NanoLC-Orbitrap mass spectrometry analysis of the SUATM129 chymotrypsin fraction containing the C1 and C17,18,19 disulfide-linked peptides. In this experiment the methionine in the peptide pair was oxidized (oxM) due to storage. A, FT full scan of the multiply charged ion species of the C1 and C17,18,19 peptides. All of the possible Cys-Cys bond configurations are shown. B, Orbitrap CID MS/MS spectra of the 1049.88477 [M+2H]2+ parent ion of the C1 and C17, C18, C19 disulfide-linked peptides. Some of the accurate mass fragment ion assignments including the two disulfide-linked pairs resulting from cleavage between C18 and C19 are indicated.