Detection of nitroxyl (HNO) by a prefluorescent probe

Recent research has shown that nitroxyl (HNO) has important and unique biological activity, especially as a potential alternative to current treatments of cardiac failure. HNO is a reactive molecule that spontaneously dimerizes and subsequently dehydrates to form nitrous oxide (N2O), making its detection in solution or biologically relevant preparations difficult. The prefluorescent probe 4-((9-acridinecarbonyl)amino)-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO-9-AC) has been used to detect HNO in aqueous solution and to differentiate it from nitric oxide (NO). TEMPO-9-AC reacts with HNO via a net hydrogen abstraction to produce the highly fluorescent TEMPO-9-AC-H and NO. The utility of TEMPO-9-AC as a probe for HNO has been shown using the common HNO donors Angeli's salt and Piloty's acid (PA) along with a recently reported HNO donor, 2-bromo-PA. The use of TEMPO-9-AC is complicated by intermolecular fluorescence quenching and competitive HNO trapping by the NO produced, but nonetheless, it can be used to study HNO reactivity in aqueous solution. Copyright (C) 2011 John Wiley & Sons, Ltd.