Development of reagents for differential protein quantitation by subtractive parent (precursor) ion scanning.

We present a generic approach for quantitative differential proteomics that reduces data complexity in proteome analysis by automated selection of peptides for MS/MS analysis according to their isotope-labeling ratio. Isotopic reagents were developed that give products which fragment easily to generate a unique pair of signature ions. Using the ion-pair ratio, we show that it is possible to select only BSA peptides (with a 3:1 light heavy isotope ratio) for MS/MS when spiked in a whole yeast extract using Parent (precursor) Ion Quantitation Scanning (PIQS) for MS/MS.