Protein and Glycoprotein Characterisation by Mass Spectrometry

Proteins are polymers made up of amino acids linked via their alpha amino and carboxyl groups respectively, creating planar interconnecting amide bonds. The order of the twenty naturally occurring amino acids in the polymer is called the amino acid sequence or primary structure, and all other levels of protein structure, including secondary (alpha helix, pleated sheet or random coil), tertiary (three dimensional) structure, or quaternary structure (interaction with a ligand or subunit in space) are fundamentally determined by the unique amino acid sequence of the protein. Determining the sequence of an unknown protein has therefore been the holy grail of protein chemistry ever since Fred Sanger’s pioneering work on the structure elucidation of Insulin – the first protein sequence determination in the 1950s1.