科研之友
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摘要
The fragmentation reactions of the MH+ ions of Leu-enkephalin amide and a variety of heptapeptide amides have been studied in detail as a function of collision energy using a QqToF beam type mass spectrometer. The initial fragmentation of the protonated amides involves primarily formation of b(n) ions, including significant loss of NH3 from the MH+ ions. Further fragmentation of these b(n) ions occurs following macrocyclization/ring opening leading in many cases to b(n) ions with permuted sequences and, thus, to formation of non-direct sequence ions. The importance of these non-direct sequence ions increases markedly with increasing collision energy, making peptide sequence determination difficult, if not impossible, at higher collision energies.
- 出版日期2013-10
