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.

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.

Four new bis-macrocyclic bolaamphiphiles were prepared to explore the effects of hydrophobic substitutions on ion transport. In bilayer vesicles the new compounds were remarkably similar to more hydrophilic derivatives prepared previously. Planar bilayer conductance experiments showed the new compounds induced an unique current-time signal consisting of a rapid rise time, followed by a slower decay time. Signal shape was cation dependent and was related to a modest selectivity between cations. Cation-anion selectivity was very high, approaching an ideal cation selectivity. One compound also showed voltage dependence of the signal shape and duration. Qualitative changes in signal shape, duration, and voltage dependence were provoked by variation in the electrolyte pH and by masking the head-group electrostatic interactions with low levels of barium ions. A model for the signal shape is proposed, involving a rapid current rise due to aggregate restructuring, followed by slower decay due to development of the local Donnan potential that results from the high cation-anion selectivity.Key words: ion channel, synthesis, bilayer membrane, bilayer clamp, mechanism.

Stormwater pollutants can have deleterious impacts on the aquatic life of receiving water bodies. This paper presents the findings of a stormwater quality monitoring program performed in the town of Jasper in Alberta, Canada. This is one of the very few studies done on a small urban settlement to identify key pollutants of concern, characterize stormwater and identify unique pollutant sources in the town. A total of 14 stormwater quality parameters were found to be of high concern to aquatic life. The most prominent pollutants were total suspended solids (TSS), metals and phosphorus which compared well with studies conducted in large urban settlements. Tourist influx contributed to high metal and petroleum hydrocarbon loads during the peak season due to high vehicular activity. Elk were found to reside in the town during summer and their fecal droppings resulted in elevated fecal coliform concentrations. It was found that winter road salting was responsible for excessive chloride concentrations observed during the spring melt. TSS concentrations were statistically correlated with various metals as well as phosphorus using Spearman's rank correlation. It was found that the current street sweeping schedule in the town coincided with lower TSS and metal loads in stormwater.