Quantitative proteomics is an essential technique for determining absolute levels of proteins of interest in biological samples. The absolute quantification (AQUA) of peptides from a trypsin digest can be determined by using isotopically labelled synthetic analogues as internal standards. These “AQUA peptides” have the same physicochemical and ionisation properties as the natural versions, but the increased molecular mass (usually 6 – 10 Da) allows ratios and hence the absolute quantity of the natural peptide to be determined. Modpep can supply highly pure AQUA peptides and amino acid analysis (AAA) can be performed on request.
