Proteins can undergo glycosylation during and/or after translation to afford glycoconjugates, which are often secreted by a cell or populate cell surfaces. Changes in the glycan portion can have a strong influence on a glycoconjugate and are associated with a multitude of human pathologies. Of particular interest are sialylated glycoconjugates, which exist as constitutional isomers that differ in their linkages (α2,3, α2,6, α2,8 or α2,9) between sialic acids and their neighbouring monosaccharides. In general, mass spectrometry enables the rapid and sensitive characterization of glycosylation, but there are challenges specific to identifying and (relatively) quantifying sialic acid isomers. These challenges can be addressed using linkage-specific methodologies for sialic acid derivatization, after which mass spectrometry can enable product identification. This Review is concerned with the new and important derivatization approaches reported in the past decade, which have been implemented in various mass-spectrometry-glycomics workflows and have found clinical glycomics applications. The convenience and wide applicability of the approaches make them attractive for studies of sialylation in different types of glycoconjugate.

蛋白质可以在翻译期间和/或翻译后进行糖基化以提供糖缀合物，这些糖缀合物通常由细胞分泌或填充细胞表面。聚糖部分的变化会对糖缀合物产生强烈影响，并与多种人类病理学有关。特别令人感兴趣的是唾液酸化糖缀合物，它们以结构异构体的形式存在，它们在唾液酸与其相邻单糖之间的连接（α2,3、α2,6、α2,8 或 α2,9）不同。一般来说，质谱法能够快速、灵敏地表征糖基化，但在识别和（相对）量化唾液酸异构体方面存在特定挑战。这些挑战可以使用唾液酸衍生化的特定链接方法来解决，之后质谱可以进行产品鉴定。本综述关注过去十年中报道的新的重要衍生化方法，这些方法已在各种质谱-糖组学工作流程中实施，并发现了临床糖组学应用。这些方法的便利性和广泛适用性使其对不同类型糖缀合物唾液酸化的研究具有吸引力。