Gycosylation is one of the most important and most complex protein post-translational modifications. Alterations in glycomic profiles have been linked to various diseases, including cancer, neurodegenerative disorders, and cardiovascular problems. Thus, new methods are needed for quantitative analysis of glycans to facilitate elucidation of the diverse biological roles of glycans and their roles in human diseases. Advances in mass spectrometry (MS)-based glycoproteomics and glycomics are increasingly enabling qualitative and quantitative approaches for site-specific structural analysis of protein glycosylation. However, quantitative analysis of native glycans remains extremely challenging due to high complexity and diversity of glycan structures, difficulty of synthesizing glycan standards, the relatively low response in MS detection, and the wide dynamic range of glycans in clinically relevant samples.
In this presentation, I will describe our recent efforts in developing chemical tags and quantification strategies for both N-glycan and intact glycopeptide analysis in biological samples. We designed and synthesized a set of 4-plex isobaric multiplex reagents for carbonyl containing compounds (SUGAR) tags for multiplexed MS2-level glycan characterization and relative quantitation. To further improve the throughput, we utilized a mass-defect concept where subtle mass differences can be introduced to different isotopologues and expanded the multiplexing capacity to 18 channels, enabling significant throughput enhancement for SUGAR tag-based quantitative glycomics. In parallel, we also develop chemical tags such as N, N-dimethylated leucine (DiLeu) for glycopeptide quantitation. Collectively, these cost-effective and novel mass defect-based labeling reagents enable robust, sensitive, and accurate glycomic and glycoproteomic analysis with enhanced quantitative performance and structural elucidation capabilities. The performance and utility of these tags will be evaluated and demonstrated by several complex biological samples in cancer biology and Alzheimer’s disease.