Electron capture dissociation and collision induced dissociation behavior of peptides containing methionine, selenomethionine and oxidized methionine

The electron capture dissociation and collision induced dissociation of doubly and triply charged ions of peptides RPLGMSPFK, RPLGM(Se)SPFK and RPLGM(O)SPFK were determined by Fourier transform ion cyclotron resonance mass spectrometry. The results suggest that ECD of analyzed species strongly depends on the nature of a single element (i.e., sulfur and selenium atoms, sulfoxide group) and can provide both primary sequence information and structural information regarding the modification. The properties of sulfur and selenium atoms are negligible in the case of CID processes. The CID loss of CH3SOH, which is unique in peptides to the Met(O) side chain, does not depend on the peptide sequence.