Negative-mode matrix-assisted laser desorption/ionization mass spectrometry of maltoheptaose and cyclomaltooligosaccharides
Negative-mode matrix-assisted laser desorption/ionization mass spectrometry of maltoheptaose and cyclomaltooligosaccharides
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负模式基质辅助激光解吸/电离质谱法测定麦芽七糖和环麦芽低聚糖
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发表时间：
2002
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通讯作者：
H. Nakanishi
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作者：
T. Yamagaki;H. Nakanishi
我们在基质辅助激光解吸/电离质谱（MALDI - MS）中使用哈尔满（9H - 吡啶并[3,4 - b]吲哚）作为中性寡糖负离子模式电离的基质。发生了源内裂解（ISD），在负离子模式线性MALDI - MS中产生碎片离子[（M - C₄H₈O₄） - H]⁻。主要观察到麦芽七糖的ISD产物离子[（M - C₄H₈O₄） - H]⁻，但未观察到去质子化分子。在纤维六糖的MALDI质谱中，观察到ISD产物离子[（M - C₄H₈O₄） - H]⁻以及去质子化分子[M - H]⁻。在寡糖的正离子模式MALDI - MS谱图中，未观察到这些ISD产物离子。在环糊精（CD）的环麦芽寡糖中，在负离子模式MALDI - MS中仅清楚地观察到去质子化分子[M - H]⁻，未观察到ISD产物离子。葡萄糖基 - β - 环糊精的糖支化环糊精结果相同。麦芽七糖的ISD产物离子[（M - C₄H₈O₄） - H]⁻因此会在还原端产生，并且对应于2, 4A裂解。在环糊精的源后裂解（PSD）碎片谱图中，观察到由2, 4A和Z裂解产生的PSD产物离子[（M - C₄H₈O₄） - H]⁻。因此，环糊精的PSD产物离子[（M - C₄H₈O₄） - H]⁻的形成与负离子模式MALDI - MS中线性寡糖的ISD产物离子的形成有关。
We used norharmane (9H-pyrido[3,4-b]indole) as a matrix for negative-mode ionization of neutral oligosaccharides in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). In-source decay (ISD) fragmentation occurred, producing fragment ions [(M-C4H8O4)-H]- in negative-mode linear MALDI-MS. The ISD product ion [(M-C4H8O4)-H]- of maltoheptaose was predominantly observed but deprotonated molecule was not. In the MALDI mass spectrum of cellohexaose, the ISD product ion [(M-C4H8O4)-H]- was observed, as was deprotonated molecule [M-H]-. In positive-mode MALDI-MS spectra of oligosaccharides, these ISD product ions were not observed. In cyclomaltooligosaccharides of cyclodextrins (CD), only deprotonated molecules [M-H]- were observed clearly and ISD product ions were not seen in negative-mode MALDI-MS. The result of sugar branched cyclodextrin of glucosyl-βCD was the same. The ISD product ion [(M-C4H8O4)-H]- of maltoheptaose would thus occur at the reducing end and corresponded to 2, 4A fragmentation. In the post-source decay (PSD) fragment spectra of cyclodextrins, PSD product ions [(M-C4H8O4)-H]- produced by 2, 4A and Z cleavage were observed. The formation of PSD product ions [(M-C4H8O4)-H]- of cyclodextrins would thus relate to that of ISD product ions of linear oligosaccharides in negative-mode MALDI-MS.