Electron transfer dissociation (ETD) and collision-induced dissociation (CID) were used to investigate underivatized, metal-cationized oligosaccharides formed via electrospray ionization (ESI). Reducing and non-reducing sugars were studied including the tetrasaccharides maltotetraose, 3α,4β,3α-galactotetraose, stachyose, nystose, and a heptasaccharide, maltoheptaose. Univalent alkali, divalent alkaline earth, divalent and trivalent transition metal ions, and a boron group trivalent metal ion were adducted to the non-permethylated oligosaccharides. ESI generated [M + Met]⁺, [M + 2Met]²⁺, [M + Met]²⁺, [M + Met – H]⁺, and [M + Met – 2H]⁺ most intensely along with low intensity nitrate adducts, depending on the metal and sugar ionized. The ability of these metal ions to produce oligosaccharide adduct ions by ESI had the general trend: Ca(II) > Mg(II) > Ni(II) > Co(II) > Zn(II) > Cu(II) > Na(I) > K(I) > Al(III) ≈ Fe(III) ≈ Cr(III). Although trivalent metals were utilized, no triply charged ions were formed. Metal cations allowed for high ESI signal intensity without permethylation. ETD and CID on [M + Met]²⁺ produced various glycosidic and cross-ring cleavages, with ETD producing more cross-ring and internal ions, which are useful for structural analysis. Product ion intensities varied based on glycosidic-bond linkage and identity of monosaccharide sub-unit, and metal adducts. ETD and CID showed high fragmentation efficiency, often with complete precursor dissociation, depending on the identity of the adducted metal ion. Loss of water was occasionally observed, but elimination of small neutral molecules was not prevalent. For both ETD and CID, [M + Co]²⁺ produced the most uniform structurally informative dissociation with all oligosaccharides studied. The ETD and CID spectra were complementary.

中文翻译：

---

未衍生化金属化寡糖的电子转移解离和碰撞诱导解离

电子转移解离（ETD）和碰撞诱导解离（CID）用于研究通过电喷雾电离（ESI）形成的未衍生化，金属阳离子化的寡糖。研究了还原糖和非还原糖，包括麦芽四糖，3α，4β，3α-半乳糖四糖，水苏糖，半乳糖，四糖麦芽七糖。一价碱金属，二价碱土金属，二价和三价过渡金属离子以及硼基三价金属离子被加成到非全甲基化的低聚糖上。ESI生成了[M + Met] ⁺，[M + 2Met] 2 ⁺，[M + Met] 2 ⁺，[M + Met – H] ⁺和[M + Met – 2H] ⁺最弱的是硝酸盐加合物，具体取决于离子化的金属和糖。这些金属离子通过ESI产生寡糖加合离子的能力具有总体趋势：Ca（II）> Mg（II）> Ni（II）> Co（II）> Zn（II）> Cu（II）> Na（ I）> K（I）> Al（III）≈Fe（III）≈Cr（III）。尽管使用了三价金属，但没有形成三重带电离子。金属阳离子可实现高ESI信号强度而不会发生甲基化。[M +大都会] ²⁺上的ETD和CID产生了各种糖苷和交叉环裂解，ETD产生了更多的交叉环和内部离子，可用于结构分析。产物离子强度基于糖苷键连接和单糖亚基以及金属加合物的身份而变化。ETD和CID表现出较高的碎片分离效率，通常具有完全的前体解离作用，具体取决于加成金属离子的身份。偶尔会观察到水的流失，但是消除中性小分子并不普遍。对于ETD和CID，[M + Co] ²⁺与所有研究的寡糖均产生最均匀的结构信息解离。ETD和CID光谱是互补的。