Abstract
An electrospray ionization ion trap/time-of-flight mass spectrometer was evaluated as a detector for identification of phenylthiohydantoin (PTH)-amino acids, the final products in the Edman sequencing process of peptides and proteins. Each of 22 PTH-amino acids studied can be characterized by well-defined mass spectral patterns. Fragmentation from source excitation followed by a long trapping period (250 ms) gave rise to unique and intense fragmentation products. This allowed for the differentiation of isomers of PTH-leucine/PTH-isoleucine and PTH-α–aminobutyric acid/PTH-α–aminoisobutyric acid. The interpretation of the fragmentation patterns is presented. The detection limits and relative detection sensitivity of 20 standard PTH-amino acids were determined. It is shown that all these compounds can be detected at the 100 fmol level.
Published Version
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