Formation and Dissociation Processes of Gas-Phase Detergent Micelles
Formation and Dissociation Processes of Gas-Phase Detergent Micelles
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DOI：
10.1021/la3002866
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发表时间：
2012-05-08
期刊：
影响因子：
3.9
通讯作者：
Robinson, Carol V.
中科院分区：
文献类型：
--
作者：
Borysik, Antoni J.;Robinson, Carol V.
在从溶液到气相的过渡过程中，胶束保护膜复合物的兴趣越来越大，这促使人们更好地理解它们的性质。我们已经使用离子迁移率质谱法来分离和分配由n-三甲基溴化铵系列洗涤剂形成的洗涤剂簇。我们发现簇大小与溶液中洗涤剂浓度无关，随着电荷状态的增加而增加，但随着烷基链长度的增加而惊人地减少。这种关系与溶液中胶束形成的热力学相矛盾。然而，同时考虑表面能和电荷的液滴模型与实验簇大小的相关性非常好。为了进一步探索气相胶束的性质，我们在串联质谱法中对它们进行了碰撞诱导解离。我们观察到前体离子簇的顺序不对称电荷分离和中性蒸发。然而，有趣的是，我们还发现较长烷基链洗涤剂的解离途径明显不同，形成的中间离子明显少于较短烷基链洗涤剂。这些实验为理解膜蛋白复合物的气相分析过程提供了必要的基础。此外，它们暗示了在气相活化过程中洗涤剂簇对蛋白质复合物提供保护的有价值的机制细节。
Growing interest in micelles to protect membrane complexes during the transition from solution to gas phase prompts a better understanding of their properties. We have used ion mobility mass spectrometry to separate and assign detergent clusters formed from the n-trimethylammonium bromide series of detergents. We show that cluster size is independent of detergent concentration in solution, increases with charge state, but surprisingly decreases with alkyl chain length. This relationship contradicts the thermodynamics of micelle formation in solution. However, the liquid drop model, which considers both the surface energy and charge, correlates extremely well with the experimental cluster size. To explore further the properties of gas-phase micelles, we have performed collision-induced dissociation on them during tandem mass spectrometry. We observed both sequential asymmetric charge separation and neutral evaporation from the precursor ion cluster. Interestingly, however, we also found markedly different dissociation pathways for the longer alkyl chain detergents, with significantly fewer intermediate ions formed than for those with a shorter alkyl chain. These experiments provide an essential foundation for understanding the process of the gas-phase analysis of membrane protein complexes. Moreover they imply valuable mechanistic details of the protection afforded to protein complexes by detergent clusters during gas-phase activation processes.