Crystal structure of a new cyclomaltoheptaose hydrate: beta-cyclodextrin.7.5H2O

Area of Science:

• Crystallography
• Carbohydrate Chemistry
• Structural Biology

Background:

• Beta-cyclodextrin (betaCD) is a cyclic oligosaccharide with a hydrophobic cavity and hydrophilic exterior.
• Understanding the hydration states of betaCD is crucial for its applications in drug delivery and molecular encapsulation.
• Previous studies have characterized fully hydrated forms of betaCD, but partially hydrated forms require further investigation.

Purpose of the Study:

• To elucidate the crystal structure of a partially hydrated form of beta-cyclodextrin (betaCD).
• To characterize the precise arrangement and distribution of water molecules within the betaCD crystal lattice.
• To compare the observed structure with previously reported hydrated forms of betaCD.

Main Methods:

• Single-crystal X-ray diffraction analysis was employed.
• The crystal structure was solved and refined using 6181 observed reflections.
• Unit cell parameters and atomic coordinates were determined for the partially hydrated betaCD complex.

Main Results:

• The crystal structure of beta-cyclodextrin (C(42)H(70)O(35).7.5H(2)O) was determined in space group P2(1).
• One water molecule was found within the betaCD cavity, occupying two partially filled positions.
• The remaining 6.5 water molecules were located between macrocycles, acting as space fillers.

Conclusions:

• The determined crystal structure represents a cage-type arrangement, consistent with other known hydrated forms of betaCD.
• The partial hydration pattern provides insights into the conformational flexibility and water-binding capabilities of betaCD.
• This structural data contributes to a comprehensive understanding of betaCD's solid-state behavior and its interactions with water.