Crystalline β-cyclodextrin · 12 H 2O reversibly dehydrates to β-cyclodextrin · 10.5 H 2O under ambient conditions

• Published in: Biochemical and biophysical research communications Vol. 188; no. 3; pp. 1060 - 1066
• Main Authors: Steiner, Thomas, Koellner, Gertraud, Ali, Shaukat, Zakim, David, Saenger, Wolfram
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 1992
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/0006-291X(92)91339-R

In contact with mother liquor, crystalline β-cyclodextrin (β-CD) hydrate has composition ∼ β-CD · 12 H 2O. If crystals are dried at ambient conditions (18°C, · 50 % humidity), the unit cell volume diminishes ∼ 30 to 50 Å 3. X-ray structure analysis of a dry crystal (0.89 Å resolution, 4617 data, R = 0.059) showed the composition β-CD · 10.5 H 2O, with ∼ 5.5 water molecules in the β-CD cavity (7 partially and 2 fully occupied sites) and ∼ 5.0 between the β-CD molecules. The positions of the β-CD host and of most of the hydration waters are conserved during dehydration, but the occupancies of the waters in the β-CD cavity diminish. Dry crystals put into solvent re-hydrate to the original form. The mechanism of de- and re-hydration is not evident.