Department of Chemistry, University of Texas at Austin, Austin, TX 78712, USA.
Phys Chem Chem Phys. 2019 May 8;21(18):9265-9276. doi: 10.1039/c9cp01144g.
As applications in mass spectrometry continue to expand into the field of structural biology, there have been an increasing number of studies on noncovalent biological assemblies. Ensuring that protein complexes maintain native-like conformations and architectures during the transition from solution to the gas phase is a key aim. Probing composition and arrangement of subunits of multi-charged complexes via tandem mass spectrometry (MS/MS) may lead to protein unfolding and the redistribution of charges on the constituent subunits, leading to asymmetric charge partitioning and ejection of a high-charged monomer. Additionally, the overall dissociation efficiency of many ion activation methods is often suppressed for low charge states, hindering the effectiveness of MS/MS for complexes that have low charge density. Ultraviolet photodissociation (UVPD) of proteins using 193 nm photons is a high-energy alternative to collisional activation and demonstrates little to no charge state dependence. Here the symmetry of charge partitioning upon UVPD is evaluated for an array of multimeric protein complexes as a function of initial charge state. The results demonstrate that high laser energies (3 mJ) for UVPD induces more symmetric charge partitioning and ejection of low-charged, presumably compact monomers than higher-energy collisional dissociation (HCD).
随着质谱分析在结构生物学领域的应用不断扩展，对非共价生物组装体的研究也越来越多。确保蛋白质复合物在从溶液到气相的转变过程中保持类似天然的构象和结构是一个关键目标。通过串联质谱（MS/MS）探测多电荷复合物的亚基组成和排列，可能导致蛋白质展开和组成亚基上电荷的重新分布，导致不对称电荷分配和高电荷单体的逐出。此外，许多离子活化方法的整体解离效率通常会受到低电荷状态的抑制，从而阻碍了 MS/MS 对低电荷密度复合物的有效性。使用 193nm 光子的蛋白质紫外光解（UVPD）是一种对碰撞活化的高能替代方法，几乎没有电荷状态依赖性。本文研究了一系列多聚体蛋白质复合物在初始电荷状态下，UVPD 时电荷分配的对称性。结果表明，UVPD 所需的高激光能量（3mJ）比高能碰撞解离（HCD）更能诱导低电荷、可能更紧凑的单体的更对称的电荷分配和逐出。
