| Analysis of large molecules from proteins to peptides and even higher mass species such as DNA is an important task, and in recent years, has been a specialty of mass spectrometry. Gaining structural information is possible using multi stage mass spectrometric techniques (MS)n. The technique of surface induced dissociation (SID) of singly protonated peptides ionized by matrix assisted laser desorption/ionization and analyzed by a tandem time-of-flight mass spectrometer with a collision surface located between the two time-of-flight mass spectrometers is described here.;The identity of positively charged product ions from SID is dependent on the velocity of the parent ions colliding at near normal angles to the SID surface. This dependence on collision velocity is evident for the entire mass range of peptides studied (280--12,384 amu). The observed trend suggests that SID has the potential to fragment very large ions, yielding product ions of certain identities, as long as, the necessary collision energy/velocity can be achieved.;SID of the protonated peptides produces product ions that fall into categories of the following types of product ions: intact molecular ions, backbone fragments, single amino acid immonium ions (H2N = CH-R)+, immonium ion fragments, and finally, sputtered surface material. The range of collision energies over which these products occurs changes based upon the mass of the ion, but is constant for collision velocity. The ranges of collision velocities for the different types of product ions are as follows: intact molecular ions and backbone fragments (<3500 m/s), single amino acid immonium ions (2600--5000 m/s), fragments of immonium ions (5000--13,000 m/s), and sputtered ions from the surface (>13,200 m/s). |
