Stable isotope-labeled standards (SIS) in combination with Mass Spectrometry based targeted proteomics provide researchers with a powerful analytical tool for protein quantification, with an assay performance now suitable for clinical studies. Assays designed for bottom-up proteomics workflows suffer from differences in digestion efficiency, which can vary significantly between peptides within a protein leading to overall compromised accuracy and precision. This can be solved by using QPrEST™ protein standards, which are added to the sample prior to proteolytic digestion as both the standard and endogenous target protein are digested together.

Different applications will be discussed, the performance under different conditions and how you best make use of QPrEST™ standards to achieve the highest quantitative performance in your proteomics assay.