[Comparison of the kinetics of ionophore-induced ion transport in conventional and solventless membranes]

In contrast to conventional membranes prepared from a mixture of glyceryl-monooleate (GMO) and decane (GMO-D) which still contain decane in the final state, the membranes formed from a mixture of GMO and squalene (GMO-S) or triolein (GMO-T) contain finally only GMO and are said to be "solventless". The use of the electric current relaxation technique following a voltage jump has allowed us to characterize the effect of the absence of solvent on the various steps of ion transport induced by nonactin. We have measured the rates of formation (kri) of dissociation (kDi) and of translocation (kis) of the ion-ionophore complex as well as the rate of translocation of the ionophore (ks). With the GMO-S and GMO-T membranes, kis is about ten times higher, ks, twice as high, and kDi twice as small than with the GMO-D membranes. The observed effects are always more prominent with the GMO-T membranes. These results can be interpreted in terms of modifications of the energy barriers in the membrane due to the absence of solvent.