UV & INFRARED MATRIX ASSISTED LASER DESORPTION & IONIZATION: TOF MS: GLYCOLIPIDS

基质辅助激光解吸/电离(MALDI)提供了 比液体二次电离质量有相当大的提高 光谱灵敏度，受抑制效果的影响较小 这可能会抑制电喷雾电离产生来自 糖偶联物。在我们的实验室里，紫外线(337 Nm)和 红外线(2.94 fm)照射用于测定 天然和衍生的鞘糖脂。有了这种技术， 分子量可在飞摩尔(Fmol)进行测量。 水平。一个潜在的缺点是很少能揭示结构 碎片离子在记录在正常线性或 反射模式，但亚稳态碎片离子信息可以 通过运行后震源中的反射仪获得 衰减(PSD)模式。亚稳态碎裂可产生丰富的产物 与以前在碰撞诱导下观察到的离子类似 裂解(CID)串联(MS/MS)质谱图。我们正在优化e 实验条件，并汇编 有序糖脂集合的PSD谱建立规则 对碎片化模式的解释。神经酰胺总大小 并且碳水化合物部分的序列可以在 Pmol水平及以下，即使对于混合物的成分也是如此。这个 正在将这种方法应用于小批量获得的糖脂 来自生物来源，并通过层析手段进行纯化。

Matrix-assisted laser desorption/ionization (MALDI) offers a considerable increase over liquid secondary ionization in mass spectral sensitivity, and is less subject to the suppression effects that may inhibit electrospray ionization production of signal from glycoconjugates. In our laboratory, both ultraviolet (337 nm) and infrared (2.94 fm) irradiation are being used for determinations of native and derivatized glycosphingolipids. With this technique, molecular weight measurements may be made at the femtomole (fmol) level. A potential disadvantage is that few structure-revealing fragment ions are observed in spectra recorded in the normal linear or reflectron modes, but metastable fragment ion information can be obtained by operation of a reflectron instrument in the post-source decay (PSD) mode. Metastable fragmentation yields abundant product ions similar to those observed previously in collision-induced decomposition (CID) tandem (MS/MS) mass spectra. We are optimizing e xperimental conditions and assembling a reference collection of the PSD spectra of ordered sets of glycolipids to establish rules for the interpretation of the fragmentation patterns. The total ceramide size and the sequence of the carbohydrate moiety can be determined at the pmol level and below, even for the components of mixtures. The approach is being applied to glycolipids obtained in small quantities from biological sources and purified by chromatographic means.