β-Cyclodextrin hydration: a calorimetric and gravimetric study (original) (raw)
Hydration of beta-cyclodextrin: A molecular dynamics simulation study
Journal of Computer-Aided Molecular Design, 2000
We study by molecular dynamics simulations the hydration of β-cyclodextrin. Our simulations show that within these barrel-shaped molecules hydrophobicity dominates, while at the top and bottom sides of the barrel interactions with water are mostly hydrophilic in nature. These results agree with crystallographic data at 120 K and, in particular, with the spontaneous hydration process of a cyclodextrin crystal in wet atmosphere. The predicted structure of the hydration shells is discussed and compared with previous molecular mechanics calculations which report an overall hydrophobic behavior. Moreover, the temperature dependence of the hydration process is discussed.
Hydration of β-cyclodextrin: A molecular dynamics simulation study
Journal of Computer-aided Molecular Design, 2000
We study by molecular dynamics simulations the hydration of β-cyclodextrin. Our simulations show that within these barrel-shaped molecules hydrophobicity dominates, while at the top and bottom sides of the barrel interactions with water are mostly hydrophilic in nature. These results agree with crystallographic data at 120 K and, in particular, with the spontaneous hydration process of a cyclodextrin crystal in wet atmosphere. The predicted structure of the hydration shells is discussed and compared with previous molecular mechanics calculations which report an overall hydrophobic behavior. Moreover, the temperature dependence of the hydration process is discussed.
Inorganic salt modulation of the aqueous solubility of betabetabeta-cyclodextrin
a-, /~-and ~-Cyclodextrins have been shown to exist as aggregates in solution bound together by a network of hydrogen bonds. Removal of this network by ionisation of the hydroxyl groups leads to a greatly increased solubility and removal of aggregation. The presence of aggregates in solution of structure breaking solutes in which the solubility of/Lcyclodextrin is greatly enhanced, leads to a proposal that the abnormally low solubility of fl-CD may be explained by the presence of aggregates and the unfavourable interaction of these aggregates with the hydrogen bonded structure of water.
Inorganic salt modulation of the aqueous solubility of β-cyclodextrin
Supramolecular Chemistry, 1993
a-, /~-and ~-Cyclodextrins have been shown to exist as aggregates in solution bound together by a network of hydrogen bonds. Removal of this network by ionisation of the hydroxyl groups leads to a greatly increased solubility and removal of aggregation. The presence of aggregates in solution of structure breaking solutes in which the solubility of/Lcyclodextrin is greatly enhanced, leads to a proposal that the abnormally low solubility of fl-CD may be explained by the presence of aggregates and the unfavourable interaction of these aggregates with the hydrogen bonded structure of water.
Food Chemistry, 2012
The water sorption and physical properties of freeze-dried b-cyclodextrin (BCD) and 2-hydroxypropyl-bcyclodextrin (HBCD) were studied. The stability of the inclusion complexes of these cyclodextrins with different hydrophobic ingredients, such as myristic acid and a-terpineol, was investigated as a function of the storage time and water content of the systems. Besides increasing its solubility, BCD ring modification with hydroxypropyl groups conferred amorficity to the dehydrated matrices, and modified the sorption properties and their ability to form hydrates. Both ligands decreased BCD and HBCD water adsorption, in comparison with the pure cyclodextrins. The water adsorption data and glass transition values obtained are consistent with the displacement of water molecules from the inner cavity of the CDs when the ligand is included. Encapsulation of non-polar ligands of linear hydrocarbon chain, like myristic acid, was initially incomplete, depending on the ligand/CD ratio, and increased with the time of storage and water content.
Vibrational Spectroscopy, 2003
b-Cyclodextrin (b-CD) hydrate was dehydrated under vacuum at room temperature (293 K) and the changes of its IR n(OH) band profile were observed. A curve fitting with Voigt functions to the band profile was able using information obtained from difference spectra. Four different fitting strategies gave similar band components. The behavior of the integrated intensities of these components upon dehydration was the basis for an assignment of these band components. The component a 3580 cm À1 is due to water molecules in the b-CD cavity and they leave very fast the macrocycle upon dehydration. Two components at 3530 and 3289 cm À1 are assigned to OH groups retained in b-CD despite dehydration, i.e. primary and secondary OH groups. The components at 3422 and 3185 cm À1 may be associated with water molecules in the interstices among b-CD molecules and linked by hydrogen bonds with them. Nevertheless, additional contributions from primary and secondary OH groups were found for these two bands.
Enthalpy of solution of α-cyclodextrin in water and in formamide at 298.15K
Thermochimica Acta, 2004
A new dissolution microcalorimeter that can measure enthalpies of dissolution of slightly soluble solids was developed by Ingemar Wadsö at Lund University, and the prototype as well as the commercial vessel were tested in our laboratory. Recently we did report the testing of the prototype and we are now extending the previous investigation to measurements with an organic solvent in the commercial vessel. The instrument performance was found to be as good with formamide as with water. The vessel was calibrated chemically (dissolution of KCl in water) and electrically, by means of a permanent and an insertion heater. The results obtained from the three methods are compared and discussed. The enthalpy of dissolution of ␣-cyclodextrin, dry and hydrated with six water molecules, was determined in water and in formamide. The results are discussed in terms of the difference between water and formamide as regarding dissolution and binding to the cyclodextrin molecule.
Energetics of Water/Cyclodextrins Interactions
Journal of Inclusion Phenomena
The heat capacities of solid γ-CD, 8.1 H2O and α-CD, 6.0 H2O have been measured between 10 and 300 K by adiabatic calorimetry. Using earlier results obtained in similar experiments with anhydrous cyclodextrins and with β-CD, 9.7 H2O, a comparative analysis has been developed. The energetic behaviours of anhydrous and hydrated cyclodextrins (CDs) have been compared in order to investigate the role of water molecules in the stabilization of the cyclodextrin's rings and on their reactivities. Calculations, based on the additivity of thermodynamic properties, provide the energetic and entropic average contributions of water molecules in each cyclodextrin. From these results, we assumed that the water–water and water–CD interactions are rather different according to the cyclodextrin. In the (β-CD, 9.7 H2O) structure, the water molecules seem to be better organised in a relatively independent network. Concerning hydrated α-CD and γ-CD, stronger water–CD interactions probably prevent a...
Inorganic salt modulation of the aqueous solubility of β-cyclodextrin
a-, /~-and ~-Cyclodextrins have been shown to exist as aggregates in solution bound together by a network of hydrogen bonds. Removal of this network by ionisation of the hydroxyl groups leads to a greatly increased solubility and removal of aggregation. The presence of aggregates in solution of structure breaking solutes in which the solubility of/Lcyclodextrin is greatly enhanced, leads to a proposal that the abnormally low solubility of fl-CD may be explained by the presence of aggregates and the unfavourable interaction of these aggregates with the hydrogen bonded structure of water.
A look inside the cavity of hydrated α-cyclodextrin: A computer simulation study
Chemical Physics Letters, 2005
Monte Carlo simulations of hydrated a-cyclodextrin are made to analyze the properties of the water molecules inside the hydrophobic cavity. An average of five water molecules is found in the cavity, where only 2.4 are hydrogen bonded to the a-CD. The hydrogen-bond interactions between the a-CD and the inner water molecules are reduced when compared with those outside the cavity. The free energy of binding one water molecule inside the hydrated a-CD is obtained using the thermodynamic perturbation theory. From these the entropy contribution is obtained to ascertain the hydrophobic strength of the cavity.