Identification of modified proteins by mass spectrometry

Because it is obvious that high-throughput genomics do not lead to a molecular description or even a prediction of protein function, modern techniques for protein analysis become increasingly more important. Sequence analysis of proteins and peptides is not limited to the elucidation of the primary structure of a protein. The analysis of posttranslational modifications is an important task of protein chemistry in proteome research. Increased sensitivity in mass spectrometry as a result of more efficient ionization techniques and better detection systems has allowed the stepwise reduction of protein quantity for analysis. Protein spots of 2D-PAGE separated samples are now sufficient for an unequivocal identification of a protein by mass spectrometry. In addition to protein identification, a closer look at posttranslational modifications is now also possible. It is assumed that modifications such as phosphorylation or glycosylation exist on every second protein and that they are important for the protein function.