Development of Single Particle Analyzer of Mass and Mobility (SPAMM)

描述(申请人提供)：质谱学正在迅速成为一种强有力的大分子络合物结构鉴定方法，可以为传统的生物物理方法提供补充信息。完整的络合物可以通过电喷雾电离从溶液中分离出来，这会给这些分子组装增加许多电荷。实验表明，在许多情况下，这些气相离子保留了其溶液相结构的许多元素。直接质量测量提供了对络合物化学计量比的快速测量，即使对于非均相混合物也是如此。复合体的碎片化可以获得关于复合体内亚单位连接性的信息。此外，基于离子迁移率的方法开始提供络合物的横截面测量，使获得互补的形状信息成为可能。将质谱学应用于更大的络合物的一个挑战是样品的异质性，这可能导致无法分辨的电荷态分布。另一个挑战是，许多质谱计的灵敏度随着质量/电荷比(m/z)的增加而降低，这使得高灵敏度的分子质量在几兆道尔顿及更高的络合物的检测变得更加困难。电喷雾电离的一个方面是荷电程度通常随着分子大小的增加而增加。这使得电荷检测质谱仪成为分析大分子络合物的一种有吸引力的手段，因为它的优点是可以很容易地检测到具有多个电荷的单个离子。由于电荷会随着分子大小的增加而增加，因此这项技术的灵敏度实际上会随着分子量的增加而提高。样品的不均一性不会干扰质量或迁移率的测量，因为每个离子都是单独分析的。我们计划开发一种单粒子质量和迁移率分析仪(SPAMM)，它将结合m/z和电荷探测测量，以便能够快速测量单个离子的质量。串联质谱仪功能将被整合到这台双静电离子陷阱仪器中，这将使测量已知质量的单个离子的碎裂光谱成为可能(初步研究将侧重于红外多光子解离，尽管也可以采用其他方法)。最后，离子迁移率能力将被集成到这个设备中，使其能够测量离子的质量，并随后获得其绝对碰撞截面，这提供了关于络合物形状的信息。也可以获得由复合体解离产生的片段的横截面，提供关于亚基连接性对复合体整体结构的贡献的信息。由于这种装置中的感应电流与大分子络合物上的电荷数量成正比，因此灵敏度应该随着颗粒尺寸的增加而增加，因此这种方法适用的多相络合物比目前商业上可用的质谱仪分析的要大得多。

DESCRIPTION (provided by applicant): Mass spectrometry is rapidly becoming a powerful method for the structural elucidation of macromolecular complexes, and can provide complimentary information to conventional biophysical methods. Intact complexes can be lifted out of solution with electrospray ionization, which adds many charges to these molecular assemblies. Experiments have shown that in numerous cases, these gas-phase ions retain many elements of their solution-phase structure. A direct mass measurement provides a rapid measure of the stoichiometry of complexes, even for heterogeneous mixtures. Fragmentation of complexes can yield information about the connectivity of subunits within the complex. Additionally, ion mobility-based approaches are beginning to provide cross-sectional measurements of complexes, making it possible to obtain complementary shape information. A challenge in applying mass spectrometry to even larger complexes is sample heterogeneity, which can result in unresolved charge-state distributions. An additional challenge is that the sensitivity of many mass spectrometers decreases with increasing mass-to-charge ratio (m/z), which makes it more difficult to detect complexes with molecular weights of several mega Daltons and higher with high sensitivity. One aspect of electrospray ionization is that the degree of charging generally increases with molecular size. This makes charge detection mass spectrometry an attractive means of analyzing large macromolecular complexes, because it has the advantage that individual ions possessing multiple charges can be readily detected. Because charge will increase with size, the sensitivity of this technique actually improves with increasing molecular weight. The heterogeneity of the sample does not interfere with mass or mobility measurements, because each ion is analyzed individually. We plan to develop a Single Particle Analyzer of Mass and Mobility (SPAMM), which will incorporate m/z and charge detection measurements so that the masses of individual ions can be rapidly measured. Tandem mass spectrometry capabilities will be incorporated into this dual electrostatic ion trap instrument which will make it possible to measure a fragmentation spectrum of an individual ion of known mass (initial studies will focus on infrared multiple photon dissociation, although other methods could also be incorporated). Finally, ion mobility capabilities will be integrated into this device to make it possible to measure the mass of an ion, and subsequently obtain its absolute collision cross section, which provides information about the shape of the complex. Cross sections can also be obtained for fragments generated by the dissociation of a complex, providing information about the contribution of subunit connectivity to the overall structure of the complex. Because the induced current in this device is directly proportional to the number of charges on the macromolecular complex, sensitivity should increase with increasing particle size making this method applicable too much larger heterogeneous complexes than can be currently analyzed with commercially available mass spectrometers.