions were extracellular in origin. Prior irradiation of chloride-containing solutions led to formation of hypochlorous acid, which was identified by detection of ring-chlorinated products when reacted with fluorescein. Prolonged irradiation of other solutions did not lead to accumulation of bactericidal agents; however, irradiation of bicarbonate-containing solutions in the presence of the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) led to formation of the EPR-detectable DMPO.CO3- adduct. The results are interpreted in terms of formation of secondary radicals, among which the carbonate and chlorine radicals are uniquely toxic to bacteria. From rate comparisons of the solution components, it was concluded that the reactions involving chloride ion are unlikely to be expressed in biological environments, but that the CO3- radical could be an important intermediary oxidant in peroxide-inflicted cellular damage, particularly in spatially confined environments such as the leukocyte phagosome.
当介质中含有氯离子或碳酸氢根离子时，悬浮于一氧化二氮饱和溶液中的细菌的辐射分解失活速率比正常本底水平显著增加。通过添加自由基清除剂（乙醇、抗坏血酸盐、过氧化氢、甘露醇、葡萄糖、乙二胺四乙酸、吡啶甲酸），可保护细菌免受这种增强的毒性影响，这表明致死反应源于细胞外。预先照射含氯溶液会导致次氯酸的形成，当与荧光素反应时，通过检测环氯化产物可鉴定出次氯酸。对其他溶液进行长时间照射不会导致杀菌剂的积累；然而，在自旋捕获剂5,5 - 二甲基 - 1 - 吡咯啉N - 氧化物（DMPO）存在下照射含碳酸氢根的溶液会导致形成可通过电子顺磁共振检测到的DMPO·CO3-加合物。这些结果可根据次级自由基的形成来解释，其中碳酸根和氯自由基对细菌具有独特的毒性。通过对溶液成分的速率比较得出结论，涉及氯离子的反应在生物环境中不太可能发生，但碳酸根自由基可能是过氧化物导致细胞损伤的重要中间氧化剂，特别是在诸如白细胞吞噬体等空间受限的环境中。
