NA+,K+-ATPASE-BASED BILAYER-LIPID MEMBRANE SENSOR FOR ADENOSINE 5'-TRIPHOSPHATE

A potentiometric sensor for adenosine 5'-triphosphate (ATP) was constructed based on a planar bilayer lipid membrane (BLM) embedded with Na+,K+-ATPase (Na+ pump). The planar bilayer lipid membranes were formed across a small circular aperture bored through a thin Teflon film by the folding of two monolayers spread on the air/water interface. The incorporation of Na+,K+-ATPase into the BLM was achieved by fusion methods. The sensor thus fabricated was found to respond potentiometrically toward ATP anions. The magnitude of the membrane potential increased with increase in the ATP concentration from 10(-6) to 10(-3) M. The detection limit was estimated to be 1.0 X 10(-6) M. The response was reasonably selective to ATP ions with the selectivity order ATP > UTP, GTP > AcP, CTP much greater than ADP. The sensor output was found to require the added K+ as expected, and was inhibited by a specific inhibitor, ouabain. The results were explained as being due to the active transport of Na+ and K+ using the hydrolysis energy of ATP, and are briefly discussed in terms of the potential use of Na+,K+-ATPase as a sensory element for ATP.