Non-zwitterionic structures of aliphatic-only peptides mediated the formation and dissociation of gas phase radical cations |
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Authors: | Lam Corey N W Ruan Eric D L Ma C Y Chu Ivan K |
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Affiliation: | Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong. |
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Abstract: | We have investigated how the non-zwitterionic and zwitterionic structures of aliphatic-only tripeptides affect the formation and dissociation of peptide radical cations in the gas phase. The non-zwitterionic forms of the aliphatic-only peptides in their metal complexes play an important role in determining whether the electron transfer pathway predominates. We extended this study by synthesizing permanent non-zwitterionic and zwitterionic forms of aliphatic-only peptide radical cations and exploring their reactivities in the gas phase. Collision-induced dissociation spectra demonstrated the feasibility of generating both non-zwitterionic and zwitterionic forms. Radical cations in zwitterionic forms may indeed mediate the beta and gamma carbon-carbon bond cleavages of leucine and isoleucine side chains from the GlyGlyXle radical peptides; this feature allows leucine and isoleucine residues to be distinguished unambiguously. |
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Keywords: | radical cationic peptides non‐zwitterionic structures peptide fragmentation copper(II) complexes electron transfer |
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