Spraggins Jeffrey M, Rizzo David G, Moore Jessica L, Rose Kristie L, Hammer Neal D, Skaar Eric P, Caprioli Richard M
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, 37205, USA,
J Am Soc Mass Spectrom. 2015 Jun;26(6):974-85. doi: 10.1007/s13361-015-1147-5. Epub 2015 Apr 23.
MALDI imaging mass spectrometry is a highly sensitive and selective tool used to visualize biomolecules in tissue. However, identification of detected proteins remains a difficult task. Indirect identification strategies have been limited by insufficient mass accuracy to confidently link ion images to proteomics data. Here, we demonstrate the capabilities of MALDI FTICR MS for imaging intact proteins. MALDI FTICR IMS provides an unprecedented combination of mass resolving power (~75,000 at m/z 5000) and accuracy (<5ppm) for proteins up to ~12kDa, enabling identification based on correlation with LC-MS/MS proteomics data. Analysis of rat brain tissue was performed as a proof-of-concept highlighting the capabilities of this approach by imaging and identifying a number of proteins including N-terminally acetylated thymosin β(4) (m/z 4,963.502, 0.6ppm) and ATP synthase subunit ε (m/z 5,636.074, -2.3ppm). MALDI FTICR IMS was also used to differentiate a series of oxidation products of S100A8 (m/z 10,164.03, -2.1ppm), a subunit of the heterodimer calprotectin, in kidney tissue from mice infected with Staphylococcus aureus. S100A8 - M37O/C42O(3) (m/z 10228.00, -2.6ppm) was found to co-localize with bacterial microcolonies at the center of infectious foci. The ability of MALDI FTICR IMS to distinguish S100A8 modifications is critical to understanding calprotectin's roll in nutritional immunity.
基质辅助激光解吸电离成像质谱技术是一种用于可视化组织中生物分子的高灵敏度和高选择性工具。然而，鉴定检测到的蛋白质仍然是一项艰巨的任务。间接鉴定策略因质量精度不足而受到限制，无法将离子图像与蛋白质组学数据可靠地关联起来。在此，我们展示了基质辅助激光解吸电离傅里叶变换离子回旋共振质谱技术用于完整蛋白质成像的能力。基质辅助激光解吸电离傅里叶变换离子回旋共振成像质谱技术为分子量高达约12 kDa的蛋白质提供了前所未有的质量分辨能力（在m/z 5000时约为75,000）和精度（<5 ppm）的组合，能够基于与液相色谱-串联质谱蛋白质组学数据的相关性进行鉴定。作为概念验证，对大鼠脑组织进行了分析，通过成像和鉴定包括N端乙酰化胸腺素β(4)（m/z 4,963.502，0.6 ppm）和ATP合酶亚基ε（m/z 5,636.074，-2.3 ppm）在内的多种蛋白质，突出了该方法的能力。基质辅助激光解吸电离傅里叶变换离子回旋共振成像质谱技术还用于区分金黄色葡萄球菌感染小鼠肾脏组织中异源二聚体钙卫蛋白的一个亚基S100A8的一系列氧化产物（m/z 10,164.03，-2.1 ppm）。发现S100A8 - M37O/C42O(3)（m/z 10228.00，-2.6 ppm）与感染灶中心的细菌微菌落共定位。基质辅助激光解吸电离傅里叶变换离子回旋共振成像质谱技术区分S100A8修饰的能力对于理解钙卫蛋白在营养免疫中的作用至关重要。
