Monosialylated

Monosialylated refers to molecules, typically glycoproteins or glycolipids, that carry a single sialic acid residue as part of their glycans. Sialic acids are a family of acidic sugars, with N-acetylneuraminic acid (Neu5Ac) being the most common in humans. In glycoconjugates, sialylation commonly occurs at the terminal positions of N-linked or O-linked glycans; monosialylated structures have one sialic acid per glycan chain, while others may be di-, tri-, or polysialylated.

Physiochemical and biological consequences: the terminal sialic acid imparts a negative charge at physiological pH, increasing hydrophilicity and influencing molecular recognition. Monosialylated glycans can modulate interactions with lectins and cell-surface receptors, and they affect serum half-life by influencing clearance pathways such as the asialoglycoprotein receptor, which preferentially removes desialylated glycoconjugates. In therapeutic proteins, sialylation patterns, including monosialylation, are a key quality attribute because they affect stability, immunogenicity, and pharmacokinetics.

Biosynthesis: sialyltransferases add sialic acid to terminal galactose residues during glycan assembly, while neuraminidases can remove it. Variation in enzyme activity, substrate availability, and processing can yield monosialylated forms.

Detection and analysis: monosialylation can be assessed by mass spectrometry, chromatographic release and labeling of glycans, or lectin-binding assays using sialic-acid–binding lectins. Understanding monosialylation is relevant for biology, biopharmaceutical development, and glycoengineering.