[18] Peptide characterization by mass spectrometry

Publisher Summary There are three distinct goals in peptide characterization: (l) confirmation of putative sequence, (2) identification and localization of amino acid modifications, and (3) sequence determination of unknown peptides. Owing to its speed, sensitivity, and versatility, mass spectrometry and more specifically tandem mass spectrometry, utilizing high- or low-energy collision-induced dissociation, plays a pivotal role in accomplishing each of these goals. Other widespread methods of peptide characterization, such as automated Edman degradation and amino acid analysis, are not discussed in this chapter; however, their absence here does not belittle their importance. Characterization of peptides, using mass spectrometric techniques, especially when coupled to high performance separations, can accomplish much. In particular, posttranslational modifications are readily identified and the modified amino acid residue(s) are pinpointed. Continuing efforts to improve sensitivity and spectral information, e.g., Fourier transform, time of flight, and ion trap mass spectrometers, should further open the field of peptide characterization to the low levels of peptides and proteins found in nature.