Surrogate Peptides

Surrogate peptides are tryptic peptides that can be identified by mass spectrometry and quantified to indicate the absolute abundance of a specific protein in a mixture or extract. To quantify the peptide, a synthetic stable-isotope labeled surrogate peptide is added to tryptic digest as an internal standard. The ‘Amino Acid Sequence’ shows the sequence of the tryptic peptide used as a surrogate for the protein. The labeled amino acids are shown in red.