Electrospray mass spectrometry and collision-induced fragmentation of 2-aminobenzamide-labelled neutral N-linked glycans
Electrospray mass spectrometry and collision-induced fragmentation of 2-aminobenzamide-labelled neutral N-linked glycans
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作者：
D. Harvey
使用电喷雾电离和碰撞诱导分解在混合 Q-TOF 仪器上检查来自高甘露糖、杂合和复杂 N 连接聚糖的单电荷和双电荷钠化加合物的正离子碎片谱，这些加合物在还原末端用 2-氨基苯甲酰胺 (2-AB) 标记。 [M + Na]+ 离子的丰度可以通过在高锥电压下操作离子源来增强，给出了信息最丰富的光谱，但是，由于单电荷离子的相对丰度作为质量函数的下降程度比双钠离子的丰度更大，因此后者对于较大的聚糖更有用。光谱比从质子化加合物获得的光谱更复杂，但比未衍生化聚糖的光谱更简单。虽然氢和钠加合物的光谱主要由 B 型和 Y 型糖苷裂解形成的离子主导，但钠加合物的光谱更复杂，包含额外的 C 和 Z 离子以及产生连接信息的跨环裂解产物。许多碎片离子是由于分子不同区域（内部碎片）糖残基的损失而通过多种途径形成的。还原端 2-AB 衍生物的存在有效地标记了分子的该区域，从而简化了光谱解释。通过该技术鉴定的结构特征包括同量异位单糖组成、是否存在核心（还原末端）连接的岩藻糖和“二等分”（4-连接至分支核心甘露糖）GlcNAc 残基以及有关分支模式的信息。
The positive ion fragmentation spectra of the singly- and doubly-charged sodiated adducts from high-mannose, hybrid and complex N-linked glycans, labelled at the reducing terminus with 2-aminobenzamide (2-AB), were examined using electrospray ionization and collision-induced decomposition on a hybrid Q-TOF instrument. [M + Na]+ ions, whose abundance could be enhanced by operating the ion source at a high cone-voltage, gave the most informative spectra but, because the relative abundance of the singly-charged ions fell as a function of mass to a greater extent than the abundance of the doubly-sodiated ions, the latter were more useful for larger glycans. The spectra were more complicated than those obtained from protonated adducts but simpler than those of the underivatised glycans. Although the spectra from both hydrogen and sodium adducts were dominated by ions formed by B- and Y-type glycosidic cleavages, those from the sodium adducts were more complex and contained additional C and Z ions together with products of cross-ring cleavages yielding linkage information. Many fragment ions were formed via multiple pathways by losses of sugar residues from different regions of the molecule (internal fragments). The presence of the reducing-terminal 2-AB derivative effectively labelled this region of the molecule, thus simplifying spectral interpretation. Structural features identified by this technique included the isobaric monosaccharide composition, presence or absence of a core (reducing-terminal) linked fucose and ‘bisecting’ (4-linked to the branching core mannose) GlcNAc residue together with information on the branching patterns.