N-terminal derivatization and fragmentation of neutral peptides via ion-molecule reactions with acylium ions: Toward gas-phase Edman degradation?

Abstract

The gas-phase ion-molecule reactions of neutral alanylglycine have been examined with various mass-selected acylium ions RCO+ (R= CH3, CD3, C6H5, C6F5 and (CH3) 2N), as well as the transacylation reagent O-benzoylbenzophenone in a Fourier transform ion cyclotron resonance mass spectrometer. Reactions of the gaseous dipeptide with acylium ions trapped in the ICR cell result in the formation of energized [M + RCO]+ adduct ions that fragment to yield N-terminal b-type and C-terminal y-type product ions, including a modified b1 ion which is typically not observed in the fragmentation of protonated peptides. Judicious choice of the acylium ion employed allows some control over the product ion typ..