School of Chemical Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China; Collaborative Innovation Center of Chemistry for Energy Materials(iChEM), Shanghai Key Laboratory of Molecular Catalysis and Functional Material, Department of Chemistry and Laser Chemistry Institute, Fudan University, Shanghai 200433, China.
Collaborative Innovation Center of Chemistry for Energy Materials(iChEM), Shanghai Key Laboratory of Molecular Catalysis and Functional Material, Department of Chemistry and Laser Chemistry Institute, Fudan University, Shanghai 200433, China.
Talanta. 2018 Aug 15;186:1-7. doi: 10.1016/j.talanta.2018.04.003. Epub 2018 Apr 3.
Cyclodextrins (CDs) are a class of macrocyclic molecules that have exhibited many promising applications in various fields. The knowledge of the complexation modes and recognition mechanisms of CDs with their guests are of paramount importance for rational design of more variants with controlled properties. Herein we investigated the binding conformations and the structural characteristics of α-/β-CD with three amino acids (AA, AA=Gly, L-Leu, L-Phe) in the gas phase by a combined experimental and computational approach. Electrospray ionization-mass spectrometry suggested the formation of 1:1 anionic complexes between CDs and AAs and the complex anions were further identified by tandem mass spectrometry. Moreover, ion mobility-mass spectrometry experiments revealed the inclusion complexation adopted for [α-CD+Gly] as well as β-CD with either amino acid, whereas [α-CD+Leu] and [α-CD+Phe] favored an exclusion conformation, indicating size-dependent binding modes. The association is primarily driven by polar interactions via the formation of hydrogen bonds. Furthermore, the relative dynamic stabilities of the complex ions were observed to be in correlation with the gas-phase basicities of the deprotonated amino acid and CD anions. These above findings are well in line with our atomistic molecular dynamics simulation results. This study advances our understanding of the mechanisms underlying CD host-guest recognition.
环糊精（CDs）是一类大环分子，在各个领域表现出许多有前途的应用。了解 CDs 与客体的配合模式和识别机制对于合理设计具有可控性质的更多变体至关重要。在此，我们通过实验和计算相结合的方法研究了 α-/β-CD 与三种氨基酸（AA，AA=Gly，L-Leu，L-Phe）在气相中的结合构象和结构特征。电喷雾电离-质谱（ESI-MS）表明 CDs 和 AAs 之间形成了 1:1 的阴离子配合物，串联质谱进一步鉴定了配合物阴离子。此外，离子淌度-质谱实验表明[α-CD+Gly]以及β-CD 与任何一种氨基酸都采用包合配合，而[α-CD+Leu]和[α-CD+Phe]则倾向于排除构象，表明存在尺寸依赖性的结合模式。这种结合主要是通过形成氢键的极性相互作用驱动的。此外，观察到配合物离子的相对动态稳定性与去质子化氨基酸和 CD 阴离子的气相碱性相关。这些发现与我们的原子分子动力学模拟结果相符。这项研究增进了我们对 CD 主体-客体识别机制的理解。
