Glycosylation, the process of co- and posttranslational protein modification with complex carbohydrates, plays an important role in the interaction, function, and solubility of proteins (11–13). It is expected that more than half of all proteins is glycosylated with one or more N-glycans (14), and commonly observed glycoforms range from high-mannose- to complex type with two to four antennae (branching N-acetylglucosamines) (Figure 1) (12, 15). These structures may be extended by additional monosaccharides such as a bisecting N-acetylglucosamine, as well as galactoses, N-acetylneuraminic acids (sialic acids), and fucoses in a variety of different positions and linkages. This leads to a large N-glycan diversity, and may also lead to the formation of specific epitopes such as sialyl-Lewis X, which can be recognized by E-selectin (12, 16).