Water inside β-cyclodextrin cavity: amount, stability and mechanism of binding

Area of Science:

• Supramolecular Chemistry
• Physical Chemistry
• Computational Chemistry

Background:

• Cyclodextrins (CDs) are cyclic oligosaccharides known for forming inclusion complexes.
• CDs can accommodate water molecules, but their hydration in the native state, particularly for beta-cyclodextrin (β-CD), is not fully understood.
• Specific questions persist regarding water molecule binding sites, stabilization factors, and the energetics of β-CD hydration.

Purpose of the Study:

• To elucidate the preferred locations for water molecule binding within the β-CD cavity.
• To identify the stabilizing forces and dominant interactions governing water clusters in β-CD.
• To determine the maximum water molecule capacity of β-CD and compare its hydration thermodynamics with α-cyclodextrin.

Main Methods:

• Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TG) for experimental characterization.
• Density Functional Theory (DFT) for theoretical investigations.
• Combined experimental and computational approach to address hydration questions.

Main Results:

• Identified specific localities within the β-CD macrocycle that exhibit strong attraction for water molecules.
• Characterized the stabilizing factors and dominant interactions (host-guest and guest-guest) in β-CD hydration.
• Quantified the maximum number of water molecules within the β-CD cavity and provided comparative thermodynamic data with α-CD.

Conclusions:

• The study provides a comprehensive understanding of β-cyclodextrin hydration, including binding sites and energetics.
• Results clarify the nature of water-β-CD interactions and the capacity of the β-CD cavity.
• Comparative analysis with α-cyclodextrin offers insights into size-dependent hydration effects in cyclodextrins.