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

基质辅助激光解吸/电离（MALDI）提供了一种 在质量上比液体二次电离有相当大的增加 光谱灵敏度高，受抑制影响小 其可以抑制电喷雾电离产生信号， 糖缀合物 在我们的实验室中，紫外线（337 nm）和 红外线（2.94 fm）辐射被用于测定 天然的和衍生的鞘糖脂。 有了这项技术， 可以在飞摩尔（fmol）下进行分子量测量， 水平 一个潜在的缺点是，很少有结构揭示 碎片离子在以正常线性或 反射器模式，但亚稳态碎片离子信息可以 通过操作后源中的反射器仪器获得 衰减（PSD）模式。 亚稳态裂解产生大量产物 离子类似于先前在碰撞诱导中观察到的离子 裂解（CID）串联（MS/MS）质谱。 我们正在优化E 实验条件和组装的参考集合， 糖脂的有序集合的PSD光谱，以建立用于糖脂的规则。 碎片化模式的解释。 神经酰胺总量 并且碳水化合物部分的序列可以在 pmol水平及以下，即使对于混合物的组分也是如此。 的 方法被应用于少量获得的糖脂 从生物来源并通过色谱方法纯化。

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.