Phosphopeptide enrichment on synthetic libraries and HeLa cells digest

2 phosphopeptide enrichment methods (TiO2 and Ti-IMAC) were evaluated on synthetic libraries and HeLa cells digest. The resulting peptides were compared to the ones without enrichment with regards to the nature of the phosphorylation site (serine, threonine, tyrosine) and the characteristics of the peptide enriched. It was found that the enrichment methods are unbiased for these properties and that the result of the enrichment reflects the original condition of the sample.