5. Protein Techniques

Upon fragmentation of a peptide bond during mass spectrometry, what ions can be detected on the spectrum?

Use the mass spectrum below & the indicated y-ion peaks (red) to reveal the sequence of the peptide.

Use the mass spectrum below & the provided chart with amino acid masses to determine the sequence of a hexapeptide (6 amino acid residues). In the mass spectrum, y ion peaks are indicated with 'y' while b ion peaks are indicated with 'b.' The N-terminal residue is given as Leu and the C-terminal residue is given as Lys. Determine the remaining amino acid sequence using either the y ions or the b ions.

In your mass-spectrometry of a pure protein with an m/z of 1,582, you found peaks of y ions with the following m/z ratios of 1,582, 1396 and 1283. The mass in Daltons for the possible relevant amino acids are provided: Y (163), N (114), W (186), D (115), G (57), L (113) and M (131). From this data, it is obvious that the C-terminal amino acid residue of the 1,582 fragment is:

Use the mass spectrum below to determine the sequence of the peptide.