Figure 6.

Workflow to assess protein amino acid composition and their associated modifications. Proteins isolated and purified before digestion or hydrolysis to their constituent amino acids. Free amino acids and/or related oxidation products are then separated by LC. For some applications, pre-column or post-column derivatization of the amino acids and related products is required before separation to enable detection and quantification using one or more detection methods, which typically include MS, fluorescence, UV or visible absorption, or electrochemical (EC) detection. Abbreviations used are as follows: MSA, methane sulfonic acid; NFK, N-formylkynurenine.