The MS PhosphoMix line of products allows for the testing of the strengths and weaknesses of phosphopeptide sample processing, mass spectrometry analysis and instrument configurations. The mixes are produced from synthetic phosphopeptides with sequences derived from naturally occurring peptides as identified by Mann et al. in HeLa cells.† Because the sequences are derived from mammalian cells, many natural phosphorylation motifs, such as those that present an abundance of proline, are represented.† Additionally, the phosphopeptide distribution in each mix has been chosen to present a broad range of characteristics, including ionizability, LC retention time, charge state, and isoelectric point. Finally, PhosphoMix-1, 2, and 3 were designed in a complementary fashion, as highlighted on the following page. For example, all three mixes contain peptides of the same sequence with different sites of phosphorylation.

Each of the three phosphopeptides mixes are available in their naturally occurring isotopic abundances (light) or as stable isotope enriched versions (heavy), making the set of products highly amenable to quantitative analyses, allowing users to compare recovery between workflows or techniques.

• Naturally occurring peptide sequences
• Broad range of peptide characteristics
• Complementary product designs
• Available in light and heavy versions