Figure 1.
Nitration of tyrosine can occur via peroxynitrite or other nitrosative agents. Tyrosine nitration reduces the pKa of the phenol to approximately 7.1,5 Thus, at physiological pH, nitrotyrosine exists in two forms: a neutral form (left) which is more hydrophobic than tyrosine1 due to internal phenol hydrogen bonding; and a significantly more polar anionic form (right). The presence of anionic nitrotyrosine is readily identified via its absorbance of visible light and its yellow color in solution.