Bimodal Complexations of Steroids with Cyclodextrins by a Flexible Docking Algorithm

Abstract

A flexible docking algorithm was developed for studying the inclusion complexes of cyclodextrins with steroids in aqueous solution by an optimization method and an empirical function. The function is used to estimate the binding free energy including intermolecular interaction energy, the conformational energy change, and the solvation energy. The bimodal complexations of twelve steroids in β- and γ-CD cavities were studied by the algorithm. For the two orientations of the guests in the cavity, the possible binding regions were investigated, and the lowest energies for the inclusion complexes in the binding regions were obtained. The stability constant for each orientation was estimated from the optimized energy components by a quantitative model. Therefore, the preferential orientations of the guests were found out from the results finally.