Negative hydrophobic ions as transport-mediators for positive ions: evidence for a carrier mechanism.

The permeability of hydrophobic cations, such as tetraphenylarsonium across biological membranes and artificial lipid membranes is strongly increased in the presence of trace amounts of hydrophobic anions like tetraphenylborate (Liberman, Y.A. and Topaly, V.P. (1969) Biofizika 14, 452--461). Voltage-jump relaxation experiments performed on thin lipid membranes support the idea that the anions, A-, act as carriers for the cations, B+, by the formation of neutral ion pairs, A-B+. Their permeability is not affected by the electric dipole potential, which hinders the movement of free cations, B+.