A spin-labeling fluorophore(NA-TEMPO.), formed by labeling a-naphthalene with a paramagnetic nitroxide (4-hydroxyl-2, 2, 6, 6-tetramethylpiperidinyl-1-oxy), was explored for biologically relevant carbon-centered radicals. The horseradish peroxidase (HPR)/H2O2 reaction was used to generate radicals in derivatives of tyrosine and phenylalanine, and the Fenton reaction was used to generate radicals in deoxyguanosine, guanosine, bovine serum albumin (BSA) and DNA. TEMPO.-NA, a weak fluorescent compound, showed a dramatic increase in fluorescence intensity after scavenging carbon-centered radicals. The spin-labeling fluorophore with dual function groups, the radical recognizing group and fluorescent group, would be significantly useful in monitoring the formation and translocation of carbon-centered radicals in complex biological systems
