Experiment and theory combine to produce a practical negative ion calibration set for collision cross-section determinations by travelling-wave ion-mobility mass spectrometry
Experiment and theory combine to produce a practical negative ion calibration set for collision cross-section determinations by travelling-wave ion-mobility mass spectrometry
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DOI：
10.1002/rcm.6266
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发表时间：
2012-07-30
影响因子：
2
通讯作者：
Mayer, Paul M.
中科院分区：
文献类型：
--
作者：
Hamilton, Jenna V.;Renaud, Justin B.;Mayer, Paul M.
基本原理 带负电离子的横截面测量相对较少。可用的校准物为 390 埃 2 至 641 埃 2 和 1174 埃 2 至 3395 埃 2 范围提供足够的横截面覆盖。这并不是特别适合确定较小离子（例如小肽）的碰撞截面。方法采用分子力学/分子动力学 (MM/MD) 模拟结合模拟退火来寻找长度为 39（单去质子化）和 513（双去质子化）的聚苯乙烯 (PS) 低聚物的低能分子构象。采用 MOBCAL 中的轨迹方法推导出它们各自的碰撞截面 O。使用 Waters Synapt G2 质谱仪中将校正的 O 值与漂移时间相关的校准图来预测 dT10 DNA -2 至 -6 电荷态的 O 值。结果 用于离子淌度谱测定的可靠负离子校准装置的计算机设计成功地使用了α，omega-羧基封端的 PS 低聚物来确定 132388 埃 2 范围内带负电离子的碰撞截面。预测 dT10 DNA 的所有电荷状态与这些离子的参考值的误差在 3% 以内。结论 a,omega-羧基封端的 PS 低聚物被发现是校准离子迁移谱仪以获得中等大小离子横截面的绝佳选择。内部侧链之间相互作用较少或较弱的低聚物（如聚乙二醇低聚物）往往具有多种低能分子构象，导致其理论上预测的碰撞截面存在较大的标准偏差。版权所有 (c) 2012 John Wiley & Sons, Ltd.
RATIONALE There are relatively few cross-section measurements for negatively charged ions. Available calibrants provide sufficient cross-section coverage for the 390 angstrom 2 to 641 angstrom 2 and 1174 angstrom 2 to 3395 angstrom 2 ranges. This is not particularly well suited for determining the collision cross-sections of smaller ions, such as small peptides. METHODS Molecular mechanics/molecular dynamics (MM/MD) simulations, coupled with simulated annealing, were used to find the low-energy molecular conformations of polystyrene (PS) oligomers of length 39 (singly deprotonated) and 513 (doubly deprotonated). The trajectory method in MOBCAL was employed to derive their respective collision cross-sections, O. A calibration plot relating corrected O values to drift times in a Waters Synapt G2 mass spectrometer was used to predict the O values for the -2 to -6 charge states of dT10 DNA. RESULTS The in silico design of a reliable negative ion calibration set for ion mobility spectrometry successfully resulted in the use of a,omega-carboxy-terminated PS oligomers to determine the collision cross-sections of negatively charged ions in the range 132388 angstrom 2. All charge states of dT10 DNA were predicted to within 3% of the referenced values for these ions. CONCLUSIONS a,omega-Carboxy-terminated PS oligomers were found to be an excellent choice to calibrate ion mobility spectrometers to obtain cross-sections for moderately sized ions. Oligomers with fewer, or weaker, interactions among the internal side chains (like poly(ethylene glycol) oligomers) tend to have a wide range of low-energy molecular conformations resulting in large standard deviations in their theoretically predicted collision cross-sections. Copyright (c) 2012 John Wiley & Sons, Ltd.