Peptide nitrile ligation enables thioester-free chemical protein synthesis
- 1Department of Chemistry
- 2Emory University
Abstract
Native chemical ligation has transformed chemical protein synthesis, yet its reliance on C-terminal peptide thioesters suffers from precursor preparation, stability and multisegment assembly. Here we report peptide nitrile ligation (PNL), a thioester-free ligation in which a stable C-terminal peptide nitrile is chemoselectively captured by an N-terminal cysteine and converted through a thiazoline intermediate into a native Xaa-Cys amide bond. Peptide nitriles are generated directly and chemoselectively from the C-terminal amides obtained using conventional Rink-amide Fmoc solid-phase peptide synthesis. PNL proceeds in aqueous buffer at pH 7.5 without an exogenous thiol catalyst, a thioester intermediate or detectable epimerization at the ligation junction. Notably, PNL enables efficient ligation at C-terminal proline junctions, a longstanding challenge in thioester-based ligation, without specialized building blocks or additional synthetic steps. The reaction tolerates internal cysteine thiols and Asn- or Gln-derived side-chain nitriles, with the latter subsequently restored to their native amides. On-demand conversion of C-terminal amide into a new nitrile enables iterative three-segment assembly. PNL therefore establishes C-terminal nitriles as stable, programmable acyl donors for thioester-free multisegment peptide ligation.
Related
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BibTeX
@misc{le2026peptide,
title = {{Peptide nitrile ligation enables thioester-free chemical protein synthesis}},
author = {Bao Quang Gia Le and Adrija Majumdar and Abhisek Kar and Shyla Singal and Anvi Anand and Monika Raj},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15011000/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15011000/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Peptide nitrile ligation enables thioester-free chemical protein synthesis
AU - Bao Quang Gia Le
AU - Adrija Majumdar
AU - Abhisek Kar
AU - Shyla Singal
AU - Anvi Anand
AU - Monika Raj
PY - 2026
DA - 2026/10/25
PB - ChemRxiv
DO - 10.26434/chemrxiv.15011000/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15011000/v1
AB - Native chemical ligation has transformed chemical protein synthesis, yet its reliance on C-terminal peptide thioesters suffers from precursor preparation, stability and multisegment assembly. Here we report peptide nitrile ligation (PNL), a thioester-free ligation in which a stable C-terminal peptide nitrile is chemoselectively captured by an N-terminal cysteine and converted through a thiazoline intermediate into a native Xaa-Cys amide bond. Peptide nitriles are generated directly and chemoselectively from the C-terminal amides obtained using conventional Rink-amide Fmoc solid-phase peptide synthesis. PNL proceeds in aqueous buffer at pH 7.5 without an exogenous thiol catalyst, a thioester intermediate or detectable epimerization at the ligation junction. Notably, PNL enables efficient ligation at C-terminal proline junctions, a longstanding challenge in thioester-based ligation, without specialized building blocks or additional synthetic steps. The reaction tolerates internal cysteine thiols and Asn- or Gln-derived side-chain nitriles, with the latter subsequently restored to their native amides. On-demand conversion of C-terminal amide into a new nitrile enables iterative three-segment assembly. PNL therefore establishes C-terminal nitriles as stable, programmable acyl donors for thioester-free multisegment peptide ligation.
ER -