Peptides ladder sequences

Top) peptide ladder sequencing principle. Phenyl isothiocyanate (PITC) produces phenylthiohydantoin (PTH) of the terminal amino acid and a new peptide with one less amino acid. Phenyl isocyanate (PIC), in low quantity, produces N-terminal phenylcarba-mate (PC) from a small fraction of each peptide. (Bottom) example of sequencing of [Glu1]fibrinopeptide B. Reproduced (modified) from Chait B.T., Wang R., Beavis R.C. and Kent S.B.H., Science, 262, 89, 1993, with permission. 

The following ion-activation techniques have been used at one time or other to sequence peptides (1) fast atom bombardment (FAB) ionization, (2) CID—tandem MS (MS/MS), (3) ESI in-source CID, (4) MALDI ion-source decay, (5) MALDI postsource decay (PSD), (6) electron-capture dissociation (ECD) and electron-transfer dissociation, and (7) peptide ladder sequencing. Because of the lack of space, only (2) and (4) will be discussed further. 

The de novo method of sequencing that uses enzymes to digest the terminal amino acids from a peptide is called peptide ladder sequencing. In this technique, an enzyme such as carboxypetidase-Y is used to digest one amino acid at a time from the C-terminus. No additional fragment peaks are formed. This method, unlike the MS-MS de novo technique, requires that the peptide be pure. In addition to the need for a pure peptide, another drawback of this technique is the somewhat lengthy sample preparation. The major advantage of this technique is the ease with which the mass spectrum can be interpreted and the partial sequence determined. 

Bartlet-Jones, M., et al. (1994). Peptide Ladder Sequencing by Mass Spectrometry Using a Novel, Volatile Degradation Reagent, Rapid Communications, in Mass Spectrometry 8 737—742. 

Peptide Ladder Sequencing (Following Bartlet-Jones Et Al.)... 

The sequence of an unknown peptide was determined with the peptide ladder sequencing technique. After treatment with an aminopaptidase and... 

Peptide Ladder Sequencing The treatment of a glycopeptide with a carboxypeptidase or aminopeptidase to generate peptide ladders, followed by MALDI-MS analysis of those ladders, is another feasible approach to identifying the site of glycosylation. This approach may not be effective with multiglycosylation sites because the enzymatic activity of these proteases is impaired at or near the site of glycosylation [84]. 

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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