Release of free amino acids upon oxidation of peptides and proteins by hydroxyl radicals

Fobang Liu, Senchao Lai, Haijie Tong, Pascale S.J. Lakey, Manabu Shiraiwa, Michael G. Weller, Ulrich Pöschl, Christopher J. Kampf

Research output: Journal article publicationJournal articleAcademic researchpeer-review

49 Citations (Scopus)


Hydroxyl radical-induced oxidation of proteins and peptides can lead to the cleavage of the peptide, leading to a release of fragments. Here, we used high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) and pre-column online ortho-phthalaldehyde (OPA) derivatization-based amino acid analysis by HPLC with diode array detection and fluorescence detection to identify and quantify free amino acids released upon oxidation of proteins and peptides by hydroxyl radicals. Bovine serum albumin (BSA), ovalbumin (OVA) as model proteins, and synthetic tripeptides (comprised of varying compositions of the amino acids Gly, Ala, Ser, and Met) were used for reactions with hydroxyl radicals, which were generated by the Fenton reaction of iron ions and hydrogen peroxide. The molar yields of free glycine, aspartic acid, asparagine, and alanine per peptide or protein varied between 4 and 55%. For protein oxidation reactions, the molar yields of Gly (∼32–55% for BSA, ∼10–21% for OVA) were substantially higher than those for the other identified amino acids (∼5–12% for BSA, ∼4–6% for OVA). Upon oxidation of tripeptides with Gly in C-terminal, mid-chain, or N-terminal positions, Gly was preferentially released when it was located at the C-terminal site. Overall, we observe evidence for a site-selective formation of free amino acids in the OH radical-induced oxidation of peptides and proteins, which may be due to a reaction pathway involving nitrogen-centered radicals.

Original languageEnglish
Pages (from-to)2411-2420
Number of pages10
JournalAnalytical and Bioanalytical Chemistry
Issue number9
Publication statusPublished - Mar 2017
Externally publishedYes


  • Amino acid analysis
  • Hydroxyl radicals
  • Oxidation
  • Peptides
  • Proteins

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry


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