A comparative study on the effectiveness of various procedures for attachment of two proteins (L-asparaginase and horse radish peroxidase) to the surface of liposomes.

Five different ways of association of proteins with the surfaces of liposomes were compared. L-asparaginase (L-asp.) and horse radish peroxidase (HRP) were used as proteins since these show a large difference in their numbers of amino groups. Liposomal association was performed by way of: 1) non-specific coating of empty liposomes; 2) incorporation after 'hydrophobisation' with palmitoylchloride; 3) as 2 with dodecanoic acid; 4) coupling to phosphatidylinositol (PI) already incorporated in the liposomal membrane; and 5) as 4 with phosphatidylethanolamine (PE). The relative effectiveness of the different procedures for coupling of the proteins to liposomes as determined by the enzyme activities of intact liposomes shows a large variation, dependent on both the method used and the protein.