Pores Formed by Bis-macrocyclic Bola-amphiphiles in Vesicle and Planar Bilayer Membranes

A new series of bis-macrocyclic bola-amphiphiles were prepared, and their transport activities in vesicle and planar bilayer membranes were evaluated. From vesicle experiments, the apparent kinetic order in transporter indicates that aggregates are the kinetically active species. Step-conductance changes observed in planar bilayer membranes indicate that the compounds act as channels. Multiple copies of the same channel form in which the conductance is controlled by the macrocyclic portions of the structures. The pores are ion-selective in the sequence Cs(+) > K(+) > Na(+) > Cl(-), controlled by the polar head-groups of the structures. The data are consistent with a model involving the formation of active dimers.