Electron capture dissociation for structural characterization of multiply charged protein cations

Area of Science:

• Mass Spectrometry
• Proteomics
• Analytical Chemistry

Background:

• Conventional MS/MS methods like collisionally activated dissociation (CAD) have limitations in cleaving backbone bonds for smaller proteins.
• Energy transfer mechanisms in ion trapping influence dissociation efficiency and selectivity.

Purpose of the Study:

• To introduce and characterize a novel radical site dissociation method for protein analysis.
• To compare the efficacy of this new method with existing techniques like CAD.
• To demonstrate the utility of the new method for de novo sequencing and localization of posttranslational modifications.

Main Methods:

• Utilizing FTMS with electron trapping electrodes to optimize electron capture by ions.
• Investigating the effect of kinetic energy differences between electrons and ions on capture efficiency.
• Analyzing dissociation patterns and fragment ion spectra generated by the new method.

Main Results:

• The new method, electron capture dissociation (ECD), cleaves more backbone bonds than CAD for proteins < 20 kDa.
• Optimized electron capture achieved 80 +/- 15% precursor ion conversion efficiency.
• ECD demonstrated complete backbone cleavage in mellitin and ubiquitin, enabling de novo sequencing.
• ECD showed higher specificity for localizing posttranslational modifications compared to CAD.

Conclusions:

• Electron capture dissociation is a powerful new technique for protein sequencing and characterization.
• ECD offers advantages over CAD in terms of backbone cleavage and localization of modifications.
• The method holds significant promise for advancing proteomic analysis.