Characterization of impurities in a synthetic renin substrate peptide by fast-atom bombardment mass spectrometry and hybrid tandem mass spectrometry.
Fast-atom bombardment mass spectrometry of a synthetic renin substrate decapeptide (Pro-His-Pro-Phe-His-Leu-Val-Ile-His-D-Lys) indicated the presence of several side-products, including a component 12 Da higher in mass. Low-energy collisionally activated decomposition analyses were performed using a hybrid tandem instrument and demonstrated that the heavier side product had two components, in which the structural modification was either at the N- or the C-terminus. Additional analyses of the N-acetyl derivative indicated that for each component the structural modification blocked a site of N-acetylation. It is suggested that the formation of these side products is attributable to the generation of formaldehyde, during removal of the histidine protecting group (benzyloxymethyl), which reacts with the N-terminus of the peptide to give an imidazolidinone structure or with the D-lysine epsilon-amine group to yield an imine. While the precise genesis of the side-products remains speculative, it is clear that the combined strategy of derivatization and tandem mass spectrometry has allowed structural conclusions concerning individual components of an isobaric mixture.
Mathews
W R
WR
Biopolymer Chemistry, Upjohn Company, Kalamazoo, MI 49001.
Runge
T A
TA
Haroldsen
P E
PE
Gaskell
S J
SJ
D000808:Angiotensinogen / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods; D016339:Spectrometry, Mass, Fast Atom Bombardment / Q000379:methods
D000808:Angiotensinogen