The approaches for analysis of N-glycans have radically altered in the last 20 years or so. Due to increased sensitivity, mass spectrometry has become the predominant method in modern glycomics. Here, we summarize recent studies showing that the improved resolution and detection by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has contributed greatly to the discovery of a large range of anionic and zwitterionic N-glycan structures across the different kingdoms of life, whereby MALDI-TOF MS in negative mode is less widely performed than in positive mode. However, its use enables the detection of key fragments indicative of certain sugar modifications such as sulfate, (methyl) phosphate, phosphoethanolamine, (methyl)aminoethylphosphonate, glucuronic, and sialic acid, thereby enabling certain isobaric glycan variations to be distinguished. As we also discuss in this review, complementary approaches such as negative-mode electrospray ionization-MS/MS, Fourier-transform ion cyclotron resonance MS, and ion mobility MS yield, respectively, cross-linkage fragments, high accuracy masses, and isomeric information, thus adding other components to complete the jigsaw puzzle when defining unusual glycan modifications from lower organisms.

中文翻译：

---

负模式质谱分析无脊椎动物、真菌和原生生物 N-聚糖

在过去 20 年左右的时间里，N-聚糖的分析方法发生了根本性的变化。由于灵敏度提高，质谱法已成为现代糖组学中的主要方法。在这里，我们总结了最近的研究，表明通过基质辅助激光解吸/电离飞行时间质谱 (MALDI-TOF MS) 提高的分辨率和检测对发现大量阴离子和两性离子 N-不同生命界的聚糖结构，因此负模式下的 MALDI-TOF MS 不如正模式下广泛执行。然而，它的使用能够检测指示某些糖修饰的关键片段，例如硫酸盐、（甲基）磷酸盐、磷酸乙醇胺、（甲基）氨基乙基膦酸盐、葡萄糖醛酸和唾液酸，从而能够区分某些同量异位聚糖变异。正如我们在本综述中还讨论的那样，负模式电喷雾电离 MS/MS、傅立叶变换离子回旋共振 MS 和离子淌度 MS 等互补方法分别产率、交联片段、高精度质量和异构信息，从而在定义来自低等生物的异常聚糖修饰时添加其他组件来完成拼图游戏。