In this study, a commercial uniform field drift tube ion mobility-mass spectrometer (IM-MS) was utilized to measure the gas-phase conformational populations of three well-studied proteins: ubiquitin (8566 Da), cytochrome c (12,359 Da), and myoglobin in both apo and holo forms (16,951 and 17,567 Da, respectively) in order to evaluate the use of this technology for broadscale structural proteomics applications. Proteins were electrosprayed from either acidic organic (pH ~3) or aqueous buffered (pH ~6.6) solution phase conditions, which generated a wide range of cation charge states corresponding to both extended (unfolded) and compact (folded) gas-phase conformational populations. Corresponding collision cross section (CCS) measurements were compiled for significant ion mobility peak features observed at each charge state in order to map the conformational landscapes of these proteins in both helium and nitrogen drift gases. It was observed that the conformational landscapes were similar in both drift gases, with differences being attributed primarily to ion heating during helium operation due to the necessity of operating the instrument with higher pressure differentials. Higher resolving powers were observed in nitrogen, which allowed for slightly better structural resolution of closely-spaced conformer populations. The instrumentation was found to be particularly adept at measuring low abundance conformers which are only present under gentle conditions which minimize ion heating. This work represents the single largest ion mobility CCS survey published to date for these three proteins with 266 CCS values and 117 ion mobility spectra, many of which have not been previously reported.

中文翻译：

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泛素、细胞色素 c 和肌红蛋白的构象图：氦和氮漂移气体中的均匀场离子迁移率测量

在这项研究中，使用商用均匀场漂移管离子迁移质谱仪 (IM-MS) 来测量三种经过充分研究的蛋白质的气相构象群：泛素 (8566 Da)、细胞色素 c (12,359 Da)、 apo 和全息形式的肌红蛋白（分别为 16,951 和 17,567 Da），以评估该技术在大规模结构蛋白质组学应用中的应用。从酸性有机 (pH ~ 3) 或水性缓冲 (pH ~ 6.6) 溶液相条件电喷雾蛋白质，这产生了广泛的阳离子电荷状态，对应于扩展（展开）和紧凑（折叠）气相构象群. 相应的碰撞截面 (CCS) 测量被编译用于在每个电荷状态观察到的显着离子迁移率峰值特征，以便绘制这些蛋白质在氦和氮漂移气体中的构象景观。据观察，两种漂移气体的构象景观相似，差异主要归因于氦气操作过程中的离子加热，因为需要在更高的压差下操作仪器。在氮中观察到更高的分辨率，这使得紧密间隔的构象异构体群的结构分辨率略好。发现该仪器特别擅长测量低丰度构象异构体，这些构象异构体仅存在于最小化离子加热的温和条件下。