AQUEOUS 2-PHASE AFFINITY PARTITIONING OF BIOTINYLATED LIPOSOMES USINGNEUTRAL AVIDIN AS AFFINITY LIGAND

Biotinylated small unilamellar liposomes were affinity partitioned in an aqueous poly(ethylene glycol)-dextran two-phase system using avidin coupled to dextran as affinity ligand. In the absence of affinity lig and more than 90% of the liposomes partitioned in the poly(ethylene gl ycol)-rich top phase, whereas in its presence more than 95% partitione d in the dextran-rich bottom phase. For this redistribution to occur 1 0 mM and above of lithium sulphate, or other appropriate salts, had to be added to the two-phase system. Without added salt the liposomes wi th complexed avidin-dextran instead partitioned in the top phase. An e xtended mixing time for the system was required for maximum redistribu tion. Less than two biotin residues per liposome, coupled via a C-6 sp acer arm, was required to redistribute the liposomes to the bottom pha se. (C) 1998 Elsevier Science B.V. All rights reserved.