Chakraborty Papri, Neumaier Marco, Weis Patrick, Kappes Manfred M
Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany.
Institute of Physical Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
J Am Soc Mass Spectrom. 2023 Apr 5;34(4):676-684. doi: 10.1021/jasms.2c00351. Epub 2023 Mar 23.
Cyclodextrin (CD) macrocycles are used to create a wide range of supramolecular architectures which are also of interest in applications such as selective gas adsorption, drug delivery, and catalysis. However, predicting their assemblies and identifying the possible isomers in CD oligomers have always remained challenging due to their dynamic nature. Herein, we interacted CDs (α, β, and γ) with a divalent metal ion, Cu, to create a series of Cu-linked CD oligomers, from dimers to pentamers. We characterized these oligomers using electrospray ionization mass spectrometry and probed isomerism in each of these isolated oligomers using high resolution trapped ion mobility spectrometry. Using this technique, we separated multiple isomers for each of the Cu-interlinked CD oligomers and estimated their relative population, which was not accessible previously using other characterization techniques. We further carried out structural analysis of the observed isomers by comparing the experimental collision cross sections (CCSs) to that of modeled structures. We infer that the isomeric heterogeneity reflects size-specific packing patterns of individual CDs (e.g., close-packed/linear). In some cases, we also reveal the existence of kinetically trapped structures in the gas phase and study their transformation to thermodynamically controlled forms by examining the influence of activation of the ions on isomer interconversion.
环糊精（CD）大环用于构建多种超分子结构，这些结构在选择性气体吸附、药物递送和催化等应用中也备受关注。然而，由于其动态性质，预测其组装方式并识别CD低聚物中可能的异构体一直具有挑战性。在此，我们使CD（α、β和γ）与二价金属离子铜相互作用，以创建一系列从二聚体到五聚体的铜连接CD低聚物。我们使用电喷雾电离质谱对这些低聚物进行了表征，并使用高分辨率捕获离子淌度光谱对每个分离出的低聚物中的异构现象进行了探测。使用该技术，我们分离出了每种铜连接CD低聚物的多种异构体，并估计了它们的相对丰度，这是以前使用其他表征技术无法实现的。我们通过将实验碰撞截面（CCS）与模型结构的碰撞截面进行比较，进一步对观察到的异构体进行了结构分析。我们推断，异构异质性反映了单个CD的尺寸特异性堆积模式（例如，紧密堆积/线性）。在某些情况下，我们还揭示了气相中动力学捕获结构的存在，并通过研究离子活化对异构体相互转化的影响，研究了它们向热力学控制形式的转变。
