Department of Chemistry and Biochemistry, University of Arizona, 1306 E University Blvd, Tucson, AZ, 85721, USA.
J Am Soc Mass Spectrom. 2019 Aug;30(8):1416-1425. doi: 10.1007/s13361-019-02174-x. Epub 2019 Apr 9.
Native mass spectrometry (MS) has become an important tool for the analysis of membrane proteins. Although detergent micelles are the most commonly used method for solubilizing membrane proteins for native MS, nanoscale lipoprotein complexes such as nanodiscs are emerging as a promising complementary approach because they solubilize membrane proteins in a lipid bilayer environment. However, prior native MS studies of intact nanodiscs have employed only a limited set of phospholipids that are similar in mass. Here, we extend the range of lipids that are amenable to native MS of nanodiscs by combining lipids with masses that are simple integer multiples of each other. Although these lipid combinations create complex distributions, overlap between resonant peak series allows interpretation of nanodisc spectra containing glycolipids, sterols, and cardiolipin. We also investigate the gas-phase stability of nanodiscs with these new lipids towards collisional activation. We observe that negative ionization mode or charge reduction stabilizes nanodiscs and is essential to preserving labile lipids such as sterols. These new approaches to native MS of nanodiscs will enable future studies of membrane proteins embedded in model membranes that more accurately mimic natural bilayers. Graphical Abstract.
天然质谱（MS）已成为分析膜蛋白的重要工具。尽管胶束去污剂是用于天然 MS 溶解膜蛋白最常用的方法，但纳米级脂蛋白复合物（如纳米盘）作为一种很有前途的补充方法正在出现，因为它们在脂质双层环境中溶解膜蛋白。然而，以前完整纳米盘的天然 MS 研究仅采用了一组质量相似的有限的磷脂。在这里，我们通过将质量彼此简单整数倍的脂质组合在一起，扩展了可用于纳米盘天然 MS 的脂质范围。尽管这些脂质组合产生了复杂的分布，但共振峰系列之间的重叠允许解释含有糖脂、固醇和心磷脂的纳米盘光谱。我们还研究了这些新脂质对纳米盘的碰撞激活的气相稳定性。我们观察到负离子模式或电荷还原稳定纳米盘，对于保护固醇等不稳定脂质是必不可少的。这些用于纳米盘天然 MS 的新方法将使未来对更准确模拟天然双层的模型膜中嵌入的膜蛋白的研究成为可能。
