Mass Spectrometry.

Mass spectrometry works on the principle that any molecule may be ionized and accelerated in an electric field.  The time that this is charged molecule needs to pass a certain distance will therefore be proportional to the number of charges, the electric field, and the mass of the molecule.  In this way complex mixtures of molecules may be analyzed, and the technique is extremely sensitive, permiting the separation of masses at the isotopic level. Mass spectrometry is a powerful analytic tool that is widely used in chemistry and protein chemistry laboratories.

The samples used proteome analyses contain a mixture of peptides derived from the hydrolytic digestion of proteins will masses typically in the 500-3000 Daltons. Specialized mass spectrometers have been developed which can accurately measure the masses of peptides to within a few parts per million (ppm), which in real terms is better than 0.1 Dalton. This high accuracy is essential for subsequent comparisons of the measured masses of the peptides with the theoretical masses calculated for the same peptides that are derived from the amino acid sequence of the protein.