Protein characterisation by isolating a single C-terminal peptide from each polypeptide in a mixture with water-stable reagents that are selective for lysine followed by detection by mass spectroscopy

摘要

A method is provided for characterising a polypeptide or a population of polypeptides, comprising the steps of: (a) optionally reducing disulphide linkages in the polypeptides, if present and capping free thiols in the polypeptides, if present; (b) contacting a sample comprising one or more polypeptides with a cleavage reagent which cleaves one or more polypeptides on the C-terminal side of a lysine residue to produce peptide fragments; (c) optionally deactivating the cleavage reagent; (d) contacting the sample with a lysine reactive agent to cap epsilon -amino groups; (e) removing those peptides having capped epsilon -amino groups; and (f) recovering the C-terminal peptides.