A Better Route To Peroxynitrite

Inorganic chemists at the Swiss Federal Institute of Technology, in Zurich, have devised a simple method for making high-purity aqueous solutions of peroxynitrite, O=N–O–O^???, a key reagent used in cell-signaling and toxicology studies (Chem. Res. Toxicol., DOI: 10.1021/tx800279n). Peroxynitrite is formed in vivo from superoxide and nitric oxide radicals. As a natural oxidizing and nitrating agent, it is a mediator of cell signaling, but at high concentrations, it can be toxic to cells. A handful of synthetic methods exist for making peroxynitrite to use in lab studies, but in all cases the product ends up contaminated with an impurity, such as nitrate or peroxide. The tetramethylammonium salt (CH₃)₄N[ONOO] is commercially available at the needed purity, but the ammonium cation can interrupt cell membrane processes, which precludes its use in most cellular studies. ETH Zurich's Willem H. Koppenol and coworkers came up with a way around these synthesis problems: They made LiONOO and NaONOO, stabilized in LiOH and NaOH, respectively, by passing a solution of (CH₃)₄N[ONOO] through a cation-exchange chromatography column.