Difficulties encountered in the detection of nitric oxide (NO) by spin trapping techniques. A cautionary note

The spin trapping technique was used in an attempt to detect the free radical nitric oxide (NO) in solution. Five different spin traps were examined, alpha-phenyl-N-tert butyl nitrone (PBN), alpha-(4-pyridyl-N-oxide) N-tert-butylnitrone (POBN), 5,5-dimethyl-pyrroline-N-oxide (DMPO), 2-methyl-2-nitrosopropane (MNP) and 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS). Our results suggest that the nitroso spin traps (MNP, DBNBS) are better suited for the identification of NO-related signals, than the nitrones, DMPO, PBN and POBN. In addition, it is shown that spin trapping of NO-related signals with nitroso and nitrone spin traps is subject to many artifacts.