Abstract
In contrast to low energy CID, high energy CID produces the characteristic fragmentations which yield to give a wealth of structural information.
The side-chain cleavage of the C-terminal amino acid of an an ion leads to a dn ion, which is useful for the differentiation of Leu and Ile in the analysis of peptide sequences. In the CID spectrum of [M+Na]+ for peptides even those lacking basic amino acid in the sequence, the [dn+Na-H]+ ions allow for the differentiation of Leu and Ile, through observation of the corresponding [an+Na-H]+ ions, whereas no an ions were seen in its [M+H]+.
The charge remote fragmentations indicate the location of branching points and substituents, as well as of double bonds of fatty acid without any derivatization. Although the charge remote fragmentations arise from closed-shell precursor ions, they show in the CID spectrum of radical cation, M+· of tocopherol, which reveal direct structural information about the isoprene chain.
The MS/MS method has also been applied to the determination of the structure of natural products, such as pittosporumxanthin B1, which feature the partial structures of antheraxanthin and tocopherol, and to the differentiation of glucose and mannose.
