Reitenbach David W, Botamanenko Daniel Y, Miller Lohra M, Jarrold Martin F
Chemistry Department, Indiana University, Bloomington, Indiana 47405, United States.
Megadalton Solutions Inc, 3750 E Bluebird Ln, Bloomington, Indiana 47401, United States.
Anal Chem. 2024 Aug 14. doi: 10.1021/acs.analchem.4c03267.
Charge detection mass spectrometry (CD-MS) allows mass distributions to be measured for heterogeneous samples that cannot be analyzed by conventional MS. With CD-MS, the / and charge are measured for individual ions using a detection cylinder embedded in an electrostatic linear ion trap (ELIT). Imprecision in both the / and charge measurements contribute to the mass resolution. However, if the charge can be measured with a precision of <0.2 e the charge state can be assigned with a low error rate and the mass resolving power only depends on the / resolution. Prior to this work, the best resolving power demonstrated experimentally for CD-MS was 700. Here we demonstrate a resolving power of >14,600, 20-times higher than the previous best. Trajectory simulations were used to optimize the geometry and electrostatic potentials of the ELIT. We found conditions where the energy dependence of the oscillation frequency becomes parabolic, and then operated with a nominal ion energy at the minimum of the parabola. The 14,600 resolving power was obtained with a beam collimator before the ELIT. With the collimator removed, the resolving power of the optimized ELIT is 7300, which is still an order of magnitude higher than the previous best. The resolving power was demonstrated by resolving the isotope distributions for peptides and proteins. High resolution CD-MS measurements were then used to resolve the glycans on a monoclonal antibody and applied to the analysis of hepatitis B virus capsids. The results indicate that procedures for adduct removal need to be improved for the full benefit of the higher resolving power to be realized for higher mass species. However, these results represent a key step toward using CD-MS to analyze very complex protein mixtures where charge states are not well resolved in the / spectrum because of congestion from numerous overlapping peaks.
电荷检测质谱法（CD-MS）能够测量传统质谱无法分析的异质样品的质量分布。利用CD-MS，通过嵌入静电线性离子阱（ELIT）中的检测筒来测量单个离子的质荷比。质荷比测量的不精确性都会影响质量分辨率。然而，如果电荷测量精度小于0.2e，则电荷态分配的错误率较低，且质量分辨能力仅取决于质荷比分辨率。在这项工作之前，CD-MS实验展示的最佳分辨能力为700。在此，我们展示了大于14,600的分辨能力，比之前的最佳结果高出20倍。通过轨迹模拟来优化ELIT的几何结构和静电势。我们发现了振荡频率的能量依赖性变为抛物线的条件，然后在抛物线最低点处以标称离子能量运行。在ELIT之前使用束流准直器获得了14,600的分辨能力。移除准直器后，优化后的ELIT分辨能力为7300，仍比之前的最佳结果高出一个数量级。通过分辨肽和蛋白质的同位素分布证明了分辨能力。然后，利用高分辨率CD-MS测量来分辨单克隆抗体上的聚糖，并应用于分析乙型肝炎病毒衣壳。结果表明，为了充分利用更高分辨能力以实现对更高质量物种的分析，需要改进加合物去除程序。然而，这些结果代表了朝着使用CD-MS分析非常复杂的蛋白质混合物迈出的关键一步，在这种混合物中，由于众多重叠峰的拥挤，质荷比谱中的电荷态无法很好地分辨。
