Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022, China.
J Am Soc Mass Spectrom. 2011 May;22(5):845-55. doi: 10.1007/s13361-011-0085-0. Epub 2011 Mar 10.
MALDI in-source decay (ISD) technique described to date has proven to be a convenient and rapid method for sequencing purified peptides and proteins. However, the general ISD still can not produce adequate fragments for the detailed structural elucidation of oligosaccharides. In this study, an efficient and practical method termed the laser-enhanced ISD (LEISD) technique of MALDI-FTICR MS allows highly reliable and abundant fragmentation of the neutral oligosaccharides, which was attributed to the ultrahigh irradiation laser of mJ level. The yield of ISD fragmentation was evaluated under different laser powers for 7 neutral oligosaccharides using DHB as matrix. Better quality ISD spectra including fragment ions in low-mass region were obtained at higher laser power. Results from the LEISD of oligosaccharides demonstrated that a significantly better signal-to-noise ratio (S/N) and more structural information could be obtained in comparison to the conventional CID. It was also suggested that the valuable A ions derived from cross-ring cleavage of the linear oligosaccharides allowed the distinction among α(1→4)-, α(1→6)-, β(1→4)-, and β(1→3)-linked isobaric structures according to fragment types and intensities. In addition, ideal fragmentation ions observed by LEISD method facilitated the determination of the sequences and branched points of complex oligosaccharides from human milk.
目前为止，基质辅助激光解吸电离源内（in-source decay，ISD）技术已被证明是一种方便、快速的测序纯肽和蛋白质的方法。然而，一般的 ISD 技术仍然无法产生足够的片段来详细阐明寡糖的结构。在这项研究中，一种高效实用的方法，即 MALDI-FTICR MS 的激光增强 ISD（laser-enhanced ISD，LEISD）技术，允许高度可靠和丰富的中性寡糖片段化，这归因于毫焦级别的超高辐照激光。使用 DHB 作为基质，在不同激光功率下对 7 种中性寡糖进行了 ISD 片段化的产率评估。在较高的激光功率下，可以获得具有更多低质量区域碎片离子的高质量 ISD 谱。寡糖的 LEISD 结果表明，与传统的 CID 相比，可以获得更好的信噪比（signal-to-noise ratio，S/N）和更多的结构信息。此外，线性寡糖的交联环裂解产生的有价值的 A 离子，根据片段类型和强度，可用于区分α(1→4)-、α(1→6)-、β(1→4)-和β(1→3)-连接的等摩尔结构。此外，LEISD 方法观察到的理想片段离子有助于确定人乳中复杂寡糖的序列和分支点。
