Ladder sequencing truncated peptides

Analysis of the mixture using matrix-assisted desorption ionization mass spectrometry (section 5.3) allows for direct sequence determination from the snccessive mass differences of the peptide ladder. The application of the volatile trifluoroethyl isothiocyanate results in a significant optimization of this procedure and allows for peptide sequencing at the femtomole level (Bartlet-Jones et al., 1994). C-terminal ladder sequencing uses ammonium thiocyanate in acetic anhydride coupled with mass spectrometric analysis of truncated peptides (Thiede et al, 1997). Matrix-assisted desorption ionization instruments with delayed extraction (Brown and Leimon, 1995) allow for the discrimination of aU amino acids, except Leu and He. 

Ladder Sequencing. Because plasma desorption mass spectra commonly reveal only molecular ions, it has become common to obtain amino acid sequences using carboxy or amino-peptidases to generate a mixture of truncated peptides whose mass differences correspond to the amino acid residues. One example of this is shown in Figure 4.15, in which bradykinin has been digested directly on the nitrocellulose foil with carboxypeptidase... 

The ability of FAB mass spectra to deliver peptide sequence information was soon recognized [15,130]. Initially, the sequence was derived from fragment ions observed in the full scan spectra [15,96]. Another approach to sequence information is to subject the peptide to enzymatic hydrolysis by a mixture of several carboxy-peptidases to produce a series of truncated molecules. The FAB spectrum of the mixture then reveals the C-terminal sequence [131,132]. In the MALDI community, this approach became known as peptide ladder sequencing [133]. 

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