Sequencing of Argentinated Peptides by Means of Electrospray Tandem Mass Spectrometry

A strategy for semiautomatic sequencing of argentinated (silver-containing) oligopeptides has been developed. Sequencing is based on a search algorithm that identifies a triplet peak relationship in a product ion spectrum of the [M + Ag]+ ion of an oligopeptide. The ions that constitute a triplet are [b n + OH + Ag]+, [b n − H + Ag]+, and [a n − H + Ag]+, which are separated by 18 and 28 m/z units, respectively. The difference in the m/z values of adjacent triplets identifies the residue that is “cleaved”. Observation of the [y n + H + Ag]+ ion containing the cleaved residue confirms the assignment. Sequencing of argentinated tryptic peptides may prove useful for automated proteome analysis via the sequence tag method.