The globular shape of gaseous ions, resulting from the ionization of large molecules such as polymers and proteins, is a recurring subject that has undergone a renewed interest with the advent of ion mobility spectrometry (IMS), especially in conjunction with theoretical chemistry techniques such as Molecular Dynamics (MD). Globular conformations result from a fine balance between entropy and enthalpy considerations. For multiply charged ions isolated in the gas phase of a mass spectrometer, the Coulombic repulsion between the different charges tends to prevent the ions from adopting a compact, and folded 3D structure. In the present paper, we closely associate data from IMS experiments and MD simulations to unambiguously access the conformations of dendrimer ions in the gas phase with special attention paid to the dendrimer structure, the generation, and the charge state. By doing so, we here combine a set of structural tools able to evaluate the (non)globular shape of ions based on both experimental and theoretical results.

中文翻译：

---

气态低电荷树枝状聚合物离子的球形如何：分子动力学/离子迁移率研究？

由大分子（例如聚合物和蛋白质）电离产生的气态离子的球形形状是一个反复出现的主题，随着离子迁移谱（IMS）的出现，尤其是与理论化学技术（例如，分子动力学（MD）。球状构象是由熵和焓之间的良好平衡引起的。对于在质谱仪气相中分离的带多个电荷的离子，不同电荷之间的库仑排斥趋向于阻止离子采用紧凑且折叠的3D结构。在本文中，我们密切关联来自IMS实验和MD模拟的数据，以明确访问气相中的树枝状聚合物离子的构型，并特别注意树枝状聚合物的结构，产生和充电状态。通过这样做，我们在这里结合了一组能够根据实验和理论结果评估离子的（非）球形形状的结构工具。