Characterization of isomeric acetyl amino acids and di ‐acetyl amino acids by LC/MS/MS

In this study, it is aimed to synthesize and characterize all acetylated p roducts of natural α-amino acids. A total of 20 Nα-acetyl amino acids (1–20), six side-chain acetyl amino acids (21–26), and six diacetyl amino acids (27–32) were synthesized and characterized by liquid chromatography-electrospray ionizationtandem mass spectrometry (LC –ESI–MS/MS). The [M + H]+ ions of all the acetyl amino acids were subjected to MS/MS experiments to obtain their structural information. Apart from the expected loss of (H2O  + CO) (immonium ions), most of the acetyl amino acids specifically showed loss of H2O and loss of a ketene (C2H2O) from [M+H]+ ions. The side-chain acetyl amino acids showed a clear-cut structure specific fragment ions that enabled easy differentiation from their isomeric Nα-acetyl amino acids. The other isomeric/isobaric acetyl amino acids could also be easily distinguished by their MS/MS spectra. The MS/MS of immonium ions of the acetyl amino acids were also studied, and they included characteristic products reflecting the structures of parent Nα-acetyl and side-chain acetyl amino acids.
Source: Journal of Mass Spectrometry - Category: Chemistry Authors: Tags: RESEARCH ARTICLE Source Type: research