Laser desorption ionization mass spectrometry of bioorganic molecules

Matrix-assisted laser desorption/ionization (LDI) mass spectrometry (MS) is a very young method that has overcome the mass limitations for the mass spectrometry of biopolymers (1-4). Four years ago, a UV-absorbing matrix was used to extend the accessible mass range of UV-LDI of peptides, and a strong dependence on the UV absorption properties of the matrix was demonstrated. The mol-wt determination capability is now ca. 300,000, and since the method is still evolving, its potential is far from fully exploited. Two other mass spectrometric methods are currently applicable to high-molecular mass determination; plasma desorption mass spectrometry ( Chapter 10 in this vol.) enables the production and detection of molecular ions of proteins up to about 30 kDa. Another recent technique, electrospray MS (5), works by spraying a solution of sample into an electric field, producing highly charged droplets, from which molecular ions are desorbed. The characteristic feature of electrospray mass spectra is a distribution of multiple-charged molecular ions, allowing mass measurement of proteins up to 70 kDa (see Chapter 8 ).