SELECTIVE EXTRACTION OF PB2-SORBING VESICLES BEARING IONOPHORES OF A NEW CLASS( BY METAL)

Phosphatidylcholine vesicles harboring three novel ionophores, based o n the condensation of Kemp's triacid with aromatic diamine spacers, ra pidly and selectively extract Pb2+ from 5 ppm aqueous solutions. Encap sulated nitrilotriacetate, a strong water-soluble chelating agent, pro vides the driving force for divalent metal ion uptake. At acidic to ne utral pH, these metal-sorbing vesicles exhibit more than 100-fold grea ter initial permeability to Pb2+ than to Cd2+. In competitive metal io n uptake studies, Zn2+ and Cu2+ were taken up more readily than Cd2+, although more slowly than Pb2+. The measured initial permeabilities fo r these systems containing the synthetic carriers were similar to thos e for vesicles containing the natural ionophore, A23187, yet showed mu ch greater selectivity for Pb2+ over Cd2+. The selectivity of metal-so rbing vesicles is determined by the complex interplay of the metal ion binding and transport characteristics of the ionophore as influenced by the vesicle bilayer microenvironment as well as encapsulated chelat or binding.