Fusion of liposomes with planar lipid bilayers.

The fusion of liposomes with planar lipid bilayers was monitored by two different methods. (a) Liposomes consisting of phospholipids and cholesterol were added to the aqueous phase bathing the cholesterol-deficient planar lipid bilayers in the presence of nystatin. The resulting increase in the planar lipid bilayer's electrical conductance was considered indicative of fusion. (b) Transplanar lipid bilayer injection of 35SO24- trapped inside the liposomes. It is shown by both methods that fusion is specifically dependent on the presence of negatively charged phospholipids both in the liposomes and the planar lipid bilayers and on Ca2+ in the aqueous phase of the fusion system.