Fragmentation behavior of metal‐coded affinity tag (MeCAT)‐labeled peptides

Quantitative proteomics has become an important method in modern life sciences. Besides protein identification, the aspect of quantification is of rapidly increasing relevance. MeCAT (metal‐coded affinity tagging) is able to provide a tool that enables relative as well as absolute quantification. For structural elucidation, knowledge on the fragmentation behavior of MeCAT‐modified peptides is highly beneficial. Therefore, the fragmentation behavior of MeCAT‐labeled peptides under collision induced dissociation (CID), electron capture dissociation (ECD) and infrared multiphoton dissociation (IRMPD) conditions was studied. Application of CID and ECD allowed a straight‐forward sequence elucidation of MeCAT‐labeled peptides. During IRMPD all MeCAT‐labeled peptides form characteristic fragments resulting from the fragmentational cleavage of the tagging group, thus, providing a screening method for the identification of labeled compounds. Furthermore, occurring side reactions during the labeling process were investigated. By‐products were structurally characterized and reaction conditions were optimized in order to prevent the formation of these. Copyright © 2009 John Wiley & Sons, Ltd.