Figure 2: Common strategies for phosphopeptide enrichment.
Low abundance phosphopeptides may be enriched from a much larger background of non-phosphorylated peptides through a variety of techniques. The most common techniques include ion exchange chromatography, metal oxide affinity chromatography (MOAC), metal ion affinity chromatography (IMAC), and immunoprecipitation methods (with phosphorylated tyrosine antibody-based enrichment being the most popular). Combining these methods in series is also common, such as SCX (strong cation exchange) enrichment or pY-enrichment followed by MOAC or IMAC, IMAC followed by MOAC, or sequential IMAC.