these results can be explained by assuming three mechanisms for salt permeation across gramicidin-containing liposomes : ( i ) the anion moves by the lipid part of the membrane whereas the cation moves by the gramicidin channel , ( ii ) movement of the undissociated acid species occurs through the lipid part of the membrane followed by cation-proton exchange via the gramicidin channel and ( iii ) the cation and anion may move simultaneously via the gramicidin channel .
C0021966
i
C0003075
anion