Peptide radical cations: gender determines dissociation chemistry

Area of Science:

• Analytical Chemistry
• Biochemistry
• Mass Spectrometry

Background:

• Peptide radicals are crucial in mass spectrometry and biological processes.
• Two main types exist: hydrogen-deficient and hydrogen-abundant radicals, with distinct dissociation chemistries.
• Hydrogen-abundant radicals yield more sequencing information due to preferential N-Cα cleavage.

Purpose of the Study:

• To compare the dissociation chemistries of hydrogen-deficient and hydrogen-abundant peptide radicals.
• To highlight the superior sequencing potential of hydrogen-abundant radicals in mass spectrometry.
• To identify the need for alternative generation methods for hydrogen-abundant radicals.

Main Methods:

• Analysis of dissociation pathways for different peptide radical types.
• Comparison of fragmentation patterns, specifically backbone cleavage sites.
• Evaluation of electron capture/transfer dissociation efficiency and limitations.

Main Results:

• Hydrogen-deficient radicals primarily undergo Cα-C cleavage, yielding a and x fragments.
• Hydrogen-abundant radicals predominantly exhibit N-Cα cleavage, producing c and z ions.
• Significant differences in dissociation products limit the overlap between radical types.

Conclusions:

• Hydrogen-abundant peptide radicals are more valuable for peptide sequencing in mass spectrometry.
• Current methods like electron capture/transfer dissociation are limited by charge reduction.
• Novel methods are required to enhance the generation of hydrogen-abundant radicals for improved sequencing.