Affinity partitioning for membrane purification exploiting the biotin–NeutrAvidin interaction: Model study of mixed liposomes and membranes

Biotinylated negatively charged liposomes as well as membranes were affinity partitioned in an aqueous poly(ethylene glycol)–dextran two-phase system using NeutrAvidin conjugated to dextran as affinity ligand. Both liposomes and membranes redistributed from top to bottom phase upon addition of NeutrAvidin–dextran. The presence of 35–60 mM Li2SO4 was necessary both to force the components into the top phase without ligand and for ligand-dependent redistribution into the bottom phase. Attaching biotin via a hexanamidohexanoyl spacer and an increased density of biotin or NeutrAvidin enhanced the affinity separation. The separation conditions in these model experiments provide a basis for affinity partitioning of membranes using other affinity ligands.