Human Erythrocyte Membrane Acetylcholinesterase. Incorporation into the Lipid Bilayer Structure of Liposomes

Abstract

Human erythrocyte acetylcholinesterase was incorporated into liposomes of different phospholipid composition by detergent depletion methods. Complete incorporation of activity into liposomes was achieved. Either by gel filtration or by dialysis 99.96% of the sodium deoxycholate originally present was removed. The preferred method of liposome formation involved the use of dialysis followed by gel filtration, as gel filtration alone resulted in liposomes heterogeneous in size. The liposomes had a diameter of about 30 nm (determined by EM and gel filtration). Studies using Triton X-100 and proteolytic enzymes revealed that at least 70% of the incorporated activity was located on the outer side of the liposomes; this percentage was even higher in small liposomes.