Patent ID: 7964362

Claim:
A method for detecting the presence or absence of a post-translational modification at a location on a target protein within a sample, comprising: (1) subjecting the target protein to a fragmentation treatment to produce a peptide fragment comprising: (i) at least one potential post-translational modification site; and, (ii) a separate proteome epitope tag (PET) comprising an amino acid sequence unique to the peptide fragment within the sample, wherein the location of the post-translational modification site and the PET within the peptide fragment is known; (2) contacting the peptide fragment with a capture agent specific for the PET, thereby to bind the peptide fragment at the PET; (3) contacting the peptide fragment bound to the capture agent specific for the PET with a secondary capture agent specific for the post-translational modification site, wherein the secondary capture agent is labeled with a detectable moiety; and (4) detecting the secondary capture agent; wherein detection of the secondary capture agent is indicative of the presence of the post-translational modification at the location within the target protein.