Chen Yanfeng, Allegood Jeremy, Liu Ying, Wang Elaine, Cachón-Gonzalez Begoña, Cox Timothy M, Merrill Alfred H, Sullards M Cameron
School of Chemistry and Biochemistry, The Parker H. Petit Institute for Bioengineering and Bioscience, 315 Ferst Drive, Georgia Institute of Technology, Atlanta, Georgia 30332-0363, USA.
Anal Chem. 2008 Apr 15;80(8):2780-8. doi: 10.1021/ac702350g. Epub 2008 Mar 4.
The quality of tissue imaging by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) depends on the effectiveness of the matrix deposition, especially for lipids that may dissolve in the solvent used for the matrix application. This article describes the use of an oscillating capillary nebulizer (OCN) to spray small droplets of matrix aerosol onto the sample surface for improved matrix homogeneity, reduced crystal size, and controlled solvent effects. This system was then applied to the analysis of histological slices of brains from mice with homozygous disruption of the hexb gene (hexb-/-), a model of Tay-Sachs and Sandhoff disease, versus the functionally normal heterozygote (hexb+/-) by imaging MALDI-MS. This allowed profiling and localization of many different lipid species, and of particular interest, ganglioside GM2, asialo-GM2 (GA2), and sulfatides (ST). The presence of these compounds was confirmed by analysis of brain extracts using electrospray ionization in conjunction with tandem mass spectrometry (MS/MS). The major fatty acid of the ceramide backbone of both GM2 and GA2 was identified as stearic acid (18:0) versus nervonic acid (24:1) for ST by both tissue-imaging MS and ESI-MS/MS. GM2 and GA2 were highly elevated in hexb-/- and were both localized in the granular cell region of the cerebellum. ST, however, was localized mainly in myelinated fiber (white matter) region of the cerebellum as well as in the brain stem with a relatively uniform distribution and had similar relative signal intensity for both hexb+/- and hexb-/- brain. It was also observed that there were distinct localizations for numerous other lipid subclasses; hence, imaging MALDI-MS could be used for "lipidomic" studies. These results illustrate the usefulness of tissue-imaging MALDI-MS with matrix deposition by OCN for histologic comparison of lipids in tissues such as brains from this mouse model of Tay-Sachs and Sandhoff disease.
基质辅助激光解吸/电离质谱（MALDI-MS）的组织成像质量取决于基质沉积的效果，对于可能溶解在用于基质应用的溶剂中的脂质而言尤其如此。本文描述了使用振荡毛细管雾化器（OCN）将基质气溶胶的小液滴喷到样品表面，以提高基质均匀性、减小晶体尺寸并控制溶剂效应。然后将该系统应用于通过成像MALDI-MS分析来自己糖胺酶β基因纯合缺失小鼠（hexb-/-）（一种泰-萨克斯病和桑德霍夫病模型）与功能正常的杂合子（hexb+/-）的脑组织切片。这使得能够对许多不同的脂质种类进行分析和定位，特别值得关注的是神经节苷脂GM2、脱唾液酸GM2（GA2）和硫脂（ST）。通过使用电喷雾电离结合串联质谱（MS/MS）分析脑提取物，证实了这些化合物的存在。通过组织成像质谱和电喷雾电离串联质谱（ESI-MS/MS）鉴定出，GM2和GA2的神经酰胺主链的主要脂肪酸均为硬脂酸（18:0），而ST的为神经酸（24:1）。GM2和GA2在hexb-/-中高度升高，并且都定位在小脑的颗粒细胞区域。然而，ST主要定位在小脑的有髓纤维（白质）区域以及脑干，分布相对均匀，并且在hexb+/-和hexb-/-脑中有相似的相对信号强度。还观察到许多其他脂质亚类存在明显的定位；因此，成像MALDI-MS可用于“脂质组学”研究。这些结果说明了使用OCN进行基质沉积的组织成像MALDI-MS对于泰-萨克斯病和桑德霍夫病小鼠模型的脑组织等组织中脂质的组织学比较的有用性。
