Evidence for reliable and consistent glycosylation of glycoprotein therapeutics is typically obtained through LC or LC-MS analysis of released N-linked glycans. However, drug discovery and development organizations, as well as regulatory agencies, frequently find value using orthogonal techniques to determine and/or confirm quantitative levels of sialic acids and monosaccharides contained in a therapeutic protein due to potential effect on biological activity and stability of the drug.
Waters offers UPLC, UHPLC, and HPLC-based C18 columns and defined application conditions that can assist scientists with the analysis and quantitation of these important glycan derived components.
Sialic Acid AnalysesA diverse range of sialic acids are found in nature, but the two major sialic acid species found on N- and O-linked glycans contained in biopharmacuticals are N-acetyl-neuraminic acid (Neu5Ac) and N-glycolyl-neuraminic acid (Neu5Gc). Since sialylation can enhance serum half-life, as well as affect biological activity, it is important to accurately monitor both the quantitative levels and types of sialic acids during all stages of the product life cycle. Many LC-based methods begin with the release of the targeted sialic acids under milder acid hydrolysis conditions (e.g., 2 M acetic acid for 2 hours at 80 °C). The released sialic acids then can be derivitized with 1,2-diamino-4,5-methylenedioxybenzene-2HCl (DMB) dye. |
Monosaccharide AnalysesThe primary monosaccharides that are found in N- and O-linked glycans are the neutral monosaccharides N-acetylglucosamine (GlcNAc), N-acetylgalactosamine (GalNAc), galactose (Gal), glucose (Glc), mannose (Man), and fucose (Fuc). The analysis of non-charged monosaccharides frequently begins by acid hydrolysis of the glycan by incubation with trifluoroacetic acid (TFA) or hydrochloric acid (HCl). Usually, a three-hour incubation at 100 °C with 2 M TFA will release all of the monosaccharides. However, it should be noted that during hydrolysis, the N-acetyl groups on GlcNAc and GalNAc are hydrolysed to glucosamine (GlcN) and galactosamine (GalN). Following hydrolysis, the released monosaccharides are derivatized using 2-aminobenzoic acid (2-AA). |