Key Benefits of Promise Proteomics
stable isotope labelled proteins
High protein purity & isotopic incorporation
Flexibility in peptide selection
Same sequence as native protein
Equivalent digestion kinetics to target
Identical to analyte in sample processing
For use in complex sample matrices
Catalogue & custom options available
A stable isotope labelled (SIL) form of an analyte protein is widely regarded as the optimal internal standard (IS) for absolute quantification of proteins using LC-MS; SIL proteins are often cited as being the “gold standard IS”.
The benefit of using a SIL protein as an internal standard is that shares the same physiochemical behaviour as the target protein analyte. This means that the IS can be introduced at the start of the sample preparation workflow and will be processed along with the analyte protein throughout the entire analytical procedure (see schematic above). The addition of SIL-proteins at the start of the sample extraction can control for variations due to immunoaffinity or other isolation techniques, enzymatic digestion, other pre-analytical treatments as well as the LC and mass spectrometric ionization.
EMA guidelines recommend the use of a SIL-protein IS whenever possible for LC-MS/MS methods. Beyond this, there is a growth in scientific literature that strongly supports the use of full length, recombinant SIL proteins as internal standards and selected publications discussing the benefits of using SIL proteins in quantitative LC-MS workflows are detailed above. Significantly, these citations illustrate that the addition of a SIL protein as an IS at the start of the sample preparation increases accuracy and precision of the quantitative LC-MS assay when compared to other IS approaches e.g. SIL peptides or SIL extended peptides.