SEQUENCING OF PEPTIDES BY TANDEM MASS-SPECTROMETRY AND HIGH-ENERGY COLLISION-INDUCED DISSOCIATION

This chapter discusses sequencing of peptides by tandem mass spectrometry and high-energy collision-induced dissociation. To ionize large polar molecules, such as peptides of a size encountered in the study of various aspects of protein structure, methods are used that impart little excess energy on the molecule. Furthermore, most of these “soft” ionization techniques produce the charged particle by addition or removal of a proton to form the very stable, even-electron ions (M + H)+ or (M - H)-, that have little tendency to fragment. The first demonstration of the generation of large protonated peptides involved fast atom bombardment (FAB), but the data and methodology discussed in this chapter utilize either Xe ° or Cs+ as primary particles. Peptides derived from proteins are linear molecules (at least after reduction of any disulfide bridges originally present) that consist of repeating units having an identical backbone, –NH–CH(R)–CO–, but differing in the nature of the side chain, R. There are only 20 different amino acids that occur in proteins (and are defined by the genetic code), in addition to the occasional occurrence of others formed by posttranslational processes. © 1990, Elsevier Inc. All rights reserved.