Our group has recently developed a protocol for the extraction and characterization of O-linked glycans (Wilkinson et al. 2021 (link)) with the following modifications. The remaining gels after N-glycan release were crushed by passing them through a small hole in the bottom of a 0.5 mL tube into a 1.5 mL tube at 14,000 rpm and dried down. Then, the crushed gels were resuspended in 250 μL of 40% dimethylamine in water containing 0.1 g/mL ammonium carbonate and transferred to G4 vials (Anton Paar, Graz, Austria). The vials were inserted into a Monowave 450 microwave reactor (Anton Paar), in which the vials were subjected to 20 min microwave radiation at 70°C and 600 W. After the reaction, the remaining solution including the pieces of gel were transferred to 2 mL tubes and neutralized with 1 M HCl (all samples were at pH 7). Samples were desalted using a Hypersep Hypercarb SPE cartridge (Thermo Fisher Scientific, Waltham, MA) and dried.