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Constructing Cyclic Peptides Using an On-Tether Sulfonium Center
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Gold(I) Cationization Promotes Ring Opening in Lysine-Containing Cyclic Peptides
David J Foreman1, John T Lawler1, Mary L Niedrauer1
1Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN, 47907-2084, USA.
Journal of the American Society for Mass Spectrometry
|June 29, 2019
Summary
This study introduces a new mass spectrometry (MS) method for sequencing cyclic peptides. Gold cationization targets lysine residues, enabling site-specific fragmentation for easier analysis.
Area of Science:
- Analytical Chemistry
- Mass Spectrometry
- Biochemistry
Background:
- Cyclic peptides present sequencing challenges due to their complex structures.
- Current mass spectrometry methods struggle with site-specific fragmentation in cyclic peptides.
Purpose of the Study:
- To develop a novel mass spectrometry (MS^n) strategy for unambiguous sequencing of lysine-containing cyclic peptides.
- To utilize gold(I) cationization for site-specific fragmentation and simplified data interpretation.
Main Methods:
- Employing cation switching ion/ion reactions to form gold(I) cationized peptide ions.
- Inducing gas-phase oxidation of lysine residues to weaken adjacent amide bonds.
- Utilizing MS^n activation for site-specific ring opening and linearization of cyclic peptides.
Main Results:
- Demonstrated a facile N-terminal cleavage adjacent to oxidized lysine residues, yielding acyclic peptide analogs.
- Generated fragment ions with common N- and C-termini, simplifying MS/MS data interpretation.
- Successfully sequenced sunflower trypsin inhibitor and a model cyclic peptide (β-Loop) using the developed strategy.
Conclusions:
- The gold(I) cationization and oxidation strategy enables site-specific ring opening of cyclic peptides.
- This method facilitates unambiguous sequencing by simplifying fragmentation patterns.
- The approach is powerful for analyzing complex cyclic peptide structures.
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