Simultaneous analysis of C-terminal amino acid residues of peptide mixtures by combination of field desorption mass spectrometry and carboxypeptidase digestion

Abstract

A novel method is described for the simultaneous analysis of C-terminal amino acid residues of peptide mixtures by combination of field desorption mass spectrometry and carboxypeptidase digestion. The method involves measurement of the mass values of quasi-molecular ions ([M+H]') of peptides and their digested fragments. The amino acid residues can he determined from the mass differences of the mass values observed in the field desorption mass spectra during digestion of peptides. As typical examples, the simultaneous determinations of the C-terminal amino acid residues of peptide mixtures prepared by tryptic digestion of P-endorphin and parathyroid peptide are described.

Fast atom bombardment and tandem mass spectrometry for sequencing peptides and polyamino alcohols

“…Two sets of mass-shifted ions are observed which indicate C'y and C'y - 17 fragment types, at m/z 351/334 and m/z 294/277. By subtracting the masses of N'y ions directly from the ( + H)+ at m/z 500, it can be seen that these ions correspond to subsequent losses of tyrosine and alanine from the N-terminus, which is suggestive of a sequence of Tyr-Ala-Gly-Phe-Leu.…”

“…The choice of a desorption technique depends on the strengths of the individual method and the type of information needed. For example, field desorption mass spectrometry (FD-MS) yields primarily molecular ion information and has been shown to be a good technique for the quantification of peptides at the nonogram level ( 14), Fragmentation information has been obtained by using collision activated dissociation (CAD) (15,16) and by submitting the sample to a digestion process (17). A static SIMS method (18) makes use of the excellent sensitivity observed for quaternary ammonium salt derivatives of small peptides to obtain sequence information with improved S/N.…”

Amino acid sequence of a heat‐stable enterotoxin isolated from enterotoxigenic Escherichia coli strain 18D

“…Some of us [8,9] recently developed a new method for sequence determination of peptide mixtures by a combination of field-desorption (FD) mass spectrometry and exopeptidase digestion. We used this method for determination of the sequence of ST,, but with FAB mass spectrometry instead of FD mass spectrometry [6,14].…”

“…However, strain 18D was found by the DNA hybridization technique to be a strain producing ST, (P. Echeverria, personal communication). Here, we describe the isolation of an ST (= ST,) from ETEC strain 18D and its sequence determination by Edman-degradation and a combination of fast atom bombardment (FAB) mass spectrometry and carboxypeptidase digestion [8,9].…”

Complete sequences of small acid‐soluble proteins from Bacillus globigii

“…22 An alternative to de novo sequencing via MS/MS analysis is the generation of a peptide ladder using carboxypeptidase enzymes, in which each segment of the ladder corresponds to an amino acid. 23,24 Finally, the expansion of genomic information and protein databases has allowed for proteins from non-sequenced organisms to be identified by inter-species homology. 25,26 Comparison of known sequences of homologous proteins from closely related organisms can also aid in sequencing of unknown proteins.…”