Phosphoamino acid analysis.

Phosphorylation of amino acid residues in proteins plays a major role in biological systems. Often, phosphorylation acts as a molecular switch controlling the protein activity in different pathways as in metabolism, signal transduction, cell division etc. Therefore, identification of phosphoamino acids in proteins is an important task in protein analysis. Since the introduction of high resolution two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) a separation of phosphorylated and dephosphorylated protein species is possible. The identification of phosphorylation sites from preparative 2-D gels need very sensitive mass spectrometry methods and a specific enrichment of the phosphoprotein or -peptide.