Cyclodextrin hexahydrate, hydrogen bonding

A molecular dynamics simulation of the crystal structures of a-cyclodextrin hexahydrate and / -cyclodextrin dodecahydrate was more successful. In both hydrates, the carbohydrate atomic positions and two third of the water positions were reproduced within the experimental accuracy, and most of the O-H 0 hydrogen bonds that had been determined by neutron diffraction studies (Part III, Chap. 18) also showed up in the simulation [360, 361]. 

When a-cyclodextrin is free in aqueous solution, it adopts the tense form found in the two hexahydrate crystal structures (Fig. 18.6 a) one glucose unit is rotated inwards to reduce the size of the a-cyclodextrin cavity so that the enclosed water molecules are held more tightly. The two intramolecular 0(2) 0(3 ) hydrogen bonds to this glucose unit are broken, the other four remain intact. 

Lesyng B, Saenger W (1981) Theoretical investigations on circular and chain-like hydrogen bonded structures found in two crystal forms of a-cyclodextrin hexahydrate. Models for hydration and water clusters. Biochim Biophys Acta 678 408-413... 

Klar B, Hingerty B, Saenger W (1980) Tbpography of cyclodextrin inclusion complexes. XII. Hydrogen bonding in the crystal structure of a-cyclodextrin hexahydrate the use of a multicounter detector in neutron diffraction. Acta Cryst B36 1154-1165... 

Lindner K, Saenger W (1982) Ibpography of cyclodextrin inclusion complexes. XVI. Cyclic system of hydrogen bonds structure of a-cyclodextrin hexahydrate, form (II) comparison with form (I). Acta Cryst B38 203-210... 

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