Structural analyses of carbohydrate moieties of glycoproteins by microwave-assisted partial acid hydrolysis and mass spectrometry

Characterization of carbohydrate moieties of glycoproteins using microwave-assisted partial acid hydrolysis (MAPAH) and mass spectrometry (MS) are described in this review. Acids including hydrochloric acid (HCl), trifluoroacetic acid (TFA), and phosphoric acid (H3PO4) can be used to induce partial hydrolysis of the carbohydrate moieties of glycoproteins in as short as 30 s of microwave exposure. High resolving power of MS allows distinction between different glycopeptide fragments. Several glycoproteins including bovine pancreatic ribonuclease B (RNase B, MW similar to 15 kDa), egg white avidin (MW similar to 16 kDa), human serum alpha(1)-acid glycoprotein (alpha(1)-AGP, MW similar to 36 kDa), horseradish peroxidase (HRP, MW similar to 44 kDa), fetal calf serum fetuin (BSF, MW similar to 45 kDa), and glucose oxidase from Aspergillus niger (GO, MW similar to 75 kDa), are used to demonstrate this technique. Information of the sugar composition and/or arrangement of the carbohydrate moieties can be readily obtained either from glycoproteins directly or digested glycopeptides of the glycoproteins. This method is fast, sensitive, and a reliable technique. Challenges when working on larger and heavily glycosylated glycoproteins are discussed.