Prell James S
Department of Chemistry and Biochemistry, 1253 University of Oregon, Eugene, OR, USA, 97403-1253.
Materials Science Institute, 1252 University of Oregon, OR, USA, 97403-1252.
Int J Mass Spectrom. 2024 Oct;504. doi: 10.1016/j.ijms.2024.117290. Epub 2024 Jul 3.
Many powerful methods in mass spectrometry rely on activation of ions by high-energy collisions with gas particles. For example, multiple Collision Induced Dissociation (CID) has been used for many years to determine structural information for ions ranging from small organics to large, native-like protein complexes. More recently, Collision Induced Unfolding (CIU) has proved to be a very powerful method for understanding high-order protein structure and detecting differences between similar proteins. Quantifying the thermochemistry underlying dissociation/unfolding in these experiments can be quite challenging without reliable models of ion heating and cooling. Established physical models of CID are valuable in predicting ion heating but do not explicitly include mechanisms for cooling, which may play a large part in CID/CIU in modern instruments. and Molecular Dynamics methods are extremely computationally expensive for modeling CID/CIU of large analytes such as biomolecular ions. In this tutorial perspective, limiting behaviors of ion kinetic energy damping, heating, and cooling set by "extreme" cases are explored, and an Improved Impulsive Collision Theory and associated software ("Ion Simulations of the Physics of Activation", IonSPA) are introduced that can model all of these for partially inelastic collisions. Finally, examples of modeled collisional activation of native-like protein ions under realistic experimental conditions are discussed, with an outlook toward the use of IonSPA in accessing the thermochemical information hidden in CID breakdown curves and CIU fingerprints.
质谱分析中的许多强大方法都依赖于离子与气体粒子的高能碰撞来实现离子活化。例如，多年来，多次碰撞诱导解离（CID）已被用于确定从小分子有机物到大型天然蛋白质复合物等各种离子的结构信息。最近，碰撞诱导展开（CIU）已被证明是一种非常强大的方法，可用于理解高阶蛋白质结构并检测相似蛋白质之间的差异。在这些实验中，如果没有可靠的离子加热和冷却模型，量化解离/展开背后的热化学过程可能极具挑战性。已建立的CID物理模型在预测离子加热方面很有价值，但没有明确包含冷却机制，而冷却机制在现代仪器的CID/CIU中可能起很大作用。分子动力学方法对于模拟诸如生物分子离子等大型分析物的CID/CIU计算成本极高。在本教程视角中，探讨了由“极端”情况设定的离子动能阻尼、加热和冷却的极限行为，并介绍了一种改进的脉冲碰撞理论及相关软件（“活化物理的离子模拟”，IonSPA），该软件可以对部分非弹性碰撞的所有这些情况进行建模。最后，讨论了在实际实验条件下对天然蛋白质离子进行碰撞活化建模的示例，并展望了使用IonSPA获取隐藏在CID分解曲线和CIU指纹中的热化学信息的前景。
