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Epimerization in peptide thioester condensation.

Authors
  • Teruya, Kenta
  • Tanaka, Takeyuki
  • Kawakami, Toru
  • Akaji, Kenichi
  • Aimoto, Saburo
Type
Published Article
Journal
Journal of Peptide Science
Publisher
Wiley (John Wiley & Sons)
Publication Date
Nov 01, 2012
Volume
18
Issue
11
Pages
669–677
Identifiers
DOI: 10.1002/psc.2452
PMID: 22972773
Source
Medline
License
Unknown

Abstract

Peptide segment couplings are now widely utilized in protein chemical synthesis. One of the key structures for the strategy is the peptide thioester. Peptide thioester condensation, in which a C-terminal peptide thioester is selectively activated by silver ions then condensed with an amino component, is a powerful tool. But the amino acid adjacent to the thioester is at risk of epimerization. During the preparation of peptide thioesters by the Boc solid-phase method, no substantial epimerization of the C-terminal amino acid was detected. Epimerization was, however, observed during a thioester-thiol exchange reaction and segment condensation in DMSO in the presence of a base. In contrast, thioester-thiol exchange reactions in aqueous solutions gave no epimerization. The epimerization during segment condensation was significantly suppressed with a less polar solvent that is applicable to segments in thioester peptide condensation. These results were applied to a longer peptide thioester condensation. The epimer content of the coupling product of 89 residues was reduced from 27% to 6% in a condensation between segments of 45 and 44 residues for the thioester and the amino component, respectively.

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