Fluorescence imaging of ABS-tagged proteins after SDS-PAGE separation Line 1: molecular weight standard (Precision Plus Dual Color, Bio-Rad); line 2: 5 μg rabbit phosphorylase b (containing 50 pmol 3-NT), non-derivatized; line 3: same protein, exposed to ABS without 3-NT reduction; line 4: same protein, 3-NT reduced and ABS-tagged; line 5: lysate of C2C12 cells exposed to peroxynitrite (50 μg protein containing 500 pmol 3-NT), after 3-NT reduction and ABS-tagging; line 6: same preparation, non-reduced, ABS tagged; line 7: same preparation, non-reduced and non-tagged control