Analysis of oligomeric complexes of the amyloid-forming FYLLYY peptide by collision-induced dissociation with electrospray ionization mass spectrometry.

The monomeric and oligomeric structures of the "FYLLYY" ß2 microglobulin (ß2m) active sequence, formed in (DMSO/CH3CN) solution, were investigated using electrospray ionization (ESI) mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Dissociation of dimer and trimer ions was investigated by tandem mass spectrometry using collision induced dissociation (CID). The covalent bond fragmentation patterns were observed in the 21+ and 32+ MS/MS spectra (21+ = [dimer+H]1+ and 32+ = [trimer + 2H]2+). A π-π stacking geometry for the FYLLYY 21+ complex and partial parallel ß-sheet geometry for the 32+ complex are proposed to be stable structures. The observed covalent bond fragment ions in the MS/MS spectra of the 32+ complex are considered to have originated from the partial parallel ß-sheet moiety. The FYLLYY → AALLGY (or FYLLAA) substituted sequence was also investigated by CID-MS/MS. Our MS/MS analysis suggests that the π-π stacking interaction structures are important in dimer binding rather than the structures of a complete parallel or anti-parallel ß-sheet 21+ complex.