Experimental and Theoretical Studies on Interaction of Environmental Estrogens with Cyclodexrtins as a Receptor Model

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The molecular inclusion of several environmental estrogens and other hormones with (β-, dimethy-β-, and trimethyl-β-cyclodextrins(CD) as receptor models in aqueous solution was investigated at different temperatures. The binding constants were calculated for each system imposing a 1:1 stoichiometry. Dimethyl-β-CD showed the highest binding constant among the three complexes. The fitness of the guest to the cavity of CD was suggested to affect the binding constant. Based on the temperature dependence of the binding constants at different temperatures, the entropy and enthalpy changes were calculated for the complex formation and contribution of entropy to the process was discussed. Molecular modeling studies were performed by means of Monte Carlo Simulation in order to determine the preferred complex formation of cyclodextrins and environmental estrogen molecules. The formation of the complex involves the phenyl group of the guest molecules which mainly interact with electrostatic interaction and hydrophobic interaction by van der Waals forces. Molecular mechanics(MM) calculations served to investigate the molecular inclusion. The more energetically stable complexes by inclusion with CD calculated based on semiempirical molecular orbital (MO) were obtained compared with CD and estrogen alone, respectively. The structural information about the preferred complex formation by inclusion from the MO calculations was also obtained and the results were compared with experimental data.