1. Department of Biochemistry, Center for Biomedical Mass Spectrometry, Boston University School of Medicine, Boston, Massachusetts 02118, United States
2. Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, United States
3. Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
4. Department of Chemical Biology and Drug Discovery, Utrecht Institute for Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, 3584 CG, Netherlands