As such, bistyrosine production is a useful marker for protein
modification by hydroxyl radicals (Giulivi et al. 2003). As
a sulfydryl amino acid, Cys is also extremely sensitive to
free radicals. Reports have shown that the cysteine:cystine
ratio of proteins is altered under oxidizing conditions
(Kalyanaraman 1995). The occurrence of these types of
reactions would explain the decrease in the number of Phe
and Cys amino acids detected in our study (Figs. 5, 6).