Comparison of the fragmentation produced by fast atom bombardment and photodissociation of peptides

Laser photodissociation has many features that make it an attractive alternative to collision-induced dissociation (CID) for sequencing peptides by mass spectrometry. In this paper we report on the photodissociation at 193 nm for two tetrapeptides (Val-Ala-Ala-Phe and Met-Arg-Phe-Ala) and a cyclic peptide, gramicidin S. The experiments are performed by using an external ion source Fourier transform mass spectrometer (FTMS) and an excimer laser. Ions are generated by particle beam bombardment and are transferred to an FTMS analyzer cell where they are trapped.