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. While trapped in the analyzer cell, the ions are irradiated with pulsed UV light from an excimer laser. Photodissociation is very efficient at 193 nm. Only a single laser pulse is required to fragment about 60% of the parent ions. Fragmentation results mainly in cleavage of the peptide bonds and produces easily interpretable mass spectra. Abundant fragment ions are produced by residues that contain high proton affinity amino acids such as proline. This indicates that the mechanism of peptide photodissociation is controlled primarily by thermodynamic factors rather than photochemical factors such as the molar absorption coefficients of the various amino acids in the chain.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of the American Chemical Society|
|State||Published - 1989|
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