Spin trapping the cysteine thiyl radical with phenyl-N-t-butylnitrone

The cysteine thiyl radical has been detected in a variety of biological systems by means of the ESR spectrum of the adduct between the radical and nitrone spin traps. 5,5-Dimethyl-1-pyroline N-oxide (DMPO) is the spin trap of choice in these studies for several reasons. However, we show here that the adduct between the cysteine thiyl radical and phenyl-N-t-butylnitrone (PBN) spin trap can be observed under certain oxidizing conditions where the adduct with DMPO is not detected. This suggests the use of PBN in searching for the thiyl radical under such conditions.