This molecule 指什么？

Nitric oxide may behave as a ROS by reacting with the superoxide anion to produce peroxynitrite (ONOO-). This molecule can either rearrange itself into relatively harmless nitrite or nitrate (page 148) or give rise to derivatives with similar biological activity to the hydroxyl radical. Conversely, nitric oxide may act as an antioxidant, binding to ferrous iron molecules and preventing them from contributing to the formation of a superoxide anion (see next) or the Fenton reaction. The in vivo role of nitric oxide as a ROS or antioxidant therefore remains unclear.3

通过与超氧阴离子反应生成过氧亚硝酸根（ONOO^-），一氧化氮可类似ROS。过氧亚硝酸根（ONOO-）可将自身重新排列成相对无害的亚硝酸盐或硝酸盐（第148页），或者产生与羟基自由基具有类似生物活性的衍生物。相反，一氧化氮可以起到抗氧化剂的作用，与亚铁分子结合，防止它们促使超氧阴离子形成（见下文）或芬顿反应发生。但一氧化氮作为ROS或抗氧化剂在体内的作用尚不清楚³。

This molecule 指什么？本来以为指一氧化氮，可下面说“相反，一氧化氮”，那就是过氧亚硝酸根（ONOO-）？可过氧亚硝酸根（ONOO-）不是“分子”是“离子”，难道翻译成“微粒”？谢谢