Mass spectrometry (MS)-based proteomics has become an essential tool for biologists over the last decade. The ability of a mass spectrometer to identify thousands of proteins from a complex biological sample has revolutionized scientific experiments. To fully understand the function of the proteome in health and disease, however, one must have the ability to accurately quantify proteins in many different types of biological samples. The invention of faster and higher resolution mass spectrometers has enabled the quantification of complex proteome dynamics. Heavy stable isotopes are routinely employed to generate precise and accurate quantitative proteomic data. Peptides labeled with heavy stable isotopes share identical biochemical characteristics to “light” or unlabeled peptides except for a difference in mass. Mixing heavy peptides with light peptides results in peptide pairs that co-elute into the mass spectrometer, which can easily distinguish between the peptides based on the mass difference. Quantifying differences between proteomes subjected to different biological conditions or experiments can be achieved when using the heavy peptides as an internal standard or a control.

CIL offers a variety of stable isotope-labeled materials for labeling or tagging a proteome for qualitative/quantitative MS-based analyses. These can be employed in such applications as biomarker screening and disease model analysis to help define systems biology, improve treatment, and better understand disease. Each section below outlines a specific application along with the stable isotope-labeled (and unlabeled) materials available therein for use.

Chemical Labeling

To aid the synthesis of stable isotope-labeled peptides, CIL offers an array of protected amino acids and preloaded resins.

Chemical Tagging

CIL offers a collection of reductive methylation reagents and a glycan-tagging kit termed INLIGHT® (Individuality Normalization when Labeling with Isotopic Glycan Hydrazide Tag) for relative quantitation.

Enzymatic Labeling

The incorporation of two 18O atoms into each C-terminus of peptides derived from proteolytic digestion of biological samples has emerged as one of the leading global labeling strategies used in comparative quantitative proteomics.

Metabolic Labeling

One type of proteome labeling introduces a stable isotope amino acid(s) to cell growth media or rodent feed.

QC and Quantitation Kits

To help expedite quality control (QC) and quantitation in proteomics, CIL offers a number of off-the-shelf kits.