Synthetic Organic Transporters that Function in Bilayer Membranes

The phospholipid bilayer surrounding cells represents a relatively impermeable barrier to the entry of nutrients and the exit of waste products. The transport proteins that regulate the passage of ions or molecules through this barrier are large and complex molecules. In order to model and thus better understand their function, we have prepared two families of transmembrane transporter molecules. We have termed the first family hydraphiles; they selectively transport sodium cation over potassium or anions. The hydraphiles use crown ethers as headgroups and entry portals and current evidence suggests that they function unimolecularly. A family of amphiphilic heptapeptides has also been developed that selectively transports chloride anion over potassium cation. These synthetic anion transporters (SATs) insert in the bilayer and form dimeric (or larger) pores that permit transport through the membrane. These two families of synthetic ion transporters will be discussed.