A comparison of positive and negative ion collision-induced dissociation for model heptapeptides with one basic residue.

The effects of the identity and position of basic residues on peptide dissociation were explored in the positive and negative modes. Low-energy collision-induced dissociation (CID) was performed on singly protonated and deprotonated heptapeptides of the type: XAAAAAA, AAAXAAA, AAAAAXA and AAAAAAX, where X is arginine (R), lysine (K) or histidine (H) residues and A is alanine. For [M + H](+), the CID spectra are dominated by cleavages adjacent to the basic residues and the majority of the product ions contain the basic residues.