Imidazole Derivatives Improve Charge Reduction and Stabilization for Native Mass Spectrometry
Imidazole Derivatives Improve Charge Reduction and Stabilization for Native Mass Spectrometry
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DOI：
10.1021/acs.analchem.9b04263
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发表时间：
2019-11-19
影响因子：
7.4
通讯作者：
Marty, Michael T.
中科院分区：
文献类型：
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作者：
Townsend, Julia A.;Keener, James E.;Marty, Michael T.
生物分子之间的非共价相互作用对其活性至关重要。天然质谱 (MS) 通过保留用于质量分析的非共价组装体（包括各种可溶性蛋白和膜蛋白的蛋白质-配体和蛋白质-蛋白质复合物）来表征这些相互作用。脂蛋白纳米盘天然 MS 的最新进展也使得能够对嵌入完整脂质双层中的抗菌肽和膜蛋白进行表征。然而，传统的天然电喷雾电离 (ESI) 会破坏不稳定的相互作用。为了稳定天然 MS 的大分子复合物，可以在 ESI 之前向溶液中添加电荷减少剂，例如三乙胺、三甲胺氧化物和咪唑。降低 ESI 期间获得的电荷可减少导致解离的库仑斥力，并且电荷减少试剂还可以通过蒸发冷却降低离子的内能。在这里，我们测试了一系列咪唑衍生物，以发现改进的电荷减少试剂，并确定它们的化学性质如何影响电荷减少功效。我们测量了它们对可溶性蛋白质复合物、洗涤剂中的膜蛋白复合物以及带有或不带有嵌入肽的脂蛋白纳米盘的影响，并使用计算化学来理解观察到的电荷减少行为。总之，我们的数据表明，与现有试剂相比，咪唑 2 位上的疏水取代基可以显着提高电荷减少和气相稳定性。这些新的咪唑衍生物将立即有益于一系列天然 MS 应用，并提供化学原理来指导新型电荷减少试剂的开发。
Noncovalent interactions between biomolecules are critical to their activity. Native mass spectrometry (MS) has enabled characterization of these interactions by preserving noncovalent assemblies for mass analysis, including protein-ligand and protein-protein complexes for a wide range of soluble and membrane proteins. Recent advances in native MS of lipoprotein nanodiscs have also allowed characterization of antimicrobial peptides and membrane proteins embedded in intact lipid bilayers. However, conventional native electrospray ionization (ESI) can disrupt labile interactions. To stabilize macromolecular complexes for native MS, charge reducing reagents can be added to the solution prior to ESI, such as triethylamine, trimethylamine oxide, and imidazole. Lowering the charge acquired during ESI reduces Coulombic repulsion that leads to dissociation, and charge reduction reagents may also lower the internal energy of the ions through evaporative cooling. Here, we tested a range of imidazole derivatives to discover improved charge reducing reagents and to determine how their chemical properties influence charge reduction efficacy. We measured their effects on a soluble protein complex, a membrane protein complex in detergent, and lipoprotein nanodiscs with and without embedded peptides, and used computational chemistry to understand the observed charge-reduction behavior. Together, our data revealed that hydrophobic substituents at the 2 position on imidazole can significantly improve both charge reduction and gas-phase stability over existing reagents. These new imidazole derivatives will be immediately beneficial for a range of native MS applications and provide chemical principles to guide development of novel charge reducing reagents.