Shi, W-Q., Dong, J-C., Zhao, Y-F. and Li, Y-M. Hydroxylation of 3-Nitrotyrosine and Its Derivatives by Gamma Irradiation. Radiat. Res. 166, 639–645 (2006).

Radiation-induced hydroxylation of 3-nitrotyrosine (3-NY) and its derivatives in aqueous solution were investigated as a function of γ-radiation dose. Irradiated 3-NY, 3-nitrotyrosine ethyl ester (3-NYE) and 3-NY containing peptide Gly-nitroTyr-Gly were separated and analyzed with reverse-phase HPLC and UV-Vis absorption spectroscopy. The structures of the hydroxylated products were confirmed by electrospray ionization mass spectrometry and ¹H-NMR spectrometry. The amounts of the hydroxylated products in irradiated 3-NY and Gly-nitroTyr-Gly solutions increased with increasing radiation dose. Tandem electrospray ionization mass spectrometry (ESI-Mass²) was performed to investigate the hydroxylation of peptide Gly-nitroTyr-Gly. These studies showed that the hydroxylation occurred at 3-NY residue. We also found that the identification of 3-NY hydroxylation in peptide could be identified by ion scanning for the specific immonium ion at m/z 197.0.