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The synthesis and characterization of a dissymmetric bis-macrocyclic bolaamphiphile ion channel is described. Bilayer-clamp experiments give rectified macroscopic current−voltage responses in which current is carried only at cis-negative potentials. Voltage and orientation-dependent irregular single-channel activity is also observed. Partial protonation of the carboxylate headgroups of the bolaamphiphile results in long-lived single channels with additional shorter-lived states of higher conductance. Single channels are also stabilized in the presence of barium cations. Vesicle experiments establish that transport activity is strongly cation- and concentration-dependent, suggesting the formation of aggregates. The voltage-gating process apparently involves the interaction of the applied potential with the molecular dipole of the bolaamphiphile which stabilizes an active aggregate.
Fyles et al. (Fri,) studied this question.