Fragmentation of negative ions from carbohydrates:: Part 1.: Use of nitrate and other anionic adducts for the production of negative ion electrospray spectra from N-linked carbohydrates
Fragmentation of negative ions from carbohydrates:: Part 1.: Use of nitrate and other anionic adducts for the production of negative ion electrospray spectra from N-linked carbohydrates
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DOI：
10.1016/j.jasms.2005.01.004
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发表时间：
2005-05-01
影响因子：
3.2
通讯作者：
Harvey, DJ
中科院分区：
文献类型：
--
作者：
Harvey, DJ
使用 Waters-Micromass Q-TOF Ultima Global 串联四极杆/飞行时间 (Q-TOF) 质谱仪，通过电喷雾从甲醇:水中的聚糖和各种盐的稀溶液中产生 N 连接聚糖的负离子光谱。与氯离子、溴离子、碘离子、硝酸根、硫酸根和磷酸根形成稳定的阴离子加合物。通过还原性 N-乙酰氨基葡萄糖 (GlcNAc) 残基的交叉环裂解而断裂的不稳定加合物与氟化物、氮化物、硫化物、碳酸盐、碳酸氢盐、氢氧化物和乙酸盐形成。由硝酸铵制备的硝酸盐加合物产生了最令人满意的光谱，因为它们相对不含源内碎裂产物，并且给出的信号强度约为由含有氢氧化铵的溶液制备的相应[M-H](-)离子的信号强度的十倍。检测限在 20 fmol 左右。中性聚糖产生单电荷离子和双电荷离子，较大的聚糖更倾向于形成双电荷离子。由于阴离子基团的电离，具有多个酸性基团的酸性聚糖产生较高电荷态的离子。单电荷离子的低能碰撞诱导分解 (CID) 谱主要由交叉环和 C 型片段组成，而正离子的相应谱主要包含 B 型和 Y 型糖苷片段。这些离子的形成可以通过最初形成的阴离子加合物从各种羟基中夺取质子来合理化。突出的糖苷和交叉环裂解离子定义了结构特征，例如两个触角各自的具体组成、平分 GlcNAc 残基的存在和岩藻糖残基的位置，这些细节很难通过常规技术确定。由于电荷集中在酸官能团而不是羟基上，酸性聚糖的断裂方式不同。 (c) 2005 年美国质谱学会。
Negative ion spectra of N-linked glycans were produced by electrospray from a dilute solution of the glycans and various salts in methanol:water using a Waters-Micromass Q-TOF Ultima Global tandem quadrupole/time-of-flight (Q-TOF) mass spectrometer. Stable anionic adducts were formed with chloride, bromide, iodide, nitrate, sulphate, and phosphate. Unstable adducts that fragmented by a cross-ring cleavage of the reducing N-acetylglucosamine (GIcNAc) residue, were formed with fluoride, nitride, sulphide, carbonate, bicarbonate, hydroxide, and acetate. Nitrate adducts prepared from ammonium nitrate produced the most satisfactory spectra as they were relatively free from in-source fragmentation products and gave signals that were about ten times as strong as those from corresponding [M - H](-) ions prepared from solutions containing ammonium hydroxide. Detection limits were in the region of 20 fmol. Neutral glycans gave both singly- and doubly-charged ions with the larger glycans preferring the formation of doubly-charged ions. Acidic glycans with several acidic groups gave ions in higher charge states as the result of ionization of the anionic groups. Low energy collision-induced decomposition (CID) spectra of the singly-charged ions were dominated by cross-ring and C-type fragments, unlike the corresponding spectra of the positive ions that contained mainly B- and Y-type glycosidic fragments. Formation of these ions could be rationalized by proton abstraction from various hydroxy groups by an initially-formed anionic adduct. Prominent glycosidic and cross-ring cleavage ions defined structural features such as the specific composition of each of the two antennae, presence of a bisecting GlcNAc residue and location of fucose residues, details that were difficult to determine by conventional techniques. Acidic glycans fragmented differently on account of charge localization on the acid functions rather than the hydroxy groups. (c) 2005 American Society for Mass Spectrometry.