2.4. Fast enzymatic release and rapid labeling of N-glycans

A standard three-step protocol of the GlycoWorks RapiFluor-MS N-Glycan kit, including quick deglycosylation, rapid labeling and SPE clean-up of labeled glycans, was applied to standard proteins and isolated membrane proteins. The standard glycoproteins used were fetuin, IgG, lactoferrin, ribonuclease B (~1 μg for each). The entire process to prepare each sample could be accomplished in 30 min [15]. The labeled glycans from each glycoprotein were stored at 4 °C until LC–MS analysis was performed.