ELECTROSPRAY IONIZATION-ION TRAP MASS-SPECTROMETRY FOR STRUCTURAL-ANALYSIS OF COMPLEX N-LINKED GLYCOPROTEIN OLIGOSACCHARIDES

Electrospray ionization-ion trap mass spectrometry, with its capacity to perform multiple stages of fragmentation (MSn), is demonstrated as an effective method for the structural characterization of permethylat ed N-linked complex glycoprotein oligosaccharides. Complex glycan stru ctural features, such as N-acetyllactosamine antennae, neuraminic acid s, and nonreducing terminal GlcNAc monosaccharides, commonly suppress cross-ring and core saccharide cleavages in traditional MS/MS experime nts. Using ion trap mass spectrometry, removal of these substituents p ermits determination of branching patterns and intersaccharide linkage s by MS3 and MS4. Both sequence and linkage data are obtained for N-ac etyllactosamine and sialyl-N-acetyllactosamine oligosaccharide antenna e from biantennary glycans using MS3, and the location of a bisecting GlcNAc residue is also established after exposing the core pentasaccha ride. Higher-order experiments further illustrate the potential of ele ctrospray ionization - quadrupole ion trap mass spectrometry for carbo hydrate analysis, as MS8 is used to produce significant and otherwise unobtainable branching information for an oligosaccharide from chicken ovalbumin. These studies constitute further evidence of the unique ro le that ion trap mass spectrometry can assume in the area of oligosacc haride analysis.