Cationic Derivatization of Oligosaccharides with Girard's T Reagent for Improved Performance in Matrix-assisted Laser Desorption/Ionization and Electrospray Mass Spectrometry

Oligosaccharides were derivatized by hydrazone formation with Girard's T reagent in order to introduce a cationic site for detection by matrix-assisted laser desorption/ionization (MALDI) and by electrospray mass spectrometry. The derivative was prepared in high yield and did not require extensive clean-up prior to mass spectrometric examination, unlike the products of the more commonly used reductive amination derivatization. The derivatives gave a ten-fold increase in detection sensitivity over that afforded by the underivatized oligosaccharides and provided intense spectra in positive-ion electrospray without the need to add cations to the solvent. In addition, the use of these derivatives removed ambiguities caused by the presence of MK+ ions that accompany the MNa+ ions formed from the underivatized sugars in MALDI. Furthermore, Girard's T derivatization overcame problems associated with the presence of reducing-terminal, N-acetylamino groups that were often introduced when the oligosaccharides were prepared by cleavage from glycoproteins with hydrazine.