Practice: Considering the mass of each residue (shown below) and the fact that not every peptide bond will break in mass spectrometry of a protein, answer the following questions.
A) If cleavage between two Gly residues does not occur, which amino acid would be identified in place of the two glycines?
a. Gly. c. Asp.
b. Asn. d. Ser.
B) What amino acid would be identified if a bond between Ser and Val did not break?
a. Trp. c. Thr.
b. Tyr. d. Val.