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  • Title: Crystalline beta-cyclodextrin.12H2O reversibly dehydrates to beta-cyclodextrin.10.5 H2O under ambient conditions.
    Author: Steiner T, Koellner G, Ali S, Zakim D, Saenger W.
    Journal: Biochem Biophys Res Commun; 1992 Nov 16; 188(3):1060-6. PubMed ID: 1445343.
    Abstract:
    In contact with mother liquor, crystalline beta-cyclodextrin (beta-CD) hydrate has composition approximately beta-CD.12H2O. If crystals are dried at ambient conditions (18 degrees C, approximately 50% humidity), the unit cell volume diminishes approximately 30 to 50 A3. X-ray structure analysis of a dry crystal (0.89 A resolution, 4617 data, R = 0.059) showed the composition beta-CD.10.5 H2O, with approximately 5.5 water molecules in the beta-CD cavity (7 partially and 2 fully occupied sites) and approximately 5.0 between the beta-CD molecules. The positions of the beta-CD host and of most of the hydration waters are conserved during dehydration, but the occupancies of the waters in the beta-CD cavity diminish. Dry crystals put into solvent re-hydrate to the original form. The mechanism of de- and re-hydration is not evident.
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