Specific Enrichment of Peptides with N-Terminal Serine/Threonine by a Solid-Phase Capture-Release Approach for...

A problem for "shot-gun" proteomics is that the peptides generated in the proteolysis step overwhelm the analytical capacity of current LC-MS/MS systems. A straightforward approach to overcome this problem is to reduce the sample complexity by isolating the representative peptides of each protein. In this study, we presented a facile solid-phase capture-release approach to selectively enrich the peptides with N-terminal serine/threonine from protein digests. This method exploited the highly efficient reaction between an aldehyde group and a hydrazine group. The excellent performance of this approach was validated using synthetic peptides as well as complex protein digests. It was found that high enrichment specificity could be obtained and the identifications for complex samples with and without enrichment were highly complementary. Besides, the enrichment of peptides with serine/threonine adjacent to different protease cleavage sites demonstrated that our method was able to enrich peptides from protein digests in a sequence specific way. As a result, this new approach provides a simple way to reduce sample complexity and facilitates the identification of low-abundance proteins.