Debois Delphine, Smargiasso Nicolas, Demeure Kevin, Asakawa Daiki, Zimmerman Tyler A, Quinton Loïc, De Pauw Edwin
Mass Spectrometry Laboratory, GIGA-R, Department of Chemistry, University of Liège, Allée de la Chimie 3, 4000, Liège, Belgium.
Top Curr Chem. 2013;331:117-41. doi: 10.1007/128_2012_363.
Matrix-assisted laser desorption/ionization (MALDI) is now a mature method allowing the identification and, more challenging, the quantification of biopolymers (proteins, nucleic acids, glycans, etc). MALDI spectra show mostly intact singly charged ions. To obtain fragments, the activation of singly charged precursors is necessary, but not efficient above 3.5 kDa, thus making MALDI MS/MS difficult for large species. In-source decay (ISD) is a prompt fragmentation reaction that can be induced thermally or by radicals. As fragments are formed in the source, precursor ions cannot be selected; however, the technique is not limited by the mass of the analyzed compounds and pseudo MS3 can be performed on intense fragments. The discovery of new matrices that enhance the ISD yield, combined with the high sensitivity of MALDI mass spectrometers, and software development, opens new perspectives. We first review the mechanisms involved in the ISD processes, then discuss ISD applications like top-down sequencing and post-translational modifications (PTMs) studies, and finally review MALDI-ISD tissue imaging applications.
基质辅助激光解吸/电离（MALDI）现在是一种成熟的方法，可用于生物聚合物（蛋白质、核酸、聚糖等）的鉴定，更具挑战性的是对其进行定量分析。MALDI光谱大多显示完整的单电荷离子。为了获得碎片，单电荷前体的活化是必要的，但在3.5 kDa以上效率不高，因此MALDI MS/MS对大分子物质来说比较困难。源内衰变（ISD）是一种可通过热或自由基诱导的快速碎片化反应。由于碎片在源内形成，无法选择前体离子；然而，该技术不受分析化合物质量的限制，并且可以对强碎片进行伪MS3操作。新型基质的发现提高了ISD产率，再结合MALDI质谱仪的高灵敏度以及软件开发，开辟了新的前景。我们首先回顾ISD过程中涉及的机制，然后讨论ISD的应用，如自上而下测序和翻译后修饰（PTM）研究，最后回顾MALDI-ISD组织成像应用。
