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Gas-phase dissociation pathways of multiply charged peptide clusters
John C Jurchen1, David E Garcia, Evan R Williams
1Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
Journal of the American Society for Mass Spectrometry
|December 4, 2003
Summary
Peptide cluster dissociation pathways, including evaporation and fission, are influenced by charge and monomer number. This research reveals insights into the fluid-like state of peptide clusters during dissociation.
Area of Science:
- Physical Chemistry
- Biophysics
- Mass Spectrometry
Background:
- Cluster dissociation studies are crucial for understanding phase transitions.
- Previous research explored diverse materials like atomic nuclei and metal clusters.
Purpose of the Study:
- To investigate peptide cluster dissociation pathways using electrospray ionization.
- To determine the factors influencing dissociation pathways in leucine enkephalin and somatostatin peptides.
Main Methods:
- Electrospray ionization was used to generate and study peptide clusters.
- Analysis of dissociation pathways: neutral monomer evaporation and cluster fission.
- Investigated leucine enkephalin (7-19 monomers, 2-5 protons) and somatostatin (5 monomers, 4 protons).
Main Results:
- Leucine enkephalin cluster dissociation pathways depend on the z²/n ratio (charge squared over monomer number).
- A transition from evaporation to fission dominance occurs around z²/n ≈ 0.5.
- Somatostatin cluster dissociation branching ratio is affected by disulfide bond reduction, not the pathway.
Conclusions:
- Peptide clusters exhibit disordered, possibly fluid, states in the transition to dissociation.
- Charge and monomer number are key determinants of dissociation pathways.
- Monomer conformational flexibility influences peptide cluster dissociation dynamics.