FIGURE 1.

MS analysis of X24-derived rhEPO glycopeptide HCSLNENITVPDTK. (A) Precursor mass range (27.6–28.7 min) displaying the X24-derived triple charged ([M+3H⁺]⁺) glycopeptide HCSLNENITVPDTK with different N-glycans attached. (B) An average mass shift of 14.0157 Da between the calculated single charged ([M+1H⁺]⁺) precursor masses (from left to right: 1216.1676 ([M+3H⁺]⁺) → 3646.4882 ([M+1H⁺]⁺); 1220.8393 ([M+3H⁺]⁺) → 3660.5033 ([M+1H⁺]⁺); 1225.5116 ([M+3H⁺]⁺) → 3674.5202 ([M+1H⁺]⁺); 1230.1816 ([M+3H⁺]⁺) → 3688.5302 ([M+1H⁺]⁺)) indicates the addition of methyl groups. Me: methyl, monoisotopic mass shift: +14.0157 Da. (C) Abbreviations and corresponding cartoons for non-pentosylated glycan structures described in this work. N-glycans are depicted according to the glycan nomenclature of the Consortium for Functional Glycomics (http://www.functionalglycomics.org), while the attachment of an unknown pentose is depicted as a red star.