Robinson Errol W, Sellon Rachel E, Williams Evan R
Department of Chemistry, University of California, Berkeley, CA 94720-1460, United States.
Int J Mass Spectrom. 2007 Jan 1;259(1-3):87-95. doi: 10.1016/j.ijms.2006.09.011.
Protonated poly(ethylene glycol), produced by electrospray ionization (ESI), with molecular weights ranging from 0.3 to 5 kDa and charge states from 1+ to 7+ were characterized using high-field asymmetric waveform ion mobility spectrometry (FAIMS). Results for all but some of the 3+ and 4+ charge states are consistent with a single gas-phase conformer or family of unresolved conformers for each of these charge states. The FAIMS compensation voltage scans resulted in peaks that could be accurately fit with a single Gaussian for each peak. The peak widths increase linearly with compensation voltage for maximum ion transmission but do not depend on m/z or molecular weight. Fitting parameters obtained from the poly(ethylene glycol) data were used to analyze conformations of oxidized and reduced lysozyme formed from different solutions. For oxidized lysozyme formed from a buffered aqueous solution, a single conformer (or group of unresolved conformers) was observed for the 7+ and 8+ charge states. Two conformers were observed for the 9+ and 10+ charge states formed from more denaturing solutions. Data for the fully reduced form indicate the existence of up to three different conformers for each charge state produced directly by ESI and a general progression from a more extended to a more folded structure with decreasing charge state. These results are consistent with those obtained previously by proton-transfer reactivity and drift tube ion mobility experiments, although more conformers were identified for the fully reduced form of lysozyme using FAIMS.
通过电喷雾电离（ESI）产生的质子化聚乙二醇，其分子量范围为0.3至5 kDa，电荷态为1+至7+，使用高场不对称波形离子迁移谱（FAIMS）进行了表征。除了一些3+和4+电荷态外，所有这些电荷态的结果都与单个气相构象异构体或一组未解析的构象异构体一致。FAIMS补偿电压扫描产生的峰可以用单个高斯函数精确拟合每个峰。峰宽随补偿电压线性增加以实现最大离子传输，但不依赖于m/z或分子量。从聚乙二醇数据获得的拟合参数用于分析由不同溶液形成的氧化型和还原型溶菌酶的构象。对于由缓冲水溶液形成的氧化型溶菌酶，在7+和8+电荷态观察到单个构象异构体（或一组未解析的构象异构体）。对于由更多变性溶液形成的9+和10+电荷态观察到两种构象异构体。完全还原形式的数据表明，对于通过ESI直接产生的每个电荷态，存在多达三种不同的构象异构体，并且随着电荷态的降低，从更伸展的结构到更折叠的结构有一个总体趋势。这些结果与先前通过质子转移反应性和漂移管离子迁移实验获得的结果一致，尽管使用FAIMS为溶菌酶的完全还原形式鉴定出了更多的构象异构体。
