C-terminal sequence determination of modified peptides by MALDI MS

Valentina Bonetto, Ann Charlotte Bergman, Hans Jörnvall, Rannar Sillard

Research output: Contribution to journalArticlepeer-review


Peptides, cleaved by a mixture of carboxypeptidases CPP and CPY, can be detected by MALDI MS and the amino acid sequence thereby determined by calculation of the differences between consecutive peaks. In the present study we have used derivatizations of Lys and Cys to facilitate identification of these residues. Since the mass values do not readily distinguish Lys from Gin, we have converted Lys to homoarginine by guanidination, allowing simple detection of Lys. To identify the Cys positions in peptides that contain cystine, cysteic acid, or carboxymethylcysteine is not possible using CPY and CPP because of the lack of proteolytic cleavage. Instead we find that identification of Cys residues within the sequence can be achieved after conversion to a basic derivative, 4-thialaminine (Thi), by trimethylaminoethylation.

Original languageEnglish
Pages (from-to)371-374
Number of pages4
JournalProtein Journal
Issue number5
Publication statusPublished - 1997


  • 4-thialaminine
  • Carboxypeptidases
  • Chemical modification
  • Homoarginine
  • MALDI mass spectrometry

ASJC Scopus subject areas

  • Biochemistry
  • Analytical Chemistry
  • Organic Chemistry
  • Bioengineering


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