Glycobiology Advance Access originally published online on October 25, 2008
Glycobiology 2009 19(2):135-143; doi:10.1093/glycob/cwn115
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Capillary electrophoresis-electrospray ionization mass spectrometry for rapid and sensitive N-glycan analysis of glycoproteins as 9-fluorenylmethyl derivatives
2 Department of Chemistry and Biomolecular Science, Macquarie University, Sydney NSW 2109, Australia
3 Bruker Daltonics K. K., 9-A-6F, Moriya 3, Kanagawa-ku, Yokohama 221-0022
4 Bechman Coulter K. K., 3-5-1, Toranomon, Minato-ku, Tokyo 105-0001
5 Department of Glycotherapeutics, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
6 Faculty of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Higashi-Osaka 577-8502
7 Department of Glycotherapeutics, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
1 To whom correspondence should be addressed: Tel: +81-6-6878-8161; Fax: +81-6-6878-8162; e-mail: kondoa{at}sahs.med.osaka-u.ac.jp
Received on May 27, 2008; revised on September 20, 2008; accepted on October 12, 2008
It is well known that most protein therapeutics such as monoclonal antibody pharmaceuticals and other biopharmaceuticals including cancer biomarkers are glycoproteins, and thus the development of high-throughput and sensitive analytical methods for glycans is essential in terms of their determination and quality control. We previously reported a novel alternative labeling method for glycans involving 9-fluorenylmethyl chloroformate (Fmoc-Cl) instead of the conventional reductive amination procedure. The derivatives were analyzed by high-performance liquid chromatography (HPLC) (Kamoda S, Nakano M, Ishikawa R, Suzuki S, Kakehi K. 2005. Rapid and sensitive screening of N-glycans as 9-fluorenylmethyl derivatives by high-performance liquid chromatography: A method which can recover free oligosaccharides after analysis. J Proteome Res. 4:146–152). This method was rapid and simple; however, it was time-consuming in terms of analysis by HPLC and did not provide so much information such as the detailed structures and mass numbers of glycans. Here we have developed a high-throughput and highly sensitive method. It comprises three steps, i.e., release of glycans, derivatization with Fmoc, and capillary electrophoresis-electrospray ionization mass spectrometry (CE-ESI MS) analysis. We analyzed several glycoproteins such as fetuin, alpha1 acid glycoprotein, IgG, and transferrin in order to validate this method. We were able to analyze the above glycoproteins with the three-step procedure within only 5 h, which provided detailed N-glycan patterns. Moreover, the MS/MS analysis allowed identification of the N-glycan structures. As novel applications, the method was employed for the analysis of N-glycans derived from monoclonal antibody pharmaceuticals and also from alpha-fetoprotein; the latter is known as one of the tumor markers of hepatocellular carcinomas. We were able to easily and rapidly determine the detailed structures of the N-glycans. The present method is very useful for the analysis of large numbers of samples such as a routine analysis.
Key words: carbohydrate / CE-ESI MS / Fmoc / glycoprotein / N-glycan