ABSTRACT

Mass spectrometry has been used to identify all types of posttranslational and other covalent modifications (for review, see [6]). In most cases, proteases of high specificity (e.g., trypsin) are used to generate pep­ tides for mass spectrometric analysis. From the difference between the pre­ dicted and observed masses, the chemical structure of even undescribed covalent modifications can be deduced. Fragmentation of the modified species, that is, tandem mass spectrometry experiments, using collisioninduced dissociation or post-source decay analysis will reveal more struc­ tural detail of the modifying group, identify the sequence of the modified peptide, and locate the site of modification. This chapter illustrates how liquid secondary ion mass spectrometry (LSIMS) with high energy collisioninduced dissociation (CID) analysis can be utilized in the structure elucida­ tion of O-linked glycopeptides.