The translocation of Ca2+ across phospholipid bilayers induced by a synthetic neutral Ca2+ -ionophore

The effect of a neutral synthetic Ca2+ -ligand, which induces selective Ca2+ transport in electrodialysis experiments in bulk membranes, on the Ca2+ permeability of phospholipid bilayers has been investigated. The ligand is able to promote the transport of Ca2+ across synthetic phospholipid bilayers and can therefore be classified as a Ca2+ -ionophore. Its activity is enhanced by the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP). The efficiency of the neutral carrier-mediated Ca2+ transport is rather low as compared with that of the charged Ca2+ -ionophore X537A. The Ca2+ selectivity of the nuetral ionophore is decreased by its incorporation in the low dielectric ambient of the phospholipid bilayer.