New experimental evidence for in-chain amino acid racemization of serine in a model peptide

Beatrice Demarchi*, Matthew Collins, Ed Bergström, Adam Dowle, Kirsty Penkman, Jane Thomas-Oates, Julie Wilson

*Corresponding author for this work

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The facile racemization of protein-bound amino acids plays an important role in the aging and pathologies of living tissues, and it can be exploited for protein geochronological studies in subfossil biominerals. However, the in-chain degradation pathways of amino acids are complex and difficult to elucidate. Serine has proven to be particularly elusive, and its ability to racemize as a peptide-bound residue (like asparagine and aspartic acid) has not been demonstrated. This study investigates the patterns of degradation of a model peptide (WNSVWAW) at elevated temperatures, quantifying the extent of racemization and peptide bond hydrolysis using reverse-phase high-performance liquid chromatography (RP-HPLC) and tracking the presence of degradation products by MALDI-MS. We provide direct evidence that, under these experimental conditions, both serine and asparagine are able to undergo racemization as internally bound residues, which shows their potential for initiating protein breakdown and provides an explanation for the presence of d-enantiomers in living mammalian tissues. © 2013 American Chemical Society.

Original languageEnglish
Pages (from-to)5835-5842
Number of pages8
JournalAnalytical Chemistry
Issue number12
Publication statusPublished - 18 Jun 2013

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