Neutral oligosaccharides were analyzed by negative-ion matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). The characteristics of fragmentation in the mass spectrometer were studied, and a new structural analysis method was established. In negative-ion MALDI-MS, the fragmentation mechanism normally includes high-energy processes. By controlling the internal energy of the precursor ion in the ion trap, these characteristics of fragmentation were changed. Fragmentation from negatively charged oligosaccharides showed identical fragment patterns, depending on linkage type and branching pattern. This analysis method offered structural information which was fundamentally unobtainable using positive ion MALDI-MS. Negative-ion MALDI-MS analyses of neutral oligosaccharides are expected to be widely used in the structural analysis of oligosaccharides.
Structural complexity and heterogeneity of glycosaminoglycans (GAGs) have troubled biochemists in the research field for many years, thereby the progress of its functional research has long been delayed. Recently, rapid progress in mass spectrometry (MS), especially a tandem MS that can perform MS/MS (MSn) experiments, has lead to its increasing use for structural studies of GAGs. By using MS, though still under research, it is becoming possible to obtain information on not only molecular weights of GAG oligosaccharides but also position of sulfation, epimerization of a uronic acid, and more detail on the oligosaccharide sequence. Further refinement of MS methodology is expected to accelerate biochemical research of GAGs as well as their medical applications.
This review presents a strategy and applications of the large-scale identification of N-glycosylated proteins and their glycosylated sites. The technology is based on the affinity capture of glycopeptides with lectins, the enzyme-mediated stable isotope-labeling of N-glycosylated sites, and the liquid chromatography/mass spectrometry (LC-MS) shotgun analysis.
Mass spectrometry (MS), which has advanced rapidly in recent years, is expected to become the tool of choice for high-throughput analysis of relationships between structures and functions of glycans. The structural analysis of glycans using MS employs a number of methods for pretreatment, derivatization, and interpretation. However, since none of these are universally applicable, researchers have to choose the most suitable method for their purpose on a case-by-case basis. MS can be used not only for structural analysis, but also for interaction analysis. Methods of analyzing glycomics using MS are still under development, and further improvement or reinforcements and interfaces with other reinforcing methodologies are expected in the future. Rather than developing a complex device or technique that must be assigned to highly trained specialists, the key to further advances in this field is to develop a technology that can be comfortably adopted by a wide range of bioresearchers.