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Stable Isotope Labelled Proteins as Internal
Standards in Quantitative LC-MS workflows

What is a Stable Isotope Labelled protein ?

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”.

SIL proteins have the same physiochemical behavior as the target proteins analyte. The internal standard 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. This allows 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

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.

How to use it ?

Our stable isotope labelled (and unlabelled) full length
recombinant protein products are especially suitable for:

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
  • Products are ready-to-use and packaged to be highly stable
  • Identical to analyte in sample processing
  • For use in complex sample matrices
  • Highly stable
  • Catalogue & custom options available
  • The addition of the SIL protein minimises variations in sample processing and reduces assay development time

Publications Citing the Benefits of using Full Length Stable Isotope
Labelled Recombinant Proteins as Internal Standards in Quantitative LC-MS