Influence of Substitution Groups on the Inclusion Complexation of β-Cyclodextrin

Molecular dynamic (MD) simulations have been performed to investigate the inclusion behavior of anthracene (ANT) into three kinds of CDs, that is, β-CD, HP–β-CD, and SBE–β-CD. MD results show that ANT can spontaneously enter into the cavity of the three kinds of CD. The difference is that ANT can only enter into the cavity of SBE–β-CD from its wide rim. The effects of the substitutional groups 2-hydroxypropyl (HP) and sulfonated butyl (SBE) on the CD structure were then investigated by analyzing the structural distortion of glucose units of each CD. It is found that the neutral β-CD shows a conical structure, while the existence of HP or SBE groups influenced the structure greatly. The secondary rim would narrow down due to the flipping of the glucose units caused by the fluctuation of substitution groups. When ANT was included inside the cavity, the cavity conformation of the three CDs has recovered to a certain degree. Meanwhile, the substitutional groups extend along the cavity axis and interact with the guest molecule. By analyzing the interactions between each CD and ANT, it is found that the substitution groups enlarged the volume of the hydrophobic cavity. Both the substitutional group and the
glucose units would contribute to the interactions with the guest molecule. The conformational change of the CD ring results in the shrinkage of the cavity, which may cause tight binding with the ANT molecule.

The manuscript is illustrated with nice computer graphics on the conformations of the complexes.

Yan X, Wang Y, Meng T and Yan H (2021) Computational Insights Into the Influence of Substitution Groups on the Inclusion Complexation of β-Cyclodextrin. Front. Chem. 9:668400.
doi: 10.3389/fchem.2021.668400