CAN NITRIC-OXIDE BE SPIN TRAPPED BY NITRONE AND NITROSO-COMPOUNDS

Increasing interest in the study of nitric oxide (NO.) in many facets of biological research neccessitates a search for accurate techniques to directly identify the free radical. One recently employed strategy for NO. detection is the method of electron spin resonance (ESR) used in combination with nitrone and nitroso spin traps. Applying this tech nique to our studies with nitric oxide synthase (NOS), we found that N O. generated directly from the enzyme system could not be detected. Fu rther investigation revealed that 3,5-dibromo-4-nitrosobenzenesulfonic acid (DBNBS) inhibited NO. generation by NOS at concentrations used f or spin trapping. Reexamining the ability of various nitrones and DBNB S to spin trap authentic NO. dissolved in buffer, we obtained ESR spec tra similar to those previously reported for the spin trap DBNBS. Howe ver, continuing our studies with (NO)-N-15. and N-hydroxylamine, we fo und these spectra to be artifactual. Our results emphasize the need to synthesize new spin traps, since currently available compounds are no t capable of spin trapping NO. generated by NOS.