Differentiation of alpha- or beta-Aspartic Isomers in the Heptapeptides by the Fragments of [M + Na](+) Using Ion Trap Tandem Mass Spectrometry

作者：Wang, Bing; Shang, Jin Zhuo; Qin, Yu Jiao; Yan, Bing Na; Guo, Xin Hua^*

来源：Journal of the American Society for Mass Spectrometry, 2011, 22(8): 1453-1462.

DOI：10.1007/s13361-011-0160-6

• Low energy CID
• alpha- or beta-Aspartic isomers
• Fragments of [M plus Na]
• Fragmentation pathway

Electrospray ionization coupled with low energy collision induced dissociation (CID) in an ion trap mass spectrometer was used to examine the fragmentation patterns of the [M + Na](+) of eight pairs of heptapeptides containing alpha- or beta-Asp residues in second and sixth amino acid positions, respectively. Selective cleavages at the peptide backbone C-terminal to two Asp residues were observed, which generated a series of C-terminal y(5) ions and N-terminal b(6) ions. Two typical ions: [y(5) + Na - H](+) and [b(6) + Na + OH](+), produced by alpha-Asp containing peptides were noted to be much more abundant than those of the peptides with beta-Asp, which could be used for distinction of the isomers in Asp2 and Asp6, respectively. In addition, a series of internal ions generated by simultaneous cleavages at Asp residues were detected. Competitive reactions of carboxylic groups occurred between Asp6 side chain and C-terminus. Formation mechanisms of most product ions are proposed. The results obtained in this work are significant since low energy CID has been demonstrated to be effective for the distinction of Asp isomers.

• 出版日期2011-8
• 单位吉林大学