Studies involving the electrostatic potential of valinomycin.

ABSTRACT

The electrostatic potential of valinomycin in various conformations as obtained by the crystal structures (uncomplexed, complexed) and theoretical considerations have been evaluated and compared. The potential energy profiles along the Ζ axis of the bracelet-like structures show a systematic variation from the uncomplexed to the complexed structure. This type of conformational change and the potential variation are probably associated with different states of ion transport, like the capture and release of ions by the ionophore. Also, the asymmetry of the molecule due to D-HyIV on one side and L-Lac on the other side is reflected in the potential values along the Z-axis, the magnitude of which, is considerable in the uncomplexed structure. The evaluation of the potential at the ab-initio level on smaller fragments indicate that the order of liganding capacity of oxygen is amide > ether > ester. Also, the inductive effects due to alkyl substitution is negligible as evidenced by the potential studies on the substituted amides and esters.