FREE-ENERGY OF ASSOCIATION OF THE K-CROWN-6 COMPLEX IN WATER - A NEW MOLECULAR-DYNAMICS STUDY(18)

We present a study of free energy profile, or potential of mean force (pmf), for the association of K+ to 18-crown-6 in water. The counterio n Cl- is included, and all long-range interactions are computed via th e Ewald summation method. The present results indicate that the minimu m free energy is located at the crown ether center of mass and similar to the complex observed in the solid state or simulated in vacuo. In addition, the crown ether retains its D-3d geometry with a small fluct uation throughout the simulations. The calculated binding free energy, and the corresponding association constant, compare reasonably with e xperimental measurements made on the same system.