Scheme 1.

Numbering system for high-mannose glycans. The circles correspond to mannose residues. The squares indicate N-acetylglucosamine residues. The solid circles and squares compose the core of the N-glycan structure. Additional mannose residues (empty circles) can be linked to the core structure and the resulting species are named according to occupying positions (circles) of the mannose residues. For Mannose7, the D₁, D₂, and D₃ isomers refer to the structures that have the last mannose residue at D₁, D₂ and D₃ positions, respectively. The C₁₃D₁₃ isomer has additional mannose residues at C₁, C₃, D₁, and D₃ positions.