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Solution versus gas-phase modification of peptide cations with NHS-ester reagents
Marija Mentinova1, Nathan Z Barefoot, Scott A McLuckey
1Department of Chemistry, Purdue University, West Lafayette, IN 47907-2084, USA.
Journal of the American Society for Mass Spectrometry
|November 15, 2011
Summary
Peptide modification differs between solution and gas phases. In solution, N-terminus modification is favored at pH 5, while gas-phase reactions preferentially target lysine residues due to charge and protonation effects.
Area of Science:
- Chemical Biology
- Mass Spectrometry
- Proteomics
Background:
- Primary amine sites in peptides are crucial for chemical modification.
- N-hydroxysuccinimide (NHS) esters are common reagents for amine modification.
- Understanding site selectivity in peptide modification is vital for proteomics and drug development.
Purpose of the Study:
- To compare the site selectivity of N-hydroxysuccinimide (NHS) ester modification on model peptide cations in solution versus the gas phase.
- To investigate the influence of solution pH and gas-phase charge distribution on primary amine modification.
- To elucidate the factors governing the reactivity of N-termini and lysine residues.
Main Methods:
- Model peptide cations were reacted with NHS ester reagents in both solution and gas phases.
- Reactions were conducted at controlled pH in solution (pH=5).
- Gas-phase reactions were analyzed using mass spectrometry, including charge inversion experiments.
Main Results:
- In solution, modification predominantly occurred at the N-terminus.
- In the gas phase, lysine residues were preferentially modified.
- The N-terminus showed limited reactivity with NHS-esters in the gas phase, attributed to charge solvation, but could be modified with a cross-linking reagent.
Conclusions:
- Site selectivity of primary amine modification in peptide cations is highly dependent on the phase (solution vs. gas).
- Protonation state and charge distribution significantly influence reactivity in different environments.
- Gas-phase charge accommodation plays a key role in directing modification sites, impacting peptide analysis and modification strategies.
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