Acid-based approach for separation of peptide epimers using IM-MS

Area of Science:

• Analytical Chemistry
• Biochemistry
• Physical Chemistry

Background:

• Chiral molecules are difficult to distinguish using ion mobility mass spectrometry (IM-MS) due to limited resolution.
• Peptide epimers, a type of stereoisomer, present a significant analytical challenge in IM-MS.

Purpose of the Study:

• To evaluate the effectiveness of complexation with organic acids for improving the ion mobility separation of peptide epimers.
• To investigate the mechanisms behind enhanced stereodifferentiation through acid-peptide complex formation.

Main Methods:

• Traveling-wave ion mobility mass spectrometry (TWIMS) was employed to analyze epimeric tripeptides.
• Complexation of peptides with various chiral and achiral organic acids (monoacids and diacids) was performed.
• Theoretical calculations and collisional dissociation studies were used to characterize the stable peptide-acid associates.

Main Results:

• Complexation with organic acids significantly improved the stereodifferentiation of peptide epimers compared to analyzing pure epimers.
• Stable gas-phase complexes were formed between epimeric tripeptides containing arginine and organic acids.
• Hydrogen bonding interactions, particularly involving arginine and tryptophan residues, were identified as key to complex stability and differentiation.

Conclusions:

• Acid-based complexation is a valuable strategy for enhancing the separation of peptide isomers using ion mobility mass spectrometry.
• The specificity of complex formation, particularly with arginine-containing peptides, contributes to improved chiral recognition.
• This approach offers a general utility for resolving challenging peptide stereoisomers in IM-MS analysis.