disialylated

Disialylated is a descriptive term used in glycobiology and lipidology to refer to molecules that bear two sialic acid residues. Sialic acids are a family of acidic sugars, most commonly N-acetylneuraminic acid (Neu5Ac), that are typically appended to underlying sugar chains at terminal positions via alpha-2,3 or alpha-2,6 linkages. When two such residues are present on a glycan or glycolipid, the molecule is described as disialylated.

In glycoproteins, disialylation often occurs on complex N-glycans with two terminal antennae that each harbor a sialic acid, producing di-sialylated glycoforms. In glycolipids, the term is routinely applied to disialogangliosides, which carry two sialic acids on their glycan headgroups. The presence of two sialic acids increases the negative charge of the molecule and can influence interactions with sialic acid–binding receptors and other lectins, as well as serum half-life and clearance mechanisms.

Biological significance of disialylation includes modulation of cell–cell interactions, immune recognition, and signaling. Altered disialylation patterns are observed in various physiological and pathological contexts, including development, inflammation, and cancer, where changes in sialylation states can affect receptor binding, immune evasion, or metastatic potential.

Detection and analysis typically rely on mass spectrometry and chromatographic methods, sometimes complemented by exoglycosidase digestion with neuraminidases to determine the number of sialic acids. Lectin binding assays using sialic-acid–specific lectins and detailed MS/MS analyses help distinguish di-sialylated from other sialylation states.